We can do statistics, we can learn about abundances and rates.
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"They're not in large numbers — their abundances are low," Dr. Voyles said.
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For example, geologists would love to send an ion microprobe that can measure elemental abundances at the scale of millionths of a meter; the abundances of particular isotopes can then be used to determine the age of a specific bit of rock in a sample.
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Additionally they calculated local bacteria abundances, but didn't average the numbers out over a whole sponge.
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Researchers made the find after analyzing the abundances of metals (heavy elements) in stars, also known as their metallicities.
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And as a seal destination, Cape Cod has it all: abundances of small fish and large beaches to haul out on.
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"The diffuse ISM was historically considered too harsh and tenuous an environment for appreciable abundances of large molecules to occur," Cordiner said.
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They hoped they would be able to link the quantity of this "environmental" DNA to those species' abundances, as measured by the trawl.
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According to a new study published in Global Biogeochemical Cycles, it all comes down to the relative abundances of nitrate, silicate, and iron.
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The relative abundances of the decay products in these meteorites allow scientists to backtrack and determine the approximate age when the initial elements formed.
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We cannot rely on the detection of a single gas but instead will need to detect several, and will need to measure their relative abundances.
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The team's models predicted galactic abundances of water and two organic molecules, methanol and formaldehyde, both with and without the blasts of an AGN phase.
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And some species change in their abundances, but it is extremely rare for native species in continental regions to become entirely extinct because of new arrivals.
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For example, the stellar abundances, combined with Ross 128b&aposs known minimum mass, suggest that the planet&aposs radius is less than 1.7 times that of Earth.
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Bartos told Gizmodo that the next step is to measure more elements with unknown abundances, create better simulations, and of course, to observe more neutron star collisions.
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Soon after moving the US, she says, she began to take the abundances of convenient living for granted, however, and realized she wanted to make a change.
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Physicists need to know the neutron's lifetime in order to calculate the relative abundances of hydrogen and helium that would have been produced during the universe's first few minutes.
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By using the abundances of certain important trace gasses in Mars' atmosphere today, scientists estimate that Mars once had a global ocean with a depth of about 23 feet.
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"With JWST we could do spectroscopy in the mid-infrared, which would be key to unveil the properties of stellar populations and chemical abundances of these galaxies," Wang said.
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And even though the abundances of elements would be different, life could form—though there are other factors like the ratio of carbon to oxygen that could affect its habitability.
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Accounts of early colonists marveling at the contrast between these unadulterated runs and the long-impoverished watercourses of their European homelands speak of abundances that would be difficult to imagine today.
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The star's abundances of these elements can help determine its exoplanet's temperature, and hint at what elements were initially available in the dust ring around the star when the planet first formed.
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That means that, if you look back in time, abundances of these elements should spike if they were produced by neutron stars, or stay relatively constant if they were produced by supernovae.
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This is because the oxygen is not mixed with the right abundances of nitrogen, carbon dioxide, methane, and all the other molecules that make Earth's air breathable to humans and other organisms.
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In a world bursting with abundances like self-driving cars and robotic personal assistants, you would think that basic needs like sustainable food sourcing and distribution would be a problem of the past.
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The researchers want to learn if the organic compounds exist at greater quantities in the shadowed regions of the Moon, and whether the abundances of those compounds vary according to depth, among other things.
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Dr. Steigman and Dr. Schramm combined forces with James Gunn, now at Princeton, to write a paper declaring that based on helium abundances, there could be no more than seven families of elementary particles.
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The team looked at how the star cluster may have moved through the galaxy, allowing them to see where supernovas could have exploded and then match that to the iron-60 abundances in the ocean.
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Its spectral signature doesn't contain evidence of hydrogen or helium, which would normally place it into one of the other supernovae categories, but SN2016iet shows abundances of calcium and oxygen not matched in other supernova observations.
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"As far as I can tell, they measured elemental abundances on the star (that's the new thing) and then do a lot of modeling and extrapolation," Guillem Anglada Escude, astronomer at Queen Mary University of London, told Gizmodo.
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What's new: In a study published Thursday in Science, scientists found that "we're losing species of birds, abundances of birds, much faster than we thought ... almost three billion or one-third since 1970," co-author Peter Marra tells Axios.
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In the above video, co-lead author Jolyon Troscianko, an ecologist at the University of Exeter, explains how QCPA can adjust images to reflect various light and color sensitivities, spatial acuities, photoreceptor abundances, and other traits that differ between animal species.
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The Atlantic's science writer Ed Yong summarizes it in a tweet:The researchers surveyed a Kodiak brown bear population in Alaska, calculated elderberry ripening dates, analyzed bear poop and estimated salmon abundances to create a picture of how the relationships changed over time.
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When Bartos and Columbia University professor Szalbocs Marka performed calculations on previously collected data from these meteorites, they found that the abundances of these elements spiked approximately 80 million years before the solar system formed, when it was just a cloud of gas and dust.
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All subjects had roughly the same amount of bacteria on their penises, but those who ended up acquiring HIV had higher abundances of the kinds of bacteria that don't need oxygen to survive (called "anaerobes"), including Prevotella, Dialister, Mobiluncus and Murdochiella, according to the study published today in the journal mBio.
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Theories of nucleosynthesis are tested by calculating isotope abundances and comparing those results with observed abundances. Isotope abundances are typically calculated from the transition rates between isotopes in a network. Often these calculations can be simplified as a few key reactions control the rate of other reactions.
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Microbialized coral reefs have relatively high bacteria abundances and reduced bacteriophage abundances. To explain this observation, Rohwer and colleagues (Knowles et al. 2016) proposed that the temperate life cycle was the predominant bacteriophage life cycle at high host abundances. The resulting bacterial lysogens would be protected from other bacteriophage via superinfection exclusion and protists via expression of virulence factors.
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A chart showing the abundances of the naturally occurring isotopes of boron.
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A chart showing the abundances of the naturally-occurring isotopes of lithium.
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This can lead to abundances, multiple published names for the same entity.
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See . Figure 16 shows the short-flux calculation and its comparison with natural r-process abundances whereas Figure 18 shows the calculated abundances for long neutron fluxes. Subsequent treatments of the r-process reinforced those temporal features. Seeger et al.
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These are most commonly used in situations limited data is available on a stock. Statistical catch at age models are based on the age structure of a fished population. These models use the proportional catch-at-age to predict the relative abundance of each age class. These calculated relative abundances are then used to estimate future abundances of the stock and harvest regulations are set based on the predicted future abundances.
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Ecology Letters 10: 995–1015 Usually relative species abundances are described for a single trophic level. Because such species occupy the same trophic level they will potentially or actually compete for similar resources. For example, relative species abundances might describe all terrestrial birds in a forest community or all planktonic copepods in a particular marine environment. Relative species abundances follow very similar patterns over a wide range of ecological communities.
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Present day elemental abundances are superimposed on an (evolving) galactic-average set of elemental abundances that was inherited by the Solar System, along with some atoms from local nucleosynthesis sources, at the time of the Sun's formation. Knowledge of these average planetary system elemental abundances is serving as a tool for tracking chemical and physical processes involved in the formation of planets, and the evolution of their surfaces. Isotopic abundances provide important clues to the origin, transformation and geologic age of the material being analyzed. Extraterrestrial materials also carry information on a wide range of nuclear processes.
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Those abundances, when plotted on a graph as a function of atomic number, have a jagged sawtooth structure that varies by factors up to ten million. A very influential stimulus to nucleosynthesis research was an abundance table created by Hans Suess and Harold Urey that was based on the unfractionated abundances of the non-volatile elements found within unevolved meteorites. Such a graph of the abundances is displayed on a logarithmic scale below, where the dramatically jagged structure is visually suppressed by the many powers of ten spanned in the vertical scale of this graph. Abundances of the chemical elements in the Solar System.
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These studies are performed in international collaborations at high-flux reactors (Institut Laue-Langevin, France) or accelerator facilities as the CERN in Switzerland or the National Superconducting Cyclotron Laboratory at Michigan State University. The nuclear structure data are also applied by Kratz to nucleosynthesis, especially the astrophysical r-process. Elemental abundances from Supernova explosions are calculated in close collaboration with Friedrich-Karl Thielemann of the University of Basel. The calculated abundances are then compared to observed stellar abundances.
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Dinosterols show similar abundances as dinocysts. Other studies found a nonlinear or did not find a direct link between dinocyst abundances and sterol concentrations. Dinosterol has been used as indicator for dinoflagellate production in the Cariaco Basin. Hydrogen isotope ratios in dinosterols can serve to reconstruct salinity semi- quantitatively.
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A 2005 study of the elemental abundances of RV Tauri stars calculated that HP Lyr had a temperature around and typical abundances for an RV Tauri variable. It also revealed that the abundances were altered by dust-gas separation in circumstellar material. HP Lyr has been included in a catalog of confirmed post-AGB stars, highly evolved and on its way to becoming a white dwarf. In 2017, the temperature was calculated to be , still one of the hottest known RV Tau variables.
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In a Muller plot, the horizontal axis typically shows time or generations and the vertical axis represents relative abundances of OTUs at the corresponding times or generations. Different OTUs are usually shown with polygons or areas with different colors, and each OTU originates somewhere in the middle of its parent area in order to illustrate their succession in the evolutionary process. One difference between Muller plots and normal bar plots of abundances is that a Muller plot depicts not only the relative abundances but also succession of OTUs based on their genealogy/phylogeny/parental relation. To generate a Muller plot one needs the genealogy/phylogeny/parental relation of OTUs and their abundances over time.
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Thermal contraction/evolution models support the presence of metallic hydrogen within the core in large abundances (greater than Saturn).
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This means that their abundances depend strongly on how much mixing occurs in stellar interiors. By studying their abundances in open cluster stars, variables such as age and chemical composition are fixed. Studies have shown that the abundances of these light elements are much lower than models of stellar evolution predict. While the reason for this underabundance is not yet fully understood, one possibility is that convection in stellar interiors can 'overshoot' into regions where radiation is normally the dominant mode of energy transport.
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In astrophysics, chemically peculiar stars (CP stars) are stars with distinctly unusual metal abundances, at least in their surface layers.
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This large enhancement over cosmic abundances is consistent with the loss of an ocean's worth of H2O over geologic time.
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Intramolecular glucose carbon isotopes from tree rings that record the period of 1961 to 1995. Adapted from Wieloch et al. 2018 In 2012, a team of scientists used NMR spectroscopy to measure all of the position-specific carbon isotope abundances of glucose and other sugars. It was shown that the isotope abundances are heterogeneous.
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The calculations by Winstanley show that photoionization and dissociation reactions play a profound role in the abundances of cyanopolyynes after about 1 million years. However, the fractional abundances of cyanopolyyne are less affected by changes in radiation field intensity past time 1 million years because the prevailing neutral-neutral reactions surpass the effects of photoreactions.
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Due to its effect on the expansion rate of the universe during Big Bang nucleosynthesis (BBN), the theoretical expectations for the primordial abundances of light elements depend on Nν. Astrophysical measurements of the primordial and abundances lead to a value of Nν = at 68% c.l., in very good agreement with the Standard Model expectation.
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Vanamo 6:1-231 The codomain of this distance function ranges from 1 (identical proportional abundances) to 0 (no taxa shared).
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The shortest-lived is 19Mg with a half-life of 5 picoseconds. The abundances of the naturally occurring isotopes of magnesium.
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For a complete list of the abundance of elements in urban soils, see Abundances of the elements (data page)#Urban soils.
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Thermal contraction/evolution models support the presence of metallic hydrogen within the core in large abundances (but still less than Jupiter).
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Both human and macaque milks contains high abundances of Streptococcus and Lactobacillus bacteria, but differ in their respective relative abundances of these taxa. Bacteria observed to be most common in healthy bovine milk include Ralstonia, Pseudomonas, Sphingomonas, Stenotrophomonas, Psychrobacter, Bradyrhizobium, Corynebacterium, Pelomonas, Staphylococcus, Faecalibacterium, Lachnospiraceae, Propionibacterium, Aeribacillus, Bacteroides, Streptococcus, Anaerococcus, Lactobacillus, Porphyromonas, Comamonas, Fusobacterium, and Enterococcus.
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Sulfur has four stable isotopes, with the following abundances: 32S (0.9502), 33S (0.0075), 34S (0.0421) and 36S (0.0002). These abundances are compared to those found in Cañon Diablo troilite. Variations in sulfur isotope ratios are used to study the origin of sulfur in an orebody and the temperature of formation of sulfur- bearing minerals.Rollinson, H.R. (1993).
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Abundances are generally expressed relative to hydrogen, the most abundant element. Different studies generally find varying values for elemental abundances. This is often because spectrographs attached to telescopes do not collect all the light from objects being observed, instead gathering light from a slit or small aperture. Therefore, different observations may sample different parts of the nebula.
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Furthermore, different seed dispersers tend to disperse seeds to different habitats, at different abundances, and distances, depending on their behavior and numbers.
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Elemental abundances derived from the spectrum indicate approximately solar metallicity, although some elements are enhanced due to the evolutionary state of HR 8752.
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The Macanal Formation contains numerous levels of fossiliferous abundances. Bivalves, ammonites and flora have been found in the formation.Patiño et al., 2011, p.
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This final burning in massive stars, called explosive nucleosynthesis or supernova nucleosynthesis, is the final epoch of stellar nucleosynthesis. A stimulus to the development of the theory of nucleosynthesis was the discovery of variations in the abundances of elements found in the universe. The need for a physical description was already inspired by the relative abundances of isotopes of the chemical elements in the solar system. Those abundances, when plotted on a graph as a function of atomic number of the element, have a jagged sawtooth shape that varies by factors of tens of millions (see history of nucleosynthesis theory).
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However, results for NGC 6543 broadly agree that, relative to hydrogen, the helium abundance is about 0.12, carbon and nitrogen abundances are both about , and the oxygen abundance is about . These are fairly typical abundances for planetary nebulae, with the carbon, nitrogen and oxygen abundances all larger than the values found for the sun, due to the effects of nucleosynthesis enriching the star's atmosphere in heavy elements before it is ejected as a planetary nebula. Deep spectroscopic analysis of NGC 6543 may indicate that the nebula contains a small amount of material which is highly enriched in heavy elements; this is discussed below.
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Nitrogen abundances and isotopic compositions in lunar samples. Richard H. Becker and Robert N. Clayton. Proc. Lunar Sci. Conf. 6th (1975); pp: 2131—2149.
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Some LCGs have oxygen abundances and luminosities similar to Lyman-break galaxies (LBGs), despite much lower redshifts, thus enabling the study of LBGs through LCGs.
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If the relative abundances cannot be identified, then the clan name is simply obtained from the QFR triangle. If the relative abundances can be obtained, one must plot the appropriate point in the VRF-MRF-SRF triangle to obtain the clan name. If the point plots in the sedarenite field, one must then normalize all the sedimentary rock fragments to 100% and attempt to find the relative abundances of carbonate rock fragments (CRFs), chert fragments and sandstone fragments (Ss) and shale fragments (Sh). Using this information one must plot the point in the CRF- chert-Ss, Sh triangle and find the appropriate clan name.
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Lemaître's model was needed to explain the existence of deuterium and nuclides between helium and carbon, as well as the fundamentally high amount of helium present, not only in stars but also in interstellar space. As it happened, both Lemaître and Hoyle's models of nucleosynthesis would be needed to explain the elemental abundances in the universe. The goal of the theory of nucleosynthesis is to explain the vastly differing abundances of the chemical elements and their several isotopes from the perspective of natural processes. The primary stimulus to the development of this theory was the shape of a plot of the abundances versus the atomic number of the elements.
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In consequence, the system loses its internal stability and cannot live on. The reason for inability to survive is the lack of mutual control of constituent abundances.
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Variations in the relative abundances of the two N2O isotopologues 14N15N18O and 15N14N18O can distinguish whether N2O has been produced by bacterial denitrification or by bacterial nitrification.
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Int J Mass Spectrom 286:53–63The unspecified samples used for analyses below were Jack Hills zircon in Australia because of the high abundances and data available.
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These differences in abundances are called "fractionations," which are characterized via stable isotope analysis.Dilution effect of site-specific enrichments. The 13C enrichment at the carboxylic acid site of an amino acid is less important as the structural resolution of the measurement is decreased to molecular average and bulk cell analyses. Isotope abundances can vary across an entire substrate (i.e., “bulk” isotope variation), specific compounds within a substrate (i.e.
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The primary component of γ Equulei is a chemically peculiar star with a stellar classification of . It has a spectrum corresponding to an A9 main sequence star, but with unusual abundances of strontium, chromium, and europium. Stars with this type of spectral peculiarity are called Ap stars. The abundances of some metals are believed to be due to chemical stratification in the slowly-rotating star, unusual for hot main sequence stars.
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Mason Gully has an unusually high porosity and different mineralogy when compared to other H5 chondrites. Its porosity comes from intergranular void spaces rather than microscopic cracks, which is likely due to the low shock the rock has experienced. Whilst lithophile elemental abundances are consistent with other H chondrites, the uranium and titanium abundances are noticeably lower. Conversely, heavy refractory elements are enriched relative to the H chondrite group.
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Planetary "Planetary" gases (P, Q, P1) are depleted in light elements (He, Ne) compared to solar abundances (see below), or conversely, enriched in Kr, Xe. in Protostars and Planets III, Levy, E., Lunine, J. eds. This name originally implied an origin, the gas blend observed in terrestrial planets. Scientists wished to stop implying this, in Handbook of Elemental Abundances in Meteorites, Mason, B. ed. but the habit was retained.
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Most other BL Her stars such as U TrA, do not show the same surface carbon excess. The elemental abundances are comparable to the cooler type-R stars.
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In order to study trace metal stable isotope biogeochemistry, it is necessary to compare the relative abundances of isotopes of trace metals in a given biological, geological, or chemical pool to a standard (discussed individually for each isotope system below) and monitor how those relative abundances change as a result of various biogeochemical processes. Conventional notations used to mathematically describe isotope abundances, as exemplified here for 56Fe, include the isotope ratio (56R), fractional abundance (56F) and delta notation (δ56Fe). Furthermore, as different biogeochemical processes vary the relative abundances of the isotopes of a given trace metal, different reaction pools or substances will become enriched or depleted in specific isotopes. This partial separation of isotopes between different pools is termed isotope fractionation, and is mathematically described by fractionation factors α or ε (which express the difference in isotope ratio between two pools), or by "cap delta" (Δ; the difference between two δ values).
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If the abundances of quartz, feldspars and rock fragments indicate that the rock is an arkose, a subarkose or a lithic arkose, one must then normalize the abundance of feldspars to 100% and attempt to identify the relative abundances of K-feldspars to plagioclase in the sample. If there is more plagioclase than there is K-feldspar, the rock is either a plagioclase arkose, a plagioclase subarkose or a lithic plagioclase arkose, respectively. If there is more K-feldspar than there is plagioclase, or if it is too difficult to make a distinction between the feldspars, the name stays as arkose, subarkose or lithic arkose, respectively. If the abundances of quartz, feldspars and rock fragments indicate that the rock is a litharenite, a sublitharenite or a feldspathic litharenite, one must then normalize the abundance of rock fragments to 100% and attempt to identify the relative abundances volcanic rock fragments (VRFs), metamorphic rock fragments (MRFs) and sedimentary rock fragments (SRFs).
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From barium (Z=56) on, all elements show the pattern of the r-process contribution to the abundances of the elements in the Solar System. Comparing the observed abundances for a stable element such as europium (Z=63) and the radioactive element thorium (Z=90) to calculated abundances of an r-process in a type II supernova explosion (as from the universities at Mainz and Basel groups of Karl-Ludwig Kratz and Friedrich-Karl Thielemann) have allowed observers to determine the age of this star to be about 13 billion years. Similar ages have been derived for other ultra-metal-poor stars (CS31082-001, BD +17° 3248 and HE 1523-0901) from thorium-to-uranium ratios.
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The Hubble Space Telescope was used to observe the ultraviolet part of the stellar spectra. This allowed the measurement of platinum, osmium and, for the first time outside of the Solar System, gold. From barium (Z=56) onward, all elements show a pattern of r-process contribution to the abundances of the elements in the Solar system. The University of Mainz and University of Basel groups of Karl-Ludwig Kratz and Friedrich-Karl Thielemann performed a comparison between the observed abundances for the stable element europium (Z=63) and the radioactive elements thorium (Z=90) and uranium (Z=92) to the calculated abundances of an r-process in a Type II supernova explosion.
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By measuring the abundance of the clumped species in standard gases formed in equilibrium at known temperatures, the thermometer can be calibrated and applied to samples with unknown abundances.
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In this section, the observed variations in hydrogen isotope abundances of water sources (hydrosphere), living organisms (biosphere), organic substances (geosphere), and extraterrestrial materials in the Solar system are described.
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QFR diagram for Folk's sandstone classification As others before him, Folk proposed a classification for sandstones based on the relative abundances of quartz (Q), feldspars (F), and rock fragments (R). These are the main poles of the classification diagram. To define the clan name one must normalize the sum of abundances of quartz, feldspars and rock fragments to 100%. This means that other constituents that don't fit in these categories are disregarded.
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Figure 2. The mechanisms with which a niche is broken. A resource pool is partitioned into niches of different sizes, which can be translated into the relative abundances of species in the total resource pool. The mechanistic models that describe these plots work under the assumption that rank abundance plots are based on a rigorous estimate of the abundances of individuals within species and that these measures represent the actual species abundance distribution.
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Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a predictive theory, it yields accurate estimates of the observed abundances of the elements. It explains why the observed abundances of elements change over time and why some elements and their isotopes are much more abundant than others. The theory was initially proposed by Fred Hoyle in 1946, who later refined it in 1954.
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Natural abundance techniques can be applied without artificial disturbance. The natural 15N abundances are expressed in delta (δ) notation relative to the 15N concentration in the air. Due to enzymatic discrimination, natural 15N abundances change slightly in microbially mediated reactions in soil. Apart from δ values, the site preference of 15N and 14N (isotopomers) for the inner or outer position within the nitrous oxide molecule has been used to determine its sources (nitrification or denitrification).
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A 2004 study revealed that fishing sites near the protected area had higher fish abundances and a larger mean fish size than sites further from the protected area. This phenomenon of increased fish abundance inside and around protected areas is called "spillover." Spillover occurs when a fish population has recovered to such high abundances within a protected area that the fish begin to leave the protected area, replenishing the surrounding fish population.
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Minutes after the Big Bang, the universe was made almost entirely of hydrogen and helium, with trace amounts of lithium and beryllium, and negligibly small abundances of all heavier elements.
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However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry.
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It identified nucleosynthesis processes that are responsible for producing the elements heavier than iron and explained their relative abundances. The paper became highly influential in both astronomy and nuclear physics.
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Carbon and oxygen nuclei collide with interstellar matter to form lithium, beryllium and boron in a process termed cosmic ray spallation. Spallation is also responsible for the abundances of scandium, titanium, vanadium, and manganese ions in cosmic rays produced by collisions of iron and nickel nuclei with interstellar matter. At high energies the composition changes and heavier nuclei have larger abundances in some energy ranges. Current experiments aim at more accurate measurements of the composition at high energies.
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RT TrA is unusual in that it is a carbon-rich cepheid variable. Unlike true carbon stars, it does not show an excess of s-process elements. It has very high surface abundances of carbon, nitrogen, iron, and some light metals, but not oxygen. The unusual abundances are believed to result from the convection of triple-alpha fusion products to the surface, and so it is expected that there will also be a high proportion of helium.
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Several surprising results have shown that within them the ratio of s-process and r-process abundances is somewhat different from that which was previously assumed. It has also been shown with trapped isotopes of krypton and xenon that the s-process abundances in the AGB-star atmospheres changed with time or from star to star, presumably with the strength of neutron flux in that star or perhaps the temperature. This is a frontier of s-process studies today.
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After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds. A chart showing the relative abundances of the naturally occurring isotopes of silicon.
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In habitats with a high food supply, the sex ratio in the adult population tends to favour females, and areas with low food abundances tend to have a larger proportion of male adults.
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Given the species' high natural abundances and their occurrence as a nuisance species in some brine shrimp / rotifer aquaculture tanks, these copepods were further researched as a potential live feed for larviculture thereafter.
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Clayton created mathematical tools for calculating the interstellar abundances of radioactive nuclei in the Galaxy. In 1964 he discovered a new method for measuring the age of interstellar nuclei based on the larger than expected observed abundances of stable daughters of radioactive nuclei.[Donald D. Clayton, “Cosmoradiogenic chronologies of nucleosynthesis”, Astrophys. J., 139, 637–63, (1964)] The decays of rhenium-187 to osmium-187 and of uranium and thorium to three differing isotopes of lead (Pb) defined the cosmoradiogenic chronologies.
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Other elements were produced in only trace abundances. The basic theory of nucleosynthesis was developed in 1948 by George Gamow, Ralph Asher Alpher, and Robert Herman. It was used for many years as a probe of physics at the time of the Big Bang, as the theory of Big Bang nucleosynthesis connects the abundances of primordial light elements with the features of the early universe. Specifically, it can be used to test the equivalence principle, to probe dark matter, and test neutrino physics.
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Position-specific isotope analysis (PSIA), also called site-specific isotope analysis, is a branch of isotope analysis aimed at determining the isotopic composition of a particular atom position in a molecule. Isotopes are elemental variants with different numbers of neutrons in their nuclei, thereby having different atomic masses. Isotopes are found in varying natural abundances depending on the element; their abundances in specific compounds can vary from random distributions (i.e., stochastic distribution) due to environmental conditions that act on the mass variations differently.
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Relatively soon afterwards, the system settles to its current state. The original chemical abundances of the two stellar components are assumed to be typical of the SMC, with metallicity 1/5th to 1/10th of solar levels. In its current evolved state, the WR component shows dramatically different abundances, with hydrogen less than 20% at the surface, nitrogen almost undetectable, significant carbon enrichment, and most of the rest helium. This is unlike galactic and LMC WN stars which are almost entirely lacking hydrogen.
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One application of Dq versus Q in ecology is characterizing the distribution of species. Traditionally the relative species abundances is calculated for an area without taking into account the locations of the individuals. An equivalent representation of relative species abundances are species ranks, used to generate a surface called the species-rank surface, which can be analyzed using generalized dimensions to detect different ecological mechanisms like the ones observed in the neutral theory of biodiversity, metacommunity dynamics, or niche theory.
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Abundances of chloroviruses vary with season, with the highest abundances occurring in the spring. Chloroviruses, such as PBCV-1, play a role in regulating host populations of zoochlorella. As mentioned previously, infection of zoochlorella occurs only when the symbiotic relationship with its host is disrupted. Infection of the algae during this stage of host/algae independence will prevent the host and algae relationship from being restored, thus decreasing the survivability of the endosymbiotic hosts of the zoochlorellae, such as Paramecium bursaria.
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The B2FH paper was ostensibly a review article summarising recent advances in the theory of stellar nucleosynthesis. However, it went beyond simply reviewing Hoyle's work, by incorporating observational measurements of elemental abundances published by the Burbidges, and Fowler's laboratory experiments on nuclear reactions. The result was a synthesis of theory and observation, which provided convincing evidence for Hoyle's hypothesis. The theory predicted that the abundances of the elements would evolve over cosmological time, an idea which is testable by astronomical spectroscopy.
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The reconstruction of the stellar surface by Doppler imaging showed it is heterogenous with regions of different chemical abundances, which seem to be associated to the geometry of the magnetic field. For instance, lithium and oxygen have high abundances in the magnetic poles and low abundances in the magnetic equator, while elements like silicon and lanthanum are concentrated in a region between the magnetic equator and poles. However, these results have been contested, and it is possible the abundance maps are spurious due to the strong magnetic field. An Alpha2 Canum Venaticorum variable, Xi Phoenicis's visual magnitude varies between 5.68 and 5.78 with a period of 3.9516 days, which is the rotation period of the star and is also associated with changes in the spectrum and the magnetic field.
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The measured abundances all agree at least roughly with those predicted from a single value of the baryon-to-photon ratio. The agreement is excellent for deuterium, close but formally discrepant for ^4He, and off by a factor of two for ^7Li (this anomaly is known as the cosmological lithium problem); in the latter two cases, there are substantial systematic uncertainties. Nonetheless, the general consistency with abundances predicted by BBN is strong evidence for the Big Bang, as the theory is the only known explanation for the relative abundances of light elements, and it is virtually impossible to "tune" the Big Bang to produce much more or less than 20–30% helium. Indeed, there is no obvious reason outside of the Big Bang that, for example, the young universe (i.e.
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This was the introduction of pollen analysis in North America; pollen diagrams today still often remain in the same format with depth on the y-axis and abundances of species on the x-axis.
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Topaz Mountain is a summit in the Thomas Range of Utah, east of the Thomas caldera. The summit and surrounding area are known for their abundances of semiprecious minerals including topaz, red beryl and opal.
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Isotopic abundances are different in morphine grown from poppies in south-east Asia versus poppies grown in south-west Asia. The same is applied to cocaine that is derived from Bolivia and that from Colombia.
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Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.
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Moraine belts are usually studied in places with palaeoglacier presented. As for ocean sediments, the variations of alkenone levels and faunal abundances were measured to model paleotemperatures in separate studies showed in the following sections.
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Reporting rates are often used as a simple quantitative indicator. A framework has also been developed to incorporate monitoring data, hierarchical modelling and sampling simulations to augment occurrence and breeding status maps with species abundances.
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Deer populations also declined on Bureau of Land Management lands. Thus, in some areas in the last 20 years, the abundances of elk have increased by about 40%, whereas deer have decreased by about 30%.
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Richness simply quantifies how many different types the dataset of interest contains. For example, species richness (usually noted ) of a dataset is the number of different species in the corresponding species list. Richness is a simple measure, so it has been a popular diversity index in ecology, where abundance data are often not available for the datasets of interest. Because richness does not take the abundances of the types into account, it is not the same thing as diversity, which does take abundances into account.
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If the hydrogen in this envelope is consumed, the star becomes hydrogen deficient and it contracts to form an EHe. Examination of element abundances from seven EHe stars agreed with those predicted by the DD model.
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Eiler, J.M., Schauble, E., 2004. {^{18}O}{^{13}C}{^{16}O} in earth's atmosphere. Geochim. Cosmochim. Acta 68, 4767–4777. # Mass spectrometric analyses of purified , to obtain δ13C, δ18O, and Δ47 (Abundances of mass-47 ) value.
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See, The Kelhini River contains abundances of both sand and gravel. The lower Klehini is located within the Alaska Chilkat Bald Eagle Preserve. Walt Disney's 1991 rendition of White Fang was filmed along the Klehini River.
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Relative species abundances tend to conform to specific patterns that are among the best-known and most-studied patterns in macroecology. Different populations in a community exist in relative proportions; this idea is known as relative abundance.
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Females bear litters of 1-4 pups, with coastal lagoons and estuaries serving as a breeding ground. Reproductive activity peaks during the rainy season from April to September, likely to correspond to high abundances of prey species.
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Most of the current supply of HREE originates in the "ion- absorption clay" ores of Southern China. Some versions provide concentrates containing about 65% yttrium oxide, with the HREE being present in ratios reflecting the Oddo–Harkins rule: even-numbered REE at abundances of about 5% each, and odd-numbered REE at abundances of about 1% each. Similar compositions are found in xenotime or gadolinite. Well-known minerals containing yttrium, and other HREE, include gadolinite, xenotime, samarskite, euxenite, fergusonite, yttrotantalite, yttrotungstite, yttrofluorite (a variety of fluorite), thalenite, yttrialite.
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However, other normalizing standards can be applied depending on the purpose of the study. Normalization to a standard reference value, especially of a material believed to be unfractionated, allows the observed abundances to be compared to initial abundances of the element. Normalization also removes the pronounced ‘zig-zag’ pattern caused by the differences in abundance between even and odd atomic numbers. The trends that are observed in "spider" diagrams are typically referred to as "patterns", which may be diagnostic of petrological processes that have affected the material of interest.
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In turn, low primary production could be one cause of heterotrophic (organism-eating, as opposed to photosynthetic) species abundances being low inside the Loop Current and Loop Current Eddies. Alternatively, temperature may play a role for low abundances of both communities: Atlantic Blue Fin Tuna have developed behavioral patterns of avoiding the high temperatures associated with warm-core features, such as the Loop Current and Loop Current Eddies, in the Gulf of Mexico. It is possible, also, that planktonic species likewise avoid the higher temperatures in these features.
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Around 1% of the mass of HH objects is made up of heavier chemical elements, including oxygen, sulfur, nitrogen, iron, calcium and magnesium. Abundances of these elements, determined from emission lines of respective ions, are generally similar to their cosmic abundances. Many chemical compounds found in the surrounding interstellar medium, but not present in the source material, such as metal hydrides, are believed to have been produced by shock-induced chemical reactions. Around 20–30% of the gas in HH objects is ionized near the source star, but this proportion decreases at increasing distances.
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Spinner dolphins may use different habitats depending on the season.Fiedler, P. C., and S. B. Reilly. (1994) "Interannual variability of dolphin habitats in the eastern tropical Pacific. II: effects on abundances estimated from tuna vessel sightings, 1975 - 1990".
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The tectonic setting for Cu deposits tends to be the Andean-type plutons intruding older continental-margin carbonate layers. The host rocks tend to be quartz diorite and granodiorite. Pyrite, chalcopyrite and magnetite are typically found in higher abundances.
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Springer-Verlag, Heidelberg, Germany. but this, too, is considered a likely underestimate. An international effort, the Antarctic Pack Ice Seal initiative, is currently underway to evaluate systematically collected survey data and obtain reliable estimates of all Antarctic seal abundances.
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Geochemical prospecting involves analyzing the chemical properties of rock samples, drainage sediments, soils, surface and ground waters, mineral separates, atmospheric gases and particulates, and even plants and animals. Properties such as trace element abundances are analyzed systematically to locate anomalies.
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Mechanistic models for niche apportionment are biological models used to explain relative species abundance distributions. These niche apportionment models describe how species break up resource pool in multi-dimensional space, determining the distribution of abundances of individuals among species. The relative abundances of species are usually expressed as a Whittaker plot, or rank abundance plot, where species are ranked by number of individuals on the x-axis, plotted against the log relative abundance of each species on the y-axis. The relative abundance can be measured as the relative number of individuals within species or the relative biomass of individuals within species.
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Relatively few studies have been undertaken on the benthic assemblages and species of mangrove forests in New Zealand. The benthic invertebrate fauna of New Zealand’s mangroves forests appear to be modest in both abundances and species diversity compared to other estuarine habitats.
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However, if used effectively on the aforementioned minerals, the K–Ca dating method provides high-precision dating comparable to other isotopic dating methods. It is also most effective, comparatively, at providing major element abundances for crustal magma sources, if used with high precision.
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Isotopes in the decay chains of actinides are unique amongst radiogenic isotopes because they are both radiogenic and radioactive. Because their abundances are normally quoted as activity ratios rather than atomic ratios, they are best considered separately from the other radiogenic isotope systems.
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Figure 6. An example of Preston's veil. Fish species abundances sampled using repeated trawling over a one-month (blue bars), two month (gold bars) and one-year period (yellow). One year of sampling indicates that the fish community is log-normally distributed.
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Declining numbers of Western Screech-Owl in the lower mainland of British Columbia. British Columbia Birds, 14, 2-11.Acker, J. (2012). Recent trends in western screech-owl and barred owl abundances on Bainbridge Island, Washington. Northwestern Naturalist, 93(2), 133-137.
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Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals.Blatt, Harvey and Robert J. Tracy, 1996, Petrology, Freeman, . Alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other volcanic rocks are illustrated in QAPF diagrams.
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The lithium depletion boundary (LDB) technique is a method proposed for dating open clusters based on a determination of the lithium abundances of a cluster's stars whose masses are at about the hydrogen burning mass limit.Darling, David. 2004. The Universal Book of Astronomy.
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It is limited to the upper 100 m of the water column in Hawaiian waters. Comparison of day and night vertical distribution of abundances suggested that a portion of the population from 50–100 m migrated into the upper 50 m at night.
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IYC: Introduction. 9 July 2009. Retrieved on 17 February 2010. Retrieved 15 April 2010 IUPAC is also known for standardizing the atomic weights of the elements through one of its oldest standing committees, the Commission on Isotopic Abundances and Atomic Weights (CIAAW).
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Some PG 1159 stars are still fusing helium.The Elemental Abundances in Bare Planetary Nebula Central Stars and the Shell Burning in AGB Stars, Klaus Werner and Falk Herwig, Publications of the Astronomical Society of the Pacific 118, #840 (February 2006), pp. 183-204, § 2.1.1, 2.1.
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Rhenium and osmium are siderophile elements which are present at very low abundances in the crust. Rhenium undergoes radioactive decay to produce osmium. The ratio of non-radiogenic osmium to radiogenic osmium throughout time varies. Rhenium prefers to enter sulfides more readily than osmium.
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As θ gets larger, the distribution becomes increasingly s-shaped (log-normal) and, as it approaches infinity, the curve becomes flat (the community has infinite diversity and species abundances of one). Finally, when θ = 0 the community described consists of only one species (extreme dominance).
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When the species abundances of an ecological system are treated with a set of differential equations, it is possible to test for stability by linearizing the system at the equilibrium point. Robert May developed this stability analysis in the 1970s which uses the Jacobian matrix.
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However, it is significantly older than the Sun, being approximately 2.2 billion years older than the Sun, at 6.9 billion years old. The fact that the abundances are so similar to the Sun's suggests that it is a potential candidate for hosting terrestrial type planets.
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U can be constrained within about 30% on Earth, but its abundance on other planets is based on "educated guesses". One difficulty with this model is that there may be significant errors in its prediction of volatile abundances because some volatiles are only partially condensed.
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Recent studies have shown that the temperate mangrove forests of northern New Zealand support high abundances of small fishes, but that New Zealand support high abundances of small fishes compared to other estuarine habitats, with most of the small fish assemblage dominated by juveniles of the ubiquitous yellow-eyed mullet (Aldrichetta forsteri), as well as juvenile grey mullet (Mugil cephalus) in the west coast estuaries. Nineteen fish species are ‘confirmed’ to be associated with mangroves, of which three species are probably partially reliant on them as juvenile nurseries. It seems unlikely that New Zealand mangroves are important as spawning grounds for coastal fish or as habitat for their larvae.
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Female P. camiguin with egg sac parasitized by a wasp In the Philippines (lanthana group), most species seem to have low abundances and very patchy distributions, with few specimens found within a very small area and none in surrounding areas of apparently similar vegetation. This may have been related to the low abundance and patchiness of suitable large leaves. Specimens are usually collected between about 50 cm above ground to about 2 m, and they are likely to occur also in higher strata of the forest, possibly in higher abundances. The web is a domed sheet, most of which is closely attached to the underside of a leaf.
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Comparison of the predictions of the standard Big Bang model with experimental measurements. The power spectrum of the cosmic microwave background radiation anisotropy is plotted in terms of the angular scale (or multipole moment) (top). From around 1950 to 1965, the support for these theories was evenly divided, with a slight imbalance arising from the fact that the Big Bang theory could explain both the formation and the observed abundances of hydrogen and helium, whereas the Steady State could explain how they were formed, but not why they should have the observed abundances. However, the observational evidence began to support the idea that the universe evolved from a hot dense state.
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The star is also poor in elements heavier than sodium: for example, the iron abundance is only 28% of the solar iron abundance. Asteroseismic observations of other pulsating Lambda Boötis stars suggest that the peculiar abundance patterns of these stars are confined to the surface only: the bulk composition is likely more normal. This may indicate that the observed element abundances are the result of the accretion of metal-poor gas from the environment around the star. In 2020, spectral analysis utilizing multiple data sources have detected an inconsistency in prior data and concluded the star carbon and oxygen abundances are the same or slightly higher than solar.
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Estimated abundances of the 83 primordial elements in the Solar system, plotted on a logarithmic scale. Thorium, at atomic number 90, is one of the rarest elements. In the universe, thorium is among the rarest of the primordial elements, because it is one of the two elements that can be produced only in the r-process (the other being uranium), and also because it has slowly been decaying away from the moment it formed. The only primordial elements rarer than thorium are thulium, lutetium, tantalum, and rhenium, the odd-numbered elements just before the third peak of r-process abundances around the heavy platinum group metals, as well as uranium.
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The discovery of DNA of Asian carp could be linked to live bait used around the Great Lakes region. The method for identifying the DNA is called environmental DNA (eDNA) surveillance. This method uses DNA that is left in the environment to identify species in low abundances.
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A fairly wide range of spectral types have been published for γ Equulei, ranging from A5 to F1, some of them also indicating unusual abundances of iron in the spectrum. γ Equulei has particularly sharp absorption lines in its spectrum, a sign of very slow rotation.
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Typical indicators for the evaluation of the ecological quality are the abundances of fish, macrozoobenthos, macrophytes and phytobenthos, and the number of type-specific taxa. Criteria to further classify the ecological status of river sections can be found in the European Directive or in country-specific guidelines.
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The molecule C3H has been observed in cold, dense molecular clouds. The dominant formation and destruction mechanisms are presented below, for a typical cloud with temperature 10K. The relative contributions of each reaction have been calculated using rates and abundances from the UMIST database for astrochemistry.
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Chemical analysis showed that the abundances of ethane and methane were roughly equal, which is thought to imply that its ices formed in interstellar space, away from the Sun, which would have evaporated these volatile molecules. Alkanes have also been detected in meteorites such as carbonaceous chondrites.
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RAVE data is available from the RAVE web server or from the VizieR catalog. The RAVE 4th Data Release, includes the radial velocities, stellar parameters (temperatures, gravities, metallicities), individual abundances and photometric parallaxes/distances as well as supplementary photometry and astrometry for roughly 500 000 stars.
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During zooplankton's vertical migration the abundances of aggregates increased while size distributions decreased. Aggregates were found in the abdomen in zooplankton indicating their grazing will fragment larger aggregates. ;Surface coagulation :Aggregates may also form from colloids trapped on the surface of rising bubbles. For example, Kepkay et al.
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Lithium represents a unique case where the natural abundances of the isotopes have in some cases been found to have been perturbed by human isotopic separation activities to the point of affecting the uncertainty in its standard atomic weight, even in samples obtained from natural sources, such as rivers.
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The Radial Velocity ExperimentRadial Velocity Experiment – RAVE measures until 2010 the radial velocities and elemental abundances of a million stars, predominantly in the southern celestial hemisphere. The 6dF multi-object spectrograph on the 1.2 m UK Schmidt telescope of the Anglo-Australian Observatory will be applied for this purpose.
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Free swimming Dinophilus taeniatus are found October to June lives in tidal pools with the diatom Enteromorpha spp. and Ulva lactuca. Numbers peak March to April and decline with rising temperature and lesser diatom abundances, the decline is due to death of reproducing adults and obligatory encystment of juveniles.
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One would expect that enrichment of heavy isotopes leads to progressively slower reactions, but the IsoRes hypothesis suggests that there exist certain resonance compositions for which kinetics increases even for higher abundances of heavy stable isotopes. For example, at 9.5% 13C, 10.9% 15N and 6.6% 18O (when all three elements are 10-35 times enriched compared to their natural abundances) and normal deuterium composition (150 ppm or 0.015%), a very strong resonance (Fig. 1C) is predicted (“super-resonance”). Yet another nontrivial prediction of the IsoRes hypothesis is that at ≈250-350 ppm deuterium content, the terrestrial resonance becomes “perfect”, and the rates of biochemical reactions and growth of terrestrial organisms further increase.
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In the late stages of hydrogen burning, mass loss is extremely high due to the high luminosity and enhanced surface abundances of helium and nitrogen. As hydrogen burning ends and core helium burning begins, massive stars transition very rapidly to the Wolf–Rayet stage with little or no hydrogen, increased temperatures, and decreased luminosity. They are likely to have lost over half their initial mass at this point. It is unclear whether triple-alpha helium fusion has started at the core of Eta Carinae A. The elemental abundances at the surface cannot be accurately measured, but ejecta within the Homunculus are around 60% hydrogen and 40% helium, with nitrogen enhanced to ten times solar levels.
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That sequence could also begin earlier in galactic time than would s-process nucleosynthesis; so each scenario fits the earlier growth of r-process abundances in the galaxy. Each of these scenarios is the subject of active theoretical research. Observational evidence of the early r-process enrichment of interstellar gas and of subsequent newly formed of stars, as applied to the abundance evolution of the galaxy of stars, was first laid out by James W. Truran in 1981. He and subsequent astronomers showed that the pattern of heavy-element abundances in the earliest metal-poor stars matched that of the shape of the solar r-process curve, as if the s-process component were missing.
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This approach is implemented in MEGAN. Another tool, PhymmBL, uses interpolated Markov models to assign reads. MetaPhlAn and AMPHORA are methods based on unique clade-specific markers for estimating organismal relative abundances with improved computational performances. Other tools, like mOTUs and MetaPhyler, use universal marker genes to profile prokaryotic species.
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The chemistry of igneous rocks is expressed differently for major and minor elements and for trace elements. Contents of major and minor elements are conventionally expressed as weight percent oxides (e.g., 51% SiO2, and 1.50% TiO2). Abundances of trace elements are conventionally expressed as parts per million by weight (e.g.
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If the relative abundances of different sedimentary rock fragments cannot be obtained, then the rock is called a sedarenite, subsedarenite or feldspathic sedarenite, respectively. The name must be as specific as possible and one must try to avoid using broad terms like litharenite or sedarenite if the necessary information is available.
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The neon isotopic content of these mantle-derived samples represents a non-atmospheric source of neon. The 20Ne-enriched components are attributed to exotic primordial rare-gas components in the Earth, possibly representing solar neon. Elevated 20Ne abundances are found in diamonds, further suggesting a solar-neon reservoir in the Earth.
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Mercury's inventory of materials by volatility is being used to evaluate different models for its formation and/or subsequent modification. Isotopic abundances indicate processes over the history of the Solar System. To an extent, all bodies formed from the presolar nebula. Various subsequent processes then alter elemental and isotopic ratios.
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Beta Cancri is an orange K-type giant, about 50 times the radius of the Sun. It is a Barium star, a type of cool giant showing enhanced abundances of Barium. It is also suspected to vary slightly in brightness. The companion is a red dwarf of the fourteenth magnitude.
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Despite two possible extirpation events in urban streams and possibly a third in a Brazos River drainage, populations of Texas Shiner temporally persist with occasional and frequent abundances among multiple and independent streams, stream reaches, and drainages. Therefore, we conclude the conservation status of the Texas Shiner is currently secure.
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Merging his cosmoradiogenic method with an earlier method based only on the abundances of uranium and thorium themselvesW.A. Fowler and Fred Hoyle, Annals of Phys. 10, 280(1960) still did not yield a consistent galactic age, however. Clayton wroteNuclear cosmochronology within analytic models of the chemical evolution of the solar neighborhood, Mon.
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The cubs always stay with their mothers for about the next two and a half years. Polar Bears follow the trace of current carrying sea ice which leads them to travel south. This often leads them to relying on trash abundances for nutrition. This food source impacts the health of polar bears negatively.
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BQ Octantis is a red giant on the asymptotic giant branch. Its spectrum has been classified as M3III or M4III. The spectrum shows abnormal abundances of s-process elements and particularly ZrO, so it is classified as an S star. These stars have dredged up fusion products from the interior, especially carbon.
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Differences in the natural abundances can also be used in systems where there is sufficient variation in the 34S of ecosystem components. Rocky Mountain lakes thought to be dominated by atmospheric sources of sulfate have been found to have different δ34S values from oceans believed to be dominated by watershed sources of sulfate.
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Salinity is a more challenging quantity to infer from paleorecords. Deuterium excess in core records can provide a better inference of sea-surface salinity than oxygen isotopes, and certain species, such as diatoms, can provide a semiquantitative salinity record due to the relative abundances of diatoms that are limited to certain salinity regimes.
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Taxonomic or phylogenetic diversity is the genetic relationship between different groups of species. Species evenness quantifies how equal the abundances of the species are.Hill, M. O. (1973) Diversity and evenness: a unifying notation and its consequences. Ecology, 54, 427–432Tuomisto, H. (2010) A diversity of beta diversities: straightening up a concept gone awry.
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Scientists use paleo- oozes as tools so that they can better infer the conditions of the paleo oceans. Paleo-ooze accretion rates can be used to determine deep sea circulation, tectonic activity, and climate at a specific point in time. Oozes are also useful in determining the historical abundances of siliceous organisms.
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Both indicators are relevant for computing biodiversity. A variety of sampling methods are used to measure abundance. For larger animals, these may include spotlight counts, track counts and roadkill counts, as well as presence at monitoring stations. In many plant communities the abundances of plant species are measured by plant cover, i.e.
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Buildings like the European Neolithic long house were made primarily of wood. Recent use of wood has been enhanced by the addition of steel and bronze into construction. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut.
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The relative abundances of different isotopes are then used to describe the chemical fractionation of different isotopes, travel in different reservoirs of non-radiogenic isotopes, and age or origins of solar system objects by the presence of radiogenic daughter isotopes.Lehto, J., X. Hou, 2011. Chemistry and Analysis of Radionuclides. Wiley-VCH.Dickin, A.P., 2005.
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Thus if k is 0.5, the most common species would represent half of individuals in the community (50%), the second most common species would represent half of the remaining half (25%), the third, half of the remaining quarter (12.5%) and so forth. Although Motomura originally developed the model as a statistical (descriptive) means to plot observed abundances, the "discovery" of his paper by Western researchers in 1965 led to the model being used as a niche apportionment model - the "niche-preemption model". In a mechanistic model k represents the proportion of the resource base acquired by a given species. The geometric series rank-abundance diagram is linear with a slope of –k, and reflects a rapid decrease in species abundances by rank (Figure 4).
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Since there are many nuclear species, a computerised reaction network is needed to keep track of how all the abundances vary together. According to the Vogt-Russell theorem, the mass and the composition structure throughout a star uniquely determine its radius, luminosity, and internal structure, as well as its subsequent evolution (though this "theorem" was only intended to apply to the slow, stable phases of stellar evolution and certainly does not apply to the transitions between stages and rapid evolutionary stages). The information about the varying abundances of nuclear species over time, along with the equations of state, is sufficient for a numerical solution by taking sufficiently small time increments and using iteration to find the unique internal structure of the star at each stage.
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The s-process was seen to be needed from the relative abundances of isotopes of heavy elements and from a newly published table of abundances by Hans Suess and Harold Urey in 1956. Among other things, these data showed abundance peaks for strontium, barium, and lead, which, according to quantum mechanics and the nuclear shell model, are particularly stable nuclei, much like the noble gases are chemically inert. This implied that some abundant nuclei must be created by slow neutron capture, and it was only a matter of determining how other nuclei could be accounted for by such a process. A table apportioning the heavy isotopes between s-process and r-process was published in the famous B2FH review paper in 1957.
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It is difficult to discern how jellyfish blooms will be affected by changing environmental conditions. Some studies indicate that changes in climate alter the phenology of jellyfish, causing temporal shifts in bloom events. Much research in the future will also investigate the impacts of short and long term environmental and climatic pressures on jellyfish abundances.
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These mean values are log[O/H]+12~8.05, which shows a clear offset of 0.65dex between the two papers' values. For these 80 GPs, Amorin et al., using a direct method, rather than strong-line methods as used in Cardamone et al., calculate physical properties, as well as oxygen and nitrogen ionic abundances.
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This range of oxygen abundances is typical of nearby lower-luminosity Blue Compact Dwarfs. These results show that the original Cardamone et al. median oxygen abundance of 12 + log O/H = ~8.7 is overestimated, as a different, empirical method was originally used, rather than the direct method by Amorin et al. and Izotov et al.
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The 'clumped' species (13C16O18O) for CO2 is a doubly substituted CO2 molecule. Isotopically substituted molecules have higher mass. As a consequence, molecular vibration reduces and the molecule develops a lower zero point energy (see Kinetic isotope effect). The abundances of certain bonds in certain molecules are sensitive to temperature at which it formed (e.g.
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Acta 68, 4779–4797. Reaction 1 will be driven to the right with decreasing temperature, to the left with increasing temperature. Therefore, the equilibrium constant for this reaction can be used as an paleotemperature indicator, as long as the temperature dependence of this reaction and the relative abundances of the carbonate ion isotopologues are known.
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Quantitative comparison of rank abundance curves of different communities can be done using RADanalysis package in R. This package uses the max rank normalization method in which a rank abundance distribution is made by normalization of rank abundance curves of communities to the same number of ranks and then normalize the relative abundances to one.
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Cufflinks takes a parsimonious approach, seeking to explain all the reads with the fewest possible number of transcripts. On the other hand, StringTie attempts to simultaneously estimate transcript abundances while assembling the reads. These methods, while reasonable, may not always identify real transcripts. A study published in 2008 surveyed 25 different existing transcript reconstruction protocols.
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The model is then evolved numerically up to the age of the Sun. Any discrepancy from the measured values of the Sun's luminosity, surface abundances, etc. can then be used to refine the model. For example, since the Sun formed, some of the helium and heavy elements have settled out of the photosphere by diffusion.
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Political messages of abundance and control were depicted using chaotic geometric imagery and camelid-like figures. Examples of surviving imagery (see image) feature multiple repeating motifs of highly geometric patterns, punctuated with highly expressive color palettes. Scholars have argued that the complexity of such designs broadcast the abilities and abundances of state- controlled resources.
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Declines in abundances of butterflyfish were due to starvation. Another adverse anthropogenic effect which alters habitat community composition is the shift from coral-dominated to seaweed-dominated benthic communities. Coral reef communities provide shelter and food resources for Butterflyfish. However, the presence of seaweed has a substantial impact on butterflyfish, as they actively avoid corals in contact with seaweed.
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Florida Museum of Natural History Ichthyology Department. Retrieved on June 18, 2009. This strongly benthic species seldom ventures more than above the substrate. The relative abundances of the horn shark and the swellshark (Centroscyllim ventriosum), which shares the same habitat, are negatively correlated because horn sharks prefer temperatures warmer than while swellsharks are more cold-tolerant.
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The primary, component A, is a first-ascent red giant with a stellar classification of K0 IIIb, having chemical abundances that match a first dredge-up mixing model. Pourbaix & Boffin (2003) estimated the mass of the primary as and the secondary as . However, Feuillet et al. (2016) derived a much lower mass estimate of for the primary.
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Keeping them as monocultures he obtained higher abundances of individual species than in polyculture. Meanwhile, significantly higher was the overall abundance of the polyculture. In 1940 Gause prepares a monograph Ecology and some problems of the origin of species. The original manuscript in Russian was not published due to start of the World War II in the Soviet Union.
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Instead they are dominated by generally older, more evolved stars that are orbiting the common center of gravity in random directions. The stars contain low abundances of heavy elements because star formation ceases after the initial burst. In this sense they have some similarity to the much smaller globular clusters. The largest galaxies are giant ellipticals.
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However, very shortly thereafter, around twenty minutes after the Big Bang, the temperature and density became too low for any significant fusion to occur. At this point, the elemental abundances were nearly fixed, and the only changes were the result of the radioactive decay of the two major unstable products of BBN, tritium and beryllium-7.
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It has very narrow lines due to a low projected rotational velocity of 6 km/s. The abundances of iron are Sun- like, while it displays an overabundance of heavier elements. Some studies have suggested it is an Am-like star. Omicron Pegasi is an estimated 184 million years old with 2.24 times the mass of the Sun.
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Some essential steps in model-atmosphere analysis for determining stellar abundances (Figure by Bengt Gustafsson, Astronomical Observatory, Uppsala). The photosphere denotes those solar or stellar surface layers from which optical radiation escapes. These stellar outer layers can be modeled by different computer programs. Often, calculated models are used, together with other programs, to calculate synthetic spectra for stars.
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The abundances of the naturally occurring isotopes of neon Neon (10Ne) possesses three stable isotopes, 20Ne, 21Ne, and 22Ne. In addition, 17 radioactive isotopes have been discovered ranging from 15Ne to 34Ne, all short-lived. The longest-lived is 24Ne with a half-life of 3.38 minutes. All others are under a minute, most under a second.
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They have highs and lows that are linked with the supercontinent cycle, although it is not clear whether this is due to changes in subduction activity or preservation. Other studies have looked at time variations of mineral properties such as isotope ratios, chemical compositions, and relative abundances of minerals, although not under the rubric of "mineral evolution".
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It is possible that these results are seasonal abundances of different sexes in the region studied. They exhibit a slight reverse sexual dimorphism with females tending to be larger than males in size. The females have no post-reproductive stage. Cetaceans in general have an interbirth interval which is the time between births of new calves.
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Lipids are of particular interest to stable isotope geochemists because they are preserved in rocks for millions of years. Monson & Hayes used ozonolysis to characterize the position-specific isotope abundances of saturated fatty acids, turning different carbon positions into carbon dioxide. Using this technique, they directly measured an isotopic pattern in fatty acids that had been predicted for years.
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The resolution of these instruments can distinguish two molecules with a 1 Dalton difference in their molecular masses; however, this difference could arise from the addition of many rare isotopes (17O, 13C, 2H, etc.). For this reason, mass spectrometers using quadrupoles or time-of-flight detection techniques cannot be used for measuring position-specific enrichments at natural abundances.
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They feed primarily on photosynthetic algae and bacteria. They are part of the microzooplankton (between 20 and 200 micrometres in size). Tintinnids are found in marine and freshwaters. However, they are most common in salt water and are usually present in concentrations of about 100 a liter but can reach abundances of several thousand per litre.
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12% of studies analyzing the effects of roads on animals have found positive effects, indicating that some species benefit from the presence of roads. The predation release hypothesis, suggesting that roads may indirectly cause increases in abundances of animals whose predators are negatively affected by road, is often attributed to most positive effects of roads on animals.
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In 2008 the MESSENGER probe's Fast Imaging Plasma Spectrometer (FIPS) discovered several molecular and different ions in the vicinity of Mercury, including H2O+ (ionized water vapor) and H2S+ (ionized hydrogen sulfide). Their abundances relative to sodium are about 0.2 and 0.7, respectively. Other ions such as H3O+ (hydronium), OH (hydroxyl), O2+ and Si+ are present as well.Zurbuchen 2008, p.
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One common method is extraction by ultrasonication with methanol followed by washes of the nonpolar solvent dichloromethane (DCM). GDGTs have characteristic [M + H]+ \- 18 and [M + H]+ \- 74 ions that, for crenarchaeol, have masses of 1218 and 1162 Da, respectively. Relative abundances of GDGTs can be determined by integrating the peak areas of their characteristic ions.
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Effects of herbivore abundance in seagrass meadows. In ecology, local abundance is the relative representation of a species in a particular ecosystem. It is usually measured as the number of individuals found per sample. The ratio of abundance of one species to one or multiple other species living in an ecosystem is referred to as relative species abundances.
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It is supposed that these meteorites arise from impacts onto small near-Earth asteroids broken off from 6 Hebe in the past, rather than originating from 6 Hebe directly. The H chondrites have very similar trace element abundances and Oxygen isotope ratios to the IIE iron meteorites, making it likely that they both originate from the same parent body.
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Stellar nucleosynthesis is the nuclear process by which new nuclei are produced. It occurs in stars during stellar evolution. It is responsible for the galactic abundances of elements from carbon to iron. Stars are thermonuclear furnaces in which H and He are fused into heavier nuclei by increasingly high temperatures as the composition of the core evolves.
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Lithium-7 is fragile in the environment at the center of a nova, so being blown out of the environment at the center is necessary for the observation of lithium. The beryllium was produced by the fusion of helium-3 with helium-4. Nucleosynthesis of lithium is important in the study of chemical abundances in the universe.
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Astronomers use several different methods to describe and approximate metal abundances, depending on the available tools and the object of interest. Some methods include determining the fraction of mass that is attributed to gas versus metals, or measuring the ratios of the number of atoms of two different elements as compared to the ratios found in the Sun.
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These generally substitute for the zinc position in the lattice. The most common are Cd and Mn, but Gallium, Germanium and Indium may also be present in relatively high concentrations (hundreds to thousands of ppm). The abundances of these elements are controlled by the conditions under which the sphalerite formed, most importantly formation temperature and fluid composition.
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The GRS is used to measure the abundance of elements on the surface of Mars. Gamma rays can be measured when cosmic rays hit the surface and cause elements to emit identifiable signatures of energy (gamma rays). Measuring these gamma rays allows for the calculation of various element abundances. Water has been inferred by calculating the abundance of hydrogen .
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However, these abundances are still under the guidelines and its unclear if this is solely related to river regulation, but also reflects other catchment inputs. The composition of algae in the free flowing snow melt rivers are typically defined by diatoms. Over 58% of taxa are diatoms, with Fragilaria spp. being the most numerically abundant taxa.
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In comparison, 35 per cent of the crust is made up of the metals sodium, magnesium, aluminium, potassium and iron; together with a metalloid, silicon. All other metals and metalloids have abundances within the crust, oceans or biosphere of 0.2 per cent or less.Nelson 1987, p. 732 Nonmetals, and metalloids, in their elemental forms are extracted from:Emsley 2001, p.
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The term within the parentheses hence equals true diversity , and equals . When all types in the dataset of interest are equally common, all values equal , and the Shannon index hence takes the value . The more unequal the abundances of the types, the larger the weighted geometric mean of the values, and the smaller the corresponding Shannon entropy.
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Component C has a stellar classification of B2 V and a mass of . It has an effective surface temperature of 24,000 K, a radius of and a bolometric luminosity of . Component E is determined to have a temperature of 13,000 K, radius of , and luminosity of . It is chemically peculiar, with high abundances of manganese and strontium.
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It is possibly a mercury-manganese (HgMn) star, but abundances of other metals are unexpectedly low. Beta Scorpii is 1.01 degree from the ecliptic and can be occulted by the Moon and, very rarely, by planets. On December 9, 1906, it was occulted by Venus. The last occultation by a planet took place on 13 May 1971, by Jupiter.
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Having exhausted the supply of hydrogen at its core, this star has expanded to 26 times the Sun's radius. Within the margin of error it has near-solar abundances of iron, suggesting a Sun–like metallicity. The star is radiating 214 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,332 K.
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Cadwallader found that individuals in slow moving areas of water would feed at mid-water in a similar fashion to introduced trout species. His study of the stomach composition of Galaxias vulgaris showed high abundances of Trichoptera (caddisfly) larvae, Corydalinae (dobsonfly) larvae, Deleatidium sp. (mayfly) larvae, aquatic Diptera, Elimidae (midges) adults and larvae, and terrestrial insects.
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Sgr dSph has multiple stellar populations, ranging in age from the oldest globular clusters (almost as old as the universe itself) to trace populations as young as several hundred million years (mya). It also exhibits an age-metallicity relationship, in that its old populations are metal poor ([Fe/H] = −1.6±0.1) while its youngest populations have super-solar abundances.
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Although the foundations of nuclear astrophysics appear clear and plausible, many puzzles remain. One example from nuclear reaction physics is helium fusion (specifically the 12C(α,γ)16O reaction), others are the astrophysical site of the r-process, anomalous lithium abundances in Population III stars, and the explosion mechanism in core-collapse supernovae and the progenitors of thermonuclear supernovae.
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The most basic measure of community diversity, alpha diversity (α-diversity), can be described as the average number of distinct taxonomic groups (e.g. unique genera or operational taxonomic unit) present, independent of their abundances, on a per sample basis. In the ζ-diversity framework this can be described as ζ1, the number of unique taxa present in one sample.
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Found in lower abundances are nitriles, ketones, esters and carbonyl sulfide. The mantles of interstellar ice grains are generally amorphous, only becoming crystalline in the presence of a star. The composition of interstellar ice can be determined through its infrared spectrum. As starlight passes through a molecular cloud containing ice, molecules in the cloud absorb energy.
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In 1997, HNC was observed along the TMC-1 ridge and its abundance relative to HCO+ was found to be constant along the ridge—this led credence to the reaction pathway that posits that HNC is derived initially from HCO+. One significant astronomical detection that demonstrated the practical use of observing HNC occurred in 2006, when abundances of various nitrogenous compounds (including HN13C and H15NC) were used to determine the stage of evolution of the protostellar core Cha-MMS1 based on the relative magnitudes of the abundances. On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution of HCN, HNC, H2CO, and dust inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON).
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A table apportioning the heavy isotopes phenomenologically between s-process and r-process isotopes was published in 1957 in the B2FH review paper, which named the r-process and outlined the physics that guides it. Alastair G. W. Cameron also published a smaller study about the r-process in the same year. The stationary r-process as described by the B2FH paper was first demonstrated in a time-dependent calculation at Caltech by Phillip A. Seeger, William A. Fowler and Donald D. Clayton, who found that no single temporal snapshot matched the solar r-process abundances, but, that when superposed, did achieve a successful characterization of the r-process abundance distribution. Shorter-time distributions emphasize abundances at atomic weights less than , whereas longer-time distributions emphasized those at atomic weights greater than .
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Often researchers use the values given by one or more diversity indices, such as species richness (which is simply a count of species), the Shannon index or the Simpson index (which take into account also species proportional abundances).Lande, R. (1996) Statistics and partitioning of species diversity, and similarity among multiple communities. Oikos, 76, 5-13.Veech, J. A. et al.
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She currently is a Professor of Astronomy at the University of Texas at Austin. Her special areas of study include chemical abundances of stars, planetary nebulae, and H II regions (interstellar gas containing ionized hydrogen). She also discovered in 1973 on photographic plates the recurrent nova V3890 Sagittarii, which erupted in May or June 1962, April 1990, and on 27 August 2019.
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QU Normae has a spectral type B1.5 Ia, a luminous supergiant that has swollen and cooled off the main sequence. Surface abundances suggest that it has not yet passed through a red supergiant phase. Around 1,820 light-years distant, it shines with a luminosity approximately 417,000 times that of the Sun and has a diameter around 58 times that of the Sun.
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That Titan might have accreted an atmosphere from the early Saturnian nebula at the time of formation also seems unlikely; in such a case, it ought to have atmospheric abundances similar to the solar nebula, including hydrogen and neon. Many astronomers have suggested that the ultimate origin for the methane in Titan's atmosphere is from within Titan itself, released via eruptions from cryovolcanoes.
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CL) and the BBN D + 4He concordance range (wider vertical bands, at 95% CL) should overlap with the observed light element abundances (yellow boxes) to be in agreement. This occurs in 4He and is well constrained in D, but is not the case for 7Li, where the observed Li observations lie a factor of 3−4 below the BBN+WMAP prediction.
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This method relies upon immunoprecipitation of RNA polymerase II. There are a number of issues with immunoprecipitation, including non-specific binding interactions which may result in the immunoprecipitation of off-target RNA molecules. The temporal resolution of NET-seq is limited to transcription elongation. While comparing relative abundances between transcripts using NET- seq is possible, it is not the intention of the method.
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The two stars in this system orbit each other over a period of 64.62 years at an eccentricity of 0.14. Both are A-type main sequence stars; the primary has a stellar classification of A2 V while its companion is A7 V. Their composite spectrum shows the properties of a Lambda Boötis star, which means it displays peculiar abundances of certain elements.
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This is an aging subgiant star, as indicated by its spectral type of B3IV. Its effective temperature of 16,100 K fits into the normal range of B-type stars: 11,000 to 25,000 K. 8 Cygni is about twice as hot as the Sun, and it is six times larger and many times brighter in comparison. The elemental abundances are near solar.
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It is roughly the same size and luminosity as its neighbour in space, M69. M70 has a very small core radius of and a half-light radius of . This cluster has undergone core collapse, leaving it centrally concentrated with the luminosity distribution following a power law. There are two distinct stellar populations in the cluster, with each displaying unique abundance abundances.
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Sometimes, however, other gods are represented along with Ala in the structure. Other sculptures which could be included are of officials, craftsmen, foreigners (mainly Europeans), animals, legendary creatures and ancestors. Mbari houses take years to build and building them is regarded as sacred. Along with being representations of abundances and harmony, they are most usually created during times of peace and stability.
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The crossover in stability is between 1 and 5 nm. At even smaller sizes, a variety of other forms of carbon such as fullerenes can be found as well as diamond cores wrapped in fullerenes. The most carbon-rich meteorites, with abundances up to 7 parts per thousand by weight, are ureilites. These have no known parent body and their origin is controversial.
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It may be a chemically peculiar Am star, which means it displays unusual abundances of certain elements in its surface layers. Tau7 Eridani appears to be a low amplitude variable that displays slight fluctuations in luminosity over a period of 7.17 days. It is slowly rotating with a projected rotational velocity of 18 km/s, and is around 387 million years old.
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The process results in the light elements beryllium, boron, and lithium in the cosmos at much greater abundances than they are found within solar atmospheres. The quantities of the light elements 1H and 4He produced by spallation are negligible relative to their primordial abundance. Beryllium and boron are not significantly produced by stellar fusion processes, since 8Be is not particle- bound.
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Hydronium, on the other hand, has several transitions that make it a superior candidate for detection and identification in a variety of situations. This information has been used in conjunction with laboratory measurements of the branching ratios of the various dissociative recombination reactions to provide what are believed to be relatively accurate and abundances without requiring direct observation of these species.
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After a reexamination, it was found that the abundances of carbon-monoxide ice and carbon dioxide ice show that short-period comets formed under warmer conditions, than the longer period comets. This shows that the short-period comets formed closer to the Sun, than the long-term comets. This discovery goes well with the measurements of Heavy Water in Hartley 2.
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Climate change has produced numerous shifts in the distributions and abundances of species. Thomas et al. (2004) went on to assess the extinction risk due to these shifts over a broad range of global habitats. Their predictive model using midline estimates for climate warming over the next 50 years suggests that 15–37% of species will be "committed to extinction" by 2050.
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Thus, it was known by Gamow and others that the abundances of hydrogen and helium were not perfectly static. According to their view, fusion in stars would produce small amounts of helium, adding only slightly to its abundance from the Big Bang. This stellar nuclear power did not require substantial stellar nucleosynthesis. The elements from carbon upward remained a mystery.
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However, some astronomers postulate that close binary central stars might be responsible for the more complex and extreme planetary nebulae. Several have been shown to exhibit strong magnetic fields, and their interactions with ionized gas could explain some planetary nebulae shapes. There are two main methods of determining metal abundances in nebulae. These rely on recombination lines and collisionally excited lines.
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The primary component is a B-type main-sequence star with a stellar classification of B9 V. It is a type of chemically peculiar star known as an HgMn star, which means it shows surface overabundancies of certain elements including mercury and manganese, and deficiencies in others including helium, cobalt, and so forth. The star has about three times the mass of the Sun and is radiating 87 times the Sun's luminosity from its photosphere at an effective temperature of about 10,500 K. The reconstruction of the surface of Phi Phoenicis by Doppler imaging showed it to be heterogeneous with regions of different elemental abundances. In particular, the star forms spots with high or low abundances of yttrium, strontium, titanium, and chromium. The comparison of the abundance maps in different epoches revealed that the spot configurations vary on monthly or yearly time scales.
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The Chart of the Nuclides, containing information such as masses, relative abundances, half-lives, neutron cross sections, and decay properties for more than 3,100 nuclides and 580 isomers was developed at KAPL. This chart is a necessity for students and professionals in nuclear physics, chemistry, engineering, and medicine around the world. The Chart has been compiled, edited and periodically revised by KAPL scientists since 1956.
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Considering the relative abundances of the elements in the universe (approximately 98% hydrogen and helium) it would be surprising to find a predominantly rocky planet more massive than Jupiter. On the other hand, models of planetary-system formation have suggested that giant planets would be inhibited from forming as close to their stars as many of the extrasolar giant planets have been observed to orbit.
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The abundances of less volatile compounds such as ammonia, water, and hydrogen sulfide in the deep atmosphere are poorly known. They are probably also higher than solar values. Along with methane, trace amounts of various hydrocarbons are found in the stratosphere of Uranus, which are thought to be produced from methane by photolysis induced by the solar ultraviolet (UV) radiation. They include ethane (), acetylene (), methylacetylene (), and diacetylene ().
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Gene co-expression networks can be interpreted as association networks between variables that measure transcript abundances. These networks have been used to provide a systems biologic analysis of DNA microarray data, RNA-seq data, miRNA data etc. weighted gene co-expression network analysis is widely used to identify co-expression modules and intramodular hub genes. Co-expression modules may correspond to cell types or pathways.
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Biotite occurs in some of these rocks, and melanite also is present. Nepheline decreases in amount as leucite increases since the abundances of the two reflect the Na:K ratio of the rock. Rocks of this group are known from Rio de Janeiro, Arkansas, Kola Peninsula (in Russia), Montana and a few other places., In Greenland there are leucite tinguaites with much arfvedsonite, (hornblende) and eudialyte.
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This is a suspected chemically peculiar star star with a stellar classification of B9 III, although Adelman et al. (2004) consider it to be a normal star with near- solar elemental abundances. It is relatively sharp-lined with a projected rotational velocity of 25 km/s. The star is radiating 318 times the luminosity of the Sun from its photosphere at an effective temperature of 11,200 K.
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Bacteria are thought to be an important contributor to the creation of petroleum source rock. However, studies have shown that abundances of bacterial biomarkers do not always reflect relative contributions to sedimentary organic carbon.Hartgers, W.A., Damste, J. S. S., Requejo, A.G., Allan, J., Hayes, J.M., de Leeuw, J.W. (1994). Evidence for only minor contributions from bacteria to sedimentary organic carbon. Nature. Vol. 369. p. 224.
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Abundances are measured or estimated for each. The mean cyclic-to-linear abundance ratio for C3H is found to be 2.7, although a large variation in this ratio is observed from source to source. In 2004, N. Kaifu et al. completed the first spectral line survey toward TMC-1 in the frequency range 8.8-50.0 GHz with the 45-m radio telescope at Nobeyama Radio Observatory.
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Although there is a core microbiome shared among castes and colonies, the alate caste gut is characterised by a significantly lower abundances of bacteria in the genus Treponema (Spirochaetes) and the class Endomicrobia (Elusimicrobia) compared to workers and soldiers. Flagellates in the class Parabasalia and the order Oxymonadida are also significantly less abundant in the alate gut, with the latter significantly reduced in dealates as well.
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Smaller reserves can be found in the United States, for example in the Absaroka Range in Montana. In 2010, South Africa was the top producer of platinum, with an almost 77% share, followed by Russia at 13%; world production in 2010 was . Large platinum deposits are present in the state of Tamil Nadu, India. Platinum exists in higher abundances on the Moon and in meteorites.
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The thorium-232 to uranium-238 ratio was used to determine the age. It is estimated to be about 12.5 billion years old, making it one of the oldest known. Compared to other ultra-metal- poor, r-process enriched stars (as CS22892-052, BD +17° 3248, HE 1523-0901) CS31082-001 has higher abundances of the actinides (Th, U), but a surprisingly low Pb abundance.
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To help mitigate this degeneracy, a star's B−V color can be used as an indicator for temperature. Furthermore, the UV excess and B−V color can be corrected to relate the δ(U−B) value to iron abundances. Other photometric systems that can be used to determine metallicities of certain astrophysical objects include the Strӧmgren system, the Geneva system, the Washington system, and the DDO system.
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In the early 1900s the model of the Big Bang theory was formulated, heavily evidenced by cosmic microwave background radiation, Hubble's law, and the cosmological abundances of elements. Space telescopes have enabled measurements in parts of the electromagnetic spectrum normally blocked or blurred by the atmosphere. In February 2016, it was revealed that the LIGO project had detected evidence of gravitational waves in the previous September.
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Also, from quotation there: Thomson, W. (1872). Rep. Brit. Assoc. xcix: "Frankland and Lockyer find the yellow prominences to give a very decided bright line not far from D, but hitherto not identified with any terrestrial flame. It seems to indicate a new substance, which they propose to call Helium." Computing relative abundances was achieved through corresponding spectroscopic observations to measurements of the elemental composition of meteorites.
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The majority of Acidobacteria are considered aerobes. There are some Acidobacteria that are considered anaerobes within subdivision 8 and subdivision 23. It has been found that some strains of Acidobacteria originating from soils have the genomic potential to respire oxygen at atmospheric and sub-atmospheric concentrations. Members of the Acidobacteria phylum have been considered oligotrophic bacteria due to high abundances in low organic carbon environments.
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It shows some enhancement of Carbon, but only to about 80% of the oxygen abundance. There is no suggestion of s-process elements being over- abundant. This is consistent with first dredge-up abundances, suggesting that most RV Tauri stars were not massive enough to experience a third dredge-up. U Mon is surrounded by a dusty circumstellar disc, a common feature of RV Tauri variables.
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Foxtail pine is restricted to the southern part of the Sierra, forming pure stands where whitebark pine would dominate further north. In addition to the species described above, Jeffrey pine and red fir, which are more commonly found in the upper montane zone, can be found at low abundances in the subalpine zone, particularly on exposed slopes where snow does not linger as long.
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At the same time, carbon and oxygen abundances are reduced. Red supergiants can be distinguished from luminous but less massive AGB stars by unusual chemicals at the surface, enhancement of carbon from deep third dredge-ups, as well as carbon-13, lithium and s-process elements. Late-phase AGB stars can become highly oxygen-enriched, producing OH masers. Hotter supergiants show differing levels of nitrogen enrichment.
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Multiple definitions and calculations of enrichment have been adopted by different researchers. Calculations of enrichment become more complex when multiple tracers are used simultaneously. Because enriched isotope preparations are never isotopically pure, i.e. they contain all the element’s isotopes in unnatural abundances, calculations of enrichment of multiple isotope tracers must account for the perturbation of each isotope ratio by the presence of the other tracers.
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Tellurium on quartz (Moctezuma, Sonora, Mexico) Native tellurium crystal on sylvanite (Vatukoula, Viti Levu, Fiji). Picture width 2 mm. With an abundance in the Earth's crust comparable to that of platinum (about 1 µg/kg), tellurium is one of the rarest stable solid elements. In comparison, even the rarest of the stable lanthanides have crustal abundances of 500 µg/kg (see Abundance of the chemical elements).
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Gamma Corvi A is a giant star with a stellar classification of B8 III and has approximately 4.2 times the mass of the Sun. It has a blue-white hue. The spectrum of this star displays an anomalously higher than normal abundance of the elements mercury and manganese, making this a Mercury-manganese star. However, there are other elements that show large over or under abundances.
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Surface abundances show enhancement of heavy elements, thought to have been dredged up during an earlier AGB phase. Carbon in particular is strongly in excess in RV Tau. RV Tau is surrounded by a dusty circumstellar disc, a common feature of RV Tauri variables. It has been suggested that the formation of the disk is related to a binary companion, but none has been detected.
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This yields orbital elements with a period of 48.3 days and an eccentricity of 0.50. The a sin i value for the primary is , where a is the semimajor axis and i is the (unknown) orbital inclination. The visible component is a well-studied magnetic chemically peculiar star with a stellar classification of . The SiSr notation indicates unusual abundances of silicon and strontium in the spectrum.
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These assemblages are marked by high abundances of taxa such as Betula, the co- occurrence of now allopatric species such as Fraxinus and Picea, and the low abundance of taxa that are now modernly abundant, such as Pinus. These associations are evident across Alaska, eastern North America, Europe and the southwestern US. The environmental conditions during the Pleistocene offered a climate that was more productive for plant species than climate conditions that exist today. This is evident through extensive records of high abundances of broadleaved trees Ulmus, Ostrya, Fraxinus and Quercus mixed with boreal conifers such as Picea and Larix during the late Holocene. New evidence states that deglacial temperatures are now hypothesized to be a major contributor to the formation of no-analog plant communities in the Midwestern US. Christensen bog fauna during this time period also represent a significant example of no- analog assemblages from the Pleistocene.
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Its surface is primarily composed of methane (CH4), nitrogen (N2), and carbon monoxide (CO) volatile ices in various spatial abundances and distribution. Though Pluto is small compared to typical planets, it has an atmosphere, though much thinner than Earth's. Containing multiple layers of haze, its atmosphere is composed mainly of nitrogen (N2) with trace amount of methane (CH4) and carbon monoxide (CO). Long-term climate cycles of planetary bodies (e.g.
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Cecilia Payne-Gaposchkin discovers that hydrogen is the most abundant element in the Sun's atmosphere, and accordingly, the most abundant element in the universe by relating the spectral classes of stars to their actual temperatures and by applying the ionization theory developed by Indian physicist Meghnad Saha. This opens the path for the study of stellar atmospheres and chemical abundances, contributing to understand the chemical evolution of the universe.
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The effectiveness of rescue effect reducing the extinction risk via dispersal also depends on the correlation of environmental fluctuations experienced by different populations. If the correlation is high, all populations decline simultaneously reducing recolonization rates of empty patches. This means that if an environmental phenomena diminishes the distributions or abundances of many populations over a big geographical area at the same time, the probabilities of a rescue effect are very low.
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Gallium does not exist as a free element in the Earth's crust, and the few high-content minerals, such as gallite (CuGaS2), are too rare to serve as a primary source. The abundance in the Earth's crust is approximately 16.9 ppm. This is comparable to the crustal abundances of lead, cobalt, and niobium. Yet unlike these elements, gallium does not form its own ore deposits with concentrations of > 0.1 wt.
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Despite the low theoretical abundance of lithium, the actual observable amount is less than the calculated amount by a factor of 3-4. This contrasts with the observed abundance of isotopes of hydrogen (1H and 2H) and helium (3He and 4He) that are consistent with predictions. Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, residuals within the paradigm of the Big Bang.
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Johns Hopkins University Press, pg. 150. . However, the lake is most famous for sockeye salmon and grizzly bears. The bears are often seen wandering around the lake or wading into it to catch fish, but they are found in the greatest abundances at Brooks Camp. } Bears are seen frequently at Brooks Falls, catching salmon there; they are the main attraction to the lake and Brooks Falls and Camp.
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Nature, 411, 296-298. Higher spring temperatures can lead to earlier increases in insect abundance, but many bird species were not able to advance their arrival dates. For example, pied flycatchers timed their egg hatch cycles with subsequent increases in food to raise as many young as possible. Spring migration based on day length had allowed flycatchers to arrive on time, and their egg laying times correlated with insect abundances.
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The energy of the gamma ray is associated with the element responsible for its emission. Due to a low signal-to-noise ratio, multiple passes were required to generate statistically significant results. At nine passes per month, it was expected to take about three months to confidently estimate abundances of thorium, potassium, and uranium, and 12 months for the other elements. The precision varies according to element measured.
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In extant organisms, isoarborinol can be found in its intact form with its polar hydroxyl group. In sediments, isoarborinol is diagenetically converted to its fully saturated form, arborane. Thus, techniques designed to extract and analyze isoarborinol must consider the chemistry of the molecule being interrogated. Common approaches to analyzing biomarker compounds include identifying their structures, quantifying their abundances and measuring the isotopic compositions of their various elements (carbon, nitrogen, sulfur, etc.).
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At an estimated age of 254 million years, this appears to be an evolved B-type giant star with a stellar classification of B9 III. It is a mercury-manganese chemically peculiar star, indicating the spectrum shows abnormal abundances of these elements. The star has about four times the radius of the Sun and it radiates 173 times the Sun's luminosity from its photosphere at an effective temperature of 10,152 K.
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"Abundances and Diversities," ibid. Page 248. A number of complete skeletons have been recovered from Colorado, New Mexico, Utah, and Wyoming, usually found in stratigraphic zones 2-6. According to radiometric dating, the Morrison sedimentary layers range between 156.3 million years ago (Mya) at the base, to 146.8 Mya at the top, which places it in the late Oxfordian, Kimmeridgian, and early Tithonian stages of the Late Jurassic period.
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"Schinus terebinthifolius". www.fs.fed.us. Retrieved 2017-11-09. Brazilian peppers are fire-adapted and produce rapidly growing sprouts following fire events, although plant size and stand density are important in determining the post-fire response, with younger plants having higher mortality rates. Fire frequency plays some role in Brazilian pepper establishment, with areas of frequent fires displaying lower abundances of the plant in contrast to areas not regularly burned.
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Despite the Florida softshell's use of alligator nests, studies have shown the highest abundance of Florida softshell turtles to persist in lakes with little to no alligators as well as high primary productivity, suggesting a combination of top-down and bottom-up influences on softshell populations.Aresco, M. J. (2009). Environmental correlates of the abundances of three species of freshwater turtles in lakes of northern Florida. Copeia, 2009 (3), 545–555.
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The Macanal Formation or Macanal Shale (, Kilm, K1m) is a fossiliferous geological formation of the Altiplano Cundiboyacense and Tenza Valley in the Eastern Ranges of the Colombian Andes. The predominantly organic shale formation dates to the Early Cretaceous period; Berriasian to Valanginian epochs and has a maximum thickness of . The Macanal Formation contains numerous levels of fossiliferous abundances. Bivalves, ammonites and fossil flora have been found in the formation.
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A major objective of the emerging field of neutrino geophysics involves extracting geologically useful information (e.g., abundances of individual geoneutrino-producing elements and their spatial distribution in Earth's interior) from geoneutrino measurements. Analysts from the Borexino collaboration have been able to get to 53 events of neutrinos originating from the interior of the Earth. Most geoneutrinos are electron antineutrinos originating in decay branches of 40K, 232Th and 238U.
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Young was part of the research team that developed the Atom Trap Trace Analysis (ATTA) methodology for counting atoms of rare isotopes whose isotopic abundances are less than one part in a trillion. ATTA is a tool that extends radiocarbon dating from 5000 yr to 200 kyr, operating on long-lived isotopes where radioactive decay counting is inefficient. ATTA has been used with 81Kr to date the groundwater of ancient aquifers.
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While an isotope effect is the physical tendency for stable isotopes to distribute in a particular way, the isotopic fractionation is the measurable result of this tendency. The isotopic fractionation of a natural process can be calculated from measured isotope abundances. The calculated value is called a "fractionation factor," and allows the effect of different processes on isotope distributions to be mathematically compared. For example, imagine a chemical reaction Reactant → Product.
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At an ecotone, species abundances change relatively quickly compared to the environmental gradient. The species distribution along environmental gradients has been studied intensively due to large databases of species presence data (e.g. GBIF) Environmental Gradients are linked to Connectivity and natural disturbance when considering river systems. A river restoration scheme must consider all of these factors before undertaking a program as these three factors are what leads to a larger biodiversity.
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Native species that forage on resources that don't originate in their same habitat. This may increase their local abundances thereby affecting other species in the ecosystem. For example, Luskin et al. (2017) found that native animals living protected primary rainforest in Malaysia found food subsidies in neighboring oil palm plantations. This subsidy allowed native animal populations to increase, which then triggered powerful secondary ‘cascading’ effects on forest tree community.
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Originally tribes / communities had abundances of cattle and land cultivation was forbidden until 1972. Now people have developed the skill of farming using the river sources, hence the utilization of the Dawa River for irrigated farming. There are small ponds built by the local people to provide water over a wide area for their animals. Communities around the Dawa River have to dig deep wells that tap underground water.
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This has been the standard method since the paper was published in 1990. With David Lai (UC San Diego), Jennifer Johnson (Ohio State University), Sara Lucatello (Osservatorio Astronomico di Padova), Alex Hager (U Minnesota) and Sten Woosley (UC Santa Cruz) published a study of the detailed abundances of extremely metal-poor stars using the results to along with theoretical yields from zero-metallicity stars to constrain models for Pop III objects.
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The stellar spectrum displays an overabundance of heavier elements; particularly silicon and gallium. These abundances may be caused by the magnetic field of the star, which produces concentrations of the observed elements in the outer atmosphere. It is a α² Canum Venaticorum-type variable star, ranging in magnitude from 5.15 down to 5.22. These variations are likely due to large spots or rings on the side of the star being observed.
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Moon and Planets 19, 109-137 (1978) Instead he predicted that unusual but predictable isotopic compositions would be found within thermally condensed interstellar grains that had condensed during mass loss from stars of differing types. He argued that such grains exist throughout the interstellar medium.D.D. Clayton and R.A. Ward, s-process studies: xenon and krypton isotopic abundances, Astrophys. J. 224, 1000-1006 (1978). This paper was submitted in 1975 to Geochim.
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The anomaly is between the Bel'kovich crater, which is wide, and the Compton crater, which is wide. The region as a whole is wide and long. The center of the region is a volcanic complex, to across, between the Bel'kovich and the Compton craters. It is from the extent of the northeastern Procellarum KREEP Terrane (an area which has high abundances of KREEP, a geochemical component of some lunar rocks).
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In 2002, Wennberg was elected chair of the Total Carbon Column Observing Network (TCCON). In 2004, the first TCCON site was established. The Total Carbon Column Observing Network is a group of about 20 ground-based sites worldwide that host Fourier transform spectrometers. The spectrometers examine near- infrared (NIR) solar absorption spectra and measure atmospheric column abundances of CO2, CH4, CO, N2O and other molecules in terrestrial ecosystems.
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Towards the end of the 20th century, technological improvements helped to further the study of planetary nebulae. Space telescopes allowed astronomers to study light wavelengths outside those that the Earth's atmosphere transmits. Infrared and ultraviolet studies of planetary nebulae allowed much more accurate determinations of nebular temperatures, densities and elemental abundances. Charge-coupled device technology allowed much fainter spectral lines to be measured accurately than had previously been possible.
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Following pioneering research into the Big Bang and the formation of helium in stars, an unknown process responsible for producing heavier elements found on Earth from hydrogen and helium was suspected to exist. One early attempt at explanation came from Chandrasekhar and Louis R. Henrich who postulated that elements were produced at temperatures between 6×109 and 8×109 K. Their theory accounted for elements up to chlorine, though there was no explanation for elements of atomic weight heavier than 40 amu at non-negligible abundances. This became the foundation of a study by Fred Hoyle, who hypothesized that conditions in the core of collapsing stars would enable nucleosynthesis of the remainder of the elements via rapid capture of densely packed free neutrons. However, there remained unanswered questions about equilibrium in stars that was required to balance beta-decays and precisely account for abundances of elements that would be formed in such conditions.
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The need for a physical setting providing rapid neutron capture, which was known to almost certainly have a role in element formation, was also seen in a table of abundances of isotopes of heavy elements by Hans Suess and Harold Urey in 1956. Their abundance table revealed larger than average abundances of natural isotopes containing magic numbers of neutrons as well as abundance peaks about 10 amu lighter than stable nuclei containing magic numbers of neutrons which were also in abundance, suggesting that radioactive neutron-rich nuclei having the magic neutron numbers but roughly ten fewer protons were formed. These observations also implied that rapid neutron capture occurred faster than beta decay, and the resulting abundance peaks were caused by so-called waiting points at magic numbers. This process, rapid neutron capture by neutron-rich isotopes, became known as the r-process, whereas the s-process was named for its characteristic slow neutron capture.
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The iron peak is a local maximum in the vicinity of Fe (Cr, Mn, Fe, Co and Ni) on the graph of the abundances of the chemical elements. For elements lighter than iron on the periodic table, nuclear fusion releases energy. For iron, and for all of the heavier elements, nuclear fusion consumes energy. Chemical elements up to the iron peak are produced in ordinary stellar nucleosynthesis, with the alpha elements being particularly abundant.
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Maternal health status is associated with changes in the bacterial composition of milk. Higher maternal BMI and obesity are associated with changes in the levels of Bifidobacterium and Staphylococcus species and overall lower bacterial diversity. Milk of women with celiac disease is observed to have reduced levels of Bacteroides and Bifidobacterium. Women who are HIV-positive show higher bacterial diversity and increased abundances of Lactobacillus in their milk than do non- HIV-positive women.
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Challenges in discerning jellyfish bloom trends partially arise from the lack of long-term data sets. This lack of data also inhibits researchers' abilities to distinguish between jellyfish bloom oscillations caused by natural versus anthropogenic impacts. One review demonstrated that there were increasing trends of jellyfish abundances in 28 out of the 45 Large Marine Ecosystems globally. However, the review notes the limitations of their analyses, given substantial time series data is unavailable.
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Notably though, the meteor is highly enriched in volatile mercury which is undetectable in the solar photosphere, and this is a major driver of the "mercury paradox" that mercury abundances in meteors do not follow its volatile nature and isotopic ratios based expected behaviour in the solar nebula. These features mean that it is often, despite its small size, included in meteorological studies. The meteorite contains dolomite, magnesite, magnetite, pentlandite and pyrrhotite.
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It is estimated that a total of around 68,000 northern right whale dolphins inhabit the Pacific Ocean. Of those, around 26,000 (the geometric mean of their abundance estimates in US waters from 2008-2014) are placed into the California/ Oregon/ Washington stock for management purposes. Their minimum population estimate is around 18,600. Their abundances and distributions along the US coast do not only vary seasonally but also interanually, making the identification of population trends difficult.
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Josef Mattauch (21 November 1895 - 10 August 1976) was a nuclear physicist and chemist. He was known for the development of the Mattauch-Herzog double- focusing mass spectrometer, for his work on the investigation of isotopic abundances using mass spectrometry, and the determination of atomic weights. Much of his career was spent at the Kaiser Wilhelm Institute for Chemistry (later the Max Planck Institute). He developed the Mattauch isobar rule ("Isobarenregel") in 1934.
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Granitoids have crystallized from felsic magmas that have compositions at or near a eutectic point (or a temperature minimum on a cotectic curve). Magmas are composed of melts and minerals in variable abundances. Traditionally, magmatic minerals are crystallized from the melts that have completely separated from their parental rocks and thus are highly evolved because of igneous differentiation. If a granite has a slowly cooling process, it has the potential to form larger crystals.
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The abundances of these algal groups are strongly related to the increase of both the oxygen deficiency in the water column and the total organic carbon content. The evidence from these algal groups suggest that there were episodes of halocline stratification of the water column during the time. A species of freshwater dinocyst—the Bosedinia was also found in the rocks dated to the time and these suggest that the oceans had reduced salinity.
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Restoration often focuses on reestablishing plant communities, probably because plants form the foundation for other organisms within the community. Restoration of faunal communities often follows the “Field of Dreams” hypothesis: “if you build it, they will come”. Many animal species have been found to naturally recolonize areas where habitat has been restored. For example, abundances of several bird species showed marked increases after riparian vegetation had been reestablished in a riparian corridor in Iowa.
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The relative abundances of the four stable isotopes are approximately 1.5%, 24%, 22%, and 52.5%, combining to give a standard atomic weight (abundance-weighted average of the stable isotopes) of 207.2(1). Lead is the element with the heaviest stable isotope, 208Pb. (The more massive 209Bi, long considered to be stable, actually has a half-life of 2.01×1019 years.) A total of 43 lead isotopes are now known, including very unstable synthetic species.
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To understand Mars' ancient climate, and whether it might have created environments habitable for life, first we need to understand Mars' climate today. Each mission to Mars has made new advances in understanding its climate. Mars has seasonal variations in the abundances of water vapor, water ice clouds and hazes, and atmospheric dust. During southern summer, when Mars is closest to the Sun (at perihelion), solar heating can raise massive dust storms.
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Picoplankton are important in nutrient cycling in all major oceans, where they exist in their highest abundances. They have many features that allow them to survive in these oligotrophic (low-nutrient) and low-light regions, such as the use several nitrogen sources, including nitrate, ammonium, and urea. Their small size and large surface area allows for efficient nutrient acquisition, incident light absorption, and organism growth. A small size also allows for minimal metabolic maintenance.
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The table gives crustal abundances of the elements commonly to rarely recognised as metalloids.Lide 2005; Wiberg 2001, p. 423: At Some other elements are included for comparison: oxygen and xenon (the most and least abundant elements with stable isotopes); iron and the coinage metals copper, silver, and gold; and rhenium, the least abundant stable metal (aluminium is normally the most abundant metal). Various abundance estimates have been published; these often disagree to some extent.
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This includes designing biochemically-inspired synthetic catalysts as well as trying O2 as a candidate for controlled, in vitro oxidation. Due to high abundances and relatively strong stabilizing capabilities within biological reactions, iron and copper enzymes inspire biomimetic synthetic catalysts. Although these reactions perform with high accuracy and selectivity within the body, many challenges arise when working with O2 in vitro because of the undesired and potentially harmful side products that can be generated.
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In the past, a luminous red nova merger, very late thermal pulse, or a diffusion-induced nova have all been suggested but there are problems with all these explanations. An analysis of the structures and isotopic abundances in the remaining nebula using the Atacama Large Millimeter Array (ALMA) in 2018 concluded that the nova and associated nebula were caused by the unusual merger of a white dwarf and brown dwarf between 1670 and 1672.
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The second generation is polluted by materials released by the first. In particular, the abundances of helium, carbon, magnesium, aluminium, and sodium differ between the two populations. Indications are this is an Oosterhoff type I, or "metal- rich" system. A 2010 study identified 245 variable stars in the cluster's field, of which 209 are RR Lyrae variables, four are Type II Cepheids, 25 are long period variables, and one is an eclipsing binary.
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Increasing temperatures and subsequent bleaching of the reefs concern scientists. The Chaetodon aureofasciatus feeds on live coral, which makes these fish particularly susceptible to habitat destruction. Morgan Pratchett (PhD Marine ecology) noted that coral degradation will have severe effects on the abundances of coral-feeding species back in 2006 (4). Since then, the Pacific coral habitat of the Golden butterflyfish has been significantly depleted due to a combination of rising temperatures, ocean acidification, pollution, etc.
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Iron and nickel are notable for being the final elements produced by stellar nucleosynthesis, and the heaviest elements formed with a supernova or similarly cataclysmic event. Iron and nickel are the most abundant metals in metallic meteoritesMason, Brian Harold (1971) Handbook of Elemental Abundances in Meteorites Gordon and Breach, New York, and in the dense metal cores of planets such as Earth. Nickel–iron alloys occur naturally on Earth's surface as telluric or meteoric iron.
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NGC 5617 appears to be gravitationally bound to Trumpler 22. The two clusters share similar radial velocities (-38.63 ± 2.25 km/s for NGC 5617 and -38.46 ± 2.08 km/s for Trumpler 22), mean metallicity (-0.18 ± 0.02 for NGC 5617 and-0.17 ± 0.04 for Trumpler 22), similar abundances across various elements, and have similar age, forming a primordial binary cluster pair. Their orbits were initially almost circular and their separation less than 20 pc.
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In 2013, the central star was detected at magnitude 20.2, with an estimated four magnitudes of extinction. The spectral type is now [WC4], a hydrogen-deficient, helium and carbon-rich object with strong emission lines. In 1921, the surface has been estimated to consist of 98% helium and 1% carbon, typical of an RCB star. By 2006, the abundances were measured as 55% helium, 45% carbon, and 5% oxygen, typical of a WC star.
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Diamonds are dated by analyzing inclusions using the decay of radioactive isotopes. Depending on the elemental abundances, one can look at the decay of rubidium to strontium, samarium to neodymium, uranium to lead, argon-40 to argon-39, or rhenium to osmium. Those found in kimberlites have ages ranging from , and there can be multiple ages in the same kimberlite, indicating multiple episodes of diamond formation. The kimberlites themselves are much younger.
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The Martian atmosphere contains high abundances of photochemically produced CO and H2, which are reducing molecules. Mars' atmosphere is otherwise mostly oxidizing, leading to a source of untapped energy that life could exploit if it used a metabolism compatible with one or both of these reducing molecules. Because these molecules can be observed, scientists use this as evidence for an antibiosignature. Scientists have used this concept as an argument against life on Mars.
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In eastern and central Maine, an average of 2.1 soras was observed in wooded swamps per 100 hours of observation during the breeding season. On a nonbreeding (August–April) site in southwestern Arizona, soras were found to use a "mixed shrub community" more than expected based on its availability. Soras were observed at low abundances on a site with douglas-fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), and trembling aspen (Populus tremuloides) in British Columbia.
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At , the species weights exactly cancel out the species proportional abundances, such that the weighted mean of the values equals even when all species are not equally abundant. At , the effective number of species, , hence equals the actual number of species . In the context of diversity, is generally limited to non-negative values. This is because negative values of would give rare species so much more weight than abundant ones that would exceed .
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These modern estimates are notably smaller than the 10,000 to 11,000 Gt C (2 m3) proposed by previous researchers as a reason to consider clathrates to be a geo-organic fuel resource (MacDonald 1990, Kvenvolden 1998). Lower abundances of clathrates do not rule out their economic potential, but a lower total volume and apparently low concentration at most sites does suggest that only a limited percentage of clathrates deposits may provide an economically viable resource.
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Published spectral types for the star vary somewhat from C54 to C64, or N6 under an older system of classification. The subscript 4 refers to the strength of the molecular carbon bands in the spectrum, an indicator of the relatively abundances of carbon in the atmosphere. V Aquilae is a variable star of type SRb. It has a published period of 400 days, but other periods are found including 350 days and 2,270 days.
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Alphard's spectrum shows a mild excess of barium, an element that is normally produced by the s-process of nucleosynthesis. Typically a barium star belongs to a binary system and the anomalies in abundances are explained by mass transfer from a companion white dwarf star. Precise radial velocity measurements have shown variations in the stellar radial velocities and spectral line profiles. The oscillations are multi-periodic with periods from several hours up to several days.
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Saturn has an observed magnetic field generated within its metallic core. Metallic hydrogen is present within the core (in lower abundances than Jupiter). Saturn has a rock and or ice core 10–30 times the mass of the Earth, and this core is likely soluble in the gas envelope above, and therefore it is primordial in composition. Since the core still exists, the envelope must have originally accreted onto previously existing planetary cores.
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Global mammal richness (2015) Global amphibian richness (2015) Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Species richness is sometime considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness.
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MWR can observe radiation from 1.37 to 50 cm in wavelength, from 600 MHz to 22 GHz in frequencies. This supports its goal of observing the previously unseen atmospheric features and chemical abundances hundreds of miles/km into Jupiter's atmosphere. MWR is designed to detect six different frequencies in that range using separate antennas. MWR views Jupiter's microwave radiation so it can see up to hundreds of miles deep into the planet.
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HR 178 is a probable binary star in the constellation Andromeda. Located approximately distant, it is an evolved Am star with a combined apparent magnitude of 6.06, meaning that it can only be seen with the naked eye on dark, clear nights. The star is suspected of variability, possibly varying between magnitudes 6.04 and 6.06. The spectrum of HR 178 has been extensively studied for establishing element abundances in the evolved Am stars.
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Blue King Crab Distribution Blue king crabs can be found in the Bering Sea in relatively small abundances compared to red king crabs. The main populations near Alaska are found near the Diomede Islands, Point Hope, St. Matthew Island, and the Pribilof Islands. Additionally, populations exist in the Norton Sound all the way to St. Lawrence Island. There are smaller populations located off the eastern coast of Asia, near northern Japan and Siberia.
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Species sorting is a mechanism in the metacommunity framework of ecology whereby species distributions and abundances can be related to the environmental or biotic conditions in a particular habitat. The species sorting paradigm describes a system of habitat patches with different environmental conditions that organisms can move between. Species are able to disperse to patches with suitable environmental conditions, resulting in patterns where environmental conditions can predict the species found in a particular habitat.
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Crustal contamination can be inferred from samples taken from two cones, and small isotopic variations for the other cones indicate at least three mantle components. The primitive magmas differ from other reported intraplate-type mafic alkalic suites by having relatively high Al2O3 and Yb, as well as low ratios of La/Yb and CaO/Al2O3. Rising Al2O3 and falling CaO, along with decreasing incompatible element abundances, are consistent with progressive partial melting.
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Additional information on Mars comes from meteorites that have landed on Earth (the Shergottites, Nakhlites, and Chassignites, collectively known as SNC meteorites). Abundances are also constrained by the masses of the planets, while the internal distribution of elements is constrained by their moments of inertia. The planets condensed from the solar nebula, and much of the details of their composition are determined by fractionation as they cooled. The phases that condense fall into five groups.
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It is a member of a moving group of stars that share a common trajectory through space, named the Kapteyn moving group. Based upon their element abundances, these stars may once have been members of Omega Centauri, a globular cluster that is thought to be the remnant of a dwarf galaxy that merged with the Milky Way. During this process, the stars in the group, including Kapteyn's Star, may have been stripped away as tidal debris.
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D. Clayton, New Astronomy Reviews 55, 155–65 (2011), section 5.5, p. 163] According to that principle rapid oxidation actually intensifies growth of large grains of carbon by keeping the population of carbon solids small so that those few can grow large by accreting the continuously replenished free carbon. This topic establishes another new aspect of carbon's uniquely versatile chemistry. Their 2017 paper also computes the abundances of molecules and of Buckminsterfullerene grains ejected along with the graphite grains.
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Global data on jellyfish populations span between 1940 and 2011 and indicate that global jellyfish populations oscillate, reaching periodic maximums every 20 years. However, there appears to be a small linear increase in jellyfish abundances beginning in the 1970s. Jellyfish blooms have increased notably in Japan, the North Atlantic Shelf, Denmark, the Mediterranean Sea, and the Barents Sea. However, there are also several examples where jellyfish populations are decreasing in areas that are heavily impacted by humans.
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In another series of experiments with the infusorians Paramecium as prey and Didinium as a predator, imitating periodical migrations, he obtained nearly ideally sinusoidal fluctuations of the abundances in this model, previously modeled only theoretically. It appeared in English as an abridged version in USA, and finally published in Russian only in 1984. One of the first acceptances of the advantages of polycultures was also obtained by Gause on Paramecium. He studied ecologically similar species of infusorians.
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In addition to the standard BBN scenario there are numerous non-standard BBN scenarios. These should not be confused with non-standard cosmology: a non-standard BBN scenario assumes that the Big Bang occurred, but inserts additional physics in order to see how this affects elemental abundances. These pieces of additional physics include relaxing or removing the assumption of homogeneity, or inserting new particles such as massive neutrinos.Soler, F. J. P., Froggatt, C. D., & Muheim, F., eds.
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NGC 1407 is X-ray luminous, with high hot gas Fe abundance, and with evidence of recurrent radio outbursts. In the central area of the galaxy are present old stars, with mean age 12.0 ± 1.1 Gyrs, that are metal rich and with supersolar abundances of α-elements. Observations indicate that NGC 1407 hasn't recently undergone strong star formation activity. The galaxy hosts a supermassive black hole with a mass 1.12 ±0.42 billion solar masses, based on velocity dispersion.
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However, helium is unusual in that its isotopic abundance varies greatly depending on its origin. In the interstellar medium, the proportion of is around a hundred times higher. Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten; this is used in geology to investigate the origin of rocks and the composition of the Earth's mantle. The different formation processes of the two stable isotopes of helium produce the differing isotope abundances.
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The majority of the BHH kimberlites are diamondiferous, in contrast to those of the Birch Mountains kimberlite field to the northeast which are mostly barren of diamonds. Based on petrography and whole-rock geochemistry, the BHH pipes are classed as Group 1A kimberlites. They have a low carbonate content, low abundances of late-stage minerals such as phlogopite and ilmenite, and a high abundance of fresh, coarse olivine.Eccles, R.D., Heaman, L.M., Luth, R.L. and Creaser, R.A. 2004.
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In May 1816 Abundance left Antwerp with statues and paintings that Napoleon and his officers had stolen; she then conveyed the art safely to Civita Vechia. The largest item was a statue of the Nile, and weighed 17,600 pounds. Cardinal Ercole Consalvi, Minister of State, came down from Rome on behalf of Pope Pius VII. A large state dinner followed, and the Cardinal invited all of Abundances officers to come to Rome at the Pope's expense.
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Time-resolved RNA sequencing methods are applications of RNA-seq that allow for observations of RNA abundances over time in a biological sample or samples. Second-Generation DNA sequencing has enabled cost effective, high throughput and unbiased analysis of the transcriptome. Normally, RNA-seq is only capable of capturing a snapshot of the transcriptome at the time of sample collection. This necessitates multiple samplings at multiple time points, which increases both monetary and time costs for experiments.
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These too may be the result of the CE interaction. In addition to a higher than normal helium abundance, the nebula displays unusually strong optical recombination lines from heavier elements; one of the highest known among PNe. These may be the result of a very late thermal pulse, or "final flash", following the initial ejection of the stellar envelope that formed the nebula. The pulse would have ejected chemically-enriched material into the old nebula, changing its abundances.
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Two of the components of this system, 5 Aquilae Aa and Ab, are Am stars. That is, they are chemically peculiar stars that show unusual abundances of elements other than hydrogen and helium. The two orbit each other with a period lasting 33.65 years at an eccentricity of 0.33. One of these stars is itself a close spectroscopic binary, with a 4.765 day period and a nearly circular orbit that has an eccentricity of just 0.02.
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With the mOTUs profiler is possible to profile species without a reference genome, improving the estimation of microbial community diversity. Recent methods, such as SLIMM, use read coverage landscape of individual reference genomes to minimize false-positive hits and get reliable relative abundances. In composition based binning, methods use intrinsic features of the sequence, such as oligonucleotide frequencies or codon usage bias. Once sequences are binned, it is possible to carry out comparative analysis of diversity and richness.
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Heceta Bank is considered a persistent biological hotspot, in terms of biomass and nekton species diversity, in the northern California Current. The most important environmental parameters provoking this feature are sea-surface temperature, salinity, and density, indicating that the mechanisms of the hotspot are related to the flow through the region and differing patterns of circulation. In addition to this, high abundances of prey (e.g., Euphausiids) favors the higher concentrations of nekton species, especially of higher trophic levels (e.g.
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After this, the relative percentages of quartz, feldspars and rock fragments are used to plot the appropriate point on a QFR triangle and obtain the clan designation. There are some exceptions when summing the abundances. Due to the difficulty in distinguishing quartz from metaquartzite rock fragments, metaquartzite is always plotted on the Q pole of the QFR diagram along with quartz. Granites and other phaneritic igneous rock fragments are plotted in the F pole of the diagram.
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Figure 1. Whittaker plot of species Rank abundance for 7 most commonly considered mechanistic models for niche apportionment. The models with steeper slopes such as the Dominance preemption model represents less even communities where a few species are highly abundant and the remaining species abundances decrease sharply (see Species evenness). Alternatively, shallow sloped models such as the Dominance Decay model are representative of more even communities where many species are equally abundant and relatively few species are rare.
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Boron samples from unusual sources, particularly non- terrestrial sources, might have measured atomic weights that fall outside this range. Atomic weight and relative atomic mass are synonyms. The standard atomic weight is a special value of the relative atomic mass. It is defined as the "recommended values" of relative atomic masses of sources in the local environment of the Earth's crust and atmosphere as determined by the IUPAC Commission on Atomic Weights and Isotopic Abundances (CIAAW).
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The solenette occurs in the northeastern Atlantic Ocean from Iceland and Scotland southward, as well as in the North Sea, Kattegat and the Baltic Sea. It also occurs in the Mediterranean Sea, including the Adriatic Sea, the Sea of Marmara, and the Bosphorus. It has been reported from a range of , but is rare in very shallow waters. The highest abundances occur at depths of in the English Channel and at in the Bay of Biscay.
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The s qualifier indicates that its absorption lines are sharp (narrow) in comparison with standard stars, caused by relatively slow rotation. It has been categorized as a hot Am star, meaning that it is a chemically peculiar, although this is now considered doubtful. The spectrum displays at least double the normal abundances of elements like magnesium, aluminum and silicon, while helium and scandium are under-abundant. Calcium, normally deficient in Am stars, has near-normal abundance.
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Ecological selection (or environmental selection or survival selection or individual selection or asexual selection) refers to natural selection without sexual selection, i.e. strictly ecological processes that operate on a species' inherited traits without reference to mating or secondary sex characteristics. The variant names describe varying circumstances where sexual selection is wholly suppressed as a mating factor. Ecologists often study ecological selection when examining the abundance of individuals per population across regions, and what governs such abundances.
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Each of these isopotologes has different thermodynamic stability. For a carbonate crystal at thermodynamic equilibrium, the relative abundances of the carbonate ion isotopologues is controlled by reactions such as: The equilibrium constants for this reactions are temperature-dependent, with a trend that heavy isotopes tend to "clump" with each other (increasing the proportions of multiply substituted isotopologues) as temperature decreases.Wang, Z., Schauble, E.A., Eiler, J.M., 2004. Equilibrium thermodynamics of multiply substituted isotopologues of molecular gases. Geochim. Cosmochim.
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If mirror matter does exist in large abundances in the universe and if it interacts with ordinary matter via photon-mirror photon mixing, then this could be detected in dark matter direct detection experiments such as DAMA/NaI and its successor DAMA/LIBRA. In fact, it is one of the few dark matter candidates which can explain the positive DAMA/NaI dark matter signal whilst still being consistent with the null results of other dark matter experiments.
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He received his B.A. in science at Boston College and his Ph.D. in Astronomy at the University of Wisconsin–Madison. He was the principal investigator for the NASA Deep Impact mission. He aided in the development of systems for surveying abundances in comets as well as techniques for determining the sizes of cometary nuclei which uses optical and infrared measurements. His studies focused on comets as well as asteroids and he also supervises numerous graduate students.
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Nature lovers will delight in the numerous species of birds, animals and vegetation found along the region's many area hiking trails. Picking strawberries, raspberries, blueberries, or gooseberries is also a favourite summer pastime. History enthusiasts can explore ancient Aboriginal pictographs that are approximately 1500 years old. Fishing and boating are popular activities with the presence of many lakes and rivers, such as Snow Lake, Wekusko Lake and the Grass River that have abundances of northern pike, walleye, and perch.
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A geoneutrino is a neutrino or antineutrino emitted in decay of radionuclide naturally occurring in the Earth. Neutrinos, the lightest of the known subatomic particles, lack measurable electromagnetic properties and interact only via the weak nuclear force when ignoring gravity. Matter is virtually transparent to neutrinos and consequently they travel, unimpeded, at near light speed through the Earth from their point of emission. Collectively, geoneutrinos carry integrated information about the abundances of their radioactive sources inside the Earth.
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The original H–O model assumed that the only difference between countries was the relative abundances of labour and capital. The original Heckscher–Ohlin model contained two countries, and had two commodities that could be produced. Since there are two (homogeneous) factors of production this model is sometimes called the "2×2×2 model". The model has "variable factor proportions" between countries—highly developed countries have a comparatively high capital-to-labor ratio compared to developing countries.
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The measure was originally proposed by Claude Shannon to quantify the entropy (uncertainty or information content) in strings of text.Shannon, C. E. (1948) A mathematical theory of communication. The Bell System Technical Journal, 27, 379–423 and 623–656. The idea is that the more different letters there are, and the more equal their proportional abundances in the string of interest, the more difficult it is to correctly predict which letter will be the next one in the string.
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The ions being produced at the filament are focussed into an ion beam and then passed through a magnetic field to separate them by mass. The relative abundances of different isotopes can then be measured, yielding isotope ratios. When these isotope ratios are measured by TIMS, mass-dependent fractionation occurs as species are emitted by the hot filament. Fractionation occurs due to the excitation of the sample and therefore must be corrected for accurate measurement of the isotope ratio.
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An environmental gradient is a gradual change in abiotic factors through space (or time). Environmental gradients can be related to factors such as altitude, temperature, depth, ocean proximity and soil humidity. Species abundances usually change along environmental gradients in a more or less predictive way. However, the species abundance along an environmental gradient is not only determined by the abiotic factor but, also by the change in the biotic interactions, like competition, along the environmental gradient.
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Thus, even though the refractory elements have the same relative abundances in the Earth as in the Solar System as a whole, there is more accessible thorium than heavy platinum group metals in the crust. The radiogenic heat from the decay of 232Th (violet) is a major contributor to the earth's internal heat budget. Of the four major nuclides providing this heat, 232Th has grown to provide the most heat as the other ones decayed faster than thorium.
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The ethane, propane, and butane components of natural gas have much shorter atmospheric lifetimes (ranging from about 1 week to 2 months) compared to methane (1-2 decades) and carbon dioxide (1-2 centuries). They consequently do not become well-mixed into the atmosphere and have much lower atmospheric abundances. Nevertheless, their oxidation ultimately leads to the creation of longer-lived carbon compounds that also disturb the atmosphere and the planetary carbon cycle through a variety of complex pathways.
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Following is a table listing the one- letter symbols, the three-letter symbols, and the chemical properties of the side chains of the standard amino acids. The masses listed are based on weighted averages of the elemental isotopes at their natural abundances. Forming a peptide bond results in elimination of a molecule of water. Therefore, the protein's mass is equal to the mass of amino acids the protein is composed of minus 18.01524 Da per peptide bond.
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The mixture is separated into eluate (m6A+ RNAs) and supernatant (m6A- RNAs) pools. External RNA Controls Consortium (ERCC) spike ins are added to the eluate and supernatant, as well as an independent control arm consisting of just ERCC spike in. After antibody cleavage in the eluate pool, each of the three mixtures are sequenced on a next generation sequencing platform. The m6A levels per site or gene could be quantified by the ERCC-normalized RNA abundances in different pools.
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The forests are characterized by small trees (5-8m), with shallow root systems, and abundant epiphytes. The epiphytes make up a large portion of the canopy, with greater abundances in high-altitude tropical elfin forests than what is found in other, non-elfin, tropical forests. Dwarf forests should be more commonly found on isolated mountains due to the massenerhebung effect. The massenerhebung effect is a phenomenon where treelines are typically higher among mountains in close proximity to other mountains.
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The Big Bang theory offers a comprehensive explanation for a broad range of observed phenomena, including the abundances of the light elements, the CMB, large-scale structure, and Hubble's law. The theory depends on two major assumptions: the universality of physical laws and the cosmological principle. The universality of physical laws is one of the underlying principles of the theory of relativity. The cosmological principle states that on large scales the universe is homogeneous and isotropic.
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Comparisons were made using the nighttime density data to avoid issues such as daytime net avoidance and to include increased nighttime abundances resulting from possible nocturnal vertical migrator species. Atlanta lesueurii was found to be most abundant at the offshore (15 nm) station during both seasons. Offshore to inshore abundance decreased most dramatically in the fall; from mean nighttime densities of 480 (15 nm) to 124 (5 nm) to 37 (1 nm) individuals beneath 100 m2 of ocean surface.
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From the 1970s until the late 1990s Mayeda and Clayton became famous for their use of oxygen isotopes to classify meteorites. They developed several tests that were used across the field of meteorite and lunar sample analysis. They studied variations in the abundances of the stable isotopes of oxygen, oxygen-16, oxygen-17 and oxygen-18, and deduced differences in the formation temperatures of the meteorites. They also worked on the mass spectroscopy and chemistry of the Allende meteorite.
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J.G. Mangum and A. Wootten report new detections of c-C3H towards 13 of 19 observed Galactic molecular clouds. They measure relative abundance of C3H to C3H2: N(c-C3H)/N(C3H2) = 9.04±2.87 x 10−2. This ratio does not change systematically for warmer sources, which they suggest provides evidence that the two ring molecules have a common precursor in C3H3+. L.A. Nyman et al. present a molecular line survey of the carbon star IRAS 15194-5115 using the 15m Swedish-ESO Submillimetre Telescope to probe the 3 and 1.3 mm bands. Comparing the molecular abundances with those of IRC + 10216, they find C3H to have similar abundances in both sources. In 1993, M. Guelin et al. map the emission from the 95 GHz and 98 GHz lines of the C3H radicals in IRC+10216. This reveals a shell-like distribution of the C3H emission and time-dependent chemistry. The close correspondence between the emission peaks of C3H and the species MgNC and C4H suggests a fast common formation mechanism, suggested to be desorption from dust grains.
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Geoscientists can directly study the nature of the subcontinental mantle by examining mantle xenolithsNixon, P.H. (1987) Mantle xenoliths J. Wiley & Sons, 844 p. brought up in kimberlite, lamproite, and other volcanic pipes. The histories of these xenoliths have been investigated by many methods, including analyses of abundances of isotopes of osmium and rhenium. Such studies have confirmed that mantle lithospheres below some cratons have persisted for periods in excess of 3 billion years, despite the mantle flow that accompanies plate tectonics.
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These regions where chaos occurs are, in the three cases analyzed in, situated at the interface between a non-chaotic four species region and a region where extinction occurs. This implies a high sensitivity of biodiversity with respect to parameter variations in the chaotic regions. Additionally, in regions where extinction occurs which are adjacent to chaotic regions, the computation of local Lyapunov exponents revealed that a possible cause of extinction is the overly strong fluctuations in species abundances induced by local chaos.
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But the lines in the stars of Oosterhoff type I (Oo I) cluster are not quite as weak as those in type II (Oo II). Hence type I are referred to as "metal-rich" (for example, Terzan 7), while type II are "metal- poor" (for example, ESO 280-SC06). These two populations have been observed in many galaxies, especially massive elliptical galaxies. Both groups are nearly as old as the universe itself and are of similar ages, but differ in their metal abundances.
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The spectrum of this star matches a stellar classification of F8 V, indicating this is an ordinary F-type main-sequence star. It is around 5.3 billion years old and is spinning with a projected rotational velocity of 5 km/s. The star has 1.2 times the mass of the Sun, 1.93 times the Sun's radius, and has near solar abundances of elements. The star is radiating 4.24 times the Sun's luminosity from its photosphere at an effective temperature of 5,908 K.
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In contrast, alkali basalts have normalized patterns highly enriched in the light REE, and with greater abundances of the REE and of other incompatible elements. Because MORB basalt is considered a key to understanding plate tectonics, its compositions have been much studied. Although MORB compositions are distinctive relative to average compositions of basalts erupted in other environments, they are not uniform. For instance, compositions change with position along the Mid-Atlantic Ridge, and the compositions also define different ranges in different ocean basins.
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Sneden (1973). This paper contains also the description of the first version of the code and has been cited about 240 times as of 2008-04-24 by publications in international journals studying the abundances of chemical elements in stars. The software package has been developed and is maintained by Christopher Sneden, University of Texas at Austin. The current supported version of the code was released in August 2010 and is described in the MOOG User's Guide (see references below).
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Plant species richness of snag forests can be much higher than in unburned forests. Bird and small mammal communities that utilize complex early seral forests forage on the abundant insects and increased abundance of seeds in the post-fire flora. These species, in turn, support an increase in raptors. Bird species such as the Black-backed Woodpecker, Olive-sided Flycatcher (Contopus cooperi), Mountain Bluebird (Sialia currucoides), Chipping Sparrow (Spizella passerina), and Mountain Quail (Oreortyx pictus) achieve highest abundances in complex early seral forests.
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The mean metallicity of the cluster is [Fe/H] = +0.03 ± 0.05 dex (as estimated by Frieal et al.) or −0.01 ± 0.04 (as estimated by Tautvaišienė et al.). Alpha-elements [Ca/Fe] and [Si/Fe] show solar ratios, [Mg/Fe] is moderately enhanced, [Ti/Fe] is slightly subsolar, [Al/Fe] is enhanced, and [Na/Fe] is significantly enhanced. THE CNO abundances in the cluster are [C/H] = −0.17 ± 0.08, [N/H] = 0.53 ± 0.07, [O/H] = 0.12 ± 0.09, and [C/N] = 0.79 ± 0.08.
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Isotope analysis can be used by forensic investigators to determine whether two or more samples of explosives are of a common origin. Most high explosives contain carbon, hydrogen, nitrogen and oxygen atoms and thus comparing their relative abundances of isotopes can reveal the existence of a common origin. Researchers have also shown that analysis of the 12C/13C ratios can locate the country of origin for a given explosive. Stable isotopic analysis has also been used in the identification of drug trafficking routes.
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They are the first pair of black holes found in a spiral galaxy like our Milky Way. The two black holes are separated by only 490 light years. The two black holes in NGC 3393 are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago. Other evidence that supports the hypothesis of the galaxy merger include high pre-shock densities in the narrow-line region and low O/H and Mg/H abundances.
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Pi1 Orionis (π1 Ori, π1 Orionis) is a star in the equatorial constellation of Orion. It is faintly visible to the naked eye with an apparent visual magnitude of 4.74. Based upon an annual parallax shift of 28.04 mas, it is located about 116 light years from the Sun. This is an A-type main sequence star with a stellar classification of A3 Va. It is a Lambda Boötis star, which means the spectrum shows lower than expected abundances for heavier elements.
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The concept of emerging ecosystems originated from the discussion of the ecological and economical fate of agricultural land once it is no longer in use Similarly to the definition of a no-analog, emerging ecosystems are considered as those that have species composition and abundances that are not seen in modern analogs. Emerging ecosystems not only encompass the understanding of ecological consequences, but also those social, economic and cultural associations. These ecosystems may provide opportunities for species to colonize new niche space.
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The parent ion fractional abundances decrease, and the daughter ion signal increases. At the dissociative photoionization threshold, E0, all parent ions, even the ones with initially 0 internal energy, can dissociate, and the daughter ion abundance reaches 100% in the breakdown diagram. If the potential energy well of the parent ion is shallow and the complete initial thermal energy distribution is broader than the depth of the well, the breakdown diagram can also be used to determine adiabatic ionization energies.
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699-724 In a newly developing environment, plant growth is often strongly influenced by the introduction of new organisms into that environment, where competitive or mutualistic relationships may develop. Often, competitive balances are eventually reached and species abundances remain somewhat constant over a period of generations. Studies done on the Norwegian Island of Svalbard, have been very useful in understanding the behavior of postglacial vegetation. Studies show that many vascular plants that are considered pioneers of vegetation development, eventually become less frequent.
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In the early nineteenth century, Joseph von Fraunhofer made the first systematic inventory of spectral lines in sunlight. Full understanding of the significance of Fraunhofer lines required a huge amount of pioneering research in astrophysics and quantum theory. Cecilia Payne (1925) demonstrated that variations in stellar line strengths can be explained by the Saha ionization equation. Payne's work lead to a major study of the chemical abundances in the solar atmosphere undertaken by H. N. Russell, Walter S. Adams, and Charlotte Moore.
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Lambda Boötis (λ Boötis, abbreviated Lam Boo, λ Boo), also named Xuange (), is a star in the northern constellation of Boötes. Based on parallax measurements, it is approximately 99 light-years from the Sun. Lambda Boötis is a white A-type main sequence dwarf with an apparent magnitude of +4.18. It is the prototype of a group of rare stars known as Lambda Boötis stars, all of which are dwarf stars with unusually low abundances of metals in their spectra.
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Regional dust storms - ones having a 1000-kilometer scale - show surprising repeatability Mars-year to Mars-year. Once every decade or so, they grow into global-scale events. In contrast, during northern summer when Mars is furthest from the Sun (at aphelion), there is an equatorial water-ice cloud belt and very little dust in the atmosphere. Atmospheric water vapor varies in abundance seasonally, with the greatest abundances in each hemisphere's summer after the seasonal polar caps have sublimated into the atmosphere.
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Nitrogen is the main gas in Triton's atmosphere. The two other known components are methane and carbon monoxide, whose abundances are a few hundredths of a percent of that of the nitrogen. Carbon monoxide, which was discovered only in 2010 by the ground-based observations, is slightly more abundant than methane. The abundance of methane relative to nitrogen increased by four to five times since 1986 due to the seasonal warming observed on Triton, which passed its southern-hemisphere solstice in 2001.
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A series of measurements of the relative abundances of the two most significant isotopes of the uranium mined at Oklo showed anomalous results compared to those obtained for uranium from other mines. Further investigations into this uranium deposit discovered uranium ore with a concentration as low as 0.44%. Subsequent examination of isotopes of fission products such as neodymium and ruthenium also showed anomalies, as described in more detail below. This loss in is exactly what happens in a nuclear reactor.
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Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them. Stable isotope geochemistry is largely concerned with isotopic variations arising from mass- dependent isotope fractionation, whereas radiogenic isotope geochemistry is concerned with the products of natural radioactivity.
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Fig 7. Simplified Sulfurimonas Food Web / Chain Photo Credits: Suman Rana Members of the bacterial genus Sulfurimonas are known to affect the relative abundance of species around them. In the case of S. gotlandica strain GD1, it was demonstrated that heterotrophic nanoflagellate (HNF) populations decreased while ciliate and dinoflagellate abundances remained relatively constant in oxygen / hydrogen sulphide rich conditions. Conversely, the opposite trend was observed in suboxic conditions, in that HNF and ciliates increased in abundance, whereas dinoflagellates remained constant.
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Three chondrites form what is known as the K (Kakangari type) grouplet: Kakangari, LEW 87232, and Lea Co. 002. They are characterized by large amounts of dusty matrix and oxygen isotope compositions similar to carbonaceous chondrites, highly reduced mineral compositions and high metal abundances (6% to 10% by volume) that are most like enstatite chondrites, and concentrations of refractory lithophile elements that are most like ordinary chondrites. Many of their other characteristics are similar to the O, E and C chondrites.
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This leads to hydronium playing a very important role in interstellar ion-neutral chemistry. Astronomers are especially interested in determining the abundance of water in various interstellar climates due to its key role in the cooling of dense molecular gases through radiative processes. However, does not have many favorable transitions for ground-based observations. Although observations of HDO (the deuterated version of water) could potentially be used for estimating abundances, the ratio of HDO to is not known very accurately.
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Surface abundances of most heavy elements on Rho Cas are enhanced relative to the Sun, but carbon and oxygen are depleted. This is expected for a massive star where hydrogen fusion takes place predominantly via the CNO cycle. In addition to the expected helium and nitrogen convected to the surface, sodium is strongly enhanced, indicating that the star had experienced a dredge-up while in a red supergiant stage. Therefore, it is expected that Rho Cas is now evolving towards hotter temperatures.
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Estimated abundances of the chemical elements in the Solar system. Hydrogen and helium are most common, from the Big Bang. The next three elements (lithium, beryllium, and boron) are rare because they are poorly synthesised in the Big Bang and also in stars. The two general trends in the remaining stellar- produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers, and (2) a general decrease in abundance, as elements become heavier.
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Barracudinas are known to inhabit mesopelagic depths throughout the world's oceans, and are predators of fish, shrimps, and squids. While many barracudina species can be found at depths of 2000 m, their highest abundances tend to occur between 200 and 1000 m. Barracudinas are not thought to participate in diel vertical migration. While they are rarely caught by fisheries, they are frequently documented in the guts of pelagic predators such as tuna, swordfish, lancetfish, Cuvier's beaked whales, and blue sharks.
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The geological record of terrestrial plants is sparse and based mostly on pollen and spore studies. Plants are relatively immune to mass extinction, with the impact of all the major mass extinctions "insignificant" at a family level. Even the reduction observed in species diversity (of 50%) may be mostly due to taphonomic processes. However, a massive rearrangement of ecosystems does occur, with plant abundances and distributions changing profoundly and all the forests virtually disappearing; the Palaeozoic flora scarcely survived this extinction.
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Biogenic methane production is the main contributor to the methane flux coming from the surface of Earth. Methane has a photochemical sink in the atmosphere, but will build up if the flux is high enough. If there is detectable methane in the atmosphere of another planet, especially with a host star of G or K type, this may be interpreted as a viable biosignature. A disequilibrium in the abundances of gas species in an atmosphere can be interpreted as a biosignature.
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To enumerate bacterial cell quantities, only small portions of bacteria in a sample are physically counted for logistical reasons, upon which total abundances are estimated by extrapolation. Mean values are then used for comparison among samples. However the accuracy of this technique, where tabulation of only a small subset is used to estimate total abundance quantities, has been brought into question. Primarily, it has been shown that the distribution of bacterial cells on counting slides can be uneven and inconsistent.
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As picoeukaryotes serve as the base for marine microbial food webs, they are intrinsic to the survival of higher trophic levels. Ostreococcus tauri has a rapid growth rate and dense blooms have been observed off the coasts of Long Island and California. Samples collected from Long Island bay were found to contain many virus-like particles, a likely cause for the decline of the bloom. Despite the large abundances of picoeukaryotes, these unicellular organisms are outnumbered by viruses by about ten to one.
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Carbonaceous chondrites, as the name suggests, contain appreciable carbon compounds. These include native carbon, simple compounds like metal carbides and carbonates, organic chains, and polycyclic aromatic hydrocarbons (PAHs). The elemental abundances of some C-chondrite groups (with the obvious exception of hydrogen, helium, and some other elements, see below) have long been known to resemble solar abundance values. The CI chondrites, in particular, correspond "quite closely, more so than does any other type of meteoric or terrestrial matter"; called "somewhat miraculous".
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In astronomy, those elements with higher atomic numbers than helium are termed "metals". The metallicity of Vega's photosphere is only about 32% of the abundance of heavy elements in the Sun's atmosphere. (Compare this, for example, to a threefold metallicity abundance in the similar star Sirius as compared to the Sun.) For comparison, the Sun has an abundance of elements heavier than helium of about ZSol = . Thus, in terms of abundances, only about 0.54% of Vega consists of elements heavier than helium.
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Longneck morel in Indiana, USA Certain Morchella species (M. eximia, M. importuna, M. tomentosa and others) exhibit a pyrophilic behaviour and may grow abundantly in forests which have been recently burned by a fire. Moderate-intensity fires are reported to produce higher abundances of morels than low- or high-intensity fires. This is caused by the soil becoming more alkaline as the result of wood ash combining with water and being absorbed into the soil which triggers the morels to fruit.
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"High Abundances of Aerobic Anoxygenic Photosynthetic Bacteria in the South Pacific Ocean". Applied and Environmental Microbiology 73 (13), 4198-4205. They are globally distributed in the euphotic zone and represent a hitherto unrecognized component of the marine microbial community that appears to be critical to the cycling of both organic and inorganic carbon in the ocean.Zbigniew S. Kolber, F. Gerald, Plumley, Andrew S. Lang, J. Thomas beatty, Robert E. Blankenship, Cindy L. Vandover, Costantino Vetriani, Michal Koblizek, Christopher Rathgeber, Paul G. Falkowsik (2001).
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The exact origins of 28,30-bisnorhopane have not been conclusively established, however, there are analytical implications towards generation from chemoautotrophic bacteria. GC-MS and other analyses of source rocks, shales containing bisnorhopane, also provide data on pristane and phytane abundances. 28,30-Bisnorhopane occurs in shales with very low pristane to phytane ratios, which is indicative of generation under anoxic conditions. These shales often also contain appreciable levels of sulfur, which has been presented as possible evidence for sulfide-oxidizing bacterial activity.
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Some heavier elements are produced by less efficient processes such as the r-process and s-process. Elements with atomic numbers close to iron are produced in large quantities in supernova due to explosive oxygen and silicon fusion, followed by radioactive decay of nuclei such as Nickel-56. On average, heavier elements are less abundant in the universe, but some of those near iron are comparatively more abundant than would be expected from this trend. Abundances of the chemical elements in the Solar System.
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Feeding by the dragonet occurs throughout the day, including the intervals between courtships and spawning. The fish feeds entirely on benthic sources, primarily copepods, amphipods, and other small invertebrates living on blades of sea grass. Species of dragonets from different locations show variations in specific food preference, attributable to the different availabilities and abundances of food organisms in those places. All of them feed by extending their highly protractible jaws toward their food and drawing it into the mouths, frequently followed by the expulsion of sand.
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As such it is generating energy at a higher rate than the Sun, with a luminosity 14 times greater. The outer atmosphere has an effective temperature of 8,930 K, which is what gives it the white-hued glow of an A-type star. It is classified as a Delta Scuti type variable star and its brightness varies by 0.02 magnitudes over periods of 0.5 to 2.4 hours. This star has been established as a Lambda Boötis star that displays low abundances of iron peak elements.
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The Procellarum KREEP Terrane is a large province on the near side of the Moon that has high abundances of KREEP. KREEP, an acronym built from the letters K (the atomic symbol for potassium), REE (rare-earth elements) and P (for phosphorus), is a geochemical component of some lunar impact breccia and basaltic rocks. The Felspathic Highlands Terrane, in contrast is composed predominantly of ancient anorthositic materials. A third terrane, the South Pole–Aitken Terrane, may simply represent deep crustal materials of the feldspathic highlands terrane.
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This results in a gradient from nutrient poor soil at the top of slopes to nutrient rich soils below. As nutrients leached are replaced by aqueous nitrates and phosphates from above, the kauri tree is less able to inhibit the growth of strong competitors such as angiosperms. In contrast, the leaching process is only enhanced on higher elevation. In Waipoua Forest this is reflected in higher abundances of kauri on ridge crests, and greater concentrations of its main competitors, such as taraire are found at low elevations.
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This minor planet was named in honor of British/American astronomer Michael Dworetsky, senior lecturer at University College London (UCL). He is an active member of the International Astronomical Union, affiliated to several divisions, including "Education, Outreach and Heritage". His research involve the stellar abundances of the mercury group of elements and has also taken a large part in the development of the undergraduate astronomy degree program. The asteroid's name was proposed by Conrad Bardwell (also see 1615 Bardwell), who made the identifications involving this minor planet.
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Oxygen-bearing molecules such as sulfur dioxide were not detected, to the surprise of astronomers. As well as these molecules, emission from heavy atoms such as iron, magnesium and silicon was detected, with abundances consistent with what would be found in a cometary nucleus. Although a substantial amount of water was detected spectroscopically, it was not as much as predicted beforehand, meaning that either the water layer thought to exist below the clouds was thinner than predicted, or that the cometary fragments did not penetrate deeply enough.
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Kappa Piscium has an apparent magnitude of 4.87 at maximum brightness and 4.95 at minimum brightness, while the visual companions have apparent magnitudes of 9.96 and 11.20. This is an A-type main-sequence star with a stellar classification of . The suffix designation indicates it is a "chemically peculiar" Ap star that displays abnormal abundances of silicon, strontium, and chromium. It is an Alpha2 Canum Venaticorum variable with a weak active magnetic field that causes it to fluctuate by 0.01 to 0.1 in magnitude as it rotates.
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In June 2010, authors R. Amorín, E. Pérez-Montero and J.M. Vílchez published a paper in The Astrophysical Journal letters titled "On the Oxygen and Nitrogen Chemical Abundances and the Evolution of the "Green Pea" Galaxies", which disputes the metallicities calculated in the original Cardamone et al. GPs paper Amorin et al. use a different methodology from Cardamone et al. to produce metallicity values more than one fifth (20%) of the previous values (about 20% solar or one fifth solar) for the 80 'starburst' GPs.
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The visible component is a chemically peculiar star with a stellar classification of ; meaning this is an A-type star with a spectrum that shows abnormally high abundances of chromium (Cr) and europium (Eu). A magnetic field has been detected and it is a source of X-ray emission with a luminosity of: log Lx = 29.1. It is spinning with a projected rotational velocity of 29 km/s and is radiating 95 times the Sun's luminosity from its photosphere at an effective temperature of 8,660 K.
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Studies of many and varied sedimentary sites are required to come to such conclusions; there are myriad bacterial species, and each organic source rock may have differing interactions with these bacteria. This is why not all bacterial influenced addition of carbon to sedimentary rocks can be excluded: each situation is unique, with varying bacteria, and varying settings. The combination of microscopic and molecular studies should be addressed when interpreting abundances of bacterial biomarkers present in a petroleum source and its influence on the total organic carbon.
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It is autotrophic for eight out of the ten essential amino acids that Buchnera produces. Although dependent, the H. defensa genome preserves more genes and pathways for cell structures and processes, than that of obligate symbionts. It also has several abundances: toxin homologs, encoding type-3 secretion systems, and putative pathogenicity loci. Additionally, H. defensa holds mobile DNA, like phage-derived genes, plasmids, and insertion-sequence elements, that feature H. defensa's dynamicness, and also show the role horizontal gene transfer has on shaping it.
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Other possible components of the Triton's atmosphere include argon and neon. Because they were not detected in the ultraviolet part of the spectrum of Triton obtained by Voyager 2 in 1989, their abundances are unlikely to exceed a few percent. In addition to the gases mentioned above, the upper atmosphere contains significant amounts of both molecular and atomic hydrogen, which is produced by the photolysis of methane. This hydrogen quickly escapes into the space serving as a source of plasma in the magnetosphere of Neptune.
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For this reason the volatile abundances of different classes of chondrites can vary. One particularly important class is the carbonaceous chondrites because of their high carbon content. In these meteorites, chondrules coexist with minerals that are only stable below 100 °C, so they contain materials that formed in both high- and low-temperature environments and were only later collected together. Further evidence for the primordial attributes of carbonaceous chondrites comes from the fact that they have compositions very similar to the nonvolatile element composition of the sun.
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Wetherill developed a technique to calculate numerically the orbital evolution and accumulation of planetesimal swarms, and he used the technique to reach specific predictions of the physical and orbital properties of terrestrial planets. His results agreed well with present observations. In addition to showing how the inner solar system formed, Wetherill's work provided the basis for a model of a giant-impact origin for the Moon and the core of Mercury. It also led to explanations for the isotopic abundances of present-day planetary atmospheres.
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Specimens at the Royal Tyrrell Museum of Paleontology, located in the Horseshoe Canyon Formation at Dinosaur Provincial Park Alberta has one of the greatest diversities and abundances of Late Cretaceous dinosaur fossils in the world. Taxa are represented by complete fossil skeletons, isolated material, microvertebrate remains, and even mass graves. At least 38 dinosaur type specimens were collected in the province. The Foremost Formation, Oldman Formation and Dinosaur Park Formations collectively comprise the Judith River Group and are the most thoroughly studied dinosaur-bearing strata in Alberta.
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The spectral class has since stayed as a G or K type supergiant, but there have been dramatic changes. The abundances of various elements have either increased or decreased: s-process elements became at least 25 times more abundant between 1967 and 1974; iron peak elements became less visible; and carbon-rich dust became strongly visible after 1992. Observations of the spectrum after 1992 are hindered by the dust formation, but the s-process and rare earth elements appear to have continued becoming more abundant.
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One study showed coral trout eating schools of fusilers in summer, and scarids during the winter. This seasonal variation is quite common in the diet of coral trout due to varying abundances of prey at different times of the year. Trout also tend to eat more food in winter, possibly to increase fat stores in preparation for reproduction in spring. They sometimes engage in cooperative hunting with the giant moray (Gymnothorax javanicus), the humphead wrasse (Cheilinus undulatus), or the big blue octopus (Octopus cyanea).
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Observed changes in the chemical abundances of different types of stars, based on the spectral peculiarities that were later attributed to metallicity, led astronomer Walter Baade in 1944 to propose the existence of two different populations of stars. These became commonly known as Population I (metal-rich) and Population II (metal-poor) stars. A third stellar population was introduced in 1978, known as Population III stars. These extremely metal-poor stars were theorised to have been the "first-born" stars created in the Universe.
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By using characteristics such as color, albedo, and thermal inertia and analytical tools such as reflectance spectroscopy and radar, scientists are able to study the chemistry and physical makeup (e.g., grain sizes, surface roughness, and rock abundances) of the Martian surface. The resulting data help scientists understand the planet's mineral composition and the nature of geological processes operating on the surface. Mars’ surface layer represents a tiny fraction of the total volume of the planet, yet plays a significant role in the planet's geologic history.
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The long periods of dormancy that seed plants can employ also makes them less vulnerable to extinction, as they can "sit out" the tough periods and wait until more clement times to leap back to life. The effect of these differences is most profoundly seen during extinction events. These events, which wiped out between 6 and 62% of terrestrial animal families, had "negligible" effect on plant families. However, the ecosystem structure is significantly rearranged, with the abundances and distributions of different groups of plants changing profoundly.
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Going up trophic levels from prey (plant) to predator (caterpillar) results in an isotopic enrichment. This same trend of enrichment is seen in many other animals - carnivores, omnivores, and herbivores - and appears to follow 15N relative abundances. Carnivores at the same trophic level tend to exhibit the same level of 2H enrichment. Because, as mentioned earlier, the amount of organic hydrogen produced from water varies between species, a model of trophic level related to absolute fractionation is difficult to make if the participating species are not known.
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He and his students used mass spectrometry to study natural variations in the isotopic abundances of hydrogen, carbon, oxygen and silicon, with applications to archeology, biochemistry, climatology, and geology. He was awarded the Wollaston Medal of the Geological Society of London in 1993. Epstein remained at Caltech as a Professor and Professor Emeritus until shortly before his death on September 17, 2001. The European Association of Geochemistry awards a Science Innovation Award medal every five years named in his honour for work in isotope geochemistry.
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Southern African wildcats are largely nocturnal, finding cover in which to rest during the day. Their habits are solitary, except for mating and raising their young, and they are highly territorial. They are adaptable predators, preferring to hunt small rodents, but able to change their diet according to seasonal and longer-term prey abundances and availability; they have been observed to take other small mammals, birds, reptiles, amphibians, insects and other invertebrates. The largest recorded prey include hares, springhares and birds up to the size of guineafowl.
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The HEAO C-2 experiment measured the relative composition of the isotopes of the primary cosmic rays between beryllium and iron (Z from 4 to 26) and the elemental abundances up to tin (Z=50). Cerenkov counters and hodoscopes, together with the Earth's magnetic field, formed a spectrometer. They determined charge and mass of cosmic rays to a precision of 10% for the most abundant elements over the momentum range from 2 to 25 GeV/c (c=speed of light). Scientific direction was by Principal Investigators Prof.
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Radioactive isotopes can be tested using the autoradiographs of gels in gel electrophoresis. The radiation emitted by compounds containing the radioactive isotopes darkens a piece of photographic film, recording the position of the labeled compounds relative to one another in the gel. Isotope tracers are commonly used in the form of isotope ratios. By studying the ratio between two isotopes of the same element, we avoid effects involving the overall abundance of the element, which usually swamp the much smaller variations in isotopic abundances.
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Thorium-containing minerals occur on all continents. Thorium is several times more abundant in Earth's crust than all isotopes of uranium combined and thorium-232 is several hundred times more abundant than uranium-235. Thorium concentrations near the surface of the earth can be mapped using gamma spectroscopy. The same technique has been used to detect concentrations on the surface of the Moon; the near side has high abundances of relatively thorium-rich KREEP, while the Compton–Belkovich Thorium Anomaly was detected on the far side.
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With the number of nucleotide changes introduced, artificial gene synthesis is often necessary for the creation of such an optimized gene. Specialized codon bias is further seen in some endogenous genes such as those involved in amino acid starvation. For example, amino acid biosynthetic enzymes preferentially use codons that are poorly adapted to normal tRNA abundances, but have codons that are adapted to tRNA pools under starvation conditions. Thus, codon usage can introduce an additional level of transcriptional regulation for appropriate gene expression under specific cellular conditions.
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In the 1980s the CRS data from both Voyagers was used to determine the abundances of energetic particles from the Sun and additional information. Another area studied in the 1980s using CRS data was variation in Galactic cosmic rays in the outer Heliosphere CRS helped predict that Voyager 1 and 2 would cross the Solar system's termination shock in 2003. This helped support the later conclusion that Voyager 1 crossed the termination shock in December 2004 and that Voyager 2 crossed it in August 2007.
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Home range sizes and overall cougar abundance depend on terrain, vegetation, and prey abundance. One female adjacent to the San Andres Mountains was found with a large range of 215 km2 (83 sq mi), necessitated by poor prey abundance. Research has shown cougar abundances from 0.5 animals to as much as 7 (in one study in South America) per 100 km2 (38 sq mi). Because males disperse farther than females and compete more directly for mates and territory, they are more likely to be involved in conflict.
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The area is internationally renowned as Important Bird Area and the high abundances qualify areas around the lake as Ramsar site. Many Palaearctic migrant water birds depend on the lake as feeding and resting grounds, including the common crane (Grus grus), Northern shoveller (Anas acuta), Black-tailed godwit (Limosa limosa), and ruff (Philomachus pugnax). Few patches of original forest vegetation and mountain ecosystem remain that have high plant endemism of global importance. Indigenous trees include: Sesa (Albizia gummifera), Birbira (Millettia ferryginea), Wanza (Cordia Africana).
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Many forest-dwelling songbirds breed in the Rocky Mountains and winter in Central and South America. Wildlife biologists suspect that population size declines in the songbirds may be partly the result of increased predation and brood parasitism. Brood parasitism by brown-headed cowbirds, for example, increases as a result of nearby logging. In conifer forests in west-central Idaho, common songbirds benefited from timber harvest, whereas the abundances declined of rare species that inhabit old-growth forests (hermit thrush, Swainson's thrush, and pileated woodpecker).
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The composition of meteorites was investigated and compared to terrestrial rocks as early as 1850. In 1901, Oliver C. Farrington hypothesised that, although there were differences, the relative abundances should still be the same. This was the beginnings of the field of cosmochemistry and has contributed much of what we know about the formation of the Earth and the Solar System. In the early 20th century, Max von Laue and William L. Bragg showed that X-ray scattering could be used to determine the structures of crystals.
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Hydrogen and helium are most common, from the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers, and (2) a general decrease in abundance, as elements become heavier. The "iron peak" may be seen in the elements near iron as a secondary effect, increasing relative abundances of elements with nuclei most strongly bound.
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Organic material naturally contains stable isotopes at different ratios in the environment, which can provide information on the origin of the food source for the organisms. Different types of organic material of food sources has different amounts of stable isotopes, which is reflected in the composition of the organism that eats these food sources. This type of analysis was first used in 2001 in conjunction with FISH to examine syntrophic relationships between anaerobic methane-oxidizing archaea and sulfate reducing bacteria. Isotopes with naturally low abundances may not be able to be detected with this method.
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242x242pxVarious types of jellyfish population booms have been recorded in fossil evidence as early as 540 million years ago during the Early Cambrian Period. Other evidence was found dating back to the Middle to Late Cambrian Period (520–540 mya) and the Neogene Period (20–30 mya). The soft-bodied anatomy of jellyfish makes fossilization rare, which provides challenges to recreate the historical abundances of blooms. Most preserved jellyfish bloom fossils are from the Cambrian period likely due to the abundance of marine life and lack of terrestrial scavengers during this time.
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Trace metal stable isotope biogeochemistry is the study of the distribution and relative abundances of trace metal isotopes in order to better understand the biological, geological, and chemical processes occurring in an environment. Trace metals are elements such as iron, magnesium, copper, and zinc that occur at low levels in the environment. Trace metals are critically important in biology and are involved in many processes that allow organisms to grow and generate energy. In addition, trace metals are constituents of numerous rocks and minerals, thus serving as an important component of the geosphere.
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Hübnerite, the manganese-rich end-member of the wolframite series, with minor quartz in the background The abundance and diversity of minerals is controlled directly by their chemistry, in turn dependent on elemental abundances in the Earth. The majority of minerals observed are derived from the Earth's crust. Eight elements account for most of the key components of minerals, due to their abundance in the crust. These eight elements, summing to over 98% of the crust by weight, are, in order of decreasing abundance: oxygen, silicon, aluminium, iron, magnesium, calcium, sodium and potassium.
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The second reason for researching non-standard BBN, and largely the focus of non-standard BBN in the early 21st century, is to use BBN to place limits on unknown or speculative physics. For example, standard BBN assumes that no exotic hypothetical particles were involved in BBN. One can insert a hypothetical particle (such as a massive neutrino) and see what has to happen before BBN predicts abundances that are very different from observations. This has been done to put limits on the mass of a stable tau neutrino.
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Rare feldspathoid-rich mafic rocks, akin to alkali basalts, may have Na2O + K2O contents of 12% or more. The abundances of the lanthanide or rare-earth elements (REE) can be a useful diagnostic tool to help explain the history of mineral crystallisation as the melt cooled. In particular, the relative abundance of europium compared to the other REE is often markedly higher or lower, and called the europium anomaly. It arises because Eu2+ can substitute for Ca2+ in plagioclase feldspar, unlike any of the other lanthanides, which tend to only form 3+ cations.
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Subdwarf B stars were discovered by Zwicky and Humason around 1947 when they found subluminous blue stars around the north galactic pole. In the Palomar-Green survey they were discovered to be the commonest kind of faint blue star with a magnitude over 18. During the 1960s spectroscopy discovered that many of the sdB stars are deficient in hydrogen, with abundances below that predicted by the Big Bang theory. In the early 1970s Greenstein and Sargent measured temperatures and gravity strengths and were able to plot their correct position on the Hertzsprung–Russell diagram.
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As with many Triassic temnospondyls, Callistomordax is considered to have been an aquatic freshwater tetrapod, evidenced by both its anatomy (e.g., lateral line system) and its depositional environment. The Lower Keuper Basin where Callistomordax was found was subjected to repeated transgression-regression cycles, resulting in mixed deposits of freshwater and marine taxa. Callistomordax is relatively rare and consists only of isolated elements in bonebeds with higher abundances of marine taxa, and the most complete specimens are found with various invertebrates and fish that suggest a relatively low salinity environment.
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Experimental data from the anaerobic phototroph Chlorobaculum tepidum indicate that microorganisms enhance sulfide oxidation by three or more orders of magnitude. However, the general contribution of microorganisms to total sulfur oxidation in marine sediments is still unknown. The Alpha-, Gamma- and Epsilonproteobacterial SOM account for average cell abundances of 108 cells/m3 in organic-rich marine sediments. Considering that these organisms have a very narrow range of habitats, as explained below, a major fraction of sulfur oxidation in many marine sediments may be accounted for by these groups.
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Terrestrial observers found ethane and methane in the comet, the first time either of these gases had been detected in a comet. Chemical analysis showed that the abundances of ethane and methane were roughly equal, which may imply that its ices formed in interstellar space, away from the Sun, which would have evaporated these volatile molecules. Hyakutake's ices must have formed at temperatures of 20 K or less, indicating that it probably formed in a denser- than-average interstellar cloud. The amount of deuterium in the comet's water ices was determined through spectroscopic observations.
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The quantity of elements heavier than helium (metallicity) is not known precisely, but the proportions are assumed to match the primordial abundances from the formation of the Solar System. The total mass of these heavier elements is estimated to be 19–31 times the mass of the Earth, with a significant fraction located in Saturn's core region. Trace amounts of ammonia, acetylene, ethane, propane, phosphine, and methane have been detected in Saturn's atmosphere. The upper clouds are composed of ammonia crystals, while the lower level clouds appear to consist of either ammonium hydrosulfide () or water.
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It is significantly faster than site-specific isotope measurements that can be performed using NMR, and can measure molecules with different rare isotopes but the same nominal mass at natural abundances (unlike GC and LCMS). It is also widely generalizable to molecules that can be introduced via gas or liquid solvent. Resolution of the Orbitrap is such that nominal isobars (e.g., 2H versus 15N versus 13C enrichments) can be distinguished from one another, and so molecules do not need to be converted into a homogeneous substrate to facilitate isotope analysis.
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She was part of the European Space Agency (ESA) SMART-1 mission. In 2006 Joy joined Birkbeck, University of London where she used the Demonstration of a Compact Imaging X-ray Spectrometer (D-CIXS) instrument, part of the SMART-1 mission, to study X-ray fluorescence from lunar samples. D-CIXS was designed by the Rutherford Appleton Laboratory (RAL) and could measure elemental abundances of magnesium, aluminium and silicon. Her work has used data from the Mercury Imaging X-ray Spectrometer (MIXS) on the BepiColombo Mercury Planetary Orbiter (MPO).
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The initial stages of the subgiant branch in a star like the sun are prolonged with little external indication of the internal changes. One approach to identifying evolutionary subgiants include chemical abundances such as Lithium which is diluted in subgiants, and coronal emission strength. As the fraction of hydrogen remaining in the core of a main sequence star decreases, the core temperature increases and so the rate of fusion increases. This causes stars to evolve slowly to higher luminosities as they age and broadens the main sequence band in the Hertzsprung–Russell diagram.
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Aside from time-series sampling, there are currently no methods for comparing more than two time points. Metabolic labeling experiments are only capable of comparing RNA abundances before and after pulse-labeling. It is of interest to be able to observe modifications to the transcriptome over a series of time points in a single sample, as this would provide increased time resolution in studies. Existing methods of metabolic labeling are of interest for this; if multiple different metabolic labels were used at differing time points this may allow for intermediate time points to be investigated.
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This is a K-type giant star with a stellar classification of K2 III:, where the semi-colon indicates some uncertainty about its spectral value. It is considered metal- rich star and is past the first dredge-up phase of its post-main sequence evolution, although it shows under-abundances of carbon and oxygen in its spectrum. The star has 1.25 times the mass of the Sun and is an estimated 6.48 billion years old. It is radiating 48 times the solar luminosity from its enlarged photosphere at an effective temperature of 4,413 K.
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The results obtained from metabarcoding are limited or biased to the frequency of occurrence. It is also problematic that far from all species have barcodes attached to them. Even though metabarcoding may overcome some practical limitations of conventional sampling methods, there is still no consensus regarding experimental design and the bioinformatic criteria for application of eDNA metabarcoding. The lack of criteria is due to the heterogeneity of experiments and studies conducted so far, which dealt with different fish diversities and abundances, types of aquatic ecosystems, numbers of markers and marker specificities.
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Spectrographic analysis of the coma of 96P/Machholz was made during its 2007 apparition, as part of the Lowell Observatory comet composition long-term observing program. When compared with the measured abundances of five molecular species in the comae of the other 150 comets in their database, these measurements showed 96P/Machholz to have far fewer carbon molecules. These other comets had on average 72 times as much cyanogen as 96P/Machholz. The only comet previously seen with similar depletion both in carbon-chain molecules and cyanogens is , but it has a substantially different orbit.
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Among his highest citation scientific papers are the discovery and collaborative study of an atypical supernova observed in 2006,, 19 June 2007."Warning shot for a cataclysm", CEA scientific news, Commissariat à l'énergie atomique et aux énergies alternatives, 14 June 2007. a scientific review on the enigmatic X-ray source Cygnus X-3 and its reported very high energy emission and the discovery of abnormal CNO abundances among accreting magnetic white dwarfs."Overabundance of nitrogen onto a magnetic white dwarf" , Paris-Meudon Observatory scientific news Paris Observatory, Mars 2003.
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The modal ratio of olivine:pyroxene is oddly low for an H5 ordinary chondrite; typical values are ~1.31, and yet modal analyses indicate the ratio for Mason Gully is as low as 0.84. Plagioclase abundance is also lower than typical values, but Fe(Ni)-metal abundances are higher than average for the H5 group. Metamorphic temperatures were determined based upon the measured oxygen fugacity, using the two-pyroxene and olivine-spinel geothermometry methods. The two-pyroxene approach yielded temperatures between 865 °C - 900 °C, whilst the olivine- spinel approach yielded a temperature of 705 °C.
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However, the chemical abundances in its outer atmosphere tell a different story, suggesting that it is a population II star with an age of 12−13 billion years. This discrepancy may indicate that the star has undergone a period of mass accretion. Possible scenarios indicate that the star has either undergone a merger with a close companion, or else interacted with the progenitor cloud of the nearby open cluster NGC 2516. The star displays convincing evidence for an infrared excess, suggesting the presence of a circumstellar debris disk of dust.
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Mu Aurigae, Latinized as μ Aurigae, is the Bayer designation for an unconfirmed binary star in the northern constellation of Auriga. It is visible to the naked eye with an apparent visual magnitude of +4.88. Based upon an annual parallax shift of as seen from Earth, is located 157 light years from the Sun. This is an A-type main sequence star with a stellar classification of A4 Vm; the 'm' suffix indicating that abnormal abundances of heavier elements appear in the star's spectrum, making this an Am star.
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Also, the Moon would have collided with and incorporated any small preexisting satellites of Earth, which would have shared the Earth's composition, including isotopic abundances. The geology of the Moon has since been more independent of the Earth. A 2012 study on the depletion of zinc isotopes on the Moon supported the giant-impact origin for Earth and the Moon. In 2013, a study was released that indicated that water in lunar magma is indistinguishable from that in carbonaceous chondrites and nearly the same as that of Earth in isotopic composition.
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Another theory on the decline of Crocidura trichura is linked to the demise of the two endemic rats, and the competition left amongst the Christmas Island shrew and the Christmas Island red crab (Gecarcoidea natalis) for leaf litter resources. The decline of predator rat species allowed for the quickened rise of G. natalis, a usual prey of the rats. This could have forced C. trichura into new habitats such as tree canopies, or sites with low crab abundances. The population of C. trichura may have been pressured by their vulnerability during weaning.
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Habitat disturbance for A. gouldi includes the removal or destruction of native riparian vegetation, bank erosion, removal of snags, stream flow alterations such as culverts and farm dams, siltation and toxic chemical runoffs. The clearance of riparian vegetation causes the destabilisation of waterway banks, which impacts the burrowing habitats for A. gouldi and increases sediment runoff into waterways. Increased sediment levels arising from agricultural and forestry related land-uses have been correlated with decreased abundances of freshwater crayfish. The increase in turbidity impacts the ability of the crayfish to effectively transpire oxygen through its gills.
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Although designated as a variable star, observations with the Hipparcos satellite showed a variation of no more than 0.02 in magnitude. In designating this as a suspected variable star, it is possible that Kappa Ophiuchi was mistaken for Chi Ophiuchi, which is a variable star. Kappa Ophiuchi belongs to an evolutionary branch known as the red clump, making it a clump giant. The surface abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is similar to the abundances of those elements in the Sun.
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Although Voyager 2 directly detected methane clouds, all other cloud layers remain speculative. The existence of a hydrogen sulfide cloud layer is only possible if the ratio of sulfur and nitrogen abundances (S/N ratio) is significantly greater than its solar value of 0.16. Otherwise all hydrogen sulfide would react with ammonia, producing ammonium hydrosulfide, and the ammonia clouds would appear instead in the pressure range 3–10 bar. The elevated S/N ratio implies depletion of ammonia in the pressure range 20–40 bar, where the ammonium hydrosulfide clouds form.
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Cafeteria roenbergensis has been found in all oceans examined, but is especially common in coastal waters. These protists occur in a type of biosphere known as "microbial assemblages". This means that they are present at such low abundances, that they are not easily detected, and can only be retrieved and isolated using specialized isolation techniques such as flow cytometry. Ishigaki and Sleigh (2001) found that C. roenbergensis ceased to reproduce when the concentration of bacteria that they were grazing on became less than 2.0×107 cells ml−1.
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The Oddo–Harkins rule holds that an element with an even atomic number (such as carbon: element 6) is more abundant than both elements with the adjacently larger and smaller odd atomic numbers (such as boron: element 5 and nitrogen: element 7, respectively, for carbon). This tendency of the abundance of the chemical elements was first reported by Giuseppe Oddo in 1914 and William Draper Harkins in 1917. Estimated abundances of the chemical elements in the solar system. Hydrogen and helium, atomic numbers are 1 and 2, respectively, are most abundant, from the Big Bang.
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The team combined data on elemental abundances produced by the Burbidges with Hoyle's hypothesis that all chemical elements might be produced in stars by a series of nuclear reactions, and Fowler's laboratory experiments on those reactions. The idea became known as stellar nucleosynthesis. They published their model in a series of papers, culminating in a magnum opus in 1957, now known as the B2FH paper after the initials of Burbidge, Burbidge, Fowler & Hoyle. Margaret Burbidge was the first author of the paper, which was written while she was pregnant.
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Tethys (lower right) near Saturn and its rings Tethys is thought to have formed from an accretion disc or subnebula; a disc of gas and dust that existed around Saturn for some time after its formation. The low temperature at the position of Saturn in the Solar nebular means that water ice was the primary solid from which all moons formed. Other more volatile compounds like ammonia and carbon dioxide were likely present as well, though their abundances are not well constrained. The extremely water- ice-rich composition of Tethys remains unexplained.
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However, in contrast to the ordinary base and precious metals, rare earth elements have very little tendency to become concentrated in exploitable ore deposits. Consequently, most of the world's supply of rare earth elements comes from only a handful of sources. Furthermore, the rare earth metals are all quite chemically similar to each other, and they are thus quite difficult to separate into quantities of the pure elements. Differences in abundances of individual rare earth elements in the upper continental crust of the Earth represent the superposition of two effects, one nuclear and one geochemical.
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First, the rare earth elements with even atomic numbers (58Ce, 60Nd, ...) have greater cosmic and terrestrial abundances than the adjacent rare earth elements with odd atomic numbers (57La, 59Pr, ...). Second, the lighter rare earth elements are more incompatible (because they have larger ionic radii) and therefore more strongly concentrated in the continental crust than the heavier rare earth elements. In most rare earth ore deposits, the first four rare earth elements – lanthanum, cerium, praseodymium, and neodymium – constitute 80% to 99% of the total amount of rare earth metal that can be found in the ore.
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The output of CAGE is a set of short nucleotide sequences (often called tags) with their observed counts. Using a reference genome, a researcher can usually determine, with some confidence, the original mRNA (and therefore which gene) the tag was extracted from. Copy numbers of CAGE tags provide an easy way of digital quantification of the RNA transcript abundances in biological samples. Unlike a similar technique serial analysis of gene expression (SAGE, superSAGE) in which tags come from other parts of transcripts, CAGE is primarily used to locate exact transcription start sites in the genome.
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It has more than double the mass of the Sun and has expanded to ten times the Sun's radius. It shines with 54–fold the Sun's luminosity, which is being radiated from its outer envelope at an effective temperature of 4,760 K. At this heat, it glows with the orange-hue of a K-type star. This has been designated a barium star, meaning its atmosphere is extremely enriched with barium and other heavy elements. However, this is disputed, with astronomer Andrew McWilliam (1990) finding normal abundances from an s-process.
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Ultra- metal-poor Population II stars in the Galactic Halo exhibit a scaled-down Solar System r-process abundance pattern. Comparing calculated and observed abundances for elements as the stable europium with radioactive ones (thorium and uranium) the age of these stars can be determined to about 13 billion years (see Sneden's Star, Cayrel's Star, BD +17° 3248, HE 1523-0901). In 1999 he received the Nuclear Chemistry Award (now Glenn T. Seaborg Award) of the American Chemical Society. In 2014, the American Physical Society rewarded him the Hans A. Bethe Prize.
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One such theory predicts that trade will be based on relative factor abundances. One of the common relative factor abundance models is the Heckscher–Ohlin model. Those countries with a relative abundance of one factor would be expected to produce goods that require a relatively large amount of that factor in their production. While a generally accepted theory of trade, many economists in the Chicago School believed that the Heckscher–Ohlin model alone was sufficient to describe all trade, while Bertil Ohlin himself argued that in fact the world is more complicated.
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And yet, these surveys have proved to be of great value in studying the bird population trends. BBS data can also be used to produce continental-scale relative abundance maps. When analyzed at larger scales, the relative abundance maps can offer a clear indication of the relative abundances of bird species that are observed by the BBS. However, maybe the most effective use of these surveys is the opportunity to analyze population change, even though they do not provide information on the factors that cause these changes in the population trends.
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Observations of the deuterated molecule, C2D, can test and extend fractionation theories (which explain the enhanced abundance of deuterated molecules in the interstellar medium). One of the important indirect uses for observations of the ethynyl radical is the determination of acetylene abundances. Acetylene (C2H2) does not have a dipole moment, and therefore pure rotational transitions (typically occurring in the microwave region of the spectrum) are too weak to be observable. Since acetylene provides a dominant formation pathway to ethynyl, observations of the product can yield estimates of the unobservable acetylene.
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It has but 93% of the mass of the Sun, while its outer atmosphere has begun to expand, reaching about 2.3 times the Sun's radius. HD 48265 is radiating 62% of the Sun's luminosity from its atmosphere at an effective temperature of 5,508 K, giving it the cool orange glow of a K-type star. Measurement of the chemical abundances of this star indicate that, compared to the Sun, it has a 95% greater proportion of elements other than hydrogen and helium—what astronomers term the star's metallicity.
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The majority of the site is made up of species-rich grassland (subcommunity MG5c), which comprises three dominant species of grass and several other grass species at lower abundances. The dominant species are Red Fescue (Festuca rubra), Common Bent (Agrostis capillaris) and Yorkshire Fog (Holcus lanatus). The less abundant species of grass include, Crested Dog’s-tail (Cynosurus cristatus), Heath-grass (Danthonia decumbens) and Cocksfoot (Dactylis glomerata). The subcommunity also has many broad-leaved herbs including Common Knapweed (Centaurea nigra), Tormentil (Potentilla erecta), Devils-bit scabious (Succisa pratensis) and Betony (Stachys officinalis).
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On the west of the site, calcareous (chalky) soils help support an ash (Fraxinus excelsior) growth underplanted by mosses, ramsons (Allium ursinum), bee and pyramidal orchids (Ophrys apifera) and (Anacamptis pyramidalis). The streams which pass through the site have eroded deeply into the rock layer to produce steep sided valleys. These valleys have alder (Alnus glutinosa), with local abundances of grey willow (Salix cinerea) above a ground flora of pendulous sedge (Carex pendula), water mint (Mentha aquatica), opposite-leaved golden saxifrage (Chrysosplenium oppositifolium) and ragged robin (Lychnis flos-cuculi).
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The later method (Etienne and Ollf 2005) uses a Bayesian simulation of the models to test their fit to empirical data. The former method, which is still commonly used, simulates the expected relative abundances, from a normal distribution, of each model given the same number of species as the empirical data. Each model is simulated multiple times, and mean and standard deviation can be calculated to assign confidence intervals around each relative abundance distribution. The confidence around each rank can be tested against empirical data for each model to determine model fit.
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Hoyle's work explained how the abundances of the elements increased with time as the galaxy aged. Subsequently, Hoyle's picture was expanded during the 1960s by contributions from William A. Fowler, Alastair G. W. Cameron, and Donald D. Clayton, followed by many others. The seminal 1957 review paper by E. M. Burbidge, G. R. Burbidge, Fowler and Hoyle is a well-known summary of the state of the field in 1957. That paper defined new processes for the transformation of one heavy nucleus into others within stars, processes that could be documented by astronomers.
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HE1327-2326, discovered in 2005 by Anna Frebel and collaborators, was the star with the lowest known iron abundance until SMSS J031300.36−670839.3 was discovered. The star is a member of Population II stars, with a solar- standardised iron to hydrogen index (Fe:H), or metallicity, of −5.6. The scale being logarithmic, this number indicates that its iron content is 1/400,000 that of the Earth's sun. However, it has a carbon abundance of roughly one- tenth solar ([C/H] = −1.0), and it is not known how these two abundances can have been produced/exist simultaneously.
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One group, studying distant quasars, has claimed to detect a variation of the fine structure constant at the level in one part in 105. Other authors dispute these results. Other groups studying quasars claim no detectable variation at much higher sensitivities. For over three decades since the discovery of the Oklo natural nuclear fission reactor in 1972, even more stringent constraints, placed by the study of certain isotopic abundances determined to be the products of a (estimated) 2 billion year-old fission reaction, seemed to indicate no variation was present.
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The primary member, designated component A, is a magnetic chemically peculiar star with a stellar classification of A1VpSiSrCr, appearing as an A-type main-sequence star with abnormal abundances of silicon, strontium, and chromium. It is an alpha2 Canum Venaticorum variable that ranges in brightness from visual magnitude 4.78 down to 4.85 with a period of 3.8567 days. The star is about 525 million years old with a projected rotational velocity of 23 km/s. It has 2.2 times the mass of the Sun and 2.3 times the Sun's radius.
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This may result in a wildfire burning out a large area, although it has been found that heather seeds germinate better if subject to the brief heat of controlled burning. In terms of managing moorlands for wildlife, in the UK, vegetation characteristics are important for passerine abundance, whilst predator control benefits red grouse, golden plover, and curlew abundances. To benefit multiple species, many management options are required. However, management needs to be carried out in locations that are also suitable for species in terms of physical characteristics such as topography, climate and soil.
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Note: This section provides a general summary of niche apportionment theory, more information can be found under niche apportionment models. Most mechanistic approaches to species abundance distributions use niche-space, i.e. available resources, as the mechanism driving abundances. If species in the same trophic level consume the same resources (such as nutrients or sunlight in plant communities, prey in carnivore communities, nesting locations or food in bird communities) and these resources are limited, how the resource "pie" is divided among species determines how many individuals of each species can exist in the community.
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The model then uses birth, death, immigration, extinction and speciation to modify community composition over time. ;Hubbell's theta The UNTB model produces a dimensionless "fundamental biodiversity" number, θ, which is derived using the formula: : θ = 2Jmv where: : Jm is the size of the metacommunity (the outside source of immigrants to the local community) :v is the speciation rate in the model Relative species abundances in the UNTB model follow a zero-sum multinomial distribution.Hubbell, S. P.; Lake J. 2003. "The neutral theory of biogeography and biodiversity: and beyond".
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BD Phoenicis is a Lambda Boötis star, an uncommon type of peculiar stars that have very low abundances of iron-peak elements. In particular, BD Phoenicis has near-solar carbon and oxygen content, but its iron abundance is only 4% the solar value. BD Phoenicis is also a pulsating variable of Delta Scuti type, varying its apparent magnitude between 5.90 and 5.94. A study of its light curve detected seven pulsation periods that range from 50 to 84 minutes, the strongest one having a period of 57 minutes and an amplitude of 9 milli- magnitudes.
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Planetary scientists classify chondritic IDPs in terms of their diminishing degree of oxidation so that they fall into three major groups: the carbonaceous, the ordinary, and the enstatite chondrites. As the name implies, the carbonaceous chondrites are rich in carbon, and many have anomalies in the isotopic abundances of H, C, N, and O (Jessberger, 2000). From the carbonaceous chondrites, we follow the trail to the most primitive materials. They are almost completely oxidized and contain the lowest condensation temperature elements ("volatile" elements) and the largest amount of organic compounds.
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According to the 14th-century classical novel Water Margin, the first 27 years of Emperor Renzong's reign were known as the "Era of Three Abundances." But this was followed by a great plague around the year 1048 that decimated the population. It was only the prayers of the priests from the Taoist sect Way of the Celestial Masters that eventually lifted this pestilence. The imperial emissary who had been sent to the Taoist monastery recklessly entered the Suppression of Demons Hall, thinking the stories of demons was a hoax to delude gullible people.
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Based on geophysical techniques, the crust is estimated to be on average about 50 km thick. Partial melting within the mantle of the Moon gave rise to the eruption of mare basalts on the lunar surface. Analyses of these basalts indicate that the mantle is composed predominantly of the minerals olivine, orthopyroxene and clinopyroxene, and that the lunar mantle is more iron-rich than that of the Earth. Some lunar basalts contain high abundances of titanium (present in the mineral ilmenite), suggesting that the mantle is highly heterogeneous in composition.
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Barndoor skate caught during an NOAA research cruise Abundances of barndoor skate dropped precipitously in the 1960s and early 1970s, coinciding with the period of intense fishing by foreign factory trawlers. The abundance remained very low through around 1990, but increased nearly exponentially from 1990–2005, and have been approaching the levels observed in the 1960s. In 1998, Casey and Myers published a controversial study claiming that barndoor skate was nearly extinct. However, they only presented data through 1993, so the recovery that started in the early 1990s was not clearly evident.
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The borders of today may not include the habitat of tomorrow, thus defeating the purpose of preservation by instead making the species range smaller and smaller if there are barriers to migration at the Northern and higher elevation boundaries of the reserve. Reserves could be designed to keep Northern migration a possibility, with boundaries farther to the North than might be considered practical looking at the today’s species ranges and abundances. Keeping open corridors between reserves connecting them to reserves to the North and the South is another possibility.
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Lava flows from mid-ocean ridge and plate boundary seamounts are mostly basaltic (both tholeiitic and alkalic), whereas flows from subducting ridge volcanoes are mostly calc-alkaline lavas. Compared to mid-ocean ridge seamounts, subduction zone seamounts generally have more sodium, alkali, and volatile abundances, and less magnesium, resulting in more explosive, viscous eruptions. All volcanic seamounts follow a particular pattern of growth, activity, subsidence and eventual extinction. The first stage of a seamount's evolution is its early activity, building its flanks and core up from the sea floor.
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Particles accelerated by these shocks are commonly observed at 1 AU below energies of about 10 MeV per nucleon. ACE measurements confirm that CIRs include a significant fraction of singly charged helium formed when interstellar neutral helium is ionized. At yet higher energies, the major contribution to the measured flux of particles is due to solar energetic particles (SEPs) associated with interplanetary (IP) shocks driven by fast coronal mass ejections (CMEs) and solar flares. Enriched abundances of helium-3 and helium ions show that the suprathermal tails are the main seed population for these SEPs.
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HD 134439 and HD 134440 are a pair of K-type runaway stars, nearly hypervelocity stars, in the constellation Libra. Although they are roughly away, they have one of the highest proper motions of any star in the sky, travelling over 3.5 arcseconds every year. The stars are believed to originate from outside of the Milky Way, likely from a destroyed, unusually dusty satellite galaxy. They have an extremely low metallicity, only about 3.5% that of the Sun, with unusual chemical abundances very different from those of stars formed anywhere in the galaxy.
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Neutron capture nucleosynthesis describes two nucleosynthesis pathways: the r-process and the s-process, for rapid and slow neutron captures, respectively. R-process describes neutron capture in a region of high neutron flux, such as during supernova nucleosynthesis after core-collapse, and yields neutron-rich nuclides. S-process describes neutron capture that is slow relative to the rate of beta decay, as for stellar nucleosynthesis in some stars, and yields nuclei with stable nuclear shells. Each process is responsible for roughly half of the observed abundances of elements heavier than iron.
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The high sensitivity of DESI in the lipid range makes it a powerful technique for the detection and mapping of lipids abundances within tissue specimens. Recent developments in MALDI methods have enabled direct detection of lipids in-situ. Abundant lipid- related ions are produced from the direct analysis of thin tissue slices when sequential spectra are acquired across a tissue surface that has been coated with a MALDI matrix. Collisional activation of the molecular ions can be used to determine the lipid family and often structurally define the molecular species.
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Artist's conception of the Milky Way Stellar archaeology is the study of the early history of the universe, based on its early composition. By examining the chemical abundances of the earliest stars in the universe: metal-poor, Population II stars; insights are gained into their earlier, metal-free, Population III progenitors. This sheds light on such processes as early star formation, nucleosynthesis in stars and supernovae, and the formation processes of the galactic halo. The field has already discovered that the Milky Way cannibalizes surrounding dwarf galaxies, giving it a youthful appearance.
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Most commonly this arises from H2O and SiO, but hydroxyl (OH) emission also occurs from narrow regions. In addition to high resolution mapping of the circumstellar material around red supergiants, VLBI or VLBA observations of masers can be used to derive accurate parallaxes and distances to their sources. Currently this has been applied mainly to individual objects, but it may become useful for analysis of galactic structure and discovery of otherwise obscured red supergiant stars. Surface abundances of red supergiants are dominated by hydrogen even though hydrogen at the core has been completely consumed.
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BD +17° 3248 is an old Population II star located at a distance of roughly in the Galactic Halo. It belongs to the class of ultra-metal-poor stars, especially the very rare subclass of neutron-capture (r-process) enhanced stars. Since about 2000, this star had been studied with 3 telescopes: a) the Hubble Space Telescope, b) the Keck I telescope and c) the Harlan J. Smith Telescope at the McDonald Observatory of the University of Texas. Elemental abundances in the range from germanium (Z=32) up to uranium (Z=92) were determined.
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Once the thermal energy dropped below 0.03 MeV, nucleosynthesis effectively came to an end. Primordial abundances were now set, with the measured amounts in the modern epoch providing checks on the physical models of this period. 370,000 years after the Big Bang the temperature of the universe fell to the point where nuclei could combine with electrons to create neutral atoms. As a result, photons no longer interacted frequently with matter, the universe became transparent and the cosmic microwave background radiation was created and then structure formation took place.
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See Abundances of the elements (data page). Most of the world's commercial neodymium is mined in China. Neodymium compounds were first commercially used as glass dyes in 1927, and they remain a popular additive in glasses. The color of neodymium compounds is due to the Nd3+ ion and is often a reddish- purple, but it changes with the type of lighting, because of the interaction of the sharp light absorption bands of neodymium with ambient light enriched with the sharp visible emission bands of mercury, trivalent europium or terbium.
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The abundances of multiply substituted isotopologues can also be affected by kinetic processes. As for singly substituted isotopologues, departures from thermodynamic equilibrium in a doubly-substituted species can implicate the presence of a particular reaction taking place. Photochemistry occurring in the atmosphere has been shown to alter the abundance of 18O2 from equilibrium, as has photosynthesis. Measurements of 13CH3D and 12CH2D2 can identify microbial processing of methane and have been used to demonstrate the significance of quantum tunneling in the formation of methane, as well as mixing and equilibration of multiple methane reservoirs.
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While plant-based diets have some variation, vegetarian and vegan diets patterns are the most common. Vegetarian diets exclude meat products but still allow for eggs and dairy, while vegan diets exclude all forms of animal products. The diets of vegetarian and vegan individuals create a microbiome distinct from meat eaters, however there is not a significant distinction between the two. In diets that are centered around meat and animal products, there are high abundances of Alistipes, Bilophila and Bacteroides which are all bile tolerant and may promote inflammation in the gut.
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In the (p)ppGpp biosynthesis cycle, NDPK serves an important role. When there is an absence of a charged tRNA in the A site of a ribosome, the ribosome will stall and trigger the synthesis of the guanosine pentaphosphate ((p)ppGpp) molecule. (p)ppGpp biosynthesis is a part of the purine metabolism pathway and coordinates a series of cellular activities in response to nutritional abundances. Synthesis of (p)ppGpp is triggered by carbon starvation, or the lack of carbon in the cell's environment, and causes the protein SpoT to activate.
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Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample. This technique has two different applications in the earth and environmental sciences. The analysis of 'stable isotopes' is normally concerned with measuring isotopic variations arising from mass-dependent isotopic fractionation in natural systems. On the other hand, radiogenic isotope analysis involves measuring the abundances of decay-products of natural radioactivity, and is used in most long-lived radiometric dating methods.
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Measurement of natural variations in the abundances of stable isotopes of the same element is normally referred to as stable isotope analysis. This field is of interest because the differences in mass between different isotopes leads to isotope fractionation, causing measurable effects on the isotopic composition of samples, characteristic of their biological or physical history. As a specific example, the hydrogen isotope deuterium (heavy hydrogen) is almost double the mass of the common hydrogen isotope. Water molecules containing the common hydrogen isotope (and the common oxygen isotope, mass 16) have a mass of 18.
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This formation showed stereospecific, catalytic synthesis of D-ribose, the only naturally occurring enantiomer of ribose. Since the detection of this organic compound, many theories have been developed related various chemical routes to explain its formation in stellar systems. star dust It was found that UV-irradiation of methanol ices containing CO yielded organic compounds such as glycolaldehyde and methyl formate, the more abundant isomer of glycolaldehyde. The abundances of the products slightly disagree with the observed values found in IRAS 16293-2422, but this can be accounted for by temperature changes.
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Fluorite, a source of fluorine Hydrogen and helium are estimated to make up approximately 99 per cent of all ordinary matter in the universe. Less than five percent of the Universe is believed to be made of ordinary matter, represented by stars, planets and living beings. The balance is made of dark energy and dark matter, both of which are poorly understood at present.Ostriker & Steinhardt 2001 Hydrogen, carbon, nitrogen, and oxygen constitute the great bulk of the Earth's atmosphere, oceans, crust, and biosphere; the remaining nonmetals have abundances of 0.5 per cent or less.
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The Cassini mission data suggest that this plume, sourced by a liquid reservoir beneath the moon's icy crust, contain organics, salts, and water-rock interaction derivatives. Thus, the ingredients for life as we know it are available in Enceladus's subsurface ocean. The THEO mission would primarily focus on whether Enceladus is habitable. It would not look for life forms directly, but for higher abundances of certain molecules, ratios of organic compounds, or chains of amino acids could all be biosignatures that all give away the presence of life.
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The 3 in column 4 means that three species, species "b", "c", and "d", have abundance four. The final 1 in column 10 means that one species, species "a", has abundance 10. This type of dataset is typical in biodiversity studies. Observe how more than half the biodiversity (as measured by species count) is due to singletons. For real datasets, the species abundances are binned into logarithmic categories, usually using base 2, which gives bins of abundance 0-1, abundance 1-2, abundance 2-4, abundance 4-8, etc.
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Such species are thus considered to be evenly split between the two adjacent classes (apart from singletons which are classified into the rarest category). Thus in the example above, the Preston abundances would be abundance class 1 1-2 2-4 4-8 8-16 species 5 0 1.5 1.5 1 The three species of abundance four thus appear, 1.5 in abundance class 2-4, and 1.5 in 4-8. The above method of analysis cannot account for species that are unsampled: that is, species sufficiently rare to have been recorded zero times.
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There are some species, including the L. corniculatus, P. montana, and La. stoechas which are highly preferred by the bee despite their relatively lower abundances. Again, these ranked preferences are similar between bees that share regions, as opposed to individual bees and their colony-mates. The yellow-faced bumblebee appears to select its foraging locations based on the diversity of available flora in a given region, as opposed to floral density. This means that the bees are willing to travel longer distances to forage from patches that have wider varieties of available floral taxa.
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From 1983 to 2003, microbiologists analyzed cell abundances in drill cores from the Ocean Drilling Program. A group led by John Parkes of the University of Bristol reported concentrations of 104 to 108 cells per gram of sediment down to depths of 500 metres (agricultural soils contain about 109 cells per gram). This was initially met with skepticism and it took them four years to publish their results. In 1998, William Whitman and colleagues published a summary of twelve years of data in the Proceedings of the National Academy of Sciences.
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The study of stable isotope biogeochemistry involves the description of the relative abundances of various isotopes in a certain chemical pool, as well as the way in which physicochemical processes change the fraction of those isotopes in one pool vs. another. Various type of notation have been developed to describe the abundance and change in the abundance of isotopes in these processes, and these are summarized below. In most cases only the relative amounts of an isotope are of interest, the absolute concentration of any one isotope is of little importance.
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Transcriptomics is the study of the transcriptome, usually by characterizing the relative abundances of messenger RNA molecules the tissue under study. According to the central dogma of molecular biology, genetic information flows from double stranded DNA molecules to single stranded mRNA molecules where they can be readily translated into function protein molecules. By studying the transcriptome, one can gain valuable insight into the regulation of gene expressions. While expression levels as the gene level can be more or less accurately depicted by second generation sequencing, transcript level information is still an important challenge.
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Trench B was dug too far away from the main site, based on the minimal findings within. Artifacts found within the trenches included ceramics, geometrically styled vessels, doll like figures, sculptures and more. A sign of human life at its earliest is noted within the darkest of dirt filled with many artifacts that lie directly beneath the altar of the temple. The piles of artifacts could be found nowhere else at the site in such abundances other than the spot in which it was believed the goddess was being worshipped.
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In general, HSPA1L is widely distributed across tissues at low abundances, but in particular, it is constitutively and abundantly expressed in the testis. Along with other heat shock proteins, this protein stabilizes existing proteins against aggregation and mediates the folding of newly translated proteins in the cytosol and in organelles. In order to properly fold non-native proteins, this protein interacts with the hydrophobic peptide segments of proteins in an ATP- controlled fashion. Though the exact mechanism still remains unclear, there are at least two alternative modes of action: kinetic partitioning and local unfolding.
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Research has shown that in freshwater environments, with a high abundances of Ca2+, the adsorption of TNT and its transformation products to soils and sediments may be lower than observed in a saline environment, dominated by K+ and Na+. Therefore, when considering the adsorption of TNT, the type of soil or sediment and the ionic composition and strength of the ground water are important factors. The association constants for TNT and its degradation products with clays have been determined. Clay minerals have a significant effect on the adsorption of energetic compounds.
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Chitinozoa may have been immature graptolites. The graptolites are colonial organic walled fossils which also occurred from the Ordovician to the Devonian; only part of their life cycle is known and it is not clear how they reproduced. It has been suggested that the Chitinozoa may represent the pre-sicula stages of graptolites - the period between the colony's sexual reproduction, and the formation of a new colony. This hypothesis appears to be supported by the co- occurrence of graptolite and chitinozoan fossils, whose abundances appear to mirror one another.
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Stellar models of the Sun's evolution predict the solar surface chemical abundance pretty well except for lithium (Li). The surface abundance of Li on the Sun is 140 times less than the protosolar value (i.e. the primordial abundance at the Sun's birth), yet the temperature at the base of the surface convective zone is not hot enough to burn – and hence deplete – Li. This is known as the solar lithium problem. A large range of Li abundances is observed in solar-type stars of the same age, mass, and metallicity as the Sun.
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There are four major types of basalt and basaltic andesite in the central Cascades: early high-alumina olivine tholeiitic (HAOT) basalt, normal High Cascade HAOT basalt, North Sister basaltic andesites, and Mount Washington type basaltic andesites. Hughes (1990) argues that their differences could be the result of different magma sources or magma evolution in open systems. Mount Washington basaltic andesites are also considered one of the three distinct mafic rock types in the High Cascade platform, with North Sister basaltic andesites and normal basalts. The three groups all exhibit different major and trace element abundances.
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Most of these species are well known to have increased in numbers following human disturbance, however. Smaller declines were observed where pythons were only recently documented and the greatest mammalian abundances were observed outside of the python's current range. Burmese pythons were the dominant predator of reintroduced marsh rabbits (Sylvilagus palustris) in Everglades National Park, and predation by pythons extirpated the rabbit population in less than 11 months.McCleery RA, Sovie A, Reed RN, Cunningham MW, Hunter ME, Hart KM (2015) Marsh rabbit mortalities tie pythons to the precipitous decline of mammals in the Everglades.
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With her research team, the Genetics and Genomics Group (G3) at PMEL, Dr. Stepien is working to develop and apply targeted high-throughput sequencing metagenomic assays to identify members of species assemblages, quantify their relative abundances, and analyze their population genetic diversity and connectivity along the Pacific coast and Alaskan waters, using environmental DNA from water and plankton tow samples. With other PMEL researchers and engineers, she is working to apply eDNA biotechnology for monitoring and assessing marine biological community dynamics from eDNA collected remotely from buoys, drones, AUVs, and gliders.
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A Muller plot, also known as Muller diagram, combines information about the succession of different OTUs (genotypes, phenotypes, species, ...) and information about dynamics of their abundances (populations or frequencies) over time. Muller plots may be used to visualize evolutionary dynamics. They may be also employed in the study of diversity and its dynamics; that is, how diversity emerges and how changes over time. R) showing the evolutionary dynamics of an artificial community They are called Muller plots in honor of Hermann Joseph Muller, who used them to explain his idea of Muller's ratchet.
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The gas giants in particular have enough gravity to retain primary atmospheres, taken largely from the presolar nebula, as opposed to the later outgassing and reactions of secondary atmospheres. Differences in gas giant atmospheres compared to solar abundances then indicate some process in that planet's history. Meanwhile, gases at small planets such as Venus and Mars have isotopic differences indicating atmospheric escape processes.{argon isotope ratio planet meteorite}{neon isotope ratio meteorite} The various modifications of surface minerals, or space weathering, is used to evaluate meteorite and asteroid types and ages.
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Two black-tailed prairie dogs In the Great Plains, the prairie dog is a keystone species. Studies comparing species abundances in areas of colonization against areas with no prairie dog colonization show clear evidence that the prairie dog does have a significant impact on its surroundings by altering vegetation and therefore affecting habitat and food availability for other species. There is a great mosaic of vegetative diversity within the Great Plains due to the prairie dog's extensive grazing on long grasses. This mosaic supports a variety of small mammals.
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Radial velocity curves for the two almost identical components The two components of ζ1 Ursae Majoris (Mizar Aa and Ab) are observed to be identical, with the exception of slightly different radial velocity variations which indicate very slightly different masses. The spectral lines of the two stars can be observed separately and both are given a spectral type of A2Vp. They are Ap stars, chemically peculiar due to stratification of some heavy elements in the photosphere of slowly-rotating hot stars. In this case, they show elevated abundances of strontium and silicon.
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The star is drifting closer with a radial velocity of −15 km/s. This object is an A-type main-sequence star with a stellar classification of A1 V. It is an estimated 388 million years old with a high rate of spin, showing a projected rotational velocity of around 118 km/s. The elemental abundances in the stellar atmosphere are close to solar, with pronounced underabundances of aluminium and strontium. The star has three times the mass of the Sun and about 2.5 times the Sun's radius.
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Determining the features and abundances of oxygen, nitrogen, and sulfur at up to 100 Bars of pressure (1451 psi) will shed light on the origins and nature of Jupiter. It is also designed to detect the amount water and ammonia deep inside Jupiter. It should also be able to provide a temperature profile of atmosphere down to 200 bar (2901 psi). Overall MWR is designed to look down as deep as roughly 1,000 atmospheres (or Bars or kPa) which is about 342 miles (550 kilometers) down inside Jupiter.
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Each of the major stable isotope systems (hydrogen, carbon, oxygen, nitrogen, and sulfur) has a wide variety of references encompassing distinct molecular structures. For example, nitrogen isotope reference materials include N-bearing molecules such ammonia (NH3), atmospheric dinitrogen (N2), and nitrate (NO3−). Isotopic abundances are commonly reported using the δ notation, which is the ratio of two isotopes (R) in a sample relative to the same ratio in a reference material, often reported in per mille (‰) (equation below). Reference material span a wide range of isotopic compositions, including enrichments (positive δ) and depletions (negative δ).
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Phosphorus is particularly important as a plant growth promoter in freshwater systems, resulting in more abundant aquatic plant life (especially Marathrum oxycarpum), providing greater shelter and food resources, enabling greater aquatic invertebrate abundance and biomass – which can be expected to result in an increased abundances and biomass of fish. M. oxycarpum is present at elevated levels in South Stann Creek, Swasey Branch and Trio Branch, all of which drain areas of granite and metasediments, and can be expected to show far greater abundance of plant life than the phosphorus-poor Bladen Branch and Richardson Creek.
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This is a metal-poor cluster, meaning the stars have a low abundance of elements other than hydrogen and helium—what astronomers term metallicity. As recently as 1995, it was considered the most metal-poor globular cluster in the Milky Way. The chemical abundances of the stars in NGC 5053 are more similar to those in the dwarf galaxy Sagittarius Dwarf Spheroidal Galaxy than to the Milky Way halo. Along with the kinematics of the globular cluster, this suggests that NGC 5053 may have been stripped from the dwarf galaxy.
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Studies on which abiotic habitat characteristics are most strongly associated with Asian clam population abundance have produced varying results. Brazilian habitats have been found to have support the largest abundances of invasive Corbicula spp. in areas with coarser dominant sediment fractions, while negatively correlated with increasing levels of organic matter. Others studies have shown abiotic habitat characteristics such as water redox potential, inorganic nutrient content, hardness, and organic matter content in tandem with the amount of very course sand combine to explain 59.3% of Corbicula population habitat association via statistical tests.
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HD 197027 (HIP 102152) is a star in the constellation Capricornus that is located about 250 light years from the Sun. The measured properties of this star are very similar to those of the Sun, making it a candidate older solar twin.ESO, The life cycle of a Sun-like star (annotated), from European Southern Observatory, 28 August 2013 The abundances of 21 elements overall are more similar to the Sun than any other known solar twin. Additionally, the effective temperature, surface gravity, and microturbulence are nearly identical to the Sun's.
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Using the Big Bang model, it is possible to calculate the concentration of helium-4, helium-3, deuterium, and lithium-7 in the universe as ratios to the amount of ordinary hydrogen. The relative abundances depend on a single parameter, the ratio of photons to baryons. This value can be calculated independently from the detailed structure of CMB fluctuations. The ratios predicted (by mass, not by number) are about 0.25 for ^4He/H, about 10−3 for ^2H/H, about 10−4 for ^3He/H and about 10−9 for ^7Li/H.
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Reports of a third component of this system now appear doubtful. The primary component, 99 Herculis A, is an F-type main sequence star with a stellar classification of F7 V. It has 94% of the Sun's mass and nearly double the luminosity, but has an estimated 10% greater radius. The effective temperature of the star's outer atmosphere is 5,938 K, giving it a white-hued glow. This is a metal-poor star, showing overall abundances of elements—other than hydrogen or helium—equal to 60% of those in the Sun.
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At the 15 nm station the species ranged downward to the greatest depths; to the 120–160 m depth interval in the spring and to the 80–120 m depth interval in the fall. Clear evidence for nocturnal vertical migration was only seen in the spring at the 1-nm station (10-m depth interval tows were taken in the upper 100 m at this shallow-water station). Highest abundances were recorded between 60 and 30 m during the day to 30 m to the surface at night.
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Isotopic composition ranges overlap for primitive and differentiated rocks, indicating that the latter was derived from fractional crystallization of the primitive magmas. Xenolith abundance in the differentiated magma hint that fractional crystallization occurred within the mantle, below entrained peridotite. Due to this depth and the estimated speed of ascent, fractionation-elevated volatiles may have been important in driving the differentiated magmas to the surface. Partial melting in the mantle, or the progressive exhaustion of incompatible elements in the source, led to a decrease in abundances of these volatiles as the field evolved.
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Thalassodendron ciliatum has a wide distribution throughout the Indo-Pacific region, but has variable abundances throughout its range. This seagrass has been recorded from the western Philippines to Borneo and Singapore, Indonesia, Papua New Guinea, the Caroline Islands, Vanuatu, Australia, India and the Maldives. It is also common from the Gulf of Oman to the Red Sea down to South Africa, Madagascar, the Seychelles, the Comores, the Mascarenes and parts of Malesia and the Solomon Islands.seagrassrecovery.com date of access Wednesday, December 11, 2013 den Hartog, C. (1970) The sea- grasses of the world.
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Notices Roy. Astron. Soc., 234, 1–36 (1988) that the discord arose from inadequate treatments of both the history of star formation in the Galaxy and of the rate of infall of pristine metal- free gas onto the young Milky Way, compounded by a prevailing but erroneous technique for computation of the radioactive abundances within interstellar gas. Reasoning that interstellar gas contains a higher concentrations of shorter-lived radioactive nuclei than do the stars, Clayton invented in 1985 new mathematical solutions for the simplified differential equations of galactic abundance evolution that for the first time rendered these relationships understandable,Donald Clayton, “Galactic chemical evolution and nucleocosmochronology: A standard model”, in Challenges and New Developments in Nucleosynthesis, W. D. Arnett, W. Hillebrandt, and J. W. Truran, eds., University of Chicago Press, 65–88 (1984); “Nuclear cosmochronology within analytic models of the chemical evolution of the solar neighborhood”, Mon. Notices Roy. Astron. Soc., 234, 1–36 (1988); “Isotopic anomalies: Chemical memory of galactic evolution”, Astrophys. J., 334, 191–195, (1988) ending decades of poor reasoning about radioactive abundances. Clayton then calculated an age of 13-15 billion years for the oldest galactic nuclei, which would necessarily approximate the long-sought age of our galaxy.
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The nominal mass for an element is the mass number of its most abundant naturally occurring stable isotope, and for an ion or molecule, the nominal mass is the sum of the nominal masses of the constituent atoms. Isotope abundances are tabulated by IUPAC: for example carbon has two stable isotopes 12C at 98.9% natural abundance and 13C at 1.1% natural abundance, thus the nominal mass of carbon is 12. The nominal mass is not always the lowest mass number, for example iron has isotopes 54Fe, 56Fe, 57Fe, and 58Fe with abundances 6%, 92%, 10%, and 2%, respectively, and a nominal mass of 56 Da. For a molecule, the nominal mass is obtained by summing the nominal masses of the constituent elements, for example water has two hydrogen atoms with nominal mass 1 Da and one oxygen atom with nominal mass 16 Da, therefore the nominal mass of H2O is 18 Da. In mass spectrometry, the difference between the nominal mass and the monoisotopic mass is the mass defect. This differs from the definition of mass defect used in physics which is the difference between the mass of a composite particle and the sum of the masses of its constituent parts.
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To this end, the probe carried imaging devices that gathered much- higher-resolution images of much more of Mercury than , assorted spectrometers to determine abundances of elements in the crust, and magnetometers and devices to measure velocities of charged particles. Measurements of changes in the probe's orbital velocity were expected to be used to infer details of the planet's interior structure. MESSENGER final maneuver was on April 24, 2015, and it crashed into Mercury's surface on April 30, 2015. The spacecraft's impact with Mercury occurred near 3:26 PM EDT on April 30, 2015, leaving a crater estimated to be in diameter.
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Synechococcus has been observed to occur at concentrations ranging between a few cells to 106 cells per ml in virtually all regions of oceanic euphotic zone except in samples from the McMurdo Sound and Ross Ice Shelf in Antarctica. Cells are generally much more abundant in nutrient-rich environments than in the oligotrophic ocean and prefer the upper, well-lit portion of the euphotic zone. Synechococcus has also been observed to occur at high abundances in environments with low salinities and/or low temperatures. It is usually far outnumbered by Prochlorococcus in all environments where they co-occur.
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In the 1957 nuclear physics course at Caltech Clayton learned from William Alfred Fowler about a new theory that the chemical elements had been assembled within the stars by nuclear reactions occurring there. He was captivated for life by that idea. Clayton completed his Ph.D. Thesis in 1961 on the growth of the abundances of the heavy elements owing to the slow capture of free neutrons (the s process) by more abundant lighter elements in stars. Clayton and his wife Mary LouNote: Mary Lou Clayton was hired by Mathew Sands on the Ford Foundation project for these lectures.
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Mononuclidic elements are of scientific importance because their atomic weights can be measured to high accuracy, since there is minimal uncertainty associated with the isotopic abundances present in a given sample. Another way of stating this, is that, for these elements, the standard atomic weight and atomic mass are the same.N. E. Holden, "Standard Atomic Weight Values for the Mononuclidic Elements - 2001," BNL-NCS-68362, Brookhaven National Laboratory (2001) In practice, only 11 of the mononuclidic elements are used in standard atomic weight metrology. These are aluminium, bismuth, caesium, cobalt, gold, manganese, phosphorus, scandium, sodium, terbium, and thorium.
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The MISE design is an imaging infrared spectrometer that could observe effectively throughout a flyby or in orbit around Europa. It is designed to operate within Europa's harsh radiation environment. MISE would cover a spectral range from 0.8 μm to 5 μm (near infrared to mid-infrared), with an instantaneous field of view of 250 μrad/pixel and a swath width of 300 active pixels. The 0.8–2.5 μm region is essential for quantifying hydrates and bulk surface composition, while the 3–5 μm spectral region is required for detecting low abundances of organics, most radiolytic products, and discriminating salts from acid hydrates.
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13–15 In 1980, Voyager 1 made the first detailed observations of Titan's atmosphere, revealing that its surface pressure was higher than Earth's, at 1.5 bars (about 1.48 times that of Earth's).Coustenis, p. 22 The joint NASA/ESA Cassini-Huygens mission provided a wealth of information about Titan, and the Saturn system in general, since entering orbit on July 1, 2004. It was determined that Titan's atmospheric isotopic abundances were evidence that the abundant nitrogen in the atmosphere came from materials in the Oort cloud, associated with comets, and not from the materials that formed Saturn in earlier times.
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1H and 31P have near 100% natural abundance, while 13C and 15N have low natural abundances. For these latter two nuclei, there is the capability of isotopically enriching desired atoms within the molecules, either uniformly or in a site-specific manner. Nucleotides uniformly enriched in 13C and/or 15N can be obtained through biochemical methods, by performing polymerase chain reaction using dNTPs or NTPs derived from bacteria grown in an isotopically enriched environment. Site-specific isotope enrichment must be done through chemical synthesis of the labeled nucleoside phosphoramidite monomer and of the full strand; however these are difficult and expensive to synthesize.
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This object is classified as an Am star, or non-magnetic chemically peculiar star of the CP1 class, which means the spectrum displays abnormal abundances of certain heavier elements. It has a stellar classification of kA2hA6mA7, which means it has the calcium K line of an A2 class star, the Hydrogen lines of an A6 star, and the metal lines of an A7 star. 49 Arietis has a moderately high rate of spin, showing a projected rotational velocity of 52 km/s, and is radiating 15 times the luminosity of the Sun from its photosphere at an effective temperature of 8,424 K.
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This is a so-called mild barium star, as identified by the mild presence of an absorption line of singly-ionized barium atoms at a wavelength of 455.4 nm. Such stars display an atmospheric overabundance of carbon and the heavy elements produced by the s-process, which was most likely transferred into the atmosphere by a wide binary stellar companion. However, in the case of 24 Aquilae, the abundances of heavy elements are near normal. At an estimated age of a half billion years, 24 Aquilae is a giant star with a stellar classification of K0 IIIa.
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400 metres) during the day but rise to surface waters (10-100 metres) at night to feed and (presumably) to avoid predators. Ridgeheads feed primarily on zooplankton, such as copepods, euphausiids, and other small pelagic crustaceans. There is also a marked segregation of life stages: larval and juvenile ridgeheads are present within the upper 200 metres of the water column, whereas adults are typically found much farther down. The family is sometimes termed pseudoceanic because, rather than having an even distribution in open water, ridgeheads occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes.
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Shortly after the war, she taught astronomy at ULO to undergraduate students from across the University of London system, including Arthur C. Clarke who was then an undergraduate at King's College London. In 1951 she took a position at the University of Chicago's Yerkes Observatory, Wisconsin, her first job in the United States. Her research during this period focused on the abundances of chemical elements in stars. She returned to the UK in 1953, when Margaret and her husband Geoffrey Burbidge were invited to work with William Alfred Fowler and Fred Hoyle at the University of Cambridge.
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Between 1 and 100 GeV, PAMELA is exposed to one hundred times as many electrons as antiprotons. At 1 GeV there are one thousand times as many protons as positrons and at 100 GeV ten thousand times as many. Therefore, to correctly determine the antimatter abundances, it is critical that PAMELA is able to reject the matter background. The PAMELA collaboration claimed in "The electron hadron separation performance of the PAMELA electromagnetic calorimeter" that less than one proton in 100,000 is able to pass the calorimeter selection and be misidentified as a positron when the energy is less than 200 GeV.
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Tagging of Pacific Predators (TOPP) began in 2000 as one of many projects formed by Census of Marine Life, an organization whose goal is to help understand and explain the diversity and abundances of the ocean in the past, present, and future. After they were formed, TOPP began by building a coalition of researchers from all over the world to find and study predators of the Pacific Ocean. Since then, they have satellite-tagged 22 different species and more than 2,000 animals. These animals include elephant seals, great white sharks, leatherback turtles, squid, albatrosses, and more.
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The subsequent years saw the resolution of the solar neutrino problem, and the long seismic observations began to allow analysis of multiple solar activity cycles. The agreement between standard solar models and helioseismic inversions was disrupted by new measurements of the heavy element content of the solar photosphere based on detailed three-dimensional models. Though the results later shifted back towards the traditional values used in the 1990s, the new abundances significantly worsened the agreement between the models and helioseismic inversions. The cause of the discrepancy remains unsolved and is known as the solar abundance problem.
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Bacteria belonging to the genus Sulfurimonas are in competition with other sulfate-oxidizing bacteria (SOB) for nutritional resources, and have been studied intensively due to their importance in the petroleum industry. SOB communities constitute physiologically diverse members of Epsilonproteobacteria, which contains the genera Sulfurimonas, Chlorobia, and Chloroflexi. All of these genera are found in petroleum reservoirs, and Sulfurimonas are present in high abundances. Members of this genus occupied approximately 26% of reservoirs, all of which differ in temperature and relative proportions of other SOB, which is further an indication that this genus is capable of growth at a wide range of temperatures.
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Orgueil is one of five known meteorites belonging to the CI chondrite group (see meteorites classification), and is the largest (). This group is remarkable for having a composition that is essentially identical to that of the sun, excluding gaseous elements like hydrogen and helium. Notably though, the Orgueil meteor is highly enriched in (volatile) mercury - undetectable in the solar photosphere, and this is a major driver of the "mercury paradox" that mercury abundances in meteors do not follow its volatile nature and isotopic ratios based expected behaviour in the solar nebula Lauretta, D.S., Devouard, B., Buseck, P.R., (1999). The cosmochemical behavior of mercury.
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The APO Galactic Evolution Experiment (APOGEE) used high-resolution, high signal-to-noise infrared spectroscopy to penetrate the dust that obscures the inner Galaxy. APOGEE surveyed 100,000 red giant stars across the full range of the galactic bulge, bar, disk, and halo. It increased the number of stars observed at high spectroscopic resolution (R ~ 20,000 at λ ~ 1.6μm) and high signal-to-noise ratio (S/N ~ 100) by more than a factor of 100. The high resolution spectra revealed the abundances of about 15 elements, giving information on the composition of the gas clouds the red giants formed from.
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It displays a mild overabundance of the element barium, which is hypothesized to have been accreted when an unresolved white dwarf companion was passing through the asymptotic giant branch (RGB) stage. The visible component displays significant overabundances of three s-process peak elements that are generated during the RGB phase, as well as a mild overabundance of carbon. In contrast, it shows severe depletion of lithium and beryllium, as well as a notable underabundance of boron. The surface abundances of these lighter elements may have been altered during the mass transfer process, having been previously consumed in the core region of the companion.
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Good was also elected President of the inorganic chemistry division of the International Union of Pure and Applied Chemistry (IUPAC) in 1981, and held the position until 1985, for two terms. She was the first woman to be elected a division head of IUPAC. As head of the inorganic chemistry division, she was responsible for overseeing the work of the commissions on nomenclature for inorganic chemistry; the Commission on Isotopic Abundances and Atomic Weights, and the commission on high temperatures and refractory materials. Her work included supervising a complete revision of the IUPAC nomenclature of inorganic chemistry or "Red Book".
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Comparability, simplicity and economy were the main considerations in designing GLORIA's standard recording design and method (Multi-Summit Approach), in order to build a world-wide network of operable sites. In each study region (target region) a suite of four monitoring locations in summit areas at different altitudes represents an elevation gradient from the treeline ecotone to the upper limits of plant life. At each location, vascular plant species and abundances are to be recorded in standardized permanent plots of different size at intervals of 5 to 10 years, along with continuous measurements of soil temperature. Several supplementary approaches, e.g.
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The definition of preference will therefore impact on understanding switching. The most common definition of preference is the relationship between the ratio of prey in the environment and the ratio of prey in a predator's diet. It has been independently proposed a number of times and is described by the equation: ::P1/P2 = c (N1/N2); alternatively, c = (P1/P2)/(N1/N2) where N1 and N2 are the abundance of prey types 1 and 2 in the environment and P1 and P2 are the abundances of the same prey types in the predator's diet. c is the preference for prey type 1.
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Sediments from a gravity core taken in 2010 in the rift valley on the Knipovich ridge in the Arctic Ocean, near the so-called Loki's Castle hydrothermal vent site, were analysed. Specific sediment horizons, previously shown to contain high abundances of novel archaeal lineages were subjected to metagenomic analysis. Due to the low density of cells in the sediment, the resulting genetic sequence does not come from an isolated cell, as would be the case in conventional analysis, but is rather a combination of genetic fragments. The result was a 92% complete, 1.4 fold-redundant composite genome named Lokiarchaeum.
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Over 1500 non-mineralized specimens, representing 50 distinct taxa that have a composition similar to earlier Burgess Shale type biotas, have been recovered from the formations in addition to a less abundant shelly fauna. The make-up of the community varies significantly through the stratigraphic sequence, with both abundances and faunal composition changing as time progresses. Small (1-3 mm wide) burrows are present in the sediment, but major burrowing is absent; this may suggest a paucity of oxygen in the water or sediment. Particularly notable is the presence of bryozoa and graptolites, forms that are absent in the Cambrian period.
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Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure free element in nature. It is most widely distributed in dusts, sands, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. Over 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass) after oxygen.Nave, R. Abundances of the Elements in the Earth's Crust, Georgia State University Most silicon is used commercially without being separated, and indeed often with little processing of compounds from nature.
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In a study by Stokes et al., habitats suitable for the native bush rat, Rattus fuscipes, of Australia are often invaded by the black rat and are eventually occupied by only the black rat. When the abundances of these two rat species were compared in different micro-habitats, both were found to be affected by micro-habitat disturbances, but the black rat was most abundant in areas of high disturbance; this indicates it has a better dispersal ability. Despite the black rat's tendency to displace native species, it can also aid in increasing species population numbers and maintaining species diversity.
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In the summer of 2010, sediments from a gravity core taken in the rift valley on the Knipovich ridge in the Arctic Ocean, near the so-called Loki's Castle hydrothermal vent site, were analysed. Specific sediment horizons previously shown to contain high abundances of novel archaeal lineages, were subjected to metagenomic analysis. In 2015, an Uppsala University-led team proposed the Lokiarchaeota phylum based on phylogenetic analyses using a set of highly conserved protein-coding genes. Through a reference to the hydrothermal vent complex from which the first genome sample originated, the name refers to Loki, the Norse shape-shifting god.
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He subsequently applied this expertise to a study of the stability of stellar magnetic fields and to the interaction of rotation and magnetic fields with convection. In cosmology, he calculated (with Hoyle) the cosmic helium abundance, stressing the importance of the number of neutrino types, and he pointed out the significance of the neutron half-life. In nucleosynthesis he calculated the abundances of iron peak elements produced at high temperatures, and recently he has been deeply involved with the chemical evolution of galaxies. He has written substantial and penetrating review articles, and text-books used the world over.
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The sulfate levels in the Proterozoic also act as proxies for atmospheric oxygen because sulfate is produced mostly through weathering of the continents in the presence of oxygen. The low levels in the Proterozoic simply imply that levels of atmospheric oxygen fell between the abundances of the Phanerozoic and the deficiencies of the Archean. 750 million years ago (Ma) there is a renewed deposition of BIF which marks a significant change in ocean chemistry. This was likely due to snowball earth episodes where the entire globe including the oceans was covered in a layer of ice cutting off oxygenation.
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In one version of the laser spray interface, explosive vaporization and mist formation occur when an aqueous solution effusing from the tip of the stainless steel capillary is irradiated from the opposite side of the capillary by a 10.6 μm infrared laser. Weak ion signals could be detected when the plume was sampled through the ion sampling orifice. When a high voltage (3–4 kV) was applied to the stainless-steel capillary, strong ion signals appeared. The ion abundances were found to be orders of magnitude greater than those obtained by conventional electrospray ionization in the case of aqueous solutions.
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Since the tags are isobaric and have identical chemical properties, the isotopic variants of the tags appear as a single composite peak at the same m/z value in an MS1 scan with identical liquid chromatography (LC) retention times. During a liquid chromatography-mass spectrometry (LC-MS) analysis, the fragmented peptides produce sequence- specific product ions. These product ions are used to determine the peptide sequence and the reporter tags whose abundances reflect the relative ratio of the peptide in the samples that were combined. The use of MS/MS is required to detect the tags, therefore, unlabeled peptides are not quantitated.
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Using the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory, Lopez observed the Galactic supernova remnant (SNR) W49B to understand the thermodynamic properties and explosive origin of the SNR. The observed electron temperature and absorbing column toward W49B suggest that the mean metal abundances are consistent with the predicted yields in models of bipolar/jet-driven core- collapse SNe. W49B is thus likely a bipolar Type Ib/Ic SN, making it the first of its kind to be discovered in the Milky Way. Lopez is interested in diversity in astronomy and is an advocate of the LGBTIQ astronomical community.
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In the latest stages of mass loss, before a star explodes, surface helium may become enriched to levels comparable with hydrogen. In theoretical extreme mass loss models, sufficient hydrogen may be lost that helium becomes the most abundant element at the surface. When pre-red supergiant stars leave the main sequence, oxygen is more abundant than carbon at the surface, and nitrogen is less abundant than either, reflecting abundances from the formation of the star. Carbon and oxygen are quickly depleted and nitrogen enhanced as a result of the dredge-up of CNO-processed material from the fusion layers.
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Theoretical work simultaneously also showed that ancient MACHOs are not likely to account for the large amounts of dark matter now thought to be present in the universe.Katherine Freese, Brian Fields, and David Graff, Limits on stellar objects as the dark matter of our halo: nonbaryonic dark matter seems to be required. The Big Bang as it is currently understood could not have produced enough baryons and still be consistent with the observed elemental abundances,Brian Fields, Katherine Freese, and David Graff, Chemical abundance constraints on white dwarfs as halo dark matter, Astrophys. J. 534:265-276,2000.
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Specifically predicting that: temporal variation might structure the cestode community, the most common cestode species in brine shrimp would be those that used the most common bird species as final hosts and that temporal variation in Artemia would track changes in abundance of their final host. Seasonal patterns of infection of F. liguloides showed to have the highest prevalence in June and the lowest in December. Although the waterbird biomass was correlated to strong seasonal patterns, the actual transmission from birds or the removal of infected shrimp showed no significant effect. There was also no clear relationship between cestode and final host abundances.
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This may indicate that even the ice-planetesimals which brought neon into Jupiter from the outer solar system, formed in a region which was too warm to retain the neon atmospheric component (abundances of heavier inert gases on Jupiter are several times that found in the Sun). Neon comprises 1 part in 55,000 in the Earth's atmosphere, or 18.2 ppm by volume (this is about the same as the molecule or mole fraction), or 1 part in 79,000 of air by mass. It comprises a smaller fraction in the crust. It is industrially produced by cryogenic fractional distillation of liquefied air.
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The brown pelican abundance has steadily recovered from the drastic population decreases in the 1940s, however bottom up control threatens the Southern California populations as food sources become diminished. It is common for forage fish populations to experience regular fluctuations, however there has been a consistent decrease in the Pacific sardine population beginning as early as 2014. In 2019 these declines were found to have reached levels which were a mere 10% of the highest reported abundances. Fluctuations in sardine populations have largely been attributed to bottom-up control, primarily including climate variability and ocean temperature.
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However, there have been other reports of detection of methane by ground-based telescopes and Curiosity rover. Trace amounts of methane, at the level of several ppb, were first reported in Mars's atmosphere by a team at the NASA Goddard Space Flight Center in 2003. Large differences in the abundances were measured between observations taken in 2003 and 2006, which suggested that the methane was locally concentrated and probably seasonal. In 2014, NASA reported that the Curiosity rover detected a tenfold increase ('spike') in methane in the atmosphere around it in late 2013 and early 2014.
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Brown dwarfs would not be stable in such a configuration. The best accepted value for an age of HR 8799 is 30 million years, consistent with being a member of the Columba association co- moving group of stars. Earlier analysis of the star's spectrum reveals that it has a slight overabundance of carbon and oxygen compared to the Sun (by approximately 30% and 10% respectively). While some Lambda Boötis stars have sulfur abundances similar to that of the Sun, this is not the case for HR 8799; the sulfur abundance is only around 35% of the solar level.
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CIA is also important in low-metallicity brown dwarfs, since "low metallicity" means reduced CNO (and other) elemental abundances compared to H2 and He, and thus stronger CIA compared to H2O, CO, and CH4 absorption. CIA absorption of H2-X collisional complexes is thus an important diagnostic of high-gravity and low- metallicity brown dwarfs. All of this is also true of the M dwarfs, but to a lesser extent. M dwarf atmospheres are hotter so that some increased portion of the H2 molecules is in the dissociated state, which weakens CIA by H2\--X complexes.
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The rates of the various nuclear reactions are estimated from particle physics experiments at high energies, which are extrapolated back to the lower energies of stellar interiors (the Sun burns hydrogen rather slowly). Historically, errors in the nuclear reaction rates have been one of the biggest sources of error in stellar modelling. Computers are employed to calculate the varying abundances (usually by mass fraction) of the nuclear species. A particular species will have a rate of production and a rate of destruction, so both are needed to calculate its abundance over time, at varying conditions of temperature and density.
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Once normalized, a direct comparison of relative transcript abundances across multiple samples of mRNA can be made. One precaution to note is that the internal control must be chosen so that it is not affected by the experimental treatment. The expression level should be constant across all samples and with the mRNA of interest for the results to be accurate and meaningful. Because the quantification of the results are analyzed by comparing the linear range of the target and control amplification, it is crucial to take into consideration the starting target molecules concentration and their amplification rate prior to starting the analysis.
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Sulfur is strongly siderophilic and only moderately volatile and depleted in the silicate earth; thus may account for 1.9 weight % of Earth's core. By similar arguments, phosphorus may be present up to 0.2 weight %. Hydrogen and carbon, however, are highly volatile and thus would have been lost during early accretion and therefore can only account for 0.1 to 0.2 weight % respectively. Silicon and oxygen thus make up the remaining mass deficit of Earth's core; though the abundances of each are still a matter of controversy revolving largely around the pressure and oxidation state of Earth's core during its formation.
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The process is slow (hence the name) in the sense that there is sufficient time for this radioactive decay to occur before another neutron is captured. A series of these reactions produces stable isotopes by moving along the valley of beta-decay stable isobars in the table of nuclides. A range of elements and isotopes can be produced by the s-process, because of the intervention of alpha decay steps along the reaction chain. The relative abundances of elements and isotopes produced depends on the source of the neutrons and how their flux changes over time.
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The main output from the QIIME pipeline is a feature table, which describes the abundances of each OTU or sequence variant in each sample. Additional tools that are relevant to ecological aspects of the samples being investigated are also provided within the pipeline, including rarefaction, alpha diversity and beta diversity calculations, visualizations such as principle coordinates analysis (PCoA) and much more. QIIME presents a very modular approach and allows multiple methods to be applied in many stages of the analysis. For example, the stage of sequences clustering can be performed using either UCLUST, CD-HIT, BLAST and more.
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The atomic mass, on the other hand, is measured using the atomic mass unit based on the mass of the carbon-12 atom. It is denoted with symbols "u" (for unified atomic mass unit) or "Da" (for dalton). The atomic masses of naturally occurring isotopes of an element determine the atomic mass of the element. When the element contains N isotopes, the expression below is applied for the average atomic mass \overline m_a: \overline m_a = m_1 x_1+m_2 x_2+...+m_Nx_N where m1, m2, ..., mN are the atomic masses of each individual isotope, and x1, ..., xN are the relative abundances of these isotopes.
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The seventh-magnitude companion, HD 36485, is a chemically peculiar B-type main-sequence star and itself a spectroscopic binary with a faint A-type companion in a 30-day orbit. It has an unusual spectrum with H-alpha emission and unusually strong helium absorption lines. It has a strong magnetic field and a very slow rotational velocity that produces chemical stratification in its atmosphere, which leads to the unusual abundances seen in the spectrum. The 14th magnitude companion is thought to be around the same distance and is a somewhat cooler and less luminous star than the Sun.
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Less than 1% of zircons detected around the world are over four billion years old. The probability of discovering at least a single over four billion-year-old zircon is very low. The abundance of over four billion-year-old zircon in the Jack Hills is anomalously high for most Archean quartzites and thus abundances probabilities of other spots are extremely low (between 0.2-0.02%).Harrison, T., Blichert- Toft, J., Mueller, W., Albarede, F., Holden, P., & Mojzsis, S. (2005). Heterogeneous Hadean hafnium; evidence of continental crust at 4.4 to 4.5 Ga. Science, 310(5756), 1947-1950.
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In a subsidy cascade, species populations at one trophic level can be supplemented by external food. For example, native animals can forage on resources that don't originate in their same habitat, such a native predators eating livestock. This may increase their local abundances thereby affecting other species in the ecosystem and causing an ecological cascade. For example, Luskin et al (2017) found that native animals living in protected primary rainforest in Malaysia found food subsidies in neighboring oil palm plantations. This subsidy allowed native animal populations to increase, which then triggered powerful secondary ‘cascading’ effects on forest tree community.
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Elliptical galaxy NGC 4889 in front of hundreds of background galaxies. Giant elliptical galaxies like NGC 4889 are believed to be the result of multiple mergers of smaller galaxies. There is now little dust remaining to form the diffuse nebulae where new stars are created, so the stellar population is dominated by old, population II stars that contain relatively low abundances of elements other than hydrogen and helium. The egg- like shape of this galaxy is maintained by random orbital motions of its member stars, in contrast to the more orderly rotational motions found in a spiral galaxy such as the Milky Way.
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The system shows the high velocity kinematic properties of a population II star, but has Sun-like abundances of most elements. This is a probable astrometric binary system with poorly constrained orbital elements. The visible member, component A, is an evolved K-type giant star with a stellar classification K2 III At about 10.6 billion years of age, it has nearly the same mass as the Sun but has expanded to five times the Sun's radius. The star shines with 21 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,491 K.
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Excesses of the decay products of the longer lived, but extinct, nuclides calcium-41 (half-life 99,400 years) and aluminium-26 (730,000 years) have also been detected in such grains. The rapid-process isotopic anomalies of these grains include relative excesses of nitrogen-15 and oxygen-18 relative to Solar System abundances, as well as excesses of the neutron-rich stable nuclides 42Ca and 49Ti. page 139 Other presolar grains (AGB star grains) provide isotopic and physical information on asymptotic giant branch stars, which have manufactured the largest portion of the refractory elements lighter than iron in the galaxy.
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Despite vigorous and continuous active development of this picture, Clayton's suggestions lay unsupported by others for a decade until such grains were discovered within meteorites. The first unambiguous consequence of the existence of stardust within meteorites came from the laboratory of Edward Anders in Chicago,B. Srinivasan and E. Anders, Science 201, 51-56 (1978) who found using traditional mass spectrometry that the xenon isotopic abundances contained within an acid-insoluble carbonaceous residue that remained after the meteorite bulk had been dissolved in acids matched almost exactly the predictions for isotopic xenon in red giant stardust.
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Presolar grains are the solid matter that was contained in the interstellar gas before the Sun formed. The stardust component can be identified in the laboratory by their abnormal isotopic abundances and consists of refractory minerals which survived the collapse of the solar nebula and the subsequent formation of planetesimals.Maria Lugaro (2005) Stardust from meteorites: An introduction to presolar grains (World Scientific, NY) To meteorite researchers, the term presolar grains has come to mean presolar grains found in meteorites, which consist overwhelmingly of stardust. Many other types of cosmic dust have not been detected in meteorites.
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Apparent competition is actually an example of predation that alters the relative abundances of prey on the same trophic level. It occurs when two or more species in a habitat affect shared natural enemies in a higher trophic level. If two species share a common predator, for example, apparent competition can exist between the two prey items in which the presence of each prey species increases the abundance of the shared enemy, and thereby suppresses one or both prey species. This mechanism gets its name from experiments in which one prey species is removed and the second prey species increases in abundance.
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The authors invoke nuclear physics processes, now known as the p-process, r-process, and s-process, to account for the elements heavier than iron. The abundances of these heavy elements and their isotopes are roughly 100,000 times less than those of the major elements, which supported Hoyle's 1954 hypothesis of nuclear fusion within the burning shells of massive stars. B2FH comprehensively outlined and analyzed the nucleosynthesis of the elements heavier than iron by the capture within stars of free neutrons. It advanced much less the understanding of the synthesis of the very abundant elements from silicon to nickel.
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For example, one model mixes two components, one with the composition of C1 chondrites and one with just the refractory components of C1 chondrites. In another model, the abundances of the five fractionation groups are estimated using an index element for each group. For the most refractory group, uranium is used; iron for the second; the ratios of potassium and thallium to uranium for the next two; and the molar ratio FeO/(FeO+MgO) for the last. Using thermal and seismic models along with heat flow and density, Fe can be constrained to within 10 percent on Earth, Venus and Mercury.
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The existence of other galaxies, one of the matters of the great debate, was settled by Edwin Hubble, who identified the Andromeda nebula as a different galaxy, and many others at large distances and receding, moving away from our galaxy. Physical cosmology, a discipline that has a large intersection with astronomy, made huge advances during the 20th century, with the model of the hot Big Bang heavily supported by the evidence provided by astronomy and physics, such as the redshifts of very distant galaxies and radio sources, the cosmic microwave background radiation, Hubble's law and cosmological abundances of elements.
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At times, the alga Dunaliella salina can also proliferate in this environment. A comparatively wide range of taxa has been isolated from saltern crystalliser ponds, including members of these genera: Haloferax, Halogeometricum, Halococcus, Haloterrigena, Halorubrum, Haloarcula, and Halobacterium. However, the viable counts in these cultivation studies have been small when compared to total counts, and the numerical significance of these isolates has been unclear. Only recently has it become possible to determine the identities and relative abundances of organisms in natural populations, typically using PCR-based strategies that target 16S small subunit ribosomal ribonucleic acid (16S rRNA) genes.
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This work resulted in the birth of the field(s) of phosphaalkene and phosphaalkyne chemistry. These species contain carbon double and triple bonded to phosphorus (C=P and C≡P) such as cyanophosphaethyne. In 1975, he became a full professor of Chemistry. This coincided with laboratory microwave measurements with Sussex colleague David Walton on long linear carbon chain molecules, leading to radio astronomy observations with Canadian astronomers revealing the surprising fact that these unusual carbonaceous species existed in relatively large abundances in interstellar space as well as the outer atmospheres of certain stars – the carbon-rich red giants.
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Therefore, subaqueous silicic pyroclastic eruptions may be diminished in the course size fraction as well as the very fine ash size fraction based on the buoyancy of the material in the water medium. These characteristics may be important in determining the style of subaqueous eruption and emplacement mechanism. The characteristics of texture, such as grain morphology and grain size abundances can also provide knowledge on the process of controlling the eruption style or transport/flow properties, whether turbulent or laminar. Seafloor exploration has discovered that more volcanic eruptions occur at the bottom of the sea than on land.
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Biolink zones are a land use category developed for biodiversity conservation and landscape adaptation under changing climates. Biolink zone was first coined in 1992 to encapsulate a potential new land-use resulting from research on vertebrate fauna of se Australia and their prospective responses to climate change (Bennett et al. 1992, Brereton et al.1995). Biolink zones are identified parts of the landscape where the functional ecological connectivity for biodiversity is enhanced and / or restored to provide space for species (and consequently ecological communities) to self adapt their distributions and abundances under changing climates through natural processes including: dispersal; re-colonisation; regeneration and restoration of ecological function (Mansergh and Cheal 2007).
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Vertical profiles are strongly influenced by hydrologic conditions and can be very variable both seasonally and spatially. Overall, Synechococcus abundance often parallels that of Prochlorococcus in the water column. In the Pacific high- nutrient, low-chlorophyll zone and in temperate open seas where stratification was recently established both profiles parallel each other and exhibit abundance maxima just about the subsurface chlorophyll maximum. The factors controlling the abundance of Synechococcus still remain poorly understood, especially considering that even in the most nutrient-depleted regions of the central gyres, where cell abundances are often very low, population growth rates are often high and not drastically limited.
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J. Letters, 399, L137 (1992) (by OSSE with Clayton a coauthor) thereby establishing this field of astronomy. CGRO, the space gamma-ray telescope mission that detected several predicted gamma-ray lines, was the second mission of NASA’s Great Observatories program. In 1977 at Rice University Clayton had been named Co-Investigator for the NASA-approved proposal for the OSSE spectrometer on CGRO, and in 1982 he summarized physical expectations for several gamma-ray-line emitting young nuclei. Key to the intense supernova radioactivity had been Clayton's 1967 discovery that rapid-silicon-burning was dominated by abundances of radioactive alpha-particle nuclei (those having equal numbers of protons and neutronsPhys. Rev. Lett.
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Notices Roy. Astron. Soc., 234, 1-36 (1988); “On 26Al and Other Short-lived Interstellar Radioactivity”, Astrophys. J. (Letters) 415, L25–L29 (1993)] For scientific studies of the identities and the initial abundances of short-lived radioactive nuclei that remained alive at differing concentrations within the interstellar gas cloud that formed the solar system, but which are now extinct in the solar system, Clayton's factor (k+1) has grown in importance owing to experimental discoveries of many such nuclei within the meteorites. These are called the extinct radioactivities because none remain on earth today but which did leave clear evidence of their prior existence in meteorites.
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Hence, spherical atoms are those of the 1st, 2nd, 7th, 12th, 15th and 18th columns of the periodic table. At Kiel, Unsöld made an intensive study of the effects of abundances, radiation damping, Doppler shifts, electric fields, and collisions on the formation and shape of spectral lines in stellar atmospheres. His analysis of the B0 star Tau Scorpii, obtained on his 1939 visit to Yerkes and McDonald Observatories, provided the first detailed analysis of a star other than the Sun, and he was able to determine the physics and composition of the star’s atmosphere.Unsöld – 1956 Bruce Medalist From 1947 to 1948, Unsöld was President of the Astronomische Gesellschaft.
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The species is found in Brazil, Colombia, Venezuela, Ecuador and Peru; also the Guianas: Guyana, Suriname, and French Guiana. Its natural habitat is tropical moist lowland rainforests. The white-plummed antbird appears in higher abundances in forests with high canopies, high vegetation complexity and many plant species In the Amazon Basin proper, except in the headwaters of central Peru, the white-plumed antbird is found only north of the Amazon River, in the northeast (Guianas) and in the northwest, from Amapa and Cayenne westward to the Andes from southern Venezuela to northern Peru. They have been found at elevations of up to elevation (Mt.
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The presence of a significant atmosphere was first suspected by Spanish astronomer Josep Comas i Solà, who observed distinct limb darkening on Titan in 1903, and confirmed by Gerard P. Kuiper in 1944 using a spectroscopic technique that yielded an estimate of an atmospheric partial pressure of methane of the order of 100 millibars (10 kPa). Subsequent observations in the 1970s showed that Kuiper's figures had been significant underestimates; methane abundances in Titan's atmosphere were ten times higher, and the surface pressure was at least double what he had predicted. The high surface pressure meant that methane could only form a small fraction of Titan's atmosphere.Coustenis, pp.
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The alterations in diversity of various marine invertebrate species such as calcareous nannofossils indicate a time when the oceans were warm and oligotrophic, in an environment with short spikes of productivity followed by long periods of low fertility. A study performed in the Cenomanian-Turonian boundary of Wunstorf, Germany, reveal the uncharacteristic dominance of a calcareous nannofossil species, Watznaueria, present during the event. Unlike the Biscutum species, which prefer mesotrophic conditions and were generally the dominant species before and after the C/T boundary event; Watznaueria species prefer warm, oligotrophic conditions. At the time, there were also peak abundances of green algal groups Botryococcus and prasinophytes, coincident with pelagic sedimentation.
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The solar wind had a velocity at the time of about , at which speed it would have taken eight days for the tail to be carried out to where the spacecraft was situated at 3.73 AU, approximately 45 degrees out of the ecliptic plane. The orientation of the ion tail inferred from the magnetic field measurements agreed with the source lying in Comet Hyakutake's orbital plane. The other team, working on data from the spacecraft's ion composition spectrometer, discovered a sudden large spike in detected levels of ionised particles at the same time. The relative abundances of chemical elements detected indicated that the object responsible was definitely a comet.
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A chemical equilibrium program normally does not require chemical formulas or reaction-rate equations. The program works by preserving the original elemental abundances specified for the gas and varying the different molecular combinations of the elements through numerical iteration until the lowest possible Gibbs free energy is calculated (a Newton- Raphson method is the usual numerical scheme). The data base for a Gibbs free energy program comes from spectroscopic data used in defining partition functions. Among the best equilibrium codes in existence is the program Chemical Equilibrium with Applications (CEA) which was written by Bonnie J. McBride and Sanford Gordon at NASA Lewis (now renamed "NASA Glenn Research Center").
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The capacity of canyons to focus and concentrate organic matter can promote high abundances and diversity of fauna. However, variability in environmental conditions and topography is very high, both within and between canyons, and this is reflected in the variability of the structure and dynamics of the biological communities.Pattenden (2009) "The influence of submarine canyons on the structure and dynamics of megafauna communities" PhD Thesis, University of Southampton Our understanding of biological processes in canyons has greatly improved with the use of submersibles and ROVs, but this research has also revealed that the relationships between fauna and canyons are more complex than previously thought.Garcia et al. (2007).
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Some of the places where plasma cosmology supporters are most at odds with standard explanations include the need for their models to have light element production without Big Bang nucleosynthesis, which, in the context of Alfvén–Klein cosmology, has been shown to produce excessive X-rays and gamma rays beyond that observed. point out that if proton fluxes with energies greater than 500 MeV were intense enough to produce the observed levels of deuterium, they would also produce about 1000 times more gamma rays than are observed. Plasma cosmology proponents have made further proposals to explain light element abundances, but the attendant issues have not been fully addressed.Ref.
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He is a Distinguished Alumnus of Flint (Michigan) Northern High School (2001) and of the Astronomy Department of the University of Michigan (2013). Known in the field of extragalactic astronomy for his early work on Low Surface Brightness Galaxies and the elemental abundances in HII Regions, McGaugh has also contributed to the study of the kinematics of galaxies, being among the first to point out that low surface brightness galaxies are dark matter dominated and that they pose the cuspy halo problem. He also coined the expression "baryonic Tully–Fisher relation." He predicted the first to second peak amplitude ratio of the acoustic power spectrum of the Cosmic microwave background radiation.
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The alpha-scattering surface analyzer was designed to measure directly the abundances of the major elements of the lunar surface. The instrumentation consisted of an alpha source (curium 242) collimated to irradiate a 10 mm diameter opening in the bottom of the instrument where the sample was located and two parallel but independent charged particle detector systems. One system, containing two sensors, detected the energy spectra of the alpha particles scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the protons produced via reaction (alpha and proton) in the surface material. Each detector assembly was connected to a pulse height analyzer.
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The biosynthesis of fatty acids begins with acetyl-CoA precursors that are brought together to make long straight chain lipids. Acetyl-CoA is produced in aerobic organisms by pyruvate dehydrogenase, an enzyme that has been shown to express a large, 2.3% isotope effect on the C2 site of pyruvate and a small fractionation on the C3 site. These become the odd and even carbon positions of fatty acids respectively and in theory would result in a pattern of 13C depletions and enrichments at odd and even positions, respectively. In 1982, Monson and Hayes developed technology for measuring the position specific carbon isotope abundances of fatty acids.
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SRM can be used for targeted quantitative proteomics by mass spectrometry. Following ionization in, for example, an electrospray source, a peptide precursor is first isolated to obtain a substantial ion population of mostly the intended species. This population is then fragmented to yield product ions whose signal abundances are indicative of the abundance of the peptide in the sample. This experiment can be performed on triple quadrupole mass spectrometers, where mass-resolving Q1 isolates the precursor, q2 acts as a collision cell, and mass-resolving Q3 is cycled through the product ions which are detected upon exiting the last quadrupole by an electron multiplier.
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Mineral abundances within the paleosols show olivine weathering to smectite and a modest depletion of phosphorus. Such hydrolytic weathering is comparable to weathering found on Earth. The chemical and morphological features of the Yellowknife Bay paleosols are a new line of evidence for late Noachian (3.7 ± 0.3 Ga) paleoclimate on Mars, and are interpreted as forming under a hyperarid frigid paleoclimate. Radiometric dating suggests the paleosols at Yellowknife Bay are 3.7 billion years old (± 0.3 billion years) and reveal a change from possible "warm and wet" conditions of the Early Noachian (~4.1-3.9 Ga) to an extreme arid and cold climate with limited soil formation.
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The mixing ratio is much lower in the upper atmosphere due to the extremely low temperature at the tropopause, which lowers the saturation level and causes excess methane to freeze out. Methane appears to be undersaturated in the upper troposphere above the clouds having a partial pressure of only 30% of the saturated vapor pressure there. The concentration of less volatile compounds such as ammonia, water and hydrogen sulfide in the deep atmosphere is poorly known. However, as with methane, their abundances are probably greater than solar values by a factor of at least 20 to 30, and possibly by a factor of a few hundred.
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It is now a red clump star which is fusing helium to carbon and oxygen in its core, a process that has not yet begun for the less massive star. Detailed analysis shows that it is nearing the end of this stage and starting to expand again which will lead it to the asymptotic giant branch. Isotope abundancesThe lithium abundance, C12/C13 ratio and C/N ratio have all declined in Capella Aa but not in Capella Ab. and spin rates confirm this evolutionary difference between the two stars. Heavy element abundances are broadly comparable to those of the Sun and the overall metallicity is slightly less than the Sun's.
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A dredge-up is a period in the evolution of a star where a surface convection zone extends down to the layers where material has undergone nuclear fusion. As a result, the fusion products are mixed into the outer layers of the stellar atmosphere where they can appear in the spectrum of the star. The first dredge-up occurs when a main-sequence star enters the red-giant branch. As a result of the convective mixing, the outer atmosphere will display the spectral signature of hydrogen fusion: the 12C/13C and C/N ratios are lowered, and the surface abundances of lithium and beryllium may be reduced.
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The presence of somewhat unequal pit house sizes, storage pits, as well as differences in the type and quality of dietary and lithic (stone tool) remains, have meant that Keatley Creek has become an important archaeological site in debates about the development of social inequality. Initial research formulated that "mass harvest and storage permitted sedentismand inequality in natural abundances led to social inequalities." Certainly, winter survival relied on extensive use of food storage, which became all the more real as the population of Keatley Creek grew. Storage technologies in the mid-Fraser were varied and included cache pits, above- ground facilities, baskets, and cords.
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Robert Michael Rich (born 1957) is an American astrophysicist. He obtained his B.A. at Pomona College in 1979 and earned his Ph.D. from the California Institute of Technology in 1986 under thesis supervisor Jeremy R. Mould. He was a Carnegie Fellow at Carnegie/DTM until 1988 when he joined the faculty of Columbia University where he was the doctoral thesis adviser to Neil deGrasse Tyson, and is on the faculty of the University of California, Los Angeles. Rich is known for his work on the Galactic bulge, including the first measurement of the distribution of stellar abundances and the first map of the bulge stellar kinematics.
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That fusion process essentially shut down at about 20 minutes, due to drops in temperature and density as the universe continued to expand. This first process, Big Bang nucleosynthesis, was the first type of nucleogenesis to occur in the universe, creating the so-called primordial elements. A star formed in the early universe produces heavier elements by combining its lighter nucleihydrogen, helium, lithium, beryllium, and boronwhich were found in the initial composition of the interstellar medium and hence the star. Interstellar gas therefore contains declining abundances of these light elements, which are present only by virtue of their nucleosynthesis during the Big Bang, and also cosmic ray spallation.
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Hydrogen and helium are most common, residuals within the paradigm of the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance of elements according to whether they have even or odd atomic numbers, and (2) a general decrease in abundance, as elements become heavier. Within this trend is a peak at abundances of iron and nickel, which is especially visible on a logarithmic graph spanning fewer powers of ten, say between logA=2 (A=100) and logA=6 (A=1,000,000).
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Because technetium is radioactive, with a half-life much less than the age of the star, its abundance must reflect its recent creation within that star. Equally convincing evidence of the stellar origin of heavy elements is the large overabundances of specific stable elements found in stellar atmospheres of asymptotic giant branch stars. Observation of barium abundances some 20–50 times greater than found in unevolved stars is evidence of the operation of the s-process within such stars. Many modern proofs of stellar nucleosynthesis are provided by the isotopic compositions of stardust, solid grains that have condensed from the gases of individual stars and which have been extracted from meteorites.
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The geometric series does not explicitly assume that species colonize an area sequentially, however, the model fits the concept of niche preemption, where species sequentially colonize a region and the first species to arrive receives the majority of resources.He , F., Tang D. 2008. "Estimating the niche preemption parameter of the geometric series" Acta Oecologica 33 (1):105-107 The geometric series model fits observed species abundances in highly uneven communities with low diversity. This is expected to occur in terrestrial plant communities (as these assemblages often show strong dominance) as well as communities at early successional stages and those in harsh or isolated environments (Figure 5).
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Using terrestrial classification schemes, all mare basalts are classified as tholeiitic, but specific subclassifications have been invented to further describe the population of lunar basalts. Mare basalts are generally grouped into three series based on their major element chemistry: high-Ti basalts, low-Ti basalts, and very-low-Ti (VLT) basalts. While these groups were once thought to be distinct based on the Apollo samples, global remote sensing data from the Clementine mission now shows that there is a continuum of titanium concentrations between these end members, and that the high-titanium concentrations are the least abundant. TiO2 abundances can reach up to 15 wt.
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BPS CS31082-0001, named Cayrel's Star ,Space Math @ NASA is an old Population II star located in a distance of 4 kpc in the galactic halo. It belongs to the class of ultra-metal-poor stars (metallicity [Fe/H] = -2.9), specifically the very rare subclass of neutron-capture enhanced stars. It was discovered by Tim C. Beers and collaborators with the Curtis Schmidt telescope at the Cerro Tololo Inter-American Observatory in Chile and analyzed by Roger Cayrel and collaborators. They used the Very Large Telescope (VLT) at the European Southern Observatory in Paranal, Chile for high-resolution optical spectroscopy to determine elemental abundances.
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At high snail densities, cordgrass can succumb to fungal infections and marsh die-off can ensue (Silliman and Bertness 2002, Silliman and Newell 2003, Silliman et al. 2005). Natural predators of the marsh snail are blue crabs (Callinectes sapidus) and terrapin turtles (Malaclemys terrapin), which historically regulated snail abundances. However, these predators have been commercially overexploited, and now suffer from diseases due to small population size, releasing the snails from consumer pressure, and allowing the snails to wreak havoc on salt marsh cordgrass populations (Silliman and Zieman 2001). Sea otter A classic example of a trophic cascade was caused by the overexploitation of sea otters in the 1980s (Estes & Duggins 1995).
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Theoretically, to determine the total abundance of a single element in an HII region, all transition lines should be observed and summed. However, this can be observationally difficult due to variation in line strength. Some of the most common forbidden lines used to determine metal abundances in HII regions are from oxygen (e.g. [O II] λ = (3727, 7318, 7324) Å, and [O III] λ = (4363, 4959, 5007) Å), nitrogen (e.g. [NII] λ = (5755, 6548, 6584) Å), and sulfur (e.g. [SII] λ = (6717,6731) Å and [SIII] λ = (6312, 9069, 9531) Å) in the optical spectrum, and the [OIII] λ = (52, 88) μm and [NIII] λ = 57 μm lines in the infrared spectrum.
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In the field of proteomics, Marcotte's contributions include developing early versions of the human protein interaction network and mapping of >7,000 human protein interactions. Marcotte and colleagues developed the spotted cell microarray technique for high-throughput measurement of protein expression, subcellular location, and function, developed algorithms for analyzing mass spectrometry data, started an open access database for mass spectrometry proteomics data, and developed the APEX method for absolute protein quantification on a proteome-wide scale. Using APEX, Marcotte and colleagues demonstrated that protein abundance in a lower eukaryote is predominantly determined by mRNA levels, while human protein abundances are determined roughly equally by transcriptional and post-transcriptional regulation.
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There are 113 total proposed reactions leading to the destruction of NH3. Of these, 39 were tabulated in extensive tables of the chemistry among C, N, and O compounds. A review of interstellar ammonia cites the following reactions as the principal dissociation mechanisms: with rate constants of 4.39×10−9 and 2.2×10−9, respectively. The above equations (, ) run at a rate of 8.8×10−9 and 4.4×10−13, respectively. These calculations assumed the given rate constants and abundances of [NH3]/[H2] = 10−5, [H3+]/[H2] = 2×10−5, [HCO+]/[H2] = 2×10−9, and total densities of n = 105, typical of cold, dense, molecular clouds.
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Anoles can function as a biological pest control by eating pest insects that may harm humans or plants. Anole abundances can be considerably higher in diversified agroecosystems (multiple different plant types) than high-intensity agroecosystems (typically only one or very few plant types, and regular use of agrochemicals), making the former particularly suitable for this type of pest control. However, because of their potential of becoming invasive species, releasing anoles outside their native range is strongly discouraged and often illegal, even if the species occurs elsewhere in a country (for example, it is illegal to release Carolina anoles in California, as its native range is in Southeastern United States).
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An example is calcium-40, with 20 neutrons and 20 protons, which is the heaviest stable isotope made of the same number of protons and neutrons. Both calcium-48 and nickel-48 are doubly magic because calcium-48 has 20 protons and 28 neutrons while nickel-48 has 28 protons and 20 neutrons. Calcium-48 is very neutron-rich for such a light element, but like calcium-40, it is stabilized by being doubly magic. Magic number shell effects are seen in ordinary abundances of elements: helium-4 is among the most abundant (and stable) nuclei in the universe and lead-208 is the heaviest stable nuclide.
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A 24 seconds resolution time tag will be interleaved with the event data to account for Bennu rotation. Images will be reconstructed on the ground after downlink of the event list. Images are formed simultaneously in 16 energy bands centered on the dominant lines of abundant surface elements from O-K (0.5 keV) to Fe-Kß (7 keV) as well the representative continuum. During orbital phase 5B, a 21-day orbit 700 m from the surface of Bennu, a total of at least 133 events/asteroid pixel/energy band are expected under 2 keV; enough to obtain significant constraints on element abundances at scales larger than 10 m.
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In contrast, conversion of the hydrogen at the C5 site from the α → β configuration reflects anaerobic microbial activity, and can be understood through isotope labeling experiments on controlled microbe experiments metabolizing the steroid of interest. One study demonstrated that there are two reactions that can produce loss of the cholesterol double bond—(1) direct reduction of double bond or (2) production of ketone prior to reduction of double bond—resulting in distinct isomerization of the hydrogen at the C5 site. The 14 and 17α hydrogen sites are more stable and undergo changes to β configuration in much lower abundances than the 5 hydrogen site.
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The alpha-scattering surface analyzer was designed to measure directly the abundances of the major elements of the lunar surface. The instrumentation consisted of an alpha source (curium 242) collimated to irradiate a 100 mm (3.94 in) diameter opening in the bottom of the instrument where the sample was located and two parallel but independent charged particle detector systems. One system, containing two sensors, detected the energy spectra of the alpha particles scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the protons produced via reactions (alpha and protons) in the surface material. Each detector assembly was connected to a pulse height analyzer.
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The alpha-scattering surface analyzer was designed to measure directly the abundances of the major elements of the lunar surface. The instrumentation consisted of six alpha sources (curium 242) collimated to irradiate a 100 mm diameter opening in the bottom of the instrument where the sample was located and two parallel but independent charged particle detector systems. One system, containing two sensors, detected the energy spectra of the alpha particles scattered from the lunar surface, and the other, containing four sensors, detected energy spectra of the protons produced via reactions (alpha and proton) in the surface material. Each detector assembly was connected to a pulse height analyzer.
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Trace amounts of methane, at the level of several parts per billion (ppb), were first reported in Mars' atmosphere by a team at the NASA Goddard Space Flight Center in 2003. Large differences in the abundances were measured between observations taken in 2003 and 2006, which suggested that the methane was locally concentrated and probably seasonal. In 2014, NASA reported that the Curiosity rover detected a tenfold increase ('spike') in methane in the atmosphere around it in late 2013 and early 2014. Four measurements taken over two months in this period averaged 7.2 ppb, implying that Mars is episodically producing or releasing methane from an unknown source.
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The photosphere shows abundances of carbon, oxygen, and nitrogen that suggest the giant has gone through its first dredge-up stage—a normal step in the evolution of a star into a red giant during which material from deep within the star is brought up to the surface by convection. With its slow rotation, Aldebaran lacks a dynamo needed to generate a corona and hence is not a source of hard X-ray emission. However, small scale magnetic fields may still be present in the lower atmosphere, resulting from convection turbulence near the surface. The measured strength of the magnetic field on Aldebaran is 0.22 Gauss.
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This meant that the original H–O model produced an alternative explanation for free trade to Ricardo's, rather than a complementary one; in reality, both effects may occur due to differences in technology and factor abundances. In addition to natural advantages in the production of one sort of output over another (wine vs. rice, say) the infrastructure, education, culture, and "know-how" of countries differ so dramatically that the idea of identical technologies is a theoretical notion. Ohlin said that the H–O model was a long-run model, and that the conditions of industrial production are "everywhere the same" in the long run.
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Unlike other young craters, it is very flat, so if it is of impact origin, perhaps the crater sunk into the soft sediments leaving only a circular 'ghost' marking the original rim. The site is very remote, but has been visited twice by scientific investigators, most recently by a team from NASA's Goddard Space Flight Center in September 2002. In both cases, the expeditions failed to find conclusive evidence for the origin of the feature. Later research of the samples collected in 2002 revealed tiny clusters composed of many glass beads in peak abundances of up to 90 clusters per kilogram at depths of .
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Natural range of sulfur isotopic composition on Earth, modified and simplified from Meija et al. (2013). Sulfur in natural materials can vary widely in isotopic composition: compilations of the δ34S values of natural sulfur-containing materials include values ranging from -55‰ to 135‰ VCDT. The ranges of δ34S values vary across sulfur-containing materials: for example, the sulfur in animal tissue ranges from ~ -10 to +20‰ VCDT, while the sulfate in natural waters ranges from ~ -20 to +135‰ VCDT. The range of sulfur isotope abundances in different natural materials results from the isotope fractionation associated with natural processes like the formation and modification of those materials, discussed in the next section.
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90% of the ice in the latter was found crystalline at temperature around 50 K. HST demonstrated that relatively old circumstellar disks, as the one around the 5-million-year-old B9.5Ve Herbig Ae/Be star HD 141569A, are dusty. Li & Lunine found water ice there. Knowing the ices usually exist at the outer parts of the proto-planetary nebulae, Hersant et al. proposed an interpretation of the volatile enrichment, observed in the four giant planets of the Solar System, with respect to the Solar abundances. They assumed the volatiles had been trapped in the form of hydrates and incorporated in the planetesimals flying in the protoplanets’ feeding zones.
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2H-Site-specific Natural Isotope Fractionation-Nuclear Magnetic Resonance(2H-SNIF-NMR) is a type of NMR specialized in measuring the deuterium concentration of organic molecules at natural abundances. The NMR spectra distinguishes hydrogen atoms in different chemical environments (e.g. The order of carbon that hydrogen binds to, adjacent functional groups, and even geminal positions of methylene groups), making it a powerful tool for position-specific isotope analysis. The chemical shift (in frequency units) of 2H is 6.5 times lower than that of 1H. Thus, it is difficult to resolve 2H peaks. To provide high-enough resolution to separate 2H peaks, high strength magnetic field instruments (~11.4T) are applied.
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Votive offerings found in the Sanctuary of Artemis Orthia were most often small but presented in large abundances. During the Archaic timeline, these offerings came in many variations and forms, leading to the assumption that the items were not specifically chosen as something that would pertain to or be associated with the god/goddess being praised. Instead, the offerings were thought to be selected from a more personal standpoint rather than something more representative of the honoured one. The idea of generosity was more important than the item itself that was being given and the connection it may of had to the god/goddess.
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Crustal thickness maps constructed using the Moon's topography and gravity field imply a thickness of about 30 km beneath the floor of this basin, in comparison to 60–80 km around it and the global average of about 50 km. The composition of the basin, as estimated from the Galileo, Clementine, and Lunar Prospector missions, appears to be different from typical highland regions. Most importantly, none of the samples obtained from the American Apollo and Russian Luna missions, nor the handful of identified lunar meteorites, have comparable compositions. The orbital data indicate that the floor of the basin has slightly elevated abundances of iron, titanium, and thorium.
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Many fundamental questions about Saturn have not have been fully investigated at the end of the Cassini mission in September 2017, because of limitations in its implementation and science instrumentation. Direct measurements of the atmospheric structure and noble gas and elemental abundances of Saturn are needed to distinguish between competing models of Solar System formation, as well as to provide an improved context for exoplanet systems. The SPRITE probe would revolutionize our understanding of Saturn's atmospheric structure and composition, and allow better understanding of extrasolar giant planets. SPRITE was proposed by Caltech's Jet Propulsion Laboratory with Principal Investigator Amy Simon at NASA's Goddard Space Flight Center.
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Information is lacking on many aspects of Sundarbans tiger ecology, including relative abundance, population status, spatial dynamics, habitat selection, life history characteristics, taxonomy, genetics, and disease. There is also no monitoring program in place to track changes in the tiger population over time, and therefore no way of measuring the response of the population to conservation activities or threats. Most studies have focused on the tiger-human conflict in the area, but two studies in the Sundarbans East Wildlife sanctuary documented habitat-use patterns of tigers, and abundances of tiger prey, and another study investigated tiger parasite load. Some major threats to tigers have been identified.
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Carole Jordan was educated at Harrow County Grammar School for Girls and at University College London (BSc 1962; PhD 1965). Her first paper, written while she was still an undergraduate, was on the distortion of lunar craters. Her PhD studies under C. W. Allen included identification of iron and other lines in the solar spectrum and the ZETA experiment, early ionisation-balance calculations, development of density-diagnostic methods using the iron lines, calculation of relative element abundances and modelling from emission-measure distributions.Account of presentation of Gold medal: Her first paper on coronal research, "The Relative Abundance of Silicon Iron and Nickel in the Solar Corona" was published in 1965.
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Such a star may leave a remnant white dwarf composed chiefly of oxygen, neon, and magnesium, provided that its core does not collapse, and provided that fusion does not proceed so violently as to blow apart the star in a supernova. Although a few white dwarfs have been identified which may be of this type, most evidence for the existence of such comes from the novae called ONeMg or neon novae. The spectra of these novae exhibit abundances of neon, magnesium, and other intermediate-mass elements which appear to be only explicable by the accretion of material onto an oxygen-neon-magnesium white dwarf.
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It is a high-amplitude δ Scuti type pulsator with light variations of about 0.15 minutes. The peculiar chemical abundances of this star are similar to those of Am stars. In 1900, William W. Campbell and William H. Wright used the Mills spectrograph at the Lick Observatory to determine that this star has a variable radial velocity. The -day period of this variability as well as 0.2 magnitude changes in luminosity demonstrated in 1935 that the variability was intrinsic, rather than being the result of a spectroscopic binary. In 1938, a secondary period was discovered and a pulsation theory was proposed to model the variation.
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Oxygyrus keraudreni is a shallow-dwelling species that normally occurs in low abundances. In the Indian Ocean was Oxygyrus keraudreni found essentially limited to the upper 100 m of the water column, with 90% between 50 m and the surface. Similarly, off Hawaii was it recorded low in numbers of individuals whose vertical range was limited to the upper 90 m of the water column, with most individuals occurring at night in the upper 45 m. In another study from the same area off Hawaii it was found that Oxygyrus keraudreni was captured in nighttime tows but was either absent or nearly so from comparable daytime ones.
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Abundances of solar system elements.Data from table 6 of The composition of the Solar System is similar to that of many other stars, and aside from small anomalies it can be assumed to have formed from a solar nebula that had a uniform composition, and the composition of the Sun's photosphere is similar to that of the rest of the Solar System. The composition of the photosphere is determined by fitting the absorption lines in its spectrum to models of the Sun's atmosphere. By far the largest two elements by fraction of total mass are hydrogen (74.9%) and helium (23.8%), with all the remaining elements contributing just 1.3%.
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Iridium has two naturally occurring, stable isotopes, 191Ir and 193Ir, with natural abundances of 37.3% and 62.7%, respectively. At least 37 radioisotopes have also been synthesized, ranging in mass number from 164 to 202. 192Ir, which falls between the two stable isotopes, is the most stable radioisotope, with a half-life of 73.827 days, and finds application in brachytherapy and in industrial radiography, particularly for nondestructive testing of welds in steel in the oil and gas industries; iridium-192 sources have been involved in a number of radiological accidents. Three other isotopes have half-lives of at least a day—188Ir, 189Ir, and 190Ir.
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24-isopropyl cholestane is an organic molecule produced by specific sponges, protists and marine algae. The identification of this molecule at high abundances in Neoproterozoic rocks has been interpreted to reflect the presence of multicellular life prior to the rapid diversification and radiation of life during the Cambrian explosion. In this transitional period at the start of the Phanerozoic, single-celled organisms evolved to produce many of the evolutionary lineages present on Earth today. Interpreting 24-isopropyl cholestane in ancient rocks as indicating the presence of sponges before this rapid diversification event alters the traditional understanding of the evolution of multicellular life and the coupling of biology to changes in end-Neoproterozoic climate.
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24-isopropyl cholestane is produced copiously by a particular group of sponges in the class Demospongiae within the phylum Porifera. Like other molecular fossils, the presence of 24-isopropyl cholestane in rocks may indicate whether demosponge were living in or near the rock's depositional environment. High abundances of 24-isopropyl cholestane are identified in the Precambrian rocks from the Hufq supergroup in Oman, suggesting the presence of sponges prior to the Cambrian explosion. However, sponges are not the only organisms that produce 24-isopropyl cholestane, so the identification of this biomarker is not uniquely linked to the presence of demosponge. While marine pelagophyte algae predominantly produce 24-n-propylcholestane, they also produce 24-isopropyl cholestane.
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Hoyle exerted strong lifetime influence on Clayton. Clayton's published collaborations with Fowler (1983 Nobel Laureate in Physics) as Fowler's research student (1957–60) and subsequently as Fowler's post-doctoral research associate (1961–63) launched Clayton's scientific career. He established himself at Caltech as a new worker in the field of nucleosynthesis in stars by calculating the first time-dependent models of both the s process and the fast neutron-capture chains of the r process of heavy-element nucleosynthesis and of the nuclear abundance quasiequilibrium that establishes the highly radioactive abundances between silicon and nickel during silicon burning in stars. He came onto the field early, when nucleosynthesis was a vibrant, modern frontier.
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Stellar sources of the short-lived radionuclides in the early solar system. Geochim. Cosmochim. Acta 73, 4922–4945; E.D. Young "Inheritance of solar short- and long-lived radionuclides from molecular clouds and the unexceptional nature of the solar system" Earth and Planetary Science Letters 392 (2014) 16–27 often unaware of Clayton's (1983) paper owing to the intervening decades. Aspects of interstellar-phase mixing are sure to remain important for decades to come while astronomers probe the circumstances of solar birth using accurate meteoritic data revealing the abundances of the extinct radioactive nuclei. Clayton therefore gave emphasis to extinct radioactivity in the Glossary of his 2003 book on isotopes in the cosmos.
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Cyst of a dinoflagellate Peridinium ovatum Dinoflagellates occur in most aquatic environments and during their life cycle, some species produce highly resistant organic-walled cysts for a dormancy period when environmental conditions are not appropriate for growth. Their living depth is relatively shallow (dependent upon light penetration), and closely coupled to diatoms on which they feed. Their distribution patterns in surface waters are closely related to physical characteristics of the water bodies, and nearshore assemblages can also be distinguished from oceanic assemblages. The distribution of dinocysts in sediments has been relatively well documented and has contributed to understanding the average sea-surface conditions that determine the distribution pattern and abundances of the taxa ().
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Chalcophile elements are those that remain on or close to the surface because they combine readily with chalcogens other than oxygen, forming compounds which do not sink into the core. Chalcophile ("chalcogen-loving") elements in this context are those metals and heavier nonmetals that have a low affinity for oxygen and prefer to bond with the heavier chalcogen sulfur as sulfides. Because sulfide minerals are much denser than the silicate minerals formed by lithophile elements, chalcophile elements separated below the lithophiles at the time of the first crystallisation of the Earth's crust. This has led to their depletion in the Earth's crust relative to their solar abundances, though this depletion has not reached the levels found with siderophile elements.
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In many places around the world, vegetation within riparian zones have been completely removed as humans have cleared land for raising crops, growing timber, and developing land for commercial or residential purposes. Removing riparian vegetation increases the erodibility of stream banks, and can also speed the rate of channel migration (unless the newly cleared banks are lined with riprap, retaining walls, or concrete). In addition, removal of riparian vegetation fragments the remaining riparian ecosystem, which can prevent or hinder dispersal of species between habitat patches. This can diminish riparian plant diversity, as well as decrease abundances and diversity of migratory birds or other species that depend on large, undisturbed areas of habitat.
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In ordinary matter, atoms of these elements consist of a nucleus surrounded by a cloud of electrons, but when the nuclei arrive as cosmic rays, they are devoid of electrons, because of collisions with atoms in interstellar matter. In both emulsions and cloud chambers, these "stripped" heavy nuclei leave an unmistakable track, which is much denser and "hairier" than that of protons, and whose characteristics make it possible to determine their atomic number. In further flights, the group showed that the abundances of elements in cosmic rays are similar to those found on earth and in stars. These results had a major impact, for they showed that studies of cosmic radiation could play a significant role in astrophysics.
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More details here: Two papers by Amorin In January 2012, authors L. Pilyugin, J. Vilchez, L. Mattsson and T. Thuan published a paper in the MNRAS titled: "Abundance determination from global emission-line SDSS spectra: exploring objects with high N/O ratios". In it they compare the oxygen and nitrogen abundances derived from global emission-line SDSS spectra of galaxies using (1) the electron temperature method and (2) two recent strong line calibrations: the O/N and N/S calibrations. Three sets of objects were compared: composite hydrogen-rich nebula, 281 SDSS galaxies and a sample of GPs with detectable [OIII]-4363 auroral lines. Among the questions surrounding the GPs are how much nebulae influence their spectra and results.
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The parent ion sits in a potential energy well, in which the lowest energy exit channel often corresponds to the breaking of the weakest chemical bond, resulting in the formation of a fragment or daughter ion. A mass spectrum is recorded at every photon energy, and the fractional ion abundances are plotted to obtain the breakdown diagram. At low energies no parent ion is energetic enough to dissociate, and the parent ion corresponds to 100% of the ion signal. As the photon energy is increased, a certain fraction of the parent ions (in fact according to the cumulative distribution function of the neutral internal energy distribution) still has too little energy to dissociate, but some do.
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However, the orbit of the stars are oriented in such a way that they periodically eclipse each other, so AR Aurigae is a variable star and its brightness varies from magnitude +6.15 to +6.82 with a period of 4.13 days. The primary component of AR Aurigae is known to be a mercury-manganese star, also known as an HgMn star. As the name implies, these stars have over-abundances of the elements mercury and manganese, and also often xenon and other elements. Because AR Aurigae is an eclipsing binary (in fact, it is the only known eclipsing binary with a mercury-manganese star), accurate characterization of its parameters has been made possible.
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Just as it's impossible to climb a staircase one step at a time when one of the steps is missing, this discovery meant that the successive capture theory could not account for higher elements. It was eventually recognized that most of the heavy elements observed in the present universe are the result of stellar nucleosynthesis in stars, a theory first suggested by Arthur Stanley Eddington, given credence by Hans Bethe, and quantitatively developed by Fred Hoyle and a number of other scientists. However, the Alpher–Bethe–Gamow theory does correctly explain the relative abundances of the isotopes of hydrogen and helium. Taken together, these account for more than 99% of the baryonic mass of the universe.
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Although, the Fe abundance is not as low as extremely metal-poor stars, the low abundances of C, Mg, and the heavy neutron-capture elements (Sr and Ba) suggest that it is a very chemically primitive object. A team of astronomers from the National Astronomical Observatory of Japan (NAOJ), the Konan University and the University of Hyogo in Japan, the University of Notre Dame, and New Mexico State University used the 8.2 m Subaru Telescope's High Dispersion Spectrograph (HDS) to study SDSS J0018−0939 in more detail. Nucleosynthesis models for supernova explosions of massive stars, which confirmed previously found early-generation stars did not readily explain the chemical abundance ratios observed in SDSS J0018−0939.
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Such a star enters the pair-instability region during its evolution but continues to collapse and finally enters an instability region with Fe photodisintegration. Such objects are called core- collapse very massive stars. Although it is not clear whether or not such a very massive star can explode, the yield of an explosion with energy of about 6 ×1053 ergs (600 foe) can simultaneously explain both the low Si abundance (compared with Mg) and the low C and Mg abundances. A star with ≲ Mms ≲ explodes because of the energy consumption arising from an electron-positron pair-production instability during the static O-burning stage, and is referred to as a pair-instability supernova (PISN).
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Fossils are found in Asian and African strata dating from the late Miocene; during the Pleistocene, they lived across large parts of Asia and East and Central Africa, and in Wallacea as far east as Timor.PaleoBiology Database: Stegodon, basic info Philippine National Museum A review of 130 papers written about 180 different sites with proboscidean remains in southern China revealed Stegodon to have been more common than Asian elephants; the papers gave many recent radiocarbon dates, the youngest being 2,150 BCE (4,100 BP).H. Saegusa, "Comparisons of Stegodon and Elephantid Abundances in the Late Pleistocene of Southern China ", The World of Elephants -- Second International Congress, (Rome, 2001), 345-349. However, Turvey et al.
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2980 Cameron, provisionally designated , is a main-belt asteroid discovered by prolific American astronomer Schelte Bus at Siding Spring Observatory, Australia, on March 2, 1981. It orbits the Sun every 4.11 years at a distance of 2.1–3.0 AU. The asteroid was named after astrophysicist and cosmogonist Alastair G. W. Cameron (1925–2005), who was associate director for theoretical astrophysics at the Harvard-Smithsonian Center for Astrophysics. He was an early advocate of the concepts of a turbulent accretion disk solar nebula, and of the origin of the Moon by a giant impact on the proto-Earth. He also studied the nucleosynthesis in stars and supernovae, and the cosmic abundances of nuclides.
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Loose correlations have been observed between estimated elemental abundances in the universe and the nuclear binding energy curve. Roughly speaking, the relative stability of various atomic nuclides has exerted a strong influence on the relative abundance of elements formed in the Big Bang, and during the development of the universe thereafter. See the article about nucleosynthesis for an explanation of how certain nuclear fusion processes in stars (such as carbon burning, etc.) create the elements heavier than hydrogen and helium. A further observed peculiarity is the jagged alternation between relative abundance and scarcity of adjacent atomic numbers in the elemental abundance curve, and a similar pattern of energy levels in the nuclear binding energy curve.
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While juvenile and adult fish have a mature immune system and can be vaccinated, the larvae of marine fish and invertebrates are prone to bacterial infections. Marine bacteria from the Roseobacter clade (alpha-proteobacteria)have shown potential as probiotic bacteria to provide an alternative to the use of antibiotics for preventing bacterial diseases. Not only can Roseobactor be used among fish and invertebrate larvae, they can also be used to antagonize fish-pathogenic bacteria without harming the fish or their live feed. Since Roseobacter has such high abundances, accounting for 15 to 20% of oceanic bacterio-plankton communities, they can be used for establishment of synthetic biology chassis for bio-geoengineering activities such as bioremediation of oceanic waste plastic.
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The number of rings in GDGT hydrocarbon chains is temperature dependent and provides the basis for the TEX86 paleothermometer, a proxy for measuring ancient sea surface temperature (SST) that relies on measurements of the abundances of crenarchaeol and its isomers. Crenarchaeol has a regioisomer which, based on radiocarbon analysis, may have a different origin than other isoprenoid GDGTs. Possible sources for the regioisomer include benthic archaea and diagensis of crenarchaeol, as the regioisomer is found in low abundance in surface waters and in cultures of pelagic thaumarchaea. Despite this, if it is excluded from TEX86 calculations, the paleothermometer's correlation with sea surface temperature becomes less apparent, indicating it is a necessary component of TEX86.
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The mass loss events can be witnessed today in the planetary nebulae phase of low-mass star evolution, and the explosive ending of stars, called supernovae, of those with more than eight times the mass of the Sun. The first direct proof that nucleosynthesis occurs in stars was the astronomical observation that interstellar gas has become enriched with heavy elements as time passed. As a result, stars that were born from it late in the galaxy, formed with much higher initial heavy element abundances than those that had formed earlier. The detection of technetium in the atmosphere of a red giant star in 1952, by spectroscopy, provided the first evidence of nuclear activity within stars.
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Beavers have also been shown to maintain habitats in such a way as to protect the rare Saint Francis' satyr butterfly and increase plant diversity. Biodiversity may also be affected by ecosystem engineer's ability to increase the complexity of processes within an ecosystem, potentially allowing greater species richness and diversity in the local environments. As an example, beavers have the capacity to modify riparian forest and expand wetland habitats, which results in an increase of the diversity of the habitats by allowing a greater number of species to inhabit the landscape. Coral-reef habitats, created by the ecosystem engineer coral species, hold some of the highest abundances of aquatic species in the world.
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Relative species abundance distributions are usually graphed as frequency histograms ("Preston plots"; Figure 2) or rank-abundance diagrams ("Whittaker Plots"; Figure 3).Whittaker, R. H. 1965. "Dominance and diversity in land plant communities", Science 147: 250–260 Frequency histogram (Preston plot): ::x-axis: logarithm of abundance bins (historically log2 as a rough approximation to the natural logarithm) ::y-axis: number of species at given abundance Rank-abundance diagram (Whittaker plot): ::x-axis: species list, ranked in order of descending abundance (i.e. from common to rare) ::y-axis: logarithm of % relative abundance When plotted in these ways, relative species abundances from wildly different data sets show similar patterns: frequency histograms tend to be right-skewed (e.g.
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The formation of cyanopolyynes in interstellar clouds is time-dependent. The formation of cyanopolyyne was studied and the abundances calculated in the dark cloud TMC-1. In the early days of the TMC-1, the governing reactions were ion–molecule reactions. During this time cyanoacetylene, HC3N, formed through a series of ion-neutral reactions, with the final chemical reaction being: :C3H2 \+ N → HC3N + H However, for time after 10,000 years the dominant reactions were neutral–neutral reactions and two reaction mechanisms for the formation of cyanopolyynes became possible. # HCN + C2H2 → HC3N # CnH2 \+ CN → HCn+1N + H for n = 4, 6, 8 The reaction mechanism that occurs in the present day depends on the environment of the cloud.
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One particularly important experimental tool in astrochemistry is spectroscopy through the use of telescopes to measure the absorption and emission of light from molecules and atoms in various environments. By comparing astronomical observations with laboratory measurements, astrochemists can infer the elemental abundances, chemical composition, and temperatures of stars and interstellar clouds. This is possible because ions, atoms, and molecules have characteristic spectra: that is, the absorption and emission of certain wavelengths (colors) of light, often not visible to the human eye. However, these measurements have limitations, with various types of radiation (radio, infrared, visible, ultraviolet etc.) able to detect only certain types of species, depending on the chemical properties of the molecules.
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BPS CS22892-0052 (Sneden's Star) is an old population II star located at a distance of 4.7 kpc in the galactic halo. It belongs to a class of ultra- metal-poor stars (Metallicity [Fe/H]=-3.1), specifically the very rare subclass of neutron-capture (r-process) enhanced stars. It was discovered by Tim C. Beers and collaborators with the Curtis Schmidt telescope at the Cerro Tololo Inter-American Observatory in Chile. Extended high-resolution spectroscopic observations since around 1995 (with Chris Sneden from the University of Texas at Austin as the leading observer) allowed observers to determine the abundances of 53 chemical elements in this star, as of December 2005 only second in number to the Sun.
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The green dragontail is not known to be threatened in most of its range but is considered vulnerable and in need of protection in peninsular Malaysia. In a study of swallowtail assemblages in Rani-Garbhanga Reserve Forest in Assam in 2003 and 2004, dragontails (Lamproptera species) were found to have one of the lowest mean abundances; both L. meges and L. curius being found in gaps (open patches) as well as in closed forest. A 2004 report had earlier suggested that the status of the green dragontail in Garbhanga Reserve Forest was "very rare"; later a total of 108 butterflies of genus Lamproptera were seen during the 2003 and 2004 survey, the species-wise breakdown not being published.
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For example, stars with a [Fe/H] value of +1 have 10 times the metallicity of the Sun (101); conversely, those with a [Fe/H] value of −1 have 1/10, while those with a [Fe/H] value of 0 have the same metallicity as the Sun, and so on. Young Population I stars have significantly higher iron-to-hydrogen ratios than older Population II stars. Primordial Population III stars are estimated to have a metallicity of less than −6.0, that is, less than a millionth of the abundance of iron in the Sun. The same notation is used to express variations in abundances between other individual elements as compared to solar proportions.
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The Solar Isotope Spectrometer (SIS) provides high-resolution measurements of the isotopic composition of energetic nuclei from He to Zn (Z = 2 to 30) over the energy range from ~10 to ~100 MeV/nucleon. During large solar events, SIS measures the isotopic abundances of solar energetic particles to determine directly the composition of the solar corona and to study particle acceleration processes. During solar quiet times, SIS measures the isotopes of low-energy cosmic rays from the Galaxy and isotopes of the anomalous cosmic ray component, which originates in the nearby interstellar medium. SIS has two telescopes composed of silicon solid-state detectors that provide measurements of the nuclear charge, mass, and kinetic energy of incident nuclei.
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The Ultra-Low-Energy Isotope Spectrometer (ULEIS) on the ACE spacecraft is an ultra-high-resolution mass spectrometer that measures particle composition and energy spectra of elements He–Ni with energies from ~45 keV/nucleon to a few MeV/nucleon. ULEIS investigates particles accelerated in solar energetic particle events, interplanetary shocks, and at the solar wind termination shock. By determining energy spectra, mass composition, and temporal variations in conjunction with other ACE instruments, ULEIS greatly improves our knowledge of solar abundances, as well as other reservoirs such as the local interstellar medium. ULEIS combines the high sensitivity required to measure low particle fluxes, along with the capability to operate in the largest solar particle or interplanetary shock events.
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Recent research on sea surface temperature (SST) for the past 15,000 years in southern Okinawa modelled the Paleoclimate of ocean sediment core (ODP 1202B) using an alkenone analysis. The results show a cooling stage at 14,300 to 13,700 years BP between Bølling and Allerød warm phases, corresponding to the Older Dryas event. Another study on an ocean sediment core from Norwegian Trench also suggests a cooling between Bølling and Allerød warm phases. The glacial polar faunal study on ocean sediment core Troll 3.1 based on Neogloboquadrina pachyderma abundances suggests that there were two cooling events before Younger Dryas in which one of the events occurred within Bølling-Allerød interstadial and can be associated with Older Dryas.
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Silicon, in contrast, interacts with only a few other atoms, and the large silicon molecules are monotonous compared with the combinatorial universe of organic macromolecules. Indeed, it seems likely that the basic building blocks of life anywhere will be similar to those on Earth, in the generality if not in the detail. Although terrestrial life and life that might arise independently of Earth are expected to use many similar, if not identical, building blocks, they also are expected to have some biochemical qualities that are unique. If life has had a comparable impact elsewhere in the Solar System, the relative abundances of chemicals key for its survival—whatever they maybe—could betray its presence.
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The period has been decreasing on average by 214 seconds/year. SV Vulpeculae is a yellow bright supergiant around twenty thousand times as luminous as the sun, with a spectral type that varies from late F to early K. It pulsates and varies in temperature from below 5,000 K to above 6,000 K. The radius is at maximum, and varies from to as the star pulsates. The mass of SV Vulpeculae is now near , and is estimated to have been about when it was on the main sequence. The rate of change of the period and the atmospheric abundances show that the star is crossing the instability strip for the second time.
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Of particular interest to this astrobiology mission, is the detection and characterization of the atmospheric methane (), as it may be of geological or biological nature. Large differences in the abundances were measured between observations taken in 2003, 2006, and on 2014 NASA reported that the Curiosity rover detected a tenfold increase ('spike') in methane in the atmosphere in late 2013 and early 2014. This suggestes that the methane was locally concentrated and is probably seasonal. Because methane on Mars would quickly break down due to ultraviolet radiation from the Sun and chemical reactions with other gases, its persistent presence in the atmosphere also implies the existence of an unknown source to continually replenish the gas.
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In 2014, HV 2112 was identified as a possible Thorne–Żytkow object (TZO) using the Magellan Clay telescope in Chile. To find candidate TZOs, Emily Levesque used the Apache Point Observatory to examine 24 red supergiant stars in the Milky Way, and the Magellan Clay telescope to look at 16 in the Large Magellanic Cloud and 22 in the Small Magellanic Cloud. The star was thought to contain unusually high levels of the elements lithium, molybdenum and rubidium that are expected only to be produced by TZOs. A 2018 paper re-appraising the properties of HV 2112 found no evidence for unusual chemical abundances and a luminosity that is lower than previously thought.
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Bernard Ephraim Julius Pagel FRS (4 January 1930 - 14 July 2007) was a British astrophysicist who worked on the measurement and interpretation of elemental abundances in stars and galaxies. The son of physician and medical historian Walter Pagel and grandson of German physician Julius Leopold Pagel, he was born in Berlin in 1930, but moved with his family to Britain in 1933 to avoid the growing Jewish persecution in Germany at that time. He was educated at Merchant Taylors' School in Northwood and at Sidney Sussex College, Cambridge, from which he graduated with first-class honours in Physics in 1950. He remained in Cambridge to pursue his doctoral studies, obtaining his PhD in 1955.
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The Commission on Isotopic Abundances and Atomic Weights (CIAAW) is an international scientific committee of the International Union of Pure and Applied Chemistry (IUPAC) under its Division of Inorganic Chemistry. Since 1899, it is entrusted with periodic critical evaluation of atomic weights of chemical elements and other cognate data, such as the isotopic composition of elements. The biennial CIAAW Standard Atomic Weights are accepted as the authoritative source in science and appear worldwide on the periodic table wall charts. The use of CIAAW Standard Atomic Weights is also required legally, for example, in calculation of calorific value of natural gas (ISO 6976:1995), or in gravimetric preparation of primary reference standards in gas analysis (ISO 6142:2006).
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This is a chemically peculiar A-type main-sequence star with a stellar classification of A1 Vp. It is a Lambda Boötis star displaying strongly-depleted iron peak and alpha process elements, but otherwise relatively normal solar abundances. The star shows no variability down to a detection limit of 1.6 millimagnitudes. It is 264 million years old with a relatively low projected rotational velocity of 18 km/s. 50 Cancri has 2.1 times the mass of the Sun and is radiating 11 times the Sun's luminosity from its photosphere at an effective temperature of 8,340 K. 50 Cancri has an infrared excess, which most likely indicates a debris disk in orbit around the host star.
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However, in 2016 Konôpková and others directly measured the thermal conductivity of solid iron at inner core conditions, and obtained a much lower value, 18–44 W/m·K. With those values, they obtained an upper bound of 4.2 billion years for the age of the inner core, compatible with the paleomagnetic evidence. In 2014, Driscoll and Bercovici published a thermal history of the Earth that avoided the so- called mantle thermal catastrophe and new core paradox by invoking 3 TW of radiogenic heating by the decay of in the core. Such high abundances of K in the core are not supported by experimental partitioning studies, so such a thermal history remains highly debatable.
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Around 25–33% of white dwarfs have metal lines in their spectra, which is notable because any heavy elements in a white dwarf should sink into the star's interior in just a small fraction of the star's lifetime. The prevailing explanation for metal-rich white dwarfs is that they have recently accreted rocky planetesimals. The bulk composition of the accreted object can be measured from the strengths of the metal lines. For example, a 2015 study of the white dwarf Ton 345 concluded that its metal abundances were consistent with those of a differentiated, rocky planet whose mantle had been eroded by the host star's wind during its asymptotic giant branch phase.
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The first brown tide in Florida began during the summer of 2012 and collapsed a few months thereafter, and the second brown tide began in the spring of 2013 and collapsed in mid-summer 2013. During the brown tides in Florida, A. lagunensis consisted of 98% of the phytoplankton community with abundances greater than 2 x 106 cells/mL. Similar to the causes of the Texas brown tides, the Florida brown tides were proliferated by high salinity, low grazing pressure, high dissolved organic nitrogen and low inorganic nutrients, and competitive advantage over other phytoplankton. However, these brown tides were short-lived compared to that in Texas, lasting no more than a few months.
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Despite being relatively close to the shore of Faial Island, this seamount was only named in 1962. According to written statements, it was the crew of the tuna fishing boat "Condor", commanded by the captain Jaime Medeiros, from Pico Island, who found it, it following indications from an old French nautical chart, which indicated in this area depths with 230 m. The fishermen of that time remember exceptional abundances of fish, wreckfish and blackspot seabreams, especially at the beginning of the exploitation of the bank: "thousands of tones of fish that they got there ... there was so may wreckfish and seabreams… ... the blackspot seabreams would not let the bait hit the bottom...".
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An Am star or metallic-line star is a type of chemically peculiar star of spectral type A whose spectrum has strong and often variable absorption lines of metals such as zinc, strontium, zirconium, and barium, and deficiencies of others, such as calcium and scandium. The original definition of an Am star was one in which the star shows "an apparent surface underabundance of Ca (and/or Sc) and/or an apparent overabundance of the Fe group and heavier elements". The unusual relative abundances cause the spectral type assessed from the Calcium K lines to be systematically earlier than one assessed from other metallic lines. Typically, a spectral type judged solely from hydrogen lines is intermediate.
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This constrains the abundances of the elements H, C and N. Two other elements are detected: phosphorus in the gas phosphine (PH3) and germanium in germane (GeH4). The helium atom has vibrations in the ultraviolet range, which is strongly absorbed by the atmospheres of the outer planets and Earth. Thus, despite its abundance, helium was only detected once spacecraft were sent to the outer planets, and then only indirectly through collision-induced absorption in hydrogen molecules. Further information on Jupiter was obtained from the Galileo probe when it was sent into the atmosphere in 1995; and the final mission of the Cassini probe in 2017 was to enter the atmosphere of Saturn.
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Since 1978, solar irradiance has been directly measured by satellites, with very good accuracy. These measurements indicate that the Sun's total solar irradiance fluctuates by +-0.1% over the ~11 years of the solar cycle, but that its average value has been stable since the measurements started in 1978. Solar irradiance before the 1970s is estimated using proxy variables, such as tree rings, the number of sunspots, and the abundances of cosmogenic isotopes such as 10Be, all of which are calibrated to the post-1978 direct measurements.Modelled simulation of the effect of various factors (including GHGs, Solar irradiance) singly and in combination, showing in particular that solar activity produces a small and nearly uniform warming, unlike what is observed.
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Mastitis has been linked to changes in human milk microbiota at the phylum level, lower microbial diversity, and decreased abundance of obligate anaerobic taxa. Women delivering term and preterm show differences in their milk microbiome composition, with mothers of term-births showing lower abundances of Enterococcus species and higher amounts of Bifidobacterium species in their milk compared to mothers of preterm births. Few studies have been conducted examining the influence of maternal diet on the milk microbiome, but diet is known to influence other aspects of milk composition, such as the lipid profile, which in turn could affect its microbial composition. Variation in the fat and carbohydrate content of the maternal diet may influence the taxonomic composition of the milk microbiome.
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At very high temperatures, as in the environment of a black hole or neutron star, high energy photon interactions with nuclei or even with other photons, can create an electron-positron plasma. In that situation the combined mass of the positive-negative charge carrier pair is approximately 918 times smaller (the proton to electron mass ratio), while the radiation pressure on the positrons doubles the effective upward force per unit mass, so the limiting luminosity needed is reduced by a factor of ≈918×2. The exact value of the Eddington luminosity depends on the chemical composition of the gas layer and the spectral energy distribution of the emission. A gas with cosmological abundances of hydrogen and helium is much more transparent than gas with solar abundance ratios.
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This allows them to occasionally boil off their surfaces and then fall again as snow, whereas compounds with higher boiling points would remain solid. The relative abundances of these three compounds in the largest KBOs is directly related to their surface gravity and ambient temperature, which determines which they can retain. Water ice has been detected in several KBOs, including members of the Haumea family such as , mid-sized objects such as 38628 Huya and 20000 Varuna, and also on some small objects. The presence of crystalline ice on large and mid-sized objects, including 50000 Quaoar where ammonia hydrate has also been detected, may indicate past tectonic activity aided by melting point lowering due to the presence of ammonia.
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The process of magnetite and greigite formation from magnetotactic bacteria and the formation of magnetofossils are well understood, although the more specific relationships, like those between the morphology of these fossils and the effect on the climate, nutrient availability and environmental availability would require more research. This however, does not alter the promise of better insight into the Earth's microbial ecology and geomagnetic variations over a large time scale presented by magnetofossils. Unlike some other methods used to provide information of the Earth's history, magnetofossils normally have to be seen in large abundances to provide useful information of Earth's ancient history. Although lower concentrations can tell their own story of the more recent paleoclimate, paleoenvironmental and paleoecological history of the Earth.
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Through comparisons of the three objects using proven methodology and analysis of metallicity, they conclude that "the high nitrogen-to-oxygen ratios derived in some Green Pea galaxies may be caused by the fact that their SDSS spectra are spectra of composite nebulae made up of several components with different physical properties (such as metallicity). However, for the hottest Green Pea galaxies, which appear to be dwarf galaxies, this explanation does not seem to be plausible." In January 2012, author S. Hawley published a paper in the Publications of the Astronomical Society of the Pacific titled "Abundances in "Green Pea" Star-forming Galaxies". In this paper, former NASA astronaut Steven Hawley compares the results from previous GP papers regarding their metallicities.
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The existence of two distinct units with the same name was confusing, and the difference (about in relative terms) was large enough to affect high-precision measurements. Moreover, it was discovered that the isotopes of oxygen had different natural abundances in water and in air. For these and other reasons, in 1961 the International Union of Pure and Applied Chemistry (IUPAC), which had absorbed the ICAW, adopted a new definition of the atomic mass unit for use in both physics and chemistry; namely, 1/12 of the mass of a carbon-12 atom. This new value was intermediate between the two earlier definitions, but closer to the one used by chemists (who would be affected the most by the change).
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320x320px The primary mechanisms that produce protein isoforms are alternative splicing and variable promoter usage, though modifications due to genetic changes, such as mutations and polymorphisms are sometimes also considered distinct isoforms. Alternative splicing is the main post- transcriptional modification process that produces mRNA transcript isoforms, and is a major molecular mechanism that may contribute to protein diversity. The spliceosome, a large ribonucleoprotein, is the molecular machine inside the nucleus responsible for RNA cleavage and ligation, removing non-protein coding segments (introns). Because splicing is a process that occurs between transcription and translation, its primary effects have mainly been studied through genomics techniques—for example, microarray analyses and RNA sequencing have been used to identify alternatively spliced transcripts and measure their abundances.
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A partially endemic fauna, comprising mainly gammaridean amphipods, thrives at the underside of ice floes. Locally and seasonally occurring at several hundred individuals per square meter, they are important mediators for particulate organic matter from the sea ice to the water column. Ice- associated and pelagic crustaceans are the major food sources for polar cod (Boreogadus saida) that occurs in close association with sea ice and acts as the major link from the ice-related food web to seals and whales. While previous studies of coastal and offshore sea ice provided a glimpse of the seasonal and regional abundances and the diversity of the ice-associated biota, biodiversity in these communities is virtually unknown for all groups, from bacteria to metazoans.
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Ammonia oxidation is important part of the nitrogen cycle, a biogeochemical cycle which cycles nitrogen through its various biological and mineral forms. AOA have been shown to dominate ammonia oxidation in the oceans and thus crenarchaeol, which is generally thought to be produced exclusively by AOA (specifically Thaumarchaeota), has been proposed as a specific biomarker for AOA and ammonia oxidation. Crenarchaeol abundance has been found to track with seasonal blooms of AOA, suggesting that it may be appropriate to use crenarchaeol abundances as a proxy for AOA populations and thus ammonia oxidation more broadly. However the discovery of Thaumarchaeota that are not obligate ammonia- oxidizers complicates this conclusion, as does one study that suggests that crenarchaeol may be produced by Marine Group II Euryarchaeota.
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The creation of free neutrons by electron capture during the rapid compression of the supernova core along with the assembly of some neutron-rich seed nuclei makes the r-process a primary process, and one that can occur even in a star of pure H and He. This is in contrast to the B2FH designation of the process as a secondary process. This promising scenario, though generally supported by supernova experts, has yet to achieve a satisfactory calculation of r-process abundances. The primary r-process has been confirmed by astronomers who had observed old stars born when galactic metallicity was still small, that nonetheless contain their complement of r-process nuclei; thereby demonstrating that the metallicity is a product of an internal process.
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The Unified Neutral Theory of Biodiversity and Biogeography (UNTB) is a special form of mechanistic model that takes an entirely different approach to community composition than the niche apportionment models. Instead of species populations reaching equilibrium within a community, the UNTB model is dynamic, allowing for continuing changes in relative species abundances through drift. A community in the UNTB model can be best visualized as a grid with a certain number of spaces, each occupied with individuals of different species. The model is zero-sum as there are a limited number of spaces that can be occupied: an increase in the number of individuals of one species in the grid must result in corresponding decrease in the number of individuals of other species in the grid.
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If all components of this simple interface are correctly placed and sized, then each substance separated by the nano-column is smoothly converted into the gas phase, the peak profile is nicely reproduced, and high quality mass spectra are generated. Major advantages of this technical solution are the following: 1) It delivers high-quality, fully library matchable mass spectra of most sub-1 kDa molecules amenable by HPLC, 2) It is a chemical ionization free interface (unless operated intentionally) with accurate reproduction of the expected isotope ion abundances, 3) Response is never influenced by matrix components in the sample or in the mobile phase, 4) It can be considered a universal detector for small molecules because response is not related to compound polarity.
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Methane (CH4) is chemically unstable in the current oxidizing atmosphere of Mars. It would quickly break down due to ultraviolet radiation from the Sun and chemical reactions with other gases. Therefore, a persistent presence of methane in the atmosphere may imply the existence of a source to continually replenish the gas. Trace amounts of methane, at the level of several parts per billion (ppb), were first reported in Mars' atmosphere by a team at the NASA Goddard Space Flight Center in 2003. Large differences in the abundances were measured between observations taken in 2003 and 2006, which suggested that the methane was locally concentrated and probably seasonal. On June 7, 2018, NASA announced it has detected a seasonal variation of methane levels on Mars.
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Stars and nebulae with relatively high abundances of carbon, nitrogen, oxygen, and neon are called "metal-rich" in astrophysical terms, even though those elements are non-metals in chemistry. The presence of heavier elements hails from stellar nucleosynthesis, the theory that the majority of elements heavier than hydrogen and helium in the Universe ("metals", hereafter) are formed in the cores of stars as they evolve. Over time, stellar winds and supernovae deposit the metals into the surrounding environment, enriching the interstellar medium and providing recycling materials for the birth of new stars. It follows that older generations of stars, which formed in the metal-poor early Universe, generally have lower metallicities than those of younger generations, which formed in a more metal-rich Universe.
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The Astrophysical Observatory Potsdam isn't used as observatory any more. Nowadays it hosts the Potsdam Institute for Climate Impact Research as part of the Albert Einstein Science Park Cross-section of the Astrophysical Observatory Potsdam The "Große Refraktor" of 1899, a double telescope with a 80cm (31.5") and 50 cm (19.5") lenses In the middle of the 19th century spectral analysis was developed by Gustav Kirchhoff and Robert Bunsen. It enabled the acquisition of information on the physical parameters and chemical abundances of stars, by the spectral analysis of their light. Foerster recognized these possibilities and initiated the building of a solar observatory in 1871 as a memorial to the crown prince, in which he emphasized the importance and profit of solar research.
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ACE also measures abundances of cosmic ray nickel-59 and cobalt-59 isotopes; these measurements indicate that a time longer than the half-life of nickel-59 with bound electrons (7.6 × 104 years) elapsed between the time nickel-59 was created in a supernova explosion and the time cosmic rays were accelerated. Such long delays indicate that cosmic rays come from the acceleration of old stellar or interstellar material rather than from fresh supernova ejecta. ACE also measures an iron-58/iron-56 ratio that is enriched over the same ratio in solar system material. These and other findings have led to a theory of the origin of cosmic rays in galactic superbubbles, formed in regions where many supernovae explode within a few million years.
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The relative delay in the recovery of benthic organisms has been attributed to widespread anoxia, but high abundances of benthic species contradict this explanation. More recent work suggests that the pace of recovery was intrinsically driven by the intensity of competition among species, which drives rates of niche differentiation and speciation. Accordingly, low levels of interspecific competition in seafloor communities that are dominated by primary consumers correspond to slow rates of diversification and high levels of interspecific competition among nektonic secondary and tertiary consumers to high diversification rates. Whereas most marine communities were fully recovered by the Middle Triassic, global marine diversity reached pre-extinction values no earlier than the Middle Jurassic, approximately 75 million years after the extinction event.
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Like Hogg Rock and other andesite lava domes in the area, it has lower incompatible element abundances than surrounding andesitic rock deposits. A 1992 element abundance analysis of Hayrick Butte andesite samples from the margin of the volcano shows a silicon dioxide (silica) level of 60.1 percent, aluminum oxide level of 18.4 percent, calcium oxide level of 6.24 percent, iron(II) oxide level of 5.55 percent, and sodium oxide level of 4.42 percent. Magnesium oxide made up 3.3 percent of the samples, with potassium oxide levels at 1.08 percent and manganese(II) oxide, phosphorus pentoxide, and titanium dioxide all below 1 percent. Additional studies from 1980 and 1983 exhibit similar levels of silica in samples from Hogg Rock and Hayrick Butte at about 59 to 60 percent.
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These feeding- suitable phytoplankton assemblages were correlated with non-mixing thermocline layers. This conjecture was supported when foul weather swept up during the study and mixed the previously stratified layers (including a particulate layer below the surface) that had been sampled and introduced to the larvae. Samples derived from the same depths that proved ideal to induce first feeding prior to the storm no longer contained the necessary phytoplankton varieties and abundances; as a result, the young larvae did not feed on the post-storm samples and were unable to survive. Thus, Lasker eventually hypothesized that high-energy events that cause destratification of ocean layers have negative impacts on first-feeding northern anchovy larvae by destabilizing and decreasing their prey availability.
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Deep- sea hydrothermal vents were found to have high numbers of viruses indicating high viral production. Samples from the Endeavour Hydrothermal Vents off the coast southwest British Columbia showed that active venting black smokers had viral abundances from 1.45x105 to 9.90x107 per mL with a drop-off in abundance found in the hydrothermal-vent plume (3.5x106 per mL) and outside the venting system (2.94x106 per mL). The high number-density of viruses and therefore viral production (in comparison to surrounding deep-sea waters) implies that viruses are a significant source of microbial mortality at the vents. Like in other marine environments, deep-sea hydrothermal viruses affect abundance and diversity of prokaryotes and therefore impact microbial biogeochemical cycling by lysing their hosts to replicate.
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At this point, the elemental abundances were nearly fixed, with the only change as some of the radioactive products of Big Bang nucleosynthesis (such as tritium) decay. The deuterium bottleneck in the formation of helium, together with the lack of stable ways for helium to combine with hydrogen or with itself (there are no stable nuclei with mass numbers of five or eight) meant that an insignificant amount of carbon, or any elements heavier than carbon, formed in the Big Bang. These elements thus required formation in stars. At the same time, the failure of much nucleogenesis during the Big Bang ensured that there would be plenty of hydrogen in the later universe available to form long-lived stars, such as our Sun.
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Measurements of small variations in the natural abundances of deuterium, along with those of the stable heavy oxygen isotopes 17O and 18O, are of importance in hydrology, to trace the geographic origin of Earth's waters. The heavy isotopes of hydrogen and oxygen in rainwater (so-called meteoric water) are enriched as a function of the environmental temperature of the region in which the precipitation falls (and thus enrichment is related to mean latitude). The relative enrichment of the heavy isotopes in rainwater (as referenced to mean ocean water), when plotted against temperature falls predictably along a line called the global meteoric water line (GMWL). This plot allows samples of precipitation-originated water to be identified along with general information about the climate in which it originated.
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Because the stars in an open cluster are all at roughly the same distance from Earth, and were born at roughly the same time from the same raw material, the differences in apparent brightness among cluster members are due only to their mass. This makes open clusters very useful in the study of stellar evolution, because when comparing one star to another, many of the variable parameters are fixed. The study of the abundances of lithium and beryllium in open cluster stars can give important clues about the evolution of stars and their interior structures. While hydrogen nuclei cannot fuse to form helium until the temperature reaches about 10 million K, lithium and beryllium are destroyed at temperatures of 2.5 million K and 3.5 million K respectively.
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Believed to have been introduced into Australia by Aboriginals between 4,600 and 18,300 years ago, the dingo's status as a native or introduced species in Australia has been a controversy. According to Dr. Mike Letnic, at the Centre for Ecosystem Science, UNSW, the dingo, as Australia's top predator, has an important role in maintaining the balance of nature and that reintroduced or existing dingo populations could increase biodiversity across more than 2 million square kilometres of Australia (Avolia 2009). Where dingoes had been exterminated, Dr. Letnic found increased abundances of introduced red foxes and herbivores, while small native mammals and grasses were lost. In 2011 the Liberal MP for Stuart, Dan van Holst Pellekaan, called for a $200 bounty on dingos.
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This quantity can vary substantially between samples because the sample's origin (and therefore its radioactive history or diffusion history) may have produced unique combinations of isotopic abundances. For example, due to a different mixture of stable carbon-12 and carbon-13 isotopes, a sample of elemental carbon from volcanic methane will have a different relative atomic mass than one collected from plant or animal tissues. The more common, and more specific quantity known as standard atomic weight (A) is an application of the relative atomic mass values obtained from multiple different samples. It is sometimes interpreted as the expected range of the relative atomic mass values for the atoms of a given element from all terrestrial sources, with the various sources being taken from Earth.
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Hydrogen Isotope Composition of Hydro-, Bio- and Geo-spheres Due to physical and chemical fractionation processes, the variations in the isotopic compositions of elements are reported, and the standard atomic weights of hydrogen isotopes have been published by the Commission on Atomic Weights and Isotopic Abundances of the IUPAC. The ratios of stable H isotopes are reported relative to the International Atomic Energy Agency (IAEA) reference water. In the equilibrium isotope reactions of Hydrogen and Deuterium in general, enrichment of the heavy isotope is observed in the compound with the higher oxidation state. However, in our natural environment, the isotopic composition of hydrogen isotopes greatly vary depending on the sources and organisms due to complexities of interacting elements in disequilibrium states.
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The island continued to be occupied by small communities for the subsequent 5000 years, with pottery (usually associated with Melanesian peoples) found at two sites, Mui (East coast of Mabuiag) and Mask Cave (on adjacent islet, Pulu) dating from approximately 2000 years ago. The past 1000 years witnessed expansion in site use, including formation of multiple ethnographically-significant 'villages', including Goemu, Wagadagam and Dabangay. During the past 400–500 years large, highly structured mounds of dugong bone, as well as shell and stone arrangements provide evidence for emerging totemic divisionsMcNiven, I. J. and Bedingfield, A. C. 2008. Past and present marine mammal hunting rates and abundances: dugong (Dugong dugon) evidence from Dabangai bone mound, Torres Strait. Journal of Archaeological Science 35: 505–15.
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In the distant past the abundances of thorium and uranium were enriched by the decay of plutonium and curium isotopes, and thorium was enriched relative to uranium by the decay of 236U to 232Th and the natural depletion of 235U, but these sources have long since decayed and no longer contribute. In the Earth's crust, thorium is much more abundant: with an abundance of 8.1 parts per million (ppm), it is one of the most abundant of the heavy elements, almost as abundant as lead (13 ppm) and more abundant than tin (2.1 ppm). This is because thorium is likely to form oxide minerals that do not sink into the core; it is classified as a lithophile. Common thorium compounds are also poorly soluble in water.
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The elements heavier than iron with origins in supernovae are typically those produced by the r-process, which is powered by supernovae neutron bursts Either interpretation, though generally supported by supernova experts, has yet to achieve a totally satisfactory calculation of r-process abundances because the overall problem is numerically formidable, but existing results are supportive. In 2017, new data about the r-process was discovered when the LIGO and Virgo gravitational-wave observatories discovered a merger of two neutron stars ejecting r-process matter. See Astrophysical sites below. Noteworthy is that the r-process is responsible for our natural cohort of radioactive elements, such as uranium and thorium, as well as the most neutron-rich isotopes of each heavy element.
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Compositionally, lava from the Newberry Volcano has varied from primitive basalts with high magnesium levels to more evolved tholeiitic and calc- alkaline deposits (based on the major element characteristics of the lavas). Primitive lavas exhibit high abundances of chromium and nickel as well as variable concentrations of fluid-mobile elements like barium and strontium. Tholeiitic and calc-alkaline lavas display overlap in magnesium, calcium oxide, and aluminum oxide levels but differ in that the tholeiites have lower contents of silica and potassium oxide and higher iron(II) oxide, titanium dioxide, and sodium oxide. There is also much overlap in isotopic composition, though the tholeiitic lavas mark the low point for 87Sr/86Sr and the high point for 143Nd/144Nd and 176Hf/177Hf.
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It works similarly to a scanning electron microscope: the sample is bombarded with an electron beam, emitting x-rays at wavelengths characteristic to the elements being analyzed. This enables the abundances of elements present within small sample volumes (typically 10-30 cubic micrometers or less) to be determinedWittry, David B. (1958). "Electron Probe Microanalyzer", US Patent No 2916621, Washington, DC: U.S. Patent and Trademark Office, when a conventional accelerating voltage of 15-20 kV is used. The concentrations of elements from lithium to plutonium may be measured at levels as low as 100 parts per million (ppm), material dependent, although with care, levels below 10 ppm are possible The ability to quantify lithium by EPMA became a reality in 2008..
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In August 2016, as Juno swung closely by the planet MWR achieved a penetration of 200 to 250 miles (350 to 400 kilometers) below the surface cloud layer. MWR is designed to make observations below the cloud- tops, especially detecting the abundances of certain chemicals and determine dynamic features. The region has not been observed like this previously. MWR was launched aboard the Juno spacecraft on August 5, 2011 (UTC) from Cape Canaveral, USA, as part of the New Frontiers program, and after an interplanetary journey that including a swingby of Earth, entered a polar orbit of Jupiter on July 5, 2016 (UTC), The electronics for MWR are located inside the Juno Radiation Vault, which uses titanium to protect it and other spacecraft electronics.
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The Inorganic Chemistry Division of the International Union of Pure and Applied Chemistry (IUPAC), also known as Division II, deals with all aspects of inorganic chemistry, including materials and bioinorganic chemistry, and also with isotopes, atomic weights and the periodic table. It furthermore advises the Chemical Nomenclature and Structure Representation Division (Division VIII) on issues dealing with inorganic compounds and materials. For the general public, the most visible result of the division's work is that it evaluates and advises the IUPAC on names and symbols proposed for new elements that have been approved for addition to the periodic table. For the scientific end educational community the work on isotopic abundances and atomic weights is of fundamental importance as these numbers are continuously checked and updated.
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Weis' innovative use of trace element and isotopic geochemistry spans a wide range of applications in the Earth and environmental sciences. Her research interests include the distribution of elements and isotopes in Earth systems with an emphasis on the use of abundances and isotopic ratios in earth (petrology/volcanology/geochronology) and environmental sciences. This includes defining the source and evolution of igneous and metamorphic rocks, the interactions between different reservoirs (mantle, crust and atmosphere) and the role of tectonic settings. Other interests include geochemical and isotopic studies of sedimentary rocks, global changes and reconstitution of past environments; distribution of pollutants in natural and anthropogenic systems; application of non-traditional heavy stable to environmental issues and analytical technique developments, techniques for high precision chemical and isotope analysis.
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They are created after the red giant phase, when most of the outer layers of the star have been expelled by strong stellar winds Once all of the red giant's atmosphere has been dissipated, energetic ultraviolet radiation from the exposed hot luminous core, called a planetary nebula nucleus (PNN), ionizes the ejected material. Absorbed ultraviolet light then energizes the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula. Planetary nebulae likely play a crucial role in the chemical evolution of the Milky Way by expelling elements into the interstellar medium from stars where those elements were created. Planetary nebulae are observed in more distant galaxies, yielding useful information about their chemical abundances.
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Other factors that broaden the main sequence band on the HR diagram include uncertainty in the distance to stars and the presence of unresolved binary stars that can alter the observed stellar parameters. However, even perfect observation would show a fuzzy main sequence because mass is not the only parameter that affects a star's color and luminosity. Variations in chemical composition caused by the initial abundances, the star's evolutionary status, interaction with a close companion, rapid rotation, or a magnetic field can all slightly change a main-sequence star's HR diagram position, to name just a few factors. As an example, there are metal-poor stars (with a very low abundance of elements with higher atomic numbers than helium) that lie just below the main sequence and are known as subdwarfs.
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HNC is intricately linked to the formation and destruction of numerous other molecules of importance in the interstellar medium—aside from the obvious partners HCN, protonated hydrogen cyanide (HCNH+), and cyanide (CN), HNC is linked to the abundances of many other compounds, either directly or through a few degrees of separation. As such, an understanding of the chemistry of HNC leads to an understanding of countless other species—HNC is an integral piece in the complex puzzle representing interstellar chemistry. Furthermore, HNC (alongside HCN) is a commonly used tracer of dense gas in molecular clouds. Aside from the potential to use HNC to investigate gravitational collapse as the means of star formation, HNC abundance (relative to the abundance of other nitrogenous molecules) can be used to determine the evolutionary stage of protostellar cores.
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Some of these radionuclides are tritium, carbon-14 and phosphorus-32. Certain light (low atomic number) primordial nuclides (some isotopes of lithium, beryllium and boron) are thought to have been created not only during the Big Bang, and also (and perhaps primarily) to have been made after the Big Bang, but before the condensation of the Solar System, by the process of cosmic ray spallation on interstellar gas and dust. This explains their higher abundance in cosmic rays as compared with their ratios and abundances of certain other nuclides on Earth. This also explains the overabundance of the early transition metals just before iron in the periodic table; the cosmic-ray spallation of iron thus produces scandium through chromium on one hand and helium through boron on the other.
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Their rich economy and advanced merchant abilities were widely known by the indigenous groups of the area and described by the Spanish conquistadores whose primary objective was the acquisition of the mineral resources of Tierra Firme; gold, emeralds, carbon, silver and copper. The Muisca economy was self-sufficient regarding the basic supplies, thanks to the advanced technologies of the agriculture on raised terraces by the people. The system of trade was well established providing both the higher social classes and the general population abundances of gold, feathers, marine snails, coca, yopo and other luxury goods. Markets were held every four to eight days in various settlements throughout the Muisca Confederation and special markets were organised around festivities where merchants from far outside the Andes were trading their goods with the Muisca.
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The "snowflakes" grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor. However, most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres of their journey, that is, within the epipelagic zone. In this way marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems: As sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source. Some deep- sea pelagic groups, such as the lanternfish, ridgehead, marine hatchetfish, and lightfish families are sometimes termed pseudoceanic because, rather than having an even distribution in open water, they occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes.
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In astronomy, the lithium problem or lithium discrepancy refers to the discrepancy between the primordial abundance of lithium as inferred from observations of metal-poor (Population II) halo stars in our Galaxy and the amount that should theoretically exist due to Big Bang nucleosynthesis+WMAP cosmic baryon density predictions of the CMB. Namely, the most widely accepted models of the Big Bang suggest that three times as much primordial lithium, in particular lithium-7, should exist. This contrasts with the observed abundance of isotopes of hydrogen (1H and 2H) and helium (3He and 4He) that are consistent with predictions. The discrepancy is highlighted in a so-called "Schramm plot", named in honor of astrophysicist David Schramm, which depicts these primordial abundances as a function of cosmic baryon content from standard BBN predictions.
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An X-ray burst is one possible site for the rp-process mechanism which involves the accretion of hydrogen and helium from one star onto the surface of its neutron star binary companion. Mass measurements are required as key inputs to network calculations used to describe this process in terms of the abundances of the nuclides produced, the light-curve profile of the X-ray bursts, and the energy produced. In the current configuration, more than 100 radioactive isotopes have been measured with half-lives much less than a second and with a precision (Δm/m) approaching 10−9. Recently, a novel injection system, the RF gas cooler, has been installed on the CPT to allow fast reaction products to be decelerated, thermalized and bunched for rapid and efficient injection.
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Approximately half of the free-living insects are habitat-specific, while the remainder are generalists found in a variety of habitats, being associated with either supralittoral or intertidal zones, Poa cookii and Pringlea antiscorbutica stands, bryophytes, lichen- covered rocks, exposed rock faces or the underside of rocks. There is a pronounced seasonality to the insect fauna, with densities in winter months dropping to a small percentage (between 0.75%) of the summer maximum. Distinct differences in relative abundances of species between habitats has also been shown, including a negative relationship between altitude and body size for Heard Island weevils. The fauna of the freshwater pools, lakes, streams and mires found in the coastal areas of Heard Island are broadly similar to those on other subantarctic islands of the southern Indian Ocean.
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The Borehole was part of southeastern part of the Polish Basin that during the Early Jurassic, where developed a shallow paralic environment, with organic carbon buried in nearshore marine environments due to intensified erosion. This Borehole shows enhanced biomass contribution from aquatic algae groups (Haptophyta, unicellular Rhodophyta and several marcoalgae), with measured proliferation of aquatic algae groups during the local parasequence “f”, documented by increased abundances of 4-Methyldiasterenes, what proves a more marine influence than on other coeval boreholes, such as the Brody-Lubienia. There is also abundance on Parkoszowice show of 4Me-diasterenes with 28 carbon atoms, that are related with synthesized by methane oxidizing bacteria. Methanotrophs commonly occur in environments where methane is produced, and implicates the presence of local Wetlands, Marsh and Lagoon environments.
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A boat navigating the town's coves In modern-day Özdere, local businesses and even district services are impacted greatly by the fluctuations and abundances of tourist revenue and revenue generated from the purchases and interactions of visitors. The promenades and walkways along the shoreline host numerous taverns, shops and restaurants that cater to visitors. Exotic jewelry stores and shopping malls within the town center and near the beach and access roads tend to attract tourists and flaunt their presence to visitors, but to a lesser extent than other nearby and arguably more popular resort towns such as Kuşadası. In the inner streets, food vendors and farmer's markets operate modestly and see more success during the summer, a high point for tourism in the town when the climate and beach conditions are more favorable.
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For example, the Lunar Prospector GRS identified several regions with high iron concentrations. Thorium concentrations on the Moon, as mapped by Lunar Prospector The fundamental purpose of the GRS experiment was to provide global maps of elemental abundances on the lunar surface. The GRS was designed to record the spectrum of gamma rays emitted by: # the radioactive decay of elements contained in the Moon's crust; and # elements in the crust bombarded by cosmic rays and solar wind particles. The most important elements detectable by the GRS were uranium (U), thorium (Th), and potassium (K), radioactive elements which generate gamma rays spontaneously, and iron (Fe), titanium (Ti), oxygen (O), silicon (Si), aluminum (Al), magnesium (Mg), and calcium (Ca), elements which emit gamma rays when hit by cosmic rays or solar wind particles.
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In some cases, stars may cross the instability strip for a fourth and fifth time when helium shell burning starts. The rate of change of the period of a Cepheid variable, along with chemical abundances detectable in the spectrum, can be used to deduce which crossing a particular star is making. Classical Cepheid variables were B type main sequence stars earlier than about B7, possibly late O stars, before they ran out of hydrogen in their cores. More massive and hotter stars develop into more luminous Cepheids with longer periods, although it is expected that young stars within our own galaxy, at near solar metallicity, will generally lose sufficient mass by the time they first reach the instability strip that they will have periods of 50 days or less.
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Young, massive and hot stars (typically of spectral types O and B) in H II regions emit UV photons that ionize ground-state hydrogen atoms, knocking electrons and protons free; this process is known as photoionization. The free electrons can strike other atoms nearby, exciting bound metallic electrons into a metastable state, which eventually decay back into a ground state, emitting photons with energies that correspond to forbidden lines. Through these transitions, astronomers have developed several observational methods to estimate metal abundances in HII regions, where the stronger the forbidden lines in spectroscopic observations, the higher the metallicity. These methods are dependent on one or more of the following: the variety of asymmetrical densities inside HII regions, the varied temperatures of the embedded stars, and/or the electron density within the ionized region.
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140Ce is the most common isotope of cerium, as it can be produced in both the s- and r-processes, while 142Ce can only be produced in the r-process. Another reason for the abundance of 140Ce is that it is a magic nucleus, having a closed neutron shell (it has 82 neutrons), and hence it has a very low cross section towards further neutron capture. Although its proton number of 58 is not magic, it is granted additional stability, as its eight additional protons past the magic number 50 enter and complete the 1g7/2 proton orbital. The abundances of the cerium isotopes may differ very slightly in natural sources, because 138Ce and 140Ce are the daughters of the long- lived primordial radionuclides 138La and 144Nd, respectively.
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In March 2004, the Mars Express science team suggested the presence of methane in the atmosphere at a concentration of about 10 ppbv. This was confirmed soon after by three ground-based telescope teams, although large differences in the abundances were measured between observations taken in 2003 and 2006. This spatial and temporal variability of the gas suggests that the methane was locally concentrated and probably seasonal. It is estimated that Mars must produce 270 ton/year of methane. In 2011, NASA scientists reported a comprehensive search using ground-based high-resolution infrared spectroscopy for trace species (including methane) on Mars, deriving sensitive upper limits for methane (< 7 ppbv), ethane (< 0.2 ppbv), methanol (< 19 ppbv) and others (H2CO, C2H2, C2H4, N2O, NH3, HCN, CH3Cl, HCl, HO2 – all limits at ppbv levels).
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The observed ratios of hydrogen to helium to deuterium in the universe are difficult to explain except with a Big Bang model. It is estimated that the abundances of deuterium have not evolved significantly since their production about 13.8 billion years ago. Measurements of Milky Way galactic deuterium from ultraviolet spectral analysis show a ratio of as much as 23 atoms of deuterium per million hydrogen atoms in undisturbed gas clouds, which is only 15% below the WMAP estimated primordial ratio of about 27 atoms per million from the Big Bang. This has been interpreted to mean that less deuterium has been destroyed in star formation in our galaxy than expected, or perhaps deuterium has been replenished by a large in-fall of primordial hydrogen from outside the galaxy.
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He is conducting research about the isotopic compositions of refractory inclusions in meteorites to understand the earliest history of the Solar System. Short- lived chronometers such as the 26Al-26Mg system can resolve time differences of only a few tens of thousands of years for events that occurred 4.55 billion years ago. Isotopic fractionation effects and the relative abundances of trace elements are used to constrain thermal histories and redox conditions in the solar nebula and on the asteroidal parent bodies of meteorites. Tiny (<10 µm in diameter) grains of silicon carbide, graphite, and other refractory minerals and rocks condensed around dying stars (mostly red giant stars and supernovae) survived potentially destructive processes in the interstellar medium and during solar system formation, and can now be found in meteorites.
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Tholins are disordered polymer-like materials made of repeating chains of linked subunits and complex combinations of functional groups. Sagan and Khare note "The properties of tholins will depend on the energy source used and the initial abundances of precursors, but a general physical and chemical similarity among the various tholins is evident." Some researchers in the field prefer a narrowed definition of tholins, for example S. Hörst wrote: "Personally, I try to use the word 'tholins' only when describing the laboratory-produced samples, in part because we do not really know yet how similar the material we produce in the lab is to the material found on places like Titan or Triton (or Pluto!)." French researchers also use the term tholins only when describing the laboratory-produced samples as analogues.
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His extensive field studies, laboratory dietary and isotopic analyses, and quantitative innovations revealed that networks of predator-prey interactions were far more complex than had been previously described. He discovered that the structure of freshwater and estuarine food webs was strongly influenced by seasonal environmental variation, selection of methods, units and resolution scales for network components, and species life history strategies influencing population dynamics and relative abundances of consumers and resources. This body of work, together with his research on fish community ecology, reveals how functional traits influence the manner that organisms respond to abiotic and biotic environmental features. Winemiller has been a proponent of the idea that universal form-function relationships and constraints result in widespread convergence of species adaptations and the structure of ecological communities in similar environments.
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The radioactive 100Sn, discovered in 1994, and 132Sn are two of the few nuclides with a "doubly magic" nucleus: despite being unstable, having very lopsided proton–neutron ratios, they represent endpoints beyond which stability drops off rapidly. Another 30 metastable isomers have been characterized for isotopes between 111 and 131, the most stable being 121mSn with a half-life of 43.9 years. The relative differences in the abundances of tin's stable isotopes can be explained by their different modes of formation in stellar nucleosynthesis. 116Sn through 120Sn inclusive are formed in the s-process (slow neutron capture) in most stars and hence they are the most common isotopes, while 122Sn and 124Sn are only formed in the r-process (rapid neutron capture) in supernovae and are less common.
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PDF Copy Because geomagnetic latitude is an important factor in auroral occurrence, (lower-latitude aurorae requiring higher levels of solar-terrestrial activity) it becomes important to allow for population migration and other factors that may have influenced the number of reliable auroral observers at a given magnetic latitude for the earlier dates. Decadal-scale cycles during the Maunder minimum can also be seen in the abundances of the beryllium-10 cosmogenic isotope (which unlike carbon-14 can be studied with annual resolution) PDF Copy but these appear to be in antiphase with any remnant sunspot activity. An explanation in terms of solar cycles in loss of solar magnetic flux was proposed in 2012. PDF Copy The fundamental papers on the Maunder minimum have been published in Case studies on the Spörer, Maunder and Dalton Minima.
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A number of detections have been made towards the end of confirming the temperature dependence of the abundance ratio of [HNC]/[HCN]. A strong fit between temperature and the abundance ratio would allow observers to spectroscopically detect the ratio and then extrapolate the temperature of the environment, thus gaining great insight into the environment of the species. The abundance ratio of rare isotopes of HNC and HCN along the OMC-1 varies by more than an order of magnitude in warm regions versus cold regions. In 1992, the abundances of HNC, HCN, and deuterated analogs along the OMC-1 ridge and core were measured and the temperature dependence of the abundance ratio was confirmed. A survey of the W 3 Giant Molecular Cloud in 1997 showed over 24 different molecular isotopes, comprising over 14 distinct chemical species, including HNC, HN13C, and H15NC.
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There are several lines of logic against interpreting 24-isopropyl cholestane as a biomarker for demosponge: # Much of the argument for Precambrian sponges is grounded in the observation that pelagophyte algae produce organic matter with a low ratio of 24-isopropyl cholestane to 24-n-propyl cholestane, but that this ratio is high in ancient rocks. However, the observed change in the sterane ratio could also be explained if algae changed the relative abundances in which they produce steranes over the past 600 million years. In a similar line of argument, it is possible that another extinct organism from which the algae descended produced organic matter with a higher ratio of 24-isopropyl cholestane to 24-n-propyl cholestane. As argued above, recent evidence has suggested that the algae's synthesis pathway only arose during the Phanerozoic, which tempers this argument.
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Primer affinity varies among all DNA sequences, which may result in biases during the amplification reaction; indeed, low-abundance samples are susceptible to overamplification errors, since the other contaminating microorganisms result to be over-represented in case of increasing the PCR cycles. Therefore, the optimization of primer selection can help to decrease such errors, although it requires complete knowledge of the microorganisms present in the sample, and their relative abundances. Marker gene analysis can be influenced by the primer choice; in this kind of analysis it's desirable to use a well-validated protocol (such as the one used in the Earth Microbiome Project). The first thing to do in a marker gene amplicon analysis is to remove sequencing errors; a lot of sequencing platforms are very reliable, but most of the apparent sequence diversity is still due to errors during the sequencing process.
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Lead's per-particle abundance in the Solar System is 0.121 ppb (parts per billion). This figure is two and a half times higher than that of platinum, eight times more than mercury, and seventeen times more than gold. The amount of lead in the universe is slowly increasing as most heavier atoms (all of which are unstable) gradually decay to lead. The abundance of lead in the Solar System since its formation 4.5 billion years ago has increased by about 0.75%. The solar system abundances table shows that lead, despite its relatively high atomic number, is more prevalent than most other elements with atomic numbers greater than 40. Primordial lead—which comprises the isotopes lead-204, lead-206, lead-207, and lead-208—was mostly created as a result of repetitive neutron capture processes occurring in stars.
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In the White Mountains, meadows formed during the Neopluvial. Glaciers grew in the Sierra Nevada, sagebrush steppe, green Mormon tea and other vegetation expanded in the Great Salt Lake region, marshes expanded in the central and northern Great Basin, mammal communities in the Lake Bonneville basin changed with the return of the long-tailed pocket mouse, the Great Basin pocket mouse and the Western harvest mouse to sites where they were not present before and increased abundances of even-toed ungulates, and tree lines dropped, with the lower limit of wooden vegetation penetrating into deserts. Counterintuitively, higher tree line elevations in the Lake Bonneville area occurred during the Neopluvial, which may indicate warmer summers. In the Owens Valley region, during the Neopluvial the human population became more sedentary and trans-Sierra Nevada trade became established ("Newberry"/"Middle Archaic Period").
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Originally, transcriptome-wide RNA abundance could only be assessed using methods such as DNA microarrays or serial analysis of gene expression (SAGE). These methods are prohibitive in differing regards; microarrays, while cheap, provide inconsistent results and SAGE is based on sanger sequencing, which provides limited throughput. Using second generation sequencing, instead of measuring relative hybridization of sequences to probes in the case of microarrays or sequencing short segments in the case of SAGE, a researcher can simply sequence the bulk RNA within a sample and measure relative abundances of specific types of RNA by comparing the number of times each RNA molecule was sequenced in a given sample. Normally, in a traditional RNA-seq, microarray, or SAGE experiment RNA is extracted from a biological sample such as cultured cells, and the RNA is analyzed using the chosen method.
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As beryllium-8 is unbound by only 92 keV, it is theorized that very small changes in nuclear potential and the fine tuning of certain constants (such as α, the fine structure constant), could sufficiently increase the binding energy of 8Be to prevent its alpha decay, thus making it stable. This has led to investigations of hypothetical scenarios in which 8Be is stable and speculation about other universes with different fundamental constants. These studies suggest that the disappearance of the bottleneck created by 8Be would result in a very different reaction mechanism in Big Bang nucleosynthesis and the triple-alpha process, as well as alter the abundances of heavier chemical elements. As Big Bang nucleosynthesis only occurred within a short period having the necessary conditions, it is thought that there would be no significant difference in carbon production even if 8Be were stable.
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It has been reported to exist in nature as a primordial nuclide, although a later study did not detect it. The second-longest-lived isotope not proven to be primordial is , which has a half-life of , about double that of the third-longest-lived such isotope (). Taking into account that all these nuclides must exist for at least , 244Pu must survive 57 half-lives (and hence be reduced by a factor of 257 ≈ ), 146Sm must survive 67 (and be reduced by 267 ≈ ), and 92Nb must survive 130 (and be reduced by 2130 ≈ ). Mathematically, considering the likely initial abundances of these nuclides, 244Pu and 146Sm should persist somewhere within the Earth today, even if they are not identifiable in the relatively minor portion of the Earth's crust available to human assays, while they should not for 92Nb and all shorter-lived nuclides.
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But, the effect of the configuration of habitat patches within the landscape, independent of the effect of the amount of habitat within the landscape (referred to as fragmentation per se), has been suggested to be small. A review of empirical studies found that, of the 381 reported significant effect of habitat fragmentation per se on species occurrences, abundances or diversity in the scientific literature, 76% were positive whereas 24% were negative. Despite these results, the scientific literature tends to emphasize negative effects more than positive effects.Fahrig, L. (2018) Forty years of biais in habitat fragmentation research, In: Effective Conservation Science: Data Not Dogma (Edited by Kareiva, Marvier and Silliman), Oxford University Press, United Kingdom Positive effects of habitat fragmentation per se imply that several small patches of habitat can have higher conservation value than a single large patch of equivalent size.
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In particular, xenon is useful for calculations of water loss over time. Not only is it a noble gas (and therefore is not removed from the atmosphere through chemical reactions with other elements), but comparisons between abundances of its nine stable isotopes in the modern atmosphere reveal that the Earth lost at least one ocean of water early in its history, between the Hadean and Archean eras. Any water on Earth during the later part of its accretion would have been disrupted by the Moon-forming impact (~4.5 billion years ago), which likely vaporized much of Earth's crust and upper mantle and created a rock-vapor atmosphere around the young planet. The rock vapor would have condensed within two thousand years, leaving behind hot volatiles which probably resulted in a majority carbon dioxide atmosphere with hydrogen and water vapor.
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Further advances were made, especially to nucleosynthesis by neutron capture of the elements heavier than iron, by Margaret and Geoffrey Burbidge, William Alfred Fowler and Hoyle in their famous 1957 B2FH paper, which became one of the most heavily cited papers in astrophysics history. Stars evolve because of changes in their composition (the abundance of their constituent elements) over their lifespans, first by burning hydrogen (main sequence star), then helium (red giant star), and progressively burning higher elements. However, this does not by itself significantly alter the abundances of elements in the universe as the elements are contained within the star. Later in its life, a low-mass star will slowly eject its atmosphere via stellar wind, forming a planetary nebula, while a higher–mass star will eject mass via a sudden catastrophic event called a supernova.
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While popularly cited as filter feeders that remove excess algae and nutrients from the water, evidence suggests that menhaden do not significantly impact water quality. Adult menhaden largely do not eat phytoplankton, whose excessive growth leads to dead zones, instead feeding mainly on zooplankton. “Time Series Mesoscale Response of Atlantic Menhaden Brevoortia tyrannus to Variation in Plankton Abundances,” Friedland, Kevin; Lynch, Patrick; Gobler, Christopher, Journal of Coastal Research, February 11, 2011 There is evidence that, because menhaden secrete nitrogen, that they may actually be a net contributor to phytoplankton growth.“Effects of Menhaden Predation on Plankton Populations in Narragansett Bay, Rhode Island,” Ann and Edward Durbin, Estuaries, September 1998 Separate, but related, to the issue of dead zones are fish kills, where large numbers of menhaden or other fish will turn up dead in a single area.
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Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006 Betelgeuse's time spent as a red supergiant can be estimated by comparing mass loss rates to the observed circumstellar material, as well as the abundances of heavy elements at the surface. Estimates range from 20,000 years to a maximum of 140,000 years. Betelgeuse appears to undergo short periods of heavy mass loss and is a runaway star moving rapidly through space, so comparisons of its current mass loss to the total lost mass are difficult. The surface of Betelgeuse shows enhancement of nitrogen, relatively low levels of carbon, and a high proportion of 13C relative to 12C, all indicative of a star that has experienced the first dredge-up.
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Minor and major volcanoes of the Northern Cordilleran Volcanic Province, including the Queen Charlotte, Denali and Tintina fault zones A range of more heavily alkaline rock types not commonly found in the Western Cordillera are regionally widespread in the Northern Cordilleran Volcanic Province. These include nephelinite, basanite and peralkaline phonolite, trachyte, and comendite lavas. The most magnesium oxide-rich nephelinites, basanites and alkaline basalts all through the Northern Cordilleran Volcanic Province display trace element abundances and isotopic compositions that are logical with an asthenospheric source like those for average oceanic island basalt and for alkaline basalts younger than five million years in the rift-related Basin and Range Province of southwestern United States and northwestern Mexico. One hypothesized explanation for oceanic island basalt in the Earth's upper mantle under the Northern Cordilleran Volcanic Province is the existence of a slab window.
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Native species that forage in farmland may increase their local abundances thereby affecting adjacent ecosystems within their landscape. For example, Luskin et al (2017) used two decades of ecological data from a protected primary rainforest in Malaysia to illustrate how subsidies from neighboring oil palm plantations triggered powerful secondary ‘cascading’ effects on natural habitats located >1.3 km away. They found that (i) oil palm fruit drove 100-fold increases in crop-raiding native wild boar (Sus scrofa), (ii) wild boar used thousands of understory plants to construct birthing nests in the pristine forest interior, and (iii) nest building caused a 62% decline in forest tree sapling density over the 24-year study period. The long-term, landscape-scale indirect effects from agriculture suggest its full ecological footprint may be larger in extent than is currently recognized.
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The elements heavier than iron with origins in dying low-mass stars are typically those produced by the s-process, which is characterized by slow neutron diffusion and capture over long periods in such stars A calculable model for creating the heavy isotopes from iron seed nuclei in a time- dependent manner was not provided until 1961. That work showed that the large overabundances of barium observed by astronomers in certain red-giant stars could be created from iron seed nuclei if the total neutron flux (number of neutrons per unit area) was appropriate. It also showed that no one single value for neutron flux could account for the observed s-process abundances, but that a wide range is required. The numbers of iron seed nuclei that were exposed to a given flux must decrease as the flux becomes stronger.
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Basalts formed at mid-ocean ridges and hotspots originate in the mantle and are used to provide information on the composition of the mantle. Magma rising to the surface may undergo fractional crystallization in which components with higher melting points settle out first, and the resulting melts can have widely varying water contents; but when little separation has occurred, the water content is between about 0.07–0.6 wt%. (By comparison, basalts in back- arc basins around volcanic arcs have between 1 wt% and 2.9 wt% because of the water coming off the subducting plate.) Mid-ocean ridge basalts (MORBs) are commonly classified by the abundance of trace elements that are incompatible with the minerals they inhabit. They are divided into "normal" MORB or N-MORB, with relatively low abundances of these elements, and enriched E-MORB.
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In the 1940s, geologist Hans Suess speculated that the regularity that was observed in the abundances of elements may be related to structural properties of the atomic nucleus. These considerations were seeded by the discovery of radioactivity by Becquerel in 1896 See also a translation by Carmen Giunta as an aside of advances in chemistry which aimed at production of gold. This remarkable possibility for transformation of matter created much excitement among physicists for the next decades, culminating in discovery of the atomic nucleus, with milestones in Ernest Rutherford's scattering experiments in 1911, and the discovery of the neutron by James Chadwick (1932). After Aston demonstrated that the mass of helium is less than four times that of the proton, Eddington proposed that, through an unknown process in the Sun's core, hydrogen is transmuted into helium, liberating energy.
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Elk at the Opal terrace at Mammoth Hot Springs, Yellowstone National Park Members of the deer family (Cervidae) are relatively common in the Rocky Mountains, and include North American elk, mule deer, white-tailed deer, woodland caribou, and moose. Population trends in North American elk and deer (mule deer and white-tailed deer combined) may be heading in opposite directions. The number of elk has increased steadily in Colorado and Wyoming, whereas the abundances of deer are showing signs of decline. Elk on U.S. Forest Service lands in the Rocky Mountains increased from 268,000 in 1965 to 372,000 in 1984. Similarly, the number of elk on Bureau of Land Management lands rose from 35,000 in 1966 to 114,000 in 1985. Meanwhile, the number of deer on U.S. Forest Service lands declined from 1,742,000 in 1965 to 1,197,000 in 1984.
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Chlorovirus titers are variable by season and location, but typically fluctuate between 1 and 100 PFU/mL, although high abundances of up to 100,000 PFU/mL may occur in some environments. Due to the rich genetic diversity and high specialization of individual species with respect to infectious range, variations in their ecology are not unusual, resulting in unique spatio- temporal patterns, which ultimately depend on lifestyle and nature of the host. As such, previous survey data highlighted two prominent seasonal abundance peaks for both Chlorella variabilis NC64A and Chlorella variabilis Syngen viruses — one in late fall, and the other in late spring to mid-summer — which is likely attributed to the fact that they share a host species. Conversely, Chlorella heliozoae SAG viruses peaked at different times of the year and generally exhibited more variability in titers, as compared to the NC64A and Syngen viruses.
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The images can be interpreted to indicate that the universe is 13.7 billion years old (within one percent error) and that the Lambda-CDM model and the inflationary theory are correct. No other cosmological theory can yet explain such a wide range of observed parameters, from the ratio of the elemental abundances in the early universe to the structure of the cosmic microwave background, the observed higher abundance of active galactic nuclei in the early universe and the observed masses of clusters of galaxies. In 2013 and 2015, ESA's Planck spacecraft released even more detailed images of the cosmic microwave background, showing consistency with the Lambda-CDM model to still higher precision. Much of the current work in cosmology includes understanding how galaxies form in the context of the Big Bang, understanding what happened in the earliest times after the Big Bang, and reconciling observations with the basic theory.
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Furthermore, since all organisms contain a slightly different genetic code, their mRNA structures differ slightly as well, however, multiple studies have been conducted that show that all properly folded mRNA structures are dependent on the primary sequence of the polypeptide chain and that the structure is maintained by dinucleotide relative abundances in the cell matrix. It has also been discovered that mRNA secondary structure is important for cell processes such as transcript stability and translation. The general idea is that the functional domains of mRNA fold upon each other, while the start and stop codon regions generally are more relaxed, which could aid in the signaling of initiation and termination in translation. If the oncoming ribosome pauses because of a knot in the RNA, then the polypeptide could potentially have enough time to fold into a non-native structure before the tRNA molecule can add another amino acid.
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1. The scale height sh is defined as , where is the gas constant, is the average molar mass in the Jovian atmosphere, T is temperature and is the gravitational acceleration at the surface of Jupiter. As the temperature varies from 110 K in the tropopause up to 1000 K in the thermosphere, the scale height can assume values from 15 to 150 km. 2. The Galileo atmospheric probe failed to measure the deep abundance of oxygen, because the water concentration continued to increase down to the pressure level of 22 bar, when it ceased operating. While the actually measured oxygen abundances are much lower than the solar value, the observed rapid increase of water content of the atmosphere with depth makes it highly likely that the deep abundance of oxygen indeed exceeds the solar value by a factor of about 3—much like other elements. 3.
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The Regolith X-ray Imaging Spectrometer (REXIS) will provide an X-ray spectroscopy map of Bennu to map element abundances. REXIS is a collaborative development by four groups within Massachusetts Institute of Technology (MIT) and Harvard University, with the potential to involve more than 100 students throughout the process. REXIS is based on flight heritage hardware, thereby minimizing elements of technical risk, schedule risk, and cost risk. REXIS is a coded aperture soft X-ray (0.3–7.5 keV) telescope that images X-ray fluorescence line emission produced by the absorption of solar X-rays and the solar wind with elements in the regolith of Bennu leading to local X-ray emissions. Images are formed with 21 arcminute resolution (4.3 m spatial resolution at a distance of 700 m). Imaging is achieved by correlating the detected X-ray image with a 64 x 64 element random mask (1.536 mm pixels).
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The proposed SPRITE atmospheric entry probe would carry a scientific instrument payload to measure Saturn's atmospheric structure, dynamics, composition, chemistry, and clouds to at least 10 bars. The conceptual payload consists of two spectrometers: a quadrupole mass spectrometer would measure noble gases and noble gas isotopes with extreme sensitivity. Of particular importance are measurements of helium (He), key to understanding Saturn's thermal evolution; and a tunable laser spectrometer that would measure molecular abundances and isotope ratios to determine the chemical structure of Saturn's atmosphere, and disequilibrium species such as carbon monoxide (), phosphine () and ethane () which can be used to infer Saturn's deep water abundance. The Atmospheric Structure Instrument (ASI) would provide the pressure and temperature profile of Saturn's atmosphere to determine the altitude profile of static stability, and when combined with cloud measurements from the nephelometer, it would elucidate processes that determine the location and structure of Saturn's multiple cloud layers.
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This was consistent with the hypothesis that the s-process had not yet begun to enrich interstellar gas when these young stars missing the s-process abundances were born from that gas, for it requires about 100 million years of galactic history for the s-process to get started whereas the r-process can begin after two million years. These s-process–poor, r-process–rich stellar compositions must have been born earlier than any s-process, showing that the r-process emerges from quickly evolving massive stars that become supernovae and leave neutron-star remnants that can merge with another neutron star. The primary nature of the early r-process thereby derives from observed abundance spectra in old stars that had been born early, when the galactic metallicity was still small, but that nonetheless contain their complement of r-process nuclei. Periodic table showing the cosmogenic origin of each element.
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As a Team Member of the NASA Astrobiology Institute from 1998–2010, Fogel worked on the Arctic Mars Analog Svalbard Expedition team in addition to her own collaborative research. One such project focused upon organic matter in carbonaceous chondrite meteorites where they measured the amino acid presence in three meteorites. First, to make sure that the amino acids were extraterrestrial in origin, they measured the 𝛿13C values of the amino acids in the meteorites, which turned out to be significantly higher than the 𝛿13C value of amino acids on Earth, confirming that they were not contamination from Earth (+31.6‰ to +50.5‰ in the meteorites relative to -70‰ to 11.25‰ present on Earth). The team of researchers also found that two of the meteorites had the highest ever detected amino acid abundances, which may be because carbonaceous chondrites are the most primitive and least altered meteorites.
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From 1980, De Laeter was elected in the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), serving as the Secretary of the Commission from 1984–1987 and as its chairman from 1988–1991. In 1984, he authored the "CIAAW Technical Guidelines" manual, which still serves as a reference for adopting new atomic weight values by the Commission. Recognising the application of mass spectrometry methods to geology in the 1970s and 1980s, de Laeter also established a series of projects with the Geological Survey of Western Australia and the University of Western Australia to develop geochronology capabilities based on the rubidium–strontium, samarium–neodymium and uranium–lead decay schemes. These projects produced a series of publications that established the geochronological framework of Western Australian geology, for example in the Pilbara Craton and establishing the extreme age of the Narryer Gneiss Terrane of the Yilgarn Craton.
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With his focus on radioactive supernova gas Clayton discovered a new chemical pathway causing carbon dust to condense there by a process that is activated by the radioactivity.“A New Astronomy with Radioactivity: Radiogenic Carbon Chemistry”, New Astronomy Reviews, 55, 155–65 (2011)] Clayton's foundational ideas for five original subfields of astrophysics are detailed in Section 5 below. They are: (1) nucleosynthesis, the assembly within stars of the atomic nuclei of the common chemical elements by nuclear reactions occurring therein; (2) astronomical detection of gamma-ray lines emitted by radioactive atoms created and ejected by supernovae; (3) mathematical models of the growth over time of the interstellar abundances of radioactive atoms; (4) predictions of the existence of interstellar cosmic dust grains from individual stars—individual chunks of long-dead stars. He named those stardust, each containing isotopically identifiable radioactive atoms of the host stars; (5) predictions of the condensation of solid grains of pure carbon within hot, oxygen-dominated radioactive supernova gases.
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While the drip lines impose the ultimate boundaries for nucleosynthesis, in high energy environments the burning pathway may be limited before the drip lines are reached by photodisintegration, where a high energy gamma ray knocks a nucleon out of a nucleus. The same nucleus is subject both to a flux of nucleons and photons, so an equilibrium is reached where mass builds up at particular nuclear species. As the photon bath will typically be described by a Planckian distribution, higher energy photons will be less abundant, and so photodisintegration will not become significant until the nucleon separation energy begins to approach zero towards the drip lines, where photodisintegration may be induced by lower energy gamma rays. At 1 × 109 Kelvin, the photon distribution is energetic enough to knock nucleons out of any nuclei that have particle separation energies less than 3 MeV, but to know which nuclei exist in what abundances one must also consider the competing radiative captures.
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Despite having the same age and presumably the same primordial composition, observations show a small difference in the metallicity of the two 16 Cygni stars. The primary star has an iron abundance of 1.26 times the solar value, compared to 1.13 for the secondary star. A similar trend has been found for all other metals, with the primary component having an average of 10% more metals than B. One possibility is that this difference is linked to the planet 16 Cygni Bb, since its formation may have removed metals from the protoplanetary disk around 16 Cygni B. However, another study found no difference in heavy element abundances between 16 Cygni A and B. Another chemical peculiarity between the stars is in their lithium abundance. Measurements of the lithium abundance in the system show a 4 times higher abundance in component A than in 16 Cygni B. Compared to the Sun, 16 Cygni A has 1.66 as much lithium, while 16 Cygni B has only 0.35.
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The goals of the mission are derived directly from the most recent decadal survey: first, to determine primordial sources of organics and the sites of organic synthesis today; and second, to determine if there are current habitats in Enceladus where the conditions for life could exist today, and if life exists there now. To achieve these goals, the ELF mission has three objectives: #To measure abundances of a carefully selected set of neutral species, some of which were detected by Cassini, to ascertain whether the organics and volatiles coming from Enceladus have been thermally altered over time. #To determine the details of the interior marine environment -- pH, oxidation state, available chemical energy, and temperature -- that permit characterization of the life- carrying capacity of the interior. #To look for indications that organics are the result of biological processes through three independent types of chemical measurements that are widely recognized as diagnostic of life.
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Rare-earth element abundances of basalts, of both terrestrial and lunar origins The Europium anomaly is the phenomenon whereby the europium (Eu) concentration in a mineral is either enriched or depleted relative to some standard, commonly a chondrite or mid-ocean ridge basalt (MORB). In geochemistry a europium anomaly is said to be "positive" if the Eu concentration in the mineral is enriched relative to the other rare-earth elements (REEs), and is said to be "negative" if Eu is depleted relative to the other REEs. While all lanthanides form relatively large trivalent (3+) ions, Eu and cerium (Ce) have additional valences, europium forms 2+ ions, and Ce forms 4+ ions, leading to chemical reaction differences in how these ions can partition versus the 3+ REEs. In the case of Eu, its reduced divalent (2+) cations are similar in size and carry the same charge as Ca2+, an ion found in plagioclase and other minerals.
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Material goods are made in large abundances and sold at cheaper costs, while in India for example, the poverty line is lowered in order to mask the number of individuals who are actually living in poverty as a result of globalization. Globalization and structural forces aggravate poverty and continue to push individuals to the margins of society, while governments and large corporations do not address the issues (George, P, SK8101, lecture, October 9, 2007). Certain language and the meaning attached to language can cause universalizing discourses that are influenced by the Western world, which is what Sewpaul (2006) describes as the "potential to dilute or even annihilate local cultures and traditions and to deny context-specific realities" (p. 421). What Sewpaul (2006) is implying is that the effect of dominant global discourses can cause individual and cultural displacement, as well as an experience of "de-localization", as individual notions of security and safety are jeopardized (p. 422).
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That theory was begun by Fred Hoyle in 1946 with his argument that a collection of very hot nuclei would assemble thermodynamically into iron Hoyle followed that in 1954 with a paper describing how advanced fusion stages within massive stars would synthesize the elements from carbon to iron in mass. Hoyle's theory was expanded to other processes, beginning with the publication of a review paper in 1957 by Burbidge, Burbidge, Fowler and Hoyle (commonly referred to as the B2FH paper). This review paper collected and refined earlier research into a heavily cited picture that gave promise of accounting for the observed relative abundances of the elements; but it did not itself enlarge Hoyle's 1954 picture for the origin of primary nuclei as much as many assumed, except in the understanding of nucleosynthesis of those elements heavier than iron by neutron capture. Significant improvements were made by Alastair G. W. Cameron and by Donald D. Clayton.
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He directed the Caltech astronomy program until 1972 and later did classified work on military reconnaissance satellites. With Leverett Davis, Jr, he demonstrated in 1949 that the magnetic field in our galaxy is aligned with the spiral arms. His theoretical work with Davis was based on the conclusion just reached by William A. Hiltner that the recently detected polarization of starlight was due to scattering off interstellar dust grains aligned by a magnetic field. Greenstein did important work in determining the abundances of the elements in stars, and was, with Maarten Schmidt, among the first to recognize quasars as compact, very distant sources as bright as a galaxy. The spectra of the first quasars discovered, radio sources 3C 48 and 3C 273, were displaced so far to the red due to their redshifts as to be almost unrecognizable, but Greenstein deciphered 3C 48 shortly before Schmidt, his colleague at the Hale Observatories worked out the spectrum of 3C 273.
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NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate Parallax is the apparent change of the position of an object, measured in seconds of arc, caused by the change of position of the observer of that object. As the Earth orbits the Sun, every star is seen to shift by a fraction of an arc second, which measure, combined with the baseline provided by the Earth's orbit gives the distance to that star. Since the first successful parallax measurement by Friedrich Bessel in 1838, astronomers have been puzzled by Betelgeuse's apparent distance. Knowledge of the star's distance improves the accuracy of other stellar parameters, such as luminosity that, when combined with an angular diameter, can be used to calculate the physical radius and effective temperature; luminosity and isotopic abundances can also be used to estimate the stellar age and mass. In 1920, when the first interferometric studies were performed on the star's diameter, the assumed parallax was .
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The short duration and falling temperature means that only the simplest and fastest fusion processes can occur. Only tiny amounts of nuclei beyond helium are formed, because nucleosynthesis of heavier elements is difficult and requires thousands of years even in stars. Small amounts of tritium (another hydrogen isotope) and beryllium-7 and -8 are formed, but these are unstable and are quickly lost again. A small amount of deuterium is left unfused because of the very short duration. Therefore, the only stable nuclides created by the end of Big Bang nucleosynthesis are protium (single proton/hydrogen nucleus), deuterium, helium-3, helium-4, and lithium-7. By mass, the resulting matter is about 75% hydrogen nuclei, 25% helium nuclei, and perhaps 10−10 by mass of lithium-7. The next most common stable isotopes produced are lithium-6, beryllium-9, boron-11, carbon, nitrogen and oxygen ("CNO"), but these have predicted abundances of between 5 and 30 parts in 1015 by mass, making them essentially undetectable and negligible. Conference: "Nuclear Physics in Astrophysics VI (NPA6) 19–24 May 2013, Lisbon, Portugal".
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These rare objects, known as metal-poor stars, are the most chemically primitive stars known, and are among the first generations of stars born in our galaxy, the Milky Way. They provide crucial information on the astrophysical nucleosynthesis sites of the chemical elements, and are powerful tracers of the assembly and evolution of large spiral galaxies. Beers’ discoveries include: (1) The identification of the first metal-poor stars with measured abundances of Uranium, enabling the determination of a radioactive decay age limit on the Universe, (2) a class of stars known as carbon-enhanced metal- poor (CEMP) stars, a subset of which are thought to reflect the nucleosynthesis products of the very first stars in the Universe, and (3) The first large-scale chronographic (age) maps of the halo of the Milky Way, which astronomers can compare with simulations of the formation of the galaxy. In 2017, Beers and his graduate students were part of a team that identified the characteristic signature of the astrophysical r-process in the kilonova associated with a neutron star merger.
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In 2018, the Gaia project of the European Space Agency, designed primarily to investigate the origin, evolution and structure of the Milky Way, delivered the largest and most precise census of positions, velocities and other stellar properties of more than a billion stars, which showed that Sgr dSph had caused perturbations in a set of stars near the Milky Way's core, causing unexpected rippling movements of the stars triggered when it sailed past the Milky Way between 300 and 900 million years ago. A 2019 study by Melendez and co-authors concluded that Sgr dSph had a decreasing metallicity trend as a function of radius, with a larger spread in metallicity in the core relative to the outer regions. Also, they did find evidence for the first time for two distinct populations in alpha abundances as a function of metallicity. A 2020 study concluded that collisions between the Sagittarius Dwarf Spheroidal Galaxy and the Milky Way triggered major episodes of star formation in the latter, based on data taken from the Gaia project.
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300pxIn physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even from place to place on the Earth, but remains relatively constant in time (on a short- term scale). As an example, uranium has three naturally occurring isotopes: 238U, 235U and 234U. Their respective natural mole-fraction abundances are 99.2739–99.2752%, 0.7198–0.7202%, and 0.0050–0.0059%. For example, if 100,000 uranium atoms were analyzed, one would expect to find approximately 99,274 238U atoms, approximately 720 235U atoms, and very few (most likely 5 or 6) 234U atoms. This is because 238U is much more stable than 235U or 234U, as the half-life of each isotope reveals: 4.468 × 109 years for 238U compared with 7.038 × 108 years for 235U and 245,500 years for 234U. Exactly because the different uranium isotopes have different half-lives, when the Earth was younger, the isotopic composition of uranium was different.
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Radiative levitation is the name given to a phenomenon that causes the spectroscopically-derived abundance of heavy elements in the photospheres of hot stars to be very much higher than solar abundance or than the expected bulk abundance; for example, the spectrum of the star Feige 86 has gold and platinum abundances three to ten thousand times higher than solar norms. The mechanism is that heavier elements have large photon absorption cross-sections when partially ionized (see opacity), so efficiently absorb photons from the radiation coming from the core of the star, and some of the energy of the photons gets converted to outward momentum, effectively 'kicking' the heavy atom towards the photosphere. The effect is strong enough that very hot white dwarfs are significantly less bright in the EUV and X-ray bands than would be expected from a black-body model. The countervailing process is gravitational settling, where, in very high gravitational fields, the effects of diffusion even in a hot atmosphere are cancelled out to the point that the heavier elements will sink unobservably to the bottom and lighter elements settle on the top.
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It is a two-dimensional graphical representation in the Segrè-arrangement with the neutron number N on the abscissa and the proton number Z on the ordinate. Each nuclide is represented at the intersection of its respective neutron and proton number by a small square box with the chemical symbol and the nucleon number A. By columnar subdivision of such a field, in addition to ground states also nuclear isomers can be shown. The coloring of a field (segmented if necessary) shows in addition to the existing text entries the observed types of radioactive decay of the nuclide and a rough classification of their relative shares: stable, nonradioactive nuclides completely black, primordial radionuclides partially black, proton emission orange, alpha decay yellow, beta plus decay/electron capture red, isomeric transition (gamma decay, internal conversion) white, beta minus decay blue, spontaneous fission green, cluster emission violet, neutron emission light blue. For each radionuclide its field includes (if known) information about its half-life and essential energies of the emitted radiation, for stable nuclides and primordial radionuclides there are data on mole fraction abundances in the natural isotope mixture of the corresponding chemical element.
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Clayton introduced the idea that the relative abundances of the isotopes in tiny solid dust grains that condensed within hot gas leaving individual stars would be observable in such single dust grains. Those grains reveal the isotopic composition of their parent stars. He named these solids stardust,Precondensed Matter: Key to the Early Solar System, Moon & Planets 19, 109 (1978) postulating thereby a new component of interstellar Cosmic dust. Stardust inherits its unusual isotopic compositions from the evolved nuclear composition of the parent star within which that grain condensed. Clayton's initial steps[ “Extinct radioactivities: Trapped residuals of pre-solar grains”, Astrophys. J., 199, 765-69, (1975); “22Na, Ne-E, Extinct radioactive anomalies and unsupported 40Ar”, Nature, 257, 36-37, (1975) focused on large isotopic excesses in supernova dust grains owing to decays of abundant short-lived radioactive nuclei that were created in the nuclear explosion and then condensed within a few months in the cooling ejecta; but it was generalized to all types of stellar mass loss in 1978.Donald D. Clayton, Precondensed Matter: Key to the Early Solar System, Moon & Planets 19, 109 (1978); "Grains of anomalous isotopic composition from novae", Clayton & Hoyle, Astrophys.J. 203, 490 (1976); “Cosmoradiogenic ghosts and the origin of Ca-Al-rich inclusions”, Earth and Planetary Sci. Lett.
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Their study was called a "major contribution" in providing data to help identify the relatively rare Population II stars. It created an unbiased sample, and doubled the number of known peculiar A-type (Ap) stars. After nineteen years of study by various investigators, in 2014, Beers et al. studied 302 of the Bidelman-MacConnell possible weak-metal stars and concluded that a metal-weak thick disk (MWTD) is present in the Milky Way galaxy, and noted its importance in understanding the development of our galaxy. In 1962 and 1966, Bidelman had reported that the wavelength of λ 3984 varied somewhat from star to star, and stated differences in the ratios of mercury isotopes could be the reason. Bidelman was the first to note this, and in 1974, Michaud, Reeves and Charland, considering the isotopic abundances to be real, and that Hg was in fact overabundant and not an artifact of blending, suggested the mercury overabundances were due to radiation pressure that caused the element to pile up until radiation and gravitational forces almost cancelled each other, then its isotopes would separate, sorting themselves. Michaud suggested that element segregation would proceed naturally due to gravitational settling and radiation pressure if the stellar atmosphere was steady.
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