So he and Veras created computer simulations of the entire range of magnetic fields and electrical conductivities observed in white dwarf stars.
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Doping cis-polyacetylene with AsF5 further increased the conductivities, bringing them close to that of copper. Furthermore, it was found that heat treatment of the catalyst used for polymerization led to films with higher conductivities.
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Applications to the Densities and Electrical Conductivities of Mixed Electrolyte and Nonelectrolyte Solutions.
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PPy is an insulator, but its oxidized derivatives are good electrical conductors. The conductivity of the material depends on the conditions and reagents used in the oxidation. Conductivities range from 2 to 100 S/cm. Higher conductivities are associated with larger anions, such as tosylate.
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Gray, p 495 Many commercial systems offer automatic temperature correction. Tables of reference conductivities are available for many common solutions.
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During the night, these numbers may decrease by a factor of ten or more. The values of these conductivities depend on local time, latitude, season and solar 11- year cycle. The height integrated conductivities become of the order of 50 S, or a total resistance of the dynamo region of about 1/50 = 0.02 Ohm during daytime conditions.Fejer, A.A., Rev. Geophys.
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These low thermal conductivities were achieved through the generation of an alternating high-porosity, low-porosity microstructure or the synthesis of a low-conductivity precursor composition with rare-earth dopants.
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While thermal bridges exist in various types of building enclosures, masonry walls experience significantly increased U-factors caused by thermal bridges. Comparing thermal conductivities between different building materials allows for assessment of performance relative to other design options. Brick materials, which are usually used for facade enclosures, typically have higher thermal conductivities than timber, depending on the brick density and wood type. Concrete, which may be used for floors and edge beams in masonry buildings are common thermal bridges, especially at the corners.
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Nellis was born in Chicago, Illinois in 1941. He received his B.S. degree in Physics from Loyola University of Chicago, College of Liberal Arts and Sciences, in 1963 and his Ph.D. degree in Physics from Iowa State University in 1968. His Ph.D. thesis research included measurements of electrical and thermal conductivities of single crystals of the Rare Earth elements Gadolinium, Terbium and Holmium in the Ames National Laboratory at Iowa State.W. J. Nellis and S. Legvold, "Thermal Conductivities and Lorenz Functions of Gadolinium, Terbium, and Holmium Single Crystals," Phys. Rev.
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Poly(3-octylthiophene) dissolved in toluene can be doped by solutions of ferric chloride hexahydrate dissolved in acetonitrile, and can be cast into films with conductivities reaching 1 S/cm. Other, less common p-dopants include gold trichloride and trifluoromethanesulfonic acid.
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The conductivity of polyacetylene depends on structure and doping. Undoped trans-polyacetylene films have a conductivity of 4.4×10−5 Ω−1cm−1, while cis-polyacetylene has a lower conductivity of 1.7×10−9 Ω−1cm−1 Doping with bromine causes an increase in conductivity to 0.5 Ω−1cm−1, while a higher conductivity of 38 Ω−1cm−1 is obtained through doping with iodine. Doping of either cis- or trans-polyacetylene leads to an increase in their conductivities. Doped cis-polyacetylene films usually have conductivities two or three times greater than doped trans-polyacetylene even though the parent film has lower conductivity.
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In heat transfer, the thermal conductivity of a substance, k, is an intensive property that indicates its ability to conduct heat. Thermal conductivity is often measured with laser flash analysis. Alternative measurements are also established. Mixtures may have variable thermal conductivities due to composition.
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Conditions for spin coating and evaporation affect device efficiency. Solvent and additives influence donor- acceptor morphology. Additives slow down evaporation, leading to more crystalline polymers and thus improved hole conductivities and efficiencies. Typical additives include 1,8-octanedithiol, ortho-dichlorobenzene, 1,8-diiodooctane (DIO), and nitrobenzene.
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LISICONs can be used as the solid electrolyte in of lithium based Solid-State Batteries, such as solid state nickel–lithium battery. For this application, solid lithium electrolytes require ionic conductivities greater than 10−4 S/cm, negligible electronic conductivity, and a wide range of electrochemcial stability.
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On the possibility of a metallic modification of hydrogen. Journal of Chemical Physics, 3, 764-770. Dynamic compression generates temperature T and entropy S on rapid compression and the product TS controls phase stability via the free energy. By tuning the magnitude and temporal shape of a reverberating shock pressure pulse, H2 dissociates to H at sufficiently large density that measured electrical conductivities of fluid H cross over from semiconducting to degenerate metal with Mott’s Minimum Metallic Conductivity at pressure 1.4 million bars (140 GPa), nine-fold H atom density in liquid H2 and calculated temperature of 3000 K. Similar electrical conductivities of H under multiple- shock compression have been measured by Fortov et al.
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The development of conducting polymers by Alan J. Heeger, Alan MacDiarmid and Hideki Shirakawa in 1975 was a break-through in point of lower ESR.About the Nobel Prize in Chemistry 2000, Advanced Information, October 10, 2000, The conductivities of conductive polymers such as polypyrrole (PPy)Y. K. ZHANG, J. LIN，Y.
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Another way is to use four-electrode conductivity sensors that are made from corrosion- resistant materials. A benefit of four-electrode conductivity sensors compared to inductive sensors is scaling compensation and the ability to measure low (below 100 μS/cm) conductivities (a feature especially important when measuring near-100% hydrofluoric acid).
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The 3ω-method (3 omega method) or 3ω-technique, is a measurement method for determining the thermal conductivities of bulk material (i.e. solid or liquid) and thin layers. The process involves a metal heater applied to the sample that is heated periodically. The temperature oscillations thus produced are then measured.
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Also, comparatively, more copper wire can fit in a given conduit than conductors with lower conductivities. This greater “wire fill” is a special advantage when a system is rewired or expanded. Copper building wire is compatible with brass and quality plated screws. The wire provides connections that will not corrode or creep.
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Due to its relatively high conductivity, blood may be used for functional imaging of perfusion in tissues and organs characterized by lower conductivities, e.g. to visualize regional lung perfusion.Kunst P.W., Vonk Noordegraaf A., Hoekstra O.S., Postmus P.E., de Vries P.M. (1998) "Ventilation and perfusion imaging by electrical impedance tomography: a comparison with radionuclide scanning." Physiol. Meas.
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As semimetals have fewer charge carriers than metals, they typically have lower electrical and thermal conductivities. They also have small effective masses for both holes and electrons because the overlap in energy is usually the result of the fact that both energy bands are broad. In addition they typically show high diamagnetic susceptibilities and high lattice dielectric constants.
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However, the stability of these doped materials is relatively low. In general, unaligned, unsubstituted PPV presents only moderate conductivity with doping, ranging from <<10-3 S/cm (I2 doped) to 100 S/cm (H2SO4-doped). Draw ratios of up to 10 are possible. Alkoxy- substituted PPVs are generally easier to oxidize than the parent PPV and hence have much higher conductivities.
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The metametals are zinc, cadmium, mercury, indium, thallium, tin and lead. They are ductile elements but, compared to their metallic periodic table neighbours to the left, have lower melting points, relatively low electrical and thermal conductivities, and show distortions from close- packed forms.Wiberg, Holleman & Wiberg 2001, p. 143 Sometimes berylliumKlemm 1950 and galliumMiller GJ, Lee C & Choe W 2002, p.
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As a solid conducting polymer electrolyte It reaches conductivities up to 100 S/m. Polypyrrole was the first conductive polymer used in polymer Al-e-caps as well as in polymer Ta-e-caps. The problem with the polymerization of PPy was the rate of polymerization. When pyrrole is mixed with the desired oxidizing agents at room temperature, the polymerization reaction begins immediately.
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By partial oxidation of the material with SbF5 conductivities of 0.3 S cm−1 could be monitored.T. Imori, V. Lu, H. Cai, T. D. Tilley, J. Am. Chem. Soc., 1995, 117, 9931. The liquid-crystalline characteristics of the poly(dialkylstannane)s permitted facile orientation of these macromolecules, for instance, by mechanical shearing or tensile drawing of blends with poly(ethylene).
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Their electrical conductivities are very sensitive to the concentration of impurities, which allows the use of doping to achieve desirable electronic properties. Hence, semiconductors form the basis of the traditional computer. This field also includes new areas of research such as superconducting materials, spintronics, metamaterials, etc. The study of these materials involves knowledge of materials science and solid-state physics or condensed matter physics.
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Optical properties of high-pressure fluid hydrogen across molecular dissociation. Proceedings of National Academy of Science (U. S.), 116, 9770-9774. Measured electrical conductivities of fluid SiH4 up to 106 GPa under multiple-shock compression with a two-stage light-gas gunZhong, X. F., Liu, F. S., Cai, L. C., Xi, F., Zhang, M. J., Liu, Q. J., Yang, Y. P. and Hao, B. B. (2014).
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Because of their large sizes and low thermal conductivities, the planetary interior pressures range up to several hundred GPa and temperatures of several thousand kelvins (K). In March 2012, it was found that the compressibility of water used in ice-giant models could be off by one third. This value is important for modeling ice giants, and has a ripple effect on understanding them.
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Rocky materials do not vary much in density and specific heat, so variations in thermal inertia are mainly due to variations in thermal conductivity. Solid rock surfaces, such as outcroppings, have high thermal conductivities and inertias. Dust and small granular material in the regolith have low thermal inertias because the void spaces between grains restrict thermal conductivity to the contact point between grains.Carr, M.H. (2006).
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Near the geomagnetic dip equator, a west-east directed electric field generates vertical Hall currents which cannot close. Therefore, a vertical polarization field builds up generating a horizontal Hall current which adds to the Pedersen current. Such enhancement is described by the Cowling conductivity. Pedersen and Hall conductivities reach maximum values near 120 to 140 km altitudes with numbers of about 1 mS/m during sunlit conditions.
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The flux freezing indicates that the magnetic field topology cannot change in a perfectly conducting fluid. However, this would lead to highly tangled magnetic fields with very complicated topologies that should impede the fluid motions. Nevertheless, astrophysical plasmas with high electrical conductivities do not generally show such complicated tangled fields. Also magnetic reconnection seems to occur in these plasmas unlike what is expected from the flux freezing conditions.
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In many high purity metals both the electrical and thermal conductivities rise as temperature is decreased. In certain materials (such as silver or aluminum) however, the value of L also may decrease with temperature. In the purest samples of silver and at very low temperatures, L can drop by as much as a factor of 10.K. Gloos, C. Mitschka, F. Pobell and P. Smeibidl. Cryogenics, 30 (1990), p.
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As the lithium purple bronze is cooled from 30 K to 20, it changes abruptly to an insulator. After reaching a minimum at about 24 K, the resistivity increases 10-fold and becomes somewhat more isotropic, with conductivities 1:25:14. The anisotropy is partially restored if a magnetic field is applied perpendicular to the b axis. The transition may be related to the onset of a charge density wave.
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Solid ceramic electrolytes can be further broken down into two main categories: ceramic and glassy. Ceramic solid electrolytes are highly ordered compounds with crystal structures that usually have ion transport channels. Common ceramic electrolytes are lithium super ion conductors (LISICON) and perovskites. Glassy solid electrolytes are amorphous atomic structures made up of similar elements to ceramic solid electrolytes, but have higher conductivities overall due to higher conductivity at grain boundaries.
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The major disadvantage of air cooling is its inefficiency. Large amounts of power must used to operate the cooling mechanism, far more than active liquid cooling. The additional components of the cooling mechanism also add weight to the BMS, reducing the efficiency of batteries used for transportation. Liquid cooling has a higher natural cooling potential than air cooling as liquid coolants tend to have higher thermal conductivities than air.
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Tong et. al reported that CNT arrays can be used effectively as thermal interface materials (TIM) due to their high conductance, which they report as ~10^5 W/m^2/K. Thermal interface materials are materials that can enhance thermal conduction at surfaces by having high thermal conductivities; it is useful to have materials which can be designed to fit any geometry. Additionally, the geometry of VANTA systems allows for anisotropic heat transfer.
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The para gene is located on the X chromosome within the Drosophila genome. There are 26 para exons, 13 are constitutively expressed in the transcript, while 15 are alternatively spliced. Alternative splicing allows for the formation of 60 unique transcripts and 57 unique polypeptides. The independent splicing of 11 exons allows for the unique cytoplasmic loops, the alternative splicing also can effect the Na+ channel kinetics, such as the varying gating conductivities.
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For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known. Graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials.
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The high thermal conductivities of beryllium and beryllium oxide have led to their use in thermal management applications. When added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron or nickel beryllium improves many physical properties. Tools made of beryllium copper alloys are strong and hard and do not create sparks when they strike a steel surface. Beryllium does not form oxides until it reaches very high temperatures.
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In 2011, N. Wakeham et al. found that the ratio of the thermal and electrical Hall conductivities in the metallic phase of quasi-one-dimensional lithium molybdenum purple bronze Li0.9Mo6O17 diverges with decreasing temperature, reaching a value five orders of magnitude larger than that found in conventional metals obeying the Wiedemann–Franz law. This due to spin-charge separation and it behaving as a Luttinger liquid. A Berkeley-led study in 2016 by Lee et al.
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Liquid electrolytes in lithium-ion batteries consist of lithium salts, such as , or in an organic solvent, such as ethylene carbonate, dimethyl carbonate, and diethyl carbonate. A liquid electrolyte acts as a conductive pathway for the movement of cations passing from the negative to the positive electrodes during discharge. Typical conductivities of liquid electrolyte at room temperature () are in the range of 10 mS/cm, increasing by approximately 30–40% at and decreasing slightly at .Wenige, Niemann, et al.
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Monteil & Vincent 1976 S and Se Commonalties between sulfur and selenium are abundantly obvious. For example, selenium is found in metal sulfide ores, where it partially replaces sulfur; both elements are photoconductors—their electrical conductivities increase by up to six orders of magnitude when exposed to light.Moss 1952 I and Xe. The chemistry of iodine in its oxidation states of +1, +3, +5, and +7 is analogous to that of xenon in an immediately higher oxidation state.
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Carbon materials have been widely used as cathodes because of their excellent electrical conductivities, large surface areas, and chemical stability. Especially relevant for lithium-air batteries, carbon materials act as substrates for supporting metal oxides. Binder-free electrospun carbon nanofibers are particularly good potential candidates to be used in electrodes in lithium-oxygen batteries because they have no binders, have open macroporous structures, have carbons that support and catalyze the oxygen reduction reactions, and have versatility. Zhu et al.
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Electrical resistivity of silane multiply shock- compressed to 106 GPa. Chinese Physics Letters, 31, 126201. are in good agreement with the electrical conductivity data measured in. Once the pressure dependence of the electrical conductivity of semiconducting and metallic fluid H was measured, those conductivities were used to address the likely cause of the unusual external magnetic fields of the planets Uranus and Neptune, which are neither dipolar nor axisymmetric as the fields of Earth and other planets with magnetic fields.
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This is due to the way that metals bond chemically: metallic bonds (as opposed to covalent or ionic bonds) have free-moving electrons that transfer thermal energy rapidly through the metal. The electron fluid of a conductive metallic solid conducts most of the heat flux through the solid. Phonon flux is still present but carries less of the energy. Electrons also conduct electric current through conductive solids, and the thermal and electrical conductivities of most metals have about the same ratio.
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Conversely, MOFs have shown encouraging proton conductivities in both low and high temperature regimes as well as over a wide range of humidity conditions. Below 100 °C and under hydration, the presence of hydrogen bonding and solvent water molecules aid in proton transport, whereas anhydrous conditions are suitable for temperatures above 100 °C. MOFs also have the distinct advantage of exhibiting proton conductivity by the framework itself in addition to the inclusion of charge carries (i.e., water, acids, etc.) into their pores.
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As far back as 1965 there are reports of semiconductor materials exhibiting electrical conductivities that are strongly affected by ambient gases and vapours.J. I. Bregman and A. Dravnieks Surface Effects in Detection, 1965 :SpartanF. Gutman and L.E. Lyons Organic Semiconductors, 1967 :Wiley However, it was not until 1985 that Wohltjen and Snow coined the term chemiresistor. The chemiresistive material they investigated was copper phthalocyanine, and they demonstrated that its resistivity decreased in the presence of ammonia vapour at room temperature.
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Angelo Battelli (28 March 1862 – 11 December 1916) was an Italian scientist, notable for having measured temperatures and heats of fusion of non-metallic substances, metallic conductivities and thermoelectric effects in magnetic metals, and the Thomson effect. He investigated osmotic pressures, surface tensions, and physical properties of carbon disulfide (CS2), water (H2O), and alcohols, especially their vapor pressures, critical points, and densities. He studied X-rays and cathode rays. He investigated the resistance of solenoids to high-frequency alternating currents.
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THz spectroscopy can be used as a non-contact analytical method. The absorption coefficient and refractive index measured by terahertz pulsed spectroscopy can be used directly to obtain the high frequency-dependent complex conductivities of materials in the 0.1 – 3 THz (3 – 100 cm−1) region of the electromagnetic spectrum."Terahertz for Material Characterization" The technology has been applied to some areas of solid state physics research such as semiconductors, high-temperature superconductors, terahertz metamaterials, carrier density dynamics, graphene, carbon nanotubes, magnetism and more.
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The objective, by John Brashear, was held in place by a special cell that compensated for the different temperature conductivities of the brass and glass so that temperature had no effect on the location or separation of the lenses. Designated as model M-505, the transit included a handing level, micrometer and a built in reversing mechanism. This transit was located in the east-central transit room allowing direct access to the clock room through a small window. The instrument cost $1200 in 1896.
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FL-Ti3C2 (the most studied MXene) nanosheets can mix intimately with polymers such as polyvinyl alcohol (PVA), forming alternating MXene-PVA layered structures. The electrical conductivities of the composites can be controlled from 4×10−4 to 220 S/cm (MXene weight content from 40% to 90%). The composites have tensile strength up to 400% stronger than pure MXene films and show better capacitance up to 500 F/cm3. A method of alternative filtration for forming MXene-carbon nanomaterials composite films is also devised.
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However, most often, because of complicated shapes with varying thermal conductivities within the shape (i.e., most complex objects, mechanisms or machines in engineering) often the application of approximate theories is required, and/or numerical analysis by computer. One popular graphical method involves the use of Heisler Charts. Occasionally, transient conduction problems may be considerably simplified if regions of the object being heated or cooled can be identified, for which thermal conductivity is very much greater than that for heat paths leading into the region.
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Aerogels are composed of 99.8% air, or empty space. This solid matter is usually made by removing the liquid from Silica Gels, leaving behind just the molecular structure of Silicon Dioxide (SiO2). Hurwitz has, instead, researched producing aerogels with a different chemical composition so the properties of aerogels, like the temperature limits, would increase and allow space travel to be safer. She has helped create an Aluminosilicate aerogel, which caused the lower thermal conductivities of the aerogels to be able to withstand temperatures higher than 900.
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A similar charging mechanism can occur within low conductivity fluids flowing through pipelines—a process called flow electrification. Fluids which have low electrical conductivity (below 50 picosiemens per meter), are called accumulators. Fluids having conductivities above 50 pS/m are called non- accumulators. In non-accumulators, charges recombine as fast as they are separated and hence electrostatic charge generation is not significant. In the petrochemical industry, 50 pS/m is the recommended minimum value of electrical conductivity for adequate removal of charge from a fluid.
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A variety of reagents have been used to dope PTs. Iodine and bromine produce highly conductive materials, which are unstable owing to slow evaporation of the halogen. Organic acids, including trifluoroacetic acid, propionic acid, and sulfonic acids produce PTs with lower conductivities than iodine, but with higher environmental stabilities. Oxidative polymerization with ferric chloride can result in doping by residual catalyst, although matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) studies have shown that poly(3-hexylthiophene)s are also partially halogenated by the residual oxidizing agent.
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Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride.
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In 1975, Peter V. Wright, a polymer chemist from Sheffield (UK), produced the first polymer electrolyte, which contained sodium and potassium salts in a polyethylene oxide (PEO) matrix. Later another type of polymer electrolytes, polyelectrolyte, was put forward, where ions moved through an electrically charged, rather than neutral, polymer matrix. Polymer electrolytes showed lower conductivities than glasses, but they were cheaper, much more flexible and could be easier machined and shaped into various forms. While ionic glasses are typically operated below, polymer conductors are typically heated above their glass transition temperatures.
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The most commonly used detectors are the flame ionization detector (FID) and the thermal conductivity detector (TCD). Both are sensitive to a wide range of components, and both work over a wide range of concentrations. While TCDs are essentially universal and can be used to detect any component other than the carrier gas (as long as their thermal conductivities are different from that of the carrier gas, at detector temperature), FIDs are sensitive primarily to hydrocarbons, and are more sensitive to them than TCD. However, a FID cannot detect water.
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Their structure permits a great interaction with organic compounds as well as increased selectivity and stability in maximum adsorption capacity. Other advantages include high electrical and thermal conductivities, high strength, high hardness. Target pollutants that can be targeted by nanomolecules are 〖NO〗_x, 〖CO〗_2, 〖NH〗_3, N_2, VOCs, Isopropyl vapor, 〖CH〗_3 OH gases, N_2 O, H_2 S. Carbon nanotubes specifically remove particles in many ways. One method is by passing them through the nanotubes where the molecules are oxidized; the molecules then are adsorbed on a nitrate species.
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While there he wrote a book, Heat and Thermodynamics (1928). His position at the National Physical Laboratory could not be held for this long, but on his return to England in 1928 he became a Moseley Research Student of the Royal Society at the Cavendish Laboratory. He became interested in functioning of the Pirani gauge, with which he investigated the thermal conductivities of gases, and of the heat conveyed to a gas by a hot wire. In 1933 he joined the Colloid Science Laboratory at Cambridge as its assistant director of research.
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Both glassy and ceramic electrolytes can be made more ionically conductive by substituting sulfur for oxygen. The larger radius of sulfur and its higher ability to be polarized allow higher conductivity of lithium. This contributes to conductivities of solid electrolytes are nearing parity with their liquid counterparts, with most on the order of 0.1 mS/cm and the best at 10 mS/cm. Functional electrolytes An efficient and economic way to tune targeted electrolytes properties is by adding a third component in small concentrations, known as an additive .
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To achieve a similar effect, sometimes a constant current power source is used in combination with an arc voltage-controlled wire feed unit. In this case, a change in arc length makes the wire feed rate adjust to maintain a relatively constant arc length. In rare circumstances, a constant current power source and a constant wire feed rate unit might be coupled, especially for the welding of metals with high thermal conductivities, such as aluminum. This grants the operator additional control over the heat input into the weld, but requires significant skill to perform successfully.
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Heat structures provided in RELAP5-3D permit calculation of heat transferred across solid boundaries of hydrodynamic volumes. Modeling capabilities of heat structures are general and include fuel pins or plates with nuclear or electrical heating, heat transfer across steam generator tubes, and heat transfer from pipe and vessel walls. Temperature-dependent and space-dependent thermal conductivities and volumetric heat capacities are provided in tabular or functional form either from built-in or user-supplied data. There is also a radiative/conductive enclosure model, for which the user may supply/view conductance factors.
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Real heads are non-spherical and have largely anisotropic conductivities (particularly white matter and skull). While skull anisotropy has a negligible effect on MEG (unlike EEG), white matter anisotropy strongly affects MEG measurements for radial and deep sources. Note, however, that the skull was assumed to be uniformly anisotropic in this study, which is not true for a real head: the absolute and relative thicknesses of diploë and tables layers vary among and within the skull bones. This makes it likely that MEG is also affected by the skull anisotropy, although probably not to the same degree as EEG.
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For example, if salinity figures of the groundwater are available and the value of hydraulic conductivity is uncertain, one assumes a range of conductivities and the selects that value of conductivity as "true" that yields salinity results close to the observed values, meaning that the groundwater flow as governed by the hydraulic conductivity is in agreement with the salinity conditions. This procedure is similar to the measurement of the flow in a river or canal by letting very saline water of a known salt concentration drip into the channel and measuring the resulting salt concentration downstream.
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Electric Wire and Cable, brochure 0001240, Cobre Cerrillos S.A., Santiago, Chile; Cocessa Technical Bulletin, Electrical Conductor Catalog 751, MADECO, 1990 Copper is the preferred conductor material for underground transmission lines operating at high and extra-high voltages to 400 kV. The predominance of copper underground systems stems from its higher volumetric electrical and thermal conductivities compared to other conductors. These beneficial properties for copper conductors conserve space, minimize power loss, and maintain lower cable temperatures. Copper continues to dominate low-voltage lines in mines and underwater applications, as well as in electric railroads, hoists, and other outdoor services.
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Ground conductivity is an extremely important factor in determining the field strength and propagation of surface wave (ground wave) radio transmissions. Low frequency (30–300 kHz) and medium frequency (300–3000 kHz) radio transmissions are particularly reliant on good ground conductivity as their primary propagation is by surface wave. It also affects the real world radiation pattern of high frequency (3-30 MHz) antennas, as the so called "takeoff angle" is not an inherent property of the antenna but a result of a ground reflection. For this reason ITU publishes an extensive world atlas of ground conductivities.
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For the British Association (1874–81) he prepared reports of a committee, consisting of himself, his colleague at Newcastle, George A. Lebour, and John T. Dunn, which was formed to determine the thermal conductivities of certain rocks. For the Monthly Notices of the Royal Astronomical Society, he prepared the annual reports on meteoric astronomy each February from 1872 to 1880 and contributed many other important papers to the Notices. In a June 1872 paper, he showed the connection between meteors (the Andromedids) and comets (Biela's Comet), and he predicted the shower which recurred on 27 November of that year.
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Glasses (non-crystalline ceramics) also are used widely as host materials for lasers. Relative to crystalline lasers, they offer improved flexibility in size and shape and may be readily manufactured as large, homogeneous, isotropic solids with excellent optical properties. The indices of refraction of glass laser hosts may be varied between approximately 1.5 and 2.0, and both the temperature coefficient of n and the strain-optical coefficient may be tailored by altering the chemical composition. Glasses have lower thermal conductivities than the alumina or YAG, however, which imposes limitations on their use in continuous and high repetition-rate applications.
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Protactinium is an actinide which is positioned in the periodic table to the left of uranium and to the right of thorium, and many of its physical properties are intermediate between those two actinides. So, protactinium is more dense and rigid than thorium but is lighter than uranium, and its melting point is lower than that of thorium and higher than that of uranium. The thermal expansion, electrical and thermal conductivities of these three elements are comparable and are typical of post-transition metals. The estimated shear modulus of protactinium is similar to that of titanium.
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It is also electrically conductive, and so needs to be applied more carefully than regular non-conductive compounds. Two thermal interfaces have already been developed: Thermal Grizzly Conductonaut and Coolaboratory Liquid Ultra, with thermal conductivities of 73 and 38.4 W/mK respectively. However, they must be carefully applied with a Q-tip (unlike ordinary thermal compounds, where no manual spreading is needed), and cannot be used on aluminum heatsinks as aforementioned. Galinstan is difficult to use for cooling fission-based nuclear reactors, because indium has a high absorption cross section for thermal neutrons, efficiently absorbing them and inhibiting the fission reaction.
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The semiconducting properties of chalcogenide glasses were revealed in 1955 by B.T. Kolomiets and N.A. Gorunova from Ioffe Institute, USSR. Although the electronic structural transitions relevant to both optical discs and PC-RAM were featured strongly, contributions from ions were not considered—even though amorphous chalcogenides can have significant ionic conductivities. At Euromat 2005, however, it was shown that ionic transport can also be useful for data storage in a solid chalcogenide electrolyte. At the nanoscale, this electrolyte consists of crystalline metallic islands of silver selenide (Ag2Se) dispersed in an amorphous semiconducting matrix of germanium selenide (Ge2Se3).
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Such differences that the presence of water entails is the ability to vaporize when in contact with water, a high density and resulting confining pressure, high viscosity relative to air and differences in the thermal conductivities/heat capacities in the air relative to water. Some understanding of subaqueous volcanoes can be inferred from knowledge of volcanic processes based on ancient successions. Subaqueous volcano deposits have been occurring in the south of Honshu, the largest island among Japan's four principal islands. The four subaqueous volcanic deposits have been documented and are located throughout Japan offer significant evidence to study.
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Vanadium pentafluoride can be prepared by fluorination of vanadium metal: : 2 V + 5 F2 → 2 VF5 Alternatively, disproportionation of vanadium tetrafluoride yields equal amounts of the solid trifluoride and the volatile pentafluoride: :2 VF4 → VF3 \+ VF5 This conversion is conducted at 650 °C. It can also be synthesized by using elemental fluorine to fluorinate industrial concentrates and raw materials so as to produce VF5 on an industrial scale. VF5 can be synthesized from the reaction of raw materials such as metallic Vanadium, ferrovanadium, vanadium (V) oxide and vanadium tetrafluoride with elemental fluorine. VF5 ionises in the liquid state as reflected by the high values of Trouton's constant and electrical conductivities.
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During his doctoral studies, Jain assisted his mentor, K. S. Krishnan, the co- discoverer of the Raman Effect, on the thermal conductivity of solids. It was during this time, the duo developed a methodology for the measurement of thermal conductivity in solids at high temperatures which was published by them in an article, Thermionic Constants of Metals and Semiconductors. II. Metals of the First Transition Group in 1952 in Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences and later explained further by way of another article, Determination of thermal conductivities at high temperatures in British Journal of Applied Physics in 1954.
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Some substances, such as non-cubic crystals, can exhibit different thermal conductivities along different crystal axes, due to differences in phonon coupling along a given crystal axis. Sapphire is a notable example of variable thermal conductivity based on orientation and temperature, with 35 W/(m⋅K) along the c axis and 32 W/(m⋅K) along the a axis. Wood generally conducts better along the grain than across it. Other examples of materials where the thermal conductivity varies with direction are metals that have undergone heavy cold pressing, laminated materials, cables, the materials used for the Space Shuttle thermal protection system, and fiber-reinforced composite structures.
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Solar energy and lightning cause natural variations in the earth's magnetic field, inducing electric currents (known as telluric currents) under the Earth's surface.Cantwell, T. (1960) Detection and Analysis of Low-Frequency Magnetotelluric Signals, PhD Thesis, Massachusetts Institute of Technology, Cambridge, Massachusetts Different rocks, sediments and geological structures have a wide range of different electrical conductivities. Measuring electrical resistivity allows different materials and structures to be distinguished from one another and can improve knowledge of tectonic processes and geologic structures. The Earth's naturally varying electric and magnetic fields are measured over a wide range of magnetotelluric frequencies from 10,000 Hz to 0.0001 Hz (10,000 s).
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At the University of Uppsala, he was dissatisfied with the chief instructor of physics and the only faculty member who could have supervised him in chemistry, Per Teodor Cleve, so he left to study at the Physical Institute of the Swedish Academy of Sciences in Stockholm under the physicist Erik Edlund in 1881. His work focused on the conductivities of electrolytes. In 1884, based on this work, he submitted a 150-page dissertation on electrolytic conductivity to Uppsala for the doctorate. It did not impress the professors, among whom was Cleve, and he received a fourth-class degree, but upon his defense it was reclassified as third-class.
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NbB2 is an ultra high temperature ceramic (UHTC) with a melting point of 3050 °C. This along with its relatively low density of ~6.97 g/cm3 and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities (Electrical resistivity of 25.7 µΩ⋅cm, CTE of 7.7⋅10−6 °C−1), properties it shares with isostructural titanium diboride, zirconium diboride, hafnium diboride and tantalum diboride. NbB2 parts are usually hot pressed or spark plasma sintering (mechanical pressure applied to the heated powder) and then machined to shape.
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Nellis has been President of the International Association for the Advancement of High Pressure Science and Technology (AIRAPT) and Chairman of the American Physical Society (APS) Topical Group on Shock Compression of Condensed Matter. He has received the Bridgman Award of AIRAPT, the Duvall Award of APS and is a Fellow of the APS Division of Condensed Matter Physics. Nellis is an author or coauthor of more than 250 published papers. Most of his research has been focused on materials during or after dynamic compression at high pressures for properties including electrical conductivities, temperatures, equation-of-state data, and shock-wave profiles to investigate compressibilities and phase transitions in liquids and solids.
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This allows this material to better insulate space shuttles and materials in space and in re-entry of the space objects, causing less damage to the shuttle itself and the people inside it. In the same research project, she experimented with aerogels by adding in Titanium to the Aluminosilicate gels, which allowed for bigger average pore sizes and higher pore volumes. She concluded that by adding Titanium to Aluminosilicate gels, the lower thermal conductivities can now go up to temperatures of 1,200 instead of the 900 limit of regular Silicon Dioxide gels. In addition, Hurwitz has conducted research that has shown a way to image aerogels with very small pores through the use of scanning electron microscopes.
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Transparent conductive oxides (TCO) are doped metal oxides used in optoelectronic devices such as flat panel displays and photovoltaics (including inorganic devices, organic devices, and dye- sensitized solar cells). Most of these films are fabricated with polycrystalline or amorphous microstructures. Typically, these applications use electrode materials that have greater than 80% transmittance of incident light as well as electrical conductivities higher than 103 S/cm for efficient carrier transport. In general, TCOs for use as thin-film electrodes in solar cells should have a minimum carrier concentration on the order of 1020 cm−3 for low resistivity and a bandgap greater than 3.2 eV to avoid absorption of light over most of the solar spectra.
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Aluminum electrolytic capacitors (Al-e-caps) with liquid electrolytes were invented in 1896 by Charles Pollak. Tantalum electrolytic capacitors with solid manganese dioxide (MnO2) electrolytes were invented by Bell Laboratories in the early 1950s, as a miniaturized and more reliable low-voltage support capacitor to complement the newly invented transistor, see Tantalum capacitor. The first Ta-e-caps with MnO2 electrolytes had 10 times better conductivity and a higher ripple current load than earlier types Al-e-caps with liquid electrolyte. Additionally, unlike standard Al-e-caps, the equivalent series resistance (ESR) of Ta-caps is stable in varying temperatures. Conductivities of some electrolytes During the 1970s, the increasing digitization of electronic circuits came with decreasing operating voltages, and increasing switching frequencies and ripple current loads.
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Furthermore, the work function of SWCNT networks is in the 4.8 to 4.9 eV range (compared to ITO which has a lower work function of 4.7 eV) leading to the expectation that the SWCNT work function should be high enough to assure efficient hole collection. Another benefit is that SWCNT films exhibit a high optical transparency in a broad spectral range from the UV-visible to the near-infrared range. Only a few materials retain reasonable transparency in the infrared spectrum while maintaining transparency in the visible part of the spectrum as well as acceptable overall electrical conductivity. SWCNT films are highly flexible, do not creep, do not crack after bending, theoretically have high thermal conductivities to tolerate heat dissipation, and have high radiation resistance.
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Uhlmann G. (1999) "Developments in inverse problems since Calderón's foundational paper", Harmonic Analysis and Partial Differential Equations: Essays in Honor of Alberto P. Calderón, (editors ME Christ and CE Kenig), University of Chicago Press, Compared to the tissue conductivities of most other soft tissues within the human thorax, lung tissue conductivity is approximately five-fold lower, resulting in high absolute contrast. This characteristic may partially explain the amount of research conducted in EIT lung imaging. Furthermore, lung conductivity fluctuates intensely during the breath cycle which accounts for the immense interest of the research community to use EIT as a bedside method to visualize inhomogeneity of lung ventilation in mechanically ventilated patients. EIT measurements between two or more physiological states, e.g.
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The MCC comprises a structural shell made of Inconel 718 which is lined with a copper-silver-zirconium alloy called NARloy-Z, developed specifically for the RS-25 in the 1970s. Around 390 channels are machined into the liner wall to carry liquid hydrogen through the liner to provide MCC cooling, as the temperature in the combustion chamber reaches 3300 °C (6000 °F) during flight – higher than the boiling point of iron. An alternative for the construction of RS-25 engines to be used in SLS missions is the use of advanced structural ceramics, such as thermal barrier coatings (TBCs) and ceramic-matrix composites (CMCs). These materials possess significantly lower thermal conductivities than metallic alloys, thus allowing more efficient combustion and reducing the cooling requirements.
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2×2 unit cell of Na3Zr2(SiO4)2(PO4) (x = 2), which is the most common NASICON material; red: O, purple: Na, light green: Zr, dark green: sites shared by Si and P One unit cell of Na2Zr2(SiO4)(PO4)2 (x = 1); red: O, purple: Na, light green: Zr, dark green: sites shared by Si and P NASICON is an acronym for sodium (Na) Super Ionic CONductor, which usually refers to a family of solids with the chemical formula Na1+xZr2SixP3−xO12, 0 < x < 3\. In a broader sense, it is also used for similar compounds where Na, Zr and/or Si are replaced by isovalent elements. NASICON compounds have high ionic conductivities, on the order of 10−3 S/cm, which rival those of liquid electrolytes. They are caused by hopping of Na ions among interstitial sites of the NASICON crystal lattice.
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This phenomenon is said to be a result of a thermal contact resistance existing between the contacting surfaces. Thermal contact resistance is defined as the ratio between this temperature drop and the average heat flow across the interface. According to Fourier's law, the heat flow between the bodies is found by the relation: where q is the heat flow, k is the thermal conductivity, A is the cross sectional area and dT/dx is the temperature gradient in the direction of flow. From considerations of energy conservation, the heat flow between the two bodies in contact, bodies A and B, is found as: One may observe that the heat flow is directly related to the thermal conductivities of the bodies in contact, k_A and k_B, the contact area A, and the thermal contact resistance, 1/h_c, which, as previously noted, is the inverse of the thermal conductance coefficient, h_c.
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The addition of 10% iridium improved upon the all- platinum Kilogramme des Archives by greatly increasing hardness while still retaining platinum's many virtues: extreme resistance to oxidation, extremely high density (almost twice as dense as lead and more than 21 times as dense as water), satisfactory electrical and thermal conductivities, and low magnetic susceptibility. The IPK and its six sister copies are stored at the International Bureau of Weights and Measures (known by its French-language initials BIPM) in an environmentally monitored safe in the lower vault located in the basement of the BIPM's Pavillon de Breteuil in Saint-CloudThe Pavillon's (and hence the BIPM's) postal address is in the neighboring commune of Sèvres, so it is often reported as being located there, but the grounds are in the commune of Saint-Cloud (OpenStreetMap). on the outskirts of Paris (see External images, below, for photographs). Three independently controlled keys are required to open the vault.
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Following his largely experimental studies in his doctoral and postdoctoral research, his interests turned increasingly to the application of statistical mechanics to problems in chemical engineering and applied physics. Much of chemical engineering involves the handling and processing of dense fluids and liquids, so that a knowledge of their thermodynamic and transport behaviour is essential to design of process equipment. It was to these areas that he addressed himself, and he has been largely responsible for the introduction of statistical mechanics and atomistic simulation methods (Monte Carlo and molecular dynamics) into chemical engineering. His research has focused on the development of reliable predictive methods based in statistical mechanics for phase and chemical equilibria for mixtures; equations of state for complex fluid mixtures, particularly those involving associating liquids and polymers; thermodynamics, transport in interfaces, including small droplets, gas-liquid and liquid-liquid interfaces and nano-porous media; prediction of viscosity, diffusion coefficients, and thermal conductivities; natural gas storage in porous media.
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