The Bosporus is so deep that it allows a countercurrent.
|
|
One countercurrent is that some movements that have animated the decade are, at bottom, old-fashioned.
|
|
McPhee writes admiringly of the Corps' grit, determination, even genius, but running through the essay is a strong countercurrent.
|
|
They have defined the recent cultural history, by not losing their individuality, countercurrent—all of them are writing future history books.
|
|
However, it should not be very difficult to resist the countercurrent and maintain Deng's vision for further reform and opening up.
|
|
All Is Forgiven between these aspects of our everyday experience (of a moment of danger) is subtle but pointed, yet never articulated as a master narrative or countercurrent; rather, everything remains intimate.
|
|
And while some countries have recently retreated from the world stage amid nationalist fervor, the ease of air travel has created a strong countercurrent of travelers looking to learn from other cultures.
|
|
A refreshing counter to sectarian strife In a country torn apart by sectarian struggle, this secular society provides a refreshing countercurrent, a sanctuary to 2 million refugees from the rest of Syria and Iraq.
|
|
Countercurrent multiplication is frequently mistaken for countercurrent exchange, a similar but different mechanism where gradients are maintained, but not established.
|
|
Mammalian kidneys use countercurrent exchange to remove water from urine so the body can retain water used to move the nitrogenous waste products (see countercurrent multiplier).
|
|
The predecessor of modern countercurrent chromatography theory and practice was countercurrent distribution (CCD). The theory of CCD was described in the 1930s by Randall and Longtin. Archer Martin and Richard Laurence Millington Synge developed the methodology further during the 1940s. Finally, Lyman C. Craig introduced the Craig countercurrent distribution apparatus in 1944 which made CCD practical for laboratory work.
|
|
Lyman C. Craig (born 1906 in Palmyra Township, Warren County, Iowa; died 1974) was a chemical researcher who worked at The Rockefeller Institute for Medical Research from 1933 onward. In 1944 he published a seminal work on countercurrent distribution, which became an important separation technique. Craig continued to develop the theory, improve the apparatus and devise new applications of the countercurrent distribution into the 1970s. Countercurrent distribution not only proved to be a useful separation technique, it also inspired the development of the field of countercurrent chromatography.
|
|
Countercurrent exchange is a key concept in chemical engineering thermodynamics and manufacturing processes, for example in extracting sucrose from sugar beet roots. Countercurrent multiplication is a similar but different concept where liquid moves in a loop followed by a long length of movement in opposite directions with an intermediate zone. The tube leading to the loop passively building up a gradient of heat (or cooling) or solvent concentration while the returning tube has a constant small pumping action all along it, so that a gradual intensification of the heat or concentration is created towards the loop. Countercurrent multiplication has been found in the kidneysBoth countercurrent exchange and countercurrent multiplication systems have been found in the kidneys.
|
|
Rete mirabile = RM Countercurrent exchange in biological systems occurred following the discovery of countercurrent multiplication systems by Werner Kuhn. Countercurrent exchange is used extensively in biological systems for a wide variety of purposes. For example, fish use it in their gills to transfer oxygen from the surrounding water into their blood, and birds use a countercurrent heat exchanger between blood vessels in their legs to keep heat concentrated within their bodies. In vertebrates, this type of organ is referred to as a rete mirabile (originally the name of the organ in the fish gills).
|
|
The settling time is a property of the solvent system and the sample matrix, both of which greatly influence stationary phase retention. To most process chemists, the term "countercurrent" implies two immiscible liquids moving in opposing directions, as typically occurs in large centrifugal extractor units. With the exception of dual flow (see below) CCC, most countercurrent chromatography modes of operation have a stationary phase and a mobile phase. Even in this situation, countercurrent flows occur within the instrument column.
|
|
Furthermore, countercurrent gas exchange at the secondary gill lamellae further maximizes oxygen uptake and carbon dioxide release.
|
|
In effect, this can be seen as a gradually multiplying effect—hence the name of the phenomena: a 'countercurrent multiplier' or the mechanism: Countercurrent multiplication, but in current engineering terms, countercurrent multiplication is any process where only slight pumping is needed, due to the constant small difference of concentration or heat along the process, gradually raising to its maximum. There is no need for a buffer liquid, if the desired effect is receiving a high concentration at the output pipe.
|
|
In 1987, the municipality of Eidskog acquired rights to the countercurrent sluice system and labeled it a landmark attraction.
|
|
Droplet countercurrent chromatography (DCCC or DCC) was introduced in 1970 by Tanimura, Pisano, Ito, and Bowman. DCCC is considered to be a form of liquid- liquid separation, which includes countercurrent distribution and countercurrent chromatography, that employs a liquid stationary phase held in a collection of vertical glass columns connected in series. The mobile phase passes through the columns in the form of droplets. The DCCC apparatus may be run with the lower phase stationary and the upper phase being introduced to the bottom of each column.
|
|
At low ambient temperature, the hemolymph flows from the thorax and abdomen simultaneously. As a result, the countercurrent exchange of heat in the petiole retains most of the energy in the thorax. When the ambient temperature is high, the countercurrent exchange is reduced such that heat is transferred from the thorax to the abdomen.
|
|
Dual-flow, also known as dual, countercurrent chromatography occurs when both phases are flowing in opposite directions inside the column. Instruments are available for dual-flow operation for both Hydrodynamic and hydrostatic CCC. Dual-flow countercurrent chromatography was first described by Yoichiro Ito in 1985 for foam CCC where gas-liquid separations were performed. Liquid–liquid separations soon followed.
|
|
Urey suggested that a more efficient but technically more complicated countercurrent system be used instead of the previous flow-through method. By November 1941, technical obstacles seemed formidable enough for the process to be abandoned. Countercurrent centrifuges were developed after the war, and today are the favored method in many countries. The gaseous diffusion process remained more encouraging, although it too had technical obstacles to overcome.
|
|
Often the preparative resins have a low efficiency due to strong axial dispersion and slow mass transfer. Then a purification in one chromatographic step is not possible. Countercurrent movement as known from the SMB process would be required. For large scale productions and for very valuable molecules countercurrent solid movement need to be applied to increase the separation efficiency, the yield and the productivity of the purification.
|
|
The result is that countercurrent exchange can achieve a greater amount of heat or mass transfer than parallel under otherwise similar conditions. See: flow arrangement. Countercurrent exchange when set up in a circuit or loop can be used for building up concentrations, heat, or other properties of flowing liquids. Specifically when set up in a loop with a buffering liquid between the incoming and outgoing fluid running in a circuit, and with active transport pumps on the outgoing fluid's tubes, the system is called a countercurrent multiplier, enabling a multiplied effect of many small pumps to gradually build up a large concentration in the buffer liquid.
|
|
Mathematical modeling studies indicate that TIW are generated by velocity shear between the westward-flowing South Equatorial Current and the eastward flowing Equatorial Undercurrent and Equatorial Countercurrent.
|
|
This flow of inlet gas and liquid in opposite directions is called countercurrent flow. This type of technology can be used for example as a wet scrubber for air pollution control. Countercurrent flow exposes the outlet gas with the lowest pollutant concentration to the freshest scrubbing liquid. Many nozzles are placed across the tower at different heights to spray all of the gas as it moves up through the tower.
|
|
Several researchers have proposed renaming both CCC & CPC to liquid-liquid chromatography, but others feel the term "countercurrent" itself is a misnomer. Unlike column chromatography and high-performance liquid chromatography, countercurrent chromatography operators can inject large volumes relative to column volume. Typically 5 to 10% of coil volume can be injected. In some cases this can be increased to as high as 15 to 20% of the coil volume.
|
|
Although any device that promotes contact between air and water strips some volatile compounds, air strippers are usually packed towers or tray towers operated with countercurrent flow of water and air. The countercurrent flow removes particles from the water and into the air. This process is known as volatization or air stripping. Water is deposited into the system through the top and air is ventilated in through the bottom.
|
|
Performing one or more countercurrent chromatography separations in conjunction with other chromatographic and non chromatographic techniques has the potential for rapid advances in compositional recognition of extremely complex matrices.
|
|
Nearly any pair of immiscible solutions can be used in countercurrent chromatography provided that the stationary phase can be successfully retained. Solvent costs are also generally lower than for high-performance liquid chromatography (HPLC). In comparison to column chromatography, flows and total solvent usage can in most countercurrent chromatography separations may be reduced by half and even up to a tenth. Also, the cost of purchasing and disposing of stationary phase media is eliminated.
|
|
Guyton, A.C. & Hall, J.E. (2006) Textbook of Medical Physiology (11th ed.) Philadelphia: Elsevier Saunder Vasospasms force adenosine to enter the capillary bed, where it vasodilates the postcapillary venules. Such differences in vessel tone create a countercurrent exchange system that attempts to retain heat. Profuse sweating would then be caused by an overwhelmed countercurrent exchange system. In addition to adenosine, other hormones may contribute to acrocyanosis such as increase blood levels of serotonin.
|
|
Unlike the descending limb, the thin ascending limb is impermeable to water, a critical feature of the countercurrent exchange mechanism employed by the loop. The ascending limb actively pumps sodium out of the filtrate, generating the hypertonic interstitium that drives countercurrent exchange. In passing through the ascending limb, the filtrate grows hypotonic since it has lost much of its sodium content. This hypotonic filtrate is passed to the distal convoluted tubule in the renal cortex.
|
|
North Equatorial Current (in black) The North Equatorial Current is a significant Pacific and Atlantic Ocean current that flows east-to-west between about 10° north and 20° north. It is the southern side of a clockwise subtropical gyre. Despite its name, the North Equatorial Current is not connected to the equator. In both oceans, it is separated from the equatorial circulation by the Equatorial Countercurrent (also known as the North Equatorial Countercurrent), which flows eastward.
|
|
In countercurrent chromatography centrifugal or gravitational forces immobilize the stationary liquid layer. By eliminating solid supports, permanent adsorption of the analyte onto the column is avoided, and a high recovery of the analyte can be achieved. The countercurrent chromatography instrument is easily switched between normal phase chromatography and reversed-phase chromatography simply by changing the mobile and stationary phases. With column chromatography, the separation potential is limited by the commercially available stationary phase media and its particular characteristics.
|
|
This, together with the organization of blood vessels and a countercurrent heat exchange system, allows the southern bluefin tuna to rapidly deliver oxygen to tissue, while preserving energy necessary for their active lifestyle.
|
|
Consequently, the total liquid surface area for contact is reduced, reducing the collection efficiency of the scrubber. Crosscurrent-flow spray tower In addition to a countercurrent-flow configuration, the flow in spray towers can be either a cocurrent or crosscurrent in configuration. In cocurrent-flow spray towers, the inlet gas and liquid flow in the same direction. Because the gas stream does not "push" against the liquid sprays, the gas velocities through the vessels are higher than in countercurrent-flow spray towers.
|
|
The countercurrent chromatography instrument must be modified so that both ends of the column have both inlet and outlet capabilities. This mode may accommodate continuous or sequential separations with the sample being introduced in the middle of the column or between two bobbins in a hydrodynamic instrument. A technique called intermittent countercurrent extraction (ICcE) is a quasi- continuous method where the flow of the phases is alternated "intermittently" between normal and reversed-phase elution so that the stationary phase also alternates.
|
|
The flow of the liquid down the tubes is driven by the vapor shear stress and the gravitational forces. The effect of the vapor shear and the gravity will lead to a higher flow rates and shorter residence time. The flow of the thin liquid film in the falling film evaporator is possible in two ways: cocurrent and countercurrent. It is cocurrent if the vapor is drawn from the top to the bottom of the tubes and vice versa for the countercurrent flow.
|
|
A high-performance countercurrent chromatography system Countercurrent chromatography (CCC, also counter-current chromatography) is a form of liquid–liquid chromatography that uses a liquid stationary phase that is held in place by centrifugal force and is used to separate, identify, and quantify the chemical components of a mixture. In its broadest sense, countercurrent chromatography encompasses a collection of related liquid chromatography techniques that employ two immiscible liquid phases without a solid support. The two liquid phases come in contact with each other as at least one phase is pumped through a column, a hollow tube or a series of chambers connected with channels, which contains both phases. The resulting dynamic mixing and settling action allows the components to be separated by their respective solubilities in the two phases.
|
|
The simplest gas centrifuge is the concurrent centrifuge, where separative effect is produced by the centrifugal effects of the rotor's rotation. In these centrifuges, the heavy fraction is collected at the periphery of the rotor, and the light fraction from nearer the axis of rotation. Inducing a countercurrent flow uses countercurrent multiplication to enhance the separative effect. A vertical circulating current is set up, with the gas flowing axially along the rotor walls in one direction, and a return flow closer to the center of the rotor.
|
|
There were no injuries either ashore or on Matanuska. After an inspection by the U.S. Coast Guard, she was deemed seaworthy and continued on to other ports to pick up passengers, though two hours behind schedule. The cause of the crash was determined to be conning errors made by the master, who attempted to use a known countercurrent to slow the ship on the approach in to port. However, the countercurrent was not present that day, resulting in a higher than expected approach speed.
|
|
The February Countercurrent (), also known as the February Adverse Current, refers to the joint efforts by a group of conservative Communist Party veterans to oppose the ultra-leftist radicalism at the beginning of the Cultural Revolution.
|
|
Countercurrent chromatography and related liquid-liquid separation techniques have been used on both industrial and laboratory scale to purify a wide variety of chemical substances. Separation realizations include proteins, DNA, Cannabidiol (CBD) from Cannabis Sativa antibiotics, vitamins, natural products, pharmaceuticals, metal ions, pesticides, enantiomers, polyaromatic hydrocarbons from environmental samples, active enzymes, and carbon nanotubes. Countercurrent chromatography is known for its high dynamic range of scalability: milligram to kilogram quantities purified chemical components may be obtained with this technique. It also has the advantage of accommodating chemically complex samples with undissolved particulates.
|
|
A rete mirabile (Latin for "wonderful net"; plural retia mirabilia) is a complex of arteries and veins lying very close to each other, found in some vertebrates, mainly warm-blooded ones. The rete mirabile utilizes countercurrent blood flow within the net (blood flowing in opposite directions) to act as a countercurrent exchanger. It exchanges heat, ions, or gases between vessel walls so that the two bloodstreams within the rete maintain a gradient with respect to temperature, or concentration of gases or solutes. This term was coined by Galen.
|
|
The purge gas from a countercurrent rotary dryer is typically only 350 °F to 500 °F and does not require cooling before entering the baghouse where fine particles are trapped. A disadvantage is that these particles may not have been decontaminated and are typically recycled to the dryer. Countercurrent dryers have several advantages over cocurrent systems. They are more efficient in transferring heat from purge gas to contaminated soil, and the volume and temperature of exit gas are lower, allowing the gas to go directly to a baghouse without needing to be cooled.
|
|
The maximum amount of heat or mass transfer that can be obtained is higher with countercurrent than co-current (parallel) exchange because countercurrent maintains a slowly declining difference or gradient (usually temperature or concentration difference). In cocurrent exchange the initial gradient is higher but falls off quickly, leading to wasted potential. For example, in the adjacent diagram, the fluid being heated (exiting top) has a higher exiting temperature than the cooled fluid (exiting bottom) that was used for heating. With cocurrent or parallel exchange the heated and cooled fluids can only approach one another.
|
|
Other countercurrent exchange circuits where the incoming and outgoing fluids touch each other are used for retaining a high concentration of a dissolved substance or for retaining heat, or for allowing the external buildup of the heat or concentration at one point in the system. Countercurrent exchange circuits or loops are found extensively in nature, specifically in biologic systems. In vertebrates, they are called a rete mirabile, originally the name of an organ in fish gills for absorbing oxygen from the water. It is mimicked in industrial systems.
|
|
Three topologies of countercurrent exchange systems Countercurrent exchange along with cocurrent exchange and contra-current exchange comprise the mechanisms used to transfer some property of a fluid from one flowing current of fluid to another across a barrier allowing one way flow of the property between them. The property transferred could be heat, concentration of a chemical substance, or other properties of the flow. When heat is transferred, a thermally-conductive membrane is used between the two tubes, and when the concentration of a chemical substance is transferred a semipermeable membrane is used.
|
|
It has also been found in Namibian ostriches and other desert birds, where a buildup of salt concentration is due to dehydration and scarcity of drinking water. In seabirds the salt gland is above the beak, leading to a main canal above the beak, and water is blown from two small nostrils on the beak, to empty it. The salt gland has two countercurrent mechanisms working in it: a. A salt extraction system with a countercurrent multiplication mechanism, where salt is actively pumped from the blood 'venules' (small veins) into the gland tubules.
|
|
From here the "C-shape" then flows eastward comprising the Subtropical Countercurrent at roughly 20 – 25⁰N, then finally the "C" wraps back towards the west forming the North Equatorial Current just south of 20⁰N. It is common for subtropical gyres to have this "C-shape" surface flow. The Subtropical Countercurrent is a shallow area of this "C"; at only about 250 dbar under the surface, circulation is a simpler closed, anticyclonic gyre. Narrow east-west frontal zones that cross the Pacific are less than 100 km wide.
|
|
Gills use a countercurrent flow system that increases the efficiency of oxygen-uptake (and waste gas loss). Oxygenated water is drawn in through the mouth and passes over the gills in one direction while blood flows through the lamellae in the opposite direction. This countercurrent maintains steep concentration gradients along the entire length of each capillary (see the diagram in the "Interaction with circulatory systems" section above). Oxygen is able to continually diffuse down its gradient into the blood, and the carbon dioxide down its gradient into the water.
|
|
The MCSGP process combines both techniques in one process, the countercurrent SMB principle and the solvent gradient batch technique. Discontinuous mode consists of equilibration, loading, washing, purification and regeneration steps. The discontinuous mode of operation allows exploiting the advantage of solvent gradients, but it implies high solvent consumptions and low productivities with respect to continuous countercurrent processes. An established process of this kind is the simulated moving bed technique (SMB) that requires the solvent-consuming steps of equilibration, washing, regeneration only once per operation and has a better resin utilization.
|
|
SMB is not readily suited for solvent gradients. Solvent gradient purification may be preferred for the purification of some biomolecules. A continuous chromatography technique to overcome the two fraction limit and to apply gradients is multicolumn countercurrent solvent gradient purification (MCSGP).
|
|
Schematic representation of solvent extraction and countercurrent stagewise process The industrial separation processes will be implemented stepwise by annular centrifugal contactors, developed for the first time at Argonne National Laboratory in the 1970s. The countercurrent process consists of the aqueous and organic phases moving continuously in opposite directions stage by stage. The two immiscible liquids enter each contactor unit, first contacted in the annular region between the housing and the spinning rotor and then centrifuged in the inner part of the unit. Two main ways are currently followed within the partitioning strategy: the heterogeneous and homogeneous recycling.
|
|
A wide variety of two-phase solvent systems consisting of at least two immiscible liquids may be employed to provide the proper selectivity for the desired separation. Some types of countercurrent chromatography, such as dual flow CCC, feature a true countercurrent process where the two immiscible phases flow past each other and exit at opposite ends of the column. More often, however, one liquid acts as the stationary phase and is retained in the column while the mobile phase is pumped through it. The liquid stationary phase is held in place by gravity or by centrifugal force.
|
|
Throughout his career, Gottschalk published extensively about the kidney and about the history of kidney research. He is particularly known for his work using micropuncture techniques to study the kidney's ability to concentrate urine, and for the theory of countercurrent multiplication explaining this ability...
|
|
The compound can then be introduced to another stationary phase to help increase the resolution of results. The flow is stopped after the target compound(s) are eluted or the column is extruded by pumping the stationary phase through the column. An example of a major application of countercurrent chromatography is to take an extremely complex matrix such as a plant extract, perform the countercurrent chromatography separation with a carefully selected solvent system, and extrude the column to recover all of the sample. The original complex matrix will have been fractionated into discrete narrow polarity bands, which may then be assayed for chemical composition or bioactivity.
|
|
Tuba Esatbeyoglu and Peter Winterhalter, J. Agric. Food Chem., 2010, 58 (8), pages 5147–5153, ; Presence in food It is found in cocoa beansIsolation of dimeric, trimeric, tetrameric and pentameric procyanidins from unroasted cocoa beans (Theobroma cacao L.) using countercurrent chromatography. Esatbeyoglu T, Wray Vand Winterhalter P, Food Chem.
|
|
Stripping is a physical separation process where one or more components are removed from a liquid stream by a vapor stream. In industrial applications the liquid and vapor streams can have co-current or countercurrent flows. Stripping is usually carried out in either a packed or trayed column.
|
|
The Yucatán Current flows strongly on the western side of the channel while the Cuban Countercurrent flows in the opposite direction on the easterly side of the channel. Underneath the Yucatán Current there is a southward-flowing Yucatán Undercurrent which takes water away from the Gulf of Mexico.
|
|
The blood exiting the efferent arterioles of these nephrons enter the vasa recta, which are straight capillary branches that deliver blood to the renal medulla. These vasa recta run adjacent to the descending and ascending loop of Henle, and participate in the maintenance of the medullary countercurrent exchange system.
|
|
These droplets are met with a countercurrent of hot gas, causing them to evaporate and leave only the solids behind. Droplets are generally dried to around 3-5%, as any lower would increase the risk of burning and anything above could possibly reduce shelf life through increased water activity.
|
|
Initially the countercurrent exchange mechanism and its properties were proposed in 1951 by professor Werner Kuhn and two of his former students who called the mechanism found in the Loop of Henle in mammalian kidneys a Countercurrent multiplierThe original lecture was published in 1951 in German. According to a book on Jewish scientists under the Reich Kuhn theorized and studied this mechanism already in the early 1940s. This was confirmed in 2001 in the translation to the original lecture published with remarks by Professor Bart Hargitay, then one of the two former student aids. Harbitay says: Before settling in Basel, Kuhn did some very fundamental work in Kiel, separating isotopes in a centrifuge.
|
|
Most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other, which increases the efficiency of oxygen-uptake from the water. Fresh oxygenated water taken in through the mouth is uninterruptedly "pumped" through the gills in one direction, while the blood in the lamellae flows in the opposite direction, creating the countercurrent blood and water flow, on which the fish's survival depends. The gills are composed of comb-like filaments, the gill lamellae, which help increase their surface area for oxygen exchange. When a fish breathes, it draws in a mouthful of water at regular intervals.
|
|
Polymerase chain reaction (PCR) assays have been proven to be more sensitive than either LAT or culture tests, and highly specific. However, PCR assays have not yet become routine in clinical settings. Countercurrent immunoelectrophoresis has been shown to be an effective research diagnostic method, but has been largely supplanted by PCR.
|
|
In addition to its function in venous return from the testes, the pampiniform plexus also plays a role in the temperature regulation of the testes. It acts as a countercurrent heat exchanger, cooling blood in adjacent arteries. An abnormal enlargement of the pampiniform plexus is a medical condition called varicocele.
|
|
C. livia kidneys, like mammalian kidneys, are capable of producing urine hyperosmotic to the plasma using the processes of filtration, reabsorption, and secretion. The medullary cones function as countercurrent units that achieve the production of hyperosmotic urine. Hyperosmotic urine can be understood in light of the law of diffusion and osmolarity.
|
|
Volumen 2. Aspectos meteorológicos y climatológico del ACMIC y su área de influencia. San José, Proyecto GEF/PNUD Conocimiento y uso de la biodiversidad del ACMIC, 184 p. Numerous oceanic currents from the central Pacific Ocean, particularly the North Equatorial Countercurrent, converge on the island and also have an important influence.
|
|
In fish a countercurrent flow (lower diagram) of blood and water in the gills is used to extract oxygen from the environment. Fig. 23 The respiratory mechanism in bony fish. The inhalatory process is on the left, the exhalatory process on the right. The movement of water is indicated by the blue arrows.
|
|
In reversed-phase (e.g. aqueous mobile phase) elution, the aqueous phase is used as the mobile phase with a less polar stationary phase. In countercurrent chromatography the same solvent system may be used in either normal or reversed phase mode simply by switching the direction of mobile phase flow through the column.
|
|
In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange. The gills push the oxygen-poor water out through openings in the sides of the pharynx. Some fish, like sharks and lampreys, possess multiple gill openings. However, bony fish have a single gill opening on each side.
|
|
In one of his addresses immediately after its emergence, for instance, Mao declared that the group was merely expressing its views and it was part of the intra-party life. In 1972, Mao backtracked on the official designation given to the February Countercurrent after the death of Chen Yi at a time when Mao felt increasingly politically isolated. Mao rushed out of bed to make an impromptu appearance at Chen Yi's funeral, signalling his attempt to reach out to the old comrades who have been purged or otherwise harmed during the Cultural Revolution. The post-Mao Communist Party reversed the verdict on the February Countercurrent, particularly following the October 6 coup of 1976 (see the fall of the Gang of Four).
|
|
Purge gas first enters an afterburner to decontaminate the fine particles, then goes into a cooling unit prior to introduction into the baghouse. Because of the higher temperature and volume of the purge gas, the baghouse and all other downstream processing equipment must be larger than in a countercurrent system. Cocurrent systems do have several advantages over countercurrent systems: The afterburner is located upstream of the baghouse ensuring that fine particles are decontaminated; and because the heated purge gas is introduced at the same end of the drum as the feed soil, the soil is heated faster, resulting in a longer residence time. Higher temperatures and longer residence time mean that cocurrent systems can be used to treat soils contaminated with heavier petroleum products.
|
|
Ravens engaged in flight are considered metabolically active. During periods of flight, the cells require more oxygen, and the heat generated must be dissipated to avoid hyperthermia. In response, the common raven experiences an increased heart rate and cardiac output. Another method used by many species of birds to regulate thermal conductance is by internally adjusting blood flow through shunt vessels. More specifically, arterial and venous blood vessels are organized to bypass the countercurrent heat exchange occurring in the upper portion of a bird’s legs. Countercurrent heat exchange involves arrangements of blood vessels that allow heat to transfer from warm arterial blood to cooler venous blood travelling to the body’s core. Through this mechanism, arterial blood remains warm before reaching the body’s periphery.
|
|
Cocurrent and Countercurrent heat exchange A cocurrent heat exchanger is an example of a cocurrent flow exchange mechanism. Two tubes have a liquid flowing in the same direction. One starts off hot at 60 °C, the second cold at 20 °C. A thermoconductive membrane or an open section allows heat transfer between the two flows.
|
|
Industrially, the elements are separated from each other by solvent extraction. Typically an aqueous solution of nitrates is extracted into kerosene containing tri-n-butylphosphate. The strength of the complexes formed increases as the ionic radius decreases, so solubility in the organic phase increases. Complete separation can be achieved continuously by use of countercurrent exchange methods.
|
|
"The Camel From Tradition to Modern Times" (PDF). UNESCO DOHA OFFICE. Maintaining the brain temperature within certain limits is critical for animals; to assist this, camels have a rete mirabile, a complex of arteries and veins lying very close to each other which utilizes countercurrent blood flow to cool blood flowing to the brain.Inside Nature's Giants.
|
|
Northern elephant seal resting in water Pinnipeds conserve heat with their large and compact body size, insulating blubber and fur, and high metabolism.Riedman, p. 14. In addition, the blood vessels in their flippers are adapted for countercurrent exchange. Veins containing cool blood from the body extremities surround arteries, which contain warm blood received from the core of the body.
|
|
VV ECMO trials are performed by eliminating all countercurrent sweep gas through the oxygenator. Extracorporeal blood flow remains constant, but gas transfer does not occur. They are then observed for several hours, during which the ventilator settings that are necessary to maintain adequate oxygenation and ventilation off ECMO are determined as indicated by arterial and venous blood gas results.
|
|
The thin ascending limb is impermeable to water; but is permeable to ions allowing for some sodium reabsorption. Na/K-ATPase is expressed at very low levels in this segment and thus this reabsorption is likely through passive diffusion. Salt moves out of the tubule and into the interstitium due to osmotic pressure created by the countercurrent system.
|
|
Another difference between the two is that plate exchangers typically serve low to medium pressure fluids, compared to medium and high pressures of shell and tube. A third and important difference is that plate exchangers employ more countercurrent flow rather than cross current flow, which allows lower approach temperature differences, high temperature changes, and increased efficiencies.
|
|
The deoxygenated water will eventually pass out through the operculum (gill cover). Although countercurrent exchange systems theoretically allow an almost complete transfer of a respiratory gas from one side of the exchanger to the other, in fish less than 80% of the oxygen in the water flowing over the gills is generally transferred to the blood.
|
|
In fish and some molluscs, the efficiency of the gills is greatly enhanced by a countercurrent exchange mechanism in which the water passes over the gills in the opposite direction to the flow of blood through them. This mechanism is very efficient and as much as 90% of the dissolved oxygen in the water may be recovered.
|
|
Mao did not come into face-to-face conflict with the generals but tacitly disapproved of their actions. The generals were denounced by Lin Biao at the Twelfth Plenum of the 8th Party Congress in October 1968 as a "serious anti-party act". Lin, who was designated as Mao's successor in April 1969, denounced the countercurrent by describing them as those who "assumed the roles of backstage bosses and instigated the masses to fight the masses" and those who proposed that, in state organs, all cadres above the department director level should be "baked" or thrown out, paralyzing the numerous states organs in the process. Although Mao wanted the leaders of the February Countercurrent criticized, he did not intend for them to be purged and moved carefully in his dealings with its members instead.
|
|
A countercurrent mechanism system is a mechanism that expends energy to create a concentration gradient. It is found widely in nature and especially in mammalian organs. For example, it can refer to the process that is underlying the process of urine concentration, that is, the production of hyperosmotic urine by the mammalian kidney. The ability to concentrate urine is also present in birds.
|
|
Countercurrent multiplication was originally studied as a mechanism whereby urine is concentrated in the nephron. Initially studied in the 1950s by Gottschalk and Mylle following Werner Kuhn's postulations,. this mechanism gained popularity only after a series of complicated micropuncture experiments.. The proposed mechanism consists of pump, equilibration, and shift steps. In the proximal tubule, the osmolarity is isomolar to plasma (300 mOsm/L).
|
|
The aforementioned hydrodynamic and hydrostatic instruments may be employed in a variety of ways, or modes of operation, in order to address the particular separation needs of the scientist. Many modes of operation have been devised to take advantage of the strengths and potentialities of the countercurrent chromatography technique. Generally, the following modes may be performed with commercially available instruments.
|
|
Pulo Anna or Puro is fringed by a coral reef extending beyond 460 m offshore. The island itself is about elliptical and measures 800 meters northeast-southwest, and is up to 550 meters wide. A village named Puro was once on the northwest side of the island. Pulo Anna lies in the flow of the Equatorial Countercurrent throughout the year.
|
|
Countercurrent swimming machines made their appearance in the 1970s, initially in the form of pump-driven jetted streams, which caused a certain amount of turbulence and an un-natural swimming environment. They were followed up in the 1980s by propeller- and paddle-wheel driven machines. These provided a smoother stream of water. Two types of exercise machines make up the second group.
|
|
This helps increase surface area and red-cell residence time. The veins and arteries are organized in a way that allows countercurrent heat exchange. They are juxtaposed and branched extensively to form rete mirabile. This arrangement allows the heat produced by the red muscles to be retained within them, as it can be transferred from the venous blood to the ingoing arterial blood.
|
|
Multi-stage flash distillation (MSF) is a water desalination process that distills sea water by flashing a portion of the water into steam in multiple stages of what are essentially countercurrent heat exchangers. Multi-stage flash distillation plants produce about 26% of all desalinated water in the world, but today virtually all new desalination plants use reverse osmosis due to much lower energy consumption.
|
|
Solvent extraction is used to extract individual lanthanoid elements from the mixtures found in nature in ores such as monazite. In one process, the metal ions in aqueous solution are made to form complexes with tributylphosphate (TBP), which are extracted into an organic solvent such as kerosene. Complete separation is effected by using a countercurrent exchange method. A number of cells are arranged as a cascade.
|
|
The eluent from one column is transferred to another; the more columns that are used, the more theoretical plates can be achieved. DCCC enjoyed some success with natural product separations but was largely eclipsed by the rapid development of high-speed countercurrent chromatography. The main limitation of DCCC is that flow rates are low, and poor mixing is achieved for most binary solvent systems.
|
|
The inlet including the compressor of a turbo and in the inlet trumpets and the inlet valves need to be as cold as possible. A countercurrent heat exchange with forced cooling air does the job. The cylinder-walls should not heat up the air before compression, but also not cool down the gas at the combustion. A compromise is a wall temperature of 90 °C.
|
|
Rotary dryer systems use a cylindrical metal reactor (drum) that is inclined slightly from the horizontal. A burner located at one end provides heat to raise the temperature of the soil sufficiently to desorb organic contaminants. The flow of soil may be either cocurrent with or countercurrent to the direction of the purge gas flow. As the drum rotates, soil is conveyed through the drum.
|
|
In the hottest temperatures, the dromedary takes water every four to seven days. This camel has a quick rate of rehydration and can drink at per minute. The dromedary has a rete mirabile, a complex of arteries and veins lying very close to each other which uses countercurrent blood flow to cool blood flowing to the brain. This effectively controls the temperature of the brain.
|
|
"Equatorial undercurrent in the Pacific Ocean revealed by new methods." Science 119 (3097) 648-649. the fourth member of the equatorial current system (the North Equatorial Current, Equatorial Countercurrent, and South Equatorial Current having been known for a century). The existence of the Equatorial Undercurrent has been amply confirmed, during measurements completed a few days before Cromwell’s death, by his colleagues J. A. KnaussKnauss, J. A. (1953).
|
|
Some birds like gulls, herons, ducks or geese can regulate their temperature through their feet. The arteries and veins intertwine in the legs, so heat can be transferred from arteries back to veins before reaching the feet. Such a mechanism is called countercurrent exchange. Gulls can open a shunt between these vessels, turning back the bloodstream above the foot, and constrict the vessels in the foot.
|
|
Chromatography methods changed little after Tsvet's work until the explosion of mid-20th century research in new techniques, particularly thanks to the work of Archer John Porter Martin and Richard Laurence Millington Synge. By "the marrying of two techniques, that of chromatography and that of countercurrent solvent extraction",Martin Martin and Synge developed partition chromatography to separate chemicals with only slight differences in partition coefficients between two liquid solvents. Martin, who had previously been working in vitamin chemistry (including attempts to purify vitamin E), began collaborating with Synge in 1938, brought his experience with equipment design to Synge's project of separating amino acids. After unsuccessful experiments with complex countercurrent extraction machines and liquid-liquid chromatography methods where the liquids move in opposite directions, Martin hit on the idea of using silica gel in columns to hold water stationary while an organic solvent flows through the column.
|
|
Although the fluid in the tubules is with a higher concentration of salt than the blood, the flow is arranged in a countercurrent exchange, so that the blood with a high concentration of salt enters the system close to where the gland tubules exit and connect to the main canal. Thus, all along the gland, there is only a small gradient to climb, in order to push the salt from the blood to the salty fluid with active transport powered by ATP. b. The blood supply system to the gland is set in countercurrent exchange loop mechanism for keeping the high concentration of salt in the gland's blood, so that it doesn't leave back to the blood system. The glands remove the salt efficiently and thus allow the birds to drink the salty water from their environment while they are hundreds of miles away from land.
|
|
Comparison of the sizes of flotation columns and Jameson Cells with similar capacities. Mechanical cells use a large mixer and diffuser mechanism at the bottom of the mixing tank to introduce air and provide mixing action. Flotation columns use air spargers to introduce air at the bottom of a tall column while introducing slurry above. The countercurrent motion of the slurry flowing down and the air flowing up provides mixing action.
|
|
A comparison between the operations and effects of a cocurrent and a countercurrent flow exchange system is depicted by the upper and lower diagrams respectively. In both it is assumed (and indicated) that red has a higher value (e.g. of temperature) than blue and that the property being transported in the channels therefore flows from red to blue. Note that channels are contiguous if effective exchange is to occur (i.e.
|
|
Studies on wild D. coriacea discovered individuals may spend as little as 0.1% of the day resting. This constant swimming creates muscle-derived heat. Coupled with their countercurrent heat exchangers, insulating fat covering, and large size, leatherbacks are able to maintain high temperature differentials compared to the surrounding water. Adult leatherbacks have been found with core body temperatures that were above the water in which they were swimming.
|
|
Extraction of polyphenols can be performed using a solvent like water, hot water, methanol, methanol/formic acid, methanol/water/acetic or formic acid etc. Liquid–liquid extraction can be also performed or countercurrent chromatography. Solid phase extraction can also be made on C18 sorbent cartridges. Other techniques are ultrasonic extraction, heat reflux extraction, microwave-assisted extraction, critical carbon dioxide, pressurized liquid extraction or use of ethanol in an immersion extractor.
|
|
Hoar WS and Randall DJ (1984) Fish Physiology: Gills: Part B – Ion and water transfer Academic Press. . Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange.
|
|
In some fish, a rete mirabile fills the swim bladder with oxygen. A countercurrent exchange system is utilized between the venous and arterial capillaries. By lowering the pH levels in the venous capillaries, oxygen unbinds from blood hemoglobin. This causes an increase in venous blood oxygen concentration, allowing the oxygen to diffuse through the capillary membrane and into the arterial capillaries, where oxygen is still sequestered to hemoglobin.
|
|
Multicolumn Countercurrent Solvent Gradient Purification (MCSGP) is a form of chromatography that is used to separate or purify biomolecules from complex mixtures. It was developed at the Swiss Federal Institute of Technology Zürich by Aumann and Morbidelli. The process consists of two to six chromatographic columns which are connected to one another in such a way that as the mixture moves through the columns the compound is purified into several fractions.
|
|
This caused him to be fascinated with the effect of countercurrents in multiplying a very small single effect to significant separations. (Journal of the American Society of Nephrology website) and confirmed by laboratory findings in 1958 by Professor Carl W. Gottschalk.. The theory was acknowledged a year later after a meticulous study showed that there is almost no osmotic difference between liquids on both sides of nephrons.. See also History of the urinary concentrating mechanism an article in 'Kidney'—the Journal of International Society of Nephrology, where Prof. Gottschalk points to the heated debate prior to the acceptance of the theory of the countercurrent multiplier action of the kidney Homer Smith, a considerable contemporary authority on renal physiology, opposed the model countercurrent concentration for 8 years, until conceding ground in 1959.Smith, Homer W., The fate of sodium and water in the renal tubules, Bull. New York Academy of Medicine 35:293–316, 1959.
|
|
In some fish, a rete mirabile fills the swim bladder with oxygen, increasing the fish's buoyancy. A countercurrent exchange system is utilized between the venous and arterial capillaries. Lowering the pH levels in the venous capillaries causes oxygen to unbind from blood hemoglobin. This causes an increase in venous blood oxygen partial pressure, allowing the oxygen to diffuse through the capillary membrane and into the arterial capillaries, where oxygen is still sequestered to hemoglobin.
|
|
Diagram of a gas centrifuge with countercurrent flow, used for separating isotopes of uranium. A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centripetal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container. A prominent use of gas centrifuges is for the separation of uranium-235 (235U) from uranium-238 (238U).
|
|
These countercurrent exchange methods extract more sugar from the cossettes using less water than if they merely sat in a hot water tank. The liquid exiting the diffuser is called raw juice. The colour of raw juice varies from black to a dark red depending on the amount of oxidation, which is itself dependent on diffuser design. The used cossettes, or pulp, exit the diffuser at about 95% moisture, but low sucrose content.
|
|
Most condensers can be divided in two broad classes. The concurrent condensers receive the vapor through one port and deliver the liquid through another port, as required in simple distillation. They are usually mounted vertically or tilted, with the vapor input at the top and the liquid output at the bottom. The countercurrent condensers are intended to return the liquid toward the source of the vapor, as required in reflux and fractional distillation.
|
|
Mammals generally have a more-vascularised glomeruli than the nephrons in birds. The nephrons of avian species can not produce urine that is hyperosmotic to the blood, but the loop of Henle utilises countercurrent multiplication which allows it to become hyperosmotic in the collecting duct. This alternation of permeability between different sections of the ascending and descending loop allows for urine osmotic pressure to be elevated 2.5 times above the blood osmotic pressure.
|
|
In 1848, the company built the first long-distance telegraph line in Europe; 500 km from Berlin to Frankfurt am Main. In the 1850s, the company was involved in building long-distance telegraph networks in Russia. In 1867, Siemens completed the monumental Indo-European (Calcutta to London) telegraph line and in 1870 a transatlantic communications cable. In 1857, Werner von Siemens described the countercurrent exchange and in 1867 a dynamo without permanent magnets.
|
|
Multistage countercurrent arrays have been used for the separation of lanthanides. For the design of a good process, the distribution ratio should be not too high (>100) or too low (<0.1) in the extraction portion of the process. It is often the case that the process will have a section for scrubbing unwanted metals from the organic phase, and finally a stripping section to obtain the metal back from the organic phase.
|
|
Countercurrent (Controcorrente) was a liberal association connected to The People of Freedom (PdL), a political party in Italy. The association was launched in 2011 by some 30 liberals who opposed Giulio Tremonti's policies as economy minister. They included Guido Crosetto, Antonio Martino, Giorgio Stracquadanio, Guido Crosetto, Isabella Bertolini, Giuseppe Cossiga and Giuseppe Moles. Some of them were also members of Christopher Columbus Foundation (Martino), while others were considered Silvio Berlusconi's loyalists (Stracquadanio).
|
|
The webbing can consist of membrane, skin, or other connective tissue and varies widely in different taxa. This modification significantly increases the surface area of the feet. One of the consequences of this modification in some species, specifically birds, is that the feet are a major location for heat loss. In birds, the legs utilize countercurrent heat exchange so that blood reaching the feet is already cooled by blood returning to the heart to minimize this effect.
|
|
Fusebox Festival is an annual festival of contemporary performance works (dance and theater) held in Austin, Texas, each spring. Founded in the mid-2000s, Fusebox is one of multiple interdisciplinary festivals that sprouted in the United States in the 2000s and was modeled on the Portland Time-Based Art Festival. In turn, Fusebox inspired other festivals, including the CounterCurrent Festival in Houston and Live Arts Exchange in Los Angeles. The festival is known for supporting local artists.
|
|
Most air breathing fish are facultative air breathers that avoid the energetic cost of rising to the surface and the fitness cost of exposure to surface predators. Red represents a higher value (e.g. of temperature or the partial pressure of a gas) than blue so the property being transported in the channels flows from red to blue. In fish a countercurrent flow (lower diagram) of blood and water in the gills is used to extract oxygen from the environment.
|
|
The use of countercurrent heat exchange with blood flow allows for regulated conservation/ elimination of heat of appendages. When ambient temperatures are low, heterotherms will constrict their arterioles to reduce heat loss along skin surfaces. The reverse occurs at high ambient temperatures, arterioles dilate to increase heat loss. At ambient temperatures below their body temperatures (thermal neutral zone (TNZ)), common ostriches decrease body surface temperatures so that heat loss occurs only across about 10% of total surface area.
|
|
Fig. 2. A comparison between the operations and effects of a cocurrent and a countercurrent flow exchange system is depicted by the upper and lower diagrams respectively. In both it is assumed (and indicated) that red has a higher value (e.g. of temperature or the partial pressure of a gas) than blue and that the property being transported in the channels therefore flows from red to blue. Note that channels are contiguous if effective exchange is to occur (i.e.
|
|
Countercurrent distribution (CCD, also spelled "counter current" distribution) is an analytical chemistry technique which was developed by Lyman C. Craig in the 1940s. Countercurrent distribution is a separation process that is founded on the principles of liquid–liquid extraction where a chemical compound is distributed (partitioned) between two immiscible liquid phases (oil and water for example) according to its relative solubility in the two phases. The simplest form of liquid-liquid extraction is the partitioning of a mixture of compounds between two immiscible liquid phases in a separatory funnel. This occurs in five steps: 1) preparation of the separatory funnel with the two phase solvent system, 2) introduction of the compound mixture into the separatory funnel, 3) vigorous shaking of the separatory funnel to mix the two layers and allow for mass transfer of compounds in and out of the phases, 4) The contents of the separatory funnel are allowed to settle back into two distinct phases and 5) the two phases are separated from each other by draining out the bottom phase.
|
|
Consequently, cocurrent-flow spray towers are smaller than countercurrent-flow spray towers treating the same amount of exhaust flow. In crosscurrent-flow spray towers, also called horizontal-spray scrubbers, the gas and liquid flow in directions perpendicular to each other. In this vessel, the gas flows horizontally through a number of spray sections. The amount and quality of liquid sprayed in each section can be varied, usually with the cleanest liquid (if recycled liquid is used) sprayed in the last set of sprays.
|
|
The Pacific NECC is a major eastward moving surface current that transports more than 20 Sv from the West Pacific warm pool to the cooler east Pacific. In the western Pacific the countercurrent is centred near 5°N while in the central Pacific it is located near 7°N.Yu et al., 2000 At the surface, the current is located on the southern slope of the North Equatorial Trough, a region of low sea level which extends from east to west across the Pacific.
|
|
In addition, passive countercurrent exchange by the vessels carrying the blood supply to the nephron is essential for enabling this function. The kidney participates in whole-body homeostasis, regulating acid-base balance, electrolyte concentrations, extracellular fluid volume, and blood pressure. The kidney accomplishes these homeostatic functions both independently and in concert with other organs, particularly those of the endocrine system. Various endocrine hormones coordinate these endocrine functions; these include renin, angiotensin II, aldosterone, antidiuretic hormone, and atrial natriuretic peptide, among others.
|
|
Typically, most modern commercial CCC and CPC can inject 5 to 40 g per liter capacity. The range is so large, even for a specific instrument, let alone all instrument options, as the type of target, matrix and available biphasic solvent vary so much. Approximately 10 g per liter would be a more typical value, that the majority of applications could use as a base value. The countercurrent separation starts with choosing an appropriate biphasic solvent system for the desired separation.
|
|
By 1982 the technology was sufficiently advanced for the technique to be called "high-speed" countercurrent chromatography (HSCCC). Peter Carmeci initially commercialized the PC Inc. Ito Multilayer Coil Separator/Extractor which utilized a single bobbin (onto which the coil is wound) and a counterbalance, plus a set of "flying leads" which are tubing that connect the bobbins. Dr. Walter Conway & others later evolved the bobbin design such that multiple coils, even coils of different tubing sizes, could be placed on the single bobbin.
|
|
In birds with webbed feet, retia mirabilia in the legs and feet transfer heat from the outgoing (hot) blood in the arteries to the incoming (cold) blood in the veins. The effect of this biological heat exchanger is that the internal temperature of the feet is much closer to the ambient temperature, thus reducing heat loss. Penguins also have them in the flippers and nasal passages. Seabirds distill seawater using countercurrent exchange in a so- called salt gland with a rete mirabile.
|
|
The cooler exit gas temperature and smaller volume eliminates the need for a cooling unit, which allows downstream processing equipment to be smaller. Countercurrent systems are effective on petroleum products with molecular weights lower than No.2 fuel oil. In cocurrent systems, the purge gas is 50 °F to 100 °F hotter than the soil discharge temperature. The result is that the purge gas exit temperature may range from 400 °F to 1,000 °F and cannot go directly to the baghouse.
|
|
Another form of resistance swimming is that in which the swimmer is unrestrained and the water is set in motion by means of mechanical devices, such as jets, propellers or paddle wheels. Such an apparatus is also known as a countercurrent swimming machine, of which a number are presently available commercially. A prototype machine was used by the Columbia University swim team in the late 1980s. Swimming machines made their appearance in the 1970s, initially in the form of jetted streams.
|
|
Retrieved April 10, 2019. Two weeks after the departure from Clarksville, the expedition arrived at Fort Massac. On November 28, it reached Fort Kaskaskia, 50 miles south of Saint Louis. The winter was spent at Camp Dubois, a temporary camp on the Illinois side of the Mississippi, across from the Missouri River's outlet. On May 14, 1804, the expedition left the camp and began the voyage up the Missouri; the strong countercurrent reduced their speed to one mile per hour.
|
|
This is where the almost complete absorption of nutritionally important substances takes place. In the device, this section is merely a straight channel, but blood particles going to the filtrate have to cross the previously mentioned membrane and a layer of renal proximal tubule cells. The second segment of the tubules is the loop of Henle where the reabsorption of water and ions from the urine takes place. The device's looping channels strives to simulate the countercurrent mechanism of the loop of Henle.
|
|
Counter-current exchange conservation circuit "Countercurrent" heat exchangers occur naturally in the circulation system of fish, whales and other marine mammals. Arteries to the skin carrying warm blood are intertwined with veins from the skin carrying cold blood, causing the warm arterial blood to exchange heat with the cold venous blood. This reduces the overall heat loss in cold water. Heat exchangers are also present in the tongue of baleen whales as large volume of water flow through their mouths.
|
|
Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In species like the Spiny dogfish and other sharks and rays, a spiracle exists near the top of the head that pumps water into the gills when the animal is not in motion. In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange. The muscles on the sides of the pharynx push the oxygen-depleted water out the gill openings.
|
|
Battery of mixer-settlers counter currently interconnected. Each mixer-settler unit provides a single stage of extraction. A mixer settler consists of a first stage that mixes the phases together followed by a quiescent settling stage that allows the phases to separate by gravity. In the multistage countercurrent process, multiple mixer settlers are installed with mixing and settling chambers located at alternating ends for each stage (since the outlet of the settling sections feed the inlets of the adjacent stage's mixing sections).
|
|
Typical countercurrent-flow spray tower. A spray tower (or spray column or spray chamber) is gas-liquid contactor used to achieve mass and heat transfer between a continuous gas phase (that can contain dispersed solid particles) and a dispersed liquid phase. It consists of an empty cylindrical vessel made of steel or plastic, and nozzles that spray liquid into the vessel. The inlet gas stream usually enters at the bottom of the tower and moves upward, while the liquid is sprayed downward from one or more levels.
|
|
There is also a South Equatorial Countercurrent (SECC) that transports water from west to east in the Pacific and Atlantic basins between 2°S and 5°S in the western basin and farther south toward the east.Reid, Jun., 1959Stramma, 1991 While the SECC is geostrophic in nature, the physical mechanism for its appearance is less clear than with the NECC; that is, Sverdrup theory does not obviously explain its existence. Additionally, the seasonal cycle of the SECC is not as defined as that of the NECC.
|
|
The Atlantic NECC consists of the eastward zonal transport of water between 3°N and 9°N, with typical widths on the order of 300 km. The Atlantic NECC is unique among the equatorial currents in that basin because of its extreme seasonality. The maximum eastward flow is attained in late boreal summer and fall while the countercurrent is replaced by westward flow in late winter and spring. The NECC has maximum transport of approximately 40 Sv (10^6 m3/s) at 38°W.
|
|
The "heart does not have to pump blood as rapidly in order to maintain a constant body core temperature and thus, metabolic rate." CCHE is present in animals like reindeer, fox and moose living in extreme conditions of cold or hot weather as a mechanism for retaining the heat in (or out of) the body. These are countercurrent exchange systems with the same fluid, usually blood, in a circuit, used for both directions of flow. Reindeer have specialised counter-current vascular heat exchange in their nasal passages.
|
|
Droplet countercurrent chromatography (DCCC) was introduced in 1970 by Tanimura, Pisano, Ito, and Bowman. DCCC uses only gravity to move the mobile phase through the stationary phase which is held in long vertical tubes connected in series. In the descending mode, droplets of the denser mobile phase and sample are allowed to fall through the columns of the lighter stationary phase using only gravity. If a less-dense mobile phase is used it will rise through the stationary phase; this is called ascending mode.
|
|
The soil may be incorporated into the asphalt as a recycling process or the treated soil may be used for other purposes. Asphalt rotary dryers are normally constructed of carbon steel and have a soil discharge temperature of 300 °F to 600 °F. Typically, asphalt plant aggregate dryers are identical to the countercurrent rotary desorbers described above and are effective on the same types of contaminants. The primary difference is that an afterburner is not required for incorporation of clean aggregate into the asphalt mix.
|
|
Using screw presses, the wet pulp is then pressed down to 75% moisture. This recovers additional sucrose in the liquid pressed out of the pulp, and reduces the energy needed to dry the pulp. The pressed pulp is dried and sold as animal feed, while the liquid pressed out of the pulp is combined with the raw juice, or more often introduced into the diffuser at the appropriate point in the countercurrent process. The final byproduct, vinasse, is used as fertilizer or growth substrate for yeast cultures.
|
|
Classic flat pipe cocurrent and counter-current exchange shown again In a countercurrent heat exchanger, the hot fluid becomes cold, and the cold fluid becomes hot. In this example, hot water at 60 °C enters the top pipe. It warms water in the bottom pipe which has been warmed up along the way, to almost 60 °C. A minute but existing heat difference still exists, and a small amount of heat is transferred, so that the water leaving the bottom pipe is at close to 60 °C.
|
|
In fish where the swim bladder is closed, the gas content is controlled through the rete mirabilis, a network of blood vessels serving as a countercurrent gas exchanger between the swim bladder and the blood. The Chondrostei such as sturgeons also have a swim bladder, but this appears to have evolved separately: other Actinopterygii such as the bowfin and the bichir do not have one, so swim bladders appear to have arisen twice, and the teleost swim bladder is not homologous with the chondrostean one.
|
|
Rete mirabile function as countercurrent heat exchangers that prevent metabolic heat loss at the gills. Warm-bodied fish, such the southern bluefin tuna, maintain their TB by varying the efficiency of heat exchangers. Some oxygen is typically lost to outgoing venous blood in the process of heat exchange, depending on heat exchanger efficiency, which can be influenced by the rate of blood flow and blood vessel diameter. As tunas migrate to greater depths, often looking for prey, they encounter cooler water temperatures at the gill surface.
|
|
The BMR is a static rate which changes depending on factors such as the time of day or seasonal activity. Like most other birds, basic physiological adaptations control both heat loss in warm conditions and heat retention in cooler conditions. Using a system of countercurrent blood flow, heat is efficiently recycled through the body rather than being lost through extremities such as the legs and feet. Living in the equatorial region of the world, the American flamingo has little variation in seasonal temperature changes.
|
|
Qiu called the day his "rebirth". After Qiu's release, marshals Liu Bocheng, Nie Rongzhen and Ye Jianying visited Qiu as he was undergoing treatment. The senseless mistreatment of Qiu was one of a series of events that pushed marshals Nie and Ye to voice their displeasure with the Cultural Revolution during the February Countercurrent, the last serious phase of dissent in the senior ranks of the party during the movement. Zhou Enlai himself asked Qiu to be restored in his leadership position in the GLD.
|
|
It props up the animal when it is cutting down a tree and acts as a rudder when it is swimming and maneuvering underwater. It also stores fat and has a countercurrent blood vessel system which allows the animal to reduce heat loss by 25% during the summer and 2% in the winter. Despite popular depictions, beavers do not use their tails to pack or carry mud. The beaver digestive system is adapted for a high-fiber diet; a cardiac gland secretes into the stomach.
|
|
The steam turbine drives a synchronous hydrogen cooled Alsthom/ABB licensed generator, which delivers 309 MW net, 330 MW gross power. Cooling water is provided by the Jiu River and condenser cooling is delivered by 7 × natural draft cooling towers in countercurrent. The power plant is required to have some regulations on their sulfur emissions, so the project may be financed by a yen-based official development assistance loan from the Japan Bank for International Cooperation (JBIC) to install flue gas desulfurization units on the power plants to remove around 95% of SO2.
|
|
This short-lived resistance was branded the "February Countercurrent"MacFaquhar and Schoenhals, pp. 195–196.—effectively silencing critics of the movement within the party in the years to come. While revolutionaries dismantled ruling government and party organizations all over the country, because power seizures lacked centralized leadership, it was no longer clear who truly believed in Mao's revolutionary vision and who was opportunistically exploiting the chaos for their own gain. The formation of rival revolutionary groups, some manifestations of long-established local feuds, led to factional violent struggles across the country.
|
|
The operating principle of CCC equipment requires a column consisting of a tube coiled around a bobbin. The bobbin is rotated in a double-axis gyratory motion (a cardioid), which causes a variable g-force to act on the column during each rotation. This motion causes the column to see one partitioning step per revolution and components of the sample separate in the column due to their partitioning coefficient between the two immiscible liquid phases. "High-performance" countercurrent chromatography (HPCCC) works in much the same way as HSCCC.
|
|
Hydrodynamic instruments are often marketed as high-speed or high- performance countercurrent chromatography (HSCCC and HPCCC respectively) instruments which rely on the Archimedes' screw force in a helical coil to retain the stationary phase in the column. The components of a CCC system are similar to most liquid chromatography configurations, such as high-performance liquid chromatography. One or more pumps deliver the phases to the column which is the CCC instrument itself. Samples are introduced into the column through a sample loop filled with an automated or manual syringe.
|
|
Historically, it was thought that no commercial countercurrent chromatograph could cope with the high viscosities of ionic liquids. However, modern instruments that can accommodate 30 to 70+ % ionic liquids (and potentially 100% ionic liquid, if both phases are suitably customized ionic liquids) have become available. Ionic liquids can be customized for polar / non-polar organic, achiral and chiral compounds, bio-molecule, and inorganic separations, as ionic liquids can be customized to have extraordinary solvency and specificity. After the biphasic solvent system has been chosen a batch of is formulated and equilibrated in a separatory funnel.
|
|
Early work in the development of liquid-liquid separation techniques was undertaken by Cornish et al. with a process called "systematic fractional distribution" as well as Randall and Longtin, however, the central figure is certainly Lyman C. Craig. Lyman Craig's development of countercurrent distribution began with studying the distribution of a pharmaceutical, mepacrine (atabrine), between the two layers of an ethylene dichloride, methanol, and aqueous buffer biphasic solvent system. The distribution coefficient (Kc which coincides with partition coefficient) of atabrine varied by the composition of the solvent system and the pH of the buffer.
|
|
In addition, they have slow-oxidative muscles centrally located within their bodies and a blood vessel countercurrent exchange system called the rete mirabile ("wonderful net"), allowing them to generate and retain body heat. The temperature inside the red muscles of a common thresher averages 2 °C (3.6 °F) above that of the ambient seawater, though significant individual variation is seen. Unlike the pelagic and bigeye threshers, the common thresher lacks an orbital rete mirabile to protect its eyes and brain from temperature changes. Immature common threshers fall prey to larger sharks.
|
|
For 235U production, the heavier stream is the waste stream and the lighter stream is the product stream. Modern Zippe-type centrifuges are tall cylinders spinning on a vertical axis, with a vertical temperature gradient applied to create a convective circulation rising in the center and descending at the periphery of the centrifuge. Diffusion between these opposing flows increases the separation by the principle of countercurrent multiplication. In practice, since there are limits to how tall a single centrifuge can be made, several such centrifuges are connected in series.
|
|
Spiral counter-current heat exchange schematic In countercurrent flow, the two flows move in opposite directions. Two tubes have a liquid flowing in opposite directions, transferring a property from one tube to the other. For example, this could be transferring heat from a hot flow of liquid to a cold one, or transferring the concentration of a dissolved solute from a high concentration flow of liquid to a low concentration flow. The counter-current exchange system can maintain a nearly constant gradient between the two flows over their entire length of contact.
|
|
The spent cooking liquor from sulfite pulping is usually called brown liquor, but the terms red liquor, thick liquor and sulfite liquor are also used (compared to black liquor in the kraft process). Pulp washers, using countercurrent flow, remove the spent cooking chemicals and degraded lignin and hemicellulose. The extracted brown liquor is concentrated, in multiple effect evaporators. The concentrated brown liquor can be burned in the recovery boiler to generate steam and recover the inorganic chemicals for reuse in the pulping process or it can be neutralized to recover the useful byproducts of pulping.
|
|
Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press. It also has a very efficient circulatory system. It possesses one of the highest blood- hemoglobin concentrations among fish, which allows it to efficiently deliver oxygen to its tissues; this is combined with an exceptionally thin blood-water barrier to ensure rapid oxygen uptake. To keep its core muscles warm, which are used for power and steady swimming, the Atlantic bluefin uses countercurrent exchange to prevent heat from being lost to the surrounding water.
|
|
The "C-shape" in the western region of the Subtropical Gyre, including the Subtropical Countercurrent, generally does not exist below 200 m. At about 1000 – 1500 m, the Subtropical Gyre is located entirely in the western region of the North Pacific near the Kuroshio Current and Kuroshio Extension. In the subtropical regions, flow is weak where influences from the Subtropical Gyre are minimal. Differences in steric heights over distances of 1000 km are on the order of 1 cm, rather than the differences of 10 cm within the area of the North Pacific Subtropical Gyre.
|
|
Each cell of the sponge's body is therefore exposed to a constant flow of fresh oxygenated water. They can therefore rely on diffusion across their cell membranes to carry out the gas exchange needed for respiration. In organisms that have circulatory systems associated with their specialized gas-exchange surfaces, a great variety of systems are used for the interaction between the two. In a countercurrent flow system, air (or, more usually, the water containing dissolved air) is drawn in the opposite direction to the flow of blood in the gas exchanger.
|
|
In 1954, a fractionation column was introduced by Kepes the resembled a CCC column divided into chambers with perforated plastic disks. Similar DCCC-type instruments have been created by A. E. Kostanyan and collaborators which employ vertical columns that are divided into partitions with porous disks. Once the columns are filled with stationary phase, the mobile phase is pumped through, not continuously but, in pulses. The solvent motion created by a pulsed pumping action creates the mixing and settling that is common to most all forms of countercurrent chromatography.
|
|
Coflore continuous countercurrent extractor. These are commonly used in industry for the processing of metals such as the lanthanides; because the separation factors between the lanthanides are so small many extraction stages are needed. In the multistage processes, the aqueous raffinate from one extraction unit is fed to the next unit as the aqueous feed, while the organic phase is moved in the opposite direction. Hence, in this way, even if the separation between two metals in each stage is small, the overall system can have a higher decontamination factor.
|
|
Elephant seals are able to slow down their heartbeat (bradycardia) and divert blood flow from the external areas of the body to important core organs. They can also slow down their metabolism while performing deep dives. Elephant seals have a helpful feature in their bodies known as the countercurrent heat exchanger to help conserve energy and prevent heat loss. In this system, arteries and veins are organized in a way to maintain a constant body temperature by having the cool blood flowing to the heart warmed by blood going to external areas of the animal.
|
|
The subtropical countercurrent (STCC) is a narrow eastward ocean current in the central North Pacific Ocean (20–30°N) where the Sverdrup theory predicts a broad westward flow. It originates in the western North Pacific around 20°N, and flows eastward against the northeast trade winds and stretches northeastward to the north of Hawaii. It is accompanied by a subsurface temperature and density front called the subtropical front, in thermal wind relation with the STCC. Furthermore, the STCC maintains a sea surface temperature front during winter and spring.
|
|
There are two types of centrifuge designed for sludge thickening and both methods depends on the same solid-liquid separation principal. The first method is "solid bowl centrifuge", a horizontally-arranged helical screw that admits sludge, removes solid in a countercurrent fashion while allowing liquids to pass through. The moving shaft consists of a set of helical scrolls which push the solid waste against the flow of incoming sludge. As solid content starts to build up, it will become too heavy and then drops down to a collection bin.
|
|
Freshwater fish gills magnified 400 times The gills of vertebrates typically develop in the walls of the pharynx, along a series of gill slits opening to the exterior. Most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other. The gills are composed of comb-like filaments, the gill lamellae, which help increase their surface area for oxygen exchange. When a fish breathes, it draws in a mouthful of water at regular intervals.
|
|
Another advantage of countercurrent chromatography is that experiments conducted in the laboratory can be scaled to industrial volumes. When gas chromatography or HPLC is carried out with large volumes, resolution is lost due to issues with surface-to-volume ratios and flow dynamics; this is avoided when both phases are liquid. 300 px The CCC separation process can be thought of as occurring in three stages: mixing, settling, and separation of the two phases (although they often occur continuously). Vigorous mixing of the phases is critical in order to maximize the interfacial area between them and enhance mass transfer.
|
|
The relative solubility of a compound in two phases is known as the partition coefficient. While one separatory funnel is useful in separating certain compound mixtures with a carefully formulated biphasic solvent system, a series of separatory funnels may be employed to separate compounds that have different partition coefficients. Countercurrent distribution, therefore, is a method of using a series of vessels (separatory funnels) to separate compounds by a sequence of liquid-liquid extraction operations. Contrary to liquid-liquid extraction, in the CCD instruments the upper phase is decanted from the lower phase once the phases have settled.
|
|
Anatomical examination indicates that the pelagic thresher is unlikely to be warm-bodied like the common thresher; it lacks a rete mirabile, a blood vessel countercurrent exchange system that prevents metabolic heat from being dissipated into the water, inside its trunk. Furthermore, its aerobic red muscles, responsible for generating heat in the common thresher, are positioned in two lateral strips just beneath the skin rather than at the core of the body. A rete system is present around the pelagic thresher's brain and eyes, albeit less developed than in the bigeye thresher, which may serve to buffer those organs against temperature changes.
|
|
Typically constructed from stainless steel, spacers are inserted to retain concentricity, while the tubes are sealed with O-rings, packing, or welded depending on the operating pressures. While both co and counter configurations are possible, the countercurrent method is more common. The preference is to pass the hot fluid through the inner tube to reduce heat losses, while the annulus is reserved for the high viscosity stream to limit the pressure drop. Beyond double stream heat exchangers, designs involving triple (or more) streams are common; alternating between hot and cool streams, thus heating/cooling the product from both sides.
|
|
The centrifugal separation continues as before (heavier molecules preferentially moving outwards), which means that the heavier molecules are collected by the wall flow, and the lighter fraction collects at the other end. In a centrifuge with downward wall flow, the heavier molecules collect at the bottom. The outlet scoops are then placed at the ends of the rotor cavity, with the feed mixture injected along the axis of the cavity (ideally, the injection point is at the point where the mixture in the rotor is equal to the feed). This countercurrent flow can be induced mechanically or thermally, or a combination.
|
|
Counter current multiplier diagram The loop of Henle is supplied by blood in a series of straight capillaries descending from the cortical efferent arterioles. These capillaries (called the vasa recta; recta is from the Latin for "straight") also have a countercurrent multiplier mechanism that prevents washout of solutes from the medulla, thereby maintaining the medullary concentration. As water is osmotically driven from the descending limb into the interstitium, it readily enters the capillaries. The low bloodflow through the vasa recta allows time for osmotic equilibration, and can be altered by changing the resistance of the vessels' efferent arterioles.
|
|
Nearly complete transfer in systems implementing countercurrent exchange, is only possible if the two flows are, in some sense, "equal". For a maximum transfer of substance concentration, an equal flowrate of solvents and solutions is required. For maximum heat transfer, the average specific heat capacity and the mass flow rate must be the same for each stream. If the two flows are not equal, for example if heat is being transferred from water to air or vice versa, then, similar to cocurrent exchange systems, a variation in the gradient is expected because of a buildup of the property not being transferred properly.
|
|
In oceanography, the Davidson Current is a coastal countercurrent of the Pacific Ocean running north along the western coast of the United States from Baja California, Mexico to northern Oregon, ending at about latitude 48°N. Its flow is adjacent to the California Current, but it flows north rather than south and hugs the coastline. The current is active year-round at 650 feet (200 meters) below sea level, but surfaces during the winter months, generally from mid-November through mid-February. In these months, northerly winds weaken and are replaced to some extent by southwesterly winds.
|
|
The Union process was an above ground shale oil extraction technology for production of shale oil, a type of synthetic crude oil. The process used a vertical retort where heating causes decomposition of oil shale into shale oil, oil shale gas and spent residue. The particularity of this process is that oil shale in the retort moves from the bottom upward to the top, countercurrent to the descending hot gases, by a mechanism known as a rock pump. The process technology was invented by the American oil company Unocal Corporation in late 1940s and was developed through several decades.
|
|
In the summer, the thermal conductance of the Arctic foxes body is 114% higher than the winter, but their body core temperature is constant year-round. One way that Arctic foxes regulate their body temperature is by utilizing a countercurrent heat exchange in the blood of their legs. Arctic foxes can constantly keep their feet above the tissue freezing point (−1 °C) when standing on cold substrates without losing mobility or feeling pain. They do this by increasing vasodilation and blood flow to a capillary rete in the pad surface, which is in direct contact with the snow rather than the entire foot.
|
|
The heat from the steam reduces the viscosity of the heavy crude oil or bitumen which allows it to flow down into the lower wellbore. The steam and associated gas rise because of their low density compared to the heavy crude oil below, ensuring that steam is not produced at the lower production well, tend to rise in the steam chamber, filling the void space left by the oil. Associated gas forms, to a certain extent, an insulating heat blanket above (and around) the steam. Oil and water flow is by a countercurrent, gravity driven drainage into the lower well bore.
|
|
Each straight arteriole has a hairpin turn in the medulla and carries blood at a very slow rate – two factors crucial in the maintenance of countercurrent exchange that prevent washout of the concentration gradients established in the renal medulla. The maintenance of this concentration gradient is one of the components responsible for the kidney's ability to produce concentrated urine. On the descending portion of the vasa recta, sodium chloride and urea are reabsorbed into the blood, while water is secreted. On the ascending portion, sodium chloride and urea are secreted into the interstitium, while water is reabsorbed.
|
|
"Desalination industry enjoys growth spurts as scary starts to bite" globalwaterintel.com. Desalination is particularly relevant in dry countries such as Australia, which traditionally have relied on collecting rainfall behind dams for water. Kuwait produces a higher proportion of its water through desalination than any other country, totaling 100% of its water use.Laurene Veale (August 19, 2015) multistage flash desalinator A – steam in B – seawater in C – potable water out D – brine out (waste) E – condensate out F – heat exchange G – condensation collection (desalinated water) H – brine heater The pressure vessel acts as a countercurrent heat exchanger.
|
|
Substances secreted include urea, creatinine, potassium, hydrogen, and uric acid. Some of the hormones which signal the tubules to alter the reabsorption or secretion rate, and thereby maintain homeostasis, include (along with the substance affected) antidiuretic hormone (water), aldosterone (sodium, potassium), parathyroid hormone (calcium, phosphate), atrial natriuretic peptide (sodium) and brain natriuretic peptide (sodium). A countercurrent system in the renal medulla provides the mechanism for generating a hypertonic interstitium, which allows the recovery of solute-free water from within the nephron and returning it to the venous vasculature when appropriate. Some diseases of the nephron predominantly affect either the glomeruli or the tubules.
|
|
As blood travels through the venules to the veins a funneling occurs called vasodilation bringing blood back to the heart. Once the blood reaches the heart it moves first into the right atrium, then the left ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste for oxygen. Oxygenated blood then flows from the lungs through the left atrium to the left ventricle where it is pumped out to the body. With respect to thermoregulation, the American flamingo has highly vascularized feet that use a countercurrent exchange system in their legs and feet.
|
|
The system is split into several sections, from which every section performs a tasks analog to the tasks of a batch purification. These tasks are loading the feed, running the gradient elution, recycling of weakly adsorbing site fractions, fractionation of the purified product, recycling of strongly adsorbing site fractions, cleaning the column from strongly adsorbing impurities, cleaning in place and re-equilibration of the column to start the next purification run. All of the tasks mentioned here are carried out at the same time in one unit. Recycling of non-pure side fractions is performed in countercurrent movement.
|
|
A striking adaptation to a very dilute diet is found in many hemipterans: a filter chamber, a part of the gut looped back on itself as a countercurrent exchanger, which permits nutrients to be separated from excess water. The residue, mostly water with sugars and amino acids, is quickly excreted as sticky "honey dew", notably from aphids but also from other Auchenorrhycha and Sternorrhyncha. Some Sternorrhyncha including Psyllids and some aphids are gall formers. These sap-sucking hemipterans inject fluids containing plant hormones into the plant tissues inducing the production of tissue that covers to protects the insect and also act as sinks for nutrition that they feed on.
|
|
Most sharks are "cold-blooded" or, more precisely, poikilothermic, meaning that their internal body temperature matches that of their ambient environment. Members of the family Lamnidae (such as the shortfin mako shark and the great white shark) are homeothermic and maintain a higher body temperature than the surrounding water. In these sharks, a strip of aerobic red muscle located near the center of the body generates the heat, which the body retains via a countercurrent exchange mechanism by a system of blood vessels called the rete mirabile ("miraculous net"). The common thresher and bigeye thresher sharks have a similar mechanism for maintaining an elevated body temperature.
|
|
Blood moving into the legs is cooled by blood returning to the body in a countercurrent heat exchange (CCHE), a highly efficient means of minimising heat loss through the skin's surface. In the CCHE mechanism, in cold weather, blood vessels are closely knotted and intertwined with arteries to the skin and appendages that carry warm blood with veins returning to the body that carry cold blood causing the warm arterial blood to exchange heat with the cold venous blood. In this way, their legs for example are kept cool, maintaining the core body temperature nearly higher with less heat lost to the environment. Heat is thus recycled instead of being dissipated.
|
|
A seven-year R&D; process produced HPCCC instruments that generated 240 g's, compared to the 80 g's of the HSCCC machines. This increase in g-force and larger bore of the column has enabled a ten-fold increase in throughput, due to improved mobile phase flow rates and a higher stationary phase retention. Countercurrent chromatography is a preparative liquid chromatography technique, however with the advent of the higher-g HPCCC instruments it is now possible to operate instruments with sample loadings as low as a few milligrams, whereas in the past hundreds of milligrams had been necessary. Major application areas for this technique include natural product purification and drug development.
|
|
Being constant swimmers required large amounts of oxygen which is achieved by water passing over their gills, which are in place of lungs to still have a large surface area through the various grooves in the gill tissue. The oxygen is obtained when they exhale and the water is pushed through their pharynx. Their blood flows in the opposite direction (countercurrent exchange) of the water over the gills in able to remove the maximum amount of oxygen from the water. They use a swim bladder to adjust their buoyancy by changing the volume of gas in the bladder to keep an overall constant volume for the bladder at different depths.
|
|
The soil discharge temperature of carbon steel drums is typically 300 to 600 degrees F. Alloy drums are available that can increase the soil discharge temperature to 1,200 degrees F. Most rotary dryers that are used to treat petroleum contaminated soil are made of carbon steel. After the treated soil exits the rotary dryer, it enters a cooling conveyor where water is sprayed on the soil for cooling and dust control. Water addition may be conducted in either a screw conveyor or a pugmill. Besides the direction of purge gas flow relative to soil feed direction, there is one major difference in configuration between countercurrent and cocurrent rotary dryers.
|
|
This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water. Urea can then re-enter the nephron and be excreted or recycled again depending on whether ADH is still present or not. The 'single effect' describes the fact that the ascending thick limb of the loop of Henle is not permeable to water but is permeable to sodium chloride. This allows for a countercurrent exchange system whereby the medulla becomes increasingly concentrated, but at the same time setting up an osmotic gradient for water to follow should the aquaporins of the collecting duct be opened by ADH.
|
|
In mechanically induced countercurrent flow, the arrangement of the (stationary) scoops and internal rotor structures are used to generate the flow. A scoop interacts with the gas by slowing it, which tends to draw it into the centre of the rotor. The scoops at each end induce opposing currents, so one scoop is protected from the flow by a "baffle": a perforated disc within the rotor which rotates along with the gas—at this end of the rotor, the flow will be outwards, towards the rotor wall. Thus, in a centrifuge with a baffled top scoop, the wall flow is downwards, and heavier molecules are collected at the bottom.
|
|
Counter heat current exchange: Note the gradually declining differential and that the once hot and cold streams exit at the reversed temperature difference; the hotter entering stream becomes the exiting cooler stream and vice versa. Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some chemical, between two flowing bodies flowing in opposite directions to each other. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. For example, in a distillation column, the vapors bubble up through the downward flowing liquid while exchanging both heat and mass.
|
|
A swimming machine is a resistance swimming apparatus, often self-contained, enabling the swimmer to swim in place. This may be accomplished either by accelerating the water past the swimmer or by supporting the swimmer, either in water or on dry land. The first type, known as a countercurrent swimming machine, usually consists of a water tank at least twice as long and about one and a half times as wide as an average person with the limbs extended. The swimmer swims unrestrained against an adjustable stream of water set in motion by means of mechanical devices, such as jets, propellers or paddle wheels.
|
|
During the 1970s, Xu studied the theoretical basis and design for solvent extraction, developed mathematical models, and made important contributions towards the development of separation processes for rare earth elements. Gao Xiaoxia's development of microanalytical techniques in polarography contributed to the success of Xu's research. Xu developed the process of countercurrent extraction (also known as series extraction or cascade extraction) and substantially reduced both the time needed to extract materials, and their resulting cost. Xu founded the Research Center of Rare Earth Chemistry as of 1986 and was essential in establishing the State Key Laboratory of Rare Earth Materials Chemistry and Applications in 1989.
|
|
A countercurrent system such as this maintains a steep concentration gradient along the length of the gas-exchange surface (see lower diagram in Fig. 2). This is the situation seen in the gills of fish and many other aquatic creatures. The gas-containing environmental water is drawn unidirectionally across the gas-exchange surface, with the blood-flow in the gill capillaries beneath flowing in the opposite direction. Although this theoretically allows almost complete transfer of a respiratory gas from one side of the exchanger to the other, in fish less than 80% of the oxygen in the water flowing over the gills is generally transferred to the blood.
|
|
The undergraduate division of the Department of Mathematics offers Bachelor of Arts (BA) and Bachelor of Science (BS) degrees in Mathematics. It consists of a wide variety of courses in pure and applied mathematics taught by a distinguished faculty with a tradition of excellence in teaching and research. Students in advanced coursework often participate in formulating models outside the field of mathematics as well as in analyzing them. For example, an advanced mathematics course in Computers in Medicine and Biology requires a student to construct two computer models selected from the following list: circulation, gas exchange in the lung, control of cell volume, and the renal countercurrent mechanism.
|
|
Equatorial Counter Current (in black) The Equatorial Counter Current is an eastward flowing, wind-driven current which extends to depths of 100-150m in the Atlantic, Indian, and Pacific Oceans. More often called the North Equatorial Countercurrent (NECC), this current flows west-to-east at about 3-10°N in the Atlantic, Indian Ocean and Pacific basins, between the North Equatorial Current (NEC) and the South Equatorial Current (SEC). The NECC is not to be confused with the Equatorial Undercurrent (EUC) that flows eastward along the equator at depths around 200m in the western Pacific rising to 100m in the eastern Pacific. In the Indian Ocean, circulation is dominated by the impact of the reversing Asian monsoon winds.
|
|
With Nils Wallin and Steven Brown he edited the interdisciplinary volume The Origins of Music. In retirement, he continues active work on theoretical topics that include the analysis of brain macrosystems and their interaction, countercurrent modelling of cortical memory, the subcortical foundations of brain mechanisms of attention and consciousness, and the biological background to human music and language.Libris, the Royal Library of Sweden search engine, is listing 21 titles as of Jan 21, 2011.Cecilia Christner Riad Ensam om att gå i takt, in: Forskning och Framtid, No. 8 (2003) - interview with Björn MerkerCurriculum Vitae by Björn Merker, 5 pages, June 2010 - read Jan 21, 2011 Merker's theory is featured at online websites, such as by McGill University.
|
|
It processes the blood supplied to it via filtration, reabsorption, secretion and excretion; the consequence of those processes is the production of urine. These include the nitrogenous wastes urea, from protein catabolism, and uric acid, from nucleic acid metabolism. The ability of mammals and some birds to concentrate wastes into a volume of urine much smaller than the volume of blood from which the wastes were extracted is dependent on an elaborate countercurrent multiplication mechanism. This requires several independent nephron characteristics to operate: a tight hairpin configuration of the tubules, water and ion permeability in the descending limb of the loop, water impermeability in the ascending loop, and active ion transport out of most of the ascending limb.
|
|
Oxygen is, therefore, able to continually diffuse down its gradient into the blood, and the carbon dioxide down its gradient into the water. Although countercurrent exchange systems theoretically allow an almost complete transfer of a respiratory gas from one side of the exchanger to the other, in fish less than 80% of the oxygen in the water flowing over the gills is generally transferred to the blood. In certain active pelagic sharks, water passes through the mouth and over the gills while they are moving, in a process known as "ram ventilation". While at rest, most sharks pump water over their gills, as most bony fish do, to ensure that oxygenated water continues to flow over their gills.
|
|
Benzer used forward genetics to investigate the genetic basis of various behaviors such as phototaxis, circadian rhythms, and learning by inducing mutations in a Drosophila population and then screening individuals for altered phenotypes of interest. To better identify mutants, Benzer developed novel apparatuses such as the countercurrent device, which was designed to separate flies according to the magnitude and direction of their phototactic response. Benzer identified mutants for a wide variety of characteristics: vision (nonphototactic, negative phototactic, and eyes absent), locomotion (sluggish, uncoordinated), stress sensitivity (freaked- out), sexual function (savoir-faire, fruitless), nerve and muscle function (photoreceptor degeneration, drop-dead), and learning and memory (rutabaga, dunce). Benzer and student Ron Konopka discovered the first circadian rhythm mutants.
|
|
The modern era of CCC began with the development of the planetary centrifuge by Dr. Yoichiro Ito which was first introduced in 1966 as a closed helical tube which was rotated on a "planetary" axis as is turned on a "sun" axis. A flow-through model was subsequently developed and the new technique was called countercurrent chromatography in 1970. The technique was further developed by employing test mixtures of DNP amino acids in a chloroform:glacial acetic acid:0.1 M aqueous hydrochloric acid (2:2:1 v/v) solvent system. Much development was needed to engineer the instrument so that required planetary motion could be sustained while the phases were being pumped through the coil(s).
|
|
Following the severe defeat of the party in the 2008 general election, a group of bertinottiani composed mainly of former members of Proletarian Democracy and led by Paolo Ferrero and Giovanni Russo Spena allied with the other minority factions, notably including Being Communists, to force Franco Giordano's resignation from secretary. Subsequently, in the July congress Ferrero's and Grassi's Refoundation in Movement motion (40.1%) faced the bulk of bertinottiani, who organized themselves around a motion named "Manifesto for the Refoundation" (47.6%) with Nichi Vendola as standard-bearer. Giannini's The Ernesto and Countercurrent (7.7%), Claudio Bellotti's HammerSickle (3.2%) and a minor group of former bertinottiani called "Disarm, Renew, Refound" (1.5%) joined forces with the Ferrero-Grassi group.
|
|
Its upper stretch near the AnhuiJiangxi border is also known as the Xin'an River (, "Newly Peaceful"); its middle stretch through the mountains of Zhejiang is also known as the Fuchun River (, "Abundant Spring River"); and the former name of its lower stretchthe Zhe () or Crooked Rivergave Zhejiang Province its name. Historically, it was first documented in the Classic of Mountains and Seas () as Zhejiang River (), later in Zhuangzi ()as Zhe River (), and in the Water Classic () as Jianjiang River (). All those names probably originate from the language of extinct Baiyue peoples. In the early 18th century, the Kangxi Dictionary () regarded Zhejiang River () as Crooked River for its crooked lower stretch and countercurrent tidal bore.
|
|
It rounds Cape Leeuwin to enter the waters south of Australia where its influence extends as far as Tasmania. The West Australian Current and Southern Australian Countercurrent, which are produced by the West Wind Drift on the southern Indian Ocean and at Tasmania, respectively, flow in the opposite direction, producing one of the most interesting oceanic current systems in the world. Its strength varies through the year; it is weakest during the summer months (winter in the northern hemisphere) from November to March when the winds tend to blow strongly from the south west northwards. The greatest flow is in the autumn and winter (March to November) when the opposing winds are weakest.
|
|
Visual Representation of Agglomeration with pneumatic mixing # Steam-jet agglomeration: A continuous process wherein fine powders are exposed to steam to provide the necessary adhesion properties. Agglomeration is controlled by particle size distribution in the raw materials, gas and steam flow conditions and the adhesion forces between the particles. After the steam section the particles are exposed to warm air flowing upwards and countercurrent to the particles, which solidifies the liquid bridges formed between the particles. Advantages: used for many years in the food industry, a continuous process #Spray drying: Spray drying starts with a liquid raw material which is sprayed as fine droplets into heated air which causes the droplets to dry into fine particles.
|
|
Although most fish are exclusively ectothermic, there are exceptions. The only known bony fishes (infraclass Teleostei) that exhibit endothermy are in the suborder Scombroidei – which includes the billfishes, tunas, and the butterfly kingfish, a basal species of mackerel – and also the opah. The opah, a lampriform, was demonstrated in 2015 to utilize "whole-body endothermy", generating heat with its swimming muscles to warm its body while countercurrent exchange (as in respiration) minimizes heat loss. It is able to actively hunt prey such as squid and swim for long distances due to the ability to warm its entire body, including its heart, which is a trait typically found in only mammals and birds (in the form of homeothermy).
|
|
For many months he participated in the field work from the HUGH M. SMITH, and for more and harder months he carried out the analysis of the observations. As a result of this pioneering work, the knowledge of the physical and biological structure of the equatorial Pacific Ocean has been vastly advanced. These achievements are the more remarkable when one notes that comparable surveys of the equatorial Atlantic and Indian oceans are still lacking. Cromwell confirmed the existence of upwelling at the equator, disproved the existence of upwelling at the northern edge of the Equatorial Countercurrent, and originated a reasonable model of wind-induced current transport in the equatorial zone Cromwell, Townsend (1953).
|
|
The politics of Zhejiang is structured in a dual party-government system like all other governing institutions in Mainland China. The Governor of Zhejiang is the highest-ranking official in the People's Government of Zhejiang. However, in the province's dual party-government governing system, the Governor is subordinate to the Zhejiang Communist Party of China (CPC) Provincial Committee Secretary, colloquially termed the "Zhejiang CPC Party Chief." Several political figures who served as Zhejiang's top political office of Communist Party Secretary have played key roles in various events in PRC history. Tan Zhenlin (term 1949-1952), the inaugural Party Secretary, was one of the leading voices against Mao's Cultural Revolution during the so-called February Countercurrent of 1967.
|
|
Kuhn received a degree in chemical engineering at the Eidgenössische Technische Hochschule (ETH, Federal Institute of Technology), in Zürich, and later a doctorate (1923) in physical chemistry. He was appointed professor of physical chemistry at the University of Kiel (1936–39) and then returned to Switzerland as director of the Physico- Chemical Institute of the University of Basel (1939–63), where he also served as rector (1955–56). In a 1951 lecture along with his student V.B. Hargitay, he was the first to hypothesize the countercurrent multiplier mechanism in the mammalian kidney, later to be discovered in many other similar biological systems.A 2001 translation of the 1951 lecture originally published in German.
|
|
Cross-section through the trunk of a porbeagle (orientation is belly-up); note the central red muscles. Like other members of its family, the porbeagle is endothermic; metabolic heat generated by its red muscles is conserved within the body by specialized systems of blood vessels called retia mirabilia (Latin for "wonderful nets"; singular rete mirabile), that act as highly efficient countercurrent heat exchangers. The porbeagle has several rete mirabile systems: the orbital retia accessing its brain and eyes, the lateral cutaneous retia accessing its swimming muscles, the suprahepatic rete accessing its viscera, and the kidney rete. Among sharks, the porbeagle's capacity for elevating body temperature is second only to the salmon shark's.
|
|
Following his doctoral work at the University of Sheffield, Sharpe continued as a postdoctoral researcher there and also at the University of Wisconsin and the University of Cambridge prior to his first academic appointment at the University of Manchester (1997). Sharpe's research focuses on cell differentiation and began with his doctoral work on differentiation of the cellular slime mould Dictyostelium discoideum but he extended this work to mammalian tissues, principally bone. In this early work he applied the technique of thin layer countercurrent distribution. Subsequently, through the study of mouse embryo differentiation and the role of homeobox sequences in DNA, his work has mainly been applied to the field of craniofacial development.
|
|
In some cases, non-aqueous biphasic solvent systems such as acetonitrile and methanol have been utilized. The main difference between DCCC and other types of countercurrent chromatography techniques is that there is no vigorous mixing of phases to enhance the mass transfer of compounds that allows them to distribute between the two phases. In 1951 Kies and Davis described an apparatus similar to the DCCC. They created a series of open tubes that were arranged in a cascade to either drip a more dense phase through an less dense stationary phase or, conversely, a less dense phase could be introduced into the bottom of the tube to dribble through the more dense phase.
|
|
Hampson-Linde cycle sketch; this sketch does not show regeneration (gas fed back to compressor) Hampson–Linde cycle; this diagram does not include the external cooler, highlight the countercurrent heat exchanger, or show significant holdup The cooling cycle proceeds in several steps: # The gas is compressed, which adds external energy into the gas, to give it what is needed for running through the cycle. Linde's US patent gives an example with the low side pressure of and high side pressure of . # The high pressure gas is then cooled by immersing the gas in a cooler environment; the gas loses some of its energy (heat). Linde's patent example gives an example of brine at 10°C.
|
|
Although the intermediately eluting MAb variant can only be obtained with 80% purity at recoveries close to zero in a batch chromatographic process, the MCSGP process can provide 90% purity at 93% yield. A numerical comparison of the MCSGP process with the batch chromatographic process, and a batch chromatographic process including ideal recycling, has been performed using an industrial polypeptide purification as the model system. It shows that the MCSGP process can increase the productivity by a factor of 10 and reduce the solvent requirement by 90%. The main advantages with respect to solvent gradient batch chromatography are high yields also for difficult separations, less solvent consumption, higher productivity, usage of countercurrent solid movement, which increases the separation efficiency.
|
|
In the kidney, the loop of Henle () (or Henle's loop, Henle loop, nephron loop or its Latin counterpart ansa nephroni) is the portion of a nephron that leads from the proximal convoluted tubule to the distal convoluted tubule. Named after its discoverer, the German anatomist Friedrich Gustav Jakob Henle, the loop of Henle's main function is to create a concentration gradient in the medulla of the kidney. By means of a countercurrent multiplier system, which uses electrolyte pumps, the loop of Henle creates an area of high urea concentration deep in the medulla, near the papillary duct in the collecting duct system. Water present in the filtrate in the papillary duct flows through aquaporin channels out of the duct, moving passively down its concentration gradient.
|
|
The previously described work of Martin and Synge impacted the development of the previously known column chromatography and inspired new forms of chromatography such as countercurrent distribution, paper chromatography, and gas-liquid chromatography which is more commonly known as gas chromatography. The modification of silica gel stationary phase led to many creative ways of modifying stationary phases in order to influence the separation characteristics. The most notable modification was the chemical bonding of alkane functional groups to silica gel to produce reversed-phase media. The original problem that Martin and Synge encountered with devising an instrument that would employ two free-flowing liquid phases was solved by Lyman C. Craig in 1944, and commercial counter-current distribution instruments were used for many important discoveries.
|
|
An evaporative light scattering detector (ELSD) is a detector used in conjunction with high-performance liquid chromatography (HPLC), Ultra high- performance liquid chromatography (UHPLC), Purification liquid chromatography such as flash or preparative chromatography, countercurrent or centrifugal partition chromatographies and Supercritical Fluid chromatography (SFC). It is commonly used for analysis of compounds where UV detection might be a restriction and therefore used where compounds do not efficiently absorb UV radiation, such as sugars, antivirals, antibiotics, fatty acids, lipids, oils, phospholipids, polymers, surfactants, terpenoids and triglycerides. ELSDs is related to the charged aerosol detector (CAD) and like the CAD, falls under the category of destructive detectors. An evaporative light scattering detector (ELSD) is able to detect all compound which are less volatile than the mobile phase, i.e.
|
|
The cycling of and excretion of urea by the kidneys is a vital part of mammalian metabolism. Besides its role as carrier of waste nitrogen, urea also plays a role in the countercurrent exchange system of the nephrons, that allows for re-absorption of water and critical ions from the excreted urine. Urea is reabsorbed in the inner medullary collecting ducts of the nephrons, Page 837 thus raising the osmolarity in the medullary interstitium surrounding the thin descending limb of the loop of Henle, which makes the water reabsorb. By action of the urea transporter 2, some of this reabsorbed urea eventually flows back into the thin descending limb of the tubule, through the collecting ducts, and into the excreted urine.
|
|
Centrifugal partition chromatography does not uses any solid stationary phase, so it guarantees a cost-effective separation for the highest industrial levels. As opposed to countercurrent chromatography, it is possible to get very high flow rates (for example 10 liters / min) with active stationary phase ratio of >80%, which guarantees good separation and high productivity. As in centrifugal partition chromatography, material is dissolved, and loaded the column in mass / volume units, loading capability can be much higher than standard solid-liquid chromatographic techniques, where material is loaded to the active surface area of the stationary phase, which takes up less than 10% of the column. Industrial instrument (RotaChrom) differ from laboratory scale instruments by the applicable flow rate with satisfactory stationary phase retention (70-90%).
|
|
The water in the mouth is, instead, forced over the gills, while the gill chambers contract emptying the water they contain through the opercular openings (Fig. 23). Back-flow into the gill chamber during the inhalatory phase is prevented by a membrane along the ventroposterior border of the operculum (diagram on the left in Fig. 23). Thus the mouth cavity and gill chambers act alternately as suction pump and pressure pump to maintain a steady flow of water over the gills in one direction. Since the blood in the lamellar capillaries flows in the opposite direction to that of the water, the consequent countercurrent flow of blood and water maintains steep concentration gradients for oxygen and carbon dioxide along the entire length of each capillary (lower diagram in Fig. 22).
|
|
The biology of the longfin mako is little-known; it is somewhat common in the western Atlantic and possibly the central Pacific, while in the eastern Atlantic, it is rare and outnumbered over 1,000-fold by the shortfin mako in fishery landings. The longfin mako's slender body and long, broad pectoral fins evoke the oceanic whitetip shark (Carcharhinus longimanus) and the blue shark (Prionace glauca), both slow-cruising sharks of upper oceanic waters. This morphological similarity suggests that the longfin mako is less active than the shortfin mako, one of the fastest and most energetic sharks. Like the other members of its family, this species possesses blood vessel countercurrent exchange systems called the rete mirabilia (Latin for "wonderful net", singular rete mirabile) in its trunk musculature and around its eyes and brain.
|
|
Dense innervation of arteries in seals by sympathetic nerves may be part of a system for maintaining vasoconstriction of the dive response independent of local metabolite induced vasodilation. Venous capacitance is highly developed, especially in phocid seals and whales, and includes a large hepatic sinus and posterior vena cava, and is thought to be related to the large blood volume of the animals. The relatively large spleen also injects extremely high hematocrit blood into the hepatic sinus during dives, and is a significant storage organ for red blood cells. Parallel counter-flowing arteries and veins characteristic of countercurrent exchange units are present in the dorsal fins, flukes, and flippers of cetaceans, and are considered to conserve body heat by transferring it to the returning venous flow before arterial blood is exposed to the high heat-loss areas.
|
|
More specifically, members of Countercurrent were committed liberals who were uncomfortable with Tremonti's policies (dirigist, in their view) and wanted a return to Forza Italia's early libertarianism and to the so-called "spirit of 1994", the year of Berlusconi's entry to politics. Somewhat surprisingly, on 3 November 2011, Stracquadanio and Bertolini signed an open letter to Berlusconi along with four recent splinters from the party (Roberto Antonione, Giustina Destro, Fabio Gava and Giancarlo Pittelli) in which they asked Berlusconi to step down and made a call for a new executive. In July 2012 Martino, Moles, Deborah Bergamini, Enrico La Loggia and Gennario Malgieri criticized the PdL's support of Monti Cabinet, which had succeeded to Berlusconi's government in November 2011, while Straquadanio left the party altogether. In September Tremonti left the PdL and Martino returned into Berlusconi's inner circle.
|
|
Counter current multiplication loop diagram A countercurrent multiplication loop is a system where fluid flows in a loop so that the entrance and exit are at similar low concentration of a dissolved substance but at the far end of the loop there is a high concentration of that substance. A buffer liquid between the incoming and outgoing tubes receives the concentrated substance. The incoming and outgoing tubes do not touch each other. The system allows the buildup of a high concentration gradually, by allowing a natural buildup of concentration towards the tip inside the in-going tube, (for example using osmosis of water out of the input pipe and into the buffer fluid), and the use of many active transport pumps each pumping only against a very small gradient, during the exit from the loop, returning the concentration inside the output pipe to its original concentration.
|
|
In the early 1960s, Derrida began speaking and writing publicly, addressing the most topical debates at the time. One of these was the new and increasingly fashionable movement of structuralism, which was being widely favoured as the successor to the phenomenology approach, the latter having been started by Husserl sixty years earlier. Derrida's countercurrent take on the issue, at a prominent international conference, was so influential that it reframed the discussion from a celebration of the triumph of structuralism to a "phenomenology vs structuralism debate." Phenomenology, as envisioned by Husserl, is a method of philosophical inquiry that rejects the rationalist bias that has dominated Western thought since Plato in favor of a method of reflective attentiveness that discloses the individual's "lived experience;" for those with a more phenomenological bent, the goal was to understand experience by comprehending and describing its genesis, the process of its emergence from an origin or event.
|
|
A group led by Francesco Ricci established the Communist Alternative Party, others, led by the Trotskyite Marco Ferrando, formed the Workers' Communist Party, while a tiny minority chose to stay in the party and launched Countercurrent. In February 2007, senator Franco Turigliatto of Critical Left, led by Salvatore Cannavò, voted twice against the government's foreign policy, leading Romano Prodi to temporarily resign from Prime Minister. In April, Turigliatto was expelled from the party and Critical Left was suspended from it, leading to its final split and establishment as a party in December. Turigliatto's ejection was supported also by Claudio Grassi (leader of Being Communists) and this caused a break-up of the faction. A group led by Fosco Giannini launched an alternative faction named The Ernesto (from the eponymous communist publication), but it would suffer the 2008 split of Communist Left, which would splinter in 2011 into Communist Left and Communists Together/The Future City.
|
|
Evaporation from the Leeuwin current during this period contributes greatly to the rainfall in the southwest region of Western Australia. Typically the Leeuwin Current's speed and its eddies are about 1 knot (50 cm/s), although speeds of 2 knots (1 m/s) are common, and the highest speed ever recorded by a drifting satellite- tracked buoy was . The Leeuwin Current is shallow for a major current system, by global standards, being about 300 m deep, and lies on top of a northwards countercurrent called the Leeuwin Undercurrent. The Leeuwin Current is very different from the cooler, equatorward flowing currents found along coasts at equivalent latitudes such as the southwest African Coast (the Benguela Current); the long Chile-Peru Coast (the Humboldt Current), where upwelling of cool nutrient-rich waters from below the surface results in some of the most productive fisheries; the California Current, which brings foggy conditions to San Francisco; or the cool Canary current of North Africa.
|
|
Kangaroo licking its arms to cool down In cold environments, birds and mammals employ the following adaptations and strategies to minimize heat loss: # Using small smooth muscles (arrector pili in mammals), which are attached to feather or hair shafts; this distorts the surface of the skin making feather/hair shaft stand erect (called goose bumps or pimples) which slows the movement of air across the skin and minimizes heat loss. # Increasing body size to more easily maintain core body temperature (warm- blooded animals in cold climates tend to be larger than similar species in warmer climates (see Bergmann's Rule)) # Having the ability to store energy as fat for metabolism # Have shortened extremities # Have countercurrent blood flow in extremities – this is where the warm arterial blood travelling to the limb passes the cooler venous blood from the limb and heat is exchanged warming the venous blood and cooling the arterial (e.g., Arctic wolf or penguinsAdaptations for an Aquatic Environment. SeaWorld/Busch Gardens Animal Information Database, 2002.
|
|
Knight has been widely exhibited, including at institutions such as Marfa Contemporary (2018), DiverseWorks Artspace (2018), Contemporary Arts Museum Houston (2018), University of Illinois - Krannert Art Museum (2017), Art League Houston (2016), She Works Flexible (2016), The New Museum (2015), Blaffer Art Museum (2014), Skowhegan Space (2014), CounterCutrent (2014) with Lisa E. Harris and M'Kina Tapscott, Project Row Houses (2013), and Crystal Bridges Museum. In 2019, Knight performed at Human Resources in Los Angeles, and was selected to be included in the 2019 Whitney Biennial, curated by Rujeko Hockley and Jane Panetta. As MF Problem with artist Robert Pruitt she is a performer in the 2019 CounterCurrent Festival. In January 2020, Knight was part of Artpace’s exhibit titled Visibilities: Intrepid Women of Artpace. Curated by Erin K. Murphy, Visibilities not only kicks off Artpace’s 25th anniversary celebration, but also highlights past artists from their International Artist-in-Residency program, such as Knight who was a resident there in Spring of 2015.
|
|
This Page Intentionally Left Blank made its world premiere at the University of Houston Cynthia Woods Mitchell Center for the Arts’ CounterCurrent Festival 2016. This performance-based docent tour deconstructed “the role of the docent and museum audio tour via an encounter with theater and dance, subverting and reconsidering how the docent typically leads viewers to observe art in the museum context.” Big Dance sought to democratize the museum space, to “disrupt, awaken, dismantle, confuse and thus revivify the viewer’s perception of art.” The audience wore headphones and toured the space in groups in groups of twenty, as the docent (Tymberly Canale) spoke about the art with a (“don’t look at that,” she says at one point, “that’s not part of the tour.”) The audience traveled from the Menil Collection's main building to Flavin's Untitled, 1996, described by Arts And Culture as “a kind of journey deeper into Tymberly’s psyche as she worms her way into our own.” Movement and theater gradually begin to take over the piece, and ultimately, the audience became part of the performance.
|
|
" Two years later, the Lebanese artist collective Dictaphone Group created the project Camp Pause, commissioned by the Beirut-based Dar El-Nimer foundation of Lebanese-Palestinian art collector Rami el-Nimer. It was exhibited at the Qalandia International Festival 2016 and at the 2017 CounterCurrent Festival in Houston, Texas. A video installation, which was contextualised by multidisciplinary research, centered on portraits of four Rashidieh residents around their everyday routes: > "Along the way, they weave narratives about the history of the land, their > arrival, the struggle to build, and everyday life in a camp situated away > from the city, bordered by agricultural fields and the sea. [..] We are > reminded through this project that the disregard of people’s pain and > personal choices, the casual racism and vilification of refugees in Lebanese > villages and towns, and the calls for grouping refugees in camps that are > easily controlled and ultimately attacked is nothing new. While the whole > world is busy discussing what they call the “refugee crisis,” we hope to > remember the importance of listening to those who are really in that crisis.
|
|