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Topic: Countercurrent exchange

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	Countercurrent exchange - Wikipedia, the free encyclopedia
		Countercurrent exchange is used extensively in biological systems for a wide variety of purposes.
		Countercurrent exchange is also a key concept in chemical engineering thermodynamics and manufacturing processes for example in extracting sucrose from sugar beet roots.
		The diagram presents a generic representation of a countercurrent exchange system, with two parallel tubes containing fluid separated by a permeable barrier.
	en.wikipedia.org /wiki/Countercurrent_exchange (669 words)

	Method and system for ion-exchanging particles - Patent 4048284
		In an embodiment of the invention, exchangeable sodium cations in fluidizable zeolitic cracking catalyst precursor microspheres are exchanged with ammonium ions on a single sectionalized vacuum belt filter with a subdivided vacuum box underneath the upper surface of the belt.
		The system also includes means for countercurrently contacting the microspheres during their serial travel with an incoming ion-exchange liquid charged to the second filter and means for washing the microspheres before they are discharged from the second filter.
		The partially exchanged cake discharged from Zone 3 of the No. 1 filter is charged by gravity from the end of the belt of the filter as the belt passes over a pulley system indicated schematically.
	www.freepatentsonline.com /4048284.html (4295 words)

	lc18thrm
		Endotherms that are routinely exposed to cold environments often rely on countercurrent exchange to minimize heat loss from the blood in their extremities.
		Countercurrent exchange permits the animal to recapture a significant fraction of this 'lost' heat.
		The anatomical basis for countercurrent exchange is that arteries lie at the center of the limb, and are surrounded by a weblike arrangement of veins.
	www.sbs.utexas.edu /shankland/lc18thrm.htm (1282 words)

	C:\COOPER\Anat118\urinary98.htm
		Renal countercurrent exchange depends on the close antiparallel association of the ascending and descending portions of the loop of Henle and vasa recta and the collecting ducts, which promotes rapid molecular transport from one to the other.
		In the kidney, countercurrent exchange of NaCl and urea allows a high concentration gradient to be maintained between the outer and inner medulla.
		Renal countercurrent exchange can be considered as operating in three different loops: the loop of Henle passes through a steep concentration gradient of NaCl and urea.
	www.sacs.ucsf.edu /home/cooper/Anat118/urinary/urinary98.htm (5030 words)

	Means and method for the recovery of expansion work in a vapor compression cycle device - Patent 4304099
		A means for the recovery of expansion work as in claim 5 wherein substantially all of said heat transfer passage is in countercurrent heat exchange relationship with a segment of said vapor compression cycle device comprising substantially all of said evaporator assembly flow path and at least a portion of said compressor suction line.
		In a preferred embodiment of the invention, the countercurrent heat exchange relationship of the heat transfer passage 8 with fluid flowing through the evaporator assembly 1 extends along substantially all of the flow path in the evaporator assembly from the coldest portion 2 to the warmest portion 3.
		2, the countercurrent exchange of heat from the fluid flowing through the heat transfer passage 8 is extended to the fluid flowing through the compressor suction line 5.
	www.freepatentsonline.com /4304099.html (3320 words)

	[No title]
		Renal mechanisms for concentrating/diluting urine: countercurrent multiplication, countercurrent exchange, and altering permeability of the collecting duct to water 2.
		Countercurrent exchange: process whereby NaCl is exchanged from blood to interstitium at a rate equal to its concentration in the interstitium 5.
		Vasa recta as countercurrent exchangers for medullary gradient: because solutes leave/enter the bloodstream via concentration gradients, countercurrent exchange occurs due to entry of solute to vasa recta down the ascending limb and subsequent exit as blood rises up the descending limb.
	www.u.arizona.edu /~ajgulbis/MedLinks/Physiology/PhysiologyType/28.doc (398 words)

	Envision It!--Concurrent and Countercurrent Exchange
		These models involve the exchange of a dissolved material from a high concentration solution to a low concentration solution where the solutions are separated by a permeable membrane.
		In both concurrent and countercurrent exchange, the experimental (or industrial) apparatus can be thought of as two parallel pipes separated by a permeable membrane.
		Since the rate of solute exchange depends on the relative concentrations of solute in the fluids at adjacent points along the permeable membrane, we must explicitly keep track of the position of each flowing fluid, bookkeeping we did not need to undertake in the simpler model.
	www.stolaf.edu /people/mckelvey/envision.dir/exchange.dir/exchange.html (2113 words)

	Comparative Anatomy Topic 4 - Form and Function (Site not responding. Last check: 2007-10-13)
		When you begin lifting weights, part of your lack of strength is due to weak muscles, but part is due to the fact that your bones can't handle the stress, they have to remodel themselves in order to accommodate the new stress.
		Countercurrent exchange is where blood in the two vessels move in opposite directions.
		Therefore, oxygen is always entering the blood, but instead of a steady change as in countercurrent exchange, the change is stepwise because the air is flowing over a latterlike structure (below, bottom).
	www.auburn.edu /academic/classes/zy/0301/Topic4/Topic4.html (3073 words)

	Excretion Notes for Biochemistry @ La Canad High School (Site not responding. Last check: 2007-10-13)
		Excessive loss of body heat is prevented by countercurrent exchange, more specifically, countercurrent heat exchangers in the circulatory system, whereby warmed blood from deep in the body passes through vessels closely paralleling those carrying cooler blood from the extremities.
		Countercurrent exchanges abound in the major blood vessels of the bluefin tuna and the in the rete mirable, a dense region of countercurrent vessels that keeps the muscles warm and active on spite of the cold surrounding water.
		The countercurrent exchange internalizes much of the heat but decreases activity in the extremities.
	www.lcusd.net /lchs/mewoldsen/Excretion.htm (1525 words)

	lc15rsp1
		The rate of gas exchange is proportional to the surface area of the respiratory surface.
		To minimize the distance between respiratory medium and the blood, the respiratory surface is typically composed of extremely thin (squamous) epithelial cells underlaid by a dense network of capillaries.
		Countercurrent exchange requires that two fluids (in this case, the external water and the blood in the gills) flow past each other in opposite directions.
	www.sbs.utexas.edu /shankland/lc15rsp1.htm (1216 words)

	Countercurrent Heat Exchange
		Countercurrent heat exchange works by way of warm blood in the arteries moving parallel and very close to the cooler venous return.
		Countercurrent heat-exchangers acting to conserve core heat are commonly found in the extremities of animals living in cold habitats, particularly in the legs or flippers of polar and cool temperate birds and mammals, the horns of some ungulates, the tails of beavers and other rodents, and the ears of Arctic hares.
		A marine mammal that employs a countercurrent heat exchange mechanism for thermoregulatory purposes.
	database.biomimicry.org /item.php?table=strategy&id=1038 (820 words)

	IONEX-Liquid Adsorption Separation Technology IDS-Water Europe (Site not responding. Last check: 2007-10-13)
		Adsorptive and ion exchange separation generally comprises a two- phase mass-transfer - an adsorption cycle and desorption cycle - separated by washing or rinsing of the solid phase between these mass transfer steps.
		The mass-transfer zone in a standard ion exchange plant is typically a small section of the actual operating bed length.
		Countercurrent contacting on a continuous basis does not suffer these limitations, because it is not a batch process.
	www.idswater.com /water/europe/puritech/ion_exchange_technologies/289_0/s_supplier_2.html (737 words)

	Adrenoceptor and Local Modulator Control of Cutaneous Blood Flow in
		Countercurrent flow was described nearly 50 years ago (e.g.
		Countercurrent exchange is useful for preserving heat so the core is not cooled by cold peripheral blood during whole-body cold exposure (Scholander and Schevill, 1955; Schmidt-Nielsen, 1983).
		Heat conservation by countercurrent exchange and blood flow distribution in rat tails and human limbs.
	calvin.linfield.edu /~mrobert/liegetext417.html (4203 words)

	Countercurrent exchange in the renal medulla -- Pallone et al. 284 (5): 1153 -- AJP - Regulatory, Integrative and ...
		Countercurrent exchange in the renal medulla -- Pallone et al.
		There is an enormous surface area for countercurrent exchange that completely prevents loss of oxygen from venous blood by enabling diffusion into blood entering from arterioles.
		The foregoing models neglect the exchange of water in the medulla.
	ajpregu.physiology.org /cgi/content/full/284/5/R1153 (6796 words)

	General Biology 2, lecture on Gas Exchange
		In these organisms, gas exchange is by diffusion between the individual cells and the external medium.
		The countercurrent exchange mechanism has evolved to improve the efficiency of oxygen transfer from the water to the blood.
		In the countercurrent exchange system in the lamellae of the fish gill, water and blood flow in opposite directions (figs.
	www.usd.edu /biol/genbio/153/ken/kr5.html (1013 words)

	Countercurrent System and the Loop of Henle (Site not responding. Last check: 2007-10-13)
		Countercurrent exchange of solutes between ascending and descending vasa recta (the renal medullary capillaries) minimizes solute washout from the medullary interstitium.
		The relatively small amount of isoosmotic fluid that flows into the medullary collecting ducts losses progressively more and more water to the hyperosmotic medullary and papillary interstitia and is finally excreted as hyperosmotic, highly concentrated urine.
		In the absence of ADH, the hyposmotic fluid that enters the DT from the loop of Henle, continues to be diluted by transport of NaCl via NaCl (thiazide sensitive) cotransporters into DT cells and via Na channels (amiloride sensitive) along the CD.
	www.acbrown.com /renal/OutLoop.htm (578 words)

	physheat
		With the arterial and venous blood flows positioned within a few cells layers of each other in the narrow petiole, the opportunity for heat exchange is great.
		The arterial blood from the abdomen is cooler because the abdomen does not require such a warm temperature as the thorax.
		The countercurrent heat exchange aids the process of warming up before flight and the muscles do not have to work as hard to reach 30 degrees C if the heat is recycled through the countercurrent heat exchange (Roberts and Harrison, 1998).
	www.bio.davidson.edu /Courses/anphys/2000/Chemotti/physheat.htm (223 words)

	Articles / Origins Issues / Running Counter to Evolution - Institute for Creation Research
		There are numerous examples of countercurrent exchange in aquatic creatures.
		Since its mouth is constantly awash with frigid water as the whale feeds, the Creator placed countercurrent exchangers in the massive tongue of some baleen whales such as the grey whale.
		As a result of this exchange, only a small amount of the animal's heat is lost to the cold waters (see Science 278:1138-1139).
	www.icr.org /article/125 (549 words)

	Modeling exchange of plasma proteins between microcirculation and interstitium of the renal medulla -- Wang and Michel ...
		Modeling exchange of plasma proteins between microcirculation and interstitium of the renal medulla -- Wang and Michel 279 (2): 334 -- AJP - Renal Physiology
		Modeling exchange of plasma proteins between microcirculation and interstitium of the renal medulla
		exchange of fluid and solute are considered by using conservation
	ajprenal.physiology.org /cgi/content/abstract/279/2/F334 (336 words)

	Continuous Ion Exchange (Site not responding. Last check: 2007-10-13)
		Countercurrent ion exchange in a column or series of columns performs very well in comparison to batch contacting, but truly countercurrent operation with both the resin and the fluid moving would be even more efficient.
		At frequent intervals, a sudden brief shock is applied to the fluid in the reverse direction.
		This is akin to having tea bags of resin and dragging them countercurrent to the flow of solution.
	www.rpi.edu /dept/chem-eng/Biotech-Environ/IONEX/continuo.htm (303 words)

	HMS Student Papers 1998 - Morphological and biochemical evidence for countercurrent heat exchange in the tuna caecum (Site not responding. Last check: 2007-10-13)
		Abstract: The viscera of bluefin tuna, Thunnus thynnus, are warm, and internal temperatures as high as 25 degrees C have been recorded in 5 degrees C water (Block, pers.
		The high heat contribution from aerobic activity, along with that contributed by digestive processes within the caecum and stomach, may be able to account for much of the heat production within the viscera.
		The endothermic nature of the organ and the parallel architecture of the vasculature suggest that countercurrent heat exchange can occur.
	www-sul.stanford.edu /depts/miller/student_papers/1998_3.html (295 words)

	Urine specific gravity (Site not responding. Last check: 2007-10-13)
		Note that neonates or very young animals may not be able to concentrate their urine as efficiently as their adult counterparts, therefore lower USGs are expected in health or as a response to azotemia in young animals.
		This is established primarily by countercurrent exchange in the loop of Henle as illustrated below.
		Medullary blood flow through the vasa recta: This is essential for operation of the countercurrent exchange mechanism.
	www.diaglab.vet.cornell.edu /clinpath/modules/ua-rout/usg.htm (486 words)

	Countercurrent Heat Exchange - Wikipedia, the free encyclopedia
		Counter-current heat exchange refers to transferring heat between 2 fluids going in opposite direction via a heat exchanger.
		The advantage this has over co-current heat exchange is because it obtains a greater log mean temperature difference along the heat exchanger surface.
		Greater the temperature difference means more heat will be exchanged.
	en.wikipedia.org /wiki/Countercurrent_Heat_Exchange (125 words)

	animal phys lecture 2 - aerial respiration
		exchange can occur between the blood and the skin, but generally only in organisms that can afford to keep the skin moist - amphibians, mostly, but a few marine snakes.
		They are holding tanks for air, not exchange organs or part of the lung proper.
		This means that the wall surface area increases (this is the area of exchange)
	nas.cl.uh.edu /novotny/aph2.htm (1303 words)

	BIOL 238 Class Notes - The Urinary System
		The term countercurrent comes from the fact that fluid is moving in opposite directions in the two limbs of the loop.
		The bicarbonate produced is retained for the buffer (as mentioned above) and exchanged for chloride, called the chloride shift.
		Hydrogen ions can be secreted during moderately acidic conditions, but when you have more severed acidity they reach their limit, called the tubular maximum.
	www.unm.edu /~jimmy/urinary_notes.htm (2282 words)

	Modeling exchange of plasma proteins between microcirculation and interstitium of the renal medulla -- Wang and Michel ...
		Schematic geometry of the countercurrent exchange system of the descending vasa recta (DVR), ascending vasa recta (AVR), and interstitial fluid (ISF).
		Marsh, DJ, and Segel LA. Analysis of countercurrent diffusion exchange in blood vessels of the renal medulla.
		Theoretical studies of steady state transcapillary exchange in countercurrent systems.
	ajprenal.physiology.org /cgi/content/full/279/2/F334 (5443 words)

	BIOL 221 Practice and Thought Questions (Site not responding. Last check: 2007-10-13)
		Contrast the operation of the positively ventilated lungs of birds to the negatively ventilated lungs of mammals.
		Describe the process of cation exchange and explain how the respiratory activities of plants help them to acquire nutrients from soils.
		Describe the countercurrent exchange systems found in the nephron.
	employees.csbsju.edu /dgbrown/BIOL221/BIOL221PAT.htm (3371 words)

	[No title]
		A prerequisite for the production of hypertonic urine, the loop acts as a countercurrent multiplier to establish an osmotic gradient in the interstitial fluid of the medulla.
		The passive exchange of salt and water between the vasa recta and the interstitium is known as the countercurrent exchange mechanism.
		It is important in carrying away water lost to the filtrate during its descent into the medulla and thus in maintaining the osmotic gradient set up by the countercurrent multiplier system of Henle's loop.
	www.loyno.edu /~chood/histnoteuro.html (3463 words)

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