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Topic: Semipermeable membrane


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In the News (Mon 24 Jun 19)

  
  Reference.com/Encyclopedia/Semipermeable membrane
A semipermeable membrane, also termed a selectively permeable membrane, a partially permeable membrane or a differentially permeable membrane, is a membrane which will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion".
An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells.
One example of a semipermeable membrane is a phospholipid bilayer, a group of phospholipids (consisting of a phosphate head and 2 fatty-acid tails) arranged into a double-layer, with the hydrophilic phosphate heads exposed to the water content outside and within the cell and the hydrophobic fatty-acid tails hidden in the inside.
www.reference.com /browse/wiki/Semipermeable_membrane   (376 words)

  
 Method for preparing semipermeable membrane compositions - Patent 4764320
The relative permeability of the membrane is the ratio of the permeation fluxes of the components to be separated, often referred to as the separation factor or selectivity of the membrane.
A hollow fiber membrane or tubular membrane device is similar in configuration to a shell-and-tube heat exchanger and comprises a plurality of parallel membrane compositions in hollow fiber or tubular form embedded in at least one tube sheet.
The semipermeable membranes prepared from the process of this invention can be used in preferred embodiments to markedly increase the concentration of hydrogen and mixtures of hydrogen, nitrogen, methane, argon and ammonia typically resulting from the synthesis or ammonia.
www.freepatentsonline.com /4764320.html   (3422 words)

  
  United States Patent Application: 0030021826
Membrane according to claim 1, characterized in that the anionic or anionizable groups of the polyacrylonitrile are selected from sulphonic, phosphonic, carboxylic, sulphuric, phosphoric groups and from salts of the aforementioned groups.
Membrane according to one of claims 1 to 4, characterized in that the cationic polymer is a polyamine.
Membrane according to one of claims 1 to 8, characterized in that the anticoagulant agent carrying anionic groups belongs to the family of glycoaminoglycans having an anticoagulant activity.
appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1='20030021826'.PGNR.&OS=DN/20030021826&RS=   (4647 words)

  
 Semipermeable membrane - Wikipedia, the free encyclopedia
A semipermeable membrane (or more accurately a selectively permeable membrane, or differentially permeable membrane) is a membrane which will allow certain molecules or ions to pass through it by diffusion (sometimes "facilitated diffusion").
Depending on the membrane and the solute, permeability may depend on solute size, solubility properties, or chemistry.
An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells.
en.wikipedia.org /wiki/Semi_permeable_membrane   (150 words)

  
 Semipermeable membrane - Patent 4272378
The present invention relates to a method for the preparation of a semipermeable membrane for reverse osmosis or ultrafiltration by exposing a porous membrane of polyacrylonitrile type polymers to a plasma thereby crosslinking the surface thereof.
According to the present invention, it is possible to prepare a polyacrylonitrile type semipermeable membrane which is free from the defects of the conventional cellulose acetate membrane, namely susceptibility to hydrolysis and deterioration by the action of bacteria, and is utilizable in the separation and concentration of substances.
An object of the present invention is to provide a method for the preparation of a semipermeable membrane for reverse osmosis and ultrafiltration which comprises exposing a porous membrane of polyacrylonitrile type polymers to a plasma thereby forming a dense crosslinked layer having a selective permeability to substances at the surface of the membrane.
www.freepatentsonline.com /4272378.html   (2985 words)

  
 NDI Terminology - membrane   (Site not responding. Last check: 2007-10-19)
plasma membrane - The structure enveloping a cell, enclosing the cytoplasm, and forming a selective permeability barrier; it consists of lipids, proteins, and some carbohydrates, the lipids thought to form a bilayer in which integral proteins are embedded to varying degrees.
postsynaptic membrane - The area of plasma membrane of a postsynaptic cell, either a muscle fiber or a neuron, that is within the synapse and has areas especially adapted for receiving neurotransmitters.
semipermeable membrane - A membrane that permits the passage of a solvent, such as water, but prevents the passage of the dissolved substance, or solute.
www.ndif.org /Terms/membrane.html   (165 words)

  
 Dried semipermeable membrane and manufacture thereof - United States Patent 4,025,439
C; and drying the membrane at a temperature less than the temperature of the heat treatment under conditions such that the coefficient of contraction is less than 1%, whereby a dried semi-permeable membrane having an open-celled structure with a pore size of a diameter less than 0.5.mu.
The use of semipermeable membranes for the desalination of sea water, the desalination of brackish water, the treatment of industrial food industry wastes and the like by reverse osmosis or ultrafiltration is well documented.
The membrane which is dried at a temperature less than the temperature of the heat treatment shows no substantial change in porosity and exhibits the original degree of semi-permeablility when the dried membrane is immersed in water.
xrint.com /patents/us/4025439   (4131 words)

  
 DC Waterworld Supermart Pvt. Ltd.
A plant cell is a semipermeable (water flows through the membrane but salts don't) membrane with the living stuff on the inside in a salt solution.
The membrane stack is two, very long semipermeable membranes with a spacer mesh between them that is sealed along the two long sides.
After the carbon filter, the water is passed through the membranes where the concentrate is recycled back to the front of the system for another pass and a bleed is taken off this line to drain.
www.watersupermart.com /faq.html   (2644 words)

  
 dialysis. The Columbia Encyclopedia, Sixth Edition. 2001-05
By the use of graded semipermeable membranes chosen to allow successively smaller molecules to pass, mixtures can be separated into components of graded ranges of molecular weight.
In such machines, blood is circulated on one side of a semipermeable membrane (often cellophane) while a special dialysis fluid is circulated on the other side.
Metabolic waste products such as urea and creatinine diffuse through the membrane into the dialysis fluid and are discarded, while loss by diffusion of substances necessary to the body (such as sodium chloride) is prevented by their presence in the dialysis fluid.
www.bartleby.com /65/di/dialysis.html   (472 words)

  
 Membranes   (Site not responding. Last check: 2007-10-19)
A cell, plasma, or cytoplasmic membrane is the semipermeable unit membrane surrounding, and defining the physical limits of a cell.
It is important when thinking about membranes to keep in mind that a typical cell membrane tends to have a different composition on one side (a.k.a., leaflet; say, the inside, or inner leaflet) than on the other (the outside, or outer leaflet).
Membrane asymmetries (which are defined to a significant extent by fixed membrane protein orientations) coupled with appropriate energy expenditure automatically maintains the internal cell environment at different solute concentrations relative to those found in the extracellular environment.
www.mansfield.ohio-state.edu /~sabedon/biol1050.htm   (1908 words)

  
 Osmosis   (Site not responding. Last check: 2007-10-19)
Osmosis is the diffusion of a solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration.
The semipermeable membrane is permeable to the solvent, but not to the solute, resulting in a chemical potential difference across the membrane which drives the diffusion.
That is, the solvent flows from the side of the membrane where the solution is weakest to the side where it is strongest, until the solution on both sides of the membrane is the same strength (that is, until the chemical potential is equal on both sides).
www.worldhistory.com /wiki/O/Osmosis.htm   (867 words)

  
 About us
According to Merriam-Webster's Collegiate Dictionary, osmosis is the "movement of a solvent through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane." That's a mouthful.
The best common example of a semipermeable membrane would be the lining of your intestines, or a cell wall.
The water pressure rises as the height of the column of salty water rises, until it is equal to the osmotic pressure.
www.eastindiaequipments.com /literature.html   (2750 words)

  
 Membrane reactors   (Site not responding. Last check: 2007-10-19)
Membrane reactors may be used in either batch or continuous mode and allow the easy separation of the enzyme from the product.
If the substrate is able to diffuse through the membrane, it may be introduced to either side of the membrane with respect to the enzyme, otherwise it must be within the same compartment as the enzyme, a configuration that imposes a severe restriction on the flow rate through the reactor, if used in continuous mode.
The kinetics of membrane reactors are similar to those of the batch STR, in batch mode, or the CSTR, in continuous mode (see later).
www.lsbu.ac.uk /biology/enztech/membrane.html   (369 words)

  
 Water.com - Water Filtration & Reverse Osmosis Systems   (Site not responding. Last check: 2007-10-19)
According to Merriam-Webster's Collegiate Dictionary, osmosis is the "movement of a solvent through a semipermeable membrane (as of a living cell) into a solution of higher solute concentration that tends to equalize the concentrations of solute on the two sides of the membrane." That's a mouthful.
A semipermeable membrane is a membrane that will pass some atoms or molecules but not others.
The best common example of a semipermeable membrane would be the lining of your intestines, or a cell wall.
www.water.com /filtration/revosm.asp   (635 words)

  
 ro
Osmosis is a special case of diffusion in which all the molecules are in water, and the water crosses a barrier called a semipermeable membrane.
Semipermeable membranes can be made of many types of materials, but typically are made of cellulose acetate or polyamide resins.
Notice that the semipermeable membrane essentially acts as a filter for the water to pass through, and in fact reverse osmosis is sometimes called "ultrafiltration."
www.csun.edu /~vchsc006/356b/ro.html   (549 words)

  
 [No title]
It is important in establishing a resting membrane poten tial for the normal nerve cell, but many other criteria have to be satisfied too for the nerve cell to function with an electrically charged membrane.
A basic condition is that the nerve cell have an intact membrane, one which is able to retain anions in the cell and not allow them to diffuse along either concentration or electrical gradients into the interstitial fluid.
There are the large impermeable anions to which the nerve cell membrane is impermeable, and of course, sodium ions for which the permeability of the membrane at rest is low, not equal to zero, but low all the same.
www.msu.edu /course/psl/431/snapshot.afs/neurophy/NEURO.01   (2830 words)

  
 Semipermeable Membrane   (Site not responding. Last check: 2007-10-19)
A membrane (as a cell membrane) that allows some molecule to pass through but not others.
This image represents the equilibration of osmotic stress among the phase under study and the external stressing solution in vast excess across a semipermeable membrane.
The membrane is impermeable to PEG and DNA.
www.websters-online-dictionary.org /definition/Semipermeable+Membrane   (316 words)

  
 Chemical osmosis: more theory
Movement of water across a semipermeable membrane, in the absence of a hydraulic pressure difference e.g.
This situation is reached if the concentration on both sides of the membrane are identical, or when a hydraulic pressure (water height difference, or hydraulic head) across the membrane is established that equals the osmotic pressure difference between the two solutions.
In Figure 5 the ideality of three clays are given according to the Fritz-Marine Membrane Model (Fritz, 1986) as a function of the porosity.
www.xs4all.nl /~keizee/research/theory.html   (1613 words)

  
 Encyclopedia: Semipermeable membrane   (Site not responding. Last check: 2007-10-19)
Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell.
Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life.
Chemistry Osmosis is the diffusion of a solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration.
www.nationmaster.com /encyclopedia/Semipermeable-membrane   (559 words)

  
 membrane
In cell, it's the diffusion of water across a semipermeable membrane.
If two solutions are connected by a hose having a semipermeable membrane, osmosis of water and diffusion of the diffusible solutes will occur in opposite directions.
Coated-pit: region of the cell membrane that is coated with clathrin on the cytosolic side.
www.bsu.edu /classes/ruch/Bio111/membrane.html   (1602 words)

  
 QUESTIONS AND ANSWERS ABOUT REVERSE OSMOSIS, WATER PURIFICATION AND FILTRATION
A plant cell is a semipermeable (water flows through the membrane but salts don't) membrane with the living stuff on the inside in a salt solution.
The membrane stack is two, very long semipermeable membranes with a spacer mesh between them that is sealed along the two long sides.
After the carbon filter, the water is passed through the membranes where the concentrate is recycled back to the front of the system for another pass and a bleed is taken off this line to drain.
www.remco.com /ro_quest.htm   (2604 words)

  
 Use of Mussels and Semipermeable Membrane Devices to Assess Bioavailability of Residual Polynuclear Aromatic ...
A new monitoring and assessment tool, the semipermeable membrane device, was also deployed to compare hydrocarbon uptake with mussels and to evaluate the route of exposure to mussels.
Accumulation levels were similar between mussels and the semipermeable membrane devices, but the distribution of individual hydrocarbons differed.
Semipermeable membrane devices show promise as monitoring tools and to provide insights into exposure pathways for biota.
www.astm.org /DIGITAL_LIBRARY/STP/PAGES/STP19866S.htm   (244 words)

  
 Watermakers, Inc.
For example, the membrane may be permeable to water molecules of dissolved salt.
If this membrane is placed between two compartments in a container, and a salt solution is placed in one half of the container and pure water in the other, water passes through the membrane while the salt cannot.
To significantly reduce the rate of membrane fouling, RO systems employ cross-flow filtration, which allows water to pass through the membrane while the separate flow of concentrate sweeps rejected salts away from the membrane surface.
www.watermakers.com /howto.htm   (337 words)

  
 Aquamarine, Inc - Theory   (Site not responding. Last check: 2007-10-19)
For example, a semipermeable membrane may be permeable to water molecules of a dissolved salt solution, but not the molecules of the dissolved salt.
If this membrane is placed between two compartments in a container, as shown in the first figure, then a salt solution is placed in one half of the container and pure water in the other, the water molecules will pass through the membrane while the salt molecules will not.
Since the membrane is not permeable to the salt molecules, the only way for this to happen in our example is for pure water to pass through the membrane to the salt water side in an attempt to dilute the salt solution.
aquamarineinc.net /ROtheory.html   (433 words)

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