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Topic: Permeability


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In the News (Fri 27 Nov 09)

  
  Permeability - Wikipedia, the free encyclopedia
Permeability (electromagnetism), in electromagnetism, is the degree of magnetisation of a material in response to a magnetic field.
Permeability (fluid), in earth sciences, is a measure of the ability of a material to transmit fluids.
Vascular permeability, the movement of fluids and molecules between the vascular and extravascular compartments.
en.wikipedia.org /wiki/Permeability   (135 words)

  
 Permeability
In SI units, magnetic flux density is measured in tesla, magnetic field strength in ampere per metre and permeability in henrys per metre.
In geology, permeability is a measure of the ability of a material (typically, a rock) to transmit fluids.
For a rock to be considered as an exploitable hydrocarbon reservoir, its permeability must be greater than approximately 100 md (depending on the nature of the hydrocarbon - gas reservoirs with lower permeabilities are still exploitable because of the lower viscosity of gas with respect to oil).
www.ebroadcast.com.au /lookup/encyclopedia/pe/Permeability.html   (240 words)

  
 Permeability - Microwave Encyclopedia - Microwaves101.com
Permeability is the unit of measure for ferromagnetism.
Permeability along with the speed of light and a property called permittivity are the three measurable constants of Maxwell's equations.
Permeability is a property which is associated with how much a material responds to a magnetic field.
www.microwaves101.com /encyclopedia/permeability.cfm   (542 words)

  
 Magnetic Permeability - LoveToKnow 1911   (Site not responding. Last check: 2007-10-20)
The permeability of a metal belonging to the ferromagnetic class - iron, nickel, cobalt and some of their alloys - is a function of the magnetic force, and also depends upon the previous magnetic history of the specimen.
As the force increases from zero the permeability of a given specimen rises to a maximum, which may amount to several thousands, and then gradually falls off, tending to become unitywhen the force is increased without limit.
It is generally of importance that the iron employed in the construction of electrical machinery should possess high permeability under the magnetic force to which it is to be subjected.
www.1911encyclopedia.org /Magnetic_Permeability   (245 words)

  
 Permeability (electromagnetism) - Wikipedia, the free encyclopedia
In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field.
Magnetic permeability is represented by the Greek letter μ.
In SI units, permeability is measured in henries per metre, or newtons per ampere squared.
en.wikipedia.org /wiki/Permeability_(electromagnetism)   (399 words)

  
 High Permeability Materials - Microwave Encyclopedia - Microwaves101.com
Permeability is a magnetic property of a material, and is often expressed as
It depends on many many factors like annealing and crystalline structure, but typically, for all ferromagnetic materials we measure permeabilities between 1 and 10000 or more, depending on their magnetic state (which is a function of its history and applied field).
Permeability is as much a property of the material's grain structure as it is a bulk property.
www.microwaves101.com /encyclopedia/highpermeability.cfm   (754 words)

  
 Current Industrial Practices of Assessing Permeability and P-Glycoprotein Interaction
The permeability studies were initiated by adding an appropriate volume of buffer containing test compound to either the apical (for apical to basolateral transport; A to B) or basolateral (for basolateral to apical transport; B to A) side of the monolayer.
Permeability is calculated based on several factors: the amount of drugs that appeared in the receiver compartment, the initial concentration in the donor compartment, and the surface area of the physical barrier (eg, lipid bilayers and cell monolayer).
The bidirectional permeability assay, where the basolateral to apical (secretory direction, B to A) permeability is compared with the apical to basolateral (absorptive direction, A to B) permeability, is regarded as the gold standard in identifying P-gp substrates because it is functionally the most direct method of measuring efflux characteristics of drug candidates.
www.aapsj.org /view.asp?art=aapsj080101   (8084 words)

  
 Intestinal Permeability, MMR, Interferon Gamma, Autism
Several quotes from their article: "...increased sucrose excretion is not a marker of H. pylori colonization but rather of the presence of [intestinal] mucosal lesions." "The results of this study emphasize that the gastric mucosa may be a portal of entry for macromolecules from the diet or from microorganisms, as shown in experimental models...
The effect of interferon-gamma on permeability was dependent on both the concentration of the cytokine and the duration of exposure to it...
A primary permeability defect was postulated in the pathogenesis of the disease.
members.jorsm.com /~binstock/perm-msc.htm   (4247 words)

  
 Soil - Permeability
Permeability is the property of soil which permits flow of water through its inter connecting voids.
Permeability is an important engineering property which governs the rate of settlement of saturated compressible soil layers and the rate of flow of Aquifer.
Permeability is taken into account for pump-ing ground water, spacing well points for de-watering foundation sites for excavation, retention of water in reservoirs, design of dams and classifica-tion of soils to be used for various zones of embankments of dams and reser-voirs.
www.sytexinstruments.com /permeability(soil).asp   (568 words)

  
 Permeability (geology) Summary
Porosity and permeability are two of the primary factors that control the movement and storage of fluids in rocks and sediments.
In geology, permeability is a measure of the ability of a material (typically, a rock or unconsolidated alluvial material) to transmit fluids through it.
Permeability is part of the proportionality constant in Darcy's law which relates discharge (flow rate) and fluid physical properties (e.g.
www.bookrags.com /Permeability_(geology)   (859 words)

  
 Permeability
Permeability is a complex function of the applied magnetic field.
A reduction in wall thickness coupled with a reduction of permeability causes the flux to flow in alternate paths.
A third, classical definition of saturation is that total magnetic saturation occurs when all of the magnetic domains are aligned and the permeability relative to that of air becomes one.
www.battelle.org /pipetechnology/MFL/Links/Permeability.html   (297 words)

  
 permeability
This assembly will be permeable to fluid flow because of the existence of spaces or pores between the yarns (inter-yarn pores).
The yarns themselves will also be permeable to fluid flow because of the spaces or pores that separate the individual filaments in the yarn (intra-yarn pores).
Tightly woven grafts have permeability below 800, tight compacted knits are from 1200 to 2000, loose knits from 2000 to 5000, and braids from 350 to 2500.
www.p2pays.org /ref/04/03837/perm/index1.html   (694 words)

  
 Relative Permeability
The concept of Relative Permeability is very simple, the measurement and interpretation of Relative Permeability versus saturation curves is not.
For the steady state method and a two fluid system, the two phases are injected at a certain volumetric ratio until both the pressure drop across the core, and the composition of the effluent, stabilize.
The Relative Permeability is calculated from the flow equations.
www.agatlabs.com /content/relativepermeability.htm   (254 words)

  
 MS 5199C: Permeability in RTM Lab
The permeability values of fiber preforms (such as the mat) are needed in RTM simulations where the fill patterns of complex geometry parts are observed, and process and mold design decisions are made.
Permeability is a directional property and it is a measure of how permeable a porous medium is (in RTM, the fibrous preform) to an impregnating fluid.
The permeability of a porous medium depends on a number of factors, mostly related to the porous architecture of the preform (capillary/spherical pores, specific surface area, porosity, etc.).
www.me.umn.edu /education/courses/ms5199/Permeability.html   (1115 words)

  
 Relative Permeability
is estimated for all the 17 simulations and the corresponding relative permeabilities of the invading phase are calculated.
Because of these arguments, the relative permeability of the invading phase is expected to scale with the saturation width.
This is expected since the size of the trapped clusters increases with the front width causing the relative permeability of the invading phase to decrease.
www.fys.uio.no /~eaker/thesis/node63.html   (1000 words)

  
 SOFIA - OFR-03-68 - Permeability of Cores
Core samples from eight borings were selected and analyzed for whole-core permeability by Core Laboratories, Inc. The full-diameter (2-in) pieces were measured (using air flow) for permeability in two horizontal directions and one vertical direction while in a Hassler rubber sleeve.
The higher permeability values appear to be related to lithofacies that have a relatively low percentage of lime mud (for example, micrite), a relatively high percentage of carbonate grains, and have undergone pervasive diagenetic leaching of skeletal grains.
The permeability of these quartz sands and mixed carbonates is generally in the moderate (200-500 md) and high (>500 md) range, as shown in Figure 8.
sflwww.er.usgs.gov /publications/ofr/03-68/permcores.html   (642 words)

  
 Celiac Disease; Intestinal Permeability Measurements; References
Gastric permeability was elevated in 60% of the celiac patients and correlated with antral intraepithelial lymphocyte counts.
Intestinal permeability (measured by a lactulose/mannitol test) was also elevated in 69% of the celiac patients and correlated with duodenal intraepithelial counts.
We studied the permeability to human alpha-lactalbumin, beta-lactoglobulin, mannitol, and lactulose on 46 occasions in 33 celiac disease patients in various phases of the disease; in addition, mannitol and lactulose permeability was studied in 18 healthy controls.
www.nutramed.com /celiac/celiacpermref.htm   (1773 words)

  
 Oilfield Glossary: Term 'permeability'
Effective permeability is the ability to preferentially flow or transmit a particular fluid through a rock when other immiscible fluids are present in the reservoir (for example, effective permeability of gas in a gas-water reservoir).
Relative permeability is the ratio of effective permeability of a particular fluid at a particular saturation to absolute permeability of that fluid at total saturation.
In magnetics, the ratio of the density of the magnetic flux, B (in units of teslas), to the strength of the magnetic field, H (in units of amperes/meter), typically in units of H/m.
www.glossary.oilfield.slb.com /Display.cfm?Term=permeability   (323 words)

  
 Wallcovering Permeability
While offering increased permeability, perforated wallcovering is not a solution for and should not be used in buildings which have or may have wall cavity moisture accumulation or other moisture problems.
Permeability is a measure of the amount of water vapor (moisture) that can pass through a specified material in a certain amount of time.
The measure and degree of permeability is expressed in units referred to as Perms.
www.omnova.com /products/wallCovering/mold.aspx   (580 words)

  
 OFITE - Reservoir Permeability Tester
The permeability of a petroleum reservoir is one of the most influential parameters in determining the production capabilities of a producing formation.
Permeability is a measure of the ability of a fluid to flow through a porous media when subjected to a differential pressure and is mathematically equated by Darcy’s law.
A typical test sequence could involve: establishing effective permeability and 100 percent saturation with a brine, reversing flow direction with oil to establish an irreducible water saturation, contaminating the core in the forward direction with possibly a drilling filtrate, and finally reversing the flow direction with oil to examine the return permeability.
www.ofite.com /products/Core/reservoir-permeability-tester.htm   (564 words)

  
 Low Magnetic Permeability Reference Materials
The determination of the relative magnetic permeability of weakly magnetic materials is an important requirement in the manufacture of devices and components for space, particle physics and defence applications.
The relative magnetic permeability of a material can be measured by the solenoid method or by the comparator method in accordance with BS 5884:1999.
A very important aspect of this technique of producing permeability standards is that the value can be tailored which allows the test instrument to be calibrated at the value of interest.
www.npl.co.uk /electromagnetic/dclf/magnetics/lowpermeabilitylc.html   (570 words)

  
 What is permeability? - a definition from Whatis.com - see also: magnetic permeability
Permeability, also called magnetic permeability, is a constant of proportionality that exists between magnetic
The permeability factors of some substances change with rising or falling temperature, or with the intensity of the applied magnetic field.
In engineering applications, permeability is often expressed in relative, rather than in absolute, terms.
whatis.techtarget.com /definition/0,,sid9_gci543303,00.html   (336 words)

  
 TRB Annual Meeting Program
In-situ air permeability measurements were made on the surface of concrete members damaged by exposure to fire.
Field air permeability results were also compared to the laboratory testing results performed on core samples removed from the structure adjacent to field air permeability locations.
The study also demonstrated the applicability of field air permeability as a rapid field indicator of sustained damage to concrete and associated drying and cracking due to exposure to elevated temperatures.
www.trb.org /am/ip/paper_detail.asp?paperid=10416   (273 words)

  
 The tool box: Permeability assays
Permeability assays using the Caco-2 colon carcinoma cell line are being used throughout the pharmaceutical industry to estimate the ability of potential drug compounds to cross the intestinal epithelium.
The conical shape of the permeability inserts used at Pharmacia allows the liquid-handling arm to sample from either of the two chambers created by the placement of the insert.
The automated assay was validated by comparing the apparent permeability coefficients Papp obtained for a set of proprietary test compounds known to represent a wide range of apparent permeabilities.
pubs.acs.org /subscribe/journals/mdd/v03/i08/html/10toolbox.html   (1434 words)

  
 GDX Instestinal Permeability Assessment Application Guide
Elevated levels of lactulose and mannitol are indicative of general increased permeability and "leaky gut" phenomena.
Permeability to lactulose can increase, indicative of "leaky gut," while permeability to mannitol may decrease, indicative of malabsorption of small molecules.
Its value in permeability alterations may result from lowering the toxin load in the lumen, thus facilitating repair.
www.gdx.net /home/assessments/ip/appguide/index4.html   (611 words)

  
 Intestinal permeability or leaky gut syndrome in crohns
Examination of intestinal permeability or leaky gut syndrome in relatives of Crohn's Disease patients sheds light on the potential genetic influence of increased intestinal permeability in the pathogenesis of Crohn's Disease.
The researchers suggest that baseline permeability may be determined by environmental factors, whereas reaction to provocation by gut toxins such as aspirin may be genetically determined.
Several studies indicate the permeability of the small intestine seems to be reflective of disease activity and potential for relapse in Crohns Disease.
www.crohns.net /Miva/education/articles/Intestinal_Permeability.shtml   (1231 words)

  
 The Permeability of Soil
Another important measure is permeability, which is the rate at which fluid can flow through the pores of a solid.
If the permeability is low, rainwater will tend to accumulate on the surface or flow across the surface if it is not level.
You can determine how many centimeters of water are permeating through the soil by measuring the distance between the starting height marker and the surface of the water.
www.seed.slb.com /en/scictr/lab/permeability/index.htm   (570 words)

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