Dissertations / Theses on the topic 'Permeability'
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1
Reid, Richard A. "Triaxial permeability device." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/20036.
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Cunningham, Michael (Michael Ian) Carleton University Dissertation Engineering Civil and Environmental. "Relative permeability measurements for two phase flow through low permeability soils." Ottawa, 1994.
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Hudd, Raymond W. "Measurement of concrete permeability." Thesis, Loughborough University, 1989. https://dspace.lboro.ac.uk/2134/6722.
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A comparison was made between a number of laboratory and in-situ concrete permeability test methods. The laboratory tests used measured air, water, and water vapour permeability, whilst the in-situ tests used were the Initial surface absorption test, the Figg air and water tests, and a new in-situ method called the Egg test; a non-destructive surface test which measures air permeability properties. An initial set of tests were carried out on six concrete mixes with water: cement(w/c) ratios between 0.3 and 0.8. These tests showed that problems existed with both the laboratory and in-situ test methods. Some of these problems arose from the preparation of specimens or test procedures and these were overcome with practice or by modifying the test methods. However, it was found that a major problem is moisture in the concrete which decreases it's measured permeability. Further tests were carried out on a second set of concrete specimens with the same mix proportions as the first and a set of mortar specimens with w/c ratios ranging from 0.3 to 1.1 and cement: sand (c: s) ratios from 1: 1 to 1: 5. Results from tests on oven dry specimens were used to compare the different methods and showed that few simple relationships existed between the different methods. Comparing the test results with the mix proportions showed that in the majority of cases, the measured permeability values increased as the w/c ratio increased, but the relationships between the tests results and c: s ratio were more complicated. After these tests had been completed, specimens from twenty six of the mixes were retested after being conditioned to various different moisture contents. The results of these tests showed that in most cases there was a rapid increase in measured permeability as the specimens dried, followed by a slower increase (in some cases a decrease) as the specimens approached an oven dry condition. To complement this study a number of methods were examined for measuring in-situ moisture content. The most promising of these was a non-destructive method which operated by measuring the electrical permittivity of the material it was placed against. Because the electrical permittivity varies with the amount of water in the concrete, it is largely independent of the type material being tested. Results from this test showed a shallow linear drop from saturated to approximately half of the saturated moisture content, followed by a steep drop towards the oven dry condition.
4
Taherzadeh, Morteza. "Nifedipine and microvascular permeability." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299874.
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Dennison, Patrick Winford. "Epithelial permeability in asthma." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/416625/.
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Our knowledge and understanding of asthma have evolved over time, leading to new and improved treatments for this disease. Despite existing treatments however, there remains to date a significant proportion of asthmatics who remain poorly controlled, with unmet needs. Most existing treatments are based on the Th2-driven inflammation model of asthma, however there is increasing recognition of the importance of the epithelium in asthma pathogenesis. It has been proposed that the asthmatic epithelium is chronically damaged and unable to repair, with increased permeability as a result. Existing treatments do not address the epithelial damage directly, however there are now available recombinant growth factors that have been shown to have beneficial effects on epithelial healing. Our hypothesis was that modification of the epithelium, in effect boosting its repair using recombinant human keratinocyte growth factor (rhKGF), would lead to improvement in clinical parameters. This was explored in several fashions. Firstly a randomised, double-blind, placebo-controlled clinical trial was performed using 20 poorly controlled, moderate asthmatics, with the active treatment group receiving parenteral rhKGF. Assessments before and after drug administration included objective, clinically relevant, measures of asthma such as airway hyperresponsiveness (AHR) measurements, spirometric measures, exhaled nitric oxide measurements and peak flow recording. Subjective, patient-centred assessments were also made using questionnaires to assess asthma control and quality of life, and bronchoscopy was performed to obtain samples to measure biological effects of the drug. KGF treatment resulted in a significantly greater improvement in the primary outcome of mannitol AHR, together with greater improvements in quality of life in the active treatment group compared to placebo. Other features (such as methacholine AHR, asthma control questionnaire scores, spirometric values, exhaled nitric oxide and peak flow variability) did not differ significantly between the groups, although this may be due to a greater than expected placebo response. Biological outcomes also did not differ significantly between the groups, although this may have been due to the sampling time-point used. Concurrently to the clinical trial above, in vitro experiments were performed on cell cultures of epithelial cells from asthmatic and healthy donors, to verify and further explore the effects of KGF on an asthmatic epithelium. Specifically mechanical wounds were inflicted on the cultures, with assessment of the repair process using wound imaging, measurement of trans-epithelial electrical resistance (TER) and permeability to FITC-labelled dextran, in the presence and absence of KGF. As a subset of these experiments, some cultures were exposed to mechanical compression using air pressure, as a mimic for bronchoconstriction, to see if KGF was effective in these circumstances. Results confirm a biological effect for KGF on wound repair in the asthmatic epithelium, which can also partially overcome the deleterious effect of compression on wound healing. An intrinsic difference in wound healing between asthmatic and healthy cohorts, as previously reported, was not apparent. Lastly the potential of nuclear medicine imaging, to assess epithelial permeability, was explored, for its potential use in future studies of asthma treatments addressing the epithelium directly. Unfortunately this was halted after a pilot study suggested potential methodological flaws – the results and conclusions from this pilot study are presented here, with suggestions for future studies in this area.
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Daly, Philip J. "Permeability of pseudomonas aeruginosa." Thesis, Aston University, 1986. http://publications.aston.ac.uk/12458/.
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Wong, Wing-yee. "Permeability studies in rock fractures." View the Table of Contents & Abstract, 2002. http://sunzi.lib.hku.hk/hkuto/record/B30109334.
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Khajeh, Ehsan. "Permeability of hypoeutectic aluminum alloys." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36586.
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The interdendritic permeability is a critical parameter that defines the feedability of the mushy zone during solidification. In this study, a theoretical expression to describe the evolution of permeability throughout the complete solidification range (from dendritic to dendritic/eutectic) of hypoeutectic aluminum alloys has been derived, verified and validated through physical and numerical modeling. The permeability of the primary, equiaxed, dendritic phase has been characterized using geometries obtained by X-ray microtomographic analysis of Al-4.5wt%Cu alloy samples quenched at different temperatures after the start of solidification. The permeability during equiaxed eutectic solidification was characterized on simulated dendritic/eutectic microstructures predicted using a Cellular Automaton technique. For both the dendritic and dendritic/eutectic structures, the permeability was characterized i) physically using large-scale analogues of the characterized microstructures and ii) numerically by predicting the flow through the simulated microstructures. The microstructural parameters were then linked to more practical parameters available in solidification models through i) developing an inverse analysis technique to characterize eutectic solidification and ii) development of a geometric model for dendritic solidification. The permeability values determined through physical and numerical modeling are in good agreement with each other and are consistent with the mathematical expression. The proposed permeability expression is valid over the complete solidification range and for a wide range of compositions. The expression reduces to the conventional Carman-Kozeny expression during dendritic solidification and/or dendritic/eutectic solidification with low density of eutectic grains. However, it deviates from the conventional Carman-Kozeny expression as the density of eutectic grains increases.
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Weaver, Laurence Trevelyan. "The intestinal permeability of infants." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289788.
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Mirza, Nabeel Aman. "Geophysical modelling of sediment permeability." Thesis, Bangor University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280908.
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Bills, Victoria Louise. "Vascular permeability in pre-eclampsia." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508075.
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Wong, Wing-yee, and 黃詠儀. "Permeability studies in rock fractures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B43895013.
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Smethurst, Paul R. "Small intestinal permeability in man." Thesis, Open University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315531.
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Evans, N. J. "Skin permeability in the newborn." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373865.
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Nordquist, Taylor James. "Permeability anisotropy of resedimented mudrocks." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99578.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 257-260).
Permeability anisotropy (ratio of horizontal to vertical permeability) is an important but uncertain parameter used in characterizing underground formations. While it is a fairly unknown parameter, it is integral for the petroleum industry, where a greater permeability anisotropy understanding can greatly aid in basin modelling, pore pressure prediction, and borehole stability. This research experimentally characterizes the permeability anisotropy of several mudrocks, which are clay-rich sedimentary formations, using re-sedimentation, a process of homogenization of naturally-occurring soils and recreation of the sedimentation environment in a controlled laboratory setting. The permeability anisotropy of resedimented Boston Blue Clay (RBBC), an illitic lean clay (CL), increases from 1.5 to 3 when mechanically compressed from 0.1 to 40 MPa, corresponding to porosities ranging from 0.55 to 0.26. Resedimented Gulf of Mexico - Eugene Island mudrock (RGoM-EI), a smectitic fat clay (CH), exhibits permeability anisotropy increasing from 1 to 5 when compressed to the same stresses, corresponding to porosities ranging from 0.6 to 0.25. Not only does smectitic RGoM-EI mudrock transition to greater anisotropy with compression, but the rate of increase accelerates with compression. These measurements are made using a commercially-available Trautwein® constant rate of strain (CRS) consolidometer with vertical drainage combined with a novel radially-outward draining CRS device. The combination of the vertically and radially draining CRS devices produces permeability anisotropy data quickly, with very little scatter. For RGoM-EI, the effects of horizontal shearing to 29.5% shear strain at 0.14 MPa on permeability anisotropy are negligible. Permeability anisotropy of the homogeneous resedimented mudrocks tested, using a cubic specimen constant head permeameter within a triaxial cell, is directly correlated to their electrical conductivity anisotropy. The permeability anisotropy values measured using this technology, however, are lower than those measured using CRS testing.
by Taylor James Nordquist.
S.M.
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Chen, Anthia Yenshiu. "The hydrodynamic permeability of sclera." Thesis, Massachusetts Institute of Technology, 1991. https://hdl.handle.net/1721.1/129505.
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Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991.Includes bibliographical references (leaves 30-31).
by Anthia Yenshiu Chen.
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991.
17
Yamakawa, Masatoshi. "Chloride permeability of distressed concrete." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1455163.
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Halihan, Todd. "Permeability structure in fractured aquifers /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Carroll, Kelly Patrick. "Permeability of Lake Ice in the Taylor Valley, Antarctica: From Permeameter Design to Permeability Upscaling." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1206545662.
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Danysh, Brian P. "Mechanisms behind lens capsule selective permeability." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 205 p, 2010. http://proquest.umi.com/pqdweb?did=1992441981&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Siddiqui, Adil Ahmed. "Towards a characteristic equation for permeability." Texas A&M University, 2008. http://hdl.handle.net/1969.1/86054.
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The characterization of reservoir permeability (k) remains the elusive challenge in reservoir engineering.
This work considers prior developments in an evolutionary sense, and, as with prior work, our goal is the
development of a "characteristic permeability relation" (CPR). To this end, we have developed 5 CPR
formulations -- 3 of which could be considered modifications of "historical" models and 2 of which are
"weighted" power law-exponential models.
In this work, we consider permeability to be only a function of two variables; k = f(ø,z) -- porosity (ø ) and
z, where z is either the water saturation (Sw) or the Archie Formation Factor (F). Our rationale in
considering k = f(ø,z) is two-fold -- first, such a formulation is a fundamental extension of the k = f( ø)
correlation work by Archie (and countless others); and second, our validation datasets are limited to
literature cases and cases obtained from industry sources -- none of which would be considered suitable
for extension beyond porosity and another variable.
We demonstrate and validate our concept of a characteristic permeability relation using various datasets
obtained from the literature and from industry sources. In this work we show that each proposed relation
has a unique character and performance -- depending on primarily on the data, rather than the functional
form of the permeability relation. Using the characteristic permeability relations developed in this work -- the proposed permeability relations can be extended to other and other data types. It may also be
possible to develop so-called "hydraulic flow unit" methods which segregate petrophysical data into
depositional flow sequences.
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Watson, Catherine E. "The permeability of Drosophila melanogaster embryos." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29203.
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Drosophila are used extensively for genetic, developmental and now molecular biology research. At present, germline transformation of these organisms can only be achieved by microinjection of P-element vectors into the pole cells of young embryos. The technique of microinjection however, requires a delicate touch and is quite laborious. Therefore, the development of a rapid and simple technique was investigated.
Electroporation, like microinjection, is a physical means of introducing DNA into a cell and is therefore potentially applicable to all cell types. Electroporation involves the use of an electrical current to create pores in the membrane of a cell. Macromolecules, such as DNA may enter a cell via these pores. Electroporation is a quick, reproducible, and efficient method for transforming cells. Through studies of the survival and permeability of Drosophila melanogaster embryos exposed to electrical currents, it was discovered that although the survival of the embryos decreased steadily as field strength increased, the embryos did not become permeable to a water soluble dye unless a pulse of 10 kV/cm was applied. Few embryos survived this extreme voltage required for dye uptake. Attempts to introduce DNA into dechorionated Drosophila embryos utilizing this technique however, produced no transformants. These results suggested that the remaining protective coatings of the dechorionated embryo were obstructing efficient pore formation, thus preventing DNA penetration.
In view of these results, methods to eliminate the wax layer, present between the chorion and vitelline membrane of laid eggs,
were examined. Wax removal by detergent solubilization, solvent extraction and melting by heating were investigated, yet did not produce a satisfactory procedure.Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate
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Lang, Mia E. "Intestinal permeability in the irradiated ferret." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7772.
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Ferrets received whole-body irradiation (5 Gy, gamma). At different times post-irradiation (PIRR, 2, 24, and 48 hours), measurements of fluid and electrolyte fluxes, and of the blood-to-lumen clearance of $\sp{51}$Cr-EDTA, were compared between in situ perfused loops of jejunum and ileum. Intestinal permeation of $\sp{51}$Cr-EDTA was increased (4x control) in both the jejunum and ileum at 2 hours PIRR. At 24 hours PIRR, $\sp{51}$Cr-EDTA permeation was the same as control. At 48 hours PIRR, jejunal permeation of $\sp{51}$Cr-EDTA was not statistically different from control animals, whereas in the ileum, $\sp{51}$Cr-EDTA permeation was increased 10x control. Absorption of luminal fluid was abolished 2 hours PIRR in the ileum. Sodium and chloride fluxes were unaffected by radiation exposure, but at 48 hours PIRR there was a significant secretion of potassium in the ileum. Diarrhea rarely occurred after the first hour post-irradiation. Serotonin, acting via 5-HT$\sb3$ receptors, was investigated as a possible mediator of radiation-induced alterations in intestinal permeability. Pretreatment with the 5-HT$\sb3$ antagonist and anti-emetic BRL 43694 significantly reduced the severity of radiation-induced vomiting. It offered some therapeutic benefit to radiation-induced diarrhea. However BRL 43694 pretreatment had no effect on intestinal permeability. (Abstract shortened by UMI.)
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Gauthier, Alain R. "The permeability of a lipid bilayer." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27136.
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This work presents results on the permeability of a lipid bilayer to water molecules. We look at the change in bilayer permeability as a function of lipid structure and area per lipid molecule. A molecular dynamic simulation (MDS) of a solvent surfactant system was used in the canonical ensemble to simulate the membranes. Permeability was obtained by calculating the permeative resistance. This method, developed by Marrink and Berendsen, allows the sampling of very long time scale events on short time scale simulations. The structural properties of the simulated bilayer are studied and compared both to atomistic MDS and experiments. The elasticity of the simulated membranes are shown to be in good agreement with experimental results. The permeation is found to increase only slightly for a relative stretch of up to 20%, a result which is qualitatively similar to recent experiments. The increase is described by a linear relation between the permeability and the relative extension. Most of the changes in the lipid bilayer are found to occur in the central part near the ends of the tails. The effect of lipid packing on bilayer permeability are also discussed.
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Taylor, Daniel J. "Transverse permeability of direct glass rovings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37986.pdf.
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Findley, Benjamin Carter. "Permeability of impacted coated composite laminates." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16702.
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Corvera, Poiré Eugenia. "Permeability of lipid bilayers containing cholesterol." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60030.
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Lipid-cholesterol bilayers are studied by means of a microscopic multi-state lattice model and Monte Carlo computer simulations. The model used is a direct extension of the Pink model for the main transition of pure lipid bilayers. Cholesterol is introduced as a bulky, rigid molecule with no internal degrees of freedom. The model is able to account for the chain melting of lipid molecules, and is expected to be valid at low cholesterol concentrations.A minimal model for the transport of ions across membranes is used to predict the changes in the passive permeability of lipid-cholesterol bilayers for different cholesterol concentrations and different lipid chain lengths. The model assigns different probabilities of transfer to bulk, clusters and interfaces. The main assumption is that, defects due to bad packing at interfacial regions, cause the membrane to be leaky and allow the ions to permeate it. Therefore the model assigns a high probability of transfer to the interfacial regions.
A peak in the permeability is observed near the transition temperature, which is in accord with experimental data. The results show an increase in the passive ion permeability for increasing cholesterol concentration for the three systems under consideration. Also, an increase in the membrane permeability is predicted for decreasing chain length for all the cholesterol concentrations studied.
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Baskerville, P. A. "The permeability of the artery wall." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376876.
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Stower, G. X. M. "The permeability of regular porous media." Thesis, University of Essex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355381.
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Perrin, Rachel Morvah. "Factors affecting permeability in diabetes mellitus." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442198.
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Amess, T. R. "The permeability of dentine to lignocaine." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319013.
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Khawaja, Mohammed. "Modelling the permeability of nitrile rubber." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/51510.
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Elastomer seals are widely used in the oil and gas industry and form small but crucial parts of critical mechanical and electronic components. Ideally, to prevent damage to such components, the seals should act as impermeable barriers. However, under the high pressures and temperatures found downhole, they are liable to suffer two main types of permeation-driven failure, either by gases permeating through the entire seal, or by dissolved gases causing swelling and rupture, in a process known as explosive decompression. Neither failure mode is particularly well understood, and experimental approaches have encountered difficulties in replicating service conditions and providing insight into the mechanisms responsible. In this work, I use a molecular-simulation-based approach to investigate the drivers of and trends in the permeation of gases as a function of the underlying polymer chemistry and the environmental conditions. I focus on two elastomers in particular that are widely used in the oil and gas industry due to their resistance to hydrocarbons and to thermal degradation: nitrile butadiene rubber, or NBR, which is a statistical copolymer of acrylonitrile and butadiene, and hydrogenated-NBR, or HNBR, which is a polymer derived from the cross-linking and saturation of NBR. For NBR, I first develop a fully atomistic model using the OPLS-AA force-field. I demonstrate that solubility increases with acrylonitrile content, the cyano group plays a crucial role in the enhanced solubility of polar gases, and that the effects of pressure and temperature are heavily gas-dependent. In contrast, the diffusivity is found to decrease with increasing acrylonitrile content. For HNBR, I show that, while the diffusivity decreases with increasing cross-link fraction, counter-intuitively, the solubility increases. The work in this thesis provides a set of molecular-level design principles for the future development of corrosion- and decompression-resistant elastomers.
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Le, Poidevin Janine. "Timber permeability : significance for joinery decay." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38083.
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Betteridge, Benjamin Grant. "LCM Permeability Characterization Over Mold Curvature." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8508.
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Composite flow simulation tools for LCM processing can be expensive and time-consuming but necessary to design a mold system with proper placement of resin inlets and vacuum outlets. Composites manufacturing engineers would benefit from data regarding the impact of mold curvature radius on resin flow. This could help determine whether or not a particular part and mold would require expensive simulation software designed to handle complex flow paths through curved fabric architectures exhibiting variable permeability over the curvature, or if simple flow modeling would provide accurate enough simulations for sound tooling setup decision making. Four molds, with double curvature having equal radii, were fabricated with radii ranging from 3.2 to 25.4 mm to characterize the permeability of two different fiber reinforcements 1) a carbon biaxial NCF and 2) a fiberglass CSM over the mold curvatures. Three infusions of each material type were conducted on each of the 4 molds for a total of 24 test infusions. Flow front position vs. time data was captured during each experimental infusion. The permeability in the bend regions, KB, was first estimated by the integrated form of Darcy's Law to evaluate the permeability for average flow across the entire bend region. This was done for both the convex and concave regions using a geometric estimate for the increased compaction in the bend regions. The permeability increases as the tool radius increases, and the rate of increase diminishes as the tool radius increases and the permeability approaches the flat region permeability. An estimate of KB for VI was then made by applying a ratio calculated from the resulting permeability from the rigid- and VI-based models in the flat regions. Generic power law fits are reported that could be used in LCM process simulation, to give a model to estimate the permeability for any bend in the reinforcement part geometry. The results suggest that any curve with a radius higher than 25 mm requires no adjustment to the flat permeability.
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Hofmann, Klaus. "Longitudinal air permeability of lodgepole pine." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/90939.
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The longitudinal air permeabilities of the wood of 1116 specimens from 279 trees, two sapwood and two heartwood replicates, representing two varieties of lodgepole pine (Pinus contorta, vars. latifolia and murrayana) were measured with a steady state apparatus. It was found that the mean ratio of sapwood to heartwood permeability was ca. 10:1 for both varieties. The mean ratio of var. latifolia to murrayana was 1.5:5 and 1.75:5 for sapwood and heartwood, respectively.
The most important source of variation following the difference between heartwood and sapwood was that among trees. Geographical locations, such as latitude and elevation did not significantly influence permeability. Tree size did, but only because the small trees (3 inch diameter) showed higher heartwood permeability and lower sapwood permeability than normal. Ca. 20 specimens of latifolia heartwood showed extremely high permeabilities. They were also deeply brown in color, which probably was caused by fungal or bacterial infestation.
Pit pore size and number per cm² were determined for sapwood by making four permeability measurements, each at a different average pressure on each specimen. A mean pit pore radius of 1.5 µm and 1.3 µm for sapwood of var. latifolia and var. murrayana was calculated. The median values between 1200-1300 pit pores per cm² indicate an average rate of tracheid connection of 1.2-1.3%.
Of the tested wood parameters including moisture content and specific gravity average ringwidth, only the permeability of var. latifolia was significantly correlated with moisture content for both heartwood and sapwood, with a negative correlation coefficient.
Water retention measurements were carried out to relate the measured gas permeability of an individual specimen to its ability to absorb water. For both varieties the retention was significantly and quadratically correlated with sapwood permeability (R² = 0.286 and 0.224) and was linearly correlated with heartwood permeability (R² = 0.488 and 0.5775). The correlation factors for the regression between retention and the logarithm of permeability were 0.239 and 0.227 for sapwood and 0.447 and 0.420 for heartwood.M.S.
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BARAI, NAMRATA D. "EFFECT OF HYDRATION ON SKIN PERMEABILITY." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1016480955.
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Gunt, Hemali B. "Hydration Effect on Human Nail Permeability." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1154112551.
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Rezai, Taha. "Structural permeability relationships of cyclic peptides /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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Singh, Kunwar Shandilya Kunal Shrawan. "Establishing permeability trend for Illinois coals /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1559857241&sid=13&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Hawkins, Brian Thomas. "Nicotinic modulation of cerebral microvascular permeability." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/289240.
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The blood-brain barrier (BBB) is the regulated interface between the peripheral circulation and the central nervous system (CNS), formed primarily by the cerebral microvascular endothelium. Tight junctions (TJ) between BBB endothelial cells restrict paracellular diffusion from blood to brain. Expression and localization of TJ proteins are modulated by multiple pathways. Disruption of TJ by disease or drugs can impair BBB function and compromise the CNS. Therefore, understanding how BBB TJ are affected by various factors is useful for the prevention and treatment of neurological diseases. Smoking is associated with increased risk of disease, including neurological disease. The effects of nicotine on endothelial cells are profound, and nicotinic acetylcholine receptors (nAChR) have been characterized in peripheral endothelial cells. However, relatively little is known about the specific effect of nicotine on the BBB. The hypothesis of this study is that nicotine increases BBB permeability by alteration of TJ via a nAChR-mediated pathway. To test this hypothesis, studies were undertaken to (1) explore the effects of nicotine on the expression and distribution of TJ proteins in cerebral microvessels; (2) determine the effect of nicotine on BBB permeability in an intact animal model; and (3) investigate the role of nAChR in the effects of nicotine on the BBB. Rats were given nicotine at a dosage designed to mimic the exposure experienced by heavy smokers. While nicotine did not alter the expression of the TJ proteins investigated, changes in their distribution were observed. Nicotine was found to increase BBB permeability to sucrose without significant changes in its initial volume of distribution. These data suggest that nicotine increases the permeability of the BBB via modulation of TJ proteins. Positive immunoreactivity was found for nAChR subunits α3, α5, α7, and β2, but not α4, β3, or β4. Nicotine was co-administered with the nicotinic antagonists mecamylamine, which readily crosses the BBB, and hexamethonium, which does not. Both of these antagonists attenuated the effect of nicotine on BBB permeability, indicating that this effect is receptor-mediated and that receptors within the CNS are probably not involved. Taken together, these data suggest a novel role for endothelial nAChR in regulation of BBB TJ and permeability.
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Florence, Francois-Andre. "Validation/enhancement of the "Jones-Owens" technique for the prediction of permeability in low permeability gas sands." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5846.
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This work presents the validation and enhancement of existing correlations for estimating and predicting
the permeability in low permeability gas sands. The "original" problem of predicting the corrected or
"liquid equivalent" permeability has been under investigation since the early 1940s â in particular, using
the application of "gas slippage" theory to petrophysics by Klinkenberg.
In the first part of this work, the viability of the Jones-Owens and Sampath-Keighin correlations for
estimating the Klinkenberg-corrected (absolute) permeability from single-point, steady-state measurements
were investigated. We also provide an update to these correlations using modern petrophysical
data.
In the second part of this work we proposed and validated a new "microflow" model for the evaluation of
an equivalent liquid permeability from gas flow measurements. This work was based on a more detailed
application of similar concepts employed by Klinkenberg. In fact, we obtained the Klinkenberg result as
an approximate form of this result. A theoretical "microflow" result was given as a rational polynomial
(i.e., a polynomial divided by a polynomial) in terms of the Knudsen number (ratio of the mean free path
of the gas molecules to the characteristic flow length (typically the radius of the capillary)), and this result
can be applied as an explicit correlation device, or as an implicit prediction model (presuming the model is
tuned to a particular data set).
The following contributions are derived from this work:
â Validation and extension of the correlations proposed by Jones-Owens and Sampath-Keighin for low
permeability samples.
â Development and validation of a new "microflow" model which correctly represents the flow of gases
in low permeability core samples. This model is also applied as a correlation for prediction of the
equivalent liquid permeability in much the same fashion as the Klinkenberg model, although the new
model is substantially more theoretical (and robust) as compared to the Klinkenberg correction model.
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Sahu, Laxmi Kumari. "Bulk and Interfacial Effects on Density in Polymer Nanocomposites." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3619/.
Full textAbstract:
The barrier properties of polymers are a significant factor in determining the shelf or device lifetime in polymer packaging. Nanocomposites developed from the dispersion of nanometer thick platelets into a host polymer matrix have shown much promise. The magnitude of the benefit on permeability has been different depending on the polymer investigated or the degree of dispersion of the platelet in the polymer. In this dissertation, the effect of density changes in the bulk and at the polymer-platelet interface on permeability of polymer nanocomposites is investigated. Nanocomposites of nylon, PET, and PEN were processed by extrusion. Montmorillonite layered silicate (MLS) in a range of concentrations from 1 to 5% was blended with all three resins. Dispersion of the MLS in the matrix was investigated by using one or a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Variation in bulk density via crystallization was analyzed using differential scanning calorimetry (DSC) and polarized optical microscopy. Interfacial densification was investigated using force modulation atomic force microscopy (AFM) and ellipsometry. Mechanical properties are reported. Permeability of all films was measured in an in-house built permeability measurement system. The effect of polymer orientation and induced defects on permeability was investigated using biaxially stretched, small and large cycle fatigue samples of PET and nylon nanocomposites. The effect of annealing in nylon and nanocomposites was also investigated. The measured permeability was compared to predicted permeability by considering the MLS as an ideal dispersion and the matrix as a system with concentration dependent crystallinity.
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Xie, Jiang. "Improved permeability prediction using multivariate analysis methods." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3223.
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Merker, Marissa C. "Persulfate transport in two low-permeability soils." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Summer2010/M_Merker_061610.pdf.
Full textAbstract:
Thesis (M.S. in civil engineering)--Washington State University, August 2010.Title from PDF title page (viewed on July 23, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 15-17).
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Yu, Miao. "Effect of persulfate formulations on soil permeability." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Summer2010/m_yu_061410.pdf.
Full textAbstract:
Thesis (M.S. in environmental engineering)--Washington State University, August 2010.Title from PDF title page (viewed on July 30, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 13-14).
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Wilms, Josefine. "On the hydrodynamic permeability of foamlike media." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1316.
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Rodriguez, Cesar Alexander. "Stress-dependent permeability on tight gas reservoirs." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1393.
Full textAbstract:
People in the oil and gas industry sometimes do not consider pressure-dependent permeability in reservoir performance calculations. It basically happens due to lack of lab data to determine level of dependency. This thesis attempts to evaluate the error introduced in calculations when a constant permeability is assumed in tight gas reservoir. It is desired to determine how accurate are conventional pressure analysis calculations when the reservoir has a strong pressure-dependent permeability. The analysis considers the error due to effects of permeability and skin factor. Also included is the error associated when calculating Original Gas in Place in the reservoir. The mathematical model considers analytical and numerical solutions of radial and linear flow of gas through porous media. The model includes both the conventional method, which assumes a constant permeability (pressure-independent), and a numerical method that incorporates a pressure-dependent permeability. Analysis focuses on different levels of pressure draw down in a well located in the center of a homogeneous reservoir considering two types of flow field geometries: radial and linear. Two different producing control modes for the producer well are considered: constant rate and constant bottom hole pressure. Methodology consists of simulated tight gas well production with k(p) included. Then, we analyze results as though k(p) effects were ignored and finally, observe errors in determining permeability (k) and skin factor (s). Additionally, we calculate pore volume and OGIP in the reservoir. Analysis demonstrates that incorporation of pressure-dependence of permeability k(p) is critical in order to avoid inference of erroneous values of permeability, skin factor and OGIP from well test analysis of tight gas reservoirs. Estimation of these parameters depends on draw down in the reservoir. The great impact of permeability, skin factor and OGIP calculations are useful in business decisions and profitability for the oil company. Miscalculation of permeability and skin factor can lead to wrong decisions regarding well stimulation, which reduces well profitability. In most cases the OGIP calculated is underestimated. Calculated values are lower than the correct value. It can be taken as an advantage if we consider that additional gas wells and reserves would be incorporated in the exploitation plan.
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Anderson, Alexander Douglas Gray. "Measurement of intestinal permeability in surgical patients." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/24575.
Full textAbstract:
Aim: The aim of this study was to investigate the use of a triple sugar test of intestinal permeability as a surrogate marker of gut barrier function in surgical patients. Methods: Original laboratory work included the development of a technique for the quantification of urinary sucralose using high performance liquid chromatography (HPLC) with refractive index detection. Other techniques used included HPLC analysis of urinary lactulose and rhamnose, quantification of urinary 51Cr-EDTA by gamma counting, and a lactulose-hydrogen breath test. The triple sugar test involved ingestion of a test drink containing sucralose (5g), lactulose (5g) and rhamnose (1g). Urine was collected for 24 hours in 2 aliquots (first 5 and last 19 hours) and sugar concentrations determined by HPLC. A 51Cr-EDTA test was administered separately as an independent measure of “whole-gut” permeability. Healthy volunteers (n=21) and ileostomists (n=18) were studied in order to investigate the sites of absorption of sugar probes. A number of patient groups were then studied; these included subjects with Crohn’s disease (n=16),acute colitis (n=18), IBS (n=11), acute pancreatitis (n=9) and patients undergoing chemotherapy (n=7). Results: Assays for urinary sugars were both accurate and precise (coefficient of variation approximately 5%). Studies in ileostomists and controls indicated that 24-hr sucralose excretion represented “whole-gut” permeability, whereas the 5-hr lactulose/rhamnose excretion ratio represented small intestinal permeability. Small intestinal permeability was increased in subjects with Crohn’s disease (p=0.007) and acute pancreatitis (p=0.004), versus controls. “Whole gut” permeability was significantly increased in patients with Crohn’s (p=0.001) and pancreatitis (p<0.001), and significantly reduced in patients undergoing chemotherapy (p=0.012). The proportion of sucralose excreted in the last 19 hours of collection was significantly increased in patients with Crohn’s (p=0.026), acute colitis (0.023) and acute pancreatitis (p=0.049), implying an increase in colonic permeability.
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Ramage, John. "Permeability of the healthy and inflamed gut." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46519.
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Mohamedelhassan, E. "Electro-osmotic permeability of a marine sediment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39859.pdf.
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