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Measurements of soil permeability anisotropy by three techniquesRoy, Pierre January 1992 (has links)
Measurements of vertical and horizontal components of hydraulic conductivity were made by the falling head permeameter, the standard piezometer and the piezometer with packing device on 4 farms in the Saint-Lawrence lowlands of Quebec, Canada. All fields are considered to be between imperfectly and slowly drained. / The values obtain by the 2 types of piezometer were calculated with the aid of 3 different equations and were compared. / The falling head permeameter technique was found to be not appropriate to study anisotropy in clay and clay loam soils due to its high variability and small volume of soil sampled. / Both piezometers were found well suited to make directional hydraulic conductivity measurements. Values of vertical hydraulic conductivity twice greater than values of horizontal hydraulic conductivity were obtained by piezometer measurements in a subsoil of a St-Benoit soil series.
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Edible food coatings to control potassium sorbate diffusion from surface into food bulk : characterization of the diffusion process in polysaccharide based filmsVojdani, Fakhrieh 23 September 1987 (has links)
Edible coatings controlling preservative migration from
surface to food bulk could inhibit surface microbial growth
which is often the main cause of spoilage for many food
products. In this project we focused our attention upon
methylcellulose, hydroxypropyl methylcellulose, and chitosan as
the structural component for such edible films. These films
were generally transparent and effective at thicknesses in the
order of 20 to 100 μm. We expect them to have little impact
on the sensory properties of a food.
Permeability cell measurements were used to evaluate the
effect of coating composition. Further film characterization included film thickness and electron microscopy studies. To
gain an understanding of the permeation process, the
permeability tests were done at 5, 24, 32, and 40°C.
Among these polysaccharide films, methylcellulose was the
most promising diffusion barrier with a permeability constant of
3.4 and 1.4xl0⁻⁸ (mg/sec cm²)(cm)/(mg/ml) at 24 and 5°C,
respectively. These barrier properties were enhanced by the
incorporation of lipids into the film formulation.
The permeability of sorbates in methylcellulose and
hydroxypropyl methylcellulose emulsified with lauric, palmitic,
stearic and arachidic acid was found to depend upon the
polysaccharide, the fatty acid chain length, and the number of
fatty acid double bonds. Potassium sorbate permeation increased
in the following order lauric>palmitic>stearic>arachidic acid.
The effect of the double bond type, i.e. cis vs. trans was also
determined. The permeability rate of potassium sorbate
increased in the order of oleic>elaidic>stearic acid.
The effect of temperature on potassium sorbate permeability
was analyzed using an Arrhenius activation energy model for the
permeation process. Permeability determinations at four
different temperatures showed excellent agreement with this
model and suggest that the permeation process is diffusion
controlled. Electron microscopy studies showed the absence of
pores, channels or other defects which might be introduced
during casting, drying, handling or permeability determination.
This observation is consistent with our hypothesis that potassium sorbate permeation is diffusion controlled.
Furthermore, our experimental data suggest that the diffusion is
controlled by the properties of the solvent embedded in the
film. Further studies are required to confirm this hypothesis.
The effect of casting technique was examined by coating a
pure polysaccharide film with a fatty acid mixture or bees wax
and by laminating a fatty acid mixture or hydrogenated palm oil
between two layers of pure polysaccharide films. Unfortunately,
most of these films cracked easily and could not be tested in
our permeability cell. On the other hand, hydroxypropyl
methylcellulose films coated with bees wax showed exceedingly
low potassium sorbate permeability values.
These modifications of the polysaccharide film properties
reduced the potassium permeability down to 10⁻⁹ to 10⁻¹¹
(mg/sec cm²)(cm)/(mg/ml) depending upon temperature, film
composition and film casting technique. A simplified procedure
previously published was used to evaluate surface microbial
stability enhancement. With this information a food processor
can select the appropriate film, application procedure and film
thickness to achieve the desired shelf life under ambient or
refrigerated storage conditions. / Graduation date: 1988
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Permeability properties of an edible methylcellulose-palmitic acid filmRico-Pena, Delmy del Carmen 15 January 1990 (has links)
The use of edible coatings in combination with antimicrobial
agents enhances the microbial stability of foods. In this study we
evaluated the potassium sorbate and sorbic acid permeability of an
edible methylcellulose (MC) - palmitic acid (PA) film with a MC:PA
ratio of 3:1.
Permeability cell measurements were used to evaluate the effect
of pH and water activity (a [subscript w]) on the film permeation rate by sorbic
acid and potassium sorbate. For films with a thickness of 55-66 pm,
potassium sorbate permeability increased from 2.3x10⁻¹⁰ to 2.0x10⁻⁸
(mg/sec cm²)/(cm)/(mg/mL) as a [subscript w] increased from 0.65 to 0.80. Films
were not stable at a [subscript w] levels above 0.80.
The permeability of the film to sorbic acid decreased from
3.3x10⁻⁸ to 9.1x10⁻¹⁰ (mg/sec cm²) (cm)/(mg/mL) when pH in the
permeability cell was increased from 3 to 7. This permeability decrease with pH could balance the loss of effectiveness of sorbates
due to the lowering of the percentage of undissociated molecules at
high pH.
Another characterization of the MC-PA film was the evaluation
of the effect of relative humidity (RH) on its oxygen transmission
rate (OTR). In general, the film was highly permeable to oxygen
(OTR values at 24°C, 660 to 1400 mL O₂ (STP)/m² 24h atm, average
film thickness of 55 μm). Therefore, there is no risk to develop
anaerobic conditions on food surfaces coated with the MC-PA film.
There was no relative humidity effect on OTR in the 0-60% RH range;
whereas, the OTR doubled when the RH was increased from 60 to 80%.
These results agree well with the moisture uptake of the MC-PA film.
Its moisture sorption isotherm shows a large moisture content
increase at RH levels larger than 60%.
The application of methylcellulose-based films as moisture
permeability barriers in simulated sundae ice cream cones showed
that a MC-PA film practically stopped moisture transfer from the ice
cream to the sugar cone. Sugar cone crispness was retained for a
period longer than three months when stored coated at -10°F and
+10°F. The crispness of commercial sundae ice cream cones is
retained for periods much less than three months. / Graduation date: 1990
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Estimation of the three-dimensional anisotropic spatial covariance of log permeability using single-hole and cross-hole packer test data from fractured granitesDepner, Joseph Scott. January 1985 (has links) (PDF)
Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1985. / Includes bibliographical references (leaves 158-160).
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Infiltration into stratified alluvium a comparison between simulated values and field measurements /Cosio, Sergio Javier, January 1988 (has links) (PDF)
Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1988. / Includes bibliographical references (leaves 163-168).
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The effect of hyaluronidase on capillary permeabilityPinson, Thomas J. January 1957 (has links)
Thesis (M.S.)--University of Michigan, Ann Arbor, 1957. / Typescript (photocopy). Includes bibliographical references (leaves 76-78). Also issued in print.
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Regulation of microvascular permeability by nitric oxide /Rumbaut, Rolando E. January 1998 (has links)
Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / "May 1998." Typescript. Vita. Includes bibliographical references (leaves 139-147). Also available on the Internet.
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Fracture occurrence and ground water pollution in Ohio's glacial and lacustrine deposits a soils, geologic, and educational perspective /Weatherington-Rice, Julie B. P. January 2004 (has links)
Thesis (Ph. D.)--Ohio State University, 2004.
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The effect of hyaluronidase on capillary permeabilityPinson, Thomas J. January 1957 (has links)
Thesis (M.S.)--University of Michigan, Ann Arbor, 1957. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 76-78).
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Intergranular water and permeability of the Lake Vostok accretion ice, Eastern AntarcticaJepsen, Steven Michael. January 2005 (has links) (PDF)
Thesis (Ph. D.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: Edward E. Adams. Includes bibliographical references (leaves 129-136).
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