The use of time domain reflectometry (TDR) to determine water content (θv) from the measurement of the apparent dielectric constant (Ka) or the square root of the apparent dielectric constant (Ka 0.5) in highly saline environments has been limited due to the dampening effect that electrical conductivity (EC) has on the TDR signal. The objective of this research was to evaluate the use of a three-rod TDR probe with a polyolefin coating on the center-conducting rod (CCRC probe) to simultaneously measure θv and EC in saline conditions where standard, non-coated TDR probes (NC probe) are ineffective. The application of a 0.00053 m thick polyolefin coating on the center-conducting rod of a CS605 TDR probe increased the capability of the probe to measure θv at EC levels as high as 1.06 S m-1 compared to 0.132 S m-1 for a NC CS605 probe. The CCRC probe was found to be incapable of determining any difference in EC levels. A 0.01 m long section or “gap” at the center of the polyolefin coating on the center conducting rod (GAP probe) was cut from the polyolefin coating to expose a section of the stainless steel center-conducting rod to allow direct contact with the material being sampled. The GAP probe was found to be capable of measuring θv and EC at EC levels as high as 0.558 S m-1. Using a water-air immersion method, a comparison between the NC probe and the CCRC and GAP probes was undertaken. The correlation between θv vs. Ka 0.5 was found to be linear for all three probes with the slope (m) of the regressed equation for the NC probe (m = 7.71) being approximately twice that of the CCRC probe (m = 4.25) and the GAP probe (m = 4.36). The intercept values were equivalent for all three probes. The linearity between θv vs. Ka 0.5 for the NC and CCRC probes using the water-air immersion method was also observed when the probes were used to measure Ka 0.5 of different sand-water mixtures. The slope of regressed equation for the NC probe in the sand-water iv mixtures (m = 7.69) was equivalent to the water-air immersion slope for the NC probe, however the intercept values for the sand-water mixtures was lower than the intercept values for the water-air immersion method. Similarly, the slope of the CCRC probe in the sand-water mixtures (m = 5.00) was equivalent to the CCRC probe water-air immersion slope. Calculated Ka 0.5 values using a waterair dielectric-mixing model (WAMM) were equivalent to measured Ka 0.5 values for the NC probe. The water air immersion method was found to provide a suitable methodology for TDR research, however a more definitive test of the coated probe response in a series of soils with a range of homogenous water contents should be completed to ascertain the reliability of the water-air immersion method. The straightforward relationship between the inverse of TDR measured impedance (ZL -1) and EC provided an effective calibration method for both the NC and GAP probes. The use of the Giese- Tiemann method to establish a calibration curve for EC measurement was limited to a maximum EC level of 0.132 S m-1 for the NC probe. The use of the cell constant method was considered to be unacceptable as a means of developing a calibration curve due to the fact that the cell constant K was not a constant value. Ka 0.5 values for the CCRC and GAP were consistently less than Ka 0.5 values for the NC probe at all qv levels except θv = 0.000 m3 m-3 or 100% air. The difference in Ka 0.5 (DKa 0.5) between the NC probe and the CCRC and GAP probes was seen to increase with increasing water content. Similarly, a measurable effect was found between the TDR waveforms for the NC probe when the probe head was surrounded completely by air when compared to the TDR waveforms for the NC probe when the probe head was completely surrounded by water. Modeled electrostatic fields for the NC and CCRC CS605 TDR probes displayed a decrease in the electric potential and electric field intensity in the region outside of the polyolefin coating of the CCRC probe compared to the NC probe. The decrease v in potential and electric field intensity became greater when the dielectric constant of the material surrounding the CCRC probe increased. The use of a polyolefin coating on the center-conducting rod with a small section of the coating removed at the midsection of rod provides an effective means of extending the application of TDR θv and EC measurement in saline environments where standard TDR probes cannot be used.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 304-311).

Since the discovery of high-temperature superconductors, there has been a worldwide effort towards the development of processes for fabricating coated conductors for power applications. Most of these processes are based on vapour phase deposition techniques that have relatively low growth rates. A high-rate processing route was proposed based on the observation of high growth rate of (RE)Ba2Cu3O7- δ superconducting compounds (RE = rareearth element) from a flux supersaturated with one or more RE elements by liquid phase epitaxy (LPE). LPE has been successfully used to grow YBCO thick films with both c- and a,b-orientations on (110) NdGaO3 substrates and pure c-oriented films on YBCO seeded (100) MgO and (100) SrTiO3 under carefully controlled growth temperature and undercooling. The film growth mode (c- or a,b-oriented) is determined by the growth rate, which is directly related to the level of RE supersaturation that could be controlled by the undercooling used along with the amount of total RE solubility in the solution. The LPE grown films were highly epitaxial and biaxially aligned with good in-plane and out-of-plane textures. YBCO thick films grown on NdGaO3 by LPE showed high Tc of ~92 K and zero-field Jc at 77 K of 2.5x105 A/cm2. The initial growth of YBCO was found to be a multi-nucleation process. However, above a critical film thickness, dislocations started to form as a lattice-misfit stress relieving mechanism that led to step formation and spiral growth around dislocation cores. The growth kinetics from an unstirred solution was found to obey a

No description available.

No description available.

The research objectives are to develop experimental and computational techniques to characterize and to study the influence of polymer coating on the mechanical response of walnut shell particles to be used as proppants. E3-ESEM and Zeiss Axiophot LM are used to study the cellular microstructure and feasibility of polymer infiltration and uniform coating. Three main testing procedures; single particle compression, heating tests on coated and uncoated walnut shell particles and 3-point flexure tests are undertaken. In in-situ ESEM observations on both the coated and uncoated particles showed signs of charring at about 175 – 200 ºC. Single particle compression test are conducted with random geometry particles and subsequently with four distinct shape categories to minimize the statistical scatter; flat top, round top, cone top, and high aspect ratio. Single particle tests on uniformly cut cuboid particles from walnut shell flakes are used to capture the nonlinear material response. Furthermore cyclic compression loads are imposed on flat top particles which reveal that significant permanent deformation set in even at low load levels. Computational models include Hertzian representation, 2D and 3D finite element models to simulate single coated and uncoated particles under compression. The elastic material with geometric nonlinear representation is not able to simulate the compression response observed during testing. The inelastic material representation is able to significantly improve the compression response and address the influence of geometric shape on particle response. A single uniform layer of polymer coat is introduced on the 3D models with nonlinear material definition. Coating provides a marginal improvement in load vs displacement response of the particles while increasing the ability of the particle to withstand higher loads.

The research objectives are to develop experimental and computational techniques to characterize and to study the influence of polymer coating on the mechanical response of walnut shell particles to be used as proppants. E3-ESEM and Zeiss Axiophot LM are used to study the cellular microstructure and feasibility of polymer infiltration and uniform coating. Three main testing procedures; single particle compression, heating tests on coated and uncoated walnut shell particles and 3-point flexure tests are undertaken. In in-situ ESEM observations on both the coated and uncoated particles showed signs of charring at about 175 – 200 ºC. Single particle compression test are conducted with random geometry particles and subsequently with four distinct shape categories to minimize the statistical scatter; flat top, round top, cone top, and high aspect ratio. Single particle tests on uniformly cut cuboid particles from walnut shell flakes are used to capture the nonlinear material response. Furthermore cyclic compression loads are imposed on flat top particles which reveal that significant permanent deformation set in even at low load levels. Computational models include Hertzian representation, 2D and 3D finite element models to simulate single coated and uncoated particles under compression. The elastic material with geometric nonlinear representation is not able to simulate the compression response observed during testing. The inelastic material representation is able to significantly improve the compression response and address the influence of geometric shape on particle response. A single uniform layer of polymer coat is introduced on the 3D models with nonlinear material definition. Coating provides a marginal improvement in load vs displacement response of the particles while increasing the ability of the particle to withstand higher loads.

Dry powder coating of pharmaceutical dosage forms has been investigated as an alternative method to commonly used liquid based coating techniques. Eudragit[trademark] L 100-55 and Eudragit[trademark] L 30 D-55 have been employed in enteric film coatings using aqueous dispersions, organic solutions and compression coating. However, the copolymer has not been investigated in dry powder coating applications. Initially, formulation factors and processing parameters were investigated for the dry powder coating of chlorpheniramine maleate tablets using Eudragit[trademark] L 100-55 as the delayed release polymer. Powder coating was studied as a method to prevent the migration of an ionizable, highly water soluble model drug into the polymeric film during the coating process. Eudragit[trademark] L 100-55 was pre-plasticized with triethyl citrate (TEC) using hot-melt extrusion and subsequently ground into a fine powder. Polyethylene glycol 3350 (PEG 3350) was used as a primer and low melting coating excipient to enhance coating powder adhesion and to improve film formation. The powder coating process was performed in a modified laboratory scale spheronizer. For the dry-powder coating of sodium valproate tablets different subcoating materials were investigated to improve powder adhesion to the substrate and to reduce the level of Eudragit[trademark] L 100-55 required for gastric resistance. PEG 3350 and Methocel[trademark] K4M were incorporated in the Eudragit[trademark] E PO and Eudragit[trademark] RL PO subcoating formulations as pore forming materials. The miscibility of the PEG 3350 and Methocel[trademark] K4M in the film coating was correlated with their ability to function as pore forming agent. The film formation process of thermally cured Eudragit[trademark] L 100-55 dry-powder coatings was characterized. The influence of film additives on relative melt viscosity, surface free energy of the polymer and the mechanical properties of powder-cast films was studied. The influence of Eudragit[trademark] E PO in Eudragit[trademark] L 100-55 film coatings applied by a dry powder coating technique on the drug release mechanism was investigated. Calculation of the Flory-Huggins interaction parameter based on solubility parameters and different analytical techniques demonstrated immiscibility of the copolymers at processing conditions. A broad range of pH dependent theophylline release profiles were obtained as a function of the polymer blend ratio. / text

Clathrin-coated pits on the plasma membrane invaginate into coated vesicles to internalize receptors and membrane. The clathrin adaptor epsin contains an aminoterminal ENTH domain that binds PI(4,5)P₂ and a carboxy-terminal domain that binds clathrin, and accessory proteins such as AP2. Here, we assessed how inter- and intramolecular factors affect the contribution of epsin to coated-pit function in living cells. We found Dictyostelium epsin was not required for global clathrin function, but plays an essential role in spore development. We demonstrated that clathrin, but not AP2, was critical for epsin to associate with clathrin-coated pits. We found that the carboxy-terminal region of epsin was essential, but not sufficient, for targeting epsin within clathrin-coated pits on the plasma membrane. In addition to targeting epsin to the membrane, the amino-terminal ENTH domain regulates the interaction between epsin and clathrin, an essential property that cannot be replaced by an alternate PI(4,5)P₂ binding domain. Moreover, the ENTH domain facilitates the functional interaction between clathrin and actin during late stages of endocytosis, possibly by regulating the activity of the adaptor Hip1r. Both the ability to bind PI(4,5)P₂ and another function mediated by residue T107 are critical for the activity of the ENTH domain. Our results support a model where the ENTH domain coordinates with the clathrin-binding C-terminal domain to allow a dynamic interaction of epsin with coated pits. Furthermore, we propose that the ENTH domain of epsin facilitates the membrane recruitment and phosphorylation of Hip1r, which in turn mediates the productive interaction of clathrin with the actin cytoskeleton at the plasma membrane. / text