Hannover, Universiẗat, Diss., 2003.

Heidelberg, University, Diss., 2003.

Hannover, Universiẗat, Diss., 2003.

Polymer-coated controlled-release fertilizers (PCFs) are the most widely used class of fertilizers in the production of container-grown nursery plants. Nutrient release from PCFs is primarily influenced by temperature. The objective of this study was to determine the influences of temperature and time on the nutrient release patterns of three PCFs (each with a rated longevity of 8-9 months), each using a different coating technology: Osmocote Plus™ 15N-3.93P-9.96K, Polyon™ 18N-2.62P-9.96K, and Nutricote™ 18N-2.62P-6.64K. The first three experiments investigated the effects of time on long-term nutrient release. In Expt. 1, each of the three PCFs were placed in flasks of distilled water maintained at 40°C for 22 weeks. Fertilizer solutions were poured off at bi-weekly intervals and measured for electrical conductivity (EC) and NO3-N, NH4-N, P, K, Fe, Mn, Cu, and Zn concentrations. Overall, nutrient release for the three PCFs was higher and more variable in the first eight weeks than later in the experiment. Polyon's™ macronutrient release was generally more gradual than that of the other products. Micronutrient release patterns varied substantially between fertilizers and nutrients. In Expt. 2, pine bark (PB)-filled containers were amended with the three PCFs and irrigated regularly in a greenhouse. PCFs were removed from containers when Osmocote Plus'™ NO₃-N supply was ~66% expended and analyzed for EC, NO₃-N, NH₄-N, and P concentration. Except for P, the percentage of each nutrient remaining was roughly comparable to those remaining at the corresponding stage of Expt. 1, suggesting that PCF nutrient release behavior in the laboratory method is comparable with nutrient release behavior in PB in the greenhouse. At the end of Expts. 1 and 2, Osmocote Plus™ had expended a higher percentage of its nutrients than the other fertilizers. In Expt. 3, substrate solutions were collected weekly from PB-filled containers (same treatments as in Expt. 2) and EC was determined. The substrate solution EC of Osmocote Plus™-fertilized PB began to decline sooner than that of the other fertilizers. Overall, these three experiments led to the conclusion that Osmocote Plus™ nutrient release declines more quickly than does Polyon™ or Nutricote™, while Polyon™ has the most gradual nutrient release pattern. The objective of the second set of experiments was to determine the effects of temperature on short-term nutrient release. In Expt. 4, 14 g of each PCF was maintained at 40°C until ~33% of the NO3-N content in Osmocote Plus™ was expended. Each fertilizer was then placed in a sand column and leached with distilled water at ~100 mL/h. Columns were then incrementally subjected to a simulated diurnal container temperature change from 20°C to 40°C and back to 20°C over a period of 20 h. Leachate was collected hourly and measured for soluble salts and NO₃-N and NH₄-N concentrations. For all fertilizers, nutrient release increased and decreased with the respective increase and decrease in temperature. Nutrient release patterns of the three fertilizers were significantly different, with Osmocote Plus™ showing the greatest overall change in nutrient release between 20°C and 40°C and Nutricote™ the least. In Expt. 5, PCFs were placed in flasks of distilled water in constant temperature baths. Initially, fertilizers were held at 40°C for three days and then at temperatures of 22, 28, 34, or 40°C for two weeks. Fertilizer solutions were poured off after the first and second weeks. Only solutions from the second week were analyzed for soluble salts and NO₃-N, NH₄-N, P, and K concentrations. For Osmocote Plus™ and Polyon™, there was a 29% to 86% (depending on the nutrient measured) mean increase in nutrient release between 22°C and 40°C, whereas for Nutricote™ there was a 345% to 364% (depending on the nutrient measured) mean increase. The overall mean increases in nutrient release in Expt. 4 were between 1032% and 4023%, whereas the mean increases in Expt. 5 were between 29% and 364%. In summary, the second set of experiments found that PCF nutrient release was highly sensitive to diurnal temperature changes. / Master of Science

No description available.

Effects of gastrointestinal transit on plasma concentrations of drugs from enteric-coated pellet formulations were demonstrated using pharmacokinetic models describing plasma concentrations of drugs from various enteric-coated pellet formulations. Gastric emptying time, lag time of emptying, and drug release rate from pellets in the small intestine, along with other pharmacokinetic parameters of drugs, were used to construct pharmacokinetic models. The models were then evaluated by comparing simulated plasma concentrations of model drugs from Monte Carlo simulations to observed plasma concentrations of these drugs from the literature. Results showed that the models described plasma concentrations of drugs from enteric-coated pellet formulations very well. Pharmacokinetic models describing plasma concentrations of drug from mixed immediate-release and enteric-coated pellet formulations were also used in simulations of bioequivalence studies. Results from the research are very useful in designing generic products of mixed pellet formulation and in refining or selecting the final product for actual bioequivalence study. Development of crushable enteric-coated formulations was presented. Nonpareil sugar pellets were spray-loaded with mixed amphetamine salts. Drug-loaded pellets were subsequently spray-coated with enteric polymer, hydrophilic gel-forming polymer, enteric polymer and/or mixture of insoluble polymer and hydrophilic polymer. The resulting pellets were then spray-coated with disintegrant and compressed to form crushable tablets. Dissolution testing of both non-compacted crushable enteric-coated tablets and crushed tablets showed that the intact crushable tablet formulations and the crushed tablet formulations were able to prevent the majority of the drug from being released in a simulated gastric dissolution medium within first 2 hours. Concept and formulations of "leaky" enteric-coated pellets were presented. "Leaky enteric-coated pellets" formulation is defined as enteric-coated pellets that allow some of the drug to be released from the formulation in acidic dissolution medium. Different approaches of making leaky enteric-coated pellets using spray-coating techniques were presented. Plasma concentrations of drug from leaky enteric-coated pellet formulations were simulated using computer simulations. The present research was based on the hypothesis that leaky enteric-coated pellets formulations were able to provide sustained-release effect on plasma concentration profiles of drugs that have the absorption window without jeopardizing their bioavailability or with improved bioavailability. / Graduation date: 2005

Preparative-scale protein separations have always been critical to the advancement of the life sciences. Among preparative-scale separation techniques, isoelectric trapping (IET) promises efficient separations and high production rates. This dissertation focuses on the improvement of two aspects of preparative-scale IET protein separations: the instrumentation used and the monitoring of the separation. The first aspect (preparative-scale) is the IET device: the improvement of a multicompartmental electrolyzer (MCE) to increase the efficiency and production rate of IET separations. The redesign focused on three major areas: (1) the sealing system, (2) the configuration of the liquid flow path, and (3) the cooling system. The second aspect (analytical-scale) is the monitoring of the IET separation: the design and manufacture of durable surface-modified capillaries which provide controlled, variable anodic and cathodic electroosmotic flow (EOF) to help develop, plan, and monitor the IET separations.

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.

No description available.

Preparative-scale protein separations have always been critical to the advancement of the life sciences. Among preparative-scale separation techniques, isoelectric trapping (IET) promises efficient separations and high production rates. This dissertation focuses on the improvement of two aspects of preparative-scale IET protein separations: the instrumentation used and the monitoring of the separation. The first aspect (preparative-scale) is the IET device: the improvement of a multicompartmental electrolyzer (MCE) to increase the efficiency and production rate of IET separations. The redesign focused on three major areas: (1) the sealing system, (2) the configuration of the liquid flow path, and (3) the cooling system. The second aspect (analytical-scale) is the monitoring of the IET separation: the design and manufacture of durable surface-modified capillaries which provide controlled, variable anodic and cathodic electroosmotic flow (EOF) to help develop, plan, and monitor the IET separations.