Eight methods were evaluated to assess potential soil S-supply to crops, and particularly to identify deficiencies in S-supply. Of these methods, three novel bioassays (sulphate production from incubation of amino acid-amended and elemental S-amended soil, and tissue S-concentrations of plants) proved better indicators (based on correlation with field crop response to S-fertilization) of S-supply than data from traditional chemical extractions. The above experiment was limited by the few soils (10) for which field S-response data was available. A second experiment was conducted with 54 soils using 6 of the 8 methods tested initially. Although no field data was available, a vast array of statistical procedures were performed which demonstrated that bioassays of soil S-supply produced related data sets but with no relation to data sets from chemical extractions. Consistent outlying of data for 2 Bangladesh soils in this experiment suggested an interesting apparent difference in the S-supply characteristics of temperate and tropical soils. The next phase of research aimed to investigate fertilizer S-supply to crops in soil. Firstly, the performance of gypsum and elemental-S were compared. Increased grain yield of barley was only achieved by gypsum application, although enhanced trace element nutrition from elemental S suggested that S-fertilization of crops influences the quality as well as the quantity of crop product. In a further pot experiment, enhancement of barley grain yield due to fertilizer S application was found only for crops grown on S-deficient soil. By labelling gypsum with ³⁵S, the fate of fertilizer in a soil/grass system was assessed. Over 4 cuts in a 12 week period, grass removed about half of applied ³⁵S with a further quarter left in the soil. The remainder was both in the roots and lost from the system. Less than 1 per cent of applied ³⁵S was recovered from microbial biomass. The final experiment investigatead the method for determining S-content of the soil microbial biomass, highlighting the need for effective chloroform removal from soil and the importance of a suitable control (a non-fumigated but evacuated soil was suggested).

Sphingomyelin (SM), a sphingolipid that is concentrated in the extracellular leaflet of the plasma membrane, can interact with cholesterol to form more ordered raft domains. The hydrolysis of SM by sphingomyelinase (SMase) generates ceramide and may redistribute cholesterol molecules to other less ordered domains. I employed carbon fibre amperometry to examine whether SM hydrolysis affected the kinetics of release of catecholamines from individual granules of rat chromaffin cells when exocytosis was triggered by elevated extracellular [K+]. Similar to cholesterol overload, SMase treatment selectively increased the proportion of stand-alone foot signals and the duration of the pre-spike foot signals; both effects could be reduced by extraction of cellular cholesterol. In contrast, the application of an exogenous ceramide did not mimic the effects of SMase. My results suggest that SMase treatment liberated cholesterol from lipid rafts to increase the persistence of the semi-stable fusion pore before the onset of rapid dilation.

No description available.

The present study is concerned with the feasibility of simulating the release and transport of a ``generic' pollutant within an urban area. The motivation behind this effort lies in the need for accurate and timely predictions of the effects of a pollutant release in a densely populated region, in order to coordinate relief and/or evacuation efforts or design rapid-response scenarios in the event of a possible accident. In order to achieve the above goal, following geometrical, physical, and algorithmic steps have to be taken, generation of a three-dimensional grid, numerical solution of the governing fluid dynamics equations, and numerically solving the transport (reaction/advection/diffusion) equations for a generic pollutant. Some preliminary results will be presented at this time. A sample of representative results will be shown for the generation and transport of a generic pollutant ``plume', using different starting wind conditions and release points. Future efforts in this endeavor will focus on obtaining reasonably accurate simulations of pollutant transport at a reasonable computational price. Specifically, ``reduced' models for the geometry and/or the governing equations will be investigated.

No description available.

Over the past 40 years, several procedures have been proposed for characterizing ideal flotation behavior. These procedures, known as release or tree analysis, generally involve multi-stage flotation in batch, laboratory flotation cells using various combinations of rougher, cleaner, and scavenger configurations. Although some of these procedures have been experimentally compared, there remains considerable controversy as to which approach best approximates the ideal flotation response. In this investigation, modeling and simulation techniques are used in conjunction with experimental studies to compare three procedures commonly used for characterizing flotation behavior. These procedures include timed release analysis, simplified release analysis, and tree analysis. Timed release analysis is shown to produce superior results to simplified release analysis and tree analysis; although simplified release analysis appears to be best suited for locating the "elbow" of the grade-recovery curve. In no case, do any of these techniques approximate a perfect separation. A novel technique, known as reverse release analysis, is described and demonstrated to be superior to the other three procedures. Finally, a theoretical methodology for obtaining the true ideal separation curve is presented. / Master of Science

No description available.

This dissertation describes the development of a new sustained release formulation of nifedipine. The new formulation was developed by coating commercially available immediate release soft elastic gelatin capsules using a spray coating technique with two different polymeric combinations. Dissolution studies were conducted and showed that controlled release of nifedipine was obtained by increasing the ratio of the water insoluble polymer in the coat and increasing the percent weight gain of the coating. Simulated plasma concentration versus time profiles after administration of 30 mg dose of selected formulations showed a prolonged nifedipine release with concentrations above the minimum effective concentration for up to 12 hours. Bioavailability and bioequivalence of tableted test formulation of verapamil HCL was determined in 8 volunteers and compared to Covera HS® under fed and fasting conditions. The 90% confidence intervals for individual percent ratios of the Cmax, AUC₀₋₅₈ and AUC₀ were not within the range of 80 - 125% in both fed fasted states, suggesting that these formulations are not bioequivalent. the bioavailability of verapamil from the new formulation was higher state but this effect was not statistically significant. Pharmacokinetics of terbinafine administered orally at single doses of 15, 30, 60 and 120 mg were determined in raptors to recommend an appropriate dosing scheduled for terbinafine in the treatment of Aspergillosis. Calculation of steady state trough terbinafine plasma concentration after administration of daily doses of 15 or 30 mg/day showed that 30 mg daily dose of terbinafine administered orally in raptors produces a steady state trough terbinafine plasma concentration above the minimum inhibitory concentration (MIC) of(0.8 1.6) µg/ml against aspregillus fumigatus. From the data, 30 mg per day oral dose of terbinafine should be the recommended dose for treatment of aspergillosis in raptors. Approximate pharmacokinetic linearity of terbinafine was demonstrated for AUC[subscript 0-t] in the dose range of 15 120 mg while non-linearity for Cmax in the same dose range was demonstrated using the power model. / Graduation date: 2005

As all the physiological processes in our body are controlled by multiple biomolecules, comprehensive treatment of certain disease conditions may be more effectively achieved by administration of more than one type of drug. Thus, the primary objective of this research was to develop a multilayered, polymer-based system for sequential delivery of multiple drugs. This particular device was designed aimed at the treatment of periodontitis, a highly prevalent oral inflammatory disease that affects 90% of the world population. This condition is caused by bacterial biofilm on the teeth, resulting in a chronic inflammatory response that leads to loss of alveolar bone and, ultimately, the tooth. Current treatment methods for periodontitis address specific parts of the disease, with no individual treatment serving as a complete therapy. The polymers used for the fabrication of this multilayered device consists of cellulose acetate phthalate (CAP) complexed with Pluronic F-127 (P). After evaluating morphology of the resulting CAPP system, in vitro release of small molecule drugs and a model protein was studied from both single and multilayered devices. Drug release from single-layered CAPP films followed zero-order kinetics related to surface erosion property of the association polymer. Release studies from multilayered CAPP devices showed the possibility of achieving intermittent release of one type of drug as well as sequential release of more than one type of drug. Mathematical modeling accurately predicted the release profiles for both single layer and multilayered devices. After the initial characterization of the CAPP system, the device was specifically modified to achieve sequential release of drugs aimed at the treatment of periodontitis. The four types of drugs used were metronidazole, ketoprofen, doxycycline, and simvastatin to eliminate infection, inhibit inflammation, prevent tissue destruction, and aid bone regeneration, respectively. To obtain different erosion times and achieve appropriate release profiles specific to the disease condition, the device was modified by increasing the number of layers or by inclusion of a slower eroding polymer layer. In all the cases, the device was able to release the four different drugs in the designed temporal sequence. Analysis of antibiotic and anti-inflammatory bioactivity showed that drugs released from the devices retained 100% bioactivity. Following extensive studies on the in vitro sequential drug release from these devices, the in vivo drug release profiles were investigated. The CAPP devices with different release rates and dosage formulations were implanted in a rat calvarial onlay model, and the in vivo drug release and erosion was compared with in vitro results. In vivo studies showed sequential release of drugs comparable to those measured in vitro, with some difference in drug release rates observed. The present CAPP association polymer-based multilayer devices can be used for localized, sequential delivery of multiple drugs for the possible treatment of complex disease conditions, and perhaps for tissue engineering applications, that require delivery of more than one type of biomolecule.

No description available.