Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 81-82). Also available in electronic version.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Ph.D.

No description available.

No description available.

Class of 2012 Abstract / Specific Aims: Assess the stability and sterility of various extemporaneously compounded captopril solution in different storage conditions. Methods: Extemporaneously prepared captopril standards and solutions tested in a high performance liquid chromatography instrument collected data on stability. In addition, physical appearance, bacterial growth and pH data were also collected. Main Results: Stability data was assessed with extemporaneously prepared captopril solutions prepared with standardized captopril powder, captopril tablets and captopril tablets with ascorbic acid included. Stability was defined as retention of at least 90% of the initial captopril concentration. Overall, all preparations were stable when stored at 4°C but only the tablet preparation was stable when stored at 25°C and 40°C. No bacterial growth was observed with any of the captopril solutions. Conclusions: Extemporaneously prepared captopril solution appears to have a shelf-life of at least 28 days when stored at 4°C.

Furosemide (Lasix®), abbreviated as FR and also known as frusemide, is a drug used for renal problems and treatment of cardiac edema. Various polymorphic forms of furosemide, dependent upon the method of preparation and thermal treatment, have been reported. The main thermal decomposition product of furosemide has been identified as saluamine. The dissolution properties of furosemide have also been reported to be improved by complexation with beta-cyclodextrin. Photostabilities of the different crystal forms have been studied. Differential scanning calorimetry (DSC) and thermogravimetry (TG) have been used to examine the thermal behaviour of furosemide itself and of its physical and kneaded mixtures with betacyclodextrin (BCD) and gamma-cyclodextrin (GCD). There is strong evidence from DSC that complex formation between FR and GCD occurs. This is supported by IR and XRD data. Decreases in the intensity and broadening of the characteristic carbonyl (1660 cm'l) and amine (1588 cm⁻¹) bands in the kneaded mixture, compared to the physical mixture, were observed with IR. X-ray diffraction results for the 1:3 molar ratio FR/GCD kneaded mixture showed a halo diffraction pattern characteristic. of an amorphous solid and did not resemble patterns from the drug, or the gamma, cyclodextrin, or the physical mixture. Photostability studies have been conducted on solid furosemide and its mixtures with GCD or BCD. An HPLC method was developed to determine the amount of drug remaining after exposure and the presence of any degradants. Results indicated that about 10% degradation of the drug occurred during exposure for 16 hours at 550 W/m², with the appearance of polar degradants. Although IR and DSC results for the 1:3 molar ratio FR/GCD kneaded mixture showed a probable strong interaction between FR and GCD, the photostability of FR was decreased. The 1 :3 molar ratio FR/BCD kneaded mixture showed less photo-degradation than the 1:3 molar ratio FR/GCD mixture under similar conditions, suggesting that inclusion of the drug molecule (FR) is different in the two cyclodextrins.

No description available.

In this thesis Liapunov's direct method is applied to transient stability study of power systems. Szego's method is applied to a second order power system in chapter two and a quadratic Liapunov function applied to the same system in chapter three. The hypervolume enclosed by the quadratic V-function is maximized. Changes in the time derivative of the quadratic V function are then made to meet the conditions of Liapunov V and V functions. Finally a maximized modified Liapunov function is constructed from a tentative quadratic function for a three-machine system. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Ceramic varistors based on ZnO, Bi2O3, Sb2O3, MnO and Co3O4 were prepared by the mixed oxide route. After milling the powders, disc shaped samples were pressed and sintered for 2 hours at temperatures in the range 950°C to 1250°C. Products were characterised in terms of phase development and microstructure by X-ray diffraction and scanning electron microscopy; electrical characterisation included current-voltage (I-V), capacitance-voltage (C-V) and degradation behaviour. Most varistors contained a three phase microstructure comprising ZnO grains (3–54 μm in size), a Bi-rich grain boundary phase and a spinel phase. Product densities were approximately 5.45 g cm-3, and nonlinear coefficients were typically in the range 5 to 53. By selective removal of either Sb2O3, or MnO or Co3O4, the role of individual components was investigated. The absence of Sb2O3 encouraged grain growth (to 40 μm) but reduced nonlinearity (to 5) and degraded the stability. The absence of Co3O4 improved the stability whilst the absence of MnO reduced the nonlinear coefficient and leakage current. The use of attrition milling yielded powders of small particle size (0.3 μm). The resulting sintered varistors exhibited a slightly smaller grain size (~ 5 μm) lower nonlinear coefficients (~ 30) but higher breakdown fields and leakage currents. Samples sintered at high temperatures (1050°C to 1250°C) degraded under electrical stress more slowly than the samples sintered at low temperature (950°C). Al-doping enhanced the nonlinearity but reduced the stability. In contrast Ag-doping reduced the nonlinearity but improved the ageing behaviour. An appropriate combination of Al and Ag doping led to varistor improvements in both nonlinearity and stability. The optimum aluminium nitrate and silver oxide levels for the varistor composition studied were found to be 500 ppm and 250 ppm, respectively. C-V measurements on this material gave barrier heights of ~ 1.7 V, and donor densities of 1.3x10^18 cm-3. One batch of samples was prepared Ga2O3 additions of 750 – 4000 ppm. Doping with Ga caused a significantly decrease in grain size to ~ 6 μm), and reduced the nonlinear coefficients (to ~25) but increased the stability in terms of breakdown fields and leakage currents.