Reactive forms of oxygen such as hydrogen peroxide cause single-strand breaks in DNA. Most of the methods for estimating such breakage and subsequent repair are designed for eucaryotic cells and methods for use with bacteria are needed. Accordingly, a method based on alkaline gel electrophoresis of DNA was developed and tested with isogenic strains of Escherichia coli deficient in one or more DNA repair enzymes, viz., recA (recA), exonuclease III (xthA), DNA polymerase I (po/A) or DNA polymerase I plus exonuclease I] (polA-xthA). For DNA analysis of single-strand breaks, samples from a cell suspension were removed at 2 min intervals following an initial 15 min exposure to 20 mmol l⁻¹ hydrogen peroxide. Catalase was added and the cells were embedded in blocks of low-melting point agarose and lysed to liberate their DNA . After alkaline gel electrophoresis, photographs of the gels were taken and the lengths of the distributions of DNA fragments were measured with a scanner and computer. The wild type and recA strain showed only a moderate increase in the length of the DNA distribution whereas the remaining strains all showed a large increase in the length of the distributions. The lengths of the distributions were correlated with cell survival at the same concentration of H₂O₂ and with the importance of particular DNA repair enzymes. Alkaline gel electrophoresis appears to be a relatively simple method for analyzing the level of H₂O₂-caused DNA damage and repair in E. coli. / Master of Science

Region detection can be defined as identifying connected components in an image. Connected component labelling is an important part of performing feature extraction. Industrial applications performing online image analysis may require a real-time implementation of a region labelling algorithm (typically processing 30 frames per second). Using application specific hardware or VLSI implementations to solve the problem sacrifices the ability to alter the design tradeoffs dynamically. General purpose software platforms are considerably slower for the task. While the massively parallel machines can accomplish the job without sacrificing the general purpose nature, they are highly un-economical. This research discusses an algorithm which was implemented on a FPGA-based reprogrammable hardware platform and demonstrates the effectiveness of custom computing platforms for high performance real-time image processing. The input to the system is VHDL, so the design can be modified very easily. Also, a variety of applications can be run on the system unlike application specific hardware or VLSI implementations. / Master of Science

Approximately one in seven women have endometriosis, a disease that may cause pain and/or infertility. Therefore, many women experience the stress of this disease in their life and yet little is known about how they cope with this stress. This study focuses on the coping resource of social support. The social support experiences of forty-six women, who participate in an endometriosis support group on the Internet, were examined. A questionnaire was designed to explore the social support experiences of these women in four relationship categories: spouse/partner, friends/extended family, others with endometriosis, and health care providers. In written responses, these women shared many poignant and compelling stories about their struggles with the disease and their experiences with social support relative to the disease. The participants’ responses were analyzed for themes. Overall themes that emerged from the analysis include: the participants wanted to be listened to and believed, they wanted their support network to be knowledgeable about endometriosis, they wanted others to understand the symptoms of the disease, and they wanted their support system to share information about the disease. / Master of Science

Code optimizing techniques can perform significantly better if the program control flow can be predicted and the frequently invoked or. computationally intensive blocks can be identified. However, generating an execution profile, apart from being time consuming, is limited to sections of the code using the chosen input set and is data-dependent. Moreover, gathering profile data might not be possible in some environments. This thesis describes a methodology to perform static analysis of the program, generates an annotated flow graph depicting the control and data dependence of the input program and predicts its timing behavior using two different approaches. The tool can be integrated into a compiler for a custom computing machine for codesign synthesis. The timing information can be used effectively by the code optimizer to identify portions of the code to be executed in hardware from the portions to be executed in software. The problem of loose time bounds in complex programs due to conditional branches and data dependent loops has been addressed by introducing an interface for high level user execution information. / M.S.

M.S.

M.S.

Intermetallic compounds are being considered for possible high temperature aerospace applications, yet they are often hampered by a lack of room temperature ductility. However, a B2 phase in the ternary Nb-Ti-Al system has been discovered which exhibits considerable ductility at room temperature. Three different alloy compositions which exhibit this ductile phase were examined by computer simulation using the Embedded Atom Method. The site occupancies of the ternary B2 structure were determined and linked to the defect interaction energies of Ti and Al in Nb. The defect structures examined in each intermetallic included anti-phase boundaries, twins, pseudo-twins, free surfaces and dislocations. An estimation of the ductility of these intermetallics was made using both the Rice and ZCT ductility criteria. Comparison of the criteria with values for other B2 intermetallics leads to the conclusion that the simulated Nb-Ti-Al B2 compounds are ductile. / M.S.

M.S.

A logit model was employed to determine the relative importance of socioeconomic factors influencing the misuse of pesticides on vegetables in Central Luzon, Philippines. The analysis revealed an increase in pesticide misuse associated with the following factors: a high value placed on advice from a chemical company representative; membership in a cooperative, village or farmers' association; and visits by a Department of Agriculture technician to discuss non-pesticide means of controlling vegetable pests. Those factors which reduced pesticide misuse included: increased age and educational attainment; access to integrated pest management training through the Farmer Field School; receiving credit from a cooperative; and agreement with the perception that killing natural enemies could hasten pest infestation. The effective rate of protection on nine pesticides was calculated to quantify the net effects of pricing and exchange rate policies on the degree of subsidy or tax experienced by pesticide importers. It was found that the effective rate of protection for the nine pesticides was between negative 12 and 25 percent when the exchange rate effects were accounted for. However, the rate of protection became more negative when the equilibrium exchange rate was used indicating that exchange rate overvaluation offset the tax pesticide importers face. In addition, the analysis indicated that pricing and exchange rate policies have created a six to eight percent subsidy on pesticide prices for the years 1989 to 1993. This subsidy on pesticides has increased both consumer and producers welfare and the quantity of pesticides used in the Philippines. / Master of Science

Microwave heating has been considered for the heating of a coating in contact with a temperature-sensitive substrate. A methodology was developed to conduct a microwave heating feasibility study for a candidate system. The study consisted of dielectric property determination, development of heat transfer models to determine the heat generation rates necessary to achieve a desired temperature distribution, calculation of the required electric field strength given the dielectric properties and heat generation rates, and examination of whether the microwave heating could be performed with available equipment. Sol-gel processing of a 1Microwave heating has been considered for the heating of a coating in contact with a temperature-sensitive substrate. A methodology was developed to conduct a microwave heating feasibility study for a candidate system. The study consisted of dielectric property determination, development of heat transfer models to determine the heat generation rates necessary to achieve a desired temperature distribution, calculation of the required electric field strength given the dielectric properties and heat generation rates, and examination of whether the microwave heating could be performed with available equipment. Sol-gel processing of a 1µm-thick boehmite coating on a non-woven polypropylene substrate was chosen as the candidate system. It was desired to selectively heat the boehmite to 2500 C without damaging the polypropylene, which degrades at 1500 C. Dielectric measurements indicated that the boehmite could be heated to 2500 C using microwave energy. Microwave heating of the system was then modeled using three techniques: an approximate analytical solution based on Composite Green's Functions, a finite difference solution, and an approximate lumped capacitance solution. It was determined that the heat generation rates necessary to produce the desired temperature distribution would require field strengths beyond practical limitations for the specific boehmite-polypropylene system considered. -thick boehmite coating on a non-woven polypropylene substrate was chosen as the candidate system. It was desired to selectively heat the boehmite to 2500 C without damaging the polypropylene, which degrades at 1500 C. Dielectric measurements indicated that the boehmite could be heated to 2500 C using microwave energy. Microwave heating of the system was then modeled using three techniques: an approximate analytical solution based on Composite Green's Functions, a finite difference solution, and an approximate lumped capacitance solution. It was determined that the heat generation rates necessary to produce the desired temperature distribution would require field strengths beyond practical limitations for the specific boehmite-polypropylene system considered. / Master of Science