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.

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.

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

The development of a power electronic circuitry for a flywheel energy storage system is discussed in the following aspects. First, due to the nature of permanent magnet brushless DC motor/generator, the operation of three-phase voltage source inverter/rectifier can be simplified to that of a bi-directional DC-DC converter, allowing the use of mostly analog control. Second, there is a problem associated with the existing six-step brushless DC motor/generator control in the generator mode. A twelve-step control scheme is proposed to solve this problem. Third, high-switching frequency is necessary for the flywheel charger/discharger in order to reduce the size/weight of the system and to synthesize the high-frequency motor/generator current waveforms. A working prototype demonstrates that a high efficiency can be achieved at 1 ~O-kHz switching frequency by the innovative ZVT soft-switched three-phase inverter/rectifier. / Master of Science

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is well known for its immunotoxic effects particularly on the thymus as well as on T and B lymphocyte functions. Previous studies have suggested that TCDD may induce apoptosis in thymocytes although its demonstration in vivo has met with limited success. TCDD has also been shown to alter the major histocompatibility complex (MHC)-encoded molecules, however, its role in immunotoxicity is not clear. In this study, we investigated the role of Fas (CD95), an important molecule involved in the induction of apoptosis, on TCDD-mediated immunotoxicity using mice bearing homozygous lpr mutation which leads to failure of expression of Fas. When TCDD was administered orally at 0, 0.1, 1.0, or 5.0 pg/kg body weight for 11 days, it was found to be less toxic to the thymocytes from C57BL/6 lpr/lpr mice (Ah-responsive, Fas⁻) when compared to C57BL/6 +/+ mice (Ah-responsive, Fas⁺). Similar results were obtained when peripheral T cell responsiveness to antigenic challenge with conalbumin was studied in these mice. When mice that differed only at the MHC were compared for immunotoxic effects of TCDD, it was noted that B10.D2 (Ah-responsive, H-2ᵈ) were more sensitive to TCDD-mediated thymic atrophy and peripheral T cell dysfunction when compared to B10 mice (Ah-responsive, H-2ᵇ). In all TCDD-sensitive strains tested, the thymic atrophy was accompanied by a uniform depletion of all four subsets of T cells (CD4⁺, CD4⁺CD8⁺, CD4⁻CD8⁻, and CD8⁺). Furthermore, in these strains, TCDD suppressed the antigen-specific peripheral T cell responsiveness but not the responsiveness of naive resting T cells to polyclonal mitogens. Lastly, using cell-mixing experiments, it was demonstrated that TCDD directly affected the T cells responding to conalbumin but not the antigen presenting cells (APCs). Together our studies demonstrate that although Ah locus plays the primary role determining the toxicity of TCDD on the T cells, there are secondary factors such as expression of Fas or the MHC-phenotype which may play an important role in TCDD-mediated immunotoxicity. The role of Fas further suggests that TCDD may induce toxicity in T cells by triggering apotosis. / Master of Science

The advent of the laser has yielded many applications in modern science. One which has recently gained popularity in the area of structural dynamics is the use of a Scanning Laser Doppler Vibrometer (SLDV) to measure the dynamic response of vibrating structures. Essential in the optimal use of such a device is an understanding of the idiosyncrasies and operating parameters which may affect the quality of the experimental data. Specifically, the quality of the data taken with an SLDV system may contain noise which, for the purpose of this investigation, will be defined as "laser noise". It is the purpose of this thesis to characterize the laser noise, and investigate its potential sources. Characterization of laser noise as a function of the range of velocities is presented. An investigation of the speckle pattern motions which correspond to the areas prone to the laser noise and the effect of increased retroreflective surface treatments are explored. Additionally, the effect of three user defined parameters of the SLDV system are examined. In order to quantify the effect of the above on the experimental data, a statistical representation of the quality of the scan data is introduced. The work presented in this thesis provides insight into the physical mechanisms and phenomenon which contribute to the occurrence of laser noise. Additionally, some guidelines which will help the experimentalist use the SLDV system more optimally are presented. Also, some recommendations on future improvements of the SLDV are made, along with proposals for future research. / Master of Science