Philosophiae Doctor - PhD / In South Africa there are currently 44.8 million people under the age of 20 years accounting for approximately 44% of the total South African population. Literature has indicated a number of lifestyle behaviors which account for most of the mortality, morbidity and social problems in adolescents. These behaviors include tobacco uses, unhealthy dietary behaviors, physical inactivity, alcohol and other drug use, risky sexual behaviors, and behaviors that result in unintentional and intentional injuries. Adolescent women are profoundly affected by a number of health risks related to their behavior. Many of these also affect their male peers such as smoking, drinking, use of other drugs, and violence, but have a special effect on women because of either higher prevalence or a relationship to other risks. Another set of risky behaviors are those uniquely linked to women's reproductive potential. The health of young people today, and the adults they will become, is critically linked to the health related behaviors they choose to adopt. It is thus vitally important for health professionals to address adolescent health issues with targeted health-related interventions and effective health-promoting programmes. The heightened adverse health effects of many risk behaviors for adolescent women and the unique risks associated with being female point to the need for gender-specific prevention efforts. The purpose of this study was to investigate health risk behaviours among black female high school learners. The study used a mixed method approach, specifically the sequential explanatory strategy. Quantitative data was collected using two self-administered questionnaires assessing six domains of health risk behaviours including cigarette use, alcohol use, drug use, sexual activity, behaviours leading to violence and behaviours related to physical activity.

Cell proliferation plays an important role in multistage chemical carcinogenesis. Again, several reports demonstrated that upregulation of metallothionein (MT) expression is associated with increased cell proliferation that may contribute to the pathogenesis of preneoplastic phenotype to frank malignancy. In this study, we evaluated the roles of early DNA damage, altered expressions of liver MT and Ki-67 nuclear antigen, and altered hepatic levels of zinc (Zn) and copper (Cu) on cell proliferation and the progression of hepatocarcinogenesis through premalignant, late premalignant and malignant transformation phases in male Sprague-Dawley rats. We have further studied the association between MT expression and cell proliferation in hepatocarcinogenesis. There was substantial induction of DNA single-strand breaks (SSBs) (P < 0.001) and development of hepatocellular premalignant lesions along with significant decrease in hepatic levels of Zn and increase in Cu content following a single, necrogenic, intraperitoneal (i.p.) injection (200 mg/Kg body weight) of diethylnitrosamine (DEN) at week 4 of the experimental protocol. Moreover, DEN + phenobarbital (PB)-treatment significantly elevated MT-, Ki-67-, and BrdU-immunoexpressions along with their immunolabeling indices. Furthermore, positive correlations between MT- and Ki-67- labeling (P = 0.0006) at various time intervals, as well as, between MT immunoreactivity and 5'-bromo-2'-deoxyuridine-labeling index (BrdU-LI) (P = 0.0007) indicate that, MT expression might be associated with Ki-67 expression and cell proliferation thereby. The study suggests that DEN treatment may lead to alteration of Zn and Cu levels resulting in early DNA damage along with elevation of MT expression that may ultimately lead to hepatic cell proliferation. The results thus provide evidence in support of the role of MT as a potential positive regulator of cell growth during the early stages of hepatocellular transformation in rats.

Carcinogen-induced formation of DNA adducts and other types of DNA lesions are the critical molecular events in the initiation of chemical carcinogenesis and modulation of such events by chemopreventive agents could be an important step in limiting neoplastic transformation in vivo. Vanadium, a dietary micronutrient has been found to be effective in several types of cancers both in vivo and in vitro and also possesses profound anticarcinogenicity against rat models of mammary, colon and hepatocarcinogenesis. Presently, we report the chemopreventive potential of vanadium on diethylnitrosamine (DEN)-induced early DNA damages in rat liver. Hepatocarcinogenesis was induced in male Sprague-Dawley rats with a single, necrogenic, intraperitoneal (i.p.) injection of DEN (200 mg/kg body weight) at week 4. There was a significant induction of tissue-specific ethylguanines, steady elevation of modified DNA bases 8-hydroxy-2′-deoxyguanosines (8-OHdGs) (P < 0.0001; 89.93%) along with substantial increment of the extent of single-strand breaks (SSBs) (P < 0.0001) following DEN exposure. Supplementation of 0.5 ppm of vanadium throughout the experiment abated the formations of O6-ethylguanines and 7-ethylguanines (P < 0.0001; 48.71% and 67.54% respectively), 8-OHdGs (P < 0.0001; 81.37%), length:width (L:W) of DNA mass (P < 0.01; 62.12%) and the mean frequency of tailed DNA (P < 0.001; 53.58%), and hepatic nodulogenesis in preneoplastic rat liver. The study indicates that 0.5 ppm vanadium is potentially and optimally effective, as derived from dose-response studies, in limiting early molecular events and preneoplastic lesions, thereby modulating the initiation stage of hepatocarcinogenesis. Vanadium is chemopreventive against DEN-induced genotoxicity and resulting hepatocellular transformation in rats.

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The dimensional stability of oriented strand board (OSB) can be affected by processing variables. This study investigated the water absorption and thickness swelling of OSB based on its board layup, type of resin, resin content, and percentage of wax. The experiment data was measured inside an environmental chamber from oven dry (OD) conditions to 80% relative humidity (RH), and from OD to 90% RH. The results suggest that single layer boards and isocyanate resin provide greater dimensional stability to OSB than three layer boards or phenol formaldehyde resin. In addition, the water absorption and thickness swell data were effectively modeled by equations developed for wood fiber/polymer composites.

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Security is a major concern is today's online world. As online activities become increasingly sensitive, service providers rely on security protocols to ensure confidentiality, integrity and authentication of their users and data. Greater assurance is provided when these protocols are verified to be correct. Strand Spaces is a method to formally analyze security protocols. The arguments are based on the messages being transmitted and received while assuming that the underlying cryptographic primitives are secure. This thesis demonstrates that the protocols Luau, pwdArmor and Kiwi are secure using Strand Spaces methodology.

Much Research on composite solid propellants has been performed over the past few decades and much progress has been made, yet many of the fundamental processes are still unknown, and the development of new propellants remains highly empirical. Ways to enhance the performance of solid propellants for rocket and other applications continue to be explored experimentally, including the effects of various additives and the impact of fuel and oxidizer particle sizes on burning behavior. One established method to measure the burning rate of composite propellant mixtures in a controlled laboratory setting is to use a constant-volume pressure vessel, or strand burner. To provide high-pressure burn rate data at pressures up to 360 atm, the authors have installed, characterized and improved a strand burner facility at the University of Central Florida. Details on the facility and its improvements, the measurement procedures, and the data reduction and interpretation are presented. Two common HTPB/AP propellant mixtures were tested in the original strand burner. The resulting burn rates were compared to data from the literature with good agreement, thus validating the facility and related test techniques, the data acquisition, data reduction and interpretation. After more than 380 successful recordings, an upgraded version of the strand burner, was added to the facility. The details of Strand Burner II, its improvements over Strand Burner I, and its characterization study are presented.

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