This thesis investigates the influence of nonrandom species loss on the structure and functioning of trophic floodplain lagoons. Two experiments were conducted based on different realistic scenarios of biodiversity loss using multitrophic fish assemblages derived from long-term survey data. Loss of fish diversity influenced overall ecosystem multifunctionality of these lagoons through complex multitrophic interactions throughout the aquatic food web. These results indicate that biodiversity loss from diverse multitrophic ecosystems can influence ecosystem structure and function and likely deviate from simplified food chain dynamics or patterns that emerged from single trophic level studies.

Microwave processing has been studied as an alternate heating technique over conventional heating for industrial applications. Some advantages include quicker and more uniform heating. Also, microwave energy offers the advantage of localized heating and smaller-sized equipment. Many ceramics, however, are difficult to heat using microwave energy by reason of the strong temperature dependence of the dielectric loss. The ability of a ceramic to absorb microwave energy, a measure of its dielectric loss, increases with temperature which makes the material more susceptible to thermal runaway. The purpose of this research is to develop a model that accurately reproduces experimental data and can be used to explore new applicator designs for continuous processing of such ceramics. A two-dimensional numerical model, created for this purpose, assumes that the ceramic is a circular cylinder that moves either longitudinally through a microwave cavity of given dimensions. By adjusting the electromagnetic field so that the absorbed power matches the measured power, the model successfully imitates experimental results and avoids thermal runaway while achieving high temperatures. / Master of Science

Objective: To investigate hearing loss among perinatally HIV-infected (PHIV+) adolescents on antiretroviral therapy (ART), and HIV-non-infected (HIV-) adolescents in Cape Town, South Africa. Methods: A cross-sectional analysis was carried out to describe the prevalence, nature and predictors (demographic, past medical history, clinical findings) of hearing loss in adolescents between 9 and 14 years of age. Screening pure-tone air-conduction (AC) thresholds above 30 decibels (dB) were considered to be indicative of debilitating hearing loss. Statistical analysis included univariate analysis and multivariate logistic regression. Results: The cross-sectional analysis included data from 540 participants; consisting 273 males (51%), 267 females, 432 PHIV+ and 108 HIV-, with a median age of 12 years. Hearing impairment was observed in 19% of all the adolescents in the study. Multivariate analysis showed the following predictors for any hearing loss: an unmarried primary caregiver (odds ratio (OR) 0.59; 95% confidence interval (CI), 0.39;0.91, p = 0.015), being female (OR 1.67; 95% CI, 1.12;2.51; p = 0.013) and reports of being troubled by ear pain or discharge in the last month (OR 2.54; 95% CI, 1.55;4.17; p = <0.001) after adjustment. Univariate analysis showed an association between hearing loss and a longer duration on ART among PHIV+ adolescents (OR 1.80, 95%CI 1.17;2.75, p = 0.007). Conclusion: The prevalence of hearing loss appears to be comparable between PHIV+ and HIVadolescents in Cape Town. In low resource settings, a history of ear pain or discharge within the last month may be used as a screening tool for a hearing assessment, and guide referral for formal hearing tests.

Much of the research on obesity has been designed to explore its relationship to the behavior of overeating. Although a number of physiological, societal, cultural and family background variables have been detailed, researchers have sought an approach that does not rely heavily on these considerations. Most weight reduction programs fail to recognize and concentrate on empirically demonstrated differences between obese and normal subjects. Researchers have shown that obese subjects seem to be more sensitive to external than internal stimuli. A behavioral approach to weight reduction that emphasizes and uses these external stimuli was hypothesized to be the treatment of choice. A Self-Modification program was designed to maximize the use of external stimuli. An Aversion Therapy approach that utilized electrostimulation was the alternative treatment procedure. The two treatment procedures were compared with a Control approach. Each of the two treatment approaches and the Control approach consisted of twelve subjects.

The correlation of cascade experimental data is one method for obtaining compressor stage characteristics. These correlations specify pressure loss and flow turning caused by the blades. Current open literature correlations used in streamline curvature codes are inadequate for general application to high-speed transonic axial-flow compressors. The objective of this research was to investigate and evaluate the available correlations and ultimately discover sets of correlations which best fit the empirical data to be used in streamline curvature codes. Correlations were evaluated against experimental data from NASA Rotor 1-B and NASA Stage 35. It was found that no universal set of correlations was valid for minimum-loss point predictions. The Bloch shock loss model showed promising results in the stall regime for supersonic relative inlet Mach numbers. The Hearsey and Creveling off-minimum-loss deviation angle prediction performed consistently better than all other correlations tested. / Master of Science

A collection of poetry concerned with loss and the act of creation.

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The phenomenon of residual inhibition, whereby the phantom sensation of tinnitus is suppressed following the presentation of a masking stimulus, has significant implications for understanding the neural basis of tinnitus itself. By using novel psychoacoustic techniques and three computer-based tools developed and applied specifically to measure tinnitus sensation and residual inhibition, a pattern emerges in which the depth and duration of tinnitus suppression relates to the center frequency of the band-passed noise masking stimulus. A correspondence between the region of hearing loss, the tinnitus spectrum and the masking stimuli most effective in suppressing tinnitus is revealed. These results suggest that cortical reorganization observed in animal models of tinnitus is not the principal basis of tinnitus, and provide a baseline for optimizing residual inhibition in individual cases and for further experiments. / Note: Pages 17-23 in this thesis were replaced with a citation due to copyright issues. / Thesis / Master of Science (MSc)