UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2004 - 200912010 - 20121

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Subject: search.filters.subject.Ionizing Radiation

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    Mechanisms of Resistance to Ionizing Radiation in Extremophiles
    (2012) Webb, Kimberly Michelle; Robb, Frank T.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Extremophiles display an astonishing array of adaptations to harsh environmental conditions. We analyzed the mechanisms of ionizing radiation resistance from a diverse group of extremophilic archaea and bacteria. In Halobacterium salinarum IR resistance is conferred by antioxidant Mn2+-complexes, and protein-free cell extracts (ultrafiltrates, UFs) of super-resistant (IR+) isolates of H. salinarum had increased concentrations of Mn, PO4 and amino acids compared to the founder strain. Proteomic analysis determined that IR+ isolates with increased Mn had elevated protein expression for central carbon metabolism, suggesting a Mn-stimulated metabolic route to increased IR resistance. We examined the role of mannosylglycerate, di-myo-inositol phosphate, and trehalose in the IR resistance of various thermophiles; aerobic thermophiles had UFs which were radioprotective of enzyme activity under aerobic conditions, which is attributed to Mn, PO4 and trehalose accumulation. In contrast, anaerobic thermophile UFs did not contain significant amounts of Mn, and were radioprotective only under anaerobic conditions; we conclude the anaerobic environment confers their IR resistance.
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    NON-INVASIVE IMAGING TECHNIQUES AS A QUANTITATIVE ANALYSIS OF SKIN DAMAGE DUE TO IONIZING RADIATION
    (2004-05-06) Vogel, Abby Jeanne; Tao, Yang; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This study tested the ability of two non-invasive techniques, thermography and near-infrared multi-spectral imaging, to quantitatively assess the response of mouse skin to a single dose of X-ray irradiation. Thermal images from an 8-12 micron thermal camera were recorded after a cold stimulation to see the thermal recovery of the skin. The irradiated areas showed a significantly faster thermal recovery than the non-irradiated areas two weeks after radiation (p < 0.05). The NIR multi-spectral imager obtained images at six specially selected wavelengths between 700 and 1000 nm. Two-layer model-based diffuse reflectance spectroscopy monitored changes in blood oxygen saturation and blood volume. Blood oxygen fractions were significantly lower after radiation (p < 0.05). Blood volume changed in six of seven irradiated mice one week after radiation. The non-invasive imaging techniques were successful in quantitatively analyzing the response of the skin to a single dose of irradiation.