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published_or_final_version / abstract / Physics / Master / Master of Philosophy

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The dynamics of a quantum system with a large number $N$ of identical bosonic particles interacting by means of weak two-body potentials can be simplified by using mean-field equations in which all interactions to any one body have been replaced with an average or effective interaction in the mean-field limit $N \rightarrow \infty$. In order to show these mean-field equations are accurate, one needs to show convergence of the quantum $N$-body dynamics to these equations in the mean-field limit. Previous results on convergence in the mean field limit have been derived for certain initial conditions in the case of one species of bosonic particles, but no results have yet been shown for multi-species. In this thesis, we look at a quantum bosonic system with two species of particles. For this system, we derive a formula for the rate of convergence in the mean-field limit in the case of an initial coherent state, and we also show convergence in the mean-field limit for the case of an initial factorized state. The analysis for two species can then be extended to multiple species.

Heavy metal contamination in food is a worldwide concern. Man-made ponds are domestic sites in the production of Procambarus clarkii and Procambarus zonangulus, two edible species of crayfish. Ponds may be constructed in former sugar cane or rice fields. Crayfish farming is an ancillary seasonal business within the rice-growing season. The use of products to control insects, pests, and weeds in rice and sugar cane production, may cause an accumulation of heavy metals in the crayfish tail within pond structures. Arsenic, cadmium, copper, and zinc are heavy metals that are absorbed through the roots of and distributed through rice products. Metabolites associated with rice products are absorbed in the human body. Research suggests that metabolites associated with heavy metals cause disease in animals and humans.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Jorge Piekarewicz, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed June 15, 2004). Includes bibliographical references.

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The mean glandular dose (MGD) was measured for a breast phantom by using molybdenum/molybdenum and molybdenum/rhodium target/filter combinations, at different kVp 26, 28 and 32 kilovolts. The phantom thickness was 7.5cm and was made of BR12 material. The change of dose was studied as a function of depth inside the phantom at different depths from the surface, namely 3.3, 4.3 and 5.3cm, by using TLDs. It was found that the MGD value for different combinations of beam quality (HVL) and energy (kVp) did not exceed the recommended values given by different protocols. The Mo/Rh target/filter required lower doses to achieve the same or better results compared with the Mo/Mo target/filter. The change in the surface dose as a function of kVp was more significant for Mo/Rh than for the Mo/Mo. Studying the change in dose within the breast, as a function of depth gives a better understanding of the interactions between radiation and tissue inside the breast. It should be noted that the MGD is a tool for optimization of the mammography parameters. However, the MGD should not be used directly to estimate the risk of determinable health effects from mammography. This will ultimately help to determine limits for the breast surface dose and a better understanding of cancer risk. In future work, we will try to measure the change of the dose as a function of depth by using more kVp, HVL, different breast composition and different target/filter combinations to give a wider picture for different situations.