University of Missouri: MOspace

    Discrete NaI(TI) crystal detector optimization for small animal SPECT molecular imaging

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (November 15, 2006)Includes bibliographical references.Vita.Thesis (Ph.D.) University of Missouri-Columbia 2005.Dissertations, Academic -- University of Missouri--Columbia -- Nuclear engineering.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Dual-modality imaging instrumentation has allowed the noninvasive analysis of preclinical models of human disease. A combined microSPECT/CT unit (Siemens) equipped with dual discrete crystal SPECT detectors was under performance evaluation in our laboratory for SPECT molecular imaging. The CT component consists of a CCD x-ray detector and a micro-focus x-ray source (40 [mu] m focal spot). MicroSPECT performance was assessed thru characteristics measurements and high resolution phantoms. Gamma camera SPECT properties investigated using Tc-99m included system photon sensitivity, detection efficiencies, detector uniformity, spectral energy resolution, spatial resolution (FWHM), count rate, and tomograhic pre-clinical performance employing a 3D-OSEM algorithm with geometrical misalignment corrections. Camera gamma-ray sensitivity was calculated to be 3.5, 37 and 73 cps/[mu] Ci for the 0.5, 2 and 3 mm pinhole apertures, respectively. Intrinsic uniformity for the central field of view was 1.42% differential and 2.99% integral. Energy spectral resolution (FWHM) at 140 keVwas 14.3% [plus or minus]1.5 %. Volumetric spatial resolution of 1.2 mm was achieved with a hot-rod Tc-99m SPECT micro-phantom. Camera count rate linearity was achieved up to 1 mCi. In-vivo osteoblastic bone lesions 0.6 mm in diameter measured by CT were also detectable with SPECT Tc-99m-HDP imaging. Spatial resolution (FWHM) results suggest that the microCAT II® SPECT unit is capable of sub-millimeter resolution, however, photon sensitivity improvements either by employing multi-pinhole collimation and/or larger crystal elements will significantly enhance the SPECT pre-clinical performance of the unit

    The effects of conceptual description and search practice on users' mental models and information seeking in a case libray with a best match search mechanism

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on July 21, 2008)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2006.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The purpose of this study is to investigate the effects of conceptual description and search practice on users' mental models and information seeking in a case library with a best match search mechanism. This study also seeks to understand how the presence of a mental model affects the users' search performance and satisfaction in this case library. The study results reveal that the conceptual description and search practice treatments do not have significantly different effects on the types of user's mental models, search correctness, and search satisfaction. However, search practice group spent significantly less time than conceptual description group in finding the results. Qualitative analysis reveals that subjects in the conceptual description group seem to have more complete mental models of the best match system than those in the search practice group. This study also finds that subjects with the best match models have significantly higher search correctness and search result satisfaction than subjects without the best match models. However, best match mental models do not guarantee less search time in finding results. This study did not find significant correlation among search time, search correctness and search satisfaction.Includes bibliographical reference

    Rivers running through : an urban environmental history of the Kansas Cities and the Missouri River

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on August 13, 2006)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2006.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] An environmental history of Kansas City and an urban history of the Missouri River, this dissertation shows how interconnected the city and the river were through the twentieth century. Examining how the river literally flowed through the infrastructure (pipes and sewers) and the citizenry (drinking water and excrement) of the Kansas Cities illuminates the interrelationships and trans-boundary connectedness of the city's social and environmental history. Exploring the intimate uses of the river also shows how public health brought residents upstream and downstream from Kansas City into relationship with each other as each part broadens to a wider set of connections, to encompass the lower Missouri River basin. Throughout the century, public health officials, sanitary engineers and citizens worked to control water quality. Despite calls in 1910 to manage the river with public health in mind, it was not until the 1960s that the river came under sanitary regulation. The question of whether the river should create economic wealth or protect human and environmental health has constituted an important debate-one that continues to be relevant to decision making today.Includes bibliographical reference

    Fuel depletion analyses at the Missouri University Research Reactor

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (March 2, 2007)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2006.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] In developing, assembling and updating safety analysis cases for nuclear power and research reactors, fuel depletion plays a major role and ultimately leads to the calculation of fuel inventory and reactivity versus burnup, important parameters required for regulatory compliance. This thesis describes the use of the Monteburns code for the Missouri University Research Reactor (MURR) fuel depletion analyses, and provides simulation comparisons with experimental results and other codes results. The model and simulation differences are assessed and an analysis of the accuracy of the Monteburns code and model for MURR is provided. This thesis also describes an application in support of the MURR Safety Analysis Report (SAR) update work.Includes bibliographical reference

    Immunity in the newborn : control by IL-13 receptor and dendritic cells

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Thesis (Ph. D.) University of Missouri-Columbia 2007."May 2007".[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Neonates are susceptible to microbial infections and allergic reactions due to lack of Th1 immunity. Utilization of a TCR transgenic T cell transfer system, we demonstrated that primary neonatal Th1 cells develop alongside Th2 cells upon priming of the newborn but undergo apoptosis upon recall with antigen. These Th1 cells were isolated, and their death was correlated with elevated IL-13R[alpha]1 chain expression. Our data suggested that IL-4 might use this receptor chain to signal for the apoptosis of Th1 cells leading to lack of Th1 immunity in neonates. The point at which neonates no longer exhibit a Th2 biased immune response has not been studied. Interestingly, we found that antigen exposure at day 6 after birth restored the secondary Th1 response concomitantly with IL-13R[alpha]1 mRNA downregulation. Our data suggest that up-regulation of IL-13R[alpha]1 at day 1 is due to delayed maturation of the CD8[alpha]+CD4- DC subset capable of IL-12 production. CD8[alpha]+CD4- DC subset transfer to 1 day old neonates diminished IL-13R[alpha]1 expression by IL-12 secretion, leading to inhibition of Th1 apoptosis and restoration of an adult-like Th1 immunity.Includes bibliographical reference

    One last good time

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on March 24, 2009)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2007.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] This dissertation consists of a book-length work of short fiction preceded by an essay called "In Defense of Starting Early." The ten stories that make up this collection are loosely linked by character and by setting - a fictional town in New Jersey called Gaston. The collection, while telling the story of its characters, also tells the story of the rise and fall of this small beach town from 1978 to 2004. The critical essay explores point-of-entry in the contemporary short story, and calls into question the conventional wisdom of beginning a story as close to the end as possible

    Games leaders play : renegade regimes and international crises

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on December 20, 2007)Thesis (Ph. D.) University of Missouri-Columbia 2007.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] My dissertation is a game-theoretic analysis of international crises between the US and renegade regimes after the Cold War. The main puzzle that leads me to conceive this project is the seemingly irrational behavior of certain leaders like Slobodan Milosevic and Saddam Hussein during crises with the US. Why, I wondered, did they risk war with the United States, while the odds are clearly against them in terms of power distribution? Why do they sometimes escalate the crisis to the point of war, a war they are likely to lose, and sometimes seek conciliation and settlement? This puzzle regarding the foreign policy behavior of renegade regimes leads to the central question of this study: what are the dynamics behind the foreign policy behavior of renegade regimes during crises? The cases include crises with Iraq (1991), Serbia (1999), and North Korea (1994). I created a theoretical framework, which is called "enhanced neoclassical realism" that brings together psychological theories of foreign policy analysis and rational choice models, and incorporates systemic and domestic constraints that leaders face to analyze their foreign policy behavior. Specifically, I am using operational code analysis, a research program on foreign policy behavior based on cognitive psychology, to capture the political elites' perceptions regarding the international system. I use large-group identity framework developed by Vamik Volkan and the logic of political survival framework by Bruce Bueno de Mesquita and his colleagues to identify the key domestic constraints on the leaders. Finally, I use extensive-form game theory to analyze their foreign policy behavior during the crises based on their perception of the international system and the domestic constraints they face

    Automated quantification of rubidium-82 myocardial perfusion images using wavelet based approach

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on October 17, 2007)Vita.Includes bibliographical references.Thesis (Ph. D.) University of Missouri-Columbia 2007.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The main work in this dissertation focuses on development of automated quantitation algorithms for Rb-82 PET images. The current methods for quantitation is model based and may fail to determine regional details as produced by higher resolution PET images. Thus automated approaches which are model-independent and detects details of the myocardium would seem valuable for accurate quantitation. Two major components of such an automated approach developed in this work are myocardial reorientation and myocardial boundary detection. The new reorientation algorithm is based on detection of myocardial contour with wavelet processing to detect the oblique angles of the myocardium. Evaluation of the reorientation algorithm is done for cardiac phantom and large number of clinical patients by comparing with user selected angles. The boundary detection algorithm is based on spherical sampling and analysis of counts based on gradient functions. For evaluation of the boundary detection algorithms, the results are compared with results from current techniques. For cardiac phantom and patients, higher degree of correlation and agreement is obtained for quantative parameters between current method and the new algorithm. Validation of the new algorithm with more patients and with results from high-resolution modalities will prove its robustness and may bring new advances in the quantitation of myocardial perfusion imaging.Includes bibliographical reference

    Effects of spin current in ferromagnets

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on August 4, 2009)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2008.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] This thesis focuses on the investigation of magnetization dynamics induced by spin transfer torques. The first part of this thesis presents the theoretical and numerical study of domain wall motion in the magnetic nanowire. The second part reports the analysis of spin-current-driven magnetization excitations in ferromagnets. Magnetic domain wall is known as the transition region between magnetic domains whose magnetization pointing in different directions. Via the movement of domain wall, these domains can rearrange themselves in response to the external magnetic field or electric current. Domain wall dynamics is an important issue in study of the dynamic behavior of magnetic systems. Transverse wall and vortex wall are two type of walls mostly observed in magnetic thin films. Analytical models for these two walls are proposed in this thesis, and their dynamic behaviors are studied by these models. Micromagnetic simulations are performed to verify our analytical results. Simulation results also reveal the physical origin of many phenomena observed in experiments. The direct interaction between conducting electrons and local moments polarizes the electron spins, and at the same time, exerts a spin torque on the magnetization. When the current density is increased higher than a critical value, the spin torque is able to drive the magnetic system out of equilibrium. Due to the existence of the magnetic damping, a steady state could still be reached in this fluctuation-dissipation system. Physical properties of this dynamic state are studied and presented.Includes bibliographical reference

    For whom does participation matter and why? : the earnings of former college athletes

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    The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on July 13, 2009)Thesis (M.A.) University of Missouri-Columbia 2008.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Previous research has found conflicting evidence regarding various consequences of athletic participation. Most scholarship has focused on the ways that athletic participation during adolescence affects labor market and educational outcomes for its participants. The current project is one of a small number which focuses on the earnings of former college athletes. Using nationally representative data from the National Educational Longitudinal Survey, the current project examines the extent to which college athletes' (both intramural and varsity) earnings are different from their non-participating peers. Further, the research investigates the role that race and gender play in predicting the relationship between early career earnings and collegiate athletic participation. The findings suggest that athletes do earn higher salaries than their peers who did not participate, but that this relationship is dependent upon race, gender, and whether the athlete participated in intramural or varsity sports. The results point to the need for scholarship which utilizes multiple theoretical frameworks to help illuminate the processes which result from athletic participation based on group differences. The paper closes with suggestions for directions of future research in the area.Includes bibliographical references
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