Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
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 give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
4 results
Search Results
Item Probing Allosteric Communication Between Disordered Surfaces in a Protein(2015) Cressman, William John; Beckett, Dorothy; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Molecular mechanisms of protein allostery are not well understood, particularly in those systems that undergo disorder to order transitions upon activation. BirA, an E.coli metabolic enzyme and transcriptional repressor, is a model allosteric protein in which corepressor, bio-5’-AMP, binding enhances dimerization by -4 kcal/mol and is coupled to disordered loop folding on both functional surfaces. In this work, BirA variants with single alanine substitutions in dimerization surface residues are investigated to further characterize communication between the two sites. Isothermal titration calorimetry (ITC) measurements of corepressor binding of these BirA variants indicate only the G142A substitution perturbs the Gibbs free energy of binding. The G142A crystal structure indicates a mechanism of communication from the corepressor binding to the dimerization surface involving α-helical extension of residues 143-146. Measurements of the heat capacity changes associated with corepressor binding to the BirA variants support a model in which the helical extension enhances dimerization by enabling the formation of a network of intramolecular interactions on the dimerization surface.Item CAUSAL OR MERELY CO-EXISTING: A LONGITUDINAL STUDY OF VIOLENCE AND DISORDER AT PLACES(2007-08-02) Yang, Sue-Ming; Weisburd, David; Criminology and Criminal Justice; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research examines the relationship between disorder and violence across geography, specifically whether disorder and violence are causally related. This issue has generated much debate in the field of criminology. The broken windows thesis argues that untended disorder will lead to crime while social disorganization theory suggests that these two phenomena are merely spuriously related. To examine the longitudinal relationship between disorder and violence, this dissertation used data from the city of Seattle, Washington and analyzed them with dynamic statistical tools. Group-based trajectory analysis was used to identify different patterns of disorder and violence. The findings reveal a moderate level of spatial association between disorder and violence. Moreover, the results show that lack of disorder may be a protective factor for places in preventing future crime. This particular finding provides a new insight for crime prevention strategy. I further use Granger causality tests to examine the causal association between disorder and violence within selected violence and disorder hotspots. Findings from the Granger causality tests indicate that disorder does not lead to violence. As such the results suggest that public policy targeting disorder may not lead to crime reduction benefits. This particular finding challenges the notion of broken windows policing. Although broken windows policing might increase the chance to apprehend criminals due to the spatial clustering of social disorder and violence, the findings suggest that reducing levels of disorder will be unlikely to have strong impacts on crime rates. Additionally, potential collateral effects of police crackdowns on disorder need to be considered. Lastly, social disorder and physical disorder seem to relate to violence differently. Specifically, social disorder corresponds with violence more strongly than physical disorder. This issue has theoretical implications and should be explored further in future research.Item Disorder and Doping in the Oxygenated Electron-doped Superconductor PCCO(2006-08-29) Higgins, Joshua Scott; Greene, Richard L; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis is composed of two parts: the first part deals with the high temperature electron-doped superconductor Pr_(2-x)Ce_(x)CuO_(4-delta); the second part deals with the diluted magnetic semiconductor Ti_(1-x)Co_(x)O_(2-delta). It is not clear why oxygen reduction and cerium doping are necessary to obtain superconductivity in the electron-doped Pr_(2-x)Ce_(x)CuO_(4-delta). I investigated the effects of oxygenation in this material using resistivity and Hall measurements. For various oxygen contents, I was able to determine that there is a separable doping and a disorder contribution to the superconducting transition temperature. I was able to quantitatively separate out these two effects and show that these two effects are opposite with regards to changes in T_(c) for overdoped thin films. The disorder component is roughly twice as large as the doping component. This analysis is also shown to be self consistent in demonstrating that the doping component of oxygen variation follows the trends of Cerium doping. For the diluted magnetic semiconductor Ti_(1-x)Co_(x)O_(2-delta), I investigated the intrinsic nature of the ferromagnetism observed in thin films. Hall effect measurements were used as the technique because ferromagnetic materials exhibit an anomalous Hall effect, which is due to an interaction between the charge carriers and the magnetic moments. I found that low carrier concentration anatase phase films did not exhibit an anomalous Hall effect, whereas high carrier concentration rutile phase films do. The presence of the anomalous Hall effect at this point cannot be attributed to an intrinsic ferromagnetism as cobalt clusters are observed in these films.Item THE IMPACT OF DISORDER ON FEAR OF CRIME: A TEST OF THE FIRST LINK OF BROKEN WINDOWS(2005-04-28) Hinkle, Joshua Conard; Weisbrud, David L; Criminology and Criminal Justice; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The broken windows hypothesis (Wilson and Kelling, 1982) suggests that disorder causes fear of crime to increase in a community, starting a chain of events that eventually leads to an increase in crime in the neighborhood. This thesis aims to improve our knowledge of the relationship between disorder and fear of crime in the context of the broken windows hypothesis using a micro-level research design. The results of this study suggest that perceptions of disorder have a strong influence on individual's fear of crime, and that perceptions of disorder appear to mediate the affects of changes in observed measures of actual disorder on fear. This suggests that the relationship hypothesized by the broken windows literature may exist, and that police may be able to indirectly reduce fear of crime by reducing disorder. The findings show that this would reduce perceptions of disorder and thereby indirectly reduce fear of crime.