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Bisphenol A (BPA) is a polymer used in the production of polycarbonate plastics and epoxy resins. An estrogen mimic, prenatal BPA exposure has been associated with several behavioral outcomes in children; however, the impact of maternal demographic and economic factors on associations between BPA and child behavioral outcomes have not been examined. The objective of this study was to examine associations between prenatal maternal urinary BPA and behavior in 4-5 year old girls, and to assess whether socio-demographic factors modify this relationship. Mothers enrolled in The Infant Development and Environment Study (TIDES) provided a single spot urine at enrollment (median gestational age 11 weeks) and completed the Behavior Assessment System for Children-2 (BASC-2) and Social Responsiveness Scale-2 (SRS-2) when their daughters were 4-5 years of age. Mother-daughter pairs with complete phthalate, BASC-2, SRS-2, and covariate data were included in this analysis (N=244). BPA was detectable in 93 % of urine samples. We used multivariable linear regression analyses to estimate associations between maternal urinary log10-transformed BPA concentration and BASC-2 subscale and composite scores and SRS-2 Total Score. To examine the role of socioeconomic and demographic factors associated with study site, we stratified by TIDES center, comparing those enrolled at University of Rochester Medical Center (URMC), a predominately lower socioeconomic population, and those enrolled elsewhere: University of Washington, University of Minnesota, and University of California San Francisco, whose populations share similar higher socioeconomic demographic characteristics. Across all centers, no associations were seen between BPA and BASC-2 or SRS-2 scores. When stratifying by center, BPA was significantly associated with greater social impairment as measured by the SRS-2 Total Score (β-coefficient [95 % confidence intervals]: 5.1 [1.0, 9.2]) in URMC participants (N=61). In non-URMC participants (N=183), BPA was significantly associated with lower BASC-2 Internalizing composite (-3.3 [-6.7, 0.0]) and Depression subscale scores (-3.4 [-6.7, 0.0]) while no associations were seen between BPA and SRS-2 scores. Our findings suggest that sociodemographic factors may modify the impacts of maternal prenatal BPA on developmental endpoints.

The future use of two-dimensional (2D) semiconducting materials for electronic device applications hinges on the ability to make low-resistance contacts. To model such contacts, an accurate expression of the image force barrier-lowering (IFBL) is needed. We derive the image-force energy by solving Poisson's equation with the boundary conditions of two metal surfaces separated by an angle omega. We show how the image-force energy can also be obtained using the method of images provided a non-Euclidian cone-manifold space is used. We calculate how much the IFBL is strengthened or weakened for various omega and angles with the 2D semiconductor. For the most prominent 2D material contact configuration, the image-force energy is reduced by a factor of 0.85, but a smaller angle between the metal surfaces can significantly increase the image-force energy. We predict that a contact with a small angle between the metal and 2D material and a surrounding dielectric with low permittivity will yield low contact resistance by enhancing IFBL., Comment: 13 pages, 5 figures

Detailed methods used in the experiment and analyses

Ten tables with statistical results, and fifteen supplemental figures.

This dissertation presents three studies that investigate extension in the Southern Snake Range (SSR) metamorphic core complex (MCC) of east-central Nevada and a thermal anomaly associated with the Gypsum Valley salt wall (GVSW) of southwestern Colorado. Low temperature thermochronologic studies using the (U-Th)/He system have been applied in numerous geologic settings to understand erosional and tectonic denudation processes. Two of the studies presented use (U-Th)/He thermochronology, combined with other techniques, to investigate the extensional history of the SSR and the extent of the GVSW thermal anomaly. Both of these studies present novel methods for understanding the thermal histories of the study area using (U-Th)/He thermochronology. The third study uses geologic mapping to document the complexly deformed upper plate of the SSR metamorphic core complex. A full abstract detailing the results of this work is available within the dissertation document.

VCU Theses and Dissertations

This paper aims to explore the meaning of the English word argument in Chinese culture and language. It first reviews the various definitions and concepts of argument in western literature and Chinese culture. Next, it argues that there is no one single all-encompassing word in Chinese that can fully represent all the meanings of the English word argument. Finally, it conducts a survey research to get the possible Chinese translations of the English word argument.

The aim of this thesis has been to explore agonism, and the relationship of individual and collective in Classical Greece, through the lens of athletic competition at the panhellenic sanctuaries. This study moves beyond the presumed dichotomy of agon and homonoia upon which the standard view of agonism in modern scholarship has been predicated to explore the ways in which agonism functions precisely within and is structured by polis society, even as the polis must negotiate constantly between the interests of collective and individual. The evidence of both athlete and polis commemorations of athletic victory suggests a dynamic tension between promoting the self and remaining, and identifying oneself as, a member of a community. When appropriately channeled into civic benefaction and mutual advantage, agonism enables the self-interest ofthe individual to function within and remain structured by the polis; when it is not channeled in this way, it creates conflict and stasis. Just as in the relationship of athlete and polis, so too the interaction of poleis with each other in the panhellenic sanctuary reveals a tension between the desires for self-promotion and membership in the collective. This creates for poleis an ambivalent dynamic of at once mutual striving and competitive distinction within a common landscape that brings local values, mythologies and heroes to the attention of a panheUenic audience. Rather than equating agonism strictly with conflict or commonality then, this study appreciates agonism as a fundamental aspect of Greek life that was both a product of and productive of rivalry and emulation at the level of athlete and polis, and polis and panhellenic community. The evidence of both athlete and polis monuments suggest that the realization of competition as peer rivalry and emulation allowed room for distinction as predicated on commonality and civic benefit, rather than individualism and egoism. Master of Arts (MA)

DNA oxidation is a process that has been implicated in mutagenesis and cancer. Previous studies to determine the pathways and products of DNA oxidation have been carried out in dilute aqueous solutions or organic solvents. These conditions may or may not be representative of the interior of a cell where there is a high concentration of biomolecules and DNA is in a highly condensed form. This work focuses on determining the role of DNA condensation on the mechanisms and products of DNA oxidation. DNA is condensed in reverse micelle (RM) media or in the presence of histone subunits. The DNA oxidation reactions are carried out using a flash/quench photochemical technique and ruthenium(II) polypyridyl complexes to produce ruthenium(III) oxidants or singlet oxygen. One-electron guanine oxidation in single- and double-stranded DNA has been investigated in anionic RMs. Tris(2-2'-bipyridine)ruthenium(II) chloride ([Ru(bpy)3]Cl2) is used to photochemically produce oxidatively generated damage to DNA that is quantified by high-resolution polyacrylamide gel electrophoresis. The steady state quenching efficiency of Ru(bpy)32+ with the oxidative quencher potassium ferricyanide (K3[Fe(CN)6]) is two-fold higher in buffer than in RMs. Consistent with the difference in quenching efficiencies in the two media, the amount of piperidine-labile oxidation products from double-stranded DNA is 1.5-fold higher in buffer than RMs. However, a 13-fold decrease is observed in RMs for single-stranded DNA. Circular dichroism spectra reveal that the single-stranded DNA undergoes a large structural change in the anionic RMs. This structural change may be due to cation-mediated adsorption of the DNA phosphates on the anionic headgroups of the surfactant, which protect the guanines from oxidation. DNA oxidation also has been investigated in the medium of cationic RMs. The oxidative chemistry is photochemically initiated using the DNA intercalator bis(bipyridine)dipyridophenazine ruthenium(II) chloride ([Ru(bpy)2dppz]Cl2) bound to double-stranded DNA in the RMs. In buffer solution, the addition of the oxidative quencher [Fe(CN)6]3- leads to an increase in the amount of piperidine-labile guanine oxidation products generated via one-electron oxidation. In RMs, however, the yield of oxidatively-generated damage is decreased. With or without [Fe(CN)6]3- quencher in the RMs, the yield of oxidatively-generated products is approximately the same. Under anaerobic conditions, samples in RMs show decreased levels of piperidine-labile oxidation products, suggesting that the primary oxidant in RMs is singlet oxygen. Guanine oxidation is enhanced in D2O and deuterated heptane and diminished in the presence of sodium azide in RMs, also supporting 1O2 as the main guanine oxidant in RMs. Isotopic labeling experiments show that the O-atom in an oxidation product produced in RMs is not from water and likely coming from O2. The observed change in guanine oxidation mechanism from a one-electron process in buffer to mostly 1O2 in RMs illustrates the importance of both DNA structure and DNA environment on the chemistry of guanine oxidation. DNA oxidation in the presence of histone subunits H1 and H3 has also been investigated. Initial one-electron and 1O2 oxidation of guanine can lead to DNA-protein cross-links. DNA-protein crosslinks between histone subunits H1 and H3 and oligonucleotides were explored with chemically modified histones with methylated lysine residues, a post-translational modification important in regulation of cellular processes including transciption. DNA-protein cross-links are observed between unmodified and methylated histone subunits. The amount of DNA oxidation is the same in the presence of histone H1 and methylated H1 but is decreased in the presence of H3 and methylate H3. This may be due to the amount and type of lysine methylation of the histone subunits. These results further show the importance of environment on DNA oxidation.

VCU Theses and Dissertations