Mercury (Hg) is a global environmental contaminant that is deposited from the atmosphere and converted to methyl mercury (MeHg) in aquatic ecosystems. Historically Hg was thought to pose a risk to aquatic but not terrestrial wildlife. Recent studies have found that MeHg can be transported via emergent aquatic insects to terrestrial ecosystems. Tetragnathid spiders are a key link between aquatic and terrestrial ecosystems because they consume emergent aquatic insects and are themselves consumed by songbirds. I studied spatial patterns in MeHg concentration in tetragnathid spiders at Caddo Lake, Texas/Louisiana, USA. I then used MeHg concentrations in spiders to estimate the potential risk to arachnivorous songbirds. At 89% of the 56 sampling sites, Hg concentrations in spiders were high enough to pose a risk to chickadee nestlings. This study suggests that terrestrial spiders that consume aquatic insects accumulate levels of MeHg that could pose a risk to songbirds at Caddo Lake.

Palladium catalyzed cross coupling reactions are one of the most utilized synthetic method(s) in carbon-carbon bond formation. But this synthetic method is problematic for alkyl reactants, due in part to undesirable beta-hydride elimination side reaction. This work aims at understanding the mechanistic aspects of alkyl cross coupling and the role of ligand in suppressing this undesired side reaction. \nDensity Functional Theory (DFT) calculations suggest that the rate of beta-hydride elimination depends on relative stabilities of agostic stereo-isomers. The stability of agostic Pd complexes are dictated by the mutual electronic trans influences of ligands and their steric properties. \nBoth sigma and pi effects contribute to the ligand's trans influencing ability. Steric effects modulate the extent of trans influence(s) and preferentially stabilize cis isomer(s). This interplay of trans influence and steric effect gives some proposed "design rules" on ligand choices in alkyl couplings. Selectivity is also increased when ligands/reactants have hemilabile properties. These results motivate rational design of improved alkyl cross coupling catalysts.

Mercury (Hg) is a toxic metal found at elevated concentrations throughout the world. Humans are exposed by consuming contaminated fish. State agencies warn the public to limit fish consumption from specific waterbodies when elevated Hg is detected (site-specific advisory). Some states issue warnings, advising limited consumption from any state waters since fish may contain high Hg (statewide advisory). I evaluated the accuracy of these advisory systems using estimated Hg concentrations in intermediate sizes of four freshwater gamefish at 866 waterbodies. Waterbodies where Hg concentrations exceeded 300 ng/g, the Environmental Protection Agency's screening value for hazardous fish, were assumed to need advisories. Comparing predicted advisories to state-issued advisories revealed most waterbodies expected to have site-specific advisories lack them. Applying statewide advisories results in warnings on waterbodies with fish below EPA advisory levels. I conclude the advisory systems fail to accurately reflect risk from fish with potentially hazardous levels of Hg.

In recent years, an increasing number of scientists have realized the potential of semiconductor nanomaterials in the biomedical field and begun to work on expanding their biological applications in areas such as biosensing, high throughput screening, and drug/gene delivery. Since the cytocompatibility of semiconductor nanomaterials can be influenced by various factors, including composition, size and morphology, cell type, specific bioassay, etc., any in vitro use of nanomaterials requires a comprehensive evaluation of toxicity in order to make full use of the material within a regulated safe range.\n Si nanowires (SiNWs) and Ge nanowires (GeNWs) have attracted more and more attention for possible use in biomedical applications due to advantages such as facile synthesis with tunable widths and lengths, high surface area, and distinct electronic, optical, chemical and thermal properties. Given the lack of useful cytotoxicity data of such nanowires that has emerged thus far, it is recognized that detailed cytocompatibility studies of exposure to SiNWs and GeNWs, and understanding of cytotoxicity mechanism are necessary before any applications can be put to real use. In this work, a detailed study of the synthesis and cytotoxicity of horizontal-oriented SiNWs and GeNWs grown from a Vapor-Liquid-Solid route is presented. Selected viability studies (MTT, Trypan Blue) were performed to evaluate the cytotoxicity of NWs on different types of cells, including HEK 293 and MCF-7. For the case of GeNWs, both Western Blot and Apo-ONE Homogenous Caspase 3/7 Assays were also performed to evaluate the mechanism of their cytotoxicity.\n The fundamental properties of other silicon-based structure related to their possible use in biotherapeutic platforms were also evaluated. These include measurements of the <italic>in vitro</italic> dissolution behavior of authentic amorphous silicon thin film transistors (a-Si TFTs), along with time-dependent stability and cytotoxicity of Fe₃O₄ nanocrystals infiltrated into nanostructured mesoporous silicon.The latter system is of particular interest as a magnetic field-assisted drug delivery vehicle.\n In addition, another unique form of Si based nanomaterial, Si nanotubes (SiNT), were also investigated in this work. Different from SiNWs, SiNTs can dissolve in aqueous media and release Si(OH)₄, which is nontoxic and readily eliminated from the kidneys. Because the dissolution behavior of SiNTs is solution-composition dependent and size-dependent, SiNTs are a candidate as a controlled release system for therapeutics. Initial cytocompatability assays and gene transfection experiments suggest that SiNTs can act as a non-toxic carrier for transfecting HEK 293 cells with a gene for green fluorescent protein (GFP) in a relatively efficient manner.

Previous theory and research shows that people can change unwanted attitudes cognitively, either by epistemic strategies (altering the perceived valence of the attitude object's attributes) or by teleologic strategies (altering the accessibility of the attitude object's attributes). Although epistemic and teleologic strategies of self-persuasion have been shown to be equally effective for immediate change, no empirical tests have shown one method to provide attitude change that is either longer lasting or less susceptible to further change compared to the other. The present research tested whether preference for epistemic versus teleologic strategies leads to new attitudes that are more persistent (Experiment 1) or resistant (Experiment 2) to change. The resistance hypothesis (in Experiment 2) was supported, but more for individuals low than high in self-control. Reasons for these discrepancies are discussed.

Dolomites are rock units that invariably record a complex history of deposition and diagenesis. Within the Slick Hills of southwestern Oklahoma, there are extensive exposures of dolomite among the carbonate outcrops of the Late Cambrian- Early Ordovician Arbuckle Group. The Kindblade Formation is a 1,400 ft (427m) thick carbonate section within the Arbuckle Group that was deposited during the Early Ordovician (485-478 Ma) and has been heavily dolomitized in areas of the Slick Hills such as Saddle Mountain. Exposures of dolomite near Blue Creek Canyon do not exhibit the pervasive dolomitization that encompasses the entire Kindblade section as described at Saddle Mountain. Instead, dolomite observed in the Blue Creek Canyon area is strata-bound in conjunction with horizons of limestone displaying varying degrees of alteration. The petrographic and geochemical analyses of these dolomites reveal a multifaceted diagenetic history including penecontemporaneous dolomitization, meteoric water mixing and exposure to hydrothermal fluids.

Characteristics of urbanization such as roads, buildings, exotic species and vegetative homogenization can create patches of habitat surrounded by poor-quality, unfavorable areas. This inhibits movement, which in turn restricts gene flow. We used radio-telemetry and genetic markers to study the movement patterns in Texas horned lizards (<italic>Phrynosoma cornutum</italic>) in the neighboring towns of Kenedy and Karnes City, Texas. Individuals had small home ranges and rarely moved across roads. Nuclear and mitochondrial DNA markers revealed low genetic diversity in these towns and another urban site at Tinker AFB in Oklahoma compared to a larger natural area in Texas. There was significant genetic structure within town on either side of large roads as well as significant genetic structure between towns. These data suggest that movement is curtailed within and between these towns which may have long-term negative impacts such as inbreeding depression and a lowered ability to adapt to changing conditions.