Habitat loss is one of the leading causes of species decline across all taxa and conservation practices require information on population trends. The Mescalero Sands ecosystem, New Mexico, USA, is experiencing landscape changes associated with oil and gas development. The dune-dwelling lizard community contains a habitat specialist, Sceloporus arenicolus, that is of particular interest because it has a very limited geographic distribution that is entirely subject to oil and gas development. Distance sampling is widely used to estimate population densities of many vertebrate taxa however assumptions can be difficult to satisfy with certain species or in certain habitats. Researchers must investigate the likelihood that assumptions can be satisfied before implementing any population sampling method. I had two objectives. First to investigate the precision of population densities of dune-dwelling lizards estimated via distance sampling that was coupled with double-observer surveys. Second to compare abundances of dune-dwelling lizards among sites that varied in oil and gas development. I conducted distance line transects and compared those density estimates to densities obtained from total removal plots. I quantified the amount of oil and gas development, habitat quantity and quality and correlated those to lizard abundances to investigate the effects of oil and gas development on lizard populations. I found large differences in density estimates from distance sampling and total removal plots that resulted from violation of distance sampling assumptions. Although distance sampling is a low cost method, it does not produce reliable density estimates for dune-dwelling lizards and is not an appropriate sampling method in this system. I did not find oil and gas development effects on the habitat quantity, quality or on the abundances of lizards. Lizard abundances were most strongly correlated to habitat quantity. Lizard abundances may be influenced by complex interactions between oil and gas development and habitat quantity and quality but controlling for those interactions was beyond the scope of my study. Before and after experiments and long-term studies at multiple sites would be required to more fully address the effects of oil and gas development on lizard populations in the Mescalero Sands.

Detailed mechanistic studies were conducted on several organic reactions that exhibit product selectivity (regio-, peri-, or enantioselectivity). The organic reactions studied were electrophilic aromatic substitutions, Diels-Alder cycloadditions of 1,3- dienes with cyclopentadieneone, Lewis acid catalyzed ene reactions with olefins, chlorinations of alkynes, and the enantioselective intramolecular Stetter reaction. Analyses of these systems were conducted by measurement of kinetic isotope effects, standard theoretical calculations, and in some cases dynamic trajectories. Mechanistic studies of electrophilic aromatic substitution, Lewis acid catalyzed ene reaction with olefins, the chlorination of alkynes, and the Diels-Alder cycloadditions of 1,3-dienes with cyclopentadienones, suggest that the origin of selectivity is not always a result of selectivity result from a kinetic competition between two closely related pathways to form distinct products. All of these systems involve one transition state on a potential energy surface that bifurcates and leads to two distinct products. In these systems, experimental kinetic isotope effects measured using natural abundance methodology, theoretical modeling of the potential energy surfaces, and trajectory analyses suggests that selectivites (regio- and periselectivities) are a result of influences by momenta and steepest-descent paths on the energy surface. The work here has shown that in order to understand selectivity on bifurcating surfaces, transition state theory is not applicable. In place of transition state energetics, the guiding principles must be those of Newtonian dynamics. In the mechanistic studies for the enantioselective intramolecular Stetter reaction, the origin of selectivity is a result of multiple transition states and their relative energies. Experimental H/D kinetic isotopes effects had lead to the conclusion that two different mechanisms were operating for reactions where carbenes were generated in situ versus reactions using free carbenes. However, 13C kinetic isotope effects and theoretical modeling of the reaction profile provide evidence for one mechanism operating in both cases.

This work investigates the effects of anthropogenic aerosols on deep convective clouds and the associated radiative forcing in the Houston area. The Goddard Cumulus Ensemble model (GCE) coupled with a spectral-bin microphysics is employed to investigate the aerosol effects on clouds and precipitation. First, aerosol indirect effects on clouds are separately investigated under different aerosol compositions, concentrations and size distributions. Then, an updated GCE model coupled with the radiative transfer and land surface processes is employed to investigate the aerosol radiative effects on deep convective clouds. The cloud microphysical and macrophysical properties change considerably with the aerosol properties. With varying the aerosol composition from only (NH4)2SO4, (NH4)2SO4 with soluble organics, to (NH4)2SO4 with slightly soluble organics, the number of activated aerosols decreases gradually, leading to a decrease in the cloud droplet number concentration (CDNC) and an increase in the droplet size. Ice processes are more sensitive to the changes of aerosol chemical properties than the warm rain processes. The most noticeable effect of increasing aerosol number concentrations is an increase of CDNC and cloud water content but a decrease in droplet size. It is indicated that the aerosol indirect effect on deep convection is more pronounced in relatively clean air than in heavily polluted air. The aerosol effects on clouds are strongly dependent on RH: the effect is very significant in humid air. Aerosol radiative effects (ARE) on clouds are very pronounced for mid-visible single-scattering albedo (SSA) of 0.85. Relative to the case without the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. The daytime-mean direct forcing is about 2.2 W m-2 at the TOA and -17.4 W m-2 at the surface. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Aerosol direct and semi-direct effects are very sensitive to SSA. The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.

In this thesis, thermal effects on Cr4+:YAG fiber are studied through numerical modeling. Crystal fiber was used as the gain medium in amplified spontaneous emission(ASE) light source, lasers, or amplifiers. Because the absorbed pump power can not be completely turned to signal in energy transition, some of the absorbed pumping power will be converted into heat, which raises the fiber temperature. In continuous-wave regime, maximum temperature, the steady-state temperature profile, and thermal stresses in the host material under single end pump are obtained by using the commercial finite elements method software ANSYS. The pump power was propagated with exponential decay inside the fiber. Because more heat was generated at the light incident region, a maximum temperature of 397K was observed from the simulation result at the same region under single-end pump of 3W. Simultaneously, a maximum tensile stress of 39 MPa was reached at the border between YAG and Silica. Finally, temperature profiles and thermal stresses were calculated in the other conditions.

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This dissertation presents an experimental and theoretical study of subsynchronous rotordynamic instability in rotors caused by interference and shrink fit interfaces. The experimental studies show the presence of strong unstable subsynchronous vibrations in two different rotor setups with interference and shrink fit interfaces that were operated above their first critical speeds. The unstable vibrations occur at the first natural frequency of the rotor-bearing system. The instability caused complete wreckage of the test rig in one of the setups showing that these vibrations are potentially dangerous to the safe operation of rotating machines. The two different rotor setups that are studied are a single-disk rotor mounted on a uniform diameter shaft and a two-disk rotor with an aluminum sleeve shrink fitted to it at the outer surface of the two disks. In the single-disk rotor, an adjustable interference arrangement between the disk and the shaft is obtained through a tapered sleeve arrangement, which acts as the interference fit joint. The unstable sub-synchronous vibrations originate from slippage in the shrink fit and the interference fit interfaces that develop friction forces, which act as destabilizing cross-coupled moments when the rotor is operated above its first critical speed. The unique contribution offered through this work is the experimental validation of a physically correct model of internal friction which models the destabilizing mechanism as a system of cross-coupled internal moments at the shrink fit interface. The dissertation describes stability simulations of various test rotor setups using the correct internal moments model. A commercial finite-element based software called XLTRCTM is used to perform rotordynamic simulations for stability studies. The method of stability study is the computation of eigenvalues of the rotor-bearing system. A negative real part of the eigenvalue indicates instability. The simulations include the test rotors that were experimentally observed as stable and unstable with shrink and interference fit interfaces in their assemblies. The dissertation also describes the simulations of various imagined rotor configurations with shrink fit interfaces, and seeks to explain how configurations differ on rotordynamic stability depending upon several rotor-bearing parameters such as geometry and elastic properties, as well as upon the amount of internal friction parameters, which differ from configuration to configuration.

Voters are exposed to vastly different campaign environments based on their geographic location. This results in heterogeneity in the intensity and communicative content that voters are exposed to across a nationally representative sample. The present analysis seeks to leverage this variance in communication environments facing voters to better capture the effects of campaign priming. I find that when taking account of the communications that voters face, the effects of priming are clearer, but also more complex. / text

This research focuses on understanding the processes involved in successful innovation---a topic that has appeared in a large body of research, but no conclusive trend has emerged about it. For this reason, I chose a different lens in order to gain a more panoramic view of the events leading up to an innovation. In particular, this research utilized a methodology and ontology that set it apart from previous work. In previous research control/exploitation and learning/exploration are either presented as two categorically separate concepts or as continuum that runs between them. This research supports the idea that innovation operates on a continuum but does not support the idea that it only occurs when the pendulum settles toward the learning/exploration side. Instead, the data shows that innovation could indeed occur at any point along the learning/exploration side of the continuum and even at the central point where learning/exploration and control/exploitation weigh evenly. To conceptualize this middle point, I term this a "syncretism" of two normally opposing forces to account for a significant portion of the interview data. / text

published_or_final_version / Biological Sciences / Master / Master of Philosophy