Physical Sciences and Mathematics Commons^™

Interference Effects Of Urban Rubble On The Radioanalytical Analysis Of Strontium, Derek Roger Mclain

UNLV Theses, Dissertations, Professional Papers, and Capstones

Most current radioanalytical protocols have been developed for the analysis of air, water, soil and bioassay samples. While these protocols build the foundation of operational environmental monitoring, they are not necessarily suitable for the analysis of samples that will be encountered in the aftermath of a nuclear incident. In such a situation, it will be important to characterize the isotopes of interest present in the affected area to obtain signatures for nuclear forensics and ensure the appropriate response. Specifically, this research is aimed at the determination of strontium-90 and its separation from zirconium-90 in a post-detonation situation.

Strontium-90’s relatively long …

The San1 Ubiquitin Ligase Functions Preferentially With Ubiquitin-Conjugating Enzyme Ubc1 During Protein Quality Control, Rebeca Lea Ibarra

UNLV Theses, Dissertations, Professional Papers, and Capstones

Protein quality control (PQC) is a critical process wherein misfolded or damaged proteins are cleared from the cell to maintain protein homeostasis. In eukaryotic cells, the removal of misfolded proteins is primarily accomplished by the ubiquitin-proteasome system (UPS). In the UPS, ubiquitin-conjugating enzymes and ubiquitin ligases append poly-ubiquitin chains onto misfolded protein substrates signaling for their degradation. The kinetics of protein ubiquitylation are paramount since a balance must be achieved between the rapid removal of misfolded proteins versus providing sufficient time for protein chaperones to attempt refolding. To uncover the molecular basis for how PQC substrate ubiquitylation rates are controlled, …

Structural Behavior Of Nbsexte2-X Superconductors Under High Pressure, Vahe Mkrtchyan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Niobium chalcogenide compounds have recently gained a great deal of interest due to the fact that a superconducting phase coexists with the charge density wave state (CDW), as well as their potential for numerous applications. Two superconducting compositions, NbSexTe2-x (x=2, 1.5) were prepared by solid state route using high purity Nb, Se, and Te powders. Powder X-ray diffraction patterns collected at ambient conditions for NbSe2 and NbSe1.5Te0.5 showed a single phase with hexagonal crystal structure, with space group P63mmc. High-pressure X-ray diffraction measurements were performed at the Advanced Photon Source at Argonne National Laboratory to investigate structural stability up to …

Novel Pathways To High-Efficiency Chalcopyrite Photovoltaic Devices: A Spectroscopic Investigation Of Alternative Buffer Layers And Alkali-Treated Absorbers, Michelle Mezher

UNLV Theses, Dissertations, Professional Papers, and Capstones

Within the past few years, breakthroughs in Cu(In,Ga)Se₂ (CIGSe) thin-film photovoltaic device efficiencies (on a laboratory scale) were achieved utilizing alkali-treated (KF) absorbers. Na incorporation in the CIGSe absorber, either diffused from the substrate or deliberately deposited, affects the surface electronic properties of the CIGSe absorber. The role of Na, however, is still not fully understood with some studies suggesting that Na also passivates defects at the grain boundaries. Replacing Na with K offered an efficiency boost resulting in KF treatments becoming the new “hot topic” in the chalcopyrite field, both in terms of understanding how the treatment changes …

Forcing Cesium Into Higher Oxidation States Via Useful Hard X-Ray Induced Chemistry At Extreme Conditions, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

Recent theoretical work published in Nature Chemistry postulates the existence of cesium in high oxidation states when bonding with fluorine. It is thus predicted to behave as a p-block element (such as xenon) at pressures above 5 GPa. At these pressures, fluorine atoms may bond with the inner p-shell electrons forming CsFn, where n may vary from 2 up to 6; thus the oxidation state of Cs may change up to 6+. My research focused on physically synthesizing these compounds and to verify that, given the right conditions, bonding doesn't only occur with valence electrons, but with the inner p-shell …

Ionic Polymer-Metal Composite Actuators Based On Nafion Blends With Functional Polymers, Jungsoo Nam

UNLV Theses, Dissertations, Professional Papers, and Capstones

Ionic polymer metal composites (IPMCs) have been an attractive research subject for use in underwater robotic applications, biomedical and biomimetic application owing to their great potential as actuators, artificial muscles, and more. IPMC is synthetic composite nanomaterial of ion exchange membranes and metal electrode. Although both components are important, the properties of ion exchange membranes should be emphasized since it is responsible of the path for the mobile ions to migrate when voltage is applied to exhibit deformation. Most of the researches that have been done on IPMCs used commercially available Nafion as their ion exchange membranes. However, its high …

The Proof Is In The Pots: Residue Analysis Of Virgin Branch Puebloan Ceramics, Brenna Lynn Wilkerson

UNLV Theses, Dissertations, Professional Papers, and Capstones

This study focuses on better understanding diet and subsistence strategies among Virgin Branch Puebloan groups living in the Moapa Valley in southern Nevada and on the Shivwits Plateau in northwestern Arizona. Gas chromatography-mass spectrometry (GC-MS) was used to identify absorbed food residues in three types of Virgin Branch Puebloan ceramics (Moapa Gray Ware, Shivwits Ware, and Tusayan Virgin Series). The data produced by the residue analysis were used to compare patterns of subsistence between Virgin Branch Puebloan sites in the lowlands along the Muddy River and at upland sites on the Shivwits Plateau as these two areas have different environments …

Direct Dissolution And Electrochemical Investigation Of Cerium And Uranium In Ionic Liquid, Janelle Droessler

UNLV Theses, Dissertations, Professional Papers, and Capstones

The solubility, coordination and speciation of f-elements in ionic liquids (ILs) has been the focus of numerous studies because the purely ionic systems have unique physical properties that can be exploited in comparison to aqueous, organic, or molten salt systems. Ionic liquids are thermally stable, have negligible vapor pressure, and are electrochemically stable at negative potentials that encompass the reduction potential of actinide species. Literature has suggested that the properties of ILs could potentially be utilized in the nuclear fuel cycle for separations and reprocessing. However, the solubility of f-elements in ILs has been significantly lower compared to traditional solvents. …

Strategic Molecular Design To Engineer The Electron Affinity Of Self-Assembling Organic Semiconductors, Kelly Nicole Zaugg

UNLV Theses, Dissertations, Professional Papers, and Capstones

Development of electron-accepting (n-type) semiconductors used in organic photovoltaic cells and field effect transistors has been an area of research with less advancement compared to their electron-donating (p-type) counterparts. Currently, the highest performing n-type semiconductor is a fullerene-based derivative (PCBM) with a favorable ELUMO of -4.08 eV. However, PCBM has limited absorption in the visible region and fixed electron affinity. This work focuses on the development of self-assembling n-type materials with controllable electronic properties by strategically lowering ELUMO to a level comparable to PCBM. Molecular design follows an acceptor-acceptor'-acceptor (A-A'-A) configuration; with A being two 2,3-dioctyloxyphenazine substituents connected to A’ …