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Full-Text Articles in Physical Sciences and Mathematics

Developments Of Machine Learning Potentials For Atomistic Simulations, Howard Yanxon Dec 2020

Developments Of Machine Learning Potentials For Atomistic Simulations, Howard Yanxon

UNLV Theses, Dissertations, Professional Papers, and Capstones

Atomistic modeling methods such as molecular dynamics play important roles in investigating time-dependent physical and chemical processes at the microscopic level. In the simulations, energy and forces, sometimes including stress tensor, need to be recalculated iteratively as the atomic configuration evolves. Consequently, atomistic simulations crucially depend on the accuracy of the underlying potential energy surface. Modern quantum mechanical modeling based on density functional theory can consistently generate an accurate description of the potential energy surface. In most cases, molecular dynamics simulations based on density functional theory suffer from highly demanding computational costs. On the other hand, atomistic simulations based on …


Chemical And Electronic Surface Structure Of Chalcopyrite-Based Thin Films For Solar Water Splitting, James C. Carter May 2020

Chemical And Electronic Surface Structure Of Chalcopyrite-Based Thin Films For Solar Water Splitting, James C. Carter

UNLV Theses, Dissertations, Professional Papers, and Capstones

In recent years, various thin film solar devices have reached markedly high efficiencies on both the laboratory and large area scale. To further evaluate their potential, and help drive device optimization of efficient solar devices, a detailed understanding of the chemical and electronic structure of the surfaces and interfaces is required. It is these interfaces that play a pivotal role in dictating aspects of device performance. Chalcopyrite-based materials, such as Cu(In,Ga)S2 (CIGS) are regarded as one of the most promising absorber materials for use in highly efficient solar devices. In the context of photoelectrochemical (PEC) hydrogen generation, the tunability of …


Characterization Of Beryllium Ion Complexation In The Presence Of Biological Buffers Using Isothermal Titration Calorimetry, Guillermo Alexander Ramirez May 2020

Characterization Of Beryllium Ion Complexation In The Presence Of Biological Buffers Using Isothermal Titration Calorimetry, Guillermo Alexander Ramirez

UNLV Theses, Dissertations, Professional Papers, and Capstones

Be2+ ion is a biologically active metal that is capable of binding to proteins and has been shown to affect various cellular processes. When treated with Be2+, certain cancer cells display cytostatic effects. GSK3β is a regulatory kinase involved in the β-catenin pathway that may be involved in producing these cytostatic effects when Be2+ binds to it. In order to determine binding parameters between Be2+ and GSK3β, isothermal titration calorimetry (ITC) can be utilized. However, titrations at physiological pH cannot be carried out due to Be2+ unique speciation at neutral pH ranges. Significant precipitation occurs at pH 6 and higher …


Investigations Of Technetium Metal And The Synthesis Of Binary Technetium Nitrides Under Extreme Conditions, Emily Siska May 2020

Investigations Of Technetium Metal And The Synthesis Of Binary Technetium Nitrides Under Extreme Conditions, Emily Siska

UNLV Theses, Dissertations, Professional Papers, and Capstones

Technetium (Tc) is the lightest of the radioactive elements and has no stable isotopes. Significant quantities of Tc are not naturally occurring on earth. However, technetium is found in high fission yield in nuclear reactors and produced for medical imaging. With its long half life, and high mobility in the environment make it of particular interest. To that end, the fundamental chemistry of Tc and Tc compounds is not as well understood compared to neighboring elements on the periodic table. Therefore, fundamental studies designed to better understand this transition metal, coupled with more targeted investigation at high temperature and pressure …


Synthesis And Characterization Of Synthetic Urban Melt Glass, Rebecca Kristien Lowe May 2020

Synthesis And Characterization Of Synthetic Urban Melt Glass, Rebecca Kristien Lowe

UNLV Theses, Dissertations, Professional Papers, and Capstones

Melt glass formed from the explosion of a nuclear device is a unique post-detonation material that can aid in the ensuing forensics investigation. Trapped in the melt glass are chemical and isotopic signatures that can provide diagnostic and source information about the weapon by comparison with documentation of previous detonations. A nuclear terrorist attack would likely take place in an urban environment and as such, the melt glass formed would consist of a complex matrix including urban materials like cement and glass, activation products from the large neutron flux that will be seen, and fission products from the detonation. The …