Physical Sciences and Mathematics Commons^™

The Dissolution And Recovery Of Critical Materials (Li2co3 And Uf6) From Ionic Liquid, Cassara Higgins

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lithium and uranium are critical materials in both the energy industry and for national security. Lithium is necessary for the next generation of batteries and 6Li is valuable for the production of tritium necessary for both fusion energy and to maintain our nuclear stockpiles. Uranium is a fuel source or precursor fuel source for commercially operating nuclear fission power. The monitoring of uranium hexafluoride (UF6) enrichment at foreign facilities is important for the monitoring of nuclear safeguards and enforcement of non-proliferation treaties. Recovery methods for lithium at the end of life of batteries are necessary to ensure abundance of the …

A Survey Of The Br´Ezis-Nirenberg Problem And Related Theorems, Edward Huynh

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nonlinear elliptic partial differential equations on bounded domains arise in several different areas of mathematics that include geometry, mathematical physics, and the calculus of variations. The Br ́ezis-Nirenberg problem is concerned with a boundary-value problem that is intimately connected to the existence of positive solutions of the Yamabe problem, of non-minimal solutions to Yang-Mills functionals, and of extremal functions to several important inequalities. Results on existence and uniqueness have been obtained in cases when the exponent is sub-critical, but such results have not been obtained when the exponent is critical due to a lack of compactness. The earliest results obtained …

Quality Assurance Procedures Implementation For Varian Truebeam, Yongquan Jiang

UNLV Theses, Dissertations, Professional Papers, and Capstones

Department of radiation oncology of Oncology Nevada updated its linear accelerator (LINAC) from Varian Clinac iX to a newer model known as Varian TrueBeam. The Varian TrueBeam LINAC includes 6x, 6xFFF (i.e., 6x without flattening filter known as flattening filter free), 10x, 10xFFF, 15x photon beams and 6e, 9e, 12e MeV electron beams. This system is also equipped with a 6 degree of freedom (DOF) couch, RapidArc, kV on board imager, MV portal imager and Cone Beam CT (CBCT) imaging. This system allows the clinical delivery of modern image guided radiation therapy (IGRT) modalities such as IMRT/VMAT, and SRS/SRT/SBRT. The …

Miocene Ichnofaunas And Mammalian Communities In The Great Basin Region, Nevada And California, Annmarie R. Jones

UNLV Theses, Dissertations, Professional Papers, and Capstones

The purpose of this dissertation is to document and interpret three new ichnofaunas and two fossil assemblages from the Neogene of Nevada and California. Ichnofossils are important for understanding behavior and geographical range of animals in the distant past and are key to locating and preserving sensitive material for future studies. I examined ichnofauna at three localities: two within the Mio-Pliocene Muddy Creek Formation of Nevada, and one within the Miocene China Ranch Beds of California. My research focuses primarily on (1) camelid and ursid ichnotaxa and how these new localities help in understanding the evolutionary history of these taxa …

Effects Of Distributed Energy Resources On The Bulk Electric System, Stryder Loveday

UNLV Theses, Dissertations, Professional Papers, and Capstones

The traditional power grid was designed with a centralized resource distribution in mind, with a relatively small number of large power generation facilities supplying the vast majority of load. With recent efforts to further diversify the power grid as well as an increased interest in renewable energy sources, there has been an unprecedented amount of new DistributedEnergy Resources (DERs) added to the grid within the last decade. This often heavily influences the local demand where these resources are installed, often causing power to flow in ways not anticipated by the original design of the grid. This thesis reviews the potential …

Revisiting The Chemistry Of Uranium And Rhenium Fluorides: Implication To Fuel Cycle And Nuclear Forensics Science, James Amos-Aimé Louis-Jean

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fluorine plays a major role in the nuclear industry where F2(g) and HF(g) are critical to the preparation of UF6 and UF4. These materials are prepared for uranium enrichment to increase the isotopic concentration of 235U. During separation efforts, the isotope 99Tc (a high yield fission product, 6.1% from 235U) is extracted along with uranium and can be converted to binary technetium fluorides (i.e., TcF4, TcF6) during re-enrichment of used uranium material. This provides a route for 99Tc to reenter the reactor environment and affect the nuclear properties of fuel pellets made with reprocessed uranium. The objective of this work …

Viability Of Energy And Fuel Sources For Interstellar Travel; Design And Feasibility Of The Construction Of Manned Interstellar Space Shuttles, Lukas Mittelman

UNLV Theses, Dissertations, Professional Papers, and Capstones

The importance of proving the viability of interstellar transport and addressing its potential hazards and pitfalls is immense. If we do not look toward the future and examine what could be waiting for us, we are doing our children, our children’s children, and so on, a disservice. Here we must attempt to lay the groundwork for our future scientists, engineers, and adventurers. Asking and answering questions like, which propulsion and energy systems must we incorporate to send us through the cosmos? Will we utilize technologies known today, such as fossil fuel rockets, fission or fusion rockets, and antimatter drives (pion …

An Empirical Investigation Into The Impact Of Automated Grading, Alex James St. Aubin

UNLV Theses, Dissertations, Professional Papers, and Capstones

Context: Computer Science enrollment has seen increases in recent years. At the University of Nevada, Las Vegas we have seen an average year to year growth rate of 17.33% in the spring and 13.71% in the fall over the past 10 years in our entry level programming course. These enrollment increases have led to considerable additional costs for grading course material.Objective: The goal of this study is to determine the impact of automatic grading systems on students. If automatic grading is at least as effective as manual grading in practice, it may reduce cost under the context of at least …

Some Graph Laplacians And Variational Methods Applied To Partial Differential Equations On Graphs, Daniel Anthony Corral

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this dissertation we will be examining partial differential equations on graphs. We start by presenting some basic graph theory topics and graph Laplacians with some minor original results. We move on to computing original Jost graph Laplacians of friendly labelings of various finite graphs. We then continue on to a host of original variational problems on a finite graph. The first variational problem is an original basic minimization problem. Next, we use the Lagrange multiplier approach to the Kazdan-Warner equation on a finite graph, our original results generalize those of Dr. Grigor’yan, Dr. Yang, and Dr. Lin. Then we …

Quantification Of Organic Carbon Sequestered By Biogenic Iron Sulfide Minerals In Long-Term Anoxic Laboratory Incubations, Nader Nabeh, Cheyenne Brokaw, Aude Picard

Life Sciences Faculty Research

Organic carbon sequestration in sedimentary environments controls oxygen and carbon dioxide concentrations in the atmosphere. While minerals play an important role in the preservation of organic carbon, there is a lack of understanding about the formation and stability of organo-mineral interactions in anoxic environments, especially those involving authigenic iron sulfide minerals. In this study, we quantified organic carbon and nitrogen sequestered in biogenic iron sulfide minerals co-precipitated with sulfate-reducing bacteria (SRB) in freshwater and marine conditions in long-term laboratory experiments. The amounts of C and N associated with biogenic iron sulfide minerals increased with increasing cell biomass concentrations available in …

Identification Of Lipid Species: Potential Biomarkers For Early Detection Of Hepatocellular Carcinoma, Kit Yee Leung, Kaylee Freitas

Undergraduate Research Symposium Posters

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. HCC is associated with cirrhosis. Poor survival rate of HCC is due to diagnosis of HCC at late stage.

Powering A Sustainable Electric Vehicle Future, Harmony Ruth, Jordan Brickman

Undergraduate Research Symposium Posters

Electric vehicle sales account for roughly 20% of total sales world wide and are projected to be 80% by 2050. China's electric vehicle market holds a 13.3% market share. China exported 550,000 electric vehicles in 2021. China represents a 54% share of the world's coal consumption as of 2020. Why study China on this issue? China is a major player in the World Economy.

Dispersion In High Temperature Superconductors, Lazar Novakovic

Undergraduate Research Symposium Podium Presentations

Superconductors are used in many different industries: Efficient power transmission, Maglev train, MRIs

Low-Cost Adsorbent For Disinfection Byproduct Removal From Drinking Water, Savanna Vacek, Suraj Pochampally

Undergraduate Research Symposium Posters

Disinfection byproducts (DBPs) are harmful contaminants that are unintentionally created in disinfected water after chlorination. Activated carbon, often expensive and difficult to acquire in low-income and rural areas, has previously been used to remove DBPs from drinking water. Biochar is made from agricultural waste (i.e. feedstock) and has been identified as a low-cost yet effective adsorbent to remote contaminants from drinking water. This work focuses on the efficacy of biochar and activated carbon to remove DBPs from drinking water for the purpose of treating drinking water after emergency chlorination. This study has the potential to help water distributors and disadvantaged …

Synthesis Of Modified Walnut Shell Biochar And Material Characterization In Ground Water Treatment, Maaike Parajes, Suraj Pochampally

Undergraduate Research Symposium Posters

Biochar (BC) is a carbon-rich material synthesized from the pyrolysis of biomasses and developed to remove soil and wastewater contaminants. The pyrolysis process involves thermally decomposing the organic materials in the absence of oxygen. Biochar has the potential to be an eco-friendly and effective adsorbent for heavy metals and toxic organic compounds. An adsorbent is a material that attracts other substances on its surface, chemically and physically. Walnut shells were chosen for the biochar modification to improve the surface morphology, pore structure, and adsorption capability.

Biochar Hydrophilicity Characterization By A Smartphone-Based Apparatus: Design, Construction, And Measurement Calibration, Emma Letourneau, Suraj Pochampally

Undergraduate Research Symposium Posters

Water contact angles are used to determine hydrophilicity, which is a material's attraction to water. A water contact angle of greater than 90 degrees indicates a hydrophobic material that repels water, whereas a contact angle of less than 90 degrees indicates a hydrophilic material [Fig. 1]. Water contact angles are measured through a goniometer, which can cost between $2000 to $10,000.

Biochar is a porous carbon material created from biological waste products, that is pyrolyzed (i.e. burned) in a low-oxygen, high heat environment. Biochar can be used to remove contaminants from water and remediate soil while reusing waste, making it …

Expanding The Library Of Planet Building Materials In Magrathea, Rosalie Chaleunsouck, Tristan Benally

Undergraduate Research Symposium Posters

Exoplanets are often modeled with fully-differentiated layers of iron, silicates, water, and gas. The large pressure and temperature ranges within each layer results in changes of phase and mineral equilibrium. MAGRATHEA is an open-course planet interior structure code with a large library of equations of state for planet building materials. This allows for the user to build detailed planet models and test differing measurements of the equation of state. We extend MAGRATHEA's library to include upper-mantle materials and various phases of iron cores. We show the impact of these materials on the characterization of rocky planet interiors.

Microbial Life In Deep-Subsurface Environments: The Role Of High Pressure In Biogeochemical Cycles, Cheyenne Brokaw

Undergraduate Research Symposium Posters

Ocean World: An ocean world is considered any planet or moon currently with a liquid ocean. While the deepest part of the Ocean (Mariana Trench, 11,000 mbsl, 110 Mpa) and the lithosphere host microbial life, it begs the question, How?

Climate Change Hope Scale: Factor Analysis In An Adult Sample, Gemma Ortega, Steven J. Glover, Jesse Tabaczynksi, Orei Z. Odents

Undergraduate Research Symposium Posters

Willpower - how much individuals believe that set goals can be met. Waypower - the extent to which individuals can think of strategies for accomplishing those goals.

The Climate Change Hope Scale (CCHS; Li & Monroe, 2017) was designed to measure three aspects of hope: 1. Personal sphere willpower and waypower (WP) 2. Collective sphere willpower and waypower (CW) 3. Lack of willpower and waypower (LW).

A three-factor model fits the CCHS among adolescents. The purpose of our study was to determine if the three-factor model fits the CCHS in adults.

Validation Of Accelerometry As A Digital Phenotyping Measure Of Negative Symptoms In Schizophrenia, Gregory P. Strauss, Ian M. Raugh, Luyu Zhang, Lauren Luther, Hannah C. Chapman, Daniel N. Allen, Brian Kirkpatrick, Alex S. Cohen

Physics & Astronomy Faculty Research

Negative symptoms are commonly assessed via clinical rating scales; however, these measures have several inherent limitations that impact validity and utility for their use in clinical trials. Objective digital phenotyping measures that overcome some of these limitations are now available. The current study evaluated the validity of accelerometry (ACL), a passive digital phenotyping method that involves collecting data on the presence, vigor, and variability of movement. Outpatients with schizophrenia (SZ: n = 50) and demographically matched healthy controls (CN: n = 70) had ACL continuously recorded from a smartphone and smartband for 6 days. Active digital phenotyping assessments, including surveys …

Systematic Paleontology, Acritarch Biostratigraphy, And Δ13c Chemostratigraphy Of The Early Ediacaran Krol A Formation, Lesser Himalaya, Northern India, Shuhai Xiao, Ganqing Jiang, Qin Ye, Qing Ouyang, Dhiraj M. Banerjee, Birendra P. Singh, A. D. Muscente, Chuanming Zhou, Nigel C. Hughes

Geoscience Faculty Research

Acritarch biostratigraphic and δ13C chemostratigraphic data from the Krol A Formation in the Solan area (Lesser Himalaya, northern India) are integrated to aid inter-basinal correlation of early–middle Ediacaran strata. We identified a prominent negative δ13C excursion (likely equivalent to EN2 in the lower Doushantuo Formation in the Yangtze Gorges area of South China), over a dozen species of acanthomorphs (including two new species—Cavaspina tiwariae Xiao n. sp., Dictyotidium grazhdankinii Xiao n. sp.), and numerous other microfossils from an interval in the Krol A Formation. Most microfossil taxa from the Krol A and the underlying Infra-Krol formations are also present in …

In Situ Recording Of Mars Soundscape, S. Maurice, B. Chide, N. Murdoch, R. D. Lorenz, D. Mimoun, R. C. Wiens, Arya Udry, The Supercam Team

Geoscience Faculty Research

Before the Perseverance rover landing, the acoustic environment of Mars was unknown. Models predicted that: (1) atmospheric turbulence changes at centimetre scales or smaller at the point where molecular viscosity converts kinetic energy into heat1, (2) the speed of sound varies at the surface with frequency2,3 and (3) high-frequency waves are strongly attenuated with distance in CO2 (refs. 2,3,4). However, theoretical models were uncertain because of a lack of experimental data at low pressure and the difficulty to characterize turbulence or attenuation in a closed environment. Here, using Perseverance microphone recordings, we present the first characterization of the acoustic environment …

Temporal Scattering, Depolarization, And Persistent Radio Emission From Magnetized Inhomogeneous Environments Near Repeating Fast Radio Burst Sources, Yuan-Pei Yang, Wenbin Lu, Yi Feng, Bing Zhang, Di Li

Physics & Astronomy Faculty Research

Some repeating fast radio burst (FRB) sources exhibit complex polarization behaviors, including frequencydependent depolarization, variation of rotation measure (RM), and oscillating spectral structures of polarized components. Very recently, Feng et al. reported that active repeaters exhibit conspicuous frequency-dependent depolarization and a strong correlation between RM scatter (σRM) and the temporal scattering time (τs), s s 1.0 0.2, both of which can be well described by multipath propagation through a magnetized inhomogeneous plasma screen. This observation strongly suggests that the temporal scattering and RM scatter originate from the same region. Besides, a particular finding of note in Feng et al. is …

Exploratory Analysis Of The Associations Between Neonicotinoids And Measures Of Adiposity Among Us Adults: Nhanes 2015–2016, Amruta M. Godbole, Sheniz Moonie, Courtney Coughenour, Cai Zhang, Aimin Chen, Ann M. Vuong

Environmental & Global Health Faculty Research

Background: Toxicology studies suggest that neonicotinoids may be associated with adiposity development via thyroid hormone disruption and increased oxidative stress. Prior epidemiological studies report mixed results for the association between neonicotinoids and adiposity measures.

Objective: To examine the association between detectable concentrations of parent neonicotinoids (imidacloprid, acetamiprid, clothianidin) and neonicotinoid metabolites (5-hydroxy-imidacloprid, N-desmethyl-acetamiprid) with adiposity measures among US adults, and whether sex modifies the associations for neonicotinoid metabolites with adiposity.

Methods: National Health and Nutrition Examination Survey (NHANES) 2015–2016 data was utilized to estimate covariate-adjusted associations between detectable neonicotinoids and fat mass index (FMI), lean mass index (LMI), waist …

3-Multi Ranked Encryption With Enhanced Security In Cloud Computing, Yeeun Kim, Junggab Son, Reza M. Parizi, Gautam Srivastava, Heekuck Oh

Computer Science Faculty Research

Searchable Encryption (SE) enables data owners to search remotely stored ciphertexts selectively. A practical model that is closest to real life should be able to handle search queries with multiple keywords and multiple data owners/users, and even return the top-k most relevant search results when requested. We refer to a model that satisfies all of the conditions a 3-multi ranked search model. However, SE schemes that have been proposed to date use fully trusted trapdoor generation centers, and several methods assume a secure connection between the data users and a trapdoor generation center. That is, they assume the trapdoor generation …

Investigating The Future Potential Of An Upgraded Alma To Image Planet-Forming Disks At Sub-Astronomical-Unit Scales, Benjamin P. Burrill, Luca Ricci, Sarah K. Harter, Shangjia Zhang, Zhaohuan Zhu

Physics & Astronomy Faculty Research

In recent years, ALMA has been able to observe large-scale substructures within protoplanetary disks. Comparison with the predictions from models of planet–disk interactions has indicated that most of these disk substructures can be explained by the presence of planets with the mass of Neptune or larger at orbital radii of ≈5–100 au. Better resolution is needed to observe structures closer to the star, where terrestrial planets are expected to form, as well as structures opened by planets with masses lower than Neptune. We investigate the capabilities of a possible extension to ALMA that would double the longest baseline lengths in …

Depression And Factors Impacting Quality Of Life Among Adults With Asthma Presence In Nevada, Elizabeth D. Kahane, Lung-Chang Chien, Brian Labus, Dharini M. Bhammar, Jocy-Anna Chevalier, Sheniz Moonie

Epidemiology & Biostatistics Faculty Research

Background: Asthma, a chronic, non-communicable disease has been shown to negatively affect mental health and quality of life among adults. Annually approximately 8% of adult Nevadans report current asthma symptoms and 12.6% report having a lifetime diagnosis. The purpose of this study was to evaluate the association between asthma and depression and explore quality of life factors affecting adult Nevadans with asthma. Methods: Using behavioral risk factor surveillance system (BRFSS) data, this study evaluated the association between self-reported asthma and depression in Nevada using weighted multiple logistic regression. BRFSS asthma call-back survey (ACBS) data were used to determine the frequency …

Dark Fluxes From Accreting Black Holes Through Several Mechanisms, Rong-Gen Cai, Sichun Sun, Bing Zhang, Yun-Long Zhang

Physics & Astronomy Faculty Research

We discuss the possibility that accreting black hole systems can be sources for dark matter flux through several different mechanisms. We firstly discuss two types of systems‘: coronal thermal plasmas around supermassive black holes in active galactic nuclei (AGNs), and accretion disks of stellar-mass X-ray black hole binaries (BHBs). We explore how these black hole systems may produce keV light dark matter fluxes and find that the dark fluxes from those sources might be too weak to account for the current XENON1T excess. On the other hand, black holes can be good accelerators to accrete and boost heavy dark matter …

Circumbinary Disk Evolution In The Presence Of An Outer Companion Star, Rebecca G. Marin, Stephen Lepp, Stephen H. Lubow, Matthew A. Kenworthy, Grant M. Kennedy, David Vallet

Physics & Astronomy Faculty Research

We consider a hierarchical triple system consisting of an inner eccentric binary with an outer companion. A highly misaligned circumbinary disk around the inner binary is subject to two competing effects: (i) nodal precession about the inner binary eccentricity vector that leads to an increase in misalignment (polar alignment) and (ii) Kozai–Lidov (KL) oscillations of eccentricity and inclination driven by the outer companion that leads to a reduction in the misalignment. The outcome depends upon the ratio of the timescales of these effects. If the inner binary torque dominates, then the disk aligns to a polar orientation. If the outer …

Macroscale Robust Superlubricity On Metallic Nbb2, Jia Wang, Chang Liu, Kaifei Miao, Kan Zhang, Weitao Zheng, Changfeng Chen

Physics & Astronomy Faculty Research

Robust superlubricity (RSL), defined by concurrent superlow friction and wear, holds great promise for reducing material and energy loss in vast industrial and technological operations. Despite recent advances, challenges remain in finding materials that exhibit RSL on macrolength and time scales and possess vigorous electrical conduction ability. Here, the discovery of RSL is reported on hydrated NbB2 films that exhibit vanishingly small coefficient of friction (0.001–0.006) and superlow wear rate (≈10−17 m3 N−1 m−1) on large length scales reaching millimeter range and prolonged time scales lasting through extensive loading durations. Moreover, the measured low resistivity (≈10−6 Ω m) of the …