Physical Sciences and Mathematics Commons^™

Instrumentation For Dynamic Nuclear Polarization And Application Of Electron Decoupling For Electron Relaxation Measurement, Nicholas Howard Alaniva

Arts & Sciences Graduate Student Theses and Dissertations

Dynamic nuclear polarization nuclear magnetic resonance (DNP NMR) exploits internal electron spin and nuclear spin interactions to increase sensitivity and uncover valuable information regarding structure and dynamics of a system. To manipulate these interactions, instrumentation is developed to combine high-power microwave and radiofrequency irradiation with the ability to spin samples at the magic angle (MAS) at temperatures from 90 K to 4.2 K. Electron decoupling uses frequency-modulated microwaves to mitigate the electron-nuclear dipolar interaction, improving signal intensity and resolution in DNP NMR experiments. Electron decoupling is combined with short DNP periods to encode electron spin information in polarized nuclear signal. …

Zirconium Tetrachloride, Fundamental Chemistry And Nuclear Fuel Cycle, Rosendo Borjas Nevarez

UNLV Theses, Dissertations, Professional Papers, and Capstones

Zirconium alloys are used in the United States as cladding materials in nuclear reactors. The purification of Zr is of relevance due to the large amount of spent nuclear fuel produced every year (2,000 metric tons per year and rising), of which 25% corresponds to radioactive zirconium cladding. Through the recovery and reuse of Zr, estimated savings of $40 million per year are estimated due to the high cost of hafnium-free nuclear grade zirconium, and also due to the minimization of nuclear waste disposal requirements.

Several chemical approaches have been proposed for the recovery and purification of Zr. Historically, a …

Arbitrary High Order Finite Difference Methods With Applications To Wave Propagation Modeled By Maxwell's Equations, Min Chen

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation investigates two different mathematical models based on the time-domain Maxwell's equations: the Drude model for metamaterials and an equivalent Berenger's perfectly matched layer (PML) model. We develop both an explicit high order finite difference scheme and a compact implicit scheme to solve both models. We develop a systematic technique to prove stability and error estimate for both schemes. Extensive numerical results supporting our analysis are presented. To our best knowledge, our convergence theory and stability results are novel and provide the first error estimate for the high-order finite difference methods for Maxwell's equations.

Evaluating Parents Sociodemographic Factors And Childhood Vaccine Decisions, Mehret Girmay

UNLV Theses, Dissertations, Professional Papers, and Capstones

Vaccination is considered one of the most successful public health achievements of the 20th century. However, with increasing vaccine skepticism emerging over the past decades, there is a threat to the ongoing sustainment of vaccine coverage within all US communities. This study evaluated and compared parents’ sociodemographic factors associated with childhood vaccine decisions. This study is a secondary analysis of 893 parents/guardians, age 18-55 years with child(ren) < 7 years living in the U.S.

Predictive analysis was conducted using multinomial logistic regression modeling was used to examine vaccine decisions (accept, hesitant, and refuse) in relation to parents’ sociodemographic factors. Overall, (66.6%) of parents accepted recommended vaccines, while …

The Retrospective Analysis Of Radionuclides In Banded Coral From The Bikini Atoll, Athena Marie Gallardo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Nuclear weapons testing conducted within the Bikini Atoll in the Marshall Islands resulted in local fallout contamination, including long lived isotopes of plutonium (Pu) and uranium (U), within the surrounding environment. The Bikini lagoon provides a continuous source of Pu (239+240Pu) and U (236U) to the Pacific Basin. The rate at which these isotopes are flushed from the lagoon to the ocean is balanced by inputs from remobilization of lagoon sediments. This research will provide a basis for predicting future change in the solubility and export potential of Pu and U in lagoon sediments. This is important to better understand …

On Algebraic Structures And Automaton For Optimal Computer Network Design And Performance Study, Xiangrong Ma

UNLV Theses, Dissertations, Professional Papers, and Capstones

For decades, study of computer networks has been concentrated on the use of the well-established OSI or TCP/IP reference models that have found tremendous success in the actual implementation of various network structures and protocols. Lack of theoretical foundation, this implementation-driven, empirical approach, however, is experiencing insurmountable difficulties in delivering, tuning for, and sustaining the promised peak performance of a computer system that is so heavily dependent on the performance of the underline computer networks. This issue is becoming particularly prevalent in today’s cloud-based high-performance computing environment where CPU-time-extensive computation loads need to get distributed among computing machines through high-speed …

Characterizing Compact Game Trees, Andrew Dubose

UNLV Theses, Dissertations, Professional Papers, and Capstones

It is well-known that the body of a game tree of height less than or equal to ω is compact

if and only if the tree is finitely branching. In this thesis, we develop necessary and sufficient

conditions for the body of any game tree to be compact.

Examination Of Maskelynite Through Static Recompression And Dynamic Compression, Justin James Reppart

UNLV Theses, Dissertations, Professional Papers, and Capstones

This is an experimental study that aims to clarify the possible formation mechanisms of maskelynite. Maskelynite is a diaplectic glass, that forms during shock compression of feldspar far below the melting point, and without fusion. Maskelynite also paramorphises precursor feldspar grains. Maskelynite is an important probe of shock-pressures at terrestrial impact sites and in many meteorites. Two mechanisms of formation of maskelynite are examined here: 1) maskelynite is result of a pressure-induced amorphization of feldspar compressed beyond its mechanical stability where the formation of thermodynamically stable phases is kinetically inhibited [1, 2]. 2) Feldspar transforms upon dynamic compression into a …

Application Of Data-Driven And Process-Based Modeling Approaches For Water Quality Simulation In Lakes And Freshwater Reservoirs, Ali Saber Sichani

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lakes and freshwater reservoirs often serve as the primary drinking and irrigation water sources for surrounding communities. They provide recreational and tourism opportunities, thereby promoting the prosperity of neighboring communities. Reliable estimates of water quality in lakes and reservoirs can improve management practices to protect water resources.

Seasonal water temperature and solar shortwave radiation variations, and their subsequent interactions with water column aquatic life, combined with seasonal variations of mixing intensity throughout the water column, result in variations of water quality constituents with depth during the annual cycle. The complexity of these variations entails the use of advanced water quality …

Carbon Management And Volatile Fatty Acid Production In Primary Clarifiers At A Wastewater Treatment Plant, Brittany Nicole Radke

UNLV Theses, Dissertations, Professional Papers, and Capstones

An increasing number of treatment plants are required to remove nutrients from domestic wastewater to lessen the impact of nutrient loading to water bodies. Enhanced Biological Phosphorus Removal (EBPR) is one of the processes commonly used to remove phosphorus from domestic wastewater. The presence of an adequate quantity of volatile fatty acids (VFA) in the wastewater influent to EBPR is important for process efficiency and stability. The objective of this research was to investigate the production of VFAs through fermentation of sludge in primary clarifiers as it related to improving nutrient removal, primarily targeting phosphorus.

The research tested, in full-scale, …

The Timing Of Dynamical Interactions Between Planets In Exoplanetary Systems, David Robert Rice

UNLV Theses, Dissertations, Professional Papers, and Capstones

During the late stage of planet formation, a system is often dynamically packed with protoplanets. These bodies collide together and are ejected from the system to form the final planets. The duration of stability before these dynamical interactions occur is dependent on the initial separation of the bodies in a system. Previous works have shown that the time before a planet-planet close encounter is exponential with the initial planet spacing measured in units of mutual Hill radius. We investigate the limitations of these previous studies. We find that systems that are initially similar can have larger differences in stability times …

On Improving Performance Of The Binary Logistic Regression Classifier, Michael Chang

UNLV Theses, Dissertations, Professional Papers, and Capstones

Logistic Regression, being both a predictive and an explanatory method, is one of the most commonly used statistical and machine learning method in almost all disciplines. There are many situations, however, when the accuracies of the fitted model are low for predicting either the success event or the failure event. Several statistical and machine learning approaches exist in the literature to handle these situations. This thesis presents several new approaches to improve the performance of the fitted model, and the proposed methods have been applied to real datasets.

Transformations of predictors is a common approach in fitting multiple linear and …

On Muddy Banks: An Ecoethnography Of A River Island Community, Nicholas Baxter

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this study, I examine the relationship between a river and a community. Specifically, I analyze the processes and patterns that organize the nature-society relationship and define the river town of Sabula, IA. To guide my historical and ethnographic analysis, I utilize a co constructionist posture (Rice 2013), which sees culture, community, economy, and physicality as much a product of bio-physical forces as social forces. My aim is to understand how Sabula is conjointly constructed and reveal the nuanced interconnections between human communities and nature through which social and environmental problems play out. My analysis clarifies patterns in residents’ identity …

Moisture Dynamics Of A Near-Surface Desert Soil, Yuan Luo

UNLV Theses, Dissertations, Professional Papers, and Capstones

Desert soils cover about one third of the Earth’s land surface. Despite their large extent, however, our understanding of desert soil hydraulic processes and properties is still rather limited. In particularly with respect to the near-surface (top centimeters) of the soil profile, which play a critical role for infiltration, redistribution and evapotranspiration of rainwater, the limiting resource for life in desert environments, but also hosts most of the biologic activity and controls runoff, erosion as well as the emission of dust (Nannipieri et al.,2003; Bradford et al.,1987). Additionally, deserts are ideal locations for electricity generation with solar energy using large-scale …

Utility Of Bench Scale Sand Tank Experiments At Assessing Permeable Reactive Barrier Design, Brandon Meier

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of this work was to evaluate the utility of bench scale sand tank experiments at assessing permeable reactive barrier (PRB) design. Our criteria for meeting this goal was that differences between PRB designs could be identified solely by measuring concentration in outflow from the sand tank models. For our PRB designs (funnel-and-gate, staggered wells, and parallel bars), numerical simulations clearly showed that PRB design had a quantifiable effect on outflow concentration, provided that the solute reacted with the PRB materials. Conversely, use of a conservative (non-reactive) solute did not allow us to discern between PRB design alternatives. Employing …

Mojave Desert Plant Community Long-Term Response To Disturbance, Dominic M. Gentilcore

UNLV Theses, Dissertations, Professional Papers, and Capstones

All vegetation communities have been shaped by disturbances. This dissertation consists of three separate chapters: Blackbrush (Coleogyne ramosissima) natural regeneration in the Great Basin-Mojave Desert Transition Zone on two fires, Long-term Response to Fire in Eastern Mojave Desert semi-arid shrubland communities, and an Annotated Checklist of Gold Butte National Monument in the Mojave-Colorado Plateau Transition Zone. The section on blackbrush natural regeneration was a long-term dataset from two fires in Basin and Range National Monument that burned in 2008 with monitoring events in 2009, 2010, 2011, 2018 and 2019. The monitoring documented some of the strongest post-fire regeneration for the …

On The Human Factors Impact Of Polyglot Programming On Programmer Productivity, Phillip Merlin Uesbeck

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyglot programming is a common practice in modern software development. This practice is often considered useful to create software by allowing developers to use whichever language they consider most well suited for the different parts of their software. Despite this ubiquity of polyglot programming there is no empirical research into how this practice affects software developers and their productivity. In this dissertation, after reviewing the state of the art in programming language and linguistic research pertaining to the topic, this matter is investigated by way of two empirical studies with 109 and 171 participants solving programming tasks. Based on the …

Pressure Driven Electronic Band Gap Engineering In Tin(Iv)-O,N Compounds, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

The intrinsic link between long-range order, coordination geometry, and the electronic properties of a system must be understood in order to tailor function-specific materials. Although material properties are typically tailored using chemical dopants, such methods can cause irreversible changes to the structure, limiting the range of functionality. The application of high pressure may provide an alternative “clean” method to tune the electronic properties of semiconducting materials by tailoring their defect density and structure.

We have explored a number of optoelectronic relevant materials with promising characteristics, specifically Sn-(O,N) compounds which have been predicted to undergo pressure-mediated opening of their optical band …

Cell Velocity Is Asymptotically Independent Of Force: A Differential Equation Model With Random Switching., J. C. Dallon, Emily J. Evans, Christopher P. Grant, William V. Smith

Faculty Publications

Numerical simulations suggest that average velocity of a biological cell depends largely on attachment dynamics and less on the forces exerted by the cell. We determine the relationship between two models of cell motion, one based on finite spring constants modeling attachment properties (a randomly switched differential equation) and a limiting case (a centroid model-a generalized random walk) where spring constants are infinite. We prove the main result of this paper, the Expected Velocity Relationship theorem. This result shows that the expected value of the difference between cell locations in the differential equation model at the initial time and at …

Devising A Scalable Synthesis To Probe The G-Protein Cell Receptor Signaling Pathway, Matthew Robert Medcalf

Arts & Sciences Graduate Student Theses and Dissertations

The G-protein coupled cell receptor signaling pathway is amongst the largest and most diverse class of cell-surface receptors in the body. Nearly 800 different genes encode for these cell membrane receptors which are responsible for mediating a variety of hormones, neurotransmitters, and sensory stimuli through the activation of intracellular G proteins. To date, roughly 34% of pharmaceuticals on the market target GPCR’s, but despite this fact, there are still many difficulties associated with targeting this family of receptors. The vast number of GPCR’s, disease states resulting from a dysregulation of multiple GPCR signaling pathways, and difficulties crystalizing and purifying the …

Coulombic And Non-Coulombic Effects Of Single And Overlapping Electric Double Layers With Surface Charge Regulation, Raviteja Vangara

Chemical and Biological Engineering ETDs

The physical origin of charged interfaces involving electrolyte solutions is in the thermodynamic equilibrium between the surface reactive groups and certain dissolved ionic species in the bulk. This equilibrium is very strongly dependent on the precise local density of these species, also known as potential determining ions in the solution. The latter, however, is determined by the overall solution structure, which is dominated by the large number of solvent molecules relative to all solutes. Hence, the solvent contribution to the molecular structure is a crucial factor that determines the properties of electric double layers. Models that explicitly account for the …

Urinary Excretion Of Mimosine Derivatives By Cows With And Without Experience In Consumption Of Leucaena Leucocephala, N. E. Ruz-Ruiz, Eduardo G. Briceño-Poot, A. J. Ayala-Burgos, C. F. Aguilar-Pérez, Francisco J. Solorio-Sánchez, Luis Ramírez-Avilés, Juan C. Ku-Vera

IGC Proceedings (1977-2023)

Leucaena leucocephala is a leguminous tree widely distributed in the tropical regions of the world. In Mexico, it has been incorporated into silvopastoral systems and is highly regarded, owing to its high content of crude protein. Nonetheless, L. leucocephala contains secondary metab-olites, such as mimosine, a non-protein free amino acid, which may induce toxic effects in unadapted ruminants that consume the forage (Hammond 1995). Although Synergistes jonesii, an anaerobic bacterium, has the ability to degrade 3,4-DHP and 2,3-DHP to non-toxic compounds (Allison et al. 1992), in Mexico its presence has not yet been confirmed. Recent work has suggested …

Urinary Excretion Of Mimosine Metabolites By Hair Sheep Fed Foliage Of Leucaena Leucocephala, L. M. Contreras-Hernández, N. E. Ruz-Ruiz, Eduardo G. Briceño-Poot, Luis Ramírez-Avilés, A. J. Ayala-Burgos, C. F. Pérez-Aguilar, Francisco J. Solorio-Sánchez, Juan C. Ku-Vera

IGC Proceedings (1977-2023)

Leucaena leucocephala is an adapted legume widely distributed in the tropical regions of Mexico. The high crude protein content of leucaena leaves renders it appropriate for ruminant feeding under commercial conditions. However, the foliage contains the non-protein amino acid mimosine, which, if consumed in high amounts, may induce toxicity in animals which have not previously consumed the legume or without microorganisms capable of degrading mimosine and its derivatives 2,3-DHP (dihydroxypyridine) and 3,4-DHP (Hammond 1995, Palmer et al. 2010, Dalzell et al. 2012). Barros-Rodríguez et al. (2012) found that dry matter intake and weight gain were reduced when …

Animal Production From New Panicum Maximum Genotypes In The Amazon Biome, Brazil, Carlos M. S. De Andrade, Luis H. E. Farinatti, Hemython L. B. Do Nascimento, Andressa De Q. Abreu, Liana Jank, Giselle M. L. De Assis

IGC Proceedings (1977-2023)

The Panicum maximum breeding program coordinated by the Brazilian Agricultural Research Corporation - Embrapa has been evaluating and selecting genotypes under different soil and climatic conditions, with the objective to release new cultivars adapted to the diverse regions of Brazil. For the Amazon biome, small-plot experiments carried out in Acre between 2003 and 2005 allowed the selection of some promising genotypes (Valentim and Andrade 2005; Valentim et al. 2006; Andrade and Valentim 2009), with higher potential for forage growth than cultivars on the market. The objective of this work was to compare 2 new P. maximum genotypes with cv. …

Tropical Grass Growth Functions Modeling By Using Nonlinear Mixed Models, A. Hernández Garay, H. Vaquera Huerta, M. Calzada Marín, E. Ortega Jiménez, J. F. Enríquez Quiroz

IGC Proceedings (1977-2023)

Nonlinear Growth curves are used for modeling plant physiological variables. These models are preferable because the polynomial coefficients of the equations have a biological significance. The response variables of the curves occurs commonly with repeated measurements over time and measurements are on different environments. The traditional statistical analysis does not include a repeated measures approach, which can lead to improper estimation of the error terms. It is important to study the growth of tropical grass (Da Silva and Carvalho 2005).

Herbage Accumulation, Nutritive Value And Persistence Of Mulato Ii In Florida, Joao M. B. Vendramini, Lynn E. Sollenberger, Graham C. Lamb, Maria L. Silveira

IGC Proceedings (1977-2023)

Grasses in the Brachiaria genus are the most widely grown forages in tropical America, occupying over 80 Mha (Boddey et al. 2004). Mulato II is apomictic and a vigorous, semi-erect cultivar resulting from 3 generations of crosses including original crosses between ruzigrass and signal-grass (cv. Basilisk, apomictic tetrapliod). According to Peters et al. (2003), Mulato produced 25% more herbage mass than palisadegrass (Brachiaria brizantha) and koroni-viagrass (Brachiaria humidicola) under similar management practices. Although Mulato II shows promise as a forage in tropical regions, herbage accumulation and persistence in subtropical areas is unknown. This publication …

Agronomic And Nutritional Evaluation Of Intraspecific Crosses In Brachiaria Decumbens, Simony A. Mendonça, Sanzio C. L. Barrios, Ulisses J. De Figueiredo, Geovani F. Alves, Cacilda B. Valle

IGC Proceedings (1977-2023)

Brachiaria decumbens cv. Basilisk is the single most important forage grass used for pastures in the tropics. This cultivar has exceptional adaptation to acid soils, vigorous growth, ease of establishment, and good forage value throughout the year, but these favourable characteristics are counteracted by its susceptibility to insect pests such as spittlebug. Breeding to produce improved cultivars within this species was impossible until 2009 due to the lack of compatible sexual ecotypes. With the success of somatic chromosome duplication of sexually reproducing diploid plants of B. decumbens (Simioni and Valle 2009), intraspecific crosses with natural apomictic tetraploid accessions were finally …

Reciprocal Recurrent Selection In The Breeding Of Brachiaria Decumbens, Sanzio C. L. Barrios, Cacilda B. Valle, Geovani F. Alves, Rosangela M. Simeão, Liana Jank

IGC Proceedings (1977-2023)

Pastures of Brachiaria decumbens cv. Basilisk radically changed the scenario of livestock production in central Brazil in the early 1970s and in fact, promoted the development of this vast region. However, despite the reasonable biomass yields and nutritional value when grown on these tropical acid soils, its susceptibility to grassland spittlebugs has limited its use. The breeding of B. decumbens in Brazil has been restricted to interspecific crosses using cv. Basilisk as a pollen donor due to the lack of compatible sexual ecotypes within this species. Recently, the successful chromosome duplication of a sexually reproducing diploid accession produced 3 successful …

ProgardesTm: A Legume For Tropical/Subtropical Semi-Arid Clay Soils, Christopher Gardiner, Nick Kempe, Iain Hannah, Jim Mcdonald

IGC Proceedings (1977-2023)

The range of available sown pasture legumes for the vast heavy clay soil regions of northern Australia has long been regarded as being deficient (Burt 1993; Jones and Clem 1997; Pengelly and Conway 2000). Indeed immense areas of northern Australia’s semi-arid clay soil regions have no sown pasture legume with proven adaptation and persistence through the long annual dry seasons (Gardiner and Swan 2008). The genus Desmanthus is a Mimosaceae legume containing some 24 species which are native to the Americas and range from being herbaceous to suffruticose in habit (Luckow 1993). Desmanthus is one of the very few legumes …

Potential Of Panicum Maximum As A Source Of Energy, Liana Jank, Edson A. De Lima, Rosangela M. Simeão, Ronimar C. Andrade

IGC Proceedings (1977-2023)

The use of plant biomass as a source of energy presents many advantages, mainly that it is a renewable, clean source of energy. Many tropical grasses have excellent po-tential as energy crops. The main one in Brazil is Pennisetum purpureum (elephant grass) owing to its very high yields. However, it is vegetatively propagated, thus more difficult to establish than seed propagated species. The use of Panicum maximum (guinea grass) is a possible alternative for use as a source of energy, due to its high yields as well as seed propagation. The objective of this research was to evaluate the potential …