Digital Commons Network^™

Magnesium Diboride Embedded Multi-Walled Carbon Nanotube Yarns, Ujjal Lamichhane

Theses and Dissertations

The discovery of superconductivity in a simple hexagonal binary compound of MgB2 at a relatively high critical temperature ~39 K renewed the interest in the field of superconductivity. Twisted laminar superconducting composite structures based on coiled multi-walled carbon nanotube (MWCNT) yarns were crafted by integrating magnesium and boron homogeneous mixture into the carbon nanotube sheets. After the ignition of the Mg/B/MWCNT system, under the controlled argon environment and uniform heating rate, the high exothermic reaction between magnesium (Mg) and boron (B) with stoichiometric ratio produced the MgB2/MWCNT superconducting composite yarns. The XRD analysis confirmed that the heated sample consists of …

Algorithmic Assembly Of Nanoscale Structures, Austin Luchsinger

Theses and Dissertations

The development of nanotechnology has become one of the most significant endeavors of our time. A natural objective of this field is discovering how to engineer nanoscale structures. Limitations of current top-down techniques inspire investigation into bottom-up approaches to reach this objective. A fundamental precondition for a bottom-up approach is the ability to control the behavior of nanoscale particles. Many abstract representations have been developed to model systems of particles and to research methods for controlling their behavior. This thesis develops theories on two such approaches for building complex structures: the self-assembly of simple particles, and the use of simple …

Elucidating The Binding Pockect Of The Gpr119 Receptor, A Type 2 Diabetes Target, Matthew Dy Rosales

Theses and Dissertations

An in-house homology model of the GPR119 receptor was used to identify residues which may affect ligand binding and ligand-dependent activity through computational and experimental studies. In a docking study comparing an agonist and its inverse agonist structural analog, Leu5.43169, L6.52242 and Ser1.324 appear to be involved in ligand binding. These residues were mutated experimentally to test the predictions of the homology model. The in vitro studies indicate that Leu5.43169 and Ser1.324 mutations cause ten-fold and six-fold decreases in ligand-induced cAMP formation, indicating their importance in ligand-induced activation. Leu6.52242 mutations show minimal effect in cAMP production, indicating a lesser involvement …

Solitary And Periodic Wave Solutions For Several Short Wave Model Equations, Andrey V. Stukopin

Theses and Dissertations

We study the periodic and solitary wave solutions to several short wave model equations arising from a so-called $\beta$-family equation for $\beta=1,2,4$. These are integrable cases which possess Lax pair and multi-soliton solutions. By phase plane analysis, either the loop or cuspon type solutions are predicted. Then, by introducing a hodograph, or reciprocal, transformation, a coupled system is derived for each $\beta$. Applying a travelling wave setting, we are able to find the periodic solutions exactly expressed in terms of Jacobi Elliptic functions. In the limiting cases of modulus k=1, they all converge to the known solitary waves.

Effects Of Artificial Substrates On The Recruitment Of Juvenile Fishes In The Northwestern Gulf Of Mexico, Stefany Salinas

Theses and Dissertations

Most artificial reefs (ARs) in the Gulf of Mexico are considered intermediate to high vertical relief structures which have recruited large predatory species indicating lack of juvenile habitat. Small, inexpensive ARs, standard monitoring units for the recruitment of reef fish (SMURFs), were deployed at eight sites at -20m as habitat for juvenile fishes to understand and determine the effects of substrate type on juvenile fishes recruitment. Each site contained four SMURFs with four treatments: small and large rubble (~10 and ~20cm), oyster shells, and bare. Surveys yielded 39 juvenile species, including one of the most economically important species, Lutjanus campechanus, …

Detection And Enumeration Of Bacterial Pathogens In The American Oyster (Crassostrea Virginica), Mohammad Maruf Billah

Theses and Dissertations

American oyster (Crassostrea virginica) is a popular seafood for its delicacy and high nutritional value. Based on increasing concern about contamination of bacterial pathogens in raw oyster, my research objectives have been focused on detection and enumeration of two important bacterial pathogens, Escherichia coli and Salmonella spp. in the American oyster in south Texas waters, local markets and controlled laboratory studies. Immunohistochemical and RT-PCR analyses showed substantial bacterial pathogen’s presence in gills and digestive glands of oysters collected from San Martin Lake and South Padre Island as well as local markets. Laboratory studies showed increasing trend of both …

Topography Estimation Using Particle Swarm Optimization, Yelbir Kazhykarim

Theses and Dissertations

The Earth’s Vertical Gravity Gradient (VGG) can be used to map seafloor topography but presents a challenging inverse problem. A promising approach is forward modeling, in which one searches over a set of candidate topographies and selects the one whose predicted VGG best fits the observed one. The main bottleneck here is solving the associated high-dimensional and non-linear optimization problem. Yang et al (2018) demonstrated a method in which the topography is parametrized by heights of mass elements on a rectangular grid and the ≈ 104 dimensional optimization problem is tackled with simulated annealing (SA). We propose a computationally much …

Effects Of Arbuscular Mycorrhizal Fungi (Amf) On Growth And Herbivore Defenses In Sorghum Sudangrass (Sorghum X Drummondii), Jasleen Kaur

Theses and Dissertations

Chapter 2: In this chapter we have examined the role of trichomes in plant stress biology, reviewed the studies on herbivore X trichome interactions, and their role in plant defences. Ultimately, we have proposed new areas of research for future work.

Chapter 3: In this chapter, we examined whether AMF has cascading effects on insect community dynamics through attraction/repulsion of beneficial and damaging insects using Sorghum-sudangrass (Sorghum x drummondii), either inoculated with commercial AMF mix or left as control in lab and field experiments. Our results suggest positive effects of AMF on plant growth, and a lower initial incidence of …

Tipping Points Of Mississippi Delta Marshes Due To Accelerated Sea-Level Rise, Torbjörn E. Törnqvist, Krista L. Jankowski, Yong-Xiang Li, Juan L. Gonzalez

School of Earth, Environmental, & Marine Sciences Faculty Publications

Coastal marshes are threatened by relative sea-level (RSL) rise, yet recent studies predict marsh survival even under the high rates of RSL rise expected later in this century. However, because these studies are mostly based on short-term records, uncertainty persists about the longer-term vulnerability of coastal marshes. We present an 8500-year-long marsh record from the Mississippi Delta, showing that at rates of RSL rise exceeding 6 to 9 mm year−1, marsh conversion into open water occurs in about 50 years. At rates of RSL rise exceeding ~3 mm year−1, marsh drowning occurs within a few centuries. Because present-day rates of …

Effects Of Incubation Temperature On Nanomechanical Properties Of Β-Lactoglobulin Amyloid Fibers, Santosh Khatri

Theses and Dissertations

Amyloid fibrils constitute a class of highly ordered nanomaterials formed by aggregates of the protein. Although The irreversible fibril formation of various proteins is related to the disorders like Alzheimer’s diseases, Creutzfeldt-Jacob and many more, amyloid fibrils have also been noticed in many physiologically beneficial roles such as in adhesive and hormone storage. Here, we compare the stiffness and structural properties of the amyloid fibers examined by the statistical approaches of single molecule atomic force microscopy images of heat-denatured β-lactoglobulin fibrils at different incubation time period (24, 48, and 72 hours). We demonstrate the gradual decrease in stiffness of the …

Survival Of Off-Host Rhipicephalus (Boophilus) Annulatus (Acari: Ixodidae) Larvae In Study Arenas In Relation To Climatic Factors And Habitats In South Texas, Usa, Emily Jesselle Zamora

Theses and Dissertations

The cattle fever tick, Rhipicephalus (Boophilus) annulatus (Say), is an economically destructive arthropod because of its ability to vector bovine babesiosis. Cattle fever ticks can spend more than 90% of their life cycle as questing larvae, but the effect of climatic factors on their off-host behavior and survival is unclear. The goal of this study was to measure the effects of specific ecological factors on off-host larvae in nature. The study was conducted in a south Texas pasture over a 20-mo period, during which time larval populations were surveyed and ambient weather variables - relative humidity and temperatures – were …

On Arnold–Villasenor Conjectures For Characterizaing Exponential Distribution Based On Sample Of Size Three, George Yanev

School of Mathematical & Statistical Sciences Faculty Publications

Arnold and Villasenor [4] obtain a series of characterizations of the exponential distribution based on random samples of size two. These results were already applied in constructing goodness-of-fit tests. Extending the techniques from [4], we prove some of Arnold and Villasenor’s conjectures for samples of size three. An example with simulated data is discussed.

Periodic Triangulations Of Zn, Mathieu Dutour Sikiric, Alexey Garber

School of Mathematical & Statistical Sciences Faculty Publications

We consider in this work triangulations of Z n that are periodic along Z n . They generalize the triangulations obtained from Delaunay tessellations of lattices. In certain cases we impose additional restrictions on such triangulations such as regularity or invariance under central symmetry with respect to the origin; both properties hold for Delaunay tessellations of lattices. Full enumeration of such periodic triangulations is obtained for dimension at most 4 . In dimension 5 several new phenomena happen: there are centrally-symmetric triangulations that are not Delaunay, there are non-regular triangulations (it could happen in dimension 4 ) and a given …

Geometric And Measure-Theoretic Shrinking Targets In Dynamical Systems, Joseph Rosenblatt, Mrinal Kanti Roychowdhury

School of Mathematical & Statistical Sciences Faculty Publications

We consider both geometric and measure-theoretic shrinking targets for ergodic maps, investigating when they are visible or invisible. Some Baire category theorems are proved, and particular constructions are given when the underlying map is fixed. Open questions about shrinking targets are also described.

The Photon Absorber And Interconnecting Layers In Multijunction Organic Solar Cell, Brishty Deb Chowdhury, Bernabe Ibarra, Federico Cesano, Yuanbing Mao, Muhammad N. Huda, Aminur Rashid Chowdhury, Carolina Olivares, M. Jasim Uddin

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

Organic photovoltaic devices have long been considered as an important alternative for coal-based energy technologies due to their low-cost, lightweight and flexible nature. However, the power conversion efficiencies of such cells are limited by thermalization and transmission losses, which can be overcome by stacking multiple cells in a tandem configuration. This approach allows utilization of the wider spectrum of solar light, helping in attaining the theoretical limits for single cell efficiency (~30%). However, the performance of such tandem organic solar cells depends largely on several factors, including the proper design of absorber, sub-cells and interconnecting layer materials. In this review, …

Fingerprints Of Binary Black Hole Formation Channels Encoded In The Mass And Spin Of Merger Remnants, Manuel Arca Sedda, Michaela Mapelli, Mario Spera, Matthew Benacquista, Nicola Giacobbo

Physics & Astronomy Faculty Publications

Binary black holes (BBHs) are thought to form in different environments, including the galactic field and (globular, nuclear, young, and open) star clusters. Here, we propose a method to estimate the fingerprints of the main BBH formation channels associated with these different environments. We show that the metallicity distribution of galaxies in the local universe along with the relative amount of mergers forming in the field or in star clusters determine the main properties of the BBH population. Our fiducial model predicts that the heaviest merger to date, GW170729, originated from a progenitor that underwent 2–3 merger events in a …

A Study On Quantization Dimension In Complete Metric Spaces, Mrinal Kanti Roychowdhury, S. Verma

School of Mathematical & Statistical Sciences Faculty Publications

The primary objective of the present paper is to develop the theory of quantization dimension of an invariant measure associated with an iterated function system consisting of finite number of contractive infinitesimal similitudes in a complete metric space. This generalizes the known results on quantization dimension of self-similar measures in the Euclidean space to a complete metric space. In the last part, continuity of quantization dimension is discussed.

Association Of Visceral Adipose Tissue And Subclinical Atherosclerosis In Us-Born Mexican Americans But Not First Generation Immigrants, Clarence Gill, Miryoung Lee, Kristina Vatcheva, Nahid Rianon, Beverly Smulevitz, David D. Mcpherson, Joseph B. Mccormick, Susan P. Fisher-Hoch, Susan T. Laing

School of Mathematical & Statistical Sciences Faculty Publications

BACKGROUND: Excess visceral adipose tissue (VAT) is a primary driver for the cardiometabolic complications of obesity; VATassociated cardiovascular disease risk varies by race, but most studies have been done on Non-Hispanics. This study aimed to evaluate the clinical and metabolic correlates of VAT, its association with subclinical atherosclerosis, and the factors affecting this association in Mexican Americans.

METHODS AND RESULTS: Participants (n=527) were drawn from the Cameron County Hispanic Cohort (CCHC), on whom a carotid ultrasound to assess carotid intima media thickness and a dual-energy X-ray absorptiometry scan to assess for VAT were obtained. Those in the highest quartiles of …

Searching For Optical Counterparts To Gravitational Waves, Richard Camuccio

Theses and Dissertations

The era of multi-messenger astronomy has begun. The coordinated activities of multiple, distinct observatories play a critical role in both responding to astrophysical transients and building a more comprehensive interpretation otherwise inaccessible to individual observations. The Transient Robotic Observatory of the South (TOROS) Collaboration has a global network of instruments capable of responding to several transient targets of opportunity. The purpose of this thesis is to demonstrate how optical observatories with small fields of view (degree) can follow up and observe astrophysical transients. TOROS facilities responded to three unique gravitational wave events during the second and third observational campaigns of …

Exploring Mechanical Properties And Configurational Energetics Of Toxbox Using Molecular Dynamics Simulation, Shams Mehdi

Theses and Dissertations

All-atom Molecular Dynamics Simulations (MDS) have been performed to obtain 5 ns trajectory of the solvated, neutralized, and equilibrated toxbox system in NPT ensemble at 300 K. This trajectory data has been used to calculate the configurational entropy of toxbox by employing a quantum mechanical approach. The method is based on evaluating determinant of the covariance matrix, built from generalized coordinates of all atoms for each frame. The upper limit to the configurational entropy of toxbox has been calculated to be 30,030 J/mol-K. A preliminary investigation has been conducted to study the effects of sequence-dependent DNA conformation (DNA Crookedness) on …

Improving The Classroom Experience By Providing Teachers With A Mindfulness Intervention, Andrea P. Almaguer-Botero

Theses and Dissertations

The purpose of this study was to improve the classroom environment for teachers by providing them with a mindfulness-based intervention. This experimental study evaluated the outcomes of an eight-week stress and mindfulness prevention intervention (SPAM) created specifically for teachers. The current study measured the following variables: mindfulness, stress, self-efficacy, job satisfaction, and well-being. This study used a four-way ANOVA (2 X 3 X 2 X 5) with two between subjects’ factors, groups and levels, and two within subjects/repeated measures factors, pre-test-posttest and scales. There were 14 teacher participants in the experimental group and 19 teacher participants in the control group. …

Robotic Swarms: Assembly And Complexity, Angel Adrian Cantu Suarez

Theses and Dissertations

This thesis focuses on the assembly of robotic swarms that move according to some global signal in a model called the “tilt” model. The model consists of a 2D board that contain open and blocked spaces, along with tiles or polyominoes that move toward a signaled cardinal direction. We look at two variations of this model called the single-step and full-tilt model, where the elements move single distances or maximally, respectively, when a signal is send. We show different methods of shape construction, defining board configurations that are universal for a set of shapes. Afterwards, we analyze different computational problems …

Exploring Pyrochlore Host For Upconversion And Downconversion Luminescence Materials, Mitzy A. Penilla Garcia

Theses and Dissertations

Pyrochlore has been the focal point of research in materials science community in the area of nuclear waste host, thermal barrier coatings, solid oxide fuel cell, catalyst, magnetism, luminescence etc. Such application arises due to their unique properties such as wide band gap, high radiation stability, low thermal conductivity, high dialectic constant. The fact it also has high structural ability, low phono energy and ability to accommodate dopant ion at both A- site and B-site; they are considered excellent host for inorganic phosphors. Here research work is directed towards synthesizing optical materials having high quantum efficiency for down-conversion (DC) and …

Individual Difference As A Factor In Ethical Decision-Making, Dan W. Reagan Jr.

Theses and Dissertations

Despite the dominance of modernistic ethics in counseling there has been a growing development of postmodern thought. There has been a growing understanding the limitations of ethical codes and purely rational thinking in ethical decision-making. Part of this new paradigm is an appreciation for the role of affect and context in the decision-making process. A post-modern approach to counseling ethics seems to be increasingly accepted among persons working in the social service field but little research has been attempted to evaluate the implications of such a change in training and practice. This study attempted to explore possible relationships between individual …

Multi Wall Carbon Nanotube (Mwcnt) Laminar Composite Structures Reinforced With Titanium Carbide (Tic), Rakibul Alam Shohan

Theses and Dissertations

Laminated composites have been widely used in weight critical structures, such as aircraft, spacecraft, bullet-proof vests, radiation protection suits, spacesuits etc., owing to their high stiffness, strength, and thermal stability. Multi Wall Carbon Nanotube (MWCNT) laminar composite have attracted a good attention for these laminar composites due to its outstanding physical and mechanical properties as well as extraordinary electrical, optical, and thermal properties. Laminar composite structures based on twisted MWCNT yarn were crafted by integrating titanium and graphene mixture at (80:20) wt. %, respectively into multi wall carbon nanotube sheets. Titanium and Graphene mixture addition has been used to improve …

The Impact Of Social Constructivist Mathematics Learning Experiences On Latino, Middle School Students’ Proportional Reasoning, Victor M. Vizcaino

Theses and Dissertations

Due to its centrality in the curriculum, research on proportional reasoning (PR) has seen a resurgence of interest. Recent research examined students’ patterns, strategies, and achievement when solving PR problems. Other studies explored PR learning trajectories. Additional studies focused on instructional interventions such as the effect of number structure, continuous, discrete, and intensive quantities to promote the development of proportional reasoning skills (PRS). The subjects of these studies have been United States white middle school students, Icelandic grade 5 girls, Spanish secondary school students, Turkish middle school students, as well as Scottish and Korean upper primary grades’ students. Few studies …

Overexpression Of Tc-Ptp In Murine Epidermis Attenuates Skin Tumor Formation, Mihwa Kim, Liza D. Morales, Cheol Jung Lee, Serena A. Olivarez, Woo Jin Kim, Joselin Hernandez, Srinivas Mummidi, Christopher Jenkinson, Andrew Tsin, Ik-Soon Jang, Thomas J. Slaga, Dae Joon Kim

School of Medicine Publications

T-cell protein tyrosine phosphatase (TC-PTP), encoded by Ptpn2, has been shown to function as a tumor suppressor during skin carcinogenesis. In the current study, we generated a novel epidermal-specific TC-PTP-overexpressing (K5HA.Ptpn2) mouse model to show that TC-PTP contributes to the attenuation of chemically induced skin carcinogenesis through the synergistic regulation of STAT1, STAT3, STAT5, and PI3K/AKT signaling. We found overexpression of TC-PTP increased epidermal sensitivity to DMBA-induced apoptosis and it decreased TPA-mediated hyperproliferation, coinciding with reduced epidermal thickness. Inhibition of STAT1, STAT3, STAT5, or AKT reversed the effects of TC-PTP overexpression on epidermal survival and proliferation. Mice overexpressing TC-PTP in …

Using Continuous Sensor Data To Formalize A Model Of In-Home Activity Patterns, Beiyu Lin, Diane J. Cook, Maureen Schmitter-Edgecombe

Computer Science Faculty Publications

Formal modeling and analysis of human behavior can properly advance disciplines ranging from psychology to economics. The ability to perform such modeling has been limited by a lack of ecologically-valid data collected regarding human daily activity. We propose a formal model of indoor routine behavior based on data from automatically-sensed and recognized activities. A mechanistic description of behavior patterns for identical activity is offered to both investigate behavioral norms with 99 smart homes and compare these norms between subgroups. We identify and model the patterns of human behaviors based on inter-arrival times, the time interval between two successive activities, for …

Entropy In Quantum Mechanics And Applications To Nonequilibrium Thermodynamics, Paul Bracken

School of Mathematical & Statistical Sciences Faculty Publications

Classical formulations of the entropy concept and its interpretation are introduced. This is to motivate the definition of the quantum von Neumann entropy. Some general properties of quantum entropy are developed, such as the quantum entropy which always increases. The current state of the area that includes thermodynamics and quantum mechanics is reviewed. This interaction shall be critical for the development of nonequilibrium thermodynamics. The Jarzynski inequality is developed in two separate but related ways. The nature of irreversibility and its role in physics are considered as well. Finally, a specific quantum spin model is defined and is studied in …

Complete Mitochondrial Genome Of Carijoa Riisei (Duchassaing & Michelotti, 1860) (Octocorallia: Alcyonacea: Stolonifera: Clavulariidae), Erin E. Easton, David Hicks

School of Earth, Environmental, & Marine Sciences Faculty Publications

We report the first complete Stolonifera mitochondrial genome. Carijoa riisei (Duchassaing & Michelotti, 1860) isolate CLP2_A03 was collected by scuba at 32 m on the USTS Texas Clipper (27° 53.7827′N, 93° 36.2702′W). The complete mitogenome has the ancestral octocoral gene order for its 14 protein-coding genes, two rRNA genes, and one tRNA gene. It is 18,714 bp (30.7% A, 15.8% C, 18.8% G, and 34.7% T). Of the Alcyonacea mitogenomes published to date, it is most genetically similar (94% uncorrected) to Sinularia ceramensis Verseveldt, 1977 (NC_044122).