Digital Commons Network^™

The Implementation Of A Fast-Folding Pipeline For Long-Period Pulsar Searching In The Palfa Survey, E. Parent, V. M. Kaspi, S. M. Ransom, M. Krasteva, C. Patel, P. Scholz, A. Brazier, M. A. Mclaughlin, Keeisi Caballero, Richard S. Camuccio

Physics & Astronomy Faculty Publications

The Pulsar Arecibo L-Band Feed Array (PALFA) survey, the most sensitive blind search for radio pulsars yet conducted, is ongoing at the Arecibo Observatory in Puerto Rico. The vast majority of the 180 pulsars discovered by PALFA have spin periods shorter than 2 s. Pulsar surveys may miss long-period radio pulsars owing to the summing of a finite number of harmonic components in conventional Fourier analyses (typically ∼16), or as a result of the strong effect of red noise at low modulation frequencies. We address this reduction in sensitivity by using a time-domain search technique: the fast-folding algorithm (FFA). We …

Antimicrobial Properties And Characterization Of Polymer/Composite Nanofibers, David De La Garza

Theses and Dissertations

Pathogenic bacteria have been the cause of many illnesses worldwide due to their rapid growth and reproduction in food and water. Bacteria-resistant antibiotics and kidney complications due to overuse of antibiotics has remained a large public health concern. The goal of this research project was to find an alternative by producing nanofibers that inhibit microbial growth utilizing Forcespinning technology. The Forcespinning of poly(acrylic acid) (PAA) with Single Wall Carbon Nanotubes functionalized with OH (SWCNT-OH) and Ag + flakes were carried out on solutions with different concentrations. Scanning electron microscopy was used to view fiber morphology and investigate the average nanofiber …

Design And Characterization Of An Affordable Laser Communication System, Andrea Tellez

Theses and Dissertations

Over the last decades, an exponential growth in communication demand has been observed. Radio Frequency (RF) band has been one of the most used bandwidths for data transmission in the world. Given the influence and the continuous growth of communication technology, the RF spectrum is overpopulated. More efficient systems are necessary to meet the communication needs of this generation. A change to optical bandwidth is the most practical alternative to deal with the congestion of radio frequency.

The aim of this thesis is to present the features of Free Space Optical links with off-the-shelf components. A description of how these …

Preconditioning Methods For Thin Scattering Structures Based On Asymptotic Results, Josef A. Sifuentes, Shari Moskow

School of Mathematical & Statistical Sciences Faculty Publications

We present a method to precondition the discretized Lippmann–Schwinger integral equations to model scattering of time-harmonic acoustic waves through a thin inhomogeneous scattering medium. The preconditioner is based on asymptotic results as the thickness of the third component direction goes to zero and requires solving a two dimensional formulation of the problem at the preconditioning step.

Thermodynamic And Kinetic Study Of The Removal Of Cu2+ And Pb2+ Ions From Aqueous Solution Using Fe7s8 Nanomaterial, Jesus Cantu, Diego F. Gonzalez, Yvette Cantu, Thomas Eubanks, Jason Parsons

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

In the present study, pyrrhotite (Fe7S8) was investigated for the removal of Pb2+ and Cu2+ ions from aqueous solution. The Fe7S8 material was prepared through a solvothermal method and was characterized using XRD. The average particle size for the nanomaterial was determined to be 29.86 ± 0.87 nm using XRD analysis and Scherrer's equation. Batch studies were performed to investigate the effects of pH, time, temperature, interfering ions, and the binding capacity of Pb2+ and Cu2+ ions to the Fe7S8 nanomaterial. During the pH profile studies, the optimum pH for the binding of Pb2+ and Cu2+ was determined to be …

Climate And Plant Controls On Soil Organic Matter In Coastal Wetlands, Michael J. Osland, Christopher A. Gabler, James B. Grace, Richard H. Day, Meagan L. Mccoy, Jennie L. Mcleod, Andrew S. From, Nicholas M. Enwright, Laura C. Feher, Camille L. Stagg

School of Earth, Environmental, & Marine Sciences Faculty Publications

Coastal wetlands are among the most productive and carbon‐rich ecosystems on Earth. Long‐term carbon storage in coastal wetlands occurs primarily belowground as soil organic matter (SOM). In addition to serving as a carbon sink, SOM influences wetland ecosystem structure, function, and stability. To anticipate and mitigate the effects of climate change, there is a need to advance understanding of environmental controls on wetland SOM. Here, we investigated the influence of four soil formation factors: climate, biota, parent materials, and topography. Along the northern Gulf of Mexico, we collected wetland plant and soil data across elevation and zonation gradients within 10 …

Effect Of Surrounding Vegetation On Microbial Survival Or Die-Off On Watermelon Surface In An Agriculture Setting, Vijay Singh Chhetri, Kathryn Fontenot, Ronald Strahan, Veerachandra K. Yemmireddy, Katheryn J. Parraga Estrada, Achyut Adhikari

School of Earth, Environmental, & Marine Sciences Faculty Publications

Preharvest contamination of produce with food borne pathogens has been a major food safety issue. In this study, we investigated the effect of surrounding vegetation on the survival of natural and inoculated generic Escherichia coli on watermelon rinds in an agricultural field setting. There was no significant difference (p > .05) on the populations of natural generic E. coli (1–1.46 log Most Probable Number (MPN)/sample) and coliforms (E. coli inoculated on watermelon rind discs was variable with the level of vegetation. A significant reduction in generic E. coli count was observed within 12 hr at all vegetation levels. After 108 …

Approximate Set Union Via Approximate Randomization, Bin Fu, Pengfei Gu, Yuming Zhao

Computer Science Faculty Publications

No abstract provided.

First Record Of Black Corals (Antipatharia) In Shallow Coastal Waters Of Northern Chile By Means Of Underwater Video, Matthias Gorny, Erin E. Easton, Javier Sellanes

School of Earth, Environmental, & Marine Sciences Faculty Publications

This record is the first report of black corals (Antipatharia) in shallow waters of the continental coast of Chile, and extends their geographical range in shallow waters of the upper continental shelf of South America by ~3000 km from Ecuador (~1°S) to Coquimbo, Chile (~29°S). Specimens were observed between 70 and 107 m on three underwater video transects executed in July 2016 on the rocky reef El Toro, which is located about 65 km northwest of Coquimbo. The images were taken with the cameras of a remotely operated vehicle (ROV) at a distance of about two meters from the rocks. …

Microwave Popped Co(Ii)-Graphene Oxide Hybrid: Bifunctional Catalyst For Hydrogen Evolution Reaction And Hydrogen Storage, Lin Wei, Karen Lozano, Yuanbing Mao

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

In an effort to develop a multifunctional catalyst for hydrogen generation and adsorption applications, a facile and cost-effective microwave popping method was used to synthesize popped graphene oxide (PGO) and Co-PGO hybrid. Both samples have been explored and compared as hydrogen storage materials and as electrocatalysts for hydrogen evolution reaction (HER) for the first time. The loading of Co(II) species on the surface of the PGO enhanced the hydrogen storage capability of PGO from 0.04wt% to 0.08wt% as measured at 293K and 800 mmHg. Co-PGO is also acting as a better electrocatalyst for HER compared to the PGO counterpart.

Source-Specific Pollution Exposure And Associations With Pulmonary Response In The Atlanta Commuters Exposure Studies, Jenna R. Krall, Chandresh N. Ladva, Armistead G. Russell, Rachel Golan, Xing Peng, Guoliang Shi, Roby Greenwald, Amit U. Raysoni, Lance A. Waller, Jeremy A. Sarnat

School of Earth, Environmental, & Marine Sciences Faculty Publications

Concentrations of traffic-related air pollutants are frequently higher within commuting vehicles than in ambient air. Pollutants found within vehicles may include those generated by tailpipe exhaust, brake wear, and road dust sources, as well as pollutants from in-cabin sources. Sourcespecific pollution, compared to total pollution, may represent regulation targets that can better protect human health. We estimated source-specific pollution exposures and corresponding pulmonary response in a panel study of commuters. We used constrained positive matrix factorization to estimate source-specific pollution factors and, subsequently, mixed effects models to estimate associations between source-specific pollution and pulmonary response. We identified four pollution factors …

The Green Bank North Celestial Cap Pulsar Survey. Iii. 45 New Pulsar Timing Solutions, Ryan S. Lynch, Joseph K. Swiggum, Louis Percy Dartez, David Day, Anthony J. Ford, Jesus Hinojosa, Fredrick A. Jenet, Sean Leake, Grady Lunsford, Alberto Mata

Physics & Astronomy Faculty Publications

We provide timing solutions for 45 radio pulsars discovered by the Robert C. Byrd Green Bank Telescope. These pulsars were found in the Green Bank North Celestial Cap pulsar survey, an all-GBT-sky survey being carried out at a frequency of 350 MHz. We include pulsar timing data from the Green Bank Telescope and Low Frequency Array. Our sample includes five fully recycled millisecond pulsars (MSPs, three of which are in a binary system), a new relativistic double neutron star system, an intermediate-mass binary pulsar, a mode-changing pulsar, a 138 ms pulsar with a very low magnetic field, and several nulling …

Novel Topological Effects In Dense Qcd In A Magnetic Field, Efrain J. Ferrer, Vivian De La Incera

Physics & Astronomy Faculty Publications

We study the electromagnetic properties of dense QCD in the so-called Magnetic Dual Chiral Density Wave phase. This inhomogeneous phase exhibits a nontrivial topology that comes from the fermion sector due to the asymmetry of the lowest Landau level modes. The nontrivial topology manifests in the electromagnetic effective action via a chiral anomaly term θ F μ ν ˜ F μ ν , with a dynamic axion field θ given by the phase of the Dual Chiral Density Wave condensate. The coupling of the axion with the electromagnetic field leads to several macroscopic effects that include, among others, an anomalous, …

Charge Transfer Dynamical Processes At Graphene-Transition Metal Oxides/Electrolyte Interface For Energy Storage: Insights From In-Situ Raman Spectroelectrochemistry, S. Gupta, S. B. Carrizosa, J. Jasinski, Nicholas Dimakis

Physics & Astronomy Faculty Publications

Hybrids consisting of supercapacitive functionalized graphene (graphene oxide; GO reduced graphene oxide; rGO multilayer graphene; MLG, electrochemically reduced GO; ErGO) and three-dimensional graphene scaffold (rGO HT ; hydrothermally prepared) decorated with cobalt nanoparticles (CoNP), nanostructured cobalt (CoO and Co 3 O 4 ) and manganese (MnO 2 ) oxide polymorphs, assembled electrochemically facilitate chemically bridged interfaces with tunable properties. Since Raman spectroscopy can capture variations in structural and chemical bonding, Raman spectro-electrochemistry in operando i.e. under electrochemical environment with applied bias is employed to 1) probe graphene/metal bonding and dynamic processes, 2) monitor the spectral changes with successive redox interfacial …

The Nanograv 11 Year Data Set: Pulsar-Timing Constraints On The Stochastic Gravitational-Wave Background, Zaven Arzoumanian, P. T. Baker, A. Brazier, S. Burke-Spolaor, S. J. Chamberlin, S. Chatterjee, B. Christy, ‪Jeffrey S. Hazboun, Jing Luo

Physics & Astronomy Faculty Publications

We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a GWB, we place constraints on a population of inspiraling supermassive black hole (SMBH) binaries, a network of decaying cosmic strings, and a primordial GWB. For the first time, we find that the GWB constraints are sensitive to the solar system ephemeris (SSE) model used and that SSE errors can mimic a GWB signal. We developed an approach that bridges systematic SSE differences, producing the first pulsar-timing …

A Comparison Of Salinity Effects From Hurricanes Dolly (2008) And Alex (2010) In A Texas Lagoon System, Joseph L. Kowalski, Hudson R. Deyoe, Gilbert H. Boza Jr., Donald L. Hockaday, Paul V. Zimba

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

A comparison of salinity effects from hurricanes Dolly (2008) and Alex (2010) in a Texas lagoon system.Hurricanes are not uncommon along the Gulf of Mexico coast, but there are few studies of the effects they have on coastal embayments. Hurricanes Dolly (2008) and Alex (2010) were both Category 2 storms affecting the Lower Laguna Madre (LLM) of Texas. Surveys were performed to assess poststorm water quality after landfall of both storms at up to 18 sample stations. The main difference between storm effects was salinity reduction because of stormwater input from the watershed. Effects from Hurricane Dolly were of short …

Search For Tensor Vector And Scalar Polarizations In The Stochastic Gravitational-Wave Background, B. P. Abbott, R. Abbott, T. D. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Wenhui Wang

Physics & Astronomy Faculty Publications

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find …

Development And Optimization Of Alumina Fine Fibers Utilizing A Centrifugal Spinning Process, Mandana Akia, Dulce Capitanachi, Misael E. Martinez, Carlos Hernandez, Hector De Santiago, Yuanbing Mao, Karen Lozano

Mechanical Engineering Faculty Publications

Highlights

• Successful synthesis of AIP/PVA composite fibers using Forcespinning® techniques.

• Optimization of the operating parameters applying response surface methodology (RSM).

• Fabrication of mesostructured gamma alumina and highly crystalline alpha alumina fine fibers.

Abstract

Aluminum isopropoxide and poly(vinylalcohol) fine fibers were successfully fabricated and optimized utilizing the response surface methodology. The optimized composite fibers showed mean fiber diameter of 304 nm. The fiber samples were calcined at different temperatures to attain both gamma and alpha phases of alumina. Various characterization methods including scanning electron microscopy, thermogravimetric analysis, x-ray diffraction and nitrogen adsorption/desorption analysis were conducted. The BET analysis …

Constraints On Cosmic Strings Using Data From The First Advanced Ligo Observing Run, B. P. Abbott, R. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Marc E. Normandin, Volker Quetschke, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

Cosmic strings are topological defects which can be formed in grand unified theory scale phase transitions in the early universe. They are also predicted to form in the context of string theory. The main mechanism for a network of Nambu-Goto cosmic strings to lose energy is through the production of loops and the subsequent emission of gravitational waves, thus offering an experimental signature for the existence of cosmic strings. Here we report on the analysis conducted to specifically search for gravitational-wave bursts from cosmic string loops in the data of Advanced LIGO 2015-2016 observing run (O1). No evidence of such …

Full Band All-Sky Search For Periodic Gravitational Waves In The O1 Ligo Data, B. P. Abbott, Teviet Creighton, Mario C. Diaz, S. R. Morriss, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Karla E. Ramirez, Robert Stone, Darkhan Tuyenbayev, Wenhui Wang

Physics & Astronomy Faculty Publications

We report on a new all-sky search for periodic gravitational waves in the frequency band 475-2000 Hz and with a frequency time derivative in the range of [-1.0,+0.1]×10-8 Hz/s. Potential signals could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the data from Advanced LIGO's first observational run O1. No gravitational-wave signals were observed, and upper limits were placed on their strengths. For completeness, results from the separately published low-frequency search 20-475 Hz are included as well. Our lowest upper limit on worst-case (linearly polarized) strain amplitude h0 is ∼4×10-25 …

Design And Development Of Inquiry-Based Materials For Conducting Observational Astronomy Research At Utrgv, Americo Francisco Hinojosa Lee

Theses and Dissertations

The purpose of this work is to develop instructional materials to enhance the expertise of students in conducting observational astronomy research. The designed instructional units aim to provide students with an adequate knowledge of astronomy and hone their skills necessary in conducting observations, collecting and analyzing data including processing of astronomical images.

The instructional design is anchored on the ADDIE model (Analyze, Design, Develop, Implement and Evaluate). The phases from ADDIE were used as a framework to accomplish the process of developing the instructional materials. After following the ADDIE, it was possible to define performance goals and tasks which were …

Underrepresentation Of Latino Students In Gifted And Talented Programs: How Appropriate Are The Assessments Used For Identification, Deidra D. Tafolla

Theses and Dissertations

This qualitative study examined the possible reasons behind the underrepresentation of Latino students in gifted and talented programs. This study investigated four South Texas school districts and their gifted and talented program matrices, by examining the manuals used to explain and describe the assessments that identify Latino students in gifted and talented programs. A matrix is a design based on a criterion that a school will use to identify gifted students. Carrillo’s (2013) Mestiz@ Theory of Intelligences (MTI) was used to analyze the manuals of the assessments most commonly used by the school districts to identify Latino students and were …

Design Of A Multidirectional Wear Testing Device For Simulating Wear Of Biocompatible Materials Used In Joint Implants, Carlos A. Rodriguez Betancourth

Theses and Dissertations

In the present work, a novel multidirectional pin-on-disc wear testing device designated CNC-POD (computer-numerical-control pin-on-disc) capable of replicating the cross-shear motions experienced by a prosthesis in vivo was designed and developed in the UTRGV in order to evaluate the wear resistance of new biomaterials. The CNC-POD consists of six temperature-controlled pin-on-disc stations mounted on a two-axis CNC table (X-Y). Each pin-on-disc station is load-programmable up to 510 Newtons (115 pounds). The CNC table allows the machine to reproduce a wide range of 2D patterns in millimeter scale on the six stations under a specific load. Friction force is measured during …

Experimental And Computational Studies Of Rotation And Proton Tunneling In Organic Molecules And Molecular Dimers, Agapito Serrato Iii

Theses and Dissertations

An introduction to the relations of classical and quantum mechanics are presented in brief. As is an overview of the instrumentation and quantum chemical analysis performed to characterize the molecules presented in in this thesis. The pure rotational spectrum of 3,3,3-trifluoro-2(trifluoromethyl)propanoic acid, perfluorobutyric acid–formic acid dimer, and tropolone–formic acid dimer were measured using high-resolution microwave spectroscopy. The spectra have been observed using a cavity-based Fourier-transform microwave (FTMW) spectrometer and/or a chirped-pulse FTMW.

Spatial And Temporal Trends In Diet For Pinfish (Lagodon Rhomboides) From Turtle Grass (Thalassia Testudinum) Beds With Contrasting Environmental Regimes In The Lower Laguna Madre, Texas, Maximiliano Barbosa

Theses and Dissertations

Seagrass meadows in far South Texas are dominated by turtle grass (Thalassia testudinum), and juvenile pinfish (Lagodon rhomboides) are abundant grazers of seagrass epifauna. As they grow, pinfish exhibit an ontogenetic dietary shift and begin consuming increasing amounts of plant material. In this study, contrasting environmental regimes in two seagrass meadows were examined to identify how they might affect pinfish diets, diet shifts, and growth across the growing season. The eastern site was sheltered from prevailing southeasterly winds by a barrier island, while the western site was shallower and subjected to higher wind energy and turbidity. …

Superharmonic Resonance Of Second Order For Electrostatically Actuated Mems Cantilevers, Martin Amador Botello

Theses and Dissertations

The nonlinear dynamics of electrostatically actuated micro-electro-mechanical system (MEMS) cantilever resonators are investigated. The applied Alternating Current (AC) voltage is in the realm of superharmonic resonance of the second order (near one-fourth of the natural frequency of the resonator) and hard excitations. Method of Multiple Scales (MMS) and Reduced Order Models (ROMs) are used to solve the dimensionless partial differential equation (PDE) of motion along with boundary and initial conditions. MMS transforms the PDE of motion into zero-order and first-order problems. ROMs uses mode shapes of vibration for undamped cantilever resonator as a basis of functions. ROM is …

Hispanic Male Self-Efficacy And Its Effect On Persistence, Jennifer Mendoza Culbertson

Theses and Dissertations

The Hispanic male population has experienced a decline in four-year college enrollment rates and bachelor degree completion within the past ten years. To address this issue, this study focused on Hispanic male college freshman students, self-efficacy, and persistence in a South Texas four-year higher education institution. The study utilized an explanatory sequential mixed-methods approach. For the quantitative analysis, an efficacy survey, College Self-Efficacy Inventory, of Hispanic male students enrolled in mandatory freshman courses was analyzed. A logistic regression analysis was conducted to determine what amount of the total variance in persistence may be accounted for by self-efficacy. Qualitative data was …

In- And Out- Of-School Literacy Practices Of Student Refugees: A Cross-Case Analysis In A South Texas Middle School, Maria L. Mendez

Theses and Dissertations

As the leading U.S. state currently welcoming all kinds of refugees, Texas has a public school system that offers a formal education to refugee students (Bureau of Population Refugees and Migration, 2015). For many student refugees, formal schooling begins in this system. Thus it is important to understand how Texas public schools support the linguistic and academic development of these diverse learners. In order to fill this research gap, this study examines student refugee school-based literacy interactions in the U.S. public school system and how these practices connect or do not connect with the literacy practices these students experience in …

Predicting Academic Success Among Mexican American Learners, Kattie A. Guerrero

Theses and Dissertations

The number of Hispanic students being enrolled in schools have doubled throughout the years. Especially in the Rio Grande Valley where the majority of the population are Mexican American. Previous studies have looked into the risk factors associated with academic failure, but they hardly look into factors that lead to a child’s school success. This study will investigate what contributes to a child’s academic success. The sample of the study was 115 students, grades 5th to 7th grade, all classified as Hispanic. The findings will state a) what variables were significantly correlated to each other b) what variables differed by …

Approximate Set Union Via Approximate Randomization, Pengfei Gu

Theses and Dissertations

We develop an randomized approximation algorithm for the size of set union problem |A1 U A2 U...UAm|, which given a list of sets A1,...,Am with approximate set size m i for Ai with mi ∈ ((1–βL)|A i|,(1+βR)|Ai|), and biased random generators with Prob(x = RandomElement(Ai)) ∈ [1–a L/Ai, 1 +aR/Ai] for each input set Ai and element x ∈ Ai, where i = 1,2,...,m. The approximation |Ai | |Ai | ratio for |A1 U A2 U...UAm| is in the range [(1–ϵ)(1–aL)(1–βL),(1+ϵ)(1+β R)(1+βR)] for any ϵ ∈ (0,1), where α L,αR,βL,βR ∈ (0,1). The complexity of the algorithm …