Digital Commons Network^™

Effects Of Scarification, Phytohormones, Stratification, Soil Types And Warming On The Germination And/Or Performance Of Three Tamaulipan Thornscrub Species, Paula Luera

Theses and Dissertations

The Tamaulipan thornforests of south Texas and northeast Mexico are an ecologically and economically important conservation hotspot. Thornforest restoration is limited by native tree and shrub seedling availability for planting. Seedling shortages arise from low seed availability and knowledge gaps regarding best practices for germinating and growing the 70+ thornforest species desired for restoration plantings. To fill key knowledge gaps, we investigated three ecologically important thornforest species with low or highly variable germination or seedling survival rates: Ebenopsis ebano, Cordia boissieri, and Zanthoxylum fagara. For each, we quantified the effects of different dosages of chemical seed treatments …

Conceptual Insight Into The Application Of Innovative Educational Methods In Astronomy, Wahltyn A. Rattray

Theses and Dissertations

University students taking introductory astronomy courses were studied with a control group enrolled in a class with standard curriculum and an experimental group enrolled in a class with a curriculum using innovative instructional methods. Using multiple assessments, I analyzed the students’ astronomy knowledge and overall class experience to determine which curriculum was more instructionally effective. The innovative methods were developed with the ADDIE method and were based on the Karplus learning cycle which provided the framework for the astronomy curriculum. The end goal of the innovative curriculum is to produce graduates with better conceptual understanding of astronomy than with the …

Exploring The Role Of Stigmatic Exudate In The Water Lily (Nymphaceae) Pollination Mechanism Using N. Ampla (Salisb. Dc.), Luis Uribe

Theses and Dissertations

Water lilies are the only known plant group that uses hyperactive nectar glands to divest pollinators of their pollen. The nectar in Nymphaea ampla is thought to contain secondary metabolites that increase pollen deposition possibly by modifying pollinator behavior. This was explored utilizing visitation and fecundity data from the field coupled with survival and behavioral experiments in the laboratory. Replacing nectar with water reduced seed set in N. ampla which was attributed to reduced visitation in water-bearing flowers and not to effects on pollinator detention time. Exposure to nectar did not reduce survivability in Apis mellifera. Pollen and nectar foragers …

Developing A Prototype Energy Harvesting Device For Powering Wireless Onboard Condition Monitoring Sensor Modules For Railway Service, Martin Amaro Jr.

Theses and Dissertations

An energy harvesting system is being developed to power a wireless bearing health monitoring device. In contrast to other monitoring systems, this wireless monitoring device is a low-powered onboard solution. Powered by a 3.7-Volt lithium-ion battery, the device can continuously function for several months on a single charge. By implementing an energy harvesting system, the life of the battery can be increased reducing the overall maintenance, electronic waste, and time needed to replace the batteries. The harvesting system uses thermoelectric generators to convert the heat generated in the bearings into electricity. The system is composed of aluminum heat sinks, a …

The Skeletal Structure Of Hot Mix Asphalt And The Effects Of Fiber Additives, Samantha A. Avila

Theses and Dissertations

Hot mix asphalt (HMA) has proven to be successful in providing a proper paving surface for transportation services throughout the world. Asphalt pavement could be altered as the gradation of the mixture is adjusted. For instance, mixtures could vary from Dense Graded (DG) that contain a fairly even percentage of all aggregate size allowing for a more compact fit to Stone Matrix Asphalt (SMA) where the coarse aggregate compromise the main skeleton while fine aggregate fills the voids. This study investigates the effects of fibers and skeletal structures on mechanical properties of HMA. Two types of fiber additives are tested …

Microwave Assisted Depolymerization Of Waste Pet Bottles Via Glycolysis, Kingsley Bassey

Theses and Dissertations

One of the most promising and sustainable chemical depolymerization methods for managing the complex environmental problem arising from waste poly(ethylene) terephthalate (PET) bottles is glycolysis. However key challenges such as longer reaction times, complex separation procedures for the depolymerized products, selectivity, thermally stable catalyst need to be addressed.

In this work, we investigated the glycolysis of waste PET under microwave conditions using 1,5,7-Triazabicyclo [4.4.0] dec5-ene (TBD) and 1,8-Diazabicyclo [5.4.0] undec-7-ene (DBU) as catalyst. We evaluated the effect of reaction parameters such as temperature, catalyst concentration and time on PET depolymerization rate (%PET conversion) and product yield. The reaction was conducted …

Synthesis And Characterization Of Copper Oxide Nanofibers, Shishir Barai

Theses and Dissertations

The aim of this study was to develop polymer-derived Copper (II) Oxide (CuO) nanofibers through centrifugal spinning technique and subsequent calcining. To obtain the force spun pre-ceramic copper acetate nanofibers, 15% wt, 25% wt, 35% wt, 50% wt% copper acetate (active material) and poly (vinyl) alcohol ( PVA) solutions was prepared with deionized water (DI) as solvent and spun at 7500 rpm in a FibeRio Cyclone. Thermogravimetric analysis (TGA) was implemented to determine the thermal degradation behavior of the pre-ceramic nanofibers. These nanofibers were then calcined at three different temperatures (500, 600 and 700°C) to produce CuO nanofibers. The microstructure, …

Bullet-Proof Boll Weevil: The History Of Boll Weevil Eradication, Evan A. Berg

Theses and Dissertations

Farmers and entomologists have all experimented with various methods to find the best way to defeat the United States' boll weevil. The techniques themselves, while expansive, can be examined within the scope of the years that they were used. This provides an exciting insight into how cotton pest management became more complex as the decades moved on and revealed how the science of cotton pest management evolved to deal with the boll weevil and other future cotton threats.

Latinas And Service-Learning In Higher Education: Voices, Experiences And Perspectives, Maria Cristina Cantu-Gutierrez

Theses and Dissertations

This is an exploratory case study that explored service-learning experiences and perceptions among Latinas enrolled in a South Texas university. This study also addresses the challenges and benefits that are associated with Latinas and service-learning in higher education as service providers. This study provides a better understanding of Latina students' experiences and perceptions of their involvement in providing services within their Latino community.

Latino/A Student Perspectives On Literacy Practices Affecting College Readiness, Danira Vanessa Cantu

Theses and Dissertations

This qualitative collective case study examines how pre-collegiate literacy practices affect Latino/a student college success. Conducted at a South Texas border-region University, this study utilized a sample of six Latino/a students enrolled in a freshman level composition course. A focus group was used to explore how academic and social literacy practices play a part in college readiness for these transitioning college students. Additionally, personal narratives were conducted as a form of counternarrative. Modeled on the theoretical framework of removing racism from school structures and closing race-related academic divides, findings included the need for social and cultural acceptance, classroom adaptability, and …

Evolutionary Development Study Of Firebrat (Thermobia Domestica), Luis Cantu Jr.

Theses and Dissertations

As most evolutionary development studies regarding wing origin take place using insects taxonomically closer to model organism, Drosophila melanogaster, there is a need of expanding studies to lower clades. While D. melanogaster is higher phylogenetically, basal clades would allow for a historical perspective of what occurs within the gene flow of conservative biomarkers. Further understanding of wings and flight would allow for a clearer understanding of how the migration of insects from sea to land has allowed them to become one of the most speciose taxa. Through the study of Thermobia Domestica, part of the Zygentoma, we expand on comprehension …

Exploring Self-Perceived Employability In People With Disabilities And Other Intersecting Identities, Kerra Lajoy Daniel

Theses and Dissertations

People with disabilities are the largest minority group in the world representing 26% of the world’s population. More specifically, in the U.S. 61 million Americans have a diagnosed disability. However, intersectionality studies have not been inclusive of this particular population and disability studies have yet to extensively examine intersectionality in PWDs. Centering individuals with disabilities who also identify with multiple marginalized social identities , such as being a woman, a person of color or a member of the LGBT community is important since these individuals’ experiences are not uniform in nature. PWDs experience higher rates of discrimination, unemployment, and …

Assessing The Effectiveness And Efficacy Of Wireless Onboard Condition Monitoring Modules In Identifying Defects In Railroad Rolling Stock, Lee R. Cantu

Theses and Dissertations

Many industries have begun shifting into the Internet of Things (IoT) in the 21st century. To help ease this transition for the rail industry, The University Transportation Center for Railway Safety (UTCRS) has partnered with Hum Industrial Technology, Inc. (HUM) to help complete the development of a Wireless Onboard Condition Monitoring system named the ‘Boomerang™’. This product allows customers to schedule proactive maintenance on their railcars to replace defective wheels and/or bearings, saving them time, money and potentially preventing costly catastrophic derailments. The UTCRS research team has established thresholds to determine defective bearings utilizing thermal and mechanical sensors.

The effectiveness …

Intimate Partner Violence In The Rio Grande Valley: The Role Of Culture, Tania Diaz

Theses and Dissertations

Mexican culture along the border towns of the Rio Grande dominates views towards women and men experiencing violence in intimate relationships. However, there is a paucity of empirical studies relating to intimate partner violence in the Rio Grande Valley. This study addresses the dynamics of abusive relationship in a Hispanic community that can be influenced by cultural concepts such as familism and marianismo. The author utilized a mixed methods approach for this study that included a sample of (n = 513) surveys and (n = 13) interviews that were analyzed separately. Multivariate logistic regression analysis was used to assess …

Comparison Of Statistical Methods For Modeling Count Data With An Application To Length Of Hospital Stay, Gustavo A. Fernandez

Theses and Dissertations

Hospital length of stay (LOS) is a key indicator of hospital care management efficiency, cost of care, and hospital planning. Therefore, understanding hospital LOS variability is always an important healthcare focus. Hospital LOS data are count data, with discrete and nonnegative values, typically right-skewed, and often exhibiting excessive zeros. Numerous studies have been conducted to model hospital LOS to identify significant predictors contributing to its variability. Many researchers have used linear regression with or without logarithmic transformation of the outcome variable LOS, or logistic regression on a dichotomized LOS. These regression methods usually violate models’ assumptions and are subject …

Characterization Of Soil Nematode Community As Influenced By Weedy Plants And Edaphic Properties, Orlando Garcia

Theses and Dissertations

Nematodes are one of the most critical species globally as they are part of most nutrient recycling. While nematodes play a vital role in nutrient cycling, little is known about them from an ecological standpoint. The majority of current research has focused on a singular component of the community, being those of herbivore/plant-parasitic nematodes. In this study, the community shifts of the nematode trophic groups were analyzed as influenced by native and invasive grasses species in the Lower Rio Grande Valley (LRGV) with the addition of edaphic soil properties.

In our study, the results indicate changes in the composition of …

Life-Cycle Cost Analysis Of The Efficient Water Fixtures And Electric Appliances Used To Minimize Water And Energy Consumption In Homes In The U.S, Miranda N. Garcia

Theses and Dissertations

Consumer interest in incorporating sustainability and efficient appliances into daily life has been growing in the past several years. While reducing their environmental impact may be a draw to some, by making the switch to water- and energy-efficient appliances many homeowners are enticed by the promise of long-term savings on utility bills. Programs such as WaterSense and Energy Star not only offer certified efficient appliances and fixtures, but they may also certify water- and energy-efficient homes. Additionally, the United States Green Building Council (USGBC) offers the LEED program (Leadership in Energy and Environmental Design) which certifies homes in a similar …

A Gis-Based Model To Assess On-Site Sewage Facility (Ossf) Contamination Risk To Local Water Resources, Alvaro Garcia

Theses and Dissertations

In a collaborative effort between Texas Water Resources Institute (TWRI), Cameron County Public Health (CCPH), Texas A&M AgriLife Extension (TAMAE), and the University of Texas Rio Grande Valley (UTRGV), a GIS database that includes relevant OSSF information, such as location, system age, lot size, and other important parameters was created.

This OSSF database, along with publicly available GIS data, was used to create an integrative GIS-based risk assessment model where OSSF risk parameters were assigned a risk factor and combined into a spatial contamination risk for surrounding areas and their receiving waterbodies. Parameters were broken down into two categories: environmental …

Early Embryology In Collembola With An Emphasis On Wing Development, Samantha A. Gonzalez

Theses and Dissertations

The primary objective of this study was to further the understanding of the wing origin in insects. Currently there are several theories which are popular such as the tergum theory, the pleural plate theory, and the dual theory of wing origin. Studies for these theories have been done on crustaceans, the ancestors to modern day insects. By utilizing a pre insect hexapod, it may be possible to better understand the transition to insect wings. Members of the Collembola species Hypogastrurid are one of these pre-insect hexapods which may provide a clue into origins of wing development. During this study, the …

The Journey Of Selected Latina Transnational Educational Leaders: Transforming Their Lives Through Educational Achievements And Successful Careers, Raquel Garcia

Theses and Dissertations

The purpose of this study was to examine the journeys of selected Latina transnationals and how they transformed their lives through educational achievements and successful careers in the borderlands of Texas. The researcher utilized a phenomenological collective case study approach that investigated how the selected Latina transnationals overcame challenges via a series of semi-structured interviews (Creswell, 2013). Latinas are forced through their journeys to negotiate multiple systems that could possibly impact their educational trajectories (Lechuga-Pena & Lechuga, 2018). Despite Latinas being seen as the other, the object, the minority, many are able to tell their own stories and liberate themselves …

Cowboy Conversations, Abraham Garza

Theses and Dissertations

I have always had a profound interest in the past; how that past affects the present, and ultimately, anticipating how the present will affect the future. Circumstances change, but the lessons we’ve learned will, inevitably, determine how we handle impending events. Using fiction as a platform, my intent is to reveal, through each chapter, how one’s past dictates future decisions.

I have been working with a vaquero, my wife’s grandfather, who was raised on different South Texas ranches. Taking odd jobs from stall boy to ranch hand, and horse trainer, his unique experiences will illustrate period-based scenarios that emphasize his …

Synthesis And Characterization Of Centrifugally Spun Molybdenum-Based Nanomaterials For Lithium-Ion Batteries, Ramiro Gonzalez Jr.

Theses and Dissertations

The work presented in this thesis focuses on the processing and development of transition metal compound composite fibers as anode materials for rechargeable lithium-ion batteries (LIBs). Among the transition metal compounds, molybdenum compounds have risen as promising candidates of advanced electrode materials, in view of their natural abundance, virtuous mechanical/thermal stability, rich chemistry, high theoretical specific capacity, and multiple oxidation states of Mo. The current work reports synthesize MoO2/C and MoO3/C composite fibers drawn from centrifugal spun ammonium molybdate/PAN precursor fibers, followed by a thermal treatment stabilizing in air and calcination under argon atmosphere. The weight ratios of (MoOx, 2 …

Data Analytics For Google Trend Search Result Of Illness Symptoms, Md Jakir Hossain

Theses and Dissertations

The outbreak of COVID-19 has escalated from March 2020. Since then, people from all over the world are curiously searching different types of illness symptoms including corona virus. Before the outbreak, people were also searching different types of symptoms at different times. Both diseases share same symptoms, but in the flu season. If certain types of symptoms are visible at summer season, then these symptoms are for corona virus. The main purpose of our study is to find out this discriminative information from these search result. We will discuss some mathematical concepts and then develop an algorithm based on those …

A South Texas Elementary School’S Transition To A Constructivist Blended Learning Model Of Instruction In Math: Perceptions Of Students And Parents, Ana Holland

Theses and Dissertations

This exploratory transcendental phenomenological study delved into the perceptions of selected South Texas public elementary school parents and students as they transitioned from traditional math practices to a personalized pedagogy which incorporated the constructivist model of instruction—blended learning. This study focused on fourth and fifth grade students engaged in the transition to blended learning for a minimum of two years and their parents. The exclusion and inclusion parent and student survey data facilitated the selection and organization of participants into focus group interviews, which aligned with a purposive sampling (Rubin & Rubin, 2012a; Mills & Gay, 2016; Creswell, 2013). Along …

Characteristics Analysis Of Electrochemical Impedance Spectroscopy (Eis) For Different Electrode Patterns, Shanzida Kabir

Theses and Dissertations

Electrochemical impedance spectroscopy (EIS) is a rapidly developing technique used in characterizing materials and interfaces. Using equivalent circuits as models can determine the electrical properties of heterogeneous systems like membranes or electrolytes. Different electrochemical processes like the electron transfer rate of a specific reaction or the capacitive behavior of the system, or even the diffusion-limited response can coincide. EIS is applicable to determine different electrochemical processes that can happen simultaneously. The purpose of this research is to find the optimal operating range for other AC electrokinetic mechanisms. Analysis of EIS can be helpful in both fundamental examinations of electrokinetic transport …

The Use Of Virtual Conference Software (Vcs) In The Workplace During Covid-19 In North America: An Empirical Validation Of Innovation Diffusion Theory, Khaleed I. Khasawneh

Theses and Dissertations

Researchers in marketing and technology realized the importance of paying more attention to how and when new technologies or innovations are adopted during crisis, and which factors impact individuals’ successful adoption. Navigating through the different stages of the present COVID-19 crisis, it has become clear that such research focus would be beneficial so that firms can shape customers' decision making process in a way that ensure successful escape of a crisis and its Destructive results on a business or organization; COVID-19 will undoubtedly not be the last global crisis we face. First, a firm understanding of the factors affecting the …

Factors That Contribute To Motivation And Student Achievement As Adolescents Transition From Elementary To Middle School Or Junior High In One Urban District In The Rio Grande Valley, Lizette Villarreal Longoria

Theses and Dissertations

This study will examine factors that contribute to the decline in achievement scores in reading and mathematics when students transition from elementary to their first year in middle school or junior high school. It will test the hypothesis that motivation is not a function of mentors, academic support, teams, parental involvement, transition experience, math perception, and reading perception for students transitioning from elementary to middle school or junior high school. In this quantitative research study, data will be collected using a multiple linear regression analysis to examine the factors that contribute to motivation and the achievement score decline in reading …

Selective Laser Melting Of Titanium Diboride: A Study Of The Energy Density Effects, Lazaro Lopez Mendez

Theses and Dissertations

Natural titanium diboride (TiB2) has been reported the 5th hardest material on earth. Due to its superior properties, such as high density, high elastic modulus, and high compressive strength, TiB2 becomes one of the most suitable ceramic reinforcements for applications with severe friction and heavy loading conditions. This study is intended to produce TiB2 using 3D additive manufacture (AM) technology, and then to understand the tribological property of the AM fabricated TiB2 specimens. In this study, a laser additive alloying (LAA) process was developed based on a Renishaw AM laser system. One mm thick samples were prepared using the LAA …

Understanding Teacher Perceptions And Experiences About Active Learning Techniques In High School U.S. History Courses At A Lower Rio Grande Valley School District, Juan J. Mendoza

Theses and Dissertations

This qualitative study explored the perceptions and experiences of teachers about the use of active learning techniques in high school United States history courses at a lower Rio Grande Valley school district. The study employed a phenomenology design for rich textural descriptions and a systematic exploration of the phenomenon of active learning techniques. Data were collected from individual semi-structured interviews and a focus group of 8 U.S. history teachers. Teacher lesson plans were examined to further corroborate evidence coded from the semi-structured interviews and focus group.

The research evidence suggested that active learning pedagogies create a progressive learning environment, they …

Flexible Quantum Dot Solar Cell With Nanostructure Titanium Dioxide Photoanode With Modified Counter Electrode, Haimanti Majumder

Theses and Dissertations

Because of unique photovoltaic properties, nanostructured morphologies of TiO2 on flexible substrate have been studied widely in recent years in dye-sensitized solar cells (DSSCs). Nanostructured electrode materials with high surface area can promote rapid charge transport and thus improve the light-to-current conversion efficiency. Herein, this project generates an improved photoanode with forest like photoactive TiO2 hierarchical microstructure using a simple and facile hydrothermal route. To improve the photocurrent efficiency, PbS quantum dot has been applied in different thicknesses to evaluate the best performance. The deposition of quantum dot was done by easy SILAR cycle. Four different SILAR cycle has been …