Theses

Permanent URI for this collectionhttps://hdl.handle.net/1969.6/1140

Browse

Recent Submissions

Now showing 1 - 20 of 397
  • Item
    Conservation genomic assessment of two imperiled freshwater fishes, Leon Springs Pupfish (Cyprinodon Bovinus) and Pecos Gambusia (Gambusia Nobilis)
    (2023-12) Bretzing-Tungate, Robert James; Portnoy, David; Conway, Kevin; Hollenbeck, Christopher
    Freshwater fishes are increasingly recognized as one of the most imperiled groups of vertebrates, with a growing body of research highlighting the significant threat posed to their biodiversity by human activities. Anthropogenic actions, such as habitat modification and destruction, pollution, overexploitation, and the introduction of invasive species, have led to a decline in the number of freshwater fish species worldwide. Addressing this imminent crisis requires comprehensive conservation efforts, stricter regulatory frameworks, habitat restoration, and heightened public awareness. This project aimed to provide data important for the conservation of two imperiled desert freshwater fishes, Cyprinodon bovinus and Gambusia nobilis, both of which are federally listed as endangered and have undergone range contractions throughout the western United States due to anthropogenic activity. Using genomic techniques, I assessed patterns of genetic diversity within and between populations of both species and screened for evidence of hybridization with introduced congeners. No evidence of contemporary hybridization was found between C. bovinus and C. variegatus, but admixture was detected among G. nobilis and its respective invasive congeners (G. geiseri and G. affinis). Fine-scale population structure was evident for both species of interest and estimates of effective population sizes were low for both species. The results of the study will help update conservation management plans to help mitigate the threat of extinction for both species.
  • Item
    Accumulation of epiphytes on Halodule Wrightii in response to nutrient enrichment in East Flats, Corpus Christi Bay and Nighthawk Bay, Upper Laguna Madre, Texas
    (2010-08) Sweatman, Jennifer L.; Cammarata, Kirk; Smee, Lee; Shirley, Thomas; Withers, Kim; Mott, Joanna; Pezold, Frank
    Increased epiphyte abundance on seagrasses is often associated with anthropogenic eutrophication of estuarine ecosystems, but the quantitative relationships are complex and not fully understood. A nutrient enrichment experiment was conducted at two sites during three seasons to measure epiphyte accumulation on Halodule wrightii and artificial seagrass substrates. A novel fluorescence imaging technique, based on excitation of phycobilin and fucoxanthin accessory pigments, was used to quantify epiphyte abundance. For natural seagrasses, significant dose-dependent increases in epiphyte accumulation occurred due to the introduction of nutrients at East Flats, during early summer and fall sampling seasons. Significant nutrient responses were also detected during late summer at East Flats, and during early summer and fall only at a hypersaline lagoon site, Nighthawk Bay. Additionally, nutrient enrichment caused significant decreases in combined seagrass and epiphyte biomass across all seasons at Nighthawk Bay, and during late summer at East Flats. At East Flats, biomass increased with increasing nutrient treatments during early summer and fall seasons. Artificial substrates failed to corroborate results of the natural seagrass experiment; however, a change in species composition was evident, but results were inconsistent across seasons and sites. These findings imply that epiphyte abundance is sensitive to nutrient enrichment under a wide range of ambient conditions, including different predominant grazer abundances, and is likely to increase with eutrophication.
  • Item
    Effects of foliarly applied amino acids on sunflower tolerance to arsenic and molybdenum, and DNA methods to characterize associated rhizosphere bacterial communities
    (2011-08) Riis-Due, Stephanie; Cammarata, Kirk; Mott, Joanna; Buck, Gregory; Balasubramanya, M.K.; Pezold, Frank
    Arsenic contamination of soil is a worldwide concern due to its impact on human health and agriculture. Phytoremediation is an emerging technology that uses plants to remediate metal contaminated sites in situ. Helianthus argophyllus is a sunflower plant that is native to South Texas, and is currently under study as a promising prospect for phytoremediation. This investigation focused on the use of foliarily applied amino acids, glycine or a mixture of cysteine and glutamate, to enhance the tolerance of Helianthus argophyllus to weekly treatments of arsenic+molybdenum (2 mM each). Plants typically died over a treatment period of 2-5 weeks, but foliar applications of glycine, in particular, reduced the yellowing of leaves and delayed the onset of toxicity symptoms and death. Other data suggests that the foliar amino acid effects are due to enhanced exclusion of the metalloids from the above-ground plant parts, possibly implicating amino acid-altered plant-rhizosphere interactions The second component of this study developed methods for the comparison of the rhizosphere communities of sunflower plants among the various treatment groups by using PCR amplification of 16S rRNA followed by denaturing gradient gel electrophoresis. Two DNA extraction kits were compared for their effectiveness at extracting amplifiable DNA from sandy and organic soils. Two sets of primers were also compared. Universal rRNA primers failed to produce any bands by DGGE. However, DGGE banding patterns form a second eubacteria-specific primer set revealed a more complex profile, including a number of unique bands, for a growth chamber soil containing a sunflower plant compared to a growth chamber control soil (without a plant) and a wild sunflower sample.
  • Item
    Microbial diversity of bleached nurdles in the NorthWest Gulf of Mexico
    (2023-08) O'Donnell, Colin Andrew; Turner, Jeffrey; Buck, Gregory; Conkle, Jeremy; Tunnell, Jace
    Nurdles are the raw material in the manufacture of plastic products. They are mass produced and transported worldwide, but accidental and negligent spills pollute marine environments. In the Gulf of Mexico (GoM), a citizen science initiative, the Nurdle Patrol, revealed that 20 of the highest nurdle-polluted beaches are found in Texas. Microorganisms, including potentially pathogenic bacteria, rapidly colonize nurdles. The purpose of this study was to broaden the understanding of nurdle-bacterial coupling through the following objectives: 1) characterize the microbial diversity of nurdles on a recreational beach compared to a natural substrate and 2) isolate potentially pathogenic members of the nurdle community and further analyze those isolates through whole-genome sequencing (WGS) and antimicrobial resistome analysis. Results show that the nurdles were colonized by a distinct (Faith’s phylogenetic distance, P < 0.001) and more uniform microbial community than beach sand. The nurdle community was dominated by Proteobacteria (69.5%) and Bacteroidota (21.7%) at the phylum level, and Rhodobacteraceae (26.2%) at the family level. Culturable members of the nurdle community included potentially pathogenic Bacillus licheniformis and Bacillus paralicheniformis. Isolates possessed antimicrobial resistance genes (e.g., ATP-binding cassette (ABC) antibiotic efflux pumps and class A Bacillus cereus Bc beta-lactamases), and two B. paralicheniformis isolates appeared to be multidrug resistant (i.e., peptide, macrolide, and penam resistant). Results demonstrate that nurdles were colonized by a distinct community compared to a natural substrate. Additionally, nurdles supported the growth of potentially pathogenic Bacillus species with the genetic potential for antimicrobial resistance. Overall, these results establish a baseline knowledge of nurdle microbial diversity in the northwest GoM.
  • Item
    Application of UAS photogrammetry and geospatial AI techniques for palm tree detection and mapping
    (2023-08) Regmi, Pratikshya; Starek, Michael; Chu, Tianxing; Medrano, Antonio
    Uncrewed aircraft systems (UAS), commonly known as drones, underwent significant advance ments in recent years, particularly in the development of improved sensors and cameras that enabled high-resolution imagery and precise measurements. This study utilized a UAS to capture aerial imagery of Texas A & M University-Corpus Christi (TAMUCC) main campus, which was then processed using Structure-from-Motion (SfM) photogrammetric software to generate orthomosaic imagery. The primary purpose of this study was to utilize the orthomosaic imagery acquired from UAS to detect, map, and quantify the number of palm trees. Initially, three deep-learning models were trained using the same set of training samples. The model exhibiting the highest performance in terms of precision, recall, and F1-Score was selected as the optimal model. The model obtained through the fine-tuning of a pre-trained GIS-based model with additional training samples was identified as the optimal choice, yielding the following values: precision=0.88, recall=0.95, and F1-score=0.91. This model successfully detected a total of 1414 sabal palm trees within our study area. The chosen optimal model was employed to examine the impact of ground sampling distance (GSD) on the deep learning model. GSD values were varied, namely 5 cm, 10 cm, 20 cm, and 40 cm. The findings revealed that the model’s performance deteriorated as the resolution decreased. Furthermore, the optimal model was subjected to an additional test using multi-temporal datasets with approximately the same GSD (1.5 cm). These datasets included one acquired a year prior to the model’s training datasets, and another obtained three months after the training datasets. Remarkably, the results demonstrated that the model maintained a comparable level of accuracy across all three testing datasets. The obtained results were verified using ground truth values taken in a small portion of the study area. This study concludes that deep learning models for object detection exhibit superior performance when fine-tuned with training samples specific to the area of interest. Furthermore, it is evident that the optimal model’s effectiveness diminishes significantly when the imagery resolution is reduced. Additionally, the performance of the deep learning model remains relatively consistent when applied to datasets acquired at different time frames, as long as the resolution of the testing data remains the same. In summary, the application of deep learning demonstrates its efficacy, user-friendliness, and time-saving capabilities for object detection. This study shows how we can use UAS and deep learning to detect palm trees. It helps us develop better ways to monitor and manage palm trees.
  • Item
    Quarter von Mises distribution
    (2023-08) Myers, Mason Gene; Guardiola, Jose; Gajamannage, Kelum; Jin, Lei
    The world today is increasingly relying on data science and statistics to analyze various types of directional data, such as text data, health studies, image processing, wireless sensor networks, environmental monitoring, robotics, and materials science. In many cases, these data exhibit positive orientation and require probability distributions that are confined to positive regions, such as the positive quarter of the unit circle. These facts highlight the main objective of this thesis, which is to propose a new transformation of the von Mises distribution specifically tailored for the positive quarter of the unit circle. Currently, no such distribution exists. The newly introduced distribution, referred to as the Quarter von Mises Distribution, has been thoroughly investigated in this work. The research includes characterizing the distribution through moments and developing its main properties. Additionally, methods for estimating the distribution parameters using maximum likelihood estimation are presented, along with a hypothesis testing approach using the likelihood ratio test. Furthermore, practical data applications are demonstrated to showcase the effectiveness of these methods. Overall, this thesis contributes to the field of data science and statistics by providing a novel distribution that can accurately model directional data restricted to the positive quarter of the unit circle.
  • Item
    A comparative analysis of georeferencing techniques for crop canopy height estimation using UAS photogrammetry
    (2023-08) Landivar Scott, Jose Luis; Starek, Michael; Bhandari, Mahendra; Chu, Tianxing
    In the rapidly evolving fields of geospatial engineering and precision agriculture, the accuracy and reliability of georeferencing techniques and Uncrewed Aircraft System (UAS) methodologies are crucial for effective decision-making and crop management. This research aims to enhance UAS Structure-from-Motion (SfM) photogrammetry data quality for crop canopy height estimation in high-throughput phenotyping. The study investigates and compares the accuracy and reliability of three distinct methods used for georeferencing of the UAS imagery, which subsequently enables more accurate SfM 3D reconstruction: Global Navigation Satellite System (GNSS) without any correction aiding (GNSS-only), GNSS+Real-Time Kinematic (RTK), receiving RTK corrections from a local base station, GNSS+Real-Time Network (RTN), receiving RTK corrections from the Texas Department of Transportation (TxDOT) GNSS reference station network. The study further assesses the correlation between manually measured plant heights and those estimated from UAS-SfM point cloud data, exploring three different Digital Terrain Model (DTM) generation techniques. The research was conducted at the Texas A&M AgriLife Research and Extension Center in Corpus Christi, Texas, USA, on corn crops grown during the 2022 agricultural season. The three DTM generation methods under consideration included 1) using a DTM acquired from a flight conducted before plant emergence, 2) creating a DTM by interpolating ground height points, and 3) implementing automatic classification algorithms. Findings initially revealed that the GNSS+RTK method consistently outperformed the other georeferencing techniques, delivering more accurate results across various dates. Despite these overall trends, there were some instances where the GNSS+RTK method did not consistently outperform the other techniques. The use of one ground control point (GCP) improved georeferencing accuracy compared to scenarios with no GCPs used, while GNSS-only without correction aiding reported the least accurate results as expected. Regarding plant height estimation, the highest accuracy was generally achieved with greater canopy cover percentages, with the optimal percentage varying depending on the data collection date and DTM creation method. The highest coefficient of determination (R2) of 0.92 between manual measurements and UAS-SfM derived plant heights was found when the DTM was either interpolated from ground height points or obtained from a pre-emergence flight.
  • Item
    Development of bis-bipyridinium and anthracene carboxyimide-based stimuli-responsive soft matter
    (2023-08) Jakharia, Vandan Paresh; Olson, Mark; Billiot, Fereshteh; Billiot, Eugene
    This thesis focuses on the design and synthesis of an array of novel amphiphilic and polymeric molecules as precursors for developing dynamic stimuli-responsive supramolecular materials by harnessing the competency of non-covalent interactions. Over the past decades, bipyridinium-based derivatives have gained tremendous attention due to their applicability as functional units in tunable supramolecular complexes. The innate propensity of functionalized bipyridinium salts to serve as a ?-electron deficient acceptor allows them to undergo ?-? stacking donor-acceptor CT interactions in the presence of ?-electron rich organic molecules. This characteristic feature was employed to develop novel bipyridinium-functionalized amphiphiles and bio-polymeric materials that are capable of engaging in molecular recognition with and facilitating the extraction of melatonin, a neurotransmitter from water. The first project reports the design and development of heptyl and glycol-bridged bis-bipyridinium-based gemini amphiphiles that can undergo template-directed self-assembly. Previous studies indicated that the electrophilic aromatic nature of tetra-cationic bis-bipyridinium gemini amphiphiles can be exploited to form ?-? stacking charge-transfer interactions with ?-electron rich molecules. Thus, in an effort to establish structure-property relationships and understand the effect of the bridging unit, varied bridged bis-bipyridinium gemini amphiphiles were synthesized. They were investigated for their use of melatonin as a template for directed self-assembly processes. The charge-transfer interactions between the units lead to absorption band formation in the visible region of the electromagnetic radiation that can be exploited for various material applications. Upon comparing, the two derivatives in detail, their micellization behavior, surface properties, thermodynamic parameters, UV-Vis absorption, and micellar size exhibited similar characteristics. However, the heptyl-bridged gemini amphiphile responded to templation much more strongly, while the glycol-bridged gemini amphiphile exhibited higher solubility, they both portrayed excellent amphiphile and surface-active characteristics. The second part of this work focuses on employing ?-electron deficient bipyridinium units to design and process functional lipoic ester-based polymeric materials for the indole-base molecular targets from water. A series of lipoic-ester based-bipyridinium functionalized polymers with varying alkyl tail lengths were developed and studied to determine structure-property correlations and analyze their material characteristics. Out of the eight-novel functionalized polymeric materials, bipyridinium-bridged lipoic ester polymer (BLEP) formed polymeric sheets while nonyl-bipyridinium-functionalized lipoic ester polymer (9C-BFLEP) formed coacervates in water. Both materials showed comparable and acceptable efficiency in adsorbing melatonin out of solution by harnessing ?-? stacking charge-transfer interactions in conjugation with the hydrophobic effect. This approach provided a quick and promising method for the remediation of indole-cored molecules from water. Lastly, an anthracene carboxyimide derivative was synthesized with the ability to undergo a photo-induced [4+4] cycloaddition dimerization process. The dimerization can easily be reversed upon heating. The compound was found to be able to have a special feature that allows them to undergo single crystal-to-single crystal photo-dimerization upon exposure to UV light. This controlled switchable characteristic property of anthracene carboxyimide are unique and can be utilized for developing tunable molecular switches with applications where stimuli-responsive materials are required.
  • Item
    Numerical investigation of the population distribution in heterogenous domain
    (2023-08) Henry, Stephen Andre; Sadosvki, Alexey; Vasilyeva, Maria; Denny, Diane; Muddamallappa, Mallikarjunaiah
    We consider the spatial-temporal model of multi-species population distribution in two-dimensional heterogeneous domains. A coupled system of time-dependent diffusion-reaction equations describes the mathematical model of such problems. To solve the problem numerically, we construct an unstructured grid that resolves inclusions on the grid level and produces a semi-discrete system using a finite element method. For time approximation, we apply an explicit-implicit scheme where the reaction term of the equation is taken from the previous time layer. We present numerical results for several test problems to investigate the influence of the geometry and parameters on time to reach equilibrium and the final equilibrium state. An extension of the model is also considered, where we add a memory effect by introducing a time-fractional multi-species model. We derive an implicit finite difference approximation for time discretization based on Caputo’s time fractional derivative. A numerical investigation is performed for various orders of the time derivative.
  • Item
    Fraud detection using optimized machine learning tools under imbalance classes
    (2023-08) Isangediok, Mary; Gajamannage, Kelum; Guardiola, Jose; Mallikarjunaiah, Muddamallappa
    Fraud detection is considered to be a challenging task due to the changing nature of fraud patterns over time and the limited availability of fraud examples to learn such sophisticated patterns. Thus, fraud detection with the aid of smart versions of machine learning (ML) tools is essential to assure safety. Fraud detection is a primary ML classification task; however, the optimum performance of the corresponding ML tool relies on the usage of the best hyperparameter values. Moreover, classification under imbalanced classes is quite challenging as it causes poor performance in minority classes, which most ML classification techniques ignore. Thus, we investigate four ML techniques, namely, logistic regression, decision trees, random forest, and extreme gradient boost, that are suitable for handling imbalance classes to maximize recall and simultaneously reduce false negatives. First, these classifiers are trained on two original benchmark unbalanced fraud detection datasets, namely, phishing website URLs and fraudulent credit card transactions. Then, three synthetically balanced datasets are produced for each original data set by implementing the sampling frameworks, namely, random under sampler, synthetic minority oversampling technique (SMOTE), and SMOTE edited nearest neighbor (SMOTEENN). The optimum hyperparameters for all 16 experiments are revealed using the method RandomzedSearchCV. The validity of the 16 approaches in the context of fraud detection is compared using two benchmark performance metrics, namely, area under the curve of receiver operating characteristics (AUC ROC) and area under the curve of precision and recall (AUC PR). For both Malware datasets, phishing website URLs, and credit card fraud transaction datasets, the results indicate that extreme gradient boost trained on the original data shows trustworthy performance in the imbalanced dataset and manages to outperform the other three methods in terms of both AUC ROC and AUC PR.
  • Item
    PH effects on solid phase extractable dissolved organic matter: Expanding the analytical window
    (2023-08) Elliott, Justin Yoshida; Abdulla, Hussain; Felix, Joseph; Hu, Xinping
    Marine dissolved organic matter (DOM) is the largest exchangeable organic carbon pool, holding comparable amounts of carbon as CO2 in the atmosphere and exceeding all biomass. DOM constituents are made up of thousands of unique organic compounds with astounding molecular diversity, featuring a wide range of hydrophobicity, size, and acidic or basic properties. Modern high resolution, high accuracy, and fast cycle time mass spectrometers can provide deep molecular insights into complex mixtures but require compatible samples. The inorganic matrix and low DOM concentrations have required organic biogeochemists to rely on Agilent Bond Elut Priority PoLutant (PPL) Solid Phase Extraction (SPE) to isolate and concentrate DOM through hydrophobic interactions. Currently, the standard SPE method has been optimized to maximize recovery? of dissolved organic carbon (DOC) through sample acidification and methanol elution. However, there is a lack of full understanding of the effect of adjusting the sample pH on the extraction efficiency of different DOM compounds. This study investigated the effects of pH modification on the SPE recoveries and the effects of various procedures on the isolated DOM. This study collected water samples from three sites to represent different marine systems (Lavaca River, Baffin Bay and Gulf of Mexico) with unique sources and signatures of DOM. Samples were acidified to pH 2, kept at natural pH, basified to pH 10 or run sequentially where the permeate was further isolated. Various modified methanol elution solvents were tested, comparing methanol, acidic methanol, basic methanol, and combinations of both. The isolated DOM was chemically characterized in positive mode separated with reverse-phase high performance liquid chromatography (RP-HPLC) and in negative mode with Anion Exchange Ion Chromatography (AEX-IC) on an Orbitrap Fusion Tribrid mass spectrometer (OT-FTMS) using data dependent acquisition (DDA). The standard SPE procedure with acidification yielded the highest recoveries but showed bias against dissolved organic nitrogen (DON). The samples that were not acidified, including natural pH or pH 10, yielded a different fraction of enigmatic DOM with a higher nitrogen percentage than the DOM isolates using the standard procedure. We found that through isolating DOM from a water sample at natural pH and pH 2, two fractions of DOM can be isolated, including hydrophobic DOM, acidic DOM, and basic DOM. These results suggest in order to better represent DOM from marine systems, collecting both fractions and analyzing in both positive and negative modes provide a more comprehensive and representative isolate of DOM.
  • Item
    A comparison of hydraulic patent tongs and oyster dredges for monitoring oyster reefs in the mission - Aransas estuary
    (2023-08) Wheat, Margaret Catherine; Pollack, Jennifer; Olsen, Zachary; Walther, Benjamin
    The Texas Parks and Wildlife Department (TPWD) currently uses dredge sampling to monitor oyster reefs open to commercial harvest. However, dredges have been shown to produce biased sampling data with regard to the density and relative sizes of the oysters collected. In this project, we compared the sampling performance of oyster dredges in reference to hydraulic (patent) oyster tongs. The objectives of this project were to: (1) Compare the density (n m-2) and size (shell height, mm) of live oysters, articulated shells of dead oysters (boxes), and disarticulated oyster shells collected using dredges and tongs across varying reef structures (assessed with acoustic mapping procedures). (2) Compare dredge vs. tong-generated metrics and evaluate resulting thresholds for opening and closing oyster harvest areas. (3) Compare the logistics of dredge versus tong sampling methods for oyster monitoring (e.g., cost, gear maintenance and operation, impacts on staff-hours). Results indicate that dredges show a size bias toward larger shells and oysters, while tongs sample a smaller area and may not accurately represent density across the entire reef extent, particularly for reefs with patchy oyster distribution and where sample size is not adequate. Although deployment, retrieval, and processing for one tong sample takes less time than for one dredge sample, tong sampling requires one additional staff member and approximately 2-3x more samples to see stabilized estimates of density, compared to dredge sampling. Based on this study, tongs may be better suited for more focused (spatially or temporally) sampling initiatives where a greater number of samples and staff time are more realistic. This is the first tong and dredge comparison in Texas estuaries that focuses on monitoring commercially harvested oyster reefs and understanding the ability of tongs and dredges to provide management metrics across a range of reef types and oyster abundances.
  • Item
    Determining Nitrogen sources and processing along the Texas Coast and potential impacts due to sea-level variations
    (2023-08) Taylor, Erin; Felix, Joseph; Murgulet, Dorina; Wetz, Michael
    The Gulf Coast of Texas has had increased incidents of eutrophication and high concentrations of fecal bacteria since 2009, which are indicators of poor water quality. Nitrogen loading in the form of both dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) sources can contribute to water quality decline. To determine the sources and processes contributing to nitrogen loading on Texas sandy barrier islands, ground-, pore- and surface waters from Galveston to Matagorda counties were analyzed for DON and DIN concentrations and isotopic composition. Additionally, groundwater elevations were monitored to determine if water table fluctuations were associated with increases/decreases in N loading. Average nitrate (NO3-), ammonium (NH4+), and dissolved organic nitrogen (DON) in surface and porewater samples were reminiscent of ocean processing. Surface water isotopic evidence indicated assimilation and competing subsurface denitrification, while porewater isotopic evidence suggested competing DNRA/denitrification coupled with nitrification processes. In contrast, NO3- was elevated at three groundwater sites, while most wells showed elevated NH4+ concentrations. Isotopic and nutrient concentration evidence indicated a septic signature with coupled denitrification/anammox and nitrification processes, along with possible saltwater intrusion. Regarding monitoring wells, depth to water (DTW) values had a positive correlation with NO3- concentrations and a negative correlation with NH4+ concentrations, indicating direct contamination from a NH4+ source at low DTW and NH4+ source processing to NO3- at high DTW. A Bayesian-type isotope mixing model estimated NO3- source contributions to Gulf surface water as septic/sewage (35.9 ± 20.5%), dog waste/gull guano (22.9 ± 17.5%), soil (22.9 ± 15.5%), and wet deposition (18.3 ± 7.8%). Nitrate source contributions to porewater were septic/sewage (35.3 ± 21.3%), soil (26.8 ± 18.7%), dog waste/gull guano (25.2 ± 19.0%), and wet deposition (12.7 ± 6.7%). Source contributions to groundwater were septic/sewage (62.6 ± 24.1%), dog waste/gull guano (15.8 ± 21.7%), wet deposition (12.8 ± 7.7%), and soil (8.8 ± 6.3%). Results indicate that there is substantial septic/sewage contamination throughout the study area and possible contamination from animal waste, with evidence of saltwater intrusion in wells. This is the first study to attempt to characterize nitrogen processing, loading, and source contributions to the area. A history of failing septic/sewage systems, along with sea level rise and the increase of more severe climatic events, is estimated to cause more saltwater intrusion and septic/sewage malfunctions to an already vulnerable coastal area. Stakeholders and decision makers can use this data as a starting point for contamination and saltwater intrusion mitigation strategies.
  • Item
    Understanding nanoplastic particle accumulation and cell response in human skin cells
    (2023-08) Simpson, Kayla Haylie; Xu, Wei; Turner, Jeffrey; Sheng, Jian; Zhu, Lin
    Environmental nanoplastic particles (NPs) are considered hazardous materials that can potentially enter human bodies through various entry pathways due to their sizes (<1µm). Studies over the past few years have produced results showing the capability of nanoplastic particles (NPs) to enter cells. However, the mechanism of NP cellular uptake remains unclear. Furthermore, the internalization and accumulation of NPs by human cells can likely be altered by the various characteristics of NPs, including materials, shapes, and surface properties. This study aimed to understand the mechanisms of NPs internalization and accumulation in skin cells, including keratinocytes, dermal fibroblast cells, and adipocytes, and how those processes can be altered by the surface coating components (surface corona). The study was conducted using fluorescence microscopy and flow cytometry to track NP endocytosis, organelle staining to determine intracellular co-localization patterns, and various assays and genetic analyses to understand how NPs affect cell functions and inflammation. The results of the present study demonstrated different internalization mechanisms of NPs depending on cell type, exposure time, particle size, and surface composition. It was also observed that specific vital organelles were more likely to co-localize with NPs, depending on particle size and exposure time. NP accumulation patterns in skin cells revealed potential mechanisms behind the impaired cellular function of cells exposed to NPs. Therefore, potential risks were determined to be associated with the exposure of human skin cells to NPs.
  • Item
    Whole genome sequencing century-old ethanol-preserved Philippine fishes
    (2023-08) Roberts, Roy Lonnie; Bird, Christopher; Seemann, Frauke; Portnoy, David
    The genomes of organisms stored in museums hold a wealth of information that is challenging to access. Recent success in sequencing desiccated museum insects involved using Whole Genome Amplification (WGA) and enzymatic repair of deoxyribose nucleic acid (DNA) damage. However, these techniques have not been tested on fishes preserved in ethanol for over a century. Here, I tested for the effects of WGA, repair, and the amount of template DNA on whole genome sequencing of historical (1908-09) and contemporary (2017-19) Philippine reef fishes. I attempted to construct 178 shotgun libraries (Illumina 2 x 150bp, 92 contemporary, 86 historical) using commercial kits and successfully produced 130 libraries (86 contemporary, 44 historical). Contrary to expectation, WGA had a negative effect on success of libraries, and repair had a small number of minor positive effects. A greater proportion of historical libraries treated with WGA failed than those that were not (37% +WGA, 65% -WGA, p=0.007). While the -WGA, historical libraries that succeeded produced less reads per unit effort than contemporary libraries (p=1.60E-07), this can be addressed by increasing the amount of DNA from historical specimens in the sequencing library. Increasing the template DNA mass was one of the best ways to improve library success, except when WGA was employed. However, only a limited amount of DNA can be obtained from historical samples using a standard commercial kit, and it would be useful to explore alternative protocols. Overall, I found the basic library preparation protocol without WGA or repair to be the best alternative for sequencing historical ethanol-preserved fish. This methodology is relatively cost-effective and can unlock the genomes of historical, ethanol-preserved fishes stored on the shelves of museums.
  • Item
    Impact of disturbances on serpulid reef and soft-sediment macrofauna in Baffin Bay, Texas
    (2023-08) Gilmore, Jennifer; Pollack, Jennifer Beseres; Wetz, Michael; Lebreton, Benoit
    In subtropical regions, low inflow estuaries are influenced by long residence times that promote hypersalinity and are intermittently affected by acute rainfall events; extreme cold temperatures, while uncommon, can also occur. Baffin Bay, TX, USA experienced a sustained period (~7 days) of freezing temperatures during “Winter Storm Uri” in February 2021, and experienced an acute freshwater flooding event three months later with a 20 unit drop in salinity. This study used benthic macrofauna from soft-sediment and serpulid reef habitats as indicators for understanding the impact of successive freeze and flood disturbances on this low inflow estuarine ecosystem. Traditional community analyses were supplemented by stable isotope analysis of basal food resources and resource use by an abundant benthic predator and economically important fisheries species, black drum (Pogonias cromis). Successive disturbances in 2021 had minimal effects on soft-sediment benthic macrofauna abundance, biomass, richness, and diversity, with values falling within historically measured ranges. Serpulid reef benthic macrofauna were lower in biomass and richness following Winter Storm Uri, and higher in abundance and richness after freshwater flooding, with values outside of historic records. Despite this fluctuation during 2021 disturbances, serpulid reef macrofauna remained higher in abundance, biomass, and richness and more stable in community composition than soft-sediment macrofauna. Greater prey availability and reliability on serpulid reefs may be important for higher-level consumers. Stable isotope results indicate reliance of black drum on benthic macrofauna prey resources in both Baffin Bay and the adjacent Upper Laguna Madre in 2021. Understanding the response of benthic macrofauna indicators to environmental disturbance from acute freeze and flood events can inform future resource management strategies, particularly in light of increasing climate variability and water resource development.
  • Item
    Characterization of green surfactants with Dicarboxylate Polar Head
    (2023-08) Fritz, Shayden; Billiot, Fereshteh; Xu, Wei; Billiot, Eugene; Olson, Mark
    There has been a growing emphasis on developing biodegradable and environmentally friendly surfactants. One such relatively new class of surfactants that fall into this category are amino acid-based surfactants. This research focused on studying the physical properties (critical micelle concentration [CMC] and hydrodynamic radius) of aspartic and glutamic amino acid-based surfactants with two different types of hydrophobic tails (saturated hydrophobic chain with 13 carbons and an unsaturated hydrophobic tail containing 11 carbons). In addition to the varying types of hydrophobic tails and polar headgroups, this study also examined what effect different types of diamine counterions had on the physical properties examined. It is interesting to note that the type of diamine counterion or the amino acid head group, for the most part, had little effect on the physical properties examined. The major factor affecting significant changes in the physical properties was the type of hydrophobic tail. The CMC value obtained for saturated 13 carbon surfactants was significantly lower compared to the surfactant with an unsaturated hydrophobic tail containing 11 carbon chains. The range for the CMC values of saturated 13 carbon surfactant was 6 to 12 mM, while the range of the CMC values of unsaturated 11 carbon surfactant was found to have a value of 33 to 52 mM. The surfactant with the unsaturated 11 carbon chain had a significantly smaller hydrodynamic radius in comparison to the saturated 13 carbon surfactant. The range of the hydrodynamic radius for the unsaturated 11 carbon surfactant had a hydrodynamic range from 1 to 5 nm and the saturated 13 carbon surfactant was between 5 to 8 nm. However, there was one exception to this trend and that was the saturated 13 carbon glutamic surfactant in the presence of 1,2 diaminoethane counterion. It had a significantly larger size than all other surfactants measured. The hydrodynamic radius that was measured from saturated 13 carbon surfactant in the presence of 1,2 diaminoethane had a value of 106.47 nm
  • Item
    Representations in Texas english language arts' textbooks: A critical literature pedagogy study
    (2023-08) Figueroa, Jeanette; Pletcher, Bethanie; Smith, Nancy; Reinhardt, Kimberly; Salter, Sarah
    This exploratory qualitative study evaluated representations in literary selections in four English Language Arts textbooks for 11th grade adopted for instructional use in the state of Texas for the 2020-21 school year. The selection of this purposive sample represented the most recent adoption for ELA since the 2010 school year. Drawing on the theoretical framework of Critical Theory (Habermas, 1975) and Critical Literature Pedagogy (Borsheim-Black, et al., 2014), this study is rooted in the belief that ideology contributes to the oppression and marginalization of people and groups (Beaudry & Miller, 2016). Since the early 1900s, scholars have reported on the cultural misrepresentations and exclusion of marginalized populations in textbooks and other reading materials used in curriculum instruction (Apple & Christian-Smith, 1991; Hickman & Portfilio, 2012; Williams & Agosto, 2012). With persisting strides towards equitable learning experiences for all students, the evaluation of textbooks provided an opportunity to critically explore the representations in literary selections published between 1970 and 2020. Grounded on a constructivist approach, an emergence of patterns and themes of representations contributed to an understanding of how and to what extent the literary selections support and mirror today’s culturally pluralistic learning environments. The following four themes emerged from an open coding and versus coding method, and thematic analysis: 1) The Journey to Seeking an Identity in the United States; 2) Redefining History and Rebuilding America; 3) Modern-Day Life; and 4) Reconnecting to the Land. Keywords: critical literature pedagogy, textbooks, instructional materials, critical theory
  • Item
    Implementing a standardized process to improve insurance pre-authorization time and subsequent delays in care
    (2023-08) Davis, Vernice; DeGrande, Heather; Beal, Lisa; Johnson, Andrew
    Background: Lack of standardization in pre-authorization processes by insurance companies has resulted in inefficiencies and delays, causing fiscal consequences and adverse impacts on patient care in various healthcare settings related to delays in care. Purpose: This quality improvement (QI) project aimed to establish, educate, and implement a standardized process for pre-authorization claims to improve knowledge of a standardized process and reduce claims decision turnaround times (TATs). Design & Methods: A standardized process was developed and implemented over a 12-week period. Nine participants received education on the required procedures for processing insurance claims. Knowledge was evaluated using a pretest-posttest design. TAT was evaluated with an existing measurement application. Results: Knowledge test scores showed a significant improvement from pre-test to post-test. A steady rise in TAT was observed. Conclusion: Future QI projects should focus on enhancing insurance pre-authorization time and reducing patient delays in care through implementing standardized processes, education, standardized process protocols, and policy changes. By considering the sustainability of these projects and incorporating continuous evaluation, stakeholder engagement, education, policy advocacy, and long-term planning, organizations can achieve lasting improvements in turnaround times and ultimately provide patients with more timely and efficient care. Keywords: utilization management, prior authorization, insurance claims, systemic review of insurance authorization.
  • Item
    Dissolved inorganic nitrogen concentrations and isotopic values of wastewater treatment plants in a semi-arid region
    (2023-08) Cox, Anthony; Felix, J. David; Wetz, Michael; Murgulet, Dorina; Abdulla, Hussain
    Wastewater treatment regulations evolve as detrimental ecological impacts of wastewater nitrogen loading becomes more apparent. Determining the significance of the N loading contribution of wastewater treatment plants to coastal waters in comparison to other primary N sources is necessary when creating efficient mitigation strategies. However, current research tends to be biased toward nitrate within effluent because it is often the main species of nitrogen entering the environment via the effluent. This work contributes concentration and isotopic data for all dissolved inorganic nitrogen (DIN) in both influent and effluent wastewater from three south Texas wastewater treatment plants equipped with activated sludge secondary treatment. The average (n=30) influent concentration of NH4+ was 2300±1100 µM, NO3- was 40.±35 µM, NO2- was 2.3±7.0 µM, and dissolved organic nitrogen (DON) was 140±41 µM. The average (n=33) effluent concentration of NH4+ was 190±270 µM, NO3- was 520±430 µM, NO2- was 14±8.0 µM, and dissolved organic nitrogen (DON) was 300±290 µM. Average isotopic ratios of influent ?15N-NH4+ (n=28) was 3.9±2.8‰, ?15N-NO3- (n=12) was 15±3.5‰, and ?18O-NO3- (n=12) 19±2.6‰. Average isotopic ratios of effluent ?15N-NH4+ (n=7) was 110±190‰, ?15N-NO3- (n=18) was 16±4.9‰, and ?18O-NO3- (n=18) 7.8±2.7‰. These wastewater isotope signatures local to the study’s semi-arid region were employed in Stable Isotope Analysis in R (SIAR) mixing model and compared to the use of literature signatures to convey the large variability in source apportionment that can be reported if locally characterized endmembers are not used in isotope source contribution models. The regional wastewater isotope signatures provided will help constrain isotope mixing models specific to the semi-arid Gulf Coast which in turn will help create informed nitrogen loading mitigation strategies. The treatment plants did not remove all the DIN in the influent and ~20% was subsequently returned to the environment. It was observed that activated sludge secondary treatment is capable of fully nitrifying raw sewage but is limited with respect to complete denitrification. Understanding the capabilities of activated sludge will help determine which tertiary treatment would be needed to remove excess anthropogenic nitrogen from wastewater. For the treatment plants in this study, simply increasing residence time may increase denitrification efficiency. The efficacy of this and other advanced treatment options should be explored further. Also, an argument for using enclosed aeration tanks to further reduce the release of anthropogenic nitrogen into the environment is given.