Digital Commons Network^™

The Importance Of Soil Carbon In Large-Scale Shrub Removal Practices In The Chihuahuan Desert, Kathleen Schaeffer

Open Access Theses & Dissertations

Shrub encroachment is a worldwide phenomenon that affects multiple biomes at different ecological and anthropogenic levels. In dryland ecosystems, shrub encroachment is a noted concern amongst land managers, as it can lead to a loss of soil resources and biodiversity. To mitigate the negative effects of shrub encroachment in Drylands, land managers can implement large-scale shrub removal practices. These land restoration practices can shift landscapes to novel ecosystems, where resulting plant communities can vary following treatments. Grass recovery or increasing herbaceous cover is often a primary goal of these treatments, however predicting which sites may show higher grass responses to …

Growth Of Purple Sulfur Bacteria Allochromatium Vinosum On Solid Phase Metal Sulfides As Sulfur And Electron Sources, Hugo Alarcon

Open Access Theses & Dissertations

Purple sulfur bacteria (PSB) are photosynthetic microorganisms known for their vital roles in geochemical cycles, especially the sulfur cycle, within anoxic photic environments. PSB are also key contributors to the nitrogen, carbon, and oxygen cycles. This study focuses on the autotrophic growth of Allochromatium vinosum, a model strain of PSB, that utilize solid-phase metal sulfides (MS) as both sulfur and electron donors. Through characterizing the growth profiles of A. vinosum on pyrite (FeS2), nickel sulfide (NiS), and iron monosulfide (FeS) nanoparticles, respectively, and investigating the bacteria-MS interaction mechanisms, this work expands our current knowledge of the metabolic capabilities and flexibility …

Examining The Association Between Emotional Intelligence, Meaning In Life, Stress, And Burnout Among Preâ??Medical Students In The United States, Nayla Paulina Paulina Bejarano Chacon

Open Access Theses & Dissertations

Background and significance: The Association of American Medical Colleges (AAMC) has estimated that by 2034 there will be a physician shortage of around 124,000 physicians. With burnout being one of the main drivers, it is crucial to assess it. Burnout is characterized by high levels of emotional exhaustion and cynicism and low levels of academic efficacy.There has been substantial research on burnout among healthcare providers across different levels of training; however, few studies have examined burnout among undergraduate students who wish to pursue a graduate degree in healthcare. Given the shortage of healthcare providers in the United States, it is …

Increases In Uvr Exposure: Local Adaptation Of A Bdelloid Rotifer, Maribel J. Baeza

Open Access Theses & Dissertations

Aquatic species living in ephemeral habitats without a continual influx of dissolved organic carbon (DOC) are at increased risk of the effects of ultraviolet radiation (UVR) as the climate changes. Climate change is predicted to cause changes in DOC, some habitats will experience extended periods of drought and reduced input from DOC sources, and other environmental features that increase UVR reaching aquatic habitats. UVR can cause damage to cellular structures and biomolecules such as DNA, proteins, and lipids. The pigmented bdelloid Philodina sp. (Philodina) found in rock pools in the Chihuahuan Desert naturally experiences high UVR, yet it appears to …

Diversity And Lifestyle In The Rotifera, Patrick D. Brown

Open Access Theses & Dissertations

Broad questions regarding community assembly and lifestyle evolution remain unanswered. To answer these questions I used rotifers, common primary consumers present in inland waters. Rotiferan presence in nearly all freshwaters makes them an ideal study system to address questions of metacommunity ecology. Additionally, rotifers possess diverse lifestyles, including sessile, swimming, colonial and solitary forms, allowing them to be used as models of lifestyle evolution. In Chapter 1, I address metacommunity ecology by focusing on inland waters of the Chihuahuan Desert as a study system and investigated rotifer community assembly therein through two published works, Brown et al., 2020 and 2021. …

X-Ray Crystal Structure Of E399q,E708q Ecm16 Double Mutant, Gileydis Guillama

Open Access Theses & Dissertations

The use of antibiotics has undoubtedly been a boon for humanity in combating infections and microbial threats. However, their widespread utilization has contributed to the emergence and spread of antibiotic resistance, which now poses a significant public health challenge. Streptomyces bacterium, produce diverse secondary metabolites with antibacterial, antifungal, antiviral, antitumoral, and immunosuppressant activities. Among these compounds is echinomycin, a nonribosomal peptide antibiotic synthesized by Streptomyces lasalocidi, which inhibits DNA replication and transcription by intercalating the DNA duplex at CpG steps. A gene called ecm16 was identified in the echinomycin biosynthetic gene cluster, which provides echinomycin self-resistance. Ecm16 recognizes DNA duplexes …

Quantifying The Contribution Of Atmospheric And Land Surface Characteristics To The Prediction Of Sub-Pixel Scale Surface Soil Moisture In The Jornada Experimental Range Through Interpretable Machine Learning, Stephanie Nicole Marquez

Open Access Theses & Dissertations

This study presents machine learning-based approaches for understanding and predicting plot-scale soil moisture's spatial variability using hydrometeorological and biogeophysical data from in-situ, multi-sensor and remote sensing sources. The high-resolution input features include numerical and categorical data such as land surface temperature, ground albedo, 1-day, 1-week and 2-week antecedent precipitation, soil type, land cover type, distance to nearest vegetation individual, terrain slope and elevation, and normalized differenced vegetation index (NDVI). Soil moisture measurements are collected within a 3 km x 3 km desert grid with Campbell Scientific Hydrosense II-12 soil moisture sensors and validated with a gravimetric method of measuring volumetric …

Comparative Study Of Supervised Classification Techniques With A Modified Knn Algorithm, Noah Owusu

Open Access Theses & Dissertations

The goal of classification is to develop a model that can be used to accurately assign new observations to labeled classes based on the patterns learned from the training data. K-nearest Neighbors algorithm (KNN) is a popular and widely used algorithm for classification, however, its performance can be adversely affected by the presence of outliers in a dataset. In this study we have modified this existing KNN algorithm that can alleviate the effect of outliers in a dataset, thereby improving the performance of the KNN algorithm. We compared the performances of the Modified KNN method and the Existing KNN algorithm …

Robust Mahalanobis K-Means Algorithm In Comparison With Other Existing Clustering Methods., Eleazer Tabi Serebour

Open Access Theses & Dissertations

This study enhances K-means Mahalanobis clustering using Density Power Divergence (DPD) for outlier handling and detection. Through the utilization of simulations and the analysis of real-world data, our approach consistently outperforms standard K-means, Mahalanobis K-means, Fuzzy C-means, and others in clustering datasets with outliers. While our method performs similarly to others on spherical datasets, it ranks second to DBSCAN for arbitrary shapes. We showcase its superiority on real-life datasets (Iris flower and wheat seed), demonstrating resilient outlier identification. By navigating various structures and cluster characteristics, our Modified Mahalanobis K-means method proves adaptable and robust, offering insights into diverse clustering scenarios. …

Structural Study Of Lsd13 And Lsd14 Type I Modular Polyketide Synthases From The Lasalocid A Biosynthesis Pathway, Dayan Viera

Open Access Theses & Dissertations

Bioactive natural products often possess a complex structure and have a large size which make their chemical synthesis highly challenging. To overcome this challenge, we are developing a biosynthetic method for production of natural products and their analogs. This technology is expected to decrease the synthesis time from years to weeks and reduce the cost of drug production by multiple orders of magnitude. We are investigating the biosynthesis pathway of lasalocid A, an anticancer antibiotic, to develop this technology. Specifically, we aim to characterize the enzymes structurally and biochemically in this pathway, thus paving the way for their rational engineering. …

Immunoreactivity Of The Serotonin-Like And Fmrf-Amide-Like Nervous Systems Of Four Gnesiotrochan Rotifers, Robert Neil Walsmith

Open Access Theses & Dissertations

Reorganization of the nervous system during metamorphosis is a common phenomenon across taxa (species through phyla). In phylum Rotifera, sessile species belonging to the superorder Gnesiotrocha metamorphose from free-swimming larvae into sessile adults. Once mature, gnesiotrochan rotifers display an intricate corona or infundibulum associated with lifestyle modalities and feeding behaviors. Here, I examine serotonin-like immunoreactivity (SLIR) and FMRF-amide-like immunoreactivity (FLIR) of the gnesiotrochans Lacinularia flosculosa, Collotheca ferox, and Acyclus inquietus with a focus on life stage and sex. Based on previous research, I hypothesize that 1) innervation of the larval nervous system will vary according to the lifestyle constraints observed …

"So That We Can Save The Earth From Dying": Highlights From A Middle School Environmental Field Day, Kenton Sena, Jill Abney, Hannah Ruehl, Chris Barton

Journal of Contemporary Water Research and Education

Continued urbanization is likely to reduce human-nature experience, transforming human-dwelt spaces into increasingly artificial environments and removing humans from interaction with non-human living things and their ecosystems. In urban spaces, outdoor experiential educational activities can help students increase their familiarity with the outdoors and get their hands dirty. This case study reports on an environmental field day for middle school students from an urban Kentucky middle school. Students rotated through three activities (picking insects out of leaf packs, testing water quality, and planting trees), then completed a brief survey designed and administered by their faculty. Students rated the tree planting …

Sea Grant Center For Great Lakes Literacy Shipboard Science Workshop Evaluation, Jennifer Hunnell, Heather A. Triezenberg, Brandon C. Schroeder, Meaghan J. Gass

Journal of Contemporary Water Research and Education

Youth have an important role in current and future Great Lakes stewardship. Educating youth and empowering them to be Great Lakes stewards requires educators to be knowledgeable and confident, and therefore more likely to engage in teaching Great Lakes literacy activities in their classroom, thus contributing to a Great Lakes-literate public. The Shipboard Science Workshop (SSW) for educators is a vessel-based professional learning opportunity aboard the U.S. Environmental Protection Agency's research vessel (R/V) Lake Guardian . During the week-long SSW, educators learn from professional scientists, Sea Grant staff, and each other about Great Lakes research through the lenses of place-based …

Exploring Versatile Glycosyltransferases From Microorganisms For Natural Product Biosynthesis, Jie Ren

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This dissertation is mainly focused on exploring versatile glycosyltransferases from different microorganisms with the purpose of biosynthesizing bioactive natural product glycosides through microbial fermentation. This engineered biosynthesis approach is environmentally friendly, safe, and efficient compared with plant extraction, chemical synthesis, and enzymatic synthesis. Additionally, we applied these characterized glycosyltransferases as efficient biocatalytic tools to produce novel glycosides to expand the chemical repertoire of nature. These novel compounds showed improved water solubility and some of them exhibited enhanced stability and biological activity, which laid the foundation for the development of new therapeutic agents.

In my dissertation research, I have discovered two …

All Good Women Are Mothers: Exploring Gender Binaries In How I Met Your Mother, Jessica Marinho

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Television is thought to be a form of entertainment through its many genres from comedy to drama, however, it is more than a relaxing pastime. Television series construct messages that influence audiences to accept specific behaviors. In this thesis, I analyzed the portrayal of the two main female characters in the popular television series How I Met Your Mother (2005-2009) and I argued how their depiction served to represent childless women as unwomanly and mothers as the ideal woman.

Cislunar Navigation Techniques And Navigation Performance Optimization, Quinn P. Moon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nova-C is a lunar lander developed by the private company Intuitive Machines to deliver commercial payloads to the Moon. The IM-1 mission set for 2023 will launch and land the Nova-C near the Moon's south pole. In this research, various navigation techniques are explored to determine the lander's position and velocity during key segments. This process is studied for key mission events including trajectory correction maneuvers (TCMs), lunar orbit insertion (LOI), and descent orbit insertion (DOI). Each mission segment, referred to as an Orbit Determination Segment (OD), is analyzed with three different navigation techniques: Monte Carlo Analysis, Linear Covariance Analysis, …

The Longitudinal Effects Of Adverse Childhood Experiences On Internalizing And Externalizing Problems: In Search Of Demographic Disparities, Cynthia M. Navarro Flores

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Children experience high rates of emotional problems (e.g., anxiety, depression) and behavioral problems (e.g., defiance, aggression) that can have long-lasting detrimental effects. Emotional/behavioral problems have been found to relate to exposure to adversity during childhood (i.e., adverse childhood experiences [ACEs]). Studies have found that rates of exposure to ACEs and emotional/behavioral problems may vary depending on one’s race/ethnicity, sex, and income. Research has not yet looked at how emotional/behavioral problems develop throughout childhood in conjunction to exposure to ACEs. The current two-paper dissertation focused on examining the individual and conjointly developing trajectories of ACEs, and emotional (i.e., internalizing problems) and …

Adverse Childhood Experiences, Discrimination, & Adulthood Health Outcomes: Impacts Of Protective And Compensatory Experiences In Childhood, Sallie A. Mack

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Adversity encompasses a wide range of stress-inducing experiences that are often prolonged and/or recurring in nature. Adverse childhood experiences (ACEs) capture adversity experienced before the age of 18, including abuse, neglect, and general household dysfunction. ACEs are widely linked to physical and mental health outcomes across the lifespan. Racial/ethnic discrimination, a form of adversity that can occur across the lifespan, has also been linked to many negative health outcomes. Protective and compensatory experiences in childhood (PACEs) are a relatively newer conceptualization of early-life resiliency factors. Early life resiliency is linked to positive health outcomes later in life. Our studies investigated …

An Evaluation Of Stress Tolerance In Restoration Plant Species In Response To Fire, Drought, And Invasive Plants Through The Lens Of Functional Traits, Adam M. Clifford

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Sagebrush communities in the Great Basin face many threats. Cheatgrass, a winter annual from Eurasia, has invaded these communities, increasing wildfire and lowering species diversity. Additionally, climate models project warmer and drier conditions throughout much of the Great Basin, likely increasing drought, cheatgrass invasion, and wildfire. Intact stands of native and introduced perennial grasses have been shown to limit invasion by cheatgrass and restore ecosystem functions. The objective of this research was to identify the functional traits and growth characteristics needed by restoration species to survive periods of drought and to evaluate varieties of commonly used restoration species for establishment, …

The Relationship Between Career Choice And Indecision Within The Career And Technical Education Pathway Model, Zak A. Konakis

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The United States is shifting the public education model toward one that favors increasing skill complexity to lead students into future careers. It is uncertain, however, if these changes are benefiting students and having the desired impact on the future workforce. Utilizing the Swiss and German dual apprenticeship and work-based learning model, Utah is attempting to bring more practical and hands-on experiential learning opportunities to students across the state. This study intended to understand if these changes are accomplishing the intended result in students in rural eastern Utah.

Furthermore, the study found that students who engage in early experiential learning …

Unraveling The Biogenesis And Roles Of Iron-Sulfur Proteins During Nitrogen Fixation By Methanosarcina Acetivorans, Jasleen Saini

Graduate Theses and Dissertations

Iron-sulfur (Fe-S) clusters, the ancient cofactors found in proteins across all life forms, play vital roles in numerous cellular processes. Fe-S clusters exhibit structural diversity, ranging from simple to complex forms. Methanogens are anaerobic archaea that produce methane as a metabolic by-product through methanogenesis, a process dependent on numerous Fe-S proteins. Notably, methanogens are capable of fixing nitrogen (diazotrophy) facilitated by the enzyme complex called nitrogenase, which contains both simple and complex Fe-S clusters. While methanogens possess the largest number of Fe-S proteins, the factors involved in Fe-S cluster biogenesis remain largely unknown. Bacteria possess three distinct and well-characterized Fe-S …

Liquid Crystalline Coacervates Composed Of Chromonic Mesogens And Polyelectrolytes, Elizabeth Adeogun

Graduate Theses and Dissertations

Complex coacervates are formed by liquid-liquid phase separation of an aqueous solution of oppositely charged ions. Although several mixtures of molecules of natural and synthetic macro-ion have been shown to form complex coacervates, the formation of liquid crystalline (LC) coacervates are sparsely reported. LC coacervates have a unique property in that they can change their shape and optical property in response to external stimuli such as changes in temperature, pH, or the presence of specific molecules. This property makes LC coacervates useful as a sensor, as they can be engineered to respond to specific stimuli and generate a measurable signal …

Time And Chance Happen To Them All: A Macroevolutionary Examination Of The Effects Of Whole Genome Multiplications, Eric Robert Hagen

Graduate Theses and Dissertations

Polyploidy, the state of having more than two complete sets of chromosomes, is common in plants and has been linked to several beneficial traits. On the macroevolutionary scale, the effects of polyploidy have been hotly debated for over one hundred years, being alternatively described as an “evolutionary dead end” and the most important discovery in evolutionary biology since Darwin and Wallace. This thesis aims to contribute to the debate by studying the diversification, biogeography, and ecophysiology of polyploid flowering plants with recently developed phylogenetic comparative methods. This dissertation has three chapters. In Chapter I, I review work on the so-called …

A Pilot Study Of Students’ Ethical Decision Making And Emotional Intelligence, Casandra K. Cox

Graduate Theses and Dissertations

Demand for ethical leaders in agriculture is high to meet 21st century goals, while ethics course offerings in land-grant institutions are limited. The purpose of this case study was to establish a baseline of current University of Arkansas Bumpers College of Agriculture, Food and Life Science (Bumpers College) agriculture and natural resource program students’ ethical decision making (EDM), as measured by the DIT-2, and emotional intelligence (EI), as measured by STEM-B and STEU-B, determine if EI mean scores predict EDM, and identify relationships between EDM or EI and demographic characteristics or lifespan experiences. An online survey design with probability sampling …

Investigation Of Consumer Freezing Practices, Condition And Duration On Palatability Of Beef, Elizabeth Sue Neal

Graduate Theses and Dissertations

The objective of these studies was to determine: the impact of extended periods of frozen storage duration and packaging type on palatability traits of cooked beef steaks from two muscles and the impact of freezing type and storage duration on objective and subjective measures of ground beef palatability traits. In study 1, no differences were elicited from any of the possible interactions (P= 0.95) for SSF or CL: package × muscle × freezing duration, package × muscle, package × duration or muscle × duration. However, freezing duration did impact both SSF (P < 0.01) and CL (P < 0.001). Generally, for both SSF and CL steaks that were frozen for 9-months elicited both the highest SSF values as well as the greatest percentage of CL among all treatments. In comparison, EM was impacted by the interaction (P = 0.059) of packaging type  muscle  freezing duration. Samples from OW GM stored for 9-months elicited the highest percentage of EM while fresh OW LL samples resulted in the lowest. Additionally, expressible moisture was impacted by the interaction (P = 0.047) of muscle  freezing duration. Among all treatments, GM steaks that were frozen for 9-months elicited the highest EM values and fresh LL samples the lowest EM values. Contrastingly, there was no significant difference observed in expressible moisture for the interaction (P  0.18) of package type  freezing duration or for the interaction (P = 0.70) of package type  muscle. Generally, fresh OW GM steaks resulted in the greatest concentration of lipid derived volatile compounds such as aldehydes, hydrocarbons and alcohols which contrasted sensory ratings of trained panelists that indicated oxidized and refrigerator-stale ratings increased as storage time increased for OW steaks. In study 2, The interaction of freezer treatment × storage duration impacted gumminess (P = 0.05), a TPA attribute. In greater detail, samples stored in RF for 6-months resulted in the greatest gumminess values (P < 0.001), while those stored in the CF for 12-months elicited the lowest (P < 0.001). Similarly, flavor development was also impacted by the interaction (P = 0.05) of freezer treatment × storage duration. Three lipid derived compounds were of greatest concentration among RF patties stored for 1-month. In contrast, the interaction of freezer treatment × storage duration elicited no impact on consumer ratings, SF or TBARS. Nonetheless, frozen storage duration impacted TPA, flavor development, consumer ratings, SF and TBARS as a main effect (P < 0.05), especially in regard to tenderness and juiciness. Moreover, beef flavor development, tenderness and juiciness are impacted by freezing duration, muscle, freezer type and packaging, however these factors are not necessarily independent of one another. Furthermore, the retail display period is a critical period for fresh beef steaks, especially when packaged in aerobic conditions. For optimal eating experience, beef products should be stored for extended periods in a vacuum packaging, in a designated freezer that is not opened frequently to allow for optimal air flow regulation and minimize freezer burn to improve tenderness and juiciness.

The Effect Of Sleep Deprivation On The Ability To Reappraise Negative Situations, Rebecca Campbell

Graduate Theses and Dissertations

Sleep and emotion regulation are important components of mental health and may function interdependently in the development and maintenance of mental health disorders. Unfortunately, there is limited experimental work on the impacts of sleep deprivation on reappraisal, a common emotion regulation strategy, in adults. Furthermore, increases in negative and decreases in positive affect are often associated with sleep loss. This study aimed to examine the relation between sleep deprivation and emotion regulation by asking adults to reappraise a series of vignettes before and after a randomly assigned night of sleep deprivation or normal sleep. Additionally, measures of self-reported emotion regulation …

Evaluation Of Biochar Rate And Hemp Cultivar For The Phytoremediation Of Heavy-Metal-Contaminated Soil From The Tar Creek Superfund Site, Dietrich Thurston

Graduate Theses and Dissertations

Soil contamination by cadmium (Cd), lead (Pb), and zinc (Zn) at the Tar Creek Superfund site in Northeast Oklahoma remains a threat to the environment and local ecosystem. Phytoremediation by industrial hemp (Cannabis sativa L.) and the use of biochar (BC) have been independently shown to be effective methods to remediate heavy-metal-contaminated soils. The objective of this greenhouse study was to evaluate the effects of industrial hemp cultivar (‘Carmagnola’ and ‘Jinma’), BC rate (0, 2, 5, and 10% by volume), soil contamination level (low, medium, and high), and their interactions on above- and belowground (AG and BG, respectively) plant dry …

Symptom Experience Of Patients With Advanced Melanoma Undergoing Immune Checkpoint Inhibitor Therapy, Natalie Jackson-Carroll

Dissertations and Theses (Open Access)

Background: Immune checkpoint inhibitors (ICIs) are novel therapeutic agents utilized in the management of advanced melanoma. Though generally well-tolerated, patients receiving ICIs experience treatment-related toxicities at varying onset and intensity. Assessment and evaluation of these toxicities and their impact on a quality of life is essential to comprehensive cancer care. Patient-reported outcomes (PRO) contribute vital data to a clinical assessment, supporting clinicians in their ability to improve outcomes. To date, there is no melanoma-specific or ICI-specific PRO measure of symptom burden available.

Purpose: The purpose of this study was to describe the symptom experience from the patient's perspective and how …

Does Herding Behavior Exist In The Cryptocurrency Market?, Anis Mnif

Doctoral Dissertations (DBA)

This paper examines herd behavior in the cryptocurrency market using data of the top 15 large cryptocurrencies and the CCi30 Index as a proxy for market return. The idea that investors mimic and follow the behavior of others in the cryptocurrency market rather than conducting their own research has received attention in the finance literature. The CSAD results in the static model detected herding but given the existence of structural breakdowns and nonlinearities in the data series, we opted to conduct a rolling window analysis. The results indicate strong herding behavior that fluctuates over time. Furthermore, results from the logistic …

Dry-Aged Beef Flavor Development, And The Effect Of High Levels Of Vitamin-E On Beef Color Stability, Nicolas Herrera

Department of Animal Science: Dissertations, Theses, and Student Research

Palatability and consumer purchasing are essential factors of fresh meat. To meet consumer expectations during purchasing and consumption, fresh beef must maintain desirable cherry-red color at retail and achieve desirable cooked flavor. Dry-aged beef popularity has grown, and identifying methods to ensure quality dry-aged meat is necessary to maintain demand. To understand dry-aged palatability, this dissertation addressed effects of moisture loss and aging time, fundamental factors of dry-aged beef, using bone-in and boneless strip loins. Study two investigated flavor development using cookery methods and internal temperatures in boneless and bone-in dry-aged beef. In study one, increased dry-aging time (creation effect) …