Digital Commons Network^™

The Influence Of Singlet Oxygen And Loss Of Function Of Fatty Acid Desaturase 7 In The Chloroplast On Aphid Resistance In Arabidopsis Thaliana, Hillary Donna Fischer

Graduate Theses and Dissertations

Fatty Acid Desaturase 7 (FAD7) is a chloroplast-localized enzyme that alters the fatty acid content of photosynthetic membranes, and that negatively regulates plant defenses against aphids. Previous studies in the model organism Arabidopsis (Arabidopsis thaliana) have shown that loss-of-function mutations in FAD7 decrease population growth of the green peach aphid (GPA; Myzus persicae Sulzer). This study further characterized the effects of a fad7 null mutant on aphids, and investigated the role of reactive oxygen species (ROS), including singlet oxygen (1O2), in plant responses to aphid resistance in fad7 as well as in wild type plants and a mutant with heightened …

Survey Of Ticks And Tick-Borne Pathogens Associated With Feral Swine (Sus Scrofa) In Arkansas, Haylee Campbell

Graduate Theses and Dissertations

Feral hogs (Sus scrofa L.) are an invasive species throughout the southeast United States and found in every Arkansas county. As feral hogs invade new habitat, they can disrupt ecosystems, damage agriculture systems, and bring ticks and tick-borne pathogens with them. There are no surveys of the tick species parasitizing the Arkansas feral hog populations or the pathogens they carry. This is a public health concern because feral hogs occupy often same geographical regions as humans and livestock and can harbor over 45 animal diseases and parasites. The ticks carried by feral hogs can carry tick-borne pathogens that can cause …

Economic And Ecosystem Impacts Of Gm Maize In South Africa, Kristiina Ala-Kokko

Graduate Theses and Dissertations

White maize in South Africa is the only staple crop produced on a widespread commercial basis for direct human consumption using genetically modified (GM) cultivars. Using a combined economic and environmental approach, we estimate the total welfare benefits attributable to GM white maize in South Africa for 2001-2018 are $694.7 million. Food security benefits attributable to GM white maize in South Africa also manifest through an average of 4.6 million additional white maize rations annually. To achieve these additional annual rations using conventional hybrid maize, the additional land required would range from 1,088 hectares in 2001 to 217,788 hectares in …

Resistance Screening And Association Mapping For Resistance To The Downy Mildew Pathogen Of Spinach, Dotun Olaoye

Graduate Theses and Dissertations

Spinach is an important cool leafy vegetable cultivated around the world, with large scale production in California and Arizona in the U.S. Spinach is a highly nutritious vegetable beneficial in the human diet. Spinach is affected by a number of biotic stressors. Downy mildew, caused by the oomycete pathogen Peronospora effusa, is a major threat to spinach as it affects the leaf quality and impacts the economic value of spinach. Several efforts have led to the development of resistant genotypes/cultivars to this pathogen. However, few studies have examined the genetics of resistance to the downy mildew pathogen in detail. This …

Spore Dispersal Of Slime Molds And Higher Fungi Via Animal Vectors, Courtney Trimble

Graduate Theses and Dissertations

Myxomycetes and dictyostelids are Amoebozoans that are cosmopolitan inhabitants of a variety of habitats, particularly forest environments. Both groups reproduce using spores which are primarily dispersed via wind in myxomycetes but this characteristic poses a problem for dictyostelids. The spores of dictyostelids are incased in a mucilaginous matrix that makes wind ineffective except in exceptional cases. It has been suggested that animals such as birds may play an important yet understudied role in the dispersal of these organisms. This study investigated how animals could potentially serve as vectors for spore dispersal of dictyostelids and myxomycetes with some limited data obtained …

Ancestral Pursuits: A Multicultural Celebration Of Identity & Race, Charlotte Cates Castro

Graduate Theses and Dissertations

Using critical historical rhetorical methods along with critical race and decolonial theory, this project situates ancestral pursuits as a communication-centered discursive formation by investigating the rhetorical strategies modern biotech and genealogy companies utilize to influence contemporary discourse around identity and belonging and narrate ethnicity and genealogy as acts of consumption. Through direct-to-consumer DNA testing and complimentary services, modern day biotech and genealogy companies like Ancestry and 23andMe market personalized insights into ancestry, genealogy, inherited traits, and health data that promise to connect users to their past, as well as to situate them in present-day society, through a deeper understanding of …

Characterization Of Protein Aggregation Using A Solid-State Nanopore Device, Mitu Chandra Acharjee

Graduate Theses and Dissertations

Protein aggregation has been linked to many chronic and devastating neurodegenerative human diseases and is also strongly associated with aging. In the case of neurodegenerative diseases, α, β tubulins and tau proteins dissociate in a neuron cell and aggregate both intra and extra-cellularly. Tau and tubulin aggregations were found as one of the major causes of many neurodegenerative diseases, such as Parkinson’s, Picks, Alzheimer’s, Huntington, and Prion. Finding the state and mechanism of protein aggregation is significant. In this work, tau and tubulin aggregations were detected in ionic solutions using the solid-state nanopore technique. Besides tau and tubulin, aggregations of …

Developing A Microdialysis Sampling-Based Biofilm/Macrophage Co-Culture Model, Alda Diaz Perez

Graduate Theses and Dissertations

The host immune system and bacterial cells are known to interact during the human lifetime. Bacteria secrete a wide variety of signaling molecules, known as quorum sensing (QSC) molecules, that modulate the host immune system. While immune-biofilm interactions involve this chemical signaling network, the mechanisms through which this occurs are not well understood. This work aimed to develop a new method that can be used not only in vitro settings but also in vivo. The microdialysis sampling technique has widely been used in in vitro and in vivo settings in humans, mice, and rats for the collection of neuropeptides, cytokines, …

Dynamics Of Hybrid Zones At A Continental Scale, Bradley T. Martin

Graduate Theses and Dissertations

Hybridization has traditionally been viewed as a happenstance that negatively impacts populations, but is now recognized as an important evolutionary mechanism that can substantially impact the evolutionary trajectories of gene pools, influence adaptive capacity, and contravene or reinforce divergence. Physiographic processes are important drivers of dispersal, alternately funneling populations into isolation, promoting divergence, or facilitating secondary contact of diverged populations, increasing the potential for hybridization. In North America, glacial-interglacial cycles and geomorphological changes have provided a dynamic backdrop over the last two million years that promoted such oscillations of population contraction and expansion. These biogeographic processes have resulted in regional …

Role Of Reptile-Invertebrate Interactions In Enigmatic Reptile Declines, Meredith Swartwout

Graduate Theses and Dissertations

Reptile populations are declining world-wide and the mechanisms behind many of these declines remain enigmatic. Food web interactions (i.e., reduced prey availability or increased predation) have been implicated behind some reptile declines. However, relatively little is known about predation on lizard and snake eggs, despite egg survival being important for population dynamics of some species. Ants are important predators of squamate reptile eggs in tropical and temperate systems. In Costa Rica, long-term declines in terrestrial anole lizards were linked with reduced leaf litter depth, a factor that could influence egg vulnerability to ant predation. Fire ants (genus Solenopsis) are aggressive …

Climate-Driven Impacts On Himalayan Aquatic Biodiversity: A Case Study Involving Snowtrout (Cyprinidae: Schizothorax), Riri Wiyanti Retnaningtyas

Graduate Theses and Dissertations

Monitoring biodiversity, to include its relative dispersal and contraction, has become a conservation task of great importance, particularly given the catastrophic and ongoing loss of habitat due to climate change. However, the timing, direction, and magnitude of these rates vary across taxa and ecosystems. Predicting specific impacts of climate change can thus be difficult and this, in turn, hampers management action. Metrics are needed to not only quantify contemporary requirements of species, but also predict potential distributions that fluctuate in lockstep with climate.

Montane ecosystems in the Himalayas are highly impacted by climate change, yet remain largely understudied due to …

Synthesis Of Bulky And Polar Galactonoamidines For The Inhibition Of The Human Α-Galactosidase, Ifedi Orizu

Graduate Theses and Dissertations

Glycosidases are amongst the most abundant enzymes in nature. This is due to their role in the degradation of carbohydrates which are the major source of carbon or earth. The absence or malfunction of glycosidases is implicated in numerous diseases such as cancers, diabetes, and lysosomal storage disorders, which make them important drug targets for study in medicinal chemistry. The seminal work by Pauling and Wolfenden showed that enzymes bind to their substrate at the transition state with very strong affinity. Wolfenden estimated the dissociation constant to be around 10-22M. This encouraged the design of glycosidase inhibitors which mimicked one …

Andragogy For All? A Look At Arkansas Community College Students' Preferences For Andragogical Assumptions, Emilee Sides

Graduate Theses and Dissertations

Community colleges are tasked with juggling multiple missions. They provide open access to education for adults in their community, work with industry partners to educate the local workforce, and provide relevant programming to the communities they serve. When compared with students at four-year institutions, community college students are older, more ethnically and racially diverse, come from lower socioeconomic statuses, and less academically prepared.

Like other community colleges across the country, one of the primary goals of Arkansas community colleges is to help their students succeed. Unfortunately, the state has historically performed poorly in regard to educational outcomes. To get the …

Population Connectivity Of The Eastern Collared Lizard Crotaphytus Collaris In Arkansas, Whitney Allison Murchison-Kastner

Graduate Theses and Dissertations

Habitat reduction and fragmentation can isolate populations and decrease genetic diversity, making them susceptible to local extirpation. Additionally, geographic barriers can further impede dispersal among populations thus reducing gene flow. Field studies suggest these factors may be responsible for the decline in Eastern Collared Lizard (Crotaphytus collaris) populations in Arkansas. To address the impacts of habitat loss and fragmentation on the Eastern Collared Lizard (C. collaris) in Arkansas, I used DNA fragment analysis to examine genetic diversity, population structure and connectivity among C. collaris populations. I do so herein by employing microsatellite data from 138 adults across 11 loci to …

An Eeg Source-Space Analysis Of The Neural Correlates Underlying Self-Regulation, Stephanie M. Long

Graduate Theses and Dissertations

Self-regulation is the cognitive process of controlling our thoughts and behaviors to be aligned with our goals. This process is used in many different contexts and has been associated with contributions from several brain regions. This research aimed to investigate differences in four prefrontal areas of the brain while participants applied four different self-regulation strategies. We recorded EEG while participants (N = 132) performed three tasks which engaged each of the four self-regulation strategies: the AX-CPT task engaged proactive and reactive control, the Go/Nogo task engaged inhibitory control, and the hybrid Flanker Global/Local task engaged the resolution of response conflict. …

Short-Term Effects Of Winter Cover Crops On Soil Properties, Yield, And Partial Returns In A No-Tillage Soybean Rotation, Drew Dillon Kirkpatrick

Graduate Theses and Dissertations

Cover crops have the potential to provide many benefits including weed suppression, erosion control, and improvements to soil quality. These benefits can be affected by species, biomass accumulation, and management practices. Although large amounts of biomass are good for maximizing benefits, it can result in problems for establishing the subsequent crop. Soybean [Glycine max (L.) Merr.] accounts for over 50% of Arkansas crop hectares annually; therefore, understanding the effect that a cover crop can have on the following soybean crop is crucial to the successful implementation of cover crops within the state. A study was established to evaluate winter cover …

Replication And Tribological Engineering Of Physical Surfaces Using Two-Photon Lithography, Shelby Robert Maddox

Graduate Theses and Dissertations

Up to one-fifth of all energy consumed each year goes directly to overcoming frictional effects. This waste will remain even if renewable energy becomes feasible as a large-scale replacement for conventional fuel sources. If that wasted energy could be saved instead, then overall energy consumption could either decrease or be redirected to where it would be most beneficial to human and environmental flourishing. To this end, there is a need for strategies and techniques to reduce frictional energy loss. It is well established that surface texturing can be used to reduce friction. There are many industrial methods in current use …

Effects Of Heme Oxygenase 1 Inducer, T-Bhq On Growth Of Multiple Myeloma Cell Lines, And On Osteoblast And Osteoclast Differention, Alyaa Alansari

Graduate Theses and Dissertations

Expansion of plasma cells within the bone marrow constitutes the onset of multiple myeloma (MM). This disease manifests clinically primarily through the formation of osteolytic bone lesions that can lead to osteoporosis. The reason for the development of such lesions is the disruption of the equilibrium between bone resorption and bone formation as a result of proliferation of osteoclasts and reduction in the number of osteoblasts in the process of differentiation of mesenchymal stem cells (MSCs). The maintenance of bone architecture is critically dependent on osteoblasts and osteoclasts, the activity of which is underpinned by a range of soluble factors. …

Sex-Based Differences In Acvr2b And Grb10 Expression In Skeletal Muscle During Induced Cancer Cachexia And Disuse, Lauren Martinez

Graduate Theses and Dissertations

Background: Muscle atrophy is the shrinkage of muscle fibers that are largely maintained by a balance of protein synthesis and degradation. Imbalances in protein synthesis and degradation are observed in different muscle atrophy disorders such as cancer cachexia and disuse. These forms of muscle atrophy produce distinct wasting pathologies that are influenced by biological sex. Activin receptor type-2B (ACVR2B) and Growth factor receptor-bound protein 10 (GRB10) have been identified as genes that potentially regulate muscle mass while also displaying sexually dimorphic differences. Purpose: To examine the influence of ACVR2B and GRB10 throughout the development of cancer cachexia and disuse-induced atrophy …

Biopolymeric Materials For Tissue Regeneration, Cell Manufacturing, And Drug Delivery, David Alfonso Castilla-Casadiego

Graduate Theses and Dissertations

The development of materials for tissue regeneration, cell manufacturing, and drug delivery is possible by the manipulation of polymer properties and the use of three different techniques including layer-by-layer, electrospinning, and molding technique.

By applying the layer-by-layer technique over biomaterials, it is possible to develop polymeric multilayers that promote a more favorable environment for cellular functionality, increasing the possibility of improving their acceptance in the area of implantation. IRVASE demonstrated being a powerful technique that allows for a reliable characterization of the physical-chemical and thermal properties of the fabricated surfaces. This opens the possibility to monitor the design of surfaces …

Statistical Machine Learning For Breast Cancer Detection With Terahertz Imaging, Tanny Andrea Chavez Esparza

Graduate Theses and Dissertations

Breast conserving surgery (BCS) is a common breast cancer treatment option, in which the cancerous tissue is excised while leaving most of the healthy breast tissue intact. The lack of in-situ margin evaluation unfortunately results in a re-excision rate of 20-30% for this type of procedure. This study aims to design statistical and machine learning segmentation algorithms for the detection of breast cancer in BCS by using terahertz (THz) imaging. Given the material characterization properties of the non-ionizing radiation in the THz range, we intend to employ the responses from the THz system to identify healthy and cancerous breast tissue …

Influence Of Local- And Landscape-Scale Factors On Avian Assemblage In Fragmented Tallgrass Prairie Landscape, Pooja Panwar

Graduate Theses and Dissertations

Agricultural expansion and increasing urbanization are driving rapid landscape modification in the Tallgrass prairies ecosystem and are affecting biodiversity at multiple spatial scales. Thus, the conservation of fragmented grassland and steeply declining grassland avifauna is dependent on the relationship between local- and landscape-scale factors and avian assemblage. We also need to understand how these factors, operating at different spatial scales, drive the occupancy of different guilds in the assemblage. We conducted repeated point count surveys during the breeding season of 2019 at 66 grassland sites across Arkansas and Missouri, USA. We developed a multi-species occupancy model to estimate species richness, …

The Effectiveness Of The Inquiry Based Learning Method In A Private Independent School Environment, Fred R. Eaves

Graduate Theses and Dissertations

The purpose of this study was to examine the effectiveness of an inquiry-based learning model (IBLM) in a small, independent school educational environment. Seisan Academy (SA) implemented a new teaching philosophy that centered around an inquiry-based learning approach with a focus on developing a more student-centered culture at the school. This new program was implemented with little feedback or measurement regarding the effectiveness of the approach. This study also looked to address the lack of formal evaluation regarding the implementation of the IBLM.

Multiple sampling strategies were implemented due to the mixed-methods nature of this study. Quantitative data collection included …

A Study Of Student Experiences In The Secondary Transition Program Through Student, Parent, And Teacher Perceptions, Kelley M. Sells

Graduate Theses and Dissertations

The purpose of this research study was to examine and analyze the perceptions of students with mild-moderate disabilities, teachers, and parents regarding the students’ experiences related to their secondary transition plan. More specifically, the qualitative single-case study sought to identify areas of alignment and divergence of these three key members’ perspectives since experiences and perceptions are unique to an individual based on the context and individual’s perspective of the event. These findings suggested that the district showed experiences of valuable student presence and input in their IEP meetings and trusting supportive student-teacher relationships. The study also revealed that significant barriers …

The Biochemical Characterization Of Aza197 And A Ras Related Protein Cdc42, Alix Montoya-Beltran

Graduate Theses and Dissertations

Eukaryotic cells contain an extensive amount of GTP/GDP binding proteins. Proteins known as Ras GTPase primary function as a binary switch, where they cycle from an on and off state when GTP or GDP are bound, respectively. They are known to play a critical role in many cellular functions where a dysregulation could potentially lead to oncogenic behavior or other malignancies. In our laboratory, our focus is the study of a Ras related protein Cell division control 42 homolog (Cdc42) which belongs to the Rho subfamily. Cdc42 plays a critical role in many biological signaling processes; therefore, its uncontrol gene …

Development Of Biomaterials For Drug Delivery, Raquel De Castro

Graduate Theses and Dissertations

Drug delivery systems (DDS) have highly evolved in the last decades with the development of hydrogels and nanoparticles. However, high systemic uptake, side effects, low bioavailability, and encapsulation efficiency continue to be a major hurdle faced by such DDSs.

Nanoparticles and hydrogels can be specifically designed for targeted DDSs to mitigate some of the problems. This dissertation aimed to design two DDSs for ocular drug delivery and one for cancer treatment. The first project sought to develop chitosan nanoparticles (Cs-NP) using PEGDA as a copolymer to encapsulate gentamicin (GtS) for ocular drug delivery. Cs-NPs contain positive charges that can interact …

Evaluation Of Nutritional Factors That Influence The Efficacy Of Tributyrin As A Feed Additive For Broilers, Brooke Bodle

Graduate Theses and Dissertations

Tributyrin (TB) is a glyceride ester of butyrate that has the potential to improve broiler performance and intestinal development. Therefore, to fully evaluate this potential, three experiments were conducted to evaluate effect of tributyrin (TB) on broiler growth performance, nutrient digestibility, carcass characteristics, intestinal morphology, and gastrointestinal function in birds fed diets varying in composition reared in battery cages and floor pens. Experiment 1 explored the supplementation of graded doses of TB and its impact upon growth performance, nutrient digestibility, and carcass characteristics in a step-down program when added to a reduced energy and amino acid diet. A linear reduction …

Economic Feasibility Of Sub-Surfaced Poultry Litter, James Timothy Stults

Graduate Theses and Dissertations

Livestock producers routinely spread fertilizer or broadcast poultry litter to improve forage production. With poultry litter widely available across the Southeastern United States and a cheaper source of plant nutrition than fertilizer when proximal to application sites, the novel application of litter below the soil surface, while costly, allows for greater nutrient retention than broadcasting. Since quantifying costs and benefits of sub-surface litter application (SSLA) is complex, we develop and present a spreadsheet tool for automated comparison between SSLA, fertilizer, and broadcasted litter for user-specific scenarios involving equipment choices (new, used, custom), desired nutrient needs for crops grown, litter nutrient …

Caring Against The Carceral: How Families Mediate The Social Death Of Incarceration, Jessica Claire

Graduate Theses and Dissertations

Incarceration, especially in the United States, is deeply related to issues of racism, poverty, and citizenship. These particular experiences are the result of a history of biopolitical control affecting Black and brown communities and have a quintessential origin in enslavement. Those who are incarcerated are isolated, dishonored, and powerless as a result of the criminalization of race and poverty. These observations led to questions surrounding the particular impact families may have on the experiences of those who are incarcerated. Families of Incarcerated Loved ones, or FOILs, mediate incarceration through intentional socialization which has the potential to counteract the realities of …

The Intersection Of Writing Process Pedagogy And Prolepsis: A Phenomenological Case Study Of Secondary Writing Instruction, Jennifer O. Peñaflorida

Graduate Theses and Dissertations

The purpose of this dissertation was to investigate the lived experiences and essences of secondary high school students and participating teachers in a three-week summer journalism camp sponsored by the National Writing Project and funded by the MacArthur T. Foundation. This study employs Moustakas' (1994) modification of the van Kaam method for phenomenological data analysis in order to reveal the intersection of writing process pedagogy and prolepsis, a writing framework I developed. Data sources included pre-and-post writing samples, semi-structured interviews, field notes and student writing artifacts which were collected between May 27, 2019 and June 14, 2019. Data were analyzed …