Digital Commons Network^™

Design, Fabrication, And Testing Of A 3d Printer Based Microfluidic System, Carlton A. Mcmullen

Graduate Theses and Dissertations

A pneumatically actuated PDMS based microfluidic devices were designed and fabricated by soft-lithography. Two types of molds were fabricated out of different material for this experiment. The first mold, (device 1), was fabricated from a sheet of Polymethyl methacrylate (PMMA) material, similar to Plexiglas. The device features were micro-engraved onto the face of the material. The second mold, (device 2), was fabricated from the use of fused deposition modeling (FDM) 3D printing. The pumping efficiency of the PDMS devices was analyzed through the characterization of the micro-pumps flowrate with respect to the pumps driving pressure and the actuation frequency. Tested …

A Comparative Study Of Medicago Truncatula Transcriptomes As They Relate To Saponin Defenses Against Insect Pests, Audra Mae Rogers

Graduate Theses and Dissertations

Triterpene saponins are a class of defensive plant-derived compounds, which have a

variety of functions including antimicrobial, insecticidal, and nematicidal activities. This

research assessed the performance of the beet armyworm, Spodoptera exigua, following ad

libero feeding on Medicago truncatula accessions differing in specialized metabolite and

saponin profiles. Insect performance did not directly relate to the foliar saponin levels in the

accessions, which was measured using HPLC mass spectrometry. Accession ESP105 had the lowest foliar saponins overall, yet had similar levels of soyasaponins compared to the other accessions. Conversely, accessions A17, PRT178, and GRC43 had high foliar saponins with particularly high …

Development Of A Design Tool For Biologically Inspired Fault Adaptive Design By Strategy Mapping, Nicholas Steven Huisman

Graduate Theses and Dissertations

A design tool for Biologically Inspired Fault Adaption that utilizes the concept of strategy mapping was developed and the development process and testing is presented in this paper. The concept of strategy mapping is derived primarily from the field of military theory and supposes that for any given specific problem, that there exists a specific solution for, a single strategy can be identified for that solution/problem combination. This strategy, when applied to the specific problem yields the specific solution. This specific solution is referred to as the “tactics” of the strategy. The strategy can also be directly applied to a …

The Aerodynamic And Dynamic Loading Of A Slender Structure By An Impacting Tornado-Like Vortex: The Influence Of Relative Vortex-To-Structure Size On Structural Loading, Matthew Nicholas Strasser

Graduate Theses and Dissertations

Structural loading produced by an impacting vortex is a hazardous phenomenon that is encountered in numerous applications ranging from the destruction of residences by tornados to the chopping of tip vortices by rotors. Adequate design of structures to resist vortex-induced structural loading necessitates study of the phenomenon that control the structural loading produced by an impacting vortex. This body of work extends the current knowledge base of vortex-structure interaction by evaluating the influence of the relative vortex-to-structure size on the structural loading that the vortex produces. A computer model is utilized to directly simulate the two-dimensional impact of an impinging …

The Effects Of Meloidogyne Incognita And Heterodera Glycines On The Yield And Quality Of Edamame In Arkansas, Juliet Fultz

Graduate Theses and Dissertations

Edamame (Glycine max), also known as vegetable soybean, was introduced to the United States from Japan in 1890 and has been growing in popularity as a nutrient-rich, low-sugar snack in recent years. In 2012, the American Vegetable Soybean and Edamame, Inc. established the first domestic commercial processing plant in Mulberry, Arkansas and contracted local growers for production. Since the crop is harvested when seed are immature, management practices are different from those for traditional soybean. Plant-parasitic nematodes, particularly Meloidogyne incognita (southern root-knot) and Heterodera glycines (soybean cyst), are common in Arkansas and are pests of concern for edamame growers. Edamame …

Development Of Pre-Stressed Cfrp Fatigue Retrofits For Common Steel Bridge Connections, Korey Albert Pough

Graduate Theses and Dissertations

Aging or deterioration of the nation’s bridge infrastructure is a significant issue that requires attention. Causes for much of this deterioration can be attributed to two main factors, 1) corrosion, and 2) metallic fatigue, both of which work together to reduce the strength and serviceability of bridge components over time. In many instances, strengthening of bridge components using localized retrofits offers an economical and fast solution for increasing the longevity of existing steel bridges; however, such retrofits must be resilient to further corrosion and fatigue damage. In this study, a localized retrofit is developed using pre-stressed Carbon Fiber Reinforced Polymer …

Rice Blast Disease In The U.S. And Africa: Determination Of Pathogen Diversity And The Identification Of Resistance Genes For Disease Management, Felix Rotich

Graduate Theses and Dissertations

Rice blast caused by Magnaporthe oryzae (= Pyricularia oryzae) B. Couch, is a leading disease of rice. Magnaporthe oryzae exhibits a high degree of diversity. The diversity of isolates of M. oryzae from Africa and the U.S. were examined using vegetative compatibility and virulence phenotyping as well as determination of variation in the avirulence gene AVRPiz-t in isolates from Africa. Also, evaluation of blast resistance genes in the interspecific rice germplasm “New Rice for Africa” NERICA was done using F2 progeny of the cross of U.S. susceptible cultivar M204 and NERICA 12. The U.S. isolates were in three vegetative compatibility …

Investigation Of A Numerical Algorithm For A Discretized Rubber-Belt Continuously Variable Transmission Dynamic Model And Techniques For The Measurement Of Belt Material Properties., Brian Gene Ballew

Graduate Theses and Dissertations

A numerical algorithm for modeling the dynamic response of a rubber-belt Continuously Variable Transmission (CVT) belt is recreated. The numerical attributes applied to the algorithm and difficulties with numerical stability are discussed in detail. The degrees of freedom of the system have been expanded to include the dynamics of the engine torque output and vehicle loads such as rolling resistance and aerodynamic drag. This was done to emphasize the use of the model as an analysis tool for simulating CVT/engine/vehicle response. The increased degrees of freedom require the addition of a linear dampening element between belt nodes to dampen resonance …

Application Of Polyacrylamide-Based Floc Logs For Turbidity Control At Highway Construction Sites, Kien Ngo

Graduate Theses and Dissertations

Runoff waters generated on highway construction sites can have turbidities in excess of the proposed EPA regulatory standard of 280 NTU due to large areas of exposed soil. The objective of this research was to develop best management practices (BMPs) for the use of anionic polyacrylamide (PAM) based Floc Logs, for turbidity control. Five commercially available types of PAM-based Floc Logs were evaluated in jar tests, using soil excavated from Cato Springs Research Center (CSRC, Fayetteville AR) and six types of clay from the Clay Minerals Society (Chantilly, VA). These results show that no single Floc Log type was suitable …

Investigation Of The Inherent Chemical, Structural, And Mechanical Attributes Of Bio-Engineered Composites Found In Nature: Alligator Gar’S Exoskeleton Fish Scales, Wayne Derald Hodo

Graduate Theses and Dissertations

The U.S. Army has determined a huge cost savings of up to 51% can be accomplished by reducing the gross vehicle weight, for their personnel carrier, by 33%. To cut cost, composite materials are needed. Man-made composites can have superior material properties (high-strength, high-fracture toughness, and lightweight), but they are prone to delamination at the glued-layered interface. In contrast, fish scale is a natural composite that has the same material properties and, additionally, tend not to delaminate.

The focus of this study was to learn how nature integrates hard and soft materials at each length scale to form a layered …

The Role Of G-Protein Signaling In Pathogenesis In Cercospora Zeae-Maydis, Brant Smith

Graduate Theses and Dissertations

Gray leaf spot, caused by Cercospora zeae-maydis, is one of the most destructive foliar diseases of maize worldwide. C. zeae-maydis orients hyphal growth towards stomata (stomatal tropism) and forms infectious structures (appressoria) that are necessary for successful infection. Although some genes involved in pathogenesis in C. zeae-maydis have been identified, the molecular mechanisms are not well understood. In fungi, heterotrimeric G-proteins consist of three subunits (α, β, and γ) and mediate responses to environmental stimuli. They regulate diverse functions, including nutrient detection, virulence, fungal development, conidiation, secondary metabolism, and pathogenesis in many plant pathogenic fungi. This research explored the role …

An Assessment Of Primary Care Physician Opinions About Supporting The Independent Autonomous Practice By Advanced Practice Nurses, James Michael Flanigan

Graduate Theses and Dissertations

The Affordable Care Act (ACA) changed the national discussion about who is the decision-maker in healthcare delivery – physicians or others that pay the bill. The federal government is the largest payer of healthcare services while states are responsible for implementing the ACA’s features. Through the ACA, the federal government endorsed non-physician primary care by advanced practice registered nurses (APRN). The research question of this study is: Why do some primary care physicians support independent autonomous practice for advanced practice registered nurses while others do not? The research question should be important to policy-makers because physicians are the predominate purchasers …

Storage Of Round And Square Switchgrass Bales: Effect Of Storage Time And Fungal Inoculation On Saccharification Efficiency, Noaa Frederick

Graduate Theses and Dissertations

To produce fermentable sugars from lignocellulosic biomass feedstock, severe pretreatment conditions are needed (either high acid concentration, temperature, or retention times). High severities can produce toxic byproducts which inhibit enzymatic hydrolysis or fermentation. In order to reduce pretreatment severities (and thus increase enzyme and fermentation efficiency), the white-rot fungus Pleurotus ostreastus was seeded into square and round bales of Kanlow switchgrass (Panicum virgastum L.) and left in the field over a period of 9 month. The laccase producing fungus is believed to selectively degrade lignin, a common plant structural polymer, which can function as an enzymatic inhibitor. Samples were taken …

Economic Feasibility Of Aquaponics In Arkansas, Leah Ashley English

Graduate Theses and Dissertations

Concerns regarding population growth and resource scarcity have led to a recent renaissance of food production research. Over the past few decades, scientists have discovered new and innovative methods for growing food that, cumulatively, may hold the key to efficiently and sustainably feeding an ever-increasing world population. One method, known as aquaponics, has shown promise as being a sustainable solution for producing food locally in all parts of the world. Although many studies have shown aquaponic food production to be technically feasible, there are relatively few studies concerning the economic feasibility of aquaponics in various regions. To determine whether aquaponics …

A Regional Approach To Analysis Of Food Security Framework And Policies Of The Economic Community Of West African States (Ecowas), Hannah Elizabeth Shear

Graduate Theses and Dissertations

Food security is always a concern for consumers, but especially for those in West Africa, where the population of food insecure people has continued to grow over the past decade despite attempts by initiatives such as the World Food Program and the establishment of Millennium Development Goals. The people of West Africa are subject to repetitive natural disasters and are often in political upheaval. Many economic policies have been established to mitigate the impact that production disasters have on the consumers; one of these policies is the utilization of regional food reserves.

In 2010, the Economic Community of West African …

Evaluating The Impacts Of Respondent Errors In Arms: A Case Of Farm Service Agency Loans, Louise Nicole Mcminn

Graduate Theses and Dissertations

Many studies have used the U.S. Department of Agriculture’s (USDA) Agricultural Resource Management Survey (ARMS) to research various aspects involving the agricultural sector in the United States. Since nonresponse and inaccurate reporting may cause significant bias in statistical analysis, research was conducted to determine the magnitude of response error on the farm debt section of the ARMS Phase III. A multinomial logit model identified demographic, structural, and financial characteristics of FSA Farm Loan Program (FLP) borrowers who refused to indicate if they had end of year farm debt, or who accurately or inaccurately classified their farm operations as having end …

Portion Size Communication By Means Of Package Design, Tami J. Strickland

Graduate Theses and Dissertations

This qualitative study assessed consumers’ current methods of determining portion sizing of chicken products and examined their perceptions of how effectively three package designs communicate portion size. Everett M. Rogers’ Diffusion of Innovations (DI) Theory analyzes the characteristics of the consumer of the innovation (adopter) and the impact these characteristics have on adopting new innovations. The innovation in this study will be the prototype packaging. Focusing on Rogers’ adopter characteristics and defined proprietary consumer segmentation characteristics, this study will be pivotal for future package design projects targeting nutrition education.

Focus group questions were scrutinized through a pilot study and revised …

Perceptions Of Agricultural Leadership Academic Programs At 1862 Land-Grant Universities, Jackson Cole Alexander

Graduate Theses and Dissertations

This study sought to characterize perceptions of agricultural leadership programs in colleges of agriculture, food, life, human, or environmental sciences at 1862 land-grant institutions. Twenty-six academic programs were identified with a major, minor, graduate degree, specialization, concentration, or certificate in agricultural leadership. Programs were identified through analyzing the APLU and USDA NIFA websites, searching academic college websites, and contacting deans and departments heads. Objectives included identifying programs, describing the need for programs, describing evolution that has taken place within the discipline, describing faculty recommendations for future development and growth in the field, and examining why faculty believe programs are relevant. …

Eicosapentaenoic Acid (Epa) From Porphyridium Cruentum: Increasing Growth And Productivity Of The Microalgae For Pharmaceutical Products, Maryam Asgharpour

Graduate Theses and Dissertations

One of the major nutritional requirements in our diet is an adequate intake of omega-3 specially eicosapentaenoic acid (EPA). In the present study, the effects of two temperatures (16°C & 20˚C) and light intensities (140 & 180µE/M2.S) and four nitrate levels (0.075, 0.3, 0.5 and 0.7g/L) on the cell growth and lipid productivity of Porphyridium cruentum, one of the most promising oil-rich species of microalgae, were investigated. A growth comparison was carried out using pure CO2 and 5% CO2/air. Additionally, the ratio of the fatty acids with omega-3 and omega-6 groups at various growth conditions were compared, since an appropriate …

Soybean Planting And Risk-Return Tradeoffs In The Mid-Southern United States, Weston Weeks

Graduate Theses and Dissertations

This thesis is comprised of two studies on the effects of soybean (Glycine max (L.) Merr.) planting date (PD) and maturity group (MG) selection on producer expected returns. Having to replant soybean after early-season planting because of poor stand establishment is costly for producers. Replanting costs have increased in the last ten years as seed and other input costs for soybean have increased. Using five years of field trial results from two locations in Arkansas, the yield response to early and late season plant population density has been estimated to determine yield and future revenue potential for the purpose of …

The Efficacy Of An Eight-Week Undergraduate Course In Resilience, Asher J. Morgan

Graduate Theses and Dissertations

The purpose of this research was to measure the efficacy of an 8-week undergraduate

course in resilience. Finding useful strategies to understand how college students manage stress

and adversity is important to college administrators. The main topics that were assessed were

resilience, well-being, and assertiveness. Participants for this study included undergraduate

students enrolled either in a 8-week course on Resilience or a Public Health course. The

Connor-Davidson Resilience Scale, Questionnaire for Eudaimonic Well-Being, and the Simple

Rathus Assertiveness Scale were used to determine the efficacy of the 8-week course. Overall,

there was not a significant difference in resilience and well-being, …

Modulation Of Valve Interstitial Cell Function Through Cell Shape And Phenotype, Atefeh Razavi

Graduate Theses and Dissertations

The aortic valve is a highly dynamic structure responding to actively to the chemical, mechanical and physical cues of the valve microenvironment. Valve interstitial cells are dispersed throughout the valve tissue and play an important role in maintaining the integrity and optimum function of the valve. They are a heterogeneous population composed of various phenotype. These phenotypes have specific functions characteristic of valve physiological and pathological conditions. The effect of mechanical loading and chemical modulators on the behavior of the valve interstitial cells have largely been studied. However the role of valve interstitial cell shape as an intrinsic physical cue …

A Comparison Of Athletic Identity And Career Maturity Of Female Student-Athletes At Different Levels Of Competition, Simeon Hinsey

Graduate Theses and Dissertations

This study explored the relationship between the athletic identity and career maturity of women’s basketball student-athletes. Differences in athletic identity and career maturity were also investigated based on a women’s basketball student-athlete’s level of competition, race, year in school, socioeconomic status, and professional athletic career aspirations. In order to examine the relationship between these variables, a convenience sample of 209 women’s basketball student-athletes from NCAA Division I (n = 62), NCAA Division II (n = 40), NCAA Division III (n = 50), and NAIA (n = 57) institutions located in the southeastern region of the United States participated in the …

Composition Of Four Selected Arkansas-Grown Non-Gmo Soybean Cultivars And The Development Of High Protein Beverage Using A Selected Soybean Protein Hydrolysate, Quyen Tran Phuong Nguyen

Graduate Theses and Dissertations

Protein beverages made with non-genetically modified (non-GM) ingredients have been in demand due to the increasing consumers’ interest in healthy eating habit. Beverages formulated with non-GM soy protein are rare in the United States market since 93% soybeans planted in U.S (2013) are labeled as GM. This study aimed to develop protein hydrolysate beverages using one cultivar among the four Arkansas grown non-GM soybean cultivars including Osage, R95-1705, R08-4004 and R05-4969. R08-4004 was selected since it had the highest amounts of the three branched amino acids including Phenylalanine (51.4 mg/g), Leucine (74.9 mg/g), and Isoleucine (49.7 mg/g) with lowest amount …

Response Of Bacterial Cells To Fluctuating Environment, Sudip Nepal

Graduate Theses and Dissertations

We have studied morphological and genomic variations occurring in a mesophilic bacterium Escherichia coli (E. coli) in a wide range of continuous and fluctuating hydrostatic pressures. For all the studies here the temperature is maintained at 37◦C, the optimal growth tem- perature of E. coli at atmospheric pressure. Cell division is inhibited at high hydrostatic pressures resulting in an increase of cell length. The increase of cell-length depends on the extent and duration of the stress applied on bacterial cells. We have studied the effect of high pressure stress in three different conditions – (i) Wild-type cells (almost no genetic …

Examining Employability As Associated With Ic3, Mos, And Aca Certifications, Kelley Leigh Todd

Graduate Theses and Dissertations

Forrier and Sels (2003) define employability as “an individual’s chance of a job on the internal and/or external labor market” (p. 106) and is important (Wittekind, Raeder, & Grote, 2010). Possessing an industry certification may be considered an example of human capital skill. The human capital theory suggests qualifications, knowledge, skills, and experience of individuals may lead to increased earnings or productivity (Becker, 1993; Rosen, 1987; Schultz, 1971). As such, the human capital theory provides a framework for studying perceived employability (Wittekind, Raeder, & Grote, 2010; Verhaar & Smulders, 1999) as associated with IC3, MOS, and ACA industry certifications.

Randall …

Optimizing A Luciferase-Based Tool For Studying The Effects Of Fatty Acid Desaturase 7 On Singlet Oxygen Accumulation In Arabidopsis Thaliana, Abeer Muhammedali Alnasrawi

Graduate Theses and Dissertations

In plants, reactive oxygen species (ROS) are generated as a byproduct of normal metabolism, as well as in response to adverse conditions such as light stress, extreme temperatures, and exposure to pests and pathogens. Singlet oxygen (1O2) is a ROS that is formed during photosynthesis in photosystem II (PSII) of the chloroplasts. Levels of 1O2 and other ROS are tightly controlled in healthy plants, but some studies suggest that levels of fatty acid desaturase (FAD) activity in Arabidopsis thaliana can influence constitutive and/or stress-responsive ROS accumulation. In this study, a luciferase-based reporter gene that is selectively stimulated by 1O2 (AAA-ATPase: …

School Counselors Lived Experience Of A Rampage School Shooting, Carleton H. Brown

Graduate Theses and Dissertations

Minimal research has been conducted to examine school counselors’ lived experiences of rampage school shootings. The purpose of this research is to increase school counselors’ knowledge and skills in responding effectively to such a crisis. A single-case qualitative dissertation study was completed at a rampage school shooting site, a middle school, and the immediate surrounding area in Bono, AR, located in the northeast part of Arkansas. School counselors’ decisions, perceived expertness, and lessons learned were investigated. Data collected included relevant research literature (including comparison research), archival records, direct observation, media reports, and interviews. Participants interviewed were individuals who lived through …

Examining Teachers' Perceptions And Adaptations Related To The First-Year Of Implementation Of The Common Core State Standards In A Rural Elementary School In Central Illinois, Jason Vicich

Graduate Theses and Dissertations

This study examined the latest mandated government policy of the Common Core State Standards (CCSS) and the Partnership for Assessment of Readiness for College and Careers (PARCC), which fully took effect during the 2014-2015 school year. The study sought to look at these changes through the eyes of a group of elementary teachers in rural Illinois as they work with and through these policy mandates during their initial year of implementation.

The study was conducted over the course of the 2014-2015 school year. Data was gathered through a three interview sequence, site visits and the administration of the SOCQ 75 …

Rupture In Abdominal Aortic Aneurysm, Qusay Alfaori

Graduate Theses and Dissertations

Quantification of abdominal aortic aneurysm development, its growth kinetics, and rupture criteria are important to decrease the risk of this life-threatening event. Uniaxial testing of healthy and collagen degraded aortic specimens from pigs was performed. A mathematical model, from the literature, for the stress-strain relationship that is suitable for describing the behavior of abdominal aortic tissue was used to derive specific tissue properties/parameters as a function of strain rate and as a function of specimen orientation. Analyses consisting of Finite Element Modeling of healthy and collagen degraded abdominal aortas were performed using ABAQUS finite element code and the measured properties. …