Digital Commons Network^™

Flow Regime Influences On Stream And Riparian Soil Carbon Dynamics In The Ozark Highlands And Boston Mountains Of Arkansas, Allyn Dodd

Graduate Theses and Dissertations

The natural flow regime exerts primacy over lotic ecosystem patterns and processes. However, little work has examined the influence of flow regime on instream and riparian carbon (C) dynamics in minimally-impacted, temperate forested systems. To date, most research efforts have focused on characterizing C movement and transformations across biomes and land use categories; however, flow regime represents an overlooked, finer level of detail that may drive differences in ecosystem function. My dissertation objective was to measure C fixation and movement within and across multiple environmental spheres (e.g. within stream channels, between stream surfaces and the atmosphere, and from riparian soils …

Determinants Of Hydration In Children: The Role Of Physical Activity And Parental Dietary Habits, Hyun-Gyu Suh

Graduate Theses and Dissertations

PURPOSE: The purpose of these studies was 1) to examine the factors that influence the water intake in children and 2) to identify the optimal time window to assess hydration status that would be equivalent to 24-hour urine sample in children. METHODS: Study 1: Data for 200 parents (age:3-13y, female:62%, BMI:28.4±7.0kg∙m-2) and 200 children (age:7.5±2.9y, female:44%, BMI:17.7±3.9kg∙m-2) were recruited. Subjects recorded their fluid and food consumption on the 2-day diary, and food data were analyzed by using the Nutrition Data System for Research (NDSR) program. Physical activity levels were assessed with the International Physical Activity Questionnaire (IPAQ). All urine samples …

Modified Landscapes, Esther Nooner

Graduate Theses and Dissertations

Modified Landscapes is a body of work that reflects serious thought regarding Nature and its future. My personal experience and beliefs are at the core of why I believe this subject to be of great importance and why it will sustain many artists’ investigations for the time to come. The influences that informed this process are explored through experiences I had traveling, reading and exploring the photograph as a material object. The manipulation of the photograph is meant to question the beautiful, untouched scene and break the Romantic gaze that is historically tied to representations of Nature and insist upon …

A Numerical Investigation Of Bio-Inspired Scaffolds And Surface Textures, Yucong Gu

Graduate Theses and Dissertations

Synthetic scaffolds are widely used as implants to repair bone fracture. Without a proper design, scaffolds could pose significant health risks to the patient and fail to heal the bone properly. A good synthetic scaffold needs to have high porosity and large pore size to allow new bone cells to form on it. However, a scaffold with higher porosity and larger pore size tends to have reduced mechanical strength. Thus, it is important to find a structural design which allows the implant to have a high porosity and large pore size while retaining high strength. In this research, a 3D-printable …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

Fluid Phase Separation Via Nanochannel Array, John Lee

Graduate Theses and Dissertations

Microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) generate ideas and techniques for creating new devices at the micro/nano scale. This dissertation study designed a gas generator system utilizing nanochannels for phase separation that is useful for micro-pneumatic actuators, micro-valves, and micro-pumps. The new gas generator has the potential to be an integral part of a propulsion system for small-scale satellites. Nano/picosatellites have limited orientation capability partly due to the current limitations of microthruster devices. Development of a self-contained micro propulsion system enables dynamic orbital maneuvering of pico- and nano-class satellites.

Additionally, the new gas generator utilizes a high efficiency, green …

Got Breadfruit? Marshallese Foodways And Culture In Springdale, Arkansas, Diana Kay Chen

Graduate Theses and Dissertations

Understanding human food choices is essential in the examination of cultural knowledge and decision-making among members of any ethnic group. Ethnographic and cognitive anthropology methods, including a novel calculation of cognitive salience, were used in this study to explore the domain of traditional Marshallese foods in Springdale, Arkansas. Springdale is home to the highest population of Marshallese people outside of the Republic of the Marshall Islands (RMI); the population is expected to rise as people continue to migrate from the RMI because of global climate change and other factors such as family ties. Studies of traditional foodways are increasingly crucial …

Cancer-Induced Muscle Wasting, Jacob Levi Brown

Graduate Theses and Dissertations

Cancer-induced muscle wasting, otherwise known as cancer-cachexia, is a wasting syndrome that occurs in approximately 80% of cancer patients that is the primary cause of death for 22%-30% of cancer cases. Cancer-cachexia may be metabolically induced; therefore, the central hypothesis of this dissertation is mitochondrial degeneration occurs before cancer-cachexia, and increased oxidative stress because of mitochondrial degeneration in muscle may instigate cancer-cachexia. Lewis Lung Carcinoma cells (LLC) or PBS (control) were injected into the hind-flank of C57Bl6/J mice at 8 wks age, and tumor allowed to develop for 1, 2, 3 or 4 wks. Mitochondrial quality, function, ROS emission, protein …

Development Of A Digital Rain-Sensing Irrigation Pump Controller And An Android Enabled Bluetooth Paddlewheel Flowmeter, Jayendra Mishra

Graduate Theses and Dissertations

For better irrigation efficiency, it is recommended that farmers track their water consumption to avoid over-irrigating. However, it is difficult to implement this as it is labor intensive to supervise pumps manually and available technologies require high investment. Therefore, a rain sensing pump controller for 3-phase electric irrigation pumps and a stand-alone portable Android enabled paddlewheel flowmeter has been developed to test their feasibility.

The pump timer is a retrofit device for irrigation pump panels. The controller allows an irrigator to start and stop the pump with less supervision. An infrared rain sensor is integrated with the controller to measure …

Consumers’ Willingness To Pay For Hydroponic Lettuce, Daniel Gilmour

Graduate Theses and Dissertations

With continued advances in hydroponic plant production technology, an increasing number of farms have begun using hydroponic techniques to grow leaf lettuce and other food crops in a controlled environment. Recent controversy about the ongoing inclusion of hydroponics in the USDA organic program has highlighted uncertainty about marketing for hydroponic crops. In November 2017, the National Organic Standards Board voted not to recommend that hydroponic farms be banned from applying for organic certification. Since then, continued controversy has led a group of organic producers to start an additional independent certification program that would exclude hydroponic crops. While hydroponic production may …

Formal Learning In An Informal Setting: The Cognitive And Affective Impacts Of Visiting A Science Center During A School Field Trip, Charlie Belin

Graduate Theses and Dissertations

With the pressures of budget cuts, many schools--particularly schools serving low-income students--are eliminating school field trips to museums, zoos, and other cultural institutions despite their widely reported utility. First, through a systematic review of the literature, I examine the findings from 17 international studies on the benefits of visiting an informal science education institution during a K-12 school field trip. Almost all pre-post studies reported a positive change in both cognitive and affective outcomes after visiting an ISEI. However, studies that also included a control group to compare students who visited the ISEI with students who had yet to visit …

Interpersonal And Ideological Kindness: A Biocultural Approach, Sally Averitt-Hubbard

Graduate Theses and Dissertations

In accordance with Richard Dawkins’ materialist “selfish gene” theory of human behavior, altruism is a subject matter that is treated conservatively by biologists, whose understanding of the human version of altruism tends toward mutualistic and sometimes reputation-based explanations of charity, kindness, and helping. Trivers (1971) first stated that non-kin altruism could evolve if altruistic behavior is balanced between partners over time, implicating a strictly mutualistic domain for kindness. But kindness herein is defined, beyond mere mutualism or reciprocity, as “the quality of being friendly, generous, and considerate.” Further, kindness tends to have an action-oriented dimension, as in Goetz et al.’s …

An Investigation Into The Relationship Between Spirituality And Coping Responses Among Women With A Visual Impairment, Sandra Marie Bullins

Graduate Theses and Dissertations

The purpose of this study was to examine coping responses, specifically by women, and the relationship between those coping responses and a woman’s self-reported spirituality. The sample was comprised of women (n = 175) from the United States and 10 foreign countries. The results of a correlational analysis showed a strong positive relationship (r= 0.46, p<0.0001) between scores on the Spirituality Assessment Scale (SAS) and the Brief Cope (BC). There were also statistically significant correlations among subscales of the SAS and BC subscales. A multivariate analysis of variance was performed to evaluate the impact that select demographic variables might have on spirituality and coping responses. The results of the MANOVA showed no effect and were not statistically significant at alpha 0.1.

Seasonal Phenology, Distribution And Treatments For Polyphagotarsonemus Latus (Banks) On Primocane-Fruiting Blackberries (Rubus L. Subgenus Rubus) In Arkansas, Jessica Anne Lefors

Graduate Theses and Dissertations

Worldwide, blackberries (Rubus L. subgenus Rubus) are an economically important crop. In 2007, Polyphagotarsonemus latus (Banks) (broad mites), were first reported damaging primocane-fruiting blackberries in Fayetteville, Arkansas. Since this time, broad mite damage to blackberries and yield loss has been reported in many states and countries. Despite the increasing reports of this blackberry pest, little is known about their population dynamics, and few treatments are available. Growers with broad mite populations need a pest management program to minimize yield loss. Therefore, there was a need to develop sampling techniques, describe broad mite seasonal phenology in blackberry fields, and determine efficacy …

Immunostimulatory Effects Of Antigen-Conjugated Inp/Zns Quantum Dot Nanoparticles In An Avian Model, Christopher Lyle

Graduate Theses and Dissertations

Due to their unique physicochemical and enhanced immunostimulatory properties, quantum dot (QD) nanoparticles have shown increasing promise in biomedical research applications including bioimaging, drug delivery, and as vaccine adjuvants. Toxicity, however, remains a concern for the use of QD in these applications and thus, there is an increased demand for effective in vitro and in vivo systems to measure the bioactivity of QD. In this study in vitro and in vivo chicken models were used to investigate the effects of QD on innate and adaptive immunity. Chicken macrophage cultures were treated in vitro with QD to measure macrophage activation and …

Structure And Property Of Polymers And Biopolymers From Molecular Dynamic Simulations, Xiaoquan Sun

Graduate Theses and Dissertations

Natural and synthetic polymers and biopolymers have been studied for a variety of applications in food emulsion, biopharmaceutical purification, tissue engineering, and biosensor. The structure and property of polymers and biopolymers are critically important to determine their functions. Molecular dynamics (MD) simulations have a unique advantage to explore the structure and property of polymers and biopolymers from the molecular level. In the dissertation, MD simulations were conducted to study the mechanisms of various biological and chemical processes controlled by polymers and biopolymers based on real-world experimental results.

Seven heptapeptides have been screened from a peptide library in our earlier study …

Novel Methodology For Emboli Analog Production And In-Vitro Simulation Of Acute Ischemic Stroke, Anne Preut

Graduate Theses and Dissertations

Stroke is the leading cause of disability and a primary cause of mortality, resulting in an estimated $33 billion dollars spent on healthcare, rehabilitation and lost productivity in the United States each year. The most prevalent cause of stroke incidents are acute ischemic events, manifested as blood clots in the vasculature supplying the brain. Current gold standard treatments have improved since 2006 with the introduction of mechanical stent retrievers; however, several issues with the current treatments to acute ischemic stroke remain. Thrombolysis of the clot with a tissue plasminogen activator may lead to weakening the vessel wall and consequently, hemorrhaging. …

A Home Security System Based On Smartphone Sensors, Michael Mahler

Graduate Theses and Dissertations

Several new smartphones are released every year. Many people upgrade to new phones, and their old phones are not put to any further use. In this paper, we explore the feasibility of using such retired smartphones and their on-board sensors to build a home security system. We observe that door-related events such as opening and closing have unique vibration signatures when compared to many types of environmental vibrational noise. These events can be captured by the accelerometer of a smartphone when the phone is mounted on a wall near a door. The rotation of a door can also be captured …

State Dependent Function And Dynamics In Cerebral Cortical Networks, Leila Fakhraei

Graduate Theses and Dissertations

Cerebral cortex exhibits vigorous ongoing, internal neural activity even with no sensory input is present or the animal is minimally engaged in a task or behavior. This internal ongoing activity is not static; the ‘cortical state’ varies ranging from synchronous and highly correlated activity to asynchronous and weakly correlated neural activity. The main goal of the work presented here is to understand how changes in cortical states effect several aspects of cortical function and dynamics.

To meet this goal, we did three separate projects. First, we compared the predictability of neuronal network dynamics across cortical states in somatosensory cortex of …

Computational Fluid Dynamics Model For Air Velocity Through A Poultry Transport Trailer In A Holding Shed, Christian Heymsfield

Graduate Theses and Dissertations

Broiler production in Arkansas was valued at over $3.6 billion in 2013 (University of Arkansas Division of Agriculture Cooperative Extension Service). Consequently, improvement in any phase of the production process can have significant economic impact and animal welfare implications. One area of concern for the poultry industry is thermal stress experienced by the birds after arrival at the processing plant and before they are taken in to be processed, during which time they are left to wait in holding sheds. Various cooling strategies exist to mitigate heat stress in holding sheds, but in most cases it is unlikely that they …

Near Bandgap Two-Photon Excited Luminescence Of Inas Quantum Dots, Xian Hu

Graduate Theses and Dissertations

Semiconductor quantum dots (QDs) confine carriers in three dimensions, resulting in atomic-like energy levels as well as size-dependent electrical and optical properties. Self-assembled III-V QD is one of the most studied semiconductor QDs thanks to their well-established fabrication techniques and versatile optical properties. This dissertation presents the photoluminescence (PL) study of the InAs/GaAs QDs with both above bandgap continuous-wave excitation (one-photon excitation) and below-bandgap pulse excitation (two-photon excitation). Samples of ensemble QDs, single QD (SQD), and QDs in a micro-cavity, all grown by molecular beam epitaxy, are used in this study. Morphology of these samples was examined using atomic force …

Examining Food Insecurity Among High School Students: A Risks And Resources Model, Jill Niemeier

Graduate Theses and Dissertations

This study examined the relationships between food insecurity, risks, and resources among adolescents attending a large high school in Northwest Arkansas. In a sample of 1,493 students, in which the majority are Hispanic/Latino and receive free and reduced lunch, food insecurity relationships were first assessed controlling for a number of sociodemographic variables, such as ethnicity, gender, and social class. In addition, a number of risk and resource variables were identified at four ecological levels: individual, family, school/peer, and community. These risks and resources were analyzed using a three-step ordinal regression model in order to examine how sociodemographic controls, risks, and …

The Incorporation Of Graphene To Lithium Cobalt Oxide As A Cathode To Improve The Performance Of Lithium Ion Batteries, Kenan Wang

Graduate Theses and Dissertations

One of the objectives of this thesis work was to investigate the cathode performance of lithium cobalt oxide (LiCoO2) incorporated with graphene powder in lithium ion batteries (LIBs). Graphene powder was incorporated into cathode materials to enhance the performance of LIBs. The other objective was to impede the construction of a solid electrolyte interphase (SEI) sheet using graphene sheet coating on its cathode.

The results of this work show that adding graphene powder improved the performance of LiCoO¬2 as a cathode material. With the incorporation of different weight percentages of graphene powder, the LiBs showed distinct changes in their charging …

Understanding The Evolution Of Surface Texture Under Boundary Lubrication, Salil T. Bapat

Graduate Theses and Dissertations

The objective of this research was to understand the evolution of surface texture under boundary/mixed lubrication (BL). Significant material/energy losses occur during BL because of direct contact between the two surfaces. Traditionally, tribofilms have been studied extensively for BL while textures have been used as a static engineering design parameter to enhance lubricant film properties. However, texture is dynamic at the tribological mating interface, where both physical and chemical interactions are continuously modulated. The evolution and the interplay between the tribofilm and texture is least studied in the literature, which is the focus of this research.

MoS2-based lubricants, known for …

Perceived Maternal Invalidation And Drinking Behavior: The Role Of Action Control, Elise Ann Warner

Graduate Theses and Dissertations

Alcohol use disorder is one of the most prevalent disorders worldwide. As such, researchers have examined factors contributing to alcohol use. Perception of emotional experiences in childhood as invalidating by parents is one factor that has been found to predict later alcohol use, though less is known about maternal invalidation specifically. Parental invalidation has also been found to predict difficulty regulating affective states (i.e., negative and positive affect), which is also a determinant of alcohol use. Further, researchers have studied temptation to drink and restraint from drinking as related to alcohol use to better understand drinking behavior. Though there appears …

Defending Wild Dogs: Population Dynamics And Disease In Endangered African Wild Dogs, Elizabeth Claire Arredondo

Graduate Theses and Dissertations

African wild dogs (Lycaon pictus) are endangered carnivores whose population is decreasing from habitat loss and fragmentation, interspecific competition, and disease. Survival rates are especially low in Kruger National Park (KNP), though it is unclear why. I estimated the abundance in KNP and survival rates over different time spans, six years and nine months, using public photographic survey data. In 2015, there were 298 (SE=12.1) individuals. Using a mark-recapture analysis in program R, I found that the survival rate between 2009-2015 was only 3.2%, and within the 9-month survey period (September 2014 – June 2015), monthly survival rates for the …

Antiproliferative Activity Of Carotenoids, Phenolic Compounds, And Volatile Terpenoids In Carrots (Daucus Carota L.), Brittany Frederick

Graduate Theses and Dissertations

Epidemiological studies have shown an association between high carrot consumption and low prevalence of cancer. This observation has been thought to be attributed to carrot carotenoids. Despite this, various intervention trials have displayed no changes in incidence or increased incidence of cancer with carotenoid supplementation. It is possible that carrot phenolics are responsible for this association, though this has not been widely accepted. Volatile terpenoids from carrots have not been studied in this regard. Therefore, the primary objective of this study was to compare the antiproliferative effects of carotenoids, phenolics, and volatile terpenoids extracted from carrots on Caco-2 colon cancer …

A Laboratory-Based Experimental Test Of Reasons For Living: Effects On Behavioral Approach Toward A Suicide-Related Stimulus, Sasha Micaella Rojas

Graduate Theses and Dissertations

There are few laboratory-based experiments that examine the effects of suicide-related risk or protective factors on suicide-related outcomes. Consistent with extant evidence-based theoretical models and treatments for suicidal behavior, it appears that increasing awareness of reasons for living may reduce risk for suicidal behavior. Thus, the current study represents an initial effort to experimentally examine the impact of bringing awareness to one’s most important reason for living on behavioral approach towards a suicide-related stimulus. Random assignment was used to assign an unselected undergraduate sample of 78 participants to complete either a script-driven imagery procedure specific to the most important reason …

Phylogeny And Evolutionary Genomics Of Non-Photosynthetic Diatoms, Anastasiia Onyshchenko

Graduate Theses and Dissertations

Diatoms are prolific photosynthesizers responsible for some 20% of global primary production. In real terms, the oxygen in one of every five breaths traces back to photosynthesis by marine diatoms. Among the tens of thousands of diatom species, a small handful of colorless diatom species in the genus Nitzschia have lost photosynthesis altogether and rely exclusively on extracellular organic carbon for growth. I used DNA sequence data to reconstruct the phylogeny of this group, and found that nonphotosynthetic diatoms are monophyletic, indicating that photosynthesis was lost just one time over the course of some 200 million years of diatom evolution. …

Glucose Level Estimation Based On Invasive Electrochemical, And Non-Invasive Optical Sensing Methods, Sanghamitra Mandal

Graduate Theses and Dissertations

The purpose of this research is to design and fabricate sensors for glucose detection using inexpensive approaches. My first research approach is the fabrication of an amperometric electrochemical glucose sensor, by exploiting the optical properties of semiconductors and structural properties of nanostructures, to enhance the sensor sensitivity and response time. Enzymatic electrochemical sensors are fabricated using two different mechanisms: (1) the low-temperature hydrothermal synthesis of zinc oxide nanorods, and (2) the rapid metal-assisted chemical etching of silicon (Si) to synthesize Si nanowires. The concept of gold nano-electrode ensembles is then employed to the sensors in order to boost the current …