Digital Commons Network^™

Understanding The Influence Of Interfacial Chemistry In Core, Core/Shell And Core/Shell/Shell Quantum Dots On Their Fluorescence Properties, Omondi Bernard Omogo

Graduate Theses and Dissertations

Colloidal semiconductor nanocrystals (quantum dots) have received a great deal of attention due to their superior size tunable properties and promising applications in many areas. Some of the most practical areas of their applications include light emitting diodes (LED), photovoltaic and biological studies. Synthetic methods of these crystals is becoming more established with new strategies being reported every now and then. However, quantitative studies connecting the processes at the interface, namely core-ligand, core-shell and shell-shells, to the overall quantum dots fluorescence properties are not well understood. Specifically for cores, relating surface-atoms interactions, solvents, ligands nature, density and functional groups on …

Primocane-Fruiting Blackberry: Optimum N-Fertilization, Jose Carlos Reynoso Campos

Graduate Theses and Dissertations

This study was conducted in 2011 at the University of Arkansas, Fayetteville to determine the optimum rate and time of nitrogen (N) application for `Prime-Ark® 45' primocane-fruiting (PF) blackberries under high tunnel conditions. There were four N treatments: Control (0), 10, 10-split, and 20 kg*ha-1 (Treatments 1, 2, 3, 4, respectively). In a randomized complete block (RCB) design, the following variables were compared: total and marketable yield, fresh weight of plant above ground, and cane diameter. Total fruit yields for Treatments 2 and 3 (2.5 and 2.5 kg, respectively) were highest and significantly different from the other treatments (p< 0.05). Marketable yield had a similar trend as total fruit yield, although not significantly different. Cane diameter and plant fresh weight were not significantly affected by fertilizer treatments. There were not significant differences in N content in leaves among treatments. Results indicated that either a single or split N application of 10 kgN*ha-1 could result in better yields.

Four …

Estimating Nitrogen Fixation Rates, Importance, And Short-Term Efficiency In Small, Temperate Reservoirs Using Delta15n Techniques, Bryant Christopher Baker

Graduate Theses and Dissertations

Nitrogen (N2) fixation can give certain species of cyanobacteria a competitive advantage in lake and reservoir phytoplankton. These species of cyanobacteria, along with others that cannot fix N2, can form toxic compounds that impair water quality when present in high concentrations. N2 fixation rates may be substantial in small (< 1.0 km2), temperate reservoirs since these systems experience thermal stratification and often nitrogen (N) limitation throughout a substantial proportion of the year. However, the effects of N2 fixation on N cycling, alleviation of short-term N limitation, and water quality are not well-understood. A mesocosm experiment and ecosystem-scale observational study were conducted to 1) determine the efficiency of N2 fixation under varying N relative to phosphorus (P) supply, 2) examine the effects of N2 fixation on autotrophic biomass accumulation and microcystin production, and 3) measure N2 fixation rates and importance to autotrophic N demand and zooplankton N assimilation. Results of the mesocosm experiment indicated that N2 fixation was increased at low N:P supply under high P. However, N2 fixation was inefficient at alleviating N limitation when fixed N was the primary source of N. Additionally, microcystin production occurred only at high N:P supply when N2 fixation was low, indicating that reducing external N inputs may have a positive effect on water quality. Results of whole-reservoir determination of N2 fixation using seston δ15N natural abundances indicated that N2 fixation rates throughout the warm season were substantial and influenced by water temperature. Annual N2 fixation rates ranged from 2.2 - 6.6 g N m-2 yr-1, and contributed up to 19% of the annual autotrophic N demand. Zooplankton were assimilating fixed N in most of the study reservoirs, representing a possible mechanism of ecosystem fixed N retention. Collectively, these results suggest that N2 fixation plays a substantial role in N cycling in small, temperate reservoirs, but likely cannot alleviate short-term N limitation.

Analysis Of Environmental Influences On Dressed Stone Decay: A Case Study Of Tafoni Development On A Hewn Djinn Block In Petra, Jordan, Kaelin M. Groom

Graduate Theses and Dissertations

Petra, Jordan captivates tourists and researchers with its dramatic sandstone cliffs, Nabatean, Roman, Byzantine and Roman architecture, and rich cultural heritage. However, increasing tourism in the valley is exacerbating stone degradation and complicating heritage management. This research analyzed environmental influences on dressed stone decay via tafoni development and evaluating cell evolution on an isolated hewn feature, known as Djinn Block X. Resembling other sandstone blocks found in the area, this irregular sandstone monument exhibits faces ranging in size from 2.5m by 3.5m to 3.9m to 4.2m (29m perimeter). Protruding features, incisions along the top, and a large platform attached to …

The Relationship Of Goal Focus To Physical Distance, Job Title And Years Served Within The University Of Arkansas Division Of Agriculture, Christina Miller

Graduate Theses and Dissertations

The purpose of this study is to determine the relationship between physical distance from the headquarters, number of years working within the Division of Agriculture, and job title compared to mission statement and goal focus. The Division of Agriculture as part of the University of Arkansas System is a unique organization because many of its employees are not physically located at the headquarter locations of Little Rock and Fayetteville. The Cooperative Extension Service, part of the Division of Agriculture, has at least one office in each of Arkansas's 75 counties as well as faculty and staff members located at five …

Identifying, Monitoring, Quantifying And Converting Algae To Bio-Fuels In Bio-Reactors, Alice C. Jernigan

Graduate Theses and Dissertations

Growing algae as a source for bio-fuels has become an area of interest due to concerns about global warming and the reliability and ecology of the production of fossil fuels. Dried algae harvested from a pilot water quality improvement technology at the Rockaway Wastewater Treatment Facility in New York were examined as a source of carbohydrates and lipids for the production of bio-fuels in bio-reactors. The length of storage time, storage conditions, sugar and lipid extraction processes, and fuel production were studied. The results show that if the algae is stored dry (0.015 g/g algae even after a year in …

The Impact Of Intolerance Of Uncertainty On International Students' Intercultural And Intracultural Conflict Management, Yekaterina Syrtsova

Graduate Theses and Dissertations

This study investigates the role of intolerance of uncertainty in international students' conflict management in intracultural and intercultural settings. International students at a large U.S. university were surveyed and their responses were analyzed using quantitative methods. Analyses indicated that the higher the intolerance of uncertainty scores, the higher the use of dominating and avoiding strategies. The results in this study also revealed that when controlling for sex, the higher the individuals' intolerance of uncertainty score, the lower their preference for integrating-compromising strategy. Finally, there were limited differences between the ways international students handle conflict with conflict partners from their own …

Health, Nutrition, And Disease In Rural Northern Jordan: A Study Of Enamel Defects Related To Childhood Stress In Skeletal Samples From The Bronze Age To The Byzantine Period, Teresa Veronica Wilson

Graduate Theses and Dissertations

Northern Jordan has seen periods of climate change, political transformation, and economic prosperity between the Late Bronze Age to the end of the Byzantine period. This research tests the assumption that the rural agricultural communities of this region were undernourished by examining the dentition for periodic childhood stress. Canine teeth from five sites (Ya'amun, Sa'ad, Yasileh, Natfieh, and Waqqas) that covered the time periods in question were collected to study overall quality of life.

The teeth were thin-sectioned and examined under a light microscope. Digital micrographs were made of the thin-sectioned teeth in order to record the number and location …

The Efficacy Of Probiotic Bacterial Isolates In Reducing Cecal Camylobacter Colonization In Broiler Chickens, Komala Arsi

Graduate Theses and Dissertations

Campylobacter is the leading cause of foodborne illness worldwide and human illnesses are often associated with consumption of poultry or poultry products. Many strategies have been tried to eliminate Campylobacter from poultry with limited success. One of the strategies to reduce Campylobacter colonization in poultry is by use of probiotics. We conducted 2 separate studies to evaluate the efficacy of probiotics against Campylobacter in broiler chickens. For our first study, GRAS (Generally Regarded as Safe) bacteria were isolated from healthy chickens and tested their efficacy against Campylobacter in vitro. Twenty six isolates with in vitro anti-Campylobacter activity were …

Rape Myths And Consent In College-Aged Southern Students, Amy Leanne Cofer

Graduate Theses and Dissertations

Rape and sexual assault are problematic issues for women on college campuses. Internal and external consent play a role in understanding sexual assault because sexual assault is defined as "nonconsensual sexual activity obtained through force, threats, intoxication, or intimidation." Factors related to understanding consent may include attitudes regarding sexual assault and rape, known as rape myths, which are defined as attitudes and false statements concerning rape that are widely known and accepted, mainly served to justify male sexual aggression towards women. The southeastern United States is known for being religiously and politically conservative, where gender roles are intertwined with a …

Porosity Development Within Lobes To Downslope Ramp Deposits On A Prograding Carbonate Shelf Of The Kinderhookian To Osagean Series In Northwest Arkansas, Elizabeth Marchese

Graduate Theses and Dissertations

Carbonate bodies with lobate geometries form a substantial part of the Osagean (early Mississippian) section in northwest Arkansas. The purpose of this study is to isolate and describe a single lobe from three-dimensional exposures in quarry walls to provide criteria by which lobe and lobe porosity can be recognized in the subsurface. Carbonate sediment generated on the Mississippian Burlington shelf moved southward by gravity flows from the shelf margin to positions on a prograding ramp in Arkansas where overlapping deposits with lobate geometries accumulated. These deposits are recognized in outcrops of the Boone Formation. Stratigraphic units within the Boone are …

Methane Emissions And Ammonia Volatilization From Drill-Seeded, Delayed-Flood Rice On A Silt-Loam Soil In Arkansas, Christopher Wade Rogers

Graduate Theses and Dissertations

The Environmental Protection Agency (EPA) currently uses a single methane (CH4) emissions factor of 160 kg CH4-C ha-1 for a primary rice (Oryza sativa L.) crop. The emissions factor is based on studies that do not adequately represent current management practices in Arkansas. Another concern is pre-flood fertilizer nitrogen (N) management, as the common N source, urea, is prone to loss via ammonia (NH3) volatilization. Thus, the objective of this research was to investigate trace gas emissions from rice on a silt-loam soil, including CH4 emissions as influenced by nitrogen (N) fertilization (i.e., optimal N and no N) in 2011, …

Impact Of Early Infestation Of Two-Spotted Spider Mites (Tetranychus Urticae) On Cotton Growth And Yield, Luis Orellana Jimenez

Graduate Theses and Dissertations

Two-spotted spider mites (Tetranychus urticae Koch, 1836) are pests of vegetables, ornamentals, and row crops around the world. Two-spotted spider mites have become an important long-season pests of cotton, causing injury to cotton from an early vegetative stage. In the past eight years, Arkansas cotton acreage treated for spider mites has more than doubled and most of the increase has been attributed to early season infestations. Yield losses of up to 30% have been observed in other studies where spider mite infestation started at third true leaf. Because of the apparent change in this pest's population dynamics, particularly at …

The Effects Of Salinity On Pythium Disease Of Rice And Soybean, Terea Jeanette Stetina

Graduate Theses and Dissertations

Increasing salinity is an important factor limiting agricultural productivity worldwide. In addition to direct effects on growth and yield, diseases also may be affected. This study characterized the effects of soil salinity on seedling disease of soybean and rice caused by Pythium spp. Controlled environment experiments on soybean used two cultivars which differed in chloride tolerance and soil treated with a CaCl₂ solution to create a range of electrical conductivity (EC) levels. For soybean, soil was either not infested or infested with Pythium sylvaticum or P. aphanidermatum (pathogenic to soybean), or P. oligandrum (not pathogenic to soybean). Twenty-one days …

Assessing Trichloromethane Formation And Control In Algal-Stimulated Waters Amended With Nitrogen And Phosphorus, Clinton Mash

Graduate Theses and Dissertations

Nitrogen (N) and phosphorus (P) enrichments can stimulate algal growth in drinking water sources, which can cause increased production of disinfection byproduct (DBP) precursors. However, the effect of systematic N and P enrichments on DBP formation and control has not been adequately studied. In this work, we enriched samples from a drinking water source - sampled on April 5, May 30, and August 19, 2013 - with N and P to stimulate algal growth at N:P ratios covering almost five orders of magnitude (0.2-4,429). To simulate DBP-precursor removal processes at drinking water treatment plants (DWTPs), the samples were treated with …

Assessing The Impact Of Chlorine Residual On Trihalomethane And Haloacetonitrile Formation Under Chlorination And Chloramination Disinfection Regimes, Thien Duc Do

Graduate Theses and Dissertations

A disinfection byproduct (DBP) formation potential (FP) test can be used to indirectly measure the concentration of DBP precursors in natural waters, permitting assessment of various DBP-related treatment processes and control strategies. While these tests require a 7-day chlorine residual (CR) between 3-5 mg L^-1 as Cl², it is not well known if this recommended residual corresponds to the true DBPFP (i.e., the maximum concentrations) for trihalomethanes (THMs) and haloacetonitriles (HANs). In this study, THMs and HANs were quantified as a function of CR under three common disinfection regimes: (1) free chlorine at pH 7.0 (FC7), (2) …

Effects Of Rain And Simulated Rain On Deoxynivalenol Levels In Grain And Chaff Of Winter Wheat With Fusarium Head Blight, Manoj Kumar Pun

Graduate Theses and Dissertations

Wheat grain affected by Fusarium head blight (FHB) contains the mycotoxin deoxynivalenol (DON) that is harmful to humans and animals. Reducing the amount of DON in grain is the goal of management practices for FHB so it is important to understand the factors affecting DON in grain. Some studies on the effects of late-season moisture found increases in DON while others found decreases due to leaching. The objectives of this study were to determine effects of late-season rain and misting on DON concentration in wheat spike tissues and to quantify the amount of DON leached from spikes. Field experiments were …

Effect Of Prescribed Burning In The Forests Of Buffalo National River, Arkansas, Francis Ndar Onduso

Graduate Theses and Dissertations

Prescribed burning (also referred to as controlled or hazard reduction burning) refers to the use of fire under controlled conditions to achieve a desired end product or goal. However, the nature and magnitude of the changes that result from prescribed burning are still incompletely known, and this is especially true for the forests of the Ozarks of northern Arkansas. The overall objective of the research project described herein was to obtain the data necessary to develop a better understanding of these changes, particularly as they relate to the use of prescribed burning as a management technique in the Buffalo National …

Effect Of Modified Starch On Bake-Only Chicken Nuggets, Sarah Purcell

Graduate Theses and Dissertations

The food industry has become increasingly focused on healthier items. Fried foods especially are actively pursuing non-fried alternatives to attract health conscience consumers. This study investigated the bake-only chicken nugget formulation in attempts to provide characteristics of fried items. Starch was hydrolyzed by amyloglucosidase to create a porous structure that had the ability to absorb oil. Oil was plated into the enzyme-treated starch and blended into nugget formulation, and the coated nuggets were steam-baked until fully cooked. The enzyme-treated starches showed a decrease in gelatinization range and pasting viscosities for all starch types. The addition of oil-plated enzyme modified starch …

Effect Of Functional Starch In Brown Rice And Grain Sorghum On Plasma Glucose And Insulin Responses In Humans, Nicole Marie Poquette

Graduate Theses and Dissertations

Diabetes and obesity are chronic illnesses increasing at dramatic rates in the U.S. and around the world. Research has looked to prevent or control diabetes and obesity through functional ingredients such as healthy-dietary carbohydrates to control blood glucose levels. Starch is a principle carbohydrate, which influences blood glucose levels, and measuring starch digestibility fractions can help predict the glucose response in the body. The objectives of this study were to investigate the functional starch content of parboiled brown rice flour and grain sorghum flour, and measure the effects on postprandial plasma glucose and insulin levels of 14 and 10 healthy …

The Effect Of Music Training On Emotion Perception In Childhood, Emese Maroti

Graduate Theses and Dissertations

Numerous studies found evidence that music training can enhance cognitive abilities both for children and adults. However, no evidence was found yet, whether music training can enhance abilities in emotion perception. I tested 8-9 year-old children on emotion perception in visual and musical contexts. The tests did not show significant difference between the musically trained and non-trained group neither in visual nor in musical context, however, when emotion scores were analyzed separately for each piece of music, musically trained children's responses reflected stereotypical modes of approaching emotional meanings in music, moreover, musically trained children's judgments were more uniform as there …

Management Of Katahdin Hair Sheep, Elizabeth Ann Backes

Graduate Theses and Dissertations

The objectives of this research were to determine the effects of different management practices on Katahdin hair sheep performance. For experiment 1, over 2 yr, 5, 0.4-ha pastures were allocated randomly to 1 of 2 grazing treatments: 1) Continuous; or 2) 4-cell rotation. Fifty yearling Katahdin ewes (53 ± 0.7 kg initial BW; 3.3 ± 0.09 initial BCS) were stratified by BW and BCS and allocated randomly to pastures in early May. Grazing d, basal cover, forage quantity or quality did not differ across treatments; however, sampling date effects were detected for forage quantity and quality. Beginning and end of …

Electrostatic Spray Application Of Food-Grade Organic Acids And Plant Extracts To Decrease Escherichia Coli O157:H7 And Salmonella Typhimurium On Select Produce, Leighanna Maeree Massey

Graduate Theses and Dissertations

Both consumers and suppliers have been negatively affected by an increase in foodborne pathogens contaminating fruits. Consequently, there is a need for the development of more efficient antimicrobials and application techniques to decrease contamination. Natural preservatives such as organic acids and plant extracts have demonstrated promising results in decontaminating produce. In addition, the effectiveness of such preservatives may be enhanced by the use of an electrostatic sprayer. The objective of this research was to determine the combinations and concentrations of organic acids and plant extract that were able to reduce Salmonella Typhimurium (ST) and Escherichia coli O157:H7 (EC) inoculated fruits …

Examining The Relations Among Trauma, Distress, Resilience, And Physical Health, Kathryn Elizabeth Chaisson

Graduate Theses and Dissertations

This study examined the role of traumatic distress as a mediator in the relation between trauma exposure and somatic malaise and healthcare utilization. Resilience was examined as a moderator between trauma exposure and somatic malaise and healthcare utilization, then between trauma exposure and traumatic distress. A total of 206 female participants recruited from an obstetrics and gynecology specialty practice completed measures of trauma exposure, traumatic distress, resilience, somatic malaise, and healthcare utilization. Multiple hierarchical regressions were performed to test the hypothesized relations. Results indicated that trauma exposure was a significant predictor of traumatic distress and resilience, and of somatic malaise …

Relationships Between Landscape Factors And Crayfish Density And The Interacting Effects Of Grazing And Increased Sedimentation On Algal Biomass, Katheryn Haley Rose

Graduate Theses and Dissertations

In recent years in the United States there has been a rapid expansion in anthropogenic sources of sediment in streams including construction, agriculture, and drilling for natural gas. Potential effects land disturbance associated with activities from natural gas development on aquatic biota in surrounding streams have not yet been well documented. An increase in inorganic sediment in streams can be detrimental to organisms through a variety of mechanisms including alteration of dominant substrate type, higher turbidity resulting in lower visibility, and burial of food resources such as algae and detritus. Increasing sedimentation in stream environments through anthropogenic disturbance is a …

Development Of Novel Subunit Vaccine Against H5n1 Influenza, Lu Zhang

Graduate Theses and Dissertations

Influenza is a common infectious disease resulting from a frequently mutated RNA virus. Vaccination is currently the most effective method to prevent people from seasonal or pandemic influenza. The production of traditional egg-based influenza vaccine is time-consuming and provides limited effect against new strains. Therefore, it is necessary to develop a rapid method to produce influenza vaccines. We proposed a novel influenza vaccine based on the E.coli expression system. Hemagglutinin (HA) is the major target surface protein of influenza virus for vaccine development. In this study, we sub-cloned the HAs encoding gene into an E. coli expression vector; the signal …

Development And Evaluation Of Chitosan Particle Based Antigen Delivery Systems For Enhanced Antigen Specific Immune Response, Bhanuprasanth Koppolu

Graduate Theses and Dissertations

Particle-based vaccine delivery systems are under exploration to enhance antigen-specific immunity against safe but poorly immunogenic polypeptide antigens. Chitosan is a promising biomaterial for antigen encapsulation and delivery due to its ability to form nano- and microparticles in mild aqueous conditions thus preserving the antigenicity of loaded polypeptides. The objective of this work is to develop a chitosan particle based antigen delivery system for enhanced vaccine response. Chitosan particle sizes, which ranged from 300 nm to 3 ìm, were influenced by chitosan concentration, chitosan molecular weight and addition rate of precipitant salt. The composition of precipitant salt played a significant …

Identification Of Biomarkers Associated With Ascites Incidence In Broilers, Kaylee Rowland

Graduate Theses and Dissertations

Poultry is key in genetic research due to breeding feasibility, relatively short generation interval, and distinct phenotypes. It is estimated that 8% of broiler deaths annually can be attributed to ascites, an economically important disease that has been challenging the industry for the past 2 decades. Genetically selected ascites resistant (RES) and susceptible (SUS) chicken lines have been established and maintained by the University of Arkansas, Fayetteville. Intensive research efforts have been made to reveal physiological and biochemical characteristics for the incidence of ascites. Since the whole genome of the major ancestral chicken, the Red Jungle Fowl, has been sequenced, …

Ecological Importance Of Ectomycorrhizal Linkages In The Ozark Mountains And The Fernow Experimental Forests, Shelly Kendra Bursick

Graduate Theses and Dissertations

Underground stem-to-stem linkages involving ectomycorrhizal (ECM) fungi are probably important in forest ecosystems, since these linkages could assist in the survival of established trees as well as increasing the growth and development of seedlings and saplings. This study compared forest communities of the Ozark Mountains of northwest Arkansas and the Fernow Experimental Forest in West Virginia by examining species richness, diversity, relative abundance, and the potential for stems to exhibit spatial distribution and clustering patterns that reflected the existence of linkages by ECM fungi. Data on forest communities in the Ozarks were obtained from eight plot locations in Devil's Den …

Analysis Of Social Networks In A Virtual World, Gregory Thomas Stafford

Graduate Theses and Dissertations

As three-dimensional virtual environments become both more prevalent and more fragmented, studying how users are connected via their avatars and how they benefit from the virtual world community has become a significant area of research. An in-depth analysis of virtual world Social networks is needed to evaluate how users interact in virtual worlds, to better understand the impact of avatar Social networks on the virtual worlds, and to improve future online Social networks.

Our current efforts are focused on building and exploring the Social network aspects of virtual worlds. In this thesis, we build a Social network of avatars based …