Life Sciences Commons^™

Phenotypic Plasticity Of Rattlesnake Trophic Morphology, Matthew Thomas Smith

Graduate Theses and Dissertations

The trophic morphology of gape-limited predators constrains the shape and size of prey items they can ingest. Trophic morphology consists of any morphological feature that is involved in the handling and ingestion of food. Diet has a profound effect on the morphology of many gape-limited predators. Identifying how prey type and resource level affect the morphology of different populations is an essential step in understanding the mechanisms contributing to patterns of morphological diversity. Species interactions (Chapter 1) induce plasticity in morphology that can lead to increased fitness, morphological divergence, and eventually speciation.

In Chapter 2, a laboratory study tested the …

Community Structure And Ecological Specialization In Plant-Ant Interactions, Paola Barriga

Graduate Theses and Dissertations

Positive associations among species have contributed to the maintenance of biodiversity. These interactions are typically studied in pairwise fashion where two interacting organisms are the focus. This dissertation uses network theory to analyze positive plant-ant associations in three Neotropical forests. Obligate plant-ant mutualisms were used, where plants host the ants in domatia and provide food bodies while the ants protect the plants and can feed them. A network approach was used to depict all obligate plant-ant interactions within a community. The main questions asked at the community level were: 1) Do network structure and levels of specialization change geographically and, …

Stress-Adaptation And Stress-Induced Changes In Campylobacter Jejuni, Geetha Sanal Kumar-Phillips

Graduate Theses and Dissertations

The foodborne pathogen Campylobacter jejuni is one of the leading causes of human gastroenteritis. This bacterium is not a robust organism compared with many other foodborne pathogens and requires special conditions in the laboratory for its growth. In nature, however, this organism is able to survive in very diverse and hostile environments and produce disease in humans. The different mechanisms by which C. jejuni survives stressful conditions in the environment remain unclear. Adhesion and invasion are thought to be important factors for the colonization of C. jejuni in the intestinal tracts of hosts. Previous research in our laboratory showed that …

The Biological Control Of Spotted Knapweed In The Southeastern United States, Carey R. Minteer

Graduate Theses and Dissertations

Spotted knapweed is an invasive, short-term-perennial plant that is native to Eurasia. It was accidentally introduced into North America in the early 1890's and has since spread across The United States and Canada. Spotted knapweed degrades rangelands and pastures by negatively impacting native plants, increasing soil surface runoff and stream sediment yields, and reducing soil infiltration. A biological control program for spotted knapweed using Larinus minutus (Coleoptera: Curculionidae), was initiated in Arkansas in 2008. In this dissertation I described the releases of L. minutus and investigated the adult activity in the southeastern United States (Chapter 1), investigated the effects of …

Life History Variation Of Common Terns In The Gulf Of Maine, Jeffery Bryant Kimmons

Graduate Theses and Dissertations

Life history is the inheritable rules that determine energy and time allocation towards different competing functions in the energy budget of an organism. Reproductive effort varies as organisms make reproductive decisions based on available energy. Factors influencing life histories are those that change energy and time budgets such as diet, competition, and environmental conditions.

Common tern (Sterna hirundo) life history phenotypes vary between islands in the Gulf of Maine. Common terns on offshore islands (>10km from mainland) and nearshore islands (5 to 10km from mainland) lay smaller clutches, hatching chicks with slower growth rates than common terns …

Effect Of Heat Treatments On The Properties Of Two Long-Grain Rice Cultivars During Storage, Youngbum Lee

Graduate Theses and Dissertations

During storage, the milling and physicochemical properties and eating quality of rice change, which is generally termed `aging'. Aged rice is preferred by processors, and there are attempts to develop accelerated aging process using various heat sources. In this study, the effects of various heat treatments and their influence on the milling, pasting, thermal, and cooking properties of two long-grain rice cultivars during storage were investigated using a full-factorial experimental design. Two long-grain rice cultivars, Wells and XP723, was treated with 8 different heat treatments including one control and stored at room temperature for 180 days. Heat treatments included 2 …

Effects Of Associated Subcortical Beetles On Oviposition Behavior And Early-Stage Survival Of Sirex Nigricornis F. (Hymenoptera: Siricidae), Ace J. Lynn-Miller

Graduate Theses and Dissertations

Sirex (Hymenoptera: Siricidae) woodwasps develop within xylem of host conifers. Sirex females drill through the bark, phloem and into xylem tissues where they deposit eggs along with a symbiotic Amylostereum fungus. The presence of Amylostereum is necessary for successful development of Sirex immatures as the larvae are unable to derive adequate nutrition from xylem in the absence of the fungus. The Eurasian woodwasp, Sirex noctilio F., was discovered in northeastern North America in 2004. Sirex noctilio has caused significant economic damage in Pinus radiata D. Don plantations of the southern hemisphere, but is of little economic significance in its native …

The Role Of Centromeric Chromatin And Kinetochore-Associated Factors In Chromosome Segregation, Wesley Williamson

Graduate Theses and Dissertations

Previous work in our lab has identified a point mutation in HTA1, one of the genes encoding histone H2A, which causes an increase-in-ploidy phenotype in Saccharomyces cerevisiae. This histone mutant strain was used to carry out a transposon insertion screen to identify suppressors of the increase-in-ploidy phenotype. This screen identified all three subunits of the Hda histone deacetylase complex, HDA1, HDA2, and HDA3. This study aims to elucidate the function of the Hda complex in chromosome segregation by exploring interactions among the members of the complex, as well as interactions between Hda complex and kinetochore components. …

Timing Of Castration, With Or Without Analgesia, On Growth Performance, Hematology, And Behavior Of Beef Calves, April C. Brown

Graduate Theses and Dissertations

Angus-sired (n = 30) and Hereford-sired (n = 32) bull calves were assigned randomly to 1 of 4 treatments. Treatments were 1) surgical castration near birth, 2) oral administration of the analgesic meloxicam (1 mg/kg of body weight) followed by surgical castration near birth, 3) surgical castration at weaning, or 4) surgical castration at weaning with oral administration of the analgesic meloxicam (1 mg/kg of body weight). Data was recorded for behavior, hematology, and growth at birth and weaning. Calf standing and lying activity was monitored at both stages by recording x and y axis positions of a data logger …

Effects Of Meloidogyne Incognita, Soil Physical Parameters, And Thielaviopsis Basicola On Cotton Root Architecture And Plant Growth, Jianbing Ma

Graduate Theses and Dissertations

The root-knot nematode, Meloidogyne incognita, and the seedling pathogen, Thielaviopsis basicola, commonly co-exist in Arkansas cotton fields and may interact resulting in increased losses. The primary objective of this research was to evaluate the effects of soil physical parameters on these soilborne pathogens and cotton growth in controlled environmental, field, and microplot studies. Controlled environmental experiments used two soil bulk densities and four pathogen treatments: non-infested soil, soil infested with M. incognita or T. basicola and soil infested with both pathogens. The results indicated bulk density generally did not affect seedling growth or disease since soils had low penetration resistance …

Genetic Diversity, Pathogenicity/Virulence Variation And Population Structure Of Rhizoctonia Spp. Associated With Rice Sheath Blight In Arkansas And Qtl Mapping For Disease Resistance, Vanina Lilian Castroagudin

Graduate Theses and Dissertations

Rice sheath blight (ShB) is one of the most prevalent diseases in rice. The significance of this disease is increasing due to more intensive production practices globally. Rhizoctonia solani Kühn AG 1 - IA [teleomorph: Thanatephorus cucumeris (A.B. Frank) Donk] is considered the primary ShB pathogen of rice. However, Rhizoctonia oryzae-sativae, Rhizoctonia oryzae, and R. solani AG 2 and AG 11, have also been isolated from sheath blight-like lesions on rice.Up to now, there is little information on genetic diversity and patterns of molecular evolution of the fungus, and there is no study on the structure of the R. solani …

Effects Of Environment And Genotype On Charcoal Rot Development On Soybeans, Micah Diane Doubledee

Graduate Theses and Dissertations

Charcoal rot of soybean, caused by the soilborne fungus Macrophomina phaseolina (Tassi) Goid, is a disease associated with high soil temperature and low soil moisture. Above-ground symptoms, which can be difficult to distinguish from drought symptoms, include low vigor, dead leaves that remain attached to the plant, early senescence and yield loss. Irrigation limits damage, but does not prevent colonization of the tissue by the pathogen. No soybean line is immune to M. phaseolina, but a few lines may have moderate resistance. The objectives of this research were to 1) determine the effects of genotype and drought on the development …

Economic Implications Of Extreme Heat Effects On Rice Yield And Milling Quality In Arkansas, Nate Lyman

Graduate Theses and Dissertations

Future increases in global surface temperature threaten those worldwide who depend on rice production for their livelihoods and food security. Past analyses of extreme heat effects on rice production have focused on paddy yield and have not accounted for the detrimental impact of extreme heat on milling quality outcomes which ultimately determine edible (marketable) rice yield and value. Using rice yield and milling quality data on six popular rice cultivars from Arkansas, USA, combined with on-site, half-hourly and daily temperature observations, this study finds a nonlinear effect of extreme heat exposure on yield and milling quality. A 1 °C increase …

Market Analysis Of Fresh Berries In The United States, Kristina Sobekova

Graduate Theses and Dissertations

This thesis contains a market analysis of fresh berries in United States. Specifically, it addresses strawberry, blueberry, blackberry and raspberry markets during 2008-2011. A double log model and the Almost Ideal Demand model are used to gain insight into the demand side of the market. An equilibrium displacement model is used to develop suggestions for producers and decision makers. The results demonstrate that retail demand for berry crops is elastic and that the different berries are substitutes for one another. The equilibrium displacement model is used to predict producer surplus changes to industry wide efforts aimed at both production efficiencies …

Characteristics Of Quality Agricultural Magazine Capstone Courses Based On The Five R'S Model, Traci Nicole Rushing

Graduate Theses and Dissertations

This study sought to assess students' and instructors' perceptions regarding the value of an agricultural communications magazine capstone course at three universities that were identified as exemplary in an effort to describe the characteristics leading to the course's success. Using a qualitative survey methodology, the investigator administered an open-response survey, conducted personal interviews with purposively-selected students in each course and the instructors, and made field observations. Both the interviews and the surveys consisted of six, in-depth questions crafted after Andreasen's (2004) of a successful magazine capstone course. Based on students' and instructors' perceptions through the lens of Andreasen's (2004) model, …

An Analysis Of The Redox Properties And Stability Of Chlamydomonas Reinhardtii Cytochrome F, Cytochrome C6, And Mutants Thereof, Nicole Lynn Vanderbush

Graduate Theses and Dissertations

This body of work presents mutagenesis studies conducted on two c-type cytochromes from Chlamydomonas reinhardtii. Cytochrome f, a unique c-type cytochrome, is investigated in regards to its redox potential, the dependence of the redox potential, and the thermal stability of the protein. The mutations made were Y1F, Y9F, Y160F, Y160L, R156L, and R156K. The residues that were mutated surround the heme. It was found that, relative to the wild-type, only the Y160L and R156 mutants showed any difference in midpoint potential at pH 7. Wild-type and mutants both had a midpoint potential that was dependent upon pH indicating that none …

The Potential Environmental Benefits Of Hybrid Rice Varieties, Haxhire Myrteza

Graduate Theses and Dissertations

With water insufficiency being already a major issue and potential carbon policies on greenhouse gas (GHG) emissions, Arkansas rice producers may need to undergo some changes in regards to rice cultivar selection. The purpose of this study is to estimate the environmental benefits of cultivating hybrid rice varieties as opposed to conventional and Clearfield rice varieties. To accomplish this goal, water use and GHG emissions were estimated on per acre (ac) and per bushel (bu) basis for most commonly cultivated rice varieties in Arkansas. The study focuses particularly on six main rice stations in the State of Arkansas. The hypothesis …

Effects Of Head Position And Head-Supported Mass On Nerve Function Of The Flexor Carpi Radialis Muscle In Healthy Individuals, Bethany Lauren Shivers

Graduate Theses and Dissertations

Long-term exposure to head-supported mass (HSM) has been linked with spinal degeneration including foraminal stenosis and disc deterioration. Anecdotally, HSM has also been linked to neck and arm pain and muscle atrophy, but nerve function has not been tested specifically. The combined effect of various head positions and HSM may be sufficient to compress the nerve root in aviators and Soldiers during job performance, potentially leading to short- and long-term neuromuscular effects. The Hoffmann (H) reflex, a well-established measure of nerve function, has shown to be sensitive to changes in nerve root space which occurs with different head positions. This …

Cell Bioenergetics In Leghorn Male Hepatoma Cells And Immortalized Chicken Liver Cells In Response To 4-Hydroxynonenal Induced Oxidative Stress, Alissa Laura Piekarski

Graduate Theses and Dissertations

Bioenergetic mechanisms responsible for ATP production are essential in carrying out maintenance and cell-specific functions. In this study, hepatocytes (liver cells) were used to test both endogenous and exogenous stress on cellular respiration. The secondary lipid peroxide, 4-hydroxynonenal (HNE), was used because it alters bioenergetics by increasing mitochondrial proton leak that attenuates mitochondrial radical production and, therefore, endogenous oxidative stress. The major objective of this study was to demonstrate effects of HNE-induced oxidative stress on avian hepatocyte bioenergetics. Various chemical which help enable the determination of oxygen (O2) consumption linked to ATP synthesis (oligomycin), maximal O2 consumption (FCCP), and proton …

Food Environment And Childhood Obesity, Yucong Jiao

Graduate Theses and Dissertations

This thesis examines whether children's food environment, especially food stores that have fresh produce, affects obesity prevalence among elementary school children in the state of Arkansas. Misclassified food outlet types in the Dun and Bradstreet commercial data set were first corrected and then food environment measures were computed and aggregated to geographic regions corresponding to school attendance areas. After applying classical panel estimation, it was found that the fixed effects model fit the data best. Results indicate that an additional supermarket within a one-mile radial of the census neighborhood block center will bring down childhood obesity prevalence by 0.58 percent, …

Evaluation Of Internal Markers For Predicting Digestibility And Fecal Output By Cattle Fed Bermudagrass Hays Of Varying Quality, Juvenal Kanani

Graduate Theses and Dissertations

The potential of in situ rumen undegradable dry matter (RUDM), indigestible neutral-detergent fiber (INDF), indigestible acid-detergent fiber (IADF), acid-detergent insoluble ash (ADIA), alkaline-peroxide lignin (APL), and acid-detergent lignin (ADL) to predict digestibility (DMD) and fecal output (FO) by cattle fed bermudagrass [Cynodon dactylon (L.) Pers.] hay-diets categorized by their low (L), medium low (ML), medium high (MH), or high (H) CP concentrations (79, 111, 131, and 164 g/kg DM, respectively) was evaluated. The second objective was to evaluate the effects of time (0600, 1200, 1800, and 2400 h) of fecal sampling on the prediction of FO and DMD. A replicated …

Characterization And Consumer Acceptance Of White Striping In Broiler Breast Fillets, Vivek Ayamchirakkunnel Kuttappan

Graduate Theses and Dissertations

White striping is an emerging issue in the broiler meat industry which causes concerns among the producers. The condition is characterized by the occurrence of white striations, parallel to the direction of muscle fibers, mainly in broiler breast fillets and thighs. Fillets can be categorized as NORM (normal or no striping), MOD (moderate) and SEV (severe) depending on the degree of white striping. As a result of few previous research studies on the condition, there is no information available on the impact of white striping on the consumer acceptance and various meat quality attributes. Our hypothesis was that the occurrence …

The Impact Of Selected Forage Legumes On Cattle Performance, Forage Production, And Soil Quality, And Evaluation Of Legume Persistence Under Grazing, Bradley Edward Briggs

Graduate Theses and Dissertations

Interest in substituting legumes for N fertilizer in beef cattle grazing systems has recently increased with rising fertilizer prices. Legumes are well known for their ability to fix atmospheric N and decrease dependence on input of N fertilizer. However, there are still difficulties associated with legume utilization including establishment and persistence. Two experiments were conducted to evaluate legume performance under herbivory. The objective of Experiment 1 was to compare forage production and beef cattle gains from annual ryegrass [Lolium multiflorum (L.)] and bermudagrass [Cynodon dactylon (L.) Pers.] pastures fertilized with N or overseeded with legumes. Gelbvieh × Angus …

Relationship Of Polymorphisms In The Fsh Beta Subunit Gene With Reproduction In Bos Taurus And Bos Indicus Cattle, Amanda Jo Davis

Graduate Theses and Dissertations

Two experiments were conducted to characterize polymorphisms (SNP) in the bovine FSHβ gene promoter region to examine breed differences in SNP, and to determine effects of SNP on reproduction in beef cattle. Experiment 1 - DNA samples were collected from 5 Angus (ANG), 13 Balancer (BAL), & 16 Brahman influenced (BI) bulls. Polymorphisms were identified by sequencing of 3 sequential PCR products from the promoter region revealed 17 SNP & 4 insertion/deletions (INDEL). Semen samples were collected and sperm quality variables determined via computer assisted sperm analysis (CASA) or stained smears. The MIXED procedure for ANG & BAL indicated interactions …

Soybean Maturity Group Tradeoffs: Irrigation, Weed Control, And Nitrogen Fixation, Ryan Wegerer

Graduate Theses and Dissertations

This thesis is divided into four chapters. Chapter I introduces the rationale behind the study and gives a brief overview of the overall study covering weed control, irrigation needs and nitrogen fixation amounts across soybean maturity group. Chapter II will go into further detail outlining the first applied experiment dealing with weed control and irrigation issues. Alternative weed control methods are analyzed in conjunction with irrigation risk analysis across soybean maturity group in response to agricultural issues of glyphosate resistance and declining ground water supply in the Arkansas delta region. Chapter III will jointly examine irrigation application amounts and nitrogen …

Impact Of Hybrid Rice On Food Security: A Spatial Equilibrium Analysis Of Global Adoption And Diffusion Of Hybrid Rice Varieties, Till Ludwig

Graduate Theses and Dissertations

Rice is the staple crop for most consumers in Asia. More than half of the global population depends on rice. However, scarce resources for agricultural production and unfavorable conditions will make it hard to meet future demand in rice and threaten future food security. Hybrid rice technology is a method to increase the productivity of resources needed for rice production. Current developments show not only yield improvements in comparison to existing conventional and hybrid varieties, but also fuel hopes for new abiotic and biotic stress tolerance. The objective of this study is to determine what impact hybrid rice varieties can …

Investing In An Agricultural Legacy, Leo Paul Goeringer

Graduate Theses and Dissertations

America's agricultural producers continue to age. According to the U.S. Census of Agriculture, the average age of farm operators increased from 55.3 in 2002 to 57.1 in 2007. During the same period, the Census shows a thirty percent decrease in the number of farmers under age 25. Young and beginning producers (YBPs) entering agriculture face high startup costs and a shortage of land to own or rent.

With these concerns in mind, this manuscript details the impact of an innovative proposed loan program for YBPs in Arkansas, which would offer concessionary interest rates and loan fees by participating banks for …

The Role Of Antioxidant Rich Berries In The Prevention Of Postmenopausal Bone Loss, Lydia Karimi Kaume

Graduate Theses and Dissertations

Postmenopausal osteoporosis is the most prevalent form of osteoporosis and results in fragility fractures. Smoking is one of the major risk factors for osteoporosis and is known to aggravate bone loss in postmenopausal women due to increased oxidative stress and inflammation. Diet-based interventions using berries have shown bone protective affects in animal studies partially due to antioxidant and anti-inflammatory properties of their phenolic compounds. The goal of this research was to determine the effects of antioxidant-rich fruits in the prevention of postmenopausal bone loss. Our first study examined the dose dependent effects of blackberries in preventing bone loss in an …

Evaluation Of Prebiotic Fibers And Pectin On Probiotic Strains And Effect Of Bacteriocin-Like Substance On The Survival Of Listeria Monocytogenes, Dolar Pak

Graduate Theses and Dissertations

Probiotics and prebiotics have been shown to provide beneficial effects on the host health and there are numerous research efforts being conducted on a variety of specific applications. However, most prebiotic carbohydrates are lower molecular weight oligosaccharides; and the health benefits of higher molecular weight pectins have not been fully evaluated. According to reviews, pectins are fermented in the large intestine due to the cooperative activities of colonic bacteria with complementary enzymatic activities. There are very few studies that demonstrate the fermentability of high methoxy pectin and low methoxy pectin by pure cultures of human isolates or probiotic bacteria. Thus, …

Part I - A Study Of The Formation Of Carbenes By Elimination Of Α-Bromosilanes And Application Toward The Synthesis Of Transition Metal Complexed Quinone Methide Analogs. Part Ii - Development Of Novel 7-Membered Ring Carbene Ligands For Palladium Catalyzed Cross Coupling Reactions., Christian Michael Loeschel

Graduate Theses and Dissertations

In part I, we wish to report our approaches toward transition metal complexed ortho-quinone methide analogs. ortho-Quinone Methides are a class of highly reactive compounds with a wide range of chemical and biological applications. Previously, a stable iron complexed benzannulated 5-membered ring quinone methide analog was reported by Allison and Neal27. Herein, we report our approaches to improve the reactivity of that system by removing benzannulation as well as changing the metal from iron to manganese and rhenium.

Furthermore, a methodological study on generating carbenes under mild conditions by elimination of α-halosilanes and its application towards metal complexed quinone methide …