Life Sciences Commons^™

Postures For Precision: An Ecological Approach To Marksmanship And The Issue Of Warfighter Load., Christopher Jay Palmer

Open Access Dissertations

The goal of this dissertation was to understand the issue of load in a more operationally realistic way, while examining underlying segmental relations and postural regulation related to functional capability. The ecological approach provides a foundation for this work, as its approach seeks understanding across nested relations and at the level of the Organism-Environment system. First, a landing task was used to examine transitions from movement to upright stance, evaluating the effects of load on changes relevant to prospective control of action. Greater negative head angles, reductions in the field of regard, and reduced variability in orienting coordination (trunk-head relations) …

Identification And Functional Characterization Of The Zebrafish Gene Quetschkommode (Que), Timo Friedrich

Open Access Dissertations

Locomotion in vertebrates depends on proper formation and maintenance of neuronal networks in the hind-brain and spinal cord. Malformation or loss of factors required for proper maintenance of these networks can lead to severe neurodegenerative diseases limiting or preventing locomotion. A powerful tool to investigate the genetic and cellular requirements for development and/or maintenance of these networks is a collection of zebrafish mutants with defects in motility. The zebrafish mutant quetschkommode (que) harbors a previously unknown gene defect leading to abnormal locomotor behavior. Here I show that the que mutants display a seizure-like behavior starting around four days post fertilization …

The Evolutionary Genetics Of Seed Shattering And Flowering Time, Two Weed Adaptive Traits In Us Weedy Rice, Carrie S. Thurber

Open Access Dissertations

Weedy rice is a persistent weed of cultivated rice (Oryza sativa) fields worldwide, which competes with the crop and drastically reduces yields. Within the US, two main populations of genetically differentiated weedy rice exist, the straw-hulled (SH) group and the black-hulled awned (BHA) group. Current research suggests that both groups are derived from Asian cultivated rice. However, the weeds differ from the cultivated groups in various morphological traits. My research focus is on the genetic basis of two such traits: seed shattering ability and differences in flowering time. The persistence of weedy rice has been partly attributed to its ability …

Mechanics And Energetics Of Footfall Patterns In Running, Allison H. Gruber

Open Access Dissertations

The forefoot (FF) running pattern has been recently advocated to improve running economy and prevent overuse injuries compared to the rearfoot (RF) pattern. However, these claims have not been supported by empirical evidence. The purpose of this dissertation was to investigate the potential advantages of RF and FF patterns to improve running economy and reduce injury risk in 20 natural RF and 20 natural FF runners.

The first study found that the RF group was more economical when performing the RF pattern at a slow, medium, and fast speed vs. FF running. Only running at the fast speed resulted in …

Molecular Mechanisms Regulating Complement Receptor 3-Mediated Phagocytosis Of Borrelia Burgdorferi, Kelly Lynn Hawley

Open Access Dissertations

The macrophage receptors that mediate phagocytosis of Borrelia burgdorferi, the Lyme disease spirochete, are unknown despite this cell type's importance in promoting pathogen clearance and inflammation-mediated tissue damage. We now demonstrate that the β2 integrin, Complement Receptor 3 (CR3), mediates the phagocytosis of opsonized and non-opsonized spirochetes by murine macrophages and human monocytes. Although, expression of the surface proteins, CspA and OspE, protects B. burgdorferi from complement-mediated phagocytosis, the versatility of CR3 counteracts the ability of B. burgdorferi to interfere with complement activation and complement-derived opsonins, thus minimizing the bacteria's anti-complement strategy. Interaction of the spirochete with the integrin is …

Refinement, Validation And Application Of A Machine Learning Method For Estimating Physical Activity And Sedentary Behavior In Free-Living People, Kate Lyden

Open Access Dissertations

There is limited knowledge of the dose-response relationship between physical activity (PA), sedentary behavior (SB) and health. Poor measures of free-living PA and SB exposure are major contributing factors to these knowledge gaps. The overall objective of this dissertation was to address these issues by refining, validating and applying a machine-learning methodology for measuring PA and SB for use in free-living people. By combining neural networks and decision tree analyses we developed a method better suited for use in free-living people. Our new method is called the sojourn method and it estimates PA and SB from a single hip mounted …

Strategies To Improve The Performance Of Antioxidants In Oil-In-Water Emulsions, Atikorn Panya

Open Access Dissertations

Due to the limited number of approved antioxidants for food applications, several alternative strategies to improve antioxidant performance have been developed by focusing on synergistic antioxidant interactions. Susceptibility to lipid oxidation in food systems is the result of the summation of antioxidative and prooxidative mechanisms. Understanding the sometimes paradoxical behavior of antioxidants and prooxidants is a vital key to design synergistic antioxidant systems suitable for particular foods. This research focused on 3 main strategies to improve the performance of antioxidant activity in oil-in-water emulsions.

The first part of this research has been focused on inhibition of lipid oxidation by a …

Fabrication, Characterization And Utilization Of Filled Hydrogel Particles As Food Grade Delivery Systems, Alison M. Matalanis

Open Access Dissertations

Filled hydrogel particles consisting of emulsified oil droplets encapsulated within a hydrogel matrix were fabricated based on the phase separation of proteins and polysaccharides through aggregative and segregative mechanisms. A 3% (wt/wt) pectin and 3% (wt/wt) caseinate mixture at pH 7 separated into an upper pectin-rich phase and a lower casein-rich phase. Casein-coated lipid droplets added to this mixture partitioned into the lower casein-rich phase. When shear was applied, an oil-in-water-in-water (O/W1/W2) emulsion consisting of oil droplets (O) contained within a casein-rich dispersed phase (W1) suspended in a pectin-rich continuous phase (W2) was formed. Acidification from pH 7 to 5 …

Biological Control Of The Ambermarked Birch Leafminer (Profenusa Thomsoni) In Alaska, Anna L. Soper

Open Access Dissertations

The ambermarked birch leafminer (AMBLM) (Profenusa thomsoni) is an invasive leafminer native to the Palearctic from the United Kingdom to Turkey to Japan. It was introduced to the eastern United States in 1921 and has since spread to the mid-western U.S. states and Canadian provinces. This leafminer was introduced to Alaska in 1996, where it has since spread over 140,000 acres, from Haines to Fairbanks. The most severe damage is found throughout the Anchorage bowl, which extends south to Girdwood and North to Wasilla. The damage caused by P. thomsoni can be severe, defoliating entire trees. In 2006, it was …

Adsorption Column Studies To Predict The Flow Of Nutrients Through Heterogenous Porous Media Under Equilibrium And Isothermal Conditions, Vijai B. Pandey

Open Access Dissertations

Because of the endangerment of life of the human beings due to the environmental pollution, a serious study of the pollution of the environment is most vital. Because of increasing surface water pollution there is great hazard of ground water pollution. About half the United States of America derives drinking water from aquifers and much of the projected demand is expected to be met from subsurface sources. Therefore, a study was needed to determine the process of ground water contamination due to nutrients, especially Nitrogen, its degree and Length and Time of Travel and factors inhibiting its flow through soil. …

Structural Studies Of Membrane-Assembled Popd And Popb, The Pseudomonas Aeruginosa Type 3 Secretion Translocators, Fabian B Romano Chernac

Doctoral Dissertations 1896 - February 2014

Transport of proteins across membranes is essential during many stages of pathogen infection and colonization of human cells. Many Gram-negative pathogens use a Type 3 Secretion (T3S) system to inject proteins into the target cell during infection. Substantial genetic and biochemical evidence suggest that proteins are translocated across the host plasma membrane through a proteinaceous pore or translocon formed by two bacterial secreted proteins: the T3S translocators. Despite its key role in pathogenesis, virtually nothing is known about the assembly mechanism, structure, and composition of this critical transmembrane complex.

To this end, a cell-free system for the structural and functional …

Minor Components And Their Roles On Lipid Oxidation In Bulk Oil That Contains Association Colloids, Bingcan Chen

Open Access Dissertations

The combination of water and surface active compounds found naturally in commercially refined vegetable oils have been postulated to form physical structures known as association colloids. This research studied the ability of 1,2-dioleoyl-sn-glycerol-3-phosphocholine (DOPC) and water to form physical structures in stripped soybean oil. Interfacial tension and fluorescence spectrometry results showed the critical micelle concentration (CMC) of DOPC in stripped soybean oil was 650 and 950 microM, respectively. Light scattering attenuation results indicated that the structure formed by DOPC was reverse micelles. The physical properties of DOPC reverse micelles were determined using small-angle X-ray scattering (SAXS) and fluorescence probes. These …

Management Of Switchgrass For The Production Of Biofuel, Leryn Elise Gorlitsky

Open Access Dissertations

Switchgrass (Panicum virgatum L.) is a warm-season perennial being considered as a biofuel to meet energy challenges. In Massachusetts, a small state where the price of land is expensive, farmers want to determine if switchgrass can produce sufficient yields for consecutive years to warrant its production. The objective of this study was to determine what harvest management practices affect the vigor and health of switchgrass and which varieties produce the best yields for biofuel production.

Four experiments were conducted from 2009-2012. Twelve varieties were tested to determine their viability in the Massachusetts climate. Five were chosen for further chemical analysis. …

Target Recognition And Competitive Synaptogenesis In The Drosophila Giant Fiber System, Jason Joseph Hill

Open Access Dissertations

The development of complex neural networks relies on a careful balance of environmental cues to guide and shape both ends of the eventual connection. However, the correct wiring of circuits whose components share molecular profiles depends on a more elaborate phenomenon, competition. Despite being highly studied, there is still a lack of understanding as to the mechanism that allows molecularly identical cells to form exclusive connections with their targets. To address this complex question, we turned to a simple circuit within the genetically tractable fly. Responsible for the escape reflex, the Giant Fiber System is comprised of bilaterally symmetrical axons …

The Influence Of Free-Living Activity And Inactivity On Health Outcomes And Responsiveness To Exercise Training, Sarah Kozey Keadle

Open Access Dissertations

On average, starting an exercise training program decreases one’s risk for chronic disease. However, there is remarkable individual variability in physiologic responses to exercise training. The activity and inactivity during the remaining 95% of the day (when the individual is not training) is rarely considered. The overall objective of this dissertation was to apply validated sedentary behavior (SB) and physical activity (PA) measurement techniques during an exercise training study to determine if time spent in SB and PA outside of training influences the physiological response to training. Twenty subjects participated in a pilot study to determine the feasibility of reducing …

Influence Of Phosphate On The Adsorption/Desorption Of Bovine Serum Albumin On Nano And Bulk Oxide Particles, Lei Song

Open Access Dissertations

This work consists of four sections: 1) the adsorption behavior of bovine serum albumin (BSA) by three types of oxide nanoparticles (NPs), TiO2 (50 ± 5 nm), SiO2 (30 ± 5nm), and Al2O3 (150 ± 5 nm for α type and 60 ± 5 nm for γ type) in deionized water; 2) phosphate adsorption on these oxide NPs and bulkparticles (BPs); 3) influence of phosphate ions on BSA adsorption; and 4) BSA desorption from oxide NPs in phosphate solution. BPs were also used for comparison with NPs. For BSA adsorption in deionized water, the adsorption maxima on oxide particles are …

Distributions Of Large Mammal Assemblages In Thailand With A Focus On Dhole (Cuon Alpinus) Conservation, Kate Elizabeth Jenks

Open Access Dissertations

Biodiversity monitoring and predictions of species occurrence are essential to develop outcome-oriented conservation management plans for endangered species and assess their success over time. To assess distribution and patterns of habitat use of large mammal assemblages in Thailand, with a focus on the endangered dhole (Cuon alpinus), I first implemented a long-term camera-trapping project carried out with park rangers from October 2003 through October 2007 in Khao Yai National Park. This project was extremely successful and may serve as a regional model for wildlife conservation. I found significantly lower relative abundance indices for carnivore species, and collectively for all mammals …

A Comprehensive Model Of Human Neuromuscular Function During Repeated Isometric Contractions: Predicting The Effect Of Age On Fatigue, Damien Mark Callahan

Open Access Dissertations

Repeated or prolonged activation of skeletal muscle results in an acute decline in the muscle's ability to produce force, which is typically referred to as fatigue. Muscle fatigue is likely related to the by-products of cellular metabolism, alterations in neural activation and diminished membrane excitability that have been shown to accompany repeated contractions. However, the complicated etiology of the fatigue process makes it difficult to understand the relative influence of these physiological responses. Computational modeling of the skeletal muscle response to repeated activation is an appealing means of gaining insight into the mechanisms of muscle fatigue. A reasonably comprehensive model …

Adaptations To Stride Patterns And Head Movements During Walking In Persons With And Without Multiple Sclerosis, Jebb Grigory Remelius

Open Access Dissertations

Many people with multiple sclerosis (MS) have difficulty with walking, which can decrease their sense of mobility. Gait stability was investigated by studying stride parameters and head movements at preferred and fixed speeds in those with MS. First, walking gait data were recorded at preferred and fixed walking speeds from 19 individuals with MS and 19 controls. Traditional gait parameters were compared, as was swing foot to center of mass (CoM) timing at mid-swing. Second, walking gait data in healthy young adults (n=20) were recorded at preferred speed and while stepping over an obstacle. Study 2 developed novel swing definitions, …