eCommons Collection:

Characterization of the Thermobifida fusca Xylanase 11A Carbohydrate-Binding Module by X-ray Crystallography

Tue, 31 Jul 2012 00:00:00 GMT

Title: Characterization of the Thermobifida fusca Xylanase 11A Carbohydrate-Binding Module by X-ray Crystallography Authors: Wolski, Paul Abstract: Xylanase 11A is an enzyme that degrades xylan. It was isolated from Thermobifida fusca, a thermophilic bacterium found in compost. Xyl11A also contains a family IIb carbohydrate-binding module (CMB), which has been found to be capable of binding to both cellulose and xylan, unlike some other family IIb CBMs. For this reason, this binding domain was chosen for characterization by X-ray crystallography. The gene for this binding domain was cloned into Escherichia coli and purified with column chromatography. Crystals were found in some crystallization screens, and diffraction of these crystals is currently pending.

Morphological Correlates of Signal Variation in Weakly Electric Mormyrid Fish

Wed, 25 Jul 2012 00:00:00 GMT

Title: Morphological Correlates of Signal Variation in Weakly Electric Mormyrid Fish Authors: Cheng, Catherine Abstract: Weakly electric fish occupy a special place in the field of neuroethology as a model system for the study of the neurobiological basis of natural behavior. Comprising two orders of freshwater teleosts, the Gymnotiformes and the Mormyriformes, weakly electric fish have evolved diverse electric organ discharges (EODs) that are used for electrolocation of objects and for sex- and species recognition, courtship, aggression, and appeasement, among other behaviors (Bullock 1982; Heiligenberb & Bastian 1984). Aside from the variety of EODs, the elements of electric communication that make it a model system include the presence of a highly specialized electrosensory system with a subpopulation of receptors and neurons dedicated to communication signal sensing, as well as the structure of the electrical signals themselves, which is relatively simple and amenable to study by experimental manipulation (Hopkins 1988). This paper presents the results of two studies on mormyrid fish and the electric organs (EOs) responsible for weak electrogenesis. In mormyrids, the electric organ is composed of four columns of serially stacked, dish-shaped electrocytes, two on each side of the spinal cord (Bennett 1970; Bass 1986). The central theme of this thesis is the relationship between electric organ morphology and EOD waveform. The first chapter presents a study of Paramormyrops kingsleyae that shows geographic variation in signals correlated with variation in electric organ anatomy. The second chapter is a descriptive study of larval and juvenile Brienomyrus brachyistius that identifies morphological correlates of EOD change in the course of development.

An Analysis of How Dairy Farmers Divide Their Time among Twelve Key Management Areas and Farm Profitability

Fri, 29 Jun 2012 00:00:00 GMT

Title: An Analysis of How Dairy Farmers Divide Their Time among Twelve Key Management Areas and Farm Profitability Authors: Braun, Carolyn Abstract: The relationship between the time dairy farm managers spent on twelve key management areas and dairy farm financial performance was analyzed. The twelve key management areas analyzed were (1) milk quality, (2) milk quantity, (3) reproduction, (4) cow comfort, (5) nutrition, (6) reducing the incidence of metabolic disorders, (7) dry cow comfort, (8) calf management, (9) financial records, (10) financial management (11) crop production and (12) human resources management. Studies in the past have analyzed the factors that affect farm financial performance. However, these studies have never looked at the breakdown of manager hours spent on the factors and how that affects profitability. A multiple regression analysis was performed using a best subsets regression to determine the variables to include in the model. A p-value<0.05 was considered significant. The time managers spend on milk quality, milk quantity, reducing the incidence of metabolic disorders and financial management had a negative relationship with net farm income without appreciation. Time spent on cow comfort, nutrition, dry cow comfort, calf management, financial records and human resources management had a positive impact on net farm income without appreciation. In this study, time spent on reproduction and crop production was not statistically significant and therefore not included in the final model. The results of this study will help dairy farm managers structure the areas they focus on in order to improve farm efficiency which will in turn lead to an increase in financial performance for the farm.

Psychopaths Online: Modeling Psychopathy in Social Media Discourse

Fri, 29 Jun 2012 00:00:00 GMT

Title: Psychopaths Online: Modeling Psychopathy in Social Media Discourse Authors: Boochever, Rachel Abstract: This is an exploratory study examining the relationship between discourse patterns in social media and undergraduate students’ levels of psychopathy when compared to discourse patterns in narratives produced in a laboratory. It expands on previous research findings that psychopathic murderers exhibit narcissistic tendencies and psychological distancing in their discourse when compared to non-psychopathic murderers. Undergraduate students’ emails, SMS messages, and Facebook messages were collected and analyzed in relation to their scores on the Self-Report Psychopathy Test III (SRP III). Findings support both main hypotheses: that discourse patterns in social media are distinctly different from discourse patterns in narratives produced in a laboratory, and that psychopathic tendencies are identifiable in social media discourse. Consistent with previous studies, students higher in psychopathy showed evidence of psychological distancing, produced less comprehensible language, potentially reflecting their low reading achievement levels, and produced more anger and swear words, consistent with the emotional deficits and disagreeableness central to psychopathy.

Examining Conceptions of Singledom among Older Ever-Singles

Fri, 29 Jun 2012 00:00:00 GMT

Title: Examining Conceptions of Singledom among Older Ever-Singles Authors: McErlean, Kimberly Abstract: With an aging population, the host of alternatives to marriage, and the number of people who remain single, ever-single older adults are an important group to understand and their responses can be valuable in helping senior living communities and others work with and provide for this segment of the population. This article draws from interviews with 12 ever-single men and women between the ages of 65 and 87 to explore their changing perspectives of themselves as ever-single, the positives and negatives they perceive with their status, and the social norms surrounding relationships. Many of the participants saw their singlehood as a process and something that opened up opportunities for them that might not have been possible had they been married. Singlehood was seen as having both upsides—such as independence—and downsides—such as lack of companionship—but all participants expressed happiness with the way their lives had turned out. While many participants indicated that marriage was an expectation in the times that they were growing up and that remaining single used to be stigmatized, almost all respondents suggested that society was moving towards acceptance of alternative lifestyles to marriage. The responses from the interviewees illustrate the process involved with being and becoming a single adult.

Inbreeding and Potential for Evolutionary Rescue after Environmental Change

Tue, 26 Jun 2012 00:00:00 GMT

Title: Inbreeding and Potential for Evolutionary Rescue after Environmental Change Authors: Blackley, Kathryn Abstract: Evolutionary rescue occurs when populations that experience a severe decline in numbers following environmental change adapt evolutionarily and so avoid extinction. However, low population size, even without extinction, can have detrimental effects such as inbreeding depression that may influence the likelihood of evolutionary rescue. The aim of this study was to determine the effect of inbreeding on the propensity for evolutionary rescue. The monogonont rotifer Brachionus plicatilis was used as the study species and environmental change was created by increasing the salinity of its medium. All rotifers used in my study were originally derived from a laboratory stock culture that had been previously forced to a population genetic bottleneck with some lineages then maintained clonally while others were induced to sexual reproduction which led to inbreeding. Populations were later subjected to the environmental change and their resulting mortality and growth during recovery were observed. Inbreeding was found to significantly decrease the ability of the populations to recover from the environmental stress.

Estimating the Effective Population Size of Crassostrea virginica

Tue, 26 Jun 2012 00:00:00 GMT

Title: Estimating the Effective Population Size of Crassostrea virginica Authors: Brown, Ashley Abstract: Effective population size (Ne) is an important parameter used to estimate the magnitude of genetic drift, a major evolutionary force, that a population experiences. Across many taxa Ne is one tenth smaller on average than the census population size because of overlapping generations, uneven sex ratios, and other demographic factors that increase the variance in reproductive success. Organisms that experience high fecundity, external fertilization, and larval dispersal, like the eastern oyster (Crassostrea virginica), are hypothesized to experience “sweepstakes reproduction”, or a high stochastic variance in reproductive success among individuals, resulting in a much lower Ne relative to Ncensus. Here the objective was to further test the sweepstakes hypothesis by estimating Ne in oyster populations using two distinct, direct measures. Temporal samples of C. virginica from two eastern Florida localities were genotyped for nine microsatellite loci to estimate Ne. Effective population size was estimated using two methods, a two sample moments-based temporal estimation and a single sample linkage disequilibrium estimation. Results from both methods are consistent with Ne between 500 and 10,000. These values are similar to past studies indicating a sweepstakes reproduction hypothesis, although not as extreme of a sweepstakes reproduction as some past work has suggested. However, predicted differences for allelic diversity and Ne were not detected between cohorts of spat (early juveniles) and local adults, preventing a strong conclusion that C. virginica is in fact experiencing sweepstakes reproduction based upon the tested indicators in this study.

The 9/11 and Vietnam Veterans Memorials: Interpreting Experience in the Landscape of Loss

Tue, 26 Jun 2012 00:00:00 GMT

Title: The 9/11 and Vietnam Veterans Memorials: Interpreting Experience in the Landscape of Loss Authors: Durgerian, Laura Abstract: Experiential memorials are agents of memory, constructing experiences for visitors that evoke memory, emotion, and thought. This project begins by defining the ‘language of loss’ and exploring the role of memorials through a literature review. It then investigates two seminal built memorials in order to gain a fuller understanding of how each employs this language of loss. Research into the contextual development of these memorials – Maya Lin’s Vietnam Veterans Memorial (1982) in Washington D.C., and Michael Arad and Peter Walker’s 9/11 Memorial (2011) in Lower Manhattan – provides a framework for interpreting each work. Following preliminary literature and design research, a series of on-site research methods were undertaken to record and map the experience of visitors to each memorial. This process intends to reveal to what degree each memorial exemplifies this definition of the experiential memorial. Research strategies included the author’s personal experience narrative, observations, photography and face-to-face interviews with visitors. Findings from this interaction, as well as interviews with knowledgeable individuals connected to each memorial, then informed a comparison of both memorials and suggestions for the design of future memorials. The findings and outcomes of this thesis aim to provide designers and scholars with knowledge of how to conceive and construct meaningful memorials that impact users and contribute to cultural memory.

Can a Text Message Influence Our Perceptions of the Physical World?: Text Messaging as a Prime for Social Support

Tue, 26 Jun 2012 00:00:00 GMT

Title: Can a Text Message Influence Our Perceptions of the Physical World?: Text Messaging as a Prime for Social Support Authors: Falisi, Angela Abstract: Previous research has found that a psychosocial resource, social support, affects a person’s perception of physical burdens, particularly the steepness of geographical slants. In fact, there is a decrease in the perceived steepness of a geographical slant when a person is in the physical co-presence of another person or after an extended period of visualization of a supportive other. The present study replicated and extended previous findings to test whether the brief activation of a supportive other by sending a text message to them affects subsequent judgments of a geographical slant. Participants who sent a text message to a friend judged a hill to be less steep than did those who were in the physical co-presence of a friend. Even after controlling for relationship duration and strength, a media effect remained. This suggests that a text message serves as a purer prime to activate the idea of a supportive other, which includes the qualities that are most relevant to the task at hand. In comparison, the prime of a physically co-present friend may elicit a broader array of qualities that might or might not be useful to the task at hand, thus diluting the effectiveness of the prime overall.

Investigations of the Source, Distribution, Expression and Physiological Function of Thiaminase I

Tue, 26 Jun 2012 00:00:00 GMT

Title: Investigations of the Source, Distribution, Expression and Physiological Function of Thiaminase I Authors: Gordon, Eric Abstract: Thiaminase I is a vitamin degrading enzyme produced by microorganisms and often found in certain metazoan animals that can cause thiamine deficiency in natural ecosystems. The physiological function of this enzyme is still unknown. We adapted a photometric assay for thiaminase I that measures the rate of disappearance of a colored co-substrate for use with a high throughput plate reader. Using this assay, we characterized the conditions that promote thiaminase I production in some thiaminase I producing microorganisms and gained evidence for and against hypotheses for various physiological functions. We also conducted surveys of diverse metazoan organisms known and not previously recognized to have thiaminase I activity and found thiaminase activity in organisms not previously known to have thiaminase activity. Research on the expression of thiaminase I has possible implications for cancer research and correction of mortality due to thiaminase-induced thiamine deficiency syndromes.