Dissertation Defenses

Doctoral students who have an upcoming dissertation oral defense are posted here. So why not take this opportunity to learn about the research that our graduate students are doing!

Dissertation Defense for Sheldon Hurst IV

Program: Microbiology: PHD

Department Contact Email: fjoyal@cisunix.unh.edu

Defense Title: Natural Products and Nematode-Microbe Interactions

Defense Date and Time: 04/25/14 12:00 pm

Defense Location: Rudman G79

Defense Advisor: Louis S. Tisa

Defense Abstract: Entomopathogenic nematodes in the family Heterorhabditidae form a specific mutualistic association with its bacterial partners of Photorhabdus sp. The growth and development of this nematode has an obligate requirement for the microbial symbiont, and recognition is strain-specific. The aim of this study was to elucidate the genome of P. temperata, identify genes that play a role in natural product production, and determine the involvement of these genes in the Photorhabdus-Heterorhabditis symbiosis. For three Photorhabdus species, genome sequences for only two species (P. luminescens and P. asymbiotica) have been established. Here, a draft genome sequence of the third species, P. temperata strain NC19 has beed determined. These data were compared to genomes of the other Photorhabdus genomes to gain insight into the symbiosis and host-pathogen associations. Also, a bank of previously generated 10,000 P. temperata transposon mutants was screened for those defective in antibiotic production. Mutants identified and confirmed were tested for symbiosis by an in vitro nematode development assay. Out of 83 antibiotic defective mutants tested 20 were altered in their symbiosis properties. The transposon insertion sites were identified for 15 mutants. Besides these mutants, the transposon insertion site for another 23 antibiotic defective mutants were identified. From these results, we have determined genes that are required for the symbiosis between Photorhabdus and Heterorhabditis, and have also identified a possible regulatory network for the production of antimicrobial natural products.


Dissertation Defense for Julia Chan

Program: Chemistry Education: PHD

Department Contact Email: cindi.rohwer@unh.edu


Defense Date and Time: 05/01/14 1:00 pm

Defense Location: Parsons Hall, Room W131

Defense Advisor: Professor Christopher F. Bauer


Julia Y.K. Chan

University of New Hampshire, May, 2014

Three research studies were conducted to monitor and understand students’ affective characteristics in the first-semester of a first-year general chemistry course. The first study investigated students’ exam achievement, attitudes, and self-concepts in a fully-randomized, experimental design, contrasting Peer-Led Team Learning (PLTL) with a control group (non-PLTL) balanced for time-on-task. Achievement was measured by exam scores and established instruments were used to assess changes in students’ affective characteristics. No differences in achievement and affective characteristics were found between the two groups. However, disaggregation by sex and class-year showed males and first-year students reported higher positive attitude, self-concept, and achievement than females and non first-year students. Overall, certain aspects of attitude and self-concept showed a slight but significant decline throughout the semester.
The second study identified academically at-risk students using a pre-selected set of affective characteristics via cluster analysis. Through the clustering of six affective variables, three distinct affective groups were delineated: low (at-risk), medium, and high. Low affective students reported lower scores on intellectual accessibility, emotional satisfaction, math self-concept, chemistry self-concept, self-efficacy, and a higher score on test-anxiety. Significant differences were found on exam performance between the

high and low affective groups with the high affective group performing significantly better than the low affective group. Furthermore, high affective students reported higher value, expectancy, and metacognitive self-regulative beliefs than low affective students.
As a follow-up to the second study, the third study looked at the extent to which students in the three clusters differ in their use of studying strategies for preparing exams and learning strategies in lecture. Students in the high affective group reported they understand the notes they take in lecture more frequently than the low group and also relied less on tutors, teaching assistants, and PLTL leaders for help when preparing for exams. Specifically, when doing a practice exam, high affective students (also high achievers) show characteristics typical of autonomous learners whereas low affective students relied less on self and more on external resources. In terms of quality time spent studying or doing chemistry-related assignments, the two groups were surprisingly indistinct. Important implications for teaching and learning are discussed.


Dissertation Defense for Matthew Cutler

Program: Sociology: PHD

Department Contact Email: deena.peschke@unh.edu

Defense Title: Seeing and Believing: The Emergent Nature of Extreme Weather Perceptions

Defense Date and Time: 06/26/14 9:00 am

Defense Location: Horton 439

Defense Advisor: Dr. Lawrence Hamilton

Defense Abstract: Perceptions of environmental issues are influenced by a variety of factors. Sociological research on this topic has largely taken a social-psychological approach and as a result the effects of community and biophysical contexts on individual perceptions are given less attention than individual-level predictors, such as political party affiliation or measures of educational attainment. Using data from the Communities and Environment in Rural America (CERA) surveys, this study will employ a mixed-effects modeling technique to investigate the influence of individual- and county-level characteristics on public perceptions of unusual or extreme weather. In addition to the survey data, this study will also utilize county-level weather events data from the National Oceanic and Atmospheric Administration's (NOAA) Storm Events Database (SED) and the Storm Prediction Center's (SPC) Severe Thunderstorm Events Archive (STSEA) in order to test whether the incidence of severe weather influences public perceptions of unusual or extreme weather. This research will add to a growing body of literature on public perceptions of environmental issues by illuminating the socio-demographic and contextual nature of individual-level perception formation through the use of integrated social and biophysical data.


Dissertation Defense for Meghan Mills

Program: Sociology: PHD

Department Contact Email: deena.peschke@unh.edu

Defense Title: The Impact of Socioeconomic Status and Goal-Striving Stress on Depression and Delinquency among Rural Youth

Defense Date and Time: 03/18/15 10:00 am

Defense Location: Carsey Institute, Huddleston Hall

Defense Advisor: Dr. Karen Van Gundy

Defense Abstract: According to the stress process framework,both socioeconomic status and goal-striving stress serve as critical chronic stressors; however, little to no research has examined the relationship between socioeconomic status, goal-striving stres, and well-being using this theoretical framework. Using longitudinal data from Waves I (2009) & II (2011) of the Rural Youth Study (RYS), my dissertation examines how goal-striving stress varies by socioeconomic status, and it investigates the impact of goal-striving stress on delinquent behaviors and depressive symptoms among rural youth over time, and net of crucial components of the stress process framework (i.e., stressful life events, family attachment, and personal resources). More specifically, my research examines the unique effects of educational, occupational, and community goal-striving stress as well as the effects of a combined measure of overall goal-striving stress.
Analyses reveal a significant negative relationship between socioeconomic status and depressive symptoms, but this relationship is mediated by family attachment. Controlling for prior depressive symptoms, only a significant positive relationship between community goal-striving stress and depressive symptoms remains. However, with regard to delinquent behaviors, educational, community, and overall goal-striving stress are significantly positively related to delinquent behaviors net of prior delinquency. Such findings remain even with statistical adjustments for socioeconomic status, stressful life events, family attachment, and personal resources.
The findings of my dissertation illustrate the importance of considering various types of goal-striving stress and considering their unique effects on different outcomes. My findings highlight the importance of a "new" type of goal-striving stress among rural youth, community goal-striving stress. Additionally, my findings indicate that goal-striving stress may be especially important for understanding the unequal social distribution of outcomes such as delinquency that are not as clearly or directly associated with socioeconomic status. Such findings highlight the important role of the stress process framework for understanding socioeconomic disparities in outcomes. In sum, goal-striving stress is a critical topic for future research using the stress process framework with important policy implications for improving the well-being of rural youth.


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