Digital Commons Network^™

Experimental Evolution Of Burkholderia Cenocepacia Biofilm Populations, Steffen R. Poltak

Doctoral Dissertations

Many biofilm populations are known for their exceptional biodiversity but the relative contributions of the forces that could promote this diversity are poorly understood. This uncertainty pervades in the well-established communities found on many natural surfaces and in long-term, chronic infections. Here we describe the parallel evolution of cooperative communities derived from a clone of Burkholderia cenocepacia during approximately 1500 generations of biofilm selection. This long-term evolution was enabled by a new experimental method that selects for daily cycles of colonization, biofilm assembly, and dispersal. Each of six replicate biofilm populations underwent a common pattern of adaptive morphological diversification, in …

The Role Of Personal And Contextual Variables In College Students' Academic Achievement, Rachel A. Rogers

Doctoral Dissertations

College matriculation rates are increasing but graduation rates are failing to parallel the increased enrollment. One reason for this discrepancy may be that many college students are unable to regulate their own learning. This dissertation examined the Self-Regulated Learning (SRL; Pintrich, 2004) model in students taking Statistics in Psychology and Research Methods. The inclusion of the constructs of possible selves and identity development in the SRL model was proposed, as was the Achievement Goal Questionnaire (AGQ; Elliot & McGregor, 2001), a measure of the 2x2 Framework of achievement goal orientation. These variables were assessed along with those included in the …

Effects Of Physical And Chemical Disturbance On Stream Ecosystem Structure And Function, Elena M. Traister

Doctoral Dissertations

A variety of natural and anthropogenic disturbances influence the structure and function of stream ecosystems. While past investigations have focused on the response of community indicators to stream disturbances, functional indicators may also be helpful for assessing stream ecosystem health. To date, few studies have compared the response of structural and functional indicators to ecosystem-level disturbances. I separately measured the effects of long-term acidification, a large-scale avulsion, and the individual and combined effects of physical streambed disturbance and altered refugia availability on stream structural and functional metrics.

I found that acidification was associated with changes in macroinvertebrate communities including reduced …

Creek Diplomacy In An Imperial Atlantic World, Deena L. Parmelee

Doctoral Dissertations

"Creek Diplomacy in an Imperial Atlantic World," argues that Creek leaders saw opportunities for Creek peoples to play an important political and economic role in the Atlantic world even while the Confederacy itself was still forming. This study explores Creek participation in the Atlantic world in two ways. First, it traces Creek diplomatic travel to European centers. Second, it examines Creek reception of European traders and diplomats in Creek towns. In this way, it traces Creek diplomacy in its external and internal forms, as Creeks moved outward to establish diplomatic relations with others, and dealt with outsiders who came to …

Learning Systems: An Ecological Perspective On Advanced Academic Literacy Practices Of Multilingual Writers, Steve Simpson

Doctoral Dissertations

Recent work in composition's leading journals has challenged the field's exclusive focus on native English speakers and has called for a more international perspective on writing research and pedagogy. This dissertation, which grew from requests from multilingual graduate students in my own institution for more advanced academic writing support, extends this call to explore ways writing programs can better account for the needs of international graduate students, a growing population in US institutions. The role English has assumed as the lingua franca of international academic communication has made writing in English a critical skill for these students' professional development. In …

Hyperpolarized Xenon-129 Magnetic Resonance Imaging Of Functional Lung Microstructure, Isabel Dregely

Doctoral Dissertations

Hyperpolarized 129Xe (HXe) is a non-invasive contrast agent for lung magnetic resonance imaging (MRI), which upon inhalation follows the functional pathway of oxygen in the lung by dissolving into lung tissue structures and entering the blood stream. HXe MRI therefore provides unique opportunities for functional lung imaging of gas exchange which occurs from alveolar air spaces across the air-blood boundary into parenchymal tissue. However challenges in acquisition speed and signal-to-noise ratio have limited the development of a HXe imaging biomarker to diagnose lung disease.

This thesis addresses these challenges by introducing parallel imaging to HXe MRI. Parallel imaging requires dedicated …

Updated Life History And Population Structure Assessment Of Spiny Dogfish, Squalus Acanthias, In The Gulf Of Maine, Walter Bubley

Doctoral Dissertations

Spiny dogfish (Squalus acanthias) are considered to be the most abundant shark species in the Western North Atlantic, but recently there was a decline in biomass estimates following a nearly ten-fold increase in fishery landings. Because fishing pressure has been shown to affect population dynamics in targeted species, an update of previous life history parameters is warranted to effectively manage the population. Although updated and accurate life history parameters are important, it is crucial that these parameters are applied to the correct populations, especially when there is evidence of population structuring in the Western Atlantic. This comprehensive study addressed the …

Conjecturing In Dynamic Geometry: A Model For Conjecture-Generation Through Maintaining Dragging, Anna Baccaglini-Frank

Doctoral Dissertations

The purpose of this research is to study aspects of the impact of Dynamic Geometry Systems (DGS) in the process of producing conjectures in Euclidean geometry. Previous research has identified and classified a set of dragging schemes spontaneously used by students. Building on these findings, the study focuses on cognitive processes that arise in correspondence to particular dragging modalities in Cabri. Specifically, we have conceived a model describing what seems to occur during a process of conjecture-generation that involves the use of a particular dragging modality, described in the literature as dummy locus dragging. In order to accomplish this goal, …

The Effects Of Didemnum Vexillum Overgrowth On Mytilus Edulis Biology And Ecology, Linda Ann Auker

Doctoral Dissertations

Didemnum vexillum is an invasive colonial ascidian in the Gulf of Maine that readily colonizes hard substrates. These substrates include hard-shelled organisms, such as the common blue mussel Mytilus edulis. Preliminary observations and short-term studies showed potential effects of epibiosis on M. edulis growth, specifically lip thickness and tissue index. This dissertation study further examined the effects of D. vexillum on growth and reproduction of, and predation on, M. edulis. Shell thickness index, tissue index, shell mass to tissue mass ratio, lip thickness and mussel length were measured throughout a 12-month period in control and overgrown mussels. Additionally, histological preparations …

Violent Video Game Exposure And Physical Aggression In Adolescence: Tests Of The General Aggression Model, Donald Bucolo

Doctoral Dissertations

The General Aggression Model indicates that long term exposure to violent video games increases aggression by altering players' aggressive personality (Anderson & Bushman, 2002). In this dissertation, cross-sectional and longitudinal tests of this mediated relation were conducted to determine if violent video game exposure had a direct effect on physical aggression as well as a direct effect via pathways through trait aggression (Buss & Perry, 1992) and normative status (Cohn & White, 1990). A category-based scale assessing violent video game exposure (Trinkner, Bucolo, Cohn, Rebellon, & Van Gundy, 2009) was used as the independent variable and a self-report measure of …

Trematode Parasites Of The Mudsnail Ilyanassa Obsoleta: An Analysis Of Parasite Communities At Different Scales, Irit Altman

Doctoral Dissertations

This research examines the ecological factors that shape trematode parasite communities of mudsnail Ilyanassa obsoleta at three different spatial scales. Nine species of trematode which obligately infect I. obsoleta during larval stages but use numerous estuarine species as second intermediate and definitive hosts are considered. The work provides the most geographically extensive examination to date of this trematode parasite community.

At the broadest scale, I. obsoleta trematodes were examined across their distributional range (Chapter 2) which includes both native and introduced populations. The results demonstrate that introduced trematode communities are characterized by lower abundance and diversity compared to native communities …

Microstructural Evolution Of Sputtered Phase Segregated Metal Composite Thin Films, Dana I. Filoti

Doctoral Dissertations

In this thesis, we present the first comparative study of crystallographic texture development in three different types of metal thin film composites: fully miscible (Au-Ag), slightly immiscible (Cu-Ag) and immiscible (Au-SiO 2). Texture development refers to the distribution of orientations of crystallites in polycrystalline thin films, and is an important part of the microstructure that determines thin film properties. A material's crystallographic texture needs to be understood because of its sensitivity to the energetic growth conditions. By controlling the microstructure, a material can be tailored to specific applications. We investigated in comparison the texture and microstructure evolution in metal composite …

Educator Perceptions Of Policies That May Impact Black Male High School Persistence, L Antonio Henley

Doctoral Dissertations

This study purposed to identify educators' perceptions about the academic state of Black males, explore the influence of policies on Black males' high school persistence, and examine differences in educator perceptions with regards to the impact of education policies on African American males. Findings indicate that educators believe that Black males are doing poorly academically and educators are concerned about the academic progress of Black males. Also, educators do not to believe that the majority of policies identified in this research have any significant impact on the high school persistence of Black males. Further, there are significant differences in educators' …

The Reminiscence Bump In Autobiographical Memory: An Investigation Of The Life Script Hypothesis, Ryan Alexander Dickson

Doctoral Dissertations

Researchers have consistently found that older adults report a higher percentage of autobiographical memories for experiences that occurred between ages 15 and 30 compared to any other period of life. This reminiscence bump is evident for memories involving positive emotions but not for memories involving negative emotions. The life script hypothesis proposes that people share cultural knowledge for the types and timing of positive landmark events expected to occur over the life course and that this shared knowledge guides the retrieval of autobiographical memories. In a series of five studies, the valence (positive and negative) and expectedness (not surprising and …

Ratiometric Fluorescent Metal Ion Indicators Based On Functionalized Poly(N -Isopropylacrylamide), Jie Du

Doctoral Dissertations

A novel type of ratiometric fluorescent indicator based on the phase transition of a well-known stimuli-responsive polymer poly(N-isopropylacrylamide) (PNIPAM) is presented. The sensing mechanism involves the polymer conformational change resulting from charge neutralization by the analyte metal ions. The ultimate goal is to develop ratiometric fluorescent indicators for free Cu(II) in environmental water analysis.

The indicators are copolymers of N-isopropylacrylamide (NIPAM) with small percentages of fluorophores and ligand monomers. The charges on the ligands prevent PNIPAM from collapsing unless neutralized upon metal ion chelation. The polymer phase transition is transduced by either fluorescence solvatochromism or fluorescence resonance energy transfer (FRET), …

Navigating The Cultural Gaps: Whiteness And Diversity In Two Elementary School Classrooms, Rachel Parse Johnson

Doctoral Dissertations

This study asked how two white, in-service elementary school teachers within the context of their classrooms navigated the cultural gaps between themselves and students from whom they differed (e.g. racially, ethnically, socio-economically, and/or linguistically). Three sub-questions examined: 1) what life experiences shaped how the teachers understood difference and diversity within their classrooms; 2) what system(s) of beliefs the teachers learned and constructed through those experiences; and 3) what identities the teachers assumed and/or assigned to themselves and their students. The study employed a sociocultural theoretical framework. Ethnographic data collection strategies included participant observation, semi-structured interviews, and material collection. Discourse analysis …

Movement And Behavior Of Ocean Sunfish, Mola Mola, In The Northwest Atlantic, Inga F. Potter

Doctoral Dissertations

The ocean sunfish, Mola mola, has a worldwide distribution and is a common resident of the NW Atlantic Ocean. Notable for its unusual anatomy and large size, the biology of the species is largely unknown. I examined the movement and behavior of M. mola using pop-up satellite archival tags (PSAT's). In addition, analysis of aerial survey data was conducted to determine the distribution of ocean sunfish (Family Molidae) in NW Atlantic shelf waters. Data was analyzed from twenty-five PSAT's deployed on M. mola in the northwest Atlantic between 2005 and 2008. Tags were attached from 7-242 days. Results indicate that …

Spatial Management Of Groundfish Resources In The Gulf Of Maine And Georges Bank, Jamie Marie Cournane

Doctoral Dissertations

In the marine environment, studies suggest that overfishing suppresses sustainability and resilience in fish populations. In the 1990s, the National Marine Fisheries Service (NMFS) implemented five large year-round fishery closures in the Gulf of Maine and Georges Bank. These closures are partially protected marine protected areas (MPAs) restricting commercial fishing with bottom-tending gears. To date, evaluation of their performance has focused on the productivity of individual species.

This research aims to understand if fish biodiversity changed after implementation of the five large fisheries closures. Here, a variety of datasets and statistical approaches are used.

Modern patterns constructed from NMFS bottom-trawl …

Factors Regulating The Production Of Stx-2 In Escherichia Coli O157:H7, Kate P. Stefani

Doctoral Dissertations

The severity of Escherichia coli O157:H7 disease is due in part to a major virulence factor produced by the microbe, the shiga-like toxin 2 (Stx-2). Antibiotic treatment to reduce pathogen numbers is controversial, as it is thought that antibiotics may increase the levels of Stx-2 released from the pathogen. Currently, recommended treatment for E. coli O157:H7 is palliative The purpose of this study was to examine three critical factors potentially important to disease outcomes, and to determine their effect on expression of the stx2 gene and on release of Stx-2 from the pathogen. Those factors selected for study were: (i) …

Somatic Condition, Growth And Distribution Of Atlantic Bluefin Tuna (Thunnus Thynnus) In The Gulf Of Maine, Walter J. Golet

Doctoral Dissertations

Atlantic bluefin tuna (Thunnus thynnus), a highly migratory apex predator, utilize temperate feeding grounds to place their tissues into positive lipid balance following reproduction and subsequent migration to northern latitudes. Commercial fishermen target Atlantic bluefin tuna between June and October, but landings have declined 70% from 2004-2009 suggesting adult bluefin tuna may no longer be utilizing the Gulf of Maine as a foraging ground. A series of linear and additive models fitted to multiple fishery dependent datasets identified significant declines in the somatic condition of Atlantic bluefin tuna in the Gulf of Maine. Significant changes in the somatic condition of …

Comprehension Of Protagonists' Goals And Intentions: The Dynamic Relation Between Reading Skill, Text Characteristics, And Reading Strategies, Jennifer J. Stiegler

Doctoral Dissertations

Studies by the National Assessment of Educational Progress (NAEP, 2009) indicate that the inability to comprehend text is one of the primary reasons students perform poorly in school Reading difficulties often persist into adulthood with 23% of U.S. adults only meeting basic reading proficiency levels (NCES, 2004). To address this problem, it is critical to identify the underlying cognitive processes that pose the greatest challenges to struggling readers. Recent research has explored basic skills (e.g., working memory capacity, suppression mechanisms, domain knowledge, and reading strategies) that have been shown to be essential for reading. To date it is unclear which …

From Biosphere To Noosphere: Vladimir Vernadsky's Theoretical System As A Conceptual Framework For Universal Sustainability Education, Irina L. Trubetskova

Doctoral Dissertations

In light of accelerating global warming and climate change, the importance of sustainability education is unquestionable. It is a requirement of our time that sustainability education must become a part of any professional curriculum in higher education because today's college students are tomorrow's decision makers and the key players at local, national, and international levels.

Although the importance of education for a sustainable future has been recognized by the global community and we are now living through the United Nations Decade of Education for Sustainable Development (2005-2014), a common conceptual approach to teaching sustainability does not exist. We face a …

Land Development In Massachusetts: Its Effect On The Environment Within Essex And Middlesex Counties From 1990 To 2007, Peter Sean Tardie

Doctoral Dissertations

Since the 1970's urban centers in and surrounding Essex and Middlesex Counties in Massachusetts have expanded and proliferated into adjacent communities. This expansion has led to the conversion of land for housing, businesses, schools, recreation, and parks, placing significant strain on existing land cover, land use, and available natural resources. Mounting growth pressures and a reduction of undeveloped land have raised serious concerns as cropland and forest fragmentation, wetland destruction, protected open-space infringement, pollution, and systematic losses of rural conditions have become obvious. To monitor development, the post-classification change detection method was applied to Landsat Thematic Mapper (TM) satellite data …

Using Lidar-Derived Vegetation Profiles To Predict Time Since Fire In An Oak Scrub Landscape In East-Central Florida, James J. Angelo, Brean W. Duncan, John F. Weishampel

Faculty Bibliography 2010s

Disturbance plays a fundamental role in determining the vertical structure of vegetation in many terrestrial ecosystems, and knowledge of disturbance histories is vital for developing effective management and restoration plans. In this study, we investigated the potential of using vertical vegetation profiles derived from discrete-return lidar to predict time since fire (TSF) in a landscape of oak scrub in east-central Florida. We predicted that fire influences vegetation structure at the mesoscale (i.e., spatial scales of tens of meters to kilometers). To evaluate this prediction, we binned lidar returns into 1m vertical by 5 x 5 m horizontal cells and averaged …

Sexual Signal Evolution Outpaces Ecological Divergence During Electric Fish Species Radiation, Matthew E. Arnegard, Peter B. Mcintyre, Luke J. Harmon, Miriam L. Zelditch, William G. R. Crampton, Justin K. Davis, John P. Sullivan, Sébastien Lavoué, Carl D. Hopkins

Faculty Bibliography 2010s

Natural selection arising from resource competition and environmental heterogeneity can drive adaptive radiation. Ecological opportunity facilitates this process, resulting in rapid divergence of ecological traits in many celebrated radiations. In other cases, sexual selection is thought to fuel divergence in mating signals ahead of ecological divergence. Comparing divergence rates between naturally and sexually selected traits can offer insights into processes underlying species radiations, but to date such comparisons have been largely qualitative. Here, we quantitatively compare divergence rates for four traits in African mormyrid fishes, which use an electrical communication system with few extrinsic constraints on divergence. We demonstrate rapid …

Effects Of Simulated Mars Conditions On The Survival And Growth Of Escherichia Coli And Serratia Liquefaciens, Bonnie J. Berry, David G. Jenkins, Andrew C. Shuerger

Faculty Bibliography 2010s

Escherichia coli and Serratia liquefaciens, two bacterial spacecraft contaminants known to replicate under low atmospheric pressures of 2.5 kPa, were tested for growth and survival under simulated Mars conditions. Environmental stresses of high salinity, low temperature, and low pressure were screened alone and in combination for effects on bacterial survival and replication, and then cells were tested in Mars analog soils under simulated Mars conditions. Survival and replication of E. coli and S. liquefaciens cells in liquid medium were evaluated for 7 days under low temperatures (5, 10, 20, or 30 degrees C) with increasing concentrations (0, 5, 10, or …

Multistate Modeling Of Habitat Dynamics: Factors Affecting Florida Scrub Transition Probabilities, David R. Breininger, James D. Nichols, Brean W. Duncan, Eric D. Stolen, Geoffrey M. Carter, Danny K. Hunt, John H. Drese

Faculty Bibliography 2010s

Many ecosystems are influenced by disturbances that create specific successional states and habitat structures that species need to persist. Estimating transition probabilities between habitat states and modeling the factors that influence such transitions have many applications for investigating and managing disturbance-prone ecosystems. We identify the correspondence between multistate capture-recapture models and Markov models of habitat dynamics. We exploit this correspondence by fitting and comparing competing models of different ecological covariates affecting habitat transition probabilities in Florida scrub and flatwoods, a habitat important to many unique plants and animals. We subdivided a large scrub and flatwoods ecosystem along central Florida's Atlantic …

Systematic Identification Of Conserved Motif Modules In The Human Genome, Xiaohui Cai, Lin Hou, Naifang Su, Haiyan Hu, Minghua Deng, Xiaoman Li

Faculty Bibliography 2010s

Background: The identification of motif modules, groups of multiple motifs frequently occurring in DNA sequences, is one of the most important tasks necessary for annotating the human genome. Current approaches to identifying motif modules are often restricted to searches within promoter regions or rely on multiple genome alignments. However, the promoter regions only account for a limited number of locations where transcription factor binding sites can occur, and multiple genome alignments often cannot align binding sites with their true counterparts because of the short and degenerative nature of these transcription factor binding sites. Results: To identify motif modules systematically, we …

Weak Antiferromagnetic Coupling In Molecular Ring Is Predicted Correctly By Density Functional Theory Plus Hubbard U, Shruba Gangopadhyay, Artëm E. Masunov, Eliza Poalelungi, Michael N. Leuenberger

Faculty Bibliography 2010s

We apply density functional theory with empirical Hubbard U parameter (DFT+U) to study Mn-based molecular magnets. Unlike most previous DFT+U studies, we calibrate U parameters for both metal and ligand atoms using five binuclear manganese complexes as the benchmarks. We note delocalization of the spin density onto acetate ligands due to pi-back bonding, inverting spin polarization of the acetate oxygen atoms relative to that predicted from superexchange mechanism. This inversion may affect the performance of the models that assume strict localization of the spins on magnetic centers for the complexes with bridging acetate ligands. Next, we apply DFT+U methodology to …

Detection Of Multidecadal Changes In Uvb And Total Ozone Concentrations Over The Continental Us With Nasa Toms Data And Usda Ground-Based Measurements, Zhiqiang Gao, Wei Gao, Ni-Bin Chang

Faculty Bibliography 2010s

Thinning of the atmospheric ozone layer leads to elevated levels of Ultraviolet-B (UVB) at the Earth's surface, resulting in an increase of health risks to living organisms due to DNA damage. This paper examines the multidecadal changes of total column ozone from 1979 to 2005 with the aid of ground-based UVB stations using the ultraviolet multifilter rotating shadow-band radiometer (UV-MFRSR). For the purpose of demonstration, four USDA ground stations, WA01, CO01, MD01, and AZ01, were selected for detailed comparisons against the satellite data. The major finding of this study is that over the course of the time series, on a …