The Role of the Dorsal Hippocampus in the Contextual Control of Appetitive Responding
Year of Dissertation:
2011
Four experiments were run using rat subjects in order to assess the impact of manipulations to the dorsal hippocampus (DH) on the contextual and temporal control of extinguished appetitive learning (e.g., magazine approach). Subjects were trained to associate discrete stimuli with food in specific locations or at specific times. The subjects then had these associations extinguished by means of omitting the food reinforcers following stimulus presentations. In order to assess contextual and temporal modulation of learning the stimuli were tested within as well as outside of the contexts or times where/when they were extinguished. Control subjects showed reduced responding when stimuli were presented within their extinction contexts (physical and temporal) whereas responding recovered outside of these extinction contexts (i.e., renewal and spontaneous recovery). In order to assess DH function in these different instances of response recovery, neurotoxic lesions of the DH prior to tests or temporary muscimol-induced inactivation of the structure were used. The results of these studies indicate that while DH manipulations fail to affect conditional control of appetitive extinction learning by physical contexts, they do impair control when temporal contexts are used as a conditional cue.
The role of apoptosis and mitosis in LDL transport across endothelial cell monolayers
Year of Dissertation:
2010
We have previously shown that leaky junctions associated with dying or dividing cells are the dominant pathway for LDL transport under convective conditions in vitro, accounting for more than 90% of the transport. To explore the role of apoptosis in the leaky junction pathway, TNFα and cycloheximide (TNFα/CHX) were used to induce an elevated rate of apoptosis in cultured bovine aortic endothelial cell (BAEC) monolayers and the convective fluxes of LDL and water were measured. Control monolayers had an average apoptosis rate of 0.30%. Treatment with TNFα/CHX induced a 18.3-fold increase in apoptosis and a 4.4-fold increase in LDL permeability (Pe). Increases in apoptosis and permeability were attenuated by treatment with the caspase inhibitor Z-VAD-FMK. Water flux (Jv) increased by 2.7-fold after treatment with TNFα/CHX, and this increase was not attenuated by treatment with Z-VAD-FMK. Immunostaining of the tight junction protein ZO-1 showed that TNFα/CHX treatment disrupts the tight junction in addition to inducing apoptosis. This disruption is present even when Z-VAD-FMK is used to inhibit apoptosis, and likely accounts for the increase in water flux. We found a strong correlation between the rate of apoptosis and the permeability of BAEC monolayers to LDL.
The Ethical Pact: Storytelling in Contemporary Autobiography
Year of Dissertation:
2012
Program:
Comparative Literature
Abstract
The American Teacher Memoir: From Confessions to the Inspirational True Story
Year of Dissertation:
2012
Over 225 American teachers have published autobiographies that recount their lives in public school classrooms, but the teacher memoir, as a literary genre, has yet to receive sustained scholarly consideration. Since at least the beginning of the common school movement in the 1830s, a movement that is chronicled by the first teacher memoirist William Alcott in his aptly named Confessions of a School Master (1839), Americans have put enormous faith in the power of schooling to create an educated citizenry that can sustain a functional democracy. Teacher memoirs combine with portrayals by historians, administrators, policymakers, and scientists to assess the success or failure of education, which is often entangled with the perceived success or failure of America itself. I read teacher memoirs in the context of educational policy and literary history to demonstrate how the cultural climate in a given era shaped the way in which teachers narrated their experiences, and, in turn, how the memoirs influenced educational debates. This study raises complex questions about the political efficacy of literary texts, contributes to discussions within autobiography theory of the ethical considerations of life writing, and enriches historical narratives of teaching and learning.
Perceptions of Community Corrections: Understanding how Women's Needs are met in an Evidence-Based/Gender-Responsive Halfway House
Year of Dissertation:
2011
This dissertation presents a qualitative study on how women perceive and experience services at an evidence-based, gender-responsive halfway house. The primary focus was to understand how the halfway house helps women address their needs as they prepare to reenter the community. The secondary focus was to understand how the halfway house implements evidence-based principles and gender-responsive strategies. This study analyzed in-depth qualitative interviews with 33 women. Data from these interviews were triangulated with observations of treatment groups and daily interactions, review of program documents, review of participant case files, and informal conversations with staff. Findings suggest that many positive and negative features of the halfway house - including social context, relationships with staff, and program policies - contribute to women's ability to address their needs and prepare for reentry. Findings also draw attention to the influence of external factors including outside resources, social networks, housing availability, the stigma of a criminal record, systemic policies, geographic boundaries, and program length of stay. The interconnections between ecological systems also influence the transitional process and were highlighted in this study. Recommendations for improving community correctional services for women were discussed.
THEORETICAL MODELING OF ELECTROMECHANICAL COUPLING BEHAVIOR OF FERROELECTRICS AND THEIR COMPOSITES
Year of Dissertation:
2009
The aim of this dissertation is to develop suitable theoretical models to study the physical properties of ferroelectrics in terms of temperature and size, and the nonlinear electromechanical coupling behavior of ferroelectrics and their composites under the different loading conditions. Three different models are introduced following applicable scale ranges. First, Texture and Anisotropy theory is used to model nonlinear behaviors of piezoelectric poly-crystals (Taylor-Bishop-Hill like model) without considering interaction between grains or domains. It is suitable in macro-scale range and can be used on both polycrystals and single crystals. Second, a micromechanics approach based on irreversible thermodynamic principle and morphology of spontaneous polarization and domain switch has been extended to study the temperature effects on BaTiO3 single crystals and further for electromechanical coupling behavior of ferroelectric composites by considering the microstructure of the system. The micromechanics approach reaches its limitation when the material size reduces to nano-scale. Finally, Ginzburg-Landau theory has been chosen to determine BaTiO3 nanowire behaviors under external loading. This powerful phenomenological method was originally developed for macro scale. Here we extend the model to be applicable at nano-scale range and study the polarization field and transition temperature in terms of the size of ferroelectric nanowires. The advantages and disadvantages of each model are discussed. All three models are also compared and verified by existing experiments.
Design of Large Pore Ordered Mesoporous Silicas, Related Silica/Polymer Composites and Carbon Replicas
Year of Dissertation:
2010
This dissertation includes four chapters, namely, the introduction to development and current research interests in mesoporous materials, the "soft-templating" synthesis of large pore 2-D hexagonal ordered mesoporous silicas, the synthesis of mesoporous polymer/silica composites via surface-initiated controlled polymerization, and the "hard-templating" method to fabricate ordered mesoporous carbons.
Aggregation and Gelation of Silica Nanoparticles
Year of Dissertation:
2011
The gelation mechanism was explored in a comprehensive way both experimentally and numerically. The gelation dynamics of a sol of colloidal silica of approximately 7 nm radius particles is studied using a combination of light scattering and rheometry. By changing the ionic strength (by addition of a salt solution resulting in different ultimate molarities) of the mixture, a stable sol can be destabilized, leading to aggregation and later gelation. The gel time t gel can be varied from hours to weeks, indicating a reaction-limited aggregation process. Static light scattering is used to extract the fractal dimension D f of the aggregates, which is found to be approximately 2. The evolution of cluster size is probed by dynamic light scattering, and follows an exponential growth. Rheometry is used to assess the gelation time and further development of the network strength after gelation. The elastic modulus (G' ) is found to scale as G' ~ &phi3.3, where &phi is the silica particle volume fraction. It was observed that the gel time (after salt solution addition) depends on both the particle volume fraction and salt concentration, showing a divergence at low volume fraction or low salt concentration. For a single solid fraction, data for the cluster hydrodynamic radius, normalized by the single particle radius, from experiments with a wide range of gel times can be collapsed onto a master curve when the time after the salt addition, t , is scaled as t/tgel; a similar collapse of viscosity and the linear viscoelastic data after gelation can be obtained using the same scaling of time. Salt concentration affects the gel time but not the strength of the gel network, thus allowing very accurate prediction of network formation times and mechanical properties.
Vascular Endothelia Growth Factor and its Receptor VEGFR2 Regulate Synaptic Protein Levels in Rat Hippocampal Neurons
Year of Dissertation:
2012
Advisor:
Patricia Rockwell
Vascular endothelial growth factor (VEGF) is a well-established angiogenic factor which also elicits protective and stimulatory effects on neuronal function. Recent studies suggest that VEGF signaling plays a critical role in modulating synaptic plasticity and enhances excitatory synaptic transmission in the hippocampus. Other growth factors including brain-derived neurotrophic factor (BDNF) and insulin have been shown to regulate synaptic ¬¬¬protein levels to stimulate neural communication but it remains unclear how VEGF participates in synapse function at the molecular level. The notion that VEGF would also modulate synaptic protein levels in differentiated hippocampal neurons has not been explored. Therefore, this work addressed whether VEGF exhibits neurotropic properties in mature rat hippocampal neurons by modulating the postsynaptic protein PSD-95 and protecting against the stress induced by nutritional deprivation. The results show that VEGF signals an increase in cell viability and increases the levels of presynaptic (synaptophysin and synapsin I) and postsynaptic (PSD-95) proteins through its cognate receptor VEGFR2. VEGF signals these events via autocrine and paracrine mechanisms. Moreover, VEGF regulates PSD-95 protein levels and synapse numbers along dendrites through the PI3K/Akt/mTOR pathway. Additional studies showed that inhibition of the Rho-associated protein kinase (ROCK) increased PSD-95 protein levels which were attenuated by VEGFR2 inhibition. Furthermore, ROCK inhibition enhanced VEGF-mediated synapse formation, survival and neurite extension. Accordingly, these findings suggest that ROCK serves as a negative regulator of VEGF signaling in mature primary hippocampal neurons. Collectively, this study revealed a novel signaling mechanism for VEGF/VEGFR-2 pathway that may function in its reported capacity to stimulate synaptic transmission. These findings implicate VEGF signaling as a potential therapeutic strategy to prevent or hinder synaptic loss in neurodegenerative disorders.
Horava Gravity: Symmetries and Generalized Particle Dynamics
Year of Dissertation:
2011
Advisor:
Alexios Polychronakos
In the search for a theory of Quantum Gravity a new proposal was recently made by P. Horava. The main feature of this new proposed theory is that it is power-counting renormalizable by construction, and could prove to be truly renormalizable, although more work is needed in this direction.