Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item The Chick or the Egg? Multi-Group, Short-Term Longitudinal Relations Between Grit and Literacy Achievement(2019) Boyars, Michal Yablong; O'Neal, Colleen R; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The impact of grit on achievement is well established, but it is unclear whether achievement impacts grit. This short-term longitudinal study examined the direction of relations between grit and literacy among diverse elementary school student groups. Most grit research features a unidirectional design (e.g., grit affects achievement). Yet, recent research supports cross-lagged models in which socioemotional skills and achievement affect one another. In addition to testing cross-lagged effects, this study examined the direction of grit-literacy relations for different demographic groups (i.e., age, gender, and dual language status). Method: Participants included upper elementary students (N = 396; 3 schools; Mage = 9.61; 55% female; 59% dual language learners; 11% Black, 6% Asian, 29% Latino/a, 8% Multiracial; 39% White). Measures were student-reported grit, teacher-reported grit, and a student literacy achievement performance task (Test of Silent Reading Efficiency and Comprehension, TOSREC). Analytic Approach: An autoregressive cross-lagged design included two time points over 4 months. A cross-lagged model was compared to unidirectional models (i.e., direct and reverse) for best fit. Multi-group analyses were then used to examine whether grit-literacy relations differed as a function of demographics. Results: The data fit the cross-lagged model better than the direct or reverse models. Within the context of a cross-lagged model – which contained both the direct and reverse effects – there was a significant relation between Time 1 literacy achievement and Time 2 student-reported Grit-PE, suggesting that literacy achievement can predict later Grit-PE. There were no demographic differences in the fit of the data with the cross-lagged model between gender, DLL status, and age groups. Findings of the current study support the examination of reciprocal effects in grit-literacy relations and its generalizability among students. Longer-term cross-lagged studies are needed to further understand the temporal sequence between grit and literacy.Item ALGAL TOXICITY AND FORMATION OF HALOGENATED ORGANIC COMPOUNDS IN BALLAST WATER AFTER OXIDATIVE TREATMENT(2019) Ziegler, Gregory; Tamburri, Mario N; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Ballast water plays a vital role in the stabilization and operations of modern ships, and it is estimated that 3 to 5 billion tons of ballast water are transferred around the world each year. However, the discharge of ballast water has led to the release of non-indigenous species, and costly and ecologically damaging biological invasions. To combat this serious problem, ballast water discharge is now regulated and ballast water management systems (BWMS) have been developed to meet required discharge limits for the release of live organisms. The most common BWMS rely on chlorination of ballast water to kill planktonic organisms but also result in the formation of disinfection by-products (DBPs) and the potential for aquatic toxicity. The research in this thesis was conducted to advance the understanding of treated ballast water toxicity, and to document the formation of higher molecular weight DBPs using ultrahigh resolution mass spectrometry. Research was conducted with commercial BWMS that were based on either direct chlorination (Ch. 2 & 3) or in-situ electrochlorination (Ch. 2 & 4). Ballast water treatment was conducted in estuarine waters of the Port of Baltimore (Patapsco River, Maryland). In Chapter 2, I tested the algal toxicity of discharged ballast water from four BWMS at the time of discharge and monthly thereafter, showing the longevity of the toxic effect of treated water on micro algae. In Chapters 3 and 4, I used ultrahigh resolution mass spectrometry to identify the molecular composition of dissolved organic matter (DOM) and halogenated DBPs after oxidative treatment of ballast water. By comparing samples before and after direct chlorination, I was able to document the changes in dissolved organic matter and the formation of numerous halogenated DBPs (Ch. 3). In Chapter 4, I was able to document the change in brominated DBPs after a period of 92 days, showing the relative persistence of dibrominated compounds. This work together demonstrates that use of traditional water treatment to solve one environmental problem may, in fact, cause other unintended consequences to aquatic ecosystems.Item An Analysis of Institutional Characteristics that Contribute to Extended Time to Doctoral Degree(2013) Frasier, Helen Schurke; O'Meara, KerryAnn; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Title of dissertation: AN ANALYSIS OF INSTITUTIONAL CHARACTERISTICS THAT CONTRIBUTE TO EXTENDED TIME TO DOCTORAL DEGREE Helen Schurke Frasier, Doctor of Philosophy, 2013 Dissertation directed by: Professor KerryAnn O'Meara Department of Counseling, Higher Education, and Special Education Many factors--individual, departmental and institutional--have been associated with longer time to degree and progress toward degree completion. Lengthy time to degree affects the availability of resources, advising, persistence, and degree completion. This research identified institutional characteristics that impacted extended time to degree, relative to discipline, in doctoral programs. The data were drawn from three years of Survey of Earned Doctorates (SED) data--2004, 2005, and 2006--and the National Research Council's (NRC) 2010 A Data-based Assessment of Research-Doctorate Programs in the United States. The sample included 18,545 student records representing 58 different fields. Extended time to doctoral degree was defined as completion equal to or greater than one standard deviation beyond the Mean, relative to discipline. The study employed descriptive statistics, Hierarchical linear models, and Analysis of Variance models to test nested student and field data against targeted independent variables in each of nine categories: socio-demographic factors, student qualities and time to degree factors, discipline and institution factors, financial support factors, support and training factors, process and procedure factors, program environment factors, research environment factors, and selectivity factors. Key findings include writing the dissertation as a critical point for reform in doctoral programs to reduce time to degree for early, average and extended completers. Relationships between diverse students, diverse faculty, and the research environment impact time to degree differently for early, average, and extended completers, which requires additional research. Child dependents increased time to degree for all completers, and primary source of support had mixed effects for early, average, and extended completers. Five recommendations for institutional interventions and additional research were developed based on the study findings: develop programs to support timely (dissertation) writing, conduct additional research on diversity and extended time to degree, develop programs for graduate student parents, reorganize doctoral student financial support mechanisms, and establish program-level review of time to degree. The recommendations are aimed at improving the culture and climate of doctoral education for all graduate students.Item A DIFFERENT WORLD: AFRICAN AMERICAN, FIRST GENERATION COLLEGE WOMEN AT A SELECTIVE UNIVERSITY(2013) Johnson, Jennifer Michelle; Fries-Britt, Sharon L.; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study was to gain a better understanding of the academic and social experiences of African American, first generation college students attending a selective university. Following interpretive case study methodology, the major research questions guiding this study were: How do African American, first generation college students describe their academic and social experiences attending a selective institution of higher education? And How do African American, first generation college students mitigate barriers to college persistence? Through demographic questionnaire responses and individual semi-structured interviews with five African American women attending the University of Pennsylvania, participants identified the ways that their collegiate experiences were shaped by their social identities, precollege academic and social experiences, and interactions with members of their campus and home communities. Findings indicated that African American, first generation college women graduate from high school with a strong academic sense of self, developed after years of parental encouragement for academic achievement and positive precollege experiences with teachers and counselors. This academic sense of self contributed to students' ability to adapt to the academic competiveness and classroom expectations of their given major upon matriculation. With time and self-reflection, students began to engage in academic behaviors linked with success. Socially, early experiences of isolation or alienation primarily occurred during students' first semester, but were mitigated through interactions with peers or engagement in campus organizations and activities. Students identified availability of financial resources, their strong support networks, and their intrinsic motivation and academic self-efficacy as factors that contributed to their college persistence within the setting of a selective university. Finally, students specifically described how five salient aspects of their identity - their race, class, academic sense of self, gender, and spirituality, influenced not only the ways they individually engaged with the college environment, but also their perceptions of various members of the campus community. The findings of this study contributes to the complexity of understanding how African American, first generation college women experience a selective campus environment. Implications for campus policies and practices, as well as recommendations for future research are presented.Item Essays on Asset Purchases and Sales: Theory and Empirical Evidence(2006-08-09) YANG, LIU; Maksimovic, Vojislav; Finance; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation consists of a theory essay and an empirical essay that investigate a firm's decision to buy or sell corporate assets. It seeks to answer the following research questions: (1) why do firms choose to buy or sell assets? (2) what makes assets in an industry more likely to be traded than assets in other industries? and (3) within an industry, why asset sales come in waves and tend to cluster over a certain time period? In my theory essay, "The Real Determinants of Asset Sales", I develop a dynamic equilibrium model that jointly analyzes firms' decisions to buy or sell assets and the activity of asset sales in the industry. In my model, a firm maximizes its value by making two inter-related decisions: how much to invest in new assets and whether to buy or sell existing assets. These decisions are made under both firm- and industry-level productivity shocks. The model is solved through simulations and it is calibrated using the plant-level data from Longitudinal Research database. I show that most of the empirical evidence documented in the literature on asset sales is consistent with value-maximizing behavior. In my empirical essay, "What Drives Asset Sales - The Empirical Evidence", I test the model's predictions using the plant-level data from Longitudinal Research Database on manufacturing firms in the period of 1973 to 2000. The patterns of transactions (firm-level purchase/sale decisions, and the cross-industry and the time-series variation in asset sales activities) are consistent with my theoretical model.Item Terrace Width Distribution and First Passage Probabilities for Interacting Steps(2005-12-05) Bantu, Hailu Gebremariam; Einstein, Theodore L; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Stochastic behavior of steps and inter-step distance is studied using Monte Carlo simulation. Terrace-step-kink model is used to represent vicinal surfaces. These vicinal surfaces consist of steps and the space between the steps called terraces. In the first part, the distribution of the width of the terraces and its relation with the strength of step-step interaction is studied. Step positions on vicinal surfaces can be mapped into the world line of fermionic particles in one dimension. The distribution of the inter-particle distance in one dimension is in turn related to the distribution of energy levels one obtains from Random Matrix theory. The energy level distribution in Random Matrix theory is nicely approximated by Wigner distribution for three symmetries described by three parameters. These parameters correspond to the step-step interaction strength in vicinal surfaces. However, when we consider vicinal surfaces the three values of step-step interaction strength are not special. Therefore, they are generalized to include all interaction strengths and it is called the generalized Wigner distribution. The Monte Carlo simulation results show that the generalized Wigner distribution is a very accurate description for the terrace width distribution. Analytical and simulation results of study of the evolution of the variance of the terrace width distribution for different physically interesting and experimentally testable situations are also presented. The analytical result is based on Fokker-Planck formalism obtained from the mapping of the vicinal surfaces into one-dimensional spinless fermionic particles. In the second part, we present the study of the effect of step-step interaction on several scaling laws one obtains from the Langevin formalism of step fluctuations. Based on the limiting processes responsible for fluctuations of isolated step, the mechanisms are divided into three universality classes: attachment-detachment, step-edge diffusion and terrace diffusion. Using Monte Carlo simulation of an attachment-detachment type process, we show that the scaling laws for width of fluctuation, correlation time and survival probabilities are affected by interaction of steps. In contradiction to what one expects from the analytical results obtained using the Gruber-Mullins picture, We also show that the correlation time increases with interaction strength.Item Exploring the Relationship Between Personal Motivation, Persistence, and Resilience and Their Effects on Academic Achievement Among Different Groups of African-American Males in High Schools(2005-05-05) Salley, Linda Delois; Weible, Thomas D; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study investigated the extent to which differences in motivation, persistence, and resilience exist among academically achieving African-American males enrolled in high school in a mid-Atlantic suburban public school system. The research questions sought to identify quantitative and qualitative variables that might contribute to academic success. The two groups of participants in this study were tenth and eleventh grade African-American males enrolled in the general curriculum or in honors and/or advanced placement classes. All participants were maintaining a 2.5 grade point average and all high schools in the district were represented in the study. The Achievement Motivation Profile instrument was administered to 140 academically achieving African-American males. Ten percent of the sample population responded to twelve interview questions. The study tested three research hypotheses: (1) there are no statistically significant differences in the mean levels of motivation between two groups of African-American males with different academic achievement records; (2) there are no statistically significant differences in the mean levels of persistence between two groups of African-American males with different academic achievement records; (3) There are no statistically significant differences in the mean levels of resilience between two groups of African-American males with different academic achievement records. T-tests and analysis of variance were used to make comparisons between the two groups. Findings from the current study revealed no statistically significant differences in means in motivation, persistence and resilience. Four themes emerged from the interviews of African-American males enrolled in honors or advanced placement high school classes. These themes were: (1) determined and persistent parental engagement; (2) setting limits and discipline; (3) child-focused love, support, communication and modeling; and (4) community connectedness and resources. Suggestions are made to replicate the study in an urban setting, again using African-American male honors and general curriculum students; to replicate the study in a rural area where three groups of African-American male students are identified: honors, general, and a group who are performing poorly in the general curriculum.; and to replicate the study using African-American females as the subjects in a similar environment. Additionally, it is important to continue searching the literature for an instrument more sensitive to differences between levels of motivation, persistence and resilience than the Achievement Motivation Profile.