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
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item ELECTROCHEM-MECHANICS CHARACTERIZATION OF SI ELECTRODE/SI BASED SOLID-STATE BATTERY(2022) Wang, Haotian; Rubloff, Gary; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Li-ion battery (LIB) is a popular energy storage device that predominates the market of microelectronics due to its high energy density and light weight. In the recent trend of electrification of vehicles, LIBs also showed promise in the application of electric vehicles but the energy density of current LIBs with graphite electrode doesn’t suffice the need of long driving range. Replacing graphite electrode with alloying type electrodes that have almost ten times higher energy density is thus a necessary route to improve the energy density of LIBs. However, alloying type electrodes, such as Si and Sn, typical undergo enormous volume change (up to 310%) during Li insertion and extraction, which lead to various mechanical problems such as cracking, delamination, and pulverization. These mechanical issues eventually cause catastrophic capacity fading in LIBs and thus, are central topics for the application of alloying type electrodes in next generation LIBs. This dissertation presents a three-phase experimental study of stress development in Si electrodes and Si based solid state batteries. In the first phase, ex-situ stress characterization in single-c Si electrode was performed to validate Raman spectroscopy as a promising stress characterization technique for Si electrode. In the second phase, in-situ stress characterization in patterned poly-c Si electrode with confocal micro-Raman setup was performed, to investigate the correlation between complex geometries and stress distribution in crystalline Si electrode and the critical size effect. In the last phase, a solid-state battery (SSB) platform device with lateral layout was proposed and validated for stress characterization in Si based SSBs. The platform device can also serve as a versatile testbed for electrochemistry study of bulk SSB components and interfaces. Overall, this dissertation demonstrates a methodology that combines Raman spectroscopy, novel design of electrochemical devices, and computational modeling as a powerful tool for electrochemo-mechanics study of alloying type electrodes and SSB systems.Item YO SOY PAZ (I AM PEACE): PILOT STUDY OF A TRAUMA-INFORMED, COMMUNITY AND MINDFULNESS-BASED PROGRAM FOR LATINO IMMIGRANTS IN MARYLAND.(2022) Munoz, Juliana; Green, Kerry M; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: One in three Latinos in the US is an immigrant. Immigrants face particular stressors that are heightened by previous traumatic experiences before, during, and after migration. Latino populations report the highest level of stress of all racial/ethnic groups in the US and the second-highest prevalence of mental health illness. Mindfulness-Based Interventions (MBIs) have shown to be successful at reducing stress and strengthening mental health in diverse populations, yet little is known about the effects of these interventions on this particular population.Methods: The pilot study tested the Yo Soy Paz (I am Peace) online synchronous program, an evidence and trauma-informed mindfulness-based intervention that was adapted for immigrant Latina mothers and the community staff members that work with them in a community setting. The eight session pilot intervention was delivered to three cohorts for a total of 41 participants, including staff and parents of youth receiving services at a local community-based organization that serves Latino immigrants. The study used the Consolidated Framework for Implementation Research (CFIR) to examine the feasibility, acceptability, appropriateness, and fidelity of the Yo Soy Paz online program. The study also examined the initial effects of the program on stress, mindfulness, mind-body connection, and subjective well-being. Qualitative and quantitative data were collected through self-reported pre-post questionnaire, fidelity checklists, and focus groups with parents and staff. Results: Acceptability, feasibility, fidelity and appropriateness scored high on the quantitative measures. Inner compatibility with the organization’s mission and vision, clients’ needs and the organization’s receptivity to implement the intervention scored in the medium range. Mothers’ and promotoras’ self-reported mean scores for subjective wellbeing and perceived physical and mental health increased significantly from baseline- to post-test. No significant changes were observed in surveys completed by the staff, even though focus group participants reported meaningful improvement. Discussion: Overall the pilot feasibility study was well received and relevant for the organization and the population they serve. MBIs for Latino immigrants and the staff that works with them have the potential to improve well-being and overall mental and physical health. The study’s findings provide guidance to others in implementing online mindfulness practices with Latino immigrants and the staff that works with them.Item RACE AND GENDER’S EFFECT ON POLICE OFFICER STRESS AND BURNOUT: A CASE STUDY OF THE BALTIMORE POLICE DEPARTMENT(2021) Duka, Leila; Xie, Min; Criminology and Criminal Justice; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Law enforcement is an inherently stressful profession because officers deal with unique strains. Experiencing extensive and consistent amounts of stress ultimately leads to burnout, ineffective, and inefficient officers. Guided by several theoretical frameworks, the current study will examine the gender and racial differences in police officers’ stress and burnout in the Baltimore Police Department (N = 878). Specifically, I use several OLS regressions to understand the scaled responses of the officers’ psychological stress, physical stress, and burnout levels. I found female officers are more likely and black officers are less likely to experience both manifestations of stress. Further, I found no sign of increased burnout levels for either group. When analyzing a potential moderation between these demographics, I also found no difference between minority groups. While only a case study, the conclusions drawn can help identify which officers are most vulnerable to high stress and burnout levels.Item Assessing the Impact of Typical Variations in Stressful Life Events on Hippocampal Development in Childhood(2021) Botdorf, Morgan; Riggins, Tracy; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The negative impact of extreme stress on early brain development is well-documented. An emerging body of work suggests that less extreme and more typical variations in stressful experiences (e.g., parental divorce, changing schools) may also exert an impact on the brain, especially in early childhood; however, more systematic research is needed. Across, three studies, this dissertation addressed this gap by exploring effects of typical variations in stressful life events on development of the hippocampus, a brain region highly susceptible to stress. Study 1a assessed the impact of stressful life events on the development of hippocampal subfield volumes (i.e., CA1, CA2-4/dentate gyrus (DG), subiculum) in an accelerated longitudinal sample of 102 4- or 6-year-old children who were each followed for 3 years. Analyses revealed that experiencing more stressful life events was related to smaller CA1 and CA2-4/DG volumes in the 6- (but not 4-) year-old cohort. Study 1b used the same sample described in Study 1a to investigate the impact of stressful life events on functional connectivity between the hippocampus and stress-related cortical regions. Analyses revealed a significant association in the 4- (but not 6-) year-old cohort, such that experiencing more stressful life events was related to greater connectivity between the hippocampus and the insula, a region important for emotional processing. Study 2 assessed moderating effects of sex and socioeconomic status (SES) on the association between stressful events and hippocampal subfield volumes using a large (n = 4,348), diverse subsample of 9-10-year-old adolescents from the Adolescent Brain and Cognitive Development Study. Analyses revealed that stressful life events were related to smaller subiculum volumes, but these associations did not vary by sex or SES. Overall, these findings provide evidence of the impact of typical variations in stressful life events on both hippocampal structure and functional connectivity. Findings also highlight the complexity of stress effects on the brain as these experiences may impact the hippocampus in an age-dependent manner. These results advance our current understanding of how stress influences hippocampal development and pave the way for studies to assess the implications of findings both for cognitive processes and the development of stress-related disorders.Item Assessment of Perceived Stress Among School-Age Children: Relations with Emotional Engagement and Literacy Achievement(2020) Meyering, Kristin M; O'Neal, Colleen; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This short-term longitudinal quantitative study is the first to examine the psychometric properties of the PSS-10 among elementary-age students and the impact of stress on school-related outcomes, including emotional engagement and literacy achievement. Participants included upper elementary students (N = 396, Mage = 9.62; 55% female; 56% dual language learners; 6% Asian, 12% Black, 28% Latino/a, and 40% White students). Emotional engagement was assessed using self- and teacher-reported questionnaires. Literacy achievement was assessed using a literacy performance task. A CFA revealed a two-factor structure for the PSS-10, including a coping factor and distress factor. The PSS-10 had adequate internal consistency but did not demonstrate adequate test-retest reliability between time points two to four months apart. Path analyses revealed that the coping factor was a significant predictor of later literacy achievement. The distress factor predicted later emotional engagement when the coping factor was removed from the model.Item Effect of grazing muzzles on grazing miniature horse behavior and physiological stress(2019) Davis, Kristina; Burk, Amy O; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Grazing muzzles are highly effective at reducing forage intake in horses and are a popular tool to control horse weight. However, grazing muzzle design may cause horses stress. The objective of these studies was to determine how grazing muzzles impact behavior and physiological stress in grazing horses. Two groups of 6 miniature horses, housed individually or in a herd, wore grazing muzzles for 0, 10, and 24 h/d. Over 9 weeks, body weight, heart rate parameters, salivary cortisol concentrations, and observations of behavior were collected. Results indicate muzzling did not seem to cause physiological stress as measured by cardiac and salivary cortisol parameters but did alter grazing and locomotive patterns. Muzzling for 24 h/d was necessary for weight loss and was associated with lower heart rate and higher heart rate variability. These findings suggest that muzzles do not cause stress in horses, even if left on for 24 h/d.Item Life Course Events and Reproductive Function: Examining the Long-Term Influence of Stress on Women's Fertility and Reproductive Health Over the Life Course(2019) Gleason, Jessica L; Thoma, Marie E; Moser Jones, Marian; Family Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Over the last decade, infertility, or the inability to achieve pregnancy after 12 months of trying, has risen to a place of public health prominence, with links being made to cardiovascular disease, diabetes, cancer, and other chronic disease. The mechanisms linking infertility to later-life morbidity are unclear, but are most likely due to shared physiologic pathways, such as chronic perturbation of the stress response axes. This investigation had three primary aims: understanding the current state of the research on psychosocial factors as precipitants of infertility by conducting a systematic scoping literature review; exploring associations between infertility-related conditions, endometriosis and uterine fibroids, and chronic inflammation and telomere attrition; and, examining the temporal influence of early life stress on infertility. For the first aim, few studies were identified that directly explored a temporal association between psychosocial factors and infertility, though these studies support the plausibility of this association. For the second aim, women with endometriosis had higher odds of having elevated levels of the inflammatory biomarker, C-reactive protein, and their telomeres shortened at a rate of 1% for every year of diagnosis of their condition. Black women with endometriosis had 13.6% shorter telomeres than those without endometriosis. For the third aim, the experience of stressful life events (SLEs) was associated with elevated odds of infertility, which increased with each increasing event, such that women reporting three and four or more events had 1.68 (CI: 1.16, 2.42) and 1.88 (CI: 1.38, 2.57) higher odds, respectively. Maternal responsiveness moderated this association, such that those with lower responsiveness had higher increasing odds of infertility with the experience of two, three, or four or more events (OR=1.98, CI: 1.01, 3.93; OR=2.63, CI: 1.18, 5.89; OR=3.07, CI: 1.53, 616). The results of this investigation indicate that there may be a temporal association between stress and infertility. Additionally, given their associations with reproductive function, inflammation and stress may be part of the shared mechanisms linking infertility to poor overall health, as well as future health outcomes.Item The Health Implications of Stress among Asian Americans in the US and Chinese In China: the Effects of Perceived Stress and Caregiving Stress on Cardiovascular Risk Factors(2018) Lu, Xiaoxiao; Lee, Sunmin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Prior research suggests that stress plays a role in the etiology and progression of cardiovascular disease (CVD). To lend a more accurate depiction of the associations between stress and CVD risk factors, this dissertation used a comprehensive approach to conceptualizing stress by assessing two dimensions of stress: perceived stress and caregiving stress. The objective of this dissertation was to investigate the associations between multiple dimensions of stress and the risk factors of CVD. This dissertation also explored the potential mechanisms that underlie the relationships between stress and CVD risk factors. In Paper 1 (Chapter 3), we assessed the associations between perceived stress and hypertension across varying levels of social support and social network among 530 Chinese, Korean and Vietnamese Americans. Results indicated that individuals with high perceived stress were 61% more likely to have hypertension compared to those with low levels of perceived stress (Odds Ratio (OR): 1.61, 95% Confidence interval (CI): 1.15, 2.46). Social support had a direct beneficial effect on hypertension, irrespective of whether individuals were under stress. In Paper 2 (Chapter 4), we used five waves of longitudinal data from the China Health and Nutrition Survey to examine the association between parental caregiving and blood pressure among 2,586 Chinese women. We found that parental caregivers were associated with higher systolic (β-coefficient (β) = 1.16; p ≤ 0.01) and diastolic blood pressure (β = 0.75; p ≤ 0.01) compared with non-caregivers across multiple waves. In Paper 3 (Chapter 5), we investigated the relationship between caregiving trajectory and Metabolic Syndrome (MetS) among 1,636 Chinese women. Three caregiving trajectories were identified by using group-based trajectory analysis. Results showed that ‘rising to high-intense’ caregivers (OR = 1.90; 95% CI: 0.90, 4.00) and ‘stable low-intense’ caregivers (OR = 1.56; 95% CI: 1.06, 2.29) were associated with higher risk of MetS compared with non-caregivers. This dissertation is innovative in its examining the associations of multiple dimensions of stress with CVD risk factors among Asian subgroups. Findings from the proposed study will be used to develop future stress management interventions, and incorporating culturally and linguistically appropriate strategies into community outreach and education to decrease cardiovascular disease risk within the Asian population.Item Understanding Teacher Stress: Relations of Implicit and Explicit Coping Processes with Teaching Outcomes(2017) Kim, Margaret Jordan; Teglasi, Hedwig; Special Education; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Teacher attrition within the first three years is a growing problem in the US. The current study focuses on teacher stress from a novel perspective by assessing how teachers cope with stresses of the profession at the earliest point in their careers – during their training. Coping is defined as a transaction between a person and their environment, influenced by conscious choices and automatic processes. Research relies on explicit measures (self-report on Likert scales) to assess coping, but critics note this approach is limited and does not assess the whole process. In addition to Likert scales, this study incorporates implicit measures (narratives, the Thematic Apperception Test), to examine the implicit processes of coping. As predicted, significant correlations were identified within, but not across methods of measurement. Implicit but not explicit measures were significantly correlated with external evaluations of teacher effectiveness. Implications for coping theory and measurement are discussed.Item Cortisol Reactivity and Observed Parenting among Mothers of Children with and without ADHD(2015) Thomas, Sharon Renee; Chronis-Tuscano, Andrea; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Parenting is a robust predictor of developmental outcomes among children with ADHD. Early parenting predicts the persistence and course of ADHD and comorbid problems above and beyond risk associated with shared genetic effects. Yet, on average, mothers of children with ADHD are less positive and more negative in their parent-child interactions compared to mothers of non-disordered children. Little is known about psychobiological markers which may be associated with individual variations in maternal parenting in families of children with ADHD. Neurobiological models of parenting suggest that maternal cortisol levels following a stressor may be positively associated with hostile and intrusive parenting; however, to date no studies have examined maternal cortisol reactivity and parenting in school-age, or clinical samples of, children. Mothers’ regulation of physiological stress responses may be particularly important for families of children with ADHD, as parenting a child with chronically challenging behaviors represents a persistent environmental stressor. The current study sought to extend the existing literature by providing an empirical examination of the relationship between maternal cortisol reactivity following two laboratory stressors and parenting among mothers of children with and without ADHD. It was hypothesized that child ADHD group would moderate the relationship between cortisol reactivity and self-reported and observed parenting. Greater total cortisol output and greater increase in cortisol during the TSST were associated with decreased positive parenting and increased negative and directive parenting, with the exception of parental involvement, which was associated with increased cortisol output during the TSST. Conversely, cortisol output during the PCI was associated with increased positive parenting, increased parental involvement, and decreased negative parenting. In contrast to the TSST, a greater decrease in cortisol during the PCI indicated more positive parenting and parental involvement. These associations were specific to mothers of children with ADHD, with the exception of maternal directiveness, which was specific to comparison mothers. Findings add to our understanding of physiological processes associated with maternal parenting and contribute to an integrative biological, psychological, and cognitive process model of parenting in families of children with ADHD.
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