Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

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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    UNDERSTANDING HONEY BEE COLONY MORBIDITY AND MORTALITY THROUGH PHYSIOLOGY AND LIFESPAN
    (2022) Nearman, Anthony James; vanEngelsdorp, Dennis; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Managed honey bee colonies (Apis mellifera) are a critical component of our agroecosystem. As such, we need to understand and address risk factors that contribute to colony loss. Fundamental to this understanding is a need to detail the connection between individual bee’s physiology, life histories, and colony fitness. In this dissertation I first present an in-depth review of honey bee physiologies important for colony success (Chapter 1); I then examine standard methods for rearing honey bees in a laboratory setting and the importance of individual bee lifespan on colony loss (Chapter 2); followed by identification of honey bee physiologies that relate to chronological age as a means of measuring colony demographics and health (Chapter 3); and then apply potential age- and disease-related physiology measures to determine associations with overwinter colony loss and known and unknown risk factor exposure (Chapter 4). Research indicates honey bee colony loss is largely driven by poor nutrition, pesticide exposure, and parasites and the viruses they vector. Management practices and techniques to mitigate the effects of these risk factors decrease loss rates but do not prevent all of them. New knowledge, therefore, is needed to address the gap in knowledge between risk exposure and colony mortality. As a honey bee colony is a complex interaction between multiple groups of individual bees, collective physiological changes among these groups hold promise for understanding why some colonies die while other do not when exposed to the same risk factors. In one experiment (Chapter 2), I demonstrate the importance of access to water on honey bee lifespan. In a literature review informed by the data obtained from these experiments, I discovered that the median lifespan of laboratory specimen has decreased by half over the past 50 years and that this change is predictive of overwinter loss rates reported by beekeepers since 2006. If the age of individual bees can affect the lifespan of a colony, I posited that physiological measures predictive of individual bee age could be useful to ascertain the demographics of a colony’s population, which would in turn be a measure of colony health. To test this hypothesis, I built upon previous physiology studies and examined age-linked cohorts of bees through the fall transition to overwinter. In doing so I derived a set of easily identifiable physiological measures either predictive of individual bee age or a possible unidentified disease state. I then applied these measures to a retrospective cohort study, where I was able to determine that changes in the prevalence among several physiologies were associated with overwinter mortality and known risk factor exposure. These methodologies and results show promise for the use of physiological measures as a potential pragmatic tool to predict colony survivorship, to diagnose past known and unknown risk factor exposures, and to further advance fundamental knowledge of the role demographics play in societal health.
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    Autochthonous and Introduced Stores of Biomass Value: Measuring Resilience Outcomes of Enset and Eucalyptus as Green Assets in Three Representative Smallholder Farm Systems of Ethiopia
    (2020) Morrow, Nathan; Hansen, Matthew C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Fundamental shifts in the ability to observe our world with synoptic satellite remote sensing and the profusion of trend tracking longitudinal data sources not only better inform us of the mounting trouble our planet is in but also provide completely new perspectives on basic shared understandings, such as how many trees grow on Earth and where they take root. Observing the dispersed pattern of increasing tree cover across a multidecadal satellite mosaic, developed by Matt Hansen and colleagues at University of Maryland at College Park, sparked an interest in the ramifications of this unanticipated change, marked clearly upon the landscape in Ethiopia. The following chapters explore the relation of changing amounts of autochthonous treelike perrenial enset and introduced eucylyptus trees, commonly found on Ethiopian farms, to smallholder resilience, food security, and well-being. Spatially informed longitudinal models for three representative subnational data sets are used to investigate the central thesis of this dissertation—trees and treelike perennials on farms in rural Ethiopia indicate a fundamental store of value in living biomass, building a household’s assets over time through improved biomass management, for resilient small farm livelihoods that ensure food security and related well-being. Green assets acting as biomass stores indicate natural “value,” representing transformed and stored energy of the sun, that Blaikie and Brookfield (1987) considered inadequately captured as a no-cost contribution to the “use value” concept in development economics, economic geography production, and income-focused research, as well as in Marx’s (1887/2013) labor-focused value constructs that only briefly acknowledge workers are helped by the transformative “natural forces” at work on the land. Model results presented in Chapters 3, 4, and 5 reveal a lack of on-farm trees and treelike perennials often indicates biomass poverty and energy insecurity. Chronic biomass poverty, measured with spatially aware hierarchal models, is related to an inability to maintain a sufficient level of essential green assets, thereby contributing to poor resilience and well-being outcomes on small farms. On the other hand, medium and longer term asset accumulation supports improved well-being when livelihood strategies make use of farm forests, other on-farm trees, and treelike perennials.
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    DIET, FOOD SECURITY, SOCIAL RELATIONSHIPS AND DEPRESSIVE SYMPTOMS IN HOMEBOUND OLDER ADULTS IN THE UNITED STATES AND THEIR IMPACT ON HEALTHCARE UTILIZATION
    (2020) Ashour, Fayrouz A.; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Homebound older adults may be at increased risk for malnutrition and social isolation, posing a potential threat to them aging in their communities and increasing healthcare cost. The Nutrition Service Program under Older Americans Act (OAANSP) was established to support older adults aging in place by delivering meals and providing nutrition-related services. Aims: 1) Examine diet quality of home-delivered meal (HDM) recipients; 2) examine direct and indirect associations between social relationships, depressive symptoms, food insecurity (FI) and diet quality; and 3) examine direct and indirect associations between social relationships, FI, diet quality and hospitalization. Methods: Data obtained from OAANSP Outcomes Evaluation study included: 1) client outcomes survey, 2) two 24-hour dietary recalls, and 3) Medicare healthcare utilization data. Dietary recalls examined diet quality by calculating 1) population-level mean HEI scores; and 2) usual vegetable and protein intakes. Diet quantity was compared to Dietary Guidelines for Americans 2010 (DGA), and structural equation modeling was used to examine direct and indirect relationships. Results: HDM recipients and controls have high prevalence of FI, 22.4% and 16.5%, respectively. HDM recipients who did not receive a meal on day of dietary recall (no-meal recipients) had significantly poorer diet quality than HDM recipients who received a meal (meal recipients) that day and control group. Quality of overall diet for meal recipients, no-meal recipients and controls did not meet recommendations for several food groups/nutrients. Compared to DGA, HDM and complementary foods were low in whole grains, dairy, fiber, and surpassed upper limit of consumption for saturated fats, refined grains, sodium and added sugar. High FI was associated with greater depressive symptoms and lower usual vegetable intake in control group. High FI was associated with lower usual protein intake in HDM recipients and controls. Both groups were at high risk for protein insufficiency, which was associated with greater hospitalization in the control group. Conclusions: HDM recipients and controls have high prevalence of FI, poor diet quality, and insufficient protein intake. Increasing funding for OAANSP can allow program expansion and improvement of HDM. Validated tools to examine social relationships and additional contributors to FI are needed
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    Examining the Food-Insecurity Obesity Paradox among Latino Immigrants
    (2019) Amador, Maria Aileen; Garza, Mary A; King-Marshall, Evelyn C; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Obesity is linked to chronic illnesses such as type 2 diabetes, cardiovascular disease, and some cancers (breast, kidney, and liver). Food insecurity refers to lack of access to nutritious and safe food. Latinos are a rapidly growing population in the US with higher levels of food insecurity than the national average, and higher obesity rates than non-Latino white adults. The “food insecurity-obesity” is a paradoxical relationship seen in rising obesity and correspondingly high food insecurity rates. We examined demographic factors, acculturation, stress, dietary habits, and food access among Latina immigrants to understand this paradox. This sub-analysis (n=128) found that education level (p=0.03) and marital status (p=0.08) were significantly and marginally significantly associated with food security level. Additionally, this analysis helped to better describe a population that lacks research. A better understanding of the “food insecurity-obesity” paradox and related factors will inform future culturally-tailored interventions to address obesity among Latina immigrants.
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    Associations among food insecurity, dietary sodium and potassium intake levels, and hypertension: a cross-sectional study based on NHANES 2007-2010 data
    (2014) Nothwehr, Ann; Carter-Pokras, Olivia; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: Food insecure persons may have diet patterns that include excessive sodium and inadequate potassium. These patterns contribute to greater risks of hypertension. Objective: Evaluate levels of association among food insecurity, dietary sodium and potassium intake levels and hypertension among NHANES 2007-2010 adult participants. Methods: Compared mean usual sodium and potassium intakes as well as mean usual sodium-potassium ratios for food secure and food insecure subpopulations. Developed regression models to predict intake levels and hypertension risk. Results: Mean usual sodium intake is not significantly different for food secure and food insecure participants. Mean usual potassium intake is significantly lower and mean usual sodium-potassium ratio is significantly higher for the food insecure subgroup. Controlling for age and household size, food insecure persons are 43% more likely to be hypertensive than food secure persons. Conclusion: Public health measures to decrease cardiovascular disease risk should include interventions designed for this vulnerable subpopulation.
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    Formal Savings & Informal Insurance in Villages: A Field Experiment on Indirect Effects of Financial Deepening on Safety Nets of the Ultra-Poor
    (2011) Flory, Jeffrey Allen; Leonard, Kenneth L.; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This thesis exploits a unique micro dataset that uses a natural field experiment to identify indirect effects of formal savings access on de facto ineligibles residing in the same community. Despite widespread interest in microfinance as a poverty-reduction tool, the indirect effects on the very poor of expanding formal financial services remain largely unexplored. This study examines evidence from a large field experiment which helps fill this gap. It also contributes to an important emerging literature on the indirect impacts of policy interventions in developing countries, often (incompletely) evaluated solely on the basis of how they impact participants and beneficiaries. In developing regions, households vulnerable to extreme poverty often benefit from long-standing local safety nets based on cash gifts and other transfers from relatives and friends, which help them smooth consumption across food-deficits and household shocks. To date, little is known about how these pre-existing practices are affected as community members begin adopting newly available formal financial services, and there remains much unexplored in the interaction of formal financial markets with informal safety nets. This paper addresses that gap by examining how formal savings expansion affects inter-household wealth transfers, with a particular emphasis on receipts by the most vulnerable. Using a rich panel dataset from Central Malawi that includes over 2,000 households, I find that experimentally boosting local savings uptake in rural areas leads to a strong positive effect on assistance receipts by non service-users during peak periods of hunger. The difference is strongest among the most vulnerable households. That is, the entrance of formal savings appears to complement local informal support systems for the highly vulnerable through an indirect mechanism, channeling greater wealth to such households during periods of food-deficits. The positive impacts of formal savings expansion on non service-users suggests that formal savings may have substantially greater benefits than would be suggested by focusing exclusively on the impacts experienced by the service-users themselves.
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    INFLUENCE OF FOOD-RELATED LIFE SKILLS ON FOOD SECURITY OF RURAL, LOW-INCOME FAMILIES
    (2004-05-12) Grutzmacher, Stephanie Kristen; Braun, Bonnie; Family Studies
    This study examined the effects of food-related life skills on food security in a sample of rural, low-income mothers. While research suggests that income and food assistance benefits do not protect low-income families from food insecurity, the potential of food resource management to optimize limited income and food assistance is unknown. Linear regression was employed to determine the extent to which food-related life skills affect food security status within the sample. Findings indicate that mothers in food secure households are significantly more likely to possess food-related life skills than mothers in food insecure households. The ability to make a family budget was a significant predictor of food security, while income relative to household size and poverty level, food stamps, and participation in WIC and the School Lunch Program were not significant predictors. Findings emphasize the importance of helping low-income families obtain skills and resources that protect them from food insecurity.