UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

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 given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Distress and Deaths of Despair in the U.S. Healthcare Delivery System: Understanding Patterns in Healthcare among Distressed Americans
    (2024) Spencer, Merianne Rose Tiglao; Chen, Jie; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The United States has experienced rising mortality rates for the past several decades. Drug poisonings have increased nearly five-fold, suicide rates by nearly 40%, and by nearly 30% percent for alcohol-induced deaths between 1999 and 2021. This collection of drug-, alcohol- and suicide deaths are oftentimes referred to as “deaths of despair”, first coined by economists Anne Case and Angus Deaton who cited health and socioeconomic disparities driving Americans into mental distress, depression, and anxiety. The impact on the mental health of Americans was further exacerbated by the COVID-19 pandemic; this exposed vulnerabilities in the mental healthcare system as well as the various stressors that negatively impacted individuals across the globe. Using nationally representative data, this dissertation delves into the deaths of despair phenomenon using a multidisciplinary health services research lens. Access, utilization, and risk from deaths of despair are examined by using psychological distress (which is treated as a proxy for despair in the first two aims). Using the Kessler-6 scale, a well-accepted and clinically valid tool for non-specific mental distress, this dissertation explores patterns of healthcare spending among those with varying severity levels of psychological distress over a two-decade period; delves into patterns of healthcare utilization among young adults aged 18-30 (a population disproportionately impacted by stressors during the COVID-19 pandemic) by psychological distress; and quantifies the risk of death among those with varying severity levels of psychological distress.
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    SURVIVING THE DEAD ZONE: INTERACTIONS AMONG JELLYFISH, COPEPODS, AND FISH IN THE CHESAPEAKE BAY
    (2020) slater, wencheng katherine; Pierson, James J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The oxygen-deficient areas (dissolved oxygen < 2 mg L-1) in oceans and estuaries have been increasing worldwide in recent decades and are especially common in populated and developed areas due to eutrophication and warming. The objectives of this dissertation were to understand the effects of hypoxia on zooplankton and the plankton foodweb in the Chesapeake Bay. The study focused on copepod (Acartia tonsa) and its major predators bay anchovy (Anchoa mitchilli), comb jellyfish (Mnemiopsis leidyi), and bay nettle (Chrysaora chesapeakii) with data collected during six cruises in 2010 and 2011 and an individual-based model. Oxygen deficiency was evaluated with both dissolved oxygen concentration (DO < 2 mg L-1) and the oxygen supply and demand of the copepod (pO2 < Pcrit). The effects of hypoxia on zooplankton concentrations were estimated with net tows, and the impact of hypoxia on the plankton foodweb were quantified by comparing copepods’ nonpredatory mortality (estimated with neutral red experiments) and predatory mortality (estimated with gut contents of comb jellyfish and bay anchovy). A copepod behavior model was also built to examine how stress-induced behavior affected copepod vertical distributions and the tradeoffs between avoiding both hypoxia and predation. The results indicated the impact of oxygen deficiency could be underestimated using solely the metric of dissolved oxygen, especially under warm and saline conditions. Both copepod and planktivorous fish concentrations were lower under hypoxic conditions, but gelatinous zooplankton concentrations were higher. Both nonpredatory and predatory mortality of copepods were higher under hypoxic conditions, suggesting a direct linkage between hypoxia and decreasing copepod abundance. Most importantly, the source of copepod mortality changed with both hypoxic severity and season: the relative importance shifted from nonpredatory in spring to a combination of predatory and nonpredatory in summer and autumn, and the dominant predators shifted from juvenile bay anchovies under moderate hypoxia to comb jellyfish under warm and severely hypoxic conditions. The model demonstrated how enhancing stress avoidance would result in aggregating at a shallower depth and thus increasing predation risk, supporting the hypothesis that behavior change under hypoxia may increase predatory mortality. Overall my research has shown that hypoxia directly decreases zooplankton abundance and increases predation impact, and avoiding hypoxia could contribute to higher predation impact.
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    THE EXAMINATION OF NATIONAL-NUTRITION POLICIES ON NONCOMMUNICABLE DISEASE MORTALITY AT VARIOUS STAGES OF ECONOMIC DEVELOPMENT: A CROSS-COUNTRY PERSPECTIVE
    (2019) Gupta, Manisha; Franzini, Luisa; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The acceleration of economic growth over the past few decades introduces the need to reorient policy to address the needs and challenges for a healthier population. This paper will review the effectiveness of national nutrition policies targeting overweight, healthy diets during pregnancy, infancy and childhood, and noncommunicable diseases (NCDs) across advanced economies and transitional economies. The level of expansion and industrialization of food systems around the world have had a direct impact on nutritional status and health. Considering the magnitude of nationwide public health responses to shifts in mortality have varied over time, this introduces the need to assess the ability for dietary-related policies to successfully reduce NCDs. Results from this analysis can provide a strong rationale as to when interventions will be most effective as well as ways in which we can carry out a timely response in establishing effective policies for countries at different levels of economic development.
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    INTEGRATING AUTOMATED IMAGING AND A NOVEL IDENTIFICATION TECHNIQUE TO ESTIMATE MORTALITY AND IDENTIFY FACTORS THAT INFLUENCE THE VERTICAL DISTRIBUTION OF CRASSOSTREA VIRGINICA LARVAE
    (2015) Goodwin, Jacob; North, Elizabeth; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Understanding the population dynamics and complete life cycle of bivalves is important for effectively manage them. Most of the literature and research to date has focused on juvenile and adult bivalves, much less is known about larvae. The larval stage of the bivalve life cycle has been difficult to study due to the lack of a rapid automated approach for identifying species. However, a new technique, called ShellBi, has emerged that utilizes color patterns on the larval shell under polarized light to identify bivalve larvae. The objective of this chapter was to review the scientific basis for ShellBi and to apply it to bivalve larvae in Choptank River with the goal of distinguishing C. virginica from seven other species that spawn at the same time. A digital camera and polarized light microscope were used to capture images of the shells of bivalve larvae under standard and cross-polarized light. Images of C. virginica were distinguishable from other species based on these patterns, especially at later stages of development. These images could serve as a visual guide to identify C. virginica collected from the Choptank River and other tributaries with similar species in Chesapeake Bay.