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 Estimating the Prevalence and Timing of Events Along the Pathway to Identification of Autism in the US 2016–2018(2021) Hanley, Allison; Nguyen, Quyhn; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The prevalence of autism spectrum disorder (ASD) has risen rapidly in the past decade. Estimates on factors associated with developmental screening and the timing of events along the diagnostic pathway can inform early identification efforts. This dissertation uses cross-sectional data from the 2016–2018 National Survey of Children’s Health to achieve 3 aims: 1) evaluate individual- and state-level sources of variance between states in developmental screening rates via multilevel models, 2) evaluate characteristics associated with the ages at which children with ASD are first diagnosed, receive an intervention plan, and begin intervention, and 3) evaluate differences in lengths of time between these events by cohort. Aim 1: The national rate of developmental screening for children ages 9 months to 5 years is 34.4% (95% Confidence Interval (CI), [34.3, 34.4]). Rates varied between states by 38%. Individual-level factors explained 6% of the variance, while income inequality and a state’s choice to track developmental screening did not explain any variance between states. Aim 2: Linear regression models adjusted for individual and household characteristics showed that compared to children aged 3–5 years at the time of the survey, children 6–11 were 18 months older at first services (? =1.49, 95% CI, [1.18, 1.81] and children aged 12–17 were 38 months older at first ASD diagnosis (? =3.16, 95% CI, [2.72, 3.60]. Aim 3: Analyses using identical models showed that compared to children aged 3–5 at the time of the survey, the interval between first plan and first services was 4 months longer for children 6–11 (? =0.34, 95% CI, [0.07, 0.61]; and 8 months longer between first ASD diagnosis and first services for children aged 12–17 (? =0.67, 95% CI, [0.28, 1.06]. Today’s children with autism receive their first diagnosis, intervention plans, and developmental services at younger ages than in the past and are moving between events with less delay compared to older children. However, the low rate of developmental screening nationwide represents missed opportunities for even earlier identification. Research is needed to identify the macro-level factors that explain the variance between states on developmental screening rates.Item METABOLIC VIRULENCE DETERMINANTS AND RAPID MOLECULAR DIAGNOSTICS OF PATHOGENIC SPIROCHETES(2016) Backstedt, Brian; Pal, Utpal; Veterinary Medical Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Borrelia burgdorferi and Leptospira interrogans are pathogenic spirochetes that elicit serious health threats, termed as Lyme disease and leptospirosis. Key areas of spirochete research involve a better understanding of their intriguing biology and infection, including identification of novel virulence factors and improvements in diagnostic and preventive methods. Notably, certain bacterial metabolic enzymes are surface-exposed, having evolved to acquire additional functions referred to as protein moonlighting that contributes in microbial virulence. Comparative genome analysis revealed that certain components of sugar metabolism pathways are either absent or seemingly inactive in pathogenic spirochetes, which were studied herein for their potential roles as metabolic virulence factors. Of nine borrelial enzymes investigated, only phosphomannose isomerase (PMI) was found to be surface-exposed and remained enzymatically active in the spirochete outer membrane. PMI is critical for mannose metabolism and facilitates the interconversion of fructose 6-phosphate and mannose-6-phosphate, although its occurrence in borrelial surface remains enigmatic. PMI may provide a critical function for B. burgdorferi viability as it is constitutively expressed and all attempts to create genetic mutants remained unsuccessful. Active immunization studies using recombinant PMI did not influence the outcome of infection within tick or murine hosts, although a significant reduction in bacterial levels within the joints of mice was recorded, suggesting its involvement in spirochete persistence in a tissue-specific manner. Despite substantial advancement, the development of more effective diagnostics for leptospirosis and Lyme disease still remains a critical need since human vaccines are unavailable. Antibiotic treatment can resolve these infections but is most effective when administered early during infection, prior to pathogen dissemination to distant organs. As diagnostic methods for spirochete infection still depends on ineffective and antiquated technologies, we sought to develop novel RNA-based assays for better detection of early spirochete infection. Results indicated that targeting specific regions of 16S and 23S ribosomal RNA targets provided the highest possible sensitivity and specificity of detection, which was far superior to current serological, microbiological or molecular methods used to detect presence of invading pathogens.Item Technoscientific Knowledge Practices of Adolescent Mental Health Care Work(2013) Nelson, Amber Dawn; Falk, William W.; Sociology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study examines the technoscientific knowledge-practices of adolescent psychotherapy. Employing an interpretive, feminist version of grounded theory, 40 interviews with psychotherapists were analyzed. Building on Science and Technology Studies and the Sociology of Health and Illness, the following research questions are asked: How are adolescent mental illnesses defined and approached within and across social worlds? How do practitioners negotiate social processes of diagnosis? In what ways does the Diagnostic and Statistical Manual (DSM) as a technology, shape the diagnostic and treatment work of mental health practitioners? In what ways does Managed Care (MC) shape adolescent mental health care? Social worlds define psychotherapy as an art and science, resist biomedicine and embrace eclectic theoretical orientations to treatment. Psychotherapists utilize Evidence Based Practices (EBPs) in their treatment plans but critique how EBPs privilege scientific evidence over patient subjectivity, social contexts and the therapeutic relationship. Psychotherapists challenge the cultural authority of the DSM and downplay its significance for clinical work. While the DSM is a socially-scripted technology, its significance is interpretively flexible. Psychotherapists employ work-arounds to the problems posed by biomedical and bureaucratic standardization, and participate in processes of cribbing. Cribbing signifies the collective knowledge building and translation work necessary to learn the codes that facilitate therapeutic service authorizations and minimize denials. The DSM technology and MC privilege a therapeutic focus on surface level symptoms and behaviors whereas psychotherapists focus on communication, relational and emotional issues. The assemblage of the DSM and MC creates diagnostic dissonance for psychotherapists--a conflict between their own theoretical orientations and the biomedical model. Biomedicalization processes are uneven and actively resisted. MC governs the clinical practices of psychotherapists. For-profit MC companies have shifted care from intense psychodynamic therapy towards short-term surface level medications and behavioral programs. MC policies limit services, over-manage treatment and harm the therapeutic relationship. MC stratifies providers and patients by encouraging seasoned professionals to leave public forms of insurance. The least experienced practitioners care for those with the most intense mental illness while those with experience opt-out and treat the worried-well.Item Automating Performance Diagnosis in Networked Systems(2012) McCann, Justin N.; Hicks, Michael W; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Diagnosing performance degradation in distributed systems is a complex and difficult task. Software that performs well in one environment may be unusably slow in another, and determining the root cause is time-consuming and error-prone, even in environments in which all the data may be available. End users have an even more difficult time trying to diagnose system performance, since both software and network problems have the same symptom: a stalled application. The central thesis of this dissertation is that the source of performance stalls in a distributed system can be automatically detected and diagnosed with very limited information: the dependency graph of data flows through the system, and a few counters common to almost all data processing systems. This dissertation presents FlowDiagnoser, an automated approach for diagnosing performance stalls in networked systems. FlowDiagnoser requires as little as two bits of information per module to make a diagnosis: one to indicate whether the module is actively processing data, and one to indicate whether the module is waiting on its dependents. To support this thesis, FlowDiagnoser is implemented in two distinct environments: an individual host's networking stack, and a distributed streams processing system. In controlled experiments using real applications, FlowDiagnoser correctly diagnoses 99% of networking-related stalls due to application, connection-specific, or network-wide performance problems, with a false positive rate under 3%. The prototype system for diagnosing messaging stalls in a commercial streams processing system correctly finds 93% of message-processing stalls, with a false positive rate of 2%.