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 RISK OF AIRBORNE INFLUENZA TRANSMISSION IN A CONTROLLED ENVIRONMENT(2019) Bueno de Mesquita, Paul Jacob; Milton, Donald K.; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Pandemic preparedness is weakened by uncertainty about the relative importance of influenza transmission modes, particularly airborne droplet nuclei (aerosols). A human-challenge transmission trial in a controlled environment was conducted to address this uncertainty. Healthy, seronegative volunteer ‘Donors’ (N=52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2) and exposed to seronegative ‘Recipients’ randomized to intervention (N=40) or control (N=35) groups. Intervention recipients wore face shields and hand sanitized frequently to limit large droplet and contact transmission. A transmitted infection, confirmed by serology in a control recipient, yielded a 1.3% SAR overall. This was significantly less than the expected 16% SAR (p <0.001) based on a proof-of-concept study that used half as many Donors and exposure days. The main difference between these studies was mechanical building ventilation in the follow-on study, suggesting a possible role for aerosols. The extent to which Donor viral shedding was similar to that of mild, natural infections and may be useful for studying transmission was investigated. The only available aerosol shedding comparison data comes from a population of adults with influenza A H3 infection enrolled on the basis of febrile illness plus cough or sore throat, or positive Quidel QuickVue rapid test (N=83). Systematic differences in case selection compared with Donors yielded more severe cases and introduced bias. To account for differences in illness severity, propensity score matching, stratification, and inverse weighting ultimately demonstrated that the experimental and naturally infected groups were too different to compare without bias. While acknowledging the uncertainty in the generalizability of the current challenge model, observed aerosol shedding and CO2 were used in the rebreathed-air version of the Wells-Riley equation to compute average quantum generation rates (95% CI) 0.029 (0.027, 0.03) and 0.11 (0.088, 0.12) per hour for infected Donors and fine aerosol shedding Donors, respectively. Donors shed 1.4E+5 (1.0E+5, 1.8E+5) airborne viral RNA copies per quantum (ID63). This dissertation provides evidence for airborne transmission, presents a methodology for estimating an airborne dose, and suggests a role for building ventilation in reducing risk and the need for future observational studies to evaluate transmission modes in non-experimental settings with greater generalizability.Item DISTRESS TOLERANCE TREATMENT FOR INNER-CITY DRUG USERS: A PRELIMINARY TRIAL(2008-04-15) Bornovalova, Marina Alexa; Lejuez, Carl; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Despite advances in preventing treatment failure, a large percentage of substance-using individuals drop out of treatment. Current work indicates that one's threshold for tolerating psychological distress (i.e., distress tolerance) is a key factor in treatment dropout. Following from this work, we developed a treatment for prevention of treatment drop-out in a residential treatment setting. Specifically 66 individuals who were a) receiving residential substance use treatment and b) evidenced deficits in distress tolerance at a baseline assessment were assigned to receive either the novel treatment (Skills for Improving Distress Intolerance, SIDI), supportive counseling (SC) treatment, or no-treatment control (NTC). We hypothesized that compared to individuals in the SC and NTC, individuals in the SIDI would show greater improvements in levels of distress tolerance, greater improvement on measures theoretically related to distress tolerance (i.e., levels of negative affect, disengagement coping, emotion regulation, self-efficacy in high-risk situations, and self-efficacy of mood regulation), and higher rates of treatment completion. Results indicated that those in SIDI evidenced greater improvement in distress tolerance, compared to SC and NTC. However, there were no significant differences in improvement in the secondary measures, except for affect regulation self-efficacy (approaching significance). It should be noted, however, that the percentage of individuals reaching clinically significant improvement showed that more individuals in SIDI, compared to SC and NTC, reached such improvement. Comparison of 30-day treatment completion showed that there were no dropouts in either SIDI or SC; all dropouts occurred in NTC. When considering dropout throughout the entire residential treatment contract (ranging from 30 to 180 days), the least dropouts occurred in SIDI, followed by SC and NTC (in this order); however, this difference was not significant. The current results suggest that SIDI is effective in increasing distress tolerance in inner-city drug users. Additionally, the variable rates of dropout that were, nevertheless, nonsiginficant suggest a need for larger-scale studies to test the effect of SIDI on dropout.Item DOSE RANGING STUDY OF LUTEIN SUPPLEMENTATION IN ELDERLY WITH AND WITHOUT AGE RELATED MACULAR DEGENERATION(2004-09-15) Moura, Fabiana Fonseca; Khachik, Frederick; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Age-related macular degeneration (AMD) is the leading cause of blindness among people over the age of 65. Epidemiological studies have indicated that people with a high intake of two dietary carotenoids, lutein and zeaxanthin that accumulate in the human macula, are at a reduced risk of AMD. Possible role of lutein and zeaxanthin in the prevention of AMD has been attributed to their antioxidant function and their ability to act as optical filters. The objectives of this study were to investigate the association between three doses of orally ingested lutein supplements and serum levels of this carotenoid in elderly with and without AMD; to evaluate the possible interaction between supplemental lutein and other dietary carotenoids, retinol, and tocopherol; to correlate the serum levels of lutein with the total macular pigment optical density (MPOD). Forty-five subjects over the age of 60 were divided into 3 groups: subjects without AMD and subjects with middle and end stage of AMD. Subjects in each group were randomized to receive one of the three doses of 2.5, 5, and 10 mg/day of lutein (containing 5% zeaxanthin) for 6 months. Subjects were followed up for 6 months. Carotenoids and their metabolites in the serum of subjects were analyzed by HPLC at weeks 0, 1, 4, 12, 26, 38, and 52. The MPOD of subjects was measured by Heterochromatic Flicker Photometry (HCFP). The data were analyzed using analysis of variance and covariance with repeated measurements (SAS, version 8.2). The mean serum concentrations of lutein in all subjects increased with supplementation. Subjects receiving 10 mg/day of lutein had a 3-4 fold increase in their serum levels of lutein, while those receiving 2.5 and 5 mg/day dose had approximately 2 fold increase. In conclusion, the serum concentration of lutein appears to be dose dependent and the presence or the absence of AMD does not interfere with the serum levels of this carotenoid. Supplemental lutein does not interact with other dietary carotenoids, retinol, and tocopherol. The results from MPOD measurements by HCFP were inconsistent and could not be used to reach any conclusion with regard to MPOD changes.