DRUM - Digital Repository at the University of Maryland

DRUM collects, preserves, and provides public access to the scholarly output of the university. Faculty and researchers can upload research products for rapid dissemination, global visibility and impact, and long-term preservation.

 
Submit to DRUM

Submit to DRUM

To submit an item to DRUM, login using your UMD credentials. Then select the "Submit Item to DRUM" link in the navigation bar. View DRUM policies and submission guidelines.
Equitable Access Policy

Equitable Access Policy

The University of Maryland Equitable Access Policy provides equitable, open access to the University's research and scholarship. Faculty can learn more about what is covered by the policy and how to deposit on the policy website.
Theses and Dissertations

Theses and Dissertations

DRUM includes all UMD theses and dissertations from 2003 forward.

Recent Submissions

Item
Neural sensitivity to social reward predicts links between social behavior and loneliness in youth during the COVID-19 pandemic
(Wiley, 2023-08-04) Dziura, Sarah L.; McNaughton, Kathryn A.; Giacobbe, Elizabeth; Yarger, Heather A.; Hickey, Alexandra C.; Shariq, Deena; Redcay, Elizabeth
Neural reward network sensitivity in youth is proposed to differentially impact the effects of social environments on social outcomes. The COVID-19 pandemic provided an opportunity to test this hypothesis within a context of diminished in-person social interaction. We examined whether neural sensitivity to interactive social reward moderates the relationship between a frequency of interactive or passive social activity and social satisfaction. Survey reports of frequency of interactions with friends, passive social media use, and loneliness and social satisfaction were gathered in 2020 during mandated precautions limiting in-person contact. A subset of participants (age = 10–17) previously participated in a functional magnetic resonance imaging (fMRI) study examining social-interactive reward during a simulated peer interaction (survey n = 76; survey + fMRI n = 40). We found evidence of differential response to social context, such that youth with higher neural reward sensitivity showed a negative association between a frequency of interactive connections with friends and a combined loneliness and social dissatisfaction component (LSDC) score, whereas those with lower sensitivity showed the opposite effect. Further, high reward sensitivity was associated with greater LSDC as passive social media use increased, whereas low reward sensitivity showed the opposite. This indicates that youth with greater sensitivity to social-interactive reward may be more susceptible to negative effects of infrequent contact than their low reward-sensitive counterparts, who instead maintain social well-being through passive viewing of social content. These differential outcomes could have implications for supporting youth during times of major social disruption as well as ensuring mental health and well-being more broadly.
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Ensuring the continued success of a mulch biowall at a trichloroethylene-contaminated superfund site: Lessons learned
(Wiley, 2023-08-03) Ghandehari, Shahrzad Saffari; Cheng, Shih-Huai; Hapeman, Cathleen J.; Torrents, Alba; Kjellerup, Birthe Veno
Trichloroethylene (TCE) is a toxic organic compound, which can adversely affect human health. The chemical is one of the most frequently found contaminants in groundwater in the United States and around the world. A landfill in Maryland contaminated with high levels of TCE decades ago was added to the U.S. Environmental Protection Agency's National Priority List (NPL) in 1994. A biowall was installed on the site in 2013 to promote the bioremediation of TCE and subsequently of its degradation products. Six-year monitoring data indicated a steady removal of >99% groundwater TCE at the wall since installation. However, a concurrent buildup of intermediate byproducts was observed downgradient of the wall. An examination of the entire system was necessary to find the reason behind the inefficiency of the biowall. In this study, the background of the site, remediation plan, and installation were assessed. Monitoring data, including the concentration of TCE and its degradation byproducts, and geochemical and physical characteristics were evaluated to understand the conditions and challenges facing decision-makers of this project and possible options to improve biowall efficacy.
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Acute cycling exercise and hippocampal subfield function and microstructure in healthy older adults
(Wiley, 2023-08-01) Callow, Daniel D.; Kommula, Yash; Stark, Craig E.L.; Smith, J. Carson
Aging is associated with deterioration in dentate gyrus (DG) and CA3, both crucial hippocampal subfields for age susceptible memory processes such as mnemonic discrimination (MD). Meanwhile, a single aerobic exercise session alters DG/CA3 function and neural activity in both rats and younger adults and can elicit short-term microstructural alterations in the hippocampus of older adults. However, our understanding of the effects of acute exercise on hippocampal subfield integrity via function and microstructure in older adults is limited. Thus, a within subject-design was employed to determine if 20-min of moderate to vigorous aerobic exercise alters bilateral hippocampal subfield function and microstructure using high-resolution functional magnetic resonance imaging (fMRI) during an MD task (n = 35) and high angular resolution multi-shell diffusion imaging (n = 31), in healthy older adults, compared to seated rest. Following the exercise condition, participants exhibited poorer MD performance, particularly when their perception of effort was higher. Exercise was also related to lower MD-related activity within the DG/CA3 but not CA1 subfield. Finally, after controlling for whole brain gray matter diffusion, exercise was associated with lower neurite density index (NDI) within the DG/CA3. However, exercise-related differences in DG/CA3 activity and NDI were not associated with differences in MD performance. Our results suggest moderate to vigorous aerobic exercise may temporarily inhibit MD performance, and suppress DG/CA3 MD-related activity and NDI, potentially through neuroinflammatory/glial processes. However, additional studies are needed to confirm whether these short-term changes in behavior and hippocampal subfield neurophysiology are beneficial and how they might relate to long-term exercise habits.
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Mountain railway alignment optimization based on landform recognition and presetting of dominating structures
(Wiley, 2023-07-23) Wan, Xinjie; Pu, Hao; Schonfeld, Paul; Song, Taoran; Li, Wei; Peng, Lihui; Hu, Jianping; Zhang, Ming
Mountain railway alignment optimization has always been a challenge for designers and researchers in this field. It is extremely difficult for existing methods that optimize alignments before major structures to generate a better alignment than the best one provided by human designers when the terrain is drastically undulating between the start and endpoints. To fill this gap, a “structures before alignments” design process is proposed in this paper. Primarily, a landform recognition method is devised for recognizing dominating landforms. Then, a bi-level alignment optimization model is proposed, with the upper level dedicated to characterizing dominating structures and the lower level focusing on optimizing the entire alignments. To solve this bi-level model, a three-stage optimization method is designed. At the first stage, a scanning process and screening operators are devised for generating all the possible locations of dominating structures. At the second stage, a hierarchical multi-criteria decision-making procedure is applied for selecting the optimized dominating structure layouts. At the third stage, alignments are optimized based on the determined structure layouts using a bi-objective optimization method, which minimizes construction cost and geo-hazard risk simultaneously. The proposed model and solution method are applied to two real-world cases whose results verify their capabilities in producing alignment alternatives with better combinations of construction cost and geo-hazard risk than manually designed alternatives.