UMD Theses and Dissertations
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Item CONSTRUYENDO GUATEMALA Tradition & Technology: Living in a 21st Century Latin American City(2024) Velasquez, Deisy Noemi; Bell, Matthew MB; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In Guatemala, 21.5% of the population is living in extreme poverty. Poverty is a leading factor in poor-conditioned housing and a high percentage of children not attending primary school. This thesis focuses on constructing communities in Guatemala using innovative solutions and sustainable materials. Mass timber construction is an energy-efficient alternative material that is changing the built environment due to its sustainability, biophilic design, construction process, and economic development. This thesis focuses on exploring timber technology in an earthquake-prone region by learning, understanding, and embracing place with new technology that can sustain the future.Item Sustainable Living: Integrating Climate Adaptation in Bangkok's Informal Settlements(2024) Pipatpongsa, Ploy; Kim, Taejun; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis intends to demonstrate how the largest urban vulnerable communities in Thailand, using the case of At Narong in Khlong Toei, an informal settlement of over 30,000 residents who rent lands adjacent to the Port Authority of Thailand (PAT) in Bangkok. The PAT plans to evict the slum dwellers and develop the land, posing a severe threat to their lives and livelihoods. The thesis a multifaceted design framework that leverages social assets to enhance community resilience and inclusivity, particularly among vulnerable populations. The site location in PAT presents an opportunity to relocate informal settlements in the Lock 1-2-3 and 70 Rai communities, proposing multipurpose wetlands that serve as flood control, recreation areas and a market plaza that encourage social interaction and community cohesion.Item TREE GENETICS AND GREENSPACE MANAGEMENT INTENSITY INFLUENCE URBAN TREE INSECT COMMUNITIES, DAMAGE, AND FOLIAR TRAITS(2024) Perry, Eva Emma; Burghardt, Karin T; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Trees are essential to well-functioning urban systems, providing services that benefit humans and wildlife. For example, arthropods that use trees in cities perform key roles in the urban food web as both prey and predators, but they can also be vulnerable to environmental stressors associated with cities. Previous work documents broad patterns in arthropod communities associated with management practice gradients in urban areas. How these patterns relate to changes in tree genetic background across management types remains a largely unexplored topic. To disentangle the genetic and management associated effects on arboreal insect abundance, communities, and foliar damage, I repeatedly sampled trees of known genetic relatedness for two commonly planted tree species: Acer rubrum (n = 65), and its non-native congener Acer platanoides (n = 71), in June and August of 2023 and 2024. I systematically selected about 3 individual trees growing in four human management intensity categories (street trees, parks and residential yards, urban forest patches, or rural forests) for each of 5 genetic lineages per tree species. I used vacuum sampling to collect mobile arthropods from the lower canopy of each focal tree in June and August of 2023 and 2024, and identified samples to order. I also assessed insect and systemic foliar damage, gall abundance, and select physiological traits in August 2024. I found the general trend of increasing total arthropod abundance with increasing management intensity. However, management effects differed across genetic background with almost ubiquitous interactions between management type and genetic lineage. The most dominant group of insects found on study trees belonged to the order Hemiptera. This group of primarily herbivorous piercing/sucking insects were the primary drivers of these overarching abundance patterns. Spiders, which were the most abundant primarily predatory arthropod order, exhibited the opposite pattern, increasing in overall abundance in the later season, decreasing with increasing management intensity, and generally not responding to tree genetic lineage. In 2024, increasing management intensity negatively affected cumulative insect herbivore damage and gall abundance, and did not vary by genetic lineage. Gall formers were found only on native Acer rubrum, with no galls sampled from the non-native A. platanoides. In contrast, systemic foliar damage did not change with management, and only varied by tree genetic lineage for Acer platanoides. Foliar photosynthetic traits’ variance by management intensity or tree genetic lineage was species dependent; A. rubrum traits varied by tree genetic lineage, while A. platanoides traits varied by management intensity. Overall, my results suggest that tree genetic background plays an important role in mediating management effects on insect populations, particularly for piercing-sucking herbivorous species, but genetic background’s effect on other metrics such as foliar damage and traits may be species-specific. Further studies should be sure to consider the structure of genetic populations when describing patterns of insect use. Results of this thesis will serve to inform best practices for urban tree management and pest mitigation, as cities work to maintain and increase urban canopy cover.Item SENSORY AND HORMONAL MECHANISMS OF EARLY LIFE BEHAVIOR IN A SOCIAL CICHLID FISH(2024) Westbrook, Molly; Juntti, Scott; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Studying the ontogeny of animal behavior is fundamental to ethology and allows understanding how behaviors in early life may affect later life success. The social cichlid Astatotilapia burtoni is an excellent model for examining the mechanisms of early life aggression due to the robust social hierarchy enforced by stereotyped, measurable social behaviors. We examine how hormonal signaling affects early life aggression through pharmacology and CRISPR-Cas9 mutants. We test which sensory pathways convey aggression-eliciting stimuli through sensory deprivation experiments. And we identify kinematic features that predict aggression through machine-learning video tracking algorithms. We observe that aggressive behaviors emerge around 17 days post fertilization (dpf), correlating with when the animals transition to free swimming away from the mother. We find that sex steroids subtly organize behavioral circuits for aggression and suggest that unknown additional mechanisms play a leading role. We show that thyroid hormone is not necessary or sufficient for the transition to aggressive behavior. We show that visual signals are necessary for the full expression of aggression, but in the absence of visual signal, low levels of aggression remain. We show that ciliated olfactory receptor signaling maintains low levels of aggression, as mutant animals display higher levels of aggressive behavior between 17 and 24 dpf. Finally, we demonstrate that swimming velocity has potential to predict aggressive instances of behavior. Together, we find multiple levels of control for early life aggressive bouts from sensory input to hormonal organization of brain circuits.Item Examining Associations between Neural Sensitivity to Social Feedback with Trait and State Loneliness in Adolescents(2024) Alleluia Shenge, Victoire; Redcay, Elizabeth; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Loneliness can be defined as the negative emotional response to an experience of discrepancy between the desired and actual quality or quantity of one’s relationships. Loneliness is associated with many negative outcomes, including depression and self-harm. This phenomenon tends to increase in adolescence and adolescents with autism spectrum disorder (ASD) are at even greater risk for developing loneliness during this time than their neurotypical peers. The present study examined how neural sensitivity to both positive and negative feedback from peers is related to loneliness and social experiences among adolescents with and without autism. In a sample of 94 adolescents (22 autistic and 72 non-autistic) ages 11-14, we used an innovative ecologically valid paradigm for fMRI task along with real-world experience sampling to assess self-reported interaction quality and state loneliness, as well as surveys to examine reports of “trait” (or stable levels of) loneliness.The results indicated group differences in both state and trait loneliness, with the autistic group showing high levels of loneliness. In addition, the autistic group had lower interaction quality compared to their non-autistic peers. However, we did not find support for associations between neural sensitivity to feedback and interaction quality or loneliness across our full group. This work provides an important first step in understanding the relation between loneliness, neural sensitivity to social feedback and social experiences and can further inform intervention for adolescents at risk for negative mental health outcomes depending on which mechanism shows an association effect on social experiences and lonelinessItem EFFECTS OF FOOD PROCESSING METHODS ON PHENOLIC ACIDS AND ANTIOXIDANT CAPACITY IN SWEET CORN(2024) Dong, Fangxiang; Yu, Liangli; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis research was designed to evaluate the effects of different food processing methods on the phenolic acid and antioxidant properties of sweet corn. Phenolic acids, such as ferulic acid and p-coumaric acid, are known for their health benefits. The research primarily focuses on two main stages of food processing: post-harvest handling and domestic cooking (boiling and steaming. These processes are evaluated to determine their impact on the soluble free, soluble conjugated, and insoluble bound forms of phenolic acids in sweet corn.Phenolic acids were analyzed by High-Performance Liquid Chromatography (HPLC). The study found that post-harvest handling significantly reduced the phenolic acid content, particularly in the insoluble bound form. Domestic cooking also led to notable reductions in phenolic content, though antioxidant activity, as measured by DPPH and ABTS assays, showed varying responses, sometimes increasing in treated samples. It was noted that different processing methods can induce structural changes that may either preserve or enhance the antioxidant properties. Furthermore, the results of this thesis explored optimal food processing techniques to maximize the retention of bioactive compounds, providing insights for better food preservation strategies.Item The "Extra Layer of Things": Everyday Information Management Strategies and Unmet Needs of Moms with ADHD(2024) Walsh, Sheila Ann; St. Jean, Beth; Information Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mothers with ADHD need to manage their symptoms while balancing parenting responsibilities. Although technology is recommended to people with ADHD, there is limited related research in human-computer interaction (HCI). To help fill this gap, the author interviewed five mothers diagnosed with ADHD. The mothers, whose voices are largely unheard in HCI research, vividly describe their challenges managing everyday information and their attempts to adapt existing systems. The study uncovers a previously unrecognized tendency among moms with ADHD to frequently switch, and sometimes abandon, tools and systems. The study contributes to HCI by linking each finding to a design consideration. The study builds upon previous findings that neurodivergent individuals benefit from externalizing thoughts, providing new insights into how and why this occurs. These findings lay the groundwork for further HCI research and human-centered design initiatives to help parents with ADHD, and their families, thrive.Item GEOMORPHIC AND HYDROLOGIC CHARACTERISTICS OF SMALL URBANIZED TRIBUTARIES TO A FALL ZONE STREAM(2024) Harris, John Allen; Prestegaard, Karen; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many rivers along the Atlantic Coast contain major knickpoints, which define the Fall Zone. These often-urbanized rivers straddle multiple physiographic regions with spatial variations in lithology, topography, and hydrology. This research evaluates the effects of mainstem channel incision and urbanization on channel and catchment morphology, bed substrate mobility, catchment water storage dynamics, and hydrologic response in tributaries of the Northwest Branch of the Anacostia River above and below the Fall Zone knickpoint. Topographic analyses show that differential incision below the mainstem knickpoint has initiated steep secondary channels incised into bedrock. Measurements at representative reaches show that bankfull shear stress exceeds critical shear stress in these newly initiated tributaries, resulting in erosive channels outside of threshold conditions. Increased urban runoff introduced at storm drain outfalls maintains these non-steady state conditions. Geophysical surveys reveal that regolith depth for water storage capacity is primarily below the flatter ridgetops of the tributary catchments, where development is concentrated. The secondary tributaries cannot access these upland storage zones, and thus have limited infiltration and recharge capacity. I installed streamgages in the tributaries and constructed catchment water balances to study storage dynamics and hydrologic response. Hydrologic consequences of urbanizing the steep secondary tributaries include flashy, elevated stormflows, greater total runoff, and reduced baseflows that are not maintained during drought periods. The combination of steep channels, thin regolith, and urban overprint limits infiltration to moderate storm responses and recharge storage. These effects were not seen in non-urbanized secondary tributaries, urbanized tributaries above the knickpoint, or the forested reference streams above the Fall Zone. These findings define the geomorphic adjustment of tributaries to differential mainstem incision and explore the hydrologic impacts of urbanizing small steep catchments with limited effective storage capacity. Supplementary files:S1: Table with the location, drainage area, stream gradient, bankfull hydraulic values, and grain size values at each Northwest Branch tributary and reference reach used in the study. S2: Spreadsheet with the water level logger gage height values collected at 5-minute intervals from April 2023-March 2024 and calculated discharge from the Northwest Branch tributary streamgages. S3: Spreadsheet with the monthly water balance values for the Northwest Branch tributary catchments and reference watersheds from April 2023-March 2024. S4: Table with the depth to bedrock values and corresponding slope angles measured from the seismic profiles and LiDAR-derived digital elevation models.Item Impact of Polymeric Drops on Drops and Films of a Different but Miscible Polymer(2024) Bera, Arka; Das, Siddhartha; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The fluid mechanics of a liquid drop impacting on another stationery (or spreading) liquid drop or on a liquid film (of thickness comparable, or smaller, or larger than the impacting drop) has attracted significant attention over the past several years. Such problems represent interesting deviations from the more widely studied problems of liquid drops impacting on solid surfaces having different wettabilities with respect to the impacting drops. These deviations stem from the fact that the resting liquid (in the form of the drop or the film) itself undergoes deformation on account of the drop impact and can significantly affect the overall combined drop-drop or drop-film dynamics. The problem becomes even more intriguing depending on the rheology of the drop(s) and the film as well as the (im)miscibility of the impacting drop with the underlying drop or the film. Interestingly, the majority of such drop-impact-on-drop or drop-impact-on-film studies have considered Newtonian drop(s) and films, with little attention to polymeric drop(s) and films. This thesis aims to bridge that void by studying, using Direct Numerical Simulation (DNS) based computational methods, the impact-driven dynamics of one polymeric drop on another (different but miscible) polymeric drop or film. As specific examples, we consider two separate problems. In the first problem, we consider the impact of a PMMA (poly-methyl methacrylate) drop on a resting PVAc (polyvinyl acetate) drop as well as the impact of a PVAc drop on a resting PMMA drop. In the second problem, we consider the impact of a PMMA drop on a PVAc film as well as the impact of a PVAc drop on a PMMA film. For the first problem, the wettability of the resting drop (on the resting surface), the Weber number of the impacting drop, the relative surface tension values of the two polymeric liquids (PVAc and PMMA), and the miscibility (or how fast the two liquids mix) dictate the overall dynamics. PVAc has a large wettability on silicon (considered as the underlying solid substrate); as a result, during the problem of the PMMA drop impacting on the PVAc drop, the PVAc drop spreads significantly and the slow mixing of the two liquids ensures that the PMMA drop spreads as a thin film on top of the PVAc film (formed as the PVAc drop spreads quickly on silicon). Depending on the Weber number, such a scenario leads to the formation of transient liquid films (of multitudes of shapes) with stratified layers of PMMA (on top) and PVAc (on bottom) liquids. On the other hand, for the case of the PVAc drop impacting on the PMMA drop, a combination of the weaker spreading of the PMMA drop on silicon and the “engulfing” of the PMMA drop by the PVAc drop (stemming from the PVAc having a smaller surface tension than PMMA) ensures that the impacting PVAc drop covers the entire PMMA drop and itself interacts with the substrate giving rise to highly intriguing transient and stratified multi-polymeric liquid-liquid structures (such as core-shell structure with PMMA core and PVAc shell). For both these cases, we thoroughly discuss the dynamics by studying the velocity field, the concentration profiles (characterizing the mixing), the progression of the mixing front, and the capillary waves (resulting from the impact-driven imposition of the disturbance). In the second problem, we consider a drop of the PMMA (PVAc) impacting on a film of the PVAc (PMMA). In addition to the factors dictating the previous problem, the film thickness (considered to be either identical or smaller than the drop diameter) also governs the overall droplet-impact-driven dynamics. Here, the impact, being on the film, the dynamics is governed by the formation of crown (signifying the pre-splashing stage) and a deep cavity (the depth of which is dictated by the film thickness) on the resting film. In addition to quantifying these facets, we further quantify the problem by studying the velocity and the concentration fields, the capillary waves, and the progression of the mixing front. For the PMMA drop impacting on the thin film, a noticeable effect is the quick thinning of the PMMA drop on the PVAc film (or the impact-driven cavity formed on the PVAc film), which gives rise to a situation similar to the previous study (development of transient multi-polymeric-liquid structures with stratified polymeric liquid layers). For the case of the PVAc drop impacting on the PMMA film, the PVAc liquid “engulfs” the deforming PMMA film, and this in turn, reduces the depth of the cavity formed, the extent of thinning, and the amplitude of the generated capillary waves. All these fascinating phenomena get captured through the detailed DNS results that are provided. The specific problems considered in this thesis have been motivated by the situations often experienced during the droplet-based 3D printing processes (e.g., Aerosol jet printing or inkjet printing). In such printing applications, it is commonplace to find one polymeric drop interacting with an already deposited polymeric drop or a polymeric film (e.g., through the co-deposition of multiple materials during multi-material printing). The scientific background for explaining these specific scenarios routinely encountered in 3D printing problems, unfortunately, has been very limited. Our study aims to fill this gap. Also, the prospect of rapidly solidifying these polymeric systems (via methods such as in-situ curing) can enable us to visualize the formation of solidified multi-polymeric structures of different shapes (by rapidly solidifying the different transient multi-polymeric-liquid structures described above). Specifically, both PMMA and PVAc are polymers well-known to be curable using in-situ ultraviolet curing, thereby establishing the case where the present thesis also raises the potential of developing PMMA-PVAc multi-polymeric solid structures of various shapes and morphologies.Item THE GUQIN IN TWENTY-FIRST CENTURY CHINA: A TRADITION REIMAGINED(2024) Yin, Xiaoshan; Witzleben, J. Lawrence; Music; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation is a musicological and anthropological examination of a Chinese instrument, the qin 琴, or guqin 古琴, a seven-string zither with an unbroken history of more than 2000 years, in its contemporary social context. The instrument, once said to be played exclusively by the elite literati in imperial China, has long been portrayed as the most representative musical icon of traditional Chinese culture. By the 1990s, the qin lost its elite status and public awareness decreased, but in 2003 the guqin and its music were proclaimed by UNESCO as a Masterpiece of the Oral and Intangible Heritage of Humanity, later known as Representative of the Intangible Cultural Heritage of Humanity (ICH). This proclamation and the national safeguarding agenda that comes along with it have evoked great enthusiasm from both the government and the public for revitalizing guqin music and culture. This process of contemporary revitalization is situated in a broader context: a national campaign to bring traditional culture back to life, reclaim the glory of the past, and build pride in Chineseness. However, there has been no detailed ethnographic study—in either English or Chinese—on developments in the qin world since the UNESCO proclamation in 2003, in contrast to the extensive historical and theoretical explorations of the instrument. My research is the first extended ethnographic study that closely examines this process of musical-cultural construction mediated by the national and regional safeguarding agenda and heritage narrative. I examine not only the musical products but also qin practitioners’ conceptualization and behavior, paying attention to the subjectivity of individual and group actors—that is, how they think of, speak about, and practice the guqin, and why. I explore how new communities and identities are being represented and/or constructed through qin performance practice and how the instrument in turn further structures the musical culture. I investigate the role the qin plays in people’s daily lives and in the cultural construction of the society, as well as the political, social, and economic powers that are mediating this musical-cultural process. My research is also in dialogue with a prevailing dichotomy between the “literati’s qin” and the “artists’ qin.” I question the historical and contemporary conceptualization of the literati, and present a new paradigm to view the qin world in China as it is socially and individually conceptualized and experienced, one which challenges essentialist ideas of the instrument being a heritage dating from time immemorial. I examine the dynamics of qin practitioners negotiating tradition and transformation as they continually reimagine and articulate the tradition. I view contemporary qin culture as multi-faceted, and I attempt to give attention and voice to different practitioners rather than labeling them or taking sides in debates. This study integrates historical, ethnographic, and musicological research methods. Historical documents that I investigated include but are not limited to nearly 150 old qin handbooks, mainly from the Ming and Qing dynasties, which contain qin music theories and repertoire, and fiction and non-fiction literature such as novels and encyclopedias. I conducted multiple field visits to mainland China during 2017–19, and intensive fieldwork there during June 2021–May 2022 and the summer of 2023. Cities that I visited include Beijing, Chengdu, Hangzhou, Kunming, Nanchang, Qingdao, Shanghai, Shenzhen, Suzhou, Yangzhou, and Zhuhai. I attended dozens of concerts, classes, and recording sessions, among other events related to the qin, and interviewed dozens of musicians and audience members. I analyze the visual and sonic expressions in stage performances and music videos, and conduct musicological studies on notation systems and practices. This dissertation is an example of “bottom-up” research in the area of ICH studies, as opposed to “top-down” research. Many studies on musical ICH in China and East Asia have dealt with top-down processes such as the UNESCO decision-making process, policy making at different levels of government, designation of heritage bearers, preservation actions, and the influence of these factors on the actual tradition and individual practitioners. A bottom-up study examines the situation in the reverse order. I focus on what is happening on the ground among grassroots practitioners and how that shapes the overall situation. My research also contributes broadly to scholarship on traditional Chinese music. Many scholars of Chinese music have written on the modernization of traditional Chinese music. The modernization process of the qin shares similarities with that of other genres, yet also demonstrates its own characteristics because of its rich written records and ICH status. A careful examination of the modernization of the qin is much needed in scholarship. This research offers ethnographic and historical data to musicologists and ethnomusicologists interested in the guqin and Chinese traditional music. Through the lens of the qin, my research deals with many aspects of Chinese cultural and social life, past and present. Therefore, this research also has the potential to be of great interest to social scientists, historians, and other scholars in Chinese and East Asian studies.