Theses and Dissertations from UMD
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Item EFFECTS OF ENVIRONMENTAL VARIABLES AND CHANGES IN SEASONAL PATTERNS ON SPATIAL DISTRIBUTIONS OF JONAH CRABS (CANCER BOREALIS) AND ATLANTIC ROCK CRABS (CANCER IRRORATUS) IN GEORGES BANK AND THE MID-ATLANTIC BIGHT, USA(2023) Wade, Kaitlynn Jean; Wilberg, Michael J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The economic and commercial importance of Jonah crabs (Cancer borealis) and Atlantic rock crabs (Cancer irroratus) has increased greatly in the USA. The objectives of my research were to determine spatial distributions, habitat preferences, and potential seasonal movements of both species. Data were obtained from the offshore Northeast Fishery Science Center bottom trawl surveys. Analyses included kernel density estimates, generalized additive models, empirical cumulative distribution functions, and ANOVAs. The spatial distributions of Jonah and Atlantic rock crabs changed over time during the 1970s – 2000s. Compared to Atlantic rock crabs, Jonah crabs preferred slightly warmer temperatures, deeper depths, and muddier sediments. Seasonally, Jonah crabs were found farther offshore in the winter and closer to shore in the fall and spring. Atlantic rock crabs were found closer inshore in the winter and spring and more offshore in the fall. Both species were found to have different seasonal patterns in the Mid-Atlantic BightItem Essays in Gender and Development(2023) SIVARAM, ANUSUYA; Goldberg, Jessica; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation consists of three essays at the intersection of gender and economics in developing countries. In chapter 1, I study the economic implications of a particular cultural practice: cousin, or consanguineous, marriage. One sixth of all marriages in Egypt are between first cousins, but there are important differences in the characteristics of individuals who select into such relationships relative to those who marry non-relatives. To measure the causal impact of the practice on socioeconomic outcomes abstracting from selection, I instrument for the probability of marrying a cousin using exogenous variation in family structure, and use weak instrument robust methods to estimate parameters and evaluate statistical significance. I find that individuals who marry a cousin because of exogenous attributes of their natal family structure are further in age from their spouse, predominantly driven by older men marrying cousins. I also find that women married to cousins receive higher levels of marital transfers that give them bargaining power within their marriages, likely as compensation for their spouse's attributes. This contrasts to patterns for those who select into cousin marriage; those individuals are younger at the time of marriage, match with partners closer to their own ages, and have no differences in the level of marital transfers exchanged. The contrast between OLS and IV results suggests that selection into cousin marriage may be motivated by anticipation of not matching on the wider marriage market, credit constraints, or the desire to consolidate property within the extended family. In chapter 2, I present baseline statistics from an experiment which examines the impact of random job offers on women's experiences of intimate partner violence in Bangladesh. This paper build on a larger study which aims to increase women's labor force participation and use of mobile money services. I collect supplementary data on women's experiences of intimate partner violence, men and women's agreement with conservative social norms, and second order beliefs regarding their community's sanction of intimate partner violence. I validate survey measures of intimate partner violence with a list randomization elicitation. I also present results from two incentivized decisionmaking activities conducted at baseline. I specify the outcomes I plan to test once endline data is available, as well as the econometric specifications I will use. Finally, I present power calculations using baseline data to determine the smallest effect sizes I can detect. Finally, in chapter 3, I study the impact of an exogenous negative shock to labor demand for female migrants within Bangladesh. I use a difference in differences strategy and compare outcomes between districts that have a history of sending migrants with those that do not, before and after the shock. I find that migrants respond to the initial shock and return to their households rather than remain unemployed in Dhaka, and that at least some of these women marry. I see no decrease in the level of investment in children's human capital, which suggests households do not revise their perceptions regarding the returns to education, and have access to other tools to smooth consumption. Finally, I see no changes in the daily agricultural wage rate for women in the years after the shock. I lack data on several important margins of adjustment which would allow us to discern the mechanisms behind the effects.Item PUBLIC MOBILITY AND THE IMPACT ON SOCIAL NETWORKS: UNDERSTANDING THE SOCIETAL AND TRANSNATIONAL COMMUNICATION OF MIGRANT NETWORKS FROM A QUALITATIVE APPROACH(2023) Iannacone, Jeannette Isabelle; Sommerfeldt, Erich J; Communication; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In considering the realities of 21st century society, research cannot overlook how livelihoods are becoming increasingly defined by one’s (in)ability for and agency over movement, i.e. mobility, especially on the transnational scale. Simultaneously, the relational turn of public relations scholarship has emphasized a network perspective, examining how a set of relations among social actors—be it people, groups, or organizations—create systems that comprise, maintain, and/or disrupt society (Yang & Taylor, 2015). As such, public relations should be inclusive of the depth of multiple, rich, and mobile relationships in social networks that span national borders. Yet the development of the network perspective in public relations has not been without its limitations, notably the absence of public perspectives, actions, and realities—all of which impact the communicative interactions that produce their social networks. This research thereby incorporates a public perspective through insights from people who migrate to highlight an increasingly important dimension to public formation and relationship dynamics: mobility. In doing so, this dissertation takes an innovative qualitative approach to social network analysis (SNA), which integrates a visual network mapping exercise alongside qualitative interviews and ethnographic observations. Findings captured how the enactment and context of mobility impact migrant network dynamics across the world as well as their subsequent communication behaviors and relational expectations, particularly with U.S. civil society organizations (CSOs). They further depicted an organizational perspective that highlighted three dichotomies to how CSOs perceive and maintain their social networks, and showcased the role of mobility as an underlying context generating distinct actors, ties, and positioning. Findings lastly emphasized entanglements between social and other forms of capital as well as patterns in who is perceived as having versus needing capital.As such, this dissertation proposes the conceptualization of the mobile social network ecology, a concept that integrates social network analysis and the experiences of public mobility by accounting for distinct publics and organizations perceptions. It allows for public relations to better consider the impacts of the enactment and context of mobility on key public relationships, inclusive of the distinct publics of the modern world, the CSOs that seek to serve them, and their linkages to civil societies on a transnational scale. Additionally, in noting the significant ties between migrant publics and migrant-serving CSOs, this dissertation connects the exchanges of (social) capital within a mobile social network ecology to relational power dynamics and differentials, emphasizing their lived, embodied impact as well as introducing a new salient category: spatial capital. All together, these contributions advance public relations in reckoning with the transnational, globalized dimensions of the modern world, showcasing how public mobility shapes and complicates our fundamental societal connections and presenting unique takeaways for the field in scholarship and practice.Item TIME IS ENERGY: DRIVERS OF MIGRATORY AND NON-MIGRATORY MOVEMENTS BY SOARING BIRDS(2020) Mallon, Julie Marie; Fagan, William F; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vultures are obligate scavengers and search over large areas for carrion, which is ephemeral. To profit from carrion, they are also obligate soarers that rely on the availability of environmental updrafts to subsidize flight. This restricts their flight spatially and temporally to where and when strong updrafts are available. In this dissertation, I investigate how Turkey Vultures (Cathartes aura) use stopovers to both avoid inclement weather and to replenish spent fuel reserves, as well as how the timing of movement activity differs according to flight mode.Using GPS-tracking data from four migratory Turkey Vulture populations, I evaluated how Turkey Vultures respond to changing weather conditions. During stopovers, movement activity was positively correlated with conditions that promote thermal development, suggesting not all stopovers are used for weather-avoidance. Turkey Vultures began stopovers immediately in response to deteriorating weather conditions but their departure from stopovers was delayed relative to improvements in weather, behavior that is consistent with an energy-minimization strategy. I estimated total energetic costs for each migration and identify probable refueling stopovers. Only long-distance Turkey Vulture migrants regularly stop to feed. Overall migratory costs are driven by migration duration, and therefore are lower in the spring when vultures migrate faster, which may contribute to seasonal differences in flight behavior. Last, I compared the non-migratory movements of 49 avian species to test for the influence of flight mode on the timing of movement activity. Terrestrial soaring birds began activity later and stopped activity earlier than other birds. This study demonstrates that flight mode influences temporal patterns of daily movement activity of birds. This dissertation enhances our understanding of how soaring birds cope with the temporal and spatial restrictions on their movements. During non-migration, soaring birds are active for longer proportions of the day to search for food over greater spatial areas than flapping birds. During migration, total energetic costs are driven more by migration duration than by behavior. Therefore, an energy minimization strategy for Turkey Vultures is also a time minimization strategy and vultures are expected to optimize their migration so that they spend the fewest days migrating as possible.Item The Ecological Velocity of Climate Change(2020) O'Leary, Donal Sean; Hurtt, George C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vegetation productivity and distributions are largely driven by climate, and increasing variability in seasonal and interannual climate is both changing the spatiotemporal patterns of resource availability across the landscape, and driving species’ migrations towards climate refugia. Climate and vegetation dynamics take place along the time dimension (e.g. earlier snowmelt and arrival of spring in temperate mountains), but they also occur throughout space, where changes in climate can be expressed as a movement across the landscape (e.g. warm temperatures and migratory animals moving uphill in spring, or tree species distributions moving uphill and towards the poles under climate change). Here, we present new methods to track the movement of climate and vegetation, quantifying the ecological velocity of climate change at the landscape scale. Our focus is on national parks of the USA, which are important study areas because of their great conservation and social value, protection from anthropogenic disturbances, and longstanding research and monitoring records. First, we explore the spatio-temporal relationships between snowmelt timing and vegetation phenology in Crater Lake National Park. We find that snowmelt timing is closely linked to spring greenup, but has far weaker influence on later season phenology, such as the senescence or growing season length. Second, we extend our comparison of snowmelt timing with vegetation phenology across space and time together as we track the speed and direction of receding seasonal snowpack (snowmelt velocity) with the ‘green wave velocity’ of spring greenness that follows. We find that snowmelt velocity has a moderate predictive power for green wave velocity in areas with steep slopes, where both phenomena are controlled by strong spatial gradients relating to elevation. Third, we extend our analysis into the future as we forecast the climate velocity of air temperature and precipitation in and surrounding national parks from 2019-2099. Here, we identify possible corridors and velocities of future climate migration across park boundaries, highlighting locations of ecological concern and climate vulnerability. Taken together, our analysis of the ecological velocity of climate change forms new connections among climate, conservation, and spatial sciences while prioritizing management-relevant deliverables.Item Effects of physico-chemical cues from the blood-brain barrier microenvironment on tumor cell migration and morphology(2019) Pranda, Marina Alexandrovna; Stroka, Kimberly M; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cancer metastasis is particularly deadly, leading to 90% of cancer deaths. During metastasis, tumor cells break off from a primary tumor and travel to distant sites. Metastasis to the brain results in a poor patient prognosis. However, several common cancers, such as breast cancer and melanoma, metastasize to the brain. In order to metastasize to the brain, tumor cells have been shown to cross the highly selective blood-brain barrier (BBB), which separates the brain parenchyma from the circulatory system. The BBB is highly impermeable, even for many chemotherapeutics, however, tumor cells are able to cross it by a poorly understood mechanism. The BBB consists of endothelial cells connected by tight junctions, and is supported by cells of the neurovascular unit, such as astrocytes. Furthermore, the composition of the extracellular matrix beyond the BBB is unique and contains hyaluronic acid (HA). In disease, HA organization or biophysical properties may become altered. The goal of this study was to investigate how specific physico-chemical interactions of tumor cells and the BBB microenvironment may impact tumor cell behavior at the BBB, as well as explore cold atmospheric plasma (CAP) as potential cancer treatment. This understanding could lead to better future therapeutics and a better prognosis for patients. We hypothesized that biophysical and biochemical cues from the BBB microenvironment, as well as the tumor cell phenotype, can influence tumor cells’ migration and morphology. In this dissertation, we investigated the interaction of tumor cells with astrocyte-secreted biochemical cues and the biophysical cues from a HA/gelatin extracellular matrix on tumor cell morphology, migration, and incorporation into an endothelium. Our results showed that tumor cell migration and morphology are significantly altered by astrocyte-secreted factors and the HA/gelatin extracellular matrix; however, the extracellular matrix is less significant during incorporation. We also showed that brain- and bone-seeking tumor cells display varied morphologies on matrices with niche-relevant mechanical properties. Finally, we demonstrated that CAP selectivity for reducing migration of tumor vs. normal cells is highly sensitive to cell culture media formulation. Together, these results provide new insights into tumor cell behavior at the BBB and inform future studies and therapeutic development.Item ECOLOGICAL CAUSES AND CONSEQUENCES OF NON-BREEDING MOVEMENTS IN A DECLINING MIGRATORY SONGBIRD, WOOD THRUSH (HYLOCICHLA MUSTELINA)(2019) Stanley, Calandra Quinn; Dudash, Michele R; Marra, Peter P; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation I evaluate the ecological correlates of non-breeding space-use strategies and how these drive within and between season movement dynamics in a declining migratory songbird, wood thrush (Hylocichla mustelina). In Chapter 1, I deployed high-resolution GPS transmitters across 5 breeding populations to quantify habitat selection as wood thrush moved across the annual cycle. I found seasonal variation in habitat selection at the regional, landscape and local scales which suggests the factors driving the evolution of habitat selection preferences vary across seasons and environmental conditions. In Chapter 2, I combined radio telemetry and GPS tracking to examine how environmental conditions drove space-use strategies during the non-breeding stationary period. I found evidence that both small- and large-scale movement dynamics were dependent on moisture levels on tropical non-breeding grounds. At small spatial scales, dry conditions drove low food availability, reduced individual body condition and these individuals had larger home ranges. In this same chapter I integrated archival GPS tag data to demonstrate that wood thrush from across the breeding range engaged in permanent large-scale mid-winter shifts in home ranges and, similar to radio-tagged birds, that individuals from wetter, higher quality habitats were more likely to use this strategy. I suggest that the facultative movements are a condition-dependent strategy allowing wood thrush to find alternative habitats as conditions deteriorate across the dry season in their non-breeding grounds. Finally, to determine how food availability may influence timing of spring migration, I performed a food manipulation experiment with captive wood thrush in Chapter 3. I found that food availability and body condition modulated the intensity, but not onset, of migratory restlessness (Zugunruhe), an index of migratory disposition in captive birds. These results suggest that non-breeding food limitations could constrain migration preparation in wood thrush. Low food availability also advanced the onset of migratory fattening. I suggest that advancing migratory fattening when food availability is low may provide a mechanism to flexibly adjust migration timing under poor environmental conditions. Together these findings suggest that wood thrush exhibit a diversity of behavioural mechanisms to handle environmental heterogeneity across the annual cycle.Item Displacement: Placemaking for the Uprooted(2018) Khan, Dur-e-Nayab; VanderGoot, Jana; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasing migration to cities in developed countries is an inevitable part of present day’s globalizing society. For those migrating, the process is often a byproduct of war or absence of opportunities in migrants’ native homelands. It is a privilege, a manner of freedom, and a chance at a higher quality of life. As waves of migrants enter foreign countries, various problems arise, exacerbated by rising impressions of detachment from the loss of everything native. Migrants also experience feelings of displacement both physical and psychological. This thesis analyzes how architecture can mediate the process of assimilation into a new geography by creating a sense of place. The argument will assert that idiosyncrasies within the population are catalysts for an enlightened culture. This thesis does not intend to solve the problem of migration, but rather open a conversation about belonging, memory, and hybridity as it applies to the migrant and the built environment. Currently, there is a lack of architectural precedent successfully accommodating migrating populations. To fill this gap, this thesis will propose both a dwelling and a gallery to raise awareness, memorialize the remaining fragments of homelands and construe immigrants’ feelings of deracination to evoke a sense of empathy. The proposal will be situated in Washington D.C. so that it may serve as a model for creating similar forums in this age of mass migration.Item Essays on Individual Responses to Labor Market Conditions and Policies(2018) Wilson, Riley; Kearney, Melissa S; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines how individuals respond to changing conditions and policies in the labor market, with a particular interest in understanding economically motivated migration and labor force attachment. I first turn to the question of labor mobility. There is long-standing academic and policy interest in the issue of economically motivated geographic mobility. I examine the recent context of localized "fracking" booms in the United States to explore the migration response to positive labor demand shocks. Using data from 1999 to 2013, I show that local fracking led to large increases in potential earnings and employment rates, as well as a sizable migration response. But, this average migration effect masks substantial underlying heterogeneity in migration behavior across both demographics and regions. Migrants to fracking areas were more likely to be male, unmarried, young, and less educated than movers more generally. Furthermore, both in- and out-migration rates increased with fracking and both flows were driven by the same demographic groups, suggesting fracking resulted in short-term migration and increased churn. An instrumental variables analysis using fracking conditions to instrument for earnings suggests that a ten percent increase in average earnings increased in-migration rates by 3.8 percent in North Dakota fracking counties, as compared to only 2.4 percent in the West, 1.6 percent in the South, and 0.5 percent in the Northeast. The difference across regions is statistically significant; robust to housing market controls, geographic spillovers, and other various specifications; and is only partially explained by differences in commuting behavior, initial population characteristics, or a non-linear relationship between earnings and migration. There is some evidence that heterogeneous information flows might be driving the heterogeneous migration response. This implies that lack of information might be dampening rates of migration to economically favorable labor markets. I next examine how labor market information affects these types of economically motivated migration decisions. Migration is a human capital investment that allows individuals to encounter more favorable labor markets. I exploit county-level variation in exposure to news about labor markets impacted by fracking, to show that access to information about potential labor market opportunities affects migration. I use pre-fracking newspaper circulation rates and content from national news outlets to capture exogenous variation in exposure to news about fracking in a particular destination. I then isolate the effect of news exposure by comparing migration flows to the same destination from differentially exposed origin counties. Exposure to newspaper articles about fracking increased migration to the areas mentioned in the news by 2.4 percent on average. News exposure also increases commuting to fracking counties. Exposure to TV news has a similar impact, and positive news about fracking increases migration more than negative news. As further evidence that news matters, Google searches for the term fracking and the names of states specifically mentioned spike after TV news broadcasts about fracking. Migration responses to news about fracking are largest from counties experiencing weak labor markets, suggesting these areas see the largest benefits to information provision. Finally, I examine how a well known government policy aimed to incentize labor force participation -- the Earned Income Tax Credit (EITC)-- affects labor force transitions. Less-educated single women frequently transition in and out of the labor force. Although there is evidence that the Earned Income Tax Credit (EITC) increases annual labor force participation, it is unclear how it affects these high frequency, within year employment decisions and entry and exit. By exploiting the panel nature of the Current Population Survey, I overcome challenges associated with compositional changes and estimate the impact of increases in EITC generosity on employment transitions. EITC expansions induce less-educated single women who were previously attached to the labor force to work more months, leading stronger labor force attachment and more annual weeks worked. This leads to less annual exit, suggesting that the documented impact of the EITC on labor force participation rates in part operates by keeping previously employed single women in the labor force. This highlights the importance of understanding how income support programs affect not only labor force participation, but transitions as well. Employment decisions respond to increases in the maximum EITC credit eligible to receive in the current year, rather than the maximum credit eligible to earn, which differ because the EITC is a tax credit transferred with a one year lag. This would be consistent with workers basing their current work decisions on their lagged experience with the EITC. Further evidence additionally suggests that the employment response to the lagged EITC amount is likely due to information about the return to work, rather than to the relaxation of liquidity constraints.Item Violence and Belonging: The impact of citizenship law on violence in Sub-Saharan Africa(2016) Fruge, Anne Christine; Birnir, Johanna K; Government and Politics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many countries in Africa are embroiled in heated debates over who belongs where. Sometimes insider/outsider debates lead to localized skirmishes, but other times they turn into minor conflict or even war. How do we explain this variation in violence intensity? Deviating from traditional explanations regarding democratization, political or economic inequality, or natural resources, I examine how nationality laws shape patterns in violence. Citizenship rules determine who is or is not a member of the national political community. Nationality laws formalize these rules, thus representing the legal bond between individuals and the state. Restrictive nationality laws increase marginalization, which fuels competition between citizenship regime winners and losers. This competition stokes contentious insider/outsider narratives that guide ethnic mobilization along the dual logics of threat and opportunity. Threats reduce resource levels and obstruct the exercise of rights. Opportunities provide the chance to reclaim lost resources or clarify nationality status. Other work explains conditions necessary for insider/outsider violence to break out or escalate from the local to the national level. I show that this violence intensifies as laws become more exclusive and escalates to war once an outsider group with contested foreign origins faces denationalization. Groups have contested foreign origins where the “outsider” label conflates internal and foreign migrants. Where outsiders are primarily in-migrants, it is harder to deny the group’s right to citizenship, so nationality laws do not come under threat and insider/outsider violence remains constrained to minor conflict. Using an original dataset of Africa’s nationality laws since 1989, I find that event frequency and fatality rates increase as laws become more restrictive. Through case studies, I explain when citizenship struggles should remain localized, or escalate to minor or major conflict. Next, I apply a nationality law lens to individual level conflict processes. With Afrobarometer survey data, I show that difficulty obtaining identity papers is positively correlated with the fear and use political violence. I also find that susceptibility to contentious narratives is positively associated with using violence to achieve political goals. Finally, I describe the lingering effects of a violent politics of belonging using original survey data from Côte d’Ivoire and Ghana.
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