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 Understanding Parent and Teacher Perspectives of Temperament Profiles in Young Children(2023) Waldrip, Sabrina M; Teglasi, Hedwig; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The study of temperament profiles is considered a person-centered approach to understanding temperament, as it takes into consideration the complex combinations and interactions of multiple traits that characterize an individual. However, most studies of temperament profiles have focused on reactive traits in infants and toddlers using parent ratings and/or laboratory conditions and since outdated methodologies. This study contributed to the temperament profile literature by exploring profiles based on parent and teacher ratings of reactive and regulatory traits of young children in kindergarten using the modern statistical technique of latent profile analysis. Kindergarten is a unique and critical time in development in which children are suddenly learning new academic, social, and self-regulatory skills as they begin formal education. Parent and teacher ratings of kindergarteners’ temperament were analyzed separately and the behavioral profiles produced by each were described. When only reactivity traits were included in the analyses, the profiles that emerged were mostly consistent with the three to four profiles that have been found in previous studies, including inhibited, exuberant, average, and/or low reactive profiles. When both reactive and regulation traits were included in the analyses, more nuanced profiles emerged that generally reflected subdivisions of the traditional reactivity profiles found in the literature but with varying levels of regulation. There were many similarities but important distinctions among the profile numbers, temperament patterns, and proportion sizes of the parent and teacher profile solutions. Neither child age nor child sex were found to be important predictors of profile membership. Despite its own limitations, the present study serves as a model for how previous methodological limitations in the field may be addressed to enhance our understanding of the complexity and nuances of temperament development and continue to push the field forward. Through such person-centered approaches, the field may one day guide parents, educators, and practitioners towards meeting the diverse needs of children with various temperament dispositions.Item Intercellular transport of RNA can limit heritable epigenetic changes(2021) Shugarts, Nathan Maxwell; Jose, Antony M; Cell Biology & Molecular Genetics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)RNAs in circulation carry sequence-specific regulatory information between cells in animal, plant, and host-pathogen systems. The accumulation of specific RNA species in circulation during human disease states therefore implicates such RNAs in disease-related gene regulation. However, mechanisms of RNA secretion, accumulation and import into cells are not well understood and yet are directly taken advantage of in the delivery of recently approved RNA-based therapeutics. In the tractable animal Caenorhabditis elegans, double-stranded RNA (dsRNA) can be delivered into circulation, accumulate within the germline and reach progeny, raising the potential for intergenerational effects from endogenous RNAs released into parental circulation. Here we provide evidence for spatial, temporal, and substrate specificity in the transport of dsRNA in C. elegans from parental circulation to progeny. Temporary loss of dsRNA transport resulted in the persistent accumulation of mRNA from a germline gene. The expression of this gene varied among siblings and even between gonad arms within one animal. Perturbing RNA regulation of the gene created new epigenetic states that lasted for many generations. Thus, one role for the transport of dsRNA into the C. elegans germline in every generation is to limit heritable changes in gene expression. We speculate that transport of extracellular RNA into germ cells in other systems could similarly buffer against heritable change across generations.Item Essays on Regulatory Uncertainty & Energy Development in the American West(2021) Hunt, Jeffrey; Linn, Joshua; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation undertakes an analysis of regulation in the American West, investigating the effects of expropriation uncertainty and technological change in the leasing process.The first chapter explores the possible expropriation of drilling rights due to the addition of the sage-grouse under the Endangered Species Act. Leveraging prior decisions of the US Fish and Wildlife Service, I estimate there was a 52.6% chance the sage-grouse would be listed. Using the real-options framework of Kellogg (2014) and constructing an extension of his simulation to accommodate expropriation risk parameterized by real-world drilling data, I find that developers are expected to delay spudding wells to wait out the uncertainty. This result is corroborated with a Cox proportional hazards model. Additionally, using a difference-in-differences model I find robust evidence that developers reduce their bids for leases commensurate with the expected reduction in profits from possible regulation, and using a conditional logit discrete choice model I find evidence that firms abandon core sage-grouse habitat. Lastly, I find no evidence that developers increase the extraction rate of drilled wells. The second chapter investigates expropriation risk in the context of ozone pollution controls from the Environmental Protection Agency. Here, I find a hurry-up-and-drill response. I place this result within the literature of the green paradox, and find that the EPA regulation did not produce a green paradox but if costs were lower, or if the regulation were modified, a green paradox would have existed and briefly result in higher emissions under a stricter regulatory regime. The policy takeaway is that regulators should avoid a long announcement period, as it gives developers time to drain wells before regulation occurs. The third chapter is a cost/benefit test of auctioning drilling leases online rather than in-person. I leverage the fact that only specific leasing jurisdictions transitioned to an online system called EnergyNet in late 2016 to estimate the causal effect of moving to online leasing. I estimate that a given parcel sold online versus in-person will generate 40% higher bids against only a 2% extra cost.Item The Role of Information in Policy Implementation(2020) Andarge, Tihitina Tesfaye; Lichtenberg, Erik; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Firms will comply with a regulation when the expected costs of noncompliance exceed the expected benefits. If the regulator has incomplete enforcement information and firms are aware of this, it will enter into their calculation of expected benefits and costs. The literature on regulatory enforcement typically assumes that the regulator is able to identify the universe of regulated firms. In my dissertation, I relax this assumption by allowing for the existence of regulatory information gaps and examine the implications for compliance and ambient environmental quality. The first chapter reviews the literature on the enforcement of environmental regulations. The second chapter examines the effect of regulatory information gaps on a firm’s compliance strategy. The theoretical results indicate that a firm with a sufficiently low probability of being subject to enforcement action will delay compliance. This prediction is tested empirically in the context of nutrient management regulations in Maryland. The econometric results indicate that the probability of being included in the MDA farm registry is associated with a statistically significant increase in the probability of being in compliance with nutrient management regulations. If information gaps have an effect on a firm’s compliance decision, then they may potentially have consequent effects on ambient environmental quality. In the third chapter, I develop a theoretical model of the firm’s optimal level of emissions under information gaps. The theoretical results indicate that the optimal level of emissions is decreasing in the likelihood of being known to the regulator. If decreases in a firm’s emissions result in decreases in ambient pollution levels, then ambient pollution levels are also decreasing in the probability of being known. I test this prediction empirically within the context of Clean Water Act (CWA) permit regulations. The empirical results indicate that a one percentage point increase in the share of firms known to the regulator results in a 0.43% - 0.49% percent decrease in ambient pollutant concentration for three out of the four pollutants. Increasing the share of known firms by 5 percentage points could lead to benefits, in terms of improved water quality, of $165.9 million per year.Item An analysis of regulatory decisions on food-use pesticides under the Food Quality and Protection Act(2012) Newcomb, Elisabeth Jo; Cropper, Maureen L; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To ensure the safety of older pesticides used in the United States, the EPA required the reregistration of pesticide uses which were first introduced before 1984. Using a dataset of reregistration outcomes for 2722 pesticide uses applied to food crops, I analyze the extent to which these decisions were determined by chronic health risks, pesticide expenditures, and other factors. I find that the dietary health risks associated with pesticides are had greater influence on actions to reduce dietary and occupational exposures than on pesticide cancellations. High population dietary risks are associated with higher rates of pesticide cancellations, though these results are insignificant. There is evidence that the EPA was more responsive to child and infant dietary risks: values above the EPA's threshold of concern were more than 10% more likely to be cancelled than those that were not (significant at the 10% level). The effects of cancer risks on EPA actions are more ambiguous, though this may be due to data limitations. The less safe pesticides are for handlers, the more often they are cancelled, but pesticide safety has a more significant correlation with reentry intervals. A one percent decrease in the safety of a pesticide to handlers predicts a reduction in reentry interval of 1.6 days (significant at the 5% level). Expenditures on individual pesticides have a strong relationship with pesticide reregistration, with an additional half million dollars in expenditures predicting a 2% increase in the probability of reregistration (significant at the 1% level). Expenditures are not so correlated with reentry intervals or changes in pesticide tolerances. After accounting for dietary risk and pesticide expenditures, Monsanto and Dow were most likely to have uses reregistered. Though there was some concern that small crops with low pesticide expenditures would suffer extra cancellations, small crop uses were no more likely to be cancelled than large crop uses. Mentions of individual pesticides in the media had no apparent relationship with the outcome of reregistration decisions.Item Does the Policy-Making Process Affect Farmer Compliance? A Three-State Case Study of Nutrient Management Regulations(2010) Perez, Michelle Reid; Nelson, Robert H.; Public Policy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A series of fishkills in 1997 in the Chesapeake Bay were linked to Pfiesteria piscicida, a rare toxic microorganism, and to nutrient pollution from agricultural sources. Manure from poultry production on the Delmarva Peninsula was regarded as the primary source of the excess nutrients. These fishkills served as a focusing event for policy-makers in Maryland, Virginia, and Delaware to update their scientific guidance on phosphorus management, promulgate agricultural regulations, and depart from decades of relying on voluntary technical and financial assistance to improve farm-related water quality problems. This dissertation conducts a comparative case study of these three states to determine if 1) the policy-making process in each state affects compliance by farmers and 2) if the laws improved farmer nutrient management behavior. Data sources include information gathered from interviews with 60 corn farmers on the Peninsula that use broiler chicken manure as fertilizer; interviews with over 60 policy stakeholders; and reviews of primary and secondary documents. Analytical methods include: political analysis of the main stages of the policy development process; policy analysis of the effectiveness of plan-based regulations; statistical tests to determine significant differences between states regarding farmer responses to Likert Opinion Statements and questions about their nutrient management practices; logit regression analysis to determine factors influential to low manure application rates; and a review of compliance data collected by the state regulatory agencies. Answers to both research questions are, overall, "yes," though this answer depends on which dataset of compliance and which metric of improved nutrient management behavior is reviewed; there are "no" answers as well. Results of this dissertation highlight the serious difficulty of regulating dispersed nonpoint source agricultural nutrient pollution through nutrient management plans. Several findings arise, including: plan-based agricultural regulations are in reality voluntary; plans prepared by private and public sector planners result in non-uniform standards; gaining "buy-in" from rather than "alienating" the regulated community likely results in better overall outcomes; regulations that account for on-the-ground realities of farming and state regulatory capacity likely achieve better overall outcomes; and focusing events that turn out to be weak can undermine the justification for new regulatory policies.Item Patterns and Complexity in Biological Systems: A Study of Sequence Structure and Ontology-based Networks(2010) Glass, Kimberly; Girvan, Michelle; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biological information can be explored at many different levels, with the most basic information encoded in patterns within the DNA sequence. Through molecular level processes, these patterns are capable of controlling the states of genes, resulting in a complex network of interactions between genes. Key features of biological systems can be determined by evaluating properties of this gene regulatory network. More specifically, a network-based approach helps us to understand how the collective behavior of genes corresponds to patterns in genetic function. We combine Chromatin-Immunoprecipitation microarray (ChIP-chip) data with genomic sequence data to determine how DNA sequence works to recruit various proteins. We quantify this information using a value termed "nmer-association.'' "Nmer-association'' measures how strongly individual DNA sequences are associated with a protein in a given ChIP-chip experiment. We also develop the "split-motif'' algorithm to study the underlying structural properties of DNA sequence independent of wet-lab data. The "split-motif'' algorithm finds pairs of DNA motifs which preferentially localize relative to one another. These pairs are primarily composed of known transcription factor binding sites and their co-occurrence is indicative of higher-order structure. This kind of structure has largely been missed in standard motif-finding algorithms despite emerging evidence of the importance of complex regulation. In both simple and complex regulation, two genes that are connected in a regulatory fashion are likely to have shared functions. The Gene Ontology (GO) provides biologists with a controlled terminology with which to describe how genes are associated with function and how those functional terms are related to each other. We introduce a method for processing functional information in GO to produce a gene network. We find that the edges in this network are correlated with known regulatory interactions and that the strength of the functional relationship between two genes can be used as an indicator of how informationally important that link is in the regulatory network. We also investigate the network structure of gene-term annotations found in GO and use these associations to establish an alternate natural way to group the functional terms. These groups of terms are drastically different from the hierarchical structure established by the Gene Ontology and provide an alternative framework with which to describe and predict the functions of experimentally identified groups of genes.Item Archaeal Transcriptional Regulation of Catabolic Carbon Monoxide Dehydrogenase in Methanosarcina species(2009) Anderson, Kimberly Lynn; Sowers, Kevin R; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In Archaea, the basal transcription machinery is eukaryotic-like, but some components, such as activator and repressor proteins, are bacteria-like. To further gain knowledge into cellular processes of Archaea, the genome of Methanosarcina thermophila was searched for helicase genes. A homolog of yeast RAD25, a gene with helicase and nucleotide excision repair (NER) abilities, was isolated. M. thermophila rad25 has the domains for helicase activity, but the C-terminal end is truncated, indicating that this protein mostly likely does not function in NER. After overexpression, helicase activity assays of Rad25 indicated that it might have helicase activity; however, there appeared to be contaminating proteins in the purification, so it was not possible to assign the activity only to Rad25. Additional work is necessary to characterize this protein. To investigate transcription, catabolic gene regulation was studied, specifically regulation of carbon monoxide dehydrogenase/acetyl CoA synthase (CODH/ACS) from Methanosarcina species. The regions upstream of the transcriptional start site, as well as the 5' leader region of cdhA, were investigated for trans factors and cis elements that might be involved in regulation. Experiments revealed that regulation of cdhABCDE does not appear to involve trans factors upstream of the transcriptional start site. However, deletion analysis indicated that the 5' leader region does have a role in regulation. Comparing the protein levels to the mRNA levels revealed there was no significant difference between the two, indicating that translational regulation was not a factor. Other experiments ruled out differential mRNA stability as a factor in regulation. A region located between +358 and +405 was important in transcriptional regulation, indicating that regulation occurred at the level of transcription elongation. A model for regulation of catabolic CODH/ACS by differential elongation is proposed. Although 5' leader regions identified for other archaeal genes have been postulated to be involved in regulation, this was the first study to demonstrate a regulatory role by an archaeal leader sequence for differential elongation. Identifying regulatory mechanism(s) of catabolic genes such as CODH/ACS is critical for understanding the regulatory strategies employed by the methanoarchaea to efficiently direct carbon and electron flow during biomass conversion to methane.Item The Economics of Nuclear Power(2006-11-28) Horst, Ronald L; Rust, John; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We extend economic analysis of the nuclear power industry by developing and employing three tools. They are 1) compilation and unification of operating and accounting data sets for plants and sites, 2) an abstract industry model with major economic agents and features, and 3) a model of nuclear power plant operators. We build a matched data set to combine dissimilar but mutually dependent bodies of information. We match detailed information on the activities and conditions of individual plants to slightly more aggregated financial data. Others have exploited the data separately, but we extend the sets and pool available data sets. The data reveal dramatic changes in the industry over the past thirty years. The 1980s proved unprofitable for the industry. This is evident both in the cost data and in the operator activity data. Productivity then improved dramatically while cost growth stabilized to the point of industry profitability. Relative electricity prices may be rising after nearly two decades of decline. Such demand side trends, together with supply side improvements, suggest a healthy industry. Our microeconomic model of nuclear power plant operators employs a forward-looking component to capture the information set available to decision makers and to model the decision-making process. Our model includes features often overlooked elsewhere, including electricity price equations and liability. Failure to account for changes in electricity price trends perhaps misled earlier scholars, and they attributed to other causes the effects on profits of changing price structures. The model includes potential losses resulting from catastrophic nuclear accidents. Applications include historical simulations and forecasts. Nuclear power involves risk, and accident costs are borne both by plant owners and the public. Authorities regulate the industry and balance conflicting desires for economic gain and safety. We construct an extensible model with regulators, plant operators, insurance companies, and consumers. The model possesses key attributes of the industry seldom found in combination elsewhere. We then add additional details to make the model truer to reality. The work extends and corrects existing literature on the definition, effects, and magnitudes of implicit subsidies resulting from liability limits.