UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

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 given thesis/dissertation in DRUM.

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Examining pre-training interpersonal skills as a predictor of post-training competence in mental health care among lay health workers in South Africa
(2023) Rose, Alexandra Leah; Magidson, Jessica F.; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
A worldwide shortage of mental health specialists contributes to a substantial global mental health treatment gap. Despite evidence that lay health workers (LHWs), or health workers with little formal training, can effectively deliver mental health care, LHWs vary widely in their abilities to competently deliver mental health care, which undermines the quality of care and patient safety. Prior research from both high-income and low- and middle-income countries suggests this variability may be predicted by LHW interpersonal skills, yet this relationship is little explored to date. The first aim of the current study, which uses an exploratory sequential mixed methods design, was to explore qualitative perspectives through semi-structured individual interviews (n=20, researchers, policymakers, NGO staff, LHWs) in Cape Town, South Africa on interpersonal skills relevant to delivery of mental health interventions by LHWs. The second aim was to quantitatively examine the preliminary effectiveness of pre-training interpersonal skills in predicting post-training competence following a mental health training among LHWs in Cape Town (n=26). Using a standardized LHW assessment measure adapted to the setting, two raters rated ten-minute standardized role plays conducted before and after the training for pre-training interpersonal skills and post-training competence. Qualitative findings highlight the perceived importance of and challenges with assessing interpersonal skills among LHWs being trained in psychological intervention. Quantitative analyses did not identify any interpersonal skills as significant predictors of post-training competence. However, interpersonal skills improved during the training itself, specifically verbal communication, suggesting the potential promise of further research in this area. Recruitment of larger samples with more variable training outcomes would be important in future studies examining predictors of LHW competence. Further research may ultimately help identify areas of intervention to support more LHWs in attaining competence and can help play an important role in increasing access to psychological services globally.
Integrated Geochemical Studies of the Shuram Excursion in Siberia and South China
(2024) Pedersen, Matthew; Kaufman, Alan J; Geology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The Ediacaran Period Shuram Excursion (SE) is a globally-distributed and highly controversial phenomenon where over millions of years, sedimentary carbonates record δ13C values of -10‰ and lower. This carbon cycle anomaly may reflect disequilibrium in the world’s oceans, driven by the oxidation of a large pool of dissolved organic carbon (DOC), with the oxidants sourced from the intense weathering of the continents, forcing major changes to ocean chemistry through the ventilation of the deep ocean, evidenced by a positive shift in carbonate uranium isotope values, and invoking the onset of early animal biomineralization. This study utilizes high-resolution carbonate Li isotopes from two SE-successions, U isotopes, REE abundances and Ce anomalies which reveal the dynamic interplay between intensified continental weathering associated with tectonic reconfiguration and the subsequent environmental and ecological response that may have been amplified by the ecosystem-engineering abilities of a newly discovered sponge-grade animal.
Eventually Stable Quadratic Polynomials over Q(i)
(2024) McDermott, Jermain; Washington, Lawrence C; Mathematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Let $f$ be a polynomial or a rational function over a field $K$. Arithmetic dynamics studies the algebraic and number-theoretic properties of its iterates $f^n:=f \circ f \circ ... \circ f$.\\ A basic question is, if $f$ is a polynomial, are these iterates irreducible or not? We wish to know what can happen when considering iterates of a quadratic $f= x^2+r\in K[x]$. The most interesting case is when $r=\frac{1}{c}$, which we will focus on, and discuss criteria for irreducibility, i.e. \emph{stability} of all iterates. We also wish to prove that if 0 is not periodic under $f$, then the number of factors of $f^n$ is bounded by a constant independent of $n$, i.e. $f$ is \emph{eventually stable}. This thesis is an extension to $\Qi$ of the paper \cite{evstb}, which considered $f$ over $\mathbb{Q}$. This thesis involves a mixture of ideas from number theory and arithmetic geometry. We also show how eventual stability of iterates ties into the density of prime divisors of sequences.
AN ARCHAEOLOGICAL INVESTIGATION OF CLOVIS BLADE TECHNOLOGY AT THUNDERBIRD (44WR11), A PALEOLITHIC STRATIFIED SITE OF THE FLINT RUN COMPLEX, WARREN COUNTY, VA
(2024) Fredrickson, Kurt N; Palus, Matthew; Anthropology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The presence of Paleoindians in the Eastern United States at the end of the Pleistocene has been a focus of scientific examination for more than a century, resulting in the discovery of numerous sites. These sites, occupied more than ten millennia ago, are extremely rare, and even more so in an undisturbed context. The Flint Run Complex in Northern Virginia contains not one, but several Late Pleistocene and Holocene open-air stratified Paleoindian sites. Thunderbird (44WR11) is the main site within the complex with evidence of human occupation in the region at around 9,990 BP. Numerous tools were recovered which fit the Clovis technocomplex and extensive analysis has been performed on bifacial technology at the site. Additionally, the identification of blades at Thunderbird would support previous assertions that the site was an important refugia on a migratory pattern where scheduled resource exploitation and toolkit refurbishments took place as part of seasonal rounds. How does the analysis of lithic blade production at the Thunderbird site (44WR11) refine our understanding of localized seasonal migration and exploitation of local resources among Paleoindian people of the Shenandoah River Valley. Confirmation of blades and their use would indicate a more robust exploitation of the region’s natural resources and reinforce previous assessments of the importance of Thunderbird as a sedentary seasonal base camp. Through the examination of 324 lithic artifacts from the site, this study seeks to identify the presence of a concerted blade manufacturing technology where it was believed one did not exist, and better understand the behaviors tied to those tools. Blades are a known part of the Clovis toolkit and have been found at sites across the United States. The identification of blades at Thunderbird will provide an expanded understating of the Clovis toolkit, the spread of blade technology, and of Paleoindian lifeways in the Middle Atlantic region.
THE STUDY OF ENERGY METABOLISM IN THE PERIPARTURIENT DAIRY COW: INVESTIGATING THE ROLE OF KETONES AND NAD+
(2024) da Silva, Mariana; Rico, Jorge Eduardo; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Dairy cows typically experience increased energy demands during the transition from gestation to lactation, and a myriad of metabolic adaptations are set in place to facilitate this transition. This thesis integrates findings from two experiments exploring energy metabolism during this critical phase. In the first experiment, the effects of hyperketonemia on dairy cow health and productivity were investigated. Eight Holstein cows (19.62 ± 5.44 days postpartum) were intravenously infused with either Na-BHB (KET) or NaCl (CON) for 48 hours. The study aimed to assess the impact of elevated beta-hydroxybutyrate (BHB) levels on blood biomarkers and immune response. Despite no significant differences in dry matter intake or overall milk yield, KET cows exhibited lower milk yield post-immune challenge (LPS bolus) and higher plasma NEFA levels. While plasma glucose concentrations remained unchanged, but BHB concentrations were significantly higher in the KET group (P < 0.001). The second experiment focused on the role of Nicotinamide Adenine Dinucleotide (NAD) coenzymes in energy metabolism during the transition from gestation to lactation. Twenty-six peripartal dairy cows were enrolled in an observational study to examine the NAD metabolome in liver, blood, and milk. Liver biopsies were performed 21 days before and 7 days after parturition, and blood samples were collected weekly. The study hypothesized that hepatic NAD levels deplete while blood and milk NAD pools increase postpartum, with a possible influence of residual feed intake (RFI). Measurements of plasma glucose, free fatty acids, BHB, and insulin, along with comprehensive NAD metabolome profiling using HPLC coupled to mass spectrometry, aimed to elucidate the relationship between NAD metabolism, metabolic biomarkers, and production performance. After calving, animals showed decreased glucose and insulin levels, and increased NEFA and BHB levels, with no significant group differences (P = 0.53). Oxidative stress markers (protein carbonyl, 8-OHdG) and total antioxidant capacity were measured on plasma. The DNA and protein oxidative stress markers remained unchanged relative to parturition, but the Low-RFI group tended to display higher antioxidant capacity (P = 0.08). NAD metabolites increased, and NAD precursor concentrations decreased in the liver. Nicotinamide Mononucleotide was higher in the High-RFI group (P = 0.04) and tended to decrease post-calving (P = 0.06). The liver NAD metabolome remained stable (P = 0.83). Both studies underscore the complexity of energy metabolism during the peripartum period in dairy cows. Collectively, our findings expand our understanding of novel aspects of energy metabolism, with potential implications for health, productivity, and disease resilience in dairy cows. Further research is essential to fully understand these mechanisms and improve management strategies for dairy cows during this critical period.
USING GEOSPATIAL INFORMATION SYSTEMS TO PREDICT THE FORM OF “ROADBEDS AND ROAD SEGMENTS” CLASSIFICATIONS FOR THE CHEROKEE TRAIL OF TEARS IN MISSOURI, 1837-1839
(2024) Lester, Ansley; Palus, Matthew M; Anthropology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This thesis aims to answer the questions, “How can we efficiently use the processes of categorization and Geospatial Information System (GIS) methods and analyses to help identify the ‘form’ that various segments on the Trail of Tears, specifically the listed National Historic Trail (NHT) of the “Cherokee Trail of Tears in Missouri, 1837-1839”? Can a predictive model be developed by looking at the spatial relationships between modern roads and the suspected paths taken by the Cherokee in 1837- 1839? If so, what other information can be gained from this approach?”The classifications are derived from the National Register of Historic Properties (NRHP) Multiple Property Documentation Form (MPDF) and discuss the classifications and criteria that segments of the Trail of Tears must meet to be considered contributing characteristics. The NRHP documentation form defines these different classes of the Trail of Tears into ‘three basic forms:1) Modern Roads, 2) Limited-Use, Passable Roads, and 3) Abandoned Roads. This thesis is limited to the segments of the Trail of Tears that fall within the Mark Twain National Forest (MTNF) boundaries. Though much of the Trail has been modified into modern roads, traces are still evident in many locations along these modern routes that hold integrity from the significant period of the late 1830s. Because the Trail of Tears passes through multiple states and traverses over 6,000 miles, managing the protection of its physical traces can be a logistical challenge for cultural resource managers. For this thesis, I developed a carefully constructed GIS model that is able to predict these classifications of various Trail of Tears segments using a sequence of geoprocessing methods, logical operators, and Boolean algebraic expressions. Using GIS, I determine the spatial relationship between the National Park Service’s Trail of Tears linear data and the extant roads that have been documented to date. I then use statistical analysis to assess the model itself and its findings. The results identified seventeen segments of the Trail that are likely to hold integrity in the roadbed and road segment form three: abandoned. This is important because this form is the most sensitive to any undertakings and includes the segments that hold the greatest amount of integrity. The results also confirmed that the Trail of Tears does have a spatial relationship with many modern and limited-use roads that are still used today. Basic statistical analysis confirmed that the sample segments used to develop the draft model are representative of the model’s outcomes when applied to a forest-wide scale and that a total of 68.94 miles of the Trail crosses through the Mark Twain National Forest. This thesis also emphasizes collaboration and consultation methods with the Cherokee Nation throughout the chapters as the way forward before this model is considered finished. The intent of this thesis is to provide a management tool for cultural resource managers to predict which segments of the Trail of Tears fall into the three classifications by using a specific set of geoprocessing methods. This tool can be helpful in identifying areas of the Trail that may hold more physical integrity than others and implementing specific protection measures from any undertakings. It also adds to our understanding of the Trail of Tears within the MTNF. This model can also contribute to our understanding of the Trail of Tears and the hardships the Cherokee faced during that time. It will also provide research and public education opportunities so we can adequately convey the significance that the Trail of Tears has in our history. This model is built to be flexible for adding additional parameters that may be added through future research or consultation. The methodology used to produce this model would stay the same if used in other areas where the Trail crosses. The input parameters are likely to differ, but the methodology would stand.
INGESTIBLE BIOIMPEDANCE SENSING DEVICE FOR GASTROINTESTINAL TRACT MONITORING
(2024) Holt, Brian Michael; Ghodssi, Reza; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Gastrointestinal (GI) diseases, such as inflammatory bowel disease (IBD), result in dilated adherens and tight junctions, altering mucosal tissue permeability. Few monitoring techniques have been developed for in situ monitoring of local mucosal barrier integrity, and none are capable of non-invasive measurement beyond the esophagus. In this work, this technology gap is addressed through the development of a noise-resilient, flexible bioimpedance sensor integrated ingestible device containing electronics for low-power, four-wire impedance measurement and Bluetooth-enabled wireless communication. Through electrochemical deposition of a conductive polymeric film, the sensor charge transfer capacity is increased 51.4-fold, enabling low-noise characterization of excised intestinal tissues with integrated potentiostat circuitry for the first time. A rodent animal trial is performed, demonstrating successful differentiation of healthy and permeable mice colonic tissues using the developed device. In accordance with established mucosal barrier evaluation methodologies, mucosal impedance was reduced between 20.3 ± 9.0% and 53.6 ± 10.7% of its baseline value in response to incrementally induced tight junction dilation. Ultimately, this work addresses the fundamental challenges of electrical resistance techniques hindering localized, non-invasive IBD diagnostics. Through the development of a simple and reliable bioimpedance sensing module, the device marks significant progress towards explicit quantification of “leaky gut” patterns in the GI tract.
Expression and Purification of the Cell-Penetrating Peptide MAP Fused to Protein Cargo
(2024) CHUNG, REN-JHE; Karlsson, Amy J; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Candida albicans is a common fungal pathogen that presents a significant public health issue due to its resistance to traditional antifungal small molecule medications. While large therapeutics offer potential as alternative treatments with novel mechanisms of action, their efficacy is hindered by low cellular uptake and limited accessibility to intracellular targets. Cell-penetrating peptides (CPPs) are promising vehicles for facilitating the intracellular delivery of large biomolecules. CPPs are short protein peptides capable of crossing various membrane barriers, even when conjugated to cargo molecules. However, producing CPP fusion proteins can be challenging due to their higher toxicity to host cells. To enhance expression, we studied and optimized several contributing factors, including expression partners, host cell strains, sequential order of CPP and cargo, and induction conditions, for the fusion of CPP MAP to the cargo monomeric enhanced green fluorescent protein (meGFP). Our findings indicated that the expression partner, combined with positioning MAP at the N-terminus of the cargo, resulted in relatively high expression levels. The highest expression level was achieved in the BL21(DE3) Escherichia coli strain, with induction at 20°C for 24 hours. These results support further research on the application of MAP recombinant proteins and lay the foundation for the generalization of CPP recombinant protein expression.
DEVELOPMENT AND VALIDATION OF A PYROLYSIS MODEL FOR FLEXIBLE POLYURETHANE FOAM
(2024) Kamma, Siriwipa; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Flexible polyurethane foam (FPUF) is a common material contained in household goods such as upholstered furniture and mattresses, which are known to significantly contribute to fire growth. An accurate prediction of fire development on FPUF containing items requires knowledge of FPUF pyrolysis and combustion properties. These properties include reaction kinetic parameters, thermodynamic parameters, and thermal transport properties. While many past studies focused on the thermal decomposing mechanism and thermodynamic properties of the reactions, the thermal transport properties have not been determined. In this study, a complete pyrolysis model of FPUF was developed by extending the thermal decomposition model from a previous study. The thermal transport properties were obtained using inverse modeling of the Controlled Atmosphere Pyrolysis Apparatus II experimental data. The complete model was validated against cone calorimetry data and found to perform in an adequate manner.
Three Clostridium species with Health Imparting Properties: In vitro Screening for Probiotic Potential
(2024) Mochama, Victor Moronge; Obanda, Diana; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This research aimed to unlock the probiotic potential of the genus Clostridium, which is often overshadowed by the predominant focus on pathogenic species. The study specifically targeted three promising Clostridium species: C. disporicum, C. celatum, and C. vincentii, which have shown potential in mitigating diet-induced obesity. Despite the challenges presented by the anaerobic growth requirements of Clostridium bacteria, the study capitalized on their capacity to sporulate. This characteristic provides an avenue to use them as probiotics, with resilient and dormant spores capable of surviving food processing and harsh stomach conditions. The resilience of these spores was examined by exposing them to oxygen, heat, gastrointestinal juices, and bile salts. The spores survived oxygen exposure, exhibited resilience to both bile salts and gastric acids, and demonstrated a survival temperature of 70°C. When exposed to suitable germination conditions in vitro, the spores successfully germinated. The study assessed the colonization potential of the bacteria by evaluating their adhesion ability, and all bacteria were found to have the adhesion ability. Furthermore, a safety assessment was conducted by examining hemolytic activity and antibiotic susceptibility to selected antibiotics. The bacteria were found to be susceptible to the antibiotics and did not exhibit hemolytic activity. Bile salt hydrolase (BSH) activity and antibacterial activities were also assessed, and none of the bacteria exhibited BSH activity or antibacterial activity. Antioxidant tests revealed that C. vincentii had the highest antioxidant properties. Assessment of anti-inflammatory properties showed that C. celatum downregulated the gene expression of cytokine inflammation markers IL-6, IL-1, and iNOS while upregulating TGF-β expression. In summary all 3 bacterial species showed good probiotic potential from the in vitro tests. Particularly the formation of resistant spores that later germinated to vegetative cells that produced molecular patterns with antioxidant and anti-inflammatory properties. This necessitates further studies on their probiotic properties.
A DEEPER DIVE INTO THE WATER: A COMPARISON OF HYDROLOGIC FEATURES AS VARIABLES IN PRECONTACT SITE LOCATION PREDICTIVE MODELS FOR THE VIRGINIA PIEDMONT
(2024) Johnson, Jeffrey Wade; Palus, Matthew M; Anthropology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The use of predictive modeling in Cultural Heritage Resource Management (CHRM) archaeology has become commonplace since its foundational principals were established in the 1980s, but criticisms of the practice persist, often centered around their lack of theory and dehumanization of the archaeological record. Proximity to water, typically expressed in the United States as distance to streamline data from the National Hydrography Dataset (NHD), is one of the most utilized variables when creating predictive models for Precontact period sites, but how does the variable “distance to streamline” compare to other hydrologic variables? In this thesis I seek to answer the question “how do distance to stream confluences and distance to wetlands compare to distance to streamline when attempting to predict Precontact site locations in the Virginia Piedmont?”The publication Quantifying the Present and Predicting the Past: Theory, Method, and Application of Archaeological Predictive Modeling (Altschul et al. 1988) is considered foundational to the practice of predictive modeling in archaeology; it is referenced frequently in modern theoretical works and throughout this thesis. The approaches to creating archaeological predictive models are typically divided into two camps: models that utilize an inductive, or correlative, approach and models that utilize a deductive, or theory driven, approach. Rather than establishing distance correlations between wetlands and stream confluences with previously recorded site data, I utilize a deductive approach where I establish the importance of those variables through archaeological theory pertaining to subsistence and settlement patterns and test their value with site data. Inductive associational models are very good at showing that archaeological site distribution is strongly patterned, but they often lack the explanatory framework that would be useful for management decisions based on their findings. The Study Area the models are tested on is located within Orange County, Virginia near the town of Locust Grove, and encompasses about 686 acres. The Study Area contains two main streams, named Cormack Run and Mine Run, the confluence of those streams and other lower order streams, as well as wetlands located adjacent to the streams. Precontact occupations have likely occurred in this region for the past 12,000 years, if not longer. The test results demonstrate that models created using deductively derived variables perform well enough to justify their use in CHRM contexts, but also include the added benefit of an explanatory framework. The guidelines for archaeological investigations in Virginia allow for the use of predictive models when conducting inventory surveys, meaning the archaeological predictive models (APM) created for this thesis could be utilized in a real-world context. The primary focus of this thesis was to determine if using hydrologic features other than streams, specifically stream confluences and wetlands, to express the distance to water variable would improve the performance of an APM. I demonstrated that, yes, other hydrologic features may be better predictors of Precontact site locations in the Virginia Piedmont. Secondarily, I hoped to show that an APM created using a deductive approach would perform well enough to be considered appropriate for use in CHRM contexts. The high probability areas of all three of the APMs I created yielded Kg values high enough to be considered as having predictive utility. This demonstrates that the use of all three of the APMs I created could be considered appropriate to guide survey efforts in a CHRM context.
DESIGN AND PERFORMANCE EXPLORATION OF A SCALED-UP MILLIGRAM-SCALE FLAME CALORIMETER
(2024) Cromwell Reed, Kyra; Raffan-Montoya, Fernando; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Fire causes thousands of lost lives and injuries, as well as billions of dollars of property damage, each year. It is critical to understand the fire hazard associated with materials used in the built environment. One method to evaluate the flammability properties of a material is through bench- scale and milligram-scale testing with apparatus such as the Milligram-Scale Flame Calorimeter (MFC). The MFC has previously been used to test samples ranging from 30 mg – 50 mg in mass. The small samples were useful for testing materials under development or materials cost prohibitive to test at larger sizes, but presented some difficulties in testing, including in sample preparation and as inconsistency in the results of testing on inhomogeneous materials. Furthermore, the small size of the MFC caused difficulty in heater manufacturing, requiring laborious by-hand construction. The size of the MFC crucible and apparatus was increased in this work to allow testing on larger sample masses, ranging in size from 90 mg – 150 mg, and for the exploration of five alternate heater manufacturing techniques. The MFC was rebuilt with a larger heater and optimized to create the best possible test conditions for this work. Tests were conducted on five polymers: polymethyl methacrylate (PMMA), polyethylene (PE), polyvinyl chloride (PVC), and polyether ether ketone (PEEK), and on a wood-based material: oriented strand board (OSB). The tests showed general consistency when materials were tested at different sample masses and sample presentations. The results for the heat release rate and heat of combustion of the materials also aligned well with testing conducted using the previous version of the MFC apparatus. The updates to the MFC conducted in this work constitute an improvement to the versatility of the apparatus, allowing for testing on larger sample masses, but future work is needed to resolve flow and exhaust issues that caused some inconsistency in the test results and to further explore and develop alternate heater manufacturing techniques.
BLACK RADIO OWNERSHIP AND THE FCC’S FAILED ATTEMPT TO DIVERSIFY THE AIRWAVES
(2024) Sundaramoorthy, Robin Mazyck; Steiner, Linda; Journalism; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
African Americans were effectively shut out of radio station ownership until the 1970s. Discriminatory practices made it virtually impossible for Blacks to acquire broadcast licenses awarded by the Federal Communications Commission (FCC). Efforts to address the issue were taken up during President Jimmy Carter’s administration when minority ownership of all broadcast facilities—television and radio—was less than one percent. What resulted was FCC Docket No. 80-90. This technical rule created 689 new frequencies on the FM band with the intent that they would give minorities more opportunities to enter broadcast ownership. While Docket 80-90 was the 90th proceeding taken up by the FCC in 1980, the ideas for Docket 80-90 emerged in the mid-to-late 1970s and were implemented in the mid-1980s and throughout most of the 1990s. Despite its momentous impact, scant scholarly attention has been given to this topic. Using a multimethod qualitative approach based on archives and lived experiences, this dissertation examines the federal government’s efforts to increase minority broadcast ownership by increasing the number of FM radio stations. It assesses the many individuals, groups, and concerned citizens who, in some cases, unknowingly opened pathways to radio ownership for minorities and created public policy. It also tells the stories of nine African Americans who benefited from this FCC rule and became radio station owners in the 1990s. To achieve this, I reviewed more than 7,000 documents at the National Archives and Records Administration (NARA), the Jimmy Carter Presidential Library and Museum, and Special Collections in Mass Media and Culture at the University of Maryland. I also conducted 50 oral history interviews. This research also takes a critical look at historiography and the tensions that arise when using archival and oral history methods in writing the story of Docket 80-90. This study is grounded in critical race theory and political economy of the media. To account for the omission of race in this theory, I suggest an elaboration on political economy of the media to consider the specific political economy of Black media because representation matters. Diverse voices, especially those belonging to people who have been historically marginalized, enrich our media systems and provide a more accurate view of the world around us. The African American broadcasters in this dissertation provided job opportunities, introduced new formats to their communities, and emphasized local news and cultural affairs programming and events. Their path to ownership, however, was a difficult one. Access to capital, racism, sexism, and other forms of discrimination plagued their endeavors. Efforts to increase minority broadcast ownership have been stunted and stymied by a convoluted combination of economic policy, judicial rulings and political maneuvering by the party that controls the White House. Since the political will to take definitive action is lacking, I suggest that professional groups create opportunities that not only help Black broadcasters enter ownership but stay there. This includes mentorship and educational programs aimed at avoiding the various pitfalls likely to occur during the first five years of radio ownership when new businesses are most likely to fail.
DIRECTED AND ELLIPTIC FLOW MEASUREMENTS: A COMPARISON BETWEEN THE PARTICIPANT AND SPECTATOR PLANES IN Pb+Pb COLLISIONS AT √sNN = 5.02 TeV WITH CMS AT THE LHC
(2024) Lascio, Samuel Andrew; Mignerey, Alice C.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Directed and elliptic flow of unidentified charged hadrons at mid-rapidity are measured as a function of transverse momentum (pT) and pseudorapidity (η) in ultra-relativistic PbPb collisions at √sNN = 5.02 TeV with the Large Hadron Collider (LHC) at CERN. The reaction plane (RP) angle is approximated using participants and spectator neutrons measured with the Compact Muon Solenoid (CMS) detector and the newly installed Spectator Reaction Plane Detector (SRPD), respectively. The SRPD is the latest addition to the existing Zero Degree Calorimeter (ZDC) designed to measure spectator neutrons +/- 140 m from the interaction point at CMS. The Event Plane (EP) Method is used to calculate the v1odd, v1even, and v2 harmonic flow parameters as functions of η and pT. The directed flow measurements using participants and spectators with CMS are compared and contrasted. Overall results are in good agreement between participants and spectators, however v1even(pT) measurements using spectators begin to show the opposite trend to those using participants at pT > 2 GeV/c. Results are compared to those obtained by A Large Ion Collider Experiment (ALICE), which is another experiment at the CERN LHC. Directed flow results do not agree with those obtained by ALICE. Additionally, the first elliptic flow measurements using the EP Method and mixed harmonics with the SRPD are reported. A slight asymmetry in v2(η) is observed using spectators. The elliptic flow results do agree with ALICE. Tracking efficiency as determined by the CMS collaboration is applied to the data and potential corruption as a result is discussed. Results strongly support continued use of the SRPD as a spectator neutron detector for reaction plane determination within the CMS ZDC.
Reimagining Black Carceral Masculinities and Community Care Work: A Study of Credible Messengers in the Nation’s Capital
(2024) Martinez, Rod; Ray, Rashawn; Sociology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The following dissertation examines a group of community workers known as credible messengers in Washington, D.C. Credible messengers have lived experience surviving carceral systems such as prisons and environments and have transformed their lives to guide, relate to, and support others who share their backgrounds. Their credibility stems directly from their intimate knowledge of the communities they serve. This dissertation project draws on qualitative interviews with male credible messengers from a more considerable multi-year evaluation of a newly implemented credible messenger program housed in a youth agency. Sociologically, the project explores Black carceral masculinities and mentoring as civic engagement. The findings reveal how men resist and challenge prevailing notions around hegemonic and carceral masculinities through their racially gendered experiences, which shape how they approach their work with youth. The study also suggests that the men engage in credible messenger work for motivations other than redemption and in service of a larger mission to Black youth and their local communities. The dissertation project also includes a conversation with a formerly incarcerated public figure from Washington, D.C., as a call to action to researchers and others to uplift the experience of impacted people and communities. The dissertation project concludes with a set of recommendations aimed at policy and practice as it relates to criminalized Black men and boys.
TIES THAT MATTER: THREE ESSAYS ON COOPERATION AMONG ARMED NONSTATE ORGANIZATIONS
(2024) Yarlagadda, Rithvik; Cunningham, David; Government and Politics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Armed non-state groups frequently cooperate with other groups, even to the point of allyingwith them. This dissertation examines the role of group leaders in understanding when and to what extent do armed groups cooperate, and the impact that cooperation has on the severity of terrorist violence. When operating in complex environments such as civil wars, armed groups face information barriers in credibly signaling to other groups about their willingness to engage in cooperation. I argue that group leader’s length of time in power and their prewar experiences help resolve the information uncertainty and promote cooperation between armed groups. Prior to assuming power, some leaders participate in a variety of military and political activities. These prewar leader experiences, I argue, condition the type of armed group cooperation that occurs during civil wars. Furthermore, I also explore if and how cooperation influences the violent behavior of armed groups. Specifically, I argue that in addition to the number of cooperative ties, the diversity and directionality of support within those ties also matter equally, if not more, in affecting the severity of armed group violence. Using a large-N design, I conduct a variety of statistical models to test my hypotheses related to the incidence, type, and effects of cooperation among armed groups. My findings show that leader tenure is positively and statistically significantly associated with the occurrence of armed group cooperation. I also find that leaders with prior military experience are more likely to engage in informal ties while prior political experience increases the odds of formal cooperation in a statistically significant manner. Lastly, the proportion of cooperative ties in which an armed group is the major provider of support is shown to have a negative and statistically significant impact on violence lethality. Overall, this study demonstrates the value of leaders in understanding the nature of armed group interactions. Cooperative ties involving armed groups are not necessarily uniform and it is recommended that both scholars and policy makers should consider the heterogeneity in ties when evaluating the risks posed by armed groups.
PARTICLE INDUCED TRANSITION IN HIGH-SPEED BOUNDARY-LAYER FLOWS
(2024) Abdullah Al Hasnine, Sayed Mohammad; Brehm, Christoph; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Boundary-layer transition to turbulence presents a critical challenge in aerospace engineering due to its impact on thermal load, especially for hypersonic vehicles. This transition, influenced by various disturbances such as acoustic waves, entropy waves, and particle impingement, follows complex and non-unique pathways to turbulence. It significantly affects the surface heat flux and thus will impact the design of thermal protection systems. This dissertation focuses on the transition process initiated by particle impingement, which introduces small-scale disturbances through a complex receptivity process that typically initiates a natural transition path. Using direct numerical simulations, this study explores the particle-induced transition process. The disturbance spectrum, consisting of both stable and unstable modes along with continuous acoustic contributions, is meticulously reconstructed near the particle impingement site using biorthogonal decomposition to assess the contributions of different eigenmodes to the initial disturbance spectrum. A large number of discrete and continuous eigenmodes are seeded, but the dominant eigenmodes capture only a small fraction of the disturbance energy, with the majority reflected into the freestream through the continuous modes associated with the continuous acoustic branches. The modeling fidelity is also investigated, particularly the particle-source-in-cell (PSIC) approach, commonly used due to its efficiency in capturing particle-flow interactions. Comparisons with the Immersed-Boundary-Method (IBM), however, reveal that PSIC inadequately captures particle-wall interactions and needs correction for accurate disturbance modeling. Finally, a reduced-order model is developed for the prediction of particle-induced transition. This model integrates data from high-fidelity simulations, linear stability theory, and a saturation amplitude model while also considering particle characteristics like size, density and concentration. The model’s capability is demonstrated for a wide range of transition scenarios, including data from the HIFiRE-1 flight test, offering a robust tool for rapid transition prediction in hypersonicvehicle design.
Essays on the Macroeconomic and Measurement Consequences of Government Systems
(2024) Navarrete, Michael Alexander; Hellerstein, Judith; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In Chapter 2, I study the macroeconomic consequences to delaying a fiscal stabilizer. Specifically, I study how delays to unemployment insurance benefits during the pandemic recession (fiscal stabilizer) affected consumption (macroeconomic consequence). The United States experienced an unprecedented increase in unemployment insurance (UI) claims starting in March 2020. State UI-benefit systems were inadequately prepared to process these claims. In states that used an antiquated programming language, COBOL, to process claims, potential claimants experienced a larger increase in administrative difficulties, which led to longer delays in benefit disbursement. Using daily debit and credit card consumption data from Affinity Solutions, I employ a two-way fixed-effects estimator to measure the causal impact of having an antiquated UI benefit system on aggregate consumption. Such systems led to a 2.8-percentage-point decline in total credit and debit card consumption relative to card consumption in states with more modern systems. I estimate that the share of claims whose processing was delayed by over 70 days rose by at least 2.1 percentage points more in COBOL states relative to non-COBOL states. Based on a back-of-the-envelope calculation using 2019 data, my results suggest that the decline in consumption in COBOL states in 2020 after the pandemic-emergency declaration corresponds to a real-GDP decline of at least $105 billion (in 2019 dollars). In Chapter 3, Joonkyu Choi, Samuel Messer, Veronika Penciakova, and I study how business formation patterns in 2020 were affected by antiquated UI benefit systems. New business formation surged after the pandemic recession, but the causes of this surge are not well understood. The expansion of UI benefits under the CARES Act, coupled with the reduction of work search, provided unemployed potential entrepreneurs with the funds and time needed to develop business ideas. States that used an antiquated programming language, COBOL, to process claims experienced a lower growth rate in UI payments per unemployed than states with more modernized systems. Using business application data from the Business Formation Statistics, we employ a two-way fixed-effects estimator to measure the causal impact of having an antiquated UI benefit system on business formation. Such systems led to a 6.6 percent decline in business applications per capita in COBOL states relative to more modernized states from March 2020 to July 2020. We also find some evidence of business quality deterioration while the Federal Pandemic Unemployment Compensation program was in effect. Our findings highlight the potential role of UI policy in contributing to economic recoveries by fostering entrepreneurship. In Chapter 4, the RESET team Gabriel Ehrlich, John Haltiwanger, David Johnson, Ron Jarmin, Seula Kim, Jake Kramer, Edward Olivares, R. Rodriguez, Mathew D. Shapiro, and I use point of sales (POS) data to construct real sales and compare these POS generated statistics to official statistics. Businesses, individuals, and government policymakers rely on accurate and timely measurement of nominal sales, inflation, and real output, but current official statistics face challenges on a number of dimensions. First, these key indicators are derived from surveys conducted by multiple agencies with different time frames, yielding a complex integration process. Second, some of the source data needed for the statistics (e.g., expenditure weights) are only available with a considerable lag. Third, response rates are declining, especially for high-frequency surveys. Focusing on retail trade statistics, we document important discrepancies between official statistics and measures computed directly from item-level transactions data. The long lags in key components of the source data delay recognition of economic turning points and lead to out-of-date information on the composition of output. We provide external data sources to validate the transactions data when their nominal sales trends differ importantly from official statistics. We then conduct counterfactual exercises that replicate the methodology that official statistical agencies use with the transactions data in the construction of nominal sales indices. These counterfactual exercises produce similar results to the official statistics even when the official nominal sales and item-level transactions data exhibit different trends.
Langlands-Kottwitz Method on Moduli Spaces of Global Shtukas
(2024) Song, Shin Eui; Haines, Thomas; Mathematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
We apply the approach of Scholze to compute the trace of Hecke operator twisted by some power of Frobenius on the cohomology of the moduli spaces of global shtukas in the case of bad reduction. We find a formula that involves orbital integrals and twisted orbital integrals which can be compared with the Arthur-Selberg trace formula. This extends the results of Ngo and Ngo Dac on counting points of moduli spaces of global shtukas over finite fields. The main problem lies in finding a suitable compactly supported locally constant function that will be plugged into the twisted orbital integrals. Following Scholze, we construct locally constant functions called the test functions by using deformation spaces of bounded local shtukas. Then we establish certain local-global compatibility to express the trace on the nearby cycle sheaves on the moduli space of global shtukas to the trace on the deformation spaces.
CONNECTING THEORY AND OBSERVATIONS OF EXOPLANET ATMOSPHERES AND SURFACES AT THE INDIVIDUAL AND POPULATION LEVEL WITH JWST
(2024) Ih, Jegug; Kempton, Eliza M.-R.; Astronomy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Observing an exoplanet’s atmosphere via photometry and spectroscopy has provided the main window to understanding its properties and processes, as the atmospheric spectra encompass information about the chemistry, thermal structure, surfaces, as well as formation history and even biology. To this end, one key science goal of the James Webb Space Telescope (JWST) is to establish whether rocky planets around M dwarfs can host atmospheres or not. JWST offers unprecedented signal-to-noise and unlocks new parameter space regimes of planets available for characterizing not only the atmosphere but also the surface. This advancement in observing capability simultaneously poses novel challenges to atmospheric characterization. My dissertation addresses some of the new challenges to atmospheric retrievals in the era of JWST and the characterization of rocky planets. Firstly, I quantified the effects of wavelength-correlated systematics on atmospheric retrievals. Wavelength-correlated noise can occur due to instrumental systematics or stellar effects and the merging of discrete data sets. I investigated the effect of correlated noise and constrained the potential biases incurred in the retrieved posteriors by performing retrievals on multiple noise instances of synthetic data. The study found that correlated noise allows for overfitting the spectrum, thereby yielding a better goodness of fit on average but degrading the overall accuracy of retrievals by roughly 1σ. In particular, correlated noise can manifest as an apparent non-Rayleigh slope in the optical range, leading to an incorrect estimate of cloud/haze parameters. Finally, I show that while correlated noise cannot be reliably distinguished with Hubble Space Telescope observations, inferring its presence and strength may be possible with JWST. Secondly, I studied the how the choice in parameterization of the atmospheric composition can influence the posterior when performing retrieval analyses on terrestrial planet atmospheres, for which the mean molecular weight is not known a priori. By performing self-retrievals and varying the parameterization, I found that the centered log-ratio transform, commonly used for this application, tends to overestimate the abundances of spectroscopically active gases when inactive ones are present. Over multiple noise instances, I found that no one parameterization method always outperforms others. Comparing the Bayesian evidences from retrievals on multiple noise instances, I found that for a given spectrum, the choice in parameterization can affect the Bayes factor of whether a molecule should be included. Alongside astrophysical effects, this remains a fundamental challenge to atmospheric retrievals for small planet and can addressed by more observations. Finally, I constrained the atmospheric thickness and characterized the surface from the first JWST measurement of thermal emission from a rocky exoplanet, TRAPPIST-1 b. I compared TRAPPIST-1 b’s measured secondary eclipse depth to predictions from a suite of self-consistent radiative-convective equilibrium models. I found that plausible atmospheres (i.e., those that contain at least 100 ppm CO2) with surface pressures greater than 0.3 bar are ruled out at 3σ, regardless of the choice of background atmosphere, and a Mars-like thin atmosphere with surface pressure 6.5 mbar composed entirely of CO2 is also ruled out at 3σ. I modelled the emission spectra for bare-rock planets of various compositions and found that a basaltic surface best matches the measured eclipse depth to within 1σ.

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