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What brain regions are responsible for conspecific mate recognition?
No full textAstatotilapia burtoni is a species of cichlid fish from East Africa. Cichlids are remarkable for having evolved into thousands of species all in the same area and yet continuously mate with their own species. Fertile females release prostaglandin F2 (PGF2) related pheromones that males need to detect in order to successfully mate (Li et al., 2024). Pheromones are important for cichlid behavior, but it is not known what brain regions in the male brain respond to female pheromones. I hypothesize that male brains will have different levels of preoptic area activation dependent on odor species. The activity marker from this experiment is strongly expressed in the POA. The males exposed to PGF2a A. Burtoni females appear to have more activation than that of the vehicle, and other species. The next step in this project is to quantify the cell number and fluorescence intensity of the POA and other regions of interest. This experiment lays the groundwork to recreate a larger trial with a bigger sample size that can determine if A. burtoni are able to detect species through pheromone signaling. This would be of large significance given the unknown mechanism through which cichlids in lake Tanganyika do conspecific mating while surrounded by thousands of fish of very similar species.This work was supported in part by grants to S.A.J. from the National Institutes of Health (R35GM142872); the National Science Foundation (IOS-1825723); the Human Frontiers in Science Program (RGY0079-2018); and a fellowship to C.G.P. from the National Science Foundation (DBI-2209257)
Merges of Smooth Classes and their Properties
No full textWe work with classes of finite structures called smooth classes, a notion which originates from Hrushovski’s constructions in [Hru93]. Under sufficient conditions, these classes have generic limits and can be thought of as generalizations of Fraisse classes and limits. Given two smooth classes, we ask whether we can merge the two classes into one class with a generic limit in a new language. This is an operation one can easily do when dealing with two traditional Fraisse classes, but smooth classes add complexity. We define these merges of classes and study the model theoretic properties of these merges and their generics. Namely, we give a characterization of the generic of the merged class relative to the generics of the original classes, strengthening a result in [EHN19]. We also discuss the properties of the generic of the merged class being atomic, saturated, and ω-categorical relative to the original generics. Merges of smooth classes have a historical place within the realm of structural Ramsey theory and the study of the Hrushovski property (EPPA). We extend merges of smooth classes tothis context, and, generalizing work done in ([EHN19], [EHN21], [HKN22]), we give examples of merges of smooth classes with the Ramsey and EPPA properties
Adaptive Reuse of Historic Tobacco Barns in Prince George's County, Maryland
No full textFinal report for PLCY400: Senior Capstone (Spring 2025). University of Maryland, College ParkThis report examines the potential for adaptive reuse practices for historic tobacco barns in Prince George’s County, Maryland. Adaptive reuse repurposes old or historic structures while retaining their original features and character.
The report lays the groundwork for future research and policy efforts to support preserving and transforming tobacco barns across the County. It aims to add to the historic preservation and local government planning literature, emphasizing tobacco barns’ cultural and historical significance. In addition, the report evaluates the existing bureaucratic structures and financial incentives to support the adaptive reuse process. The findings are based on various data including interviews with experts, archival research, and three site visits serving as case studies.
Based on the research and findings, the report recommends that the Prince George’s County government create an efficient process to promote adaptive reuse practices for historically significant agricultural buildings, including tobacco barns.Prince George's County, M
A Customizable Interface for Samplesort and Radix Sort
No full textSorting is one of the most widely studied problems in computer science. Many parallel algorithms exist for both comparison and integer sort. In our project we focus on Samplesort, a variation of Quicksort using multiple pivots selected from a sample of the input sequence. We are interested in improving its performance on shared-memory architecture.
Samplesort can be deconstructed into primitives — pivot selection, partitioning into buckets, base case sort, and recursion. Different implementations of these primitives have been developed in the literature for specific purposes, such as reducing auxiliary space usage and taking advantage of vectorization. However, these specialized primitives may not perform well outside of their niche.
Our work focuses on creating a general-purpose Samplesort which will conveniently deliver the best combination of these primitives for each user’s needs, which we achieve by designing a customizable interface in which different versions of the primitives can be inserted. We will implement and benchmark different combinations of leading variants, as well as our own variants, of each of the primitives on a variety of data types and input distributions, then analyze the results to determine which combinations function the best in different situations. By design, future researchers will be able to add and benchmark their own primitives using our interface. Our research will offer greater understanding of Samplesort, and will make high-performance parallel comparison sort more convenient to benchmark for future researchers, as well as more accessible to users
ELEMENTARY MUSIC TEACHER EXPERIENCES & EXPRESSIONS OF AGENCY IN AN ASYNCHRONOUS, ONLINE TEACHER STUDY GROUP ON TRAUMA-INFORMED APPROACHES IN MUSIC EDUCATION
No full textThe purpose of this study was to examine elementary general music teachers' views on trauma-informed music approaches while engaged in a professional development (PD) experience. Further, I explored elementary music teachers’ sense of agency in applying trauma-informed approaches in their teaching praxis. To examine music teachers’ perspectives about trauma-informed education, I investigated teachers’ behaviors, stated beliefs, and written responses in an online study group focused on trauma-informed approaches in music education. Research questions addressed participants’ engagement in the online study group, the alignment of their responses with trauma-informed principles (SAMHSA, 2014) and dimensions of teacher agency (Priestley et al., 2015), and their recommendations for future trauma-informed PD efforts.
Using an instrumental case study design (Stake, 2003), I facilitated an eight-week asynchronous, online PD study group for five elementary music teachers. Teachers’ experiences throughout the PD course (November 2024-February 2025) served as the broader phenomenon of interest. Participants engaged with module materials (e.g., articles, videos, podcasts, book chapters, blogs), guided reflection journals, and group discussions. As a point of triangulation, I employed repeated measures of a teacher agency scale (Leijen et al., 2024) which I adapted for the present study. Using my positionality as an experienced PD facilitator, elementary general music teacher, and survivor of trauma & abuse, I reflexively analyzed and interpreted the data using my research questions and theoretical framework as a guide.
Findings indicated that music teacher participants desired more concrete, actionable strategies for implementing trauma-informed approaches, specifically in the context of music teaching & learning. Teachers also demonstrated their awareness of trauma-informed approaches as connected to culture, diversity, inclusion, and equity. While teachers frequently commented on student behaviors when referencing trauma-informed practices, participants simultaneously problematized reactionary trauma-informed approaches and the notion of trauma being “brought into” schools. Instead, participants named their critical, active role in demonstrating emotional regulation. Further, teachers positioned the music classroom as a “natural” place to facilitate connection and support. Despite participants’ commitment to asset-based pedagogies, participant responses revealed how teachers may be perpetuating and sustaining deficit approaches in their attempts to enact trauma-informed approaches
THE LIVED EXPERIENCE OF RESILIENCE IN AFRICAN-BORN BLACK WOMEN LIVING WITH HIV AND ENGAGED IN CARE THROUGH COMMUNITY-BASED ORGANIZATIONS IN THE UNITED STATES: A CRITICAL INTERPRETIVE PHENOMENOLOGICAL ETHNOGRAPHY
No full textAfrican-born Black women living with HIV (ABWLWH) represent a growing yet understudied population in the U.S. Despite often presenting for HIV care at later and more advanced stages of the illness, ABWLWH have higher survival rates than other demographic groups. However, no U.S.-based studies to date have examined the resilience factors that contribute to these outcomes. Existing research typically adopts deprivation-based frameworks, which overlook the strengths and resources that support resilience in this population. This dissertation employs a strengths-based approach, integrating critical interpretive phenomenology and ethnography to explore the lived experiences and meaning of resilience among ABWLWH in the U.S. engaged in care through community-based organizations (CBOs).
The study situates resilience within the intersecting contexts of participants' identities as Black African immigrant women and as individuals living with HIV. Over the course of sixteen months in the field, I volunteered at a CBO that served as the study’s primary research site and conducted direct ethnographic observations. I engaged in participant observations at support group meetings with participants and conducted in-depth interviews and informal conversations with eight ABWLWH who were receiving support and services through the CBO.
This study offers a nuanced understanding of how ABWLWH develop, maintain, and interpret their experiences of resilience amidst intersecting challenges related to migration, stigma, economic instability, and structural barriers. The findings contribute to a deeper understanding of resilience as a dynamic, socially embedded process and offer insights to inform more equitable, culturally grounded support systems and interventions for ABWLWH
TOWARD JUSTICE FOR ALL: AN ANALYSIS OF STATE HISTORIC PRESERVATION PLANS
No full textThis research investigates how contemporary historic preservation practice reflects the evolving concepts of justice. While there are assumptions about how notions of justice, which are inherently abstract and multifaceted, are or are not represented in historic preservation, little data exists to support how they are conceptualized and implemented. This study explores whether and how the influence of justice theories are explicit in preservation practice by analyzing a key planning tool: state historic preservation plans. For this research, I used justice theory from planning and preservation perspectives to develop a framework that informs a national analysis of all current state preservation plans in the United States as of July 2023. This is combined with an in-depth case study of the Maryland plan, which was selected for its reputation for planning innovation. Through thematic analysis, archival research, interviews, and participant observation, the study identifies core themes that signal how justice is understood and operationalized in state preservation plans.
Findings from the national analysis demonstrate considerable variation in justice notions expressed within plans, influenced by external factors such as timing, political context, and authorship. Plans emphasize a resource-focused interpretation of justice, driven by programmatic, regulatory, and funding structures. I identify public participation—influenced by planning guidance—as a primary means through which the plans align with justice theories. The Maryland case study demonstrates a broader and more integrated application of justice notions, highlighting themes such as transparency, education, and the inclusion of intersecting priorities like housing, climate, and economic development.
The research concludes that, while theories of justice are present in preservation planning, their influence is uneven and often constrained by conventional disciplinary norms. However, state preservation plans have the potential to serve as models for advancing a more people-centered, interdisciplinary approach to justice in preservation, redefining the role of the preservation planner, and broadening the field’s impact
UNCERTAINTY IN DIRECTIONAL REPRESENTATIONS, PREIMAGES OF KERNEL TRANSFORMATIONS AND APPLICATIONS
No full textThis dissertation develops theoretical and computational advances in discrete directional time–frequency analysis, phase retrieval, kernel‑based inverse problems, and applications to electron microscopy denoising. Chapter 3 presents sharp uncertainty inequalities for the Directional Gabor Ridge Transform (DGRT) and its weighted variant (DWGRT) within a discrete‐frame framework, yielding explicit bounds on spatial support and directional frequency localization. These results extend classical continuous uncertainty principles to fully discrete directional frames and provide explicit guidance on window lengths, orientation sampling, and weight functions.
Chapter 4 formulates undersampled short‑time Fourier magnitude inversion as a supervised learning problem. I design a compact neural network trained with adversarial and reconstruction losses that reconstructs eight‑thousand‑sample audio segments from four‑thousand magnitude measurements. Extensive experiments demonstrate rapid convergence and superior numerical and perceptual quality compared to Griffin–Lim, including downstream classification accuracy improvements.
In Chapter 5, I implement and compare three deterministic kPCA pre‑image algorithms: fixed‑point iteration, kernel ridge regression, and Schölkopf’s method, applying them across MNIST, CIFAR‑10, and SVHN under noise‑free and noisy scenarios. Metrics of PSNR, SSIM, and PCC identify each solver’s strengths and limitations. Motivated by these findings, I introduce DCGAN‑KPCAnet and WGAN‑KPCAnet, two generative adversarial inverse solvers that learn the kPCA mapping directly. WGAN‑KPCAnet consistently exceeds the best deterministic solver in reconstruction fidelity, structural preservation, and noise robustness.
Chapter 6 integrates cosine‑similarity kPCA denoising into graphene‑liquid‑cell and single particle cryo‑EM pipelines. By replacing masking and averaging with kPCA inversion, I achieve substantial improvements in two‑dimensional projection quality and enable high‑resolution three‑dimensional reconstructions that reveal dynamic structural states. Kernel parameter selection, computational scalability, and software integration are discussed.
Together, these contributions establish new discrete uncertainty bounds, demonstrate the efficacy of learning‑based phase retrieval, advance kernel pre‑image algorithms through generative modeling, and apply kernel PCA denoising to challenging electron microscopy data, bridging fundamental mathematics with practical signal processing applications
Essays on Macroeconomics and Financial Frictions
No full textA central question in macroeconomics is how financial frictions—factors that limit agents’ ability to borrow and secure financing—affect real economic outcomes. This dissertation investigates these frictions along three dimensions. First, it examines how earnings-based covenants (EBCs)—a clause in debt contracts limiting a firm’s borrowing capacity to a multiple of its earnings—lead firms to reduce intangible investment in the short run, yet ultimately lower borrowing costs and boost investment. Second, it explores how the strictness of financial covenants—beyond EBCs—shapes firms’ investment responses to unexpected changes in interest rates. Finally, it assesses whether non-bank financial intermediaries (NBFIs), such as Exchange-Traded Funds (ETFs), amplify or dampen global capital flow volatility and financial instability.
Motivated by the empirical fact that EBCs are prevalent among U.S. nonfinancial public firms, the first chapter, “Earnings-based Covenants and Intangible Investment,” studies how these covenants affect corporate intangible investment uses a combination of theoretical modeling, empirical methods, and quantitative analysis. Under current accounting rules, intangible investment must be expensed in the period it is incurred, while tangible investment is capitalized. This means that higher intangible investment reduces a firm’s current earnings. Consequently, firms may cut back on intangible investment to avoid violating EBCs in the short term. In the data, I find that firms subject to EBCs significantly reduce their intangible investments compared to firms not bound by these covenants when they are concerned about potential violations. I do not find such a pattern for tangible investment. However, this result does not imply that EBCs are bad for firms. EBCs protect lenders by acting as an early intervention mechanism, lowering ex-ante borrowing costs and potentially increasing investment. To assess the macro-level impact of EBCs, I develop a quantitative dynamic model with heterogeneous firms that captures these competing forces. The calibrated model reveals that EBCs on net lead to higher intangible capital and output by lowering borrowing costs. Meanwhile, excluding intangible investment from accounting earnings would lead to further gains in both investment and output.
The second chapter, “Transmission of Monetary Policy Shocks: The Role of Financial Covenants,” empirically studies how the strictness of financial covenants affects firms’ investment responses to monetary policy shocks. Using lender-specific financial shocks, which are arguably independent of borrowers’ fundamentals, I find that investment of borrowers with loan contracts containing stricter financial covenants is significantly more (less) responsive to contractionary (expansionary) monetary policy shocks than for borrowers with looser covenants. These findings are not driven by variation across borrowers in default risk, suggesting that financial covenants may serve as an important mechanism through which shocks to lenders can affect monetary policy transmission.
Chapter 3, “NBFIs and the Cyclicality of Global Portfolio Investment,” coauthored with Katharina Bergant and Damien Puy, studies the macroeconomic implications of NBFIs, such as ETFs, in emerging markets. International capital flows are increasingly intermediated by non-bank financial institutions. Focusing on the rise of passive investment vehicles, we examine whether the presence of ETFs makes capital flows to emerging markets more volatile, as well as the potential macroeconomic implications for countries receiving these flows. We find that ETFs are indeed two to three times as sensitive to global uncertainty shocks as traditional mutual funds. However, we find no evidence that countries with a higher share of ETFs in their investor base experience stronger adverse macroeconomic effects, such as lower returns, higher sensitivity of overall portfolio inflows, or higher exchange rate volatility
A STUDY TO CORRELATE SOLDER AGE WITH PHASE SIZE AND COMPOSITION ENRICHMENT
No full textThis dissertation research aims to develop a forensic technique to identify and mitigate counterfeiting of microelectronics through correlation of phase size and composition enrichment of Sn-Pb solder with aging. Phase coarsening as a rate of time and temperature is measured, but the focus is on correlating this with phase enrichment, specifically how the percentage of Sn in the α-Pb phase changes with time and temperature. It is hypothesized that the two metrics will evolve differently with time as the system moves toward equilibrium thus giving a more difficult signature to counterfeit. Since Sn-Pb solder has been around for many years and older samples are readily available, this material has been selected for the basis of the research and several samples have been collected. To start, these samples are characterized using the Scanning Electron Microscope with Energy Dispersive Spectroscopy. Following the analysis on the time-aged samples, fresh samples are made and temperature-aged in an oven. Samples are thermally-aged for varying amounts of time and analyzed in the same way as the initial time-aged samples. All of these data points are used to create a method to estimate solder age. A secondary goal of this thesis project is to enable application of this method to lead-free solders, which are more complex. Other parameters, such as intermetallic compounds and their interactions are considered in additional systems to correlate age. Having developed this tampering and counterfeit mitigation technique, it can be used to determine if components have been added or replaced at a date after the initial manufacture