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Assessment of Drivers of Light Attenuation in Virginia Reservoirs
Get PDFWater clarity in aquatic ecosystems is crucial for submerged vegetation and algal dynamics. We investigated the factors influencing light attenuation (kd) by measuring total suspended solids (TSS), chlorophyll-a (CHLa), and chromophoric dissolved organic matter (CDOM) across thirteen stations located in seven reservoirs. Average kd was 1.69 m-1 (range: 0.37-3.99 m-1), with photic depths averaging 3.27 m (range: 1.15-12.43 m). TSS was the primary predictor of light attenuation (R² = 0.57, P = 0.003, SE = 0.053). Average TSS values for each site were multiplied by the slope of the kd-TSS relationship to find the proportion of kd attributed to TSS. A similar analysis was performed for CDOM by relating residual kd (i.e., kd after accounting for the effects of TSS) to determine the rate of change in light attenuation per unit of CDOM. Using this method, TSS was estimated to account for 57% ± 1% of attenuation, while CDOM explained 27% ± 1%. CHLa had minimal impact on kd across most sites, except Lake Anna, where it was the primary driver. This difference is likely due to Lake Anna’s larger size, which leads to longer water residence times. These longer times allow more opportunity for algal growth and provide a greater capacity for upstream sedimentation, which reduces the impact of particulates on water clarity. The negligible impacts of CHLa on kd in the remainder of sites are consistent with the analysis of particulate organic carbon, which showed that organic matter is a relatively minor component of TSS (32% on average). Regional differences also emerged: Piedmont reservoirs showed TSS dominance of light attenuation (61% of kd), while light attenuation of Southeastern Plains sites were more CDOM-influenced (51% of kd). Secchi depth exhibited a moderate relationship with kd when using site average data (R² = 0.45, P = 0.012, SE = 0.31), though it was insignificant at individual stations, suggesting limited predictive power at finer spatial scales
Kernel-based Partial Sufficient Variable Screening and Dimension Reduction with Categorical Controls
No full textVariable selection and dimension reduction are two fundamental components of modern statistical and machine learning methodologies for analyzing high-dimensional datasets, which have become increasingly prevalent in the era of Big Data. However, most existing methods primarily focus on continuous data, despite many practical datasets containing both continuous and categorical variables. To address this challenge, this dissertation develops novel approaches for variable screening and dimension reduction specifically tailored to high-dimensional data involving categorical predictors.
For regression analyses with mixed predictor types, we propose a unified framework that constrains sufficient reduction of continuous variables through subpopulations defined by categorical variables. Leveraging reproducing kernel-based ANOVA statistics, a model-free extension of classical ANOVA methods used in linear models, we identify important individual predictors and linear combinations of predictors without imposing stringent modeling assumptions. Unlike traditional marginal screening methods, our screening approach evaluates each predictor in the presence of others, and hence improves variable selection accuracy. Following the identification of candidate predictors, we further introduce a kernel-based sequential least squares method that efficiently reduces dimensionality by extracting a few critical linear combinations from the selected predictors. Compared to existing partial sufficient dimension reduction methods, our technique offers greater flexibility as it requires neither predefined model structures nor strong assumptions about predictor distributions. Additionally, our method accommodates both continuous and categorical response variables and does not rely on slicing when dealing with continuous responses. Theoretical and computational aspects of the proposed methods are developed. Comprehensive simulation studies demonstrate their effectiveness across various regression and classification scenarios, supported by illustrative real-data applications
Senior Recital, Arianna Greggs, violin
Get PDFSenior recitalArianna Greggs, violinDaniel Stipe, pianoMagdalena Adamek, pianoMonday, April 28, 2025 at 4:00 p.m.W.E. Singleton Center for the Performing Arts922 Park Avenue | Richmond, VirginiaThe presentation of this senior recital will fulfill in part the requirements for the Bachelor of Music degree in Performance. Arianna Greggs studies violin with Prof. Susanna Klein
Exploring the Neural Consequences of Stress and Inflammation in a Monogamous Rodent: a Path to Understanding Loss
No full textAmericans are experiencing an increased prevalence of social isolation and loneliness. A loss of social buffering can occur through loss of loved ones and grief, decline in community support, or a combination following a bout of grief. The perception of loss and loneliness is a complicated entanglement of human emotions and past experiences, and it can be difficult to quantify these states through self-reporting. However, the physical manifestation and consequences are readily identifiable as a burden on cognitive performance, cardiac health, immune system dysregulation, and an increased risk of mortality. Clinical studies have explored the impact of loss on physical metrics using functional neuroimaging and biomarkers of stress with data implicating the neurobiology of loss as a distinct neuropsychiatric disorder. Disturbance of neural processes suggest loss can be a chronic stress disorder with disruption in synaptic function and homeostasis. Foundational preclinical models of social disruption to enable mechanistic examinations of loneliness-related patterns observed in the clinic are still limited. The use of socially monogamous rodents that exhibit post-separation dysregulation of neuroendocrine mechanisms have provided insights into the neurobiology of loss. However, there is a critical gap between understanding the pathology of loneliness or loss in a mechanistic manner that allows us to construct a therapeutic approach to help patients. The goal of this dissertation is to expand our preclinical understanding of partner loss and social isolation to establish a context for exploring the effects of synaptic dysfunction following social disruption within the socially monogamous Peromyscus californicus (California mouse) species. We demonstrate that synaptic mitochondria respiration is altered following social isolation in female mice, but not males, and both sexes have an intensive neuroinflammation response to a systemic endotoxin challenge. Additionally, we explore the impact of aging on gene expression in California mice. These data are positioned to increase our capabilities to explore the neurobiology of loss from the lens of separation as a species relevant chronic stressor, while providing a framework for designing future studies leveraging the California mouse
Imagine Being Free: Decolonizing Actor Training In University and Conservatory Programs
Get PDFWhile blackface is considered the first proper form of American theater, I want to consider how the auction of enslaved Africans functioned as the original form of American theater. The auction block acted as a kind of interactive performance in which enslaved bodies were surveilled and evaluated as a kind of spectacle. In many ways, the auction block inaugurated White viewing practices of the Black body that reverberated in the day-to-day practices of slavery and subsequent visual media like the refashioning of blackface minstrel tropes within contemporary entertainment (plays, television, film). In Imagine Being Free: Decolonizing Actor Training in University and Conservatory Programs, I assert that the auction of enslaved Africans curated viewing practices on the part of whites that now serve as guiding principles in contemporary acting technique programs throughout the U.S.
In this project, I demonstrate how the anti-Black ancestry of American theater, exhibited in the auction block, blackface minstrelsy, and current viewing practices of Black performers, has had a lasting influence on MFA, BFA, and conservatory acting technique programs. The questions animating this dissertation are “How has American theater’s relationship with racist viewing practices of Black folk created a curated, and intentional space of anti-Blackness within the pedagogy of technical acting training?” And “What steps can be taken to amend these bias practices?” I argue that these programs replicate how Black bodies were displayed on the auction block. Additionally, these programs take their cues from earlier Black minstrel performances. In this project, I look at three main actor training techniques: 1) Voice for the Actor, 2) Character Analysis, and 3) Speech and Dialect, to demonstrate their reliance on white normativity in their training techniques.
Character Analysis teaches the actor how to analyze characters beyond the depth of the text. The students should understand their character and how their experiences influence their acting choices. Speech and Dialect training uses the international phonetic alphabet to teach actors more flexibility in their performances by switching between accents for a desired character sound. And, Voice for the Actor, teaches actors to care for their voices and create the clearest sound from their vocal cords. These practices are considered integral parts of any acting training technique program, but current teaching practices are all premised on variants of white normative speech. Character Analysis’ attributes desired preferred characteristics with qualities of white characters. Speech and Dialect uses “neutral American,” a sound indicative of white men from northeast Ohio, as the sound standard for all actors. Finally, Voice for the Actor’s desire to have a clear sound is often replaced with a desire to have a sound mirroring mirrored after upper-middle class white Americans.
These three areas of study are considered the most imperative for acting training students, yet the pedagogical design of these practices proves reliant on archaic and anti-Black viewing practices. I argue that these techniques are anti-Black and dependent on white normativity. My project introduces equitable and liberatory training practices, such as implementing the creation of a personal international phonetic alphabet chart for each student, addressing the use of white normativity in character analysis, and expanding conventional vocal qualities which define the elements of a “free and natural voice” (Linklater, 3) by analyzing the perceived condition of sound in performance. Acting technique programs need to understand that the painful and dangerous perceptions of Blacks perpetuated throughout our entertainment media is not just attributed to the choices of mainstream media, but the disempowering nature of our programs. Acting technique training must imagine itself in the midst of liberation and be free from images of captivity. We must begin to build new pedagogical practices that can meet actors where they are because where they are will always be enough.
My research is deeply informed by and indebted to: Thomas F. Defrantz and Anita Gonzalez’s Black Performance Theory (2014), Patricia Fletchers Classically Speaking (2013), Kristin Linklater’s Freeing the Natural Voice (1976), Uta Hagen’s Respect for acting (1973), Sharell Luckett and Tia M. Shaffer’s Black Acting Methods (2016), Joy Degruy’s Post Traumatic Slave Syndromen (2005), Anne C Bailey’s The Weeping Time (2017), Donald Boogle’s Black Beginnings: From Uncle Tom to Birth of a Nation, Toms, Coons, Mulattoes, Mammies and Bucks: an interpretation of Blacks in American Films (1973) and the International Phonetic Alphabet Chart (1886). These texts offer theoretical frameworks and methodological grounding that inspire how my project intersects performance, theater, and Black history.
The theories used throughout my project are Afrofuturism and Black Performance Theory supported by Black Feminist literature. Afrofuturism is an active methodology that believes in the fundamentals of imagination and works to create possibilities in Black folks present and future. Afrofuturism functions to explore how African Americans view themselves (Strait,12), while simultaneously using history and fantasy to connect Black folk to their ancestry and carry them towards untapped explorations of liberation. Black Performance Theory reexamines Blackness through performance. It explores how performance can further interrogate Black identities by looking through immigration, migration, nonlinearity, violence, spirit, and imagination. Additionally, I will utilize auto-ethnographic investigations, calling on my personal experiences as a professional actor and a student actor.
The theater theorists used in my project are Uta Hagen, Constantin Stanislavski, Sanford Meisner, Cristal Chanell Truscott’s SoulWork and Tawnya Pettiford-Wates’ Ritual Poetic Drama. Uta Hagen as a theater theorist focuses on emotional memory, sense memory, the five senses, substitution and identity. Constantin Stanislavski’s methodology focuses on the importance of imagination, attention, actor transformation and the practice of emotional memory. Cristal Chanelle Truscott’s SoulWork recognizes soul as a practice revolving around collaboration. Soul integrates the collective whole and demands practitioners to identify the cultural nuances of self. Tawnya Pettiford-Wates’ Ritual Poetic Drama (RPD) works as a “tool for artists to access their own individual creative content, potency and power as artists” (Wates, 107). Wates explores how the traditional Western classical training of actors, particularly Black actors, affects the internal development of Black artists and creates deficits in their relationship with themselves. Because classical acting training focuses so heavily on traditional Western methodologies, non-white actors are often left severely disconnected from their cultural ethos. Student actors dedicate two, three, or four years to submerging themselves in Western traditions, and by the time they emerge, they have the potential of losing their traditional performance practices.
My work will not create style-specific methodologies but rather neutralize acting theory technique so that it functions as a platform for actors to explore with the intent of curiosity, instead of an exploration that demands essential change. Moreover, my project argues for an actor-centered training program that prioritizes the autonomy, creativity, and innovation of the actor in their training
Development of a Mediation Model of Pain Cognition in Adult Patients with Sickle Cell Disease
Get PDFPain is a hallmark of Sickle Cell Disease (SCD), a genetic hemoglobinopathy characterized by chronic hemolytic anemia, vaso-occlusion, and organ damage. While acute vaso-occlusive crises (VOC) have been extensively studied, the mechanisms underlying chronic pain and its interplay with brain function remain unclear. This dissertation investigates the relationships between cerebral blood flow (CBF), fluid cognition, and pain sensitivity in adults with SCD, utilizing advanced imaging techniques and validated assessment tools.
Arterial spin labeling (ASL) and functional magnetic resonance imaging (fMRI) were employed to measure CBF and brain activity, respectively. Pain sensitivity was assessed using the Pain Sensitivity Questionnaire (PSQ), and fluid cognition was evaluated through the NIH Toolbox. An exploratory mediation model was developed to investigate the role of altered cerebral hemodynamics and cognitive function in shaping pain cognition.
Key findings revealed significant disruptions in brain hemodynamics and reduced cognitive performance in SCD patients compared to healthy controls. Elevated regional CBF was associated with lower cognitive flexibility and slower processing speed, while heightened pain sensitivity correlated with altered brain activity in regions implicated in pain modulation and interoception. These findings suggest that chronic cerebral ischemia and neuroplastic changes may contribute to central sensitization and pain amplification in SCD, though further studies with larger samples are needed to confirm these associations..
This study provides novel insights into the neural mechanisms underlying pain cognition in SCD, highlighting the complex interplay between ischemia-induced brain alterations, cognitive dysfunction, and chronic pain. The findings underscore the need for targeted interventions to address both the physiological and cognitive dimensions of pain in SCD, offering a foundation for improved pain management strategies and quality of life for affected individuals
The Bacteriostatic, Regenerative, and Immunomodulatory Properties of Extracellular Matrix Particles for Lung Injury
Get PDFAcute respiratory distress syndrome (ARDS) is a prevalent, life-threatening lung condition, affecting nearly 200,000 Americans annually, with a 40% international mortality rate. There is no cure for ARDS, and current pharmacological treatments have limited effectiveness. Symptoms can be mitigated with mechanical ventilation, though this often leads to ventilator-induced lung injuries (VILI) and puts critically ill patients at risk of infections, including ventilator-associated pneumonia (VAP). A promising therapeutic is the extracellular matrix (ECM), a complex network of structural proteins and bioactive molecules that has been shown to have anti-inflammatory properties and prevent fibrosis. We aim to utilize the regenerative and immunomodulatory effects of decellularized extracellular matrix (dECM) obtained from both pig lung (PL) and mouse mesenchymal stromal cell (mMSC) matrices. Through various fabrication methods, we have found that dECM particles have a wide range of immunomodulatory and antimicrobial properties. The mMSC and PL dECM nanoparticles were fabricated via electrospray deposition with tunable sizes ranging from 145-275 nm and negative zeta potentials (~ -11 mV), giving them the ability to reach distal respiratory regions and penetrate the surfactant and mucus membranes in the lungs. We also fabricated an aerosolized powder of PL dECM via spray drying, which has shown similar pro-regenerative effects on damaged tissue. We found that the mMSC ECM nanoparticles have a dose-dependent bacteriostatic effect on gram-negative bacteria strains, inhibiting the growth of common pneumonia-causing pathogens Pseudomonas aeruginosa and Escherichia coli. Both the mMSC dECM nanoparticles and PL dECM spray-dried particles have demonstrated accelerated wound healing on injured cultures of both mMSCs and human lung epithelial cells. Our mMSC ECM treatments demonstrated immunomodulatory properties that show promise in suppressing inflammation and promoting resolution in a pro-inflammatory induced environment. Due to the versatile formulation options and matrix sources, our ECM particles can be tailored for different lung applications and demonstrate improved healing of injured lungs while inhibiting bacterial growth, making them a promising therapeutic biomaterial for aiding VAP recovery and treating ARDS patients
GBA Deficiency Promotes α-Synuclein Accumulation in Cellular Models of Parkinson’s Disease
No full textParkinson’s Disease (PD) is characterized by progressive neuronal degeneration, reduced dopamine levels, and aggregation of the protein ⍺-synuclein, leading to the formation of Lewy bodies. Mutations in the GBA1 gene, which encodes the enzyme glucocerebrosidase (GBA), have been linked to PD. GBA hydrolyzes glucosylceramides (GlcCer) into ceramide and glucose. A loss-of-function mutation causes lipid accumulation in lysosomes, disrupting cellular function. This study investigated how GBA knockouts affect ⍺-synuclein accumulation in neuronal cell lines. SK-N-SH and SH-SY5Y cells were chosen to examine cellular apoptosis and ⍺-synuclein levels, providing a model for studying neurodegenerative processes and cellular effects of GBA depletion.1 GBA was knocked out in both lines, with colonies screened through PCR and confirmed by western blot. Knockout lines showed reduced growth and altered morphology compared to wild type cells. Apoptosis markers were elevated in both knockout lines, indicating increased neuronal cell death. Analysis of ⍺-synuclein levels in the SH-SY5Y cells exhibited increased ⍺-synuclein aggregation and accumulation, whereas SK-N-SH cells had a decrease with GBA knocked out. Other tested cell types also showed elevated ⍺-synuclein accumulation. In SH-SY5Y cells, the absence of GBA promotes aggregation, while SK-N-SH cells have opposite effects. This highlights the importance of cellular context in PD mechanisms and suggests that GBA may have variable effects depending on cell type
Expression Analysis of Floral Symmetry Candidate Genes in Browallia speciosa
No full textStamen structure and development is one of the deciding factors for an angiosperm’s pollination syndrome. The Solanaceae hold particular interest in understanding pollination and stamen relationships due to their development of bilateral symmetry (zygomorphy), and visitation by a variety of pollinators. Previous studies have implied that floral symmetries of the Solanaceae are not solely determined by CYC2-like genes, particularly regarding the zygomorphic corolla. This is unusual, as CYC2-like genes and their homologs have been found to control the floral symmetry in a majority of studied angiosperms, especially in core eudicots. Browallia speciosa Hook. is a particularly interesting organism due to its three different types of stamens, whose structures aid a unique pollination process. This project aims to investigate the molecular basis for the development of different floral organs and bilateral symmetry of B. speciosa. To achieve this, RNA-seq data was analyzed to explore differential gene expression across 5 different floral organs of B. speciosa, and the candidate genes that are likely responsible for its symmetry and floral organ development were identified. Analysis of Browallia speciosa’s de novo transcriptome revealed differential expression of TCP-like transcription factors, along with ANT-like, BOP-like, JAG-like, PAN-like, RBE-like, and ARGOS-like genes. Along with this, gene ontology enrichment analyses highlighted fruit ripening, lipid metabolism, and secondary metabolite synthesis pathways as promising novel avenues for understanding floral symmetry and reproduction. In the future, these results may serve as the basis for functional and molecular studies to confirm the functions of these master genes, and to investigate their downstream regulations. As the molecular comprehension of floral symmetry and pollination expands, we are able to make more informed decisions regarding the stewardship of consequential crops and plants
Exploring the Role of Government Funding and Policy Criteria in Greening Projects: A Case Study of Southside Richmond
Get PDFThis thesis explores how government and private funding structures and policy criteria influence community-based organizations (CBOs) engaged in urban greening projects, focusing on Southside Richmond, Virginia through a case study of a local CBO. Using a multi-method approach including document analysis, secondary data review, and autoethnographic reflection, the research suggests a gap between visibility and influence for CBOs, showing that their decision-making authority often varies while they are publicly recognized. The study also reveals that public documentation of funders\u27 community engagement is often performative or symbolic rather than structurally embedded in decision-making processes. In addition, funding remains a barrier, with grant requirements such as match contributions and administrative burdens. Recommendations to address structural inequities in greening partnerships include incorporating reparative justice frameworks, power mapping strategies, and greater organizational and community autonomy