41656 research outputs found
Sort by
Probing the \u27MeV Gap\u27: Discovery and Characterization of Persistent and Transient MeV-GeV Gamma-ray Sources with the Fermi Large Area Telescoope
Get PDFThe MeV Gap is a moniker for the energy regime E~0.1-100 MeV that has lacked sensitive observations for the last 20 years. This is not out of scientific disinterest, but observational challenges. The only instrument currently available to make observations in the MeV Gap is the Fermi Large Area Telescope (LAT). For the first time ever, Fermi-LAT has been leveraged to push its observational capabilities to its absolute lower energy limit to end this 20-year observational gap. Observing the MeV sky is imperative for identifying some of the most luminous galaxies in the Universe known as blazars. The brightest blazars have emission that is dominated by MeV energies. Powered by supermassive black hole accretion, MeV blazars are found at high redshift, therefore their identification can help to understand the presence of supermassive black holes very early in the Universe as well as being sources of extragalactic neutrinos, whose origin is still not precisely known. Furthermore, Galactic gamma-ray sources, and other gamma-ray objects without a precise origin have neglected study. This dissertation identified 450 MeV-bright objects, 62 which are newly discovered gamma-ray emitters. Additionally, a historical investigation identified the demographic and rate of Galactic gamma-ray flaring sources which can be used to constrain theoretical models on the evolution of objects such as binaries and pulsar wind nebulae. Lastly, this work found 21 X-ray counterparts for unidentified gamma-ray sources and classified them with an improved machine learning algorithm, helping to streamline future classifications of unknown gamma-ray objects
Mapping Teacher and Librarian Perspectives Through a Qualitative Descriptive Study of Book Bans in South Carolina
Get PDFThis study analyzed findings from four data collection pieces with Critical Discourse Analysis, in which participants met in focus groups to discuss their experiences with book bans and curriculum censorship. The five focus groups included Upstate middle school English teachers, Upstate high school English teachers, Upstate middle school librarians, Upstate high school librarians, and participants from the Midlands and Lowcountry of South Carolina. There were two primary research questions and two sub-questions: (1) What do educators and librarians in grades 6-12 say about how power functions in engaging or challenging current curricula and book censorship trends?; (1a) How do middle and secondary teachers and librarians experience these current curricula and book censorship trends regionally across South Carolina?; (1b) How do experienced (4-9 years) and veteran (10+ years) teachers and librarians in middle and secondary schools experience these current curricula and book censorship trends in South Carolina?; (2) In what ways do South Carolina English teachers and librarians advocate for intellectual freedom in the face of increasing book bans and curriculum censorship?
Through four phases of qualitative research based on experiences with censorship in their classrooms or libraries, participants met with their focus groups twice on Zoom (at the beginning and end of the study) to discuss their experiences with book bans and to plan ways to advocate against censorship. Participants also wrote a two-page personal narrative and volunteered for an individual interview. Through qualitative analysis, I listened to the experiences of middle and high school teachers and librarians in public schools in South Carolina. I found differences between regions in South Carolina and years of experience for educators. Findings also illustrated how teachers and librarians felt about censorship, power, advocacy, and agency.
Both teachers and librarians allow students to choose their texts to avoid threats of indoctrination. Regionally, the Upstate reported more restrictions than the Midlands or Lowcountry, though the Midlands had a high-profile case, and the Lowcountry saw an attempt at mass banning. Experienced teachers in all three regions were less likely to resist censorship than veteran teachers since they felt newer to education and worried more about losing their jobs. Overall, educators in South Carolina felt afraid of repercussions and frustrated with vague policies and administrative oversight. Despite the emotional toll, educators found ways to collaborate as they looked forward to advocating together and finding agency in the face of censorship
Toward the Application of Natural Language Processing in Electronic Health Record Analysis for Taxonomy Development
No full textElectronic health records (EHRs) are pivotal resources for nurse practice because they increase the timeliness and reliability of patient information at the point of care and support access by multiple healthcare providers and the individual patients themselves. However, it is widely recognized that data extraction from EHRs is challenging due to the variability in the language used in clinical care notes and the lack of standardized terminology across healthcare systems. The broad objective of this dissertation is to develop taxonomy-based classification models for nursing care by applying feature engineering approaches to EHRs that include nursing care of ostomy patients following ostomy surgery. The clinical significance of this work is to better understand practice-level differences and terminology differences in ostomy nursing care for acute-care settings. This dissertation addresses three specific aims. Aim 1 identified machine learning methodologies and their parameters for training natural language processing (NLP) models to extract non-coded data from EHRs. Aim 2 conducted a retrospective analysis on EHRs relevant to ostomy surgery to assess ostomy nursing care and patient outcomes in acute-care systems. AIM 3 developed a taxonomy-based risk model applicable to ostomy nursing care. This dissertation contributes to the growing field of Natural Language Process in healthcare by demonstrating how taxonomy-based classification models can be applied to extract and analyze nurse care data from EHRs. The findings show the critical role of data extraction and bridging the gap between clinical practice and machine learning, ultimately enhancing the usability of nursing-related information within EHR systems
Live-Streaming E-commerce: The Role of Firms And Influencers In Driving Sales
Get PDFLivestreaming is a transformative technology that removes the limitations of time and lo- cation, enabling real-time interaction between hosts and audiences. When combined with online shopping, it creates livestreaming e-commerce, a fast-growing marketing channel where influencers promote products live and engage directly with consumers.
My doctoral dissertation explores how firms and influencers collaborate effectively in this emerging retail space. Livestreaming e-commerce offers new opportunities for reaching consumers, but also raises questions about how to manage partnerships and present products in a dynamic, real-time setting. Specifically, I investigate how firms should choose and switch influencers over time, and how influencers can best select and promote products during livestream events.
The dissertation consists of three chapters examining firm–influencer collaboration from different angles. The first chapter analyzes how firms should switch influencers over time and shows that switching to a moderately similar influencer can improve sales by balancing familiarity and reach. The second chapter focuses on how influencers diversify their product assortment, finding that timing and audience–product fit are key to maintaining viewer engagement. The third chapter investigates how visual and textual features of ad content affect attention during livestreams, showing that while rich features increase attention overall, they can backfire when placed next to visually competitive ads.
Together, these chapters contribute to our understanding of how firms and influencers can optimize their collaboration in livestreaming e-commerce. The dissertation offers new insights into digital marketing, influencer strategy, and consumer attention in interactive online environments
Ceramic Membrane Evaluation via Automated Filtration Systems for Water Treatment and Resource Recovery
Get PDFMembranes are an advanced and mature water and wastewater treatment technology. Membrane fouling is a key difficulty for all membrane filtration processes, leading to significant attention in the literature over the years. A common problem in laboratory-scale membrane research is that the testing methods in the laboratory are often quite different than industrial applications due to the limitations of manual experimental setups. An automated membrane filtration apparatus was built in the lab to solve this problem by allowing long-term filtration, frequent backwash and CIP, and high-accuracy operation. The filtration system achieves different cleaning strategies for both theoretical research and practical water and wastewater scale-up experiments. The embedded control algorithms achieve operational accuracy in terms of maintaining flux and/or trans-membrane pressure (TMP) at their desired set points. A flux-step function enables operators to measure critical flux automatically. The filtration system handles a variety of microfiltration and ultrafiltration membranes in crossflow or dead-end mode with backwash integration, CIP capability, and aeration scouring. Synthetic rendering wastewater and raw rendering wastewater were applied to test the apparatus in the lab and in the field, respectively. The control algorithms successfully dampened oscillations using custom calibration curves. Three backwash-CIP strategies were tested with both wastewater types. The first was time-triggered backwash and cycle number-triggered CIP, which resulted in stable and reliable operation but required close operator control and thus was not fully automated. The second strategy was time-triggered backwash with TMP-triggered CIP, which responded quickly to water quality fluctuations and achieved full automation, but the TMP target had to be carefully set to enhance the efficiency of CIP. The third strategy was target-TMP backwash with duration triggered CIP, which can achieve the most advanced and flexible filtration system, though setting up this level of automation complexity in the field was challenging. Both backwash and CIP frequencies responded to real-time performance automatically. Ultimately, the automated lab-scale filtration apparatus operated similarly to full-scale systems, which should help fill the gap between laboratory research and scale-up of industrial applications.
By using the automated filtration apparatus, supersaturated CO2-enhanced backwash (SCEB) was tested as an alternative to clean-water backwash to enhance the effectiveness of foulant removal for ceramic microfiltration membranes. Membrane backwash and chemical-enhanced backwash are standard methods to clean fouled membranes. Air bubbles are also commonly used to tangentially scour the feed side surface of micro- and ultrafiltration membranes to add scouring and loosen cake layers; this is called air-assisted backwash. Unlike air-assisted backwash, SCEB forces dissolved CO2 and CO2 bubbles through membrane pores. In this study, transmembrane pressure (TMP) and flux profile during SCEB were directly analyzed to reveal the exact nucleation location. The results from constant-flux filtration show that SCEB recovered more filtration TMP compared to DI water backwash, which saved 6.5%, 2.7%, and 6.9% of the energy during lake water, activated sludge, and rendering wastewater filtration, respectively. Visualization of the membrane permeate was done for the first time, confirming that CO2 bubbles did not form before entering the membrane matrix. The pressure and flux profiles of SCEB itself were directly monitored. The pressure profile from constant-flux backwash was analyzed to further understand the cleaning mechanism. The results from constant-flux SCEB showed more negative pressure than DI water backwash, which means that CO2 bubbles went through the membrane pores and created more resistance during SCEB. The visualization confirms that CO2 bubbles nucleated inside the membrane pores rather than on the filtrate side to clear the foulant blocked deep inside the membrane matrix. The behavior of CO2 bubbles can be divided into three stages during SCEB: i) permeate flush out, ii) bubble concentration growth, and iii) bubble concentration equilibrium. The last stage had the highest concentration of CO2 bubbles, which work as pore-scrubbing entities and play an important role in better cleaning effectiveness because of the higher nucleation rate, extra shear stress, and greater lifting force.
Membrane cleaning for membrane bioreactors is also challenging, especially for the anaerobic membrane bioreactors (AnMBRs). A pilot scale AnMBR system was used to treat synthetic municipal wastewater combined with pretreated crop harvest waste for direct hydroponic reuse. The AnMBR system was built on top of the automated filtration apparatus to improve some shortcomings, allowing an even higher data acquisition rate, more flexible parameter inputs, and more accurate flow rate results. Membrane performance was evaluated at different hydraulic retention times (HRT) and cross-flow velocities (CFV), suggesting that both parameters influenced membrane performance. When HRT was higher than 1 day, CFV dominated the membrane performance, and membrane resistance showed a decreasing trend. When HRT was lower than 1 day, even though the CFV was increased correspondingly, membrane resistance presented an increasing trend. Membrane performance was also evaluated with crop harvest waste addition. Crop harvest waste was pre-treated with two methods: physical grinding and biological fermentation. Two harvest waste additions both increased membrane resistance; fermented harvest waste increased the membrane resistance more than the other type. Bioreactor performance under the two pretreatment methods was similar; fermented harvest waste produced more methane due to its high ratio of volatile fatty acid concentration. Desired nutrients, such as ammonia, total phosphorus, and sulfate, were leached from both harvest waste types, which could be a way to reduce fertilizer use in future direct hydroponic reuse applications
GROSSLY MISUNDERSTOOD: How Two Low Socioeconomic Black Parents in the Rural South Perceive Their Involvement in Their Children\u27s Education
Get PDFABSTRACT
The purpose of this study was to investigate the perceptions of low-socioeconomic Black parents living in the rural South regarding education. The study was designed to amplify the voice a marginalized community that is misunderstood regarding their children’s education. Using a detailed narrative design, I interviewed two single-parent families living in a Section 8 apartment complex to capture their perceptions of their children’s education.
In this study, the participants were single mothers who expressed their desires and goals for their children. In addition, these mothers shared their backgrounds and experiences growing up and attending school, which shaped and molded their parental skills.
The primary significance of this study is to provide information that will support educational leaders attempting to build relationships within the Black rural community in the South. This research can influence educational practices by serving as a reference for teachers to understand the various types of parental involvement. For research purposes, this study serves as a foundation for extended research throughout rural Southern communities to continue giving marginalized communities a voice regarding education
Investigating the Influence of the Extracellular Matrix on Triple Negative Breast Cancer in Diverse Patient Samples
No full textTriple negative breast cancer (TNBC) is an aggressive subtype of breast cancer associated with poor prognosis, high rates of recurrence, and few targeted treatment options. The heterogeneity of TNBC and high metastatic potential complicates treatment strategies, making identifying the mechanisms that drive disease progression essential.
African American (AA) women are disproportionately affected by TNBC and experience higher incidence rates, worse prognoses, and lower survival rates compared to their European American (EA) counterparts. Recent investigations have revealed ancestry-based differences in both molecular mechanisms and the tumor microenvironment, though most preclinical models and clinical trials still lack sufficient representation of global diversity. This dissertation explores molecular mechanisms of cancer and metastasis by utilizing in vitro and ex vivo samples from diverse patients and employs novel machine learning approaches to characterize gene and protein expression further.
The epithelial to mesenchymal transition (EMT) is a dynamic process by which cancer cells convert from an epithelial to a mesenchymal phenotype, characterized by increased migration and invasiveness. Tumor biopsy samples from AA and EA patients revealed differential expression of 5 EMT-associated proteins quantified by a deep-learning AI model. Further, we analyzed gene expression from four regions across the tumor and surrounding extracellular matrix. Machine learning models highlighted the tumor/matrix border regions as the most distinctive between groups and identified over 20 differentially expressed EMT-associated genes.
One gene of interest is S100A4, a protein that functions both intra- and extracellularly to promote tumor progression and metastasis. This study shows that S100A4 knockout via CRISPR-Cas9 decreases the migratory and invasive capacity of TNBC and non-tumorigenic mammary cells from diverse patients. Simulated co-culture with fibroblasts induced contrasting responses in cell lines from AA and EA patients, and mRNA expression analysis revealed time-dependent suppression of EMT gene pathways.
This work addresses critical gaps in existing TNBC research and lays the foundation for future preclinical models that consider ancestry as a fundamental variable, advancing breast cancer treatment and outcomes
Perspectives on Clinical Oncogenomics: Secondary Germline Variants Associated With Tumor Genomic Profiling in Community Cancer Care and Advanced Practitioner Oncogenomic Proficiency
No full textPrecision medicine in oncology is defined by the sequencing of tumor genomic variants that can be used to identify targeted treatment for patients. Secondary pathogenic and likely pathogenic germline variants (P/LPGVs) can incidentally be detected on tumor genomic profiling (TGP). With the rise in precision medicine over the past 15 years, secondary P/LPGVs on TGP have been an increasingly important clinical issue. However, there are factors that can lead to misidentification and underreporting of P/LPGVs. Germane to this clinical practice issue is healthcare provider oncogenomic literacy and proficiency.
A scoping review was conducted to evaluate the variability of the prevalence of P/LPGVs on TGP in patients with solid tumor malignancy. Sixteen articles published between 2016 and 2024 were included in the review with considerable variability noted in the prevalence of P/LPGVs. Potential factors contributing to the variability included the numbers of cancer susceptibility genes and tumor types included, and population size. Next, a retrospective review studied the concordance rate between P/LPGVs on TGP and confirmatory germline testing at two community cancer centers. A high concordance rate of P/LPGVs was observed between the two types of testing, indicating that TGP can help identify cancer susceptibility genes in patients whether they qualify for hereditary cancer syndrome screening or not. The identification of P/LPGVs on TGP does require follow-up confirmatory germline testing in these patients. Secondary analyses were completed of off-tumor genotype-phenotype correlations and variant allele frequency of P/LPGVs on TGP.
A quasi-experimental pretest posttest study evaluated advanced practitioners practicing in hematology/oncology regarding self-reported oncogenomic training and proficiency concepts at baseline. The proficiency concepts were reassessed after the intervention of an educational module. The study results indicate that an educational module is one way to address a perceived lack of oncogenomics training and proficiency by APs. Advanced practitioners are integral to oncology care and therefore require adequate training and knowledge to provide comprehensive cancer care to patients
Essays on Credit Default Swaps
Get PDFThis dissertation focuses on the investigation of the credit derivative market. It consists of an analysis of credit default swaps (CDS) based on corporate bonds and a study of the indexed CDS—the ABX.HE index, which references subprime residential mortgage-backed securities as the underlying reference entities.
The first chapter examines the CDS pricing model and explores the key determinants of the price error measured by the absolute value of the CDS-bond basis. Specifically, I assess the efficiency of different risk-free rate proxies--Treasury Yields, EFFR/OIS rates and SOFR/OIS rates--in the CDS pricing model. The result indicates that Treasury yields overperform the other two proxies in improving pricing accuracy. To estimate the theoretical CDS spread, I compare two pricing models: one based on conditional default probabilities and another based on unconditional default probabilities. The findings suggest that the unconditional default probabilities approach provides CDS estimates closer to the market-quoted value for bonds rated B and above. This study also covers the period of the COVID-19 pandemic, revealing that pricing accuracy decays during economic downturns. Moreover, even though categorical factors such as credit ratings and sector contribute to price discrepancies, the idiosyncratic factors play a dominant role in driving the price error.
Chapter two analyzes the ABX.HE index from early 2006 to mid-2012 to explore the subprime residential mortgage-backed securities market. In the beginning, the introduction of mortgage-backed security (MBS), collateralized debt obligation (CDO) and credit default swap (CDS) provides the context for the creation of the ABX.HE index. After outlining the criteria and mechanics of the index, the event study method is employed to examine the influence of default risk and market liquidity-related events on the ABX.HE index price. The results show that news about alleviating default risk does not improve the index price. Nonetheless, senior securities are still expected to respond to their rating downgrades and possible downgrades from credit agencies. Moreover, rating downgrades and possible downgrades in the insurance sector tend to influence securities with median quality. In the market liquidity improvement sector, monetary policies are more likely to improve subordinated securities and above. Events concerning fiscal policies passed by the House improve more subindices than other fiscal policy categories. Finally, the most interesting observation is that the abnormal index return is more likely to happen on a day with multiple liquidity events
Navigating the Tides of Change: Girls’ Experiences in Scouts BSA
Get PDFOn February 1, 2019, Boy Scouts of America officially accepted girls into its signature program (ages 11–18) and changed its name to Scouts BSA. This historic shift provided a novel opportunity for researchers to investigate the experiences of some of the first 13 girls to enter this traditionally all-boy space and examine how participation influenced sense of self and purpose. A qualitative phenomenological approach was adopted to explore girls’ experiences and perceptions and meanings they constructed, using secondary data consisting of 38 transcribed interviews from all 13 girls. Girls ranged in age from 12–18 years old (M = 13.72, SD = 1.51), were mostly white (84.6%), and came from predominantly upper middle-income households (69.2%). Our analysis revealed expanded sense of self and empowerment to be the essences of girls’ experiences in Scouts BSA, which contributed to identity and purpose development. Subthemes included feelings of competence and confidence, embracing “boy activities,” and focus on rank advancement