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Structural and Spectral Control in Solar Nanophotonics
No full textThis dissertation examines the structural control of light absorption in nanophotonic systems, presenting both conventional and innovative strategies to enhance optical performance. The research is structured into four key sections, each addressing critical aspects of photovoltaic systems and plasmonic tuning of optical spectra.
The first section focuses on material utilization in traditional photovoltaic systems, specifically in the context of Maryland's climatic and operational conditions. It investigates challenges related to energy generation and waste management, providing insights into the implications of long-term waste accumulation. This section also highlights the importance of recycling and circular economy policies at the state level. It sets the stage for exploring thin-film and third-generation photovoltaics, emphasizing the need for innovative approaches to improve efficiency and sustainability.
The second section delves into novel photovoltaic materials, particularly lead sulfide colloidal quantum dots (PbS-CQDs), which represent a promising third-generation photovoltaic material. These nanoscale materials offer exceptional tunability in optical and electronic properties, making them ideal for near-infrared (NIR) photovoltaics. The research explores their material characteristics, device design, and operating principles, incorporating machine learning techniques to enhance characterization of CQD solar cells. Additionally, this section presents a comparative study of vertical and lateral CQD field-effect transistors, demonstrating applications in photosensing and advanced material characterization.
In the third section, the focus shifts to photonic band engineering and advanced patterning techniques for CQD films to achieve spectral tuning beyond their intrinsic properties. Through simulation methodologies and modern data-driven techniques—collectively known as inverse design—the research explores novel tandem solar cell architectures. Computational design studies are presented, addressing metamaterial optical parameter extraction, near-perfect absorbance in plasmonically enhanced 2D materials, and spectral tuning using aperiodic plasmonic arrays.
The final section investigates the optical properties of core-shell plasmonic nanoparticles. It introduces the spectral tuning capabilities enabled by manipulating nanoparticle shapes, with an emphasis on aluminum as an abundant plasmonic material. Additionally, it examines gold nanoshells and the impact of ligand and solvent modifications in aerosolized phases on their optical behavior. These findings demonstrate strategies for fine-tuning plasmonic aerosols for applications ranging from atmospheric sensing to energy harvesting
Sporting a Baltimore Chinese Identity in 20th-Century Baltimore
Get PDFIn the mid-twentieth century, Baltimore’s Chinese community was no stranger to sports. Through playing in, spectating, and organizing matches and tournaments, the Chinese community engaged with sports on their own terms. Participating in the wider Baltimore sports scene provided crucial points of contact between the Chinese community and other segments of Baltimore society. A baseball match was utilized as a fundraising opportunity during the Second Sino-Japanese War, and talented Chinese individuals such as Thomas and James Goon were able not only to enter white spaces but win recognition and respect from white Baltimoreans due to their athletic prowess.
Sports played an even more crucial role in the Baltimore Chinese community by serving as a social space facilitating interactions among peers through Baltimore’s Chinese basketball and softball teams. Through practice and participation in regional tournaments, co-ethnic sports offered invaluable moments for social interaction between those of not only similar heritage and experience but also age. I argue that it was such spaces of interaction that were critical in the production and maintenance of a “Baltimore Chinese” identity among Baltimore’s Chinese youth.
Working on the history of sports in Baltimore’s Chinese community presents challenges associated with studying a small, transient population that left relatively few written records. To remedy the inadequacies of available sources, I relied on oral histories from individuals who had grown up in Baltimore in the mid-twentieth century.
Through my analysis, I aim to demonstrate that, rather than merely a tool of assimilation, sports was an avenue for Chinese youth to exercise agency by negotiating a communal identity. Furthermore, even though the vast majority of Chinese youth experienced constraints on their time, energy, opportunities, and social circles as a result of racial discrimination enacted against them and their parents, many had a vibrant social life that defied their socio-economic circumstances
Incorporating Technical Requirements and Requirements Tracing into the Air Force Acquisition's Pre-Milestone A Phase
Get PDFThe Air Force has been under constant scrutiny in program execution: F-35 program delays, costly F-22 upgrades, severe delay to the Combined Joint All-Domain Command and Control (JADC2), and other weapon system developments. Countless weapon systems suffered development delays and significant cost increases throughout a weapons’ lifecycle. The Department of Defense is not new to system development and providing key capabilities to the Warfighter, however, it has consistently been unable to meet the capability needs of end users in estimated programmatic times. A contributing factor includes the lack of understanding operational requirements and the translation to technical requirements. Program offices in the Air Force are employed with program managers and engineers to develop and progress the capability development of weapon systems, but they do not necessarily know the operational needs/requirements. This causes confusion and development of capabilities that do not meet the needs of the Warfighters. Thus, causing additional cost overruns and delayed program execution. Within the Major Capability Acquisition’s lifecycle, Milestone A is where the operational requirements are developed and defined using the Capability Based Assessment, Initial Capabilities Document, and the draft Capabilities Development Document. The purpose of this study is to show the benefit of understanding the transition of operational requirements to technical requirements and tracing each requirement to the capability needs defined by the operators. There is a clear need to incorporate a draft Technical Requirements Document (TRD) and a Requirements Traceability Matrix (RTM) within Milestone A to provide cost and schedule savings because it would outline a development plan for a weapon system that meets the intent of the operators and provide a technical context for lead developers to create the system. This paper will investigate the contributing factors of development roadblocks and the benefits of having a TRD/RTM in the Pre-Milestone A of any acquisition lifecycle
Characterizing and Assessing Prehabilitation Among Medicare Fee-for-Service Beneficiaries Undergoing Lower Extremity Joint Replacement
No full textAbstract
Introduction: Preoperative rehabilitation (“prehabilitation”) may impact postoperative outcomes for older adults undergoing lower extremity joint replacement (LEJR), with potential implications for value-based care. Little is known about the utilization and effect of LEJR prehabilitation in the era of bundled payment.
Objectives: To identify and characterize LEJR prehabilitation utilization using Medicare claims data (Aim 1), assess the impact of mandatory bundled payment on prehabilitation delivery (Aim 2), and determine the association between LEJR prehabilitation and post-operative utilization-based measures of short-term recovery, testing for differences by bundled payment status (Aim 3).
Methods: This study used administrative claims data from Medicare fee-for-Service beneficiaries ages 65 and older who received elective inpatient LEJR between 2015-2019. Trends in prehabilitation utilization were examined using Cochran-Armitage tests, and multivariable linear regression models tested characteristics associated prehabilitation utilization. Prehabilitation attributes (timing, volume, services) were summarized (Aim 1). Difference-in-differences estimations were used to determine the impact mandatory bundled payment on delivery of prehabilitation (Aim 2). Stratified propensity-weighted regressions were used to test associations between prehabilitation and inpatient length of stay, use and volume of 90-day post-acute home health services, and all-cause 90-day readmission among non-frail vs frail or pre-frail patients receiving hip vs knee replacement reimbursed via bundled or traditional payment (Aim 3).
Results: Prehabilitation receipt increased annually and reached 11.2% by 2019; 55% of facilities delivered prehabilitation between 2016-2019. A trial of mandatory bundled payment was associated with a 3.5 percentage point greater increase in the proportion of facilities delivering of prehabilitation in treatment vs control areas. In stratified analyses, prehabilitation was associated with shorter length of stay and lower 90-day postacute home health utilization for hip and knee replacement patients under bundled payment. For traditionally-reimbursed LEJR, only knee replacement patients experienced a significant effect of prehabilitation on postoperative outcomes, and there was greater risk of 90-day readmission.
Conclusion: Utilization of prehabilitation to prepare patients for LEJR is steadily increasing, especially among providers subject to bundled payment. We find broader evidence of an effect between prehabilitation and postoperative utilization under bundled vs traditional reimbursement for LEJR, suggesting more efficient patient recovery, with possible implications for value-based care
Long-Term Impact of Traditional Cardiovascular Risk Factors on All-Cause Mortality in People Living With or at Risk for HIV: Insights From the ALIVE Cohort Study
Get PDFAs people living with HIV (PLWH) live longer, cardiovascular disease (CVD) has become a major cause of death. However, the prognostic value of traditional modifiable CVD risk factors—hypertension, diabetes, dyslipidemia, and smoking—remains unclear in this population.
We analyzed data from 5,674 participants in the ALIVE (AIDS Linked to the Intravenous Experience) cohort from 2004 to 2020. CVD risk factors were assessed at baseline. Hypertension was defined as systolic BP ≥130 mmHg or diastolic BP ≥80 mmHg, or antihypertensive use. Diabetes was defined as a self-reported diagnosis or HbA1c ≥6.5%. Hyperlipidemia was defined as total cholesterol ≥200 mg/dL, self-report, or lipid-lowering therapy. Smoking was based on recent self-report. Mortality was identified via the National Death Index and medical records. Cox models adjusted for demographics, HIV status, BMI, substance use, and CVD history were used to assess associations with mortality. Population attributable fractions (PAFs) and subgroup analyses by HIV status, age, sex, and race were also conducted.
Over a median follow-up of 15 years, 1,224 deaths occurred. Hypertension (HR: 1.19, 95% CI: [1.04–1.37]) and diabetes (HR: 1.40, 95% CI: [1.23–1.60]) were significantly associated with mortality. These associations were stronger among HIV-negative individuals but not significant in PLWH (p-for-interaction ≤0.001). Dyslipidemia was inversely associated with mortality (HR: 0.81, 95% CI: [0.71–0.92]), with a stronger effect in PLWH (HR: 0.63, 95% CI: [0.51–0.78]; p-for-interaction = 0.005). Smoking showed no significant association with mortality. PAFs indicated that hypertension and diabetes accounted for 9.3% and 7.4% of deaths, respectively.
Hypertension and diabetes were the leading contributors to mortality, especially among HIV-negative individuals. The use of lipid-lowering therapy showed a strong protective effect, particularly in PLWH. Despite suboptimal risk factor management in this population, our findings highlight the continued importance of controlling traditional CVD risk factors in individuals living with or at risk for HIV
Leveraging Meta-analytic Topic Maps to Identify and Remove Residual Motion Artifacts from fMRI Data
Get PDFHead motion during functional magnetic resonance imaging (fMRI) can seriously affect the integrity of the blood-oxygen-level-dependent (BOLD) signal and lead to biased or distorted inferences about neural responses to tasks or resting state. Most studies treat motion purely as a technical artifact to be removed, but overlook the possibility that sudden or voluntary head movements may evoke neural responses that can produce systematic variance in the BOLD signal, potentially leading to false inferences if not properly accounted for. Here, we leverage large-scale meta-analytic brain maps to (1) model the temporal and spatial characteristics of the head-motion-evoked BOLD response during resting state in a sample of healthy young adults, and (2) evaluate the effects of regressing out this modeled evoked response, compared to using standard motion regression, on resting-state data and subject-level contrasts for a working memory (WM) task. Analysis revealed that head movements produced a systematic increase in BOLD activation around 3.6 seconds post-movement, and this activation was particularly prevalent within voxels associated with motor-related meta-analytic topics. Because of this, we introduce a new method of motion regression, which involves convolving subject-level thresholded framewise displacements (FDs) with the topic-modeled BOLD response to motion, and then including this as a regressor in the subject-level general linear model (GLM). We found that this method of motion regression, which we call FD-regression, was more effective at reducing BOLD activations due to head motion in resting-state data than standard motion regression. However, FD-regression had little to no effects on subject-level WM contrasts. That is, average correlations between subject-level WM contrasts and the WM/cognitive load meta-analysis topic map did not change significantly after applying FD-regression. We conclude that while FD-regression may be an effective method for reducing BOLD signal associated with head motion in resting-state data, further analysis is needed to evaluate its effects on data quality for task-based fMRI
The relationship between the use of virtual communication and the mental health of caregivers of older adults
No full textUse of virtual communication technologies, such as phone calls, video calls, and text messaging between caregivers, older adult care recipients, and healthcare providers increased during the COVID-19 pandemic. However, it remains unclear how use of virtual communication relates to caregiver mental health. Guided by the Source, Message, Channel, Outcome Model of Communication, we conducted a systematic review and cross-sectional analysis of a nationally representative dataset to explore how virtual communication patterns between caregivers, care recipients, and healthcare providers are associated with caregiver mental health outcomes.
First, we systematically reviewed 21 studies on virtual communication and mental health among family members of ICU patients. Phone and video calls were the most common forms of communication, primarily between family members and ICU clinicians. Mental health outcomes, including anxiety, depression, stress, and PTSD, either improved or remained stable following virtual communication. Qualitative meta-synthesis revealed two key themes: (1) anxiety related to communication uncertainty and (2) mixed emotional responses to video calls.
Next, we analyzed national cross-sectional data from the National Study of Caregiving and National Health and Aging Trends Study. First, we examined communication frequency and modality among non-cohabitating caregivers and care recipients with and without dementia. Care recipients with dementia used internet-based communication (e.g., Facebook, Zoom) less frequently than care recipients without dementia. Among dyads, phone calls were the most common modality, emailing, text messaging and video calls were less commonly used. Caregiver/care recipient dyads with dementia were more likely to use video calls. Communication modality was not associated with caregiver anxiety or depression, but high communication frequency was associated to twice the odds of anxiety. Additionally, we analyzed communication frequency and perceived helpfulness between caregivers and healthcare providers. High communication frequency and high perceived helpfulness were both associated with twice the odds of anxiety among caregivers, but not depression.
Overall, this research underscores the complex relationship between virtual communication and caregiver mental health. Frequent, clear, and preferred-modality communication may help support caregiver well-being. These findings are especially relevant as virtual communication remains a vital tool for caregivers who cannot always be physically present for their care recipient
ENGINEERING MODIFICATION-RESCUE SYSTEMS FOR INTEGRATIVE USE IN INSECT POPULATION REPLACEMENT GENE DRIVES
No full textCRISPR-Cas9 gene drives hold great potential for insect population suppression and replacement strategies to control mosquito-borne diseases such as malaria. These nuclease-based gene drives rely on double-strand breaks (DSBs) and homology-directed repair (HDR) to rapidly propagate genes of interest through target populations. However, the emergence of cleavage-resistant alleles via non-homologous end joining (NHEJ) or pre-existing genetic polymorphisms in natural populations which resist nuclease-based cutting and efficient HDR limits the temporal persistence and potential utility of CRISPR-Cas9 gene drives for sustained malaria control. To overcome these limitations, in this thesis, we conceptually propose a novel gene drive system called CRISPR-Assisted Transport And then Propulsion Using Linked Transgenes (CATAPULT). CATAPULT integrates CRISPR-Cas9-based gene drives with two transgenic cassettes that induce and rescue post-zygotic fitness effects, respectively, which we have termed Modification-Rescue (MOD/RESC) systems. To initially pilot MOD/RESC designs for use in CATAPULT gene drives, we first engineered a candidate MOD/RESC system in Drosophila melanogaster employing a protease-cleavable version of E2F1stable, an S-phase-stabilized transcription factor, as a MOD construct, and Tobacco Etch Virus (TEV) protease as a RESC construct. We employed Multiple Sequence Alignments and 3D structural modelling through AlphaFold to engineer two TEV-cleavable variants (E2F1TEV-CS2 and E2F1TEV-CS3) and achieved efficient PhiC31-mediated genomic integration at the attP40 landing site in D. melanogaster, generating multiple stable transgenic fly lines for each construct. Additionally, we designed two nuclear-localized TEV protease constructs (TEV and hyperTEV60) and successfully integrated them into the attP2 landing site in D. melanogaster, generating viable transgenic lines. We also conducted preliminary phenotypic analyses using two cell-type specific drivers (Act88F-Gal4 and tubP-Gal4) to assess whether wing flight muscle-specific or ubiquitous expression of wild-type E2F1 (E2F1WT) or E2F1stable could induce deleterious fitness effects, as previously reported. We determined that targeted expression of E2F1WT and E2F1stable in flight muscles did not significantly affect viability or wing morphology. In contrast, ubiquitous expression of E2F1WT resulted in complete lethality, confirming the potential of E2F1 as a MOD effector. This study lays the groundwork for developing a multiplexed gene drive system that mitigates the emergence of drive-resistant alleles. Future work will involve evaluating the functional compatibility of MOD/RESC systems with CRISPR-Cas9 based drives to improve gene drive persistence and effectiveness in Drosophila melanogaster and, subsequently, medically important mosquito species
A TRANSLATIONAL APPROACH FOR IDENTIFYING NOVEL REGULATORS OF CORTICAL PROJECTION DURING NEURAL DEVELOPMENT
No full textUnderstanding how cortical connectivity emerges during early brain development is a fundamental question in neuroscience. In this thesis, we employed a translational approach to identify novel regulators of cortical neuron development by focusing on genes associated with human neurodevelopmental disorders. We used layer 2/3 callosal projection neurons (CPNs) in the mouse somatosensory cortex as our model system, as they can be targeted by in utero electroporation (IUE) and thus represent are experimentally accessible for studying cortical development in vivo.
We screened 140 disorder-related genes that are highly expressed in layer 2/3 CPNs but lack well-defined roles in neural development. Using an miRNA-based loss-of-function strategy, we performed simultaneous IUE-based knockdowns of randomly paired genes to determine if their loss leads to neuronal migration and morphology defects in the mouse cortex at postnatal day 14. From this screen, we identified 21 gene pairs that produces notable phenotypes, ranging from isolated migration defects to dendritic or axonal defects, with some pairs displaying complex multi-phenotypic disruptions. Further separation of these gene pairs pinpointed specific genes underlying the observed phenotypes, culminating in the identification of Nfix as a pivotal regulator whose embryonic knockdown caused pronounced migration delays, dendritic simplification, and aberrant axon trajectories.
To elucidate the role of Nfix in aberrant axon projection, we utilized light-sheet microscopy and single-neuron tracing to reconstruct three-dimensional axonal projections throughout the entire mouse brain. This revealed ectopic branching in white matter and altered contralateral outgrowth in Nfix-deficient neurons, suggesting that miswired cortical circuits in Nfix-related disorders, including Malan and Marshall-Smith syndromes, may underlie neurodevelopmental deficits.
Taken together, this work integrates in vivo screening with detailed morphological analyses to identify crucial disorder-related genes, including Nfix, that shape dendritic architecture and axonal targeting in the developing cortex. By demonstrating Nfix as a central orchestrator of CPN development and interhemispheric connectivity, these findings advance fundamental insights into cortical circuit assembly and underscore how disruptions in this pathway may contribute to neurodevelopmental disorders
Identification of Novel Regulator in Low-Density Lipoprotein Uptake
No full textCardiovascular disease remains the leading cause of mortality in the United States, with atherosclerosis serving as a primary driver of disease progression. Elevated low-density lipoprotein (LDL) levels are a well-established risk factor for atherosclerosis, and understanding the mechanisms governing LDL uptake and regulation is essential for developing novel therapeutic strategies. To identify previously unrecognized regulators of LDL uptake and cholesterol homeostasis, we conducted a genome-wide CRISPR screen using amphotericin B selection in three human cell lines. Amphotericin B preferentially kills cells with increased plasma membrane cholesterol, enabling the identification of genes that reduce plasma membrane cholesterol by altering cholesterol transport or LDL receptor (LDLR) activity. Our screen revealed 18 significantly enriched genes across at least two cell lines, which had uncharacterized roles in cholesterol metabolism. In this study, I systematically characterized two of these genes, integrin β1 (ITGB1) and DDB1- and CUL4-associated factor 7 (DCAF7), in a human pancreatic ductal adenocarcinoma cell line (Pa03c). Flow cytometry-based LDL uptake assays demonstrated that ITGB1 knockdown and knockout had no detectable effect on LDL uptake. However, DCAF7 knockdown resulted in an approximately 40% reduction in LDL uptake, accompanied by a decrease in LDLR transcription and protein levels. Growth assays demonstrated that DCAF7 knockdown slowed cell growth, indicating that effects on LDL uptake may be attributed to impaired cell proliferation rather than a direct role in cholesterol regulation. Additionally, I tested amphotericin B resistance for all 18 candidate genes in two of the three cell lines used in the original CRISPR screen. I confirmed amphotericin resistance for 6 genes in one or more tested cell lines and nominating these genes for additional study. These findings highlight the power of functional CRISPR screens in uncovering novel regulators of cholesterol metabolism and provide a foundation for mechanistic studies to explore the interplay between cholesterol regulation and broader cellular processes. Elucidating these pathways may reveal new targets for therapeutic intervention in atherosclerosis and cardiovascular disease