Dissertation Defense Announcements

Recent advancements in single-cell RNA sequencing have revolutionized our understanding of gene expression regulation under various biological contexts, providing higher resolution and system-level insights compared to traditional bulk RNA sequencing methods. In this dissertation, we utilize single cell RNA-seq (scRNA-seq) along with various statistical tools to unveil the stress response and developmental transcriptomic landscape of four model organisms. First, we sequenced yeast cells under three stress treatments (hypotonic condition, glucose starvation and amino acid starvation) using a full-length single-cell RNA-Seq method. We found that though single cells from the same treatment showed varying degrees of uniformity, technical noise and batch effects can confound results significantly. However, upon careful selection of samples to reduce technical artifacts and account for batch-effects, we were able to capture distinct transcriptomic signatures for different stress conditions as well as putative regulatory relationships between transcription factors and target genes.
Our results show that a full-length single-cell based transcriptomic analysis of the yeast may help paint a clearer picture of how the model organism responds to stress than do bulk cell population-based methods. Second, we present a transcriptomic level analysis into the oogenesis of C. elegans hermaphrodites. We dissected a hermaphrodite gonad into seven sections corresponding to the mitotic distal region, the pachytene, the diplotene, the early diakinesis region and the 3 most proximal oocytes, and deeply sequenced the transcriptome of each of them along with that of the fertilized egg using a single-cell RNA-seq protocol. We identified specific gene expression events as well as gene splicing events in finer detail along the oocyte germline and provided novel insights into underlying mechanisms of the oogenesis process. Furthermore, through careful review of relevant research literature coupled with patterns observed in our analysis, we attempt to delineate transcripts that may serve functions in the interaction between the germline and cells of the somatic gonad. These results expand our knowledge of the transcriptomic space of the C. elegans germline and lay a foundation on which future studies of the germline can be based upon. Lastly, we profiled mature oocytes and 1-cell zygotes of mice and rats to uncover elusive transcriptomic dynamics in the maternal to zygote transition. We confirm the existence of early gene expression in the mouse zygotic while revealing a similar chain of events occurring in the rat zygote. We observe an increase in nascent transcription in both species. Moreover, we find subtle but pervasive signals of differential splicing of genes related to key early zygotic activities occurring in both species. Meanwhile, we find distinct profiles of alternative polyadenylation between zygotes and oocytes in both species, specifically in genes related to major processes within the zygote. Finally, although a more dynamic transcriptomic landscape exists in the mice zygote, the rat zygote also displays similar transcriptomic features, suggesting that minor zygotic activation in rat occurs earlier than originally thought.

The need to supply electricity to the building sector is growing worldwide. Currently, integrating photovoltaic (PV) panels into building rooftops is the primary method for harnessing solar energy. However, this practice, along with the use of solar farms, contributes to power grid fluctuation issues, known as the duck curve. Two main issues associated with the duck curve are PV power curtailment at midday and a sudden increase in utility operation during late afternoon hours. These problems are more significant in regions with higher PV power penetration into the grid, raising concerns that the current power grid infrastructure may not be able to accommodate the operation of conventional utilities alongside PV power generators.
Since the building sector is a major electricity consumer, supplying this sector's demand with an optimized PV system that not only meets building electricity needs and reduces energy consumption but also mitigates duck curve issues can significantly contribute to energy sustainability. This thesis investigates the impact of Building-Integrated Photovoltaic (BIPV) systems in mitigating power grid fluctuations through a comprehensive analysis. The findings of this study are presented in four research papers, each addressing a specific aspect of the main research objective. A brief summary of the findings is as follows:
Paper One: "Circuit Connection Reconfiguration of Partially Shaded BIPV Systems: A Solution for Power Loss Reduction" explores solutions to tackle power drops in BIPV façades due to partial shading conditions. The paper presents a novel circuit connection that significantly reduces power output reduction in BIPV façade systems.
Paper Two: "Comprehensive Analysis of Energy and Visual Performance of Building-Integrated Photovoltaics in All ASHRAE Climate Zones" examines various BIPV typologies, including PV-south louvers and PV-mounted roofs, in terms of building energy consumption, PV power output, and occupants' visual comfort. Results indicate that PV-south louvers significantly reduce building energy consumption in very hot, hot, and warm climates. In colder climates with significant heating demands, roof-mounted systems provide a better balance between power generation and solar heat gain. PV-south louvers effectively reduce glare on office working surfaces while providing the desired illuminance levels for occupants. However, PV-mounted roofs can cause excessive illuminance, leading to disturbing glare over large portions of the floor area.
Paper Three: "Assessing the PV-Integrated South Façade in Mitigating the BIPV System Oversupply" evaluates the effectiveness of PV-south louvers in reducing BIPV power curtailment at midday. The results show that these typologies effectively reduce power curtailment in very hot, hot, and warm climates, except in warm-marine sub-climate zone (3C). In mixed climates, the performance of these typologies varies across different months.
Paper Four: "Assessing the Impact of PV-Integrated West Façade in Alleviating the Duck Curve Steep Ramp in All ASHRAE Climate Zones" investigates the impact of PV-west fins on alleviating the duck curve's steep ramp in the late afternoon. The impact is limited in very hot and hot climates but shows more potential in warm, mixed, and cool climates. Cold, very cold, and Arctic climates exhibit higher effectiveness during warmer months.
This thesis provides a comprehensive analysis of the impact of BIPV systems in mitigating the duck curve issue. By optimizing BIPV configurations and understanding their performance across different climate zones, the findings of this thesis offer valuable insights into improving building energy and BIPV power production efficiency as well as addressing grid stability issues associated with the fast-growing integration of PV systems into the built environment.

Quality STEM education in secondary and post-secondary schools is vital to the advancement of knowledge and technology for the United States. Quality STEM education is found where evidence-based teaching practices are implemented in the classroom. This dissertation focuses on two programs and their impact on their participants with the goals of providing quality STEM education. The STEM Academy is a faculty learning community with goals to support faculty members in implementing new evidence-based teaching practices at UNC Charlotte. The second program is Summer Ventures in Science and Mathematics (SVSM) Nanoscale Science course for high school students in North Carolina. The data for investigating the experiences of the participants in the STEM Academy was collected through semi-structured individual interviews as well as focus groups. The transcripts of these were thematically coded to find consensus on the benefits of the STEM Academy and the barriers to implementing new evidence-based teaching practices. The data for investigating the impact of the SVSM Nanoscale Science course and its revisions was collected through the grading of student final papers using a rubric specific to the Big Ideas in Nanoscale Science (BINS) and the experimental design process. Also, students were given the Student Attitudes towards STEM (S-STEM) survey at the beginning and end of the course. The results of the STEM Academy interviews and focus groups yielded 11 themes; six describing benefits and five describing barriers identified by the participants. These results can help to reform and grow the STEM Academy for future participants to meet its goals of supporting faculty members in implementing evidence-based teaching practices in STEM classrooms at UNC Charlotte. The results of grading the student final papers from the SVSM Nanoscale Science course showed significant improvements to writing research questions, designing experiments, and writing conclusions about their findings for students in the second cohort compared to the first cohort. These findings indicate the revisions to the course had a positive impact on student outcomes. The S-STEM survey results show the students maintained or slightly improved their positive attitudes towards STEM after participating in the SVSM course.
Key words: Nanoscale Science, Evidence-Based Teaching Practices, Faculty Learning Community

Combat, a common source of trauma in the military, is consistently predictive of post-traumatic stress disorder (PTSD) among service members deployed to Iraq and Afghanistan. PTSD has detrimental effects on post-deployment health and psychosocial functioning. The cognitive model of PTSD posits that automatic threat appraisals maintain PTSD when they generalize to safe situations. As a result, the ability to modify this automatic response may support re-adaptation to the civilian context following deployment. Executive functioning (EF) includes suppressing automatic, incorrect responses (inhibition), generating and holding on to alternative, more context-appropriate perspectives (working memory), and flexibly shifting toward them (cognitive flexibility) and may act as a buffer by enabling re-consideration of trauma appraisals that otherwise maintain the combat exposure-PTSD relationship. Additionally, the anterior cingulate cortex (ACC), a brain region within the ventromedial prefrontal cortex, supports decision-making in uncertain contexts, regulating emotion to prevent incorrect automatic threat responses. Consequently, a smaller ACC volume may be associated with a diminished ability to adjust incorrect automatic threat appraisals. Using data from the Chronic Effects of Neurotrauma Consortium Study 34 (CENC-34) examining health outcomes following combat exposure and neurotrauma, the present study examined the factor structure of EF, and examined the resulting EF components and ACC volume as moderators in the relationship between combat exposure and PTSD, including PTSD symptom severity as well as diagnostic status. Participants were Iraq and Afghanistan Veterans (N = 241) who passed performance and symptom validity thresholds. Factor analysis of EF tests yielded two components, Cognitive Flexibility and Working Memory. After adjusting for age, sex, years of education, time since trauma, current Major Depressive Disorder (MDD) diagnosis, and presence of deployment mTBI, EF components were not associated with PTSD symptoms or diagnosis, and no support was found for an interaction between either component and combat exposure. In these models, combat exposure was significantly associated with PTSD symptoms and PTSD diagnosis. Similarly, after adjusting for age, current MDD diagnosis, presence of deployment mTBI, and total intracranial volume, combat exposure and ACC volume were not associated with PTSD symptoms or diagnosis and results did not support an interaction effect between combat exposure and ACC volume. Unexpectedly, across all models, current MDD diagnosis was the most consistently predictive of PTSD symptoms and PTSD diagnostic status. The present work was an initial foray toward advancing theoretical, empirical, and clinical understandings of the factors contributing to persistent PTSD in Veterans. Our replication of the association between MDD and PTSD underscores the need to comprehensively assess for relevant comorbidities in clinical settings. Additionally, with combat exposure as a significant predictor of PTSD symptom severity, individuals exposed to combat may benefit from periodic screenings to enable early detection and intervention.