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Market and Emissions Impact of All-Electric Aircraft
No full textAviation sector greenhouse gas (GHG) emissions are projected to grow nearly 50% by 2050, motivating exploration and future adoption of reduced-emissions aircraft. While all-electric aircraft (AEA) generate effectively zero in-flight GHG emissions, their prospect for commercial implementation faces critical challenges: most notably the comparatively poor specific energy of batteries relative to aviation fuel. Unanswered questions exist regarding the prospective market and emissions impact of future AEA. This dissertation addresses these knowledge gaps, building on detailed AEA designs available in the literature to quantify AEA market impact and emissions reduction potential across thousands of varying model inputs, market bases, emissions scenarios, and timeframes. This work compares the energy consumption and emissions of conventional aircraft and AEA for every domestic commercial flight in the United States ��� nearly 9.2 million flights in total ��� determining feasibility of electrification, energy requirements, and greenhouse gas emissions for each route and providing novel quantitative estimates of potential AEA impact in the United States.
This dissertation demonstrates clear, albeit conditional, pathways for AEA to reduce aviation sector emissions. Modern-day lithium-ion batteries have insufficient energy for use in the aviation sector: AEA potential hinges on development of batteries with a specific energy three to four times greater than modern batteries. Unlike hydrocarbon-powered aircraft, the emissions footprint for AEA varies by point-of-departure based on power sector emissions generated during battery charging. Assuming historic trends in power sector emissions persist, AEA offer regional potential in the Pacific Northwest, California, and the East Coast, but would have limited national impact reducing aviation sector emissions: at maximum market penetration 1.74% to 7.95% depending on emissions timeframe for a 1000 Wh/kg onboard battery. Achieving greater emissions reduction requires transition to reduced-emissions power generation. Assuming net-zero power sector emissions, AEA could reduce total domestic aviation sector emissions by more than 27% at maximum market penetration while capturing the majority of the aviation market in terms of total flights and passenger count but would require roughly 2% of total US electricity generation (96.6 TWh). These results are highly sensitive to inherent uncertainty in the radiative forcing of non-CO��� emissions and vary by emissions model and timeframe
Generational Ethnography in Post-1974 Cyprus: Island Narratives and Shifting (Im)Mobility Through Nation-Making, Belonging, Identity, and Border Realities
No full textThe 1974 conflict and the troubles of the 1960s in Cyprus hold a unique position from an anthropological forced migration studies perspective. The Coup D���etat and the following Turkish intervention in 1974 was the tipping point of the inter-ethnic conflict in Cyprus, which led to thousands of Cypriots becoming refugees through the division of the island. Through extended interviews, this study looks at both Greek and Turkish Cypriot perceptions of the events before the 1974 conflict and the 1974 conflict, casting light on forced migration within the conflict. This study discusses how forced migration and ethnic cleansing divided the once-intermixed ethnic community. Additionally, this study looks at the transgenerational understanding of the ethnic, political, and geographical national divide of Cyprus through the dispersed communities. An understanding of the complex structure of the Cypriots from this study hopes to expedite the solutions to the issues of the current climate of the island
The BAZ Family of Chromatin Remodelers in Colorectal Cancer: Insights into Oncogenesis, Alternative Splicing and Chemosensitization
No full textColorectal cancer (CRC) poses a significant healthcare challenge worldwide, necessitating a deeper understanding of the molecular mechanisms underlying its pathogenesis for improved therapeutic interventions. This thesis investigates the BAZ (Bromodomain Adjacent to Zinc finger) family of chromatin remodelers and their intricate involvement in CRC. The BAZ family members, including BAZ1A, BAZ1B, BAZ2A, and BAZ2B, exert critical regulatory functions in chromatin architecture and transcription, impacting various cellular processes from development to disease.
In colorectal cancer, BAZ1A is overexpressed, and its depletion resulted in diminished cell viability, increased apoptosis, augmented DNA damage, and cellular senescence, concomitant with the downregulation of components within the Wnt/��-catenin signaling pathway. In vivo studies corroborated these findings, revealing that knockdown of BAZ1A leads to diminished tumor growth and alterations in chromatin regulation. Interestingly, BAZ1A undergoes alternative splicing, which is promoted by treatment with histone deacetylase inhibitors, thereby highlighting its therapeutic potential. Remarkably, the full-length form of BAZ1A is implicated in DNA repair mechanisms, while its alternatively spliced counterpart is susceptible to increased DNA damage and sensitivity to DNA-damaging agents. These observations underscored the oncogenic role of BAZ1A in colorectal cancer and the importance of considering an oncogene���s alternative splicing patterns.
Similar to BAZ1A, BAZ2A is also upregulated in CRC and associated with reduced patient survival. Functional studies demonstrated their roles in inhibiting cell viability, colony formation, and modulating Wnt/��-catenin signaling. Inhibition of BAZ2A led to reduced tumor growth rates in mouse models, where it also affected histone modification patterns, favoring a less repressive chromatin state, and influencing major histocompatibility complex (MHC) regulation.
In contrast to BAZ1A and BAZ2A, BAZ1B knockdown enhanced cell viability, colony formation, and altered cell cycle progression, suggesting a tumor-suppressive role in metastatic CRC. BAZ1B impacted c-MYC expression independently of the Wnt/��-catenin pathway, and influenced p53 and p21 levels, implicating its involvement in tumor suppressive pathways.
Overall, the study underscores the potential of BAZ family members as therapeutic targets in CRC. Future research should focus on elucidating their molecular mechanisms, translating findings into clinical applications, and exploring combination therapies to improve treatment outcomes for CRC patients, thus advancing more personalized therapeutic approaches for CRC
Investigating Chronic Enterocolitis in Rhesus Macaques (Macaca mulatta) as a Natural Model for Post-Infectious Irritable Bowel Syndrome and the Role of Campylobacter spp. in Disease Development
No full textCampylobacter jejuni and C. coli represent the leading causes of bacterial gastroenteritis in humans worldwide and up to 20% of infections will result in post-infectious irritable bowel syndrome (PI-IBS). Investigations into the pathogenesis of PI-IBS have been hampered by lack of a complete animal model for the syndrome. We aimed to investigate the chronic diarrhea syndrome known as chronic enterocolitis (CE) in rhesus macaques (Macaca mulatta), and the potential contribution of Campylobacter infection to this syndrome, as a naturally occurring model of PI-IBS. We characterized subjective and objective variables in sections of the lower intestinal tract in 16 healthy rhesus macaques and compared these results to a cohort of 37 animals euthanized for CE. Similar to PI-IBS, animals with CE had elevated total leukocyte populations in the large intestine and significantly increased intraepithelial CD3+ T cells in the colon and rectum. Unlike PI-IBS, neutrophils were increased in CE and enteroendocrine cells, enterochromaffin cells, and mast cells displayed no differences between study groups. We then utilized culture, qPCR, and whole genome sequencing (WGS) to characterize the Campylobacter sp. circulating in the study colony. Culture and WGS of 275 samples yielded a non-clonal population of 103 C. coli and 8 C. jejuni isolates, each containing genes for all three subunits of cytolethal distending toxin. Certain MLSTs were found only in animals with intestinal disease and some only in healthy animals. Antimicrobial resistance patterns were similar between these isolates and human reports. qPCR detected a higher prevalence of both bacteria than culture, the quantity of bacteria was significantly higher in animals with intestinal disease, and nearly 1/3 of animals were positive for both C. jejuni and C. coli. Using generalized linear mixed modeling, the only significant risk factor for the presence of Campylobacter sp. or intestinal disease was young age. Ultimately, we added to the understanding of CE, identifying areas where the syndrome overlaps with PI-IBS and areas that warrant further investigation, and advanced our knowledge of Campylobacter sp. circulating in rhesus macaques, allowing honing of future studies to investigate a causal link between the bacteria and CE as exists in PI-IBS
Optical Distortion in Hypersonic True Flight Enthalpy Flows
No full textA simplified, blunt-nose wedge model was tested over a range of realistic hypersonic flight conditions to evaluate several aero-optic diagnostic measurement techniques. A two-dimensional 10��� half angle wedge of width 0.47 m and blunt-nose radius 1 cm test article was designed and tested in an experimental campaign in Texas A&M University���s hypervelocity expansion wind tunnel. The aero-optic diagnostic techniques employed in this work included schlieren photography, linear array focused laser differential interferometry, Michelson interferometry, and optical emission spectroscopy. Experimental test conditions comprised Mach numbers of 6, 9, 12, and 15, realistic-flight flow enthalpy, and static temperatures between 200 K and 270 K. Hypersonic flow features such as bow shocks, natural light emission, and boundary layers were captured in schlieren recordings. Index of refraction fluctuation power spectral density data were recorded between frequencies of 100 kHz and 10 MHz at multiple points near the surface of the test arti-cle. The data suggested that eddies causing density fluctuations at rates greater than 2 MHz and between 7.30 mm and 10.63 mm tall developed in the boundary layer for unit Reynolds numbers between 11 �� 106 m���1 and 12 �� 106 m���1
Centering Cemeteries in Environmental Justice: Observing Community Connectivity in Historic Texas Black Cemeteries
No full textThis research seeks to create new knowledge on Black cemeteries by employing methodologies that are innovative within the field of urban planning. Drawing from concepts borrowed from Black Geographies and Anthropology, particularly Participatory Geographic Information Systems (PGIS) methods, this study aims to delve into the intricate dynamics and significance of Black cemeteries within their respective communities. The significance of Black cemeteries transcends their role as mere burial sites; they serve as crucial spaces for memorialization, historic preservation, and community cohesion. Over generations, these cemeteries have acted as repositories of collective memory, fostering a sense of continuity, and belonging among community members. Moreover, they function as dynamic hubs of activity, where rituals, events, and ongoing preservation efforts contribute to the creation of a shared sense of space and identity. Furthermore, the interconnectedness of Black cemeteries unveils a broader network of stewards and community members dedicated to place-making and heritage preservation. These networks facilitate land-use planning and address environmental justice issues by promoting resource sharing and skill exchange among communities. This research highlights the relevance of local histories and the engagement of local stewards in the preservation and management of Black cemeteries. However, the primary contribution lies in the incorporation of local knowledge into urban planning practices related to cemetery management. It emphasizes the importance of recognizing and valuing the intrinsic significance of these cemeteries within the context of environmental justice movements. In conclusion, safeguarding and advocating for the preservation of Black cemeteries is not merely an act of historical conservation but a fundamental aspect of social and environmental justice efforts. The utilization of geo-humanities as a tool in this research allows for a nuanced understanding of memorialization, place-making, visibility, accessibility, and vulnerability at the granular level, as evidenced through two case studies
Comparing Single-Level Regression Based Methods for Analyzing Nested Data When the Extent and Location of Clustering Are Systematically Varied
No full textCollecting and analyzing clustered data is inevitable in educational research. Often, applied researchers will use traditional multilevel modeling to account for the non-independence of observations that result from clustering. However, multilevel models are more complex and have additional data requirements or assumptions relative to a single-level model that applies a correction to the standard errors. Using Monte Carlo Simulations, this work examines the efficacy of various single-level regression-based alternatives for analyzing clustered data when the data-generating model assumes predictors at the lowest level of clustering have both within and between-level variance as well as the effect of different centering choices ��� aspects missing from many contemporary works. The results of this study indicate that correcting standard errors using Taylor Series Linearization or the CR2 correction are the most flexible single-level regression-based methods for analyzing clustered data, as long as within-level predictors are group-mean centered, and the group mean for each cluster is re-introduced. Under these conditions, unbiased standard errors for within and between level estimates are recovered, even with few clusters. However, if within-level predictors are not centered, these corrections lead to increasingly negatively biased standard errors for the within-level estimate as the extent of clustering in the predictors increases, especially when the number of clusters is small. Next, fixed-effects modeling always recovered unbiased standard errors as long as slopes could be assumed to be non-randomly varying; even slight violations of this assumption lead to negatively biased standard errors for within-level estimates. Finally, examining nested data without correcting the standard errors (regular ordinary least squares regression) or using the DEFT correction is not recommended. These methods only lead to unbiased standard errors for within or between-level estimates under conditions that are not likely to be satisfied in real data analysis
A Numerical Study on the Multiline Ring Anchor in Sand
No full textThe Multiline Ring Anchor is an anchor solution designed to meet the growing demands of the offshore renewable energy sector in the country. It has been presented as an alternative to conventional anchor systems with its enhanced engineering efficiency and financial sustainability. The present doctoral work offers an assessment of the geotechnical performance of the anchor, to aid its transition from theory to practice.
A numerical study was undertaken to achieve a comprehensive understanding of the behavior of the anchor as a support system for arrays of offshore floating wind turbines. Its response under monotonic load conditions from different mooring systems is simulated using finite element analysis. The study was primarily divided into two phases ��� the first focused on the purely vertical capacity of the MRA in drained sand, with an emphasis on its end bearing behavior; and the second studied the response of the MRA when subjected to an inclined tensile pull while exploring the effects of the combination of loading conditions on it. Additionally, as a preliminary step in the analysis of the anchor under partial drainage conditions, a hypoplastic constitutive law is explored as an alternative to the Mohr Coulomb model.
The study finally presents a simple empirical model to estimate the vertical and the inclined ultimate capacities of the MRA in drained sands, along with a means to determine the optimum loading conditions, as functions of the padeye location and load inclination angle
Integrated Protein Turnover: Toward a New Understanding of Cellular Protein Metabolism
No full textProtein metabolism lies at the heart of cellular health. However, the intersections between protein anabolism and catabolism are not completely understood. Here we propose a new view on cellular protein metabolism, the integrated protein turnover model, which we argue better explains the events and evidence underlying anabolic and catabolic states in cells. Instead of viewing protein synthesis and breakdown as separate pathways, we argue that these processes are fundamentally and inextricably linked, and that overall anabolism and catabolism are the result of simultaneous and coordinated action of all the protein metabolic machinery, encompassing the mTOR, autophagic, and ubiquitin-proteasome pathways. We provide the first direct evidence that autophagy is required for protein synthesis in muscle, such that mTORC1-mediated anabolism cannot occur without input from the autophagic pathway. We further show that expression of a select autophagy gene, ATG4B is high in lung and pancreatic cancers and its expression is associated with mortality. Inhibiting ATG4B suppresses cancer cell growth and protein synthesis, allowing for targeting of both autophagic and anabolic markers of metabolism. Finally, we demonstrate that microRNA are a viable candidate for the regulation of the overall proteostatic network, and that removing select microRNA (mir15a/16) from skeletal muscle activates muscle anabolic signaling, while restoring these same microRNA slows anabolism and growth in cancer. Our results demonstrate the strength of the integrated protein turnover model, and indicate new avenues for both the understanding and targeting of protein metabolism in health and disease
An Economic Analysis of Dynamic and Causal Impacts on the Red Meat Market in the United States
No full textThe red meat market has recently undergone several significant changes in response to changing market conditions, supply chain shocks, and policy impacts. The overall objective of this study is to contribute a better understanding of how segments of the red meat industry respond to shocks. Specifically, this study (1) uses a vector error correction model and directed acyclic graphs to analyze the dynamic interactions and causal effects between cold storage stocks, prices, imports, and exports in the red meat market (2) analyzes the impacts of California���s Proposition 12 animal welfare law on retail and wholesale prices using a difference-in-differences framework and (3) analyzes the dynamic interactions and causal inference patterns of U.S. pork exports to Mexico to further investigate the causes of changing pork export patterns and the impact of the price spread between bone-in and boneless hams on pork exports (volume) to Mexico.
The first essay finds that imports and exports are primary drivers of changes in pork and beef cold storage stocks. The second essay finds that California���s Proposition 12 and Massachusetts��� Question 3 have resulted in price increases ranging from 6% to 21% throughout the supply chain. Finally, the last essay finds that a shock in price spread would cause a long-term impact on bone-in ham exports to Mexico, that a shock in price spread would only account for a small amount of forecast error variation in bone-in exports, and that there is not a direct contemporaneous causal relationship between the two. Ultimately, this study provides valuable information to producers, policy-makers, consumers, and other stakeholders regarding how segments of the red meat industry responds to changing market conditions, supply chain shocks, and policy impacts