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The Formulation of a Consequence-Informed Methodology for the Design of Physical Protection Systems at Advanced Commercial Reactor Facilities
No full textThe survivability of the domestic nuclear power industry depends on the cost-competitiveness of safe and secure nuclear power generation. Advanced reactor design concepts aim to have increased safety margins over traditional large Light Water Reactors (LWRs). With increased safety margins comes the potential for a corresponding decrease in off-site risk to the general public from a hypothetical release of radioactivity caused by an accident or deliberate sabotage. Without sacrificing safety or security, advanced reactor designers may be able to achieve capital and operational cost improvements over current LWRs, in part, by designing less burdensome Physical Protection Systems (PPS), and by placing response forces off-site. To accommodate these developments, the U. S. Nuclear Regulatory Commission (NRC) is drafting new regulations for physical security when licensing through the current 10 CFR 50 or 52, along with drafting an entirely new licensing framework, 10 CFR 53.
This dissertation presents a novel technology-inclusive consequence-informed methodology for the selection of the optimal licensing path for the design of Physical Protection Systems (PPS) at advanced fixed-site commercial nuclear power facilities, and applies the methodology to a hypothetical reactor facility containing a microreactor design. The resulting methodology incorporates current and proposed regulatory limits for off-site dose consequence to the general public to guide the licensing applicant in choosing the licensing pathway which best suits their desired financial costs and PPS design characteristics. For the methodology application to a microreactor site, newly allowed PPS characteristics in proposed NRC draft regulations were incorporated into the ultimate PPS design. MELCOR code analysis of potential adversary-executed sabotage actions, and off-site doses predicted by the MACCS code, were coupled to determine off-site consequence of the facility while PathTrace and SCRIBE 3D were used to develop a PPS model of the facility for effectiveness testing. The resulting PPS was compared to a PPS at the same facility designed following traditional security licensing requirements in 10 CFR 73. Results of the comparison demonstrated an increase in necessary capital costs for the construction of a facility with enough delay to accommodate a 30-minute off-site response force response time. However, the reduction in security force staffing showed the potential for significant savings in operational staffing
John Bickham field notebook: AK15501-AK16000.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK16001-AK16500 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
ScrollStats: An Automated Tool for Deciphering Meander Scrolls and Uncovering the Hidden Paths of Meander Migration
No full textScroll bars are arcuate, elongated landforms deposited along the inner banks of meandering rivers. This deposition occurs within zones of flow separation typically during discrete high-flow events. As the channel meanders, scroll bars are deposited successively in its wake and are preserved by stabilizing vegetation, leaving behind a well-preserved, visually intuitive migration history in the resulting ridge and swale topography (RST). Because of this episodic deposition, bar location and orientation can serve as a record for migration history while specific bar morphology can contain information about the hydrologic conditions under which the bar was deposited. ScrollStats is an open-source GIS tool developed to digitize and extract this morphological information from DEMs of the RST of meandering bends. ScrollStats produces two primary data products 1) migration pathways derived from preserved scroll bar location and orientation and 2) a ridge area raster delineating the ridge areas within the DEM. From these data products, ScrollStats calculates a suite of ridge morphometrics (ridge width, amplitude, and spacing) for every intersection of an identified ridge and migration pathway, covering the entirety of the bend's interior. In this paper, we showcase the capabilities of ScrollStats on a compound bend of the Lower Brazos River, Texas, USA. We also demonstrate how ScrollStats compares to other methods previously used to extract morphometrics from RST and how it can be used to expand upon previous findings in the literature. ScrollStats allows researchers to extract floodplain morphometrics previously unavailable, enabling new research into bend-scale migration dynamics and linkages between hydrologic process and the resulting landforms
A Comparative Analysis of Archaeological and Textual Evidence for Danubian Watercraft, First to Fourth Centuries CE
No full textThe Danube is one of the longest rivers in the world and has been a life source for peoples settled around it for millennia. Alongside local groups, Greeks and Romans used the river as a throughway. Though there are many accounts of the Danube in Roman history, few of them provide insight into what types of vessels were using along the river, despite many documented interactions with local groups. The archaeological record along the Lower Danube, that is the section from the Iron Gates to the Danube Delta, has begun to reveal more evidence of both Roman and local boats used along the ancient course of the Danube, but many of these are found in rescue excavations with limited recording available. In this thesis I combine these two fragmentary sources to examine if the literary accounts are reflective of the archaeological evidence regarding local boatbuilding traditions. Though brief, there are terms in literature which indicate construction methods (����������������), and hull shape (cavatis arborum alveis vs. truncis), which are reflected several times in the archaeological record. Other literary descriptions reveal little about the vessels themselves, but the contexts in which they are found are reflective of Roman perceptions of the users of the vessels. These sources both undermine the capability of the locals to boost military morale and also demonstrate their efficacy, as the Romans were intimidated by those who used the Danube for raiding and stealth attacks. Flat-bottomed barges fastened with closely spaced iron clamps also appear in the archaeological record several times along the Lower Danube and in the greater Danube Basin. Further archaeological research is needed to bolster this theory of a regional vessel type, and such work may continue to yield multiple ship types in the same contexts, increasing the number and variety of vessels from antiquity and perhaps revealing a regional tradition through time. Though there is still much to be excavated, this research has revealed the disparity between Roman descriptions of vessels in use along the Lower Danube and the reality of such boats by examining the archaeological evidence and contextualizing the Roman literature
The Joppa Environmental Health Project: Evaluating Local Air Quality and Respiratory Health in Dallas' Environmental Justice Neighborhoods
No full textDue to historical racial segregation, People of Color (POC) and low socioeconomic status groups experience disproportionate exposure to particulate matter (PM) air pollution. Fine PM (PM2.5) pollution is associated with several health effects, including cardiovascular and lung disease, respiratory mortality, and adverse birth outcomes. There is a need to characterize environmental and health disparities in susceptible populations like environmental justice (EJ) communities. In Dallas, Texas, EJ communities such as Joppa and ���Singleton��� are POC neighborhoods that are surrounded by multiple pollutant sources. Using a community-based participatory research (CBPR) approach, the Joppa Environmental Health Project (JEHP) was formed in 2020 with the primary objective to assess residents��� perceptions of air pollution and other health concerns through a community household health survey and to evaluate PM pollution through the installation of a local air monitoring network. To carry out these objectives, the following aims are addressed in this dissertation: 1) apply a CBPR approach to facilitate community engagement and action-oriented research on PM pollution and respiratory health in Joppa; 2) quantify daily and monthly PM2.5 concentrations in Joppa and ���Singleton��� using low-cost sensors, PurpleAir and SharedAirDFW; and 3) examine the association between daily PM2.5 exposure and airway inflammation in children residing in Joppa.
Strong community engagement activities and efforts from our steering committee yielded a high neighborhood survey response rate (51%). A high lifetime asthma rate (18%) was also observed among survey respondents. Monitor data demonstrated elevated levels of PM2.5 concentrations in Joppa. Last, active airway inflammation was observed in children who were not diagnosed with asthma. Overall, the application of this research facilitated robust community engagement and resident-led research to address critical neighborhood concerns. Subsequently, an asphalt batch plant in Joppa voluntarily relocated operations in June of 2023. The steering committee organized a new group known as Justice for Joppa/Justicia para Joppa to sustain momentum created by this work, targeting local zoning and land use policies. Future work from this research will involve the placement of a permanent medical clinic in Joppa where residents will have access to long-term health support (i.e., chronic disease diagnosis and management)
Probing Membrane Protein-Ligand Interactions Using Native Mass Spectrometry
No full textThe cell membrane, essential for cellular structure and function, is composed largely of membrane proteins and lipids. While transmembrane proteins are known for their critical roles in various physiological processes such as maintaining cell resting potential and facilitating molecule transport, the specific interactions between these proteins and different lipid moieties are not fully understood. In this study, we employed native mass spectrometry as a primary tool to unravel these interactions, capitalizing on its unique ability to preserve non-covalent interactions in biomacromolecules.
Our investigation comprised two distinct approaches: single ligand screening and multi-omic screening. Through single ligand screening, we identified specific lipid moieties that bind to the mammalian two-pore domain potassium channel TRAAK. This approach not only pinpointed the preferred lipids but also revealed a dose-response relationship with TRAAK potassium efflux in functional assays. On the other hand, our multi-omic analysis yielded significant findings. It corroborated the unique allosteric modulation observed between cardiolipin and phosphatidylethanolamine in their interaction with the E. coli ammonium channel AmtB, aligning with previous research. Additionally, this approach led to the discovery of a complex allosteric modulation involving TRAAK, phosphatidylserine, and cupric ions. Impressively, these interactions were maintained when ejected from proteoliposomes, bridging our functional assays, and validating our methodologies.
Moreover, our research broke new ground with the synthesis of novel charge-reducing molecules. This advancement has significantly enhanced the study of less stable membrane proteins, paving the way for more comprehensive exploration of membrane protein-lipid interactions. Overall, our findings contribute substantially to the understanding of cellular membrane dynamics and functionality, marking a significant stride in the field of cellular biology
Target Identification Using Single Cell RNA-Seq: Algorithms and Applications
No full textTarget identification is a crucial step in the drug development process, significantly affecting the success rate and efficiency of bringing new therapies to market. Recent advancements in single-cell RNA sequencing and computational tools have accelerated the identification and validation of therapeutic targets by enabling a deeper understanding of disease mechanisms at the cellular level. However, challenges such as inadequate understanding of the molecular basis of certain diseases and limitations in current single-cell data analysis methods, particularly in capturing gene regulatory relationships, continue to hinder the full exploitation of these technologies in precision medicine.
To this end, we aim to enhance target identification in scRNA-seq, crucial for unraveling cellular differentiation and disease mechanisms. Firstly, we develop ���scInTime���, a computational method that capitalizes on single-cell trajectory data and gene regulatory networks to accurately identify master regulators of cellular differentiation. This algorithm aims to overcome the existing challenges in mapping cell fate decisions, a critical step in advancing personalized medicine. Secondly, we propose to undertake an integrated scRNA-seq data analysis to investigate the association between pyroptosis and the severity of COVID-19. This research is expected to shed light on the immune response to SARS-CoV-2 and identify potential targets for therapeutic intervention. By focusing on the mechanisms underlying severe COVID-19 cases, we anticipate contributing to the global effort in combating the pandemic. Thirdly, we address metabolic diseases, specifically investigating the role of hepatocyte adenosine kinase in fat deposition and liver inflammation. Here, we aim to elucidate the molecular pathways that lead to excessive fat storage and inflammation in the liver, offering targets for the treatment of metabolic syndromes. Finally, we conduct a sex-based study on the role of RSPO3 in estrogen-mediated sex differences. Understanding the molecular bases of sex differences in diseases is critical for the development of gender-specific therapies and this study will contribute to that knowledge base.
Overall, our goal is to leverage scRNA-seq for precise target identification, addressing significant gaps in the understanding of cellular differentiation and disease. This thesis is designed to set the stage for a series of investigations that will collectively advance our knowledge in the field and lead to novel therapeutic strategies
On the Security of End-to-End Encrypted Messaging and Calling Applications
No full textIn recent years, the use of end-to-end encrypted messaging and calling applications has risen, driven by the need for secure communications. While these applications protect against unauthorized access, concerns about potential vulnerabilities have emerged. End-to-end encryption (E2EE) aims to safeguard private communications, yet fears of eavesdropping and communication manipulation linger, especially from government entities or attackers. Despite its effectiveness, E2EE integrity can be compromised, like through key substitution attacks. Worries center on authentication ceremonies and potential user errors leading to man-in-the-middle (MitM) attacks. Additionally, the introduction of client-side scanning (CSS) in secure applications to detect harmful content raises privacy concerns. CSS���s local processing or endpoint filtering could undermine the promised encryption guarantees.
In this dissertation, we delve into the complexities surrounding the use of end-to-end encrypted messaging and calling applications, addressing issues of impersonations, MitM attacks, authenti-cation ceremonies, and the topic of CSS technology. Our work provides a systematic analysis of E2EE functionality and authentication ceremonies in popular applications. We propose an auto-mated approach to enhance and streamline the authentication ceremony within encrypted applications. Our work highlights vulnerabilities in voice-based authentication and stresses the need for stronger security measures. Additionally, we investigate the risks of using social media networks in the authentication ceremony and examine potential threats related to CSS technologies and their impact on E2EE principles.
Our dissertation provides the following contributions: First, we conduct a comprehensive security analysis of existing studies, identifying flaws and vulnerabilities in widely used encrypted applications, particularly focusing on authentication ceremonies. Second, we explore automated methods to enhance the authentication ceremony and reduce reliance on user interaction. Third, we undertake simulated investigations to identify potential vulnerabilities arising from exclusive reliance on a voice channel for the authentication ceremony in a real-world end-to-end encrypted application. This could compromise the security of static media and textual communications. The insights from our study suggest enhancing the security of end-to-end encrypted apps by using phonetically distinct words for codes, implementing warnings for suspicious voice code usage, employing multiple authentication channels, and prioritizing ongoing research for stronger security measures. Fourth, we introduce a novel investigation targeting social media authentication ceremonies, illustrating potential risks associated with user impersonation through counterfeit ac-counts. Our study suggests enhancing social media authentication security by displaying comprehensive user details, promoting hands-on user verification, using visual cues for unique identifiers, advocating continuous monitoring and adaptation, and fortifying end-to-end encrypted applications with multi-channel authentication. Lastly, we introduce an encrypted keyboard to address concerns related to CSS technology
Unraveling the Complexity of Cdec Expression During Clostridioides difficile Sporulation: Insights into the Role of Sigma Factors and Non-Coding RNA on Cdec Expression
No full textGram-positive, obligatory anaerobic Clostridioides difficile (C. difficile) is a spore-forming, obligate anaerobic bacterium that causes diarrhea and other healthcare-associated illnesses globally. This study aimed to identify the sigma factor boxes in the promoter region of cdeC that affect the early and late stages of C. difficile sporulation. Therefore, we first identified the sigma factors' positions in the promoter region. Then, we constructed transcriptional fusions containing a different deletion of these sigma factors and introduced them into the C. difficile R20291CM210 WT strain. However, no detectable fluorescence was observed due to lack of sporulation in the C. difficile R20291CM210. Both increasing the time of incubation and increasing thiamphenicol concentrations failed to induce sporulation for R20291CM210. After that, we introduced all transcriptional fusions into the C. difficile R20291CM196 WT strain. We found out that only P���ncRNA-cdeC-mScarlett transcriptional fusion that contains the promoter region with a deletion of the ncRNA shows a modest fluorescence signal compared to other fusions. These results suggest that ncRNA located in the promoter region of cdeC may have an activity for cdeC expression during sporulation
Essays in Climate Risk, Residential Mobility, and Housing Security
No full textThe combination of climate change and economic growth in disaster-prone regions increasingly exposes the population to extreme weather events. In Chapter 1, I use property-level data to quantify the magnitude of climate risk across Texas, highlighting regional variation in exposure that challenges individuals, businesses, and industries across the state.
While the aggregate impacts of natural disasters are well documented, much less is known about the individual responses to these environmental shocks. In Chapter 2, I estimate the average treatment effects of flood damage using a fuzzy regression discontinuity design in the context of Hurricane Harvey, which damaged more than 200,000 homes in Houston, Texas in 2017. I leverage the relationship between flooding and a home���s elevation, exploiting a discontinuous increase in damage from 48,000 once water reaches the first floor. I provide evidence that disaster damage induces homeowners to relocate from their pre-storm residence while simultaneously preventing their decision to sell their property. The impacts on residential mobility attenuate over time, but I document a persistent divergence in the location and type of housing selected by damage-induced movers. My results indicate that flood damage makes people more likely to move shorter distances, and damage-induced movers are more likely to transition out of homeownership. Despite the combined shock to shelter and wealth, I find that flooded households are more likely to sort into higher-income census tracts in the aftermath of Hurricane Harvey.
Housing security is a critical component to wellbeing that extends beyond the context of environmental shocks. In Chapter 3, I explore how housing security relates to tenants��� criminal activity by analyzing the final stage of the eviction process. In particular, I exploit quasi-random variation in eviction executions to identify the impact of extending or shortening the enforcement process on tenants��� arrest propensity. I find no evidence that extending this process affects the likelihood of arrest, but statistical noise from data constraints may contribute to the uncertainty