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FACILITATION OF THE STUDY OF MANTLE DYNAMICS THROUGH CALCIUM STABLE ISOTOPE MODELING AND SIMULANT GLASS SYNTHESIS
Get PDFI utilized new mineral-melt Ca isotope fractionation factors from Li et al. (2025) (the manuscript that this thesis is adapted from) to model the Ca isotope effects on both melts and residues during partial melting of spinel peridotite at 1-2 GPa, garnet peridotite at 3-7 GPa, and garnet pyroxenite / eclogite at 2.5-20.7 GPa. The model predicts that silicate melts only have δ44/40Ca [delta calcium forty-four over calcium forty] up to 0.12 lower than their source value, consistent with previous estimates. Importantly, partial melts of spinel peridotite, garnet peridotite, and garnet pyroxenite / eclogite exhibit overlapping δ44/40Ca [delta calcium forty-four over calcium forty] values, if their mantle sources have the same δ44/40Ca [delta calcium forty-four over calcium forty]. In contrast to silicate melts, the model predicts that carbonatitic melts can have δ44/40Ca [delta calcium forty-four over calcium forty] up to 0.24 lower than their mantle source, and the largest δ44/40Ca [delta calcium forty-four over calcium forty] effect is found in carbonatitic melts produced under shallow mantle transition zone conditions. In both cases, partial melting alone cannot explain the full range of δ44/40Ca [delta calcium forty-four over calcium forty] values observed in natural basalts and carbonatites, and at least part of this variation must reflect δ44/40Ca [delta calcium forty-four over calcium forty] variations of their mantle sources.
The model calculations show that residues of partial melting always have δ44/40Ca [delta calcium forty-four over calcium forty] higher than their mantle source, with the highest δ44/40Ca [delta calcium forty-four over calcium forty] at 0.40 higher than the source value. This range is much smaller than that observed in natural ultramafic rocks that might represent residues of partial melting. In addition, the range and direction of intermineral Ca isotope fractionation factors predicted in the modeled residues for the mineral pairs orthopyroxene-clinopyroxene and garnet-clinopyroxene are much more restricted than those observed in natural ultramafic rocks, including peridotites, garnet pyroxenites, and eclogites. Therefore, most natural ultramafic rocks have likely experienced more complicated petrogeneses than partial melting.
In Chapter 2, the process of creating a simulant glass for the lower mantle mineral davemaoite is documented
Marking Boundaries: The Use of Gendered Language in Syriac Apocalyptic Literature
No full textDuring the sixth and seventh centuries, as internal and external conflict confronted the Roman Empire through both political and religious strife as well as foreign invasion, a surge of apocalyptic expectations arose within Roman Christian communities. Christians living on the eastern edge of the Empire utilized apocalyptic literature as a method of expressing their anxieties around not only the coming end-time, eschaton in Greek, but also around the political, social, and religious changes they were experiencing. Syria authors of apocalyptic literature during the sixth and seventh centuries used gendered language to create meaningful differences between themselves and the characters villainized within this literature. The dichotomies manufactured within these texts between the heroic, masculine figures and the feminized non-Christians and heretical Christians builds upon literary tropes of the idealized man and uncontrolled barbarians, using both historical and scriptural references to emphasize the “correctness” of their own performance of masculinity and the “incorrectness” of the masculinity displayed by opposing groups. By adding gender theory to the study of late antique Syriac apocalyptic literature, I will show that these sixth- and seventh-century Syriac authors used masculinity as a tool to build boundaries between themselves and others in an effort to emphasize their own correct masculine practice, which was defined by control of themselves and others, and which in turn suggested their right to represent the contested title of Christian orthodoxy
BLACK AND WHITE AMERICANS’ REACTIONS TO PARTNER CONTENT STRATEGIES IN INTERRACIAL INTERACTIONS
No full textSelf-disclosure in interracial interactions can foster friendship and reduce prejudice. However, it is unclear how individuals respond when self-disclosure is solicited from a different-raced interaction partner. Such solicitations may communicate interest and liking (thus fostering positive impressions) or they may violate social norms discouraging intimacy in interracial interactions (thus fostering negative impressions). We tested these competing hypotheses among Black Americans and White Americans, who were led to believe they were about to engage in an interaction with either a Black or White partner who either invited self-disclosure or did not based on the topics they asked the participant to discuss. A series of Partner Race x Conversation Topic interactions revealed that Black participants did not form more negative impressions of White partners who broached intimate topics but formed more negative impressions of White partners who avoided intimacy. White participants’ impressions of White partners did not vary as a function of intimacy level. However, White participants formed less positive impressions of Black partners who posed high relative to low intimacy questions
Contributions of the fatty acid kinase system beyond exogenous fatty acid uptake in Enterococcus faecalis
No full textEnterococcus faecalis is a commensal of the gastrointestinal tract of mammals but can found in a range of environments including the bloodstream during infection and the vagina as a causative agent of aerobic vaginitis. These environments contain host-derived free fatty acids that can be used in membrane synthesis by E. faecalis through its Fatty Acid Kinase (Fak) system. While work in other species have shown contributions of the Fak system in pathogenesis, little is known how it impacts the colonization and survival of E. faecalis in various host environments. Using E. faecalis OG1RF and OG1RF derivatives deleted for multiple fakB genes, I demonstrated that the Fak system contributes to growth in bile, a component found within the native environment of the intestine, as well as contributed to membrane fluidity when cells are grown in human serum. Some of these impacts appear to be due to the presence of host-derived unsaturated fatty acids, oleic and linoleic acids. I further demonstrate that the Fak system contributes to E. faecalis colonization in a murine vaginal model. Strains deleted for one or multiple fakB genes were reduced in number within reproductive tissues. However, I noted that this reduction may not be due to an immune response determined via Enzyme-Linked Immunosorbent Assays (ELISA). Further analyses suggest that this reduced survival is likely not due to sensitivity to hydrogen peroxide, which is often produced during an inflammatory response. Preliminary in vitro data does suggest that sensitivity to cationic antimicrobial peptides may contribute to poor survival. The experiments performed herein show potential roles of the Fak system in vaginal ascension to the uterus in a murine model, modulating sensitivity to cationic antimicrobial peptides, and maintaining membrane fluidity when exogenous fatty acids are present. Furthermore, this work provides a strong foundation and rationale for further experimentation in the role of the Fak system in enterococcal pathogenesis
Development of a Thermoelectric-Based Thermal Death Time (TDT) Sandwich Device
No full textA thermoelectric-based Thermal Death Time (TDT) sandwich device was developed with an active cooling feature to improve the precision and repeatability of microbial inactivation experiments. The system incorporates a Takagi–Sugeno (TS) fuzzy logic-based adaptive PID controller that can adjust PID gains in real time, ensuring stable temperature regulation and responsive during the heating, holding, and cooling phases. The fuzzy PID performed well compared to a conventional PID at 56, 58, and 60 °C, with 93.98%, 92.73%, and 81.21% of time hold within ±1 °C of the setpoint temperatures and lower RMSE values (0.60-0.74 °C vs. up to 1.60 °C). The device achieved rapid come-up times (44–50 s) and relatively fast cooling times of 22–26 seconds. The thermal performance was also evaluated across five diverse food matrices (blueberry juice, whole-fat milk, evaporated milk, chicken broth, and mashed potatoes), demonstrated consistent come-up times (43-45 seconds) and better thermal uniformity, with RMSE values ranging from 0.66 to 0.83°C, except chicken broth (1.08°C). Whole-fat milk and evaporated milk were kept within a ±1 °C tolerance level of around 88% of the holding time at 60°C. In contrast, mashed potatoes and blueberry juice were maintained at 72 and 78%, respectively. The isothermal inactivation of Escherichia coli K12 in blueberry juice was conducted utilizing the developed device. Isothermal treatments at 54 °C and 56 °C for 10 minutes resulted in decreases of 6.45 and 5.29 log CFU/mL, with D-values of 8.77 and 4.35 min, respectively. These findings demonstrate the device\u27s ability to provide reliable thermal control and microbial lethality evaluation, which supports its use in food safety and thermal process validation
RELATIONSHIP OF EXPECTED PROGENY DIFFERENCES (EPDS) AND BULL REPRODUCTIVE EFFICIENCY
No full textBull selection in the beef industry is commonly based on a combination of visual appraisal and genetic merit, often expressed through Expected Progeny Differences (EPDs). While EPDs are valuable tools for selecting growth, carcass, and maternal traits, no current EPD directly evaluates semen quality or the likelihood of passing a breeding soundness exam (BSE), key indicators of bull fertility. To better understand the relationship between genetic potential and actual reproductive performance, two studies investigated associations between Angus bull EPDs and fertility outcomes using two datasets. The first study analyzed 167 Angus bulls undergoing BSEs, evaluating semen quality, scrotal circumference, and pass/fail classification according to Society for Theriogenology guidelines. The second study evaluated 13 Angus bulls used in fixed-time artificial insemination (FTAI) programs, where fertility was measured based on actual pregnancy rates in the field. EPDs for multiple traits, including docility (DOC), were included in both analyses. Across both studies, the docility EPD (DOC) consistently showed significant associations with fertility outcomes. In Study 1, bulls with higher DOC scores were less likely to pass a BSE and more likely to exhibit abnormal sperm morphology, including head, midpiece, and tail defects. Similarly, in Study 2, bulls in the High Fertility group had significantly lower DOC values compared to their lower-performing counterparts. These results suggest that while EPDs are not direct fertility measures, certain traits, such as DOC, may offer predictive value for reproductive performance. Incorporating such indicators may enhance bull selection strategies for improved herd fertility
OPTIMIZING OPEN MPI POINT-TO-POINT COMMUNICATION: DATATYPE ENGINE AND COMPRESSION HIDING
No full textIn the era of Exascale computing, the efficiency of scientific applications is increasingly constrained by communication overhead rather than computational capacity. This dissertation addresses two critical bottlenecks in MPI (Message Passing Interface) communication: inefficient handling of non-contiguous data and unexploited opportunities for hiding compression overhead for the communication data.
The first part of this work focuses on enhancing the Open MPI datatype engine. By redesigning internal datatype representations using a flattened IOVEC format and introducing Memory Access Rearrangements (MARs), this study minimizes the bookkeeping overhead associated with packing complex datatypes. A comprehensive performance model is developed to predict packing efficiency. Additionally, Just-In-Time (JIT) compilation is integrated into the datatype engine using libgccjit, allowing runtime generation of tailored packing functions. These functions eliminate conditional branching and are particularly effective for pipelined communication, yielding speedups of up to 3.65x. To mitigate the JIT compilation overhead, an offline caching mechanism is introduced, enabling reuse of compiled functions across multiple runs.
The second part of the dissertation explores early compression techniques to hide the overhead of data compression in MPI communication. A novel framework is proposed that leverages the Linux userfaultfd (uffd) mechanism to detect write access and strategically offload compression to idle CPU resources. By overlapping compression with the delay between the last write and message transmission, the framework masks compression latency without disrupting application logic. A detailed evaluation across representative benchmarks and real-world MPI applications demonstrates that this approach can potentially reduce communication time while preserving correctness and portability.
Together, these contributions present a holistic enhancement of the Open MPI communication stack. By bridging datatype optimization and early compression hiding, this work improves communication efficiency and scalability on current and emerging HPC platforms. The solutions are implemented as lightweight extensions at the MPI user level, requiring minimal developer intervention, and are compatible with existing MPI applications
PROPOSED METHODOLOGIES FOR PEBBLE BED REACTOR SPENT FUEL CHARACTERIZATION
No full textThe management and handling of spent nuclear fuel (SNF) from pebble bed reactors (PBRs) requires reliable estimates of bulk fuel characteristics long after discharge. Historical efforts have been focused on light water reactor (LWR) fuels and have not been updated to reflect the distinctive features of PBR fuel, particularly the identification of the key parameters that would need to be tracked and recorded to achieve a reasonable prediction. This work addresses the question: “What reactor parameters and fuel conditions must be tracked to reasonably predict SNF characteristics from pebble bed reactors?”
The central hypothesis is that average discharge burnup and cooling time are sufficient to accurately estimate SNF characteristics relevant to radiological dose rate, criticality safety, and decay heat, provided that the effects of other parameters are incorporated through bounding calculations. To evaluate this claim, an extensive set of simulations was performed using SCALE 6.3.2, including TRITON, ORIGEN, KENO-VI, MAVRIC, TSUNAMI, and OBIWAN modules. Impactful parameters were identified, best modeling practices identified and utilized and impacts inherent to reactor’s operation were demonstrated. Lastly, a broad parameter space was explored—enrichment, specific power, fuel temperature, burnup, and cooling time—and automated via Python workflows on high-performance computing (HPC) resources using SLURM, an open-source workload manager and job scheduler for Linux clusters.
Key outputs such as criticality, decay heat, and radiological dose rates were analyzed for the spent fuel across the parameter space. A cluster-based statistical method was applied to group data and generate ±2σ uncertainty envelopes. Results demonstrate that once the impact of non-tracked parameters is captured as bounding variability, SNF behavior correlates strongly with only burnup and cooling time. These findings suggest that future SNF reporting and management strategies for PBRs can be streamlined, reducing data collection burdens while preserving safety margins. The results support regulatory, design, and operational planning efforts for entities responsible for handling advanced reactor spent fuel
Ecological and Geochemical Factors Underlying the Distribution of the Aerobic Methane-Oxidizing Microbial Community in Aquatic Systems
No full textMethane gas plays an important role in both modulating global temperatures and in providing carbon to deep-sea ecosystems. Aerobic methanotrophs, microbes that oxidize methane into more labile compounds, mitigate its global warming potential and make methane-derived carbon accessible to entire ecosystems. While capable of oxidizing methane without assistance from other microbes, a growing body of evidence suggests that nonmethanotrophic methylotrophs—bacteria that cannot oxidize methane but can oxidize other single-carbon compounds like methanol—may aid in this process, leading to higher rates of methane oxidation. While much research has been conducted investigating how aerobic methanotrophs alone respond to changing environmental conditions, how co-occurring nonmethanotrophic methylotrophs also respond to those conditions is often overlooked. It is also unclear what factors influence the taxonomic and functional distribution of the aerobic methane-oxidizing community on a fine-scale in natural ecosystems.
My dissertation utilizes two culture-independent techniques—16S rRNA gene amplicon sequencing and shotgun metagenomics—to investigate how biotic and geochemical factors combine to influence the structure and capabilities of naturally occurring aerobic methane-oxidizing communities. First, I review current knowledge regarding aerobic methanotrophs and their proposed syntrophic partner species that aid in the process of methane oxidation, the nonmethanotrophic methylotrophs. Then, novel in situ incubation technology is used to study how aerobic methanotrophs and nonmethanotrophic methylotrophs in a methane-rich lake each respond to natural variations in geochemistry and in turn affect the methane oxidation rate constant. Next, the community structure, response to geochemical and physical environmental factors, and spatiotemporal stability of the overall prokaryotic community and specifically of the aerobic methane-oxidizing community is investigated throughout two North Atlantic seep fields over two years. Finally, the functional potential of the microbial community within those two seep fields is assessed within the recovered metagenome-assembled genomes and functional roles that Methylophilaceae, Thioglobaceae, and Nitrosopumilaceae may play in the aerobic methane-oxidizing community is determined
Biophysical Impacts of Mixed Chain Phospholipids on Membrane Structure and Phase Behavior: Insights from Molecular Dynamics and Experimental Approaches
No full textLipid bilayers are essential for all forms of life and are comprised of hundreds of structurally distinct lipids. Arguably, one of the most important lipid bilayers in nature is the eukaryotic plasma membrane (PM) that forms the external barrier of all living cells. Given the vast diversity of lipid types and structures, a major challenge in membrane biophysics is determining how specific lipid classes contribute to physical properties of the PM. One understudied class of phospholipids consists of lipids where both the chains are saturated but differ in the number of carbons. These mixed chain lipids are thought to alter midplane interactions as compared to their symmetric counterparts. Here, we developed novel methodologies to investigate the fundamental biophysical properties of mixed chain lipids both in vitro and in silico. All-atom molecular dynamics simulations were used to explore the effect of acyl chain mismatch on bilayer properties at an atomic scale. Complementary experimental techniques including FRET, confocal fluorescence microscopy, and cryogenic electron microscopy were used to examine model membrane systems exhibiting phase separation. Simulations reveal that chain mismatch and glycerol backbone positioning significantly influence bilayer properties such as bending modulus, interdigitation, and upward acyl chain snorkeling dynamics. The application of a novel phenomenological model for FRET data enabled precise determination of the miscibility transition temperature and phase behavior of mixed chain lipid systems composed of a high-melting lipid, low melting lipid and cholesterol. Complementary experimental findings further demonstrated that the positional transposition of acyl chains on the glycerol backbone significantly impacts lateral lipid organization in the membrane and other bilayer properties. These findings and methods enhanced our understanding of membrane biophysics, establishing a strong foundation for future studies on the structure, dynamics, and function of complex biomembranes