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Novel Applications of Stable Metal Isotope Geochemistry to Understand Ore Formation
No full textMetals including molybdenum (Mo) and iron (Fe) are critical resources for modern society. These metals are extracted from various types of ore deposits including porphyry (Mo) and skarn (Fe and Mo) and are predominantly used in steel production and contribute to technological, industrial, and energy production. However, as population, industrialization, and technology continue to grow and advance, the demand for metals like Mo and Fe will increase, requiring the discovery of new resources. Understanding geochemical behavior and the geological processes that transport and concentrate these metals in the crust can help scientists better develop ore deposit models and discover additional resources. One way to achieve this is to develop new geochemical tools to elucidate the ore-forming processes recorded in rocks and minerals. This dissertation utilizes the stable isotope systems of Mo and sulfur (S) in molybdenite (MoS2) and Fe in garnets to develop and refine geochemical techniques that can be used to understand ore deposit formation.
Chapter 2 applies the isotope pairing technique using Mo and S isotopes in MoS2 to develop a new method to illuminate Mo isotope variation in magmatic-hydrothermal systems. The results indicate that Mo-S isotope pairs can distinguish deposit types, which was not possible using Mo isotopes alone. When paired with Mo isotopes, S isotope ratios reveal information about the source fluid while Mo isotope ratios provide insight into processes during ore formation. More work is needed to further develop this technique.
Chapter 3 presents the first experimental work to preliminarily quantify the Mo isotope fractionation factor between MoS2 and an aqueous fluid at magmatic-hydrothermal conditions (800°C, 150 MPa). The data confirm that Mo isotope fractionation is controlled by redox and Mo coordination; MoS2 preferentially incorporates the lighter Mo isotopes while the fluid retains the heavier Mo isotopes. These results also support the hypothesis proposed by previous studies that Rayleigh fractionation is the main factor controlling Mo isotope variation observed among magmatic-hydrothermal ore deposits.
Chapter 4 focuses on the Tibes Fe skarn in Puerto Rico as a case study to test the use of Fe isotope geochemistry in garnets to elucidate fluid evolution during skarn formation. The data from this work reveal that the bulk Fe isotope compositions measured across the garnet populations capture a subtle change in fluid redox conditions over time. The oldest population has the highest isotope ratios while the youngest population has the lowest Fe isotope ratios, suggesting that fluid conditions evolved from relatively oxidizing to reducing. This trend was also observed on the crystal scale with the garnet cores having isotopically heavier compositions compared to garnet rims. These results demonstrate the promise of Fe isotopes in garnets as effective tracers of fluid evolution during skarn formation
Structural Characterization and Life Cycle Assessment of Conventional and Rejuvenated Cold Recycled Mixtures at the NCAT Test Track
No full textWith growing interest in replacing conventional asphalt concrete (AC) mixtures on low volume roads, cold recycling mixtures incorporating 100% reclaimed asphalt pavement (RAP)
have gained significant attention. Recent advancements include the use of engineered
emulsions, polymer-modified emulsions, and rejuvenators to enhance cold recycling
performance. This thesis focuses on the structural characterization and environmental
evaluation of both conventional and rejuvenated Cold Central Plant Recycling (CCPR)
mixtures.
Five test sections were constructed on an off-ramp at the National Center for Asphalt
Technology (NCAT) Test Track in 2021 to assess field performance. Structural characterization
of CCPR mixtures was conducted using four approaches: effective structural number, modulus
correlation, field performance data, and empirical design charts. Results showed that
conventional CCPR mixtures exhibited higher structural layer coefficients (0.41–0.45) than
rejuvenated CCPR mixtures (0.28–0.34). These values were assessed using the AASHTOWare
Pavement ME Design software, incorporating mix-specific dynamic modulus and calibrated
rutting transfer functions. Simulated rutting at design life confirmed the accuracy of the derived
coefficients.
Additionally, a comparative Life Cycle Assessment (LCA) was performed to evaluate
the environmental impacts of the CCPR sections relative to a conventional AC control section.
While all CCPR sections demonstrated a 38–62% reduction in global warming potential
(GWP), some impact categories such as smog formation and ozone depletion potential were
elevated in rejuvenated mixes, primarily due to the rejuvenators use
Illuminating the Experiences of Non-Offending Caregivers: A Critical Narrative Exploration of Navigating Child Abuse Systems
No full textThis critical narrative inquiry explored the lived experiences of Non-offending
Caregivers (NOCs) impacted by child maltreatment. The literature on Adverse Childhood
Experiences (ACEs) has demonstrated significant focus on child maltreatment from a prevention
and awareness perspective. NOCs are mentioned as both risk and protective factors in this
regard. Evidence-based treatment modalities emphasize the important role NOCs have in a
child’s recovery from trauma. Literature has begun to explore concerns that impact NOCs from a
very limited perspective, typically in reference to a child’s healing journey. Through a semi
structured interview protocol, this study explored the stories of 11 NOCs who detailed their
varied experiences while navigating child abuse systems. This included their involvement with
Child Advocacy Centers (CACs) and the various agencies and personnel involved through a
Multiple Disciplinary Team (MDT) approach. The findings illuminated NOCs’ experiences of
both individual themes, unique to their involvement, and collective themes shared amongst
participants. The overarching collective themes included (1) Communication and Information
Access, (2) Supportive Guidance, (3) Transition, and (4) Teamwork/Collaborative Processes.
Each theme provides meaningful implications for counselor education and training, clinical
practice, and multidisciplinary team-based efforts. Furthermore, the study’s limitations provide
opportunities for future research development
In-Situ Bacterial Detection in Liquids Using Novel Bio-Free and Bio-Hybrid Biosensors
No full textThe detection of bacteria in liquid is crucial to a wide range of applications, from clinical diagnostics and water safety to food processing and pharmaceutical quality control. While each application involves a different liquid environment, the core sensing mechanisms can remain platform-consistent when carefully designed. This study therefore focuses on developing two adaptable biosensing platforms that can operate effectively in complex liquid samples. To validate performance and showcase real-world utility, urinary tract infection (UTI) diagnosis is chosen as a test scenario, representing a medically relevant and chemically challenging background. The study develops and evaluates two biosensing strategies: a bio-hybrid magnetostrictive particle (MSP) sensor and a novel, bio-free dielectric spectroscopy-based approach, each designed to independently address the challenge of in-situ bacterial detection in liquid environments. In the first project, an optimized MSP biosensor was developed and tested for detecting Escherichia coli (E. coli) in urine. Extensive fabrication refinements were introduced to improve sensor uniformity and resonance stability. These enhancements significantly reduced baseline drift and mechanical noise. The resulting MSP sensors, functionalized with specific antibodies, were integrated into a closed-loop fluidic system. When tested with urine samples spiked with E. coli, the system reliably detected bacterial concentrations as low as 10⁴ CFU/mL within 30 minutes and revealed that slope provided sensitive quantification during early-stage binding. By systematically varying bacterial concentrations, a semi-quantitative measurement protocol was validated and showed clear dose-dependent shifts. These findings validated the MSP platform’s capability for rapid, real-time diagnostics. The second project explored the development of a bio-free, dielectric spectroscopy platform using rod, plate, and interdigitated electrode configurations. Dielectric/electric parameters were measured across multiple media, bacterial concentrations. Electrode material and geometry were shown to influence bacterial response by altering the relative contributions of bulk liquid versus electrochemical double layer (EDL) and modifying the structure and thickness of the EDL itself. These shifts provide strong evidence that geometry and surface chemistry act as tunable filters, selectively amplifying bacterial-induced changes in dielectric spectra and make them suitable as spectral fingerprints for the presence of bacteria. Interdigitated electrodes at microscale added additional complexity, capturing subtle changes in spectral shape through derivative analysis. Further, Direct Current (DC) bias was introduced as a tunable stimulus to modulate the EDL and track dynamic spectral shifts. Bacterial suspensions displayed distinct stabilization behaviors under DC stimulation, particularly in capacitance, offering a new temporal axis for bacterial detection. Across dielectric sensor platforms, machine learning models were trained to recognize spectral patterns linked to bacterial presence. These findings confirm that dielectric responses encode both immediate and time-resolved information that can be exploited for robust, pattern-based classification. Together, the MSP and dielectric systems represent two independent sensing strategies: one leveraging biochemical binding for selective detection, and the other employing bio-free mechanisms based on intrinsic properties. Each system offers unique strengths and constraints, and their development highlights how distinct physical principles can be harnessed to address common diagnostic challenges in complex liquid environments, paving the way for a new generation of bacterial sensors combining hardware engineering, signal modeling, and data-driven intelligence
Adapting the Reconnecting to Internal Sensations and Experiences Intervention for Veterinary Students
No full textVeterinary students and professionals are at elevated risk for suicidal thoughts and behaviors compared to other high-risk occupational groups and the general population (Karaffa & Hancock, 2019; Nett et al., 2014; Schernhammer & Colditz, 2004; Skipper & Williams, 2012; Tomasi et al., 2019). Notably, veterinary students and professionals report stigmatizing attitudes about psychological treatment and several barriers to mental health care. The brief, online Reconnecting to Internal Sensations and Experiences (RISE) intervention (Smith et al., 2021, 2022, 2023) may be an accessible, effective treatment for improving interoceptive awareness, a transdiagnostic risk factor for psychopathology and suicide, among veterinary students and professionals. However, the feasibility and acceptability of the RISE intervention has not yet been examined in this population. Utilizing a mixed methods approach, we conducted a theater test of the RISE intervention to adapt the program for a new population of veterinary students consistent with the Administration phase of the ADAPT-ITT model (Wingood & DiClemente, 2008). Among our sample of 24 veterinary students, 15 (62.5%) completed the full intervention. Veterinary students reported that the RISE intervention was helpful, acceptable, effective for coping with veterinary and non-veterinary distress; was relevant to their veterinary training; and was not likely to be associated with negative side effects. Participants also recommended modifications to the RISE intervention for veterinary students. The results from the present study may be used to inform subsequent phases of the ADAPT-ITT model, with the ultimate goal of developing a brief, accessible intervention that improves interoception, psychological functioning, and suicide outcomes among veterinary students
A Generic Digital Twin Ecosystem for Computer Numerical Control Manufacturing Processes
No full textThis dissertation considers the design and implementation of a generic Digital Twin Ecosystem (DTE) for computer numerical control (CNC) manufacturing processes. The DTE architecture integrates real-time data acquisition, processing, and synchronization with the physical CNC assets, while accurately modeling their behavior under various operating conditions. The DTE utilizes two major components, namely the data Acquisition, Processing, and Distribution Component (APDC) and the Virtual Representation Component (VRC), which is developed using the Unity real-time development platform. The DTE is verified and validated through testing and experimentation in Additive and Subtractive Manufacturing case studies. Metrics consider response time, sequencing accuracy, seamless integration, job duration, virtual-to-physical mapping accuracy, and process-specific variables. The DTE is a unified platform for twinning and simulation. It achieves this by providing two modes of operation: the online mode allows for real-time process replication, ideal for monitoring and remote management, while the offline mode supports asynchronous G-code simulation, enabling what-if analysis and exploration of process variables. The two modes can be combined to enable predictive capabilities for autonomous process intervention. Industry professionals and academic scholars could use the DTE to make informed data-driven decisions, optimize machining processes, and ensure cost-effective and safe operations. This research contributes to the advancement of Digital Twin technology, particularly in CNC machining, fostering innovation in the manufacturing sector, and promoting the development of practical, cost-efficient, and reliable cyber-physical industrial systems, enhancing operational capabilities and productivity
Design and Commissioning of a Thermal Radiation Chamber with Design Confirmation via Finite Element Model
Get PDFResearch into low heat transfer internal combustion engine technology has led to a need
for new testing devices that can generate heat flux at levels similar to those found in a
Homogeneous Charge Compression Ignition engine (~1.0 MW/m2) but isolated from the
reciprocal pressure environment. A Thermal Radiation Chamber was developed to accommodate
this need. This system uses a graphite resistive heating element to generate resistive joule
heating. The heat flux is measured via custom, high speed heat flux sensors made by IR
Telemetrics of the same construction utilized in numerous internal combustion engine research
studies. A stainless steel wheel, featuring two cut-outs and cooled by internal water channels,
rotates between the graphite heating element and the custom probes to mimic the required
periodicity of the heating events. A finite element simulation was created to predict the response
of the heat flux sensors so that the requisite distance between the graphite element and the
custom heat flux sensors could be predicted such that the probes, even if coated with an
insulative substance, would still register temperature swings beyond their measurement
uncertainty (~1.1°C or 0.4% of full scale).
Informed by the finite element solution, the radiation chamber design was finalized, and
the device was constructed and commissioned. Subsequently, several experimental trials were
conducted to validate the finite element model predictions. The Thermal Radiation Chamber
exceeded its design requirements, generating over 2.0 MW/m2 and temperature swings observed
to exceed 15°C. The simulation accurately predicted the shape of the response of the heat flux
sensors. With small modifications, the model was brought into quantitative agreement with the
experimental data and now stands ready for further application in designing insulative coatings
for low heat rejection internal combustion engines
Bank Expansion, Fintech Disruption, and Capital Market Choices: Understanding Financial Institutions and Investment Decisions
No full textIn the first study, we examine the impact of geographic expansion of intrastate Bank Holding Companies (BHCs) on their funding costs following changes in intrastate branching restrictions in the U.S. Unlike intrastate BHCs, many of interstate BHCs expand not only across state lines but also within their home states, making it challenging to determine whether the effects of geographic expansion on main variables of interest are solely due to entering new states or further expanding within their home states. We consider this important factor in our empirical analysis and find that intrastate geographic expansion, on average, lowers funding costs for intrastate BHCs. These funding cost reductions for the intrastate BHCs are stronger in retail funding than wholesale funding. In addition, results from moderating effects0F suggest that 1) these effects on funding cost reductions are lessened when BHCs expand into counties that have highly correlated natural conditions with their home counties and that experience more natural disasters; 2) these reductions in funding costs from intrastate geographic diversification are more pronounced for BHCs that experience less agency friction.
In the second essay, we analyze lending behaviors of institutional and retail investors during COVID-19. By comparing loan records funded by both types of investors, we find that retail investors act as stable fund providers throughout the pandemic. In contrast, institutional investors quickly withdraw their investment. Consequently, this contraction in credit supply significantly affected financially constrained borrowers after the outbreak. Furthermore, although institutional investors demonstrate an advantage in selecting higher-quality loans before the pandemic, this advantage diminishes as delinquency rates decrease for retail investor-funded loans and increase for institutional-funded loans, ultimately resulting in no significant difference. Lastly, institutional investors, especially active ones, display strong risk-averse behavior during the uncertainty phase. We attribute institutional investors' behavior to their higher sensitivity to systemic risks and monetary policy changes during the pandemic. In contrast, retail investors are drawn to the unique features of the crowdfunding model, finding marketplace lending platforms to be a relatively low-risk investment option amid limited alternatives.
The third essay investigates Special Purpose Acquisition Companies (SPACs), also known as "blank check" companies. We conduct a cross-sectional analysis of stock returns for private companies going public via SPAC IPOs, finding that warrants, time-to-merger, and deal value are negatively associated with de-SPAC returns. In addition, we examine factors influencing a private firm’s decision to choose a SPAC IPO over a traditional IPO, with Lasso variable selection revealing new significant variables. Our comparison of return performance between SPAC IPO mergers and traditional IPOs shows that SPAC IPOs underperform in terms of three-month returns, though there are no significant differences in initial-day, six-month, or one-year returns. In terms of risk-adjusted returns, the two types of IPOs perform similarly, with mixed results on relative riskiness, but minimal economic differences
Evaluation of Methods to Predict and Measure Out-of-plane Bending and Shear Stiffnesses in Cross-Laminated Timber Panels
No full textCross-laminated timber is an innovative mass timber construction material that takes advantage of many of the strengths that timber provides while also helping to address many of timber's limitations. Most of the current research is primarily focused on the strength of CLT elements, however, there remains a gap in the current research with respect to the out-of-plane effective flatwise shear rigidity of short-span cross laminated timber elements. Along with this investigation of shear rigidity, this study aims to evaluate the accuracy of a direct method of measuring both bending stiffnesses and shear rigidity. To properly assess the various method’s abilities to accurately measure stiffness, the shear span-to-depth ratio, loading configuration, axis of loading and width of CLT panel elements were varied.
A total of 45 beam-type one-way panel bending tests were conducted and different types of instrumentations were used to measure bending stiffnesses and shear rigidity. For example, linear variable differential transformers (LVDTs) were used to measure the apparent bending stiffness, inclinometers measuring both the end rotation and rotation of the member under the load points were used in two different methods to measure the effective bending stiffness. The average shear rigidity of a unit section was measured using diagonal string potentiometers. The study found that for CLT specimens with low shear span-to-depth ratios (equal to or less than 5.0), both the apparent bending stiffness and the measured shear rigidity were consistently greater than design guidance is currently accounting for. It was also found that the effective bending stiffness was consistently lower than design guidance predicts. Overall, this study contributes to furthering our understanding of the stiffness and rigidity of CLT panels
Honors College Membership and Participation in High-Impact Practices
Get PDFThis study examines the relationship between Honors College membership and participation in high-impact practices (HIPs) at a large, public research university in the southeastern United States. Grounded in theoretical frameworks of adult learning, including andragogy, self-directed learning, and experiential learning, this research investigates how honors education supports student engagement and the development of career readiness competencies during the critical period of emerging adulthood.
Using institutional data gathered through the Campus Engagement and Experience Survey (CEES), administered over three years, the study analyzes undergraduate participation in five HIPs: internships, cooperative education experiences, undergraduate research, diversity/global learning, and ePortfolios. Quantitative methods, including chi-square tests of independence and binary logistic regression, were employed to assess differences in HIP participation between honors and non-honors students. The analysis also considers demographic variables such as gender, race, college affiliation, and STEM classification to explore their influence on HIP engagement.
Findings suggest that honors students participate in HIPs at significantly higher rates than their non-honors peers, particularly in undergraduate research and diversity/global learning. These patterns persist even after controlling for demographic factors. The results underscore the potential of honors education to cultivate career readiness by aligning with the core principles of adult learning and providing enriched, self-directed, and experiential learning environments. The study contributes to a broader understanding of how institutional structures—such as honors colleges and honors programs—can foster lifelong learning and support a student’s transition from college to career. This research offers practical implications for higher education administrators and honors program leaders seeking to design inclusive, high-impact educational experiences that advance student success and post-graduation outcomes. It also addresses gaps in the literature by highlighting the unique role of honors education in promoting engagement, career competency development, and long-term employability among emerging adult learners