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Study of the Electrical Behavior of CsPbBr3 Single Crystal and Films under Visible and High-Energy Photons
No full textCsPbBr3 is a promising material due to its capability to detect high-energy radiation and applications in solar materials. A detailed study of the electrical behavior under γ-radiation is crucial for understanding the effects of radiation. In this work, we have studied the electrical behavior of CsPbBr3 single crystal and undoped and poly(methyl methacrylate) (PMMA)-doped films of CsPbBr3. We have introduced a new method for the growth of undoped and doped films. The X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analysis show the quality of the undoped, and PMMA-doped films is comparable to that of a single crystal (SC) based on purity. The current-voltage characteristic indicates that the SC and undoped film are more sensitive to ultraviolet light, but the PMMA-doped film is more sensitive to 532 nm. Also, the current under γ-radiation is lower than the dark current for SC and undoped film while is greater for PMMA-doped film when traced from 0 to −20 V. While the current-time characteristics indicate the current under γ-radiation is less negative than the dark current collected at −20 V for SC, undoped, and PMMA-doped films. The mobility-lifetime product is highest for SC, moderate for undoped film, and lowest for PMMA-doped film. These findings clarify some of the understanding of the device physics under visible and high-energy photons for optoelectronic and high-energy radiation detection
Trans-crustal magmatic processes revealed by amphibole breakdown textures at the Quillacas monogenetic volcanic center, Bolivia
Get PDFAmphibole exerts a fundamental control on arc magma petrogenesis, differentiation, and the long-term evolution of the arc crust. This study identifies two texturally distinct amphibole populations within andesitic lavas and entrained hornblendite cumulates at the Quillacas monogenetic volcanic center in the Eastern Altiplano, Bolivia. Within the hornblendites, all amphiboles are tschermakitic, large (≤800 μm) with thick, granular reaction rims (avg. 27 μm thickness). In the host andesites, tschermakites are also the dominant amphibole species but are smaller (250–400 μm) with thin, symplectic reaction rims (avg. 7–9 μm thickness). An intergrowth of symplectic and granular reaction rims is also observed in this population. The amphibole populations within the Quillacas magmatic system also record irregular volumetric decomposition where amphibole is replaced by mineral aggregates of plagioclase, pyroxene, and oxide within the crystal. This suggests the occurrence of a relatively slow reaction between the amphibole and melt trapped in fractures and cleavages during decompression-induced degassing. Geothermobarometry indicates that the hornblendite cumulate tschermakites crystallized at P-T conditions ranging from 467 to 598 ± 12 % MPa and 945–991 ± 22 °C. The host andesite tschermakites crystallized at P-T conditions ranging from 448 to 570 ± 12 % MPa and 928–1004 ± 22 °C. These geothermobarometric constraints correspond to depths of 16–24 km, which, within this region of the Central Andean crust, coincides with a regionally extensive low-seismic velocity zone. The texturally distinct amphibole populations imply that a multi-stage trans-crustal magmatic system is likely present beneath the Quillacas volcanic center. In this scenario, a crystal mush zone exists at upper crustal depths where the hornblendite cumulate tschermakites initially crystallized. Magma recharge into this mush zone initiated a reaction between hornblendite cumulates and the melt which formed the amphibole granular rims. This recharge event also transported the host andesite tschermakites that subsequently developed symplectic rims due to heating and ascent-driven decompression. This study supports the presence of amphibole-dominated mush filters in the upper crust of the Central Andean arc and advances our understanding of amphibole\u27s role in the evolution of arc magmatic systems
Quantum Harmonic Analysis on the Unweighted Bergman Space of the Unit Ball
No full textWe study quantum harmonic analysis (QHA) on the Bergman space A2(Bn) over the unit ball in Cn. We formulate a Wiener’s Tauberian theorem, and characterizations of the radial Toeplitz algebra over A2(Bn). We discuss the α-Berezin transform and investigate the question of approximations by Toeplitz operators
Profinite properties of algebraically clean graphs of free groups
Get PDFWe prove that for every prime p algebraically clean graphs of groups are virtually residually p-finite and cohomologically p-complete. We also prove that they are cohomologically good. We apply this to certain 2-dimensional Artin groups
Investigation of Subcellular Damage and Long-term Non-Cancerous Cardiovascular Effects Following Whole-Body Photon Irradiation
Get PDFCurrent radiobiological models focus primarily on nuclear DNA damage and fail to fully explain radiation-induced noncancerous health effects. This dissertation investigates whether non-nuclear subcellular structures contribute to radiation-induced biological damage through experimental biomarker analysis and computational microdosimetry. The central hypothesis posits that whole-body photon irradiation results in subcellular non-nuclear damage, specifically increased circulating mitochondrial DNA concentrations, that correlates with radiation dose and long-term noncancerous effects such as cardiovascular disease.
Specific Aim 1 measured mitochondrial and nuclear DNA concentrations in banked blood samples from 72 Chinese rhesus macaques that previously received whole-body photon irradiation ( Gy) from Cobalt-60 or LINAC sources. Using quantitative polymerase chain reaction, cell-free DNA concentrations were analyzed at two timepoints and correlated with irradiation history and medical observations. While conventional statistical analysis did not demonstrate significant dose-response relationships, exploratory analysis revealed suggestive associations between mitochondrial DNA levels and both radiation exposure and cardiovascular health issues. A significant positive correlation () was observed between nuclear and mitochondrial DNA concentration changes, suggesting coordinated cellular damage mechanisms.
Specific Aim 2 developed a simplified computational cardiac myocyte model for 3D Monte Carlo transport calculations using PHITS. The model incorporated key organelles with realistic chemical compositions. Simulations with 10 million primary photons revealed that secondary electrons constituted the primary energy deposition mechanism. Critically, smaller organelles like the inner mitochondrial matrix and endoplasmic reticulum demonstrated significantly higher energy deposition density per unit volume compared to larger structures, with 28 of 52 energy-depositing electrons producing statistically significant biological damage events.
The integration of experimental and computational approaches supports the hypothesis that mitochondrial and endoplasmic reticulum dysfunction contributes meaningfully to radiation-induced cellular damage beyond nuclear DNA injury. These findings challenge conventional radiobiological frameworks and demonstrate that significant subcellular dysfunction may occur even when nuclear DNA damage is not immediately lethal, potentially contributing to delayed cardiovascular pathology. This work has important implications for radiation protection, radiotherapy treatment planning, and understanding dose-response relationships for noncancerous late effects in occupational and clinical radiation exposure scenarios
Low Temperature Methane Coupling with CO and CO2
No full textMethane is the smallest hydrocarbon and the most abundant component in natural gas. Despite its availability, its chemical utilization has remained limited due to the challenges associated with direct methane activation and conversion. Most of the methane oxidation and oxidative carbonylation reactions in literature have been carried out at high-pressure using batch reactors or at ambient pressure using flow reactors. While batch reactors have been shown to have higher product yields, they are limited in their capability to provide real-time kinetic insights and comprehensive mechanistic understanding of the reactions involved due to the long residence time. This limits rationalization of catalyst designs for improving catalytic performance and possible process commercialization.
In contrast, continuous flow reactors allow for variable residence times and reactant partial pressures and thus offer a more robust platform for understanding reaction pathways in real-time. While continuous flow reactors have been employed to investigate methane partial oxidation reaction, most of these studies have been limited to near-ambient pressure operation. As a result, there exists a knowledge gap between high-pressure batch reactors and ambient-pressure flow reactors.
This dissertation describes our efforts to bridge this knowledge gap and investigates the conversion of methane into value-added oxygenates and products under high-pressure and relatively mild temperatures using continuous flow reactors. Chapter 2 demonstrates the conversion of CH4 and CO2 with C2H4 and O2 over Pd-Au/CeO2 at 200°C, producing propene, acetone, and methyl acetate. In situ DRIFTS confirmed the formation of methoxy adspecies on Pd-Au/CeO2 from CH4 and CO2, which is believed to be a reaction intermediate to methyl acetate.
Chapter 3 explores methane oxidative carbonylation over Rh/ZSM-5 catalysts with CH4, CO, O2, and steam cofeeding. Acetic acid and methanol are the major oxygenate products, with kinetic and methanol cofeed experiments indicating that the CH3 moiety of acetic acid originates from methane and the CO of the carboxyl group originates from carbon monoxide, with no evidence for methanol carbonylation.
In chapter 4, catalyst testing on Au/ZSM-5 catalysts synthesized using different methods revealed that larger Au nanoparticles favor the formation of oxygenates. Collectively, these studies provide evidence for low temperature methane activation and coupling and provide mechanistic insights for methane valorization catalyst design
MAXIMUM EXPOSURE: SUPPORTING INTERNATIONAL STUDENTS SOCIAL ADJUSTMENT WHILE ATTENDING A HISTORICALLY BLACK COLLEGE OR UNIVERSITY (HBCU)
No full textAbstract
The purpose of this qualitative study was to investigate social engagement among international students attending a Historically Black College or University (HBCU). Specifically, the study explored how campus leadership and the broader campus community can promote social integration and engagement for international students. Prior research has shown that international students face unique challenges in their social adjustment and academic success, often requiring tailored institutional support (Andrade, 2006; Hendrickson, Rosen, & Aune, 2011; Perry, 2016; Zhang & Goodson, 2011). This study employed a narrative inquiry approach and included seven international students currently enrolled at an HBCU in the southern United States. The use of a fictional institution, Spice University, allowed for ethical anonymity while representing a composite of common HBCU experiences. Through in-depth interviews and participant storytelling, this study aimed to identify barriers to social adjustment and understand how international students acclimate to on-campus environments. Findings revealed that while participants valued the familial atmosphere, cultural pride, and supportive faculty relationships at HBCUs, they experienced challenges related to limited pre-arrival communication, under-resourced international offices, and difficulties building peer relationships with domestic students. Despite these barriers, students demonstrated strong adaptability and a desire for deeper cultural engagement. Participants emphasized the importance of intentional programming, peer mentorship, and visible international representation in fostering a sense of belonging. The insights gained from this study provide actionable recommendations for improving institutional support, expanding inclusive practices, and strengthening international student programming at HBCUs. This research takes place during a time of heightened political uncertainty in the United States, as the 2025 political administration introduces new immigration policies and revisits international education priorities. Such shifts have direct implications for international students’ visa stability, campus climate, and their overall sense of security and belonging. The findings of this study underscore the urgent need for HBCUs and other institutions to advocate for inclusive practices, strengthen international student support systems, and ensure that global learners are protected and valued as integral members of the academic community
A SYSTEMS ENGINEERING APPROACH TO IMPROVE ALARM MANAGEMENT AND NURSE MENTAL WORKLOAD
Get PDFAlarm fatigue has been a consistent problem nurses have experienced for decades. The effects of excessive nuisance alarms leads to adverse effects such as desensitization, missed alarms, frustration, and increased risk to patient safety. Other research has provided explanations on alarm fatigue causes and developed solutions for reducing nuisance alarms or minimizing effects, but few have examined the problem from a sociotechnical systems perspective. This study applied the Systems Engineering Initiative for Patient Safety (SEIPS) framework to define, design, and test an alarm management intervention compatible with a Progressive Care Unit (PCU)’s sociotechnical subsystems. The SEIPS application is unique from previous research in that the framework examines the complex alarm system to find the root cause and provide solutions that minimize interfering with patient care. The research utilized a multi-step approach following the SEIPS framework. The first step involved studying the sociotechnical system of the PCU and describing nurses’ perceptions of alarms through a Cognitive Task Analysis (CTA). The second step used the Plan-Do-Check-ACT (PDCA) cycle to identify leading issues of nuisance alarms and feasible improvement options to design an intervention model. The third step tested the intervention in a controlled simulation where nurses and nursing students updated fabricated medical records while responding to audible alarms. The CTA findings showed that alarm related stress and boredom increase during the shift and effort and mental demand had the most significant effect on alarm related workload. The SEIPS framework identified sociotechnical systems compatible solutions through additional telemetry monitor and reduced volume of low priority alarms to the address alarm fatigue and reduce overall workload. The results of the intervention testing showed a 62% increase in work performance, an average 37% increase in alarm response accuracy, and decreased emotional stress (23%), frustration (42%), and confusion (31%). This research provides evidence that the SEIPS framework can effectively address nuisance alarm problems by describing the PCU’s sociotechnical system, nurse’s perception of alarms, and systematically identifying problems and creating solutions compatible with the sociotechnical system. The findings contribute to the main commission of addressing hospital alarm fatigue and improving alarm related workflow while reducing adverse effects
Hardware Acceleration for Efficient Cybersecurity and Forensics at Scale
No full textThe escalating volume and velocity of data are outpacing conventional, CPU-centric security paradigms, which creates architectural bottlenecks that inhibit real-time threat analysis and forensic investigation. This vulnerability is aggressively exploited by botnets and ransomware, which have emerged as the preeminent malware threats endangering modern digital infrastructure. This dissertation confronts these challenges by devising and evaluating a suite of cyber defenses that embed machine learning (ML) and statistical analytics directly into programmable hardware. By distributing these functions across two primary vantage points, namely, the network and the end-host, this research establishes a new paradigm for efficient, scalable, and high-speed security and forensics. This work begins by leveraging the network vantage point of P4-programmable switches to tackle threats and related forensic analysis at line rate. We present novel frameworks that embed classifiers into the data plane to identify botnet propagation and ransomware activity from a minimal number of packets, even when encrypted. These in-network techniques are complemented by a lightweight statistical engine for mitigating the large-scale Distributed Denial-of-Service (DDoS) attacks commonly launched by botnets. Additionally, a switch-based fingerprinting mechanism is introduced for the forensic attribution of Internet of Things (IoT) devices, which are often co-opted into botnets. From the end-host vantage point, this dissertation introduces accelerated, host-level defenses to expedite security and forensic workloads, as well as to preserve CPU resources. We demonstrate how a Smart Network Interface Card (SmartNIC) can mitigate DNS cache poisoning, which can be harnessed by adversaries for delivering botnet and ransomware payloads. Furthermore, this research pioneers the use of Computational Storage Drives (CSDs) for near-data processing. In particular, we offload a deep learning classifier to the drive\u27s integrated FPGA to analyze API call sequences, which enables the system to halt ransomware encryption at its inception and accelerate incident response. Collectively, these independent contributions establish a validated portfolio of hardware-accelerated cyber defenses and forensic analytics. The evaluations confirm that these systems demonstrate significant performance gains and resource efficiency, thereby offering a practical path for enhancing both security postures and forensic capabilities in modern, high-velocity data environments