Doctor of Philosophy, The Ohio State University, 2018, Astronomy

The technological advances of the recent years have allowed for the proliferation of relatively inexpensive charge-coupled devices (CCDs) and other imaging hardware that has revolutionized modern astronomy. The burgeoning field of transient astronomy is perhaps the largest benefactor of these advances, and as a result, high cadence, all-sky surveys are becoming a reality. New transient phenomena are discovered and studied in depth on a regular basis, and the datasets of ``normal'' transients are becoming richer by the day. However, transient phenomena are intimately connected to their environment, and understanding this connection can provide insight that the study of transient phenomenology alone cannot. In this dissertation, I leverage the statistical power of modern all-sky surveys to investigate the nature of transients, the properties of their host galaxies, as well as the techniques and tools we use to study both.

Master of Science in Engineering, Youngstown State University, 2023, Department of Mechanical, Industrial and Manufacturing Engineering

The field of metal additive manufacturing has experienced significant growth in recent years, and Laser Hot Wire Directed Energy Deposition (LHW-DED) has emerged as a popular technology due to its ease of use and ability to produce high-quality metal parts. In this study, we used a nonlinear transient thermo-mechanical coupled finite element model (FEM) in ANSYS APDL to conduct a detailed thermal and structural analysis of the laser hot wire DED metal additive manufacturing process. This analysis aimed to characterize the distortion caused by thermal effects and investigate the transient thermal process. In this study H13 iron chromium alloy material was deposited on an A36 low carbon steel substrate using a bidirectional laser toolpath. To record the temperature profile during printing, we employed a FLIR Infrared (IR) camera, while thermocouples mounted to the base plate measured heat transfer for validation purposes. Post-processing analysis was conducted using the CREAFORM laser 3D scan and Geomagic-X software to measure deformation from the nominal printed geometry. Overall, this study provides a significant contribution to our understanding of laser hot wire DED metal additive manufacturing, which will undoubtedly lead to further advancements in the field. This research has the potential to improve the productivity and quality of the additive manufacture of metals.

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2022, Photochemical Sciences

Our overall goal here in this dissertation is to develop silicon-based hybrid materials that are potential high stability materials replacements for those in current electronics systems. To design the hybrid structures, a unique class of silicon-based compounds, silsesquioxanes (SQ) was used as the building block. SQs are three dimensionally compact Si-O bonded, cage-type compounds that can be synthesized to contain a variety of functional groups on each of the cage vertices. They offer useful properties such as thermal and photo stability, a high degree of functionalization, solution processability, and facile synthesis. The works in this dissertation focus on mixed functional (vinyl/phenyl) SQs of different sized cages containing 8, 10, and 12 silicon atoms. They are synthesized by fluoride catalyzed rearrangement reaction in a statistically controlled manner to achieve the desired vinyl groups for oligomerization. Spectroscopic measurements in picosecond/subpicosecond timeframes were performed before evaluating their potential applications. In chapter 2, vinyl/phenylSQs are cross-coupled by 4-di-bromo-aromatic linkers: Benzothiadiazole (BT), Phenanthrenequinone (PQ), Ethyl-carbazole (EC) and Phenyl-carbazole (PC). To compare photophysical properties between caged and non-caged structures, bis-tri-alkoxysilyl (linker) model compounds are synthesized. Luminescence quantum yields for oligomers are generally lower than the corresponding model compounds (except for PQ) which denotes non-radiative energy transfer possibility in oligomer. In addition, rapid transient absorption anisotropy decay (10's ps in oligomers) provide signatures for excitation energy transfer between linker chromophores in oligomers. In chapter 3, we have designed hybrid oligomers with a vinyl/phenylSQ cage backbone linked with cross-linkers including 2,7-dibromo-9-fluorenone, 2,7-dibromo-9,9-dimethylfluorene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-dibromopyridine, 2,6-dibromopyridine, 2, (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2019, Physics

In this work, scanning probe microscopy (SPM) methods are developed and extended to spatially resolve performance-hampering electrically-active defects, known as traps, present in AlGaN/GaN Schottky barrier diodes (SBDs) and high electron mobility transistors (HEMTs). Commercial devices used in these studies were cross-sectioned to expose electrically-active regions which are traditionally inaccessible to SPM techniques. Surface potential transients (SPTs) are collected over the cross-sectioned faces of devices using nanometer-scale scanning probe deep-level transient spectroscopy (SP-DLTS), a millisecond time-resolved derivative technique of scanning Kelvin probe microscopy (SKPM) that was implemented with a custom system designed to study SBDs and HEMTs in cross-section. Detected SPTs are indicative of carrier emission from bulk defect-related trap states. In conjunction with similar measurements of these trap states using macroscopic techniques, finite-element simulations provide strong, corroborating evidence that observable SPTs are produced by traps located in the bulk of these samples and are therefore not a result of surface states or surface-related phenomena. GaN-based materials offer advantages over many alternatives in high-frequency and high-voltage applications. Features including a wide bandgap and a large breakdown voltage often translate to improved efficiency, performance, and cost in many electronic systems. However, GaN-based material research is still maturing, and charge trapping may be a limiting factor in GaN electrical performance and therefore hinder its widespread application and adoption. Determining the signatures and spatial distributions of active traps in GaN devices is critical for understanding trap-related mechanisms of device failure as well as the growth or fabrication steps which may be responsible for introducing these defect states. Powerful techniques like deep-level transient spectroscopy (DLTS) exist for identifying specifi (open full item for complete abstract)

PhD, University of Cincinnati, 2010, Medicine : Molecular, Cellular and Biochemical Pharmacology

The transient outward current (Ito) is a major repolarizing current in the heart and is heterogeneously expressed across the ventricular wall. Marked reduction of Ito density is consistently observed in human heart failure (HF) and animal HF models. It was proposed that this Ito reduction contributes to a significant action potential duration (APD) prolongation and to the impaired contractility in failing heart. In addition, a high density of Ito in the right ventricular (RV) epicardial myocytes has been suggested to play a critical role in the arrhythmogenesis for the Brugada syndrome, an arrhythmia that is responsible for up to 12% of sudden cardiac deaths. Due to the lack of a specific Ito blocker, however, whether above suggestions are true is still under question. This dissertation, use the dynamic clamp to specifically simulate Ito in ventricular myocytes, delineates the role of Ito in regulating cardiomyocytes electrical and mechanical functions. Firstly, to understand the role of Ito in regulating the AP morphology and duration, we introduced simulated Ito conductance in guinea pig and canine endocardial ventricular myocytes using the dynamic clamp technique. The effects of simulated Ito in both types of cells were complex and bi-phasic, separated by a clear density threshold of about 40 pA/pF. Below this threshold, simulated Ito resulted in a distinct phase 1 notch, and had little effect on or moderately prolonged the APD. Ito above the threshold resulted in all-or-none repolarization and precipitously reduced the APD. We conclude that, in animals such as dogs and guinea pigs that have a broad cardiac AP, Ito does not play a major role in setting the APD. We next examined the influence of Ito on the mechanical properties of canine ventricular myocytes. In endocardial myocytes, where the native Ito is small, simulation of an epicardial-level Ito by the dynamic clamp significantly suppressed cell shortening by 19%. The peak amplitude of Ca2+ transient was (open full item for complete abstract)

Master of Science in Mechanical Engineering, Cleveland State University, 2025, Washkewicz College of Engineering

The design and functionality of poppet relief valves in hydraulic systems are critically dependent on a comprehensive understanding of flow behavior and the forces acting within the valve. This study presents an investigation employing three simulation models: a transient dynamic Computational Fluid Dynamics (CFD) model, a simplified one-dimensional (1D) model, and a steady-state CFD model. The objective of the study is to evaluate the effectiveness of these models in predicting flow forces in a direct-acting poppet relief valve. The 3D steady-state CFD model offers an in-depth analysis of steady-state flow characteristics, capturing details of fluid dynamics and pressure distributions. The 3D CFD model offers an in-depth analysis of transient flow characteristics, capturing intricate details of fluid dynamics and pressure fluctuations. In contrast, the 1D model serves as a rapid and cost-effective alternative, providing a streamlined approach for preliminary assessments. Key parameters such as pressure dynamics, poppet lift, and resultant flow forces were analyzed to compare the accuracy and applicability of each modeling strategy. The results show that the steady-state CFD and Amesim models demonstrated strong validation against experimental data, with mean average errors of 0.65% and 3.27%, respectively. In contrast, the transient dynamic CFD model exhibited challenges at lower and higher flow ranges with a final mean average error of 16.43%. By highlighting both CFD and 1D modeling techniques along with test data validation, this paper aims to enhance confidence in analytical models used for valve analysis and design. The insights gained from this research have significant implications for minimizing noise, instability, and vibration in hydraulic applications, including those in oil and gas industries and off-highway vehicles. Ultimately, this work contributes to the optimization of hydraulic valve performance, paving the way for more reliable and ef (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2025, Computer Science and Engineering

Microarchitectural vulnerabilities originate from disparities between software assumptions regarding hardware behavior and the actual functioning of the underlying hardware. Transient execution vulnerabilities are prominent reflections of this gap that stem from the extensive speculation implemented in modern high-performance microprocessors. Identifying all possible vulnerabilities in complex designs is very challenging. One of the challenges stems from the lack of visibility into the transient micro-architectural state of the processor. Prior work has used covert channels to identify data leakage from transient state, which limits the systematic discovery of all potential leakage sources. In this thesis, we present IntroSpectre, a pre-silicon framework for early discovery of transient execution vulnerabilities. IntroSpectre addresses the lack of visibility into the microarchitectural processor state by integrating into the register transfer level (RTL) design flow, gaining full access to the internal state of the processor. Full visibility into the processor state enables IntroSpectre to perform a systematic leakage analysis that includes all micro-architectural structures, allowing it to identify potential leakage that may not be reachable with known side channels. We implement IntroSpectre on an RTL simulator and use it to perform transient leakage analysis on the RISC-V BOOM processor. We identify multiple transient leakage scenarios, most of which had not been highlighted on this processor design before. While microarchitectural vulnerabilities are typically more challenging to exploit than purely software-based bugs, their increasing prevalence in recent security publications is a significant concern, particularly in multi-tenant environments. With the widespread adoption of cloud systems in recent years, there is a growing concern regarding the security and privacy of users who share the same hardware platform. To address this, hardware manufactur (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Chemistry

Eumelanin is a black-brown pigment and is the most studied type of melanin, which acts as a sunscreen and antioxidant in human organisms. Despite decades of studies, the macromolecular structure of this pigment is still unknown. Past researchers were able to identify the initial steps of eumelanogenesis, which starts with the oxidation of L tyrosine to 5,6 dihydroxyindole (DHI) and 5,6 dihydroxyindole carboxylic acid (DHICA). The rapid and spontaneous oxidation and polymerization of DHI and DHICA results in insoluble black product formation. While these compounds are the last relatively stable precursors that have been isolated for studies, theoretical studies have highlighted the critical role of their respective oxidized forms, indole-5,6-quinone (IQ) and indole-5,6-quionone carboxylic acid (IQCA). However, until now the study of these oxidized molecules was not possible due to their instability. The first part of this dissertation focuses on the stabilized IQ molecules (IQ Me) studied through various spectroscopic techniques, including steady-state absorption and photoluminescence measurements and transient absorption (TA) spectroscopy. IQ-Me reveals unprecedented properties like broad absorption extending into the near-infrared (NIR) region, ultrafast nonradiative decay to the ground state without the formation of harmful intermediates in polar environment like acetonitrile. These unexpected properties are unique to a small molecule like IQ-Me and they resemble eumelanin's light-induced sunscreening behavior. These spectroscopic studies provide the first experimental characterization of the photophysical and photochemical properties of the oxidized monomer (IQ-Me). The following chapter investigates the role of the microenvironment on the excited-state decay channel of eumelanin subunits. The oxidized IQ molecule has a ditopic character with H-bond accepting and donating moieties, which drives intermolecular hydrogen bonding in nonpolar solvents like cyclohe (open full item for complete abstract)

Master of Science (M.S.), University of Dayton, 2024, Mechanical Engineering

Posturography provides insight into balance and postural stability but has little evidence of its effectiveness in its ability to predict falls, an event that happens to over 25% of senior adults each year. Analysis of transient responses within force plate center of pressure (COP) data and inertial measurement unit (IMU) acceleration data could increase the effectiveness of posturography in predicting senior fallers. Fifty adults aged 60 or older volunteered to participate in a balance assessment wherein three perturbations (cognitive, visual, and weight shift) were tested, and the response collected. Typical balance COP metrics such as sway range in addition to the transient metrics of ellipse area, mean velocity, and root mean squared (RMS) were calculated. While there were no significant differences observed between fallers and non-fallers, the data showed a promising effect of the transient analysis in that fallers generally exhibited higher values in the calculated metrics, as expected. Additionally, strong correlations were observed between the IMU and force plate. A larger sample size may provide a more comprehensive investigation of the effect of transient balance in identifying and predicting fallers in senior adults.

Master of Science, Miami University, 2024, Chemistry and Biochemistry

Chapter 1 introduces carbodiimide-driven anhydride formation from carboxylic acids, a useful reaction in a variety of non-equilibrium systems. It also introduces established techniques for regulating this reaction. Multiple strategies to control deactivation (anhydride hydrolysis) rates have been reported, but control over activation (anhydride formation) rates is limited. It also explores the role that pyridine already plays within established carbodiimide systems. Chapter 2 explores the reversible reaction of pyridine derivatives with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide methiodide in water to form adducts. These adducts are unreactive with carboxylic acids and thus reduce the anhydride formation rate while prolonging carbodiimide lifetime. The best results are obtained with 4-methoxypyridine. We demonstrate that this strategy can be used to control the formation of transient polymer network hydrogels, in one example increasing the time to reach peak modulus by 86% and the lifetime by 43%. Chapter 3 concludes and summarizes the work completed in Chapters 1-2 and provides future directions and opportunities with the carbodiimide adduct system. The appendix includes supporting information.

Doctor of Philosophy, The Ohio State University, 2024, Mechanical Engineering

In this dissertation, a series of experiments were carried out to investigate the auto-ignition process of transient fuel jets and sprays issuing into high-temperature, environments. Novel high-speed imaging and laser diagnostic techniques were developed and applied to characterize mixing and turbulent flow conditions prior to and at the onset of ignition. In addition, this research examines the topology and dynamics of ignition kernels as they grow and transition into a stable flame. Research was carried out primarily in canonical atmospheric pressure experiments, but a new high-pressure spray test facility is developed in this work with preliminary measurements presented, demonstrating new experimental capabilities. Specific contributions of this dissertation include: (1) characterization of the transient mixing processes of variable-density atmospheric pressure jets both before and after ignition, (2) determination of the most probable mixing and turbulent flow conditions leading to local auto-ignition, (3) statistical evaluation of the dynamic growth and transport of ignition kernels, (4) construction and characterization of a novel high-pressure, high temperature spray and combustion facility, and (5) demonstration of high-speed mixture fraction measurements in non-reacting and reacting sprays at realistic thermodynamic conditions. First, a series of transient gas-phase fuel jets issuing into a high-temperature, vitiated environment at atmospheric pressure was investigated. A well-known jet-into-hot coflow configuration was utilized with the addition of a fast-acting solenoid valves to achieve pulsed fuel injection in an environment with well-defined boundary conditions. Four test conditions were studied to examine the effects of variations in jet Reynolds number, the fuel mixture composition, and coflow temperature. High-speed laser Rayleigh scattering (LRS) was performed at 10 kHz to measure the mixture fraction and temperature fields from fuel injection (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Electrical and Computer Engineering

Contactless, nondestructive measurements of minority carrier lifetime by transient microwave reflectance (TMR) and photoluminescence are used to study the carrier dynamics of several ternary materials: InGaAs, GaAsSb, and InAsSb. As contactless measurements, TMR and photoluminescence can determine quality of as-grown wafers. The minority carrier lifetime is inversely proportional to the diffusion component of the dark current and can be used as an indicator of device performance, without the need for full device fabrication. The ability to yield useful information about wafer quality without the time and cost used for fabrication allows for quick feedback to growers. GaAsSb and InGaAs lattice-matched to InP are candidates for short-wave infrared (SWIR) detection at 1.5 μm, a wavelength used for eye safety and optical communication. The high speed or low signal applications at this wavelength benefit from the use of separate absorber, charge, and multiplier (SACM) avalanche photodiodes (APDs). In these devices, the absorber is optimized for detection at the wavelength of interest, and the multiplier is optimized for gain through impact ionization. InGaAs-based SACM APDs are a mature technology and are available commercially. The multipliers paired with InGaAs, however, typically have high noise. Research into low-noise multipliers has resulted in the demonstration of AlGaAsSb as a low noise material. When AlGaAsSb is paired with InGaAs, the grading material AlInGaAs creates a conduction band offset with AlGaAsSb, limiting bandwidth. GaAsSb lattice-matched to InP has similar properties to InGaAs and could be implemented without a conduction band offset due to the grading material being AlGaAsSb. When a GaAsSb/AlGaAsSb SACM APD was demonstrated, it was found to have higher dark current than commercial InGaAs-based devices. Because these materials are so similar, this was unexpected. As mentioned, the diffusion component of the dark current is inversely proportio (open full item for complete abstract)

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Environmental Engineering

Parameter estimation problems are ubiquitous in the field of environmental engineering, for example, in natural systems, an accurate assessment of the nutrient processing capacity of mountain streams is important for the estimation of nutrient load delivered by these streams to downstream water bodies. Similarly, in urban water systems, the ability to optimize pump operations in drinking water networks (DWN) to reduce energy costs is critically dependent on the ability to predict consumer demands that are often estimated from indirect measurements. Parameter estimation problems are challenging, as they are often ill-posed, and without proper considerations given to parameter uncertainty and observability, incomplete or sometimes incorrect conclusions might be drawn. The objectives of this research focus on considerations in parameter estimation, in the field of hydrology and hydraulics, in the fist two studies, and the remaining two studies focus on developing real-time optimal operation frameworks for urban water systems. In the first study, uncertainty in the parameters of the transient storage model (TSM) was estimated using the Markov chain Monte Carlo method, revealing the presence of large uncertainty in the TSM parameters. The TSM is a popular model used by researches to characterize the nutrient (e.g., nitrogen and phosphorus) processing capacity of small streams. The presence of broad uncertainty in the TSM parameters can be of significant interest to regulatory bodies, such as the Chesapeake Bay program who uses these parameter values to develop guidelines for different stakeholders. The second study introduces a consumer node clustering method using self-organizing map (SOM) in DWNS to improve the observability of estimated demands of the clusters. High frequency (e.g., hourly) consumer demands in DWNs are key parameters that drive system hydraulics and are rarely measured directly, and hence are estimated from indirect measurements. Consum (open full item for complete abstract)

Master of Science (M.S.), University of Dayton, 2023, Electro-Optics

There are an increasing number of applications for high power lasers in medicine, industry and the military. Fiber lasers present an attractive alternative to traditional laser types; however, when operating at high power levels, fiber lasers are subject to detrimental nonlinear effects. Stimulated Brillouin scattering (SBS) is a nonlinear acousto-optic interaction where a stimulated acoustic wave scatters light, which limits the laser output. This thesis presents a theoretical and experimental framework for Brillouin scattering in continuous wave and pulsed beam regimes. Stimulated Brillouin scattering was observed in optical fibers in stationary and transient beam excitations and Brillouin frequencies are presented for different optical fibers with pulsed beam widths ranging from 15 ns to 500 ns.

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2023, Photochemical Sciences

The very initial photoprocesses of relevant chromophores and organic molecular probes can provide important mechanistic insight into designing more robust and useful compounds for targeting in vivo applications, drug delivery, as well as an overall understanding of significant biological functions. Therefore, examining and comprehending these ultrafast processes is critical. In this dissertation, the elucidation of excited state dynamics of several molecular probes and organic systems is obtained from the results of multiple femtosecond transient absorption experiments. Chapters I and II detail the theoretical and experimental aspects, respectively, of this dissertation as fundamental and practical methods are addressed. The first chapter will cover laser spectroscopy and associated theories surrounding the technique relevant to the work discussed herein in general, while the second chapter will discuss specifics of experimental design and practices used for data analysis. The third chapter focuses on a photochromic system, trans-4,4'-azopyridine, capable of undergoing trans-cis isomerization upon irradiation and how similar and different this compound's dynamics are compared to trans-azobenzene and other azo dyes in general. An unusual trend in the quantum yield increasing upon exciting with higher excitation photon energies is linked to vibrational coherence observed for an in-plane bending mode. Chapter IV delves into a project on two polymethine cyanine dyes, which are utilized for deep tissue imaging due to their absorption and emission in the shortwave infrared region. The excited state dynamics in the fluorescent state and non-radiative relaxation mechanisms in this state, discovered to be competing photoisomerization and the energy gap law relaxation pathways, are analyzed and discussed. Finally, Chapter V describes work on a series of enaminones where the question of if and how excited state intramolecular proton transfer plays a role in the excited state m (open full item for complete abstract)

Doctor of Philosophy, Miami University, 2023, Chemistry and Biochemistry

In the future, well-engineered and optimized flexible electronic devices will be woven into everyday accessories such as clothes, furniture, safety, and healthcare monitoring devices. Dynamic polymer nanocomposites (DPNs) are an excellent class of materials that have a huge potential in the future of flexible electronics. DPNs are achieved through macromolecular engineering of dynamic polymers enhanced with electrically conductive nanofillers or nanocomposites with self-healing capabilities enabled via dynamic chemical linkages. Integration of multiple types of dynamic linkages into one polymer network is challenging and not well understood especially in the design and fabrication of DPNs. This dissertation presents facile methods for synthesizing flexible, healable, conductive, recyclable, and thermoresponsive DPNs using three dynamic chemistries playing distinct roles. Dynamic hydrogen bonds account for material flexibility and recycling character. Thiol-Michael exchange accounts for thermoresponsive properties. Diels-Alder reaction leads to covalent bonding between polymer matrix and nanocomposite. Overall, the presence of multiple types of orthogonal dynamic bonds provided a solution to the trade-off between enhanced mechanical performance and material elongation in DPNs. Efficient reinforcement was achieved using <1 wt.% carbon nanotubes (CNT) as nanofillers. Increased mechanical strength, electrical conductivity, and re-processability were achieved all while maintaining material flexibility and extensibility, hence highlight the strong promise of these DPNs in the rapidly growing fields of flexible compliant electrodes. Additionally, structure-property relationships highlighting the impact of network architecture, chain-length, cross-link density, and CNT loading are explored. Controlled addition of CNT as nanofiller produces electrically conductive and mechanically enhanced DPNs with demonstrated application in the regulation of current flow towards a (open full item for complete abstract)

Doctor of Philosophy (PhD), Wright State University, 2023, Biomedical Sciences PhD

Transient receptor melastatin 7 (TRPM7) functions both as an ion channel and a protein kinase. TRPM7 has been implicated in Mg2+ homeostasis, embryogenesis, cardiac automaticity, and immunity. The purpose of this research was to deepen our understanding of TRPM7 channel and kinase functions. To this end, we used two transgenic mouse models: the TRPM7 gain-of-function (GOF) and TRPM7 kinase-dead (KD) mice to address the consequences of increased channel activity and kinase inactivation, respectively. Global deletion of TRPM7 or the kinase domain alone are embryonic lethal, therefore, we used the TRPM7 GOF mouse to investigate germline transmission. We examined embryo development stages that follow placenta formation. We found that the GOF point mutation is post-placental lethal, and embryos at the specified developmental stages undergo intrauterine growth restriction (IUGR). The heterozygous GOF mice were viable. IUGR affects the development of organs such as the heart, brain and intestines. To ascertain the consequences of IUGR in our heterozygous GOF mice, we examined their body composition and behavior. We also examined how dysregulation of this channel is affected under hypomagnesemic conditions. Hypomagnesemic GOF mice were smaller than WT littermates and had lower lean mass. Low Mg2+ diet for at least two weeks reduced serum levels of Mg2+ roughly by half, and decreased viability of both WT and GOF mice. GOF and WT mice behaved similarly in working memory and anxiety tests, suggesting that brain development was not grossly impaired. TRPM7 protein is highly expressed in immune cells, where it was first identified, and we used the TRPM7 GOF and KD mouse models to address TRPM7 channel function in splenic macrophages. We measured the basal phagocytic activity of splenic macrophages in vitro. The phagocytic activity in KD mice was potentiated, pointing to suppressive effect of the kinase. Finally, we examined the roles of Ca2+ and Mg2+ in phagocytosis. We found tha (open full item for complete abstract)

Master of Science in Engineering, Youngstown State University, 2023, Rayen School of Engineering

Lithium-ion batteries have revolutionized our everyday lives by laying the foundation for a wireless, interconnected and fossil-fuel-free society. Additionally, the demand for Li-ion batteries has seen a dramatic increase, as the automotive industry shifts up a gear in its transition to electric vehicles. To optimize the power and energy that can be delivered by a battery, it is necessary to predict the behavior of the cell under different loading conditions. However, electrochemical cells are complicated energy storage systems with nonlinear voltage dynamics. There is a need for accurate dynamic modeling of the battery system to predict behavior over time when discharging. The study conducted in this work develops an intuitive model for electrochemical cells based on a mechanical analogy. The mechanical analogy is based on a three degree of freedom spring-mass-damper system which is decomposed into modal coordinates that represent the overall discharge as well as the mass transport and the double layer effect of the electrochemical cell. The dynamic system is used to estimate the cells terminal voltage, open-circuit voltage and the mass transfer and boundary layer effects. The modal parameters are determined by minimizing the error between the experimental and simulated time responses. Also, these estimated parameters are coupled with a thermal model to predict the temperature profiles of the lithium-ion batteries. To capture the dynamic voltage and temperature responses, hybrid pulse power characterization (HPPC) tests are conducted with added thermocouples to measure temperature. The coupled model estimated the voltage and temperature responses at various discharge rates within 2.15% and 0.40% standard deviation of the error. Additionally, to validate the functionality of the developed dynamic battery model in a real system, a battery pack is constructed and integrated with a brushless DC motor (BLDC) and a load. Moreover, because of the unique pole ori (open full item for complete abstract)

Doctor of Philosophy (Ph.D.), Bowling Green State University, 2023, Photochemical Sciences

Ultrafast time-resolved pump-probe spectroscopy is an ultimate method for revealing fundamental photophysical and photochemical processes that govern the evolution of molecular systems. This method can be used to study organic, inorganic, biological molecules, as well as materials, unraveling the response of the sample to photoexcitation on very rapid timescales from femtoseconds (10-15 s) to picoseconds (10-12 s), which response frequently defines molecular properties and functions. Excited-state relaxation dynamics of a paradigm ruthenium nitrosyl complex, an important sub-class of nitric oxide carriers, is studied by means of ultrafast dispersed, broadband transient absorption spectroscopy. A computational extension is performed for related NO-releasers such as trans [RuNOL2Cl3] complexes which possess coordinated derivatives of biologically-relevant nicotinic and isonicotinic acids. Further studies to develop NO releasers, including those involving covalent linkage sites as isonicotinic/nicotinic derivatives for potential application as photochemical drugs, can rely on the findings in the ultrafast study of [RuNOCl5]2- dynamics as involvement of the triplet states rather than linkage isomers. Further, molecular properties of compounds related to the perovskite-based photovoltaic were computationally investigated. The electron-rich series of [I3]-, [TeI4]2-, and [BiI6]3- compounds were discussed in detail with a focus on three-center four-electron bond, which plays an important role in the compounds containing heavy-atoms. Excited-state relaxation dynamics in a polyhalogenated compound (CH2BrI) were investigated by means of computational dynamics on the earliest timescale of 100 fs following excitation of this molecule into two electronic states of spectroscopic interest. The computed pump probe spectra yield the time occurrence and spectral position of the absorption and stimulated emission transitions of the involved product states. The results are instrument (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Chemistry

Energy demands from increasing population are expected to double by 2050 and more than triple by the end of 2100. The urgent need for renewable and carbon-free energy sources demands scientists to pursue alternative ways to replace petroleum, coal, and natural gas as energy sources. Solar fuels have the potential to serve as an outstanding source of energy, since the energy from sunlight that reaches the Earth every hour is 173,000 terawatts. One key factor required to utilize solar fuels is to increase the ability of the light-harvesting process and the chemical bond-forming reactivity of photocatalysts. This dissertation demonstrates the design and characterization of dirhodium Rh2(II,II) complexes for photocatalysis with red light and the effect of ligand modification on the electronic structure and steric hindrance on the systems, as well as their ability for solar energy storage through the production of hydrogen, a clean fuel. In Chapter 4, a series of three dirhodium complexes with varying electron donating abilities of the formamidinate ligands were synthesized with general formula cis–[Rh2(DPhB)2(bncn)2](BF4)2 (DPhB = diphenyl-formamidinate, bncn = benzo[c]cinnoline). These complexes were found to act as single-molecule photocatalysts for H2 production in the presence of 0.1 M p-toluenesulfonic acid and the sacrificial electron donor BNAH (1-benzyl-1,4-dihydronicotinamide). The most efficient catalyst in this series is able to achieve turnover numbers (TONs) up to 250 upon 24 h irradiation with red light. The one-component catalytic system does not require any other catalyst, electron relay, or light absorber. Upon excitation, these complexes are able to store two electrons on each molecule after two stepwise reductive quenching steps by BNAH and provide protonation sites for the catalysis to generate H2 to proceed. These properties are essential for the complexes to act as single-molecule photocatalysts. The substitution of the bridging ligands affects (open full item for complete abstract)