Doctor of Philosophy, The Ohio State University, 2020, Physics

This work uses computer simulations to investigate intense laser-plasma interactions. First, we use two-dimensional particle-in-cell (PIC) simulations and simple analytic models to investigate the laser-plasma interaction known as ponderomotive steepening. When normally incident laser light reflects at the critical surface of a plasma, the resulting standing electromagnetic wave modifies the electron density profile via the ponderomotive force, which creates peaks in the electron density separated by approximately half of the laser wavelength. What is less well studied is how this charge imbalance accelerates ions towards the electron density peaks, modifying the ion density profile of the plasma. Idealized PIC simulations with an extended underdense plasma shelf are used to isolate the dynamics of ion density peak growth for a 42 fs pulse from an 800 nm laser with an intensity of 1018 W cm-2. These simulations exhibit sustained longitudinal electric fields of 200 GV m-1, which produce counter-steaming populations of ions reaching a few keV in energy. We compare these simulations to theoretical models, and we explore how ion energy depends on factors such as the plasma density and the laser wavelength, pulse duration, and intensity. We also provide relations for the strength of longitudinal electric fields and an approximate timescale for the density peaks to develop. These conclusions may be useful for investigating the phenomenon of ponderomotive steepening as advances in laser technology allow shorter and more intense pulses to be produced at various wavelengths. We also discuss the parallels with other work studying the interference from two counter-propagating laser pulses. Next we investigate the development of ultra-intense laser-based sources of high energy ions, which is an important goal, with a variety of potential applications. One of the barriers to achieving this goal is the need to maximize the conversion efficiency from laser energy to ion energy (open full item for complete abstract)

Committee: Chris Orban PhD (Advisor); Enam Chowdhury PhD (Committee Member); Douglass Schumacher PhD (Committee Member); Richard Furnstahl PhD (Committee Member) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2018, Electrical and Computer Engineering

This thesis presents theoretical and experimental investigation of wider bandgap AlGaN channels to achieve superior gain linearity and output power density in III-Nitride transistors. GaN high electron mobility transistors (HEMTs) exhibit high saturation velocity and large breakdown field, resulting in unprecedented power densities at microwave frequencies. However, their cutoff frequency and gain reduce significantly as the gate bias or current density increase, causing non-linear behavior and soft gain compression at peak efficiencies. This phenomenon is shown to be related to the sheet density dependence of velocity in HEMTs. Velocity-field measurements are carried out on unique test structures as a function of sheet charge density, which revealed strong density dependence of saturation velocity. To realize constant velocity profile as a function of gate bias, polarization graded field-effect transistors (PolFETs) with engineered charge and capacitance profiles are discussed. Constant cutoff frequency and maximum oscillation frequency over wide gate-bias and output current range are achieved in highly-scaled PolFETs, indicative of enhanced gain linearity. AlN with extremely large bandgap of 6.2 eV can withstand significantly higher breakdown field than GaN channels, which could enable higher voltage, as well as higher charge density for the same device dimensions. To realize superior breakdown voltage and current density, AlGaN channels with high Al-content are investigated. Theoretical calculation of the low-field electron mobility in AlGaN channel HEMTs, as well as its implication on the high-field transport are discussed. A major limiting factor in the development of AlGaN channel transistors, thus far, has been high-resistance ohmic contacts. Contact layers with compositional grading (i.e. electron affinity grading) are shown to mitigate this issue significantly. Specific contact resistance of 2x10-6 ohm.cm2, and average lateral breakdown field of 2 MV/cm a (open full item for complete abstract)

Committee: Siddharth Rajan (Advisor); Wu Lu (Committee Member); Aaron Arehart (Committee Member); Ayman Fayed (Committee Member) Subjects: Electrical Engineering; Solid State Physics

Doctor of Philosophy, The Ohio State University, 2016, Physics

Over the past two decades, a number of experiments have been performed demonstrating the acceleration of ions from the interaction of an intense laser pulse with a thin, solid density target. These ions are accelerated by quasi-static electric fields generated by energetic electrons produced at the front of the target, resulting in ion energies up to tens of MeV. These ions have been widely studied for a variety of potential applications ranging from treatment of cancer to the production of neutrons for advanced radiography techniques. However, realization of these applications will require further optimization of the maximum energy, spectrum, or species of the accelerated ions, which has been a primary focus of research to date. This thesis presents two experiments designed to optimize several characteristics of the accelerated ion beam. The first of these experiments took place on the GHOST laser system at the University of Texas at Austin, and was designed to demonstrate reliable acceleration of deuterium ions, as needed for the most efficient methods of neutron generation from accelerated ions. This experiment leveraged cryogenically cooled targets coated in D2O ice to suppress the protons which typically dominate the accelerated ions, producing as many as 2 x 10^10 deuterium ions per 1 J laser shot, exceeding the proton yield by an average ratio of 5:1. The second major experiment in this work was performed on the Scarlet laser system at The Ohio State University, and studied the accelerated ion energy, yield, and spatial distribution as a function of the target thickness. In principle, the peak energy increases with decreasing target thickness, with the thinnest targets accessing additional acceleration mechanisms which provide favorable scaling with the laser intensity. However, laser prepulse characteristics provide a lower bound for the target thickness, yielding an optimum target thickness for ion acceleration which is dependent on the las (open full item for complete abstract)

Committee: Linn Van Woerkom (Advisor); Robert Perry (Committee Member); Richard Furnstahl (Committee Member); Gregory Lafyatis (Committee Member) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2016, Physics

Here I present an experimental, theoretical, and computational exploration of an extremely efficient scheme for laser-based acceleration of electrons. A series of experiments were performed at the Air Force Research Laboratory in Dayton, OH, to show that a high-repetition-rate short-pulse laser (3 mJ, 40 fs, 1 kHz) normally incident on a continuous water stream can accelerate electrons in the back-reflection spray with >1% laser-to-electron efficiency for electrons >120 keV, and with >MeV electron energies present in large number. Characterization of the accelerated electrons was followed by explorations of appropriate focal conditions, pre-plasma conditions, and laser-intensity parameters. These experiments show clear signatures of plasma instabilities, with substantial 3ω/2 and ω/2 optical harmonics detected concurrently with efficient electron acceleration. Particle-in-cell (PIC) simulations of high-intensity laser interactions are able to reproduce the electron energies and acceleration efficiencies, as well as plasma instabilities. Analysis of the simulations suggest that electrons are accelerated by a standing wave established between incident and reflected light, coupled with direct laser acceleration by reflected light. Using hydrodynamic simulations of the laser pre-pulse interaction as initial conditions for PIC simulations of the main-pulse interaction clarifies mechanisms by which experimental manipulation of pre-pulse has effectively determined electron-acceleration efficiency in the laboratory.

Committee: Richard R. Freeman (Advisor); Linn D. Van Woerkom (Committee Member); Junko Shigemitsu (Committee Member); Michael Lisa (Committee Member) Subjects: Physics

MS, University of Cincinnati, 2011, Engineering and Applied Science: Mechanical Engineering

High density polyethylene (HDPE) is a common polymer material that is widely used in industrial applications. While significant amount of efforts have been devoted to understanding the constitutive behavior of HDPE, very little work has been performed to investigate the material response of HDPE at high strain rate and high temperature. The main objective of this research is to develop a constitutive model to bridge this gap by focusing on the non-linear stress-strain behavior in the high strain rate and high temperature range. A series of monotonic uniaxial compressive tests have been conducted at high temperature (100°C) and high strain rate (1/s) to characterize the HDPE behavior. Based on the experimental results, existing hyperelastic material models such as Mooney-Rivlin, Ogden, Arruda-Boyce, are assessed with the use of ABAQUS (a finite element software). Based on extensive comparisons, a new three-dimensional constitutive model for HDPE has been proposed. The constitutive equation integrates the basic mechanisms proposed by Boyce et al. [6] and Shepherd et al. [8]. The total stress is decomposed into an elastic-viscoplastic representation of the intermolecular resistance acting in parallel with a time and temperature dependent network resistance of polymer chains. Material constants involved in the model were calculated by fitting the compressive test results to the proposed constitutive equations. A constitutive solver for the proposed model has been developed. The stress-strain relation resolved from the constitutive model closely matches the corresponding ones from the experiments.

Committee: Dong Qian PhD (Committee Chair); Shepherd Shepherd PhD (Committee Member); Yijun Liu PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, University of Akron, 2024, Polymer Engineering

In this work, High Density Polyethylene (HDPE) composites were made using Torrefied Soybean Hulls (TSBH) and Carbon Black (CB) to study the interactions affiliated with the TSBH content for as-received as well as size-reduced particles. The Milled TSBH (MTSBH) was shown to integrate well at low loadings, but showed signs of favoring filler-filler interactions over filler-matrix interactions, reducing the overall effectiveness as the loadings increased. Rheological testing showed that the higher-loaded MTSBH composites behaved similar to composites with larger particles as the loading increased, indicating that clusters had formed. Unmilled TSBH (UTSBH) showed good mechanical strength, but the particle size was shown to limit its ability to integrate into the material, even at low loadings. The addition of CB was shown to have the most impact on the low loading MTSBH composites, where the MTSBH-CB interactions were shown to influence the filler network in electrical resistance testing where a nonlinear trend was observed in the composite resistivity with the addition of MTSBH. In UTSBH composites, there were less signs of CB-UTSBH interactions due to the relatively large particle size. To contrast the hydrophilic matrix behavior of HDPE, Nylon-6 (PA6) was used as a matrix for the TSBH composites. In cases where either TSBH filler was used, the composite performance was shown to improve to a greater degree than in the case of HDPE due to the hydrophilic groups contained in the PA6 backbone. Similar to the HDPE composites, the TSBH particles showed a lack of effectiveness at higher filler loadings, though MTSBH showed more effective integration which indicates that this is a result of particle size. The CB and MTSBH showed synergistic effects with high CB and low MTSBH loading during cyclic tension testing, where the increase in strain energy density required for a test was less when the CB was present that when it was not. This effect was seen throughout the mono (open full item for complete abstract)

Committee: Erol Sancaktar (Advisor); Kevin Cavicchi (Committee Chair); Wieslaw Binienda (Committee Member); Steven Chuang (Committee Member); James Eagan (Committee Member) Subjects: Chemical Engineering; Materials Science; Mechanics; Plastics

Master of Science, The Ohio State University, 2023, Welding Engineering

High energy density welds have complex weld geometries due to the deep penetrations and low heat input associated with these processes, making it viable for many applications (aerospace, medical, defense, etc.). These complex geometries lead to difficulties in characterizing the transition between the conduction and keyhole weld mode geometries for this welding process. An ytterbium doped fiber laser with a beam diameter of 0.6 mm was used to make partial penetration autogenous weld on the nickel-based alloy, Inconel 690. Laser powers ranged from 600W – 2800W and travel speeds ranged from 5 mm/s – 150 mm/s to analyze characterization techniques of the weld's formation through conduction to keyhole mode. Six characterization techniques were attempted, with the final technique having two methods compared. First, the depth-to-width measurement were analyzed for a sudden increase as the power increased for welds made at the same travel speed. Evidence for a shift in depth-to-width ratios as the weld geometries transition were seen. A change in convexity of the weld pool measurements using ImageJ software proved a viable method for characterizing the weld mode. Uniformity was seen along the weld root's penetration was seen for longitudinal cross-sections for keyhole and conduction mode weld geometries. Weld roots within the transition of these modes showed nonuniform weld root penetrations. Inline Coherent Imaging was used to see if any notable changes of the weld's formation through the keyhole profile. Finally, analysis of the solidification rate and subsequent solidification parameters was done using a traced solid liquid interface and cell spacing measurements. These results were inconclusive as a current method of characterization, but solidification rate values were compared to those measured through cellular grain growth analysis. Cellular grain growth analysis showed that both plan and longitudinal weld cross-sections are needed when analyzing the solidifica (open full item for complete abstract)

Committee: Carolin Fink (Advisor); Boyd Panton (Advisor); Wei Zhang (Committee Member) Subjects: Engineering; Materials Science

Master of Science (MS), Ohio University, 2023, Mechanical Engineering (Engineering and Technology)

Bituminous coal was utilized as a particulate filler in polymer-based composites to fabricate standard 1.75 mm coal-plastic composite filaments for use in commercially available fused deposition modeling 3D printers. The composites were formulated by incorporating Pittsburgh No. 8 coal into polylactic acid, polyethylene terephthalate glycol, high-density polyethylene, and polyamide-12 resins with loadings ranging from 20 wt.% to 70 wt.%. CPC filaments were extruded and printed using the same processing parameters as the respective neat plastics. All coal-plastic composite filaments exhibited uniform particle dispersion throughout the microstructure. The mechanical properties of the 3D printed composites were characterized and compared to composites fabricated using traditional compression molding. Tensile and flexural moduli as well as hardness had direct proportionality with increasing coal content while flexural strength, tensile strength, and impact resistance decreased for most composite formulations. Interestingly, polyamide-based composites demonstrated greater maximum tensile and flexural strengths than unfilled plastic. Microscopy of as-fractured samples revealed that particle pull-out and particle fracture were the predominant modes of composite failure. The introduction of coal reduced the coefficient of thermal expansion of the composites, ameliorating the warping problem of 3D printed high-density polyethylene and allowing for additive manufacturing of an inexpensive and widely available thermoplastic. The high-density polyethylene composites demonstrated increased heat deflection temperatures, but all composites maintained comparable glass and metal transition temperatures, allowing them to be processed with commercial 3D printer extruders. The composites exhibited decreased specific heat capacities suggesting lower energy requirements for processing the material. Coal reduced the composite thermal conductivities compared to the neat plastics but improv (open full item for complete abstract)

Committee: Jason Trembly (Advisor); Yahya Al-Majali (Committee Member); Brian Wisner (Committee Member); David Drabold (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering; Sustainability

Doctor of Philosophy (PhD), Wright State University, 2023, Engineering PhD

Blood flow dynamics plays a critical role in maintaining tissue health, as it delivers nutrients and oxygen while removing waste products. It is especially important when there is a disruption in cerebral autoregulation due to trauma, which can induce ischemia or hyperemia and can lead to secondary brain injury. Thus, there is a need for noninvasive techniques that can allow continuous monitoring of blood flow during intervention. Optical techniques have become increasingly practical for measuring blood flow due to their non-invasive, continuous, and relatively lower-cost nature. This research focused on developing a low-cost, scalable optical technique for measuring blood flow by implementing speckle contrast optical spectroscopy using a fiber-camera-based approach. This technique is particularly well-suited for measuring blood flow in deep tissues, such as the brain, which is challenging to access using traditional optical methods. A two-channel continuous wave speckle contrast optical spectroscopy device was developed, and the device was rigorously tested using phantoms. Then, it is applied to monitor blood flow changes in the brain following traumatic brain injury (TBI) in mice. The results indicate that trauma-induced significant blood flow decreases consistent with the recent literature. Overall, this approach provides noninvasive continuous measurements of blood flow in preclinical models such as traumatic brain injury.

Committee: Ulas Sunar Ph.D. (Advisor); Tarun Goswami Ph.D. (Committee Member); Keiichiro Susuki Ph.D. (Committee Member); Robert Lober M.D., Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Biophysics; Engineering; Optics

Doctor of Philosophy, Case Western Reserve University, 2022, Molecular Medicine

Cardiovascular disease (CVD) is the leading cause of death worldwide. Traditional risk factors of CVD fail to elucidate the significantly increased CVD risk observed in patients with renal disease. Non-traditional risk factors are thought to contribute to this unexplained risk, through the action of lipoproteins. Historically the lipoprotein high- density lipoprotein (HDL) has been found to be cardio protective through reverse cholesterol transport in epidemiological studies. HDL is a heterogeneous particle comprised of a variety of constituents, the major constituent being apolipoproteinA-I (apoA-I). Post-translational modifications, including but not limited to carbamylation, chlorination, nitration and glycosylation, will render HDL dysfunctional. Evidence suggests that through a process known as protein carbamylation of apoA-I, the particle no longer functions in a cardio protective role but becomes pro-atherogenic. Protein carbamylation occurs through two different pathways. The first is a chemical reaction, which results in response to substantially increased levels of urea observed in chronic and ESRD. The second enzymatic reaction occurs during leukocyte activation of myeloperoxidase (MPO, at sites of inflammation. This process results in the addition of a “carbamoyl” moiety to amines of proteins and amino acids. Studies have been performed analyzing (carbamylated HDL) c-HDL function but have not identified the relationship of site-specific carbamylation of apoA-I/ HDL within human atheroma. As declining kidney function potentially alters the structure and function of c-HDL, the effect of carbamylation becomes increasingly relevant in understanding the pathophysiology of CVD progression. Our goal is to expand our understanding of HDL structurally and clinically through uncovering the site-specific protein carbamylation patterns. We hypothesized that insights into the chemical environment within the human artery wall could be gained by monitoring site-specif (open full item for complete abstract)

Committee: Stanley Hazen (Advisor) Subjects: Biomedical Research

Doctor of Philosophy, The Ohio State University, 2021, Materials Science and Engineering

Crystal plasticity modeling was used to understand the deformation process of FCC metals and alloys. Firstly, we investigated the issue of cube texture development during static recrystallization of FCC metals, which has been vigorously debated over the last 70 years. A Full-field elasto-viscoplastic fast-Fourier transform (EVP-FFT)based crystal plasticity solver coupled with dislocation density based constitutive model was employed to understand the deformation process in copper under plane strain compression. Simulation results revealed that the grains with initially cube orientation retained a small fraction of the cube component in the deformed state, whereas, some of the grains with initially non-cube orientations developed the cube component during the deformation. For strain up to 0.46, non-cube grains which are within 10-20 deg from the ideal cube orientation showed the highest affinity to develop the cube component during deformation. However, the cube component developed during the deformation was unstable and rotated away from the cube orientation with further deformation. With increasing strain up to 1.38, some of the grains with higher angular deviation from the ideal cube orientation also developed the cube component. No particular axis preference was observed for the non-cube grains, rather, the evolution of the cube component becomes dynamic at larger strain. Rotation of the non-cube grains towards the cube component is mainly driven by the local relaxation of the imposed boundary conditions. Significant changes in lattice rotation and slip activity were observed with different relaxed constraints. Best correlation was found for the e13 strain component and the development of cube component. Analysis of the disorientation angle and the dislocation density difference with the neighboring locations showed that the cube component developed during the deformation can play a significant role during nucleation. (open full item for complete abstract)

Committee: Stephen Niezgoda (Advisor); Michael Mills (Committee Member); Yunzhi Wang (Committee Member) Subjects: Materials Science; Mechanics; Metallurgy

Master of Science, The Ohio State University, 2021, Earth Sciences

Brittle fragmentation is a common rock failure process near Earth's surface and occurs at strain rates ranging from tectonic to shock. At the scale of fault damage zones, brittle damage by tensile fragmentation during earthquake rupture introduces intense fracturing and secondary porosity, altering both the mechanical constitutive behavior and permeability of the damage zone rocks. Modeling and experiments suggest that there exists a relationship between fragment size and strain rate above a given strain rate threshold, yet the factors that control this threshold are not fully understood. Factors that are thought to influence the relationship between strain rate and fragmentation include (i) differences in applied stress state (e.g., tension vs. compression), and (ii) material properties (e.g., crystalline vs. granular rocks, variations in mineralogy, or preexisting damage). In this study a modified sample configuration for a Split Hopkinson Pressure Bar is used to investigate tensile fragmentation in comparison to deformation formed by traditional uniaxial compression experiments. This study begins with an analysis of the influence of lithology on brittle fragmentation under dynamic tensile loading. Four rock types are compared, including diabase, granite (Westerly Granite), welded tuff, and sandstone (Berea Sandstone). Over the range of strain rates tested, diabase and granite have the greatest rate of increase in tensile strength with strain rate. The strain rate and tensile strength measurements performed in this study are combined with results in the literature to develop an empirical equation for rock strength as a function of strain rate that follows a sigmoidal trend. This empirical relationship is then used to predict fault damage zone widths by comparing the dynamic tensile strength to the tensile stress decay predicted by the analytical model for dynamic mode-II rupture. The second section of this study focuses on the influence of preexisting macroscopi (open full item for complete abstract)

Committee: William Griffith (Advisor); Joachim Moortgat (Committee Member); Derek Sawyer (Committee Member) Subjects: Earth; Geology; Geophysics

Doctor of Philosophy, The Ohio State University, 2021, Materials Science and Engineering

From long-hauling vehicles operating in marine environments to reusable rockets aiming to take civilization beyond earth, from oil and gas pipelines transporting fossil fuels to offshore wind turbines and solar panels generating renewable energy, from chemical refinery operations to long-term storage of nuclear waste in underground cannisters, corrosion is one of the common denominators that play a critical role in the operational safety and performance limitations of the respective industries. Practicing corrosion control to minimize material degradation to within a desired safety threshold and a well-understood controllable margin that can be readily managed relies on mechanistic understanding of the science behind corrosion and the application of that scientific understanding to engineer solutions. Through decades of experimental investigations, empirical knowledge has accumulated, corrosion mechanisms proposed, and mitigation strategies practiced by the corrosion scientists and engineers. In the era of Integrated Computational Materials Engineering, the emergence of the first principles approach, as formulated in the density functional theory, provides an atomic level “virtual microscope” for probing corrosion mechanisms that occur at the interfaces that terminate materials and initiate interactions with environment. Applying DFT to investigate corrosion science presents unique challenges and opportunities. A multi-physics framework must be developed to systematically address these challenges. The frameworks proposed in this thesis require the electronic work functions and the species adsorption energies as inputs, which are readily computable in the state-of-the-art DFT code. The purpose of the framework is to bridge the electrochemical properties of alloys at the interface to the macroscale observable parameters measured in a laboratory setting. Two classes of alloys will serve as the framework testing ground: precipitation hardened aluminum alloys; and Ni (open full item for complete abstract)

Committee: Christopher Taylor (Advisor); Gerald Frankel (Advisor); Narasi Sridhar (Committee Member) Subjects: Chemistry; Condensed Matter Physics; Materials Science

Doctor of Philosophy, Case Western Reserve University, 2020, Molecular Medicine

Objective: Prostate cancer is the second leading cause of cancer-related deaths among men in the US. Although some reports show high concentrations of HDL cholesterol increase risk for prostate cancer, this association has not been consistent. High density lipoprotein (HDL) metabolism, is facilitated largely by scavenger receptor class B, type 1 (SR-B1) that mediates its uptake into cells, and ABCA1 that mediates its generation. SR-B1 is upregulated in prostate cancer tissue, whereas some evidence suggests that ABCA1 is downregulated in the disease. Our efforts were to determine if SR-B1-dependent HDL uptake and/or HDL biogenesis by ABCA1 export of lipids to apoA1 promotes prostate cancer cell proliferation and disease progression. Hypothesis: HDL uptake by SR-B1 drives prostate cancer proliferation and disease progression, whereas ABCA1 mediated lipid efflux decreases prostate cancer proliferation and disease progression (Fig. Abstract) Methods and Results: Here, we report that knockout (KO) of SR-B1 via CRISPR/Cas9 editing led to reduced HDL uptake into prostate cancer cells, and reduced their proliferation in response to HDL. In vivo studies using syngeneic SR-B1 wildtype (SRB1+/+) and SR-B1 KO (SR-B1-/-) prostate cancer cells in WT and apolipoprotein-AI KO (apoA1-KO) C57BL/6J mice showed that WT hosts, containing higher levels of total and HDL-cholesterol, grew larger tumors than apoA1-KO hosts with lower levels of total and HDL-cholesterol. Furthermore, SR-B1-/- prostate cancer cells formed smaller tumors in WT hosts, than SR-B1+/+ cells in same host model. Tumor volume data was overall consistent survival data. Conclusion: The results suggest that HDL through tumoral SR-B1 significantly influences the proliferation of prostate cancer cells and is a driver of the disease. Further investigation is needed to conclusively determine how HDL metabolism by ABCA1 influences prostate cancer cells and its impact on disease progression.

Committee: Jonathan Smith PhD (Advisor); Angela Ting PhD (Committee Chair); W.H. Wilson Tang MD (Committee Member); J. Mark Brown PhD (Committee Member); Nima Sharifi MD (Committee Member) Subjects: Cellular Biology; Medicine; Molecular Biology; Oncology

Doctor of Philosophy, Case Western Reserve University, 2020, Geological Sciences

Silicate and carbonate melts in the Earth's mantle play a crucial role in the chemical differentiation and heat transfer of the planet, and are largely responsible for the mantle heterogeneities observed geochemically and geophysically. In order to better model mantle melting, magma differentiation and solidification, and to understand the stability, transport of mantle melts and their effects on seismic observations, the knowledge of the physical properties (e.g., sound velocity, density) and equation of state (EOS) of melts are essential. However, the sound velocity and density of melts relevant to mantle processes are still poorly constrained due to experimental challenges to measure these properties of melts at extreme conditions. In this dissertation, I have studied the EOS of silicate and carbonate melts at high pressure and temperature conditions, with a focus on Mg, Fe and Na-rich silicate melts as well as pure carbonate melts, by developing new techniques for high-pressure sound velocity and density measurements on melts, including the in-situ ultrasonic technique and high-pressure X-ray microtomography. Various high-pressure cell designs combined with synchrotron techniques allow us to obtain the first high-pressure sound velocity dataset for silicate melts in the diopside (CaMgSi2O6)-hedenbergite (CaFeSi2O6) join (Chapters II and IV), and for carbonate melts in the MgCO3-CaCO3 join (Chapter VI). The differences of the elastic properties between silicate glasses and their corresponding liquids are revealed (Chapter III). New high-pressure density data using X-ray microtomographic reconstruction for sodium-rich jadeite melt are also reported (Chapter V). The results of these studies have significant implications for several geophysical problems, including the stability and possible density crossover of melts in the Earth's mantle, the origin of the seismic low-velocity regions in the mantle, the solidification of early magma oceans, and the fate of subducte (open full item for complete abstract)

Committee: Zhicheng Jing (Advisor); James Van Orman (Advisor); Steven Hauck II (Committee Member); Ralph Harvey (Committee Member); Daniel Lacks (Committee Member) Subjects: Earth; Geology; Geophysics; Mineralogy; Petrology

Master of Science in Biomedical Engineering (MSBME), Wright State University, 2019, Biomedical Engineering

Neurovascular coupling is an important concept that indicates the direct link between neuronal electrical firing with the vascular hemodynamic changes. Functional Near Infrared Spectroscopy (fNIRS) can measure changes in cerebral vascular parameters of oxy-hemoglobin and deoxyhemoglobin concentrations and thus can provide neuronal activity through neurovascular coupling. Currently many commercial fNIRS devices are available, but they are limited by the number of channels (usually having only 8 detectors), which can limit the sensitivity, contrast, and resolution of imaging. High-density imaging can improve sensitivity, contrast, and resolution by providing many measurements and averaging the signals originating from the target cerebral focus area compared to background tissue. Here a multi-channel, low-cost, high-density imaging system based on scientific CMOS (Complementary Metal-Oxide-Semiconductor) detector will be presented. The CMOS camera is fiber-coupled such that on one end fibers are focused on the pixels on the CMOS camera, which allows individual pixels (or binned sub-pixels) to act as detectors, while the other end of the fibers can be positioned on a wearable optical probe. After the device details, I will show the device validation using a series of the dynamic flow phantom experiments mimicking the brain activation and finally human motor cortex experiments (finger tapping experiments). The results demonstrate that this system can obtain high-density data sets with higher contrast and resolution. This wearable, high-density optical neuroimaging technology is expected to find many applications including pediatric neuroimaging at clinics and assessing human cognitive performance.

Committee: Ulas Sunar Ph.D. (Advisor); Keiichiro Susuki Ph.D. (Committee Member); Tarun Goswami Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Engineering; Optics

PhD, University of Cincinnati, 2018, Medicine: Pathobiology and Molecular Medicine

Background: Atherosclerosis is a multifactorial inflammatory disease that begins with the accumulation of lipid in arterial endothelium. Atherosclerosis is the leading cause of deaths attributable to cardiovascular disease in the United States. Epidemiological studies showing high-density lipoprotein (HDL) cholesterol is inversely correlated with atherosclerosis has made it a pharmacological target for preventing cardiovascular disease. However, outcomes from clinical trials have raised questions about HDL's protective properties. Investigating the molecular interactions of apolipoprotein (apo)A-I, which accounts for approximately 70% of total HDL protein, can help translate HDL structure to cardioprotective function. Lecithin: cholesterol acyl transferase (LCAT) is a critical HDL-modifying protein that performs a key function in reverse cholesterol transport by using apoA-I as a cofactor to esterify cholesterol. Data from our lab and others demonstrate that apoA-I molecules dimerize into an antiparallel stacked ring-structure that encapsulates lipid in reconstituted (r)HDL. Cross-linking analysis of rHDL implies that apoA-I molecules exist in at least two distinct organizations: one with helix 5 of an apoA-I molecule adjacent to helix 5 of its antiparallel partner (5/5 helical registry), and the other in a 5/2 registry. We hypothesized that the orientation of apoA-I molecules on rHDL modulates LCAT activity. Objective: Identify the mechanism by which apoA-I activates LCAT to determine how HDL interacts with its immense proteome. Linking HDL structure and function will allow for therapeutic development that targets HDL-associated inflammatory diseases. Major Findings: 1) Antiparallel apoA-I molecules adopt a thumbwheel mechanism to generate a discontinuous epitope for LCAT activation. Site-directed cysteine mutagenesis was used to “lock” two apoA-I molecules into an antiparallel 5/5, 5/2, and 5/1 helical registry on rHDL. The 5/5 mutant demonstrated higher LCAT acti (open full item for complete abstract)

Committee: William Sean Davidson Ph.D. (Committee Chair); Christopher A. Crutchfield Ph.D. (Committee Member); Philip Howles Ph.D. (Committee Member); Francis McCormack M.D. (Committee Member); Thomas Thompson Ph.D. (Committee Member); Laura Woollett Ph.D. (Committee Member) Subjects: Pathology

Doctor of Philosophy, The Ohio State University, 2018, Plant Pathology

Phytophthora sojae is the causal agent of Phytophthora root and stem rot of soybean. One of the most effective disease management strategies against this pathogen is the use of resistant cultivars, primarily through single gene, Rps-mediated resistance. However, numerous populations of P. sojae have adapted to most Rps genes that are deployed in modern soybean cultivars, rendering them susceptible to this pathogen. Quantitative resistance, conferred by quantitative disease resistance loci (QDRL), offers an alternative to Rps-based resistance. Previous studies mapped two QDRL to chromosome 19 in the soybean cultivar Conrad, which has a high level of quantitative resistance. A recombinant inbred line (RIL) population derived from a cross of Conrad by Sloan (a moderately susceptible cultivar) used for mapping these QDRL was advanced to the F9:11 generation. This population was used to map/re-map the QDRL towards three isolates of P. sojae, and one isolate each of Pythium irregulare and Fusarium graminearum, using the SoySNP6K BeadChip for high-density marker genotyping. A total of ten, two, and three QDRL and suggestive QDRL were found that confer resistance to P. sojae, Py. irregulare, and F. graminearum, respectively. Individual QDRL explained 2-13.6% of the phenotypic variance (PV). One QDRL for both Py. irregulare and F. graminearum co-localized on chromosome 19. This resistance was contributed by Sloan and was juxtaposed to a QDRL for P. sojae with resistance contributed from Conrad. Alleles for resistance to different pathogens contributed from different parents in the same region, the number of unique QDRL for each pathogen, and the lack of correlation of resistance suggest that different mechanisms are involved in resistance towards these three pathogens. Interestingly, the QDRL located on chromosome 19 contained several genes related to auxin processes, which are known to contribute to susceptibility to several pathogens in Arabidopsis and may contribute to su (open full item for complete abstract)

Committee: Anne Dorrance Ph.D. (Advisor); Joshua Blakeslee Ph.D. (Committee Member); Leah McHale Ph.D. (Committee Member); Christopher Taylor Ph.D. (Committee Member); Feng Qu Ph.D. (Committee Member) Subjects: Plant Pathology

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

I present computational simulations of the efficient production of relativistic electron beams from the interaction of an intense, short-pulse laser normally incident on a solid density target in which electrons are accelerated backwards, or counter to the laser incidence direction. This effect, called the standing wave effect, was discovered in an experiment at the Air Force Research Laboratory (AFRL), Dayton OH, with such a laser (780nm wavelength, 1018 W/cm2 intensity, 40 femtosecond pulse) that observed the laser acceleration of backwards directed beams of electrons to MeV energies, an energy exceeding the energy scale for this laser intensity known as the ponderomotive scale. Moreover, this acceleration was observed to have a high laser-to-electron beam energy conversion ratio exceeding one percent (1%) for super-ponderomotive energies. These aspects make this effect attractive as a laser-based electron acceleration scheme. Understanding the laser and plasma physics behind the effect is interesting from a fundamental research perspective; evaluating its effectiveness at other intensity regimes or other target configurations is important to those who seek to employ the effect in electron beam applications, those who study the theory of laser and plasma physics, and for those who perform experiments in regimes where this effect may be of relevance. In this work I present a set of simulations with the Large Scale Plasma code, a Particle-in-Cell code that is apt to model such ultraintense laser interactions, to pursue this end of illuminating the relevant physics of this mechanism. I present the first fully three-dimensional (3D) simulations of the standing wave effect in order to further validate two-dimensional (2D(3v)) simulations performed by the AFRL group, finding that while some characteristics of the accelerated beam differ, the peak electron energy and total energies of beams produced in 2D(3v) are comparable with 3D simulations. After this, I present a (open full item for complete abstract)

Committee: Christopher Orban Prof. (Advisor); Enam Chowdhury Prof. (Committee Member); Schumacher Douglass Prof. (Committee Member); Furnstahl Richard Prof. (Committee Member) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2017, Nuclear Engineering

Pyroprocessing is an electrochemical method that is capable of separating uranium (U) and minor actinides from LiCl-KCl eutectic salt where used nuclear fuel (UNF) is dissolved. During the process, fission products including rare earth metals (RE) continually accumulate in the salt and eventually affecting uranium recovery efficiency. To reduce the salt waste after uranium and minor actinides recovery, electrolysis is performed to drawdown rare earth materials from molten salt to restore salt initial state. Present research focus on the development of RE fundamental physical properties in LiCl-KCl eutectic salt. These properties includes apparent potential, activity coefficient, diffusion coefficient and exchange current density. Additional properties including charge transfer coefficient and reaction rate constant are calculated during the analysis. La, Nd and Gd are three RE that we are particularly interested in due to the high ratio of these elements in UNF (La, Nd), the well-studied properties in dilute solution to provide a base for comparison, and the highest standard potential among all RE (Gd). Fundamental properties of La, Nd, Gd in LiCl-KCl eutectic salt are studied at a temperature ranging from 723 K to 823 K and RE concentration ranging from 1 wt% to 9 wt%. These properties are studied by electroanalytical methods including Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Tafel method, Chronocoulummetry (CC) and Chronopoentiometry (CP). BET model that considers the RE adsorption on the electrode is developed for diffusion coefficient analysis. Electrode kinetic model is developed to account for mass transfer effect during the analysis of exchange current density. Correlations of diffusion coefficient, apparent potential, exchange current density with temperature and concentration are developed. These fundamental data are integrated with a electrolysis model to predict the electrolysis process for RE drawdown from LiCl-KCl sa (open full item for complete abstract)

Committee: Jinsuo Zhang (Committee Chair); Marat Khafizov (Advisor); Lei Cao (Committee Member); Longya Xu (Committee Member) Subjects: Chemistry; Nuclear Engineering