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

Here we present investigations on the structure and mechanics of molecular force sensors and DNA nanodevices using a combination of computational and experimental approaches. This work implements a range of methods from all-atom and coarse-grained molecular dynamics to cryogenic and transmission electron microscopy. All-atom molecular dynamics simulations were employed to characterize the mechanical properties of peptide-based and DNA-based molecular force sensors. The simulations revealed that the stiffness of peptide-based sensors, derived from spider silk or synthetic peptides, is consistent with theoretical predictions and experimental measurements. However, the formation of transient secondary structures in spider silk-based sensors and overstretching in DNA-based sensors can influence their elastic responses, highlighting the importance of considering these factors in sensor design. The research also explored the use of DNA origami nanostructures for delivering gene templates for homology-directed repair (HDR) in human cells. Coarse-grained simulations (oxDNA) guided the design of DNA nanostructures, and experiments demonstrated their efficacy in enhancing HDR efficiency compared to unstructured DNA, particularly when delivered using Cas9 virus-like particles (VLPs). This finding suggests the potential of DNA nanostructures for targeted gene delivery and genome editing applications. Furthermore, the dissertation explored the development of DNA-origami-protein hybrid devices for cryogenic electron microscopy characterization of protein interactions and force spectroscopy applications. Preliminary data demonstrated the feasibility of integrating peptide-based force sensors into DNA nanostructures, which is a step toward enabling the real-time measurement of mechanical forces applied to proteins. These hybrid devices hold promise for studying protein mechanics, folding, and interactions at the nanoscale, with potential applications in biomedical research, for (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2024, Industrial and Systems Engineering

This dissertation addresses two applied problems relating to images. The first relates to images of pipeline corrosion and the second relates to images of the human brain and individuals with Attention-Deficit/Hyperactivity Disorder (ADHD). The corrosion of oil and gas pipelines is important because there are thousands of leaks every year costing billions of dollars for cleanups. ADHD is important because a substantial fraction of the world population has the disorder causing significant suffering and hundreds of billions of dollars of losses to the world economy. To address both image analysis problems, novel statistical and operations research techniques are proposed which have potentially wide applicability. Relating to pipeline corrosion, an established simulation method is called the “voxel” method which permits predictions about how images and pipelines or other media will change as corrosion evolves. In most realistic cases, we find that the parameter values or “inputs” (Xs) needed to run the simulation are unknown. We only have the images which are essentially outputs (Ys) which can be generated by real world experiments or simulations. The phenomenon of having incomplete inputs for simulation is common in many engineering and science situations and a critical challenge for both people and artificial intelligence. We and others have called this important subject, “empirical forward-inverse estimation” since we can gather data (empirically) in the forward manner progressing from assumed inputs (Xs) to measured outputs (Ys) and then generate inverse predictions from Ys to Xs. With (hopefully) accurately estimated X values, the experimental setup or simulation can then predict the future corrosion evolution and whether repair in critically needed. Relating to forward-inverse analyses, 24 variants of an established two stage method or framework are studied in relation to enhanced inverse prediction accuracy for two test cases including pipeline corrosion (open full item for complete abstract)

PhD, University of Cincinnati, 2021, Arts and Sciences: Chemistry

Microtubules (MTs) are intracellular biopolymers made of aß-tubulin heterodimer subunits, which are crucial for various cellular activities such as protein trafficking, chromosomal segregation, intracellular transport, and mitosis. The dynamic behavior of MTs during these cellular processes are regulated by a large and diverse group of proteins called microtubule-associated proteins (MAPs). MT severing enzymes are MAPs that belong to the AAA+ (ATPases associated with various cellular activities) superfamily. These enzymes are known to oligomerize into ring-shaped hexamers, with a central pore lined by pore loops with crucial functional roles, to perform their function of removing subunits from MTs. Recent data from the literature supports a model where the enzyme uses large-scale motions of its hexameric structure to generate directional forces large enough to pull out tubulin subunits from the lattice. This action corresponds to one of the proposed models of severing, called the unfoldase model. We probed the unfoldase model by applying a force on the C-terminal ends of tubulin dimers in a lattice using coarse-grained simulations. At the same time, we explored the conformational dynamics, asymmetric pore motions, and inter/intraring interactions of the severing enzymes using all-atom molecular dynamics simulations. Our simulations results compared with the experimental severing assays revealed that the experimental data is the best fit by a model of cooperative removal of protofilament fragments by severing enzymes, which depends on the severing enzyme concentration and placement on the MT lattice. From the all-atom simulations, we determined that the dynamic stability of the central pore of a severing enzyme involves a network of salt bridges that connect conserved motifs of central pore loops. Clustering analysis of severing proteins showed that they are characterized by weaker interprotomer coupling and stronger intra protomer stabilization through salt bridges (open full item for complete abstract)

Doctor of Philosophy (PhD), Wright State University, 2007, Engineering PhD

Design of the next generation of ion engines can benefit from detailed computer simulations of the plasma in the discharge chamber. In this work a complete particle based approach has been taken to model the discharge chamber plasma.This is the first time that simplifying continuum assumptions on the particle motion have not been made in a discharge chamber model. Because of the long mean free paths of the particles in the discharge chamber continuum models are questionable. The PIC-MCC model developed in this work tracks following particles: neutrals, singly charged ions, doubly charged ions, secondary electrons, and primary electrons. The trajectories of these particles are determined using the Newton-Lorentz's equation of motion including the effects of magnetic and electric fields. Particle collisions are determined using an MCC statistical technique. A large number of collision processes and particle wall interactions are included in the model. The magnetic fields produced by the permanent magnets are determined using Maxwell's equations. The electric fields are determined using an approximate input electric field coupled with a dynamic determination of the electric fields caused by the charged particles. In this work inclusion of the dynamic electric field calculation is made possible by using an inflated plasma permittivity value in the Poisson solver. This allows dynamic electric field calculation with minimal computational requirements in terms of both computer memory and run time. In addition, a number of other numerical procedures such as parallel processing have been implemented to shorten the computational time. The primary results are those modeling the discharge chamber of NASA's NSTAR ion engine at its full operating power. Convergence of numerical results such as total number of particles inside the discharge chamber, average energy of the plasma particles, discharge current, beam current and beam efficiency are obtained. Steady state results for th (open full item for complete abstract)

Master of Science, Miami University, 2024, Mechanical and Manufacturing Engineering

Pitting corrosion is a significant and costly issue in engineering applications, leading to irreversible structural damage and degraded mechanical properties due to surface-level chemical reactions. While corrosion has been extensively studied, the mechanisms underlying nucleation remain poorly understood. In this study, experimental data were used to generate atomic bicrystal models with specific Euler angles, resulting in varying local geometric structures and potential energies for individual atoms. Purely mechanistic molecular dynamics simulations were performed to determine the atomic activation energies of different atomic groups. Atoms located on step edges and grain boundaries were generally found to have lower activation energies compared to those on flat surfaces, indicating that these regions are generally more stable and less susceptible to corrosion. Additionally, grain boundary energy was computed for three distinct bicrystals identified in experiments, revealing that there may be a relationship between the degree of mismatch between grains and grain boundary energy.

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

In the seconds following their formation in core-collapse supernovae, `proto'-neutron stars (PNSs) drive neutrino-heated magneto-centrifugal winds. The neutrino-driven wind phase during the cooling of the PNS lasts $\sim 1-100$\,s. We construct unprecedentedly realistic models of the PNS cooling phase using two-dimensional axisymmetric magnetohydrodynamic simulations. We include the effects of neutrino heating and cooling, employ a general equation of state, consider strong magnetic fields along with a dynamic PNS magnetosphere, and include the effects of PNS rotation. We show that relatively slowly rotating magnetars (strongly magnetized PNSs) with initial spin periods $P_{\star0} \gtrsim 100$\,ms spin down rapidly during the cooling epoch. For polar magnetic field strengths $B_0\gtrsim10^{15}$\,G, we show that the spindown timescale is of the order seconds in early phases. We show that magnetars with mass $M$ born with $B_0$ greater than $\simeq1.3\times10^{15}\,{\rm\,G}\,(P_{\star0}/{400\,\rm\,ms})^{-1.4}(M/1.4\,{\rm M}_\odot)^{2.2}$ spin down to periods $> 1$\,s in just the first few seconds of evolution. We discuss the implications for observed magnetars, including the discrepancy between their characteristic ages and supernova remnant ages. On the other hand, we show that rapidly rotating magnetars with initial spin periods $P_{\star 0}\lesssim 4$\,ms and $B_0\gtrsim 10^{15}$\,G can release $10^{50}-5\times 10^{51}$\,ergs of energy during the first $\sim2$\,s of the cooling phase. Based on this result, it is plausible that sustained energy injection by magnetars through the relativistic wind phase can power gamma-ray bursts (GRBs). We also show that magnetars with moderate field strengths of $B_0\lesssim 5\times 10^{14}$\,G do not release a large fraction of their rotational kinetic energy during the cooling phase and hence, are not likely to power GRBs. We hypothesize that moderate field strength magnetars can be central engines of superluminous supern (open full item for complete abstract)

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

Femoroacetabular impingement syndrome (FAIS) is a leading cause of debilitating hip pain in young, active individuals and is defined by motion-related pain in the presence of structural variants in bony morphology. Diagnosis of FAIS has increased rapidly over the past two decades, and the syndrome primarily affects physically active persons between the ages of 15 and 35. FAIS leads to severe functional limitations across a wide range of activities from sport participation to getting into and out of a vehicle. This young patient population reports poor quality of life similar to that reported by those diagnosed with hip osteoarthritis, and current treatment methods including surgery and rehabilitation often result in unsatisfactory patient outcomes. Poor quality of life, low patient-reported function, and significant activity limitations often persist regardless of treatment. At present, morphological features (e.g., joint shape) prevail as the primary defining element of FAIS, despite that over 50% of athletes have morphologies associated with FAIS and are completely asymptomatic. Improved outcomes for individuals with FAIS may rely on the ability to identify, characterize, and address motion-related sources of symptoms beyond joint shape. Cumulative load on the hip, due to a combination of biomechanics and free-living movement patterns, could influence symptoms and may be important treatment targets in FAIS. Individuals with FAIS display strength deficits in all muscle groups surrounding the hip. Of these muscles, hip flexor weakness may be especially problematic as it routinely persists after treatment and has been associated with worse patient reported outcomes and increased severity of intra-articular damage. The iliopsoas is the primary hip flexor and a major contributor to hip joint loads during both gait and non-weightbearing tasks. As such, iliopsoas weakness may cause unfavorable forces within the joint. Pain caused by altered mechanical loading of the h (open full item for complete abstract)

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

Polymers have gained attention for their use as solid electrolytes in lithium-ion batteries due to their high energy density and enhanced safety. To increase cation conductivity in solid-state polymer electrolytes, particularly at room temperature, a range of polymer systems have been explored extensively in recent years. Understanding the ion behavior in polymer systems at the molecular level is essential. Generic coarse-grained bead-spring models are widely used to describe polymeric systems in molecular dynamics simulations, which have demonstrated qualitative consistency with a variety of structural and dynamic results from experiments. When ions are present, additional model features are needed to account for their longer-ranged interactions with each other (typically through Coulomb interactions within a uniform dielectric constant background) and for their interactions with polarizable polymers. For example, using additional pairwise potentials or embedding the classic Drude oscillator to achieve polarizable modeling. One objective of this research is to study the ion behavior across various polymer systems by employing a pairwise solvation potential. Additionally, this study aims to develop the Drude oscillator integrated model in coarse-grained polymer simulations to study ion-containing polymer electrolytes. We first studied the single-ion block copolymers, which are gaining interest as potential electrolytes with high cation transference numbers. Because anions are tethered to the polymer chains, the cation transference number, which is the fractional contribution of cation conductivity to overall ion conductivity, is unity in the limit that transport of the polymer chains is negligible. Such a high transference number is of interest in reaching a high charging rate and avoiding concentration polarization that is possible in salt-doped systems. However, tethered anions may decrease polymer and cation dynamics and thus reduce cation conduction. To (open full item for complete abstract)

PhD, University of Cincinnati, 2024, Engineering and Applied Science: Electrical Engineering

This dissertation work deals with the development of refined models of field emission (FE) from carbon nanotubes (CNTs). The first project described focuses on an efficient algorithm computing the temperature distribution along a CNT during FE, considering the substrate as a perfect heat sink at temperature T₀. It incorporates Joule heating effects, radiative losses, and recently reported analytical expressions for emission current density and heat exchange at the CNT tip, including Nottingham-Heating and Henderson-Cooling effects. Temperature dependencies of CNT's electrical resistivity and thermal conductivity are also included. Simulation times for calculating CNT FE characteristics and temperature distribution were found to be about two orders of magnitude faster compared to numerical methods accounting for both current and energy exchange at the CNT tip. The algorithm was adapted to analyze the impact of thermal contact resistance on the FE properties of a CNT. Using a boundary condition from literature, thermal contact resistance effects at a CNT/chuck interface were accounted for, with the chuck assumed as a perfect heat sink at temperature T₀. Results demonstrate that current constriction at the CNT/chuck contact point induces self-heating effects, which escalate with higher thermal contact resistance values. Consequently, this increases the temperature profile along the CNT, including its tip temperature, and augments the FE current beyond values presumed with the CNT/chuck interface at T₀. The fractional change of emission current with applied external electric field was calculated for increasing thermal resistivity values of the CNT/chuck interface. Next, the effect of electrostatic forces on the FE properties of flexible emitters as a function of the strength of the applied (macroscopic) external electrostatic field are investigated. Results show that deflection of a flexible metallic CNT due to an externally applied electrostatic field inc (open full item for complete abstract)

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

This research introduces an Origami-inspired dynamic spacecraft radiator, capable of adjusting heat rejection in response to orbital variations and extreme temperature fluctuations in lunar environments. The research centers around the square twist origami tessellation, an adaptable geometric structure with significant potential for revolutionizing radiative heat control in space. The investigative involves simulations of square twist origami tessellation panels using vector math and algebra. This study examines both a two-dimensional (2- D), infinitely thin tessellation, and a three-dimensional (3-D), rigidly-foldable tessellation, each characterized by an adjustable closure or actuation angle “φ”. Meticulously analyzed the heat loss characteristics of both the 2D and 3D radiators over a 180-degree range of actuation. Utilizing Monte Carlo Ray Tracing and the concept of “view factors”, the study quantifies radiative heat loss, exploring the interplay of emitted, interrupted, and escaped rays as the geometry adapts to various positions. This method allowed for an in-depth understanding of the changing radiative heat loss behavior as the tessellation actuates from fully closed to fully deployed. The findings reveal a significant divergence between the 2D and 3D square twist origami radiators. With an emissivity of 1, the 3D model demonstrated a slower decrease in the ratio of escaped to emitted rays (Ψ) as the closure/actuation angle increased, while the 2D model exhibited a more linear decline. This divergence underscores the superior radiative heat loss control capabilities of the 2D square twist origami geometry, offering a promising turndown ratio of 4.42, validating the model's efficiency and practicality for radiative heat loss control. Further exploration involved both non-rigidly and rigidly foldable radiator models. The non-rigidly foldable geometry, initially a theoretical concept, is realized through 3D modeling and physica (open full item for complete abstract)

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

Cadherins are a family of large transmembrane glycoproteins instrumental in facilitating organ formation during morphogenesis in vertebrates and invertebrates. At the cellular level, they are involved in adhesion, signaling, recognition, mechanotransduction, and motility. In the modern classification of the cadherin superfamily, classical cadherins with five extracellular cadherin (EC) repeats as well as clustered and non-clustered -protocadherins with six or seven EC repeats have been well-studied and their homophilic/heterophilic interactions with molecules on the same (cis) cell or opposite (trans) cells have been characterized. Complexity arises when the number of EC repeats increases with diverse Ca2+ coordination at linker regions between two consecutive EC repeats. In larger cadherins, such as cadherin-23 (CDH23), protocadherin-15 (PCDH15) and cadherin epithelial growth factor (EGF) Laminin-G (LAG or LamG) seven pass G-type receptor-1 (CELSR1), the structural flexibility afforded by different Ca2+ coordination plays determinant roles in their adhesion capacity during inner-ear mechanotransduction and planar cell polarity (PCP). CDH23 and PCDH15, each with 27 and 11 EC repeats, connect two adjacent hair- like protrusions known as stereocilia together atop of a hair cell, the primary mechanosensory cell in the inner ear. Through heterophilic interactions between their first two N-terminal EC repeats, CDH23 and PCDH15 form a filament known as the tip link. In response to sound, stereocilia undergo displacement and the tip link experiences tension, which opens the ion-conducting mechanotransduction channels on the tip-link's lower end to send signals to the brain. The heterophilic trans tetrameric complex formed by CDH23 and PCDH15, and the cis interactions along the length of PCDH15 have been well-studied in the past but full-length ectodomain structures and high-resolution structural models of complete CDH23 and PCHD15 ectodomain have not been resolved. H (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Aerospace Engineering

Reynolds Averaged Navier Stokes is likely remain one of the primary design tools for hypersonic vehicles for the foreseeable future. As such, the shortcomings of existing models represent a limiting factor in the aerotheromdynamic predictions required for vehicle design. Most modern turbulence models are based on compressible flow extensions to models developed using incompressible flow data and thus do not take into account intrinsically high-speed phenomena such as bulk dilation. The resulting error and uncertainties lead to overly conservative designs, resulting in heavier than necessary vehicles and degraded mission performance. In this manuscript a new Direct Numerical Simulations database on a turbulent boundary layers subject to pressure gradients induced by forwards and backwards facing wall curvature is presented. The database simulates a Mach 4.9 flow over a nearly adiabatic wall with a friction Reynolds number of Reτ = 1100 prior to wall curvatures. The flow conditions and baseline wall geometries studied within are representative of companion wind tunnel experiments conducted in a high-speed blow down wind tunnel at the National Aerothermochemistry Laboratory at the Texas A&M University. The wall steepness of the baseline forwards and backwards facing wall shapes were systematically varied to induce a fully attached, incipiently/weakly separated, or fully separated flow to occur. This database was then used to characterize the resulting flow fields of each wall shape, investigating how the varied wall steepness affects the mean and turbulent flow field. As wall steepness was increased the resulting wall shapes caused the flow to separate. For the backwards facing wall shape the unsteadiness of the separation bubble resulted in vortical ejection events to occur near the mean-flow reattachment point, while the forward facing wall shape resulted in a breathing motion where the separation bubble would grow up and collapse back down th (open full item for complete abstract)

MS, Kent State University, 2023, College of Arts and Sciences / Department of Physics

Tightly bent DNA is found in both biology and structural DNA nanotechnology. Examples include the nucleosome where DNA is tightly wrapped around histone proteins, or DNA catenanes and DNA-lipid nanodiscs. Understanding and predicting the physical and mechanical properties of the involved DNA is important in both cases, but experiments are limited by the cost of synthetic DNA and the spatial and temporal resolution of assays. Physical models developed for computer simulations are an alternative approach to study DNA-based materials and biological complexes. In this thesis, nicked double-stranded DNA (dsDNA) minicircles are studied using coarse-grained molecular dynamics simulations. These minicircles experience high bending strain due to their small radii and high curvature. They may adopt either a stacked state, forming an eccentric ring, or adopt a kinked state, where a sharp, local bend in the duplex forms to alleviate bending strain. While relaxed dsDNA has an accepted helical repeat of 10.5 base pairs (bp) per turn, there is contention regarding the helical repeat of tightly bent dsDNA. The analysis of structural deformations around the nick site is used to capture the fraction of stacked nicked minicircles as a function of DNA length, which can be used to determine the preferred helical repeat of tightly bent dsDNA. In these simulations, we found no significant difference in the helical repeat of relaxed dsDNA (~10.55 bp/turn) and tightly bent dsDNA (~10.52 bp/turn). This analysis was repeated for several temperatures, and a linear unwinding of the duplex with temperature was found, with a slope of 0.0013 bp/turn 1/(°C). Next, we studied the effect of a second structural defect on the stability of the nick site of nicked minicircles. Additional defects include an omitted nucleotide (gap) and an added nucleotide (bulge) to a strand. We found that adding some defects such as a gap to a nicked minicircle suppresses kinking at the nick site, while other defects (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2023, Chemical Engineering

The increasing population, along with a rise in the standard of living, has led to the demand for energy and chemicals reaching unprecedented levels. To fulfill these demands, fossil fuels are being utilized, causing enormous CO2 emissions, resulting in the climate change problem faced by humanity today. Although the past couple of decades have witnessed growth in sustainable renewable energy sources, fossil fuels are still projected to remain the dominant contributor to the energy production scenario. It is important to understand that fossil fuels are not only limited to power and electricity generation, but they also serve as feedstocks for the production of several specialty and commodity chemicals. The commodity chemical industry, which includes the manufacture of syngas, hydrogen, methanol, ammonia, etc., accounts for more than a third of total industrial energy consumption. The current processes for the generation of these chemicals suffer from drawbacks such as high endothermic heat input, use of energy-intensive unit operations, coke deposition on the catalyst, unsafe operation, and reliance on the economics of scale for feasibility. Despite their limitations, these processes are critical to the world, and advancements are underway to improve their overall efficiency. However, to mitigate dependence on fossil fuels considering the need for decarbonization, new technologies that can efficiently utilize domestic and waste sources such as biomass, hydrogen sulfide gas, stranded natural gas, and waste plastics for the production of commodity chemicals are required. Furthermore, technologies that achieve process intensification to enhance product yields and efficiencies or render safer operations are also essential, even if, in some cases, the complete elimination of fossil fuels cannot be achieved. Chemical looping is a promising technology that can effectively utilize various sources for the sustainable and economical production of chemicals. It involves split (open full item for complete abstract)

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

The lipid bilayer's integrity is essential for cell function as it acts as the primary barrier against external molecules like drugs and peptides, which can alter the bilayer's physical properties. This dissertation investigates how amphetamine (AMPH) and methamphetamine (METH), and the charged HIV1-TAT peptide impact the stability of lipid bilayers, using a home-built lipid bilayer apparatus that enables real-time monitoring through electrical and fluorescence measurements. Our findings indicate that AMPH and METH increase the lipid bilayer's ion permeability, with METH having a greater destabilizing effect. High concentrations of these stimulants, akin to levels in blood plasma of individuals with stimulant-related brain injuries, lead to pore formation in the bilayer. The extent of destabilization correlated with the drug concentration. We also studied the translocation dynamics of the charged HIV1-TAT peptide across the lipid bilayer. The analysis of current fluctuations showed that successful translocation of the TAT peptide is concentration-dependent, highlighting the significance of charge in inducing membrane deformation or pore formation. Additionally, molecular dynamic simulations were used to explore AMPH interactions with the lipid bilayer in greater detail. The results revealed AMPH's preferred orientation during interaction and its hydrophobic nature, as evidenced by the larger energy barrier encountered in the hydrophilic head group regions of the lipid bilayer. To complement these findings, we utilized surface-enhanced Raman spectroscopy (SERS) to estimate the concentrations of AMPH within lipid bilayers. The data showed a positive correlation between characteristic peak heights and AMPH concentrations. Moreover, whole-cell patch clamp measurements on neuronal cells were employed to examine AMPH's effects in a more intricate lipid environment. This research contributes to the understanding of how stimulants and charged peptides interact with lipid bi (open full item for complete abstract)

PhD, University of Cincinnati, 2023, Arts and Sciences: Chemistry

Severe heat shock, cellular stress, and mutations can cause massive protein misfolding and aggregation, resulting in the loss of essential cellular activity. ClpB is a double-ring hexameric structure that contains two AAA+ (ATPases Associated with diverse cellular Activities) nucleotide binding domains (NBDs) per protomer. Threading of substrate proteins through the narrow central pore is promoted through the application of mechanical force by central pore loops (PLs) in repetitive allosteric cycles of ClpB. Despite recent advancements in ClpB studies, it is still unclear how ClpB performs its disaggregation activity. In the prokaryotic cell, energy-dependent proteases are essential in controlling metabolic pathways and the cell cycle. The ClpP peptidase oligomerizes as two stacked heptameric rings and encloses a degradation chamber. To ensure selective degradation, substrate protein access to the chamber is controlled by a gating mechanism of its axial pore, which involves conformational transition of N-terminal loops of ClpP subunits. Even though ClpP conformations have been studied extensively, it is still unclear about the mechanism of allosteric communication in the gating mechanism. I present three studies to address the issues mentioned above. First, I performed all-atom molecular dynamics simulations for two distinct conformations, "ring" and "spiral" to study the asymmetric conformational dynamics of ClpB. The analysis indicates that the ClpB hexameric pore is stabilized by a network of inter-protomer salt bridges formed by the conserved pore loops located in the central channel. Clustering of dynamic motions suggests strong inter-protomer collaboration between domains of neighboring protomers in the asymmetric hexamer. Collective motions, investigated using Principal Component Analysis, reveal the importance of axial motions of the central pore loops are in agreement with the substrate translocation mechanisms of ClpB identified in experimental studies. I (open full item for complete abstract)

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

Icing, or the formation of ice from water via freezing or water vapor via desublimation, is a phenomenon that commonly occurs within air cycle-based refrigeration systems and requires thermal control that limits system performance. In aircraft applications icing frequently occurs in the heat exchangers and turbine(s) that are part of the air cycle machine, the refrigeration unit of the environmental control system. Traditionally, water vapor is removed from an air cycle machine via condensing in a heat exchanger and subsequent high-pressure water separation. This approach is not capable of removing all of the vapor present at low altitude conditions, corresponding to a high risk of icing. To mitigate icing under these conditions, a membrane dehumidifier is considered to separate the water vapor that remains after condensing and liquid water separation. Three distinct investigations are conducted as part of this work. The first is aimed at modeling approaches for desublimation frosting, or frost growth on sufficiently cold flat surfaces. This results in a novel, analytical, and non-restrictive solution well-suited for representing frost growth and densification in moist air heat exchangers. The second investigation concerns membrane dehumidification and module design. A custom component model is developed and verified under aircraft conditions, then the Pareto frontier of volumetrically efficient membrane modules is characterized via a multi-objective optimization study. The final investigation evaluates three two-wheel air cycle subsystem architectures with differing dehumidification approaches: (1) condenser-based, (2) membrane dehumidifier-based, and (3) combined. Steady-state simulations are run for each of these over a range of flow rates and altitudes. The results demonstrate that incorporating a membrane dehumidifier reduces the turbine inlet saturation temperature, which mitigates icing in the turbine and reduces the required bypass fl (open full item for complete abstract)

Doctor of Philosophy (PhD), Wright State University, 2022, Computer Science and Engineering PhD

Inadequate professional training and practices related to health care may result in severe complications to care experiences and outcomes. Moreover, healthcare professionals are as susceptible to the possibility of implicit biases as any other group. Importantly, the health care training is critical and challenging as minor prejudicial beliefs have an adverse influence or serious consequences on patients' health outcomes. Thus, facilitating serious role-playing virtual care practices along with raising awareness of healthcare professionals about the enduring impact of implicit/explicit biases and Social Determinants of Health (SDH) on health outcomes assist to advance the patient-provider relation, care experiences (e.g., healthcare experience and patient care experience), and promote health equity. In addition, employing the “learning by doing” approach for health care practices directly in real-life is less preferred wherein high-risk care is essential. Thus, there is a high scope and demand for the utilization of alternative ways which can facilitate a self-driven and self-motivational digital experiential learning approach with the integration of innovative computer technology that encourages learners to acquire professional development skills. The primary focus of this research is to deliver Computer-Supported Experiential Learning (CSEL) and Computer-Supported Expert-Guided Experiential Learning (CSEGEL) approaches to deliver professional development skills (e.g., healthcare skills). Specifically, this research and development deliver CSEL and CSEGEL approaches-based serious role-playing games or mobile applications as digital experiential learning tools by integrating first-person virtual role-playing scenarios to enhance healthcare skills (e.g., cultural humility, professional communication, awareness of the enduring impact of both social determinants of health and implicit/explicit biases on health outcomes, and compassionate and empathetic attitude) of (open full item for complete abstract)

Master of Science, The Ohio State University, 2022, Mechanical Engineering

Increased posterior tibial slope (PTS) has been shown to increase the risk of ACL injury. Anterior closing wedge proximal tibial osteotomy (ACWPTO) is a surgical procedure that involves removing a wedge of bone from the anterior part of the tibia to reduce the PTS and reduce the risk of anterior cruciate ligament (ACL) injury. Current ACWPTO technique literature does not agree on an ideal post-operative PTS range. Additionally, there is little quantitative justification for the post-operative ACWPTO slope values selected. Current research also does not examine the impact of variable ligament stiffnesses in combination with variable PTS. The goal of this research was to analyze the effect that variable ligament stiffnesses and variable PTS have on knee biomechanics with the goal of informing clinicians in the planning of ACLR and ACWPTO procedures. An additional goal was to define an optimal PTS range that would protect the knee from injury. This research utilized a previously validated Oxford Rig simulation of a deep squat to analyze the effect that varying PTS and knee ligament stiffness has on ACL force, ACL strain, anterior-posterior (A/P) translation, and medial-lateral (M/L) tibiofemoral (TF) contact location. 125 forward dynamics simulations were run representing 3 different ACL stiffnesses, 3 different PCL stiffnesses, 5 different knee types with variable collateral ligament and posterior capsule stiffnesses, and PTS values ranging from -0.484° - 14.516° representing both anterior tibial slope (negative PTS values) and posterior tibial slope (positive values). 86/125 of the simulations were successful. The stiffness of the collateral ligaments in the knee had little effect on the results. Additionally, the trends between ACL force, ACL strain, A/P translation and PTS were found to be linear. This made it difficult to identify a cut-off point to determine an ideal PTS range. In this study, the magnitudes of ACL force, ACL strain, and A/P translation contrasted (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2022, Aerospace Engineering

Rectangular propulsion nozzles offer thrust-vectoring and air-frame-integration advantages over their more commonly studied circular counterparts. However, they display many distinguishing features which violate assumptions, such as azimuthal homogeneity, typically used in acoustic prediction tools for circular jets. In the present work, we examine the turbulent dynamics of rectangular jets from a range of nozzle geometries and operating conditions with the aim of highlighting their distinct nearfield dynamics and developing simplified models for their acoustics. First, the nearfield dynamics of a heated overexpanded rectangular jet of aspect ratio~(AR) two are examined with an implicit Large-Eddy Simulation using experimental data for validation purposes. The conical nozzle, representative of practical configurations, results in multiple shock trains from the throat region as well as the overexpanded operating condition. Each train introduces unsteadiness that influences the external shock cell and plume structure. A detailed analysis of the terms contributing to the turbulent kinetic energy (TKE) is performed to examine the evolution of the plume. The major axis shear layer experiences significant amplification of the TKE compared to the minor axis, particularly near the core-collapse region, and thus, pressure fluctuations in the near acoustic field are correspondingly larger in that direction. The most prominent source of TKE in this region is associated with strong mean flow gradients across the major axis shear layer and larger corresponding cross-correlations of velocity fluctuations. These effects are shown to be consistent with protrusions of vortical perturbations arising in the minor axis shear layer into the potential core. The evolution of pressure perturbations from asymmetric to axisymmetric occurs relatively quickly, to achieve agreement with far-field experimental data. Given the overall similarity of the acoustics from both low AR rectang (open full item for complete abstract)