MS, University of Cincinnati, 2019, Engineering and Applied Science: Materials Science

Molecular dynamics simulations rely on integrating the newtonian equations of motion for a system. Consequently depending upon the requirements, we can sample a micro-canonical ensemble(constant energy) or canon- ical ensemble(constant temperature). This method of changing basic molecular dynamics equations for maintaining constant temperature (average) is called a thermostat algorithm. Molecular dynamics simulations in which we add artificial terms to achieve other boundary conditions (constant temperature) may cause the problems. So in order to avoid these problems we use modified equations only to the atoms far from the important regions where the atoms in the important regions obey Newton's original equation of motion. We can make the temperature(average) constant by four methods. They are Anderson thermostat, Berendenson thermostat, Nose-Hoover thermostat, and Langevin(stochastic) thermostat. The final aim is to change temperature by fixing the total kinetic energy of the system. Finally we ensure not only to maintain temperature constant but also to make the average temperature of a system constant and obtain a correct probability distribution curve of temperature. In the present work, we choose a nickel single crystal as our substrate. We run constant temperature simulations using langevin thermostat at temperatures 100K and 1000K. We run these simulations using different langevin friction values, time step and number of time steps. Consequently we obtain different probability distribution curves of temperature. Finally we choose the optimal conditions of the time step, langevin friction and no of time steps to obtain the accurate probability distribution of the Temperature. In the present work, we maintain the average temperature of Ni substrate constant by Noose Hoover temperature thermostat and Noose Hoover temperature barostat. Then we determine the lattice constant of Ni single crystal by running Molecular dynamics simulations at constant NPT(constan (open full item for complete abstract)

Committee: Woo Kyun Kim Ph.D. (Committee Chair); Yao Fu Ph.D. (Committee Member); Donglu Shi Ph.D. (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2005, Molecular Genetics

Wnt pathways are highly conserved pathways that regulate key processes such as cell type specification and migration of cells during animal development. The C. elegans vulva displays symmetry such that the posterior half of the vulva forms a mirror image of the anterior half. We observed that nuclear levels of POP-1 also display similar mirror symmetry in the developing vulva. We are studying the processes that establish this mirror symmetric pattern of POP-1 localization. Because mutations in the putative WNT receptors lin-17/frizzled and lin-18/Ryk were known to cause defects in the posterior half of the vulva, we examined POP-1 localization patterns in these mutants. We observed that POP-1 localization is reversed in the posterior most part of the vulva with respect to wild-type, in these mutants. lin-17/lin-18 double mutants show a more penetrant reversal of POP-1 localization, suggesting that LIN-17 and LIN-18 act in a semi-redundant manner to reorient POP-1 localization in the posterior half of the vulva. We have investigated the mechanisms by which two other P ectoblasts, P11 and P12 are specified. Prior studies have shown that lin-44/Wnt, lin-17/Frizzled and bar-1/canonical b-catenin function in P12 specification. We have obtained additional evidence that a canonical Wnt pathway functions in P12 specification. We have demonstrated that activated forms of BAR-1 (deltaNBAR-1) are sufficient to cause a P11 to P12 transformation. Interestingly, time-course studies with deltaNBAR-1 expression suggest that Wnts may act at the same time as the EGF pathway, suggesting the requirement of two parallel pathways. We predict a function for POP-1 in P12 specification as BAR-1 and b-catenins in other organisms are known to act primarily through TCFs to activate transcription. We found that the pop-1 hypomorphs, hu9 and q645 that should reduce bar-1 activity cause a low rate of P12 to P11 transformations. This supports the hypothesis that POP-1 acts in P12 specification in (open full item for complete abstract)

Committee: Russell Hill (Advisor) Subjects: Biology, Cell

PhD, University of Cincinnati, 2023, Medicine: Immunology

Cognate interaction between effector memory CD4+ T cells (TEM) and dendritic cells (DCs) induces innate inflammatory cytokine production, resulting in detrimental outcomes such as autoimmune pathology and cytokine storms. We previously established that TEM cells use TNF superfamily ligands to activate DCs, yet whether this interaction with DCs induces other cell intrinsic changes that influence inflammatory responses by DCs has never been investigated. Here we have made a surprising discovery that TEM cells trigger double-strand DNA breaks via mitochondrial ROS production in interacting DCs. Initiation of the DNA damage response in DCs leads to activation of a cGAS-independent, non-canonical STING-TRAF6-NFκB signaling axis. Consequently, STING deficient DCs display reduced NFκB activation leading to significant defects in transcriptional induction and functional production of IL-1β and IL-6 following their interaction with TEM cells, both in vitro and in vivo. The discovery of TEM cell-induced innate inflammation through DNA damage and a non-canonical STING-NFκB pathway presents this pathway as a potential target to alleviate T cell driven inflammation in autoimmunity and cytokine storms.

Committee: Chandrashekhar Pasare Ph.D. (Committee Chair); Jonathan Katz Ph.D. (Committee Member); Sing Sing Way M.D. Ph.D. (Committee Member); William Miller Ph.D. (Committee Member); Daniel Starczynowski Ph.D. (Committee Member); Leah Claire Kottyan Ph.D. (Committee Member) Subjects: Immunology

PHD, Kent State University, 2022, College of Arts and Sciences / Department of Physics

Nucleic acids play a significant role in biological processes involving genetic information, such as replication, transcription, and translation. Aside from the well-known canonical double helix structure, DNA can adopt a variety of alternative non-canonical structures such as DNA hairpins, holiday junctions, cruciforms, triplexes, or G-quadruplexes (GQ). GQ structures may form in the guanine-rich (G-rich) regions of the genome, including telomeres, promoters, and other significant regulatory sites. Formation of GQs at telomeres protects chromosome ends against degradation and end-to-end joining. The cytosine-rich (C-rich) sequences that are complementary to GQ forming sequences can adopt an intercalated motif (i-motif) structure at acidic pH. In addition to their physiological functions, both the GQ and the i-motif have potential biotechnological applications. In my dissertation, I will describe several projects on single molecule fluorescence and force spectroscopy studies of GQ and i-motif structures. In the first study, we developed a multiplexed, high throughput single-molecule force sensor that converts fluorescence signal into force information by hybridizing the ends of short looped double-stranded DNA (dsDNA) with a nucleic acid secondary (NAS) structure, such as a hairpin or a GQ. When looped, the dsDNA maintains a constant tension across the ends of the NAS. Initially, we completed proof-of-principle studies on this system using different lengths of dsDNA and hairpin structures under various salt conditions. Later, we applied this method to study of the interaction of an under-tension GQ structure with a destabilizing protein, Replication Protein A (RPA), and a stabilizing small molecule, an oxazole telomestatin derivative. The force applied to the GQ via the looped dsDNA was calibrated, with the help of a collaborator, against high-resolution optical tweezers measurements, which is only a few picoNewtons for the construct and assay conditions we used. (open full item for complete abstract)

Committee: Hamza Balci (Advisor); John Portman (Committee Member); Liang-Chy Chien (Committee Member); Soumitra Basu (Committee Member); Thorsten-Lars Schmidt (Committee Member) Subjects: Biophysics; Physics

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

The effect of varying submergence on the transonic flow past canonical wall-mounted hemispheres is investigated at a freestream Mach number, M = 0.8 using Delayed Detached Eddy Simulations (DDES). Four submergence levels are considered ranging from a full hemisphere (100% exposed) to a highly submerged case where the equator is well below the waterline (40% exposed). Analysis of the mean characteristics indicates a reduction in strength and extent of dominant flow topology, including the horseshoe vortex and the counter-rotating vortices in the wake. Additionally, it is found that the mean line of surface separation moves downstream with submergence. This finding is validated with analysis of the unsteady streamwise shock position, which indicates the mean shock foot position also moved downstream with submergence. However, the frequency associated with the streamwise motion of the shock remains consistent between the cases in terms of a suitably non- dimensionalized Strouhal number, StD ∼ 0.26. The unsteady surface forces and modal analysis are used to quantify the effect of submergence on two correlated shock-wake modes, as these are dominant unsteady features in flow over full hemispheres. The first mode is the “breathing” mode, corresponding to spanwise symmetric wake shedding and correlates to streamwise shock oscillations. The second mode is the “shifting”, corresponding to spanwise anti-symmetric wake shedding and correlates with the spanwise rocking of the shock. Proper Orthogonal Decomposition (POD) is used to isolate and rank the different modes; as the hemisphere is submerged, there is an evident change in prominence from the anti-symmetric shifting to the symmetric breathing mode. Dynamic Mode Decomposition (DMD) is used to investigate the spectral content of these modes; the results show that the breathing mode collapses at a frequency of StD ∼ 0.26 for all cases, while the shifting mode extends over a broad frequency range of StD between 0.13 and 0.21.

Committee: Jack McNamara (Committee Member); Datta Gaitonde (Advisor) Subjects: Aerospace Engineering

Doctor of Philosophy, Case Western Reserve University, 2021, Molecular Medicine

Mechanism-based therapies that mitigate phenotypic modulation of vascular smooth muscle cells (SMC) represent appealing targets to improve outcomes of vascular intervention by limiting restenosis. Canonical transient receptor potential channel subtype-6 (TRPC6) is upregulated in arterial segments following balloon angioplasty, though its role in the pathogenesis of neointimal hyperplasia (IH) is unclear. We hypothesized that TRPC6 is required for maintenance of myocardin expression and stabilizes the contractile phenotype in SMC to reduce stenosis in a model of arterial intervention. In this study, histologic evaluation of TRPC6-/- common carotid arteries (CCA) demonstrated subtle structural deficits, including luminal dilation, medial thinning and decreased elastin lamella compared to WT CCA. These structural deficits were associated with reduced myocardin expression in TRPC6-/- CCA homogenates. To assess the effects of TRPC6 on arterial healing after vascular intervention, WT and TRPC6-/- mice were subjected to carotid wire injury. Evaluation at 28 days post injury demonstrated that luminal stenosis, negative arterial remodeling and neointimal hyperplasia were accentuated in TRPC6-/- mice compared to WT mice. TRPC6-/- carotid arteries showed increased medial and neointimal cell proliferation after injury. Immunohistochemistry suggested persistent attenuation of contractile biomarker expression in the media of TRPC6-/- CCA but complete restoration of contractile biomarker expression in in the media of WT CCA 28 days after wire injury. In vitro, cultured primary aortic TRPC6-/- SMC showed decreased expression of SM22, MYH11 and myocardin. Loss of contractile biomarker expression in TRPC6-/- SMC was accompanied by the emergence of IH-related behaviors including enhanced proliferation and migration. Acute siRNA-mediated knockdown of TRPC6 in immortalized arterial SMC was sufficient to induce myocardin downregulation and phenotypic modulation. In total, these results (open full item for complete abstract)

Committee: Linda Graham MD (Advisor); Jonathan Smith PhD (Committee Chair); Christine Moravec PhD (Committee Member); Mitchell Olman MD (Committee Member); Edward Maytin MD PhD (Committee Member) Subjects: Medicine; Molecular Biology; Surgery

Master of Science, Miami University, 2020, Chemistry and Biochemistry

Holins are membrane proteins encoded by bacteriophages for promoting cell lysis by forming fatal "holes." In phage infections of gram-negative bacteria cell lysis occurs destroying the three layers of the cell envelope: cytoplasmic membrane, peptidoglycan layer, and outer membrane by Holin, Endolysin, and Spanin proteins respectively. Holins are the key determinant of the host lysis timing in phage infections. Canonical holins of phage lambda are of two types, actual lethal holin - S105, and antiholin - S107 as a result of the dual start motif of the Sλ gene that encodes them. Previously, the structural dynamics and topology of this system have not been studied using EPR spectroscopy in native membrane mimetics. In this study, SDSL-EPR spectroscopy is used to unravel structural dynamics and topology of the S105 in a micelle, liposome, and SMALPs environments. CW-EPR line shapes of selected MTSL labeled cysteine mutants across the three transmembrane domains and C-terminus of S105 were used to probe the dynamics of S105. CW-EPR power saturation experiments were used to determine the topology of different segments of S105 in a membrane utilizing the accessibility of paramagnetic relaxants O2 and NiEDDA. Successful insertion of S105 in membrane mimetics was confirmed by this study.

Committee: Gary Lorigan Ph.D. (Advisor); Carole Dabney-Smith Ph.D. (Committee Chair); Richard Page Ph.D. (Committee Member); Scott Hartley Ph.D. (Committee Member) Subjects: Biochemistry; Chemistry; Physical Chemistry

Master of Science, Miami University, 2018, Chemical, Paper and Biomedical Engineering

Molecular force fields are not typically parameterized for properties such as surface tension at vapor-liquid equilibrium and so their performance when determining this property is difficult to predict. Grand canonical transition matrix Monte Carlo (GC-TMMC) molecular simulation is implemented in GOMC, an open source GPU-optimized Monte Carlo simulation code, which allows for a direct calculation of surface tension to compare the performance of standard Lennard-Jones and Mie n-6 potentials optimized for vapor-liquid equilibrium. While TraPPE demonstrates systematic errors in calculating this property, it significantly outperforms the Mie n-6 potential due to the latter's parameterization for saturated vapor pressure increasing the interfacial free energy relative to what TraPPE predicts.

Committee: Andrew Paluch (Advisor); Alan Ferrenberg (Committee Member); Catherine Almquist (Committee Member) Subjects: Chemical Engineering

Master of Science (M.S.), University of Dayton, 2018, Electro-Optics

In this thesis, Electro-Optic (EO) range signatures are obtained with a Short-Wave Infrared Super-Continuum Laser (SWIR-SCL) source. 3D printed canonical targets of interest are illuminated by the SWIR-SCL pulsed laser. The scattered laser light from the target is directly detected in mono-static and bi-static configurations with a fast, high bandwidth Indium Gallium Arsenide (InGaAs) PIN photodiode. Temporal pulse returns provide target shape, orientation, and surface roughness information. Spatial and temporal analysis of the collected intensity distribution is performed in MATLAB. Macro and micro surface properties are identified from the collected data by correlating pulse amplitude variations with known range scenes. Finally, range resolution improvement is investigated by means of Tomographic Reconstruction using Radon Transforms and by image processing techniques such as Deconvolution.

Committee: Edward Watson Ph.D. (Advisor); Paul McManamon Ph.D. (Committee Member); Joe Haus Ph.D. (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Engineering; Experiments; Optics; Physics; Scientific Imaging

Doctor of Philosophy, Miami University, 2018, Microbiology

RNA is an important regulator of gene expression within bacterial, eukaryotic, and archaeal cells. This work focuses on two aspects of RNA regulation: the first half investigates the role of regulatory features within the 5' untranslated leader region (UTR) of the E. coli aroL mRNA and the second half focuses on an sRNA in S. oneidensis MR-1. The 5'UTR of mRNAs contain information necessary for ribosome recognition and subsequent translation initiation. Translation initiation is a prominent part of gene expression, as it is the rate-limiting step of translation. The 70S ternary initiation complex contains initiator tRNA and the mRNA's start codon positioned in the P-site of the 70S ribosome. The Shine-Dalgarno (SD) sequence within the 5'UTR of the mRNA is an important feature that helps facilitate the initial interaction between the mRNA and the 30S subunit. Translation of mRNAs lacking an SD has been reported and suggests that alternative mechanisms of mRNA-30S interactions exist. The aroL mRNA contains a short open reading frame within its 5'UTR. Ribosome binding and expression assays showed that this open reading frame gets translated, and its translation affects aroL translation downstream. The upstream open reading frame binds 30S subunits in the absence of a canonical SD sequence. In this work, we have shown that multiple signals in the mRNA (upstream and downstream of the AUG) contribute to 30S binding to and translation from the AUG start codon. In this work we have also characterized an sRNA, a ryhB homologue, in S. oneidensis MR-1. sRNAs contain regulatory features in their sequence and structure that help regulate translation of bacterial mRNAs in response to environmental cues. Similar to what has been reported in E. coli, the sRNA is regulated in response to iron limitation in S. oneidensis MR-1 and may have a regulatory role in iron metabolism.

Committee: Mitch Balish (Advisor) Subjects: Microbiology; Molecular Biology

Master of Science in Engineering (MSEgr), Wright State University, 2017, Electrical Engineering

Considerable literature exists in linear algebra to solve the generalized eigenvalue, eigenvector problem (F - λ G)v = 0 where F, G ∈ ℜ(s × s), are square matrices. However, a number of applications lend themselves to the case where F, G ∈ ℜ(s × t), and s = t. The existing methods cannot be used for such non-square cases. This research explores structural decomposition of a matrix pencil (F - λ G), s = t to compute finite values of λ for which rank(F - λ G) < min(s,t). Moreover, from the decomposition of the matrix pencil, information about the order of λ at infinity, the Kronecker row and column indices of a matrix pencil can also be extracted. Equally important is the computation of non-zero vectors w ∈ ℜ(1 × s) and v ∈ ℜ(t × 1) corresponding to each finite value of λ, such that w(F - λ G) = 0 and (F - λ G)v = 0. Algorithms are developed for the computation of λ, w, and v using numerically efficient techniques. Proposed algorithms are applied to problems encountered in system theory and illustrated by means of numerical examples.

Committee: Pradeep Misra Ph.D. (Advisor); Xiaodong Zhang Ph.D. (Committee Member); Luther Palmer III Ph.D. (Committee Member) Subjects: Electrical Engineering; Mathematics

Doctor of Philosophy in Urban Education, Cleveland State University, 2017, College of Education and Human Services

International students face many challenges as they adapt to a new host country. These challenges are present in social, psychological, academic, and career domains of life. Although students aim to reduce the difficulties encountered in the acculturation process, negative experiences often have a harmful impact. Acculturative stress can negatively affect mental and physical health, as well as career outcomes. The literature focusing on the career-related needs and placement concerns of international students with relation to acculturative stress is scare and needs further exploration. The present study investigated the relationship between acculturative stress and the career outcomes of work hope, career outlook, occupational awareness, career agency, career aspirations (leadership, achievement, and educational), and job-search self-efficacy. The findings from this investigation suggested that international students who reported more acculturation difficulties associated with Perceived Discrimination, Perceived Hate and Fear, and to a lesser extent Homesickness; also tended to report less Work Hope, a more Negative Career Outlook, lower Achievement Aspirations, Leadership Aspirations, Educational Aspirations, Career Agency, and Job Search Self-Efficacy.

Committee: Donna Schultheiss Ph.D. (Committee Chair); Phillips Julia Ph.D. (Committee Member); Stead Graham Ph.D. (Committee Member); Horvath Michael Ph.D. (Committee Member); Perry Justin Ph.D. (Committee Member) Subjects: Counseling Psychology; Education; Mental Health; Teaching

Doctor of Philosophy, The Ohio State University, 1979, Graduate School

Committee: Not Provided (Other) Subjects: Statistics

Doctor of Philosophy, The Ohio State University, 2016, Biomedical Sciences

Biallelic mutation of the APC tumor suppressor gene occurs in a high percentage of colorectal tumors and is considered the critical event driving tumor initiation in the large intestine. The APC protein performs multiple functions, including negative regulation of the canonical WNT signaling pathway by both cytoplasmic and nuclear mechanisms. As a result, APC suppresses proliferation, cell cycle progression, and genomic instability, while facilitating differentiation, normal directional migration, and apoptosis. The contribution of APC to these phenotypes is not mediated exclusively through its effects on canonical WNT signaling, but also through WNT-independent functions of the APC protein. Intriguing reports that APC interacts with chromatin to repress key WNT-activated targets prompted this study's initial hypothesis that the chromatin-associated fraction of APC regulates gene transcription through multiple mechanisms, both WNT-dependent and WNT-independent. Chromatin immunoprecipitation and next-generation sequencing identified more than 6,000 genomic peaks associated with the APC protein. Target selection was performed by comparison to whole transcriptome sequencing data from APC-deficient and APC wild- type colon cancer cell lines and mouse tumors. 175 transcripts whose expression changes upon APC loss are linked to genomic regions physically associated with the APC protein. Motif analysis of APC-associated genomic peaks found that binding sites for the TCF7L2 and AP-1 transcription factors are overrepresented and occur in many of the same peaks. Luciferase reporter assays indicate that APC antagonizes canonical WNT signaling not only at WNT-activated genes such as PHLDB2 (Pleckstrin Homology Like Domain Family B Member 2), but also at WNT-repressed genes such as MALL (Mal, T-Cell Differentiation Protein-Like). A transcriptional element within the first intron of the MALL gene mediates transcriptional repression by the canonical WNT (open full item for complete abstract)

Committee: Joanna Groden PhD (Advisor); Albert de la Chapelle MD, PhD (Committee Member); Kay Huebner PhD (Committee Member); Mark Parthun PhD (Committee Member); Jeffrey Parvin MD, PhD (Committee Member) Subjects: Biomedical Research

Doctor of Philosophy, Miami University, 2016, Microbiology

The process of translation initiation involving the purine-rich Shine-Dalgarno sequence in bacteria has been well studied. However, approximately one-half of the mRNAs across prokaryotic genomes do not contain a Shine-Dalgarno sequence. Therefore, it is important to understand the mechanism and ribosome recognition signals involved in the Shine-Dalgarno-independent translation initiation, which is yet to be elucidated. To do this, leaderless mRNAs lacking a 5'-UTR are utilized to examine the roles of 5'-terminal AUGs in ribosome recognition. In this study, we identified AUGs at the 5'-terminus of canonical Shine-Dalgarno-led mRNAs and examined their ability to act as initiation codons for leaderless mRNA translation. The identified 5'-terminal AUGs were found to specify open reading frames that were translated at varying levels of expression, with some playing a role in downstream coding sequence regulation. Further investigation into one 5'-terminal AUG-led canonical mRNA, ptrB, identified a novel regulation mechanism that is distinct from the Shine-Dalgarno mechanism. This novel mechanism is instead controlled by the 5'-terminal AUG and can regulate in a gene context independent manner making it ideal for genetic engineering purposes. To further understand how the 5'-AUG is recognized and bound by ribosomes, a cross-linking method was developed to identify the initial interactions between leaderless mRNAs and the ribosome. Overall, this study provides insight into 5'-terminal AUG-directed translation and the role of 5'-AUGs in ribosomal recognition, binding and translational regulation.

Committee: Gary Janssen (Advisor); Mitchell Balish (Advisor); Eileen Bridge (Committee Member); DJ Ferguson (Committee Member); Xiao-Wen Cheng (Committee Member); Jack Vaughn (Committee Member) Subjects: Microbiology

Doctor of Philosophy, University of Akron, 2014, Secondary Education

This study sought to determine the impact digital readers had upon the meaning-making behaviors of secondary students as they read a canonical text on digital readers as part of a traditional high school English curriculum. A secondary purpose of the study was to determine how students' screen-based literacy practices did or did not intersect with their in-school practices. In addition, the study examined how the teacher made pedagogical decisions related to implementing the digital readers during a unit studying Frankenstein as part of a traditional English class course of study. Employing a descriptive case study design (Merriam, 2009; Stake, 1995), this qualitative study sought to explore how interacting with the unique features of a digital reader within a school context can affect secondary students. The case of this study was defined as one secondary language arts teacher and a class of her students. The 16 students participating were all high school seniors nearing the final weeks of school. In order to understand the phenomenon of interest more fully, 11 students participated in individual interviews. In addition to semi-structured interviews of the teacher and students, data collection included transcribed observational notes, responses to two questionnaires, and pertinent artifacts. Inductive data analysis was ongoing during data collection (Merriam, 2009) through use of the constant-comparative method (Glaser & Strauss, 1967; Miles, Huberman, & Saldana, 2014). Data analysis revealed four findings: (a) students' use of the digital readers significantly altered the transactional nature of a reading event; (b) implementing digital readers allowed students' greater agency than conventional print text; (c) students defended a traditional autonomous model of literacy at school; and (d) situational factors inherent to schools challenged the teacher's implementation of digital literacy practices. Scholars have begun to examine the social, cul (open full item for complete abstract)

Committee: Evangeline Newton Dr. (Advisor); Susan Kushner Benson Dr. (Advisor); Denise Stewart Dr. (Committee Member); Harold Foster Dr. (Committee Member); William Kist Dr. (Committee Member) Subjects: Education; Language Arts; Literacy; Literature; Middle School Education; Reading Instruction; Secondary Education; Teaching

Doctor of Philosophy, The Ohio State University, 2011, Materials Science and Engineering

Materials properties depend on processes that take place on a variety of time scales. These range from atomic vibrations or dislocation-mediated slip processes, which have typical time scales of hundreds of femtoseconds (fs) to hundreds of picoseconds (ps), to diffusion, which may take place on the order of seconds or longer. This disparity in time scales leads to difficulties when trying to model slower processes where individual atomic motions may be important, such as diffusion controlled boundary migration and dislocation climb. A straightforward molecular dynamics (MD) approach, with a typical time step of 1 fs, would require an enormous computation time to adequately capture these processes. This work presents a novel method, called Diffusive Molecular Dynamics (DMD), which can capture the diffusion time scale while retaining the atomic spatial resolution by coarse-graining over atomic vibrations and evolving a site-probability representation of atomic density clouds. DMD solves master equation on a moving atomic grid. It combines long-range elastic effects and short- range atomic interactions simultaneously with gradient thermodynamics. DMD has been applied to nanoindentation, hot isostatic pressing of nanoparticles, climb of edge dislocation and diffusional void growth. In nanoindentation, the simulations demonstrate that displacive plasticity depends sensitively on the remnant debris of prior diffusional plasticity. This is evident from dislocation structure, reduction in yield load and stiffness due to surface step formed by surface diffusion at low indentation rates and/or at high temperatures. In hot isostatic pressing, DMD captures the evolution of multiple nanoparticle compact to theoretical density revealing significance of rigid-body motion, and diffusional and displacive processes in obtaining the final microstructure. Dislocation nucleation triggered by diffusive void growth is also a coupled diffusive-displacive phenomenon captured by DMD. This (open full item for complete abstract)

Committee: Yunzhi Wang PhD (Advisor); Suliman Dregia PhD (Committee Member); Wolfgang Windl PhD (Committee Member) Subjects: Engineering; Materials Science; Physics

Doctor of Philosophy, The Ohio State University, 2010, ED Physical Activities and Educational Services

The purpose of the study was to examine the relationships among perceived effectiveness of NBTAs, extent of advice networks, and perceived job outcomes in a semiconductor manufacturing company in Korea, using a mixed method. The data for the quantitative study were collected from an online survey questionnaire. The population consisted of all employees (N=15,000) who were working in production facilities of the company or branch offices in Korea. The total number of respondents was 188 out of 375 employees randomly selected, with an overall response rate of 50.13%. The data for the qualitative study were gathered from semi-structured interviews with eight employees who responded to the online survey. Canonical correlation analysis and hierarchical regression analysis were utilized to analyze the survey data. Additionally, content analysis was employed to analyzed and interpret the interview data. The results showed that on-the-job training approaches and training approaches within a business unit were perceived to be more helpful than common training approaches to develop advice relations. Yet, no relationships were found between advice networks and the perceived effectiveness of NBTAs. The results also indicated that no mediation occurred between the perceived effectiveness of NBTAs and perceived job outcomes. Although the study failed to reveal the mediation between the perceived effectiveness of NBTAs and perceived job outcomes, the findings from the quantitative and qualitative studies provided evidences that NBTAs helped individuals develop advice networks, and the development of advice networks through NBTAs had an impact on individual job performance and job satisfaction. In addition, the results of this study identified four processes which create advice networks through training approaches: 1) developing advice networks based on job-relatedness, 2) sharing a common interest among others, 3) spending time doing group activities with others, and 4) spending (open full item for complete abstract)

Committee: Ronald Jacobs PhD (Advisor); Joshua Hawley EdD (Committee Member); Larry Miller PhD (Committee Member) Subjects: Adult Education

Doctor of Philosophy, The Ohio State University, 2009, Electrical and Computer Engineering

This dissertation presents a new set of three-dimensional scattering feature models for synthetic aperture radar (SAR). We develop a set of parametric models of canonical shapes that capture aspect-dependent, high-frequency scattering for bistatic (and monostatic) 3D SAR phase history responses. The models are parameterized by the shape location, orientation, and size as well as the radar transmitter and receiver antenna aspects and frequency. We develop the models by combining physical optics (PO) and uniform theory of diffraction (UTD) planar scattering solutions to approximate 3D scattering responses of canonical shapes. We validate the models using scattering prediction software and show that the proposed models capture well the mainlobe responses of each shape. Thus, the proposed models may be used to accurately predict first-order scattering of scenes comprised of such shapes.The second part of this dissertation focuses on the inverse problem of discerning the types of canonical shapes in a scene and estimating their corresponding model parameters from observed SAR phase history data. We present discrimination methods for classifying observed scattering into the geometric shape types. We compute the Cramer-Rao bounds for the models and characterize model parameter estimation accuracy for two estimation schemes. Finally, we present a feature extraction algorithm that classifies and estimates the canonical features from polarimetric phase history data. We use non-quadratic regularization to form sparsity-constrained 3D SAR images that are used to initialize the scatterer location, orientation, and size estimates. We test the feature extraction algorithm on simulated phase histories for densely-sampled and sparsely-sampled, monostatic and bistatic 3D SAR apertures. We show that even for sparsely-sampled apertures, the feature extraction algorithm is able to estimate geometric scattering features in the scene. Feature extraction for the proposed canonical shape mo (open full item for complete abstract)

Committee: Randolph Moses PhD (Advisor); Lee Potter PhD (Committee Member); Emre Ertin PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2007, Mathematics

Coxeter groups arise in many parts of mathematics as groups generated by reflections. They provide an important source of examples in geometric group theory, where "virtual" properties of infinite groups, that is, properties of subgroups of finite index, are of strong interest. This dissertation focuses on virtual properties of infinite Coxeter groups. The following results are proved: (1) The intersection of a collection of parabolic subgroups of a Coxeter group is a parabolic subgroup; (2) The center of any finite index subgroup of an irreducible, infinite, non-affine Coxeter group is trivial; (3) Any finite index subgroup of an irreducible, infinite, non-affine Coxeter group cannot be expressed as a product of two nontrivial subgroups. Then, a unique decomposition theorem for subgroups of finite index in a Coxeter group without spherical or affine factors is proved based on (2) and (3). It is also proved that the orbit of each element other than the identity under the conjugation action in an irreducible, infinite, non-affine Coxeter group is an infinite set, which implies that an irreducible, infinite Coxeter group is affine if and only if it contains an abelian subgroup of finite index. Besides these, new proofs are given for the statement that the center of an irreducible, infinite Coxeter group is trivial, and a stronger version of this statement.

Committee: Michael Davis (Advisor) Subjects: Mathematics