Doctor of Philosophy, The Ohio State University, 2023, Electrical and Computer Engineering

Beta-phase gallium oxide (β-Ga2O3), with its ultrawide band gap energy (~4.8 eV), high predicted breakdown field strength (6-8 MV/cm), controllable n-type doping and availability of large area, melt-grown, differently oriented native substrates, has spurred substantial interest for future applications in power electronics and ultraviolet optoelectronics. The ability to support bandgap engineering by alloying with Al2O3 also extends β-(AlxGa1-x)2O3 based electronic and optoelectronic applications into new regime with even higher critical field strength that is currently unachievable from SiC-, GaN- or AlxGa1-xN- (for a large range of alloy compositions) based devices. However, the integration of β-(AlxGa1-x)2O3 alloys into prospective applications will largely depend on the epitaxial growth of high quality materials with high Al composition. This is considerably important as higher Al composition in β-(AlxGa1-x)2O3/Ga2O3 heterojunctions can gain advantages of its large conduction band offsets in order to simultaneously achieve maximized mobility and high carrier density in lateral devices through modulation doping. However, due to the relative immaturity of β-(AlxGa1-x)2O3 alloy system, knowledge of the synthesis and fundamental material properties such as the solubility limits, band gaps, band offsets as well as the structural defects and their influence on electrical characteristics is still very limited. Hence, this research aims to pursue a comprehensive investigation of synthesis of β-(AlxGa1-x)2O3 thin films via metal organic chemical vapor deposition (MOCVD) growth methods, building from the growth on mostly investigated (010) β-Ga2O3 substrate to other orientations such as (100), (001) and (-201), as well as exploring other polymorphs, such as alpha (α) and kappa (κ) phases of Ga2O3 and (AlxGa1-x)2O3 to provide a pathway for bandgap engineering of Ga2O3 using Al for high performance device applications. Using a wide range of material characterization techniqu (open full item for complete abstract)

Committee: Hongping Zhao (Advisor); Siddharth Rajan (Committee Member); Steven A. Ringel (Committee Member); Sanjay Krishna (Committee Member) Subjects: Condensed Matter Physics; Electrical Engineering; Engineering; Materials Science; Nanoscience; Nanotechnology; Physics

Doctor of Philosophy, The Ohio State University, 2008, Materials Science and Engineering

Microstructural evolution in Beta Titanium alloys is an important factor that governs the properties exhibited by them. Intricate understanding of complex phase transformations in these alloys is vital to tailor their microstructures and in turn their properties to our advantage. One such important subject of study is the nucleation and growth of alpha precipitates triggered by the compositional instabilities in the beta matrix, instilled in them during non equilibrium heat treatments. The present work is an effort to investigate such a phenomenon.Here studies have been conducted primarily on two different Beta-Titanium alloys of commercial relevance- Ti5553 (Ti-5Al-5Mo-5V-3Cr-0.5Fe), an alloy used in the aerospace industry for landing gear applications and, TNZT (Ti-35Nb-7Zr-5Ta), a potential load bearing orthopedic implant alloy. Apart from the effect of thermal treatment on these alloys, the focus of this work is to study the interplay between different alpha and beta stabilizers present in them. For this, advanced nano-scale characterization tools such as High Resolution STEM, High Resolution TEM, EFTEM and 3D Atom Probe have been used to determine the structure, distribution and composition of the non equilibrium instabilities such as beta phase separation and omega phase, and also to investigate the subsequent nucleation of stable alpha. Thus in this work, very early stages of phase separation via spinodal decomposition and second phase nucleation in titanium alloys are successfully probed at an atomic resolution. For the first time, atomically resolved HRSTEM Z-contrast image is recorded showing modulated structures within the as-quenched beta matrix. Also in the same condition HRTEM results showed the presence of nanoscale alpha regions. These studies are revalidated by conventional selected area diffraction and 3D atom probe reconstruction results. Also TEM dark field and selected area diffraction studies are conducted to understand the effect of quenching (open full item for complete abstract)

Committee: Hamish L. Fraser PhD (Advisor); Rajarshi Banerjee PhD (Committee Member); James C. Williams PhD (Committee Member); William A.T. Clark PhD (Committee Member) Subjects: Materials Science

Master of Science in Chemistry, Youngstown State University, 2022, Department of Biological Sciences and Chemistry

Gas-phase ligand exchange reactions of a series of metal beta-diketonate complexes were observed to occur within a triple quadrupole mass spectrometer. Calcium beta-diketonate complexes, when co-sublimed with other metal beta-diketonate complexes, were observed to undergo partial, mixed, and complete ligand exchange. Calcium-containing species were also found to cluster leading to multiple metal and ligand additions. The gas-phase reactions reported herein provide additional evidence into the gas-phase ligand exchange of beta-diketonates.

Committee: Brian Leskiw PhD (Advisor); Ganesaratnam Balendiran PhD (Committee Member); Josef Simeonsson PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry; Gases; Inorganic Chemistry; Physical Chemistry

Master of Science in Mechanical Engineering, Cleveland State University, 2018, Washkewicz College of Engineering

In metallurgy, Titanium has been a staple for biomedical purposes. Its low toxicity and alloying versatility make it an attractive choice for medical applications. However, studies have shown the difference in elastic modulus between Titanium alloys (116 GPa) and human bone (40-60 GPa) contribute to long term issues with loose hardware fixation. Additionally, long term studies have shown elements such as Vanadium and Aluminum, which are commonly used in Ti-6Al-4V biomedical alloys, have been linked to neurodegenerative diseases like Alzheimers and Parkinsons. Alternative metals known to be less toxic are being explored as replacements for alloying elements in Titanium alloys. This research will focus on advanced processing and characterization of beta-phase Titanium alloys for biomedical applications. The microstructure, mechanical and electrochemical properties of these alloys have been analyzed and compared with C.P. Titanium. The main objective is to study the effect of different alloying elements on microstructure, phase transformation and mechanical properties of these newly developed beta-phase Titanium alloys and establish new avenues for the future development of biocompatible Titanium alloys with optimum microstructure and properties.

Committee: Tushar Borkar Ph.D (Committee Chair); Taysir Nayfeh Ph.D (Committee Member); Jason Halloran Ph.D (Committee Member) Subjects: Biomedical Research; Design; Materials Science; Mechanical Engineering

Master of Science in Chemistry, Youngstown State University, 2017, Department of Chemistry

A series of gas-phase reactions were performed via co-sublimation within a triple quadrupole electron impact mass spectrometer. Novel alkaline earth and transition metal bis-diisopropylacetylacetonate coordination complexes were synthesized and observed to undergo gas-phase ligand exchange with select alkaline earth and transition metal bis-acetylacetonate and bis-trifluorotrimethylacetylacetonate complexes, and are reported herein for the first time. Also, novel alkaline earth and transition metal coordination compounds were characterized via x-ray crystallography. The results from these gas-phase experiments further establish the foundation of ligand exchange for this class of compounds.

Committee: Brian Leskiw PhD (Advisor); Howard Mettee PhD (Committee Member); Sherri Lovelace-Cameron PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry; Inorganic Chemistry; Physical Chemistry

Doctor of Philosophy (PhD), Wright State University, 2016, Electrical Engineering

This dissertation considers the optimization of radar performance within the structure imposed by a coded Orthogonal Frequency Division Multiplexing (OFDM) format required to achieve an acceptable communication link. The dual goal of achieving both satisfactory radar and communication performance raises challenges that can be substantively addressed by combining phase coding and modulation techniques to provide the temporal and spectral structure necessary to implement simultaneous radar and communication operations. In particular, the specific techniques, as introduced within this dissertation, of using the Multi-Frequency Complementary Phase Coded (MCPC) sequences, as prescribed by Levanon and Mozeson, for simultaneous radar and wireless communication operations represent a novel contribution and offers a significant improvement in the study, implementation, and performance of dual use radar and communication waveforms and signal processing techniques. Specific contributions of this dissertation include: 1) as will be demonstrated, not all valid MCPC sequences can be used for data transmission, and, therefore, a subset of MCPC sequences are chosen with consideration to radar detection performance, 2) communication operation is improved through the introduction of an algorithm that enables Gray codes to be applied to MCPC sequences, 3) the orthogonality of MCPC sequences is exploited to overcome the effects of multipath fading and intercarrier interference, 4) a new detector type, termed the Beta detector, is developed for both communications operations and radar detection, 5) a radar detection method, termed Polar Signal Detection, is developed that combines the Beta detector with a traditional matched filter detector to achieve superior detection performance as compared to traditional Cell-Averaging Constant False Alarm Rate (CA-CFAR) detectors in multi-target environments, and 6) a novel method of measuring Doppler frequencies is introduced that is superior t (open full item for complete abstract)

Committee: Zhiqiang Wu Ph.D. (Advisor); Fred Garber Ph.D. (Committee Member); Kefu Xue Ph.D. (Committee Member); Bin Wang Ph.D (Committee Member); Chi-Hao Cheng Ph.D. (Committee Member); Vasu Chakravarthy Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science in Chemistry, Youngstown State University, 2014, Department of Chemistry

A series of gas-phase reactions were performed via co-sublimation using a triple quadrupole electron impact mass spectrometer. Novel palladium ß-diketonate complexes, along with several other species containing different metals and ligands were synthesized and observed to readily undergo ligand exchange in the gas phase and are reported herein for the first time. Selective reactions were also conducted involving Pd and Ni complexes utilizing the collision cell of the mass spectrometer as a reaction vessel. Results from these gas-phase reactions shed light on the mechanism of ligand exchange for this class of metal ß-diketonate complexes.

Committee: Brian Leskiw Ph.D. (Advisor); Howard Mettee Ph.D. (Committee Member); Ganesaratnam Balendiran Ph.D. (Committee Member) Subjects: Analytical Chemistry; Chemistry; Gases; Inorganic Chemistry; Physical Chemistry

Master of Science in Chemistry, Youngstown State University, 2014, Department of Chemistry

A series of gas-phase ligand exchange reactions involving Cadmium trifluorotrimethylacetylacetonate (Cd(tftm)2) were examined using a triple quadrupole mass spectrometer. Multiple co-sublimation experiments were explored with various metal ß-diketonates where several partial and complete ligand exchange processes were observed and are reported herein for the first time. In an attempt to elucidate possible mechanisms leading to the formation of the mixed ligand complex, select ion-neutral experiments were conducted within the collision cell of the triple quadrupole mass spectrometer.

Committee: Brian Leskiw PhD (Advisor); Howard Mettee PhD (Committee Member); Ganesaratnam Balendiran PhD (Committee Member) Subjects: Analytical Chemistry; Chemistry; Inorganic Chemistry; Physical Chemistry

Master of Science in Chemistry, Youngstown State University, 2008, Department of Chemistry

A series of gas-phase reactions between various transition metal β-diketonate complexes were observed in situ using a double sector mass spectrometer. Co, Ni, Cu, Zn and Al complexes with the ligands 2,4-pentanedione, 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione were used. Metal center and ligand effects are investigated. Ligand exchange reactions were observed to occur readily between binary combinations of most complexes and an ion-neutral reaction mechanism is proposed. Heteroleptic species were also synthesized through ligand exchange reactions in solvo to yield monomeric and dimeric structures of heteroleptic nickel species with the ligands 2,4-pentanedione and 1,1,1,5,5,5-hexafluoroacetylacetonate.

Committee: Brian D. Leskiw PhD (Advisor); Larry S. Curtin PhD (Committee Member); Howard D. Mettee PhD (Committee Member) Subjects: Chemistry

Doctor of Philosophy, The Ohio State University, 2011, Chemical Physics

Laser spectroscopy is a powerful tool to study the structure and photochemistry of molecules at selected electronic states. Under jet-cooled conditions, the rotational spectrum can be simplified with less congestion on the rotational contour owing to the low J population on the ground electronic state. Laser induced fluorescence (LIF), stimulated emission pumping (SEP), and cavity ringdown spectroscopy (CRDS) apparatuses are used to measure the methoxy(CH3O·), β-hydroxyethylperoxy (HOC2H4OO·) and nitrate (NO3·) radicals. The novel laser spectroscopy apparatuses are designed for the direct measurement to the forbidden electronic state attributed to the selection rules or low absorption cross section. The spectroscopic analysis applies the least-square fitting to determine the molecular parameters in Hamiltonians as well as the vibronic coupling induced distortion of molecular structure. Furthermore, in the collaboration with Dr. W. Leo Meerts (Radboud University, The Netherlands), the quantum mechanical model is also adapted to the evolutionary algorithm to investigate the biological evaluation on spectrum simulation.The ~A2A1-~X2E3/2 and ~X2E1/2-~A2A1 electronic transitions of methoxy and all four deuterium isotopologues are measured with a LIF/SEP apparatus that is both high-resolution (Δν ∼ 250 MHz) and and high-accuracy (Δσ ∼ 50 MHz). Since the ~X2E1/2 state is not thermally populated in a jet-cooled environment, the complementary SEP experiment directly interrogates the ~X2E1/2 level of methoxy by depleting the fluorescence from the ~A2A1 state. The global analysis of the microwave, LIF, and SEP data breaks correlations in the microwave data and provides better determinations for the ~X and ~A states′ parameters. The jet-cooled ~A-~X origin band spectra of 1G2G3 conformer of β-hydroxyethylperoxy have been recorded by a CRDS appratus with a laser source linewidth  ∼ 70 MHz in the near IR region. The spectra of four deuterium-substituted isotopologues have been (open full item for complete abstract)

Committee: Terry Miller A. (Advisor); Frank DeLucia (Committee Member); Walter Lempert (Committee Member); Guanglong He (Committee Member) Subjects: Physical Chemistry

Doctor of Philosophy, The Ohio State University, 2008, Nursing

The total cesarean rate in the United States in 2006 was 466% greater than in 1970 (31.1% and 5.5%, respectively). Among term, low-risk, nulliparous women, a cesarean rate of 25% was reported by the Centers for Disease Control and Prevention in 2005. These rates are higher than ever before and farther from national objectives. While in some cases necessary for the health of the mother and/or neonate, cesareans are major surgical procedures that carry multiple short- and long-term risks. It is suggested that a cesarean rate between 5-10% for any world region seems to achieve the best outcomes, whereas a rate higher than 15% seems to result in more harm than good. Studying factors that may contribute to cesareans must be a research priority.Dystocia (i.e., slow, abnormal progression of labor) is the most common indication for cesareans. Clinically, dystocia is generally defined as a delay in cervical dilation progression beyond which accelerative interventions, e.g., uterine contraction augmentation via oxytocin administration, are considered justifiable. Rates of augmentation in contemporary practice suggest that the clinical expectations of nulliparous labor have surpassed normalcy. Hence, it is possible that current definitions of dystocia, in terms of cervical dilation rates, may be inappropriately defined. The first manuscript of this dissertation document presents a systematic review aimed at identifying the norms and limits of active phase labor length and active phase cervical dilation rates in low-risk, nulliparous women with spontaneous labor onset in order to better define labor expectations. It is concluded that active phase labor is longer and has a wider range of normal than is generally appreciated. Likewise, overall linear rates of cervical dilation in the active phase are not as steeply sloped as traditionally believed. Although the cause(s) of true labor dystocia can rarely be diagnosed with objective certainty, the greatest contributor is inefficien (open full item for complete abstract)

Committee: Elizabeth J. Corwin PhD, RN (Advisor); Karen L. Ahijevych PhD, RN, FAAN (Committee Member); Nancy A. Ryan-Wenger PhD, RN, FAAN (Committee Member) Subjects: Biomedical Research; Health Care; Nursing; Obstetrics