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 (PhD), Ohio University, 2022, Physics and Astronomy (Arts and Sciences)

The work and results discussed in this dissertation are presented in two parts. In the first part, the low energy 3He-alpha elastic scattering has been treated in a halo effective field theory (halo EFT) that exploits the separation of scales in this reaction. The amplitude up to next-to-next-to-leading order has been computed, developing a hierarchy of the effective-range parameters (ERPs) that contribute at various orders of the EFT. The resulting formalism has been used to analyze data for recent measurements at center-of-mass (CM) energies between 0.38 and 3.12 MeV using the scattering of nuclei in inverse kinematics (SONIK) gas target at TRIUMF as well as older data in this energy regime. A likelihood function that incorporates the theoretical uncertainty due to truncation of the EFT at a certain order has been employed in a Bayesian analysis of the posterior probability distribution of the ERPs. The posterior distributions of the ERPs and other relevant parameters have been obtained using Markov Chain Monte Carlo sampling. It is found here that the inclusion of a small amount of data on the analyzing power Ay is crucial to determine the sign of the p-wave splitting. The combination of Ay and SONIK data constrains all ERPs up to O(p^4) in both s- and p-waves quite well. The asymptotic normalization coefficients and s-wave scattering length are found consistent with a recent EFT analysis of the capture reaction 3He(alpha, gamma)7Be. In the second part, an additional contribution to the amplitude due to the vacuum polarization (VP) effect has been considered. The formalism to include this effect in all partial wave channels has been developed in terms of a VP phase shift, which is only tiny fraction of the sum of nuclear and coulomb phase shift. Exactly the same Bayesian modeling and sampling method used in the first part has been used to extract the ERPs when the effect of VP has been included. The change in chi-square, $\Delta \chi^2 = +0.19$ when the VP eff (open full item for complete abstract)

Committee: Daniel Phillips (Advisor); Rida Benhaddou (Committee Member); Carl Brune (Committee Member); Charlotte Elster (Committee Member) Subjects: Physics

Master of Science, The Ohio State University, 2012, Human Ecology: Human Nutrition

The absorption of xenobiotics into systemic circulation is impacted by phase II metabolism in the small and large intestine. Enterocytes are absorptive cells in the small intestine that are involved in the metabolism and transport of nutrients and xenobiotics from the lumen to systemic circulation. The inflammatory condition is known to affect endogenous nutrient metabolism and xenobiotic metabolism in the liver. In contrast, minimal attention has been given to the impact of inflammation on the digestion and absorption of dietary compounds. This study examined the influence of an inflammatory environment on the metabolism and distribution of alpha-mangostin in enterocyte-like Caco-2 cells grown on porous membrane inserts. alpha-Mangostin belongs to a family of prenylated polyphenols referred to as xanthones that have antioxidant and anti-inflammatory activities. Xanthones are relatively abundant in the pericarp of mangosteen fruit. Exposure of highly differentiated Caco-2 cells grown to inflammatory cytokines was associated with decreased expression of uridine diphosphate glucuronsyltransferases 1A (UGT1A) and increased beta-glucuronidase activity in Caco-2 cells. Pre-treatment with a pro-inflammatory cocktail altered the metabolism and distribution of alpha-mangostin in three-compartment culture model. The inflammatory state was associated with an increase in the concentration of free alpha-mangostin in Caco-2 cells and the basolateral compartment compared to control cultures. Exposure to pro-inflammatory cytokines also decreased the amount of phase II metabolites (glucuronidated/sulfated) of alpha-mangostin in Caco-2 cells and basolateral medium. This reduction in phase II metabolites of α-mangostin is explained, in part, by reduced expression of UGT1A and increased activity of beta-glucuronidase in Caco-2 cells. Collectively, these findings suggest that inflammation may alter absorption of alpha-mangostin.

Committee: Mark Failla PhD (Advisor); Earl Harrison PhD (Committee Member); Ouliana Ziouzenkova PhD (Committee Member) Subjects: Biology; Nutrition