Thesis (Ph. D.)--University of Wisconsin--Madison, 1976. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 211-215).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The reaction of butyrospermol with hydrogen chloride has been investigated. Butyrospermol has been shown to possess a typical, triterpenoid Ring A and to be a member of the group of triterpenes typified by euphol. The reaction of euphol with hydrogen chloride has also been investigated and compared with that of butyrospermol. The chemistry of isoeuphenyl acetate has been studied and a complete structure for euphol has been proposed. The tetracyclic triterpenes have been classified into two groups, on the basis of spectroscopic and molecular rotation evidence.

No description available.

Thesis (M.S.)--Ohio University, June, 1999. / Title from PDF t.p.

Thesis (Ph. D.)--Ohio University, November, 1999. / Title from PDF t.p.

No description available.

This dissertation study describes the development of novel heteroepitaxial growth of 3C-SiC layers by chemical vapor deposition (CVD). It was hypothesized that chloride addition to the "traditional" propane-silane-hydrogen precursors system will enhance the deposition growth rate and improve the material quality via reduced defect density. Thermodynamic equilibrium calculations were performed to obtain a criterion for which chloride specie to select for experimentation. This included the chlorocarbons, chlorosilanes, and hydrogen chloride (HCl) chloride containing groups. This study revealed no difference in the most dominant species present in the equilibrium composition mixture between the groups considered. Therefore, HCl was the chloride specie selected to test the hypothesis. CVD computerized fluid dynamic simulations were developed to predict the velocity, temperature and concentration profiles along the reactor. These simulations were performed using COMSOL Multiphysics and results are presented. The development of a high-temperature (1300 °C -1390°C) 3C-SiC growth process resulted in deposition rates up to ~38 µm/h. This is the highest value reported in the literature to date for 3C-SiC heteroepitaxy. XRD FWHM values obtained varied from 220 to 1160 arcsec depending of the process growth rate or film thickness. These values are superior or comparable to those reported in the literature. It was concluded from this study that at high deposition temperatures HCl addition to the precursor chemistry had the most significant impact on the epitaxial layer growth rate. Low-temperature (1000-1250°C) 3C-SiC growth experiments evidenced that the highest deposition rate that could be attained was ~2.5 µm/h. The best quality layer achieved in this study had a FWHM of 278 arcsec; which is comparable to values reported in the literature and to films grown at higher deposition temperatures in this study. It was concluded from this work that at lower deposition temperatures the HCl addition was more beneficial for the film quality by enhancing the surface. Surface roughness values for films grown with HCl additive were 10 times lower than for films grown without HCl. Characterization of the epitaxial layers was carried out via Nomarski optical microscopy, FTIR, SEM, AFM, XRD and XPS.

This study presents airborne measurements of HO2NO2, HCl and SO2 using chemical ionization mass spectrometry (CIMS) during the Intercontinental Chemical Transport Experiment (INTEX) field campaign, an intensive study to characterize the chemical composition of the troposphere in the eastern United States, Mexico City, and the North Pacific which is the outflow region of Asia. The first direct in situ measurements of HO2NO2 were made in the free troposphere over the eastern U.S. during summer 2004. The highest mean mixing ratio of 76 pptv (median = 77 pptv, = 39 pptv) was observed in the altitude range of 8-9 km. Highly constrained steady state calculations of HO2NO2 using measured HOx levels are poorly correlated with observed HO2NO2 in the upper troposphere (8 km < z < 12 km; the median ratio of [HO2NO2]SS-MEA/[HO2NO2]MEA = 2.9). However, steady state HO2NO2 using model-derived HOx shows reasonable agreement with measurements in the free troposphere ([HO2NO2]SS-MEA/[HO2NO2]MEA = 1.3). The vertical distribution of HCl was measured over the north Pacific during May 2006 from the marine boundary layer (MBL) up to lower stratosphere. Recent stratospheric influence in the upper troposphere (8 km < z < 12 km) was efficiently identified from enhanced HCl (up to ~100 pptv) relative to very low background levels (< 2pptv). In the remote MBL, the acidification of seasalt aerosols by HNO3 appeared to be the major source of HCl, with level consistently over 20 pptv (up to 400 pptv). The distribution of SO2 was measured in the outflow region of the eastern U.S. and Asia; two major anthropogenic SO2 source regions. This study presents vertical and horizontal distributions of SO2 and relevant gas phase and aerosol parameters to characterize SO2 transport in the troposphere. SO2 in the boundary layer was efficiently transported to the upper troposphere by deep convection and frontal uplift processes. High SO2 in convective plume in the upper troposphere were strongly correlated with ultrafine aerosols.Conversely, SO2 from frontal uplift shows a strong correlation with non-volatile aerosols. Comparisons of SO2 products from global 3-D chemical transportation models (GEOS-CHEM and MOZART) with observations suggest that sulfur sources are relatively well described but that the oxidation mechanism needs refinement.

An examination of the seasonal and spatial distribution of Polar Stratospheric Clouds (PSCs) inferred from standard temperature profiles in the lower-middle atmosphere above Antarctica, as derived from the Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) satellite observations and NCEP/NCAR assimilations, is provided. Chemical volume mixing ratio (VMR) observations of EOS Aura MLS v2.2 hydrogen chloride (HCl) were used to show the interannual variability of PSC formation with respect to stratospheric chlorine partitioning during five Southern Hemisphere Antarctic seasons from 2005 to 2009. A remarkable first set of results, obtained from an algorithm developed for modelling HCl depletion areas in the Antarctic polar vortex region, and based on satellite observations, is presented. In particular, the analysis of HCl concentration data obtained from 2006 indicated that the area processed for HCl was larger than the area of PSC during some periods of Antarctic winter, and that this result was robust with respect to the various PSC formation and HCl depletion thresholds utilized. The results suggest that an underestimation in chlorine activation area can occur when temperature thresholds for PSC formation thresholds are employed. The work presented here also evaluated chlorine activation via sulfate aerosol (SA) in the Southern Hemisphere 2006 stratosphere, based on satellite measurements of water vapor (H2O) and constant values of SA, by implementing the TACL formula of Drdla and Müller [2010] in contrast to the TNAT formula of Hanson and Mauersberger [1988]. The results indicated that the former formula was not completely sufficient for accurately modeling areas of depleted HCl and chlorine deactivation for all pressure surfaces in the Antarctic stratosphere. Based on the results of this study, the role of SA in chlorine activation appears to be more important at lower altitudes than for areas higher in the stratosphere.