We use rst-principles calculations based on density functional theory to study the structural properties and pressure-induced solid-solid phase transitions of ZnO. Both the local-density approximation (LDA) and the PBE96 form of the generalized gradi- ent approximation (GGA) are employed together with the projector augmented wave (PAW) method to mimic the electron-ion interaction. The electronic structure is investigated by the HSE hybrid functional and a partially self-consistent GWapprox- imation. We consider the wurtzite (B4), rocksalt (B1), zinc blende (B3), CsCl (B2), PbO (B10), NaTl (B32), WC (Bh), BN (Bk), NiAs (B81) and AsTi (Bi) modi cations of ZnO. The calculated structural properties in the B4, B3, B1 and B2 phases compare acceptably well with those found in previous theoretical studies, as is the transition pressure between them. We nd that the B4 phase is the most preferred low-pressure candidate in ZnO while the B2 phase is favorable at high pressures. Apart from the previously reported B4!B1!B2 phase transition, our study reveals other possible paths for a transition from B4 to B2 phase with the Bk, Bh, B10, and B81 structures as intermediate phases. It is found that the HSE and the GW approach o¤er a signif- icant improvement to the prediction of band-gaps in ZnO. The band-gaps are found to increase with increasing pressure leading to the structural phase transitions.

The nature and magnitude of experimental errors due to ⁶⁵Zn adsorption by inorganic surfaces was examined in a laboratory system designed to measure ⁶⁵Zn uptake by marine phytoplankton. In the pH range, 6.3±.1 to 7.5±.1, a precipitate formed in the algal nutrient medium selected for the system. To this seawater-base medium, zinc was added only as carrier-free ⁶⁵Zn. The precipitate increased in both volume and tendency for ⁶⁵Zn uptake as the pH increased. At a pH of 7.5±.1 the particles, predominantly orthophosphates, accumulated 70 percent of the ⁶⁵Zn in the medium in 24 hours. It was therefore concluded that ⁶⁵Zn adsorption by undetected precipitates could result in serious errors in measurements of ⁶⁵Zn uptake by marine phytoplankton. Equilibrium of ⁶⁵Zn adsorption by Pyrex glass surfaces was attained between .50 and 2.0 hours elapsed time. Found to be negligible at pH values less that 6.0±.1, such uptake was a linear function of the hydrogen ion concentration in the pH range, 6.7±.1 to 8.2±.1. Pretreatment of the glass surfaces with dimethyldichiorosilane (General Electric "Dry Film") reduced ⁶⁵Zn adsorption by over 80 percent. The relationship between percent ⁶⁵Zn sample adsorption and wetted glass surface area/pipette sample volume was shown to be linear for volumetric pipettes of the size range, 1-15 ml. At a pH of 7.5±.1, ⁶⁵Zn adsorption was negligible for most laboratory glassware, but increased with increased pH. At a pH value of about 8.0, glassware having surface area/sample volume ratios as small as those of 15 and 20 ml volumetric pipettes adsorbed 7 to 11 percent of the contained sample activity. Two prerinses with the sample liquid were required to reduce such errors by a factor of one half. / Graduation date: 1971

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1931. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed February 9, 2010) Includes bibliographical references (p. 53) and index (p. 54).

Abstract: Functionalization of the ubiquitous bis(imino)acenaphthene ligand class has been explored. The successful functionalization of this ligand type was found to be dependent upon the steric congestion encompassing the N-C-C-N fragment of the aryl substituted BIAN ligand. The sterically directed functionalization was found to proceed via either a radical backbone dearomatization route or a nucleophilic imine C-alkylation pathway. The structures of each of the functionalized BIAN derivatives were examined by means of single crystal X-ray crystallography. The foregoing reactions were also probed by EPR spectroscopy and DFT-D calculations in order to help elucidate the nature of the driving forces that are involved in BIAN functionalization. A series of aryl substituted BIAN zinc(II) chloride complexes were also prepared and their photophysical properties were investigated. Initially, four different methylated aryl substituents were examined, namely the 4-methylphenyl, 3,5-dimethylphenyl, 2,4,6-trimethylphenyl, and 2-methylphenyl derivatives. Examination of these four complexes revealed them to be non-emissive in solution. However, it was also determined that the 4-methylphenyl and 3,5-dimethylphenyl substituted complexes were emissive in the solid state. On the other hand, the 2,4,6-trimethylphenyl, and 2-methylphenyl complexes were found to be non-emissive in the solid state. The origins of the emissions of the foregoing complexes were also probed by means of TD-DFT calculations. The tuning of the stereoelectronic properties of a series of para-substituted aryl BIAN zinc(II) chloride complexes was undertaken with the view to modifying their solid state photophysical properties. For example, changing the electronic properties of the flanking para-substituted aryl substituents permitted tunability within the range of the red-orange-yellow emissions. Tunability was also achieved by employing a variety of different recrystallization techniques for growing the various structures, polymorphs, and solvatomorphs of each BIAN zinc(II) chloride complex. Boron arsenide, a somewhat neglected semiconductor compound, has been examined for its potential use as a high thermal conductivity material. High quality single crystal BAs microstructures have been synthesized and characterized by means of powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy. The thermal conductivity properties of the BAs microstructures have been probed using microheater devices. / text

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Many of the symptoms of zinc deficiency and diabetes are the same, and are related to increased inflammation. Zinc supplementation may improve immunity and glycemic control, and reduce inflammation. The purpose of this study was to determine if marginal zinc deficiency (MZD) worsens and zinc supplementation (ZS) improves diabetes and immune parameters in Zucker diabetic fatty (ZDF) rats. Male ZDF rats were fed MZD (4 mg Zn/kg diet), zinc control ([ZC], 30 mg Zn/kg diet), or ZS (300 mg Zn/kg diet) diet, and lean ZDF rats fed ZC diet for 8 weeks. Parameters of diabetes, inflammation, and immune cell proportions and function were assessed. Results showed that MZD may exacerbate diabetes but had little effect on the immune parameters, while ZS had little effect on diabetes but may worsen immune function. Overall, it is the balance between zinc deficiency and toxicity that is necessary for optimal health improvements.

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