The tarnishing of electrum (40 atom % Ag) at 750°C and a sulfur fugacity of -2.8 to -2.9 1og₁օ atmospheres is heterogenous and irreversible. This is the case even though these conditions are less than 37°C and .4 log₁օ atmospheres above the point at which tarnish is first observed on the electrum. The tarnish forms initially on the grain boundaries and lattice defects of the electrum. With time, the interiors of the electrum grains become completely masked by tarnish except for narrow untarnished borders adjacent to the grain boundaries. Microprobe analysis indicates that the untarnished borders are depleted in silver and thus cannot tarnish at 750°C. The conclusion is drawn that the tarnish forms as an external layer which destroys the original composition of the adjacent electrum by preferentially removing silver. The silver depletion near the grain boundaries is thought to be caused by rapid diffusion of silver along grain boundaries to the electrum-tarnish interface. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Covalent antibody recruiting molecules (cARMs) are synthetic chemical tools that direct antibodies naturally present in human serum to tumor receptors leading to immune recognition and elimination. cARMs have three general features: an antibody binding domain (ABD), an antibody labelling domain (ALD), and a tumor binding domain. Proximal to the ABD, the ALD contains an electrophilic group which is attacked by a nucleophilic amino acid residue on the target antibody upon cARM binding. Previous cARMs use an acyl-imidazole (AL) ALD to successfully covalently recruit anti-dinitrophenyl IgG validated via fluorescence SDS-PAGE,and form immune complexes with PSMA+ HEK cells in ADCP flow experiments.1 Through MS analysis, AL cARMs were demonstrated to target lysine-59 of antiDNP.1 Problematically, there are several properties associated with AL chemistry that limit the therapeutic potential of associated cARMs. These limitations include limited stability in vivo, single amino acid (lysine) selectivity, and modest intramolecular protein labelling rates (10-5 s-1)1. To target novel antibody residues and possibly improve the rate of antibody labelling, a second generation of cARMs has been developed using sulfur fluoride exchange (SuFEx) chemistry as the ALD. Sulfur fluorides have been broadly used in academic and industrial applications due to intrinsically high stability and broad amino acid reactivity.2 SuFEx cARMs are hypothesized to have enhanced hydrolytic stability compared to AL cARMs. This thesis explores the synthesis, stability, binding, and labeling kinetics of SuFEx cARMs to advance cARM design and development for in vivo applications. This research contributes collectively to the design and development of novel therapeutics in chemical biology and immune-oncology research. / Thesis / Master of Science (MSc)

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xvii, 217 p. : ill. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1950. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 66-77).

No description available.

The sulfur supply situation in the international market is expected to change considerably in the future. Previously, sulfur supply came from mineral deposits and depended on the availability of reserves and conditions in the industry. These mineable deposits have deteriorated as production costs increased, as result of exploiting lower-quality reserves, increases in energy consumption, and environment costs. In addition, less expensive, non-discretionary, abatement sulfur has emerged as a result of the enforcement of public environmental regulations, product market specifications, and transportation technologies which require the removal of sulfur from sulfur-bearing products. These developments are seen as molding the conditions in the international sulfur market of the future. The market is expected to be characterized by: (1) a potential for an abundant supply of low-cost market-insensitive sulfur; (2) the declining role of those resources which have been supplying relatively high-cost discretionary sulfur; and (3) a broader supply base in terms of both source type and geographical distribution. This study provides a future perspective of the non-communist international sulfur market in view of the emerging non-discretionary sulfur sources and the declining role of conventional sulfur sources. The international sulfur market is divided into ten regional markets, defined primarily by geographic location, production and consumption concentration. Supply is divided into: non-discretionary and discretionary sulfur. Supply and demand are projected primarily econometrically, and surplus or deficit regions are identified. Two types of projection methods are used: regression based and non-regression based. The choice of the method used for a region is based on: (1) the availability of historical data, and (2) how closely the past and future economics of a region are expected to be related. The conclusions of this study are: (1) on world basis, sulfur is expected to be in continued excess; (2) virtually all sulfur is expected to come from non-discretionary sources; (3) some regions are expected to have a supply deficit, most will have supply surpluses; (4) the co-existence of deficit and surplus regions will result in inter-regional or international trade. However, the resulting trade pattern will be quite different from the present pattern; (5) the basis for price determination and the relative levels are expected to change; and (6) discretionary sulfur will be permanently forced out of the market.

This study was designed to determine if Alberta's sulfur blocks were inhabited by microorganisms which contribute to oxidation of elemental sulfur. The first objective was to elucidate a functional method of differentiating between viable and non-viable organisms in environmental samples. The second objective was to use this and other more established microbiological analyses to characterize the microbial population inhabiting the block and determine if they influence elemental sulfur oxidation.<p>In order to differentiate between viable and non-viable microorganisms, I relied on a DNA binding agent called ethidium monoazide bromide (EMA). Based on previous literature, I was able to test its activity in different environmental samples. Treatment with EMA inhibits the amplification of free DNA, whereas DNA protected by the membranes of viable cells is not affected. After finding that killed pure culture cells had a substantial reduction in their DNA amplification I proceeded to inoculate the same species of killed and viable cells into either soil, biofilm, or elemental sulfur samples obtained from Syncrude's Phase I sulfur block. I have found the EMA treatment to be sufficient at inhibiting amplification of DNA from non-viable cells inoculated into both the soil and sulfur samples, but not in the biofilms. <p>In achieving the second objective I designed experiments which tested in vitro and in situ samples of the sulfur block. Bioreactors containing microbiological inoculants from water running off the sulfur block were compared to sterile bioreactors for levels of acidity, sulfate accumulation and microbial population. Comparison between the surface block samples and the matrix samples showed a higher number of bacteria in the surface samples; however, the differences between the two bioreactor treatments were not significant. Bioreactors which received sterile water did not increase in acidity or sulfate accumulation. The two treatments which were inoculated with 10% sulfur block run off increased by 3 and 4.3 mM sulfate, and 8.6 x 10-3 and 1.8 x 10-2 hydronium ion concentration, in the surface and matrix treatments respectively. In situ samples obtained by coring the sulfur blocks showed that microbial inhabitants are present throughout the block depth profile with a discontinuous pattern, which could be attributed to the fractures associated with the solidification of the block and subsequent colonization. The level of microbiological inhabitants ranged from 2.5 to 5.5 log heterotroph colony forming units g-1 sulfur, and 3.19 x 101 to 1.62 x 102 A. thiooxidans amplified copy numbers, and 1.23 x 103 to 1.11 x 104 Eubacteria amplified DNA copy numbers ìg-1 of extracted DNA from EMA treated sulfur block samples. Most probable number counts for autotrophs only detected organisms along the 0-10 cm depth of the block. <p>The results of this study suggest that the use of ethidium monoazide bromide is a suitable method of detecting the large and varied microbial population inhabiting Alberta's sulfur blocks which can influence the level of block oxidation. The level of microorganisms present in the block is varied, which may parallel the varied pockets of air and water collected in the geomorphic fractures. Microbial communities residing in the sulfur block are partially responsible for sulfur oxidation. Methods aimed at reducing the level of sulfur oxidation must aim to reduce both the chemical and biological pathways leading to sulfur oxidation.

Sulfur tetrafluoride was shown to be a useful reagent in preparing salts of ReVIIO2F4−, IVOF4−, and IVIIO2F4−. Sulfur tetrafluoride reacts with oxo-anions in acetonitrile or anhydrous HF (aHF) via fluoride-oxide exchange reactions to quantitatively form oxide fluoride salts, as observed by Raman and 19F NMR spectroscopy. Pure Ag[ReO2F4] as well as the new CH3CN coordination compounds [Ag(CH3CN)2][ReO2F4] and [Ag(CH3CN)4][ReO2F4]•CH3CN were prepared. The latter was characterized by single-crystal X-ray diffraction. The reaction of [N(CH3)4]IO3 with SF4 in acetonitrile gave the new [N(CH3)4][IOF4] salt. Sulfur tetrafluoride forms Lewis acid-base adducts with pyridine and its derivatives, i.e., 2,6-dimethylpyridine, 4-methylpyridine and 4-dimethylaminopyridine, which have recently been identified in our lab. In the presence of HF, the nitrogen base in the SF4 base reaction systems is protonated, which can formally be viewed as solvolysis of the SF4•base adducts by HF. The resulting salts have been studied by Raman spectroscopy and X-ray crystallography. Crystal structures were obtained for pyridinium salts: [HNC5H5+]F−•SF4, [HNC5H5+]F−[HF2−]•2SF4; 4-methylpyridinium salt: [HNC5H4(CH3)+]F−•SF4, [HNC5H4(CH3)+][HF2−]; 2,6-dimethylpyridinium salt: [HNC5H3(CH3)2+]2[SF5−]F−•SF4; 4-dimethylaminopyridinium salts: [HNC5H4N(CH3)2+]2[SF5−]F−•CH2Cl2, [NC5H4N(CH3)2+][HF2−]•2SF4; and the 4,4’-bipyridinium salts: [HNH4C5−C5H4N+]F−•2SF4, [HNH4C5−C5H4NH2+]2F−•4SF4. These structures exhibit a surprising range of bonding modalities between SF4 and fluoride and provide an extensive view of SF4 in the solid state. For the first time, the solid-state structure of SF4 was elucidated by single-crystal X-ray diffraction. The structure can best be described as a network with weak intermolecular S---F contacts formed exclusively by the axial fluorines that exhibit more ionic character. A similar structural motif was found in the novel [HNC5H3(CH3)2+]2[SF5−]F−•4SF4 salt which contains layers of SF4. Adduct formation of SF4 with oxygen-bases was observed for the first time. These SF4•O-base adducts (SF4•OC4H8, SF4•(OC4H8)2, SF4•(CH3OCH2)2, SF4•(O=C5H8)2) were synthesized, isolated, and characterized at low temperatures. The structures were elucidated by X-ray crystallography and Raman spectroscopy. The characterization of the SF4•ketone adduct (SF4•O=C5H4) is of great significance, since SF4 can serve as a fluorinating agent towards carbonyl groups. These adducts offer the first extensive view of dative O---S(IV) bonds. / xviii, 177 leaves : ill. ; 29 cm

Thesis (M.S.)--Ohio University, November, 2000. / Title from PDF t.p.