Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Ph. D.)--University of Queensland, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 129-133). Also available on the Internet.

Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008. / Lowell, Robert, Committee Chair ; Newman, Andrew, Committee Member ; Peng, Zhigang, Committee Member.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 96-99).

This literature review analyses and discusses different theories and results regarding impact of volcanic eruptions on climate change in Earth's history. Present global warming has been attributed to anthropogenic emissions of greenhouse gases, mainly carbon dioxide, however changes in global temperatures have occurred before the onset of anthropogenic emissions. Certain prehistoric climate changes are thought to be caused by emissions of volcanic gases to the atmosphere. Many studies have investigated the connection between volcanic events and subsequent changes in global temperatures. A majority have concluded that volcanic sulfur dioxide is the main direct and indirect climate forcing gas influencing temperatures over time. Increased volcanic activity over the last 15 years is thought to be an inhibiting factor on present global warming. This is supported by evidence of past volcanic events preceding global cooling and warming periods during Holocene and prehistoric times. Further, there are indications that factors such as geographical position, season, gas composition, magnitude and duration of an eruption influences the extent of the climate forcing.Records of climate such as ice cores and tree growth rings and isotopic characterization have made it possible to identify volcano eruptions over time and determine the identity of the erupting volcano. Past and present data from these can be used to gain a better understanding of past climate changes as well as making predictions about future changes as a result volcanic eruptions. However, accuracy regarding temporal and spatial resolution of these records is of great importance for the validity of the results.

Iron-sulfur clusters, an important class of redox active cofactors, are ligated by protein-based Cys ligands in a variety of nuclearities. Traditionally, these clusters serve as one-electron transfer units, though many clusters are capable of catalytic activity and sensing functions. Recently, a greater number of iron-sulfur clusters with non-Cys ligation have been identified, wherein one or more of the Cys ligands are replaced by an alternative amino acid residue such as His or Asp. In most cases the role of this ligand substitution is unknown. Some hypotheses are that non-Cys ligation may modify reduction potential, allow for proton-coupled electron transfer, or modulate cluster stability. The human mitoNEET protein contains a 1-His, 3-Cys ligated [2Fe-2S] cluster, identified by the presence of a CDGSH peptide motif. MitoNEET is a binding target for the type II-diabetes drug, pioglitazone, and is implicated in controlling mitochondrial iron levels. How exactly mitoNEET functions in the cell is unknown, as is the role its uniquely ligated FeS cluster may play. This thesis uses mitoNEET as a model for the study of non-Cys ligated FeS clusters and their biological function. Protein film voltammetry was used to examine the pH-dependent electrochemical properties of the mitoNEET cluster, indicating that multiple as yet unidentified protonations control redox potential and that drug binding impacts cluster reduction and protonation. Additionally, the effect of reduction and protonation on cluster and protein structure instability was examined through absorbance and circular dichroism measurements, suggesting an important role for cluster lability in protein function. The CDGSH-motif family of [2Fe-2S] cluster-binding proteins was examined using protein similarity networks. This technique highlights the evolutionary relationship among these proteins, and has led to further work examining the DUF1271 domain containing proteins E. coli YjdI and A. vinosum Alvin0680 (a CDGSH-DUF1271 fusion). This work furthers the scientific knowledge of non-Cys ligated Fe-S clusters by improving our understanding of how the mitoNEET His-ligand contributes to proton-coupled electron transfer and cluster instability, and how the broader class of CDGSH-motif proteins is organized.

CORREIA, L. M. Fe2O3 ou Co3O4 suportados em sílicas mesoporosas modificadas com NH4F e Ti para adsorção de benzotiofeno e reação de oxidação catalítica seletiva parcial de H2S a S. 2017. 233 f. Tese (Doutorado em Engenharia Química)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Hohana Sanders (hohanasanders@hotmail.com) on 2017-10-03T18:25:12Z No. of bitstreams: 1 2017_tese_lmcorreia.pdf: 3519700 bytes, checksum: 80fb75064a529c39bee1587404389fd8 (MD5) / Approved for entry into archive by Marlene Sousa (mmarlene@ufc.br) on 2017-11-08T14:44:39Z (GMT) No. of bitstreams: 1 2017_tese_lmcorreia.pdf: 3519700 bytes, checksum: 80fb75064a529c39bee1587404389fd8 (MD5) / Made available in DSpace on 2017-11-08T14:44:39Z (GMT). No. of bitstreams: 1 2017_tese_lmcorreia.pdf: 3519700 bytes, checksum: 80fb75064a529c39bee1587404389fd8 (MD5) Previous issue date: 2017-07-31 / The presence of sulfur (S) in automotive fuels must be retrain, once it generates air pollution and promotes damage to the motor (corrosion), affecting the health of living beings. The conventional process of hydrodesulfurization (HDS) for sulfuric compounds removal, used by petrochemical industries, generates large amount of H2S, which can be used in selective partial oxidation reaction of H2S to S. The HDS treatment process is not effective to remove refractory compounds at low concentrations of S, making polish techniques, such as adsorption, necessary due to environmental constraints increase. This situation has led to a need of deeper research in the area of sulfur compounds removal in fossil fuels (gas and diesel). Thus, the development of methodologies to prepare and characterize new adsorbents with high sulfur removal are necessary. The adsorption of BT (standard organic molecule contained in gas and diesel) was investigated using a regular mesoporous silica SBA-15 type and modified with NH4F, and impregnated with Fe and Co respectively. The experiments were done in batch, with different initial BT concentrations (3-15 mmol.L-1) at different temperatures (30 °C, 40 °C and 50 °C). In the second part of the research, the H2S was partially oxidized to S and SO2 using a tubular fixed bed catalytic reactor, containing mesoporous silica HMS, SBA-15, and MCM-41 modified with NH4F and Ti, and respectively Fe2O3 and Co3O4. The catalytic tests were conducted at 180 °C and 170 oC. Reactional conditions were a catalyst mass of 100 mg (40-60 mesh), operating with a 125 mL.min-1 total flow, with molar ratio H2S/Air/He (1/5/94). The brackets, adsorbents and active phases of mesoporous catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), adsorption and desorption isotherms at -196°C, x-ray photoeletronic spectroscopy (XPS), Fourier transform infrared (FTIR), Elemental analysis (CHNS) and spectroscopy of UV-visible region. The results show that mycotoxin adsorbents are promising for the hydrodesulfurization process for BT removal, especially, the sample (15Co/SBA-15/NH4F). All the prepared catalysts are active and promising for the elementary S production. The most stable catalyst was 15Fe/MCM-41, obtaining conversion values of H2S (89.72%), selectivity of S (96.19%), and selectivity of SO2 (3.81%) at 180 °C and 360 min of reaction time in the H2S to S selective oxidation partial reaction in gas phase / A presença de enxofre (S) nos combustíveis automotivos deve ser combatida, uma vez que gera a poluição atmosférica e traz prejuízos ao motor (corrosão), afetando também à saúde dos seres vivos. O processo convencional de hidrodessulfurização (HDS) para remoção dos compostos de S, utilizado pelas indústrias petroquímicas, gera elevada quantidade de H2S, o qual pode ser utilizado na reação de oxidação seletiva parcial de H2S a S. O processo de tratamento por HDS não é eficaz para remoção de compostos refratários em baixas concentrações de S, o que torna necessário a técnicas de acabamento como a adsorção, devido a um aumento nas restrições ambientais. Essa situação tem levado a uma necessidade de maiores pesquisas na área de remoção de sulfurados nos combustíveis (gasolina e diesel). Assim, busca-se desenvolver metodologias para preparar e caracterizar novos adsorventes com elevada capacidade de remoção de enxofre. A adsorção de BT (molécula orgânica modelo contida na gasolina e diesel) foi investigada utilizando-se sílicas mesoporosas do tipo SBA-15 e modificadas com NH4F, e impregnadas respectivamente com Fe e Co. Os experimentos foram feitos em batelada, com diferentes concentrações iniciais de BT (3-15 mmol/L) e temperaturas distintas (30 oC, 40 oC e 50 oC). Na segunda parte da pesquisa o H2S foi parcialmente oxidado a S e SO2 utilizando um reator catalítico de leito fixo do tipo tubular, contendo sílica mesoporosa do tipo HMS, SBA-15, e MCM-41 modificadas com NH4F e Ti, e respectivamente Fe2O3 e Co3O4. Os testes catalíticos foram conduzidos a uma temperatura de reação de 180 ºC e 170 oC. As condições reacionais foram massa do catalisador de 100 mg (40-60 mesh), operando com uma vazão total de 125 mL min-1, com razão molar H2S/Ar/He (1/5/94). Os suportes, adsorventes e as fases ativas dos catalisadores mesoporosos foram caracterizados por difração de raios-X (DRX), microscopia eletrônica de transmissão (MET), isotermas de adsorção e dessorção a -196 oC, espetroscopia fotoeletrônica de raios-X (XPS), infravermelho com transformada de Fourier (FTIR), análise elementar (CHNS) e espectroscopia da região do UV-visível. Os resultados demonstram que os adsorventes são promissores para o processo de hidrodessulfurização para a remoção da molécula de BT, especialmente, a amostra (15Co/SBA-15/NH4F). Todos os catalisadores preparados são ativos e promissores para produção de S elementar. O catalisador mais estável foi 15Fe/MCM-41, obtendo-se valores de conversão de H2S (89,72%), seletividade a S (96,19%), e seletividade a SO2 (3,81%) na temperatura de 180 oC e tempo reacional de 360 min na reação parcial de oxidação seletiva de H2S a S em fase gás

Coal is a combustible sedimentary rock composed of a complex heterogeneous mixture of mostly organic constituents and minor inorganic phases. Coal is a vital energy resource providing more than half of the electric power generated in the United States. However, coal combustion is responsible for a significant portion of anthropogenic release of different toxic elements including sulfur into the environment. Therefore, deciphering the residence of the different fractions of sulfur in coal is essential. In this study, eight different sulfur fractions from Pennsylvanian-age coal samples collected from the Murphysboro, Mount Rorah, Springfield (No. 5), and Herrin (No. 6) coal seams from the Illinois Basin were separated using a wet sequential chemical extraction procedure in order to evaluate the coal quality and to test the efficiency of this technique. The average weight percent of sulfur in each seam was 1.98%, 2.1%, 2.26%, and 2.4%, respectively, showing that the coal samples were of medium-sulfur-type. Among the eight different sulfur fractions extracted, kerogen sulfur was found to be the most abundant, followed by sulfate sulfur, fulvic acid sulfur, pyritic sulfur, and elemental sulfur. However, XRD and coal petrography revealed the significant amounts of pyrite still present in the coal sample even after pyritic sulfur extraction, indicating that the finely disseminated pyrite in the coal was not completely removed during the sequential extraction. The sulfur isotopic study showed the average δ34S values of pyritic sulfur and sulfate sulfur in the Murphysboro coals as 7.82 / and 2.44 / and that of Mount Rorah coals were 10.68 / and 7.87 /, respectively. The heavier δ34S values of pyritic sulfur compared to the sulfate sulfur can be explained by a bacterial sulfate reduction (BSR) model in a closed system where most of the sulfate reservoir was consumed at the top of the seam. Similarly, the average δ34S values of elemental sulfur for the same coals (8.05 / and 14.54 /, respectively) were also heavier than the sulfate sulfur which suggests the pyrite oxidation followed by disproportionation of intermediate sulfur species. The δ34S values of handpicked pyrite samples and the mercury concentration for the Herrin (No.6) and Springfield (No. 5) coals indicated at least two stages of hydrothermal inputs into these coal seams. SEM/EDS and petrographic microscopy of the Illinois coal samples revealed the presence of different syngenetic and epigenetic sulfur-containing minerals such as framboidal pyrite, euhedral pyrite, galena, anhydrite, anglesite, and also non-sulfur containing minerals such as calcite and clay. Based on these results, it can be said that sulfur in Illinois coals is present in different phases extractable by wet sequential chemical extraction however; care should be taken during each individual extraction step to obtain better results.

xv, 108 p. : ill. (chiefly col.) / Aqueous aerosol surfaces are an important platform for chemical reactions through which gases are transported in the atmosphere. The chemical complexity of aqueous aerosols is well-established, but many questions remain about the molecular nature of their surfaces, particularly with respect to the uptake of gases. The pollutant sulfur dioxide, SO₂, has been implicated in environmental phenomena such as acid rain, climate change, and cloud formation. SO₂ is fundamentally interesting because it forms spectroscopically identifiable complexes with water at aqueous surfaces. This dissertation aims to understand how temperature and aqueous composition impact the formation of surface complexes between water and SO₂. Vibrational sum frequency spectroscopy (VSFS), a surface specific technique, is used to probe the vibrational modes of water and small organic molecules, investigating changes to the overall orientation, bonding environment, and structure of interfaces when aqueous surfaces are exposed to SO₂. SO₂ adsorption to water at tropospherically relevant temperatures (0--23 °C) is examined first. The results show enhanced SO₂ surface affinity at colder temperatures, with most of the topmost water molecules showing evidence of binding to SO₂ at 0 °C compared to a much lower fraction at room temperature. Surface adsorption results in significant changes in water orientation at the surface but is reversible at the temperatures examined. The surface and vibrational specificity of these studies can be used to distinguish between the effects of surface adsorption compared to bulk accommodation. This distinction is utilized to demonstrate that SO₂ complexation is independent of solution acidity, confirming that bulk absorption is unnecessary for surface adsorption to occur. Finally, the impact of the organic species succinic acid and formaldehyde on the formation of surface SO₂ complexes is examined. These experiments indicate that SO₂ surface complexation occurs primarily with water but that surface active organic species may interact with gases under certain circumstances, namely when the organic species are more chemically reactive towards the gas. These studies have important implications for atmospheric chemistry and the uptake of gases, particularly in the complex aqueous environments expected in the troposphere. / Committee in charge: Dr. Paul C. Engelking, Chair; Dr. Geraldine L. Richmond, Advisor Dr. Jeffrey A. Cina, Member; Dr. Thomas R. Dyke, Member; Dr. Alan D. Johnston, Outside Member