Дисертації з теми "Sulfur Dot"

Synchrotron-based spectroscopic techniques enable investigations of the many important biological and environmental functions of the ubiquitous element sulfur. In this thesis the methods for interpreting sulfur K-edge X-ray absorption near edge structure (XANES) spectra are developed and applied for analyses of functional sulfur groups. The influence of coordination, pH, hydrogen bonding, etc., on the sulfur 1s electronic excitations is evaluated by transition potential density functional theory. Analyses have been performed of reduced sulfur compounds in marine-archaeological wood from historical shipwrecks, including the Vasa, Stockholm, Sweden and the Mary Rose, Portsmouth, U.K.. The accumulation of sulfur as thiols in lignin-rich parts of the wood on the seabed is also a probable pathway in the natural sulfur cycle for how reduced sulfur enters fossil fuels via humic matter in anaerobic marine sediments. Sulfur K-edge XANES spectra for several biochemical model compounds and for coexisting isomeric sulfur species in cysteine and sulfite(IV) aqueous solutions have been analyzed with the aid of theoretical calculations. Cysteine derivatives are important for biochemical detoxification, and mercury(II) cysteine complexes in solution have been structurally characterized by means of Extended X-ray Absorption Fine Structure (EXAFS), Raman and 199Hg NMR spectroscopy. Lanthanoid(III) ions were found to coordinate eight dimethyl sulfoxide oxygen atoms in a distorted square antiprism in the solid state and in solution, by combining crystallography, EXAFS, XANES and vibrational spectroscopy. The mean M-O bond distances for the disordered crystal structures are in good agreement with those from the lattice-independent EXAFS studies. The different sulfur K-edge XANES spectra for the dimethyl sulfoxide ligands in the hexasolvated complexes of the trivalent group 13 metal ions, Tl(III), In(III), Ga(III) and Al(III), were interpreted by theoretical calculations.

Ce travail porte sur la synthèse, la caractérisation et l’évaluation en catalyse de réduction des protons en dihydrogène, de nouveaux complexes de Ni(II), Co(III), Cu(II) et Pd(II) basés sur des ligands de type thiosemicarbazone. La nature de l’espèce catalytique active a été étudiée par voltampérométrie cyclique et des propositions de mécanisme ont été formulés sur la base de calcul quantique de type DFT.Le premier chapitre introduit le contexte scientifique. Le second chapitre concerne la synthèse et la caractérisation des ligands de type N2S2 et des complexes mononucléaires associés de Ni, Cu et Pd. Le troisième chapitre présente la synthèse et la caractérisation de complexes binucléaires de Co et trinucléaire de Ni.Les études électrochimiques de ces complexes dans le DMF en présence d’une source de protons, nous a permis d’évaluer leur efficacité catalytique. Nos résultats montrent que les complexes du Cu et du Pd présentent une vague irréversible spécifique pour la réduction des protons, mais une décomposition est observée durant l’électrolyse. Par contre, les complexes de Ni et de Co ont montré une stabilité électrochimique ainsi que de bonnes performances catalytiques. En particulier, le nouveau complexe mononucléaire de Ni présente des propriétés catalytiques remarquables qui le classent parmi les meilleurs catalyseurs de la réduction des protons décrits dans la littérature. L’ensemble de ce travail fourni une description complète du comportement électrochimique des ligands de type N2S2 complexés à des métaux de transition. Il permet d’envisager des développements futurs dans l’amélioration des propriétés catalytiques de ces complexes
This work focuses on the synthesis, the characterization and the catalytic evaluation in the reduction of protons into dihydrogen, of new complexes of Ni(II), Co(III), Cu(II) and Pd(II) based ligands Type thiosemicarbazone. The catalytically active species during the process of the proton reduction was studied by cyclic voltammetry and mechanisms were formulated on the basis quantum chemical calculation.The first chapter introduces the scientific context, the goals and the main objectives of this work. The second chapter concerns the synthesis and the characterization of the N2S2 ligands and their associated mononuclear complexes, Ni, Cu and Pd. The third chapter presents the synthesis and the characterization of binuclear Co and trinuclear Ni based on N2S2 ligand.Electrochemical studies of these complexes in DMF in the presence of a proton source (trifluoroacetic acid), allowed us to evaluate their catalytic efficiency. Our results show that Cu and Pd complexes have a specific irreversible wave for the reduction of protons, but decomposition is observed during electrolysis, which makes these uninteresting complexes for the reduction of protons.On the contrary, Ni and Co complexes showed an electrochemical stability and good catalytic performances. In particular, the new mononuclear Ni complex exhibits remarkable catalytic properties that rank it among the best catalysts for the reduction of protons reported in the literature. All this work provided a complete description of the electrochemical behavior of N2S2 thiosemicarbazone ligands complexed to transition metals. It allows considering future developments in improving the catalytic properties of these complexes

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.

In this thesis, simple methods to determine sulfide at low levels (µg L-1) in aqueous samples and sediments by water free hydrogen sulfide vapor generation using a commercially available vapor generation accessory have been developed. The hydrogen sulfide is then introduced in the ICP-QMS, equipped with an octopole collision/reaction cell which is vented with hydrogen and helium gases, or in the ICP-AES where the optical path between the plasma and the monochromator is purged with nitrogen. Moreover some studies have been conducted for the determination of arsenic by ICP-MS in natural waters with high sodium and chloride content. Spectral and non spectral interferences on arsenic measurement have been investigated and different experiments have been developed to solve such interferences (optimizations of the cell collision conditions, arithmetic corrections, introduction of small amounts of alcohol). Finally, the use of the DGT technique (diffusive gradients in thin films) has been evaluated in acidic samples and mining wastes for the firs time.
En aquesta tesi, s’han desenvolupat mètodes senzills per a la determinació de sulfur a baixes concentracions (µg L-1) en mostres aquoses i sediments mitjançant la generació de sulfur d’hidrogen, utilitzant un accessori de generació d’hidrurs comercial. Un cop format el sulfur d’hidrogen, aquest es pot introduir a l’ICP-QMS, equipat amb una cel•la de col•lisió/reacció o a l’ICP-AES amb el pas entre el plasma i el monocromador purgat amb nitrogen. També s’han fet alguns estudis per determinar arsènic amb ICP-MS en aigües naturals amb alt contingut de sodi i clor. S’han estudiat les interferències espectrals i no espectrals sobre aquest element i s’han dut a terme diferents experiments per a resoldre-les (optimització de la cel•la de col•lisió, aplicació de correccions matemàtiques, introducció de petites quantitats d’alcohol). Finalment, s’ha avaluat l’ús de la tècnica de DGT (diffusive gradients in thin films) en mostres àcides (pHs de 5 a 10) i residus de mineria per primera vegada.

Orientador: Reges Heinrichs
Resumo: O enxofre é, provavelmente, o macronutriente menos empregado nas adubações, o que resulta na redução de rendimento e qualidade de forragem. Entre os nutrientes, apresenta um importante papel por participar em várias funções biológicas, faz parte da composição dos aminoácidos cisteína, metionina e cistina, acetil-CoA, bem como de enzimas que participam da fotossíntese e o metabolismo do nitrogênio. O objetivo foi avaliar a produção e estado nutricional dos capins Piatã e Mombaça em resposta a aplicação de doses e fontes de sulfato e enxofre elementar em Argissolo Vermelho Amarelo. Em virtude disso, realizou-se dois experimentos em casa de vegetação na Faculdade de Ciências Agrárias e Tecnológicas, UNESP, Campus de Dracena – SP, o primeiro foi no período de janeiro a março de 2017 e o segundo de outubro a janeiro de 2018, com o capim Piatã e de Mombaça, respectivamente. O delineamento experimental foi em blocos casualizados com quatro repetições, arranjados em esquema fatorial, 4x5, com quatro fontes de enxofre (Gipsita, Fosfogesso, S elementar em pó e S elementar pastilhado) e cinco doses de enxofre (0, 50, 100, 150 e 200 mg kg-1).Foram determinados os parâmetros biométricos como número de perfilhamento, massa seca da parte aérea (MSPA) e massa seca de raízes (MSR). O estado nutricional das plantas foi avaliado por meio da leitura SPAD e análise de macronutrientes N, P, K, Ca, Mg, S na parte aérea das plantas. Avaliou-se também o enxofre residual do solo e o pH do solo. Os res... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre

High fossil fuel consumption in transportation and industry results in an increase of the emission of green-house gases. To preserve clean air, new strategies are required. The main intention is to decrease the amount of CO2 emission by using lean-burn engines while increasing the combustion efficiency and decreasing the fuel consumption. However, the lean-burn engines have high air-to-fuel ratio which complicates the reduction of the oxides of nitrogen, NOx . The emission of these highly noxious pollutants, NOx , breeds both environmental and health problems. Thus, new catalytic strategies have been steadily developed. One of these strategies is the NOx storage and reduction (NSR) catalysts. Since the reduction of the NOx under excess oxygen condition is very difficult, the NSR catalysts store the NOx until the end of the lean phase that is subsequently alternated with the rich-fuel phase during which the trapped NOx is released and reduced. To develop NSR technology, different storage materials, the coverage of these metals/metal-oxides, support materials, precious metals, temperature, etc. have been widely investigated. In this thesis, the (100) surface of BaO with dopants (K, Na, Ca and La), (100) and (110) surfaces of Li2O, Na2O and K2O are investigated as storage materials. In addition, alkali metal (Li, Na and K) loaded (001) surface of TiO2 (titania) anatase is investigated as a support material for the NOx storage and reduction catalysts. The main aim is to increase the sulfur resistance. The introduction of the dopants on the BaO (100) surface has increased the stability of the NO2 . The combination of local lattice strain and different oxidation state, which is obtained by the La doped BaO (100) surface, benefit both NO2 adsorption performance and sulfur tolerance. The binding energies of NO2 adsorption configurations over the alkali metal oxide (100) and (110) surfaces were higher than the binding energies of SO2 adsorption configurations. The stability of all of NO2 adsorption geometries on the alkali metal-loaded TiO2 (001) surface were higher than the stability of SO2 adsorption geometries. Increasing basicity enhanced the adsorption of NO2 molecule.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O objetivo do trabalho foi avaliar a viabilidade técnico-econômica da poda associada ao controle químico no manejo da leprose. Visou também, investigar as relações entre leprose e características da planta, bem como o efeito de sucessivas aplicações de calda sulfocálcica sobre propriedades químicas do solo. O experimento foi conduzido de 2003 a 2010, totalizando sete safras, em um pomar de laranja „Pera‟ localizado no município de Reginópolis-SP. Neste pomar foram realizadas podas severas e leves, e replantio, e aplicações de acaricidas para controlar do ácaro vetor Brevipalpus phoenicis. Realizaram-se levantamentos populacionais do B. phoenicis e de ácaros predadores, quantificação da produção, incidência e severidade da leprose, assim como a viabilidade de cada estratégia empregada foi calculada. Nas duas últimas safras do experimento realizaram-se avaliações das características físico-químicas dos frutos, análises foliares e de solo. Após as sete safras, verificou-se que a poda utilizada isoladamente não foi suficiente para o controle da leprose, sendo necessária a associação de outras táticas. A poda leve associada a acaricidas específicos foi à tática mais eficiente e viável economicamente. Os parâmetros físico-químicos de frutos não foram afetados pela alta severidade leprose na planta, indicando que os frutos que permanecem na planta até a colheita apresentam características idênticas às plantas isentas de leprose. Entretanto, embora a leprose não afete a qualidade do suco, afeta significativamente a produtividade da planta, podendo reduzi-lá a zero. As plantas com maior severidade da leprose apresentaram menores teores foliares de cálcio e maiores teores de potássio, fósforo e nitrogênio. As várias aplicações de calda sulfocálcica sobre as plantas proporcionaram maior teor de enxofre no solo nas camadas de 0-20 cm e de 20-40 cm
The aim of this work was to evaluate the technical and economic feasibility of pruning associated with chemical control in citrus leprosis management. And also investigate the relationship among the disease and properties plant, as well as the effect of successive applications of lime sulfur on chemical properties of soil. The study was conducted from 2003 to 2010, totaling seven seasons in an orange plantation of the „Pear‟ variety in the city of Reginópolis-SP. In the orchard were realized severe and light pruning over citrus trees and replanting and pesticide spraying to control Brevipalpus phoenicismite, the disease vector. There had been performed B. phoenicis and predator mite population surveys, yield evaluation, leprosis incidence, as well as the variability of each strategy was also measured. By the two last seasons during the experiment was carried out fruit physical and chemical properties evaluation, leaf and soil analysis. After seven seasons period, it was observed that the pruning only is not able to control leprosis by itself, being necessary another strategy associated. The light pruning associated to the specific acaricide application was the more efficient and economically viable. The main fruit physical and chemical parameters were not affected by the leprosis incidence, what shows that the fruit that remain on the plant until the harvest have identical characteristics to that plant free from the disease. However, although the leprosis not affect juice quality, the disease reduces production significantly. The plant presenting higher leprosis severity present lower leaf calcium content and higher potassium, phosphorus and nitrogen contents.The various lime sulfur spray on the plant had provided a highersulfur content at 0 - 20 cm and 20 - 40 cm soil depth

Luminogens are molecules that emit light upon exposure to high-energy light, and fluorophores are one class of luminogens. Applications of fluorophores range from microviscosity sensors to light emitting diodes (LEDs), as well as biosensors, just to name a few. Many of these applications require the fluorophore to be in the aggregate or solid state. Some fluorophores become highly emissive in the aggregate state; these fluorophores are aggregation-induced emission (AIE) luminogens. Currently, very few quantum mechanical mechanisms have been proposed to describe the unique AIE behavior of luminogens. Boron difluorohydrazone (BODIHY) dyes are a new type of AIE fluorophore. The bright emission is from the S>1 excited state (“anomalous” emission) contrary to Kasha’s Rule. Thus, the mechanism Suppression of Kasha’s Rule (SOKR) was proposed to be responsible for the family of BODIHY dyes. We hypothesize that the SOKR mechanism can explain AIE as well as the anomalous emission of other fluorophores. New BODIHY derivatives (para-CO2H BODIHY, aluminum difluorohydrazone (ALDIHY), and paranitro ALDIHY) were predicted to be bright anomalous fluorophores through density functional theory (DFT) and time-dependent DFT (TDDFT) investigations. In addition, a series of anomalous fluorophores were investigated to determine if their photophysical properties could be explained by the SOKR mechanism (azulene, 1,6-diphenyl-1,3,5hexatriene, and zinc tetraphenylporphyrin). Finally, several triazolopyridinium and triazoloquinolinium dyes were computationally investigated by DFT and TDDFT calculations, and an accurate computational model for the large Stokes shifts of these dyes was developed. In conclusion, a better understanding of the photophysical properties through DFT and TDDFT modeling and spectroscopic investigation of hydrazone-based fluorophores has been achieved. In addition, the metal active sites and cofactors of metalloproteins were probed by optical spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and DFT modeling. In conjunction, these techniques can be used to elucidate the electronic structure responsible for the unique function of these metalloproteins. Specifically, a novel ironsulfur cluster of a metalloprotein that may be involved in endospore formation of Clostridium difficile, CotA, was characterized by magnetic circular dichroism (MCD) spectroscopy. We propose that CotA contains a high-spin [4Fe-4S] cluster and a Rieske [2Fe-2S] cluster. It appears that the multimerization of the protein is related to the cluster conversion at the interface of monomeric subunits where two [2Fe-2S] clusters combine to form the [4Fe-4S] cluster. In addition, a putative cobalamin acquisition protein from Phaeodactylum tricornutum, CBA1, was not expressed at sufficient concentrations in Escherichia coli for spectroscopic investigation. Finally, a new technique was developed using cobalt-59 NMR spectroscopy to better understand the nucleophilic character of cobalt tetrapyrroles, such as cobalamin (vitamin B12), as biological cofactors as well as synthetic catalysts. New insight into the electronic structure provides valuable information related to the mechanism of these metalloproteins.

Le principe du stockage en milieu géologique profond est de confiner les colis de déchets par un ensemble de barrières ouvragée et géologique. Les eaux souterraines constituent l'un des principaux points faibles de la sûreté d'un stockage en contribuant à l'altération des barrières et à la migration des radionucléides à travers la géosphère. Ainsi, la compréhension des processus susceptibles de retarder cette migration est fondamentale pour évaluer la sûreté d'un stockage. Le but de nos travaux est d'étudier les processus de sorption entre des phases de sulfures métalliques, présentes sous forme d'inclusions dans la barrière géologique, et deux produits de fission à vie longue, l'iode et le sélénium. Après validation des protocoles mis en place pour limiter la dégradation par oxydation des solides étudiés (pyrite FeS2 et chalcopyrite CuFeS2), nous nous sommes attachés à décrire leur réactivité en milieu aqueux et en présence d'iode ou de sélénium. Les études potentiométriques montré que la réactivité de surface des sulfures métalliques étudiés était très faible en raison d'une surface spécifique très basse. Les études expérimentales de sorption ont montré d'une part l'absence d'affinité entre les iodures et les surfaces de sulfures métalliques et d'autre part une sorption significative de sélénium à la surface des différents solides. Les études spectroscopiques (XPS et SAX) ont permis de montrer que le sélénium était présent sous forme réduite au degré d'oxydation (-II) à la surface des sulfures métalliques. Le comportement du sélénium a finalement été décrit à l'aide de la théorie de complexation de surface avec le modèle de la double couche
The storage of high-level nuclear wastes in a geological disposal is based on the concept of confinement by a multibarrier system. Transport by groundwaters is the most likely means for radionuclides to migrate through the engineered and geological barriers. Understanding processes which could delay this migration is therefore fundamental to ensure the timelessness of a deep geological repository. The present study was initiated to investigate sorption processes between sulfides minerals, present as inclusions in temperate soils, and two long-life fission products, iodine and selenium. All experiments were performed in strict anoxic conditions in order to prevent the studied solids (pyrite FeS2 and chalcopyrite CuFeS2) from oxidation. Potentiometric studies showed a weak reactivity of the metallic sulfides surfaces attributed to a low specific surface. Sorption experiments showed no affinity between iodide and metallic sulfides surfaces whereas selenium was well retained by the differents solids. Spectroscopic studies (XPS and XANES) showed a reduction of SeIV to Se-II on the sulfide surfaces. Selenium behaviour was finally described with the diffuse layer model using the surface complexation theory

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Tese (Doutoramento)
IPEN/T
Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP

Orientador: Celso Eduardo Benedetti
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Xylella fastidiosa e Agrobacterium tumefaciens são bactérias fitopatogênicas que infectam, respectivamente, o interior do xilema e de tecidos vasculares de raiz, ambientes cuja tensão de oxigênio é relativamente baixa. Uma vez que Xylella e Agrobacterium são bactérias estritamente aeróbicas, elas apresentam o operon bigR, responsável pela detoxificação do sulfeto de hidrogênio ou gás sulfídrico, um potente inibidor do citocromo c oxidase e respiração aeróbica. O operon bigR codifica cinco proteínas denominadas Blh (Beta-lactamase-like hydrolase), BigR (biofilm growth-associated repressor), um repressor transcricional e regulador do operon, e MP1-3, proteínas que compõem um transportador de membrana. Em trabalho anterior, foi demonstrado que mutantes de Agrobacterium deficientes na produção de Blh acumulavam gás sulfídrico, enquanto mutantes no repressor BigR secretavam mais sulfito, indicando que a proteína Blh convertia gás sulfídrico em sulfito e que este, que também é tóxico, seria exportado pelo complexo MP1-3. Além disso, dados de modelagem molecular indicaram que Blh poderia desempenhar funções de sulfotransferase e dioxigenase de enxofre, uma vez que apresenta os domínios DUF442 (rodanase) e ETHE1 (dioxigenase). A fim de testar tais hipóteses, este trabalho teve como principais objetivos a caracterização enzimática dos domínios DUF442 e ETHE1 da Blh de Xylella e Agrobacterium, como também confirmar interações proteína-proteína entre os componentes do operon bigR. Ensaios de atividade enzimática usando-se proteínas recombinantes purificadas confirmaram a função de dioxigenase de enxofre e de rodanase dos domínios ETHE1 e DUF442, respectivamente. Além disso, verificou-se que ambos os domínios produzem sulfito como produto final da reação, embora atuando em substratos diferentes. Ainda, ensaios de duplo híbrido de levedura mostraram haver inúmeras interações entre as proteínas do operon bigR, mas não entre os dois domínios DUF442 e ETHE1 de Blh que, de acordo com os ensaios enzimáticos, atuam de forma independente.
Abstract: Xylella fastidiosa and Agrobacterium tumefaciens are phytopathogenic bacteria that infect, respectively, the xylem vessels and root vascular tissues, where the oxygen tension is relatively lower. Since Xylella and Agrobacterium are strict aerobic organisms, they use the bigR operon for the detoxification of hydrogen sulfide, a potent inhibitor of cytochrome c oxidase and aerobic respiration. The bigR operon encodes five proteins designated Blh (Beta-lactamase-like hydrolase), BigR (biofilm growth-associated repressor), a transcriptional repressor that regulates the operon, and MP1-3, proteins that act as a membrane transporter. In a previous work, it was shown that Agrobacterium mutants deficient in Blh production accumulated hydrogen sulfide, whereas BigR-deficient mutants secreted sulfite at higher levels than the wild type bacteria, indicating that Blh converted hydrogen sulfide into sulfite, which would be exported by the MP1-3 complex. In addition, molecular modeling indicated that Blh could function as a sulfur transferase and sulfur dioxigenase, since it carries a DUF442 (rhodanese) and ETHE1 (dioxygenase) domains. To test such hypothesis, this work aimed to demonstrate the enzymatic activities of the DUF442 and ETHE1 domains of Blh from Xylella and Agrobacterium, as well as to confirm protein-protein interactions between components of the bigR operon. Enzyme activity assays using the purified proteins confirmed the sulfur dioxygenase and rhodanese activities of the ETHE1 and DUF442 domains, respectively. In addition, it was found that both domains produce sulfite as a final product, although having different substrates. Furthermore, yeast two-hybrid assays showed that many of the bigR operon proteins interact with each other, suggesting the formation of a protein complex. However, no physical interactions were detected between DUF442 and ETHE1 domains, which, according to the enzyme activity assays, act independently.
Mestrado
Microbiologia
Mestra em Genética e Biologia Molecular

Orientador: Carlos Amadeu Leite de Oliveira
Banca: Celso Omoto
Banca: Mário Eidi Sato
Banca: Nilza Maria Martinelli
Banca: Marcelo da Costa Ferreira
Resumo: O objetivo do trabalho foi avaliar a viabilidade técnico-econômica da poda associada ao controle químico no manejo da leprose. Visou também, investigar as relações entre leprose e características da planta, bem como o efeito de sucessivas aplicações de calda sulfocálcica sobre propriedades químicas do solo. O experimento foi conduzido de 2003 a 2010, totalizando sete safras, em um pomar de laranja „Pera‟ localizado no município de Reginópolis-SP. Neste pomar foram realizadas podas severas e leves, e replantio, e aplicações de acaricidas para controlar do ácaro vetor Brevipalpus phoenicis. Realizaram-se levantamentos populacionais do B. phoenicis e de ácaros predadores, quantificação da produção, incidência e severidade da leprose, assim como a viabilidade de cada estratégia empregada foi calculada. Nas duas últimas safras do experimento realizaram-se avaliações das características físico-químicas dos frutos, análises foliares e de solo. Após as sete safras, verificou-se que a poda utilizada isoladamente não foi suficiente para o controle da leprose, sendo necessária a associação de outras táticas. A poda leve associada a acaricidas específicos foi à tática mais eficiente e viável economicamente. Os parâmetros físico-químicos de frutos não foram afetados pela alta severidade leprose na planta, indicando que os frutos que permanecem na planta até a colheita apresentam características idênticas às plantas isentas de leprose. Entretanto, embora a leprose não afete a qualidade do suco, afeta significativamente a produtividade da planta, podendo reduzi-lá a zero. As plantas com maior severidade da leprose apresentaram menores teores foliares de cálcio e maiores teores de potássio, fósforo e nitrogênio. As várias aplicações de calda sulfocálcica sobre as plantas proporcionaram maior teor de enxofre no solo nas camadas de 0-20 cm e de 20-40 cm
Abstract: The aim of this work was to evaluate the technical and economic feasibility of pruning associated with chemical control in citrus leprosis management. And also investigate the relationship among the disease and properties plant, as well as the effect of successive applications of lime sulfur on chemical properties of soil. The study was conducted from 2003 to 2010, totaling seven seasons in an orange plantation of the „Pear‟ variety in the city of Reginópolis-SP. In the orchard were realized severe and light pruning over citrus trees and replanting and pesticide spraying to control Brevipalpus phoenicismite, the disease vector. There had been performed B. phoenicis and predator mite population surveys, yield evaluation, leprosis incidence, as well as the variability of each strategy was also measured. By the two last seasons during the experiment was carried out fruit physical and chemical properties evaluation, leaf and soil analysis. After seven seasons period, it was observed that the pruning only is not able to control leprosis by itself, being necessary another strategy associated. The light pruning associated to the specific acaricide application was the more efficient and economically viable. The main fruit physical and chemical parameters were not affected by the leprosis incidence, what shows that the fruit that remain on the plant until the harvest have identical characteristics to that plant free from the disease. However, although the leprosis not affect juice quality, the disease reduces production significantly. The plant presenting higher leprosis severity present lower leaf calcium content and higher potassium, phosphorus and nitrogen contents.The various lime sulfur spray on the plant had provided a highersulfur content at 0 - 20 cm and 20 - 40 cm soil depth
Doutor

Cette thèse visait l’étude des micro-environnements géochimiques créés par la présence de l’herbier de Zostera noltei et de son réseau racinaire dans le Bassin d’Arcachon ainsi que ses effets 1) sur l’écologie des foraminifères benthiques, un groupe d’organismes présent en grand nombre dans les sédiments et dont l’influence sur les cycles biogéochimiques reste mal connue et 2) sur les espèces chimiques et les flux benthiques associés. Pour y répondre, une stratégie multidisciplinaire a été mise en place. L’étude écologique des foraminifères benthiques à l’échelle centimétrique, conduite dans des sédiments avec et sans végétation en février et juillet 2011, a montré la présence de trois espèces majeures aux métabolismes spécifiques. L’herbier de Zostera noltei semble influencer la densité et la profondeur de vie des espèces calcaires hétérotrophe (Ammonia tepida) et mixotrophe (Haynesina germanica), présentes près de la surface des sédiments. La troisième espèce (Eggerella scabra), au métabolisme anaérobie encore inconnu, est retrouvée sur au moins 7 cm de sédiment et semble préférer le carbone organique issu de la dégradation de l’herbier. En surface, la contribution des foraminifères à la reminéralisation aérobie a été évaluée à 7 % soit 5 fois plus que lors des études précédentes dans d’autres environnements marins. La présence de l’herbier influence également la géochimie du sédiment où des structures enrichies en fer dissous et appauvries en sulfure sont observables en 2D grâce aux gels DET-DGT développés ici. Le phosphate dissous semble dépendre de la demande des zostères et est observé à forte concentration uniquement sous forme de spots. Une tranche de sédiment, prélevée en vis-à-vis du gel DET-DGT visait la réalisation de cartes de la phase solide et de la densité des foraminifères. Bien que ce travail reste inachevé, des méthodes comme la micro-fluorescence et la micro-tomographie aux rayons X donnent des perspectives prometteuses. De nouvelles voies de recherches ont ainsi été ouvertes grâce à des méthodologies innovantes combinant physiologie, écologie et géochimie
This thesis aimed to study the geochemical microenvironments created by Zostera noltei meadows and its root system in Arcachon Basin and to evaluate the effect of these microenvironments 1) on living benthic foraminifera ecology, a group of organisms present in large densities in sediment which impact on marine biogeochemical cycles remain poorly known and 2) on the chemical species and associated benthic fluxes. To fulfill these objectives, a multidisciplinary strategy was developed. The study of benthic foraminiferal ecology at centimeter scale, conducted in sediments with or without vegetation in February and July 2011, has shown the presence of three major species with specific metabolisms. Zostera noltei meadows seem to influence the densities and the living depth of heterotrophic (Ammonia tepida) and mixotrophic (Haynesina germanica) calcareous species, present in the sediment surface. The third species (Eggerella Scabra), which anaerobic metabolism is still to discover, is found throughout the sedimentary column and seems to prefer the organic matter coming from the degradation of the seagrass. In surface sediment, the contribution of these three species to aerobic remineralization was estimated at 7%, i.e. 5 times more than the maximum rates previously recorded in marine environments. The presence of the seagrass also influences geochemistry where enriched iron and depleted sulfide structures are observable in 2D thanks to DET-DGT gels developed here. Dissolved phosphorus depended on seagrass uptake and was highly concentrated only as scattered spots. A slice of sediment, taken face to face with the DET-DGT gel, was also conducted during this study aiming to map the solid phase and foraminiferal density. Despite this work is still in progress, methods such as X-ray microfluorescence and microtomography showed promising perspectives. New research pathways have been opened through technological developments and innovative approaches combining physiology, ecology, and geochemistry

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:11/04051-3

Orientador: Maria Cecilia de Figueiredo Toledo
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Embora os sulfitos sejam utilizados amplamente na indústria de alimentos, a ingestão desses aditivos têm sido associada a reações adversas em humanos, tais como broncoespasmos em indivíduos asmáticos sensíveis. Em avaliação da exposição aos sulfitos conduzida pelo Comitê Conjunto FAO/OMS de Peritos em Aditivos Alimentares (JECFA) durante sua 51º reunião em 1998, concluiu-se que o consumo de determinados alimentos e bebidas pode resultar em valores de ingestão de sulfitos acima da Ingestão Diária Aceitável (IDA) de 0,7 mg/kg peso corpóreo/dia, expressa como dióxido de enxofre (SO2). Com base nessas informações, o Comitê do Codex sobre Aditivos e Contaminantes de Alimentos (CCFAC) recomendou que a exposição diária a sulfitos a partir de todos os alimentos e bebidas fosse novamente avaliada pelo JECFA. O presente trabalho teve como objetivo a determinação analítica dos níveis de sulfito residual em vinhos e em sucos de frutas disponíveis comercialmente na região de Campinas, utilizando para isso o método oficial de Monier-Williams otimizado. Os níveis de sulfitos determinados foram comparados com valores máximos estabelecidos pela legislação brasileira e posteriormente utilizados para estimar a contribuição de vinhos e sucos de frutas como fonte de ingestão diária desses conservadores na dieta. Foram adquiridas 75 amostras de vinhos (66 de marcas nacionais e 9 de outros países da América do Sul), 15 de outras bebidas alcoólicas (sidras, fermentados de frutas, espumantes e filtrados de vinho), e 39 amostras de sucos de frutas nacionais entre concentrados (37) e prontos para o consumo (2). Em todas as amostras de vinhos e de outras bebidas alcoólicas analisadas (n=90) os níveis de sulfito, expressos como SO2, ficaram abaixo de 350 mg/L (limite máximo de uso estabelecido pela legislação brasileira), sendo que a maioria das amostras (90%) apresentou teores de sulfitos de até 150 mg/L. As amostras de sucos de frutas apresentaram concentrações de sulfitos abaixo de 50% do limite máximo permitido de 200 mg/L (333 mg/L para suco de caju). A exposição aos sulfitos pelo consumo de vinhos foi avaliada combinando níveis médios de sulfitos determinados analiticamente com estimativas de consumo hipotético em três cenários distintos (consumo diário de 150, 300 ou 450 mL). Os dados de ingestão indicaram que o consumo diário de 150 mL de vinho pode contribuir com mais de 50% da IDA desses aditivos, caso a concentração de sulfitos presente seja igual ou superior a 150 mg/L. A contribuição dos sucos de frutas para a ingestão de sulfitos foi avaliada utilizando-se dados de consumo de adolescentes brasileiros, entre 11 e 17 anos, obtidos por um questionário recordatório de 24 horas. A ingestão média de sulfitos a partir do consumo de sucos de frutas ficou bem abaixo da IDA estabelecida pelo JECFA. No entanto, estimativas a percentil 95 indicaram que o consumo de sucos de frutas contendo sulfitos em concentrações iguais ou superiores a 40 mg/L (como foi o caso dos sucos de acerola, goiaba, manga, abacaxi e tomate) pode resultar em valores de ingestões desses aditivos iguais ou acima da IDA. Embora os resultados obtidos nesse estudo indiquem que as concentrações de uso dos sulfitos pela indústria de vinhos e sucos de frutas estejam abaixo dos limites máximos estabelecidos pela legislação brasileira, a IDA desses aditivos pode ser excedida por indivíduos que consomem regularmente grandes quantidades desses produtos
Abstract: ANALYTICAL DETERMINATION OF SULPHITES IN WINES AND FRUIT JUICES AND ESTIMATION OF THEIR INTAKE. Although sulphites are used worldwide in the food industry, they have been implicated in causing adverse-type reactions in humans, such as asthmatic reactions (bronchospasms) in some subjects with asthma. Additionally, it was reported by the Joint Expert Committee on Food Additives (JECFA) at its fifty-first meeting that the consumption of certain foods and beverages may result in intakes of sulphites above the Acceptable Daily Intake (ADI) of 0.7 mg/kg body weight, driving the Codex Committee on Food Additives and Contaminants to recommend Member States to monitor sulphite intake in their countries. The present work aimed on determining the residual sulphite content in a variety of wines and sulphite-containing fruit juices commercially available in the region of Campinas-SP in order to check whether current uses of these preservatives are in accordance with the Brazilian legislation. These data were also used to estimate the contribution of wines and fruit juices to the intake of sulphites in Brazil. Seventy-five samples of wines (66 of national brands and 9 of brands from other South American countries), 15 samples of other alcoholic beverages (ciders, fruit-based beverages and sparkling wines), and 39 samples of national fruit juices, either concentrated (37) or ready-to-drink (2) were collected on the market, and analysed for sulphites using the optimized Monier-Williams distillation method. All samples of beverages presented residual sulphite levels, expressed as sulphur dioxide, below 350 mg/L (maximum permitted level established by the Brazilian legislation) with most samples (90%) containing residual sulphite up to 150 mg/L. The samples of fruit juices presented residual sulphite levels below 50% of the national maximum permitted level of 200 mg/L (333 mg/L for cashew apple juice). To estimate the contribution of wines to the intake of sulphites three hypothetical scenarios of wine daily consumption were assumed: 150, 300 and 450 mL. The data on intake indicated that the daily consumption of 150 mL of wine that contain sulphites at the level equal to or above 150 mg/L may contribute with more than 50% of the ADI of these additives. The contribution of fruit juices to the sulphite intake was assessed using consumption data from a group of 11-17 year-old Brazilian adolescents generated by a 24-hour dietary recall. The calculated sulphite intakes for average consumers of fruit juices were lower than the ADI set by the JECFA. However, estimates at the 95th percentile indicated that the consumption of juices containing sulphites at a concentration of 40 mg/L or above, what is the case of Antilles cherry, guava, mango, pineapple, and tomato juices, may lead to the intakes of these additives equal to or above the ADI. Despite the results have indicated that the actual use of sulphites by the industry in wines and fruit juices are well below those legally permitted by the Brazilian legislation, the ADI of sulphites may be exceeded by individuals whose dietary patterns lead to a high regular consumption of wines and sulphite-containing fruit juices
Doutorado
Ciência de Alimentos
Doutor em Ciência de Alimentos

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

L'un des procédés catalytiques du raffinage du pétrole, essentiel pour l'obtention de carburants propres (essence) vise à sélectivement hydrodésulfurer (HDS) les molécules soufrées (thiophènes) en évitant l’hydrogénation des molécules oléfiniques (HydO), afin de préserver l’indice d’octane des essences. La phase active des catalyseurs d'HDS est composée d'une phase disulfure de molybdène (MoS2), promue par du Co ou du Ni, et appelée "Co(Ni)MoS". La compréhension à l'échelle moléculaire de l’origine de la sélectivité HDS/HydO est l'enjeu de cette thèse. A l'aide de la modélisation moléculaire ab initio couplé à des modèles thermodynamiques, nous étudions premièrement la nature des sites actifs et la morphologie des phases Co(Ni)MoS en milieu réactionnel (HDS). Nous proposons, ensuite, une interprétation de la sélectivité HDS/HydO basée sur l'adsorption sélective de deux réactifs modèles (thiophénique et oléfinique) en fonction des conditions d'HDS. Le rôle clef des promoteurs est mis en évidence. Une interprétation électronique de l'adsorption des molécules est fournie.

Ce travail de thèse a permis d’obtenir une caractérisation à l’échelle atomique des feuillets (Co)MoS2 et (Ni)WS2 de catalyseurs d’hydrotraitement supportés sur alumine et de déterminer l’impact d’un additif organique, l’acide citrique (CA). Dans cette étude des techniques avancées ont été mises en œuvre telles la caractérisation par adsorption de CO à basse température suivie par spectroscopie IR (IR/CO), des calculs DFT et des observations par microscopie électronique haute résolution en mode transmission et par STEM HAADF.Sur les catalyseurs non promu à base de W et de Mo, l’adsorption de CO permet de discriminer les sites des bords M- et des bords S- des feuillets de TMS. La détermination des coefficients d’extinction molaire des bandes liées au CO adsorbé permet de déduire la morphologie des feuillets. L’HR STEM HAADF confirme que l’addition de CA modifie la morphologie des feuillets TMS d’un triangle tronqué à une forme hexagonal.Sur les catalyseurs promus NiW et CoMo, la microscopie electronique montre que l’addition de CA diminue la taille des feuillets de TMS et conduit aussi à la création de petits clusters (<1 nm). L’analyse de particules isolées par HR STEM HAADF permet d’identifier la nature des atomes du bord du feuillet de TMS. Ainsi la microscopie et l’IR/CO mettent en évidence que au sein d’un même feuillet sulfure peuvent coexister des bords totalement promus, et partiellement promus
This work was focused on obtaining an atomic scale characterization of the (Co)MoS2 and (Ni)WS2 slabs of hydrotreating catalysts supported on alumina and to determine the impact of citric acid (CA) addition. In this study, advanced techniques were implemented such as low temperature CO adsorption followed by IR spectroscopy (IR/CO), DFT calculations and high resolution electron microscopy observations in transmission mode and by STEM HAADF.On the non-promoted W and Mo catalysts, CO adsorption makes it possible to discriminate between the sites of the M- and S- edges of the TMS slabs. The determination of the molar extinction coefficients of the adsorbed CO bands allows the morphology of the slabs to be deduced. HR STEM HAADF confirms that the addition of CA modifies the morphology of the TMS slabs from a truncated triangle to a hexagonal shape.On the promoted NiW and CoMo catalysts, electron microscopy shows that the addition of CA decreases the size of the TMS slabs and also leads to the creation of very small clusters (<1 nm). The analysis of isolated particles by HR STEM HAADF allows identifying the nature of the atoms on the edge of the TMS slabs. Thus microscopy and IR/CO show that within the same sulfide slabs, can coexist edges that are fully promoted and partially promoted

The research work described in this thesis presents the synthesis, characterization and properties of a new family of trimetallic M₃(μ₃-S)(μ₂-S)₃ molybdenum and tungsten sulfide clusters. Functionalization of the cluster unit has been done by incorporating different chelating ligands such as diphosphines and heterodentate aminophosphines in order to confer specific physicochemical properties such as water solubility or catalytic activity. In particular, water soluble diphosphines and aminophosphines have been coordinated to the M₃S₄ unit in order to evaluate the potential applications of these new derivatives in environmentally friendly biphasic catalysis and homogenous organic catalysis, respectively.

The first chapter of the thesis describes the background, relevance and importance of the chemistry of transition metal clusters. General aspects on the chemistry of molybdenum and tungsten trinuclear clusters are shown together with their last novel applications. The second chapter shows the main objectives of this research project.

The preparation and characterization of novel water soluble cluster compounds of formula [M₃S₄X₃(hydroxyalkyldiphosphine)₃]⁺ (M=Mo, W; X=Cl, Br; hydroxyalkyldiphosphine = dhprpe, dhbupe) is described in chapter 3. Detailed studies based on ³¹P{¹H} NMR and electrospray ionization mass spectrometry techniques have been carried out in order to understand the complex pH dependent aqueous speciation of these water soluble clusters.

In chapter 4, the synthesis of molybdenum (IV) hydroxo [Mo₃S₄(dmpe)₃(OH)₃]⁺  and hydrosulfido [Mo₃S₄(dmpe)₃(SH)₃]⁺ trimetallic cuboidal cluster complexes is presented. A comparative study between molybdenum and tungsten of the gas-phase aldehyde production from the M₃S₄ ethoxo complexes combining collision induced dissociation experiments with computational DFT calculations is also discussed.

In chapter 5, the catalytic activity of molybdenum and tungsten (IV) cluster hydrides of formula [M₃S₄H₃(dmpe)₃]⁺ (M=Mo, W) in the regioselective hydrodefluorination of pentafluoropyridine at the 4-position has been evaluated. A mechanism for the catalytic reaction has been proposed based on experimental results and DFT calculations. Additionally, the fluorinated [M₃S₄F₃(dmpe)₃]⁺ complexes have been fully characterized.

In chapter 6, an aminophosphine ligand, (2-aminoethyl)diphenylphosphine (edpp),  containing a NH₂ protonic function has been coordinated to the molybdenum and tungsten M₃(μ₃-S)(μ-S)₃ cluster unit to afford for the first time trimetallic aminophosphine complexes. The activity of the molybdenum [Mo₃S₄X₃(edpp)₃]⁺ (X=Cl, Br) clusters in the catalytic transfer hydrogenation of nitroarenes has been investigated. Cluster catalysis is demonstrated from reaction monitoring using a pressurized sample infusion (PSI) ESI mass spectrometric technique. The reactivity of the tungsten [W₃S₄Br₃(edpp)₃]⁺ cation  towards alcohols, bases and halides salts has been investigated using a combination of spectrometric and spectroscopic techniques.  Molybdenum and tungsten [M₃S₄X₃(edpp)₃]⁺ (X=Cl, Br) complexes have been derivatized to afford a novel family of  trinuclear clusters bearing alkoxo terminal ligands.

In Chapter 7, details of the synthetic procedures together with the experimental and theoretical characterization are shown. Finally, chapter 8 shows the main conclusions of this Ph. D. thesis.

A presente Dissertação relata o estudo conformacional e das interações eletrônicas dos α-(etilsulfonil)-tioacetatos de fenila-para-substituídos X-Φ-S-C(O)-CH2-SO2-Et, sendo X substituintes atraentes, hidrogênio e doadores de elétrons, isto é, X= NO2 (1), Cl (2), Br (3), H (4), Me (5) e OMe (6) através da espectroscopia no Infravermelho, apoiada por cálculos ab initio e difração de Raio-X. Os dados obtidos indicaram a existência dos confôrmeros gauche1(s-trans) e um gauche2(s-cis), sendo este último bem mais estável do que o primeiro. Assim sendo, pode-se concluir que o componente de menor freqüência de maior intensidade da banda de carbonila corresponde ao confôrmero mais estável s-cis e o de maior freqüência de menor intensidade da banda da carbonila corresponde ao confôrmero s-trans menos estável. Diferentemente do que ocorre na maioria dos compostos carbonílicos α-heterossubstituídos, pode-se constatar que o aumento da polaridade do solvente origina uma população relativa gauche2(s-cis)/gauche1 (s-trans) praticamente constante em todas a série dos tioésteres estudados (1 )-(6). Este comportamento está de acordo com a menor basicidade dos tioésteres em relação às outras classes de compostos carbonílicos. Os dados dos cálculos ab initio indicam que: a) As interações orbitalar e eletrostática Oγ-(SO2)...........Cγ+(CO) estabilizam as conformações gauche2(s-cis) e gauche1(s-trans) praticamente na mesma extensão; b) A interação Oγ-(CO)...........Sγ+(SO2) estabiliza a conformação gauche2 (s-cis) em maior extensão do que a gauche1 (s-trans); c) A interação por ponte de hidrogênio Oγ-(CO)...........Hγ+(SO2Me)...........é mais forte no rotâmero gauche2(s-cis) do que no rotâmero gauche1 (s-trans). Os dados no Infravermelho indicam um aumento progressivo da população relativa gauche2(s-cis)/gauche1(s-trans) para os compostos de (1)-(6) em todos os solventes indo-se na posição para do grupo fenilsulfonila de substituintes atraentes a doadores de elétrons. Adicionalmente, constata-se no Infravermelho a ocorrência em CCl4 de deslocamentos de freqüência (Δν) mais negativos para o rotâmero gauche2(s-cis) do que o rotâmero gauche1(s-trans) dos compostos de (1)-(6), em relação aos tioacetatos de fenila correspondentes. Os dados no I.V. apoiam fortemente nos α-(etilsulfonil)-tioacetatos de fenila-para-substituídos (1)-(6) a ocorrência das interações orbitalares e eletrostáticas acima mencionados que estabilizam a conformação gauche2(s-cis) em maior extensão do que a gauche1(s-trans). Contrariamente ao nosso estudo anteriores de β-ceto-sulfonas, este comportamento pode ser atribuído à predominância das interações Oγ-(CO)...........Sγ+(SO2) e Oγ-(CO)...........Hγ+(SO2Me) sobre Oγ-(SO2)...........Cγ+(CO). De fato substituintes doadores de elétrons aumentam a densidade eletrônica sobre o átomo de oxigênio carbonílico, e desta forma facilitam as interações Oγ-(CO)...........Sγ+(SO2) e a Oγ-(CO).........Hγ+(SO2Me). Contrariamente, os substituintes em para atraente de elétrons diminuem a densidade eletrônica no átomo de oxigênio da carbonila e deste modo fazem com que a referida interação toma-se mais difícil de ocorrer. A análise por difração de Raio-X mono cristal dos α-etilsulfoniltioacetatos de fenila-(4) e de -para-metilfenila-(5) indicou que estes compostos no estado sólido encontram-se na conformação gauche2(s-cis), porém, ligeiramente distorcida em relação à mesma conformação presente no estado gasoso e em solução. A cela unitária do cristal é estabilizada pelo ganho de energia obtido tanto pelo acoplamento dos momentos de dipolos como também pela formação de ligações de hidrogênio intermoleculares Hγ+(orto)..........Oγ-(CO) e Hγ+(CH2CH3)...........Oγ(CO).
This thesis reports the conformational and electronic interaction studies of some p-substituted S-phenyl α-(ethylsulfonyl)-thioacetates Ph-SC(O)CH2SO2Et, being X electron-attracting, hydrogen and electron-donating para-substituents [X= NO2 (1), Cl (2), Br (3), H (4), Me (5) and OMe (6)], through IR spectroscopy supported by ab initio calculations and X-ray diffraction. The obtained data indicated the occurrence of two stable conformations i.e. the gauche2(s-cis) and the gauche1 (s-trans), being the former the most stable one. Therefore it may be concluded that the lower frequency more intense carbonyl doublet component is the most stable gauche2(s-cis) conformer while the higher frequency less intense doublet component is the least stable gauche1(s-trans) conformer. Differently from the majority of the α-heterosubstituted carbonyl compounds, the increasing polarity of the solvent effect originates an almost constant gauche2(s-cis)/gauche1(s-trans) population ratio for the whole series (1)-(6). This behaviour seems to be in line with the smaller basicity of the thioesters in comparison with the other classes of carbonyl compounds. The ab initio data indicate that: a) the Oγ-(SO2)..........Cγ+(CO) orbital and Coulombic interactions stabilise both the gauche2(s-cis) and gauche1 (s-trans) conformations almost to the same extent; b) the Oγ-(CO)..........Sγ+(SO2) interaction stabilises gauche2(s-cis) conformer into a greater extent than the gauche1(s-trans) conformer; e) the hydrogen bond interaction Hγ+(SO2Me)..........Oγ-(CO)) is slightly stronger for the gauche2(s-cis) conformer than that for the gauche1(s-trans) conformer. The IR data indicate that there is a progressive increase of the gauche2(s-cis)/gauche1(s-trans) population ratio for the whole series (1)-(6), on going at the para position of the phenylsulfonyl group, from electron attracting to electron donating substituents. Moreover there is, in carbon tetrachloride, a larger negative carbonyl frequency shifts (Δν) for the gauche2(s-cis)conformer of the title compounds (1)-(6) with respect to the gauche1(s-trans) conformer relative to the corresponding parent S-phenyl thioacetates (7)-(12). Therefore the IR data strongly support for the p-substituted S-phenyl α-(ethylsulfonyl)-thioacetate series the occurrence of the orbital and electrostatic interactions which stabilise the gauche2(s-cis) conformer into a larger extent than the gauche1(s-trans)conformer. Differently from the previously studied β-carbonyl-sulfones, this behaviour can be mainly ascribed to the predominance of the summing up of the Oγ-(CO)..........Sγ+(SO2) and Hγ+(SO2Me)..........Oγ-(CO) interactions over the Oγ-(SO2)..........Cγ+(CO) interaction. In fact, the electron donating para substituents increases the electron density on the carbonyl oxygen atom, and thus facilitates both the Oγ-(CO)..........Sγ+(SO2) and Hγ+(SO2Me)..........Oγ-(CO) interactions. On the other hand the electron attracting para substituents decreases the electron density on the carbonyl oxygen atom and thus make the referred interactions more difficult to occur. X-ray single crystal diffraction analyses for the S-phenyl-(4) and S-p-methylphenyl-(5), α-(ethylsulfonyl)-thioacetates indicated that these compouns exist in the solid state in a geometry which is reasonably close to the more stable gas and solution gauche2(s-cis) conformation. Furthermore in order to obtain the larger energy gain from the crystal packing, the slightly distorted gauche2(s-cis) geometry of compounds ( 4) and (5) is stabilised in the solid though dipole moment coupling along with the intermolecular Hγ+(o-Φ)..........Oγ-(CO) and Hγ+(CH2CH3)..........Oγ-(CO) hydrogen bond interactions.

O uso de antibióticos para tratamento da mastite bovina subclínica durante a lactação apresenta restrições econômicas e a administração indiscriminada e inadequada destes medicamentos os torna potencialmente tóxicos aos animais e aos consumidores finais dos produtos lácteos. A utilização de medicamentos homeopáticos oferece menor custo, facilidade de administração, não há risco de resistência microbiana e não é necessário o descarte do leite dos animais em tratamento. Além disso, a homeopatia é reconhecida no Brasil como especialidade médica veterinária e aceita para uso no sistema de produção animal orgânico. Portanto, o presente trabalho teve como objetivo avaliar a eficácia de dois protocolos homeopáticos para tratamento da mastite bovina subclínica durante a lactação. O experimento foi realizado no período de seis meses e dividido em duas etapas. Na Etapa I, um grupo foi medicado com Sulphur 30CH, enquanto que o outro recebeu placebo. Na Etapa II, um grupo foi medicado com Calcarea carbonica 30CH e o outro grupo recebeu placebo. Os medicamentos foram administrados a cada trinta dias na Etapa I e a cada quinze dias na Etapa II. Em cada etapa foram coletadas amostras de leite antes, durante e após o tratamento. Para avaliar a eficácia dos protocolos, durante o experimento foram analisadas 138 amostras de leite na Etapa I e 72 amostras na Etapa II, realizando-se prova de Tamis, California Mastitis Test (CMT), contagem de células somáticas (CCS), quantificação de polimorfonucleares (PMN) e mononucleares (MN) por microscopia óptica, exame microbiológico e mensuração da produção leiteira. As análises estatísticas foram realizadas utilizando o software Graphpad Instat 1990-93. Os protocolos homeopáticos testados não diminuíram a celularidade do leite, pois não houve diferenças significativas nos resultados do CMT e da CCS no decorrer do experimento. Também não foi constatada nenhuma alteração significante na produção láctea. O microrganismo isolado com maior frequência no rebanho estudado foi o Corynebacterium bovis. Porém, não houve diferenças significativas em relação à frequência de isolamento deste microrganismo ao longo dos tratamentos, indicando a sua permanência nas glândulas mamárias. Além disso, observou-se durante todo o experimento o predomínio de células PMN em relação às MN. Sugere-se o estudo de novos protocolos homeopáticos com outros medicamentos, potência e frequência de administração, a fim de buscar alternativas para o tratamento de vacas com mastite subclínica
The use of antibiotics for treatment of bovine subclinical mastitis during lactation presents economic restrictions and the indiscriminate and inappropriate administration of these drugs makes them potentially toxic to animals and consumers of dairy products. The use of homeopathic medicine offers lower cost, ease of administration, no risk of microbial resistance and is not necessary to discard milk from animals under treatment. Furthermore, homeopathy is recognized as a medical specialty in Brazil and support for veterinary use in organic livestock production system. Therefore, this study aimed to evaluate the effectiveness of two protocols for homeopathic treatment of bovine subclinical mastitis during lactation. The experiment was performed between six months and divided into two stages. In Phase I, one group was treated with Sulphur 30CH, while the other received placebo. In Phase II, one group was treated with Calcarea carbonica 30CH and the other group received placebo. The drugs were administered every thirty days in the Phase I and every fifteen days in the Phase II. At each step the milk samples were collected before, during and after treatment. To evaluate the effectiveness of the protocols during the experiment were analyzed 138 samples of milk at Phase I and 72 samples at Phase II, performing proof Tamis, California Mastitis Test (CMT), somatic cell count (SCC), quantification of polymorphonuclear (PMN) and mononuclear (MN) by optical microscopy, microbiological examination and measurement of milk production. Statistical analysis was performed using the software Graphpad Instat 1990-93. The homeopathic protocols tested not diminished cellularity of milk because there were no significant differences in the results of CMT and SCC during the experiment. Nor was it found no significant change in milk production. The organism isolated most frequently in the herd studied was Corynebacterium bovis. However, no significant differences were observed in the frequency of isolation of this microorganism during the treatments, indicating his permanence in the mammary glands. Furthermore, it was observed during the experiment a predominance of PMN cells compared to MN. It is suggested the study of new protocols with other homeopathic medicines, potency and frequency of administration, to find alternatives for the treatment of cows with subclinical mastitis

A reaeração superficial é um importante fenômeno físico responsável pela transferência de massa do oxigênio atmosférico para o curso de água, através da interface ar-água. Esse fenômeno é caracterizado quantitativamente pelo coeficiente de reaeração superficial (K2). O K2 pode ser influenciado por diversos fatores naturais, em especial, a turbulência, que é afetada pelas características físicas, hidrológicas e hidráulicas do escoamento da água. Este coeficiente é comumente utilizado em modelos ambientais de qualidade da água, o que implica na necessidade da sua correta estimativa. A estimativa do K2 pode ser realizada por meio de métodos e modelos de predição, entre os métodos destacam-se o traçador gasoso e a sonda solúvel flutuante. O objetivo principal desta pesquisa foi verificar a variabilidade espacial e temporal do K2 em cinco trechos de quatro riachos tropicais localizados no município de São Carlos-SP, em um ano de amostragem. Nesses trechos foram mensuradas as principais variáveis químicas, físicas, hidrológicas e hidráulicas do escoamento da água, além do K2 e a velocidade de dissolução de uma sonda solúvel flutuante (VS). A estimativa do K2 ocorreu pelo método do traçador gasoso, sendo o SF6 e o NaCl os traçadores utilizados. A estimativa do VS ocorreu pelo método da sonda solúvel flutuante, confeccionada com ácido oxálico dihidratado e no formato esférico. Análises estatísticas de correlação (Spearman, r) e variância (Kruskal-Wallis) foram realizadas, e modelos de regressão linear simples (RLS) e múltipla (RLM) foram desenvolvidos. Os trechos apresentaram profundidades e larguras médias inferiores a 0,42 m e 3,27 m, respectivamente. A vazão e a velocidade (U) média variaram de 0,001 m3.s-1 a 0,110 m3.s-1 e de 0,01 m.s-1 a 0,33 m.s-1, respectivamente. Os números de Reynolds e Froude (Fr) foram inferiores a 34070 e 0,36, respectivamente. Os K2 variaram de 16,90 dia-1 a 373,80 dia-1 e os VS, de 0,08 mm.min-1 a 0,77 mm.min-1. Os resultados demonstraram variação espacial significativa e temporal não significativa para as variáveis físicas, hidrológicas, hidráulicas, e também para o K2 e VS. U e Fr foram as principais variáveis que se correlacionaram com o K2 (r > 0,68). Um adequado modelo RLM de predição do K2 (R² = 0,75), baseado em todas as variáveis físicas, hidrológicas e hidráulicas e no VS, foi obtido. O modelo RLS, baseado apenas na relação entre K2 e VS, não foi adequado (R² = 0,43) para a predição do K2. A razão entre os fenômenos da reaeração superficial e dissolução da sonda solúvel flutuante não foi constante, e foi afetada pela turbulência na interface ar-água, o que indicou que o método da sonda solúvel flutuante ainda precisa ser aprimorado. Espera-se que, além de gerarem dados sobre um método (sonda solúvel flutuante) e tema (reaeração superficial) ainda relativamente pouco estudados em riachos tropicais, as informações apresentadas sobre as principais variáveis intervenientes no fenômeno de reaeração superficial e dissolução em riachos possam oferecer direcionamentos a estudos ambientais, especialmente àqueles que versam sobre a qualidade dos recursos hídricos.
Surface reaeration is an important physical phenomenon responsible for the transfer of atmospheric oxygen mass into the water course through the air-water interface. This phenomenon is quantitatively characterized by the surface reaeration coefficient (K2). K2 can be influenced by several natural factors, especially turbulence, which is affected by the physical, hydrologic and hydraulic characteristics of the watercourse. This coefficient is commonly used in environmental models of water quality, which implies the need for its correct estimation. The estimation of K2 can be performed by models of prediction and methods, among the methods the gas tracer and the floating soluble probe stand out. The aim of this research was to verify the spatial and temporal variability of K2 in five stretches of four tropical streams located in the city of São Carlos-SP, in a year of sampling. In these stretches the main chemical, physical, hydrological and hydraulic variables of the watercourse were measured, besides K2 and the dissolution rate of the floating soluble probe (VS). The estimation of K2 occurred by the gas tracer method, with SF6 and NaCl being the tracers used. The VS estimation was carried out by the floating probe method, made with oxalic acid dihydrate and in spherical format. Statistical analyzes of correlation (Spearman, r) and variance (Kruskal-Wallis) were performed, and simple linear regression (SLR) and multiple linear regression models (MLR) were developed. The stretches presented mean depths and widths of less than 0.42 m and 3.27 m, respectively. The flow rate and average velocity (U) ranged from 0.001 m3 s-1 to 0.110 m3s-1 and from 0.01 m.s-1 to 0.33 m.s-1, respectively. The Reynolds and Froude (Fr) numbers were less than 34070 and 0.36, respectively. The K2 ranged from 16.90 day-1 to 373.80 day-1 and the VS, from 0.08 mm.min-1 to 0.77 mm.min-1. The results showed significant spatial variation and a non-significant temporal variation for the physical, hydrological and hydraulic variables, as well as for K2 and VS. U and Fr were the main variables that correlated with K2 (r > 0.68). A suitable MLR prediction model of K2 (R² = 0.75), based on all physical, hydrological and hydraulic variables and VS, was obtained. The SLR model, based only on the relationship between K2 and VS, was not adequate (R² = 0.43) for K2 prediction. The ratio between the phenomena of surface reaeration and dissolution of the floating soluble probe was not constant and was affected by turbulence at the air-water interface, which indicated that the floating soluble probe method still needs to be improved. It is expected that, in addition to generating data on a method (floating soluble probe) and surface (surface reaeration) that are still relatively little studied in tropical streams, the information presented on the main variables involved in the phenomenon of surface reaeration and dissolution in streams may offer environmental studies, especially those dealing with the quality of water resources.

Le dopage non covalent de nanostructures carbonées par transfert de charge depuis/vers des molécules donneuses ou acceptrices (EDA) ou bien par des molécules d’acide sulfurique H2SO4, est considéré comme potentiellement intéressant pour de nombreuses applications. Parmi celles-ci on peut citer: capteur chimique, transistor à effet de champ, et d’autre l'électronique. Cependant, d'un point de vue théorique, on en sait peu au sujet de ces processus de transfert de charge par électrons ou par trous.Dans un premier temps, nous nous sommes intéressés à l’interaction entre des molécules d’acide sulfurique et des nanostructures modèles, car elles sont capables de doper des nanotubes, de s’intercaler dans le graphite et même d’aligner les tubes dans une phase nématique, ce qui pourrait mener à la création de matériaux composites à forte valeur ajoutée.Bien que certaines études théoriques DFT ont été menées récemment, leurs résultats restent source de confusion. Par exemple, même s’il est rapporté un transfert de charge entre une molécule de H2SO4 et un plan de graphène, tous nos efforts pour reproduire ces calculs ont été infructueux. Nous proposons dans ce travail de thèse, un mécanisme de réaction qui expliquent la "protonation" des parois du tube, tel que proposé dans la littérature. Enfin nous proposons un scénario possible pour une meilleure compréhension de la structuration à grande échelle des molécules d'acide autour de points d'ancrage, telles que des défauts, de la structure carbonée
Non-covalent doping of carbon nanostructures by charge transfer from/to donor/acceptor molecules (EDA) or by H2SO4 molecules, be it with holes or electrons, is usually thought as potentially interesting for many applications of carbon based nano-devices. However, from a theoretical point of view, little is known about such “charge transfer” processes.Employing first-principles method based on Density Functional Theory (DFT), we have studied in details, and proposed a model to rationalize, the interaction between a prototypical donor molecule the tetrathiafulvalene (TTF), a standard acceptor organic molecule, tetracyanoethylene (TCNE) and carbon nanostructures: graphene layer and SWNTs with various chiral indices. Main results concern structural and thermodynamic aspects including dispersion forces effects, and evidently electronic structure modifications of the nanostructures. Various adsorption modes and concentration effects have been investigated. At very low coverage values, we have reported a charge transfer between graphene and TCNE or TTF. Moreover, we have shown that the charge transfer can be enhanced by increasing the concentration of those two EDA molecules, as it has been demonstrated experimentally. Those results are beneficial for comprehending the nonchemical doping mechanism in graphene structure by means of charge transfers. Considering the interaction between these prototypical molecules and carbon nanotubes, we have found that charge transfers tend to decrease while the curvature of nanotube is increasing. Besides, a strong influence of the metallic/semi-conductor character of the SWNTs can be observed and be explained by the change of polarisability of the curved carboneous substrates. Additionally, we have studied the adsorption properties of sulfuric acid molecules, in its non-hydrated form, on carboneous nanostructures. Against the common believe, no charge transfer is observed in the H2SO4@graphene or H2SO4@CNTs cases, even at very high concentrations. Instead, in order to elucidate the origin of p-doping observed experimentally, we have proposed that molecule is responsible of the reversible doping. Besides we have shown that a proton transfer could cause the experimental phenomenon of crystallization of H2SO4 molecules on SWNT’s surface. Finally in such process, defects like vacancy are of first importance, since they could provide anchorage points for hydrogen atoms. The results of the present work will certainly help to understand the charge transfer and doping mechanism of carbon nanostructures by means of non-covalent functionalization, which is a promising method for their future applications

As aminas heterocíclicas alifáticas, piperidina, piperazina e pirrolidina, interagem com o dióxido de enxofre, gasoso ou líquido, dando origem a uma série de compostos em diferentes estequiometrias, os quais foram investigados fundamentalmente por técnicas espectroscópicas vibracionais, infravermelho e Raman, utilizando-se como técnicas auxiliares a espectroscopia eletrônica, espectros de massas e de ressonância magnética nuclear. Os resultados obtidos caracterizam as espécies estudadas como complexos moleculares formados entre as aminas e o SO2, especialmente devido aos deslocamentos de frequências observados nos espectros Raman, para os modos vibracionais de estiramento simétrico e deformação angular do dióxido de enxofre. Os dados indicam no sentido do estabelecimento de intensas ligações de hidrogênio, as quais devem desempenhar importante papel na estabilização dos complexos. Os deslocamentos observados nos espectros Raman encontram-se de acordo com o comportamento previsto para a interação de transferência de carga, em que o LUMO do SO2 apresenta caráter antiligante em relação à ligação S-O e ligante em relação à interação O-O.
The interaction of alifatic heterocyclic amines piperidine, piperazine and pyrrolidine, with sulfur dioxide yields a variety of products of different stoichiometry. The investigation of the formed species were carried out mainly by vibrational spectroscopic techniques, infrared and Raman, and electronic spectroscopy, mass spectrometry and nuclear magnetic resonance spectra were used as auxiliary techniques. The obtained results indicate that the studied species are charge transfer molecular complexes due to the frequency shifts of the symmetric stretching and angular deformation modes of sulfur dioxide in the Raman spectra. The data are in agreement with an S-O antibonding and a O-O bonding character of the LUMO of SO2. Hydrogen bonds play an important role in the complex stabilization.

Medidas de tempo de vôo, em cinco diferentes temperaturas, foram realizadas em enxofre ortorrômbico para vários campos elétricos, tanto positivos como negativos. O trânsito dos portadores negativos foi mais extensivamente analisado e para baixas intensidades de luz, isto é, o caso do sinal fraco, os seguintes fatos foram verificados; a) não foi detectada dependência da mobilidade com o campo elétrico; b) a razão da corrente no tempo t para a corrente inicial mostrou não ser uma função universal do tempo, (isto é, independente do campo aplicado). Transporte dispersivo, discernível através da dependência da mobilidade com o campo elétrico, foi detectado pelo fato a. Contudo, para o transporte não dispersivo nós devemos esperar que a corrente normalizada leve a uma função universal do tempo, somente dependente do tempo de captura e, eventualmente, do tempo de soltura dos portadores, contrário ao que foi encontrado em b. A parte principal desta tese foi dedicada a testar nossos resultados com modelos existentes e o efeito esperado da falha das suposições nos resultados. Nós fomos então levados a um novo modelo, o qual explicou razoavelmente os resultados; a luz joga portadores, não só no canal normal de condução, mas também em um nível extra, confinado à região superficial, caracterizado por uma mobilidade dependente da profundidade. Soluções numéricas foram obtidas para confirmar a validade das soluções analíticas aproximadas obtidas. Um modelo aproximado foi desenvolvido para explicar o efeito do campo elétrico na extração de portadores da zona iluminada
Time off light measurements, in five different temperatures, were carried out in orthorhombic sulphur for various electric fields, both positive and negative. The transit of negative carriers were more thoroughly analyzed and at low light intensities, that is, the small signal case, the following facts were well established; a) no electric field dependence of the mobility was detected, b) the ratio of the current at a time t to the initial current was found not to be a universal function of the time (that is, independent of the applied field). Dispersive transport, discernible through its field dependent electron mobility, is ruled out by a. However, for non dispersive transport, we should expect the normalized current to lead to a universal function of time, only dependent of the trapping and, eventually, de-trapping times of the carriers, contrary to what was found in b. The main part of this thesis was devoted to test our results with the existing models and the expected effect of the breakdown of the simplified assumptions on the results. We were thus lead to a new model, which reasonable explained the results: light put carriers, not only in the normal conduction channel, but also in an extra level, confined to the surface region, characterized by a depth dependent mobility. Computer solution were carried out to confirm the validity of approximate analytic solutions thus obtained. An approximate model was also developed to explain the effect of the electronic field on the extraction of carriers from the illuminated zone

L’utilisation du dioxyde de carbone (CO₂) comme source de composés C1 pour la chimie fine est intéressante d’un point de vue économique et pour des raisons écologiques. Issu de l’oxydation de la matière carbonée, le CO₂ est un gaz non-toxique, abondant et peu coûteux. Sa transformation en produits chimiques présentant de hautes valeurs ajoutées est actuellement entravée par sa stabilité thermodynamique. Afin de développer de nouveaux processus et catalyseurs pour la réduction catalytique du CO₂, une compréhension détaillée des mécanismes réactionnels de l’activation et de la réduction de ce gaz est nécessaire. En utilisant comme catalyseurs des paires de Lewis frustrée (FLPs) contenant une base azotée liée à un ion silicénium, les influences respectives de l’adduit CO₂-FLP et du réducteur ont été déterminées expérimentalement et par calcul DFT dans le cadre de l’hydroboration du CO₂ en équivalent de méthanol. Une nouvelle réaction visant à la création de liaisons carbone–carbone par le transfert du fragment pyridyle de molécules de pyridylsilanes (C₅H₄N–SiMe₃) sur le CO₂ était également étudiée. Le mécanisme réactionnel de cette transformation a été établi sur la base de calculs théoriques. Nous avons montré le double rôle du CO₂ qui est à la fois un réactif et un catalyseur de la réaction de transfert du groupe pyridyle. La compréhension fine de cette réaction nous a permis de l’étendre à la formation de sulfones et sulfonamides qui sont des groupements chimiques essentiels dans le domaine pharmaceutique. En utilisant le SO₂ à la fois comme catalyseur et réactif, des silanes aromatiques et hétéro-aromatiques ont été transformés en sulfones correspondants en une seule étape. Finalement, nous avons trouvé un couplage croisé original, de type Hiyama, entre espèces aromatiques électrophiles et des espèces C(sp2)–Si nucléophiles en présence de SO₂
The use of CO₂ as a C1 chemical feedstock for the fine chemical industry is interesting both economically and ecologically, as CO₂ is non-toxic, abundant and cheap. Nevertheless, transformations of CO₂ into value-added products is hampered by its high thermodynamic stability and its inertness toward reduction. In order to design new catalysts able to overcome this kinetic challenge, a profound understanding of the reaction mechanisms at play in CO₂ reduction is needed. Using novel N/Si+ frustrated Lewis pairs (FLPs), the influence of CO₂ adducts and different hydroborane reducing agents on the reaction mechanism in the catalytic hydroboration of CO₂ were investigated, both by DFT calculations and experiments. In a second step, the reaction mechanism of a novel reaction for the creation of C–C bonds from CO₂ and pyridylsilanes (C₅H₄N–SiMe₃) was analyzed by DFT calculations. It was shown that CO₂ plays a double role in this transformation, acting both as a catalyst and a C1-building block. The fine understanding of this transformation then led to the development of a novel approach for the synthesis of sulfones and sulfonamides. Starting from SO₂ and aromatic silanes/amine silanes, these products were obtained in a single step under metal-free conditions. Noteworthy, sulfones and sulfonamides are common motifs in organic chemistry and found in a variety of highly important drugs. Finally, this concept was extended to aromatic halides as coupling partners, and it was thus shown for the first time that a sulfonylative Hiyama reaction is a possible approach to the synthesis of sulfones

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
Os manguezais sÃo ecossistemas complexos e que possuem uma dinÃmica marcada pela interaÃÃo de diversos fatores, tanto biÃticos (vegetaÃÃo, macrobiota), quanto abiÃticos (temperatura, regime de chuvas, amplitude das marÃs). A interaÃÃo desses fatores influencia diretamente as condiÃÃes fÃsico-quÃmicas e biolÃgicas do meio, refletidas em parÃmetros como pH e Eh. Nas Ãreas de manguezais, condiÃÃes como o hidromorfismo fazem com que a forma preponderante de obtenÃÃo de energia seja a ReduÃÃo Bacteriana do Sulfato, que està diretamente relacionada com o ciclo do ferro desses locais. Diante disso, percebe-se a necessidade de mais estudos nesse ramo da CiÃncia do Solo, tendo em vista que os processos envolvidos nesses locais ainda sÃo pouco conhecidos, principalmente nos manguezais de Ãreas de clima semiÃrido. Sendo a regiÃo do estuÃrio do rio Acaraà â CE uma Ãrea inserida nesse contexto e com sazonalidade marcante, um estudo do solo e da Ãgua intersticial dessa Ãrea foi realizado com o objetivo de se avaliar o comportamento das espÃcies de ferro e enxofre, levando-se em consideraÃÃo parÃmetros tais como as variaÃÃes estacionais da regiÃo, profundidade e presenÃa ou nÃo da vegetaÃÃo, bem como a atividade microbiana. Para obtenÃÃo de um estudo detalhado desses solos, foram determinados pH, Eh, teor de matÃria orgÃnica, sulfato e cloreto na Ãgua intersticial, salinidade, extraÃÃo sequencial de ferro, bem como a respirometria em trÃs Ãreas do manguezal do rio Acaraà com predomÃnio de plantas do gÃnero Rhizophora e Avicennia, bem como em uma Ãrea nÃo vegetada. De uma forma geral, os dados obtidos mostram que os manguezais sÃo Ãreas levemente Ãcidas ou atà mesmo alcalinas, alÃm de serem ambientes fortemente redutores. Dentre as fraÃÃes de ferro analisadas, observa-se que suas concentraÃÃes variam entre as Ãreas, uma vez que as condiÃÃes fÃsico-quÃmicas predominantes nos pontos de amostragem escolhidos sÃo diferentes entre si. AlÃm disso, observou-se que a transiÃÃo do perÃodo chuvoso para o de estiagem promove um maior acÃmulo de sais no solo, evidenciado pelos aumentos das concentraÃÃes dos Ãons e dos valores de salinidade. Nesse contexto, o aumento da taxa de evapotranspiraÃÃo surge como fator determinante para mudanÃas nas condiÃÃes fÃsico-quÃmicas do meio, pois promove uma circulaÃÃo de ar no solo mais eficiente. Por fim, foi constatado que os parÃmetros analisados e a presenÃa da vegetaÃÃo local possuem uma relaÃÃo de interdependÃncia bastante significativa e desempenham um papel fundamental na dinÃmica do ecossistema. AlÃm disso, observou-se que a sazonalidade marcante da regiÃo e os fatores por ela governados contribuem de forma direta para a oxidaÃÃo de sulfetos, alterando a mineralogia e as caracterÃsticas fÃsico-quÃmicas das Ãguas intersticiais e solo desse manguezal.
Mangroves ecosystems are complex and have a dynamic marked by the interaction of several factors, both biotic (vegetation, macrobiotics), and abiotic (temperature, rainfall, tidal range). The interaction of these factors influences directly the physicalchemical and biological environment, reflected in parameters such as pH and Eh. In mangrove areas, as conditions hydromorphism cause the prevailing form of procurement of energy is the bacterial sulfate reduction, which is directly related to the iron cycle of these locations. Given this, we see the need for further studies in this branch of Soil Science, in view of the processes involved in these places are still poorly understood, especially in mangrove areas in semiarid climate. Since the estuary of the river Acaraà â CE an area within this context and with marked seasonality, a study of soil and pore water of this area was conducted with the aim of evaluating the behavior of iron and sulfur species, taking into account parameters such as seasonal variation in the region, depth and presence or absence of vegetation, and microbial activity. To obtain a detailed study of soils, soil pH, Eh, organic matter content, sulfate and chloride in pore water, salinity, sequential extraction of iron and respirometry were done in three areas of mangrove river Acaraà predominantly plant the genus Rhizophora and Avicennia, as well as a non-vegetated area. Overall, our data show that mangrove areas are slightly acidic or even alkaline environments and are strongly reducing. Among the fractions analyzed for iron, it is observed that their concentrations vary between areas, since the physicochemical conditions prevailing at the sampling points chosen are different. Furthermore, we observed that the transition from rainy to dry season promotes a greater accumulation of salts in the soil, as evidenced by increases in ion concentrations and salinity. In this context, the increased rate of evapotranspiration emerges as a determinant for changes in the physicochemical conditions of the medium, because it causes a movement of air in the soil more efficiently. Finally, we found that the parameters measured and the presence of local vegetation have an interdependent relationship and play a very significant role in ecosystem dynamics. Furthermore, we observed that the marked seasonality of the region and the factors which it ruled directly contribute to the oxidation of sulfides by changing the mineralogy and the physico-chemical properties of soil and interstitial waters of mangrove.

Abstract Exhaust gas emissions, e.g. nitrogen oxides (NOx), hydrocarbons (HCs) and carbon monoxide (CO), are harmful to human health and the environment. Catalysis is an efficient method to decrease these emissions. Unfortunately, the fuels and lubricant oils may contain chemical impurities that are also present in exhaust gases. Thus, catalytic materials with high activity and chemical resistance towards impurities are needed in the abatement of exhaust gas emission. In this thesis, the aim was to gain new knowledge about the effects of chemical impurities on the behaviour and activity of the catalysts. To find out these effects, the impurities existing in the exhaust gas particulate matter after combustion of biofuels and fossil fuels were analysed. The studied zeolite (ZSM-5), cerium-zirconium mixed oxides (CeZr and ZrCe) and silicon-zirconium oxide (SiZr) based catalysts were also treated with impurities to simulate the poisoning of the catalysts by, e.g. potassium, sodium, phosphorus and sulphur, using gas or liquid phase treatments. Several characterization techniques were applied to find out the effects of impurities on catalysts’ properties. The activity of catalysts was tested in laboratory-scale measurements in CO and HC oxidation and NOx reduction using ammonia (NH3) and hydrogen (H2) as reductants. The results revealed that the CeZr based catalysts had a high activity in NOx reduction by NH3 and moderate activity by H2. Sulphur was proven to enhance the activity of CeZr catalysts in NOx reduction. This is due to an increase in chemisorbed oxygen after the sulphur treatment on the catalyst surface. Instead, in HC and CO oxidation reactions, sulphur had a negligible impact on the activity of the SiZr based diesel oxidation catalyst. Thus, both CeZr and SiZr based catalysts can be utilized in exhaust gas purification when sulphur is present. ZSM-5 based catalysts were proven to be resistant to potassium and sodium. Alternatively, the activity of SiZr based catalysts decreased due to phosphorus. Thus, the removal of biomaterial-based impurities from the exhaust gases is needed to retain high catalyst activity in the exhaust gas after-treatment system
Tiivistelmä Pakokaasupäästöissä olevat typen oksidit (NOx), hiilivedyt (HCs) ja hiilimonoksidi (CO) ovat haitallisia ihmisten terveydelle ja ympäristölle. Katalyysi on tehokas menetelmä vähentää näitä päästökomponentteja. Polttoaineet ja voiteluöljyt sisältävät epäpuhtauksia, jotka siirtyvät myös pakokaasuihin. Tästä johtuen pakokaasupäästöjen hallinnassa tarvitaan katalyyttimateriaaleja, joilla on hyvä vastustuskyky myrkyttymistä vastaan. Tavoitteena oli saada uutta tietoa kemiallisten epäpuhtauksien vaikutuksesta katalyyttien toimintaan. Biopolttoaineiden sisältämät mahdolliset epäpuhtaudet selvitettiin analysoimalla fossiilisen ja biopolttoaineen palamisessa muodostuvia partikkeleita ja vertaamalla niitä polttoaineiden hivenaineanalyysiin. Tutkimuksessa käytetyt zeoliitti (ZSM-5), cerium-zirkonium-sekaoksidi (CeZr) ja pii-zirkonium-oksidipohjaiset (SiZr) katalyytit käsiteltiin epäpuhtauksilla (kalium, natrium, fosfori ja rikki) kaasu- ja nestefaasissa. Tutkimuksessa käytettiin useita karakterisointitekniikoita, joiden avulla selvitettiin epäpuhtauksien vaikutuksia katalyyttien ominaisuuksiin. Katalyyttien toimintaa testattiin laboratoriomittakaavan kokeissa CO:n ja HC-yhdisteiden hapetuksessa sekä NOx:ien pelkistyksessä käyttäen ammoniakkia (NH3) tai vetyä (H2) pelkistimenä. Tulokset osoittavat, että CeZr-pohjaisten katalyyttien aktiivisuus NOx:ien pelkistyksessä oli hyvä käytettäessä pelkistimenä NH3:a ja kohtalainen käytettäessä vetyä. Rikki paransi CeZr-katalyyttien aktiivisuutta NOx:ien pelkistyksessä, mikä johtui kemiallisesti sitoutuneen hapen osuudesta katalyyttien pinnoilla. Vastaavasti hiilivetyjen ja CO:n hapetusreaktioissa rikki ei vaikuttanut SiZr-pohjaisten dieselhapetuskatalyyttien aktiivisuuteen. Sekä CeZr- ja SiZr-pohjaisia katalyytteja voidaan siten käyttää rikkiä sisältävien pakokaasujen puhdistuksessa. SiZr-pohjaisten katalyyttien aktiivisuus laski fosforin vuoksi. ZSM-5-pohjaiset katalyytit olivat vastustuskykyisiä kaliumille ja natriumille. Kestäviä katalyyttejä on siten kehitettävä, mikäli biopolttoaineiden sisältämien epäpuhtauksien poistaminen polttoaineista ei ole mahdollista

A presente tese trata de α-sulfonil carbânions, trazendo uma contribuição para a compreensão da sua estabilidade conformacional e reatividade frente a reagentes eletrofílicos. As reações investigadas foram as alquilações e sulfenilações de α-sulfonil tioésteres e as descarboxilações alquilativas dos ácidos α-fenilsulfonil-α-fenilpropanóicos racêmico e opticamente ativo. A apresentação e discussão dos resultados das reações de alquilação e sulfenilação é precedida por uma revisão bibliográfica que apresenta os trabalhos mais relevantes da literatura sobre as reações de α-sulfonil carbânions com diversos eletrófilos, envolvendo reações tais como: halogenação, alquilação, acilação, condensação e sulfenilação. Os estudos das reações de alquilação, por nós efetuados com dois diferentes α-sulfonil tioésteres, empregando o método em fase homogênea, indicaram que, no caso dos haletos de metila, etila e alila, foram obtidas misturas dos produtos mono- e di- alquilados, enquanto que no caso do brometo de benzila houve formação exclusiva de produtos monoalquilados (ver arquivo). Entretanto, a alquilação pelo emprego do método de catálise de transferência de fase (CTF), efetuada com o α-fenilsulfonil tioacetato de metila, conduziu exclusivamente aos produtos monoalquilados correspondentes, independentemente do reagente alquilante empregado (ver arquivo). Estes resultados mostraram a superioridade do método em transferência de fase sobre o em fase homogênea. Os estudos das reações de sulfenilação, efetuados com o α-fenilsulfonil tioacetato de metila e os seus derivados α-alquilsubstituídos, empregando o método CTF, conduziram exclusivamente aos produtos monossulfenilados (ver arquivo). Neste caso, o método em transferência de fase também se mostrou superior ao em fase homogênea, sendo os produtos monossulfenilados obtidos em maior rendimento. É sugerido um mecanismo para as reações de alquilação e sulfenilação de α-sulfonil tioésteres em CTF, empregando sistema sólido / líquido, o qual explica a ausência, nestas condições reacionais, dos produtos dialquilado e dissulfenilado. A apresentação e discussão dos resultados das reações de descarboxilação alquilativas dos ácidos α-fenilsulfonil-α-fenilpropanóicos racêmico e opticamente ativo é precedida por uma introdução que apresenta os estudos mais relevantes da literatura sobre as reações de descarboxilação de ácidos α-sulfonil carboxílicos na presença de eletrófilos, tais como hidrogênio, halogênio, carbono e enxofre. São de especial interesse os estudos envolvendo o curso estereoquímico da reação de descarboxilação protonativa de ácidos α-sulfonil carboxílicos opticamente ativos em meio alcalino, demonstrando a grande estabilidade do α-sulfonil carbânion, que retém a sua configuração original, sendo esta mantida mesmo após a protonação. Estas investigações se relacionam com os nossos estudos de descarboxilação alquilativa dos ácidos α-fenilsulfonil-α-fenilpropanóicos racêmico e opticamente ativo, efetuados em continuação aos estudos anteriores de descarboxilações alquilativas dos ácidos α-fenilsulfonil-α-fenil carboxílicos realizados no nosso laboratório. Os nossos resultados mostraram que é possível obter a sulfona tetrassubstituída pela reação do ácido α-fenilsulfonil-α-fenilpropanóico com iodeto de etila na presença de NaH / DMSO, desde que se expulse o CO2 formado na reação (ver arquivo). É apresentada a síntese do ácido α-fenilsulfonil-α-fenilpropanóico opticamente ativo, o qual foi obtido por vários passos reacionais, através da resolução do ácido α-fenilsulfenil-α-fenilpropanóico e a sua posterior oxidação. A configuração de ambos os compostos foi determinada pela análise de raios X, mostrando ser o isômero S. As sínteses destes ácidos foram efetuadas por dois métodos distintos, constituídos de 3 e 5 passos reacionais. Entretanto, não foi possível obter a sulfona tetrassubstituída opticamente ativa pela reação do ácido α-fenilsulfonil-α-fenilpropanóico opticamente ativo com iodeto de etila nas mesmas condições empregadas no caso do composto racêmico correspondente. Foi obtido um esclarecimento do processo da descarboxilação de ácidos α-sulfonil carboxílicos a partir de cálculos semi-empíricos que mostraram a existência de duas etapas intermediárias na descarboxilação dos respectivos carboxilatos, ou seja, uma em que o CO2 se liga ao carbânion (I) e outra, de mais baixa energia, em que ele se liga ao oxigênio sulfonílico (II) (ver arquivo). Foram fornecidas provas, através de experiências comparativas de alquilação e protonação, que para que o α-sulfonil carbânion mantenha a sua configuração, é necessário que o eletrófilo reaja com o carbânion antes da expulsão total de CO2, isto é, na fase em que ele se encontra ligado ao oxigênio sulfonílico (II). Este é o caso da descarboxilação protonativa, que mostrou ocorrer com retenção da configuração na experiência por nós realizada. A racemização que ocorre no caso da descarboxilação alquilativa foi atribuída à pequena janela de reação, que impede a aproximação do reagente alquilante. Foi por nós sugerido que a ligação do CO2 ao oxigênio sulfonílico seria responsável pela barreira rotacional que mantém a assimetria do α-sulfonil carbânion, tornando-o conformacionalmente estável. No decorrer do presente estudo foram sintetizados 11 compostos ainda não descritos na literatura, entre eles: três α-bromo tioésteres, cinco α-sulfonil tioésteres, quatro α-sulfonil tioésteres α-sulfenilados e uma sulfona tetrassubstituída.
This thesis gives a contribution to the chemistry of α-sulfonyl carbanions, such as the comprehension of its conformational stability and reactivity towards electrophilic reagents. The investigated reactions were alkylation and sulfenylation of α-sulfonyl thioesters and the decarboxylative alkylation of racemic and optically active α-phenylsulfonyl-α-phenylpropanoic acids. The presentation of the results and the discussion of the alkylation and sulfenylation reactions are preceded by a bibliographic revision describing the most important reports in the literature concerning the reactions of α-sulfonyl carbanions with different electrophiles, such as: protonation, halogenation, alkylation, acylation, condensation and sulfenylation. Our studies of the alkylation reaction, carried out with two different α-sulfonyl thioesters, employing homogeneous media, indicated that in the case of methyl, ethyl and allyl halides, mixtures of mono- and dialkylated products were obtained. However, in the case of benzyl bromide, the corresponding monoalkylated compound was obtained as the only reaction product (see file). On the other hand, the alkylation of methyl α-phenylsulfonyl thioacetate by PTC method afforded, exclusively, the corresponding monoalkylated products. These results show the superiority of the PTC method over the homogeneous one (see file). The sulfenylation reactions carried out with methyl α-phenylsulfonyl thioacetate and their α-alkylsubstituted derivatives employing PTC conditions, afforded only monosulfenylated α-sulfonyl thioesters as the only reaction products. Also in this case, the PTC method showed to be superior to give the monosulfenylated products in higher yields (see file). A mechanism for the alkylation and sulfenylation reactions in solid / liquid PTC system, which explains the absence of the dialkylated and disulfenylated products is suggested. The presentation and discussion of the results for the alkylative decarboxylation reactions of racemic and optically active α-phenylsulfonyl-α-phenylpropanoic acids is preceded by a bibliographic introduction reporting the most important works in the literature concerning the decarboxylation of α-sulfonyl carboxylic acids in the presence of electrophiles such as hydrogen, halogens and sulfur. Specially important are the studies on the stereochemical course of the base-catalyzed protonative decarboxylation of optically active α-sulfonyl carboxylic acids, showing the high stability of the a-sulfonyl cabanion, which retains its original configuration even after protonation. There is a link between these investigations and our studies of the alkylative decarboxylation of racemic and optically active α-phenylsulfonyl-α-phenylpropanoic acids, which are undertook in continuation to our investigations on the alkylative decarboxylation of α-phenylsulfonyl-α- phenyl carboxylic acids. Our results showed that it is possible to obtain the tetrasubstituted sulfone from the reaction of α-phenylsulfonyl-α-phenylpropanoic acid with ethyl iodide, in the presence of NaH / DMSO as base, provided that the CO2, which is formed during the reaction, is expelled (see file). The synthesis of the optically active α-phenylsulfonyl-α-phenylpropanoic acid containing several reaction steps is presented, through the resolution of the α-phenylsulfenyl-α-phenylpropanoic acid, followed by its oxidation. The configurations of both acids were determined through X-rays analyses, and showed to be S. However, it was not possible to obtain the optically active tetrasubstituted sulfone from the reaction of optically active α-phenylsulfonyl-α-phenylpropanoic acid with ethyl iodide in the experimental conditions employed for the corresponding racemic acid. The insight for the decarboxylation process of the α-sulfonyl carboxylic acids was obtained from semi-empiric calculations that showed the existence of two intermediate steps in the decarboxylation of the corresponding carboxylates, one of which with CO2 bonded to the carbanion and another one, of lower energy, in which the CO2 is linked to the sulfonyl oxygen (see file). Proofs were provided, through the comparative experiments of alkylation and protonation for the optically active α-sulfonyl acid, that for retention of configuration of the α-sulfonyl carbanion it is necessary that the reaction of the carbanion with the electrophile takes place before the total expulsion of CO2, i.e., when it is linked to SO2. It was suggested that the CO2-OSO linkage could be responsible for the rotational barrier, which maintains the symmetry of the a-sulfonyl carbanion, which becomes conformationaly stable. Finally, eleven new compounds were prepared in the course of the present study such as: three α-bromo thioesters, five α-sulfonyl thioesters, four α-sulfenylated α-sulfonyl thioesters and one α-tetrasubstituted sulfone.

O petróleo é uma complexa mistura de compostos orgânicos e inorgânicos em que predominam os hidrocarbonetos e que apresentam contaminações variadas, entre essas os compostos de enxofre. Esses além de gerarem inconvenientes durante os processos de refino do petróleo, como corrosão nos equipamentos e envenenamento de catalisadores dos processos de craqueamento, também representam um grande problema para o meio ambiente e para a saúde da população, principalmente em relação à poluição atmosférica. Além das emissões de compostos de enxofre oriundas da própria refinaria, com destaque para os óxidos de enxofre e o sulfeto de hidrogênio, os compostos de enxofre, que não são retirados durante o refino e estão presentes nos derivados do petróleo, provocam a emissão de uma grande quantidade de poluentes na atmosfera durante o processo de queima dos combustíveis. Os efeitos dos CRE na atmosfera urbana ainda não são muito conhecidos, o que justifica um estudo mais profundo desses compostos, que além de causarem danos a saúde da população, podem influenciar na formação do ozônio troposferico
Oil is a complex mixture of organic and inorganic compounds predominantly hydrocarbons and contaminants that have varied between these sulfur compounds. These drawbacks besides generating processes during oil refining, such as corrosion of equipment and poisoning of catalytic cracking processes, also represent a major problem for the environment and health of the population, especially in relation to air pollution. Besides the emissions of sulfur originating from refinery itself, especially the oxides of sulfur and hydrogen sulfide, sulfur compounds, which are not removed during the refining and are present in the petroleum, cause the emission of a wide amount of pollutants in the atmosphere during the fuel combustion. The effects of the CRE in the urban atmosphere are not yet known, which justifies a deeper study of these compounds, which, and to harm the health of the population, may influence the formation of tropospheric ozone

O presente trabalho tem como objetivo caracterizar o aco inoxidavel ferritico UNS S44400 quanto a sua resistencia a corrosao em comparacao a dois acos inoxidaveis austeniticos UNS S30403 e S31603, utilizando ensaios de perda de massa e eletroquimicos, tanto em meio acido quanto em meio contendo cloreto. A utilizacao dos inoxidaveis ferriticos vem crescendo em detrimento da utilizacao dos austeniticos tanto no Brasil, quanto no mundo, principalmente devido ao cenario instavel do preco do Ni. Sendo assim, cada vez mais se torna necessaria a obtencao de argumentos tecnicos e cientificos que permitam comparar diferencas entre as duas familias, mostrando suas vantagens e desvantagens. Os metodos utilizados para a avaliacao da resistencia a corrosao generalizada foram perda de massa (apos imersao) e polarizacao potenciodinamica em 0,5M H2SO4. A resistencia a corrosao por pite foi estudada atraves de polarizacao potenciodinamica ciclica em 3,5%NaCl. No caso especifico dos meios contendo cloreto, alem de se estudar os materiais com acabamento de lixa #600, obtido em laboratorio, optou-se por um estudo mais detalhado em funcao do acabamento superficial obtido em usina. Os acabamentos examinados foram: (i) material recozido, decapado em Usina e lixado em laboratório (até lixa #600) - (LL); (ii) material recozido e decapado em Usina - (RD); e (iii) material recozido, decapado em Usina, tratado termicamente em laboratório e lixado (até lixa #600) - (SL). Em meio acido, os acos austeniticos nao apresentaram corrosao, enquanto o ferritico apresentou uma taxa de corrosao constante de 0,0146 mg.cm-2.min-1 (8,4x10-4 A.cm-2) para imersoes ate 24h. Pela aplicacao do metodo de extrapolacao do trecho linear de Tafel foi obtido valor similar de densidade de corrente, de 4,57x10-4 A.cm-2, ou seja possuem a mesma ordem de grandeza. Diferentemente dos resultados obtidos em meio acido, nos ensaios de resistencia a corrosao em meio contendo cloreto, o aco UNS S44400 apresentou potencial de pite superior (em 3,5%NaCl) ao UNS S30403 e valores muito proximos ao do aco UNS S31603, para todas as condicoes de acabamento superficial examinadas. Alem disso, foi observado um relevante efeito das condicoes de tratamento termico de solubilizacao dos materiais: o tratamento de solubilizacao realizado em laboratorio aumentou o potencial de pite. Os resultados de potencial de pite medio - Ep - obtidos antes do tratamento termico foram: 77mVAg/AgCl para o UNS S44400, 43mVAg/AgCl para o UNS S30403 e 345mVAg/AgCl para o UNS S31603, sendo que apos solubilizacao o Ep medio foi de: 336mVAg/AgCl; 294mVAg/AgCl e 374mVAg/AgCl, respectivamente. Por sua vez, ha diferenca de desempenho quando aplicados os diferentes acabamentos superficiais. Com relacao ao acabamento proveniente de Usina, ou seja, recozido e decapado (RD), foi o que resultou em melhor desempenho. Apesar da media resultante alta para o acabamento RD, a dispersao dos resultados tambem foi alta. Comparando-se os acos UNS S44400 e UNS S31603, recozidos e decapados o 444 teve um potencial de pite de (500 + 173)mVAg/AgCl, e o aco 316 apresentou (568 + 167)mVAg/AgCl. Nota-se, portanto, que quando a aplicacao exige resistencia a corrosao em meio contendo ion cloreto, o aco 444 pode substituir o 316L.
The main reason of this work is the characterization of the ferritic stainless steel UNS44400 regarding its corrosion resistance when compared to two austenitic steels, UNS 30403 and UNS31603, using loss of weight and electrochemical tests, in acid and chloride environments. The application of ferritic stainless steel is increasing, both in the Brazilian an international market, especially because of the nickel cost instability. So, more information is necessary regarding each kind of material, allowing the comparison of these two families showing their advantages and disadvantages in different applications. For that reason, the main purpose of this work is the characterization of the corrosion resistance of a ferritic stainless steel, UNS S44400, comparing it with two austenitic stainless steels, UNS S30403 and S31603. Weight loss and electrochemical tests were conducted in acid or chloride environments. The general corrosion resistance was analyzed through weight loss measurements and electrochemical polarization in 0,5M H2SO4. The pitting corrosion resistance was studied through polarization in 3,5%NaCl. For the tests in chloride environment, it was done a study comparing laboratory and mill finishing proceducts: annealed and pickled and wet sand in laboratory - (LL); annealed and pickled - (RD); annealed and pickled, heat treated in laboratory and wet sand in laboratory - (SL). In acid environment, the austenitic stainless steel did not show weight loss, while the ferritic had a constant corrosion rate of 0,0146 mg.cm-2.min-1 (8,4x10-4. A.cm-2) until 24 hours of immersion. This result was confirmed by the extrapolation of linear portion of the polarization curves (Tafel method), whose current density was 4,57x10-4 A.cm-2. In chloride environment, the UNS S44400 steel showed higher pitting potential in 3,5%NaCl compared to UNS S30403 and similar results for all finishes when compared with UNS S31603. Besides, it was observed that the heat treatment that was done in laboratory raised pitting potential. The pitting potential results were: before heat treatment, 77mVAg/AgCl for UNS S44400, 43mVECS, for UNS S30403 and 345mVAg/AgCl for UNS S31603; and after heat treatment they were: 336mVAg/AgCl; 294mVAg/AgC; and 374mVAg/AgCl, respectively. The annealed and pickled material that was tested directly from the Mill (RD) presented the highest pitting potential showing the importance of pickling process. Comparing the annealed and pickled UNS S44400 steel with UNS S31603, the mean pitting potential was (500 + 173)mVAg/AgCl and (568 + 167)mVAg/AgCl respectively, and considering the deviation of the tests, it was proved that it is possible to apply both UNS S44400 or UNS S31603 when a high pit corrosion resistance is required.

This paper deals with the late Viking age/early medieval grave field in Björned, Torsåker parish, Ångermanland County in northern Sweden. The grave field in Björned is rare because it has all the signs of being Christianized before the surroundings. This awakes questions such as if the people of Björned came from another place and brought the religion with them or if someone else did that for them. To find these answers I have analysed the stable isotope ratios [delta]13C, [delta]15N and [delta]34S in human bone collagen. Through these stable isotopes we can not only see what the people consumed but also where their food had its origin. It seems like several people from the grave field had a different origin then the rest.

During recent decades many lakes have become browner in the northern hemisphere and more specific in Sweden. This process is called brownification. Brownification of lakes makes it more difficult to clean water to drinking water and may have negative ecological effects on biota. Browning of lakes is generally thought to be caused by an increase of humic substances that consist of organic matter which colour the water brown or yellow. However, more recent studies show that dissolved iron can interact with humic substances in browning lakes. Since the concentrations of dissolved iron have increased during recent years and the mechanisms behind brownification and the contribution of iron to this process is not clearly understood it is important to investigate this subject. In this study 17 lakes in south of Sweden were sampled for iron concentration, dissolved organic carbon (DOC), absorbance (420nm) and pH. Further, data was added about atmospheric sulphur deposition and additional data from 17 lakes in the north part of Sweden. Iron had a stronger significant correlation towards absorbance than DOC had in the south of Sweden. A similar amount of dissolved iron seems to colour lakes differently based on their location in Sweden. This indicates that different mechanisms are involved in the interaction between iron and absorbance. However, pH had a stronger relationship with absorbance than either DOC or iron. Overall results suggested that iron do have a strong browning effect on Swedish fresh water lakes in the presence of DOC and that iron-increase driven processes may be due to a change of pH.

O presente estudo teve como objetivo avaliar a conversão dos açúcares do bagaço de cana em etanol, com foco na integração entre o pré-tratamento com H2SO4 diluído, sacarificação com celulases comerciais e fermentação com Scheffersomyces stipitis DSM- 3651, buscando-se uma configuração simplificada. Previamente aos ensaios de integração, o bagaço foi moído para a redução de sua heterogeneidade granulométrica. Após a moagem, o bagaço foi submetido a fracionamento, por fluxo de ar, separando frações de fibras e finos. Estas frações foram submetidas a analise composicional e observou-se que a fração de finos possui elevados teores de cinzas e extrativos, além de baixo teor de lignina em relação à fração de fibras, entretanto a estratégia de fracionamento do bagaço não foi seletiva. Os experimentos de definição da condição de pré-tratamento mais adequada para a avaliação entre integração entre sacarificação e fermentação foram conduzidos em reator Parr (2 gal) com 2Kg de mistura reacional, incluindo bagaço (10%), água e ácido. Três condições operacionais de pré-tratamento foram avaliadas: 140°C/1%H2SO4/20 min, 150°C/2% H2SO4/30 min e 160°C/3% H2SO4/40 min. Após o pré-tratamento, o slurry foi separado em sólido pré-tratado e hidrolisado hemicelulósico, por filtração. Em seguida o bagaço pré-tratado foi lavado exaustivamente com água destilada e submetido à hidrólise enzimática com celulases (10 FPU/g bagaço) por 72h. Paralelamente, o hidrolisado foi submetido à fermentação com S. stipitis (3 g/L) por 120h. As composições das frações geradas após o pré-tratamento (bagaço pré-tratado, hidrolisado e água de lavagem), quanto aos teores de açúcares e sólidos (solúveis e insolúveis) foram determinadas. As três condições de pré-tratamento levaram a remoção completa de hemicelulose do bagaço, e o aumento da severidade do pré-tratamento acarretou em aumento da eficiência de sacarificação dos sólidos pré-tratados, porém em menor recuperação de glicose após hidrólise enzimática. Por outro lado, o aumento da severidade do pré-tratamento prejudicou a recuperação de açúcares no hidrolisado hemicelulósico, elevando concentrações de ácido acético, furfural e HMF, resultando em inibição completa de fermentação daqueles obtidos nas condições de 150°C e 160°C. A conversão do sólido prétratado (lavado ou não-lavado) + hidrolisado (destoxificado ou não), e do slurry completo (destoxificado ou não) ambos obtidos após pré-tratamento à 140°C, foi avaliada em duas configurações, respectivamente: \"Fermentação do hidrolisado hemicelulósico (FHH), em separado da sacarificação do sólido pré-tratado e da fermentação do hidrolisado celulósico, separadas (SHF)\" e \"Sacarificação do sólido pré-tratado, em separado da co-fermentação dos hidrolisados celulósico e hemicelulósico, integradas (ISHCF)\". Na primeira, observouse que a destoxificação do hidrolisado com lacase (1U/mL) aumentou a produção de etanol, e possibilitou a redução do tempo de conversão em 48h. A sacarificação de sólidos não-lavados foi prejudicada pela presença de compostos solúveis e o condicionamento com lacase não influenciou a eficiência de sacarificação. A eficiência máxima de conversão em configuração de SHF+FHH foi de 28,4%, devido a não lavagem do sólido pré-tratado (13,7%) e destoxificação do HH (14,7%). Em ISHCF, observou-se que a eficiência de conversão de slurry integral destoxificado com lacase é mais alta (38,9%) do que em SHF+FHH, devido a não separação sólido-líquido e maior disponibilidade de açúcares.
This study aimed to evaluate the conversion of sugarcane bagasse into ethanol, focusing on integration between pretreatment with dilute H2SO4, saccharification with commercial cellulases and fermentation with Scheffersomyces stipitis DSM-3651, in a simplified design process. Prior to integration assays, the bagasse was milled to reduce its granulometric heterogeneity. After milling, the fractions of bagasse (fiber and pith) were separated by air flow. These fractions had their chemical composition determined and it was observed that pith fraction has higher content of ash, soluble extractives and low lignin content than fiber fraction; however the separation method was not selective. The experiments to define the most suitable pretreatment condition for evaluating the integration between saccharification and fermentation were conducted in a Parr reactor (2 gal) with 2 kg of reaction mixture, including bagasse (10%), water and acid. Three operational conditions of pretreatment were evaluated: 140°C/1% H2SO4/20min, 150°C/ 2% H2SO4/30 min and 160°C/3% H2SO4/40min. After pretreatment, the slurry was separated in pretreated solid and hemicellulosic hydrolyzate, by filtration. The pretreated solid was thoroughly washed with distilled water and submitted to enzymatic hydrolysis with cellulases (10 FPU / g residue) for 72h. In parallel, the hemicelullosic hydrolyzate was submitted to fermentation with S. stipitis (3 g / L) for 120h. The compositions of the fractions generated after pretreatment (pretreated bagasse, hemicellulosic hydrolyzate and washing water), regarding sugars and solids (soluble and insoluble) contents were determined. All pretreatment conditions led to complete removal of hemicellulose from the bagasse, and the increase of pretreatment severity improved the saccharification yield of pretreated solid, but, leaded to low recovery of glucose after enzymatic hydrolysis. On the other hand, the increase of pretreatement severity impaired the recovery of sugars in hemicellulosic hydrolysate besides increasing the concentrations of acetic acid, furfural and HMF, resulting in complete inhibition of fermentation of those obtained under the pretreatement conditions of 150°C and 160°C. The conversion of pretreated solid (washed and non-washed) + hemicellulosic hydrolyzate (with or without detoxification) and of the whole slurry, both obtained at 140°C was evaluated in two process designs, respectively: \"Fermentation of hemicellulosic hydrolyzate (FHH), separated from hydrolysis of pretreated solid and fermentation of cellulosic hydrolyzate, separately (SHF)\" and \"Integrated hydrolysis of pretreated solid separated from co-fermentation of cellulosic and hemicellulosic hydrolysates (ISHCF)\". In the first, it was observed that the detoxification of the hydrolyzate with laccase (1U / ml) improved the ethanol production, particularly for conversion time. The saccharification of non-washed solid was hampered by the presence of soluble compounds and its conditioning treatment with laccase did not influence the saccharification yield. The maximum conversion efficiency in SHF + FHH configuration was 28.4% due to not washing the pretreated solid (13.7%) and detoxification of hemicellulosic hydrolysate (14.7%). In the second process design, it was observed that the conversion efficiency of whole slurry, with laccase detoxification, was higher (38.9%) than in the separate configuration, with a lower conversion time.

The transport of elements by streams from headwater regions to the sea is influenced by landscape characteristics. This thesis focuses on the influence of landscape characteristics (e.g. proportion of wetland/forest coverage) on temporal and spatial variations of Fe, Mn, S and trace elements (As, Co, Pb) in streams located in northern Sweden, a boreal region characterized by coniferous forests and peat wetlands.

Water samples from a network of 15 streams revealed a different hydrogeochemistry in forested catchments compared to wetland catchments. The temporal variation was dominated by spring flood, when concentrations of Fe, Mn and trace elements increased in forested headwaters. However, in streams of wetland catchments concentrations decreased, but Pb concentrations were higher in comparison to other streams. Both Fe and Pb showed positive correlations with wetland area, while Co correlated with forest coverage. The anthropogenic contribution of As and Pb appear to be larger than the supply from natural sources.

During spring flood SO₄^2- decreased in most streams, although concentrations increased in streams of wetland catchments. Concentrations of SO₄^2- were higher in streams of forested catchments than in wetland dominated streams, the former being net exporters of S and the latter net accumulators. Isotope values of stream water SO₄^2- (δ³⁴S_SO4) were close to that of precipitation during spring flood, indicating that the major source of S is from deposition. The results show that, although emissions of anthropogenic S have been reduced, there is still a strong influence of past and current S deposition on runoff in this region.

In conclusion, wetlands are key areas for the hydrogeochemistry in this boreal landscape. The findings emphasize the importance of understanding stream water chemistry and element cycling from a landscape perspective. This may be important for predicting how boreal regions respond to environmental disturbances such as climate change.

INTRODUÇÃO: Metionina (Met), cisteína (Cys), homocisteína (Hcy) e taurina (Tau) são os quatro aminoácidos sulfurados (AAS), mas apenas a Met e Cys são incorporadas em proteínas. Os três principais produtos doS AAS, glutationa, (GSH), Hcy e Tau influenciam, principalmente, as respostas inflamatória e imune. A Tau e GSH diminuem a inflamação, enquanto que a Hcy apresenta efeito oposto. Os pacientes HIV+ apresentam baixos níveis de GSH e outros nutrientes antioxidantes, mostrando relação direta entre Cys (e GSH) com células CD4+. Não se conhece o mecanismo pelo qual as mudanças na ingestão dos AAS influenciam este fenômeno. Paralelamente, as relações entre Hcy, doenças inflamatórias e alterações in vitro no comportamento das células imunes levantou ressalvas sobre a suplementação de dietas com AAS. OBJETIVOS : investigar as vias dos AAS em pacientes HIV+ nas condições de jejum e pós-sobrecarga de Met frente à dieta habitual (OH) isolada ou acompanhada da suplementação de Cys (NAC) ou glutamina (Gln). MÉTODOS : 12 pacientes HIV+ (6 M e 6 F, de 25 a 36 anos), sob tratamento anti-retroviral pelo esquema tríplice, sem infecções secundárias e 20 controles saudáveis (10M e 10F, 23-28 anos) foram randomicamente distribuídos para suplementação com NAC (N-acetilcisteína, 1g/d) ou Gln (20 g/d) em estudo cruzado com 7 dias de dieta separados por uma semana de washout (Wo com DH). Amostras de sangue após jejum noturno de 10 a 12 horas foram coletadas antes (MO) e após (M1) cada regime dietético. A seguir, os indivíduos ingeriram metionina (100 mg/kg), com coletas de sangue após 2 e 4 horas para a determinação da área abaixo da curva (AAC). No MO, ambos os grupos foram avaliados quanto à antropometria (IMC, kg/m2), funções glomerular (uréia, creatinina) e hepatocelular (γ-GT), estados nutricional (albumina, cálcio, ácido fólico e vitamina 812) e antioxidante (ácido úrico, GSH, GSSG, Hcy), glicose, lipídios (triacilgliceróis e frações de colesterol) e AAS, serina (Ser), glicina (Gly), glutamato (Glu) e Gln. O grupo HIV também foi caracterizado pela carga viral e contagem de CD4+ e CD8+. As comparações estatísticas entre os grupos e entre as dietas mostraram homogeneidade para IMC, albumina, cálcio, vitamina 812, Hcy, HDL-colesterol, uréia e creatinina. Os pacientes apresentaram valores maiores de glicose, triacilgliceróis, γ-GT, LDL-colesterol e GSSG paralelalemente às menores concentrações de ácido úrico, GSH e todos os AAS, exceto Hcy. A sobrecarga de metionina igualou (pelos valores de delta) os grupos para Met, Hcy, Tau e Gln. As suplementações de NAC e Gln levaram o grupo HIV+ a concentrações maiores de GSH (NAC > Gln), atuando diferentemente em seus precursores: G/y (Gln > NAC) e Cys (NAC > Gln) e resultando em consumo similar de Ser e produção de Tau. Ambas as dietas reduziram GSSG/GSH (NAC > Gln) e apenas NAC aumentou (6 x) a Hcy. Esta última foi piorada pela sobrecarga de Mel. Assim, HIV+ resulta em deficiências múltiplas de vitaminas e aminoácidos levando a menores níveis de GSH e GSSG/GSH mais elevada. Os principais problemas de menor formação de Cys e menor incorporação de Cys em GSH foram resolvidos dando-se Met, NAC e Gln aos pacientes, ainda permanecendo a desvantagem do aumento da Hcy com Met ou suplementação de NAC.
BACKGROUNO: Methionine (Met), cysteine (Cys), homocysteine (Hcy), and, taurine (Tau) are the 4 sulfur-containing amino acids (SAA), but only Met and Cys are incorporated into proteins. The 3 major products of SAA, glutathione (GSH), Hcy and Tau influence, mainly, inflammatory and of immune responses. Tau and GSH ameliorate inflammation whereas Hcy has the opposite effect. HIV+ patients present low levelis of GSH and other antioxidants nutrients, showing a direct relationship between Cys (and GSH) with CD4+/ cells. How changes in SAA intake influence this phenomenon is unknown and the relationships among Hcy, inflammatory diseases, and in vitro alterations in immune cell behavior create a cautionary note about supplementation of diets with SAA. OBJECTIVE: To investigate SAA pathways in HIV+ patients on fast and Met-overload (Met-DL) states after taken diet habitual without (HD) or with supplements of Cys (NAC) or glutamine (Gln). METHOOS: 12 HIV+ (6M and 6F, 25-36 yrs old) patients under HAART without secondary infections and 20 healthy (10M and 10F, 23-28 yrs old) controls were randomly assigned to either NAC (N-acetylcysteine, 1g/d) or Gln (20g/d) diets, in a 7-day diet crossover design, separated by a 7-day washout (with HD) period. Blood samples were drawn after overnight fast before (MO) and after each dietary treatments (M1) for the resting measurements. Immediately after blood sampling ali subjects started the Met-DL by ingesting at once 100 mg Met/kg BW and having the blood draw after 2 and 4 hours for the area under the curve (AUC) determination. At MO both groups were assessed for anthropometry (BMI, kg/m2), glomerular (plasma urea and creatinina) and hepatocellular (plasma γGT activity) funetions, nutritional (albumin, calcium, folic acid and vitamin B12) and antioxidant (uric acid, GSH, GSSG, Hey) states, glucose, lipids (triglycerides and cholesterol fractions) and SAA, serine (Ser), glyeine (Gly), glutamate (Glu) and Gln. The HIV+ group was characterized also by viral load, CD4+ and CD8+ counts. The statistical comparisons between groups and among diets showed group homogeneity for 8MI, albumin, calcium, vitamin B12, Hey, HDL-cholesterol, urea and creatinine. The patients presented higher values of glucose, triglycerides, γ-GT, LDL-cholesterol, and GSSG along with lower concentrations of uric acid, GSH and all but Hcy amino acids. The Met-OL equalized (Δ values) the groups for Met, Hcy, Tau and Gln. NAC and Gln diets led the HIV+ group to a higher concentrations of GSH (NAC > Gln) by acting differently on its precursors: Gly (Gln > NAC) and Cys (NAC > Gln), resulting similar consumption of Ser and production of Tau. Both diets reduced GSSG/GSH (NAC > Gln) and only NAC increased (6 x) Hey. The later was worsened by Met-OL. Thus HIV+ results in multiple deficiencies of vitamins and amino acids leading to lower levels of GSH and higher GSSG/GSH ration. The main problems of lower formation of Cys and low ineorporation of Cys and Gly into GSH were greatly solved by giving Met, NAC and Gln to the patients, hence remaining the drawback of increasing Hcy with Met or NAC supplements.

Le fonctionnement d'une électrode positive de batterie au lithium repose sur la possibilité d'intercaler de façon réversible du lithium au sein du matériau qui la constitue. Une telle réaction conduit souvent à une perte de la cristallinité du matériau. Une démarche théorique permettant d'accéder à la structure du composé et à la modélisation de son comportement électrochimique est présentée dans ce mémoire. La première partie expose les fondements de la DFT (Density Functional Theory), et les mérites respectifs des méthodes FLAPW (Full potential Linearized Augmented Plane Waves) et PP/PW (Pseudopotential / Plane Waves). La seconde partie rappelle quelques concepts fondamentaux d'électrochimie comme le processus d'intercalation, les aspects thermodynamiques et les relations avec la structure électronique. Ensuite, une démarche basée sur l'optimisation de la géométrie de différentes hypothèses structurales est présentée. Cette démarche a été appliquée à l'étude d'un composé modèle LiMoS2, et a ensuite été étendue à des composés d'intérêt industriel tels que LixV2O5 (0 ≤ x ≤ 3). Ainsi, pour LiMoS2 et ω-Li3V2O5, les structures optimisées permettent de simuler des diagrammes de diffraction RX en très bon accord avec l'expérience. Ceci a donc permis, dans le cas de LixV2O5, une modélisation des premières décharges partant de α-V2O5 et de γ'-V2O5. Afin de mieux comprendre l'origine de la distorsion dans LiMoS2 et des variations de potentiel des courbes électrochimiques de LixV2O5, une analyse de la liaison chimique a également été réalisée. Ces résultats mettent clairement en évidence le fait qu'une approche couplant calculs de premiers principes et expériences constitue une aide efficace à la détermination de la structure de composés mal cristallisés. Une telle démarche contribue à la compréhension des transformations structurales induites par l'intercalation du lithium dans des oxydes de vanadium et peut ainsi être utile à la recherche de nouveaux matériaux de batteries.

In recent years carbon-based nanomaterials are growing rapidly in the field of science and technology, due to the tunable optical and physical properties such as electronic arrangement, photostability, flexibility and excellent biocompatibility. Considering, the emerging materials of carbon family such as graphene, graphene oxide (GO) and it derivative, carbon nanotube, fullerene, covalent organic framework (COF) carbon nitride (g-C3N4) and carbon dots (C-Dots) has been highlighted. Based on their structure and morphology, the carbon-based materials have received immense interest in the fields of catalysis, electronic, photonic devices, sensors, molecular recognition and biomedical applications. At the same time, it is also reported that the tunable size and shape of the materials (extended -conjugation, state of oxidation etc.) has shown significant attention in antibacterial activity, relative molar extinction coefficient and cellular internalization, molecular recognition etc. Hence this chapter has shortly provided the literature background of preparation and applications of carbon-based materials. Further information regarding synthesis of different type of carbon and sulfur-based luminescent materials and their functionalization are reported in the literature. Finally, a stack of literature reports towards the materials and biological applications such as biomolecular recognition, cellular imaging, sensing and stimuli responsive systems.

COS and CS₂ are sulfur compounds that are formed in natural waters. These compounds are also volatile, which leads them move into the atmosphere and serve as critical precursors to sulfate aerosols. Sulfate aerosols are known to counteract global warming by reflecting solar radiation. One major source of COS and CS₂ stems from the ocean. While previous studies have linked COS and CS₂ formation in these waters to the indirect photolysis of organic sulfur compounds, much of the chemistry behind how this occurs remains unclear. This study examined this chemistry by evaluating how different organic sulfur precursors, water quality constituents, and temperature affected COS and CS₂ formation in natural waters.

In the first part of this thesis (chapters 2 and 3), nine natural waters ranging in salinity were spiked with various organic sulfur precursors (e.g. cysteine, cystine, dimethylsulfide (DMS) and methionine) exposed to simulated sunlight over varying exposures. Other water quality conditions including the presence of O₂, CO and temperature were also varied. Results indicated that COS and CS₂ formation increased up to 11× and 4×, respectively, after 12 h of sunlight while diurnal cycling exhibited varied effects. COS and CS₂ formation were also strongly affected by the DOC concentration, organic sulfur precursor type, O₂ concentration, and temperature while salinity differences and CO addition did not play a significant role.

To then specifically evaluate the role of DOM in cleaner matrices, COS and CS₂ formation was examined in synthetic waters (see chapters 4 and 5). In this case, synthetic waters were spiked with different types of DOM isolates ranging from freshwater to ocean water along with either cysteine or DMS and exposed to simulated sunlight for up to 4 h. Surprisingly, CS₂ was not formed under any of the tested conditions, indicating that other water quality constituents, aside from DOM, were responsible for its formation. However, COS formation was observed. Interestingly, COS formation with cysteine was fairly similar for all DOM types, but increasing DOM concentration actually decreased formation. This is likely due to the dual role of DOM on simultaneously forming and quenching the reactive intermediates (RIs). Additional experiments with quenching agents to RIs (e.g. ³DOM* and ·OH) further indicated that ·OH was not involved in COS formation with cysteine but ³DOM* was involved. This result differed with DMS in that ·OH and ³DOM* were both found to be involved. In addition, treating DOM isolates with sodium borohydride (NaBH₄) to reduce ketone/aldehydes to their corresponding alcohols increased COS formation, which implied that the RIs formed by these functional groups in DOM were not involved. The alcohols formed by this process were not likely to act as quenching agents since they have been shown to low in reactivity. Since ketones are known to form high-energy-triplet-states of DOM while quinones are known to form low-energy-triplet-states of DOM, removing ketones from the system further supported the role of low-energy-triplet-states on COS formation. This was initially hypothesized by findings from the testes on DOM types. In the end there are several major research contributions from this thesis. First, cysteine and DMS have different mechanisms for forming COS. Second, adding O₂ decreased COS formation, but it did not stop it completely, which suggests that further research is required to evaluate the role of RI in the presence of O₂. Lastly, considering the low formation yields of COS and CS₂ formation from the organic sulfur precursors tested in this study, it is believed that some other organic sulfur precursors are missing which are likely to generate these compounds to higher levels and this needs to be investigated in future research.

碩士
國立臺灣大學
化學研究所
93
Thiathiophthene(TTP), a planar molecule with two fused heterocyclic five-membered rings and essentially a linear S-S-S bond, is a molecule of great interest due to the unusual bonding characters and the possible aromatic properties of the two five-memberd rings. In order to understand the remarkable bonding properties, the electron density distribution of one of the derivatives, i.e. 2,5-dimethyl-3,4-trimethylene-6a -thiathiophthene (C10H12S3), was investigated both by single crystal X-ray diffraction and by DFT calculations. The X-ray crystal structure of C10H12S3 was studied both at 295 K and at 100 K. The Space group is C2/m at 295 K, which is transformed to P21/n at 100 K. The mirror symmetry perpendicular to 2-fold axis disappears at low temperature. Such reduction of symmetry elements was also found in a previous study on the 2,5-dimethyl-6a-thiathiophthene. The bond lengths of two S-S bonds are crystallographically same [2.3341(8)Å] at 295K, but are significantly different [2.3274(5) and 2.3393(5) Å] at low temperature. The experimental electron density is produced according to multipole model. The theoretical electron density is calculated by DFT calculation, where the basis set of 6-31G** is used for all the atoms but an additional diffuse function is added for S atom. Results on the electron density distribution will be presented in terms of deformation density, Laplacian maps and the topological properties. Sulfur K-edge X-ray absorption spectroscopy (XAS) is also undertaken to further our knowledge on the electronic configuration of S atom.

A l’heure actuelle, les biocarburants renouvelables et qui ne nuit pas à l'environnement sont à l'étude intensive en raison de l'augmentation des problèmes de santé et de la diminution des combustibles fossiles. H2 est l'un des candidats les plus prometteurs en raison de ses caractéristiques uniques, telles que la densité d'énergie élevée et la génération faible ou inexistante de polluants. Une façon attrayante pour produire la H2 est par les bactéries photosynthétiques qui peuvent capter l'énergie lumineuse pour actionner la production H2 avec leur système de nitrogénase. L'objectif principal de cette étude était d'améliorer le rendement de H2 des bactéries photosynthétiques pourpres non sulfureuses utilisant une combinaison de génie métabolique et le plan des expériences. Une hypothèse est que le rendement en H2 pourrait être améliorée par la redirection de flux de cycle du Calvin-Benson-Bassham envers du système de nitrogénase qui catalyse la réduction des protons en H2. Ainsi, un PRK, phosphoribulose kinase, mutant « knock-out » de Rhodobacter capsulatus JP91 a été créé. L’analyse de la croissance sur des différentes sources de carbone a montré que ce mutant ne peut croître qu’avec l’acétate, sans toutefois produire d' H2. Un mutant spontané, YL1, a été récupéré qui a retenu l'cbbP (codant pour PRK) mutation d'origine, mais qui avait acquis la capacité de se développer sur le glucose et produire H2. Une étude de la production H2 sous différents niveaux d'éclairage a montré que le rendement d’YL1 était de 20-40% supérieure à la souche type sauvage JP91. Cependant, il n'y avait pas d'amélioration notable du taux de production de H2. Une étude cinétique a montré que la croissance et la production d'hydrogène sont fortement liées avec des électrons à partir du glucose principalement dirigés vers la production de H2 et la formation de la biomasse. Sous des intensités lumineuses faibles à intermédiaires, la production d'acides organiques est importante, ce qui suggère une nouvelle amélioration additionnel du rendement H2 pourrait être possible grâce à l'optimisation des processus. Dans une série d'expériences associées, un autre mutant spontané, YL2, qui a un phénotype similaire à YL1, a été testé pour la croissance dans un milieu contenant de l'ammonium. Les résultats ont montré que YL2 ne peut croître que avec de l'acétate comme source de carbone, encore une fois, sans produire de H2. Une incubation prolongée dans les milieux qui ne supportent pas la croissance de YL2 a permis l'isolement de deux mutants spontanés secondaires intéressants, YL3 et YL4. L'analyse par empreint du pied Western a montré que les deux souches ont, dans une gamme de concentrations d'ammonium, l'expression constitutive de la nitrogénase. Les génomes d’YL2, YL3 et YL4 ont été séquencés afin de trouver les mutations responsables de ce phénomène. Fait intéressant, les mutations de nifA1 et nifA2 ont été trouvés dans les deux YL3 et YL4. Il est probable qu'un changement conformationnel de NifA modifie l'interaction protéine-protéine entre NifA et PII protéines (telles que GlnB ou GlnK), lui permettant d'échapper à la régulation par l'ammonium, et donc d'être capable d'activer la transcription de la nitrogénase en présence d'ammonium. On ignore comment le nitrogénase synthétisé est capable de maintenir son activité parce qu’en théorie, il devrait également être soumis à une régulation post-traductionnelle par ammonium. Une autre preuve pourrait être obtenue par l'étude du transcriptome d’YL3 et YL4. Une première étude sur la production d’ H2 par YL3 et YL4 ont montré qu'ils sont capables d’une beaucoup plus grande production d'hydrogène que JP91 en milieu d'ammonium, qui ouvre la porte pour les études futures avec ces souches en utilisant des déchets contenant de l'ammonium en tant que substrats. Enfin, le reformage biologique de l'éthanol à H2 avec la bactérie photosynthétique, Rhodopseudomonas palustris CGA009 a été examiné. La production d'éthanol avec fermentation utilisant des ressources renouvelables microbiennes a été traitée comme une technique mature. Cependant, la plupart des études du reformage de l'éthanol à H2 se sont concentrés sur le reformage chimique à la vapeur, ce qui nécessite généralement une haute charge énergetique et résultats dans les émissions de gaz toxiques. Ainsi le reformage biologique de l'éthanol à H2 avec des bactéries photosynthétiques, qui peuvent capturer la lumière pour répondre aux besoins énergétiques de cette réaction, semble d’être plus prometteuse. Une étude précédente a démontré la production d'hydrogène à partir d'éthanol, toutefois, le rendement ou la durée de cette réaction n'a pas été examiné. Une analyse RSM (méthode de surface de réponse) a été réalisée dans laquelle les concentrations de trois facteurs principaux, l'intensité lumineuse, de l'éthanol et du glutamate ont été variés. Nos résultats ont montré que près de 2 moles de H2 peuvent être obtenus à partir d'une mole d'éthanol, 33% de ce qui est théoriquement possible.
Currently, renewable and environmentally friendly biofuels are under intensive study due to increasing health concerns and diminishing fossil fuels. H2 is one of the most promising candidates due to its unique characteristics, such as a high energy density and low to non-existent generation of pollutants. One attractive way to produce H2 is through photosynthetic bacteria which can capture light energy to drive H2 production with their nitrogenase system. The major aim of this study was to improve H2 yield of the purple non-sulfur photosynthetic bacteria using a combination of metabolic engineering and design of experiments. One hypothesis was that H2 yield could be improved by redirection of Calvin-Benson-Bassham cycle flux to the nitrogenase system which catalyzes the reduction of protons to H2. Thus, a PRK, phosphoribulose kinase, knock out mutant of Rhodobacter capsulatus JP91 was created. Analysis of growth with different carbon sources showed that this mutant could only grow in acetate medium without, however, producing any H2. A spontaneous mutant, YL1, was recovered which retained the original cbbP (encoding PRK) mutation, but which had gained the ability to grow on glucose and produce H2. A study of H2 production under different illumination levels showed that the yield of YL1 was 20-40% greater than the wild type JP91 strain. However, there was no appreciable improvement of the H2 production rate. A kinetic study showed that growth and hydrogen production are strongly linked with electrons from glucose being mostly directed to H2 production and biomass formation. Under low to intermediate light intensities, the production of organic acids was significant, suggesting further improvement of H2 yield is possible by process optimization. In a related series of experiments, another spontaneous mutant, YL2, which has a similar phenotype to YL1, was tested for growth in ammonium-containing media. The results showed that YL2 could only grow with acetate as carbon source, again, without producing any H2. Prolonged incubation in media not supporting growth of YL2 enabled the isolation of two interesting secondary spontaneous mutants, YL3 and YL4. Western blot analysis showed that both strains had constitutive nitrogenase expression under a range of ammonium concentrations. The genomes of YL2, YL3 and YL4 were sequenced in order to find the mutations responsible for this phenomenon. Interestingly, mutations of nifA1 and nifA2 were found in both YL3 and YL4. It is likely that a conformational change of NifA alters the protein-protein interaction between NifA and PII proteins (such as GlnB or GlnK), enabling it to escape regulation by ammonium and thus to be capable of activating nitrogenase transcription in the presence of ammonium. It is not clear how the synthesized nitrogenase is able to maintain its activity since in theory it should also be subject to posttranslational regulation by ammonium. Further evidence could be obtained by studying the transcriptome of YL3 and YL4. An initial study of H2 production by YL3 and YL4 showed that they are capable of much greater hydrogen production than JP91 in ammonium medium, which opens the door for future studies with these strains using ammonium-containing wastes as substrates. Finally, the biological reformation of ethanol to H2 with the photosynthetic bacterium, Rhodopseudomonas palustris CGA009 was examined. Ethanol production with microbial fermentation using renewable resources has been treated as a mature technique. However, most studies of the reformation of ethanol to H2 have focused on chemical steam reforming, which usually requires a high energy input and results in toxic gas emission. Thus biological reformation of ethanol to H2 with photosynthetic bacteria, which can capture light to meet the energy requirement of this reaction, seems to be more promising. A previous study had demonstrated hydrogen production from ethanol, however, the yield or the duration of this reaction were not examined. A RSM (response surface methodology) analysis was carried out in which three key factors, light intensity, ethanol and glutamate concentrations were varied. Our results showed that nearly 2 moles of H2 could be obtained from one mole of ethanol, 33% of what is theoretically possible.