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Controles deposicionais e diagenéticos das propriedades petrofísicas dos reservatórios aptianos/barremianos do Grupo Lagoa Feia no norte da Bacia de CamposHerlinger Júnior, Ronaldo January 2016 (has links)
Os reservatórios lacustres do Grupo Lagoa Feia, seção rift da Bacia de Campos, margem Leste brasileira, tem mantido há décadas uma expressiva produção a partir de campos localizados em águas rasas. A descoberta de grandes acumulações na seção rift e sag (pré-sal) da Bacia de Santos reativou a exploração por reservatórios análogos na Bacia de Campos e em outras bacias marginais. Um estudo petrográfico e petrofísico sistemático foi executado sobre os reservatórios rift da Formação Coqueiros e sag da Formação Macabu do Norte da Bacia de Campos, com objetivo de caracterizar os principais controles sobre a gênese e evolução daqueles reservatórios não-convencionais e seus sistemas porosos. As principais petrofácies de reservatório reconhecidas foram grainstones e rudstones bioclásticos, arenitos ooidais argilosos e dolomitos na Formação Coqueiros, e crostas coalescentes e não-coalescentes de calcita fascicular, rudstones e grainstones intraclásticos e dolomitos na Formação Macabu. A evolução dos reservatórios bioclásticos foi controlada pelo balanço entre dissolução ou neomorfismo dos bioclastos aragoníticos de bivalves, favorecendo a geração de porosidade móldica pouco conectada, ou a preservação da porosidade interpartícula bem conectada, controlando a permeabilidade dos reservatórios. Os arenitos de oóides de argilas magnesianas sofreram dissolução e substituição por dolomita e sílica, o que gerou sistemas porosos altamente heterogêneos, compostos por poros móldicos, intercristalinos, vugulares e microcristalinos. O crescimento de agregados cristalinos arborescentes nas crostas coalescentes de calcita gerou porosidade de crescimento do arcabouço primária, que foi reduzida principalmente por cimentação dolomítica, ou alargada por dissolução, o que ampliou sua permeabilidade. Crostas nãocoalescentes de calcita mostram forte interação com argilominerais magnesianos, que preenchem interstícios, e/ou estão intercalados com as crostas. Sua porosidade está relacionada com a dissolução das argilas, o que produziu baixa permeabilidade. Rochas intraclásticas comumente mostram matriz argilosa, ou estão compactadas e cimentadas. Onde exibem porosidade interpartícula primária ou dissolução da matriz, podem ter boas porosidades e permeabilidades. A dolomitização heterogênea de ambas as Formações em alguns casos destruiu a porosidade primária ou eodiagenética, ou em outros gerou altos valores de porosidade e permeabilidade nos dolomitos. Relações de substituição e de compactação indicam que muitos dos processos diagenéticos ocorreram durante a eodiagênese, controlados principalmente pela instabilidade da aragonita nos reservatórios bioclásticos da Formação Coqueiros, e dos argilominerais magnesianos na Formação Macabu. Este estudo representa a primeira caracterização petrográfica publicada dos reservatórios carbonáticos não-convencionais do sag, e salienta a importância crucial dos estudos petrográficos sistemáticos para a compreensão e previsão da qualidade de reservatórios complexos. / Lacustrine carbonate reservoirs from the Lagoa Feia Group, rift section of Campos Basin, offshore eastern Brazil, have sustained for decades a significant production from shallow water oil fields. The discovery of giant accumulations in the rift and sag (pre-salt) section of the adjacent Santos Basin has reactivated the exploration for equivalent reservoirs in the Campos Basin and in other marginal basins. A systematic petrographic and petrophysical study was performed on the rift Coqueiros Formation and the sag Macabu Formation carbonates from the Lagoa Feia Group in northern Campos Basin, in order to characterize the main controls on the origin and evolution of those unconventional reservoirs and their pore systems. The main types of reservoir petrofacies recognized were grainstones and bioclastic rudstones, magnesian clay ooidal arenites and dolostones from the Coqueiros Formation; coalescent and non-coalescent crusts of fascicular calcite, intraclastic rudstones and grainstones, and dolostones from the Macabu Formation. The evolution of bioclastic reservoirs was controlled by the balance between dissolution and neomorphism of the aragonitic bivalve bioclasts, favoring the generation of poorly-connected moldic porosity or the preservation of well-connected interparticle porosity, which controlled the permeability of the reservoirs. The magnesian clay (stevensite) ooidal arenites suffered dissolution and replacement by dolomite and silica, what generated highly heterogeneous pore systems, composed by moldic, intercrystalline, vugular and microcrystalline pores. The growth of crystal shrubs in coalescent calcite crusts generated growth-framework primary porosity, which was reduced mostly by dolomite cementation, or enlarged by dissolution, what enhanced their permeability. Non-coalescent calcite crusts usually show strong interaction with syngenetic magnesian clay minerals, which fill interstices and/or are interbedded with the crusts. Their porosity is related to dissolution of the clays, what generated poor permeability. Intraclastic rocks usually display clay matrix, or are compacted and cemented. Where they show interparticle primary porosity or matrix dissolution, they may have good porosities and permeabilities. The heterogeneous dolomitization of both formations, either destroyed the primary or early diagenetic porosity, or generated high porosity and permeability values in the dolostones. Relationships of replacement and compaction indicate that most of the diagenetic processes occurred during eodiagenesis, controlled mostly by the instability of the aragonite in the bioclastic Coqueiros reservoirs, and of the magnesian clay minerals in the Macabu Formation. This study represents the first published petrographic characterization of the unconventional sag carbonate reservoirs, and stresses the crucial importance of systematic petrographic studies for the understanding and prediction of the quality of complex reservoirs.
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Desenvolvimento de materiais bioinspirados contendo Sr2+ para modificação de superfícies de Ti / Design of bioinspired materials containing Sr2+ for modification of Ti surfacesCruz, Marcos Antônio Eufrasio 15 January 2018 (has links)
Ao longo dos últimos anos, Sr2+ tem sido aplicado em estudos in vitro e in vivo como um importante agente para o estímulo de osteogênese. Dessa forma, a criação de matrizes bioativas contendo Sr2+ é uma tendência na área de modificações de superfícies metálicas para aplicações em implantes de substituição óssea. Nesta dissertação, desenvolvemos sistemas bioinspirados que possam atuar como carreadores de Sr2+ em biomateriais. Na primeira parte, superfícies de Ti foram modificadas com filmes híbridos contendo SrCO3 e ou CaCO3. A formação dos filmes híbridos foi mediada pela deposição de filmes Langmuir-Blodgett sobre superfícies de Ti. Essas matrizes altamente organizadas atuaram como molde para a deposição de filmes híbridos contínuos e homogêneos sobre as superfícies. A resposta biológica desses materiais foi avaliada por cultura de osteoblastos in vitro, indicando que os materiais não são tóxicos e, em especial, que a associação entre SrCO3 e CaCO3 dá origem a recobrimentos com composição e propriedades superficiais otimizadas que induzem melhores respostas osteogênicas. Na segunda parte, foi sintetizado um novo complexo entre morina e Sr2+. A estrutura desse complexo foi inspirada no fármaco ranelato de estrôncio, um dos compostos mais utilizados para o tratamento da osteoporose. Dessa forma, aliamos a propriedade antioxidante da morina, um flavonóide natural, e a atividade osteogênica do Sr2+ para desenvolver um novo composto bioativo. A estrutura do complexo morina-Sr2+ foi caracterizada por diferentes técnicas espectroscópicas, onde determinamos que a complexação ocorre com a estequiometria 1:1. Visando o desenvolvimento de recobrimentos bioativos para superfícies metálicas, estudamos também a complexação entre morina e Sr2+ em monocamadas de Langmuir. Através da caracterização físico-química das monocamadas contendo morina na presença de Sr2+, observamos que é possível formar multicamadas auto-organizadas contendo o complexo morina-Sr2+ sobre superfícies sólidas. Essas matrizes mostram-se promissoras para uso em modificações de superfícies com propriedades osteogênicas. Por fim, o último sistema apresentado nessa dissertação é a criação de matrizes auto-organizadas de colágeno tipo I, mimetizando a organização hierárquica dessa proteína no tecido ósseo. Para isso, a auto-organização das fibrilas de colágeno sobre superfícies sólidas foi mediada por um processo onde o substrato é lentamente emerso de uma solução contendo moléculas de colágeno. Essa emersão faz com que forças competitivas (fricção e tensão superficial) atuem na interface sólido-líquido-ar e promovam o alinhamento das fibrilas de colágeno auto-organizadas no menisco da solução/substrato. A estrutura dos filmes finos assim formados foi caracterizada e mostrou-se ser dependente da concentração, pH e força iônica da solução de colágeno. Filmes de colágeno altamente orientados formados por essa metodologia poderão ser utilizados como sistemas carregadores de Sr2+ através da biomineralização de hidroxiapatita. Por fim, nessa dissertação foram apresentados três sistemas distintos com um ponto comum: a atuação como matrizes carreadoras de Sr2+. Por meio da densa caracterização da composição e das propriedades superficiais, mostramos que esses sistemas são promissores para o uso como recobrimentos bioativos sobre superfícies de Ti / In the past few years, Sr2+ has been described to play a fundamental role on the bone osteogenesis, as demonstrated by in vitro and in vivo studies. Therefore, the design of bioactive coatings containing Sr2+ is an interesting approach to modify metallic implants for bone regeneration. Herein, we described the development of bio-inspired systems to act as carriers of Sr2+ in biomaterials. In the first section, Ti surfaces were modified by hybrid films containing SrCO3 and or CaCO3. The formation of hybrid films was mediated by the deposition of Langmuir-Blodgett films on the Ti surfaces. Those matrices act as a template for the organized nucleation and growth of biominerals. By this methodology, continuous and homogeneous thin films were formed on the Ti surfaces. The biological response was accessed by in vitro osteoblasts culture. The hybrid films were nontoxic to the osteoblasts and we observed that the association of SrCO3 and CaCO3 resulted in a coating displaying a synergic composition and surface properties that induced better metabolic responses on the cultured osteoblasts. In the second section, we described the synthesis of a new Sr2+-morin complex. The structure of the complex was inspired by the strontium ranelate, one of the most used drugs for osteoporosis treatment. This way, we aimed to ally the antioxidant properties of morin, a natural flavonoid compound, and the osteogenic behavior of Sr2+ to design a new bioactive compound. The chemical structure of the complex was determined by spectroscopic techniques and we observed that the complexation happens at the stoichiometry 1:1. To design bioactive coatings on Ti surfaces, we also performed the complexation between the strontium and morin directly on Langmuir monolayers. By physicochemical characterization, we identified that multilayers containing the Sr2+-morin complex can be built on solid supports. These results show that Sr2+-morin can be a promising approach to design biofunctional coatings on metallic surfaces. In the last section, we described the creation of hierarchical collagen thin films, mimetizing the structure found on bone tissue. To this, solid supports were pulled out from collagen solution at a controlled rate. In this approach, the self-templating is mediated by competing forces (i.e. surface tension and friction) that act in the meniscus placed between the solution and the support. This process allows the deposition of self-aligned collagen fibers on surfaces. The film\'s structure was characterized and is dependent on pH, pulling rate, ionic and collagen concentration of the solution. In the future, these films will be applied to create mineralized functional coatings containing Sr2+. In conclusion, the materials developed herein has an important point in common: they are different matrices to carry Sr2+ ions. By the composition and surface characterization performed herein, we believe that these materials can be applied in the design of biofunctional coatings for metallic implant surfaces
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Estabilidade de silicatos e carbonatos nas condições termodinâmicas do manto terrestre / Stability of silicates and carbonates in the thermodynamic conditions of the Earths mantleSantos, Samuel Silva dos 28 September 2018 (has links)
Observações diretas das propriedades do interior da Terra são muito restritas. A maior parte das informações advém de estudos indiretos ligados à geofísica, os quais necessitam ser relacionados a estudos de materiais em laboratório para serem corretamente interpretados. Experimentos de laboratório, no entanto, precisam ser realizados em condições extremas de pressão e temperatura, o que constitui uma tarefa muito difícil de ser alcançada. Nesse contexto, estudos teóricos são fundamentais no suporte à elaboração de modelos sobre a estrutura e a composição interna da Terra. O objetivo de nosso trabalho é utilizar métodos de primeiros princípios para ajudar a elucidar o comportamento dos silicatos (MgSiO3 e CaSiO3) e dos carbonatos (MgCO3 e CaCO3) de magnésio e cálcio nas condições termodinâmicas extremas do manto. O estudo da estabilidade energética desses silicatos e carbonatos, bem como o de outros minerais que compõem o manto, fornece novas evidências sobre a melhor forma de o cálcio ser incorporado nessa região profunda, além de determinar qual carbonato é o principal hospedeiro de carbono nas profundezas da Terra. As propriedades dos sistemas foram obtidas através da teoria do funcional da densidade, considerando diversas aproximações para a energia de troca e correlação, e o método PAW (Projector Augmented Wave). As propriedades termodinâmicas foram investigadas usando a aproximação quase harmônica e a teoria de perturbação do funcional da densidade. As simulações computacionais foram efetuadas utilizando o código Quantum ESPRESSO. Observamos que a decomposição dos silicatos em seus respectivos óxidos alcalinos terrosos, MgO e CaO, mais SiO2 não é favorável. Além disso, a coexistência dos silicatos MgSiO3 e CaSiO 3 é mais estável do que a formação de ligas do tipo Mg1xCaxSiO3. Dessa forma, concluímos que o cálcio, no manto, existe numa fase independente, fazendo parte de um silicato (CaSiO3). Nossos resultados mostraram que a decomposição dos carbonatos em seus respectivos óxidos alcalinos terrosos, MgO e CaO, mais CO2 também é desfavorável, indicando que deve existir uma baixa concentração de CO 2 livre no manto, e que o carbonato de magnésio é mais estável do que o carbonato de cálcio. Portanto, nossa investigação propõe que o MgCO3 é o principal hospedeiro de carbono, na forma oxidada, no manto. Por fim, notamos que as propriedades estruturais e termodinâmicas são melhores descritas quando a energia de van der Walls é adicionada à energia de troca e correlação, indicando que esses cálculos mais precisos constituem um passo importante para melhorar a construção de modelos teóricos sobre as propriedades e a composição do manto. / Direct observations of the Earths interior properties are very restricted. Most of the information comes from indirect studies related to geophysics, which need to be related to materials studies in the laboratory to be correctly interpreted. Laboratory experiments, however, need to be performed under extreme pressure and temperature conditions, which is a very difficult task to achieve. In this context, theoretical studies are fundamental in supporting the elaboration of models on the structure and internal composition of the Earth. The purpose of our work is to use first principles methods to help elucidate the behavior of magnesium and calcium silicates (MgSiO3 and CaSiO3) and carbonates (MgCO3 and CaCO3) under the extreme thermodynamic conditions of the lower mantle. The study of the energy stability of these carbonates and silicates, as well as of other mantle minerals, provides new evidence on how calcium can best be incorporated into the mantle and to determine which carbonate is the main carbon host in the Earths deep mantle. The properties of the systems were obtained within the density functional theory, using several approximations for the exchange and correlation energy, and the PAW (Projector Augmented Wave) method. The thermodynamic properties were investigated using the quasi-harmonic approximation and the density functional perturbation theory. The computational simulations were performed using the Quantum ESPRESSO code. We observe that the decomposition of the silicates in their respective alkali earth oxides, MgO and CaO, plus SiO2 is not favorable. In addition, the coexistence of silicates MgSiO3 and CaSiO3 is more stable than the formation of alloys like Mg1xCaxSiO3. Thus, we conclude that the calcium in the lower mantle exists in an independent phase, being part of a silicate (CaSiO3). Our results also indicate that the decomposition of the carbonates into their respective alkali earth oxides, MgO and CaO plus CO2 is unfavorable, showing that there should be a low concentration of free CO2 in the mantle and that the magnesium carbonate is more stable than calcium carbonate. Therefore, our investigation proposes that MgCO3 is the main oxidized carbon host in the lower mantle. Finally, we note that the structural and thermodynamic properties are best described when the van der Walls interactions are taken into account in the exchange and correlation energy, indicating that these more accurate calculations constitute an important step to improve the construction of theoretical models on the properties and composition of the mantle.
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Caracterização de silicatos e carbonatos de cálcio aplicados à dosimetria de doses altas / Characterization of silicates and calcium carbonates applied to high-dose dosimetryVila, Gustavo Barretto 12 March 2013 (has links)
A forma isomórfica predominante nos biominerais (casca de ostra, coral, madrepérola e concha) estudados foi a aragonita. Contudo, o surgimento da fase calcita deu-se à temperatura de 500°C a uma taxa de aquecimento de 10°C/s para todas as amostras; e para a amostra de coral, à temperatura de 400°C, independente da taxa de aquecimento. O elemento mais abundante nas amostras de biominerais foi o Ca na forma de CaO e para os silicatos (tremolita, diopsídio e rodonita), o Si na forma de SiO. O elemento traço mais presente nas amostras de biominerais foi o Fe. A análise de ressonância paramagnética eletrônica mostrou as linhas de Mn2+ nas amostras de coral e madrepérola, antes da irradiação. Para amostras irradiadas, os defeitos encontrados foram os radicais CO2-, CO33-, CO3-, SO2-, SO3-, e num intervalo de g entre 2,0010 e 2,0062. Na análise por absorção óptica dos biominerais foram encontradas transições devido à presença de Mn nas amostras. Foi observado um pico termoluminescente (TL) em aproximadamente 140°C para os biominerais e em 180°C para os silicatos, cuja intensidade depende diretamente da dose. Para amostras expostas a diferentes tipos de radiações, o pico TL ocorre em temperaturas mais baixas. Para as curvas dose-resposta obtidas para esses materiais, foi possível determinar um intervalo de linearidade para o qual a sua aplicação em dosimetria de doses altas se torna possível. Levando-se em consideração o tipo de radiação, dentre os biominerais e os silicatos, obteve-se a menor dose detectável (40mGy), para a radiação gama em amostra de casca de ostra utilizando-se a técnica de medição de luminescência opticamente estimulada (LOE). Para radiação beta, as amostras de tremolita e diopsídio obtiveram a menor dose detectável (60mGy). No geral, obteve-se uma boa reprodutibilidade para as amostras, utilizando-se as técnicas TL, LOE e emissão exoeletrônica termicamente estimulada (TSEE) para as radiações alfa, beta e gama. Portanto, pode-se concluir que as amostras caracterizadas neste trabalho podem ser utilizadas como detectores/dosímetros de doses altas. / The predominant isomorphous form in the biominerals studied in this work (oyster shell, coral, mother of pearl and shell) was aragonite. The appearence of the calcite phase occurred at 500°C at a heating rate of 10°C/s for all samples except for the coral sample, which was 400°C, independent of the heating rate. The most abundant element in the biominerals samples was Ca in the CaO form, and in the silicates (tremolite, diopside and rhodonite) Si in the SiO form. The most common trace element observed in the biominerals samples was Fe. The analyses of electron paramagnetic resonance showed lines of Mn2+ in the coral and mother-of-pearl samples before irradiation. In the case of the irradiated samples, the defects found were CO2-, CO33-, CO3- and SO2-, in the g range between 2.0010 and 2.0062. In the analyses by optical absorption of biominerals, transitions due to the presence of Mn in the samples were found. A thermoluminescent (TL) peak at approximately 140°C was found for the biominerals and at 180°C for silicates, which intensity depends directly on the dose. For samples exposed to different types of radiation, the TL peak occurred at lower temperatures. From the dose-response curves obtained for these materials, it was possible to determine a linear range for which their application in high dose dosimetry becomes possible. Taking into account the radiation type, among biominerals and silicates, the lowest detectable dose (40mGy) to gamma radiation was achieved for oyster shell samples using the measuring technique of optically stimulated luminescence (OSL). Using beta radiation, for diopside and tremolite samples the lowest detectable dose of 60mGy was obtained. For all samples, using the TL, OSL and thermally stimulated exoelectron emission (TSEE) techniques in alpha, beta and gamma radiation beans a good response reproducibility was obtained. Therefore, the samples characterized in this work are suitable to be used as high dose detectors/dosimeters.
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Quantitative paleoenvironmental analysis of carbonate platform sediments on the Marion Plateau (NE Australia, ODP Leg 194)Sheps, Kathryn 01 November 2004 (has links)
The Marion Plateau is a carbonate-platform complex on the passive northeast Australian margin. During ODP Leg 194, a series of eight sites, on two transects, were drilled through Oligocene to Holocene mixed carbonate and siliciclastic sediments that record the depositional history of the Marion Plateau. Major sediment constituents, including benthic foraminifers, were counted from thin sections made from samples taken from three drilling sites: bryozoan-dominated northern highstand platform site 1193 and northern lowstand ramp site 1194, and coralline red algae-dominated southern platform site 1196.
Quantitative multivariate analysis of benthic foraminiferal assemblages revealed three paleoenvironmentally relevant groups of taxa. The first group, dominated by Amphistegina and Lepidocyclina, was found at all three sites and is interpreted to be representative of euphotic open-shelf deposition in less than 50 m water depth. The second group was dominated by Cycloclypeus, Operculina and planktonic foraminifers. This group was found at all three sites, but was more common from sites on the northern platform and is interpreted to represent deposition in deep, oligophotic water, in greater than 50 m water depth. The third group, consisting of soritids, alveolinids, Austrotrillina and Flosculinella, was found only in sediments from the southern platform and is interpreted to represent deposition in a restricted, shallow-marine environment, in less than 20 m water depth, consistent with a sea-grass meadow. These three groups of taxa record changing paleoenvironments on the Marion Plateau, and reveal the depositional histories of the Marion Plateau's carbonate platforms.
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Structure et hétérogénéité d'une plate-forme récifale Miocène (Majorque) ; implication pour les intrusions d'eau salée en zone côtièreMaria-Sube, Yves 13 December 2007 (has links) (PDF)
Les intrusions d'eau salée en zone côtière constituent une menace pour la population. Celles-ci sont particulièrement dommageables en contexte carbonaté. Nous avons étudié le récif corallien Miocène du sud-est de Majorque afin de comprendre la relation entre structure géologique et intrusion. Pour cela nous avons utilisé des méthodes multi-scalaires et multi-disciplinaires. Les mesures dans 25 forages sur l'ensemble de la plateforme corallienne ont permis de préciser la structure stratigraphique et certains éléments de la tectonique régionale. Le récif prograde dans la direction NE-SO, en partant de l'Aquitanien pour aboutir au Messinien. La Crise de Salinité Messinienne entraîne une disparition des coraux méditerranéens et se traduit par un Complexe Carbonaté Terminal qui s'étend sur une grande partie des coraux autrefois vivants de Majorque. A l'échelle du site expérimental, l'étude de la composition minérale, de la texture et de la diagenèse ont permis de caractériser l'hétérogénéité de la séquence carbonatée. Des couches de minéralisation accompagnées de dolomitisation et de faible porosité correspondent à différents niveaux eustatiques post-dépositionnels. Les causes de l'existence et de l'orientation des fractures sont étudiées. La relation de perméabilité à porosité est précisée. La structure de porosité est étudiée par comparaison entre la porosité primaire et la porosité secondaire. Cette étude contribue à la connaissance du site le mieux documenté au monde pour l'évolution des réservoirs carbonatés récifaux, avec applications pour les intrusions d'eau salée et l'extraction des hydrocarbures.
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Stabilité et réactivité des carbonates à très hautes pression et température. Implications pour le stockage du carbone dans le manteau terrestreBiellmann, Claudine 05 November 1993 (has links) (PDF)
La teneur en C02 de l'atmosphère actuelle et son évolution au cours des temps géologiques dépend du cycle du carbone. Une bonne compréhension de ce cycle bio-gébchimique complexe passe par la connaissance du contenu des différents réservoirs (externes ou internes) impliqués et des flux entre eux. En particulier, pour rendre compte des concentrations universelles de carbone sur la terre, il faut considérer qu'il existe du carbone en quantité importante dans le manteau terrestre. Dans celui-ci, le carbone peut se trouver piégé sous différentes formes, et entre autres, dans les carbonates. Afin de tester cette hypothèse, nous avons étudié la stabilité et le comportement physico-chimique des carbonates dans les conditions de pression et de température du manteau supérieur et inférieur. Ces conditions, de 1 à 50 GPa, pour des températures comprises entre 1000 et 3000 K ont été obtenues à l'aide de cellules à enclumes de diamant. La spectroscopie Raman à haute pression ou haute température a permis de suivre in situ les modifications structurales de l'aragonite, de la calcite, de la dolomite et de la magnésite. Des synthèses expérimentales en cellule à enclumes de diamant chauffée par laser ont été réalisées. L'observation par microscopie électronique analytique en transmission des produits trempés a permis de montrer que les carbonates sont des phases stables dans les conditions du manteau. Le carbonate stable en présence de silicates du manteau est un carbonate magnésien ; il existerait dans le manteau en tant que phase individuelle de structure très probablement analogue à celle de la magnésite stable à basse pression / basse température, ou dans une solution solide de type MgO-MgC03' En conclusion, on peut estimer que les carbonates, et en particulier la magnésite, sont de potentielles phases hôtes du carbone dans la quasi totalité du manteau terrestre.
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Analyse de la composition élémentaire de Pecten maximus par HR-ICP-MS Element 2 : développements méthodologiques et interprétations écologiques.Richard, Manuel 23 September 2009 (has links) (PDF)
La composition élémentaire des coquilles de bivalves pourrait, selon la communauté scientifique internationale, être modulée par les variations spatiales ou temporelles du milieu ambiant tel la température, la salinité, la productivité primaire.... Toutefois, un ensemble de travaux ont mis en évidence que la présence des éléments mineurs et en traces dans les coquilles sont souvent spécifiques aux espèces considérées ou dépendent de plusieurs paramètres environnementaux. En conséquence, des recherches supplémentaires s'avèrent nécessaires afin de mieux comprendre la modalité d'incorporation de ces potentiels traceurs dans la matrice carbonatée. L'objectif de ce travail de thèse était de développer des méthodologies analytiques sur un spectromètre de masse haute-résolution couplée à une source plasma (HR-ICP-MS Element 2 de Finigan) pour déterminer quantitativement un nombre important d'éléments en traces dans des matrices de carbonate de calcium (CaCO3). Deux méthodes (le couplage LA-ICP-MS et l'analyse en mode liquide) ont été développées afin de placer sur une échelle calendaire (± 3 jours) les variations ontogéniques des teneurs élémentaires dans les valves de P. maximus. Les résultats d'analyses obtenus sur une même valve gauche par les deux méthodes, montrent que les profils élémentaires demeurent reproductibles quels que soient les concentrations rencontrées et le transect choisi sur la valve. Les teneurs élémentaires dans les valves de P. maximus mesurées sur l'ICP-MS Element 2 sont en accord avec les valeurs obtenues précédemment sur la même population et la même année de croissance lorsque l'on se réfère aux résultats pionniers acquis par le laboratoire de Pau (LA-ICP-MS quadripolaire) L'analyse en mode liquide de trois transects de croissance d'une même valve démontre que la distribution élémentaire est homogène dans la matrice carbonatée de la coquille Saint-Jacques. Les résultats d'analyses de deux éléments en traces (Mo et Li) dans les valves de P. maximus ont été détaillés. Les variations de la concentration valvaire en molybdène sont reproductibles entre plusieurs individus issus d'une même population pendant différentes années et lorsque différents écosystèmes côtiers bretons sont étudiés (Rade de Brest, baie de Saint-Brieuc et Belle-Ile en mer). Chaque profil varie à un niveau voisin des limites de détection de l'appareil de mesure, mais est ponctué par un voire deux enrichissements épisodiques printaniers (mai). Parmi toutes les hypothèses discutées pour expliquer ces événements (pics en Mo), l'ingestion de cellules phytoplanctoniques ayant utilisées les nitrates comme source d'azote apparait la plus vraisemblable (ces cellules présenteraient une concentration forte en Mo suite au rôle de Mo lors de l'activité enzymatique de la nitrate réductase) La faible variabilité inter-individuelle des concentrations valvaires en Li d'une même population suggère l'influence d'un paramètre environnemental ou physiologique pour expliquer l'incorporation du lithium au sein des valves. Toutefois, les variations ontogéniques de la teneur coquillière en lithium chez P. maximus diffèrent selon l'année étudiée. Certaines populations de P. maximus présentent de brusques augmentations transitoires de la teneur en Li pendant leur période de croissance. Notre étude n'a pas pu mettre en évidence un lien généralisable entre ces pics en Li et un paramètre environnemental. Cependant, ces enrichissements en Li semblent apparaître quelques jours après des floraisons phytoplanctoniques de diatomées. En outre, nous constatons que le bruit de fond de la teneur en Li serait majoritairement lié à la vitesse de croissance de l'animal.
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Designing star-like block-copolymers as compartmentalized nanostructures for drug delivery applicationsEngstrand, Johanna January 2010 (has links)
<p>This thesis describes syntheses and characterization of star-like amphiphilic block copolymers consisting of poly(ethylene glycol) (PEG) as the hydrophilic block,polycarbonate as the hydrophobic block and an amine-containing dendrimer as the core molecule. The macromolecules were synthesized by either a convergent or adivergent approach that includes tandem click reactions and ring opening polymerizations (ROP) of methyl trimethyl carbonates (MTC) with differentfunctionalities. The ROP of MTC monomers was performed using organocatalysts that allow mild reaction condition and reasonable molecular weight distribution(PDI~1.3). These synthetic approaches provide the resultant polymers with three different conformations, which are; mikto-arm type, comb-block with short PEGbrushes, and linear block with long PEG chain. The star-like polymers that were synthesized were all water soluble and most of them formed nano aggregates inwater. Different morphologies were observed in AFM study depending on the polymer conformation. Interestingly, some of them had indications pointing towards alower critical solution temperature.</p>
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Early and Late Diagenetic Processes of Mississippian Carbonates, Northern U.S. RockiesKatz, David Allen 17 September 2008 (has links)
Integrated sequence stratigraphy and geochemistry has significantly improved our knowledge of the formation and distribution of early and late diagenetic products in North American Mississippian carbonates. Deposition of the Madison Limestone occurred in concert with a major perturbation to the global C-pool, the timing of which was constrained by comparing secular variations in the delta13C values from the Madison Limestone with limited biostratigraphy. These early constraints were then improved by peak matching of 87Sr/86Sr values from this study with European brachiopod 87Sr/86Sr. The secular variations in the delta13C values were then applied as a chronostratigraphic tool to outcrops and subsurface core. As a result, our sequence stratigraphic interpretations and knowledge regarding lateral facies variability in carbonate rocks is significantly improved. Geographic variability in the magnitude of the delta13C values is also documented along the dip-transects which suggests that marine waters experienced increasing restriction in a landward direction. These results show how local changes to the C-pool are controlled by the morphology of the depositional system which can significantly affect the original signal of the global carbon pool. The geographic variability in the delta13C and delta18O values from reservoir quality dolomites along the mid-to-upper Madison ramp suggest they also precipitated from a restricted water mass with increased salinity, temperature and alkalinity which in turn, were responsible for the distribution of massive quantities of strataform dolomite deposited during the continental transgression at the beginning of the Mississippian. Trace element and 87Sr/86Sr values from strataform dolomite suggest initial formation from Mississippian seawater and slight resetting during shallow burial diagenesis. Petrography indicates that the formation of this dolomite ceased in the shallow burial environment, between the Mississippian and Permian. These dolomites are cross-cut by comparatively small volumes of geothermal-hydrothermal dolomite associated with Laramide-age breccias and fractures. Tectonic-hydrothermal activity associated with the Laramide Orogeny was responsible for late stage calcite cemented fractures and breccias which cross-cut all carbonate rocks discussed in this thesis. Radiogenic 87Sr/86Sr, depleted delta18O and enriched delta13C values and the hottest fluid inclusions measured in this study suggest the late stage calcite formed in the hydrothermal environment and under the most open-system and water-dominated conditions. Tectonic-diagenesis is ultimately responsible for establishing vertical barriers in the otherwise porous and permeable strataform dolomites.
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