Dissertationen zum Thema „Sulfate formation“
Um die anderen Arten von Veröffentlichungen zu diesem Thema anzuzeigen, folgen Sie diesem Link: Sulfate formation.
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Machen Sie sich mit Top-50 Dissertationen für die Forschung zum Thema "Sulfate formation" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Sehen Sie die Dissertationen für verschiedene Spezialgebieten durch und erstellen Sie Ihre Bibliographie auf korrekte Weise.
1
Sachin, Kunagalli Natarajan. „An integrated approach to predict ettringite formation in sulfate soils and identifying sulfate damage along SH 130“. Texas A&M University, 2004. http://hdl.handle.net/1969.1/1358.
Annotation:
Expansive soils are treated with anhydrous or hydrated lime. The use of calcium-based stabilizers such as calcium oxide (lime) in sulfate-bearing clay soils has historically led to distress due to the formation of an expansive mineral called ettringite and possibly another such mineral, thaumasite. Predicting the precipitation of these minerals is a complex problem related not only to soil composition but also construction methods, availability of water, ion migration, and whether the expansive mineral growth can be accommodated by the void structure in the surrounding soil. In trying to control the damage associated with such occurrences, engineers have attempted to determine a threshold value of soluble sulfates, a quantity that is relatively easy and quick to measure, at which significant ettringite growth and, therefore, structural distress occurs. Unfortunately, experience alone and rules-of-thumb based on experience are not sufficient to deal with this complex issue. This thesis describes how thermodynamic geochemical models of lime-treated soil can be used as a first step toward establishing problematic threshold levels of soluble sulfates for a specific soil. A foundation for the model development is presented, and two different soils are compared to illustrate their very different sensitivities to ettringite growth upon the addition of hydrated lime.
Various soil series along the route of SH 130 between Austin and San Antonio have been identified to contain soluble sulfate that may pose a problem for soil stabilization using lime and cement. Since the model predicts ettringite growth based upon site-specific properties, this thesis also shows how the model can be used to assess the potential amelioration effects of soluble silica.
Research was conducted at the Texas Transportation Institute to develop a methodology for identifying areas which are susceptible for ettringite formation. The proposed methodology uses a magnetometer to quickly screen large areas for high sulfate. Application of GIS to identify ettringite formation using soils, topographical, and geological maps is also illustrated in this thesis.
2
Mikkanen, Pirita. „Fly ash particle formation in kraft recovery boilers /“. Espoo [Finland] : Technical Research Centre of Finland, 2000. http://www.vtt.fi/inf/pdf/publications/2000/P421.pdf.
3
Lee, Charles Chi-Woo. „Multiple stable oxygen isotopic studies of atmospheric sulfate : a new quantitative way to understand sulfate formation processes in the atmosphere /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9970662.
4
Fox, Miranda Lynn. „Identifying soils with potential of expanding sulfate mineral formation using electromagnetic induction“. Texas A&M University, 2004. http://hdl.handle.net/1969.1/1171.
Annotation:
Sulfate-bearing soils are a problem in highway construction as they combine with materials used for lime stabilization to form minerals, particularly ettringite, that expand and induce heave in the stabilized soil. This research involves quantifying sulfate in soils that may be potentially used in highway construction using electromagnetic induction. The objectives are to: 1) document electrical conductivity (EC) variability within selected sites that contain sulfate-bearing materials, and 2) determine if electromagnetic induction has potential for locating hazardous levels of sulfate-bearing materials.
The 0.43 ha study area is located in the Blackland Prairies and is a Vertisol known to contain gypsum at the time of site selection. Apparent EC using a model EM38 electromagnetic induction instrument was measured at 200 locations in July and November 2003, using a sampling grid with 5-m spacings. Representative rows and columns were selected from the map of apparent electrical conductivity, and soil cores taken to a depth of 1.5 m at 29 points. Soil samples were obtained by dividing cores into depth increments of 0 to 25 cm, 25 to 75 cm, and 75 to 150 cm. Laboratory analyses were run for each sample and included moisture content, EC and soluble cations and anions of the saturated paste extract, and percent gypsum. Elevation measurements were made to determine if changes in elevation related to EC measurements.
Apparent EC proved to be more successful at detecting soluble salts during the dry sampling period (July) when the effect of soil moisture content was less. For July data, EC and gypsum were significantly correlated in the deepest samples (r2 = 0.51 and 0.15, respectively) to apparent EC. Further, soluble sulfate was significantly correlated to apparent EC (r2 = 0.30) at a depth of 25 to 75 cm. Results suggest that the EM38 can be used successfully to map variability of soil salinity across a field, but although correlation exists between apparent EC and sulfate-bearing materials, it is not sufficiently strong to serve as a good predictor for conditions surrounding lime-induced heave in soil.
5
Masters, Erika N. „Colloid Formation for the Removal of Natural Organic Matter during Iron Sulfate Coagulation“. Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/43756.
Annotation:
Removal of organic matter is increasingly important to drinking water utilities and consumers. Organic matter is a significant precursor in the formation of disinfection by-products (DBPs). The maximum contaminant levels for (DBPs) are decreasing and more DBPs are believed carcinogenic. Traditional coagulation focuses on the removal of particulate matter and in the last decade soluble species have also been targeted with high coagulant doses. However, colloidal matter is smaller than particulate matter and therefore not easily removed by conventional drinking water treatment. This research focused on the conversion of soluble organic matter to colloids using relatively low doses of ferric sulfate coagulant and the subsequent removal of the colloids by filtration during drinking water treatment. The goal is to achieve enhanced removal of soluble organic matter with minimal chemical costs and residual formation.
This study investigated the effects of pH, iron coagulant dose, turbidity, organic matter concentration, and temperature on colloid formation. Characterization of the colloidal organic matter was attempted using zeta potential and sizing analyses. Cationic low molecular weight, nonionic high molecular weight, and cationic medium molecular weight polymers were evaluated on their removal of colloidal organic matter.
Colloidal organic matter formation was affected by changes in coagulation pH, coagulant dose, and organic matter concentration, whereas turbidity and temperature did not significantly impact colloid formation. Decreased coagulation pH caused increased organic carbon removal. As coagulant dose was increased, colloid formation initially increased to maximum and subsequently rapidly decreased. Colloid formation was increased as the organic matter concentration increased. Due to low sample signal, the colloids could not be characterized using zeta potential and sizing analyses. In addition, polymers were ineffective for aggregating colloidal organic matter when used as flocculant aids.Master of Science
6
Brown, Anissa Joy. „Function of heparan sulfate proteoglycans (HSPGs) and heparanase (HPSE) in endochondral bone formation“. Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 225 p, 2008. http://proquest.umi.com/pqdweb?did=1597617551&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
7
Mofaddel, Nadine. „Contribution à l'étude de systèmes quaternaires : exploitation de sulfates alcalins et dédoublement de molécules chirales par formation de diastéréoisomères“. Rouen, 1989. http://www.theses.fr/1989ROUES013.
Annotation:
Dans le cadre de la détermination des domaines de cristallisation d'espèces définies dans un système d'ordre élevé, deux systèmes quaternaires sont étudiés. Le premier système est Na2So4 - K2SO4 – (NH4)2SO4 – H2O : l'isotherme 18°C est dressé, définissant les domaines de stabilité des différentes phases rencontrées. Le deuxième système est le système réciproque: l'isotherme 20°C montre la possibilité de dédoublement d'un composé racémique. Une étude critique des travaux antérieurs est apportée
8
Katragkou, Eleni. „Aircraft based measurements of atmospheric sulfur dioxide and ground based measurements of gaseous sulfur (VI) in the simulated internal flow of an aircraft engine implications for atmospheric aerosol formation /“. [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969654588.
9
Queiroz, Juliana Cristina de. „Desenvolvimento de metodologias para a determinação da atividade biogênica de bactérias redutoras de sulfato“. Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=8930.
Annotation:
Comissão Nacional de Energia NuclearA corrosão causada por H2S biogênico frequentemente resulta em danos extensos na indústria do petróleo. O presente trabalho avaliou parâmetros de crescimento microbiano e aplicou metodologias de determinação de sulfetos por técnicas espectrofotométrica na região da luz visível e radiorespirométrica para avaliação da atividade metabólica, correlacionando com a população de bactérias redutoras de sulfato, determinada através da técnica do Número Mais Provável (NMP). Amostras de água de formação e consórcio de BRS foram avaliadas através do arraste de sulfetos estáveis produzidos biogenicamente e quantificados por espectrofotometria. O cálculo das velocidades instantâneas e específicas de produção de sulfetos permitiu avaliar de que maneira alguns parâmetros de crescimento microbiano podem afetar o metabolismo das BRS. A detecção de concentrações traço de sulfetos biogênicos pode ser realizada através de ensaios radiorespirométricos. Para isto, diluições em série de água do mar sintética com três amostras distintas foram avaliadas. Os testes realizados indicam que o acréscimo do tempo de incubação de cultura microbiana anaeróbia mista contribuiu para o aumento das capacidades de redução de sulfato, assim como o aumento das fontes de carbono. Ambas as técnicas provaram ser um rápido teste para a detecção de sulfetos biogênicos, particularmente aqueles associados aos produtos de corrosão, sendo uma ferramenta muito útil para monitoração e controle de tanques de armazenamento de água e óleo, plataformas continentais de petróleo e diversos tipos de reservatórios. O presente trabalho prevê a continuidade dos experimentos, através de avaliação de um maior universo de amostras da indústria do petróleo e medições menos espaçadas da técnica espectrofotométrica, além da avaliação radiorespirométrica em modo contínuo, evitando os efeitos inibitórios do H2S
Corrosion caused by biogenic H2S often results in extensive damage, being one of the main problems of petroleum industry. The objective of the present work was to evaluate microbial growth parameters and apply methodologies for sulfide detection by spectrometric at visible light and radiorespirometric techniques for estimate the metabolic activity, correlating with population of Sulfate Reducing Bacteria, through the More Probable Number (MPN) technique. Samples of formation water and SBR consortium were evaluated through drag of stable sulfides biogenically produced and quantified by spectrometry. The calculations of instant and specific rates of sulfide production allow evaluating how some microbial growth parameters may affect the SRB metabolism. The detection of trace concentrations of biogenic sulfides, undetectable by spectrometry technique, may be realized by radiorespirometric assays. For this step, serial dilutions of synthetic seawater with three distinct samples were evaluated. The realized test indicates that increasing the time of incubation of a mixed anaerobic microbial culture contributed to an increase in the capabilities of sulfate reduction, as well as the amount of carbon source. Both techniques proved to be a rapid test for the detection of biogenic sulfides, particularly those associated to corrosion products, being an useful tool for monitoring and controlling oil/water storage tanks, petroleum continental platforms and several types of reservoirs. The present work provides the continuous of the experiments, using a bigger universe of samples of petroleum industry and less spaced measuring of spectrometric technique, further the radiorespirometric evaluation in continuous mode, avoiding the H2S inhibitory effects
10
Pagot-Mathis, Véronique. „Prevention de la formation intra-oculaire de fibrine par le dermatane sulfate : etude experimentale chez le lapin“. Toulouse 3, 1989. http://www.theses.fr/1989TOU31503.
11
Alsari, Alsdeg M. „The effect of sodium dodecyl sulfate solutions as gelation media on the formation of PES membranes“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ48125.pdf.
12
Liu, Xiaosong. „The Expression of Cell Surface Heparan Sulfate Proteoglycans and Their Roles in Turkey Skeletal Muscle Formation“. The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1049125572.
13
Shih, Wen-Yi. „Formation and control of calcium sulfate dihydrate (gypsum) crystallization on RO membranes and surrogate polymeric surfaces“. Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1383480211&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
14
Dyer, Thomas J. „Elucidating the formation and chemistry of chromophores during kraft pulping“. Diss., Available online, Georgia Institute of Technology, 2005, 2004. http://etd.gatech.edu/theses/available/ipstetd-1018/.
15
Wu, Xiaofen. „Structure and function of microbial communities in acid sulfate soil and the terrestrial deep biosphere“. Doctoral thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-52538.
Annotation:
This thesis describes the use of different DNA sequencing technologies to investigate the structure and function of microbial communities in two extreme environments, boreal acid sulfate soil and the terrestrial deep biosphere. The first of the two investigated environments was soils containing un-oxidized metal sulfides that are termed ‘potential acid sulfate soil’ (PASS) materials. If these materials are exposed to atmospheric oxygen by either natural phenomena (e.g., land uplift) or human activities (e.g., drainage) then the metal sulfides become oxidized and the PASS becomes acidic and is defined as an ‘acid sulfate soil’ (ASS). The resulting acid and metal release from metal sulfide oxidation can lead to severe environmental damage. Although acidophilic microorganisms capable of catalyzing acid and metal release have been identified from many sulfide mineral containing environments, the microbial community of boreal PASSs/ASSs remains unclear. This study investigated the physicochemical and microbial characteristics of PASSs and ASSs from the Risöfladan experimental field in Vasa, Finland. Sanger sequencing of 16S rRNA gene sequences of microorganisms present in the PASSs and ASSs were mostly assigned to acidophilic species and environmental clones previously identified from acid- and metal-contaminated environments. Enrichment cultures inoculated from the ASS demonstrated that the acidophilic microorganisms were responsible for catalyzing acid and metal release from PASSs/ASSs. Lastly, the study investigated how to mitigate metal sulfide oxidation and the concomitant formation of sulfuric acid by treating ASSs in situ with CaCO3 or Ca(OH)2 suspensions. The DNA sequencing still identified acidophilic microorganisms after the chemical treatments. However, the increased pH during and after treatment suggested that the activity of the acidophiles might be inhibited. This study was the first to identify the microbial community present in boreal PASSs/ASSs and suggested that treatment with basic compounds may inhibit microbial catalysis of metal sulfide dissolution. The second studied environment was the deep, dark terrestrial subsurface that is suggested to be both extremely stable and highly oligotrophic. Despite the scarcity of carbon and energy sources, the deep biosphere is estimated to constitute up to 20% of the total biomass on earth and thus, represents the largest microbial ecosystem. However, due to the difficulties of accessing this environment and our inability to cultivate the indigenous microbial populations, details of the diversity and metabolism of these communities remain largely unexplored. This study was carried out at Äspö Hard Rock Laboratory, Sweden and utilized second-generation sequencing to identify the taxonomic composition and genetic potential of planktonic and biofilm populations. Community DNA sequencing of planktonic cells from three water types at varied age and depth (‘modern marine’, ‘undefined mixed’, and ‘old saline’) showed the existence of ultra-small cells capable of passing through a 0.22 μm filter that were phylogenetically distinct communities from the >0.22 μm fraction. The reduced cell size and/or genome size suggested a potential adaptation to the oligotrophic environment in the terrestrial deep biosphere. The identified planktonic communities were dominated by Proteobacteria, Candidate divisions, unclassified archaea, and unclassified bacteria. Functional analysis of the assembled genomes showed that the planktonic population from the shallow modern marine water demonstrated a predominantly anaerobic and heterotrophic lifestyle. In contrast, the deeper, old saline water was more closely aligned with the hypothesis of a hydrogen-driven deep biosphere. Metagenomic analysis of subsurface biofilms from ‘modern marine’ and ‘old saline’ water types suggested only a subset of populations were involved in initial biofilm formation. The identified biofilm populations from both water types were distinct from the planktonic community and were suggested to be dominated by hydrogen fed, chemolithoautotrophic and diazotrophic populations.
16
Gu, Yushan. „Experimental pore scale analysis and mechanical modeling of cement-based materials submitted to delayed ettringite formation and external sulfate attacks“. Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC2075/document.
Annotation:
Ce travail de recherche a pour but d’étudier des matériaux cimentaires soumis à des attaques sulfatiques selon trois différentes conditions : attaques sulfatiques externes (ASE), formation différée d’ettringite communément appelée attaque sulfatique interne et l’effect couplé des deux réactions, ainsi que de proposer un mécanisme uniforme pour les dégradations causées par ces réactions. En se basant sur le mécanisme proposé, un model poro-mécanique est proposé pour simuler l’expansion induite par les produits expansifs néoformés pendant la dégradation. Cette étude inclut trois parties : dans la première partie, les dégradations des éprouvettes de pâte de ciment correspondant à deux types de ciments (CEM I et CEM III) et deux dimensions exposées à trois différents types d’attaques sulfatiques (ASE, ASI, et le couplage des deux réactions), sont étudiés et comparés : variations de longueur, de masse, ainsi que des observations visuelles. Les éprouvettes exposées au couplage ASE-ASI montrent la cinétique d’expansion la plus rapide et le degré de dégradation le plus important, comparé aux autres cas. Ensuite, la structure poreuse des pâtes de ciment avant et après les attaques sulfatiques est caractérisée en utilisant différentes techniques : porosimétrie à mercure (MIP), sorption dynamique de vapeur (DVS), porosité accessible à l’eau ou essais de dissolution par traitement thermique. En comparant les variations de la distribution de la taille des pores des pâtes de ciment exposées à différentes conditions, les cristaux néoformés se trouvent précipités à la fois dans les pores capillaires et les pores des C-S-H. En plus de l’évolution de la distribution de la taille des pores pendant l’ASI, un mécanisme de dégradation est proposé : les cristaux néoformés (l’ettringite) sont précipités dans les grands pores, sans provoquer une expansion manifeste, et ils sont ensuite précipités dans les pores capillaires et les pores des C-S-H, ce qui induit un gonflement. Par ailleurs, le volume des pores occupé par les produits de l’ASI sont libérés après des essais de dissolution par traitement thermique, ce qui confirme la formation de produits d’expansion dans cette gamme de pores. Enfin, en se basant sur les résultats expérimentaux montrant que l’ettringite se forme en allant des grands pores vers les plus petits, un model poro-mécanique est proposé pour simuler l’expansion des matériaux cimentaires soumis à des attaques sulfatiques. Le modèle est basé sur la croissance contrôlée en surface et les propriétés physicochimiques pour l’ASE et l’ASI, malgré les différences entre ces deux réactions. Deux constantes indépendantes : ai et ap sont proposées pour représenter la cinétique de l’invasion des cristaux et la déformation. De plus, le modèle peut être couplé avec toutes les théories mécaniques, par exemple : l’élasticité, la plasticité, la théorie de l’endommagement ou autres. Le modèle illustre bien le processus de cristallisation et il prédit l’expansion correspondante à la fois à l’ASE et l’ASIThis work aims to study cement-based materials subjected to sulfate attacks in three different conditions: External Sulfate Attack (ESA), Delayed Ettringite Formation (DEF) and the Coupling effect of both, and to propose the same damage mechanism for all of them. Based on the proposed mechanism, a poromechanical model is established to simulate the expansion induced by expansive crystals during the degradation. The study includes the following three parts. In the first part, the degradation of cement paste specimens with two kinds of cement type (CEM I and CEM III) and two dimensions (2 2 12 cm3 and 11 11 22 cm3) exposed to three sulfate attack conditions (ESA, DEF, and Coupling effect) are studied and compared, including the length variation, mass variations, and observations. The specimens exposed to the coupling effect show the fastest kinetics and the most serious degree of degradation compared to the other cases. Then, the pore structure of cement pastes before and after sulfate attacks is characterized via different techniques: MIP, DVS, water accessible tests and heat-based dissolution tests. By comparing the variation of pore size distribution of cement pastes exposed to different conditions, the generated crystals are found to be precipitated both in capillary and gel pores. In addition to the evolution of pore size distribution during DEF, a damage mechanism is proposed: the generated crystals (ettringite) precipitate in the big pores without inducing an obvious expansion, and then penetrate into capillary and gel pores, which leads to a swelling. Moreover, the pore volume occupied by DEF induced products is released after heat-based dissolutiontests, which further confirms the formation of expansive products in that porerange. Finally, based on the experimental conclusion that ettringite forms through the large to small pores in all cases, a poromechanical model is proposed to simulate the expansion of cement-based materials submitted to sulfate attacks. The model is based on the surface-controlled growth and physicochemical properties both for ESA and DEF, despite the different source of sulfate ions. Two independent constants, ai and ap, are proposed to represent the kinetics of crystal invasion and deformation. Moreover, the model could be coupled with any mechanical theories, e.g. elasticity, plasticity, damage theory or any other. The model well illustrates the crystallization process and well predicts the corresponding expansion both in ESA and DEF
17
Ma, Junjun. „Synthesis and Optimization of ‘Sugar tongs’ Lock Neutraligands of the Chemokine CXCL12“. Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS241.
Annotation:
L’Héparane Sulfate (HS) est un polysaccharide linéaire hautement sulfaté largement présent à la surface des cellules ou dans la matrice extracellulaire des tissus animaux. L’HS est l'un des polymères les plus hétérogènes et présente une alternance de domaines fortement sulfatés (S) et faiblement sulfatés (A). L'exposition à la surface cellulaire de ces domaines SAS permet d'établir des interactions spécifiques avec des protéines basiques présentant des topologies de charges complémentaires, permettant la régulation de leurs activités biologiques. CXCL12, une protéine de la famille des chimiokines se liant aux chaînes d’HS, est l'unique ligand naturel du récepteur CXCR4. La signalisation CXCL12/CXCR4 est impliquée dans divers processus biologiques dont l'hématopoïèse, la réponse immunitaire et la migration des cellules cancéreuses et leur prolifération. La conception de glycoligands pouvant se lier spécifiquement à CXCL12 pourrait permettre de moduler son interaction avec son récepteur et donner accès à une substance thérapeutique innovante pour le traitement de plusieurs types de cancer. Nous avons ainsi imaginé la construction d’un ligand tridentate symétrique comportant une partie centrale de type fragment d’HS synthétique (dp4) dont les extrémités réductrice (ER) et non réductrice (ENR) seraient reliées à des ligands capables d'occuper une partie du site de liaison à CXCR4.Grâce à de précédents travaux sur l'IFN-γ, une cytokine se liant aux chaînes HS, notre laboratoire a déjà démontré que la préparation de mimes de SAS pouvait être obtenue en reliant deux fragments d’HS synthétiques (domaines S) par leur ER via des bras espaceurs de type PEG et de longueur différente pour mimer les domaines A. Afin d’adapter cette stratégie à la préparation de neutraligands de CXCL12 et d’une nouvelle génération de mimes de SAS, ce programme doctoral visait (i) à établir une stratégie générale de modification de l’ER et l’ENR de fragments d’HS, (ii) à établir des conditions efficaces de réactions de couplage pour (iii) synthétiser des ligands de CXCL12 ainsi que de nouveaux mimes de SAS. Nous avons sélectionné deux réactions orthogonales de couplage dans le panel de Chimie Click, à savoir la formation de triazole «CuAAC» et la «ligation oxime». Afin de déterminer la faisabilité de transformation des deux extrémités de fragments d’HS pour réaliser ces réactions de couplage, nous avons optimisé les conditions de ces modifications sur un disaccharide modèle dérivé du cellobiose. Tout d’abord, en utilisant la procédure de couplage thiol-ène décrite par notre équipe, nous avons introduit une amine sur l'ER de ce disaccharide et optimisé les conditions d’une séquence monotope transfert de diazo/CuAAC permettant la conversion sélective de cette amine en azoture puis son couplage avec des alcynes vrais. Cette séquence a également pu être appliquée à des acides aminés libres pour la préparation de dérivés organofluorés. Ensuite, l'installation d'un motif aldéhyde sur l’ENR du composé modèle a été obtenue par une séquence en trois étapes comportant une allylation décarboxylante de type Tsuji-Trost de la position O-4 de l'unité NR, une dihydroxylation de l’éther d’allyle obtenu et enfin une coupure oxydante du diol formé. En plus d'explorer la sélectivité de la coupure oxydante en faveur de diols vicinaux acycliques en présence de diols cycliques portés par le squelette saccharidique, nous avons également optimisé les conditions de la réaction de formation d’oximes pour obtenir une seconde procédure monotpe de coupure oxydante/formation d’oxime pour la modification rapide de l’ENR de fragments d’HS. Cette stratégie de fonctionnalisation sélective de l’ER et l’ENR d’oligosaccharides a été implémentée dans notre voie actuelle de synthèse de fragments d’HS : elle a été appliquée de manière représentative à un fragment tétrasaccharidique d’HS qui permettra la préparation de neutraligands de CXCL12 et de mimes de SASHeparan sulfate (HS) is a class of linear and highly sulfated polysaccharides widely present in animal tissues, onto the cell surface or into the extracellular matrix. HS is one of the most heterogeneous polymers and presents an alternation of highly sulfated domains (S domains) and weakly sulfated one (A domains). Exposition of those SAS domains at the cell surface permits the establishment of specific interactions with proteins displaying complementary charge topologies, leading to the regulation of their biological activities.CXCL12, a HS-binding protein, member of the chemokine family of pro-inflammatory mediators, is the unique natural ligand of CXCR4 receptor. CXCL12/CXCR4 signaling is involved in several biological processes, including hematopoiesis, immune response and cancer metastasis. The design of HS type ligands that could bind specifically to CXCL12 to block or modulate its interaction with its receptor should give access to therapeutic substance being able to modulate its activity and allow treatment of several cancer types. To this aim, we planed to construct a symmetric tridentate ligand of CXCL12 in which the reducing end (RE) and non-reducing end (NRE) of a short synthetic HS fragment (dp4) would be connected to ligands able to occupy part of the CXCR4 binding site. Thanks to previous investigation onto IFN-γ, a cytokine that binds tightly to HS chains, our lab already demonstrated that the preparation of SAS mimics should be reached by connecting two synthetic HS fragments (S domains) by their RE through a PEG-type spacer differing in length to mimic internal A domain. To adapt this strategy to the preparation of CXCL12 neutraligands and new type of SAS mimics, this PhD program aimed (i) to establish a general strategy of modification of the HS fragments RE and NRE, (ii) to setup efficient conditions of ligation reactions for (iii) the preparation of CXCL12 neutraligands as well as a second generation of SAS mimics. We selected our two orthogonal ligation reactions into the Click Chemistry panel: “the CuAAC” triazole formation and the “oxime ligation”. In order to setup the practicability of this strategy of transformation of the two HS fragments ends, we optimized reaction conditions onto model disaccharide derived from cellobiose. On one hand, by using thiol-ene coupling procedure reported by our lab, we introduced an amino group to the RE of this disaccharide and optimized reactions conditions of a one-pot diazotransfer reaction/CuAAC sequence, allowing the selective conversion of this amino group into azide and its coupling with alkyne derivatives. To demonstrate the robustness of this sequence, we applied it to the direct modification of free amino acids for the preparation of organofluorine derivatives. On the other hand, the installation of an aldehyde motif onto the NRE of the model compound was obtained via a three steps sequence involving a Tsuji-Trost decarboxylative allylation of the position O-4 of the NRE unit, dihydroxylation of the resulting allyl ether and finally oxidative cleavage of the formed diol. Besides exploring the possibility of the selectivity of the oxidative cleavage in favor of vicinal acyclic diols without affecting cyclic diols of the disaccharide backbone, we also optimized the reaction conditions of oxime ligation to obtain a second one-pot procedure of oxidative cleavage/oxime ligation for the rapid modification of the NRE of HS fragments. This strategy of functionalization of the RE and NRE of oligosaccharides was implemented into our current synthetic pathway of preparation of HS fragments: a tetrasaccharidic HS fragment was representatively modified using this strategy for the synthesis of CXCL12 neutraligands and SAS mimics
18
Jackson, Rebecca. „Augmenting osteogenesis through chemical and mechanical stimulation : the use of loading and heparan sulfate to enhance in vitro osteoblast differentiation and bone formation /“. [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18976.pdf.
19
Barbarulo, Rémi. „Comportement des matériaux cimentaires : actions des sulfates et de la température“. Cachan, Ecole normale supérieure, 2002. http://www.theses.fr/2002DENS0014.
20
Rong, Yi. „Formation du sulfate de calcium hémihydrate de type α à partir de gypse par un procédé de dissolution-cristallisation : étude cinétique expérimentale et modélisation“. Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM070/document.
Annotation:
De nombreuses transformations de solides en solution, polymorphiques ou non, en industrie minérale ou pharmaceutique, se déroulent par la dissolution d'un premier solide en vue de la cristallisation du second. Au lieu de la voie traditionnelle de séchage, la transformation du gypse (sulfate de calcium dihydrate) en alpha-bassanite (sulfate de calcium hémihydrate) peut s’effectuer en solution aqueuse : en augmentant suffisamment la température, le gypse devient plus soluble dans l'eau que l’hémihydrate, qui a alors la possibilité de cristalliser. Un appareillage et un mode opératoire originaux ont été conçus pour investiguer la sensibilité de la cinétique de la transformation et des caractéristiques des cristaux d’hémihydrate obtenus à ces conditions opératoires. En effet, cette voie de dissolution-recristallisation permet le contrôle du facteur d'aspect des cristaux d’hémihydrate, voire celui de leur taille moyenne et de leur dispersion de taille, par le choix de ses conditions physico-chimiques : température, pH, utilisation d’additifs, et ensemencement de la solution avec des particules d’hémihydrate appropriées. Les techniques d'analyse images sont développées afin d'identifier le rapport d'aspect des particules. Un modèle cinétique prenant en compte la dissolution du gypse, la nucléation et la croissance du sulfate de calcium hémihydrate, les équilibres en phase aqueuse et de solubilité, a été élaboré, et ses équations résolues avec le logiciel MATLAB. Couplée à une méthode numérique d'optimisation, cette résolution sous MATLAB permet d'examiner la validité des hypothèses sur les processus retenus et d'identifier leurs paramètres cinétiquesIn mineral or pharmaceutical industry, many transformations of solids in solution (polymorphic or not), take place by the dissolution of the first solid and the crystallization of the second solid. Instead of the traditional drying process, the conversion of gypsum (calcium sulfate dihydrate) to alpha-bassanite (calcium sulphate hemihydrate) can be carried out in aqueous solution by increasing the temperature sufficiently. At this moment, the gypsum becomes more soluble in water than the hemihydrate, which then has the possibility to crystallize. An apparatus and an original procedure have been designed to investigate the sensitivity of the kinetics of transformation and the characteristics of the hemihydrate crystals obtained under its operating conditions. In fact, this dissolution-recrystallization route allows to control the aspect ratio of the hemihydrate crystals, and even their average size and size dispersion, by the choice of its physicochemical conditions such as temperature, pH, use of additives, and seeding the solution with the appropriate hemihydrate particles. Image analysis techniques are developed to identify the aspect ratio of the particles.A kinetic model taking into account the dissolution of gypsum, the nucleation and the growth of calcium sulphate hemihydrate and their equilibrium in aqueous phase and solubility had been developed and the equations of this model are solved with the help of MATLAB software. Coupled with a numerical optimization method, this resolution under MATLAB makes it possible to examine the validity of the assumptions on the selected processes and to identify their kinetic parameters
21
Divet, Loïc. „Les réactions sulfatiques internes au béton : contribution à l'étude des mécanismes de la formation différée de l'ettringite“. Paris, CNAM, 2001. http://www.theses.fr/2001CNAM0375.
Annotation:
Certaines structures en béton présentent une fissuration dont l'origine est parfois attribuée à un gonflement provoque par la formation différée de l'ettringite. L'étude de matériaux en service montre que cette maladie ne concerne pas uniquement les bétons traités thermiquement, mais peut aussi se rencontrer dans les ouvrages en béton de grande masse. Pour ces derniers, le cycle thermique apparaît plus intense compte tenu de la durée de maintien à haute température. Plusieurs paramètres apparaissent indispensables à la réaction : dosage en ciment élevé, bétonnage en période estivale, nature du ciment (alcalins, so 3 et c 3a), conditions d'humidité élevée, nature minéralogique des granulats. Deux mécanismes réactionnels peuvent être à l'origine de cette réaction. Le travail expérimental a consisté à les étudier séparément in vitro. Nous montrons que les ions so 4 2 peuvent se fixer par adsorption physique à la surface des c-s-h. Ce phénomène est susceptible d'empêcher partiellement la formation initiale d'ettringite et est favorisé par une élévation de la température et/ou de la basicité du milieu. A travers une expérimentation sur des phases synthétisées, nous mettons également en évidence une libération importante d'ions so 4 2 provenant des sulfoaluminates de calcium hydrates gouvernée par la température et la concentration en ions oh. Par contre, les ions al(oh) 4 apparaissent plus difficilement libérables. Ces deux mécanismes génèrent donc des sulfates qui se trouvent, soit en solution dans la phase aqueuse du béton, soit physiquement adsorbes aux c-s-h et qui peuvent, a terme, lorsque certaines conditions chimiques sont atteintes, participer à la formation d'ettringite délétère pour le béton. Des modifications importantes dans la microstructure des c-s-h formes à 60 et 90\c ont également été mises en évidence. Il apparaît que les amas de c-s-h présentent une porosité plus grossière qui facilitera le transfert local des ions sulfate vers des sites réactionnels.
22
Messaoudene, Nafa. „Etude de la formation et de l'inhibition des dépôts de sulfate de baryum dans les champs pétroliers : application au champ algérien de Tin Fouyé Tabankort“. Toulouse, INPT, 1990. http://www.theses.fr/1990INPT031G.
Annotation:
Dans les champs petroliers en depletion on utilise frequemment en recuperation assistee l'injection d'eau. Il se pose alors le probleme de compatibilite chimique entre l'eau d'injection et l'eau de gisement. Malheureusement on assiste dans bien des cas apres leur melange a la formation de depots dans les puits producteurs et/ou dans les installations de surface. Ils sont constitues dans la plupart des cas de sulfate de baryum. Il est donc indispensable d'inhiber ces precipitations en reagissant au niveau de la germination et de la croissance des cristaux par utilisation de produits appropries de type polyacrylate de poids moleculaire voisin de 2000. Pour optimiser ce type de traitement il est indispensable de maitriser les differents mecanismes mis en jeu. Compte tenu du nombre important de parametres intervenants, nous avons utilise dans notre etude la methodologie des plans factoriels fractionnaires permettant de hierarchiser ces parametres et d'en connaitre leurs interactions. Apres une etude en laboratoire, nous sommes passes a l'essai pilote sur le site de tin fouye tabankort en algerie. Les resultats sont tres satisfaisants et corroborent parfaitement les etudes en laboratoire
23
Oakley, Lisa Marie. „Enhanced Resolution of the Paleoenvironmental and Diagenetic Features of the Silurian Brassfield Formation“. Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1369340395.
24
Banks, Jonathan [Verfasser]. „Sulfate mineral scaling during the production of geothermal energy from sedimentary basin formation brines: A case study at the Groß Schönebeck in-situ geothermal laboratory, Germany / Jonathan Banks“. Berlin : Freie Universität Berlin, 2013. http://d-nb.info/103663826X/34.
25
Urupina, Darya. „Uptake and reactivity of sulfur dioxide gas onto Icelandic volcanic dusts“. Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0022.
Annotation:
Ces travaux de thèse portent sur l’étude des interactions du dioxyde de soufre (SO2) gazeux avec des poussières volcaniques islandaises. Ils intègrent cinq échantillons naturels de poussières volcaniques: Hagavatn, Mýrdalssandur, Maelifellssandur, Dyngjusandur and Eyjafjallajökull. Les interactions hétérogènes entre SO2 et les poussières volcaniques sont abordées avec plusieurs techniques expérimentales complémentaires. Les profils temporels associés à la capture de SO2, caractérisés par les coefficients de capture en régime stationnaire ont été renseignés expérimentalement. Ces paramètres sont des données d’importance pour les modèles atmosphériques. Des mécanismes réactionnels décrivant la formation des espèces de surface résultant de l’interaction de SO2 avec la surface des poussières sont proposés. Une nouvelle méthode analytique permettant l’extraction et la quantification d’espèces soufrées de surface a été développée et validée. Cette méthode est à présent disponible tant pour l’étude de processus hétérogènes en laboratoire que pour la caractérisation d’échantillons de terrain. Il a été mis en évidence que l’interaction de SO2 avec les poussières volcaniques est un processus de long terme. Les produits formés en surface sont stables et influencent les propriétés des particules minérales. Il a été démontré expérimentalement que l’humidité relative présente une influence marquée sur la capture et la transformation de SO2. La composition de surface des particules minérales est aussi un élément clé, particulièrement pour des humidités relatives inférieures à 30%. Enfin, ces travaux montrent l’importance d’avoir recours à des échantillons minéraux naturels pour assurer une bonne représentativité des études portant sur les processus atmosphériques hétérogènes impliquant des particules minéralesThis thesis investigates the interactions of sulfur dioxide (SO2) gas with Icelandic Volcanic Dusts. Five natural volcanic dust samples were used for the study: Hagavatn, Mýrdalssandur, Maelifellssandur, Dyngjusandur and Eyjafjallajökull. The heterogeneous interactions of gas-phase SO2 with volcanic dusts are investigated using a number of complimentary techniques. Temporal profiles of SO2 uptake and, more precisely, the steady state uptake coefficients have been determined experimentally. These are important kinetic parameters that can be implemented in models. Mechanisms of formation of various surface species resulting from the interactions of SO2 with the surface of dusts are proposed. A new method for quantification of surface sulphur species has been developed and validated. This method can now be used both for further laboratory investigations and in field measurements. It is evidenced that the interactions of SO2 gas with the volcanic dust is a long continuous process. The products formed on the surface are stable and definitely influence the mineral particle properties. It is evidenced that the interactions of SO2 gas and volcanic particles are highly influenced by humidity and by UV light. The influence of surface composition also plays an important role especially at levels of humidity equal or lower than 30% RH. This work emphasizes the importance of using relevant natural dust samples in order to study the heterogeneous atmospheric phenomena involving natural solid particles
26
Pays, Laurent. „Développement de l'innervation cutanée chez l'embryon d'oiseau : relations entre expression différentielle de molécules matricielles et d'adhésion, différenciation de la peau et formation du pattern nerveux“. Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10218.
Annotation:
Dans ce travail consacre a la morphogenese du systeme nerveux peripherique, nous avons pris comme modele la mise en place de l'innervation cutanee chez l'embryon d'oiseau. Dans un premier temps, nous avons etudie les etapes precoces de cette innervation, en parallele avec l'expression de molecules neuronales d'adhesion cellulaire telles que l'axonine-1 et ben. Par immunohistochimie sur coupes, nous avons montre que ces deux antigenes etaient exprimes par les fibres nerveuses en croissance allant innerver la peau, et que cette expression etait regulee au cours du developpement. Il semble donc que l'axonine-1 et ben soient impliquees dans la mise en place de l'innervation cutanee, intervenant en particulier dans de la fascicularisation des fibres nerveuses sensorielles entre elles, et/ou avec les fibres motrices cutanees. La peau synthetise sans doute un ou plusieurs facteurs responsables de l'arret de l'expression de ces deux molecules, car celles-ci sont reexprimes par des neurones cultives in vitro en l'absence de tissu cible. Dans une deuxieme partie de ce travail, nous avons analyse les modalites de developpement du pattern fin d'innervation cutanee, c'est-a-dire la formation d'anneaux nerveux a la base des plumes, ainsi que les roles que jouent dans ce phenomene differents composes matriciels, en particulier les proteoglycannes a chondroitine sulfate. Par des approches experimentales (traitements a l'hydrocortisone ou a l'acide retinoique), par l'etude d'embryons mutants cou-nus, et par des experiences in vitro de cultures de neurones ganglionnaires en presence de divers glycosaminoglycannes et de co-cultures de peau et de ganglions rachidiens, nous avons pu montrer que la morphogenese des anneaux nerveux etait toujours associee a celle des plumes, et que les proteoglycannes a chondroitine sulfate jouaient un role preponderant dans la formation des anneaux nerveux.
27
Colman, Charlotte. „Gypsum residues in fine recycled aggregates : effects on mechanical and microstructural properties of cementitious composites“. Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0012.
Annotation:
Les sables recyclés représentent un flux important de déchets provenant de la démolition d’anciennes structures en béton. Ils ne sont jusqu’à présent pas valorisés à cause d’une absorption d’eau élevée, d’une densité plus faible et d’une teneur en fines plus importante que dans les granulats naturels. De plus, ils sont souvent contaminés par des sulfates. Ces sulfates pourraient provenir du plâtre du bâtiment démoli ou du ciment résiduel qui est couramment présent dans ces matériaux. Le taux de sulfate recommandé pour les granulats recyclés est inférieur à 0,2 % en masse selon la norme EN206, afin de limiter le risque d’attaque sulfatique : la réaction entre les composants du ciment, l’eau et les sulfates entraîne la formation de minéraux expansifs comme l’ettringite. Cette expansion peut éventuellement conduire à une fissuration du matériau et à une perte générale des performances mécaniques. Une étude systématique a permis de mettre en évidence que les sables recyclés provenant des centres de recyclage contenaient de 0,15 à 0,80 % de sulfates ce qui est plus ce qui est autorisé. Néanmoins, ces quantités n’ont pas engendré de gonflement ni de dégradation lorsque les granulats contaminés ont été incorporés dans des mortiers. Une teneur en sulfate très élevée de 3 % a été nécessaire pour observer une expansion significative ; toutefois l’expansion a pu être contrôlée en augmentant l’alcalinité d’un mélange. Des bétons fabriqués avec différents niveaux de sulfates ont présenté des gonflements ou non : l’ampleur d’expansion n’était pas proportionnelle à la teneur en sulfate. Le seuil qui a déclenché la réaction de gonflement dépendait aussi du type de granulat. Les résultats de cette étude fournissent des recommandations pour l’utilisation de sables recyclés contaminés par des résidus de gypse : une teneur en sulfate jusqu’à 0,3 % pourrait être possible, et même plus en fonction de certains paramètres et compositions de mélange. La limite actuelle est de 0,2 % semble trop stricte et freine la valorisation de sables recyclés dans des bétons durables et résistantsFine recycled aggregates are an important waste steam coming from the demolition of old concrete structures. They are up to now not valorized because of an increased water absorption, lower density and higher fines content compared to natural aggregates. Moreover, they often have a high sulfate concentration. These sulfates could have originated from plaster in a demolished building, or from the residual cement that is commonly present in these materials. The sulfate level of recycled aggregates is recommanded to stay under 0.2 mass% by standard EN206, to limit the risk on sulftate attack: the reaction between cement components, water and sulfates results in the formation of expansive minerals such as ettringite. This expansion can eventually lead to cracking of the material and a general loss in mechanical performances. Fine recycled aggregates from recycling plants did contain 0.15 to 0.80 % of sulfates which is more than allowed, but these amounts did not cause any swelling or degradation when the aggregates were incorporated into mortars. A very elevated sulfate content of 3 % was needed to observe significant expansion, and even this level of contamination could be mitigated by increasing the alkalinity of a mix. Concretes made with varying sulfate levels either expanded or they didn’t: the absolute swelling amount was not proportional to its sulfate content. The actual threshold concentration that started the swelling reaction was dependant on the type of coarse aggregate. The results of this study provide recommandations for the use of fine recycled aggregates contaminated with gypsum residues : a sulfate content of at least 0.3 % could be possible, and even more if certain parameters and mix compositions can be adjusted accordingly. The current limit of 0.2 % seems too strict and hinders the valorization of fine recycled aggregates in high quality construction applications
28
Siekmann, Arndt. „Dynamic visualization and genetic determinants of Sonic hedgehog protein distribution during zebrafish embryonic development“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1101915621750-69414.
Annotation:
The correct patterning of embryos requires the exchange of information between cells. This is in part achieved by the proper distribution of signaling molecules, many of which exert their function by establishing gradients of concentration. Because of this property they were named "morphogens", or "form giving" substances. Among these, proteins belonging to the Hedgehog (Hh) family have received much attention, owing to their unusual double lipid modification and their involvement in human disease, causing congenital birth defects and cancer. Great efforts have been made in order to elucidate the mechanisms by which Hh molecules are propagated in the embryo. However, no conclusive evidence exists to date to which structures these molecules localize and how they, despite their membrane association, establish a gradient of concentration. Therefore, I decided to study the distribution of the vertebrate Hh homolog, Sonic Hedgehog (Shh) in developing zebrafish embryos. By fluorescently tagging Shh proteins, I found that these localize to discrete punctate structures at the membranes of expressing cells. These were often regions from which filopodial protrusions emanated from the cells. Puctate deposits of Shh were also located outside of expressing cells. In dividing cells, Shh accumulated at the cleavage plane. Furthermore, by making use of confocal microscopy and time lapse analysis, I visualized Shh proteins moving in filopodial extensions present between cells. This suggests a novel mechanism of Shh distribution, which relies on the direct contact of cells by filopodia for the exchange of signaling proteins. In a second part of my thesis, I characterized genes implicated in regulating Shh protein distribution and signaling function. I cloned three zebrafish genes belonging to the Ext1 (exostosin) family of glycosyltransferases required for the synthesis of Heparan Sulfate Proteoglycans and established a tentative link of these genes to somitic Hh signaling. In addition, I characterized the developmental expression and function of zebrafish Rab23, a small GTPase, which acts as a negative regulator of the Shh signaling pathway. Performing knock-down experiments of zebrafish Rab23, I found that Rab23 functions in left-right axis specification, a process previously shown to depend on proper Shh signaling.
29
Faure, Chrystel. „Effet comparé du sulfate de cholestérol et du cholestérol sur la formation, la dynamique et l'hydratation de bicouches lipidiques modèles : une appproche par RMN des solides, diffraction des rayons X et des neutrons“. Bordeaux 1, 1996. http://www.theses.fr/1996BOR10632.
Annotation:
Le cholesterol et le sulfate de cholesterol sont deux steroides communs a de nombreux systemes biologiques aussi varies que les membranes plasmiques ou la couche cornee de la peau. Leur structure chimique est voisine, pourtant, une alteration de leur population relative dans ces milieux conduit a de graves troubles de l'organisme (perturbation du phenomene de fusion membranaire, epaississement de la peau. . . ) revelant de profondes differences comportementales entre ces deux molecules. Pour tenter de mieux comprendre un tel antagonisme, plusieurs etudes physisocochimiques comparatives sont presentees dans ce manuscrit. La resonance magnetique des solides permet de suivre leur effet respectif sur la dynamique de chaines phospholipidiques au sein de bicouches modeles et sur l'hydratation interfaciale de ces feuillets lamellaires. Par diffraction des neutrons, la position verticale du sulfate de cholesterol dans des bicouches modeles est determinee et comparee a celle du cholesterol. Enfin, l'influence des deux lipides sur la formation de phases lamellaires dans des systemes a base de ceramides modelisant la couche cornee est etudiee par diffraction des rayons x. Ces analyses revelent des differences sensibles entre les deux steroides: le sulfate de cholesterol ordonne moins les chaines phospholipidiques que le cholesterol, il est plus hydrate et occupe deux positions dans les bicouches, l'une enfouie dans la zone hydrophobe, l'autre au contact de la phase aqueuse. Enfin, il facilite la formation d'une phase lamellaire en presence de ceramides. Nous interpretons ces resultats par le caractere hydrophile plus marque du sulfate de cholesterol et expliquons ainsi partiellement leur antagonisme dans les systemes biologiques
30
Boumezioud, Mohamed. „Complexion de métaux de transition par des hydroxyquinolines en milieux homogènes et microhétérogènes : Influence de l'hydrophobie du ligand sur la cinétique réactionnelle dans des phases microémulsions“. Nancy 1, 1987. http://www.theses.fr/1987NAN10276.
Annotation:
Étude de la complexation de métaux de transition (nickel, cobalt) par des ligands bidentes du type hydroxy-8 quinoline dans des milieux homogènes (eau et méthanol) et des milieux microhétérogènes (solution micellaire, microémulsion), tant du point de vue thermodynamique que cinétique
31
Johnson, Graham Richard. „The Formation and Growth of Marine Aerosols and the Development of New Techniques for their In-situ Analysis“. Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16117/1/Graham_Johnson_Thesis.pdf.
Annotation:
Marine aerosols have attracted increasing attention over the past 15 years because of
their potential significance for global climate modelling. The size distribution of these
aerosols extends from super-micrometer sea salt mode particles down through 150 nm
accumulation mode particles, 40 nm Aitken mode particles and nucleation mode
particles which extend from 25 nm right down to clusters of a few molecules. The
process by which the submicrometer modes form and grow and their composition
have remained topics of debate throughout this time in large part because of the
difficulties associated with determining their composition and relating it to proposed
models of the formation process.
The work compared the modality of marine aerosol influencing the South-east-Queensland region with that of other environmental aerosols in the region. The aerosol was found to be consistent with marine aerosols observed elsewhere with
concentrations below 1000 cm-3 and frequently exhibiting the distinct bimodal structure associated with cloud processing, consisting of an Aitken mode at approximately 40 nm, an accumulation mode in the range 100-200 nm and a coarse mode attributed to sea salt between 600 and 1200 nm.
This work included the development of two new techniques for aerosol research. The first technique measures aerosol density using a combination of aerosol size distribution and gravimetric mass concentration measurements. This technique was used to measure the density of a number of submicrometer aerosols including
laboratory generated NaCl aerosol and ambient aerosol. The densities for the laboratory generated aerosols were found to be similar to those for the bulk materials used to produce them. The technique, extended to super-micrometer particle size range may find application in ambient aerosol research where it could be used to discriminate between periods when the aerosol is dominated by NaCl and periods
when the density is more representative of crustal material or sulfates. The technique
may also prove useful in laboratory or industrial settings for investigating particle
density or in case where the composition is known, morphology and porosity.
The second technique developed, integrates the existing physicochemical techniques
of volatilisation and hygroscopic growth analysis to investigate particle composition
in terms of both the volatilisation temperatures of the chemical constituents and their
contribution to particle hygroscopic behaviour. The resulting volatilisation and humidification tandem differential mobility analyser or VH-TDMA, has proven to be a valuable research tool which is being used in ongoing research.
Findings of investigations relating the composition of the submicrometer marine
aerosol modes to candidate models for their formation are presented. Sea salt was not
found in the numerically dominant particle type in coastal nucleation mode or marine
Aitken and accumulation modes examined on the Southeast Queensland coast during
periods where back trajectories indicated marine origin. The work suggests that all
three submicrometer modes contain the same four volatile chemical species and an
insoluble non-volatile residue. The volatility and hygroscopic behaviours of the
particles are consistent with a composition consisting of a core composed of sulfuric
acid, ammonium sulfate and an iodine oxide coated with a volatile organic compound.
The volume fraction of the sulfuric acid like species in the particles shows a strong
dependence on particle size.
32
Johnson, Graham Richard. „The Formation and Growth of Marine Aerosols and the Development of New Techniques for their In-situ Analysis“. Queensland University of Technology, 2005. http://eprints.qut.edu.au/16117/.
Annotation:
Marine aerosols have attracted increasing attention over the past 15 years because of their potential significance for global climate modelling. The size distribution of these aerosols extends from super-micrometer sea salt mode particles down through 150 nm accumulation mode particles, 40 nm Aitken mode particles and nucleation mode particles which extend from 25 nm right down to clusters of a few molecules. The process by which the submicrometer modes form and grow and their composition have remained topics of debate throughout this time in large part because of the difficulties associated with determining their composition and relating it to proposed models of the formation process. The work compared the modality of marine aerosol influencing the South-east-Queensland region with that of other environmental aerosols in the region. The aerosol was found to be consistent with marine aerosols observed elsewhere with concentrations below 1000 cm-3 and frequently exhibiting the distinct bimodal structure associated with cloud processing, consisting of an Aitken mode at approximately 40 nm, an accumulation mode in the range 100-200 nm and a coarse mode attributed to sea salt between 600 and 1200 nm. This work included the development of two new techniques for aerosol research. The first technique measures aerosol density using a combination of aerosol size distribution and gravimetric mass concentration measurements. This technique was used to measure the density of a number of submicrometer aerosols including laboratory generated NaCl aerosol and ambient aerosol. The densities for the laboratory generated aerosols were found to be similar to those for the bulk materials used to produce them. The technique, extended to super-micrometer particle size range may find application in ambient aerosol research where it could be used to discriminate between periods when the aerosol is dominated by NaCl and periods when the density is more representative of crustal material or sulfates. The technique may also prove useful in laboratory or industrial settings for investigating particle density or in case where the composition is known, morphology and porosity. The second technique developed, integrates the existing physicochemical techniques of volatilisation and hygroscopic growth analysis to investigate particle composition in terms of both the volatilisation temperatures of the chemical constituents and their contribution to particle hygroscopic behaviour. The resulting volatilisation and humidification tandem differential mobility analyser or VH-TDMA, has proven to be a valuable research tool which is being used in ongoing research. Findings of investigations relating the composition of the submicrometer marine aerosol modes to candidate models for their formation are presented. Sea salt was not found in the numerically dominant particle type in coastal nucleation mode or marine Aitken and accumulation modes examined on the Southeast Queensland coast during periods where back trajectories indicated marine origin. The work suggests that all three submicrometer modes contain the same four volatile chemical species and an insoluble non-volatile residue. The volatility and hygroscopic behaviours of the particles are consistent with a composition consisting of a core composed of sulfuric acid, ammonium sulfate and an iodine oxide coated with a volatile organic compound. The volume fraction of the sulfuric acid like species in the particles shows a strong dependence on particle size.
33
Kiventerä, J. (Jenni). „Stabilization of sulphidic mine tailings by different treatment methods:heavy metals and sulphate immobilization“. Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223964.
Annotation:
Abstract Millions of tons of mine tailings are generated worldwide annually. Since many valuable metals such as Ag, Cu, Pb, Zn, Au and Ni are usually incorporated into sulphidic minerals, a large proportion of the tailings generated contain high amounts of sulphates and heavy metals. Some of these tailings are used as paste backfill material at mining sites, but large amounts are still being deposited into the tailings dams under water coverage. Sulphidic minerals are stable underground but after mining of the ore and several processing steps these minerals can be oxidized when they come into contact with water and air. This oxidation generates acid and thus reduces the pH of the surrounding environment. Furthermore, the heavy metals present in the mine tailings can be leached into the environment. This phenomenon, called Acid Mine Drainage (AMD), is one of the most critical environmental issues related to the management of sulphidic-rich tailings. Since AMD generation can still occur hundreds of years after closure of the mine, the mine tailings need stable, sustainable and economically viable management methods in order to prevent AMD production in the long term. The aim of this PhD thesis was to study various solidification/stabilization (S/S) methods for the immobilization of sulphidic mine tailings. The main focus was to develop a suitable chemical environment for achieving effective heavy metal (mainly arsenic) and sulphate immobilization while simultaneously ensuring good mechanical properties. Three treatment methods were tested: alkali activation, stabilization using hydrated lime (Ca(OH)2) and blast furnace slag (GBFS), and calcium sulphoaluminate-belite (CSAB) cement stabilization. The mine tailings used in this study contained large amounts of sulphates and heavy metals such as Cr, Cu, Ni, Mn, Zn, V and As. The leaching of arsenic and sulphates from powdered tailings exceeded the legal limits for regular and inert waste. All treatment methods were found to generate a hardened matrix that was suitable for use as a backfilling or construction material, but the calcium-based binding system was the most suitable for effective immobilization of all the heavy metals (including arsenic) and the sulphates. Precipitation in the form of calcium sulphates/calcium arsenate and the formation of ettringite are the main stabilization methods employed in calcium-based stabilization/solidification (S/S) systems. Some evidence of physical encapsulation occurring simultaneously with chemical stabilization was noted. These results can be exploited further to develop more sustainable mine tailing management systems for use in the future. The tailings could be stored in a dry landfill area instead of in tailing dams, and in this way a long-term decrease in AMD generation could be achieved, together with a high potential for recyclingTiivistelmä Monet arvometallit kuten kulta, kupari ja nikkeli ovat sitoutuneena sulfidipitoisiin mineraaleihin. Louhittaessa ja rikastettaessa näitä sulfidimineraaleja syntyy miljoonia tonneja sulfidipitoisia rikastushiekkoja vuosittain. Rikastushiekat voivat sisältää myös runsaasti erilaisia raskasmetalleja. Osa rikastushiekoista hyödynnetään kaivostäytössä, mutta suurin osa rikastushiekoista läjitetään edelleen ympäristöön rikastushiekka-altaisiin veden alle. Kun sulfidipitoinen malmi kaivetaan ja käsitellään, sulfidiset mineraalit hapettuvat ollessaan kosketuksissa veden ja hapen kanssa. Hapettuessaan ne muodostavat rikkihappoa, laskien ympäristön pH:ta jolloin useimmat raskasmetallit liukenevat ympäristöön. Muodostuvia happamia kaivosvesiä voi syntyä vielä pitkään kaivoksen sulkemisen jälkeen ja ovat näin ollen yksi suurimmista kaivosteollisuuteen liittyvistä ympäristöongelmista. Lisäksi suuret rikastushiekka-altaat voivat aiheuttaa vaaraa myös ihmisille, mikäli altaan rakenteet pettävät. Rikastushiekkojen kestäviä ja ympäristöystävällisiä varastointimenetelmiä täytyy kehittää, jotta näitä ongelmia voidaan tulevaisuudessa ehkäistä. Tässä työssä tutkittiin menetelmiä, joilla kultakaivoksella syntyvät sulfidipitoiset vaaralliseksi jätteeksi luokitellut rikastushiekat saataisiin stabiloitua tehokkaasti. Työssä keskityttiin kolmeen erilaiseen menetelmään: alkali-aktivointiin, stabilointiin kalsiumhydroksidin ja masuunikuonan avulla ja stabilointiin CSAB sementin avulla. Valmistettujen materiaalien mekaanisia ja kemiallisia ominaisuuksia arvioitiin. Tavoitteena oli ymmärtää, miten eri menetelmät soveltuvat raskasmetallien (erityisesti arseenin) ja sulfaattien sitoutumiseen ja mikä on eri komponenttien rooli reaktioissa. Alkali-aktivoimalla rikastushiekkaa sopivan sidosaineen kanssa saavutettiin hyvät mekaaniset ominaisuudet ja useimmat haitta-aineet sitoutuivat materiaaliin. Ongelmia aiheuttivat edelleen sulfaatit ja arseeni. Kalsiumpohjaiset menetelmät sitoivat raskasmetallit (myös arseenin) ja sulfaatit tehokkaimmin. Sulfaatit ja arseeni saostuivat muodostaen niukkaliukoisia komponentteja kalsiumin kanssa. Samanaikaisesti rakenteeseen muodostui ettringiittiä, jolla on tutkitusti hyvä kyky sitoa erilaisia raskasmetalleja rakenteeseensa. Raskasmetallit myös kapseloituivat rakenteen sisään. Työn tuloksia voidaan hyödyntää, kehitettäessä rikastushiekkojen turvallista varastointia. Kun materiaalille saavutetaan riittävän hyvä lujuus ja kemiallinen stabiilius, rikastushiekat voitaisiin läjittää tulevaisuudessa kuivalle maalle altaan sijaan. Näin vältyttäisiin rikastushiekka-altaiden rakentamiselta ja voitaisiin vähentää happamien kaivosvesien muodostumista pitkällä ajanjaksolla. Saavutettujen tulosten perusteella rikastushiekkoja voidaan mahdollisesti tulevaisuudessa hyödyntää myös erilaisissa betonin tapaisissa rakennusmateriaaleissa
34
Carrigan, William J. „Stable isotope ratios of carbonate and sulfide minerals from the Gunflint Formation: Evidence for the origin of iron formations“. Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5785.
Annotation:
The $\sim$1.9 Ga Gunflint Formation is a Lake Superior type iron-formation, located in the Thunder Bay district of northwestern Ontario, that was deposited on a shallow shelf analogous to modern carbonate environments. Carbonate minerals in the iron-rich lithofacies of the Gunflint Formation include siderite, ankerite, and calcite. Petrographic evidence indicates that siderite precipitation initiated either within the water column or at the sediment/water interface and continued during very early diagenesis. Ankerite and calcite formed during early to late diagenesis as pore-filling cements and as replacements of other minerals. The iron-poor limestone facies contains very early diagenetic dolomite and early to late diagenetic calcite. $\delta\sp $C values of carbonate minerals from unmetamorphosed rocks range between 0 and $-6\perthous$ (PDB). The values near 0$\perthous,$ which are considered to be representative of the basin water composition, indicate that the primary source of carbon was marine bicarbonate. The lighter values indicate that a minor component of oxidized organic carbon was added during early diagenesis. The heaviest $\delta\sp $O values for unmetamorphosed carbonate minerals range between $-$5 and $-7\perthous$ (PDB), which is the same range of values observed for many early Proterozoic marine carbonates. $\delta\sp $O values of carbonate minerals are the result of isotopic exchange with pore waters, originally of marine composition, at increasing temperatures and/or are the result of isotopic exchange with $\sp $O-depleted meteoric water during early diagenesis. Disseminated fine-grained, very early diagenetic pyrite is widespread throughout the formation, usually in amounts less than about 2%. However, pyrite is locally observed as laminae or thin layers, suggesting that some pyrite may have formed at or above the sediment/water interface. Low S/C ratios indicate that dissolved sulphate was the limiting factor in pyrite formation. $\delta\sp{34}$S values between +5 and +12$\perthous$ (CDT) imply that sulfide formed by bacterial sulphate reduction under closed system conditions. In the lower part of the Gunflint Formation coarse-grained pyrite and pyrite concretions are associated with syndepositional faults. High S/C ratios and highly variable $\delta\sp{34}$S values ($-$33 to +35$\perthous)$ suggest an external source of sulphate was introduced by fluids moving upward along these faults. The Gunflint basin is best characterized by a stratified water column with high concentrations of dissolved ferrous iron below the redox boundary. Volcanic activity or rifting within this basin contributed a high flux of reducing hydrothermal solutions to the seawater. Hydrothermal activity was probably the dominant source of iron, although reduction of detrital ferric iron may have contributed significant amounts of dissolved iron. During periods of increased tectonic activity, the expansion of the redox boundary to shallower water allowed the transport of iron to the shallow shelf. Ferric iron-bearing minerals would have been precipitated on the shelf by oxidation in surface waters whereas ferrous iron-bearing minerals would have been precipitated under more reducing conditions either in deeper water or in sheltered environments. The transition to the iron-poor limestone member resulted from a lowering of the redox boundary. (Abstract shortened by UMI.)
35
Bulbul, Sevtac. „Hydrate Formation Conditions Of Methane Hydrogen Sulfide Mixtures“. Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608140/index.pdf.
Annotation:
The objective of this study is to determine hydrate formation conditions of methane- hydrogen sulfide mixtures. During the study, an experimental work is carried out by using a system that contains a high-pressure hydrate formation cell and pressure-temperature data is recorded in each experiment. Different H2S concentrations and both brine and distilled water are used in the experiments and the Black Sea conditions, which are suitable for methane-hydrogen sulfide hydrate formation are examined.
Considering the pressure-temperature data obtained, hydrate equilibrium conditions are determined as well as the number of moles of free gas in the hydrate formation cell. The change in the number of moles of free gas in the hydrate formation cell with respect to time is considered as a way of determining rate of hydrate formation. Effects of H2S concentration and salinity on hydrate formation conditions of methane-hydrogen sulfide mixtures are also studied. It is observed that an increase in the salinity shifts the methane-hydrogen sulfide hydrate equilibrium condition to lower equilibrium temperatures at a given pressure. On the other hand, with an increase in H2S concentration the methane hydrogen sulfide hydrate formation conditions reach higher equilibrium temperature values at a given pressure. After the study, it can be also concluded that the Black Sea has suitable conditions for hydrate formation of methane hydrogen sulfide mixtures, considering the results of the experiments.
36
Wacey, David. „Microbial mediation of dolomite formation : geochemical and microbial investigations in the Coorong region of South Australia“. Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:cf6d606d-7304-4610-80db-a362745bc1f9.
Annotation:
Dolomite is shown to precipitate in laboratory experiments that simulate the microbiogeochemical conditions prevailing during the later stages of evaporation in the ephemeral, hypersaline, dolomitic lakes of the Coorong region, South Australia, where microbially-dominated ecosystems support intensive bacterial sulphate reduction. Analyses of numerous lake- and pore-water samples from Coorong lakes document rapid geochemical changes with depth and time. Extremely high sulphate and magnesium ion concentrations occur in lake waters and decline rapidly with depth in pore waters through the sulphate reduction zone. Ultimately sulphate ions are totally consumed but magnesium ions are replenished, presumably from desiccated cyanobacterial sheaths. Carbonate concentrations in pore waters reach levels up to 100 times those of normal seawater. Most-probable-number counts show that large populations of sulphate-reducing bacteria are present in sediment cores, while sulphur isotope analysis of residual lakewater sulphate indicates that microbial fractionation takes place in all the study lakes. Microbes from the lakes were cultured in the laboratory under anoxic conditions and viable populations were injected into vials containing a sterilised granular substrate immersed in a simulated lakewater solution. Falls in the levels of sulphate ion concentration and rising pH in selected vials were interpreted as due to active bacterial sulphate reduction accompanied by increased concentrations of carbonate. After 1 month, subspherical nano-grains of dolomite were precipitated. This study proposes that bacterial sulphate reduction overcomes kinetic constraints on dolomite formation by removing the sulphate ions and releasing magnesium and calcium ions from neutral ion pairs, and by generating elevated carbonate concentrations in a hypersaline and strongly electrolytic solution. Microbiogeochemical and isotopic data therefore demonstrates that bacterial sulphate reduction controls dolomite precipitation in both the laboratory experiments and the lake sediments. It is proposed that dolomite formation through bacterial sulphate reduction provides a process analogue that is applicable to thick platformal dolostones of the past, where benthic microbial communities were the dominant colonisers of the shallow marine environment.
37
Mullaugh, Katherine M. „Formation and persistence of cadmium sulfide nanoparticle in aqueous solution“. Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 232 p, 2009. http://proquest.umi.com/pqdweb?did=1885682071&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
38
Cong, Rongjuan Pelton Robert H. „PEO/poly(vinyl phenol-co-styrene sulfonate) aqueous complex formation /“. *McMaster only, 2002.
39
Simpson, Graham P. „Sulfate reduction and fluid chemistry of the Devonian Leduc and Nisku formations in south-central Alberta“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/NQ38505.pdf.
40
Hintze, Vera, Sergey Samsonov, Sandra Rother, Sarah Vogel, Sebastian Köhling, Stephanie Moeller, Matthias Schnabelrauch et al. „Sulfated Hyaluronan Derivatives Modulate TGF-β1:Receptor Complex Formation: Possible Consequences for TGF-β1 Signaling“. Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230329.
Annotation:
Glycosaminoglycans are known to bind biological mediators thereby modulating their biological activity. Sulfated hyaluronans (sHA) were reported to strongly interact with transforming growth factor (TGF)-β1 leading to impaired bioactivity in fibroblasts. The underlying mechanism is not fully elucidated yet. Examining the interaction of all components of the TGF-β1:receptor complex with sHA by surface plasmon resonance, we could show that highly sulfated HA (sHA3) blocks binding of TGF-β1 to its TGF-β receptor-I (TβR-I) and -II (TβR-II). However, sequential addition of sHA3 to the TβR-II/TGF-β1 complex led to a significantly stronger recruitment of TβR-I compared to a complex lacking sHA3, indicating that the order of binding events is very important. Molecular modeling suggested a possible molecular mechanism in which sHA3 could potentially favor the association of TβR-I when added sequentially. For the first time bioactivity of TGF-β1 in conjunction with sHA was investigated at the receptor level. TβR-I and, furthermore, Smad2 phosphorylation were decreased in the presence of sHA3 indicating the formation of an inactive signaling complex. The results contribute to an improved understanding of the interference of sHA3 with TGF-β1:receptor complex formation and will help to further improve the design of functional biomaterials that interfere with TGF-β1-driven skin fibrosis.
41
Qu, Deyu. „Electro-formation of self-assembled monolayers of thiol and sulfide on gold“. Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6229.
Annotation:
The electro-deposition of thiol and sulfide monolayers has been studied with Electrochemical Quartz Crystal Microbalance (EQCM), chronoamperometry, FTIR, and cyclic voltammetry. The surface concentrations of alkanethiols/alkanethiolates calculated from the oxidative charge and from the EQCM signal using the Sauerbrey equation are in excellent agreement for depositions done in alkaline and pH neutral aqueous solutions. This allowed the measurement of the kinetics of the oxidative deposition of alkanethiols and alkanethiolates on gold. These experiments show that the oxidative depositions of alkanethiols and alkylthiolates occur in two steps. The oxidative deposition can be described by a combination of a potential dependent instantaneous nucleation-growth process and a potential independent Langmuir process. These results show that the rate of deposition of these compounds as well as their coverage can be controlled by an applied electric field. The effects of temperature and concentration on the oxidative deposition process are also reported. The electro-deposition of sulfide was found to be complex. In a pH neutral solution, sulfides go through a slow dissociative adsorption process and form a monolayer of thiolates. In alkaline solution, the oxidative adsorption of sulfide is faster. This observation is compatible with an SNZ reaction between physisorbed sulfides and hydroxyl ions.
42
Brion, Jean-Marc. „Contribution à l'étude des mécanismes de formation de couches de transfert non métalliques sur un outil en coupe continue d'aciers de décolletage a inclusions contrôlées“. Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL043N.
Annotation:
On présente l'étude des mécanismes de formation des couches de transfert sélectif (CTS) de sulfures de manganèse sur un outil de coupe a partir des seules inclusions contenues de façon contrôlée dans l'acier usiné. On montre que la stabilité de la CTS sur l'outil correspond à un équilibre dynamique entre sa vitesse d'alimentation et sa vitesse d'érosion avec l'adhérence inclusion/outil comme mécanisme clé gouvernant cette stabilité. Cette adhérence est liée à l'affinité chimique entre l'élément métallique actif présent à la surface de l'outil (Zr, ti) et le soufre des inclusions de l'acier exprimée en termes d'enthalpie de formation du sulfure correspondant. Par spectroscopie des électrons Auger en mode balayage, nous avons réussi à comprendre le mécanisme le plus probable d'accrochage des sulfures de manganèse sur des outils mixtes composes de carbures WC et tic. A l'endroit des carbures simples de type wc, on assiste a une usure diffusionnelle classique qui se traduit par leur dissociation et évacuation continuelles. En revanche, l'élément de transition (ti) dans les carbures actifs également dissociés forme, avec les inclusions de l'acier usine, une fine couche d'oxysulfure stable, et certainement adhérente, qui interrompt cette dissociation et constitue une base d'accrochage pour d'autres sulfures. Dans la même logique, on constate que la continuité chimique du compose actif à la surface de l'outil (outils revêtus) favorise encore la stabilité des CTS. Bien que d'importance cruciale, la maitrise compositionnelle de la surface de l'outil ne peut avoir qu'un rôle de révélateur du flux d'alimentation en inclusions provenant du copeau. On montre le rôle capital qui revient au contrôle inclusionnaire en matière de composition des inclusions principalement mais aussi en termes de morphologie et de déformabilité relative inclusion/matrice
43
Kanukuntla, Vijaya. „Formation of Sulfide Scales and Their Role in Naphthenic Acid Corrosion of Steels“. Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1199733762.
44
Henri, Caroline. „Étude de la formation de l'ettringite secondaire avec divers types de sulfates alcalins et dosages en gypse“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0031/MQ67285.pdf.
45
Henri, Caroline. „Étude de la formation de l'ettringite secondaire avec divers types de sulfates alcalins et dosages en gypse“. Sherbrooke : Université de Sherbrooke, 1999.
46
Leflaive, Philibert. „Etude de la formation et de la réactivité des composés soufrés dans les conditions du craquage catalytique“. Poitiers, 1999. http://www.theses.fr/1999POIT2313.
Annotation:
L'objectif de ce travail etait d'identifier l'origine des composes soufres (alkylthiophenes a chaines courtes) contenus dans l'essence de craquage catalytique et de comprendre leur mode de formation. Deux voies principales menant a ces produits ont ete envisagees : - un craquage direct des alkylthiophenes a longues chaines (atlc) susceptibles d'etre contenus dans les charges, - une reaction secondaire de recombinaison de l'hydrogene sulfure issu des molecules soufrees des charges avec les olefines ou les dienes obtenus par craquage des hydrocarbures. Ces deux voies ont ete examinees en analysant la reactivite de molecules modeles a 500\c sur un catalyseur commercial de fcc. L'etude de la transformation du 2- et du 3-n-hexylthiophene a montre que la production des molecules soufrees contenues dans l'essence a partir des atlc est possible si ces derniers sont presents dans les charges de craquage. Cependant, la formation de thiophene et de ses derives a chaine(s) courte(s) respectivement par desalkylation et par rupture de la chaine laterale ne sont pas les voies majoritaires de transformation des atlc. En effet, la selectivite en ces produits n'excede pas 30% et les atlc se desulfurent, contrairement a leurs homologues a chaines courtes. L'etude de la transformation du thiophene, des methylthiophenes et du 2-ethylthiophene a confirme que ces composes sont relativement stables dans les conditions du craquage catalytique. Pour la seconde voie, l'etude de la transformation d'olefines et de dienes en presence d'hydrogene sulfure a montre que la formation d'alkylthiophenes a partir de ces reactifs est possible. Les rendements obtenus sont cependant tres faibles (i. E. Inferieurs a 2%). Le mecanisme suppose de la reaction est la formation d'un thiol par addition nucleophile d'h 2s suivie d'une cyclisation en derives du tetrahydrothiophene qui se deshydrogenent ensuite en alkylthiophenes. L'etude des thiols et du tetrahydrothiophene intermediaires confirme ce resultat.
47
Chevrier, Vincent. „Approche magnétique de la formation du régolithe martien : étude sur analogues terrestres et expérimentaux“. Aix-Marseille 3, 2004. http://www.theses.fr/2004AIX30061.
Annotation:
Les résultats des missions spatiales montrent la présence d'un régolithe martien fortement altéré, dont une origine possible provient de l'altération du substrat basaltique primaire par l'atmosphère et l'hydrosphère. Cette hypothèse d'altération météorique est testée sur un analogue terrestre : la dolérite de Ferrar provenant d'Antarctique et sur un certain nombre de minéraux altérés sous atmosphère martienne. L'altération météorique en conditions martiennes génère des phases fortement magnétiques, soit héritées de la roche mère (titanomagnétite), ou des apports exogéniques (fer métal), soit néoformées (maghémite). Les (oxy)hydroxydes rouges (goethite et hématite) ainsi que la plupart des phases secondaires détectées dans le régolithe martien (sulfates et carbonates), résultent aussi des processus d'altération météorique. Enfin cette étude démontre la possibilité d'altération en l'absence d'O2, l'eau constituant alors le principal moteur des réactions d'oxydation de la surfaceResults of Martian spacecraft missions have evidenced the presence of a strongly altered regolith, of which possible origin is alteration of primary basaltic substrate by atmosphere and hydrosphere. This hypothesis of weathering is tested on a terrestrial analogue: the Ferrar dolerite from Antarctic and on some phases experimentally altered in a simulated Martian atmosphere. Meteoric weathering under Martian conditions produces strongly magnetic phases, either inherited from parent bedrock (titanomagnetite), either from exogenic contribution (iron metal), or neoformed (maghemite). Red ferric (oxy)hydroxides (goethite and hematite) as well as most secondary phases detected in the Martian regolith, i. E. Sulfates and carbonates, may also result from weathering. Finally this study demonstrates that weathering may occur in the absence of O2. Water is then the main reactive species, responsible for oxidation reactions of the surface
48
Wang, Moran. „Network modelling of the formation and fate of hydrogen sulfide and methane in sewer systems“. Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18325/.
Annotation:
Hydrogen sulfide is produced by sulfate reducing bacteria, which are mainly associated with the biofilms covering the surfaces in rising mains. Sulfide control strategies commonly used such as chemical dosage are costly for long-term management. The effect of physical and hydraulic conditions of sewers on sulfide formation has been investigated in recent years. One of the key parameters in modelling the formation of hydrogen sulfide is the pipe area- volume ratio (A/V), as this indicates the relative contribution between biofilm and wastewater processes. The A/V is naturally related to the pipe diameter. A high A/V is associated with small pipe diameter, and would lead to a high contribution from the biofilms and hence the potential for high hydrogen sulfide formation. However, it would also decrease the residence time of the wastewater, which would tend to decrease the amount of hydrogen sulfide formed. Based on the results of in-sewer process modelling, this study quantifies the importance of the pipe diameter and pumping strategy for optimal design for rising mains, to minimise hydrogen sulfide production, either to improve the life time for the downstream sewer structures or to minimise the potential chemical dosing needed in the rising mains. The model results from this study show optimal diameter options for both existing rising mains in terms of minimum hydrogen sulfide formation. The sensitivity analysis on model parameter based on the case studies also indicates the most uncertain parameters and COD fractions. Methane is a problem acknowledged in some sewer networks around the world and is particularly of concern in China where sewer explosions can occur. Septic tanks are integrated parts of many Chinese sewer systems and methane is believed to be produced not only in sewer pipes, but also in septic tanks. Work has been done to look at how the anaerobic digestion model can be applied in combinations with sewer processes models to describe such a system. Model simulation results on methane formation in rising mains is similar to reported literature. The field measurements in the Chinese sewer system demonstrated high gas phase hydrogen sulfide and methane concentrations both in gravity systems and rising mains due to the surcharging sewer conditions. Future work has been proposed according to the local problems by discussing the benefits of applying sewer process and anaerobic digestion models based on this study.
49
Lee, Sukyeon. „Electrically Controlled Formation and Release of Admicelles for Solid Phase Extraction“. TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1334.
Annotation:
Solid phase extraction is one of the most widely used methods to concentrate diluted compounds in a solution. Substances can be extracted into admicelles and hemimicelles, which are surface adsorbed micelles and surfactant monolayers, respectively. Investigations of the electrical control of surfactants on surfaces for the purpose of analyte preconcentration prior to chromatographic analysis are presented. The surfactant layer serves as the “stationary phase” in a solid phase extraction sorbent scenario. Analytes are adsorbed on this layer, and then released from the solid phase via surfactant removal. The attachment and removal of the surfactant are controlled by means of an electric field. Because the surfactant-analyte association is released by electrical control, organic solvents, which are used in conventional solid phase extraction, are not required. Therefore, this procedure is advantageous for method development and environmental concerns. Presented is the preconcentration of a test probe, 2-naphthol, using electrical control of the formation and release of dodecyl sulfate on planar gold, gold coated stainless steel, and a porous stainless steel frit, using impedance spectroscopy to observe the layer formation with various surfactant concentrations and applied potentials.
50
Schrader, Devin Lee. „The Formation and Alteration of the Renazzo-Like Carbonaceous Chondrites“. Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/223379.
Annotation:
This study investigates the pre-accretionary formation conditions of individual minerals within chondrules and whole-rock parent asteroid processes from the Renazzo-like carbonaceous (CR) chondrites. It presents a comprehensive work on the whole-rock O-isotope composition, sulfide-bearing opaque minerals, and type-II chondrules within the CR chondrites. Whole-rock O-isotope composition and minerals present in type-II chondrules are found to be related to the degree of parent asteroid aqueous alteration. Primary minerals within chondrules, formed prior to accretion of the CR chondrite parent asteroid, are used to constrain both the environment and the conditions present during chondrule formation.Chondrule formation, as recorded by chondrules in the CR chondrites, took place under dust- and ice-rich conditions relative to solar values. Type-II (FeO-rich) chondrules contain FeO-poor fragments compositionally similar to type-I (FeO-poor) chondrules; the formation of type-II chondrules may have occurred after the formation of type-I chondrules. The dust and ice abundances present during type-II chondrule formation were higher than those of type-I chondrules, although both populations probably exchanged with the same ¹⁶O-poor gas reservoir. Both the oxygen fugacity (fo₂) and sulfur fugacity (fs₂) appear to have increased from type-I to type-II chondrule formation, and between individual type-II chondrules. The increase in fo₂ and fs₂ may be due to the dissipation of H2 in the early Solar System. Gas-solid oxidation/sulfidation of Fe,Ni metal is recorded in both type-I and type-II chondrules. This corrosion occurred either during chondrule cooling after formation, or during chondrule reheating events, and suggests that S was present in the gas phase. After chondrule formation the CR chondrite parent asteroid accreted ¹⁶O-poor ice and experienced variable degrees of aqueous alteration, possibly due to heterogeneity in accreted ice or ammonia abundances and/or differing depth within the asteroid. Individual regions of the asteroid experienced different degrees of brecciation, perhaps a result of impacts, which fragmented chondrules and mixed together material that experienced different degrees of aqueous alteration. This process resulted in the heterogeneous nature of the CR chondrites.These observations constrain the formation conditions of a minor body, the CR chondrite parent asteroid, a remnant from the earliest stages of planet formation.