The solvent-producing clostridia are well known for their ability to produce acetone, butanol and isopropanol in industrial fermentation. Production of these compounds occurs in cells that have completed a metabolic switch under specific growth conditions. Knowledge of the regulation of the metabolic switch will make the industrial process more reliable. From an isopropanol-producing strain Clostridium beijerinckii NRRL B593, a gene which encodes a putative NtrC-like regulatory protein was cloned and sequenced. The gene codes for a polypeptide of 632 amino acids and has been designated the stc gene. Expression of the stc gene was confirmed by RT-PCR. The co-presence of the stc gene with the adh gene which encodes a primary/secondary alcohol dehydrogenase in isopropanol-producing clostridia suggests that the stc gene may be functionally related to isopropanol production. From C. beijerinckii NRRL B592, a region which encompassed the solvent-production genes ald (aldehyde dehydrogenase), ctfA and ctfB (acetoacetate: butyrate/acetate CoA-transferase) and part of adc (acetoacetate decarboxylase) was cloned and sequenced. The organization of these genes was similar to that in C. beijerinckii NRRL B593. Northern analysis indicated that these four genes were co-transcribed on the same messenger RNA in C. beijerinckii NRRL B593. Therefore, in C. beijerinckii, the sol operon consists of the ald -ctfA-ctfB-adc genes, which differs from the sol operon in Clostridium acetobutylicum. / Master of Science

The use of sol-gel immobilization in the fabrication of microarrays is a relatively new approach that has shown potential to become a leading methodology in this field. However, there are a limited number of assay systems that have been reported using this method. Furthermore, methods to produce high-density sol-gel-derived microarrays have not been reported. Herein, two novel assays utilizing sol-gel-derived microarrays are presented. In the first case, the solid phase of sol-gel-derived microarrays was employed as a detection platform for monitoring the activity of glycogen synthase kinase 3-β (GSK3β) in solution using a phosphospecific stain. Using this assay format, the ability to detect hyperphosphorylated product over the pre-phosphorylated substrate was demonstrated and a z' value of 0.49 was obtained, indicating amenability to small molecule screening. Secondly, a fluorogenic assay for acetylcholinesterase (AChE) was development that is compatibility with sol-gel derived microarrays and standard imaging instrumentation. A thiol-reactive fluorogenic dye, typically used for detection of thiolated oligonucleotides, was successfully used to monitor AChE activity both in solution and in silica. Further, a functional sol-gel-derived AChE microarray was fabricated and activity on array was detected. We have also reported on the optimization of materials for the fabrication of high-density kinase microarrays using sol-gel immobilization. By employing a directed criteria-based screen, optimal materials were quickly and efficiently identified. Two materials, 1.5SS/1PV A/Glycerol and 0.25DGS, were identified as the optimal materials for fabrication of sol-gel-derived functional microarrays. / Thesis / Master of Science (MSc)

No description available.

The functionality of a novel 3-dimensional betavoltaic battery design will be investigated to improve conversion efficiency over existing planar devices. A beta-emitting isotope of nickel, Ni-63, is embedded in the volume of empty space between self-assisted p-i-n junction gallium phosphide nanowires to improve the beta capture efficiency. Parameters such as nanowire pitch, diameter, and height will influence the efficiency and were investigated thoroughly. Material selection was performed based on the following considerations. Gallium phosphide is chosen to achieve a high open circuit voltage under beta exposure. Ni-63 has an optimal beta energy spectrum for a nanowire device and a half-life of 101 years for long term application. The majority of the work focused on the development of the fabrication process, particularly the radioactive source deposition. The method used for embedding the source was a citrate-based sol-gel which was spun onto the sample. This method was modified for this nanowire application and specific challenges to the process are outlined. Furthermore, the obstacles of working with radioactive materials will be discussed. The first nanowire-based betavoltaic device is reported to produce beta-generated current and achieved a beta conversion efficiency of 0.03%. Investigation of the junction was performed to provide future improvements to the efficiency. Additionally, simulated IV curves for a non-active sample exhibited a possible conversion efficiency of 1.92%. / Thesis / Master of Applied Science (MASc)

The sol-gel process has been employed to generate hybrid inorganic-organic network materials. Unique ceramers were prepared based on an alkoxysilane functionalized soft organic oligomer, poly(propylene oxide) (PPO), and tetramethoxysilane (TMOS). Despite the formation of covalent bonds between the inorganic and organic constituents, the resulting network materials were phase separated, composed of a silicate rich phase embedded in a matrix of the organic oligomer chains. The behavior of such materials was similar to elastomers containing a reinforcing filler. The study focused on the influence of initial oligomer molecular weight, functionality, and tetramethoxysilane, water, and acid catalyst content on the final structure, mechanical and thermal properties. The sol-gel approach has also been exploited to generate thin, transparent, abrasion resistant coatings for metal substrates. These systems were based on alkoxysilane functionazized diethylenetriamine (DETA) with TMOS, which generated hybrid networks with very high crosslink densities. These materials were applied with great success as abrasion resistant coatings to aluminum, copper, brass, and stainless steel. In another study, intercalated polymer-clay nanocomposites were prepared based on various epoxy networks montmorillonite clay. This work explored the influence of incorporated clay on the adhesive properties of the epoxies. The lap shear strength decreased with increasing clay content. This was due to a reduction in the toughness of the epoxy. Also, the delaminated (or exfoliated) nanocomposite structure could not be generated. Instead, all nanocomposite systems possessed an intercalated structure. The final project involved the characterization of a series of metallocene catalyzed linear polyethylenes, produced at Phillips Petroleum. Polyolefins synthesized with such new catalyst systems are becoming widely available. The influence of molecular weight and thermal treatment on the mechanical, rheological, and thermal behavior was probed. Although the behavior of this series of metallocene polyethylenes was not unlike that of traditionally catalyzed materials, this work is one of the first comprehensive studies of these new linear polyethylenes. The main distinction between the metallocene and traditional Ziegler-Natta catalyzed polyethylenes is the narrow molecular weight distributions produced by the former (for this series of materials, 2.3< Mw  Mn <3.6). / Ph. D.

L'utilisation de revêtements sol-gel pour la protection contre la corrosion des métaux est une alternative aux traitements à base de chromates, proscrits du fait de leur forte toxicité. Ces travaux de thèse ont porté sur la caractérisation de revêtements sol-gel hybrides organique-inorganique contenant des pigments inhibiteurs de corrosion non toxiques, pour la protection contre la corrosion de l'alliage d'aluminium 2024. Tout d'abord, la caractérisation par spectroscopie d'impédance électrochimique de différents revêtements relativement poreux a permis d'analyser l'influence de l'épaisseur, de la température de séchage, de l'hydrolyse de la partie silane et du ratio silane/amine sur les performances du revêtement, en particulier des propriétés barrière. Puis, l'ajout d'un époxy dans la formulation a permis d'augmenter de façon significative les propriétés barrière du film. Les diagrammes d'impédance présentent une dispersion en fréquence, exprimée en termes de « constant phase element (CPE) », en haute et basse fréquence. En haute fréquence, ce comportement a été analysé à l'aide d'un modèle qui permet d'obtenir des profils de résistivité dans l'épaisseur du revêtement et au cours du temps d'immersion. Ce modèle est appliqué pour la première fois à l'étude de revêtements. Différents pigments inhibiteurs de corrosion ont ensuite été incorporés dans des revêtements de porosité différente. L'action des inhibiteurs est exacerbée lorsqu'ils sont incorporés dans un revêtement poreux. Néanmoins, lorsqu'ils sont incorporés dans un film dense, les performances vis-à-vis de la résistance à la corrosion sont élevées. / The use of sol-gel coatings for the protection against the corrosion of metals is an alternative to chrome-based treatments, banned for the industry for their high toxicity. This work is based on the characterisation of hybrid organic-inorganic coatings, filled with non-toxic corrosion inhibitors, for the protection against the corrosion of aluminium alloy 2024. First, the characterisation by electrochemical impedance spectroscopy of different, relatively porous coatings, allowed the investigation of the influence of thickness, drying temperature, silane hydrolysis, and the silane/amine ratio on the coating performances, in particular the barrier properties. Then, the addition of an epoxy compound in the formulation allowed a significant increase in the film barrier properties. The impedance diagrams show a frequency dispersion, expressed in terms of a constant phase element (CPE), both in the high and low frequency range. In the high frequency range, this behaviour was analyzed using a model that allows obtaining resistivity profiles in the thickness of the coating and with immersion time. This model is applied for the first time to study coatings. Different corrosion inhibitors were then incorporated in coatings of different porosity. The action of the inhibitors was heightened when they are incorporated in a porous coating. Nevertheless, in a dense coating, the performances towards corrosion are high.

L’objectif de cette thèse était d’identifier les principaux indicateurs de disponibilité de l’azote dans les sols forestiers et ensuite de déterminer les mécanismes impliqués dans le contrôle de la minéralisation de l’azote et de la nitrification par les essences forestières. Différents indicateurs de la disponibilité en azote des sols ont été comparés dans 50 hêtraies du Nord Est de la France représentant une large gamme de type de sol. L’effet des essences a été étudié sur un cambisol hyperdystric acide dans le site de Breuil (Morvan, France). Le potentiel net de minéralisation de l’azote est corrélé négativement avec le pH du sol et positivement avec le rapport C/N microbien. Le pourcentage de nitrification est fortement corrélé à une combinaison du pH avec le rapport C/N du sol ou à la composition de la végétation. Dans le site de Breuil, le pourcentage de nitrification du sol est élevé sous le hêtre, le pin laricio et le douglas tandis qu’il est très faible sous le Sapin, l’Epicéa et la forêt native (taillis sous futaie à base de hêtre et de chêne). La permutation des carottes de sols entre ces peuplements montre que sous les peuplements forts nitrifiants, la colonisation racinaire est lente et le pourcentage de nitrification est stimulé très rapidement (<16 mois). Sous les peuplements peu nitrifiants, la colonisation racinaire est très rapide mais la réduction du pourcentage de nitrification est assez lente (>28 mois). Par ailleurs, la coupe à blanc stimule très rapidement la nitrification sous la forêt native. L’ensemble de ces résultats converge vers un contrôle fort du cycle de l'azote par les racines, mais le mécanisme exact reste inconnu. / The aim of this thesis was to identify the main indicators of N availability in forest soils and thereafter to determine mechanisms by which tree species control soil N mineralization and nitrification. Various indicators of N availability were compared within 50 beech forests covering a large range of soil types in northeastern France. Thereafter, the effect of six tree species was studied in an acidic cambisol hyperdystric at the experimental site of Breuil (Morvan, France). Potential net N mineralization was negatively correlated with soil pH and positively with microbial C/N ratio. Percent nitrification was strongly correlated with the combination of soil pH and soil C/N or with the combination of Ellenberg’s indices of N availability or Ecoplant C/N and Ellenberg’s indices of acidity (R) based on the vegetation community composition. At the Breuil experimental site, the percent nitrification was high in beech, Corsican pine and Douglas fir plantations whereas it was very low in the Nordmann fir and the spruce plantations and the native forest stands (an old coppice with standard dominated by beech and oak). The exchange of soil cores between stands showed that under the « High nitrifying stands », root colonization was low and percent nitrification was quickly stimulated (<16 months). In « Low nitrifying stands », root colonization was very quick but percent nitrification decreased slowly (>28 months). Percent nitrification was quickly stimulated by clear felling of the native forest. Our results converge toward a strong influence of roots on the nitrogen cycle in forest ecosystems but it needs further efforts to identify the mechanism.

Le contrôle de la qualité des ressources en eau nécessite des outils de détection en continu et in situ. Dans ce contexte, les biocapteurs sont prometteurs dans le développement de nouveaux systèmes pour une détection précoce. On peut citer deux exemples dans des domaines aussi variés que la détection précoce de corrosion bactérienne ou la détection de la formation d'espèces biologiques responsables de maladies dégénératives.Ce travail propose la conception et la réalisation d'un biocapteur pour la détection de molécules d'intérêt biologiques. La réalisation de ce biocapteur est basée sur le dépôt de matériaux hybrides organiques/inorganiques à la surface d'un transducteur piézoélectrique.La première étape consiste à développer des matériaux fonctionnalisés innovants permettant l'encapsulation d'espèces biologiques. Pour cela deux voies ont été étudiées. La première passe par l'utilisation d'un acrylate type "acide aminé" le N-acryloyglycine (NAGly) permettant la synthèse de matériaux sous forme de film. La seconde utilise un autre type d'acrylate, le N-acryloxysuccinimide (NAS) couplé au 2-hydroxyethylacrylate (HEA) aboutissant un hydrogel fonctionnalisé. Les différentes mesures montrent que dans tous les cas, ces réseaux sont interpénétrés et permettent l'encapsulation de biomolécules.Pour la détection de ces espèces, un biocapteur piézoélectrique est développé dans la deuxième étape. Un dispositif expérimental développé au laboratoire assure la mesure et le suivi de l'évolution des propriétés viscoélastiques d'un matériau en contact avec un transducteur piézoélectrique. En effet, ces propriétés caractéristiques sont extraites à partir d'un modèle électrique original tenant compte simultanément des évolutions électriques et mécaniques du matériau. Ce capteur (transducteur + matériau déposé en surface) mis au contact avec les biomolécules permet leur détection et quantification.Les résultats montrent une corrélation entre le module visqueux du biocapteur et la concentration en biomolécules du milieu en contact. Cette corrélation est une première étape vers le développement d'un biocapteur piézoélectrique pour la détection et la quantification sélective de différentes espèces biologiques en solution. / The control of the quality of water resources requires tools for continuous and in-situ detection. In this context, biosensors are interesting in the development of new systems for early detection. For examples we can note the interest in the early detection of bacterial corrosion or the formation of biological species responsible of degenerative diseases.This work proposes the design and implementation of a biosensor for the detection of biological molecules. The realization of this biosensor is based on the deposition of organic/inorganic materials on the surface of a piezoelectric transducer.The first step is the development of innovative functionalized materials for encapsulation of biological species. For this, two approaches have been studied. The first involves the use of an "amino acid" acrylate, the N- acetylglycine (Nagly) for the synthesis of thin film. The second uses an other acrylate, the N- acryloxysuccinimide (NAS) copolymerized with 2- Hydroxyethyl acrylate (HEA) to form a functionalized hydrogel. The different measures show that in all cases, these networks are interpenetrating and allow the encapsulation of biomolecules.For the detection of these species, a piezoelectric biosensor is developed in the second step. An experimental device, developed in the laboratory, measures and monitors the evolution of the viscoelastic properties of a material in contact with a piezoelectric transducer. Indeed, these characteristics are extracted from an original electric model that take into account simultaneous electrical and mechanical changes in the material. This sensor (transducer and material deposited on the surface) in contact with biomolecules, enables the detection and quantification of these biomolecules.The results show a correlation between the viscous modulus of the biosensor and the concentration of biomolecules in contact. This correlation is a first step in the development of a piezoelectric biosensor for detection and selective quantification of different biological species in solution.

Le diagnostic moléculaire est un diagnostic basé sur l’analyse des acides nucléiques nécessite incontestablement la préparation d’échantillon. Cette préparation à pour objectif d’extraire des acides nucléiques d’un milieu généralement très complexe, de les purifier, de les concentrer voir les transporter dans des microsystèmes utilisés comme outils de diagnostic. Aujourd’hui, l’utilisation de nouvelles technologies et en particulier l’utilisation de supports solides ont permis de palier à un grand nombre de problèmes comparé aux méthodes conventionnelles. L’évolution de ces supports solides en particules colloïdales a permis de répondre à la demande des nouvelles technologies en apportant, une grande surface spécifique, une séparation rapide suite au caractère magnétique, un transport simple dans les microsystèmes et une chimie de surface modulable pour une bonne extraction de l’analyte recherchée. Ainsi, l’objet de cette étude est la synthèse de la silice magnétique submicronique en taille pour l’extraction des acides nucléiques. La synthèse de la silice magnétique a été conduite en trois étapes. Dans un premier temps, la synthèse de ferrofluide organique a été réalisée par coprécipitation des chlorures ferriques et ferreux en basic avant transfert en milieu organique. La deuxième étape a été la préparation d’émulsions magnétiques stables, fortement magnétiques (pour une séparation rapide) et de taille relativement homogène et reproductible. Le ferrofluide préparé organique préparé a été émulsionné pour préparer une émulsion huile dans l’eau (O/W) en utilisant un tensioactif anionique. L’émulsion magnétique a été ensuite encapsulée par une écorce de silice via le procédé sol-gel. Le procédé d’encapsulation a été optimisé via une étude systématique et par une caractérisation physicochimie et colloïdale complète de particules. La caractérisation morphologique des particules obtenues a montré une structure coeur magnétique et une écorce de silice parfaitement homogène. Ces particules de silice magnétique ont été utilisées pour étudier l’adsorption des acides nucléiques (fragment d’ADN) en fonction du pH et de la salinité. Les résultats montrent une bonne capacité d’adsorption des acides nucléiques et également un bon relargage. Ce résultat encourageant montre que ces particules peuvent être utilisées dans le diagnostic moléculaire où l’extraction, la purification et la concentration des acides nucléiques sont très recherchées / Currently, the genetics and DNA-based applications are developing very vast. All these applications such as gene therapy, diagnosis and PCR (polymerase chain reaction) require a previous step, which is the isolation and purification of genetic materials from their compartment. Taking care that the extraction method should produce the DNA in high purification state and in good conditions. The DNA extraction and purification are well known from long time ago, but these methods are time and organic solvents consuming. Nowadays, new nanotechnology-based techniques allow establishing rapid, efficient, environment respecting and cheaper isolation methods for DNA extraction. Silica-coated magnetic emulsions as a form of core-shell were successfully synthesized for magnetic separation of DNA. Magnetic core is the separation tool and silica shell is the DNA capturer and releaser part. The silica-coated magnetic emulsions synthesis was carried out in three steps. Starting from the organic ferrofluid synthesis by the coprecipitation of ferrous and ferric chlorides in aqueous ammonium hydroxide solution. The iron oxide nanoparticles were coated with oleic acid layer and redispersed in octane. Second step consisted of preparation of magnetic emulsion. The obtained ferrofluids used as oil to prepare oil in water emulsion (O/W) and SDS was used as surfactant. Then, the magnetic emulsion particles, the magnetic droplets, were coated with silica shell using the sol-gel process. The encapsulation was performed using TEOS as silica precursor and its hydrolysis was catalyzed by ammonium hydroxide. Particles characterization showed that the performed synthesis produced perfect core-shell particles. These particles have been used to study the DNA binding in different conditions of pH, ionic strength and DNA concentration in solution. Results show good fixation and release of DNA molecules by the silica magnetic particles. In addition to the extraction results, the colloidal stability and speed separation of silica coated magnetic particles, these particles can be recommended as strong DNA separation tools

[pt] Foram desenvolvidos nanocompósitos de óxidos dopados com níquel metálico pelo processo Sol-Gel modificado pelo uso do PVA (Álcool Polivinílico) na função de matriz de crescimento dos nanocompósitos. Os precursores dos óxidos foram os nitratos de seus próprios metais. Foram sintetizados três tipos de nanocompósitos óxido de magnésio, óxido de alumínio e óxido de zinco. O trabalho envolveu quatro etapas principais: levantamento bibliográfico, desenvolvimento e caracterização dos nanocompósitos e uso dos nanocompósitos como catalisadores na síntese de nanotubos de carbono. O desenvolvimento dos nanocompósitos foi motivado pela necessidade de materiais com tamanho e estrutura controláveis para emprego como catalisadores pela indústria. Na síntese dos nanocompósitos foi usada uma relação de PVA/ Água de 1/12 que depois foi variada para avaliar a influência sobre a força de hidrólise, a relação entre metal da matriz e níquel metálico foi de 9:1, em porcentagem em massa. Também foi avaliada a influência do surfactante Dodecil Sulfato de sódio (SDS) e do hidróxido de amônio na síntese dos nanocompósitos. Os nanocompósitos sintetizados neste trabalho foram testados como catalisadores no crescimento de nanotubos de carbono pela técnica de High Vacuum Chemical Vapor Deposition (CVD). Os catalisadores utilizados tinham tamanho de cristalito aproximado de 11nm no caso de óxido de magnésio e de 5 nm no caso do óxido de alumínio, o níquel metálico formado nestes suportes estava bem disperso e com dimensões estimadas de 3nm. Nanotubos de carbono de uma camada e mais de uma camada foram obtidas somente quando o suporte do níquel metálico era o óxido de magnésio. Os nanotubos foram caracterizados por Raman e microscopia eletrônica de varredura. / [en] Metallic Nickel and oxide nanocomposite have been developed by Sol-Gel process modified by the use of PVA (polyvinyl alcohol) as a matrix for the growth of the nanocomposites. The oxides precursors were nitrates from their own metal. Three types of oxides were synthetized, magnesium oxide, aluminum oxide and zinc oxide. This work is presented in four sections: literature survey, development and characterization of nanocomposites and the use of nanocomposites as catalysts in the synthesis of carbon nanotubes. The development of these nanocomposites was motivated by the need for materials with controllable size and structure for use as catalysts in industry. The synthesis of the nanocomposites used a ratio of PVA / water of 1/12 that was later varied to evaluate the influence of the force of hydrolysis, the relationship between the matrix oxide metal and metallic nickel was 9:1 in mass percentage. The influence of the surfactant sodium dodecyl sulfate (SDS) and the ammonium hydroxide was also evaluated in the nanocomposites synthesis. The nanocomposites synthesized in this work were tested as catalysts in the growth of carbon nanotubes by the technique of High Vacuum Chemical Vapor Deposition (CVD). The catalysts used had a crystallite size of approximately 11nm in the case of magnesium oxide and 5 nm in the case of aluminum oxide, metallic nickel formed on these supports was well dispersed with a size of 3nm. Single layer and multiple layer carbon nanotubes were obtained only when magnesium oxide was the nickel substrate. The nanotubes were characterized by Raman and scanning electron microscopy.