No description available.

Cette thèse est consacrée à l'étude des structures atomiques des phases icosaédriques de type F et leurs dislocations.<br /><br />Dans cette étude nous avons d'abord construit une structure générique permettant de traiter dans un seul schéma les phases icosaédriques de type F connues. Afin de valider ce modèle nous avons synthétisé quelques compositions suggérées par ce dernier. Ces synthèses ont permis entre autres de découvrir deux nouvelles phases quasipériodiques à la stoechiométrie Al66,08Cu21,35Mn8,29Fe4,28 , l'une icosaédrique (métastable) de type F et l'autre décagonale (stable). Elles ont montré, à une composition au-delà de celles déjà étudiées dans le système (Al,Pd,Fe), l'existence d'une phase F-IQC.<br /><br /> Globalement, ces résultats expérimentaux d'études de nouvelles phases icosaédriques ont permis de montrer la fiabilité du modèle : sur les trois essais de nouvelles compositions, deux ont montré l'existence de phases icosaédriques de type F et la troisième a mis en évidence une phase décagonale en relation d'épitaxie canonique avec la phase icosaédrique brut métastable (axe 10 confondu avec un axe 5).<br /><br />Possédant un modèle fiable nous avons donc pu y introduire des dislocations. Nous avons ainsi précisé la géométrie des dislocations à l'échelle atomique, hors de la zone de cœur, dans les phases F-IQC. Dans cette structure nous avons aussi identifié les mouvements des phasons et tenté d'apporter des éléments de réponse aux mouvements de ces dislocations.

Les diagrammes d’équilibre sont le point de départ et la ligne directrice qui permet de prévoir et contrôler les phases pouvant se former au cours de différents processus industriels. Bien que l’étude expérimentale soit nécessaire pour les systèmes binaires et ternaires, elle est difficilement envisageable pour déterminer les diagrammes de phases des systèmes d’ordre supérieur sur de larges gammes de composition et de température. Afin de contourner ce problème, la méthode dite CALPHAD (CALculation of PHAse Diagram) a été développée. Son principe consiste à optimiser les paramètres des modèles thermodynamiques utilisés pour décrire l´énergie libre de Gibbs de chaque phase à partir d’informations expérimentales ou estimées (ab-initio). Le modèle appelé « Compound Energy Formalism » (CEF) est largement utilisé pour décrire les phases qui présentent plusieurs sous-réseaux. Ce modèle et ceux qui en dérivent permettent la modélisation d'une grande variété de composés. Les activités menées au cours de ce travail ont permis de développer une nouvelle approche du CEF (NACEF) basée sur une étude mathématique de ses paramètres thermodynamiques. Elle a conduit à une nouvelle formulation de la fonction d'énergie libre de Gibbs faisant intervenir de nouveaux paramètres indépendants. Cette nouvelle approche a été utilisée dans le cadre de ce travail afin de modéliser les phases intermétalliques binaires constituée de deux sous-réseaux présentant des défauts uniquement de type anti-sites (A,B)a(A,B)b. Le système Al-Fe-Nb sur lequel porte notre étude a été choisi en raison de son importance dans la fabrication de nombreuses familles d'alliages tels que les aciers, les alliages légers et plus récemment dans le développement de nouveaux matériaux réfractaires à base Nb pour des applications à hautes températures. Dans ce travail, de nouvelles modélisations des bordures binaires Al-Nb et Fe-Nb et pour la première fois du ternaire Al-Fe-Nb sont proposées en utilisant la NACEF et en s’appuyant sur les informations issues de la littérature ou obtenues dans cette étude. / The equilibrium diagrams are the starting point and the guideline to predict and control the microstructure that will form during processing materials. Despite experiments being necessary in binaries and ternaries systems, it is difficult to experimentally determine phase diagrams of higher orders systems over wide ranges of compositions and temperature. The CALPHAD (CALculation of PHAse Diagrams) method was developed in order to solve this problem. The essence is to optimize the parameters of thermodynamic models that describe the Gibbs free energies of each phase aiming to reproduce the experimental and estimated (ab-initio) data. The compound energy formalism (CEF) is widely used in order to describe phases which present several sublattices. It allows the modeling of a large variety of phases and numerous methods have been developed to treat different situations. The activities in this work developed a new approach of the CEF (NACEF) based on a mathematic analysis of the parameters which leads to a new formulation of the Gibbs free energy function evolving new independent parameters in which new independent parameters are obtained to express the Gibbs free energy. This approach was used in this work to describe the intermetallic phases with two-sublattice in which the only defect type is anti-sites (A,B)a(A,B)b. The Al-Fe-Nb system was chosen due to its importance for the manufacturing process of several families of alloys currently used, e.g. steels, light alloys, and also for the development of new materials for high temperatures application. The binaries Al-Nb and Fe-Nb were reassessed and the Al-Fe-Nb system was assessed for the first time using literature information and new experimental data. / Os diagramas de equilíbrio são o ponto de partida e a diretriz para prever e controlar a microestrutura ao final do processamento de um material. Apesar de experimentos serem necessários em sistemas binários e ternários, é muito difícil determinar experimentalmente diagramas de fase de sistemas de ordens superiores numa vasta amplitude de composições e temperatura. A fim de solucionar este problema, o método CALPHAD (CALculation of PHAse Diagrams) foi desenvolvido. A essência consiste em aperfeiçoar os parâmetros de modelos termodinâmicos que descrevem as energias livres de Gibbs de cada fase de modo a reproduzir as informações experimentais ou estimadas (ab-initio). O compound energy formalism (CEF) é amplamente utilizado para descrever fases que apresentam várias sub-redes. Ele permite a modelagem de uma grande variedade de fases e vários métodos têm sido desenvolvidos para o tratamento de diferentes situações. As atividades deste trabalho ajudaram a desenvolver uma nova abordagem para o CEF (NACEF) com base em um estudo matemático dos seus parâmetros termodinâmicos que levou a uma nova formulação para função da energia livre de Gibbs envolvendo novos parâmetros independentes. Esta nova abordagem tem sido utilizado como parte do presente trabalho para modelar fases intermetálicas binárias constituídas de sub-redes cujo único defeito é do tipo anti-sítio (A,B)a(A,B)b. O sistema Al-Fe-Nb foi escolhido devido a sua importância para o processo de fabricação de diversas famílias de ligas usadas atualmente, e.g. aços, ligas leves e, além disto, é um sistema importante para o desenvolvimento de materiais para aplicações em altas temperaturas. Neste trabalho os binários Al-Nb e Fe-Nb foram reavaliados e o sistema Al-Fe-Nb foi modelado pela primeira vez utilizando as informações da literatura e novos dados experimentais.

No description available.

Présente chez les mammifères, mitoNEET (mNT) est une protéine à centre Fe-S ancrée à la membrane externe de la mitochondrie. Cette protéine dimérique possède un centre [2Fe-2S] par monomère lié de façon atypique à la protéine par trois cystéines et une histidine. Notre équipe a auparavant montré l’implication de mNT dans une nouvelle voie de réparation du centre [4Fe-4S] de l’Iron Regulatory Protein-1 (IRP-1), régulateur majeur de l’homéostasie du fer intracellulaire, par transfert du centre Fe-S de mNT à l’IRP-1 à réparer. Au cours de ma thèse, je me suis focalisée sur la caractérisation in vitro de la réaction de transfert de centre Fe-S de mNT vers une protéine réceptrice modèle, l’apo-ferrédoxine d’E. coli. En combinant des approches de biochimie et biophysique (réalisées en collaboration) à l’aide de protéines purifiées, cette étude a permis de démontrer que mNT agit comme un interrupteur moléculaire : lorsque son centre Fe-S est réduit, la protéine est extrêmement stable et le centre ne peut être ni perdu ni transféré; une fois oxydé, il peut alors être transféré à une protéine réceptrice. La présence d’oxygène n’affecte pas cette réaction même s’il s’agit d’un déterminant majeur de la stabilité de la protéine. De plus, la vitesse de transfert du centre est très sensible au pH, ce qui fait de mNT un senseur de pH. Ces études ont aussi montré que mNT est extrêmement résistante à H2O2 en comparaison à d’autres protéines de transfert de centre Fe-S. J’ai également étudié l’interaction d’une molécule anti-oxydante, le resvératrol-3 sulfate, avec mNT. Pour finir, je me suis intéressée à l’effet du glutathion sur mNT. Acteur majeur de la régulation de l’homéostasie rédox, le glutathion existe sous deux formes: oxydée (GSSG) et réduite (GSH). J’ai alors constaté que le GSH déstabilise fortement mNT à certains pH et peut même se lier à cette protéine. La fonction thiol du GSH et la formation de radicaux sur cette dernière sont clairement impliquées dans la déstabilisation de mNT. / Present in mammals, mitoNEET (mNT) is an Fe-S protein anchored to the outer mitochondrial membrane. This dimeric protein contains a [2Fe-2S] per monomer with an atypical ligation involving three cysteines and one histidine. Previously, our team proposed that mNT is involved in a new pathway dedicated to the reparation of the oxidatively damaged [4Fe-4S] cluster of human iron-regulatory protein-1 (IRP-1)/cytosolic aconitase, a key player of the regulation of cellular iron homeostasis. This reparation occurs via Fe-S cluster transfer from mNT to IRP-1 to repair. In the course of my thesis, I focused on the characterization of cluster transfer reaction from mNT to a model receptor protein, the E. coli apo-ferredoxin. Using purified proteins and combining biochemical approaches with biophysical ones performed in colaboration, this study showed that mNT acts as a redox switch: when the Fe-S cluster is reduced, the protein is extremely stable and it cannot be lost or transferred; when it is oxidized, it can be transferred to a receptor protein. Dioxygen does not affect this transfer reaction whereas this is a major determinant of protein stability. The transfer speed is highly sensitive to pH. Thus, mNT seems to act also as a pH sensor. Moreover, this study shows that mNT is extremely resistant to H2O2 compared to other Fe-S cluster transfer proteins. I also looked at the interaction of an antioxidant molecule, the resveratrol-3-sulfate, with mNT. Finally, I studied the effects of glutathione on mNT. Major player of the regulation of redox homeostasis, glutathione exists under two states: a reduced state (GSH) and an oxidized one (GSSG). I observed that GSH strongly destabilizes mNT at specific pHs and can even directly interact with the protein. The thiol function of GSH and the radical formation on this function are clearly involved in the mNT Fe-S destabilization.

The aim of the current study was to determine the organic iron (Fe) requirements of gilthead sea bream (Sparus aurata). A total number of four experiments have been carried out each one for 12 weeks, in order to address and extend the knowledge on nutritional issues and challenges related with the culture of the gilthead sea bream in the Greek aquaculture industry and therefore enhance the fish health status under intensive culture conditions. These experiments aimed to determine the optimum level of organic Fe supplemented in commercial type diets of sea bream, the comparison between an organic Fe form and two inorganic Fe forms added in the diet of the fish, the effect of supplemented organic Fe on sea bream species exposed to oxygen deprivation stressors related to poor aquaculture husbandry practices and finally the interaction of organic Fe in the diet of sea bream with various levels of other trace minerals (Zn, Cu). The parameters evaluated were the growth performance of the fish, the Fe concentration in three selected tissues (the spleen, the liver and the muscle), the haematological status of the fish (the haematocrit, the red blood cell count, and the haemoglobin) and both the humoral and cellular immunology of the fish (the antibacterial activity of serum and the respiratory burst respectively). 150 mg/Kg of added organic Fe appears to be the recommended level as well as the minimum amount on fish exposed to overstocking conditions. The comparison between the two inorganic Fe forms (Ferrous Sulphate and Ferrous Carbonate) added in the diets show no significant effect on the fish. While, the fish fed the diets with 150 mg/Kg organic Fe and Cu levels lower that 5 mg/Kg had higher Hb values.

This study focuses on investigating the effect of the electronic spin transition of iron on the elasticity of the candidate lower mantle ferropericlase (Mg,Fe)O. This may be relevant to our understanding of the seismic velocity structures of the Earth’s lower mantle. The elastic constants of (Mg₀.₉₂Fe₀.₀₈)O at high-spin (HS) state, low-spin (LS) state, and through the pressure-induced HS-to-LS transition has been measured using both Brillouin Light Scattering (BLS) and Impulsive Stimulated Scattering (ISS). There is a large pressure range in which c₁₁ and c₁₂ exhibit a softening, while c₄₄ does not register such an anomaly. Compared with previously published data of ferropericlase with similar compositions ([Marquardt et al., 2009b], BLS measurement of (Mg₀.₉Fe₀.₁)O and [Crowhurst et al., 2008], ISS measurement of (Mg₀.₉₄Fe₀.₀₆)O), this study provides more reliable elastic constants measurements by taking the advantage of simultaneous measurements on Vp and Vs using both BLS and ISS. Our results show that bulk sound velocity of ferropericlase has a large but smooth softening in the spin transition pressure region. The elastic constants of ferropericlase at the spin transition region and the LS state have been well studied in this thesis, and a relaxation behavior has also been observed in this study. Those two subjects are not well documented in literature. The temperature effect of the spin state transition and its consequential effect on mineral’s elastic properties have not been studied in this project, but further research on this subject will follow. However, even in the room temperature, our results don’t show sudden changes in seismic velocities. Moreover, current theoretical and experimental studies [Sturhahn et al., 2005, Tsuchiya et al., 2006, Lin et al., 2007] indicate that the spin transition takes place over an extended range of depth along an expected lower-mantle geotherm, where sudden changes in compressional and bulk sound velocity are not expected. / text

Finite element models are used frequently in both engineering and scientific research. While they can provide useful information as to the performance of materials, as length scales are decreased more sophisticated model descriptions are required. It is also important to develop methods by which existing models may be verified against experimental findings. The present study evaluates the ability of various finite element models to predict materials behaviour at length scales ranging from several microns to tens of nanometers. Considering this motivation, this thesis is provided in manuscript form with the bulk of material coming from two case studies. Following an overview of relevant literature in Chapter 2, Chapter 3 considers the nucleation of delta-zirconium hydrides in a Zircaloy-2 matrix. Zirconium hydrides are an important topic in the nuclear industry as they form a brittle phase which leads to delayed hydride cracking during reactor start-up and shut-down. Several FE models are used to compare present results with literature findings and illustrate the weaknesses of standard FE approaches. It is shown that standard continuum techniques do not sufficiently capture the interfacial effects of an inclusion-matrix system. By using nano-scale material descriptions, nucleation lattice strains are obtained which are in good agreement with previous experimental studies. The motivation for Chapter 4 stems from a recognized need to develop a method for modeling corrosion behaviour of materials. Corrosion is also an issue for reactor design and an ability to predict failure points is needed. Finite element models could be used for this purpose, provided model accuracy is verified first. In Chapter 4 a technique is developed which facilitates the extraction of sub-micron resolution strain data from correlation images obtained during in-situ tensile deformation. By comparing image correlation results with a crystal plasticity finite element code it is found that good agreement between the two exists. The method outlined is material independent and could be applied to most metallurgical studies. Chapter 5 reviews the findings of each case study and makes suggestions as to the direction of future research. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-09-30 16:05:52.934

In diesem Beitrag werden neben der detaillierten Betrachtung der Wandervorgänge von Lagerringen primär die Simulationsmethodik bezüglich elastischer Zwischenschichten sowie die Ergebnisse einer FE-Parameterstudie präsentiert. Der Fokus liegt dabei auf Wälzlageraußenringen von Radiallagern unter Punktlast.

Memoria (licenciado en ciencias jurídicas y sociales) / El objeto de estudio de la presente memoria es el análisis del principio de buena fe procesal de acuerdo a la normativa procesal nacional vigente, así como del artículo sexto del Proyecto de Código Procesal Civil, determinando los alcances que dicho concepto puede tener en nuestro ordenamiento y los posibles conflictos constitucionales que se pueden generar a través de su aplicación. En el primer capítulo se sientan las bases del tema, delimitando los usos de la palabra principio, las funciones que ellos cumplen en nuestro ordenamiento y su relación con el concepto de norma. Luego se distingue entre principios del proceso y del procedimiento con el objeto de encuadrar al principio de la buena fe en una u otra categoría. Lo anterior permite entrar de lleno al análisis del concepto de buena fe, realizado en el capítulo segundo, contraponiendo las principales posturas doctrinarias que buscan definirlo, para luego abordar los fundamentos que se han otorgado para incluirlo dentro del ordenamiento procesal. En el capítulo tercero se realiza un estudio pormenorizado de la consagración de la buena fe en materia procesal, abarcando tanto el Código de Procedimiento Civil, el Código del Trabajo y además la normativa incluida en el Proyecto de Código Procesal Civil. Considerado lo anterior es que, en el capítulo cuarto del presente trabajo, se analizan los conflictos que genera el concepto de buena fe y se otorgan lineamientos generales para posibles soluciones, ya sea vía doctrinaria o legislativa.