Дисертації: "Calcul in situ"

1

Dirand, Estelle. "Développement d'un système in situ à base de tâches pour un code de dynamique moléculaire classique adapté aux machines exaflopiques." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAM065/document.

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L’ère de l’exascale creusera encore plus l’écart entre la vitesse de génération des données de simulations et la vitesse d’écriture et de lecture pour analyser ces données en post-traitement. Le temps jusqu’à la découverte scientifique sera donc grandement impacté et de nouvelles techniques de traitement des données doivent être mises en place. Les méthodes in situ réduisent le besoin d’écrire des données en les analysant directement là où elles sont produites. Il existe plusieurs techniques, en exécutant les analyses sur les mêmes nœuds de calcul que la simulation (in situ), en utilisant des nœuds dédiés (in transit) ou en combinant les deux approches (hybride). La plupart des méthodes in situ traditionnelles ciblent les simulations qui ne sont pas capables de tirer profit du nombre croissant de cœurs par processeur mais elles n’ont pas été conçues pour les architectures many-cœurs qui émergent actuellement. La programmation à base de tâches est quant à elle en train de devenir un standard pour ces architectures mais peu de techniques in situ à base de tâches ont été développées.Cette thèse propose d’étudier l’intégration d’un système in situ à base de tâches pour un code de dynamique moléculaire conçu pour les supercalculateurs exaflopiques. Nous tirons profit des propriétés de composabilité de la programmation à base de tâches pour implanter l’architecture hybride TINS. Les workflows d’analyses sont représentés par des graphes de tâches qui peuvent à leur tour générer des tâches pour une exécution in situ ou in transit. L’exécution in situ est rendue possible grâce à une méthode innovante de helper core dynamique qui s’appuie sur le concept de vol de tâches pour entrelacer efficacement tâches de simulation et d’analyse avec un faible impact sur le temps de la simulation.TINS utilise l’ordonnanceur de vol de tâches d’Intel® TBB et est intégré dans ExaStamp, un code de dynamique moléculaire. De nombreuses expériences ont montrées que TINS est jusqu’à 40% plus rapide que des méthodes existantes de l’état de l’art. Des simulations de dynamique moléculaire sur des système de 2 milliards de particles sur 14,336 cœurs ont montré que TINS est capable d’exécuter des analyses complexes à haute fréquence avec un surcoût inférieur à 10%
The exascale era will widen the gap between data generation rate and the time to manage their output and analysis in a post-processing way, dramatically increasing the end-to-end time to scientific discovery and calling for a shift toward new data processing methods. The in situ paradigm proposes to analyze data while still resident in the supercomputer memory to reduce the need for data storage. Several techniques already exist, by executing simulation and analytics on the same nodes (in situ), by using dedicated nodes (in transit) or by combining the two approaches (hybrid). Most of the in situ techniques target simulations that are not able to fully benefit from the ever growing number of cores per processor but they are not designed for the emerging manycore processors.Task-based programming models on the other side are expected to become a standard for these architectures but few task-based in situ techniques have been developed so far. This thesis proposes to study the design and integration of a novel task-based in situ framework inside a task-based molecular dynamics code designed for exascale supercomputers. We take benefit from the composability properties of the task-based programming model to implement the TINS hybrid framework. Analytics workflows are expressed as graphs of tasks that can in turn generate children tasks to be executed in transit or interleaved with simulation tasks in situ. The in situ execution is performed thanks to an innovative dynamic helper core strategy that uses the work stealing concept to finely interleave simulation and analytics tasks inside a compute node with a low overhead on the simulation execution time.TINS uses the Intel® TBB work stealing scheduler and is integrated into ExaStamp, a task-based molecular dynamics code. Various experiments have shown that TINS is up to 40% faster than state-of-the-art in situ libraries. Molecular dynamics simulations of up to 2 billions particles on up to 14,336 cores have shown that TINS is able to execute complex analytics workflows at a high frequency with an overhead smaller than 10%

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Meyer, Lucas. "Deep Learning en Ligne pour la Simulation Numérique à Grande Échelle." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALM001.

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Nombreuses applications d’ingénieries et recherches scientifiques nécessitent la simulation fidèle de phénomènes complexes et dynamiques, transcrits mathématiquement en Équations aux Dérivées Partielles (EDP). Les solutions de ces EDP sont généralement approximées au moyen de solveurs qui effectuent des calculs intenses et génèrent des quantités importantes de données. Les applications requièrent rarement une unique simulation, mais plutôt un ensemble d’exécutions pour différents paramètres afin d’analyser la sensibilité du phénomène ou d’en trouver une configuration optimale. Ces larges ensembles de simulations sont limités par des temps de calcul importants et des capacités de stockage mémoire finies. La problématique du coût de calcul a jusqu’à présent encouragé le développement du calcul haute-performance (HPC) et de techniques de réductions de modèles. Récemment, le succès de l'apprentissage profond a poussé la communauté scientifique à considérer son usage pour accélérer ces ensembles de simulations. Cette thèse s'inscrit dans ce cadre en explorant tout d'abord deux techniques d’apprentissage pour la simulation numérique. La première propose d’utiliser une série de convolutions sur une hiérarchie de graphes pour reproduire le champ de vitesse d’un fluide tel que généré par le solveur à tout pas de temps de la simulation. La seconde hybride des algorithmes de régression avec des techniques classiques de réduction de modèles pour prédire les coefficients de toute nouvelle simulation dans une base réduite obtenue par analyse en composantes principales. Ces deux approches, comme la majorité de celles présentées dans la littérature, sont supervisées. Leur entraînement nécessite de générer a priori de nombreuses simulations. Elles souffrent donc du même problème qui a motivé leur développement : générer un jeu d’entraînement de simulations fidèles à grande échelle est laborieux. Nous proposons un cadre d’apprentissage générique pour l’entraînement de réseaux de neurones artificiels à partir de simulations générées à la volée tirant profit des ressources HPC. Les données sont produites en exécutant simultanément plusieurs instances d’un solveur pour différents paramètres. Le solveur peut lui-même être parallélisé sur plusieurs unités de calcul. Dès qu’un pas de temps est simulé, il est directement transmis pour effectuer l’apprentissage. Aucune donnée générée par le solveur n’est donc sauvegardée sur disque, évitant ainsi les coûteuses opérations d’écriture et de lecture et la nécessité de grands volumes de stockage. L’apprentissage se fait selon une distribution parallèle des données sur plusieurs GPUs. Comme il est désormais en ligne, cela crée un biais dans les données d’entraînement, comparativement à une situation classique où les données sont échantillonnées uniformément sur un ensemble de simulations disponibles a priori. Nous associons alors chaque GPU à une mémoire tampon en charge de mélanger les données produites. Ce formalisme a permis d’améliorer les capacités de généralisation de modèles issus de l’état de l’art, en les exposant à une diversité globale de données simulées plus riches qu’il n’aurait été faisable lors d’un entraînement classique. Des expériences montrent que l’implémentation de la mémoire tampon est cruciale pour garantir un entraînement de qualité à haut débit. Ce cadre d’apprentissage a permis d’entraîner un réseau à reproduire des simulations de diffusion thermique en moins de 2 heures sur 8TB de données générées et traitées in situ, améliorant ainsi les prédictions de 47% par rapport à un entraînement classique
Many engineering applications and scientific discoveries rely on faithful numerical simulations of complex phenomena. These phenomena are transcribed mathematically into Partial Differential Equation (PDE), whose solution is generally approximated by solvers that perform intensive computation and generate tremendous amounts of data. The applications rarely require only one simulation but rather a large ensemble of runs for different parameters to analyze the sensitivity of the phenomenon or to find an optimal configuration. Those large ensemble runs are limited by computation time and finite memory capacity. The high computational cost has led to the development of high-performance computing (HPC) and surrogate models. Recently, pushed by the success of deep learning in computer vision and natural language processing, the scientific community has considered its use to accelerate numerical simulations. The present thesis follows this approach by first presenting two techniques using machine learning for surrogate models. First, we propose to use a series of convolutions on hierarchical graphs to reproduce the velocity of fluids as generated by solvers at any time of the simulation. Second, we hybridize regression algorithms with classical reduced-order modeling techniques to identify the coefficients of any new simulation in a reduced basis computed by proper orthogonal decomposition. These two approaches, as the majority found in the literature, are supervised. Their training needs to generate a large number of simulations. Thus, they suffer the same problem that motivated their development in the first instance: generating many faithful simulations at scale is laborious. We propose a generic training framework for artificial neural networks that generate data simulations on-the-fly by leveraging HPC resources. Data are produced by running simultaneously several instances of the solver for different parameters. The solver itself can be parallelized over several processing units. As soon as a time step is computed by any simulation, it is streamed for training. No data is ever written on disk, thus overcoming slow input-output operations and alleviating the memory footprint. Training is performed by several GPUs with distributed data-parallelism. Because the training is now online, it induces a bias in the data compared to classical training, for which they are sampled uniformly from an ensemble of simulations available a priori. To mitigate this bias, each GPU is associated with a memory buffer in charge of mixing the incoming simulation data. This framework has improved the generalization capabilities of state-of-the-art architectures by exposing them during training to a richer diversity of data than would have been feasible with classical training. Experiments show the importance of the memory buffer implementation in guaranteeing generalization capabilities and high throughput training. The framework has been used to train a deep surrogate for heat diffusion simulation in less than 2 hours on 8TB of data processed in situ, thus increasing the prediction accuracy by 47% compared to a classical setting

3

Ali, Hassan. "Caractérisation améliorée des sols par l'essai de chargement de pointe au piézocone. Application au calcul des fondations profondes." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2010. http://tel.archives-ouvertes.fr/tel-00629642.

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L'essai de chargement d'une pointe pénétrométrique (Cone Loading Test, essai CLT) est un nouvel essai de reconnaissance des sols in situ, qui constitue une amélioration majeure de l'essai de pénétration statique avec une pointe piézocône (CPTu). L'essai de chargement de pointe consiste à interrompre la pénétration classique (EN ISO 22476-1) à une cote souhaitée et à réaliser un chargement par paliers successifs de la pointe jusqu'à la rupture du sol.La courbe de chargement, reliant la pression appliquée sur la pointe au tassement de celle-ci,est riche en renseignements sur la déformabilité des sols. L'essai permet donc une caractérisation améliorée des sols en fournissant des paramètres de déformabilité aussi bien que les paramètres de résistance obtenus lors d'un essai de pénétration statique classique.La validation de la méthode d'essai et de son protocole expérimental, a été effectuée selon trois voies complémentaires : expérimentale, numérique et physique. Au niveau expérimental, plusieurs campagnes d'essais ont été réalisées en choisissant des sites intéressants pour le projet et contenants une importante base de données (essais in situ,au laboratoire, essais de pieux, essais sismiques...) comme le site des argiles des Flandres de Merville, un site sableux à Utrecht aux Pays-Bas, et un site sableux à Limelette en Belgique.Les résultats des différentes campagnes ont montré qu'il est possible d'avoir des courbes de chargement exploitables pour le calcul d'un module de déformation, utilisable et comparable en tout point aux modules obtenus par d'autres types d'essais. L'essai est adapté à un panel de sol très varié. Il est plus représentatif de l'état initial dans le sol que d'autres types d'essais.Par ailleurs les conditions aux limites sont bien maîtrisées.Au niveau numérique, une large étude paramétrique a été menée avec le logiciel Plaxis, pour tester l'influence de la géométrie de la pointe, du type de chargement, du modèle de comportement, des paramètres du sol, ainsi que des conditions initiales et au limite du problème. Des essais CLT ont été également réalisés sur des modèles réduits en centrifugeuse, pour tester l'influence de quelques paramètres comme la vitesse de chargement, la géométrie de l'embout de la pointe, la densité du massif ainsi que le niveau de g. Ces essais ont été associés à des essais de chargement de pieu instrumenté et des essais de fondations superficielles et profondes afin de pouvoir relier les paramètres mécaniques de l'essai CLT au comportement des ouvrages. En considérant que la pointe du pénétromètre est un modèle réduit de pieu, une retombée directe de l'essai CLT est sa capacité d'être un outil de dimensionnement de fondations. A cet effet, une méthode directe utilisant la résistance de pointe et le frottement latéral limite de l'essai CLT a été proposée pour calculer la capacité portante et prédire le tassement d'un pieu.Cette méthode consiste en une nouvelle approche transformant les courbes de chargement et celles de mobilisation de frottement d'un essai CLT point par point en courbe charge-déplacement d'un pieu (courbes t-z).

4

Ricard, Nadine. "Estimation de teneurs en minéraux industriels par analyse d'images "in situ" : application au gisement d'andalousites de Glomel (Côtes d'Armor)." Montpellier 2, 1995. http://www.theses.fr/1995MON20035.

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L'objectif de cette these est de mettre au point une nouvelle methode de dosage et de reconnaissance de l'andalousite de glomel (cotes d'armor). Apres une presentation de la carriere d'andalousites de glomel, nous abordons les deux phases essentielles de cette methode: l'estimation de la teneur en andalousites sur une image par analyse d'images et l'estimation de la teneur d'un front a l'aide de la geostatistique. Une derniere partie degage les caracteristiques de cette methode par rapport a celle traditionnellement employee

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Thébault, Simon Romain. "Contribution à l'évaluation in situ des performances d'isolation thermique de l'enveloppe des bâtiments." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI008/document.

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Dans un contexte d’économie d’énergie et de réduction des émissions de gaz à effet de serre, de nombreux efforts ont été réalisés en France pour renforcer l’isolation de l’enveloppe des bâtiments afin de contribuer à réduire les consommations de chauffage. Toutefois, il arrive souvent que la performance thermique calculée avant construction ou rénovation ne soit pas atteinte sur le terrain (erreur de calcul, défauts de mise en œuvre, etc.). Or, pour pouvoir généraliser la construction de bâtiments à basse consommation et la rénovation, il faut pouvoir garantir aux maîtres d'ouvrage une performance réelle de leur bâtiment après travaux. Le fait de mesurer in situ la performance intrinsèque d'isolation thermique de l'enveloppe permet de contribuer à cette garantie. Il existe à l’échelle internationale de nombreuses méthodes basées sur le suivi des consommations et des conditions thermiques intérieures et extérieures. Certaines ont déjà fait leurs preuves sur le terrain, mais sont souvent soit contraignantes, soit peu précises. Et surtout, les calculs d’incertitude associés sont souvent rudimentaires. L’objectif de ce travail financé par le CSTB est de consolider scientifiquement une nouvelle méthode de mesure de la qualité d’isolation globale d’un bâtiment à réception des travaux (méthode ISABELE). Dans le premier chapitre, un état de l'art sur les méthodes existantes a été réalisé afin de dégager des pistes d'amélioration sur la base d'une synthèse comparative. La piste prioritaire identifiée porte sur le calcul d'incertitude (un point central du problème). La propagation des erreurs aléatoires par un approche bayésienne ainsi que des erreurs systématiques par une approche plus classique feront l'objet de la méthodologie globale proposée dans le second chapitre. L'une des importantes sources d'incertitude porte sur l'évaluation du débit d'infiltration. La caractérisation de cette incertitude et de l'impact sur le résultat de mesure fera l'objet du troisième chapitre, avec un comparatif de différentes approches expérimentales (règle du pouce, modèles aérauliques, gaz traceur). Enfin, une amélioration de la prise en compte de la dynamique thermique du bâtiment au cours du test sera proposée dans le dernier chapitre. Son fondement repose sur l'adaptation du modèle thermique inverse en fonction du bâtiment et des conditions du test. Pour cela, une sélection parmi une banque de modèles simplifiés est réalisée sur la base de critères statistiques et du principe de parcimonie. Ces différentes dispositions ont été testés sur une large série de mesures menées sur un même bâtiment à ossature bois (chalet OPTIMOB). La robustesse et la précision du résultat de mesure ont ainsi pu être légèrement améliorées. La méthode de calcul du débit d'infiltration, ni trop simple ni trop complexe, a pu également être validée. Enfin, le temps de mesure minimal nécessaire a pu être déterminé en fonction de la classe d'inertie du bâtiment
The global context of energy savings and greenhouse gases emissions control led to significant efforts in France to boost the thermal insulation in buildings in order to reduce heating consumption. Nevertheless, the stated thermal performance before construction or refurbishment is rarely achieved in practice, for many reasons (calculation errors, defects in materials or workmanship, etc.). Yet, guaranteeing the real thermal performance of buildings on the spot is crucial to enhance the refurbishment market and the construction of energy efficient buildings. To do so, measurement techniques of the intrinsinc thermal insulation performance indicators are needed. Such techniques already exist worldwide, and consist in processing the measurement data from the indoor and outdoor thermal conditions and the heat consumption. Some of them have already proved themselves in the field, but are either binding or very imprecise. And above all, the related uncertainty calculations are often rough. The objective of this thesis funded by CSTB is to consolidate a novel measurement method of the thermal insulation quality of a whole building after reception of work (ISABELE method). In the first chapter, a state of the art of the existing methods allows to identify possible ways to pursue this goal from a comparative synthesis. The primary reflection is about the uncertainty calculation method (which is a central issue). The second chapter presents a global methodology to combine the propagation of random and systematic errors from bayesian and classical approaches. One of the most important uncertainty sources deals with the infiltration air flow evaluation during the test. The third chapter investigates the characterization of this uncertainty, as well as its impact on the final result, depending on the chosen experimental approach (rule of thumb, simplified aeraulic models, tracer gases). Lastly, an improvement of the inclusion of the bluiding thermal dynamics during the test will be proposed in the last chapter. The basis of this improvement is to adapt the inverse model according to the building type and the test conditions. To do so, the proposed algorithm selects a model form a variety of simplified greybox models based on statistical criteria and parcimony. All these contributions have been tested on a large serie of measurements on a same timber-framed building (OPTIMOB shed). The robustness and precision of the results have been slightly improved. The intial infiltration air flow calculation, neither too simple of too complicated, has also been validated. Finaly, a better ordrer of magnitude of the minimal test duration has been determined, depending on the building inertia

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Honore, Valentin. "Convergence HPC - Big Data : Gestion de différentes catégories d'applications sur des infrastructures HPC." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0145.

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Le calcul haute performance est un domaine scientifique dans lequel de très complexes et intensifs calculs sont réalisés sur des infrastructures de calcul à très large échelle appelées supercalculateurs. Leur puissance calculatoire phénoménale permet aux supercalculateurs de générer un flot de données gigantesque qu'il est aujourd'hui difficile d'appréhender, que ce soit d'un point de vue du stockage en mémoire que de l'extraction des résultats les plus importants pour les applications.Nous assistons depuis quelques années à une convergence entre le calcul haute performance et des domaines tels que le BigData ou l'intelligence artificielle qui voient leurs besoins en terme de capacité de calcul exploser. Dans le cadre de cette convergence, une grande diversité d'applications doit être traitée par les ordonnanceurs des supercalculateurs, provenant d'utilisateurs de différents horizons pour qui il n'est pas toujours aisé de comprendre le fonctionnement de ces infrastructures pour le calcul distribué.Dans cette thèse, nous exposons des solutions d'ordonnancement et de partitionnement de ressources pour résoudre ces problématiques. Pour ce faire, nous proposons une approche basée sur des modèles mathématiques qui permet d'obtenir des solutions avec de fortes garanties théoriques de leu performance. Dans ce manuscrit, nous nous focalisons sur deux catégories d'applications qui s'inscrivent en droite ligne avec la convergence entre le calcul haute performance et le BigData:les applications intensives en données et les applications à temps d'exécution stochastique.Les applications intensives en données représentent les applications typiques du domaine du calcul haute performance. Dans cette thèse, nous proposons d'optimiser cette catégorie d'applications exécutées sur des supercalculateurs en exposant des méthodes automatiques de partitionnement de ressources ainsi que des algorithmes d'ordonnancement pour les différentes phases de ces applications. Pour ce faire, nous utilisons le paradigme in situ, devenu à ce jour une référence pour ces applications. De nombreux travaux se sont attachés à proposer des solutions logicielles pour mettre en pratique ce paradigme pour les applications. Néanmoins, peu de travaux ont étudié comment efficacement partager les ressources de calcul les différentes phases des applications afin d'optimiser leur temps d'exécution.Les applications stochastiques constituent la deuxième catégorie d'applications que nous étudions dans cette thèse. Ces applications ont un profil différent de celles de la première partie de ce manuscrit. En effet, contrairement aux applications de simulation numérique, ces applications présentent de fortes variations de leur temps d'exécution en fonction des caractéristiques du jeu de données fourni en entrée. Cela est dû à leur structure interne composée d'une succession de fonctions, qui diffère des blocs de code massifs composant les applications intensive en données.L'incertitude autour de leur temps d'exécution est une contrainte très forte pour lancer ces applications sur les supercalculateurs. En effet, l'utilisateur doit réserver des ressources de calcul pour une durée qu'il ne connait pas. Dans cette thèse, nous proposons une approche novatrice pour aider les utilisateurs à déterminer une séquence de réservations optimale qui minimise l'espérance du coût total de toutes les réservations. Ces solutions sont par la suite étendues à un modèle d'applications avec points de sauvegarde à la fin de (certaines) réservations afin d'éviter de perdre le travail réalisé lors des réservations trop courtes. Enfin, nous proposons un profiling d'une application stochastique issue du domaine des neurosciences afin de mieux comprendre les propriétés de sa stochasticité. A travers cette étude, nous montrons qu'il est fondamental de bien connaître les caractéristiques des applications pour qui souhaite élaborer des stratégies efficaces du point de vue de l'utilisateur
Numerical simulations are complex programs that allow scientists to solve, simulate and model complex phenomena. High Performance Computing (HPC) is the domain in which these complex and heavy computations are performed on large-scale computers, also called supercomputers.Nowadays, most scientific fields need supercomputers to undertake their research. It is the case of cosmology, physics, biology or chemistry. Recently, we observe a convergence between Big Data/Machine Learning and HPC. Applications coming from these emerging fields (for example, using Deep Learning framework) are becoming highly compute-intensive. Hence, HPC facilities have emerged as an appropriate solution to run such applications. From the large variety of existing applications has risen a necessity for all supercomputers: they mustbe generic and compatible with all kinds of applications. Actually, computing nodes also have a wide range of variety, going from CPU to GPU with specific nodes designed to perform dedicated computations. Each category of node is designed to perform very fast operations of a given type (for example vector or matrix computation).Supercomputers are used in a competitive environment. Indeed, multiple users simultaneously connect and request a set of computing resources to run their applications. This competition for resources is managed by the machine itself via a specific program called scheduler. This program reviews, assigns andmaps the different user requests. Each user asks for (that is, pay for the use of) access to the resources ofthe supercomputer in order to run his application. The user is granted access to some resources for a limited amount of time. This means that the users need to estimate how many compute nodes they want to request and for how long, which is often difficult to decide.In this thesis, we provide solutions and strategies to tackle these issues. We propose mathematical models, scheduling algorithms, and resource partitioning strategies in order to optimize high-throughput applications running on supercomputers. In this work, we focus on two types of applications in the context of the convergence HPC/Big Data: data-intensive and irregular (orstochastic) applications.Data-intensive applications represent typical HPC frameworks. These applications are made up oftwo main components. The first one is called simulation, a very compute-intensive code that generates a tremendous amount of data by simulating a physical or biological phenomenon. The second component is called analytics, during which sub-routines post-process the simulation output to extract,generate and save the final result of the application. We propose to optimize these applications by designing automatic resource partitioning and scheduling strategies for both of its components.To do so, we use the well-known in situ paradigm that consists in scheduling both components together in order to reduce the huge cost of saving all simulation data on disks. We propose automatic resource partitioning models and scheduling heuristics to improve overall performance of in situ applications.Stochastic applications are applications for which the execution time depends on its input, while inusual data-intensive applications the makespan of simulation and analytics are not affected by such parameters. Stochastic jobs originate from Big Data or Machine Learning workloads, whose performanceis highly dependent on the characteristics of input data. These applications have recently appeared onHPC platforms. However, the uncertainty of their execution time remains a strong limitation when using supercomputers. Indeed, the user needs to estimate how long his job will have to be executed by the machine, and enters this estimation as his first reservation value. But if the job does not complete successfully within this first reservation, the user will have to resubmit the job, this time requiring a longer reservation

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Brunet, Laurence. "Repartition spatiale de la densite electronique moleculaire en composantes atomiques in situ." Paris 6, 1987. http://www.theses.fr/1987PA066042.

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Modelisation originale de la densite electronique moleculaire par la superposition de densites atomiques spheriques, centrees sur les noyaux a partir de calculs d'orbitales moleculaires, avec trois invariants : la charge totale, le potentiel electrons-noyaux, le moment dipolaire. Description de la methode numerique pour determiner les densites associes aux atomes dans une base d'orbitales gaussiennes. Renseignements obtenus sur les modifications spatiales de la charge electronique par formation de liaisons, sur les facteurs de structure atomiques effectifs, apres transformation de fourier, en tenant compte de l'effet de l'environnement. Extension de la methode a la decomposition de la densite electronique moleculaire en densites composantes, autres qu'atomiques et non necessairement centrees sur les noyaux. Outre les applications a l'etude de la structure et des proprietes electroniques des molecules, proposition d'utilisation au calcul des polarisabilites optiques (lineaires ou non), a l'analyse des donnees cristallographiques obtenues par diffraction de rayon x et a la prevision de la structure des cristaux moleculaires

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Corfdir, Alain. "Analyse de la stabilité d'ouvrages en gabions cellulaires par la théorie du calcul à la rupture." Phd thesis, Marne-la-vallée, ENPC, 1997. http://www.theses.fr/1997ENPC9704.

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Les gabions cellulaires sont constitués d'une enceinte de palplanches métalliques remplies d'un remblai frottant. Ils sont utilisés dans des sites portuaires ou fluviaux comme soutènements ou comme batardeaux. Bien qu'utilisés depuis plus de 80 ans, leur fonctionnement mécanique n'est qu'imparfaitement compris et des accidents surviennent encore, y compris en cours de construction. L'emploi des méthodes fondées sur la théorie du calcul à la rupture peut contribuer à fonder le dimensionnement de ces ouvrages sur des bases rigoureuses. Le calcul à la rupture des gabions cellulaires présente plusieurs particularités : géométrie authentiquement tridimensionnelle, modélisation mixte des éléments constitutifs (enceinte de palplanches modélisées comme une coque, matériau de remblai modélisé comme un milieu continu 3D). Les travaux antérieurs utilisant le calcul à la rupture ont toujours considéré des cinématiques dans lesquelles les palplanches restaient droites. La modélisation coque des palplanches permet notamment d'envisager des cinématiques avec des déformations en flexion des palplanches ce qui correspond à certaines observations d'accidents ou de modèles réduits à grande échelle. Donnons maintenant le plan général de ce mémoire. Un premier chapitre introductif rappelle la constitution des gabions et des gabionnades, leurs utilisations et leurs méthodes de dimensionnement. Le chapitre 2 donne les bases de la modélisation des gabions que nous utiliserons dans la suite. Les chapitres 3, 4, 5 et 6, appliquent les méthodes statiques et cinématique au gabion isolé et à la gabionnade. Le chapitre 7 est consacré à la comparaison des résultats avec des données de différents types : mesures in situ, cas d'accident, essais sur modèles réduits
Cellular cofferdams are constituted by a shell of steel sheetpiles filled with sand or gravel backfill. They are used in harbour or fluvial locations as earth or water retaining structures. Although they have been in use for more than 80 years, their mechanical behaviour is still poorly understood and accidents still occur even during construction. The use of design methods based on yield design theory can contribute to found the design of cellular cofferdams on rigorous bases. The yield design of cellular cofferdams has some particular characteristics : true 3-dimentional geometry, mixed modelling of the structure (the sheetpiles are modelled as a shell, the backfill as a 3-dimensional ontinuous media). Modelling sheetpiles as a shell makes it possible to consider kinematic fields with flexure strain of the sheetpiles. Flexures strain has been observed on some accidents and some model tests. The present work opens with an introductory chapter dealing with the construction of cellular cofferdams, their applications and design methods. Chapter 2 deals with the modelling of cellular cofferdams. Chapters 3, 4, 5 and 6 deal with the application of static and kinematic methods to a single cofferdam cell and to cellular cofferdams. In chapter 7, the results are compared to data from different sources : filed measurements, case of accident, model tests

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Aifaoui, Nizar. "Intégration CAO-Calcul : une approche par les features de calcul." Valenciennes, 2003. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/98068c03-3ddc-4cd1-89d0-d3ed317dff1c.

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Les travaux de recherche ont eu lieu entre le LAMIH, équipe Systèmes de Production de l'UVHC et LGM de l'ENIM de Tunisie sous la co-direction des professeurs René SOENEN et Abdelwaheb DOGUI. L'objectif de notre travail est de contribuer à l'intégration des tâches de l'analyse mécanique dans les phases amont de la conception. Nous proposons une approche permettant d'assister et de guider le concepteur dans la démarche de modélisation et de résolution de problèmes de calcul typiques couramment rencontrés en conception. Cette approche est basée sur le concept original de feature de calcul. Ce concept a été émergé à la lumière d'une analyse expérimentale des processus de conception-calcul de plusieurs cas concrets de conception, choisis pour leur complémentarité et leur représentativité. Des classes de features caractérisant les problèmes de calcul rencontrés dans les domaines de modélisation de produit les plus concernés par le calcul ont été proposées. Ensuite, un catalogue de features, inspiré des problèmes de calcul rencontrés dans l'étude expérimentale a été développé. Ce catalogue englobe une liste non exhaustive de features de calcul particulières. Nos propositions incluent les diagrammes de classes UML du catalogue, ainsi que les processus de sélection et d'instanciation des features à partir du catalogue. Dans ces travaux, les avantages et les limites de l'approche proposée sont mis en évidence suite à une validation expérimentale du concept de feature de calcul sur des cas de conception
This research work is the result of the cooperation between the LAMIH-SP of the UVHC and the LGM of the ENIM of Tunisia and is guided by professor René SOENEN and professor Abdelwaheb DOGUI. The goal of the work is to contribute to a better integration of mechanical analysis tasks in the early design process. We present intended to aid and to guide the designer in the modeling and in the resolution of typical mechanical analysis problems, which are usually encountered in design processes. This approach is based on the original concept of Analysis Feature. This concept emerged on the basis of an experimental study of the design-analysis processes of several real design cases, which were chosen for their complementarity and their representativity. The classes of features characterizing the analysis problems encountered in two product modeling levels, which are the most concerned by analysis tasks, have been proposed. Then, a catalogue of particular features, inspired from the analysis problems encountered in the experimental study, has been developed. This catalogue includes a set of particular analysis features. Our proposals include the UML class diagram of the catalogue and the processes for the selection and the instanciation of catalogue features. In this work, the advantages and the limits of our approach are identified using an experimental validation of the concept of analysis feature based on a real design cases

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Silva, Kélio Garcia [UNESP]. "Avaliação in situ da capacidade remineralizadora de selantes que contenham fosfato de cálcio amorfo e/ou fluoreto." Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/104232.

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Made available in DSpace on 2014-06-11T19:33:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-20Bitstream added on 2014-06-13T21:05:39Z : No. of bitstreams: 1 silva_kg_dr_araca.pdf: 1119234 bytes, checksum: 5618d5d8828102cf1192a2ce0a173ef5 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O objetivo desse estudo foi avaliar in situ o potencial remineralizador de selantes que contenham fosfato de cálcio amorfo e/ou fluoreto com lesão artificial de cárie em esmalte de superfície lisa. Dez voluntários participaram desse estudo triplo cego com duração de 5 dias para cada grupo (esmalte desmineralizado + Fluroshield, esmalte desmineralizado + Aegis (ACP), esmalte desmineralizado + Fluoreto (experimental), esmalte desmineralizado + ACP + Fluoreto (experimental) e esmalte desmineralizado – Controle) e intervalo de 7 dias entre eles. Dez dias antes do início e durante todo o experimento os voluntários utilizaram dentifrício não fluoretado. Após o período experimental, foram avaliadas a porcentagem de recuperação de microdureza de superfície (%MDS), recuperação da área mineral integrada (_Z) e determinada a concentração de fluoreto (μg F/mm3), cálcio (μg Ca/mm3) e fósforo (μg P/mm3) presentes no esmalte. Os dados obtidos da %MDS e _Z foram submetidos à Análise de Variância seguida do teste de Tukey, e os do fluoreto, cálcio e fósforo foram submetidos ao teste de Kruskal-Wallis (p<0,05). Todas as variáveis foram submetidas à análise de regressão e ajustadas de acordo com a tendência. Os grupos de materiais com fluoreto e/ou ACP apresentaram maior capacidade remineralizadora (%MDS e _Z) quando comparado com o grupo Controle. O grupo com apenas ACP apresentou resultado melhor ou semelhante quando comparado com os outros grupos e a associação do ACP e fluoreto não mostrou ser mais eficiente. A lesão de cárie mostrou-se mais remineralizada na distância de 150 ìm quando comparada com a de 600 ìm para os valores de %MDS. As concentrações de fluoreto, cálcio e fósforo presentes no esmalte variaram de acordo com o grupo analisado. Entre as variáveis avaliadas, somente foi verificada correlação entre %MDS e _Z.
The purpose of this study was to evaluate in situ the remineralizing potential of sealants containing amorphous calcium phosphate and/or fluoride in artificially induced carious lesions on smooth enamel surfaces. Ten volunteers took part in this triple-blind study, which had the duration of 5 days for each group: demineralized enamel + Fluroshield; demineralized enamel + Aegis (ACP); demineralized enamel + Fluoride (experimental); demineralized enamel + ACP + Fluoride (experimental) and demineralized enamel (Control). A wash-out period of 7 days was allowed between the treatments. Ten days before and during the whole experiment the volunteers used a non-fluoridated dentifrice. After the experimental period, the percentage recovery of surface microhardness (%RSM) and the recovery of integrated mineral area (HZ) were evaluated. The concentration of fluoride (Jg F/mm3), calcium (Jg Ca/mm3) and phosphorous (Jg P/mm3) present in enamel was also determined. Data obtained from %RSM and HZ were submitted to Analysis of Variance and Tukey’s test. Data from fluoride, calcium and phosphorous concentration were submitted to Kruskal-Wallis test. Significance level was set at 5%. All variables were also evaluated by regression analysis and adjusted according to the tendency. The groups with materials containing fluoride and/or ACP presented a higher remineralizing capacity (%RSM and HZ) than the Control group. The group with material containing only ACP showed a better or similar result compared to the other groups. The association between ACP and fluoride did not show a greater efficacy. For %RSM, the 150-Jm distance showed a higher remineralization of the artificially induced carious lesions compared to the 600-Jm distance. The concentrations of fluoride, calcium and phosphorous present in enamel varied according to the group.

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Mahdavi, Chahrokh. "Analyse probabiliste du comportement des sols et des ouvrages. Evaluation des risques dans les études géotechniques de traces de remblais sur sols mous." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1985. http://tel.archives-ouvertes.fr/tel-00523281.

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Lors des études de tracés routiers ou autoroutiers dans les zones de sols compressibles, la reconnaissance géotechnique des sols utilise différentes techniques de sondage, de prélèvement d'échantillons de sol intact ou remanié, d'essais en place et d'essais en laboratoire. Ces sondages et essais sont répartis régulièrement le long du tracé envisagé, mais ils ne concernent qu'une fraction minime du sol qui aura à supporter le remblai, de sorte qu'il existe une certaine incertitude sur les propriétés réelles de ces sols. Cette incertitude sur les propriétés mécaniques des sols se traduit par une incertitude sur la représentativité des résultats des calculs réalisés lors de l'élaboration du projet. Le travail réalisé dans le cadre de cette thèse porte sur le traitement quantitatif de cette incertitude dans le cas des calculs de stabilité à court terme des remblais sur sols mous. Le traitement de l'incertitude sur les propriétés de résistance au cisaillement non drainé des sols mous a été effectué en suivant la démarche habituelle des ingénieurs chargés d'élaborer de tels projets : - définition de couches homogènes du point de vue de la nature et des principes généraux de comportement des sols, - utilisation éventuelle de corrélations pour compléter les données directement utilisables pour les calculs, - définition de valeurs "représentatives" des différents paramètres nécessaires au dimensionnement. A partir de cette étape de l'étude, on passe à un traitement de type probabiliste, afin de déterminer l'incertitude sur la valeur estimée du coefficient de sécurité le long du tracé et de calculer des probabilités de rupture. L'analyse des résultats de la reconnaissance géotechnique a été effectuée en utilisant les méthodes de géostatistique. Tous les traitements effectués sur les données sont représentés sur l'écran d'une console de visualisation interactive, qui sert également à transmettre à la chaîne de traitement les instructions qui lui sont nécessaires. L'estimation des valeurs des paramètres mécaniques du sol entre les sondages de reconnaissance est effectuée au moyen du programme Bluepack de l'E.N.S.Mines de Paris. Pour le calcul de la stabilité du remblai, on a utilisé un schéma de calcul en rupture circulaire, en analysant la stabilité de blocs de sol cylindriques et de longueur limitée. Le calcul de la loi de probabilité des valeurs du coefficient de sécurité, dont on déduira la probabilité de rupture, est effectué par la méthode de Monte Carlo. La méthode développée dans le cadre de cette thèse a été appliquée à l'analyse de la stabilité d'un long remblai sur sols mous dont la construction a été étudiée dans le sud-ouest de la France. L'étude permet de retrouver par le calcul un résultat bien connu, qui est qu'il existe une longueur critique vis à vis de la stabilité du remblai, et de prévoir la position de cette zone le long du tracé. La méthode d'étude ainsi développée constitue une première étape dans la résolution de ce problème complexe de la prévision des risques de rupture sur les tracés de remblais sur sols mous, compte tenu du volume limité des reconnaissances qu'il est possible d'effectuer en pratique.

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Lamara, Hakim. "Arithmétique floue phi-calcul : applications à la classification et à la commande." Valenciennes, 2007. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/e0b34e62-5b3a-4313-872d-e7bb535ff619.

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Cette thèse propose une arithmétique pratique de calcul d’intervalles et quantités floues. Ces derniers sont modélisés, non pas par leurs fonctions d’appartenance classiques, mais par une fonction de répartition cumulée inspirée des statistiques. Cette proposition se veut innovante et pratique pour traiter des données imprécises et incertaines avec l’introduction de quelques idées dans ce sens. Cette approche n’a pas évidement pour objectif de remettre en cause un certain nombre de méthodes existantes dans la littérature, mais offre une autre manière de raisonner et de résoudre certaines problématiques avec une implémentation et modélisation plus simples. La proximité de cette méthode avec les probabilités et les statistiques classiques a conduit à mettre un accent sur des applications d’analyse de données imprécises, et à une extension des outils statistiques. Néanmoins, une arithmétique assez riche et cohérente basée sur les techniques de la logique floue et du calcul par intervalles a été proposée. De nombreux exemples didactiques sont présentés au cours de ce travail pour faciliter la compréhension de notre démarche. Le but de ce mémoire est de démontrer dans un premier temps la faisabilité et l’applicabilité de nos propositions. Les résultats des applications, que ce soit en analyse de données objectives et subjectives, ou bien en commande à modèle interne des systèmes non linéaires (avec notamment une application en temps réel sur un système non linéaire et imprécis), montrent l’intérêt du f-calcul. D’autres développements mathématiques et extensions aux autres domaines laissent augurer des perspectives intéressantes dans un futur proche
The presented Ph. D. Thesis proposes a practical arithmetic to calculate fuzzy intervals and quantities. The latter are modelled by an accumulative distribution function based on classical statistics instead of classical membership functions. This innovative work effectively deals with imprecise data and uncertainties by exploiting some ideas in the direction described above. Existing methods found in the specialized literature are not disregarded, though this thesis intends to present another way of reasoning and solving certain problems with a simpler implementation. Since the proposed method is close to probability and classical statistics, it has lead –at a first stage-to stressing the analysis of imprecise data as well as to extend the statistical tools. Nevertheless, a complete and coherent arithmetic based on fuzzy logic techniques and interval analysis has been proposed. A number of illustrative examples have been presented through this work to facilitate the understanding of our approach. The thesis’ objective is to show the feasibility and applicability of our claims. Results obtained in applications, both on the analysis of objective-subjective data and on the internal nonlinear model control (with special emphasis on a real-time application for a non-linear imprecise system) have proved the effectiveness of j-calculus. Other mathematical developments and extensions to other areas suggest that interesting perspectives in the future will arrive

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Michaels, Christopher. "Evidence based ex situ husbandry for captive amphibians." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/evidence-based-ex-situ-husbandry-for-captive-amphibians(54a41c4e-a6cb-471c-8c16-ef012f61cd35).html.

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Amphibians are declining worldwide in response to pressures that are too numerous, difficult and rapid to ameliorate in the wild before some taxa become extinct. Ex situ conservation, whereby animals are maintained in captivity until threats in the wild have been resolved, is the only means of saving up to five hundred amphibian species. Amongst political, financial and practical hurdles, the most fundamental problem for these programmes is lack of knowledge about how to maintain species successfully in captivity. Captive populations have failed to survive or reproduce and, furthermore, captive husbandry may produce animals unsuitable for reintroduction through intra or inter-generational changes. These problems entirely undermine initiatives and if ex situ programs are to succeed, evidence based captive husbandry is needed to support captive breeding programs. In this thesis, I quantify our ignorance of amphibian requirements in captivity. Furthermore, I present investigations into fundamental areas ofamphibian husbandry, about which we currently know very little. I investigate the relationship between amphibians and Ultraviolet B (UVB) radiation and examine the relationship between UVB provision and calcium provision and evaluate routes of dietary calcium supplementation. I also present data on the effects of enrichment and rearing environment on the growth, fitness, behaviour and dermal bacterial communities of captive amphibians. These results, from a range of areas of amphibian husbandry, together demonstrate the power of the captive environment to influence the phenotype and therefore the fitness of amphibians, even within single generations. Additionally, I provide some of the first data addressing key areas of amphibian husbandry that until now have been led mostly or entirely by anecdote and hearsay.

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Ben, Amara Abdelmejid. "Contribution à l'intégration de la composante calcul dans une démarche de conception fonctionnelle intégrée." Valenciennes, 1998. https://ged.uphf.fr/nuxeo/site/esupversions/b7fe1d63-64fe-46b1-9e20-5f9d5d6d372d.

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La conception mécanique assistée par ordinateur est un processus complexe unissant différentes activités. L’intégration de ces activités est nécessaire pour satisfaire aux exigences actuelles de l'ingénierie (simultanée, concourante, communicante). Ce besoin est confronté à des problèmes de modélisation, de structuration de données et de communication interprocessus. Dans ce mémoire, nous nous intéressons à l'intégration CAO/calcul. Nous présentons une approche originale permettant d'intégrer ces activités à différents niveaux du processus de conception mécanique. Nous présentons dans le premier chapitre une étude des différentes étapes de conception des produits mécaniques, afin d'identifier les techniques, méthodes et modèles de calcul utilises dans chacune de ces étapes. Nous analysons dans le deuxième chapitre le problème de l'intégration CAO/calcul. Nous commençons par la définition des exigences de l'intégration des fonctions et des outils relatifs à ces deux domaines. Nous présentons ensuite un état de l'art permettant d'identifier les facteurs clés du problème considéré. Cela nous permet d'introduire notre point de vue, qui s'articule autour des trois composantes suivantes : méthode de conception, modèle de produit et modèle de processus de conception. Notre contribution personnelle fait l'objet du chapitre trois. D’abord, nous détaillons la méthode de conception fonctionnelle permettant de couvrir l'activité de conception, depuis l'expression du besoin jusqu'aux étapes du domaine pré-manufacturier. Nous proposons ensuite la structure et les concepts du modèle de processus et du modèle de produit que nous proposons pour satisfaire les exigences de l'intégration CAO/calcul. Dans le chapitre quatre, nous décrivons l'outil informatique que nous avons développé pour illustrer notre approche. Sur la base d'un exemple d'application, le cinquième chapitre est consacré à l'évaluation du système informatique et a la présentation de nos perspectives de recherche
Computer Aided Design more than ever appears as a complex process adressing different activities : geometric modelling, expert knowledge management, simulation, analysis, manufacturing, etc. The integration of the different tools supporting these activities is necessary, but it is faced with the problem of multiple modelling, data structuring, inter-process communication, etc. In this thesis report, we specifically address the problem of CAD/ Analysis integration. We present an original approach to integrate analysis tasks in the mechanical design process, from two points of view : function and tools. In the first chapter, we present the different stages of the mechanical design process and we identify methods, algorithms and models used in these stages. In the second chapter, we detail the problem of CAD/ Analysis integration. We begin by identifying the requirements of the integration of the functions and relative tools to these two domains ( CAD and Analysis). The reported state of the art allows us to identify the main key factors related to the problem of CAD/Analysis integration. This bibliography synthesis is used to introduce our point of view, which considers the three following aspects : Design Method, Product Model and Process Model. In the third chapter, we detail our contribution to integrate analysis tasks into the design. First, we introduce a feature- based functional design method which allows to support the proposed integration approach. Chapter four details the F-CAD (Functional Computer Aided Design) system implementation. The F-CAD system illustrates our methods, techniques and models. First, we present CAS. CADE object oriented software development platform. Then, we detail the implementation issues. In this section, we specify the required packages, classes and the related data structure. The communication protocols between different modelling tools are also addressed. In the fifth chapter, we finally present the design case study used to evaluate the developed methods, techniques and models. Based on this evaluation, we finally introduce our future research interests

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Asmi, Dwi. "Microstructural design and characterisation of alumina/hexaluminate composites." Thesis, Curtin University, 2001. http://hdl.handle.net/20.500.11937/2194.

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A study was conducted to investigate a novel route to low cost processing of alumina/calcium-hexaluminate (A/CA6) composites. The objectives of this study were to: (a) develop A/CA6 and ß-spodumene modified A/CA6 composites using an in-situ reaction sintering method and functionally-graded A/CA6 using an infiltration technique, and (b) evaluate the effects of CA6 platelets on the ensuing physical and mechanical properties. The study has revealed that the processing procedures played an important role in the microstructural development of A/CA6 composites. The microstructure-property relationships of these materials were found to be strongly influenced by the presence of CA6 phase.The A/CA6 composites were synthesised by in-situ reaction sintering of alumina powder and (0, 5, 15, 30, 50 and 100 wt%) CA6 precursor. The phase relations and development of this system were monitored using quantitative x-ray diffraction (XRD) and neutron diffraction (ND). Rietveld analysis which showed the CA6 content to increase in proportion with the increase of CA6 precursor added. The XRD study revealed that the CA and CA2 phases started to develop at approximately 1000 and 1100°C and transformed to CA6 phase at 1400T. Similarly, the dynamic high temperature ND study showed that the corresponding calcium aluminates phases commenced to develop at 1000°C and 1200°C and then eventually transformed to CA6 at 1400°C.The presence of the plate-like CA6 grains in the system was revealed by the back-scattered SEM imaging and confirmed by the Ca x-ray map. Although the presence of CA6 caused the reduction of hardness, the fracture toughness of A/CA6 composites were improved when compared with alumina. It was found that the presence of CA6 hindered the processes of sintering and densification in alumina matrix.The use of ß -spodumene had been investigated as a liquid-phase-sintering aid for the densification of A/CA6 composites. XRD, ND, differential thermal analysis (DTA), scanning electron microscopy (SEM) and Vickers indentation were used to characterise the effects of ß -spodumene on the phase relations, densification, microstructure and mechanical properties. The results showed that the presence of ß -spodumene had a profound influence on the phase relations, densification and microstructure of A/CA6 composites. Quantitative XRD and ND Rietveld analysis showed that the addition of > 2.5 wt% ß -spodumene caused the reduction of CA6 content due to the formation of ß -quartz solid solution. The reduction of porosity in the presence of ß -spodumene suggests that it may be used as an effective sintering aid for improving the densification of A/CA6 composites. However improvements in hardness and fracture toughness were not achieved probably due to the presence of large spherical pores as well as the formation of recrystallised ß -spodumene and ß -quartz solid solution.A functionally-graded alumina/calcium-hexaluminate (A/CA6) composite was successfully synthesised through infiltration of porous alumina preform with a solution containing calcium-acetate. The infiltration kinetics of liquid into porous alumina preform had also been investigated. It was found that the infiltration rate equation proposed by Washburn is most suitable for describing the effects of preform sintering temperature, viscosity and multiple infiltrations on the infiltration characteristics. The influence of applied pressure is consistent with the model proposed by Darcy, where the applied pressure enhances the infiltration rate behaviour. Key parameters for the optimum processing conditions of preforms for subsequent infiltration have also been identified.The graded composition character of the functionally-graded A/CA6 composites were characterised by XRD and synchrotron diffraction (SRD). Depth-profiling of compositions with XRD and SRD Rietveld refinement showed that the concentration of CA6 decreased with depth, while that of A1203 increased with depth. Both XRD and SRD results showed that CA and CA2 phases formed initially at 1000°C and 1300°C, respectively, but remained stable even at 1400°C, before eventually transformed to CA6 at 1650°C. These results are consistent with those of dynamic high temperature ND data.The graded microstructure was revealed by SEM back-scattered imaging whereby the content of CA6 platelets was most abundant near the surface and decreased with increasing depth towards the bulk. The presence of CA6 phase in the composite fire at 1400°C was also confirmed by the transmission electron microscopy (TEM) observation in conjunction with energy dispersive spectroscopy (EDS). The hardness results of the graded material showed that the graded-region was softer than the non-graded region as a result of the presence of softer CA6 phase in the former. However, the fracture toughness in the graded region was found to be higher than the non-graded region which might be attributed to the display of toughening processes such as crack deflection and grain bridging.

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Schimmelpfennig, Irene. "L'isotope cosmogénique Cl-36 dans les minéraux riches en Ca et en K : développements analytiques, calibrations des taux de production et inter-calibration avec le He-3 et le Ne-21." Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2009. http://tel.archives-ouvertes.fr/tel-00468337.

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Les taux de production du nucléide cosmogénique 36Cl par spallation du Ca et du K (SLHL) proposés actuellement dans la littérature montrent des divergences allant jusqu'à 50% (Gosse and Phillips, 2001). Nous avons pu montrer que des fortes teneurs en Cl dans les roches utilisées pour les calibrations précédentes entraînent une surestimation de ces taux de production, lié à la production de 36Cl à partir du 35Cl qui est peu contrainte. Nous avons entrepris une nouvelle calibration à partir de laves datées indépendamment entre 0.4 et 32 ka situées au Mt. Etna (38°N, Italie) et au Payun Matru (36°S, Argentine). Le 36Cl a été mesuré dans des feldspaths riches en Ca et en K, mais faibles en Cl. A partir d'une approche bayesienne incluant toutes les incertitudes, les taux de production obtenus sont de 42.2 ± 4.8 atomes 36Cl (g Ca)-1 an-1 pour la spallation du Ca et de 124.9 ± 8.1 atomes 36Cl (g K)-1 an-1 pour la spallation du K, avec les facteurs d'échelle calculés selon Stone (2000). Quatre autres modèles de facteurs d'échelle sont également proposés avec des résultats très semblables. Ces nouveaux taux de production sont en accord avec les valeurs précédemment obtenues par d'autres auteurs avec des échantillons faibles en Cl. Finalement, les concentrations en 36Cl, 3He et 21Ne ont été mesurées dans des pyroxènes prélevés entre 1000 et 4300 m dans des laves du Kilimandjaro (3°S). Les rapports entre ces nucléides ne montrent pas de dépendance altitudinale, ce qui suggère que les taux de production ne varient pas d'un nucléide à l'autre avec l'altitude.

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Karadas, Ozge. "Collagen Scaffolds With In Situ Grown Calcium Phosphate For Osteogenic Differentiation Of Wharton." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612975/index.pdf.

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COLLAGEN IN SITU GROWN CALCIUM PHOSPHATE SCAFFOLDS FOR OSTEOGENIC DIFFERENTIATION OF WHARTON&rsquo
S JELLY AND MENSTRUAL BLOOD STEM CELLS Karadas, Ö
zge M.Sc., Department of Biotechnology Supervisor : Prof. Dr. Vasif Hasirci Co-Supervisor: Assoc. Prof. Dr. Gamze Torun Kö
se February 2011, 91 pages The importance of developing new techniques for the treatment of bone and joint diseases is increasing continuosly together with the increase of human population and the average life span. Especially bone fractures as a result of osteoporosis are often seen in humans older than 50 years old. The expenses of bone and joint disease operations are very high and the duration of recovery is long. Because of these reasons World Health Organization, The United Nations and 37 countries announced that the years 2000-2010 is the Bone and Joint Decade. Tissue engineering is an alternative approach to clinically applied methods. In this study collagen scaffolds crosslinked with genipin, to improve the stability of foams in culture media, were prepared by lyophilization. To mimic the natural bone structure calcium phosphate mineral phase in the foam was formed by wet chemical precipitation. Collagen concentration (0.75% and 1%, w/v), freezing temperature (-20 oC and -80 oC) of the collagen solution before lyophilization and immersion duration (2x4 h and 2x48 h) of the foams in calcium and phosphate solutions for wet chemical precipitation were changed as process v parameters of foam production. Pore size distribution and porosity analysis as well as compression test were performed for characterization of the scaffolds. The foam with 1% w/v collagen concentration, frozen at -20 oC before lyophilization and immersed for 2x4 h in calcium and phosphate solution was chosen for in vitro cell culture studies. The defined foam had 70% porosity and pore sizes varying between 50 and 200 &mu
m. The elastic modulus and compressive strength of the foam was calculated as 127.1 kPa and 234.5 kPa, respectively. Stem cells isolated from Wharton&rsquo
s jelly (WJ) and menstrual blood (MB) were seeded to foams to compare their osteogenic differentiation. Both cells are isolated from discarded tissues and used in this study as an alternative to the commonly used cells which are isolated by invasive techniques such as bone marrow stem cells. Cells were seeded to collagen foams with and without calcium phosphate (CaP). It was observed that WJ cells proliferated during 21 days on collagen foams without CaP, but MB cell number decreased after day 14. Collagen foams with CaP supported the alkaline phosphate (ALP) activity compared to tissue culture polystyrene (TCPS) and foams without CaP. Contrarily lower cell numbers achieved on CaP containing collagen foams, possibly because of the calcium and phosphate concentration changes in the medium and as the result of osteogenic differentiation. ALP activity of both cell types increased almost 10 times and specific ALP activity (activity per cell) increased 40 times and 150 times for WJ and MB cells, respectively on the CaP containing foams compared to TCPS. Therefore, in this study it was shown that in situ CaP formed collagen foams induce osteogenic differentiation of WJ and MB cells, and these cells isolated from discarded tissues can be used as alternative cell sources in bone tissue engineering applications.

18

Billersjö, Sofia. "In-situ remediation of benzene-contaminated groundwater – A bench-scale study." Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171834.

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During the construction of the new urban area in the north-eastern part of Stockholm, Stockholm Royal Seaport, groundwater with extremely elevated levels of the carcinogenic aromatic hydrocarbon benzene was discovered in the area Hjorthagen. Such a contamination can be remediated in-situ by the use of chemical oxidation and biodegradation. Due to the fact that many factors such as contaminant composition, groundwater characteristics and temperature vary between sites, smaller bench scale studies are usually conducted before the full scale remediation on site. Little published research exists on the ability of these remediation techniques in areas with lower groundwater temperature such as Stockholm, why the need of a bench-scale study in this case is even larger. The objective of this master thesis is to, out of three investigated remediation agents, find the most suitable one for remediation of the benzene-contaminated groundwater in Hjorthagen. This was made in the form of a bench-scale study and the techniques studied were chemical oxidation, for which the two agents hydrogen peroxide (uncatalyzed and catalyzed in the form of Fenton’s reagent) and persulfate (activated with iron (II)) were used, and biological degradation by the use of a calcium peroxide-based compound. The study showed that the benzene-contaminated groundwater was best remediated with Fenton’s reagent, which was able to degrade the benzene with great success.

19

Lacrampe, Marie-France. "Ecoulement des polymères thermoplastiques dans le moule d'injection : Analyse expérimentale et validation d'un modèle de calcul." Valenciennes, 1993. https://ged.uphf.fr/nuxeo/site/esupversions/b265390d-1490-4919-bd16-24982b59b519.

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Cette étude a nécessité l'instrumentation de quatre outillages d'injection en capteurs de pressions et thermocouples. Nous avons montré que les débits volumiques moyens mesures pendant le remplissage sont différents des débits volumiques imposes, et que le paramètre le plus significatif est la géométrie de l'empreinte. Nous avons également montré que le débit volumique au front de matière évolue de façon significative pendant la phase de remplissage. Un modèle simple a permis d'attribuer ces différents phénomènes à la compressibilité du matériau et à sa viscosité de volume (tres supérieure à sa viscosité de cisaillement) qui ne sont généralement pas pris en compte lors des simulations de la phase de remplissage. Une étude paramétrique de l'influence des conditions de transformation, et de la géométrie de l'empreinte sur les pressions mesurées en fin de remplissage pour différents matériaux a été réalisée. La comparaison des résultats de cette étude à ceux des simulations correspondantes par un logiciel commercial de référence est en tendance satisfaisante. Les écarts calcul-mesuré pour des conditions de transformation extrêmes ont été attribué d'une part à l'utilisation par ce modèle d'une loi de comportement trop simple, et d'autre part à la méthode de calcul employée qui n'utilise pas de discrétisation dans l'épaisseur de l'empreinte. Une comparaison similaire a ponctuellement été réalisée sur l'évolution de la pression en différents points du disque d'épaisseur 2 mm pendant le remplissage. Elle a validé le choix de la pression de fin de remplissage comme critère de jugement de la qualité de la modélisation. Nous avons ponctuellement réalisé des simulations avec un logiciel plus élaboré. Les résultats obtenus sont similaires à ceux fournis pour cette géométrie par le logiciel de référence.

20

Ferreira, Nádia de Souza [UNESP]. "Monitoramento do perfil microbiológico de dentes com infecção endodôntica primária durante terapia com diferentes medicações intracanal." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/123299.

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Os objetivos deste estudo foram: 1. Correlacionar características clínicas e radiográficas com a microbiota presente no canal radicular de dentes com infecção primária; 2. Monitorar o perfil microbiológico após o preparo biomecânico e uso de diferentes medicações intracanal; 3) Verificar a susceptibilidade de complexos microbianos a diferentes medicações intracanal. Trinta dentes unirradiculares com necrose pulpar e lesão periapical visível radiograficamente foram submetidos ao tratamento endodôntico utilizando hipoclorito de sódio 2,5% como solução irrigadora e divididos em 3 grupos de acordo com a medicação intracanal utilizada: hidróxido de cálcio P.A. + solução salina fisiológica; hidróxido de cálcio P.A. + Zingiber officinale (extrato glicólico de gengibre); hidróxido de cálcio P.A. + gel de clorexidina 2%. Foram realizadas coletas do canal radicular com cones de papel absorvente após a abertura coronária, após a instrumentação e após 14 dias de ação da medicação intracanal. Para análise do conteúdo microbiológico dos canais radiculares, as amostras foram analisadas a partir de sondas de DNA pelo método de hibridização DNA-DNA checkerboard. Além disso, foi realizado teste de avaliação da atividade antimicrobiana do tratamento clínico por cultura microbiológica. Os resultados foram submetidos à análise estatística pelo teste de tendência linear, teste exato de Fisher, teste pareado de Wilcoxon e teste de Mann-Whitney, valor de p < 0,05. Houve associação entre dor à palpação e complexos roxo, verde e laranja. Fístula foi associada ao complexo vermelho. Maiores áreas de reabsorção foram associadas à presença de Capnocytophaga ochracea. Foi observada redução de bactérias após o tratamento endodôntico. Ao utilizar o método de hibridização DNA-DNA checkerboard, as bactérias mais prevalentes foram Strepctococcus anginosus....
The objectives of this study was: 1. Correlate clinical and radiographic features and microbiota present in root canal of teeth with primary infection; 2 Monitoring the microbiological profile after biomechanical preparation and use of different intracanal medications; 3) Verify the microbial susceptibility of bacterial complexes of different intracanal medications. Thirty single-rooted teeth with pulp necrosis and periapical lesion are undergoing treatment using 2.5% sodium hypochlorite as irrigating solution and divided into 3 groups according to the intracanal medication used: calcium hydroxide + saline solution, calcium hydroxide + 20% ginger glycolic extract, calcium hydroxide + 2 % chlorhexidine gel. Samples of the root canal were taken with absorbent paper cones after the coronal opening, after instrumentation and 14 days after medication. For analysis of the microbial content of the root canal the samples were analyzed from DNA probes using the method of DNA-DNA hybridization checkerboard. In addition, tests of antimicrobial activity of clinical treatment were performed by microbiological culture. The results were statistically analyzed with linear trend test, Fisher’s exact test, Wilcoxon matched pairs test and Mann-Whitney post hoc Dunn test. For all performed tests, a P-value < 0.05 was set as statically significant. There was an association between pain on palpation and purple, green and orange complex. Sinus tract was associated with the red complex. Bone resorptions were associated with the presence of Capnocytophaga. ochracea. The reduction of bacteria was observed after endodontic treatment. By using the method of checkerboard DNA-DNA hybridization, the more prevalent bacteria were Strepctococcus anginosus, Veillonella parvula, Parvimonas micra, Enterococcus faecium and Capnocytophaga ochracia, both initially and after biomechanical preparation. All treatments reduced ....

21

Rizk, Guillaume. "Parallelization on graphic hardware : contributions to RNA folding and sequence alignment." Rennes 1, 2011. https://ecm.univ-rennes1.fr/nuxeo/site/esupversions/df86b1c1-46f8-4fe8-ac6c-fb4920b31b84.

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La bioinformatique nécessite l'analyse de grandes quantités de données. Avec l'apparition de nouvelles technologies permettant un séquençage à haut débit à bas coût, la puissance de calcul requise pour traiter les données a énormément augmenté. . Cette thèse examine la possibilité d'utiliser les processeurs graphiques (GPU) pour des applications de bioinformatique. Dans un premier temps, ce travail s'intéresse au calcul des structures secondaires d'ARN. Ce problème est en général calculé par programmation dynamique, avec un algorithme qui pose de sérieux problèmes pour un code GPU. Nous introduisons une nouvelle implémentation tuilée qui fait apparaitre une bonne localité mémoire, permettant ainsi un programme GPU très efficace. Cette modification permet également de vectoriser le code CPU et donc de faire une comparaison honnête des performances entre GPU et CPU. Dans un deuxième temps, ce travail aborde le problème d'alignements de séquences. Nous présentons une parallélisation GPU d'une méthode utilisant une indexation par graines. L' implémentation sur GPU n'étant pas efficace, nous nous tournons vers le développement d'une version CPU. Notre contribution principale est le développement d'un nouvel algorithme éliminant rapidement les nombreux alignements potentiels, basé sur le précalcul de portions de la matrice de programmation dynamique. Ce nouvel algorithme a conduit au développement d'un nouveau programme d'alignement très efficace. Notre travail fournit l'exemple de deux problèmes différents dont seulement un a pu être efficacement parallélisé sur GPU. Ces deux expériences nous permettent d'évaluer l'efficacité des GPU et leur place en bioinformatique
Bioinformatics require the analysis of large amounts of data. With the recent advent of next generation sequencing technologies generating data at a cheap cost, the computational power needed has increased dramatically. Graphic Processing Units (GPU) are now programmable beyond simple graphic computations, providing cheap high performance for general purpose applications. This thesis explores the usage of GPUs for bioinformatics applications. First, this work focuses on the computation of secondary structures of RNA sequences. It is traditionally conducted with a dynamic programming algorithm, which poses significant challenges for a GPU implementation. We introduce a new tiled implementation providing good data locality and therefore very efficient GPU code. We note that our algorithmic modification also enables tiling and subsequent vectorization of the CPU program, allowing us to conduct a fair CPU-GPU comparison. Secondly, this works addresses the short sequence alignment problem. We present an attempt at GPU parallelization using the seed-and-extend paradigm. Since this attempt is unsuccessful, we then focus on the development of a program running on CPU. Our main contribution is the development of a new algorithm filtering candidate alignment locations quickly, based on the pre computation of tiles of the dynamic programming matrix. This new algorithm proved to be in fact more effective on a sequential CPU program and lead to an efficient new CPU aligner. Our work provides the example of both successful an unsuccessful attempts at GPU parallelization. These two points of view allow us to evaluate GPUs efficiency and the role they can play in bioinformatics

22

Girinsky, Olivier. "Pré-industrialisation d'un procédé de consolidation de sol par bio-calcification in situ." Phd thesis, Université d'Angers, 2009. http://tel.archives-ouvertes.fr/tel-00557098.

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Dans les pays à fort risque sismique, les fondations bâties sur un sous-sol trop meuble peuvent avoir des conséquences désastreuses. En effet, dans certain cas, les mouvements sismiques provoquent des tassements, en particulier lorsque les sous-sols granulaires sont saturés en eau. Ce phénomène dit de liquéfaction ou perte de la résistance des sols, résulte de la montée de la pression interstitielle de l'eau lorsque les vibrations sismiques tendent à tasser les grains les uns contre les autres. Pour éviter l'effondrement des édifices, le génie civil renforce la résistance mécanique des terrains plus ou moins perméables, en procédant à des injections de matériaux par le biais de forages. Afin d'améliorer les procédés de consolidation des sols, une nouvelle technique compte apporter une réponse en utilisant des cristaux de carbonate de calcium précipités in situ par voie microbiologique. La précipitation bactérienne du carbonate de calcium peut s'accomplir par l'hydrolyse de l'urée, via l'enzyme uréase. Ceci conduit à l'alcalinisation du micro environnement, permettant la précipitation d'ions carbonates en présence d'ions calcium. Sporosarcina pasteurii a été choisi car c'est un micro-organisme alcalinophile, non pathogène et détenteur de concentration intracellulaire élevée en uréase. L'objectif était d'utiliser industriellement ce micro-organisme pour son pouvoir calcifiant, afin d'améliorer la cohésion des grains de sol, en milieu saturé, sans en obturer la porosité. Trois axes de recherche menés conjointement, ont été définis pour ce travail de préindustrialisation du procédé de bio consolidation in situ. Le premier axe a été l'obtention d'un milieu de production de biomasse, industriel, permettant de stabiliser l'accession aux fortes activités enzymatiques. Cette étape est indispensable du fait des exigences d'application du procédé sur le chantier, éloignées des conditions physiologiques de la bactérie S. pasteurii. Il a été vital de décoder les modalités et la composition d'un milieu de culture industriel propre à favoriser la production de S. pasteurii et d'uréase. Ce travail a établi les principaux paramètres de suivi de culture et leur signification physiologique. Il a permis d'étudier la régulation de la synthèse de l'enzyme uréase et de proposer un modèle de régulation chez S. pasteurii. Le second aspect de recherche s'est attaché à créer une solution calcifiante à partir d'un mélange d'urée et de sel de calcium. Des colonnes de sable fin ont été utilisées pour évaluer l'impact, sur la bio calcification, de deux sources de sel de calcium, le nitrate et le chlorure de calcium. Les résultats mettent en avant, l'existence d'une réduction de la vitesse d'hydrolyse en présence d'ion calcium et l'absence de différence significative de résistance à la compression (RC) entre les deux sels. D'autre part, lorsque les activités enzymatiques d'hydrolyse sont moindres, le processus de bio calcification, paraît plus stable et efficace. De nombreuses images au microscope électronique à balayage (MEB) ont confirmé ces résultats. Enfin, une amélioration du procédé vient de la proposition d'une solution calcifiante, additionnée de très faibles quantités de matière organique, afin de favoriser l'élongation des cristaux de carbonate de calcium dans les zones inter-granulaires. Le troisième axe a été la mise en place pour une application en chantier, d'un protocole d'injection en colonne de sable fin d'une suspension de biomasse suivie d'une solution calcifiante. Ces travaux ont permis d'identifier, une corrélation entre les zones de dépôt de biomasse et les portions de sable consolidés, ainsi que les principaux facteurs responsables de l'hétérogénéité de la bio calcification. La densité cellulaire et la granulométrie bactérienne définissent par filtration mécanique et physicochimique un premier profil de distribution de la biomasse en milieu poreux. En fonction du niveau d'activité enzymatique et de la qualité de la suspension bactérienne injectée, la solution calcifiante interagit en précipitant sous forme de flocs et en amenant un changement local de viscosité. Pendant l'injection, l'écoulement des fluides redéfinit le premier profil de biomasse par un lessivage au sein du système poreux. La granulométrie du sable et la vitesse d'injection influencent également le lessivage. Grâce à ces travaux, l'hétérogénéité de la bio-calcification a été diminuée en intégrant dans le protocole d'injection, des temps d'arrêt d'injection pour l'immobilisation des fluides.

23

Eroini, Violette. "Kinetic study of calcium carbonate formation and inhibition by using an in-situ flow cell." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550812.

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A major challenge faced by the oil and gas industry is the minimisation of scale formation within installations; new regulations are requiring conventional inhibitors to be replaced by green scale inhibition strategies, which may involve anti-fouling surfaces. In order to improve inhibition methods, understanding scale formation on surfaces, and the kinetics of surface scaling processes is a necessity. This study focused on two main objectives. Firstly, the ability of different surfaces to reduce or modify calcium carbonate scale formation was assessed with the final objective being to understand what constitutes a surface that minimises the potential for scaling. Seven different surfaces have been tested, stainless steel, stainless steel pre-treated with Polyphosphinocarboxilic Acid (PPCA), Polytetrafluoroethylene (PTFE), Diamond-Like Carbon (DLC), ceramic and polymer coated stainless steels and an isotropic superfinished stainless steel surface (ISF). A subset of these surfaces was eroded within a Submerged Impinging Jet (SIJ) to assess the possible effect of in-service performance. The surfaces were first characterised by contact angle, roughness measurements, and Energy Dispersive X-ray (EDX). The amount of scale and the morphology of the crystals were assessed using Scanning Electron Microscopy (SEM). The second part of the project uses a relatively new way to assess both precipitation and deposition in-situ and in real-time. A new rig has been designed permitting in-situ and real-time measurements of turbidity in the bulk and observation on the surfaces. Twelve different conditions were tested involving 4 brines and 3 temperatures. Image analysis of the image capture was used to assess the surface coverage, number of object and average size of the particles with time, allowing the kinetics to •be evaluated. From the results, a systematic ranking of the surface resistance to scaling has been established together with an improved description of the scale deposition process. The characteristics of the surface involved in the scale process appear to be a combination of surface chemistry, roughness, and topography and varies from one substrate to another. The kinetics (rate constant) of precipitation and deposition differed but a polynomial relation of third order was discovered between both. The kinetics of both processes was found to be highly temperature dependant.

24

Lee, Alasdair Peter. "In situ Raman spectroscopic studies of the iron and calcium containing biominerals in chiton teeth." Thesis, Lee, Alasdair Peter (2000) In situ Raman spectroscopic studies of the iron and calcium containing biominerals in chiton teeth. PhD thesis, Murdoch University, 2000. https://researchrepository.murdoch.edu.au/id/eprint/51705/.

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The iron and calcium biominerals of the major lateral teeth of the chitons, Acanthopleura hirtosa, Acanthopleura echinata, Plaxiphora albida, Cryptoplax striata, Ischnochiton australis, and Acanthopleura rehderi, have been characterised in situ at all stages of mineralization, with laser Raman microscopy. Mature teeth do not contain goethite and ferrihydrite, both of which have been isolated in early stage teeth. Deposition of magnetite in the posterior region of tooth cusp occurs on two fronts simultaneously, from both the anterior and posterior. In contrast, the lepidocrocite region, where present, is formed by aggregation over the whole extent of the interior surface. A thin veneer of ferrihydrite over the posterior surface of the magnetite prevents this region from undergoing oxidation prior to use. The first evidence for conditions favouring the deposition of hematite over goethite in biological systems is shown. Hematite is uniquely located in micro-domains of teeth at a critical stage of development, at the transition between iron and calcium biomineralisation. The Raman spectrum of biogenically produced hematite is distinctly differently from geological and synthetic material. Calcium biomineralisation in the major lateral teeth of Acanthopleura echinata takes place as an ordered process from the top of the tooth core under the tab region, down its interior surface and down the lepidocrocite layer, before extending outwards to the anterior surface at the junction zone. Mineralization is not initiated until the lepidocrocite layer has isolated the core from the magnetite cap. The junction zone, previously shown to be a region of high ion density, is shown to be free of mineral deposits. In contrast to previous work, the cores of P. albida, C. striata, and I. australis, are shown to contain amorphous ferric iron oxide minerals and not the previously described ferric phosphate. Mineral deposition progresses in the same manner as all other chitons studied, from posterior to anterior and from tooth tip towards the base.

25

Ferreira, Lilian [UNESP]. "Características bioquímicas e microbiológicas do biofilme dentário formado in situ sobre materiais que contêm flúor ou fosfato de cálcio amorfo." Universidade Estadual Paulista (UNESP), 2010. http://hdl.handle.net/11449/95473.

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Made available in DSpace on 2014-06-11T19:27:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-24Bitstream added on 2014-06-13T18:56:30Z : No. of bitstreams: 1 ferreira_l_me_araca.pdf: 1328677 bytes, checksum: e8654f5c6e3eb77d8eb2d430f398667d (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Muito tem se avaliado a respeito das propriedades físicas e químicas dos selantes de fóssulas e fissuras, mas pouco sobre seus efeitos no biofilme dentário. O objetivo deste estudo foi analisar as características bioquímicas e microbiológicas do biofilme dentário formado in situ sobre materiais que liberam flúor ou cálcio e fosfato. Dez voluntários utilizaram dispositivo intrabucal palatino contendo corpos-de-prova de materiais (Fuji IX GP, Auralay XF e Aegis) ou blocos de esmalte bovino. A fase experimental consistiu de 4 etapas de 8 dias cada e a utilização de sacarose para formação do biofilme. No 7º dia dos períodos experimentais foi determinado o pH do biofilme e no 8º dia, o biofilme dentário formado foi coletado para determinação de flúor (F), cálcio (Ca), fósforo (P) e polissacarídeos extracelulares insolúveis (PEI) além da microbiota. Verificou-se a liberação de F, Ca e P de cada material e dos blocos de esmalte após ciclagem de pH. Após a verificação da homogeneidade dos dados, testes paramétricos e não-paramétricos foram realizados para análise dos resultados (p<0,05). O biofilme dentário formado sobre os materiais que liberam flúor apresentou maior presença de F, Ca e P e menor número de estreptococos do grupo mutans quando comparado ao bloco de esmalte. Após o uso da sacarose (7º dia), o pH do biofilme foi maior na presença do material ionomérico. O biofilme sobre o material que contém fosfato de cálcio amorfo mostrou similar concentração de Ca e P, quando comparado aos materiais que contém flúor, e uma ação tamponante no meio, sem efeito na microbiota. Concluiu-se que os materiais que liberam flúor aumentaram as concentrações de F, Ca e P e diminuíram a de PEI e a microbiota cariogênica do biofilme dentário; e o que contém fosfato de cálcio amorfo aumentou as concentrações de Ca e P
The chemical and physical properties of the pit and fissures sealants have been widely evaluated but rare researches focus on the effects on dental plaque. The aim of this study was to evaluate the biochemical and microbiological characteristics of the in situ dental plaque formed on materials that release fluoride or calcium and phosphate. Ten volunteers wore an intraoral palatal device containing specimens of materials (Fuji IX GP, Auralay XF and Aegis) or bovine enamel blocks. The experimental phase consisted of 4 stages with duration of 8 days each and use of sucrose to form the dental plaque. The dental plaque pH was determined at the 7th day of the experimental periods and the dental plaque was collected at the 8th day to determine the fluoride (F), calcium (Ca), phosphorus (P), insoluble extracellular polysaccharides (EPS) and microbiota. It was observed release of F, Ca and P from each material and from the enamel blocks after pH cycling. After verification of data homogeneity, parametric and non-parametric tests were performed (p<0.05). The dental plaque formed on the materials that release fluoride presented more F, Ca and P and reduced number of Streptococcus mutans in comparison to the enamel block. After use of sucrose (7th day), the dental plaque pH was higher with the presence of ionomeric material. The dental plaque on the material containing amorphous calcium phosphate exhibited similar Ca and P concentration compared to the ones on fluoride materials, and buffering action with no effect on the microbiota. It was concluded that the materials that release fluoride increased F, Ca and P concentrations, decreased EPS concentration and the cariogenic microbiota of the dental plaque; the amorphous calcium phosphate material increased concentrations of Ca and P

26

Wei, Caijie, and 魏才倢. "Calcium-based coating on the surface of nanoscale zero-valent iron (nZVI) for improvement of its stability and transport in environmental remediation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/197497.

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Zero valent iron (ZVI) has demonstrated its reactivity and effectiveness for in-situ groundwater and soil remediation. The potential of the high reducing activity of nanoscale ZVI (nZVI) for environmental decontamination has attracted more attentions in recent years, as nZVI may be injected with water to the pollution sites for in-situ remediation. However, rapid oxidation and instant agglomeration of nZVI make it difficult for large-scale engineering application. Effort has been made to improve the stability and mobility of nZVI for effective in-situ remediation. In the present study, a novel Ca-based surface coating method has been developed for protection of nZVI and enhancement of its transport in environmental applications. A simple thermal deposition method was employed to coat a Ca-based layer on the surface of micro- or nano- ZVI particles in water or methanol environment. According to microscopic observations, Ca(OH)2 nano-layer was formed on the ZVI surface. A clear core-shell structure was observed for the coated nZVI/Ca(OH)2 particles based on the TEM observations. The Ca(OH)2 coating layer had a thickness about one fifth of the nZVI diameter and the Ca to Fe ratio was below 0.2. With the Ca(OH)2 shell, nZVI particles can be effectively protected against corrosion according to the standard natural spray corrosion tests. Thus, the Ca(OH)2 coating layer is able to greatly improve the stability of nZVI during storage, transportation and application. In addition, based on the result of the dissolution tests, the Ca(OH)2 shell could be readily dissolved in water with a low Ca content or a low ionic strength. After dissolution of the Ca(OH)2 shell, the reactivity of nZVI was found to be at the similar level as bare nZVI, which could remove Cr(VI) from water by more than 90% in about 20 min. The pseudo-first order rate constants for Cr(VI) reduction by bare nZVI and nZVI/ Ca(OH)2 after shell dissolution were 0.064 and 0.072 min-1, respectively. Moreover, the Ca(OH)2 coating shell would not only function as a protection layer but also improve the mobility of nZVI particles in in-situ applications. The aggregation and sedimentation of nZVI/Ca(OH)2 particles became considerably slower compared to bare nZVI without the coating. Clean-bed water filtration tests were conducted with sand and glass columns to evaluate the mobility and transport of nZVI in porous media. The results show that bare nZVI in the particle suspension deposited mostly at the top of the filters with little penetration. In comparison, the nZVI/Ca(OH)2 particles were able to penetrate through the filter media during the filtration process, and the dark iron particles could fill up the entire filter columns. The penetration rate increased from nearly 0 m/hr for bare nZVI to 0.43 m/hr for nZVI/Ca(OH)2 through the filter media. The Ca-based coating materials are known as of low cost and environmentally friendly. Thus, the new coating method developed in this study provides a cost-effective means for both the protection of nZVI and improvement of its transport and delivery in porous media for environmental decontamination.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

27

Asmi, Dwi. "Microstructural design and characterisation of alumina/hexaluminate composites." Curtin University of Technology, Department of Applied Physics, 2001. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=13122.

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A study was conducted to investigate a novel route to low cost processing of alumina/calcium-hexaluminate (A/CA6) composites. The objectives of this study were to: (a) develop A/CA6 and ß-spodumene modified A/CA6 composites using an in-situ reaction sintering method and functionally-graded A/CA6 using an infiltration technique, and (b) evaluate the effects of CA6 platelets on the ensuing physical and mechanical properties. The study has revealed that the processing procedures played an important role in the microstructural development of A/CA6 composites. The microstructure-property relationships of these materials were found to be strongly influenced by the presence of CA6 phase.The A/CA6 composites were synthesised by in-situ reaction sintering of alumina powder and (0, 5, 15, 30, 50 and 100 wt%) CA6 precursor. The phase relations and development of this system were monitored using quantitative x-ray diffraction (XRD) and neutron diffraction (ND). Rietveld analysis which showed the CA6 content to increase in proportion with the increase of CA6 precursor added. The XRD study revealed that the CA and CA2 phases started to develop at approximately 1000 and 1100°C and transformed to CA6 phase at 1400T. Similarly, the dynamic high temperature ND study showed that the corresponding calcium aluminates phases commenced to develop at 1000°C and 1200°C and then eventually transformed to CA6 at 1400°C.The presence of the plate-like CA6 grains in the system was revealed by the back-scattered SEM imaging and confirmed by the Ca x-ray map. Although the presence of CA6 caused the reduction of hardness, the fracture toughness of A/CA6 composites were improved when compared with alumina. It was found that the presence of CA6 hindered the processes of sintering and densification in alumina matrix.The use of ß -spodumene had been investigated as a liquid-phase-sintering aid for ++
the densification of A/CA6 composites. XRD, ND, differential thermal analysis (DTA), scanning electron microscopy (SEM) and Vickers indentation were used to characterise the effects of ß -spodumene on the phase relations, densification, microstructure and mechanical properties. The results showed that the presence of ß -spodumene had a profound influence on the phase relations, densification and microstructure of A/CA6 composites. Quantitative XRD and ND Rietveld analysis showed that the addition of > 2.5 wt% ß -spodumene caused the reduction of CA6 content due to the formation of ß -quartz solid solution. The reduction of porosity in the presence of ß -spodumene suggests that it may be used as an effective sintering aid for improving the densification of A/CA6 composites. However improvements in hardness and fracture toughness were not achieved probably due to the presence of large spherical pores as well as the formation of recrystallised ß -spodumene and ß -quartz solid solution.A functionally-graded alumina/calcium-hexaluminate (A/CA6) composite was successfully synthesised through infiltration of porous alumina preform with a solution containing calcium-acetate. The infiltration kinetics of liquid into porous alumina preform had also been investigated. It was found that the infiltration rate equation proposed by Washburn is most suitable for describing the effects of preform sintering temperature, viscosity and multiple infiltrations on the infiltration characteristics. The influence of applied pressure is consistent with the model proposed by Darcy, where the applied pressure enhances the infiltration rate behaviour. Key parameters for the optimum processing conditions of preforms for subsequent infiltration have also been identified.The graded composition character of the functionally-graded A/CA6 composites were characterised by XRD and synchrotron ++
diffraction (SRD). Depth-profiling of compositions with XRD and SRD Rietveld refinement showed that the concentration of CA6 decreased with depth, while that of A1203 increased with depth. Both XRD and SRD results showed that CA and CA2 phases formed initially at 1000°C and 1300°C, respectively, but remained stable even at 1400°C, before eventually transformed to CA6 at 1650°C. These results are consistent with those of dynamic high temperature ND data.The graded microstructure was revealed by SEM back-scattered imaging whereby the content of CA6 platelets was most abundant near the surface and decreased with increasing depth towards the bulk. The presence of CA6 phase in the composite fire at 1400°C was also confirmed by the transmission electron microscopy (TEM) observation in conjunction with energy dispersive spectroscopy (EDS). The hardness results of the graded material showed that the graded-region was softer than the non-graded region as a result of the presence of softer CA6 phase in the former. However, the fracture toughness in the graded region was found to be higher than the non-graded region which might be attributed to the display of toughening processes such as crack deflection and grain bridging.

28

Level, Pascal. "Contribution à l'élaboration d'une stratégie de calcul en dynamique des grandes structures : Développement et intégration des méthodes de réanalyse modale." Valenciennes, 1989. https://ged.uphf.fr/nuxeo/site/esupversions/ddd3277b-ac0d-4f10-a671-4f9e5d5af490.

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Etude de cinq méthodes de réanalyse modale, évitant le calcul direct des nouvelles solutions propres après modification de la structure; implantation numérique et calculs d'essai. Détermination de la meilleure méthode (méthode de partition des matrices de modification)

29

Goueygou, Marc. "Formulation explicite de la réponse impulsionnelle de sources planes non bafflées : application au calcul du rayonnement acoustique des structures vibrantes." Valenciennes, 1997. https://ged.uphf.fr/nuxeo/site/esupversions/01f4b2b2-cfee-44ed-9ff4-28b2d7bc04f8.

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Le travail présenté dans ce mémoire consiste à développer et a valider une nouvelle méthode de calcul du rayonnement acoustique des structures vibrantes. Cette méthode s'applique au cas de sources planes non bafflées de géométrie quelconque. Contrairement aux méthodes basées sur l'équation intégrale (BIE), elle repose sur une formulation explicite de la réponse impulsionnelle du système source, milieu de propagation, point d'observation. Cette formulation constitue une généralisation de l'intégrale de Rayleigh au cas de sources non bafflées. D’autre part, le calcul numérique de la réponse est effectue directement dans le domaine temporel, en utilisant l'algorithme de la représentation discrète. Cette méthode est utilisée pour étudier la réponse large bande de sources de forme simple. Nos calculs sont ensuite confrontes avec des solutions analytiques et des résultats obtenus par un code éléments finis. Enfin, les réponses calculées par notre méthode sont comparées avec celles enregistrées sur une structure vibrante réelle. Ces différentes comparaisons s'avèrent globalement satisfaisantes et démontrent la validité de notre approche. Par rapport aux méthodes éléments finis, la méthode développée présente l'avantage d'un formalisme simple et d'une mise en œuvre aisée. Contrairement à d'autres méthodes basées sur une formulation explicite, elle ne se limite pas seulement au cas de sources bafflées. Ainsi, elle peut être utilisée comme un moyen de prévision du bruit impulsionnel, ou bien comme un outil simple et rapide pour la modélisation de transducteurs large bande.

30

Gu, Jie. "Characterization of in-situ Ca²⁺ -sensing mechanisms and stanniocalcin-1 target cells in gills of Japanese eels." HKBU Institutional Repository, 2014. https://repository.hkbu.edu.hk/etd_oa/74.

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Calcium ion has diverse beneficial roles in living organisms. Failure in Ca2+ homeostasis affects a variety of molecular and cellular processes, ultimately leading to many pathological consequences. In mammals, body Ca2+ homeostasis is maintained by the coordinated calcium (re)absorption that occurs in the small intestines, kidneys and bones, and is under tight hormonal control. In fish, two special organs, Corpuscles of Stannius (CS) glands and gills form a regulatory circuit to detect and regulate blood Ca2+ homeostasis. However, the underlying molecular mechanism in the regulation of gill Ca2+ uptake has not been fully examined. Moreover, some putative biological active substances in CS glands have not been identified. To address these research questions, a euryhaline fish, Japanese eel (Anguilla japonica) was used as an animal model for the study. Fish gill is equipped with epithelial calcium channel (ECaCl) as gatekeeper of Ca2+ entry, and membrane Ca2+-ATPase (PMCA) for Ca2+ efflux. To test if branchial ECaCl and PMCA responded to change in water Ca2+ level, we investigated the changes in fish adapted in artificial freshwater (AFW), Ca2+-deficient AFW (D-AFW) or high Ca2+-AFW (H-AFW). Our data illustrated both short-term and long-term effects on modulations of the transporters. The changes correlated with expression levels of stanniocalcin-1 (STC-1) in CS glands. This part of study supports the regulatory circuit between gills and the glands. In primary cell culture of Japanese eel gill cells, Ca2+ sensing was shown to be mediated by Ca2+ sensing receptor (CaSR) coupled to phospholipase C (PLC)-extracellular signal-regulated kinase (ERK) and PLC-inositol triphosphate (IP3)-Ca2+/calmodulin-dependent protein kinase-II (CaMK-II) pathways. And CaSR-STC-1/cyclo-oxygenase-2 (COX-2) mediated protective pathway in gill cells that exerts a possible protective mechanism against an increase in intracellular Ca2+ levels associated with transepithelial Ca2+ transport. Apparently, the protective effects against Ca2+-mediated cytotoxicity of gill cell were mediated by STC-1 binding on gill cells that led to elevations of cytosolic cAMP. In a follow-up experiment of using Ca2+-imaging system in a model of thapsigargin (TG)-induced elevation of cytosolic Ca2+, a hypocalcemic action of STC-1 was demonstrated and was found to be mediated by cAMP and COX-2 pathway. To further determine the gene expressed in CS gland responsive to changes in water salinity, the first transcriptome database of CS glands from fish adapted in freshwater or seawater condition. A de novo assembly of RNA sequencing data generated 11747 unigenes and revealed 475 genes that were differentially expressed. Three functional clusters: (1) Ca2+-metabolism, (2) blood pressure and (3) ion-osmoregulation were revealed. Gene targets, in addition to STC-1 in related to the regulation of calcium metabolism and blood pressure, like calcitonin, atrial natriuretic peptide-converting enzyme and endothelin-converting enzyme 1 were identified. Taken together this thesis described a comprehensive study on the functional circuit between gills and CS glands to decipher the regulation and functions of transporters and hormones in calcium metabolism in fish.

31

Lussou, Philippe. "Calcul du mouvement sismique associé à un séisme de référence pour un site donné avec prise en compte de l'effet site : méthode empirique linéaire et modélisation de l'effet de site non-linéaire." Phd thesis, Grenoble 1, 2001. http://tel.archives-ouvertes.fr/tel-00685419.

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Deux approches sont mises en oeuvre pour calculer le mouvement sismique associé à un séisme de référence en considérant les conditions locales du site étudié : " loi empirique " et " site spécifique". Dans la première partie de la thèse (approche " loi empirique"), de nouvelles lois d'atténuation sont déterminées à l'aide des données du réseau japonais K-NET. La classification de site se fait à l'aide de VS 30 (célérité moyenne des ondes de cisaillement sur 30 mètres de profondeur) mesuré in situ et/ou de Fo (fréquence prédominante du site déterminée à l'aide d'enregistrements de séismes). A l'aide de ces deux paramètres, de nouveaux systèmes de classification de site sont proposés et appliqués au spectre de réponse en accélération, ainsi qu'à d'autres paramètres de description du mouvement sismique (durée, intensité, etc). Dans la deuxième partie de la thèse le site étudié est décrit par un milieu stratifié horizontal composé de couches homogènes dont le comportement est modélisé par simulation numérique. Trois codes de calcul sont utilisés pour évaluer l'effet de site non linéaire : SHAKE (linéaire équivalent), NOAH et CYBEROUAKE (non linéaires). Les tests réalisés dans cette partie ont mis en évidence les faiblesses du modèle linéaire-équivalent par rapport aux modèles non linéaires pour les fréquences supérieures à 5 Hz. Par ailleurs, des calculs effectués à partir d'enregistrements obtenus à Port Island et Kushiro Port (Japon) ont montré l'intérêt d'utiliser des enregistrements obtenus en profondeur pour réaliser des calculs non linéaires. A la suite de ces tests, le site du Synchrotron (Grenoble) est étudié afin d'évaluer l'influence du comportement mécanique des couches superficielles de sol sur le mouvement sismique. Il ressort de cette étude que le mouvement sismique prévisible sur le site étudié dépend davantage de l'effet de site global dû à la géométrie tri-dimensionnelle de la cuvette grenobloise que de l'effet de site local (sols superficiels).

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Jennings, A. E. "Dopaminergic control of astrocytic calcium dynamics in situ and its potential effect on local synaptic activity." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1451904/.

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Astrocytes in culture display large cytosolic calcium increases upon stimulation with dopamine, however the mechanism and physiological significance of this calcium response is still unknown. In this thesis, I demonstrate that hippocampal astrocytes in situ respond to dopamine with similar large calcium transients. I also describe a novel astrocyte calcium decrease, which appears specific to dopaminergic stimulation. Dopamine is a potent neuromodulator of hippocampal synaptic activity, as are astrocytes. However, I found no evidence to suggest that dopamine-induced calcium transients in astrocytes affect excitatory synaptic transmission and its short-term plasticity in the hippocampal stratum radiatum. In perforant path - CA1 pyramidal synapses of stratum lacunosum-moleculare, astrocytes were found to lessen the inhibitory effect of dopamine on evoked PTP. This work shows for the first time that astrocytes in situ can robustly respond to dopamine with a complex Ca2+ signal thus may participate in dopaminergic signalling in the brain.

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Hillers, Maike. "Cristallisation dans un verre d'aluminosilicate de calcium : effet du bore et apport de techniques in situ." Orléans, 2007. http://www.theses.fr/2007ORLE2054.

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La cristallisation est un phénomène qui intéresse directement les procédés d’élaboration et de formage verriers. Dans ce travail, nous étudions les mécanismes de cristallisation dans des verres du système CaO-Al2O3-SiO2-B2O3. Il s’agit d’évaluer l’effet d’un ajout progressif d’oxyde de bore et l’influence de paramètres tels que la granulométrie et la voie d’élaboration sur la croissance cristalline. Différentes techniques comme l’analyse thermique, les microscopies optique et électronique à balayage, la diffraction des rayons X et les spectroscopies Raman et RMN ont été utilisées pour caractériser la cristallisation de verres entre 0 et 10 % de B2O3. Nous avons caractérisé les phases qui cristallisent : la wollastonite, la pseudowollastonite, l’anorthite, le quartz et la cristobalite. Les températures de liquidus et de transition vitreuse diminuent avec l’ajout de bore. Les vitesses maximales de croissance diminuent également avec l’augmentation de la teneur en bore. L’étude structurale par RMN (11B, 27Al, 29Si) a révélé que la formation d’unités BO4 est favorisée avec l’ajout de bore. La mobilisation du calcium par le bore pourrait expliquer l’effet inhibiteur du bore par rapport à la croissance cristalline. Les techniques in situ de MEB et DRX en température ont apporté des informations complémentaires sur l’évolution des vitesses de croissance et sur les séquences de cristallisation : la vitesse de croissance n’est pas constante mais diminue avec le temps ; dans les verres à faibles teneurs en bore, la dernière phase cristalline à apparaître est la cristobalite, dans les verres plus riches en bore c’est l’anorthite.

34

Hao, Yan. "Automated Reductions of Markov Chain Models of Calcium Release Site Models." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539623353.

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Markov chain models have played an important role in understanding the relationship between single channel gating of intracellular calcium (Ca2+) channels, specifically 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs), and the stochastic dynamics of Ca2+ release events, known as Ca2+ puffs and sparks. Mechanistic Ca2+ release site models are defined by the composition of single channel models whose transition probabilities depend on the local calcium concentration and thus the state of the other channels. Unfortunately, the large state space of such compositional models impedes simulation and computational analysis of the whole cell Ca2+ signaling in which the stochastic dynamics of localized Ca2+ release events play an important role. This dissertation introduces, implements and validates the application of several automated model reduction techniques that significantly reduce the computational cost of mechanistic compositionally defined Ca2+ release site models.;A common feature of Ca2+ channel models is the separation of time scales. For example, the well-known bell-shaped equilibrium open probability of IP3Rs can be reproduced by Markov Chain models that include transitions mediated by fast Ca2+ activation and slower Ca2+ inactivation. Chapter 2 introduces an automated model reduction technique that is based on fast/slow analysis that leverages these time scale differences. Rate constants in the single channel model are categorized as either fast or slow, groups of release site states that are connected by fast transitions are identified and lumped, and transition rates between reduced states are chosen consistent with the conditional probability distributions among states within each group. The fast/slow reduction approach is validated by the fact that puff/spark statistics can be efficiently computed from reduced Ca2+ release site models with small and transient error.;For Markov chain Ca2+ release site models without time-scale separation, the manner in which the full model states should be aggregated for optimal reduction is difficult to determine a priori. In Chapter 3, a genetic algorithm based approach that mimics the inheritance, mutation and selection processes of natural evolution is implemented to reduce these models. Given a full model of interest and target reduced model size, this genetic algorithm searches for set partitions, each corresponding to a potential scheme for state aggregation, that lead to reduced models that well-approximate the full model. A whole cell model with coupled local and global Ca2+ signaling is simplified by replacing a compositionally defined full Ca2+ release site model with a reduced model obtained through the genetic algorithm.;In Chapter 4, a Langevin formulation of Ca2+ release sites is introduced as an alternative model reduction technique that is applicable when the number of channels per Ca2+ release site is too large for the previously discussed reduction methods, but not so large that the stochasticity of Ca2+ release is negligible. The Langevin formulation for coupled intracellular Ca2+ channels results in stochastic differntial equations that well-approximate the corresponding Markov chain models when release sites possess as few as 20 channels, and the agreement improves as the number of channels per release site increases. Importantly, the computational time required by the Langevin approach does not increase with the size of Ca2+ release site.

35

Yousfi, Nabil. "Contribution à l'optimisation aérodynamique des formes des véhicules de tourisme et utilitaires à l'aide des critères d'angles privilégiés entre arêtes." Valenciennes, 2000. https://ged.uphf.fr/nuxeo/site/esupversions/d3a343b6-be81-4c58-a9bf-d13019371942.

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De nos jours, les véhicules terrestres doivent répondre parfaitement aux attentes de l'utilisateur, qui devient de plus en plus exigeant, obligeant ainsi les constructeurs à entamer une rude concurrence dans le domaine de l'aérodynamique. En effet, les gains en performances dynamique et aérodynamique se réduisent très sensiblement depuis quelques années. Le champ d'écoulement autour de ces véhicules est très complexe, caractérisé par une tridimensionnalité : le décollement, le plaquage et la génération de vortex. Nous présentons une étude concernant l'optimisation aérodynamique des formes de véhicules terrestres. L’originalité de notre travail consiste à introduire les angles privilégiés dans la conception des maquettes représentant les véhicules de tourisme et industriels. Nous avons mis en place un dispositif de mesure de coefficient de pénétration dans l'air (c x), de coefficient de pression locale (c p) et de visualisation de l'écoulement autour des maquettes. Les résultats obtenus à partir des expériences effectuées sur les différentes maquettes réalisées ont confirmé l'importance des angles privilégiés associés aux bombements des surfaces planes dans la conception des formes de carrosseries. Un choix judicieux de ces angles entre arêtes a permis d'obtenir à travers la visualisation, un écoulement exempt de décollement et un sillage stable confirmant ainsi les bons résultats obtenus par les mesures de c x et de c p.

36

Franchini, Patrick Lorenzo Angelo. "Structure/Function in the CD site of parvalbumin : understanding calcium affinity using synthetic single site EF-hand peptides." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0020/NQ46344.pdf.

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37

Sanni, Olujide Samuel. "Calcium carbonate surface/bulk scaling mechanisms and kinetics in a once-through in-situ flow visualization rig." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/16419/.

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Scale management is usually a complex mixture of prediction, inhibition and sometimes removal strategies. Investigations into scale formation have largely been focused on precipitation in the bulk solution by assuming that surface scaling always results from pre-precipitated crystals in the bulk solution. Recent observations have shown that bulk and surface scaling do not share the same trends with respect to crystal growth kinetics and inhibition as such the relationship between these two scaling processes are being given attention in the literature. Despite much recent attention on scale formation on surface, there is still not a full mechanistic understanding of how scale layers build on component surfaces. Most of the previous studies have been carried out in a closed system where the saturation ratio was decreasing as a function of time. As such, the understanding of the precipitation/deposition system needs a suitable methodology to build an accurate surface deposition kinetic model. The objectives of this study are to develop a once-through flow rig system suitable to distinctively study bulk precipitation and surface scaling processes and also to improve on the understanding of surface scale deposition mechanisms and kinetics at constant supersaturation. The in-situ flow rig is designed to combine measurement of turbidity in the bulk and real-time visualization of scale build up on a solid surface. Calcium carbonate (CaCO¬3) surface and bulk scaling deposition were followed in-situ and in real-time in a newly developed flow rig that allows assessment and control of various scaling indices and parameters. The kinetics and mechanisms of CaCO3 surface scaling are evaluated from images taken with time using the image analysis protocols to determine the surface coverage, number of particles and average size of the crystal. Brines with different values of saturation ratio (SR) 15, 25, 45, 60, 70 and 90 were tested at 25˚C and 40˚C. The effects of SR, flow rates and temperature on scale deposition were studied. The flow rates used are 10ml/min, 20ml/min and 40ml/min. Also, the influence of SR and inhibitor concentration on surface inhibition efficiency of Polyphosphinocarboxylic acid (PPCA) were studied. The newly developed set-up allows for a mechanistic understanding of scale build up on the surfaces in flowing conditions at constant SR and helps to improve the understanding of both bulk precipitation and surface deposition scaling kinetics. Results show that at low SR, the residence time from the mixing point to sample was shorter than the induction time for bulk precipitation and, as a result, there are no crystals in the bulk solution as the flow passes the sample. Therefore, in contrast to popular thinking, the study has shown that crystals present on the surface are not always the result of a secondary deposition process occurring after the precipitation mechanism which occurs in the bulk solution. The determination of surface crystallization mechanisms and kinetics allow for the correct type and dosage of inhibitor to be selected. Addition of inhibitors at the bulk minimum inhibition concentration (MIC) actually aggravates surface scaling.

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Rakotozandriny, Karol. "Investigation of Calcium Oxalate Crystallization under Microfluidic Conditions for the Understanding of Urolithiasis." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS347.pdf.

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Ces cinquante dernières années, la prévalence croissante de la lithiase urinaire souligne l’importance de comprendre les processus causant la formation des calculs rénaux. L’étude de la cristallisation des oxalates de calcium (CaOx, composé inorganique majoritaire des calculs) a été largement caractérisée en condition batch, qui est néanmoins loin d’être considéré comme biomimétiques vis-à-vis de l’environnement rénal ou de l’écoulement urinaire. Au cours de cette thèse, nous avons développé une puce microfluidique réversible contenant un microcanal mimant un canal collecteur du néphron. In vivo, des calculs de CaOx peuvent s’y former en réponse à une sursaturation en ions Ca2+(aq) and Ox2-(aq). Dans le microcanal, la cristallisation des CaOx a été induite par mélange co-laminaire d’ions Ca2+(aq) et Ox2-(aq) à des concentrations simulant l’hypercalciurie et l’hyperoxalurie modérée. La microscopie électronique à balayage et la spectroscopie Raman ont été utilisées pour caractériser nos résultats. Elles ont montré que les CaOx précipitent dans le microcanal en un mélange de whewellite (CaC2O4.H2O, COM) et de weddellite (CaC2O4.2H2O, COD), tel qu’observer par les médecins. Des observations in situ sur la cinétique de croissance des CaOx ont pu être collectées grâce à notre plateforme microfluidique. Elles confirment les effets des conditions hydrodynamique et chimique sur la croissance, la phase et la morphologie des CaOx. Dans une tentative de se rapprocher d’un modèle plus biomimétique, la surface du microcanal a été modifiée avec de l’hydroxyapatite afin de mimer la formation de cristaus de CaOx sur plaque de Randall
Over the past decades, the increase in kidney stone formers has raised the importance to understand the biomineralization process responsible for urolithiasis. Calcium oxalate (CaOx) crystallization – kidney stone main inorganic compound – has largely been characterized under batch synthesis conditions that cannot be regarded as biomimetic with respect to the microscale environment in the kidney and to the urinary flow. In this work, we used a reversible microchannel to mimic the collecting duct in the nephron where CaOx stones can form due to supersaturated levels in calcium and oxalate ions. Within the channel, CaOx crystallization was induced under co-laminar mixing of Ca2+(aq) and Ox2-(aq) ions matching pathological concentrations – i.e. hypercalciuria and moderate hyperoxaluria. Scanning electron microscopy and Raman spectroscopy were used to support our investigations. They showed that CaOx crystals precipitate in a mixture of monohydrated whewellite (CaC2O4.H2O, COM) and dihydrated weddellite (CaC2O4.2H2O, COD) in the microchannel, similar to what is observed by the physicians. In situ information on the kinetics of CaOx crystal growth could be acquired in our microfluidic system. They confirmed the effect of the hydrodynamic and chemical conditions on the growth kinetics and the final chemistry (phase, shape) of the formed CaOx crystals. In a trial to achieve a more complex biomimetic model (formation of kidney stones on a Randall’s plaque), hydroxyapatite was grown also in the microchannel and the CaOx crystal formation was investigated

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Barrière, Frédéric. "Contribution à la modélisation du site molybdène de la nitrogénase électrochimie, chimie et calculs d'orbitales moléculaires." Brest, 1999. http://www.theses.fr/1999BRES2001.

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Le premier chapitre de cette these fait le point sur ce qui est connu a propos de la structure et de la fonction de la nitrogenase fer-molybdene ainsi que sur les differentes approches suivies en chimie pour tenter de repondre aux questions qui restent en suspens. En effet le site precis ou l'azote moleculaire est coordine et active sur le site actif de cette enzyme n'est pas encore connu. Les trois chapitres suivants illustrent chacune des approches possibles : modelisation fonctionnelle, modelisation structurale et chimie theorique respectivement. Le deuxieme chapitre traite de la deprotection electrochimique d'un site de coordination pour substrats insatures dans mo#2(cp)#2(sme)#3(cl). Le transfert d'electron rend le site de coordination accessible mais il ne s'ouvre reellement qu'en presence du substrat, evitant ainsi de possibles reactions de desactivation. L'affinite relative du site pour differents substrats dont l'un ne serait pas reductible permet de suggerer un mecanisme possible d'inhibition d'une reaction catalytique. Dans le troisieme chapitre l'electrochimie et la synthese de clusters mofe#3s#4, qui sont des modeles structuraux du centre molybdene de la nitrogenase, sont exposees. Une attention particuliere est portee au degre de l'interaction electronique dans les molecules etudiees entre deux sites redox equivalents ou non. Enfin, dans le quatrieme chapitre nous essayons de rechercher, a l'aide de la methode de huckel etendue, les conditions de l'activation de n#2 au centre molybdene de la nitrogenase en etudiant des modeles fonctionnels simples qui interagissent avec l'azote moleculaire, des modeles structuraux et un modele du site actif de l'enzyme.

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Ugenti, Maria Paola <1977&gt. "Characterization of L-type Calcium Channel Binding-Site of a new class of Calcium modulators by a Multidisciplinary approach." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1277/1/Ugenti_MariaPaola_tesi.pdf.

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Many potential diltiazem related L-VDCC blockers were developed using a multidisciplinary approach. This current study was to investigate and compare diltiazem with to the newly developed compounds by mouse Langendorff-perfused heart, Ca2+-transient and on recombinant L-VDCC. Twenty particular compounds were selected by the ligand-based virtual screening procedure (LBVS). From these compounds, five of them (5b, M2, M7, M8 and P1) showed a potent and selective inotropic activity on guinea-pig left atria driven 1 Hz. Further assays displayed an interesting negative inotropic effect of M2, M8, P1 and M7 on guinea pig isolated left papillary muscle driven at 1 Hz, a relevant vasorelaxant activity of 5b, M2, M7, M8 and P1 on K+-depolarized guinea-pig ileum longitudinal smooth muscle and a significant inhibition of contraction of 5b, M2, M8 and P1 on carbachol stimulated ileum longitudinal smooth muscle. Wild-type human heart and rabbit lung α1 subunits were expressed (combined with the regulatory α2δ and β3 subunits) in Xenopus Leavis oocytes using a two-electrode voltage clamp technique. Diltiazem is a benzothiazepine Ca2+ channel blocker used clinically for its antihypertensive and antiarrhythmic effects. Previous radioligand binding assays revealed a complex interaction with the benzothiazepine binding site for M2, M7 and M8. (Carosati E. et al. J. Med Chem. 2006, 49; 5206). In agreement with this findings, the relative order of increased rates of contraction and relaxation at lower concentrations s(≤10-6M) in unpaced hearts was M7>M2>M8>P1. Similar increases in Ca2+ transient were observed in cardiomyocytes. Diltiazem showed negative inotropic effects whereas 5b had no significant effect. Diltiazem blocks Ca2+current in a use-dependent manner and facilitates the channel by accelerating the inactivation and decelerating the recovery from inactivation. In contrast to diltiazem, the new analogs had no pronounced use-dependence. Application of 100 μM M8, M2 showed ~ 10% tonic block; in addition, M8, M2 and P1 shifted the steady state inactivation in hyperpolarized direction and the current inactivation time was significantly decreased compared with control (219.6 ± 11.5 ms, 226 ± 14.5 vs. 269 ± 12.9 vs. 199.28 ± 8.19 ms). Contrary to diltiazem, the recovery from the block by M8 and M2 was comparable to control. Only P1 showed a significantly decrease of the time for the recovery from inactivation. All of the compounds displayed the same sensitivity on the Ca2+ channel rabbit lung α1 except P1. Taken together, these findings suggest that M8, M2 and P1 might directly decrease the binding affinity or allow rapid dissociation from the benzothiazepine binding site.

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Ugenti, Maria Paola <1977&gt. "Characterization of L-type Calcium Channel Binding-Site of a new class of Calcium modulators by a Multidisciplinary approach." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1277/.

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Many potential diltiazem related L-VDCC blockers were developed using a multidisciplinary approach. This current study was to investigate and compare diltiazem with to the newly developed compounds by mouse Langendorff-perfused heart, Ca2+-transient and on recombinant L-VDCC. Twenty particular compounds were selected by the ligand-based virtual screening procedure (LBVS). From these compounds, five of them (5b, M2, M7, M8 and P1) showed a potent and selective inotropic activity on guinea-pig left atria driven 1 Hz. Further assays displayed an interesting negative inotropic effect of M2, M8, P1 and M7 on guinea pig isolated left papillary muscle driven at 1 Hz, a relevant vasorelaxant activity of 5b, M2, M7, M8 and P1 on K+-depolarized guinea-pig ileum longitudinal smooth muscle and a significant inhibition of contraction of 5b, M2, M8 and P1 on carbachol stimulated ileum longitudinal smooth muscle. Wild-type human heart and rabbit lung α1 subunits were expressed (combined with the regulatory α2δ and β3 subunits) in Xenopus Leavis oocytes using a two-electrode voltage clamp technique. Diltiazem is a benzothiazepine Ca2+ channel blocker used clinically for its antihypertensive and antiarrhythmic effects. Previous radioligand binding assays revealed a complex interaction with the benzothiazepine binding site for M2, M7 and M8. (Carosati E. et al. J. Med Chem. 2006, 49; 5206). In agreement with this findings, the relative order of increased rates of contraction and relaxation at lower concentrations s(≤10-6M) in unpaced hearts was M7>M2>M8>P1. Similar increases in Ca2+ transient were observed in cardiomyocytes. Diltiazem showed negative inotropic effects whereas 5b had no significant effect. Diltiazem blocks Ca2+current in a use-dependent manner and facilitates the channel by accelerating the inactivation and decelerating the recovery from inactivation. In contrast to diltiazem, the new analogs had no pronounced use-dependence. Application of 100 μM M8, M2 showed ~ 10% tonic block; in addition, M8, M2 and P1 shifted the steady state inactivation in hyperpolarized direction and the current inactivation time was significantly decreased compared with control (219.6 ± 11.5 ms, 226 ± 14.5 vs. 269 ± 12.9 vs. 199.28 ± 8.19 ms). Contrary to diltiazem, the recovery from the block by M8 and M2 was comparable to control. Only P1 showed a significantly decrease of the time for the recovery from inactivation. All of the compounds displayed the same sensitivity on the Ca2+ channel rabbit lung α1 except P1. Taken together, these findings suggest that M8, M2 and P1 might directly decrease the binding affinity or allow rapid dissociation from the benzothiazepine binding site.

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Kirchheim, Ana Paula. "Aluminatos tricálcico cúbico e ortorrômbico : análise da hidratação in situ e produtos formados." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/14404.

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A composição do clínquer controla a cinética da hidratação do cimento, devido às fases potencialmente mais reativas. O aluminato tricálcico (C3A) é a fase que reage mais rápido quando em contato com a água, formando rapidamente os aluminatos de cálcio hidratado (C3AH6, C4AH19 e C2AH8), com a liberação de elevada quantidade de calor. Para casos práticos, o sulfato de cálcio é adicionado ao clínquer para retardar esta reação. Na presença do sulfato de cálcio, o produto formado da reação com o C3A é o trissulfoaluminato de cálcio hidratado (etringita). Geralmente, a forma cristalina do C3A sintetizado durante o processo de clinquerização é cúbica. No entanto, o íon Na+, pode ser incorporado na estrutura cristalina do C3A, em substituição ao Ca2+, levando à modificação da forma cristalina de cúbica para ortorrômbica. Alguns estudos realizados apresentam interessantes resultados sobre a interferência desta fase modificada na hidratação do cimento, afetando o início de pega e a trabalhabilidade da matriz cimentícia. Os maiores problemas são observados em cimentos Portland branco onde, em função da necessidade de redução da quantidade de ferroaluminato tetracálcico (C4AF), ocorre um incremento na quantidade de C3A. Existe uma grande lacuna referente às características específicas de cada aluminato na ausência e na presença de gipsita e hidróxido de cálcio. Desta forma, mostra-se interessante a observação das características das fases do clínquer, principalmente quando se trata dos aluminatos, visto que este seria um passo importante no entendimento dos problemas de início de pega. O presente estudo utiliza fases puras (C3A cúbico e ortorrômbico) sintetizadas em laboratório, para, desta forma, focar as reações independentemente, isolando-as das demais. A associação de diferentes técnicas que possibilitam avaliar a hidratação in situ, com dois métodos originais de análise, utilizando radiações síncrotron, bem como análise de características reológicas e utilização de técnicas clássicas possibilitaram traçar algumas contribuições. Os resultados mostraram que existem grandes diferenças na hidratação de cada aluminato, sendo o ortorrômbico mais reativo nas primeiras idades quando em presença de gipsita, formando primeiramente a etringita. Na ausência de gipsita, o C3A cúbico se mostrou mais reativo, formando primeiro os aluminatos de cálcio hidratados e com maior liberação de calor. O hidróxido de cálcio, saturando a água da mistura, retardou as reações iniciais do C3A ortorrômbico na ausência de gipsita e, em maiores idades, retardou a formação de etringita em pastas de C3A com gipsita e 10% de hidróxido de cálcio.
The clinker composition controls the kinetics of cement hydration mainly due to the presence of potentially more reactive phases. The reaction of tricalcium aluminate C3A with water is almost immediate. Crystalline hydrates, such as C3AH6, C4AH19 and C2AH8 are quickly formed with generation of a large amount of heat. In presence of calcium sulfate, the product formed from the C3A reaction is ettringite or high-sulfate calcium aluminate. The alkalis can be incorporated into a number of phases in the clinker and often Na2O is taken up by the C3A. When C3A is synthesized in the presence of these elements, it changes its crystal lattice and the formation of the orthorhombic phases occurs. Earlier studies have already shown interesting interference from this phase on the cement hydration. Significant problems are found in white Portland cement, where the necessity of reducing the amount of tetracalcium ferroaluminate (C4AF) leads to an increase of the C3A content. There is a large gap in understanding the specific characteristics of each crystalline form of C3A in presence and absence of gypsum and calcium hydroxide. Therefore, characterization of the cement phases is important, especially when it is related to the aluminates (cubic and orthorhombic), since this would be a step to further understand the setting problems. The present study uses pure phases (cubic and orthorhombic C3A) synthesized in laboratory, to focus on the reactions independently, isolating the reactions of the others phases. The experimental research integrated two different synchrotron radiation techniques that enable the study of the hydration in situ with rheological analysis and classical techniques allowing to obtain contributions in the hydration of each C3A. The results showed that there are significant differences in the hydration of each aluminate, and the orthorhombic C3A is more reactive in early ages when in presence of gypsum, by forming ettringite first. In absence of gypsum the cubic C3A was more reactive, forming first calcium aluminates hydrates and generating a higher amount of heat. The ettringite formation and the heat evolution of pastes in presence and absence of gypsum were delayed when calcium hydroxide was present in the mixture.

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Garry, Andrew. "An in situ study to determine the effects of casein phosphopeptide-amorphous calcium phosphate toothpaste in orthodontic patients." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2034461/.

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Objectives: To investigate the remineralisation of enamel subsurface lesions with CPP-ACP toothpaste compared with regular fluoride toothpaste in orthodontic patients. Design: Randomised controlled clinical trial with a cross-over design. Setting: Orthodontic department at the Liverpool University Dental Hospital. Participants: 12 orthodontic patients receiving fixed orthodontic treatment. Methods: Demineralised sub-surface enamel lesions were placed in situ onto a fixed appliance in the lower premolar region. Participants were randomly allocated to receive either standard fluoride toothpaste or a CPP-ACP paste (GC Tooth Mousse™) in addition to the fluoride toothpaste. Transverse Microradiography (TMR) was used to analyse and compare the mineral content profiles of the lesions. Results: Mineral loss ΔZ reduced by 15.4% and 24.6% for the fluoride and CPP-ACP groups respectively, with a statistical significant difference between these groups (p = 0.023). Lesion depth reduced by 1.6% and 11.1% for fluoride and CPP-ACP groups respectively, with a statistically significant difference between these groups (p = 0.037). Lesion width reduced by 4.5% and 15.3% for fluoride and CPP-ACP groups respectively, with a statistically significant difference between these groups (p=0.015). Conclusion/Implications: Remineralisation occurred during the in situ phase regardless of treatment group allocation, however the CPP-ACP combined with fluoride group demonstrated a statistically significant increased remineralising effect. CPP-ACP paste may be beneficial for patients undergoing orthodontic treatment who are at high risk of demineralisation or who have demonstrated early signs of white spot lesion formation. Trial Registration: Registered on Current Control Trials http://www.controlled-trials.com/ISRCTN04899524.

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Ferreira, Veridiana Lopes. "Evolução da microestrutura do hexaluminato de cálcio (CaAl12O19) formado in situ para obtenção de cerâmicas refratárias porosas." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-29042016-084458/.

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Cerâmicas porosas combinam baixa condutividade térmica com elevada estabilidade química, dimensional e refratariedade. Devido a isso, seu uso como isolante térmico em altas temperaturas (T >1000°C) tem se apresentado como uma importante solução para reduzir o consumo energético. Dentre as diversas matérias primas utilizáveis nessa aplicação, o hexaluminato de cálcio (CaAl12O19 ou CA6) é um novo tipo promissor de refratário leve. Entre suas características mais importantes, destacam-se o alto ponto de fusão (1875°C) e a dificuldade intrínseca para densificar, devido à morfologia dos cristais em forma de placas que permite manutenção da porosidade em altas temperaturas, e por longos tempos. Apesar do grande interesse tecnológico e dos diversos estudos relatando propriedades e aplicações, há poucos trabalhos descrevendo a evolução da microestrutura de estruturas porosas formadas \"in situ\" a partir de fontes de Al2O3 e CaO. Sabendo que essa rota de processamento permite significativa economia de energia e tempo, compreender os mecanismos e variáveis envolvidos torna-se um importante ponto de investigação. Neste trabalho, foram preparadas composições com diferentes proporções de Al2O3 e CaCO3 por meio de prensagem uniaxial. Após tratamento térmico (500-1500°C), as amostras foramcaracterizadas em relação à porosidade total, resistência à ruptura por flexão, módulo elástico, fases numeralógicas formadas, dilatação térmica linear e morfologia. Os principais fatores que afetaram a evolução da microestrutura porosa foram o teor de CaCO3 adicionado ao sistema, o tamanho médio dessas partículas e a temperatura final de tratamento térmico. Para todas as composições com CaCO3, verificou-se que a formação de poros após a decomposição do CaCO3 (650-720°C) não afetou o nível total de porosidade da estrutura. Entre 1300-1400°C ocorreu a formação de fases intermediárias (CaAl2O4 e CaAl4O7) com composição eutética e baixo ponto de fusão ao redor dos poros. Em 1500°C, essas fases líquidas adquiriram a composição do hexaluminato e se cristalizaram, gerando estruturas porosas e com razoável resistência mecânica.
Porous ceramics combine low thermal conductivity with high chemical and dimensional stability and refractoriness. Therefore, their use as insulators at high temperatures (T>1000°C) has emerged as an important solution for the reduction ofenergy consumption. Among the various raw materials to be used for such a purpose, calcium hexaluminate (CaAl12O19 or CA6) is a promising new type of lightweight refractory material. Some ofits most important features include high melting point (1875°C) and intrinsic difficulty to densify due to the morphology of its plate-like crystals that enables the maintenance of porosity at higher temperatures and for longer times. Despite the great technological interest it has drawn and the development of studies on its properties and applications, the literature reports few studies on the evolution of its microstructure formed in situ from Al2O3 and CaO sources. Because this processing route significantly saves energy and time, the mechanisms involved must be understood. This dissertation addresses the preparation of compositions with different proportions of Al2O3 and CaCO3 by uniaxial pressing. After heat treatment (500-1500°C), samples were characterized regarding total porosity, tensile strength by bending, elastic modulus, formed phases, dilatometric analyzis and scanning electron microscopy. The main factors that affected the evolution of the porous microstructure were the CaCO3 content added to the system, average size of the particles and the final temperature of the heat treatment. The formation of pores after the CaCO3 (650-720°C) decomposition did not affect the level of total porosity significantly. The formation of intermediate phases (CaAl2O4 and CaAl4O7) with eutectic composition and low melting point surrounding the pores was observed between 1300-1400°C. At 1500°C, such liquid phases displayed a hexaluminate composition and crystallized, which resulted in porous structures of reasonable strength.

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Francisco, Silvana Boldrini. "Efeito de formulações de dentifricios com CaCO3 versus SiO2 na inibição da desmineralização do esmalte dental : estudo in situ." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289304.

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Orientador: Jaime Aparecido Cury
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: Carbonato de cálcio precipitado (CaCO3) é o principal abrasivo usado nos dentifrícios comercializados no Brasil. Devido suas propriedades tamponante e alcalinizante, ele poderia reduzir a acidogenicidade bacteriana, potencializando o efeito do flúor no desenvolvimento da cárie dental. Utilizando-se o modelo intra-oral de curta duração (ZERO et aI. J Dent Res.71: 871-8, 1992), avaliou-se o efeito do CaCO3, na redução da desmineralização do esmalte dental. Blocos de esmalte (5 x 5 mm), de microdureza superficial pré-deterrhinada, foram cobertos por uma camada de bactérias ("placa artificial ") obtidas a partir de uma cultura de S. mutans, e colocadas em placas palatinas confeccionadas para os voluntários (aprovado pelo Comitê de Ética e Pesquisa da FOP UNICAMP). O estudo foi do tipo cruzado e os 10 voluntários foram submetidos a três grupos de tratamento: Controle (escovação sem dentifrício), com dentifrício contendo 1500 ppm de F (MFP) à base de sílica (SiO2) ou carbonato (CaCO3) . Ao mesmo tempo que os voluntários escovaram seus dentes com os dentifrícios, os dispositivos ficaram mergulhados na suspensão (1:3) dos mesmos, sendo que o grupo controle ficou imerso em tampão bicarbonato 20 mM, pH 7,0 . Imediatamente após a escovação os dispositivos foram colocados na boca. Esperou-se 20 minutos para ação dos dentirncios na "placa artificial" após o que a sacarose a 20% foi bochechada. Decorridos 45 minutos da metabolização da sacarose pela "placa artificial", os dispositivos foram removidos para análises. No esmalte foi determinada a microdureza superficial e calculada a porcentagem de perda de dureza em relação à inicial (%PDS) , assim como a incorporação de flúor pelo esmalte. Na "placa artificial", foram analisadas as concentrações de flúor iônico (FI) e ionizável (MFP) Os resultados (médias i: desvio padrão) , respectivamente para os Grupos controle, MFP/Si02 e MFP/CaC03 em termos da média das distâncias foram: % PDS: 24, 75i: 3,33a; 7,70::i:O,32b; 3,54::i:O,32c.. Concentrações de flúor (ppm) no esmalte: 1273,22 i: 267,2a; 1713,64 i: 426,Oa; 1565,03 i: 351,3a. Flúor na placa «_g/g): FI= 0,02 i: O,Ob; 0,93 i: 0,6ab; 1,36 i: 1,Oa.; MFP = 0,14 i: O,la; 1,78 i: 1,26b; 1,40 i: 0,9b. Médias seguidas de letras distintas diferem entre si (p<0,05). Os resultados mostraram que CaC03 reduz a desmineralização do esmalte, sugerindo que o abrasivo pode contribuir para um maior efeito do flúor de dentifrício no controle da cárie dental
Abstract: Precipitated ca1cium carbonate (CaCO3) is the main abrasive used in dentifiices comercialized in Brazü. It may reduce bacterial acidogenicity, potentiating the effect of fluoride in the development of dental caries due to its aIkaline and buífering capacities. The effect of CaCO3 on the reduction of enamel demineralization was evaluated by using the short-tenn intra-oral model (Zero et ai., J Dent Res. 71: 871 - 8,1992). Enamel blocks (5 x 5 mm), with known surfãce microhardness, were covered with a layer of bacteria (tltest plaque") obtained ftom a culture of S. _utans, and were placed on palatal appliances manufactured for the volunteers (approved by the Research and Ethics Committe of FOP UNICAMP). This study fiad a crossover design and 10 volunteers were submitted to 3 treatment groups: control (brushing without dentiftice), with dentifiice containing 1500 ppm F (MFP) and silica (SiO2) or carbonate (CaCO3)' At the same time that the volunteers brushed their teeth with the dentifiices, the appliances were placed in a suspension of the same dentifiice (1 :3). In the control group, the appliance was immersed in 20 mM bicarbonate buffer, pH 7. Immediately after the toothbrushing the appliances were put back in the mouth After 20 minutes of dentifrice action on "artificial plaque", 200Á! Sucrose solution was rinsed. After 45 minutes of sucrose fennentation by "artificial plaque", the appliances were removed. Enamel surface microhardness and the percentage of change in relation to baseline (%SMC) were calculated, as well as fluoride uptake in enamel. In artificial plaque, the concentration of ionic fluoride (FI) and fluoride as monofluotphosphate was detennined (MFP). The results (means :t s.d.) respectively for the control, MFP/SiO2 and MFP/CaCO3 in tenns the media at the distances were: %SMC: 24.75:1: 3.33a; 7.70:tO.32b; 3.54:tO.32c.. Fluoride concentration in enamel was:: 127322 :!:: 267.2a; 1713.64 :!:: 426.0a; 1565.03 :I: 351.3a. Fluoride in plaque ({Jtglg): FI= 0.02 :!:O.Ob; 0.93:!:: 0.600; 1.36:!:: 1.0a.; MFP = 0.14 :!:: 0.1a; 1.78:!:: 1.26b; 1.40:!:: 0.9b. Means followed by distinct letters differ ftom each other (p<0.05). The results showed that Caco3 reduces enamel demineralization, suggesting that the abrasive may contribute to a higher effect offluoride present in the dentifiice on dental caries control
Doutorado
Biologia e Patologia Buco-Dental
Doutor em Odontologia

46

Mahmood, Samira Rashid. "Vascular calcium adenosine triphosphatase as a site of noradrenaline and hypotensive drug action." Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1626.

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47

Silva, Kélio Garcia. "Avaliação in situ da capacidade remineralizadora de selantes que contenham fosfato de cálcio amorfo e/ou fluoreto /." Araçatuba : [s.n.], 2007. http://hdl.handle.net/11449/104232.

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Orientador: Denise Pedrini
Banca: Alberto Carlos Botazzo Delbem
Banca: Robson Frederico Cunha
Banca: Maria Aparecida de Andrade Moreira Machado
Banca: Marinês Nobre dos Santos Uchôa
Resumo: O objetivo desse estudo foi avaliar in situ o potencial remineralizador de selantes que contenham fosfato de cálcio amorfo e/ou fluoreto com lesão artificial de cárie em esmalte de superfície lisa. Dez voluntários participaram desse estudo triplo cego com duração de 5 dias para cada grupo (esmalte desmineralizado + Fluroshield, esmalte desmineralizado + Aegis (ACP), esmalte desmineralizado + Fluoreto (experimental), esmalte desmineralizado + ACP + Fluoreto (experimental) e esmalte desmineralizado - Controle) e intervalo de 7 dias entre eles. Dez dias antes do início e durante todo o experimento os voluntários utilizaram dentifrício não fluoretado. Após o período experimental, foram avaliadas a porcentagem de recuperação de microdureza de superfície (%MDS), recuperação da área mineral integrada (_Z) e determinada a concentração de fluoreto (μg F/mm3), cálcio (μg Ca/mm3) e fósforo (μg P/mm3) presentes no esmalte. Os dados obtidos da %MDS e _Z foram submetidos à Análise de Variância seguida do teste de Tukey, e os do fluoreto, cálcio e fósforo foram submetidos ao teste de Kruskal-Wallis (p<0,05). Todas as variáveis foram submetidas à análise de regressão e ajustadas de acordo com a tendência. Os grupos de materiais com fluoreto e/ou ACP apresentaram maior capacidade remineralizadora (%MDS e _Z) quando comparado com o grupo Controle. O grupo com apenas ACP apresentou resultado melhor ou semelhante quando comparado com os outros grupos e a associação do ACP e fluoreto não mostrou ser mais eficiente. A lesão de cárie mostrou-se mais remineralizada na distância de 150 ìm quando comparada com a de 600 ìm para os valores de %MDS. As concentrações de fluoreto, cálcio e fósforo presentes no esmalte variaram de acordo com o grupo analisado. Entre as variáveis avaliadas, somente foi verificada correlação entre %MDS e _Z.
Abstract: The purpose of this study was to evaluate in situ the remineralizing potential of sealants containing amorphous calcium phosphate and/or fluoride in artificially induced carious lesions on smooth enamel surfaces. Ten volunteers took part in this triple-blind study, which had the duration of 5 days for each group: demineralized enamel + Fluroshield; demineralized enamel + Aegis (ACP); demineralized enamel + Fluoride (experimental); demineralized enamel + ACP + Fluoride (experimental) and demineralized enamel (Control). A wash-out period of 7 days was allowed between the treatments. Ten days before and during the whole experiment the volunteers used a non-fluoridated dentifrice. After the experimental period, the percentage recovery of surface microhardness (%RSM) and the recovery of integrated mineral area (HZ) were evaluated. The concentration of fluoride (Jg F/mm3), calcium (Jg Ca/mm3) and phosphorous (Jg P/mm3) present in enamel was also determined. Data obtained from %RSM and HZ were submitted to Analysis of Variance and Tukey's test. Data from fluoride, calcium and phosphorous concentration were submitted to Kruskal-Wallis test. Significance level was set at 5%. All variables were also evaluated by regression analysis and adjusted according to the tendency. The groups with materials containing fluoride and/or ACP presented a higher remineralizing capacity (%RSM and HZ) than the Control group. The group with material containing only ACP showed a better or similar result compared to the other groups. The association between ACP and fluoride did not show a greater efficacy. For %RSM, the 150-Jm distance showed a higher remineralization of the artificially induced carious lesions compared to the 600-Jm distance. The concentrations of fluoride, calcium and phosphorous present in enamel varied according to the group.
Doutor

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Milovanovitch, Vladan D. "Comportement dynamique des barrages en béton et prise en compte des effets de site sur les ondes sismiques incidentes." Phd thesis, Ecole Nationale des Ponts et Chaussées, 1992. http://tel.archives-ouvertes.fr/tel-00529511.

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L'influence des effets de site sur la réponse sismique des barrages-voûtes a été étudiée récemment par différents auteurs. Dans les travaux effectués jusqu'à présent l'excitation sismique est utilisée de différentes façons, mais toujours en se limitant à quelques angles d'incidence d'ondes sismiques, définis à l'avance. Les réponses des barrages-voûtes dans ces conditions ne représentent que des cas particuliers sur lesquels sont basées les conclusions. La méthode des surfaces d'énergie présentée dans ce travail, représente une méthode générale (et en même temps économique) qui se sert du balayage tridimensionnel fin sur tous les angles d'incidence dans l'espace, pour différents types d'ondes sismiques et leurs différentes célérités de propagation. L'excitation sismique est représentée par les ondes P, SV, SH et ondes de Rayleigh. Leurs expressions ont été développées en séries limitées et remplacées par différentes combinaisons de fonctions de forme dont les coefficients sont les fonctions d'angles d'incidence et de direction. Cette méthode nous permet de définir les intervalles d'angles d'incidence les plus dangereux et ceux les moins dangereux pour un barrage ainsi que l'influence et l'importance des effets de site sur la réponse sismique des barrages-voûtes. Dans les conditions générales d'angles d'incidence, plusieurs paramètres ont été variés et analysés à l'aide de 12 différents modèles qui représentent des systèmes complexes du barrage-voûte avec son réservoir et la masse rocheuse qui les entoure. Ces paramètres sont : les angles d'incidence , la position du noeud dans le barrage, les célérités de propagation d'ondes du champ proche dans la roche, les célérités de propagation d'ondes du champ lointain, les effets de site, les types d'ondes, la compressibilité de l'eau, la présence de la retenue pleine, le changement de la taille et de la forme du réservoir, la direction de la vallée, des petites modifications de la forme de la frontière du modèle numérique, l'utilisation des éléments fluides pour modéliser le réservoir. La méthode d'énergie maximale traite le problème extrémal de l'énergie dans le barrage sur l'espace des fonctions de forme. L'excitation sismique est représentée par un signal plus complexe que celui obtenu par des ondes P, S V, SH et ondes de Rayleigh. Dans les analyses sismiques sur les effets maxima on détermine également des mouvements "éventuels" de la roche qui donnent l'énergie maximale dans le barrage. Les conclusions donnent un apport théorique basé sur les analyses paramétriques effectuées dans ces conditions générales d'angles d'incidence, ainsi qu'un apport pratique qui montre le moyen de détermination de la position du barrage la plus favorable par rapport aux intervalles d'angles prédominants de séismes (en remplissant en même temps les autres conditions nécessaires: statiques, géologiques etc.). Dans le domaine théorique cette thèse élargit et classifie nos connaissances sur les phénomènes des effets de site, en premier lieu l'influence sur le barrage (structure étendue) du massif rocheux, dont les propriétés mécaniques sont exprimées par la célérité de propagation d'ondes sismiques et de l'interaction barrage-fluide du lac de retenue. La méthode présentée dans ce travail ainsi que le logiciel entièrement créé pour le même travail peuvent être applicables, avec peu de modifications, sur d'autres structures étendues dont le comportement sismique est décrit dans le domaine linéaire de façon suffisamment correcte.

49

Jagannathan, Deepak. "Calcium-Silicate-Hydrate in cementitious systems : chemomechanical correlations, extreme temperature behavior, and kinetics and morphology of in-situ formation." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/92651.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 96-102).
Concrete, the second most used material on the planet, is a multi-scale heterogeneous material. A fundamental component known as Calcium-Silicate-Hydrate which forms from the reaction between cement and water is the binding phase in concrete. Curiously, this is the least understood component of concrete because of its porous amorphous structure. Further, beyond mere scientific curiosity, cementS̆s industry large carbon footprint due to its volume of usage sets up a practical context to seek improvements in concrete performance and equip concrete with additional functionalities. It is our contention that we can better understand the least known and crucial component of concrete, Calcium-Silicate-Hydrate, to inform the design of next generation of high performance concrete. With this broad theme, this thesis presents three different aspects of properties of Calcium Silicate Hydrate: chemomechanical correlations, behavior under extreme temperature and pressures, and kinetics and nanostructure of in-situ formation. Calcium Silicate Hydrate (C-S-H) formed in-situ in concrete is believed to have a layered structure with silicate chains similar to crystal structures of Tobermorite and Jennite. Its chemical composition, characterized by Ca/Si ratio, must therefore influence its silicate chain structure and thus its mechanical properties. We explore the correlation between CS- H composition and its mechanical properties. By varying chemical composition of cement clinkers and supplementary cementitious materials, water/cement ratios, and hydration temperatures, we prepare cement pastes with different C-S-H of different C/S ratios. We use nanoindentation and X-ray spectroscopy to respectively measure the mechanical properties and composition of C-S-H. We then study the mechanical performance of C-S-H at elevated temperatures. This is relevant in the design of infrastructure that can sustain extreme events such as blasts and high velocity impacts. As a starting point for concrete that would enable such infrastructure, we use ultra high performance concrete (UHPC). We use nanoindentation and X-ray spectroscopy to respectively measure mechanical properties and composition of individual components of UHPC. We compare the composition and properties of C-S-H found in UHPC to that found in ordinary cement pastes (OPC). Our grid nanoindentation experiments also reveal an artifacts created by the incorporation of steel fiber reinforcements in UHPC. We find that steel fiber reinforcements disrupt the perfect packing of constituent materials in UHPC to create capillary porosity at microscale. Further, we study the mechanical properties of C-S-H in concrete specimens subjected to high temperatures of 400°C and 1000°C. As a product of the reaction between cement and water, the properties of C-S-H are ultimately controlled by the reaction. To obtain quantitative kinetics, we use time-lapse optical microscopy to study hydration of micron sized monoclinic C₃S particles with in droplets of water of 50 [mu]m. Using Raman spectroscopy, we characterize the hydration product growing inside these droplets.
by Deepak Jagannathan.
S.M.

50

Plusquellec, Gilles. "Analyse in situ de suspensions de silicate de calcium hydraté : application aux interactions ioniques à la surface des particules." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS046/document.

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Cette étude a pour objectif d’étudier expérimentalement les interactions entre différents anions (chlorure, bromure, nitrate et sulfate) et le silicate de calcium hydraté (C-S-H) afin de construire un modèle thermodynamique capable de prédire cette interaction. Des suspensions de C-S-H synthétisées ont été mises en contact avec différents types de sel (sel de calcium ou d’alcalins). L’influence de la température et de l’incorporation d’aluminium au sein de la structure du C-S-H ont également été prises en compte.L’utilisation d’une méthode d’analyse classique de ce type de système (c’est-à-dire séparation des phases liquide et solide puis analyse de la solution) a révélé ses limites avec, entre autres, une mauvaise reproductibilité des résultats. L’étape de séparation des phases s’est trouvée être à l’origine des difficultés rencontrées.Une seconde méthode d’analyse ne nécessitant pas de filtration des suspensions de C-S-H a été mise au point pour cette étude.Les résultats obtenus ont alors démontrés la non-adsorption des chlorures, nitrates ou bromures par les particules de C-S-H : ces anions n’ont qu’un rôle de compensation de charge au sein de la couche diffuse entourant les particules en suspensions.Les ions calcium (dans le cas d’ajout de sel de calcium) ne s’adsorbent que très faiblement à la surface du C-S-H. Ceci n’est pas influencé par la présence d’aluminium dans la structure. Une température plus faible (5°C) ou plus élevée (40°C) conduit à une adsorption plus faible, voire nulle.L’utilisation d’un modèle thermodynamique de simulation de C-S-H (développé dans une autre étude) a permis de reproduire les résultats expérimentaux obtenus, confirmant donc la validité de ces derniers mais également celle du modèle utilisé
This project aims to study the interactions between calcium silicate hydrate (C-S-H) and different anions (chlorides, bromides, nitrates and sulfates) in order to build a thermodynamic model and then be predictable. The simplified system CaO-SiO2-H2O is studied by synthesizing C-S-H suspensions and mixing them with different kind of salts (calcium salt or alkali salt). The influence of the temperature and the presence of aluminum in the structure of the C-S-H is also examined.A classical way to investigate this kind of system is to separate the liquid phase from the solid phase in order to analyze them separately. Nevertheless, this step has a large influence on the system, and the experimental results suffer from a really bad reproducibility.Another analysis method has then been developed in order to avoid the separation of the different phases. The results show that there is no adsorption of chlorides, bromides or nitrate on the surface of the C-S-H. They only have a role as a charge compensator in the diffuse layer around the particles in suspension.The calcium cation (in the case of calcium salt addition) can be adsorbed by C-S-H, but in a small quantity. The substitution of silicon by aluminum in C-S-H doesn’t have any influence on this phenomenon. A higher or lower temperature results in a weaker adsorption, even inexistent.Those experimental results have been reproduced by using a thermodynamic model developed in a previous study. Thus, the validity of the experimental part but also the one of the model are confirmed

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