To see the other types of publications on this topic, follow the link: PGCD.
Dissertations / Theses on the topic 'PGCD'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'PGCD.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Bouraoui, Rachid. "Calcul sur les grands nombres et VLSI : application au PGCD, au PGCD étendu et à la distance euclidienne." Phd thesis, Grenoble INPG, 1993. http://tel.archives-ouvertes.fr/tel-00343219.
Full textAbstract:
Dans le cadre de cette thèse nous avons étudie l'implantation des algorithmes de l'arithmétique en ligne. En particulier, la réalisation de deux circuits destines aux applications exigeant une précision infinie est exposée. En effet, dans de nombreux domaines tels que la génération de nombres aléatoires, cryptographie, calcul formel, arithmétique exacte, réduction de fraction en précision infinie, calcul modulaire, traitement d'images..., les opérateurs classiques manquent d'efficacité. Face a ce type de problèmes, un remède peut être apporte par le calcul en ligne selon lequel les calculs sont faits en introduisant les opérandes en série chiffre a chiffre en notation redondante. Nous obtenons ainsi un haut degré de parallélisme et une précision variable linéairement. Le premier circuit présenté implante un algorithme de pgcd nomme Euclide offrant, d'après les simulations, le meilleur compromis cout matériel/performance. Il donne également les coefficients de Bezout. Ce circuit est appelé a résoudre les problèmes lies au temps de calcul du pgcd par les méthodes classiques rencontrées dans beaucoup d'applications. Une deuxième application montre la possibilité de fusionner des opérateurs en ligne afin d'obtenir un opérateur complexe. L'exemple traite dans cette thèse est celui de la distance euclidienne: z=x#2+y#2 utilisée, entre autres, pour la resolution du moindre carre des systèmes linéaires
2
SEDJELMACI, SIDI MOHAMED. "Contribution au calcul parallele du pgcd de deux entiers." Paris 13, 1999. http://www.theses.fr/1999PA132031.
Full textAbstract:
La complexite du calcul du plus grand commun diviseur (pgcd) de deux entiers en parallele est encore un probleme ouvert et on ne sait pas s'il est dans la classe nc ou p-complet. Les meilleurs algorithmes connus a l'heure actuelle sont ceux de chor and goldreich et de sorenson qui ont une complexite de o (n/logn) en temps utilisant o(n 1 + ) processeurs sur des crcw pram. La premiere partie de ce travail est consacree a un bref historique du probleme et un rappel sur la complexite en parallele. Nous proposons ensuite une classification d'algorithmes du pgcd selon qu'ils manipulent les premiers ou les derniers bits des nombres. Le chapitre 3 porte sur des ameliorations de l'algorithme de weber (un des plus puissants algorithmes paralleles) et l'etude de sa complexite dans le pire des cas. Nous presentons dans le chapitre 4 une nouvelle technique de division modulaire (appelee ppi pour pen and paper inverse) avec ses multiples applications. Au chapitre 5, nous suggerons la notion de reduction comme outil d'etude pour les algorithmes du pgcd et proposons une nouvelle reduction appelee reduction k-aire rapide (ou fast k-ary). Une extension aux reductions mixtes est traitee en chapitre 6. Elles sont obtenues en combinant plusieurs reductions a la fois. En conclusion, nous exposons quelques remarques ainsi que certaines voies de recherche futures.
3
RUPPRECHT, DAVID. "Elements de geometrie algebrique approchee : etude du pgcd et de la factorisation." Nice, 2000. http://www.theses.fr/2000NICE5389.
Full textAbstract:
Cette these presente quelques resultats novateurs de geometrie algebrique approchee, branche recente de la geometrie algebrique effective. Les algorithmes habituels dans ce domaine reposent sur l'utilisation de nombres exacts et sont mis a defaut lorsque nous devons utiliser des approximations numeriques. Nous proposons ici non seulement de nouveaux algorithmes prenant en compte le fait que nous ne disposons que de donnees approchees, mais surtout nous donnons des theoremes permettant de certifier les resultats obtenus, ainsi que des implementations efficaces et utilisables de ces algorithmes. L'etude se decompose en deux grandes parties. Tout d'abord, nous etudions le calcul du pgcd approche de deux ou plusieurs polynomes d'une variable. Nous proposons, analysons et comparons plusieurs algorithmes permettant ce calcul et donnons plusieurs criteres certifiant les resultats, ce qui constitue l'un des points fondamentaux de ce travail. Cette etude est realisee aussi bien dans un cadre reel que dans un cadre p-adique. Nous appliquons ensuite ces resultats a l'etude des decompositions sans facteur carre d'un polynome a coefficients reels. Nous abordons, ensuite, l'etude de la factorisation de polynomes. Dans un premier temps, nous detaillons un nouvel algorithme, tres rapide, de factorisation absolue d'un polynome a deux variables a coefficients rationnels. Ce nouvel algorithme est base en grande partie sur des calculs approches, avant de retourner finalement une reponse exacte. Il sert ensuite de base a un algorithme calculant une factorisation approchee d'un polynome a deux variables a coefficients reels.
4
Lhote, Loïck. "Algorithmes du PGCD et Fouille de Données : le point de vue de l’analyse dynamique." Caen, 2006. http://www.theses.fr/2006CAEN2021.
Full textAbstract:
Cette thèse aborde deux domaines de l'algorithmique: la fouille de données et l'arithmétique. Le point de vue adopté est celui de l'analyse en moyenne et, plus précisément, celui de l'analyse dynamique, qui combine des méthodes d'analyse d'algorithmes et des systèmes dynamiques. Les algorithmes de type Euclide calculent le pgcd de deux nombres ;ce sont donc des briques de base du calcul formel, mais leur comportement probabiliste fin reste encore mal connu. Tout récemment, les méthodes dynamiques ont permis des avancées significatives dans ce domaine. Nous étendons cette approche à l'analyse fine d'autres paramètres, comme la complexité binaire et la taille des restes. Ces paramètres s'avèrent essentiels pour l'analyse de l'algorithme de type diviser pour régner introduit par Knuth et Schönhage. Nous utilisons également l'analyse dynamique dans le calcul prouvé de grandeurs spectrales. L'approche dynamique s'adapte aussi à l'algorithme d'Euclide sur les polynômes, même si, dans ce cas, les méthodes de la combinatoire analytique classique s'appliquent déjà. Nous abordons également la fouille de données. Nous nous limitons à des bases de données binaires où la connaissance se représente sous forme de 'motifs fréquents'. Le nombre de ces motifs est un paramètre essentiel pour les algorithmes. D'après les expérimentations, il varieconsidérablement selon les paramètres de la base, et l'analyse dans le pire des cas n'est donc pas significative en pratique. Dans cette thèse, nous élucidons le comportement moyen du nombre de motifs fréquents dans un modèle très général, où les bases sont construites à partir de sources possiblement corrélées<br>This thesis deals with two main algorithmical domains : Data Mining and Arithmetical computations. In both, we are interested in the average-case analysis of algorithms, and, we adopt more precisely the dynamical analysis point of vue which is a mixed method between Analysis of Algorithms and Dynamical Systems. The Euclid algorithms compute the gcd of two numbers ; these are fundamental blocks in computer algebra, but their fine probabilistic behavior is always unknown. Thanks to Dynamical Analysis methods, recent important results have been obtained. In this thesis, we extend this approach to a precise analysis of parameters, as the binary complexity or the size of remainders. These parameters are essential for the Divide and Conquer gcd algorithm due to Knuth-Schönhage. Dynamical Analysis is also used for proven computations of spectral constants. The dynamical approach is then adapted to on polynomial Euclid algorithms even if, in this case, classical Analytic Combinatorics already applies. We also deal with Data Mining. We restrict ourselves to binary databases where the knowledge is represented by 'frequent patterns'. The number of frequent patterns is essential for analysing algorithms but experiments show that it significantly changes with the parameters of the database. Then, the worst case analysis is not meaningful in practice. In this thesis, we elucidate the average beahvior of the number of frequent patterns under a large model of databases built with eventually correlated sources
5
MORENO, MAZA MARC. "Calculs de pgcd au-dessus des tours d'extensions simples et resolution des systemes d'equations algebriques." Paris 6, 1997. http://www.theses.fr/1997PA066471.
Full textAbstract:
Cette these est consacree a la resolution des systemes d'equations polynomiales a l'aide d'ensembles triangulaires. Une premiere partie consiste en la presentation de deux algorithmes permettant de calculer des pgcd de polynomes a coefficients dans une tour d'extensions simples. Le premier, realise avec renaud rioboo, s'applique aux tours algebriques. Le second, est une adaptation du precedent au cas plus general des tours separables. Ces algorithmes ont permis l'implantation efficace de deux methodes proposees par daniel lazard pour resoudre les systemes d'equations algebriques a l'aide d'ensembles triangulaires. Ces programmes ont permis la resolution automatique de problemes, inaccessibles auparavant. La deuxieme de ces methodes n'etait qu'esquissee ; aussi une seconde partie est consacree aux developpements theoriques necessaires a une implantation correcte. De plus, un travail d'unification theorique et de comparaison experimentale avec les methodes voisines de wu wen-tsun, dongming wang et michael kalkbrener a ete realise avec philippe aubry.
6
Roch, Jean-Louis. "Calcul formel et parallélisme : l'architecture du système PAC et son arithmétique rationnelle." Phd thesis, Grenoble INPG, 1989. http://tel.archives-ouvertes.fr/tel-00334457.
Full textAbstract:
Pac est un système de calcul formel dédié a une machine Mind massivement parallèle. Dans une première partie, l'architecture du système est décrite. Elle est illustrée par une modélisation théorique et pratique de la parallélisation du produit de deux polynômes. Le système Pac est implante sur la machine t40 de Fps (32 processeurs). Dans une deuxième partie, l'arithmétique nodale en précision infinie sur les rationnels est étudiée. Différents algorithmes sont dégagés, notamment pour la multiplication, la division et le pgcd d'entiers de taille quelconque. Une vectorisation de l'arithmétique de base est discutée et expérimentée
7
Stehlé, Damien. "Algorithmique de la réduction de réseaux et application à la recherche de pires cas pour l'arrondi defonctions mathématiques." Phd thesis, Université Henri Poincaré - Nancy I, 2005. http://tel.archives-ouvertes.fr/tel-00011150.
Full textAbstract:
Les réseaux euclidiens sont un outil particulièrement puissant dans<br />plusieurs domaines de l'algorithmique, en cryptographie et en théorie<br />algorithmique des nombres par exemple. L'objet du présent mémoire est dual : nous améliorons les algorithmes de réduction des réseaux,<br />et nous développons une nouvelle application dans le domaine<br />de l'arithmétique des ordinateurs. En ce qui concerne l'aspect algorithmique, nous nous intéressons aux cas des petites dimensions (en dimension un, où il s'agit du calcul de pgcd, et aussi en dimensions 2 à 4), ainsi qu'à la description d'une nouvelle variante de l'algorithme LLL, en dimension quelconque. Du point de vue de l'application, nous utilisons la méthode<br />de Coppersmith permettant de trouver les petites racines de polynômes modulaires multivariés, pour calculer les pires cas pour l'arrondi des fonctions mathématiques, quand la fonction, le mode d'arrondi, et la précision sont donnés. Nous adaptons aussi notre technique aux mauvais cas simultanés pour deux fonctions. Ces deux méthodes sont des pré-calculs coûteux, qui une fois <br />effectués permettent d'accélérer les implantations des fonctions mathématiques élémentaires en précision fixée, par exemple en double précision.<br /><br />La plupart des algorithmes décrits dans ce mémoire ont été validés<br />expérimentalement par des implantations, qui sont<br />disponibles à l'url http://www.loria.fr/~stehle.
8
Luu, Ba Thang. "Représentation matricielle implicite de courbes et surfaces algébriques et applications." Phd thesis, Université de Nice Sophia-Antipolis, 2011. http://tel.archives-ouvertes.fr/tel-00610499.
Full textAbstract:
Dans cette thèse, nous introduisons et étudions une nouvelle représentation implicite des hypersurfaces rationelles et des courbes rationnelles plongées dans un espace projectif de dimension arbitraire. Nous illustrons les avantages de cette représentation matricielle en abordant plusieurs problèmes importants intervenant en conception géométriqueassistée par ordinateur: les problèmes d'intersection entre deux courbes, entre une courbe et une surface ou bien encore entre deux surfaces, le problème d'appartenance d'un point à une courbe ou une surface, le problème du calcul de la pré-image d'un point donné par une paramétrisation et enfin le problème du calcul des singularités d'une courbe rationnelle. L'approche développée dans ce travail de thèse est basée sur la combinaison de méthodes symboliques et numériques. En effet, un première étape symbolique consiste à transformer le problème considérer en un pinceau de matrices. La deuxième étape consiste alors à calculer les valeurs propres généralisées de ce pinceau à l'aide de méthodes numériques. Pour cela, un algorithme d'extraction de la partie régulière d'un pinceau univarié, respectivement bivarié, de matrices non carrées est présenté. Une implémentation de ces travaux dans les systèmes de calcul formel Mathemagix et Maple est présentée en appendice. Le dernier chapitre est conscré à un algorithme qui, étant donné un ensemble de polynômes univariés f1 , ..., fs construit un ensemble de polynômes u1 , ..., us dont les degrés sont prescrits, tels que le degré du pgcd(f1 + u1 , ..., fs + us ) est supérieur ou égal à un entier donné sous des hypothèses de généricité.
9
Jellis, Christopher Henry. "Metalearning : PGCE students learning about learning." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2583/.
Full textAbstract:
As students, trainee teachers are required to reflect upon and take ownership of their own learning, but because of their future position as teachers, they also have to understand the learning of others. Trainee teachers have many ideas about teaching, but unless they have previous experience in the field, it is likely that their main understanding of what constitutes teaching and learning will be from their experiences of themselves as students. Many trainee teachers follow an uninterrupted route from school to university and then straight onto a PGCE course and will throughout their time in education have been experiencing teaching only from one direction 一 that of a student. During this time, many will develop ideas about what teachers actually do, but since a lot of what teachers do is preparation outside of the classroom, can students really get a balanced idea of the working life of a teacher? Trainee teachers, and indeed all postgraduate students need to reflect on their own learning in order to maximise their ability to assimilate and understand new information. This is the idea behind the concept of metalearning. Metalearning is a comparatively new phrase and as such, its meaning is still evolving. Originally defined by John Biggs (1985) as a process of being aware, and taking control, of one's own learning, it has subsequently been revisited and redefined. Some authors equate the concept with a practical form of metacognition, others with ideas involving reflective practice whilst others consider the phrase to mean "learning about learning" (Jackson, 2004). In the text which follows, the word is taken to mean "learning about learning" which could, in many cases be shown to subsume both the metacognitive and reflective theories. In any case, it is a very apt description of the principal role of trainee teachers. This longitudinal study tracks a group of trainee teachers following a PGCE course in order to observe their development and understanding of learning, both their own and that of their pupils and also to gain some insights into the experience of being a PGCE student in the 21 St Century.
10
Reyes, Pilar. "Science PGCE students' understanding of secondary science teaching." Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246757.
Full text
11
Hedrick, Shannon. "IDENTIFICATION OF HUMAN PGC-1α-b ISOFORMS USING A NOVEL PGC-1α-b SPECIFIC ANTIBODY". VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3225.
Full textAbstract:
Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is known as the master regulator of mitochondrial biogenesis. PGC-1α holds this role by acting as a transcriptional coactivator for an array of transcription factors and nuclear hormone receptors, such as NRF-1/2 and ERRα/γ, whose downstream targets function in mitochondrial biogenesis and oxidative phosphorylation. PGC-1α is regulated both at the transcriptional and post-translational level in several signaling pathways, including p38 MAPK and AMPK. This regulation affects which transcription factor binding events can occur in a given tissue, and thus affects regulation of PGC-1α target genes. PGC-1α is downregulated in many neurodegenerative disorders as well as in muscular dystrophies, diabetes, and aging. Therefore, PGC-1α is prized as a potential therapeutic target to create novel treatments for these various diseases.However, details governing the spatio-temporal regulation of PGC-1α are not completely understood, and overexpression of PGC-1α throughout the body or even in certain tissues or subsets of cells have had detrimental effects in animal and cell models. Therefore, it is necessary to gain knowledge of how to modulate PGC-1α in a tissue-specific manner utilizing these different levels of regulation in order to develop novel therapies. In order to further understand all the functions that have been attributed to PGC-1α, the PGC-1α isoforms need to be accounted for and understood in human tissues. Several murine isoforms have been published, as well as several human brain and muscle isoforms. However, most of these isoforms have only been validated as mature transcripts, and it is not known whether they produce functional protein. Our lab has identified the isoform b transcript in human brain tissue via 5’ RACE and have developed an isoform b specific antibody. This project aimed to characterize the isoform b transcripts and also to validate and optimize this antibody for immunoblotting conditions for detection of further PGC-1α-b isoform protein variants in human tissues. Preliminary studies in our lab have shown that in postmortem frontal cortex from age-matched PD and healthy patients, isoform a transcript levels were 10-15 times more abundant than that of isoform b. These differences in regulation could be partially attributed to the isoform b promoter region being heavily methylated, as shown in this thesis through bisulphite cloning and sequencing as well as 454 bisulphite sequence analysis. The high degree of methylation, correlated with the low level of isoform b transcript in brain and it is not known whether this transcript would be translated into protein in this tissue. In order to probe for isoform b protein expression using human cell lines and tissues, however, it was necessary to create a recombinant protein in order to have a positive control with which to optimize our novel antibody. In our previous 5’ RACE studies, an alternatively spliced PGC-1α-b transcript was found which coded for an early stop codon. This truncated isoform was called PGC-1α-b-3T1, and mature transcript was found in both human skeletal muscle and brain. For this project, PGC-1a-b-3T1 was cloned from human skeletal muscle into a bacterial expression vector to create a recombinant GST fusion protein. This protein was used to validate and optimize our PGC-1α-b specific antibody as well as to determine sensitivity and specificity. The purified recombinant protein contained 3 bands of lower molecular weight that were detected via western blot with both GST and the PGC-1α-b specific antibody. These bands were trypsin cleaved and subjected to mass spectrometry analysis, which verified that all bands detected by the PGC-1a-b specific antibody contained the epitope sequence, and thus binding was specific. This protein was then used to determine western blotting conditions and sensitivity, which is 10 ng using a 1:100 dilution of the antibody. This antibody was then used to probe SH-SY5Y WCL, a human neuroblastoma cell line. Peptide competition assay confirmed 5 PGC-1α-b specific proteins in these lysates. The sizes of these proteins matched to several murine PGC-1α-b isoforms as well as putative PGC-1α-b versions of PGC-1a-a isoforms. These findings provided the putative identities of several endogenous functional human PGC-1α-b isoforms. Mammalian overexpression vectors of these isoforms are still in development. By using this antibody and these expression vectors to further characterize these isoforms, including determining tissue specificity, more knowledge of PGC-1α will be gained. This information could then be used to develop novel, tissue specific treatments for pharmacological intervention of diseases characterized by PGC-1α misregulation.
12
Malmgren, Helena. "Patients’ experiences of Preimplantation Genetic Diagnosis (PGD)." Thesis, Uppsala universitet, Institutionen för folkhälso- och vårdvetenskap, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230901.
Full textAbstract:
The aim of the present study was to investigate the experiences and attitudes concerningpreimplantation genetic diagnosis (PGD) among the couples that have undergone PGD in Sweden.PGD is an alternative to conventional prenatal diagnosis for couples with a high risk of having a childwith genetic disease. Couples opting for PGD have to perform in vitro fertilisation, generatedembryos are subjected to biopsy and diagnosis, and healthy embryos can be transferred to the femaleuterus. Hopefully a pregnancy will be established. However, PGD is a strategy that implies bothphysical and psychological stress, and it is not obvious that this is an easier alternative than prenataldiagnosis. A questionnaire was sent to 116 couples that had carried out at least one PGD treatmentcycle. The response rate was 89%, thus almost all couples treated in Sweden since the start in 1995was represented. Results: The stress, both psychologically and physically, caused by the PGD treatment was evaluatedsomewhere between “As expected” and “More stressful than expected”. The stress experienced duringthe PGD treatments was not associated with the couples’ previous reproductive experiences. The mostphysical stressful event was the oocyte retrieval and the most psychologically stressful period was“waiting for a possibly/ hopefully embryo transfer”.The majority of couples that had performed prenatal diagnosis on a spontaneous pregnancy andexperienced a PGD treatment reported that PGD was more physically stressful (54%), but that prenataldiagnosis was more psychologically stressful (51%). The couples reported the reproductivealternatives chosen after PGD closure, and couples performing PGD at the present rated futurereproductive alternatives. Results indicated that ocyte- and sperm donations were a less attractivealternative than for example adoption. Participants in the study also had the opportunity to state forwhom /which indications PGD should be an option. Conclusion: The stress associated with performing PGD or prenatal diagnosis is extensive and noneof the alternatives is an obvious choice. PGD was reported as more physical stressful, but prenataldiagnosis was more psychologically stressful. The reproductive pathways chosen after PGD closurewas reported, and surprisingly sperm and oocyte donations were not attractive alternatives. The choiceof reproductive alternatives might be influenced by the information and support provided by thehealthcare personal. Knowledge about the experience of PGD treatments is of great importance forthose that meet these couples for genetic and reproductive counselling, in order to give them propercare and to better meet their demand of information and support.
13
Reis, Jonatha Oliveira de Matos. "Error estimation and adaptivity for PGD solutions." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/671779.
Full textAbstract:
A significant part of the current research efforts in computational mechanics is focused on analyzing and handling large amounts of data, exploring high dimensional parametric spaces and providing answers to increasingly complex problems in short or real-time. This alludes to concepts (like digital twins) and technologies (like machine learning), methodologies to be considered in combination with classical computational models. Reduced Order Models (ROM) contribute to address these challenges by reducing the number of degrees of freedom of the models, suppressing redundancies in the description of the system to be modeled and simplifying the representation of the mathematical objects quantifying the physical magnitudes.
Among these reduce order models, the Proper Generalized Decomposition (PGD) can be a powerful tool, as it provides solutions to parametric problems, without being affected by the "curse of dimensionality", providing explicit expressions, computed a priori, of the parametric solution, making it is well suited to provide real-time responses. The PGD is a well-established reduced order method, but assessing the accuracy of its solutions is still a relevant challenge, particularly when seeking guaranteed bounds of the error of the solutions it provides.
There are several approaches to analyze the errors of approximate solutions, but the only way that provides computable and guaranteed error bounds is by applying dual analysis. The idea behind dual analysis is to use a pair of complementary solutions (one that is compatible, and the other equilibrated) for a specified problem and to use the difference between these solutions, which bounds their errors. Dual analysis is also effective to drive mesh adaptivity refinement processes, as it provides information of the contribution of the elements to the error, either in a global or in a local framework.
In this work we deal with finite element solutions for solid mechanics problems, computing compatible and equilibrated PGD solutions, using them in the context of dual analysis. The PGD approximations are obtained with an algebraic approach, leading to separable solutions that can be manipulated for an efficient computational implementation. We use these solutions to obtain global and local error bounds and use these bounds to drive an adaptivity process. The meshes obtained through these refinements provide solutions with errors significantly lower than those obtained using a uniform refinement.<br>Una parte importante de los esfuerzos de investigación actuales en mecánica computacional se centra en analizar y manejar grandes cantidades de datos, explorar espacios paramétricos de alta dimensión, y proporcionar respuestas a problemas cada vez más complejos en un tiempo breve o en tiempo real. Esto alude a conceptos (como gemelos digitales) y tecnología (como aprendizaje automático), metodologías a ser consideradas en combinación con modelos computacionales clásicos. Los modelos de orden reducido (ROM) contribuyen a abordar estos desafíos al reducir el número de grados de libertad de los modelos, suprimir redundancias en la descripción del sistema a modelar, y simplificar la representación de los objetos matemáticos que cuantifican las magnitudes físicas. Entre estos modelos de orden reducido, la PGD (del inglés Porper Generalized Decomposition) puede ser una herramienta poderosa, ya que proporciona soluciones a problemas paramétricos, sin verse afectada por ¿el problema de la dimensionalidad¿. La PGD proporciona expresiones explícitas, calculadas a priori, de la solución paramédica, por lo que es adecuado para proporcionar. La PGD es un método de reducción de orden bien establecido, pero evaluar la precisión de sus soluciones sigue siendo un desafío relevante, en particular cuando se buscan límites garantizando el error de las soluciones que proporciona. Existen varios enfoques para analizar los errores de las soluciones aproximadas, pero la única forma de proporcionar límites de error computables y garantizados es mediante la aplicación de un análisis dual. La idea del análisis dual es utilizar un par de soluciones complementarias(una que sea compatible y la otra equilibrada) para un problema específico. La diferencia entre las dos soluciones es lo que limitará el error. El análisis dual también es efectivo para impulsar procesos de refinamientos de adaptabilidad de malla, ya que proporciona información sobre la contribución de los elementos al error, sea en un marco global o local. En este trabajo tratamos con soluciones de elementos finitos para problemas de mecánica de sólidos , calculando soluciones PGD compatibles y equilibradas, utilizándolas en contexto análisis dual. Las aproximaciones PGD se obtienen con un enfoque algebraico, lo que lleva a soluciones separables para obtener límites en el error globales como locales, y los empleamos para impulsar un proceso de adaptabilidad. Las mallas producidas a través de estos refinamientos proporcionan soluciones con errores significativamente más bajos que las obtenidos usando un refinamiento uniforme.<br>O cenário atual da pesquisa em mecanica computacional está focado em analisar grandes quantidades de dados, explorar grandes espaços paramétricos e fornecer respostas a problemas cada vez mais complexos em tempo (quase) real. Podemos relacionar esses desafios a conceitos como gemeos digitais, e tecnologias como aprendizado de máquinas, que se combinam com modelos computacionais clássicos. Os Modelos de Ordem Reduzida (MOR) contribuem para solucionar esses problemas atraés de uma reduccao dos graus de liberdade destes modelos, suprimindo redundàncias na descriçao dos sistemas e simplificando a sua representaçao matemática.
Dentre estes modelos de ordem reduzida a PGD (de Proper Generalized Decomposition, em portuguès Decomposiçao Generalizada Característica) pode ser uma poderosa ferramenta, fornecendo soluçoes paramétricas que nao sao afetadas pelo “maldiçao da dimensionalidade”. A PGD prove expressçoes explicitas das soluçoes paramétricas, sendo estas calculadas a priori, o que torna este método vantajoso quando se buscam soluçoes em tempo real. A PGD ´e uma metodologia bem estabelecida, mas avaliar a preciçao das aproximaçoes obtidas ainda é uma questao relevante, particularmente quando se procuram majorantes do erro das suas soluçoes, que sejam garantidos.
Existem diversas maneiras de analisar os erros das aproximaçoes que obtemos, mas a única forma de obter soluçoes com majorantes dos erros garantidos é aplicando uma análise dual. A ideia por trás da análise dual é utilizar um par de soluçoes complementares (uma solu¸c˜ao compatível e uma soluçao equilibrada) para um problema específico e usar a diferença entre essas soluçoes.
Ela é também efetiva para direcionar processos de refinamentos de malhas, já que é possível obter a contribuiçao dos elementos para o erro tanto num contexto local quando global.
Neste trabalho lidamos com soluçoes de elementos finitos para problemas de mecánica dos sólidos, calculando soluçoes compatíveis e equilibradas para soluçoes PGD e usando estas na análise dual do erro. As aproximaçoes por PGD sao obtidas utilizando um método algébrico, o que resulta em soluçoes separáveis que podem ser manipuladas para uma eficiente implementaçao computacional. Utilizamos estas soluçoes para obter majorantes locais e globais para o erro e usamos esses majorantes para direcionar processos adaptativos ótimos. As malhas obtidas através desse processo de refinamento geram soluçoes com erros significativamente menores que aquelas obtidas através de um refinamento uniforme.
14
Shaughnessy, Julie M. "Student experience of a Primary Post-Graduate Certificate in Education (PGCE)." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298897.
Full text
15
Sibileau, Alberto Pedro. "Computational vademecums for lattice materials using algebraic PGD." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667577.
Full textAbstract:
This dissertation is motivated by the concept of materials by design. Focusing on structures, this states that the properties in a mechanical component are not only inherited by its constituent material, but also by the shape in which this one is distributed in space. Although this notion has been developed for thousands of years in architecture, its relevance at a smaller scale has not been conceived until the arrival of additive manufacturing technologies.
The materials by design approach is certainly multidisciplinary, from the study of the shape, its representation in CAD, to the final manufacturing by 3D printing. We here assess the first one, by means of numerical simulations. These play an important role, by reinforcing our physical intuition in the resolution of the following question: which is the material structure at a small scale (meso-structure) that features some prescribed properties at a global scale (bulk material).
We introduce the material meso-structure as a lattice model with a parametric shape. The mechanical properties arising at the global scale are recovered by solving an equilibrium problem. Naturally, this one acquires the parametric nature of the lattice model. The main difficulty to handle the emerging mechanical properties of the bulk parametrically, is that the computational complexity of numerical simulations increases exponentially with the number of parameters.
To overcome this, we resort to the Proper Generalized Decomposition (PGD), which provides explicit parametric solutions of our equilibrium problem. As a major contribution, we obtain the parametric solutions of the algebraic equations arising from different lattice structures using the same PGD framework. In this sense, the algebraic PGD works as a non-intrusive solver, which is not limited to structural problems but in general, any discrete form of a parametrized linear PDE.
The parametric mechanical properties of 2D and 3D lattice materials are explicitly represented by the PGD solutions or computational vademecums. In particular, we reproduce the response of orthotropic Poisson's ratios in terms of the design parameters. Extreme negative values are identified, a characteristic that is relevant regarding the outperforming of auxetic (or negative Poisson's ratios) properties compared to conventional materials. Moreover, these computational vademecums could be further exploited to tailor the material design through multi-objective and constraint optimizations, providing an efficient tool to browse the parametric design space.
Finally, we extend our parametric analysis using geometrically nonlinear finite elements to compute equilibrium, and the algebraic PGD a posteriori to interpolate their response. This is achieved with very good accuracy, for engineering purposes, at a considerably low number of modes. The nonlinear parametric framework surely broadens the range of applications, and we highlight this in two distinctive situations. First, we demonstrate its capability to describe the loading magnitude as an extra parameter to the material properties behavior. Last but not least, we show its potential to perform buckling analysis of lattice structures, as a function of the geometric parameters and the loading magnitude itself.<br>Este trabajo está motivado por el concepto del diseño de materiales a medida. Centrándose en estructuras, esto significa que las propiedades de un componente mecánico no sólo se heredan por su material constitutivo, sino también por la forma en la que éste se distribuye en el espacio. A pesar de que esta idea se haya desarrollado hace miles de años en arquitectura, su relevancia en un tamaño de escala menor no se ha concebido posible hasta el advenimiento de las tecnologías de manufactura aditiva. El diseño de materiales a medida es ciertamente multidisciplinario, desde el estudio de la forma, su representación en CAD, hasta su fabricación por medio de impresoras 3D. Aquí nos focalizamos en el primer aspecto, utilizando simulaciones numéricas. Éstas juegan un rol esencial, ayudando a nuestra intuición física en la respuesta del siguiente interrogante: ¿cuál es la estructura de un material en un pequeño tamaño de escala (meso-estructura), que determina ciertas propiedades mecánicas deseadas en un tamaño de escala grande? En este sentido, introducimos una meso-estructura de material a través de un modelo de tipo lattice, cuya forma está parametrizada. Las propiedades mecánicas, resultantes a gran escala, se derivan resolviendo un problema de equilibrio. Naturalmente, este problema hereda la parametrización introducida para el modelo lattice. La dificultad de resolver las propiedades mecánicas resultantes, de manera paramétrica, reside en que la complejidad computacional de las simulaciones numéricas se incrementa exponencialmente con el número de parámetros. Para evitar este infortunio, nos remitimos al método PGD (Proper Generalized Decomposition), que provee una solución paramétrica explícita de nuestro problema de equilibrio en cuestión. Como contribución destacada, obtenemos la solución paramétrica del sistema de ecuaciones algebraicas, resultante de diversas estructuras de tipo lattice, utilizando el mismo algoritmo PGD. En este sentido, la PGD algebraica funciona como un solver no intrusivo, cuyo uso no está limitado sólo a problemas estructurales sino a cualquier forma discreta de una ecuación diferencial en derivadas parciales (EDP) paramétrica. Las propiedades mecánicas paramétricas de materiales tipo lattice en 2D y 3D son representadas de manera explícita por soluciones PGD, también llamadas vademécums computacionales. En particular, obtenemos la respuesta de módulos de Poisson ortotrópicos, en función de los parámetros de diseño. Valores negativos extremos son identificados, una característica que es relevante en cuanto que ciertas propiedades auxéticas, esto es, relacionadas con módulos de Poisson negativos, resultan superiores en performance en comparación a los materiales convencionales. Además, los vademécums computacionales pueden utilizarse para explotar el diseño de materiales a medida a través de optimizaciones numéricas multi-objetivo, ya que permiten explorar las diversas soluciones en el espacio paramétrico de manera eficiente. Finalmente, este análisis paramétrico es extendido a no-linealidades geométricas, utilizando elementos finitos para resolver equilibrio, y la PGD algebraica a posteriori para interpolar su respuesta. Los resultados muestran una muy buena precisión, en términos ingenieriles, para un número de modos considerablemente bajo. El análisis no lineal amplía el rango de aplicaciones, para lo cual nos centramos en dos situaciones diversas. Primero, demostramos la capacidad de describir el comportamiento de las propiedades mecánicas teniendo a la magnitud de carga como un parámetro extra. Finalmente, demostramos el potencial de realizar el análisis de pandeo de estructuras tipo lattice, en función de los parámetros geométricos y de la magnitud de carga.
16
Karamanlidis, Georgios. "PGC-1α gene regulation in adipocyte cell lines." Thesis, University of Aberdeen, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424949.
Full textAbstract:
The cold-inducible PPAR co-activator PGC-1α has been reported to play a pivotal role in the control of pre-adipocyte differentiation to brown adipose tissue (BAT) and mitochondriogenesis. The overall aim of this study was to investigate the transcriptional control of PGC-1α gene in brown and white adipose tissue (WAT) precursor cells. Fragments up to 1.8kb of the rat PGC-1α proximal promoter were cloned into a pGL3 luciferase reporter vector and transfected into 3T3-L1 (WAT pre-adipocyte cell line) and HIB-1B (BAT pre-adipocyte cell line). The phenotype of these cell lines was confirmed by histological and biochemical characterisation. When cells were induced to differentiate, even the shortest (264bp) reporter construct supported luciferase expression in HIB-1B, but not in 3T3-L1 cells. cAMP stimulation induced endogenous PGC-1α expression only in HIB-1B cells. Putative transcription factor binding sites were identified in the 264bp proximal promoter using both EMSA and promoter analysis software. Mutation of the cAMP response element at -183 to -175 abolished completely the cAMP response of the promoter in 3T3-L1 cells, but only attenuated this response in HIB-1B cells. this suggested that other indirect pathways were acting for the cAMP stimulation of this promoter in HIB-1B cells. Additional pathways through which differential control of the proximal PGC-1α promoter region could occur were next considered. A putative C/EBP site at -101 to -94 was also implicated in the transcriptional control of this promoter. Over-expression of C/EBPβ increased the activity of the promoter and rescued the response of PGC-1α in the 3T3-L1 cells. Similar to PGC-1α, C/EBPβ was cAMP induced only in HIB-1B cells.
17
Courard, Amaury. "PGD-Abaques virtuels pour l'optimisation géométrique des structures." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN010/document.
Full textAbstract:
Lors de l'optimisation géométrique de structures, un grand nombre d'évaluations de champs est nécessaire. L'idée, développée dans cette thèse, est la construction efficace et rapide d'approximations de ces champs à travers la Proper Generalized Decomposition (PGD), une méthode de réduction de modèle. Les résultats, calculés une fois pour toutes, sont stockés dans des abaques virtuels pour une utilisation ultérieure dans un processus d'optimisation. Le problème considéré est paramétrique et les paramètres définissent la géométrie. Ce type de problème est particulièrement adapté à la PGD. En effet, de nombreux travaux ont traité de la résolution de problèmes paramétriques et des premières études ont porté, en particulier, sur la prise en compte de paramètres géométriques. Toutefois, ce qui caractérise nos travaux est d'aller vers des outils aptes à traiter des situations significatives de la complexité des problèmes rencontrés au niveau industriel. En particulier, l'exploitation de codes éléments finis commerciaux est une contrainte majeure. Il a été décidé de développer des méthodes permettant de traiter des problèmes à paramètres géométriques par la PGD, et, en partenariat avec AIRBUS Defence & Space, d'appliquer ces techniques à un démonstrateur industriel présentant une géométrie complexe (type splines) et de fortes non-linéarités (géométriques, matériaux). Notre démarche a été implémentée dans un process industriel utilisant des codes éléments finis commerciaux. On propose aussi une nouvelle extension de la PGD aux paramètres discrets autorisant la prise en considération, dans une même résolution, de configurations de structures complètement différentes (cas de chargement, matériaux, etc.)<br>During shape optimisation of structures, numerous evaluations of fiels are necessary. The idea, developed in this PhD thesis, is the efficient construction of approximations of these fiels through the Proper Generalized Decomposition (PGD), a model reduction technique. The results, computed once and for all, are stored in virtual charts for a subsequent use into an optimisation process. Geometry variations correspond to a parametric problem, where the parameters is the geometry. This kind of problem is well suited for PGD. Many studies dealt with the resolution of parametric problems and recent works treated, particularly, the introduction of geometric parameters. However, our approach is to deal with configurations of the complexity of industrial problems. The use of commercial finite elements software is a crucial issue. It was decided, in partnership with AIRBUS Defence & Space, to develop techniques allowing the resolution of geometrically parametrised problems thanks to PGD and to apply them to an industrial demonstrator. The geometry considered is defined by splines and the behaviour of the structure is highly non-linear (geometric and material non-linearities). The approach was implemented into a genuine industrial design process using commercial finite elements software. The thesis proposed, also, a new extension of PGD to discrete parameters. It allows to take into account completely different configurations (loadings, materials, etc.) in the same resolution
18
Yeomans, Robin Michael. "The influence of school staffs on primary PGCE trainee teachers' professional learning." Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/1160.
Full textAbstract:
This thesis is a multi-case study of the placement professional learning of fifteen primary PGCE trauiees within the school-based part of teacher training. It is concerned with the influence of individual staff, especially mentors and host class teachers, as well as of whole staffs and sub-groups, on adult and pupil oriented aspects of teachers' jobs (though excluding a detailed study of the development of subject knowledge or of specific classroom skills). A participant observer strategy was used within a grounded theory approach to develop agenda for semi-structured interviews with trainees. The main findings are that trauiees leamt through four modes of learning: as observers, participating observers, participants and observing participants. Self-reliance was important for trainees' learning, but relationships with individual staff (especially mentors and host class teachers) were important and constractive influences when such staff adopted a 'learner modeV of intervention. Whole staffs were important influences on trainees' professional development when trainees were accepted as fiill or quasi-staff members, particularly in terms of the interadult dimensions of teachers' jobs. Trainees were expected to 'fit in' with staffs' wa.ys of working, even when their value systems clashed with those of placement teachers. Then, trainees were often constrained by a power imbalance implicit in their status as leamers. Trainees responded by compHance, engagement, strategic compromise or nonconformity, with engagement most likely to gain staff support and enhance trainees' learning. Conclusions are that school-based training underestimates the complexity of workplace learning, and that inequity is possible. Staff cultures influence powerfiilly both trainees' learning and staffs' treatment of them. PGCE trainees tend not to become acculturated, though sometimes at the cost of restricted capacities to leam. Learning about the uiteradult dimensions of teachers' jobs is haphazard, and is largely ignored by official teacher training curricula. Finally, specific reconunendations are made for trainees, placement schools, university teacher trainees and national teacher training policies.
19
Paillet, Charles. "Nouvelles démarches de réduction de modèles pour le traitement des problèmes à très grand nombre de paramètres." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN015/document.
Full textAbstract:
Alors que la simulation numérique prend aujourd'hui une place essentielle dans de nombreuses branches de l'ingénierie, les évolutions incroyables des moyens de calculs peinent à compenser la complexité croissante des modèles que les ingénieurs sont amenés à traiter. Dans ce contexte, les modèles réduits sont de véritables outils d'aide à la décision car ils permettent, une fois construits, d'évaluer un très grand nombre de scénarios en temps quasi réel. En particulier, la méthode PGD (Proper Generalized Decomposition) initiée au LMT a connu de très nombreux développements (problèmes non linéaires, multiéchelles, multiphysiques...) et conduit à des gains en temps CPU pouvant atteindre plusieurs ordres de grandeur.Malheureusement, l'essor de ces modèles réduits est actuellement freiné par la difficulté à les calculer lorsque le nombre de paramètres à prendre en compte augmente. Toutes les techniques de réduction de modèles actuelles (PGD comprise) peinent à traiter des problèmes à très grand nombre de paramètres (la limite actuelle tourne autour de la vingtaine de paramètres), ce qui constitue un verrou scientifique majeur pour l'essor de ces techniques. Cette thèse présente une adaptation de la méthode PGD qui permet le traitement de tels problèmes.Trois contributions principales ont permis d'atteindre de telles performances. D'une part, une nouvelle structure de données plus proche de la physique du problème a été développée. Elle introduit deux échelles de représentation des fonctions paramétriques et donne son nom à la méthode : la Parameter-Multiscale PGD. Par ailleurs, une discrétisation spatiale discontinue particulièrement adaptée à nos méthodes de résolution a été implémentée, la WTDG (Weak Trefftz Discontinuous Galerkin). Enfin de nouveaux algorithmes ont été développés pour construire des modèles réduits qui permettent des gains de temps conséquents pour des problèmes ayant jusqu'à mille paramètres<br>Numerical simulation is nowadays a major tool in a large number of engineering fields. Nevertheless, even the recent incredible improvements of the computational power can hardly compensate the increasing complexity of the models used by engineers. In this context, Reduced Order Models (ROM) can be major decision-maker tools because, once they have been computed, they can be used to evaluate a very large number of test cases in a duration close to real time. The PGD (Proper Generalized Decomposition) in particular, is a method introduced at the LMT which has been adapted to many cases (non-linear problems, multiscale, multiphysics) and leads to savings of CPU time reaching several orders of magnitude.Unfortunately, it is currently difficult to build ROM with an increasing number of parameters. All the actual model reduction technics (including the PGD) can hardly solve problems with a high number of parameters (the current limit is about twenty parameters). It is a major barrier to a larger development of these methods. This PhD thesis presents a new methodology based on the PGD able to take into account high numbers of parameters.This goal has been achived thanks to three major contributions. First, a new data structure faithfull to mecanical properties of the problem has been developed. To that end, two different scales are introduced in the parametric space, giving its name to our method : Parameter-Multiscale PGD. Furthermore, the WTDG (Weak Treffz Discontinuous Galerkin) method has been inpemented. It is a discontinuous spatial discretisation adapted to our resolution techniques. Finally, new algorithms have been developed to built reduced order models of problems taking into account up to one thousand parameters
20
Karamitri, Angeliki. "Transcriptional regulation of PGC-1a in adipocyte cell lines." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490817.
Full textAbstract:
PGC-la, a cold inducible coactivator of PPARy, has been reported to play an important role in the control ofpre-adipocyte differentiation to brown adipose tissue (BAT) and the expression of the BATspecific gene, uncoupling protein 1 (UCP I). The overall aim of this study was to compare the transcriptional control of PGC-la in brown (HIB-IB) and white (3T3-Ll) adipose tissue precursor cells. To achieve this, a 264bp reporter construct of the PGC-la proximal promoter (PGC-I a-pGL3), that was shown to support luciferase expression to a greater extent in HIB-IB compared with 3T3-LI cells, was used under basal and cAMP stimulated conditions. This fragment of the promoter contains a cAMP response element (CRE) at which a broad array of the bZIP family of transcription factors can potentially bind. Electrophoresis mobility shift assays using a PGC-Ia-CRE oligonucleotide indicated that CREB, ATF-2 and CIEBPfj but not CIEBPa or ClEBP5 bound to the CRE on the PGC-Ia promoter region in HffilB and 3T3-Ll cells. Co-transfection ofHIB-IB and 3T3-LI cells with PGCIa- pGL3 and expression plasmids for CIEBPa, CIEBPfj and ClEBP5 showed that C/EBP(3 but to a lesser extent C/EBP5 and CIEBPa, conferred a marked increase on the promoter activity under forskolin stimulated conditions. The stimulatory effect of CIEBP(3 was abolished when the CRE site was mutated demonstrating that CIEBP(3 stimulates transcription of PGC-la by acting through the CRE site. CIEBP(3 induction of the PGC-la expression was confirmed by demonstrating that PGC-Ia mRNA levels were increased after CIEBP(3 overxpression and forskolin stimulation to. Expression ~f UCP-I mRNA was also increased in 3T3-Ll cells under CIEBPI1 overxpression and forskolm stimulation suggesting that CIEBPI1 was able to reprogramme 3T3-LI cells to the BAT lineage. To establish the mechanism for the effect of CIEBP(3, I further characterised the PGC-Ia-CRE by investigating the effects of overexpressing CRE-associated transcription factors, using PGC-l reporter assays. CREB was able to increase PGC-la transcription, whereas ATF-2 and CHOP-tO overexpression resulted in decreases in transcriptional activation conferred by CIEBP(3. Results fro~ chromatin immunoprecipitation assays showed that CIEBPI1 and CREB were the strongest protem complexes bound to the CRE site under CIEBP,6 overexpresion and forskolin stimulated conditions, while ATF-2 and CHOP-tO binding was diminished. The results demonstrated that different combinations of transcription factors binding to the proximal CRE ofPGC-Ict. may be responsible for the differential response ofPGC-Ia. expression to cAMP in brown versus white adipose tissue.
21
Capaldo, Matteo. "A new approximation framework for PGD-based nonlinear solvers." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN011/document.
Full textAbstract:
Le but de ce travail est d'introduire un cadre d'approximation, la Reference Points Method, afin de réduire la complexité de calcul des opérations algébriques lorsqu'elles concernent des approximations à variables séparées dans le cadre de la Proper Generalized Decomposition.La PGD a été introduite dans [1] dans le cadre de la méthode LaTIn pour résoudre efficacement des équations différentielles non linéaires et dépendants du temps en mécanique des structures. La technique consiste à chercher la solution d'un problème dans une base d'ordre réduit (ROB) qui est automatiquement et à la volée générée par la méthode LaTIn. La méthode LaTIn est une stratégie itérative qui génère les approximations de la solution sur l'ensemble du domaine espace-temps-paramètres par enrichissements successifs. Lors d'une itération particulière, la ROB, qui a déjà été formée, est d'abord utilisée pour calculer un nouveau modèle réduit (ROM) et, donc, pour trouver une nouvelle approximation de la solution. Si la qualité de cette approximation ne suffit pas, la ROB est enrichie avec la génération d'un nouveau produit de fonctions PGD en utilisant un algorithme de type 'greedy'.Les techniques de réduction de modèle sont particulièrement efficaces lorsque le ROM a besoin d'être construit qu'une seule fois. Ce n'est pas le cas pour les techniques de réduction de modèle quand elles concernent des problèmes non linéaires. En effet, dans un tel cas, les opérateurs qui sont impliqués dans la construction du ROM varient au cours du processus itératif et des calculs préliminaires ne peuvent pas être effectués à l'avance pour accélérer le processus 'online'.Par conséquent, la construction du ROM est un élément coûteux de la stratégie de calcul en terme de temps de calcul. Il en découle la nécessité d'évaluer, à chaque itération, la fonction non linéaire de grande dimension (et éventuellement sa jacobienne) et ensuite sa projection pour obtenir les opérateurs réduits. Cela représente un point de blocage des stratégies de réduction de modèle dans le cadre non linéaire. Le présent travail a comme but une réduction ultérieure du coût de calcul, grâce à l'introduction d'un nouveau cadre de rapprochement dédiée à la stratégie de calcul LaTIn-PGD. Il est basé sur la notion de temps, de points et de paramètres de référence et permet de définir une version compressée des données. Comparé à d'autres techniques similaires [3,4] cela ne se veut pas une technique d'interpolation, mais un cadre algébrique qui permet de donner une première approximation, peu coûteuse, de toutes les quantités sous une forme à variable séparés par des formules explicites. L'espace de données compressées présente des propriétés intéressantes qui traitent les opérations algébriques élémentaires. Le RPM est introduit dans le solveur LaTIn-PGD non linéaire pour calculer certaines opérations répétitives. Ces opérations sont liées à la résolution du problème du temps / paramètre qui implique la mise à jour de l'opérateur tangent et la projection de ce dernier sur la base réduite. La RPM permet de simplifier et de réduire le nombre d'opérations nécessaires.[1] Ladevèze P., Sur une famille d’algorithmes en mécanique des structures, Comptes Rendus Académie des Sciences. Paris. Ser. II 300, pp.41-44, 1985.[2] Chinesta, F., Ladevèze, P., and Cueto, E. A short review on model order reduction based on proper generalized decomposition. Archives of Computational Methods in Engineering, 18, pp.395-404, 2011.[3] Barrault M., Maday Y., Nguyen N., Patera A., An ’empirical interpolation’ method: application to efficient reduced-basis discretization of partial differential equations, Comptes Rendus Académie des Sciences. Paris. Ser. I, 339, pp. 667-672, 2004.[4] Chaturentabut S., Sorensen D., Nonlinear model reduction via discrete empirical interpolation, Society for Industrial and Applied Mathematics 32(5), pp.2737-2764, 2010<br>The aim of this work is to introduce an approximation framework, called Reference Points Method (RPM), in order to decrease the computational complexity of algebraic operations when dealing with separated variable approximations in the Proper Generalized Decomposition (PGD) framework.The PGD has been introduced in [1] in the context of the LATIN method to solve efficiently time dependent and/or parametrized nonlinear partial differential equations in structural mechanics (see, e.g., the review [2] for recent applications). Roughly, the PGD technique consists in seeking the solution of a problem in a relevant Reduced-Order Basis (ROB) which is generated automatically and on-the-fly by the LATIN method. This latter is an iterative strategy which generates the approximations of the solution over the entire time- space-parameter domain by successive enrichments. At a particular iteration, the ROB, which has been already formed, is at first used to compute a projected Reduced-Order Model (ROM) and find a new approximation of the solution. If the quality of this approximation is not sufficient, the ROB is enriched by determining a new functional product using a greedy algorithm.However, model reduction techniques are particularly efficient when the ROM needs one construction only. This is not the case for the model reduction techniques when they are addressed to nonlinear problems. Indeed, in such a case, the operators which are involved in the construction of the ROM change all along the iterative process and no preliminary computations can be performed in advance to speed up the online process. Hence, the construction of the ROM is an expensive part of the calculation strategy in terms of CPU. It ensues from the need to evaluate the high-dimensional nonlinear function (and eventually its Jacobian) and then to project it to get the low-dimensional operators at each computational step of a solution algorithm. This amounts to being the bottleneck of nonlinear model reduction strategies.The present work is then focused on a further reduction of the computational cost, thanks to the introduction of a new approximation framework dedicated to PGD-based nonlinear solver. It is based on the concept of reference times, points and parameters and allows to define a compressed version of the data. Compared to other similar techniques [3,4] this is not an interpolation technique but an algebraic framework allowing to give an inexpensive first approximation of all quantities in a separated variable form by explicit formulas. The space of compressed data shows interesting properties dealing the elementary algebraic operations. The RPM is introduced in the PGD-based nonlinear solver to compute some repetitive operations. These operations are related to the resolution of the time/parameter problem that involves the update of the tangent operator (for nonlinear problems) and the projection of this latter on the Reduced Order Basis. For that the RPM allows to simplify and reduce the number of operations needed.[1] Ladevèze P., Sur une famille d’algorithmes en mécanique des structures, Comptes Rendus Académie des Sciences. Paris. Ser. II 300, pp.41-44, 1985.[2] Chinesta, F., Ladevèze, P., and Cueto, E. A short review on model order reduction based on proper generalized decomposition. Archives of Computational Methods in Engineering, 18, pp.395-404, 2011.[3] Barrault M., Maday Y., Nguyen N., Patera A., An ’empirical interpolation’ method: application to efficient reduced-basis discretization of partial differential equations, Comptes Rendus Académie des Sciences. Paris. Ser. I, 339, pp. 667-672, 2004.[4] Chaturentabut S., Sorensen D., Nonlinear model reduction via discrete empirical interpolation, Society for Industrial and Applied Mathematics 32(5), pp.2737-2764, 2010
22
Allier, Pierre-Eric. "Contrôle d’erreur pour et par les modèles réduits PGD." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLN063/document.
Full textAbstract:
De nombreux problèmes de mécanique des structures nécessitent la résolution de plusieurs problèmes numériques semblables. Une approche itérative de type réduction de modèle, la Proper Generalized Decomposition (PGD), permet de déterminer l’ensemble des solutions en une fois, par l’introduction de paramètres supplémentaires. Cependant, un frein majeur à son utilisation dans le monde industriel est l’absence d’estimateur d’erreur robuste permettant de mesurer la qualité des solutions obtenues. L’approche retenue s’appuie sur le concept d’erreur en relation de comportement. Cette méthode consiste à construire des champs admissibles, assurant ainsi l’aspect conservatif et garanti de l’estimation de l’erreur en réutilisant le maximum d’outils employés dans le cadre éléments finis. La possibilité de quantifier l’importance des différentes sources d’erreur (réduction et discrétisation) permet de plus de piloter les principales stratégies de résolution PGD. Deux stratégies ont été proposées dans ces travaux. La première s’est principalement limitée à post-traiter une solution PGD pour construire une estimation de l’erreur commise, de façon non intrusive pour les codes PGD existants. La seconde consiste en une nouvelle stratégie PGD fournissant une approximation améliorée couplée à une estimation de l’erreur commise. Les diverses études comparatives sont menées dans le cadre des problèmes linéaires thermiques et en élasticité. Ces travaux ont également permis d’optimiser les méthodes de construction de champs admissibles en substituant la résolution de nombreux problèmes semblables par une solution PGD, exploitée comme un abaque<br>Many structural mechanics problems require the resolution of several similar numerical problems. An iterative model reduction approach, the Proper Generalized Decomposition (PGD), enables the control of the main solutions at once, by the introduction of additional parameters. However, a major drawback to its use in the industrial world is the absence of a robust error estimator to measure the quality of the solutions obtained.The approach used is based on the concept of constitutive relation error. This method consists in constructing admissible fields, thus ensuring the conservative and guaranteed aspect of the estimation of the error by reusing the maximum number of tools used in the finite elements framework. The ability to quantify the importance of the different sources of error (reduction and discretization) allows to control the main strategies of PGD resolution.Two strategies have been proposed in this work. The first was limited to post-processing a PGD solution to construct an estimate of the error committed, in a non-intrusively way for existing PGD codes. The second consists of a new PGD strategy providing an improved approximation associated with an estimate of the error committed. The various comparative studies are carried out in the context of linear thermal and elasticity problems.This work also allowed us to optimize the admissible fields construction methods by substituting the resolution of many similar problems by a PGD solution, exploited as a virtual chart
23
Puddifoot, Clare Anne. "Neuroprotection from the huntingtin-repressed transcriptional coactivator PGC-1α". Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8055.
Full textAbstract:
The transcriptional coactivator PPARgamma coactivator 1alpha (PGC-1α) is a regulator of mitochondrial biogenesis and function and is decreased in the striatum of patients with Huntington’s Disease (HD). HD is an autosomal dominant neurological disorder caused by a polyglutamine repeat in the huntingtin protein which leads to degeneration of striatal and cortical tissues. PGC-1α undergoes targeted downregulation by mutant huntingtin protein (mtHtt) and PGC-1α knockout mice have striatal lesions similar to HD transgenic mice. Exogenous PGC-1α partially reverses the toxic effects of mutant huntingtin in cultured striatal neurons while in vivo administration of PGC-1α to the striatum in a mouse model of HD reduces neuronal volume loss. Synaptic N-methyl-D-aspartate receptor (NMDAR)- activity can drive the expression of PGC-1α which is neuroprotective against oxidative and excitotoxic stress in vitro whereas extrasynaptic NMDAR expression is increased in HD. Excessive NMDAR activity, specifically through extrasynaptic rather than synaptic NMDARs, leads to excitotoxic death in neurons and its regulation has been targeted in the search for therapeutic interventions for multiple neurological disorders. The data presented in this thesis show that the repression of PGC-1α by mtHtt may be significant in the dysregulation of NMDARs in HD. Both PGC-1α knockdown and mutant huntingtin are found to increase extrasynaptic NMDAR activity and excitotoxicity in a non-additive way, suggesting common regulatory mechanisms. Furthermore exogenous PGC- 1α expression is sufficient to reverse this increase in extrasynaptic NMDAR currents and excitotoxicity by mtHtt. This thesis adds mechanistic insight into previous understanding of the synergistic roles of mtHtt, NMDAR activity and PGC-1α in HD. Finally, we show that chronic knockout of PGC-1α in the PGC-1α(-/-) mouse causes distinct alterations in glutamatergic signaling that do not mimic the observation of acute knockdown of PGC-1α. We propose that the loss of PGC-1α in a number of neurological disorders contributes to concurrent increases in aberrant glutamate signaling and excitotoxicity in these diseases.
24
Brook, Victoria G. "Student teachers' decision-making about working at Masters level on their PGCE courses." Thesis, London Metropolitan University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590098.
Full textAbstract:
Decisions about different educational pathways have been linked extensively with inequality of outcome and explaining this link has been a focus of much recent research. The emphasis for such research has largely been at key transition points such as secondary school choice and entry to Higher Education. A key question has been the extent to which decisions are influenced by the structuring effects of social class and cultural background or individual agency. This study examines the educational decision-making of graduate student teachers in relation to whether or not to take Masters level credits on courses of Initial Teacher Education. It uses a mixed methods case study approach to collect data from the staff, student teachers and documentation within an Initial Teacher Education department of a Higher Education Institution. The study draws upon a Bourdieuian theoretical perspective to understand the individual nature of the decision-making process and how it led to patterns of inequality. The process of decision-making is considered through the interrelated dimensions of agency, contexts and values. The study reveals that the student teachers' decision-making was multifaceted, and demonstrates the different ways in which important factors were linked and dependent on the overlapping influences of socio-cultural background. The majority of student teachers decided not to take Masters level credits, in many cases seeing the Masters level pathway as too risky. The major influential factors included concerns about time and workload and fear of failure with perceptions of level of academic skills contributing towards this. For some student teachers the perceived value of Masters level for teaching and aspirations for personal progression were also important factors. The study also demonstrates that inequitable patterns of outcome related to student teachers' characteristics could be aggregated from individual decisionmaking. The study draws the conclusion that the introduction of differentiated educational pathways should be accompanied by careful monitoring to ensure that the aims of widening participation are not compromised. Recommendations are made for the types of support that could accompany this particular case of educational decision-making and lessen any stratifying effects. These recommendations could be transferrable to other situations where decisions have to be made about a particular educational pathway.
25
Jarvis, Janis. "Learning preference of undergraduates and PGCE students in relation to subjects of study." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392212.
Full text
26
Heyberger, Christophe. "PGD espace-temps adaptée pour le traitement de problèmes paramétrés." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2014. http://tel.archives-ouvertes.fr/tel-01048636.
Full textAbstract:
Cette thèse s'intéresse à la question récurrente qu'est la résolution d'un problème pour un grand nombre de configurations différentes. Malgré l'augmentation constante de la puissance de calcul que l'on connait aujourd'hui, le traitement direct d'un tel problème reste souvent hors de portée. La technique qui est développée ici est basée sur l'utilisation de la Proper Generalized Decomposition (PGD) dans le cadre de la méthode LATIN. On étudie tout d'abord la capacité de cette technique de réduction de modèle à résoudre un problème paramétré pour un espace de conception donné. Lors du traitement d'un tel problème, on génère une base réduite que l'on peut réutiliser et éventuellement enrichir en traitant un par un les problèmes correspondants aux jeux de paramètres étudiés. Le but devient alors de développer une stratégie, inspirée par la méthode " Reduced Basis ", afin d'explorer de façon rationnelle l'espace des paramètres. L'objectif étant de construire, avec le minimum de résolutions, une base réduite " complète " qui permet de résoudre tous les autres problèmes de l'espace de conception sans enrichir cette base. On commence dès lors par montrer l'existence d'une telle base complète en extrayant les informations les plus pertinentes des solutions PGD d'un problème pour tous les jeux de paramètres de l'espace de conception. On propose ensuite une stratégie rationnelle pour construire cette base complète sans la nécessité préalable de la résolution du problème pour tous les jeux de paramètres. Enfin, les performances de la méthode proposée sont illustrées sur plusieurs exemples, montrant des gains conséquents lorsque des études récurrentes doivent être menées.
27
Llimona, Flávia. "Co-ativador de transcrição gênica PGC-1 na pancreatite aguda." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/5/5165/tde-20052011-174649/.
Full textAbstract:
PGC-1 é uma família de coativadores de fatores de transcrição que controlam a expressão de diversos genes envolvidos na homeostase energética celular. As isoformas PGC-1 e estão presente em tecidos com alto metabolismo oxidativo e são capazes de aumentar biogênese mitocondrial, -oxidação de ácidos graxos e gliconeogênese em resposta à exposição ao frio, jejum e exercício. Inicialmente mostramos que macrófagos in vitro aumentaram a expressão de PGC-1 após 1h da exposição à zymosan. Com isso, hipotetizamos que PGC-1 poderia ter sua expressão aumentada em resposta a um insulto bacteriano. Para verificar nossa hipótese analisamos a expressão de PGC-1 em um modelo de pancreatite aguda (PA), caracterizada por uma forte resposta inflamatória estéril inicial, seguida, após poucos dias, por translocação bacteriana intestinal e infecção disseminada. PA foi induzida por infusão retrograda de taurocolato de sódio (2,5%). Também analisamos PGC-1 em um modelo de sepse por ligadura e perfuração cecal (CLP), cujo conteúdo intestinal é depositado no peritôneo, causando infecção grave local e disseminada. Animais tratados com Imipenem durante 48h após PA também foram analisados, bem como a interferência de PGC-1 ASO no processo de fagocitose. A expressão de PGC-1 e foi medida por PCR quantitativo. PA foi confirmada pelo aumento da amilase sérica e a inflamação sistêmica ratificada por leucocitose. PGC1 aumentou no baço e nos leucócitos circulantes 48h após PA e no lavado peritoneal 24h após PA e CLP. No entanto, PGC1 diminuiu no baço 24h após PA. Tratamento com Imipenem diminuiu PGC- 1. A diminuição de PGC-1 após transfecção com ASO levou à redução do processo de fagocitose. Assim, concluímos que ocorre aumento de PGC-1 na presença de bactérias e esse aumento está relacionado com fagocitose<br>PGC1 is a family of transcriptional coactivators that controls the expression of several genes involved in cell energy homeostasis. PGC1 isoforms and are present in tissues with high oxidative metabolism and are able to enhance mitochondrial biogenesis, -oxidation of fatty acids and gluconeogenesis in response to exposure to cold, fasting and exercise. Initial results showed macrophages in vitro present increased PGC-1 expression after 1h exposure to zymosan. Thus, we hypothesized that PGC-1 could be up-regulated in response to bacterial insult. We tested our hypothesis following PGC-1 expression in an acute pancreatitis (AP) model, characterized initially by a strong sterile inflammatory response, followed, few days later, by bacterial intestinal translocation and disseminated infection. AP was induced by retrograde infusion of sodium taurocholate (2.5%). We also analysed PGC-1 in a model of sepsis by cecal ligation and puncture (CLP), whose intestinal content is deposited in the peritoneum, causing a severe local and disseminated infection. Animals submitted to PA and treated with Imipenem for 48 hours were also analyzed, as well as the interference of PGC-1 ASO in phagocytosis process. PGC-1 and expression were measured by quantitative PCR. AP was confirmed by increased blood amylase and the systemic inflammation was noted by leukocytosis after 48h. PGC1 was increased in spleen and circulating leukocytes 48h after AP and in peritoneal lavage 24h after AP and CLP. On the other hand, PGC1 was decreased in spleen 24h after AP induction. Imipenem treatment decreased PGC-1. The decreased of PGC-1 after ASO transfection led to a reduction of phagocytosis process. Thus, we conclude there is a PGC-1 increase in bacterial presence and this increase is related to phagocytosis
28
Barbarulo, Andrea. "On a PGD model order reduction technique for mid-frequency acoustic." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2012. http://tel.archives-ouvertes.fr/tel-00822643.
Full textAbstract:
In many industrial contexts, such as aerospace applications or cars design, numerical prediction techniquesbecome more and more useful. They restrict the use of real prototypes to a minimum and make easier thedesign phase. In such industries and in the specific for acoustic, engineers are interested in computing theresponses of systems on frequency bands. In order to predict the vibration behavior of systems overfrequency bands, standard numerical techniques usually involve many frequency-fixed computations, atmany different frequencies. Although it is a straightforward and natural mean to answer to the posed problem,such a strategy can easily lead to huge computations, and the amount of data to store often increasessignificantly. This is particularly true in the context of medium frequency bands, where these responses havea strong sensitivity to the frequency. In this work PGD (Proper Generalized Decomposition), in a first time, isapplied to found a separate functional representation over frequency and space of the unknown amplitude ofVTCR (Variational Theory of Complex Rays) formulation on a reduced frequency space. This allows tocalculate an high quality mid-frequency response over a wide band without a fine frequency discretization,saving computational resources. Moreover the PGD representation of the solution allows to save a hugeamount of space in term of stored data. In a second time, PGD technique as been applied to extend itspeculiarity to mid-frequency wide band with uncertainty.
29
Austin, Shane. "The impact of PGC-1alpha on the intrinsic properties of mitochondria." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110743.
Full textAbstract:
PGC-1alpha is a key factor controlling mitochondrial biogenesis. In this thesis, we demonstrate that PGC-1alpha is also a central regulator of the intrinsic properties of mitochondria. Using mitochondria isolated from muscle tissues of MCK- PGC-1alpha Tg mice that ectopically express PGC-1alpha under the control of the muscle creatine kinase promoter, we observed significant changes in their intrinsic properties compared with wild-type controls. The results illustrate that PGC-1alpha changes the respiratory and ROS generation capacities of mitochondria, while maintaining their topology/sidedness of ROS production. Additionally, PGC-1alpha did not alter the fraction of electrons escaping the respiratory chain to react with oxygen during oxygen consumption, ensuring a tight coupling between the respiratory and ROS generation capacities of mitochondria. These changes in the intrinsic properties of mitochondria upon ectopic expression of PGC-1alpha were accompanied by modifications in the expression of several components of the respiratory chain. Together, these data reveal that PGC-1alpha does not only change the number of mitochondria in cells but also the intrinsic properties of individual mitochondria within the cell.<br>PGC-1alpha est un facteur clé contrôlant la biogénèse mitochondriale. Dans cette thèse, nous démontrons que PGC-1alpha est aussi un régulateur important des propriétés intrinsèques des mitochondries. Utilisant des mitochondries isolées de tissus musculaires de souris transgéniques MCK-PGC-1alpha qui expriment ectopiquement PGC-1alpha sous le contrôle du promoteur de la créatine kinase musculaire, nous avons observé des changements significatifs à leurs propriétés intrinsèques comparativement à des mitochondries de souris sauvages. Spécifiquement, nous démontrons que PGC-1alpha change les capacités respiratoires et génératrices d'espèces réactives oxygénées (ROS) des mitochondries, bien qu'il maintienne leur topologie de production de ROS. De plus, PGC-1alpha n'altère pas la fraction d'électrons qui s'échappent de la chaine respiratoire pour ensuite réagir avec l'oxygène durant le processus de consommation d'oxygène, assurant un couplage étroit entre les capacités respiratoires et génératrices de ROS des mitochondries. Ces changements des propriétés intrinsèques des mitochondries suivant l'expression ectopique de PGC-1alpha ont été accompagnés de modification de l'expression de plusieurs composantes de la chaine respiratoire. Ensemble, ces données révèlent que PGC-1alpha change non seulement le nombre de mitochondries dans les cellules, mais aussi les propriétés intrinsèques des mitochondries individuelles.
30
Zou, Xi. "Simulation tools for biomechanical applications with PGD-based reduced order models." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/481988.
Full textAbstract:
Numerical simulation tools are generally used in all modern engineering fields, especially those having difficulties in performing large number of practical experiments, such as biomechanics. Among the computational methods, Finite Element (FE) is an essential tool. Nowadays, the fast-growing computational techniques, from the upgrading hardware to the emerging of novel algorithm, have already enabled extensive applications in biomechanics. For applications that require fast response and/or multiple queries, Reduced Order Modelling (ROM) methods have been developed based on existing methods such as FE, and have eventually enabled real-time numerical simulation for a large variety of engineering problems.
In this thesis, several novel computational techniques are developed to explore the capability of Proper Generalised Decomposition (PGD), which is an important approach of ROM. To assess the usability of the PGD-based ROM for biomechanical applications, a real human femur bone is chosen to study its mechanical behaviour as an example. Standard image-based modelling procedure in biomechanics is performed to create an FE model which is then validated with in vitro experimental results.
As a basis of this work, the medical image processing has to be performed, in order to generate an available FE model. This model is validated according to data collected from a previously performed \textit{in vitro} experimental test. The full procedure of image-based model generation and the validation of generated model is described in Chapter 2.
As a major objective of this thesis, a non-intrusive scheme for the PGD framework is developed in Chapter 3. It is implemented using in-house developed Matlab (Mathworks, USA) code to conduct the PGD work flow, and calling Abaqus as an external solver for devised fictitious mechanical problems.
The transformation of data from computed tomography (CT) image set to FE model including inhomogeneous material properties is subjected to some physical constraints, and when applying the load, there are also geometric constraints limiting the locations where load could be applied. These constraints will lead to a constrained parameter space, which possibly has difficulty to be separated in a Cartesian fashion. Therefore, a novel strategy to separate the parameters in a collective manner is proposed in Chapter 4.
Chapter 5 details a comprehensive application in biomechanics, the methodologies proposed in Chapter 3 and 4 are applied on the practical model generated in Chapter 2. As a typical application of the PGD vademecum, a material property identification problem is discussed. Further PGD vademecum is generated using the identified material properties with variable loading locations, and with this vademecum, real-time mechanical response of the femur is available.
In addition, for the purpose of extending the methodologies to orthotropic materials, which is commonly used in biomechanics, in Chapter 6 another linear elastic model is investigated with the non-intrusive PGD scheme. Nowadays, isogeometric analysis (IGA) is a very popular tool in computational mechanics. It is appealing to take advantage of non-uniform rational B-splines (NURBS) to discretise the model. For PGD, using B-splines for the discretisation of the parameter space could improve the quality of vademecum, especially for problems involving sensitivities with respect to the parameters during the online computations.
It is important and necessary to extend the PGD framework to nonlinear solid mechanics, because most biological soft tissues have been observed nonlinear mechanical behaviours. Consequently, in Chapter 7 we have developed a PGD framework for the St.Venant-Kirchhoff constitutive model using the Picard linearisation which is consistent with the fixed-point iteration algorithm commonly used in PGD.
In Chapter 8, conclusive remarks are addressed as well as forecasts of possible future works.
31
Bellafante, Elena. "PGC-1β regulates mitochondrial metabolic pathways in the gut-liver axis". Thesis, Open University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578563.
Full textAbstract:
ROS production is proportional to the increase in mitochondrial respiration and electron chain activity. Numerous factors (including radiations, oxygen shortage, carcinogens and inflammation) can give rise to ROS, ultimately leading to ROS- mediated genomic instability and cancer. Under normal conditions, the balance between ROS levels are tightly controlled by an inducible antioxidant program that responds to cellular stressor, including enzymes such as superoxide dismutase, catalase, and those involved in glutathione metabolism. Some components of the ROS scavenging pathway are linked to mitochondrial oxidative metabolism by the PGC-l coactivators that enable cells to maintain normal redox status in response to changing oxidative capacity. The increase in mitochondrial number stimulated by these proteins could cause an increase in the production of ROS. Therefore, if ROS production were proportional to the increase of electron transport activity stimulated by the PGC-l proteins, these molecules would ultimately drive ROS levels higher. However, PGC-la is able to upgrade aerobic energy metabolism in tissues with high aerobic demand promoting ROS formation on one hand and ROS scavenging .systems on the other. Since the role of PGC-l ß in this process is completely unknown and ROS production is .commonly linked to mitochondrial dysfunctions that, in turn, are linked with several diseases, such as intestinal cancer and several metabolic diseases including steatohepatitis, we decided to investigate whether PGC-l ß could be involved in the mitochondrial homeostasis and ROS generation in two different organs, the intestine and the liver.
32
Dumon, Antoine. "Réduction dimensionnelle de type PGD pour la résolution des écoulements incompressibles." Phd thesis, Université de La Rochelle, 2011. http://tel.archives-ouvertes.fr/tel-00644565.
Full textAbstract:
L'objectif de ce travail consiste à développer la méthode de résolution PGD (Proper Generalized Decomposition), qui est une méthode de réduction de modèle où la solution est recherchée sous forme séparée, à la résolution des équations de Navier-Stokes. Dans un premier temps, cette méthode est appliquée à la résolution d'équations modèles disposant d'une solution analytique. L' équation de diffusion stationnaire 2D et 3D, l'équation de diffusion instationnaire 2D et les équations de Burgers et Stokes sont traitées. Nous montrons que dans tous ces cas la méthode PGD permet de retrouver les solutions analytiques avec une précision équivalente au modèle standard. Nous mettons également en évidence la supériorité de la PGD par rapport au modèle standard en terme de temps de calcul. En effet, dans tous ces cas, laPGD se montre beaucoup plus rapide que le solveur standard (plusieurs dizaine de fois). La résolution des équations de Navier-Stokes isothermes et anisothermes est ensuite effectuée par une discrétisation volumes finis sur un maillage décalé où le couplage vitesse-pression a été géré à l'aide d'un schéma de prédiction-correction. Dans ce cas une décomposition PGD sur les variables d'espaces uniquement a été choisie. Pour les écoulements incompressibles 2D stationnaire ou instationnaire, de type cavité entrainée et/ou différentiellement chauffé, les résultats obtenus par résolution PGD sont similaires à ceux du solveur standard avec un gain de temps significatif (la PGD est une dizaine de fois plus rapide que le solveur standard). Enfin ce travail introduit une première approche de la résolution des équations de transferts par méthode PGD en formulation spectrale. Sur les différents problèmes traités, à savoir l'équation de diffusion stationnaire, l'équation de Darcy et les équations de Navier-Sokes, la PGD a montré une précision aussi bonne que le solveur standard. Un gain de temps a été observé pour le cas de l'équation de Poisson, par contre, concernant le problème de Darcy ou les équations de Navier-Stokes les performances de la PGD en terme de temps de calcul peuvent encore être améliorées.
33
Barroso, Wermerson Assunção. "PGC-1 alfa como regulador inflamatório na esteato-hepatite não-alcoólica." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/5/5165/tde-06062016-125337/.
Full textAbstract:
A doença hepática gordurosa não-alcoólica (NAFLD, do inglês) é a manifestação clínica hepática da síndrome metabólica, cuja incidência aumenta consideravelmente em todo o mundo. A NAFLD pode progredir para um estado de esteatohepatite não-alcoólica (NASH, do inglês), caracterizado por inflamação hepatocelular, com ou sem fibrose. Dados na literatura mostram que o coativador-1 alfa do receptor ativado por proliferadores de peroxissoma gama (PGC-1alfa), além de estar envolvido em diversos processos metabólicos, representa uma estratégia terapêutica promissora na modulação da inflamação. Neste projeto investigamos as alterações inflamatórias no fígado induzida por dieta hiperlipídica e o papel do PGC-1alfa nesse processo. Camundongos C57black/6 receberam dieta hiperlipídica contendo 30% de gordura por 10 semanas. O peso dos animais foi avaliado semanalmente. Após a eutanásia, o tecido adiposo intra-abdominal (retroperitoneal e periepididimal) foi coletado e pesado. Analisamos o perfil glicêmico e lipídico sérico e expressão de genes envolvidos no metabolismo glicêmico e lipídico. Avaliou-se também o aspecto histológico e a inflamação do tecido hepático por quantificação das citocinas IL-6, TNF-alfa e IL-1beta. A dieta rica em gordura conduziu a um aumento dos depósitos de gordura intra-abdominal, hiperglicemia e hiperlipidemia. Os animais também apresentavam esteatohepatite, com aumento de citocinas pró-inflamatórias e diminuição na expressão de PGC-1alfa no tecido hepático. O envolvimento do PGC-1alfa na produção de mediadores inflamatórios por hepatócitos foi avaliado em células HepG2 utilizando RNA de interferência (RNAi). O knockdown da expressão de PGC-1alfa causou aumento na expressão e liberação de IL-6 em hepatócitos via aumento na fosforilação de IkBalfa e consequente ativação do NFkB. Portanto, nossos dados mostram que o PGC-1alfa inibe a produção de mediadores inflamatórios (IL-6) em hepatócitos, e fornecem novas evidências das conexões existentes entre as vias metabólicas e imunes<br>Nonalcoholic fatty liver disease (NAFLD) is the liver clinical manifestation of the metabolic syndrome, whose incidence increases considerably around the world. NAFLD may progress to a state of non-alcoholic steatohepatitis, characterized by hepatocellular inflammation, with or without fibrosis. Data in the literature show that the peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1alfa), a protein involved in various metabolic processes, represents a promising therapeutic strategy in the modulation of inflammation. In this project, we investigate the inflammatory changes in the liver induced by high fat diet and the role of PGC-1alfa in this process. C57black/6 mice were fed a high fat diet containing 30% fat for 10 weeks. The weight of the animals was measured weekly. After euthanasia, the intra-abdominal adipose tissue (retroperitoneal and periepididymal) was collected and weighed. We have analyzed the glycemic and serum lipid profile and expression of genes involved in glucose and lipid metabolism. We also assessed liver morphology by HE staining and inflammation by quantification of the cytokines IL-6, TNF-alfa and IL-1beta. The high fat diet led to an increase in intra-abdominal fat deposits, hyperglycemia and hyperlipidemia. Animals also presented steatohepatitis, an increased proinflammatory cytokines and decreased PGC-1alfa expression in the hepatic tissue. The involvement of PGC-1alfa on inflammatory mediators production by hepatocytes was evaluated in HepG2 cells using RNA interference (RNAi). The knockdown of PGC-1alfa expression caused an increase in IL6 expression and release by hepatocytes via the increase in the IkBalfa phosphorylation and subsequent activation of NFkB. Therefore, our data show that PGC-1alfa inhibits the production of inflammatory mediators (IL-6) in hepatocytes and provide further evidence of the connections between the metabolic and immune pathways
34
Lloyd, Michele. "'A long weekend' : a case study of student teachers' experiences of a secondary PGCE course." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302265.
Full text
35
Evans, Carol Ann. "The relationship between the cognitive style(s) and preferred teacher style(s) of PGCE students." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/1077/.
Full text
36
SILVA, Alexandra Rodrigues Pereira da. "Estudo das propriedades bioquímicas de sistemas poliméricos arborescentes PGLD-AAS para o tratamento do câncer." reponame:Repositório Institucional da UNIFEI, 2008. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1620.
Full textAbstract:
Submitted by Margareth Ribeiro (meg@unifei.edu.br) on 2018-09-04T13:43:22Z
No. of bitstreams: 1
dissertacao_0032859.pdf: 3659313 bytes, checksum: 50f9a87611f53b582856313ecddfa61f (MD5)<br>Made available in DSpace on 2018-09-04T13:43:22Z (GMT). No. of bitstreams: 1
dissertacao_0032859.pdf: 3659313 bytes, checksum: 50f9a87611f53b582856313ecddfa61f (MD5)
Previous issue date: 2008-04<br>O principal objetivo deste trabalho é relatar a hemocompatibilidade e propriedades antitumorais do dendrímero de poliglicerol salicilado (PGLD-AAS). O dendrímero de
poliglicerol (PGLD) foi preparado seguindo a metodologia sintética divergente. A natureza da estrutura do PGLD foi caracterizada pelas técnicas GPC e 13C-NMR. O dendrímero de poliglicerol salicilado foi preparado pela esterificação do ácido acetilsalicílico com o PGLD. A adsorção protéica, adesão plaquetária, formação de trombo e propriedades anticoagulantes foram conduzidas por experiências in vitro para analisar a interação do sangue com o PGLD-AAS. A citotoxicidade do conjugado foi estudada contra células de mamíferos (CHO). O dendrímero sintetizado (PGLD) apresenta baixa dispersão em peso molecular (Mw/Mn = 1,05) e um grau de ramificação (GR) de 0,82, caracterizando a estrutura dendrítica do polímero. Investigações sobre adsorções de proteínas albumina do soro humano e fibrinogênio mostraram que o PGLD-AAS adsorve mais albumina que fibrinogênio. As micrografias eletrônicas digitais do PGLD-AAS após contato com o sangue mostraram um comportamento hemocompatível do conjugado bioativo. As análises clínicas TTPA e TP indicam que o PGLD-AAS exibe boa atividade anticoagulante. A constante dielétrica de PGLD-AAS em solução fisiológica indica que este dendrímero
bioativo não induz agregação de células sanguíneas. O conjugado PGLD-AAS exibe
especificidade e bioatividade contra o câncer de mama humano derivado da linhagem celular MCF-7. A droga diminuiu a viabilidade celular em uma maneira dose dependente, exibindo uma IC50 de 88,6 ± 5,3 μM, com 50 μM PGLD-AAS. O PGLD-AAS induziu alterações morfológicas na membrana celular da linhagem MCF-7. A bioquímica e estudos in vitro indicam que PGLD-AAS parece ser um promissor agente antineoplásico.
37
Moya, Mario Raul Angel. "Using language learning strategies to develop ab-initio PGCE students' skills in primary modern languages." Thesis, University of Bedfordshire, 2014. http://hdl.handle.net/10547/320282.
Full textAbstract:
The announcements concerning the introduction of modern languages in Key Stage Two in England (https://www.education.gov.uk/schools/teachingandlearning/ curriculum/national curriculum2014, [accessed 8 March 2013]), although not a new initiative, have renewed the need to train generalist primary teachers in teaching modern languages. Following an initial announcement of the introduction of the English Baccalaureate, the poor outcomes achieved by England in the European languages survey (COE, 2012) and the news that modern languages would be part of the primary curriculum (http://www.bbc.co.uk/news/education-18531751 [accessed 21 June 2012]) contributed to refreshing the agenda of languages in the country and the role of early second language learning appears to be slowly resurrecting. In order to provide trainee teachers with the skills necessary for teaching young learners modern languages, this study focuses on increasing subject knowledge and pedagogical competence in a short time by developing trainees’ reflective practice, broadly following the tradition of strategy-based instruction (Macaro, 2001; Cohen, 2007; Oxford, 2011), but within a social constructivist understanding of learning using collaboration. The research, which follows a mixed method case study approach, proposes and trials a teaching approach that incorporates language learning strategies in a collaborative manner. The design of a revised strategy-based approach has a three-fold purpose: (i) to enable primary trainee teachers to develop the linguistic skills necessary to teach another language through the use of the linguistic knowledge they already possess in their own mother tongue (Saville-Troike, 2012); (ii) to use self-regulation to build confidence and competence in the target language; and (iii) to enable trainees and pupils to develop their language learning autonomy. Results indicate that, within the case studies reported here, such an approach seemed to be an effective way of learning and teaching another language simultaneously for adults, as it provided ab-initio language learners with a basis for the development of linguistic skills thus increasing their capacity for languages. Whilst there is no claim to generalisation here, the studies indicate that using language learning strategies may create and sustain interest and engagement in the subject—a condition that has been identified as critical to the success of any teaching approach. Whilst the results were positive in terms of developing acceptable levels of linguistic competence in adult learners over a short time, the use of a strategy-based method with children did not prove satisfactory, perhaps because of the high metacognitive demands placed on them when they had not yet developed high level abstract thinking, particularly the amount of prior knowledge needed and the language required to verbalise complex cognitive processes.
38
Bamba, Funck Jessica. "Etude des isoformes du gène PGC-1a dans le développement musculaire chez le bovin." Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0057/document.
Full textAbstract:
Le coactivateur de facteurs de transcription PGC-1a (PPARC1A) est connu pour jouer un rôle clé dans la thermogénèse adaptative ainsi que dans l’homéostasie et la croissance musculaire chez l’homme et la souris. Le gène codant pour PGC-1 est contrôlé par deux promoteurs et est soumis à un épissage alternatif, il en résulte de multiples protéines. Chez le bovin, malgré son implication dans la croissance et dans les caractéristiques du lait relevée par des études de SNP, le gène et les transcrits de PGC-1a restent peu étudiés. Ainsi, notre objectif a été de mettre en évidence la structure et l’expression des transcrits de PGC-1a chez le bovin. Nous avons montré que deux formes longues PGC-1a-a et PGC-1a-b étaient exprimées chez le bovin de même que deux formes tronquées NT-PGC-1a-a et NT-PGC-1a-b (aussi appelé PGC-14). En conditions basales, les formes tronquées sont plus exprimées que les formes longues dans le muscle squelettique. De plus, les transcrits dérivants du promoteur proximal sont prédominants, ce qui suggère que NT-PGC-1a serait la forme prédominante dans le muscle squelettique bovin. Nous avons également créé des lignées cellulaires sur-exprimant indépendamment les formes longues ou tronquées et montré que la sur-expression des isoformes bovins entrainait une différenciation accrue des myoblastes associée à une augmentation de l’expression d’IGF-1 et une sousexpression de la myostatine. La multitude d’isoformes codée par le gène PGC-1a ainsi que leur implication dans la myogenèse positionne PGC-1a en gène d’intérêt dans l’étude de la variabilité phénotypique retrouvé chez certaines races bovines. De plus, les transcrits de PGC-1a semblent être de puissants modulateurs de la masse musculaire. PGC-1a pourrait donc être un gène de plus à étudier lors de la sélection des animaux domestiques présentant une plus grande musculature<br>The transcriptional co-activator PGC-1α (PPARGC1A) has been reported to play a key role in adaptive thermogenesis and to influence muscle homeostasis and growth in mouse and human. PGC-1α has a complex structure with multiple protein domains whose gene is controlled by two promoters and is subject to alternative splicing events. In cattle, very little is currently known about PGC-1α, despite its implication in growth and milk characteristics revealrd by SNP study. So, the aim of our study was to investigate the presence and the structure of bovine PGC-1α alternative transcripts. We found different transcripts, two full-length isoforms named PGC-1α-a and PGC-1α-b, and two truncated forms, NT-PGC-1α and PGC-1α4. In basal conditions, our results showed that the truncated forms are the most expressed in bovine muscle. In addition, the transcripts derived from the proximal promoter are predominant, suggesting that NT-PGC-1 would be the main form. Finally, we showed that the overexpression of either fulllength or truncated isoforms of bovine PGC-1 enhances myoblasts differentiation. The multiplicity of isoforms resulting from PGC-1α as well as their implication in myogenesismakes PGC-1α as a gene of interest for the study of the muscular phenotypic variability found in different cattle breeds. In addition, PGC-1 transctipts appear to be a strong modulators of muscle mass. So the bovine PGC-1a isoforms could be used to engineer future breeds with higher muscularity
39
Lima, Tanes Imamura de. "Controle molecular da função mitocondrial pelos co-reguladores transcricionais PGC-1? e NCoR1 em células musculares." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/17/17131/tde-26042018-135946/.
Full textAbstract:
A capacidade de sincronizar vias metabólicas a estímulos ambientais é um aspecto central da homeostase em mamíferos. Dentro desse contexto, o controle molecular da função mitocondrial representa um aspecto fundamental e defeitos na integridade desse sistema podem levar a severas perturbações à homeostase celular levando a um amplo espectro de doenças como a obesidade e o diabetes tipo 2. O controle transcricional do metabolismo energético é um processo dinâmico que depende da ação coordenada de fatores de transcrição, enzimas modificadoras de cromatina e coreguladores transcricionais. Co-reguladores podem agir como interruptores transcricionais ativando ou reprimindo a atividade de receptores nucleares. Neste estudo, demonstramos que o coativador PGC-1? e o co-repressor NCoR1 são importantes mediadores do metabolismo energético e da homeostase redox mitocondrial em células musculares. Nossos resultados sugerem que os efeitos desses co-reguladores são mediados pela transativação do elemento responsivo de PPAR (PPRE) em promotores de seletos grupos de genes. Ainda, a indução da capacidade oxidativa e da defesa antioxidante pelo silenciamento de NCoR1 ou pela expressão de PGC-1? atenua a produção de espécies reativas de oxigênio e a morte celular induzida por estresse metabólico. Essas evidências sugerem que o equilíbrio entre a ativação e a repressão transcricional em promotores contendo PPREs exerce um papel central na função mitocondrial em células musculares esqueléticas. Coletivamente, os resultados deste estudo indicam que o antagonismo entre os coreguladores PGC-1? e NCoR1 é um componente central no controle da função mitocondrial representando uma interface promissora para o desenvolvimento de novas abordagens terapêuticas para o tratamento e prevenção da disfunção metabólica.<br>The ability to synchronize metabolic pathways to environmental stimuli is a central aspect of mammalian homeostasis. Within this context, the molecular control of mitochondrial function represents a fundamental aspect and defects in the integrity of this system can lead to severe disturbances to cellular homeostasis causing a wide spectrum of pathologies such as obesity and type 2 diabetes. Transcriptional control of energy metabolism is a dynamic process that depends on the coordinated action of transcription factors, chromatin modifying enzymes, and transcriptional co-regulators. Co-regulators can act as transcriptional switches activating or repressing the activity of nuclear receptors. In this study, we demonstrated that the co-activator PGC-1? and NCoR1 co-repressor are essential mediators of energy metabolism and mitochondrial redox homeostasis in muscle cells. Our results suggest that the effects of these co-regulators are mediated by the transactivation of the PPAR responsive elements (PPREs) in promoters of selected gene groups. Furthermore, the oxidative capacity and antioxidant defense induction by either NCoR1 knockdown or PGC-1? overexpression attenuates the production of reactive oxygen species and cell death induced by metabolic stress. These evidence suggest that the balance between activation and transcriptional repression in promoters containing PPREs exert a central role in mitochondrial function in skeletal muscle cells. Collectively, the results of this study indicate that the antagonism between the co-regulators PGC-1? and NCoR1 is a central component of mitochondrial function representing a promising interface for the development of novel therapeutic approaches for the treatment and prevention of metabolic dysfunction.
40
Glentis, S. "Whole genome amplification for PGD and PND : molecular and a-CGH diagnosis." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18554/.
Full textAbstract:
Whole genome amplification amplifies the entire genome in a few hours from samples of minimal DNA quantities, even from single cells. This may have many applications, especially in prenatal diagnosis, PGD and PGS. The hypothesis for chapter 3 was: Can multiple displacement amplification (MDA) be used as a universal step prior to molecular analysis for PGD? WGA using MDA (Qiagen) was used on single cells in order to overcome the problem of limited DNA in PGD. MDA allows the diagnosis through haplotyping or a combination of direct and indirect mutation analysis. Different cell types, including buccal cells, lymphocytes, fibroblasts and blastomeres were examined. A modification on the cell lysis buffer was also tested in order to achieve more accurate results. PGD seems to benefit from MDA when multiple tests are performed for direct and indirect analysis. The modified lysis buffer (exclusion of DTT) produced better results than the other lysis buffers and buccal cells do not produce as accurate results as other cell types. The hypothesis was met as the amount of DNA produced by MDA can be used for direct and indirect testing and haplotyping. The hypothesis for chapter 4 was: Is it possible to accurately assess the chromosomes of a single cell by a-CGH? WGA was achieved by MDA and GenomePlex (Sigma) on single lymphocytes, fibroblasts and blastomeres prior to a-CGH analysis. The difficulty of this technique was the high background noise that was produced by WGA that makes interpretation difficult. Different lysis buffers, modifications of the WGA reaction and analysis software were examined for better results. A-CGH slides from different companies and institutions were used. The results showed that GenomePlex produced less background noise compared to MDA but the amplification efficiency of the technique was less reliable. The BlueGnome Cytochip arrays produced the best compared to arrays from any other companies or institutions. More experiments would be necessary to determine if the hypothesis was met as a number of chromosomal abnormalities detected were not always confirmed by other experiments. The hypothesis for chapter 5 was: Can aneuploidy be detected in coelomic fluid using a-CGH? The possibility of using WGA and a-CGH on coelomic fluid was tested as this could be used as an early form of prenatal diagnosis. Coelomic fluid was collected between the 5th and 11th week of pregnancy from women undergoing termination of pregnancy. MDA and GenomePlex were used to amplify the DNA prior to a-CGH analysis. Both genomic (high resolution) and constitutional (low resolution) arrays were tested. The results showed that aneuploidy can be detected by a-CGH. BlueGnome Cytochip slides produced the best results. A triploid sample was detected as normal. The hypothesis was met and even higher resolution could be achieved with the use of GenomePlex and BlueGnome Cytochip arrays. WGA may be very important for downstream genetic tests when the DNA is from very low quality and quantity. Further optimisation of the technique is needed in order to achieve similar results to those of good quality genomic DNA. Arrays from different companies or institutions may produce very different results. In conclusion, the results showed that WGA can benefit PGD and PND, and a-CGH gives great potential to PGS and coelomic fluid diagnosis.
41
Baartman, Nomakhaya. "Perspectives of Post Graduate Certificate in Education (PGCE) students on the effectiveness of school based mentoring." Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/5641.
Full textAbstract:
Effective mentoring is essential for the development of student-teachers. A sequential explanatory mixed method study was conducted in order to analyse the perspectives of Post Graduate Certificate of Education (PGCE) students on the effectiveness of school based mentoring. Thirty-six (36) PGCE students from a higher education institution in the Eastern Cape participated in this study. Firstly, quantitative questionnaires were used to gather data from all the participants followed by qualitative semi–structured interviews from a purposive sample of five (5) participants in order to enrich the study. This study analysed PGCE students’ perspectives of mentor teacher practices. In doing so the study evoked Hudson and Peards’ Five Factor Mentoring Model. This model includes Personal Attributes, Systems Requirements, Pedagogical Knowledge, Modelling and Feedback. From the findings, PGCE students reported that Teaching Practice (TP) is a stressful period full of anxieties, excitement and fears, hence they need to be guided and supported by knowledgeable and specialist teachers (mentors). Mentors play a significant role in supporting and guiding student-teachers during TP. From the analysis of PGCE students’ perspectives, the research suggested that those who were supported and guided by their mentors experienced positive mentoring during TP. Those who experienced negative mentoring reported limited time for mentoring and unavailability of the mentors as the causes. They further expressed that they wished mentors were understanding, good models who treated them as teacher candidates not as students and gave them constructive feedback. Finally, they indicated that the partnership between host schools and the university needs to be improved.
42
Mitani, Tadahiro. "Principles for the regulation of multiple developmental pathways by a versatile transcriptional factor, BLIMP1." Kyoto University, 2018. http://hdl.handle.net/2433/231007.
Full text
43
Tertrais, Hermine. "Développement d’un outil de simulation pour le chauffage de matériaux composites par micro-ondes." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0061/document.
Full textAbstract:
Le travail présenté dans cette thèse s’inscrit dans le contexte du développement de nouveaux procédés pour la mise en forme de matériaux composites pour répondre aux contraintes industrielles de gain de temps et d’énergie. Le procédé de chauffage par micro-onde reposant sur un principe de chauffage volumique permet de garantir ces avantages. L’inconvénient majeur est que le comportement du champ électrique lors de l’interaction entre matériaux composites et micro-ondes est peu connu. L’objectif de cette thèse est donc de proposer des solutions numériques pour approfondir la connaissance du procédé et la physique associée afin de mettre en avant ses capacités quant à un développement industriel. Pour ce faire, le travail réalisé est axé autour de trois verrous. En premier lieu, une nouvelle méthode numérique est proposée afin de résoudre les équations de Maxwell en 3D dans un stratifié composite. Prendre en compte le comportement 3D est essentiel afin de décrire avec précision l’impact des différentes couches du matériau et de leur épaisseur sur la propagation du champ électrique. Dans un second temps, la simulation électromagnétique est couplée à une résolution thermique afin de simuler le procédé de chauffage d’une pièce composite. Différents paramètres du procédé sont étudiés afin de mettre en avant les plus sensibles pour l’utilisation du chauffage micro-onde pour les matériaux composites. Enfin, l’attention du lecteur est portée sur le développement d’une méthode de simulation pour un contrôle en temps réel du procédé en comparaison avec des essais expérimentaux<br>The context of the present work is the development of new processes for the heating and forming of composite materials in order to provide an answer to the industrials needs for less energy and less time-consuming processes. In that sense, microwave heating is perfect match as it relies on volumetric heating. The major drawback is that the behaviour of the electric field while interacting with composite material is poorly known. Therefore, the main objective of this thesis is to provide numerical solutions to go more deeply in the understanding of such process and put forward its capabilities for an industrial development.To fulfil this objective, the work is oriented over three main axes. First, an innovative simulation tool is presented in order to solve the Maxwell’s equations in a thin multi layered domain. Taking into account the 3D behaviour of the electric field is a major issue in order to describe precisely the impact of the different plies of the laminate on the propagation of the electric field.Then, the electromagnetic simulation is coupled with a thermal simulation in order to simulate the full heating process of a composite part. Parameters of the process are investigated to bring forward the most crucialones. Finally, real-time control of the process is tackled using a model order reduction simulation technique. These results are compared to experimental work on two sets of samples
44
Shaw, Pamela Anne. "How far should, or can, a school based partnership PGCE, which involves co-operation between participants from different institutions, approximate to a learning organisation? : an interpretive, evaluative case study of a school based partnership PGCE in d." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262738.
Full text
45
Passos, Luis Augusto Abreu da Cunha. "A sinalização do co-ativador de transcrição PGC-1beta e sua relevância para a proliferação celular e desenvolvimento de melanoma." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/5/5165/tde-31032015-162021/.
Full textAbstract:
PGC-1 beta é um co-ativador de transcrição gênica responsável pela regulação do metabolismo celular, principalmente na biogênese e função mitocondrial, disponibilidade de substrato e síntese de lipídios. Nos últimos anos, outras isoformas de PGC-1 têm sido descritos como participantes na gênese e manutenção de tumores. Portanto, nosso objetivo foi determinar se o PGC-1beta está relacionado ao aumento da proliferação celular de células de melanoma. Inicialmente, foi demonstrado que os níveis de RNAm e proteína de PGC-1beta são muito mais elevados em linhagens de células de melanoma (Tm1 e Tm5) do que na linhagem parental de melanócitos não tumorais (Melan-a) como detectado por PCR quantitativa e western blotting. A fim de descobrir uma relação causal entre a expressão de PGC-1? e crescimento celular da linhagem Tm5, células de tal linhagem foram transfectadas com um oligonucleotídeo antisense (ASO) contra PGC-1beta. As células tratados com ASO apresentaram níveis mais baixos de RNAm e proteína PGC-1beta, além de redução em sua atividade avaliada pela expressão de genes PGC-1beta dependentes. Além disso, as células transfectadas apresentaram uma taxa de proliferação inferior em comparação com células de controle Tm5. Este fenômeno também foi observado in vivo. Quando injetadas em camundongos, as células Tm5 desenvolvem-se em um tumor que atinge 1,34 ± 0,20 cm3 após nove dias. Tumores tratados com ASO após o mesmo tempo apresentaram volume tumoral de 0,75 ± 0,05 cm3. Este crescimento não estava relacionada à necrose tumoral, mas sim com a proliferação reduzida de células. Finalmente, verificamos se o mesmo fenômeno seria observado em humanos. A expressão PGC-1beta foi muito maior em amostras de melanoma do que em nevos, alterações não-malignas da pele com alto conteúdo de melanina. Por conseguinte, conclui-se que a expressão PGC-1? está aumentada no melanoma, tanto murino e humano, e que o bloqueio da sua atividade leva à diminuição da proliferação celular e crescimento tumoral<br>PGC-1beta is a co-activator of gene transcription primarily responsible for the regulation of cellular metabolism, mainly in mitochondrial biogenesis and function and also substrate and lipid synthesis. In recent years, other isoforms of PGC-1 have been described as participating in the genesis and maintenance of tumors. Therefore, our objective was to determine whether PGC-1beta is related to increased proliferation of melanoma cells. Initially, it was demonstrated that mRNA and protein levels of PGC-1beta are much higher in melanoma cell lines (Tm1 and TM5) than in the non-tumoral parental lineage melanocytes (melan-a) as detected by quantitative PCR and Western blotting. In order to find a causal relationship between the expression of PGC-1beta and cell growth, Tm5 lineage cells were transfected with an antisense oligonucleotide (ASO) against PGC-1beta. The cells treated with ASO had lower levels of PGC-1beta mRNA and protein, as well as reduction in its activity detected by quantitation of PGC-1beta dependent genes expression. Furthermore, transfected cells showed a lower rate of proliferation compared to Tm5control cells. This phenomenon was also observed in vivo. When injected into mice, Tm5 cells develop a tumor which reaches 1.34 ± 0.20 cm3 after nine days. Tumors treated with ASO, after the same time, presented tumor volume of 0.75 ± 0.05 cm 3. This growth was not related to tumor necrosis, but with reduced cell proliferation. Finally, we checked whether the same phenomenon would be observed in humans. The PGC-1beta expression was much higher in melanoma samples than in nevi, a non-malignant skin alteration filled with melanin. Therefore, we concluded that PGC-1beta expression in melanoma is increased, both in murine and human, and that blocking its activity leads to decreased cell proliferation and tumor growth
46
Whiting, Caroline. "School based training : a comparative case study of an articled teacher course and a one year PGCE." Thesis, University of Plymouth, 1994. http://hdl.handle.net/10026.1/760.
Full textAbstract:
This research is based on a case study of two primary Post Graduate Certificate in Education (PGCE) courses at the same university which was carried out at a time of rapid change and major reform. One of those courses, the Articled Teacher (AT) PGCE was of the 'school based' variety much heralded at the time as the way forward for the preparation of teachers. In this scheme, learner teachers were based, usually alone, for two years in one school in the care of a mentor, with a chance of a 'teaching practice' in another school. The ATs came into the university for seminars, lectures and tutorials. The other route was a more traditional one year course where the students, 75 in number, were based in the university and were sent out, sometimes alone, sometimes in groups, into two or three different schools for 'teaching practice' or 'school experience'. The research focussed on three major factors in making comparisons between the two groups: 1) patterns of loyalty to, and support from, the university and the school; 2) the sources of their theorising about teaching - the ATs relying more on their own personal experience mainly because of their constant need to survive in their schools; 3) the differences between the course providers in schools and in the university which were more important for the ATs because of their course's emphasis on 'partnership' rather than 'integration'. The findings of the fieldwork are placed in the context of a discussion of the recent reforms in initial teacher education with particular reference to their implications for school based training.
47
Smith, Matthew T. "An investigation into the epistemological trajectories of PGCE student teachers as predicated by their espoused pedagogical beliefs." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7917/.
Full textAbstract:
Postgraduate trainee teachers undergo profound shifts in their pedagogical understanding and practices through the year that they are taught at a UK Higher Education Institution. Using an ‘explanatory sequential design’ mixed methods approach in a paired pre–post data retrieval scheme, this longitudinal study investigated the espoused pedagogical beliefs of three cohorts of PGCE trainees at the onset, and toward the end, of their studies in a primary initial teacher education department in a major HEI in the UK, with corroborative results and discussion from further cohorts. Using an adaptation of the ‘practices’ scale of Swan (2006), trainees’ pedagogical beliefs were charted and described on a created continuum running from transmissionist to child-centred through answering 25 items, and shifts from pre-course to post-course were investigated on two fronts – individually and for each ‘practice’ under study. Two general principles are represented in the data: trainees seem to either make rather more radical shifts towards child-centeredness or more slight shifts towards a more teacher centred orientation. The average shift documents a significant trend towards a greater learner-centrism across all cohorts in the longitudinal study, which was further explained and substantiated by the qualitative comments from participants in the Community of Inquiry sessions that were run.
48
McDougall, Christopher W. "Uncertain risks, responsibilities & regulations : the ethics & control of PGD in Canada." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33915.
Full textAbstract:
The current state of preimplantation genetic diagnosis technology is presented, as are the biological principles and medical procedures that make it possible. The arguments of both proponents and those with social and ethical reservations about the broader implications of the technique are carefully reviewed, and the limitations of the dominant medical model approach to the technique are exposed. A discussion of reproductive autonomy in light of emerging testing applications of PGD not directly related to the avoidance of serious genetic abnormalities in the resulting child demonstrates the complexity of both clinical decision-making and public policy formulation with regard to PGD. Recently proposed legislation in Canada reflects such complexities, and highlights the lack of social consensus on the appropriate uses of, and restrictions on, PGD. A variety of "soft law" instruments, notably professional codes of practice and research guidelines implemented by institutional ethics committees, may mitigate some of the uncertainty surrounding PGD in Canada, but their limited applicability and espousal of the medical model approach render questionable their capacity to reconcile tolerance of pluralism with respect for human life, diversity, and reproductive autonomy.
49
Sczelecki, Sarah. "Understanding the function of PGC-1α Isoforms in ß-cell survival and diabetes". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119519.
Full textAbstract:
Peroxisome proliferator-activated receptor gamma (PPARγ) co-activator 1 alpha (PGC-1α) is a transcriptional co-activator responsible for mitochondrial biogenesis and oxidative metabolism. Many isoforms of PGC-1α have been described in the literature, most of which are shown to function similarly to the canonical PGC-1α protein. Recently, however, a novel isoform of PGC-1α was identified, PGC-1α4. It was shown to have a different, yet complementary function to canonical PGC-1α (PGC-1α1) in muscle. It is also expressed in other metabolically active tissues; however, it is unknown whether it has additional distinct tissue-specific functions. Furthermore, PGC-1α plays an important role in controlling metabolism in pancreatic β-cells and expression of the co-activator is decreased in diabetic islets; however, the role of PGC-1α isoforms in diabetes is unknown. Our objective is to determine whether PGC-1α4 has a unique function in β-cells and whether it plays a role in the pathogenesis of diabetes. We show that stimulation with forskolin, exendin-4 and a cytokine cocktail of TNFalpha, IL-1beta and IFNgamma, induced specific PGC-1α isoforms in β-cells. Following over-expression of these isoforms in INS-1 cells, PGC-1α4 prevented the cleavage of caspase-3 in response to cytokines, suggesting that the novel isoform is uniquely anti-apoptotic. To assess whether PGC-1α isoforms play a role in β-cell survival in vivo, mice with a β-cell specific PGC-1α knockout of all isoforms were subjected to low-dose streptozotocin (STZ) treatment to induce β-cell apoptosis. Unexpectedly, knockout mice were protected from STZ induced hyperglycemia. However, there was no difference in percentage of cleaved caspase-3 positive cells in control versus knockout mice, suggesting no difference in apoptosis. Therefore, PGC-1α4 could be a novel factor important for β-cell survival and over-expression of this unique isoform may protect against the pathogenesis of diabetes.<br>Peroxisome proliferator-activated receptor gamma (PPARγ) co-activator 1 alpha (PGC-1α) est un co-activateur transcriptionnel responsable de la biogenèse mitochondriale et du métabolisme oxydatif. De nombreux isoformes de PGC-1α ont été décrits dans la littérature, dont la plupart ont été démontrés comme fonctionnant de manière similaire à la protéine PGC-1α canonique. Récemment, cependant, un nouvel isoforme de PGC-1α a été identifié, PGC-1α4, possédant une fonction différente mais complémentaire de la protéine canonique (PGC-1α1) dans le muscle. PGC-1α4 est également exprimé dans d'autres tissus métaboliquement actifs, mais il n'est pas connu s'il démontre de nouvelles fonctions dépendantes du tissu. PGC-1α joue un rôle important dans la regulation métabolique des cellules β du pancreas; de plus l'expression du co-activateur est dérégulée dans les îlots de Langerhans de patients diabétiques. Notre objectif est de déterminer si PGC-1α4 a une fonction unique dans les cellules β du pancréas et s'il joue un rôle dans la pathogenèse du diabète. Nous montrons que la stimulation avec la forskoline, l'exendine-4 et un cocktail de cytokines, TNFalpha, IL-1beta et IFNgamma, induit les isoformes de PGC-1α dans les cellules β. Suite à la surexpression des isoformes dans les cellules INS-1, PGC-1α4 empêche le clivage de la caspase-3 en réponse à des cytokines, suggérant qu'uniquement le nouvel isoforme est anti-apoptotique. Pour déterminer si les isoformes de PGC-1α jouent un rôle dans la survie des cellules β in vivo, les souris déficientes de tous les isoforms de PGC-1α, spécifiquequement dans les cellules β, ont été soumises à une faible dose de streptozotocine (STZ) provoquant l'apoptose des cellules β. De façon inattendue, les souris déficientes en PGC-1α ont été protégées contre l'hyperglycémie induite par la STZ. Cependant, il n'y avait pas de différence du pourcentage de cellules en apoptose chez les souris témoins par rapport aux souris déficientes. Donc, PGC-1α4 pourrait être un nouveau facteur important pour la survie des cellules β du pancreas et la surexpression de cette isoform unique, peut protéger contre la pathogenèse du diabète.
50
Gali, Ramamoorthy Thanuja. "Role of PGC-1β and TIF2 co-regulators in mouse skeletal muscle function". Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAJ095.
Full textAbstract:
Le muscle squelettique (MS) est un tissu métabolique important. L'objectif de ma thèse était de caractériser le rôle des corégulateurs de la transcription, PGC-1β (transcriptional coactivator peroxisome proliferator-activated receptor-gammacoactivator 1beta) et TIF2 (Transcriptional Intermediary Factor 2) dans ce tissu. Mon travail a démontré que PGC-1β limite le stress oxydatif est crucial dans le maintien de la structure et de la fonction mitochondriale, via le contrôle de l’expression de gènes impliqués dans les voies de signalisation liées à l’énergie, à la dynamique mitochondriale et à la machinerie d’import mais n'est pas indispensable pour le contenu mitochondrial. Mon travail aussi démontré que TIF2 de la MS a un impact négatif sur la durée de vie des mammifères. De plus, la déplétion de TIF2 conduit à une protection partielle du MS contre les dommages oxydatifs induits par le stress. Ainsi notre travail représente une avancée dans l’établissement futur de traitements contre les troubles liés au stress oxydatif et au vieillissement<br>Skeletal muscle (SM) accounting for ~ 40% of total body mass is an important metabolic tissue. The aim of my thesis was to characterize the role of transcriptional coregulators, peroxisome proliferator-activated receptor-gamma coactivator-1β (PGC-1β) and transcriptional intermediary factor 2 (TIF2) in this tissue. My work demonstrated that PGC-1β is crucial to maintain SM mitochondrial structure and function, by controlling expression of genes involved in energy pathways, mitochondrial dynamics and import machinery, but is dispensable for mitochondrial content and fiber type maintenance. Furthermore, it limits oxidative stress. The second part of my work demonstrated that myofiber TIF2 has negative impact onmammalian life span. Moreover, TIF2 ablation leads to partial protection of SM from oxidative stress-induced damage. In conclusion, our work provides a better understanding of SM homeostasis regulation and insights in treatments for disordersrelated to oxidative stress and aging