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1
Aubry, Le Manh Carole. "Imagerie par résonance magnétique obligatoire (IRMO) : réflexion sur la pratique des examens d'imagerie dans la lombalgie et la lombosciatique." Bordeaux 2, 1998. http://www.theses.fr/1998BOR23009.
2
Vaiedelich, Enzo. "Les agents de contraste radicalaires pour l'IRM de demain." Electronic Thesis or Diss., Aix-Marseille, 2023. http://www.theses.fr/2023AIXM0049.
Abstract:
Ce travail présente la synthèse de nouvelles sondes radicalaires sensibles à l'activité enzymatique. Ces nitroxydes à shift sont synthétisés dans le but de nouvelles méthodes de détection de l'activité enzymatique par RPE. De plus, ces sondes permettent une application en IRM-PDN en tant que nouveaux agents de contraste pour l'IRM et ainsi la mesure in-vivo de l'activité enzymatique. De ce fait, elles pourraient un jour remplacer les agents de contraste actuels, en grande majorité fait à partir de gadolinium. La première partie est consacrée à l'état de l'art dans le domaine des agents de contraste et de l'IRM-PDN. La deuxième partie est consacrée à l'établissement des voies de synthèse des cibles proposées en 17 et 18 étapes, et à l'amélioration des 6 premières étapes déjà réalisées au sein de l'équipe CRAB de l'ICR. La troisième et dernière partie est consacrée à l'étude cybotactique de certains intermédiaires de synthèse possédant des caractéristiques particulières. Ainsi, il y sera détaillé des interactions attendues ou non entre solvant et intermédiaires de synthèseThis work presents the synthesis of new radical probes sensitive to enzyme activity. These shift nitroxides are synthesized for new methods of detecting enzyme activity by RPE. In addition, these probes allow application in MRI-PDN as new contrast agents for MRI and thus in-vivo measurement of enzyme activity. As a result, they could one day replace the current contrast agents, mostly made from gadolinium. The first part is devoted to the state of the art in the field of contrast agents and MRI-PDN. The second part is devoted to the establishment of the synthesis paths of the proposed targets in 17 and 18 steps, and to the improvement of the first 6 steps already achieved within the CRAB team of the ICR. The third and final part is devoted to the cybotactic study of certain synthetic intermediates possessing characteristics. Thus, it will be detailed of the expected or not interactions between solvent and synthesis intermediates
3
Renauld, Emmanuelle. "Les morphologies du thalamus, du corps géniculé latéral et de la radiation optique n'influencent pas les ondes alpha EEG." Mémoire, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6810.
Abstract:
Résumé : Au repos, l'activité du cerveau d'un humain sain est caractérisée par de larges fluctuations dans la bande de fréquences de 8-13 Hz d'un électroencéphalogramme (EEG), connue sous le nom de bande alpha. Bien qu'il soit établi que son activité varie d'un individu à l'autre, peu d'études se sont intéressées à la façon dont elle peut être reliée aux variations morphologiques des structures du cerveau. Entre autres, on pense que le corps géniculé latéral (CGL) et ses fibres efférentes (la radiation optique) jouent un rôle clé sur l'activité alpha, bien qu'il n'est pas certain que leur forme ou leur grosseur contribuent à sa variabilité inter-individuelle. Considérant l'utilisation courante d'EEG dans la recherche fondamentale ou clinique, ce sujet est important, mais difficile à traiter vu les problèmes associés à une bonne segmentation du CGL et de la radiation optique. Pour cette raison, nous avons utilisé la résonance magnétique de diffusion (IRMd), la résonance magnétique fonctionnelle (IRMf) et l'EEG sur 20 sujets sains pour mesurer la structure et la fonction, respectivement. L'analyse de la structure a nécessité une nouvelle approche semi-automatique pour segmenter le CGL et la radiation optique, qui nous a permis de mesurer plusieurs variables, telles que le volume et la position. Ces mesures correspondent bien aux connaissances sur la morphologie de ces structures basées sur des études post-mortem, et pourtant, nous avons trouvé que leur variabilité inter-sujet n'influençait pas la puissance des ondes alpha ou leur fréquence-type (p>0.05). Ces résultats suggèrent que la variabilité alpha soit médiée par d'autres sources structurelles. Notre méthodologie pourra servir pour de futures recherches sur l'influence de l'anatomie sur la fonction en IRMf, tomographie par émission de positron (TEP), EEG, etc., ou pour améliorer les recherches cliniques sur la radiation optique.Abstract : At rest, healthy human brain activity is characterized by large electroencephalography (EEG) fluctuations in the 8-13 Hz range, commonly referred to as the alpha band. Although it is well known that EEG alpha activity varies across individuals, few studies have investigated how this may be related to underlying morphological variations in brain structure. Specifically, it is generally believed that the lateral geniculate nucleus (LGN) and its efferent fibres (optic radiation, OR) play a key role in alpha activity, yet it is unclear whether their shape or size variations contribute to its inter-subject variability. Given the widespread use of EEG alpha in basic and clinical research, addressing this is important, though difficult given the problems associated with reliably segmenting the LGN and OR. For this, we employed a multi-modal approach and combined diffusion magnetic resonance imaging (dMRI), functional magnetic resonance imaging (fMRI) and EEG in 20 healthy subjects to measure structure and function, respectively. For the former, we developed a new, semi-automated approach for segmenting the OR and LGN, from which we extracted several structural metrics such as volume, position and diffusivity. Although these measures corresponded well with known morphology based on previous post-mortem studies, we nonetheless found that their inter-subject variability was not significantly correlated to alpha power or peak frequency (p > 0.05). Our results therefore suggest that alpha variability may be mediated by an alternative structural source and our proposed methodology may in general help in better understanding the influence of anatomy on function.
4
Vigneau-Roy, Nicolas. "Structure et fonction du cerveau : lien entre la densité vasculaire régionale et l'amplitude du signal BOLD." Mémoire, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6370.
Abstract:
Résumé: L’Imagerie par Résonance Magnétique fonctionnelle est devenue un des outils principaux pour mesurer l’activité cérébrale chez l’Homme de façon non-invasive. Le type de séquence plus fréquemment utilisé à ces fins est le signal dépendant du niveau d'oxvgène sanguin (BOLD signal) car il reflète les changements hémodynamiques associés à l’activité cérébrale et offr l’avantage d'être relativement facile à mesurer. Cependant, cette mesure est dépendante du niveau de désoxyhémoglobine, présent dans les veines. L'architecture structurelle de ces dernières varie considérablement d'une région du cerveau à l'autre et cela fait en sorte qu'il est ardu de savoir si les différences inter-régionales sont dues à des différences au niveau de l’activité neuronale ou de la structure vasculaire. C'est pour répondre à cette question que nous avons observé la relation entre les variations régionales de densité vasculaire (VAD) et l’amplitude du signal BOLD au repos et en présence d'un stimulus. Nous avons implémenté une méthode de segmentation des veines pour des images en pondération de susceptibilité (SWI). Nous avons également utilisé une méthode de segmentation des tissus (Morphométrie Basée sur les Voxels (VBM )) pour séparer les tissus et calculer une mesure de densité de matière. Nous avons trouvé qu'indépendamment de la taille des voxels, les variations régionales d'amplitude du signal BOLD au repos et du signal évoqué par une tâche sont mieux corrélées avec la VAD qu'avec la densité de matière grise. En utilisant un modèle linéaire général, nous avons observé qu'une grande partie des variations régionales au repos pouvait être modélisée par la VAD. En somme, nos résultats suggèrent que le signal BOLD au repos est intimement relié à la structure vasculaire. Utiliser la densité vasculaire afin de calibrer les mesures d'amplitude du signal BOLD au repos nous permettra d'interpréter de façon plus précise et d'obtenir de meilleures informations sur les différences observées entre plusieurs groupes de sujets et de patients. // Abstract: Functional Magnetic Resonance Imaging (fMRI) has become one of the primary tools used for non-invasively measuring brain activity in humans. For the most part, the blood oxygen level-dependent (BOLD) contrast is used, which reflects changes in heinodynamics associated with active brain tissue. The main advantage of the BOLD signal is that it is relatively easy to measure and thus is often used as a proxy for comparing brain function across population groups (i.e. control vs. patient). However, it is particularly weighted towards veins whose structural architecture is known to vary considerably across the brain. This makes it difficult to interpret whether differences in BOLD between cortical areas reflect true differences in neu-ral activity or vascular structure. We therefore investigated how regional variations of vascular density (VAD) relate to the amplitude of resting-state and task-evoked BOLD signals. To address this, we first developed an automated method for segmen-ting veins in images acquired with susceptibility weighted imaging (SWI), allowing us to visualize the venoms vascular tree across the brain. In 19 healthy subjects, we then applied Voxel-Based Morphometry (VBNI) to Ti-weighted images and compu-ted regional measures of gray matter density (GNID). We found that, independent of spatial scale. regional variations in resting-state and task-evoked fNIRI amplitude was better correlated to VAD compared to GRID. Using a general linear model (GLNI). it was observed that the bulk of regional variance in resting-state activity could be modelled by VAD. Taken together, our results suggest that resting-state BOLD signals are signifi-cantly related to the underlying structure of the brain vascular system. Calibrating resting BOLD activity by venous structure may result in a more accurate interpreta-tion of differences observed between cortical areas and/or individuals.
5
Berto, Vanessa de Faria. "Irmão Sol, Irmã Lua : gênero, poder e clausura em um mosteiro da Ordem de Santa Clara de Assis - São Paulo /." Marília, 2015. http://hdl.handle.net/11449/128004.
Abstract:
Orientadora: Lídia Maria Vianna PossasBanca: Sueli Andruccioli Felix
Banca: José Geraldo Bertoncini Poker
Banca: Ivan Esperança Rocha
Banca: Emerson José Sena da Silveira
Resumo: A presente investigação científica procurou conhecer as formas de vivência e convivência que as monjas da Ordem de Santa Clara de Assis estabeleceram para si, quando de sua chegada ao Estado de São Paulo. Em outras palavras, a pesquisa buscou compreender as mudanças e as permanências presentes nessa realidade específica, tão singular tanto para o Seculum quanto para a própria vida eclesiástica, a partir da análise das constantes (re)significações que as Irmãs Clarissas realizam sobre sua própria situação. Para tal intento, foi necessário contextualizar as origens do monaquismo e da clausura religiosa e como tais se expandiram no Ocidente, principalmente a partir dos preceitos do Franciscanismo e das Regras criadas tanto por Francisco quanto por Clara de Assis, no século XIII. Para além deste levantamento historiográfico, foi preciso também traçar a trajetória das mulheres que comungam destes ideias monásticos, desvelando a condição feminina no interior dos muros do claustro, bem como as relações constituídas não apenas com a hierarquia clerical católica, mas com a sociedade laica, em geral. Na abordagem da vivência Clariana contemporânea do mosteiro paulista foi possível constatar que as monjas, ao mesmo tempo em que se adaptaram a uma realidade capitalista e globalizada para sobreviver sócia e economicamente, ainda se mantiveram atentas aos preceitos de sua fundadora, organizando-se em unidades cenobíticas e ritmando seu cotidiano pelos Ofícios das Horas. As práticas do silêncio e da solidão nas celas, a profissão e os votos de pobreza pessoal, obediência e castidade permaneceram como partes inerentes à vocação Claridiana. Assim, no estudo da religiosidade monástica da Ordem de Santa Clara possibilitou-se o conhecimento de seus ritos e suas solenidades, de ontem e hoje, nos quais as monjas estabelecem e reforçam seus vínculos com o sagrado.
Abstract: The present scientific research sought to understand the ways of living and coexistence that the nuns of St. Clare of Assisi Order provide for them, upon their arrival in the State of São Paulo. In other words, the search aimed to understand the changes and permanencies present in this specific reality, such singular for both the Seculum as well as for the very ecclesiastical life, through the analysis of the constants (re) significations that the Poor Claries perform about your own situation. For this purpose, it was necessary to contextualize the origins of monasticism and religious closure and as these both were expanded in the West, mainly from the precepts of the Franciscanism and Rules created by both Francisco and Clare of Assisi, in the thirteenth century. Beyond this survey historiographical, was also necessary to trace the trajectory of women who share these ideas monastic, revealing the feminine condition inside cloister walls, as well as established relationships not only with the Catholic clerical hierarchy, but with the secular society in general. In the approach of contemporary Clarian experience of São Paulo Monastery was can see that the nuns, at the same time that have adapted to a capitalist and globalized reality to survive economically and in society, still remained attentive to the precepts of its founder, organizing in Coenobitical units and animating their daily lives by the Crafts of the Hours. The practice of silence and solitude in the cells, the profession and the vows of personal poverty, obedience and chastity remained parties involved in St. Clare vocation. Thus, the study of monastic religious of the Order of St. Clare possible to the knowledge of their rites and their ceremonies, yesterday and today, in which the nuns establish and strengthen their ties with the sacred.
Doutor
6
Berto, Vanessa de Faria [UNESP]. "Irmão Sol, Irmã Lua: gênero, poder e clausura em um mosteiro da Ordem de Santa Clara de Assis - São Paulo." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/128004.
Abstract:
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000851736.pdf: 1538453 bytes, checksum: f1282a58b2f941def9b2b4c5443dffbd (MD5)A presente investigação científica procurou conhecer as formas de vivência e convivência que as monjas da Ordem de Santa Clara de Assis estabeleceram para si, quando de sua chegada ao Estado de São Paulo. Em outras palavras, a pesquisa buscou compreender as mudanças e as permanências presentes nessa realidade específica, tão singular tanto para o Seculum quanto para a própria vida eclesiástica, a partir da análise das constantes (re)significações que as Irmãs Clarissas realizam sobre sua própria situação. Para tal intento, foi necessário contextualizar as origens do monaquismo e da clausura religiosa e como tais se expandiram no Ocidente, principalmente a partir dos preceitos do Franciscanismo e das Regras criadas tanto por Francisco quanto por Clara de Assis, no século XIII. Para além deste levantamento historiográfico, foi preciso também traçar a trajetória das mulheres que comungam destes ideias monásticos, desvelando a condição feminina no interior dos muros do claustro, bem como as relações constituídas não apenas com a hierarquia clerical católica, mas com a sociedade laica, em geral. Na abordagem da vivência Clariana contemporânea do mosteiro paulista foi possível constatar que as monjas, ao mesmo tempo em que se adaptaram a uma realidade capitalista e globalizada para sobreviver sócia e economicamente, ainda se mantiveram atentas aos preceitos de sua fundadora, organizando-se em unidades cenobíticas e ritmando seu cotidiano pelos Ofícios das Horas. As práticas do silêncio e da solidão nas celas, a profissão e os votos de pobreza pessoal, obediência e castidade permaneceram como partes inerentes à vocação Claridiana. Assim, no estudo da religiosidade monástica da Ordem de Santa Clara possibilitou-se o conhecimento de seus ritos e suas solenidades, de ontem e hoje, nos quais as monjas estabelecem e reforçam seus vínculos com o sagrado.
The present scientific research sought to understand the ways of living and coexistence that the nuns of St. Clare of Assisi Order provide for them, upon their arrival in the State of São Paulo. In other words, the search aimed to understand the changes and permanencies present in this specific reality, such singular for both the Seculum as well as for the very ecclesiastical life, through the analysis of the constants (re) significations that the Poor Claries perform about your own situation. For this purpose, it was necessary to contextualize the origins of monasticism and religious closure and as these both were expanded in the West, mainly from the precepts of the Franciscanism and Rules created by both Francisco and Clare of Assisi, in the thirteenth century. Beyond this survey historiographical, was also necessary to trace the trajectory of women who share these ideas monastic, revealing the feminine condition inside cloister walls, as well as established relationships not only with the Catholic clerical hierarchy, but with the secular society in general. In the approach of contemporary Clarian experience of São Paulo Monastery was can see that the nuns, at the same time that have adapted to a capitalist and globalized reality to survive economically and in society, still remained attentive to the precepts of its founder, organizing in Coenobitical units and animating their daily lives by the Crafts of the Hours. The practice of silence and solitude in the cells, the profession and the vows of personal poverty, obedience and chastity remained parties involved in St. Clare vocation. Thus, the study of monastic religious of the Order of St. Clare possible to the knowledge of their rites and their ceremonies, yesterday and today, in which the nuns establish and strengthen their ties with the sacred.
7
Atherton, Karen. "Irma." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/647.
8
Jacoutot, Samuel. "Synthèse de sondes nitroxydes pour la détection de l’activité enzymatique : application à la spectroscopie par RPE et à l'IRM rehaussée par effet Overhauser." Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0489.
Abstract:
Ce travail présente la synthèse de nouvelles sondes radicalaires sensibles à l’activité enzymatique. Ces sondes, appelées «nitroxydes à shift», sont synthétisées dans le but de développer des nouvelles méthodes de détection de l’activité enzymatique par RPE, mais également pour une application en diagnostic par IRMO. Ces nitroxydes pourraient alors constituer une alternative intéressante aux agents de constrates à base de gadolinium. La première partie est consacrée à l’optimisation de la voie de synthèse du nitroxyde à shift libre, intermédiaire de synthèse crucial. Le rendement a donc été amélioré à 13 % contre 2 % sur 10 étapes de synthèse. La seconde partie se concentre sur la synthèse de différentes sondes radicalaires à partir du nitroxyde à shift libre. La synthèse de nitroxydes adaptés au développement d’une nouvelle méthode analytique pour la détection de lipases par RPE est décrite. Des sondes adaptées à la détection précoce de maladies pulmonaires été préparées : l’une est actuellement utilisée pour le développement de l’IRM à champ terrestre, et l’autre a permis de développer le premier exemple de détection d’une maladie par IRMO in vivo. Finalement, ce manuscrit décrit la synthèse de la première famille de nitroxydes à shift prometteurs pour le diagnostic précoce de cancers par IRMOThis work presents the synthesis of new radical probes to investigate enzymatic activity. Those probes, named “shifting nitroxides”, are synthesized to develop new methods for the detection of enzymatic activity using EPR, but also for an application in diagnosis by OMRI. The shifing nitroxides could then be an efficient alternative to the gadolinium based contrast agents. The first part focused on the optimization of the synthesis of the free shifting nitroxyde, a key synthetic intermediate. The yield has been improved from 2 to 13 % over ten synthetic steps. The second part is devoted to the synthesis of several nitroxides based probes from the free shifting nitroxide. Thus, this manuscript describes the synthesis of nitroxydes suitable for the detection of lipases by EPR spectroscopy. Other probes have been synthesized for the early detection of pulmonary inflammations: one is currently used for the development of earth’s magnetic field MRI, and the other has been used to develop the first example of in vivo detection of a disease by OMRI. Finally, the synthesis of the first family of shifting nitroxydes recognized by UPA is also described. These probes are then promising for the early diagnosis of cancers using OMRI
9
Dassi, Tatiana. "É, vida loka irmão." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/94093.
Abstract:
Dissertação (mestrado) - Unversidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas, Programa de Pós-Graduação em Antropologia Social, Florianópolis, 2010Made available in DSpace on 2012-10-25T06:27:27Z (GMT). No. of bitstreams: 1 284038.pdf: 1072542 bytes, checksum: ecf4f629f4007c24ca69bd3797a7762a (MD5)
O presente trabalho é fruto de uma pesquisa com jovens em duas instituições que aplicam as chamadas medidas socioeducativas, uma de internação e outra de semi-liberdade. Assim, os sujeitos da pesquisa são jovens que o Estatuto da Criança e do Adolescente, o ECA, classifica como "adolescentes em conflito com a lei". O foco da pesquisa são os sistemas de percepção e avaliação do mundo acionados pelos jovens, que operam distinguindo o bem do mal, o justo do injusto, como princípios de ação. O objetivo da pesquisa é, a partir da temática das moralidades, construir um modelo interpretativo atento às múltiplas dimensões de suas experiências - como um caminho para evitar a captura destes sujeitos exclusivamente sob a forma de "vítimas" ou "vitimadores" - e provocar o deslocamento analítico do "sujeito-vítima" para o "sujeito-agente". A ideia é ver a experiência "vivida" como um tema genuíno de investigação, para melhor compreensão das formas culturais da vida. Para tanto, a categoria vida loka funciona como um ponto de partida, pois é acionada pelos próprios sujeitos como uma chave de interpretação e de significação para suas experiências e trajetórias. Em resumo, o texto procura mostrar a necessidade de se considerar a multivocalidade dos sujeitos em "conflito com a lei", e faz uma crítica da leitura focada exclusivamente nos direitos do sujeito, apontando o rendimento analítico da leitura dos sujeitos dos direitos.
10
Tessari, Silvia. "Il corpus innografico attribuito a Fozio. Edizione critica e analisi musicale." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3425314.
Abstract:
The aim of the dissertation is to collect in one corpus all the Byzantine hymns (almost forty) that are attributed to Photius by the manuscript tradition or, in some cases, by the assumptions made in the editiones principes. In the case of hymns already published, I review the question of the attribution, re-publishing them on the base of a wider paradosis. Some unedited have been identified thanks to the recensio carried out by me (manuscripts from Paris, Lesbos and St. Catherine Monastery – Mount Sinai) and are published here for the first time. All of them are translated into Italian. I analyze issues related to structure, language and style of the hymns, in order to collect any evidence that could bring light on the identity of the hymnographer who wrote them, so far tacitly identified with the patriarch of Constantinople Photius (858-867, 877-886). Because we cannot consider the corpus simple “poetry”, but hymnody, ie intended to be sung at liturgical functions, together with the philological study, I deepened my knowledge in Byzantine musical palaeography, transcribing into staff-notation the melody of each hymn from at least three manuscripts, written in Middle-byzantine notation, dating from the Twelfth to the Sixteenth Century, and making a comparison with the oldest sources (in Palaeo-byzantine musical notation). The study of the melodic line (cadences, coincidence of textual and musical accents) made it possible to evaluate from time to time metric anomalies found in the text of the hymns, justifying or correcting them according to the strict union between words and music.Scopo della dissertazione è raccogliere in un corpus i componimenti innografici bizantini (una quarantina) che sono attribuiti a Fozio dalla tradizione manoscritta o, talvolta, solo dagli editori. Nel caso di inni editi, si riesamina la questione dell’attribuzione, ripubblicando i componimenti sulla base di una più vasta recensio da me condotta. Si dà inoltre la prima edizione di alcuni inediti tratti da codici custoditi a Parigi, a Santa Caterina del Sinai, a Lesbo. Gli inni sono tutti tradotti in lingua italiana. Affronto in dettaglio le questioni inerenti struttura, stile e metrica dei componimenti, al fine di raccogliere tutti gli elementi che possano portar luce sull’identità dell’innografo che li scrisse, sinora identificato con il patriarca di Costantinopoli Fozio (858-867; 877-886). Poiché il corpus considerato non è semplice poesia, ma innografia, destinato cioè ad essere cantato durante le funzioni liturgiche ortodosse, a fianco dello studio filologico si è intrapreso quello della paleografia musicale bizantina, trascrivendo su pentagramma la melodia di ciascun inno da almeno tre fonti manoscritte, vergate in notazione mediobizantina, databili dal XII al XVI secolo, e operando un confronto con testimonianze più antiche (in notazione musicale paleobizantina). Lo studio della linea melodica (cadenze, coincidenza di accenti testuali e musicali) ha consentito di valutare di volta in volta le anomalie metriche riscontrate nel testo degli inni, giustificandole o emendandole in base allo stretto connubio tra parola e musica.
11
Danet, Lola. "Recollection et familiarité chez 12 patients présentant un infarctus thalamique gauche : étude comportementale, en imagerie structurale et fonctionnelle de repos." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30335/document.
Abstract:
La mémoire de reconnaissance nous permet à la fois de détecter rapidement un stimulus précédemment perçu (familiarité), et de récupérer des informations relatives au contexte de notre rencontre avec ce stimulus (recollection). Les modèles neuro-anatomiques d'Aggleton et Brown (1999) puis d'Aggleton et al. (2011) postulent que le noyau antérieur (NA) du thalamus et le tractus mamillo-thalamique (TMT) du fait de leurs connexions avec l'hippocampe font partie du circuit de la recollection tandis que le noyau dorso-médian (DM) participerait à la familiarité en raison de ses connexions avec le cortex périrhinal. Dans cette thèse nous avons testé cette hypothèse d'indépendance. 12 patients avec un infarctus thalamique gauche ont été recrutés ainsi qu'un groupe de sujets contrôles appariés. Tous les participants ont été soumis à un bilan neuropsychologique, à trois tâches expérimentales de mémoire de reconnaissance et à un examen d'IRM morphologique et d'IRM fonctionnelle de repos. Selon les tâches nous avons estimé la contribution de la recollection et de la familiarité à la réponse sur la base de la verbalisation de la source, du degré de confiance dans la réponse ou de la catégorisation des réponses. Les lésions thalamiques ont été quantifiées et localisées automatiquement grâce à une nouvelle approche méthodologique que nous avons développée. Le profil neuropsychologique des patients a mis en évidence une amnésie antérograde verbale et un trouble exécutif modéré (Etude 1). Les lésions atteignaient principalement le DM alors que le NA était intact chez tous. Le TMT était lésé chez les 7 patients les plus amnésiques (Etudes 1 et 2). La recollection était altérée chez les patients quelle que soit la tâche alors que la familiarité était préservée. De plus l'indice de recollection corrélait avec la lésion du DM (Etude 2). Enfin, des corrélations ont été trouvées dans l'étude en connectivité fonctionnelle entre la disconnexion thalamo-frontale et la recollection (Etude 3). En somme, ces résultats signifient i\ qu'une lésion du NA n'est pas nécessaire pour causer une amnésie ii\ qu'une lésion du DM est suffisante pour causer un défaut de recollection mais pas nécessaire pour atteindre la familiarité iii\ qu'une lésion du TMT prédit une amnésie sévère, enfin iv\ que le réseau reliant fonctionnellement le DM au cortex préfrontal semble être impliqué dans l'expérience subjective de la mémoire de reconnaissance plutôt que dans ses contenus. Ils suggèrent de plus que le modèle d'Aggleton et al (2011) devrait être révisé en ce qui concerne la relation familiarité / DMRecognition memory allows determining whether a stimulus has been previously encountered based on either a rapid detection process (familiarity) or a longer retrieval of the context associated with the stimulus (recollection). Aggleton and Brown's model (1999) and Aggleton and colleagues (2011) postulated that recollection and familiarity are anatomically and functionally independent. They hypothesized that the anterior nucleus (AN) / mamillothalamic tract (MTT) complex of the thalamus would be critical for recollection due to its connections with the hippocampus. The Mediodorsal (MD) nucleus would support familiarity owing to its links with the perirhinal cortex. In this thesis we tested this independence hypothesis. The 12 subjects with a pure left thalamic infarction were included along with a healthy matched control group. Every subject underwent a neuropsychological assessment, three experimental verbal recognition memory tasks, a high-resolution structural volumetric MRI scan and resting state functional imaging. Recollection and familiarity estimations were derived from subjective reports or responses categorization. We specifically developed the methods used to automatically analyse the volume and localization of the lesions. Patients performed worse than controls on verbal memory and to a lesser extent on executive tasks (Study 1). Most of the lesions were located in the MD while no lesion of the AN was found. The seven patients exhibiting MTT damage had the lowest memory performance (Studies 1 and 2). Recollection was lower in patients than in controls in all the three tasks whereas familiarity was systematically normal. In addition we found a significant correlation between the recollection index and the DM damage, suggesting that DM is directly involved in recollection (Article 2). Finally the functional connectivity results showed a correlation between recollection and a pattern of thalamofrontal disconnection in the patients, helping to understand the DM-recollection relationship. Overall, the findings of the different studies mean that i\ AN damage is rare and is not necessary to cause an amnesia, ii\ MD damage is sufficient to cause a recollection impairment but not necessary to impair familiarity, iii\ MTT damage predicts the severity of the amnesia, iv\ the network linking functionally the MD with the prefrontal cortex seems to be involved in the subjective experience associated with recognition memory
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Nicolodi, Sabrina. "Estudo do Exchange Bias em filmes de IrMn/Al2O3/Co e IrMn/Cr/Co." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/30991.
Abstract:
Neste trabalho estudamos a interação de troca entre a camada antiferromagnética (AFM) de IrMn, e a ferromagnética (FM) de Co, no sistema IrMn/Co através de uma camada espaçadora. Usamos dois materiais com propriedades distintas como espaçador, ou o Cr (um material antiferromagnético com anisotropia fraca) ou a alumina (Al2O3, material isolante, não-magnético), para analisarmos o alcance dessa interação. Caracterizamos o sistema através de diferentes técnicas, ou seja, medidas de magnetização estática, ressonância ferromagnética, difratometria e refletividade de raios-X, microscopia de força atômica e microscopia eletrônica de transmissão. Tratamentos térmicos na presença de campo magnético foram feitos a fim de maximizar o efeito de exchange bias. Inicialmente, investigamos como utilizar adequadamente os diversos modelos fenomenológicos na interpretação de dados experimentais. Mostramos, através da utilização de dois modelos e de um simples experimento, a importância de considerarmos a distribuição de eixos fáceis e a anisotropia uniaxial do material FM. Negligenciar essas considerações pode ser a causa, ou pelo menos parte, das grandes diferenças relatadas em trabalhos experimentais referente à avaliação da interação FM/AFM obtida por meio de diferentes técnicas de medida. Também mostramos que, mesmo quando o modelo descreve corretamente uma bicamada que apresenta exchange bias, nenhuma das técnicas convencionais de caracterização, reversíveis ou irreversíveis, aplicadas à mesma amostra, é capaz de distinguir entre os campos de acoplamento de troca e o de anisotropia AFM, se a razão entre estes for suficientemente grande ou pequena. Demonstramos que o valor do acoplamento FM/AFM pode ser determinado a partir da variação da coercividade com a espessura da camada AFM. Dos resultados experimentais (tanto nas medidas de magnetização quanto nas de ressonância ferromagnética) obtidos para as tricamadas IrMn/Al2O3/Co, é ressaltada a variação do campo de exchange bias com o aumento da espessura da camada isolante e nãomagnética de alumina. Foi observado que a intensidade do acoplamento entre Co e IrMn diminui exponencialmente com o aumento da espessura da camada de alumina, sendo esta supressão muito abrupta, com decaimento pelo menos quatro vezes mais rápido que os anteriormente relatados. Estes resultados foram explicados em termos da perda do contato direto entre as camadas AFM e FM com o aumento da espessura da alumina. A série de IrMn/Cr/Co apresentou um comportamento oscilatório das grandezas campo de exchange bias e coercividade em função da espessura da camada de cromo, bastante peculiar. O valor do campo de anisotropia rodável, obtido a partir das simulações de FMR, tem sinal oposto ao do caso clássico, indicando que este campo é antiparalelo ao campo magnético externo aplicado. Ainda observa-se uma tendência geral de aumento do campo de anisotropia rodável com a espessura de Cr sugerindo que, nestas amostras, há uma grande contribuição proveniente da camada de Cr para esse campo.The present work reports on the exchange interaction between an antiferromagnetic (AFM) layer, i.e., IrMn, and a ferromagnetic (FM) one, Co, in IrMn/Co systems across spacer layers. Two materials with distinct properties were used as spacers, namely Cr (weak anisotropy antiferromagnet) and alumina (Al2O3, a non-magnetic insulator material), in order to investigate the intensity of this coupling. The systems were characterized using several different techniques, i.e., static magnetic characterization, ferromagnetic resonance, X-ray diffractometry and small-angle reflectivity, atomic force microscopy as well as highresolution transmission electron microscopy. Magnetic annealing was used in order to maximize the exchange-bias effect. First, it was investigated how to correctly employ different phenomenological models for experimental data interpretation. It was demonstrated, through two models and a straightforward experiment, that it could be very important to consider the easy-axis distributions and the uniaxial anisotropy of the FM material. Neglecting these distributions or underestimating the FM anisotropy could be the reason, at least in part, for the significant differences in the evaluation of the AFM/FM exchange coupling obtained via different measurement techniques reported in experimental works. It was also shown here that even when the adopted model describes correctly the EB system, none of the conventional reversible or irreversible techniques, applied to the same sample, is capable to distinguish between the exchange coupling and the AFM anisotropy fields if their ratio is sufficiently high or low. It is demonstrated that the values of AFM/FM coupling can be properly determined with the help of the variation in the coercivity with the AFM layer thickness. In the experimental results (obtained here using both static magnetic characterization and ferromagnetic resonance) of the IrMn/Al2O3/Co trilayers, special attention was paid on the EB field variation with the thickness of the non-magnetic insulator alumina spacer. It was observed that the IrMn/Co coupling strength decreases exponentially with the alumina spacer thickness, being the exponential decay length at least four times smaller than the values previously reported for exchange-bias systems. Such a rapid suppression of the coupling is explained in terms of the prompt loss of the direct contact between the antiferromagnet and the ferromagnet with the alumina layer's thickness. The IrMn/Cr/Co series presented an oscillatory behavior of both exchange bias and coercive fields as a function of the Cr layer thickness, which is rather peculiar. The value of the rotatable anisotropy field, estimated from the ferromagnetic resonance measurements, shows a sign oppose to that normally obtained, indicating that this field is antiparallel to the external applied magnetic field. Moreover, the general tendency for enhancement of the rotatable anisotropy field with the Cr spacer thickness suggests that, in these samples, there exists a considerable contribution coming from the Cr layer to this field.
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Grau, Ingeborg, and Walter Schicho. "In memoriam Irmi Maral-Hanak." Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-90295.
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Sousa, Marcos Antonio de. "Estudo do fenômeno de exchange bias em bicamadas NiFe/IrMn e tricamadas NiFe/IrMn/Co." Universidade Federal de Goiás, 2013. http://repositorio.bc.ufg.br/tede/handle/tede/3619.
Abstract:
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This work reports the study of the phenomenon of exchange bias in NiFe/IrMn bilayers and NiFe/IrMn/Co trilayers. In the NiFe/IrMn bilayers, ferromagnetic resonance experiments at X and Q bands microwave frequencies reveal that spin wave and NiFe resonance modes are excited by the oscillating microwave field. Angular variations of the absorption fields in the plane of the films for both resonance modes shows the effect of the unidirectional anisotropy field, whose intensity is twice larger for the spin wave mode, due to an additional contribution of an unidirectional surface anisotropy. The experiments also indicate the presence of a uniaxial anisotropy of the NiFe layer, apparently dependent on the applied magnetic field. The magnetic parameters of both resonance modes were deduced considering a generalized phenomenological model which also includes the contribution of a rotatable anisotropy. In the NiFe/IrMn/Co trilayers, the angular variations of the resonance field in the plane of the films reveal the effect of the unidirectional anisotropy field for both independent resonance modes of NiFe and Co layers. The ferromagnetic resonance results combined with magnetometry data show that the exchange bias phenomenon at the NiFe/IrMn interface influences the same phenomenon at the IrMn/Co interface, and that this effect must be mediated by a spiral structure of spins across the IrMn antiferromagnetic layer. For both systems studied, the values of the exchange bias field deduced from the ferromagnetic resonance experiments are consistent with the values given by magnetization measurements.
Este trabalho relata o estudo do fenômeno de exchange bias em bicamadas NiFe/IrMn e tricamadas NiFe/IrMn/Co. Nas bicamadas NiFe/IrMn, experimentos de ressonância ferromagnética, em Bandas X e Q de frequência de micro-ondas, revelam que um modo de ressonância de ondas de spin e o modo de ressonância da camada de NiFe são excitados pelo campo oscilante de micro-ondas. Variações angulares dos campos de absorção no plano dos filmes mostram para os dois modos de ressonância o efeito do campo de anisotropia unidirecional, cuja intensidade é duas vezes maior para o modo de onda de spin, devido a uma contribuição adicional de uma anisotropia de superfície unidirecional. Os experimentos indicam também a presença de uma anisotropia uniaxial da camada de NiFe, aparentemente dependente do campo magnético aplicado. Os parâmetros magnéticos dos dois modos de ressonância foram deduzidos considerando um modelo fenomenológico generalizado que inclui também a contribuição de uma anisotropia rodável. Nas tricamadas NiFe/IrMn/Co, as variações angulares de campo de ressonância no plano dos filmes revelam o efeito do campo de anisotropia unidirecional sobre os modos de ressonância independentes das camadas de NiFe e Co. Os resultados de ressonância ferromagnética combinados com os dados de magnetometria, mostram que o fenômeno de exhange bias na interface NiFe/IrMn influencia o mesmo fenômeno na interface IrMn/Co, e que esta influência deve ser mediada por uma estrutura espiral de spins através da camada antiferromagnética de IrMn. Para os dois sistemas estudados, os valores do campo de exchange bias dados pelos experimentos de ressonância ferromagnética estão de acordo com os valores fornecidos por medidas de magnetização.
15
Shang, T., H. L. Yang, Q. F. Zhan, Z. H. Zuo, Y. L. Xie, L. P. Liu, S. L. Zhang, et al. "Effect of IrMn inserted layer on anomalous-Hall resistance and spin-Hall magnetoresistance in Pt/IrMn/YIG heterostructures." AMER INST PHYSICS, 2016. http://hdl.handle.net/10150/622466.
Abstract:
We report an investigation of anomalous-Hall resistance (AHR) and spin-Hall magnetoresistance (SMR) in Pt/Ir20Mn80/Y3Fe5O12 (Pt/IrMn/YIG) heterostructures. The AHR of Pt/IrMn/YIG heterostructures with an antiferromagnetic inserted layer is dramatically enhanced as compared to that of the Pt/YIG bilayer. The temperature dependent AHR behavior is nontrivial, while the IrMn thickness dependent AHR displays a peak at an IrMn thickness of 3 nm. The observed SMR in the temperature range of 10-300 K indicates that the spin current generated in the Pt layer can penetrate the IrMn layer (<= 3 nm) to interact with the ferromagnetic YIG layer. The lack of conventional anisotropic magnetoresistance (AMR) implies that the insertion of the IrMn layer between Pt and YIG could efficiently suppress the magnetic proximity effect (MPE) on induced Pt moments by YIG. Published by AIP Publishing.
16
Graef, Marc de. "IRM de l'endométriose externe." Montpellier 1, 2000. http://www.theses.fr/2000MON11100.
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Silbermann-Hoffman, Olivia. "IRM et corps calleux." Université Louis Pasteur (Strasbourg) (1971-2008), 1991. http://www.theses.fr/1991STR1M155.
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Goursaud, Olivier. "La pelvimetrie par irm." Université Louis Pasteur (Strasbourg) (1971-2008), 1992. http://www.theses.fr/1992STR1M070.
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Oldrini, Guillaume. "Dépistage en IRM mammaire." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0282/document.
Abstract:
L’IRM mammaire a une place prépondérante dans l’imagerie mammaire. Son utilisation plus large est limitée notamment par son coût et le nombre limité de machines. Nous avons travaillé sur plusieurs aspects de cette problématique. Dans un premier temps, nous avons modifié le positionnement en passant du procubitus au décubitus. Ceci a permis de montrer que le décubitus permettait une meilleure corrélation topographique des lésions avec l’échographie et était mieux toléré par les patientes. Dans un deuxième temps, nous avons étudié les facteurs de réduction du temps d’acquisition par l’intermédiaire des séquences à haute résolution temporelle et d’un protocole abrégé. Ces changements devraient permettre de faciliter l’accessibilité de l’IRM aux patientes, de réduire son coût tout en conservant les mêmes valeurs de sensibilité et spécificité que le protocole standardBreast MRI has a prominent place in breast imaging. Its wider use is limited in particular by its cost and the limited number of machines. We have worked on several aspects of this problem. In a first step, we changed the positioning from procubitus to decubitus. This showed that the decubitus allowed a better topographic correlation of the lesions with the ultrasound and was better tolerated by the patients. In a second step, we studied the factors of reduction of the acquisition time via the sequences with high temporal resolution and an abbreviated protocol. These changes should make it easier for patients to access MRI, reduce costs while maintaining the same sensitivity and specificity values as the standard protocol
20
Meslinas, Nerijus. "Sluoksniuotų konstrukcinių elementų stiprumas ir irimo modeliavimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050722_152604-82100.
Abstract:
Fracture of layer structural elements depends on fracture of different layers and interlayer zones. Cases of layer structural elements fracture are ana-lysed in this research. Due to materials heterogeneity and technologies of manufacturing, medium layer (interlayer) appears. This layer influences defor-mation, stresses distribution and fracture of the structure. Often medium layer is weakest link of structural layer element and interlayer fracture called delamina-ting can appear.
21
Schofield, Ian Sean, and University of Lethbridge Faculty of Arts and Science. "The IRMA III control and communication system." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2005, 2005. http://hdl.handle.net/10133/277.
Abstract:
The IRMA III infrared radiometer is a passive atmospheric water vapor detector designed for use with interferometric submillimeter arrays as a method of phase correction. The IRMA III instrument employs a distributed, multi-tasking software control system permitting precise fine-grained control at remote locations over a low-bandwidth network connection. IRMA's software is divided among three processors tasked with performing three primary functions: command interpretation, data collection and motor control of IRMA's Alt-Az mount. IRMA's hardware control and communication functionality is based on compact, low cost, energy efficient Rabbit 2000 microcontroller modules, selected to meet IRMA's limited space and power requirements. IRMA accepts scripts defined in a custom, high level control language as its method of control, which the operator can write or dynamically generated by a separate GUI front-end program.xi, 193 leaves : ill. ; 28 cm.
22
Dahl, Regan Eugene, and University of Lethbridge Faculty of Arts and Science. "Optimisation of the instrumental performance of IRMA." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2008, 2008. http://hdl.handle.net/10133/682.
Abstract:
The Infrared Radiometer for Millimetre Astronomy (IRMA) is a passive atmospheric
water vapour monitor developed at the University of Lethbridge. It is a compact,
robust, and autonomous instrument, which is capable of being operated remotely. The
latest model is based on a PC/104 running an AMD 133 MHz SC520 processor, which
allows for more flexible control of the unit. The modifications and upgrades to the software required for the transition to this new platform are discussed in this thesis. In addition to software optimisation, a new calibration method has been developed as the unit has become better understood. This method has been verified through test campaigns carried out in Lethbridge and Chile. The results of these tests are included in this thesis.xii, 141 leaves : ill. (some col.) ; 28 cm. --
23
Sadeghiani, Parmis. "Determinantes do Investimento Directo Estrangeiro no Irão." Master's thesis, Instituto Superior de Economia e Gestão, 2012. http://hdl.handle.net/10400.5/10413.
Abstract:
Mestrado em Ciências EmpresariaisNo seguimento de um processo de internacionalização existem riscos e benefícios, que deverão ser analisados. Para tal foi feito um estudo mais aprofundado e pormenorizado do mercado iraniano, com o objetivo de analisar as motivações e os obstáculos do ponto de vista de Investimento Directo Estrangeiro (IDE). Foi utilizada uma metodologia predominantemente quantitativa e hipotética-dedutiva, de forma a analisar a significância estatística dos determinantes e a sua relação com o fluxo de IDE. Os resultados indicaram que o fluxo de IDE no Irão está no âmbito dos determinantes tradicionais, considerados para os outros mercados.
Following a process of internationalization there are risks and benefits that must be examined. For that reason a more profound and detailed study of the Iranian market was done with the objective of examining the motivations and obstacles from the point of view of Foreign Direct Investment (FDI). A methodology predominantly quantitative and hypothetically deductive was used, to be able to examine that statistical significance of the conclusions and its relation to the flow of FDI .The results showed that the flow of FDI in Iran are inside of the traditional determining factors that are used for other markets.
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Bidault, François. "Optimisation des séquences IRM et positionnement en carcinologie cervico-faciale de la TEP-IRM." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASL060.
Abstract:
Le bilan d’imagerie des cancers des voies aérodigestives supérieures utilise l’imagerie par résonance magnétique (IRM) et l’imagerie de tomographie par émission de positons (TEP). La TEP-IRM réunit ces deux imageries et permettent (sic) d’envisager l’exploration multiparamétrique des cancers ORL. La mise en place d’un protocole d’imagerie TEP-IRM pose des questions d’instrumentation. Les objectifs étaient de : quantifier et corriger le phénomène d’entrée de coupe artériel sur les séquences IRM de perfusion /perméabilité ; mesurer la précision des cartographies de valeur des temps de relaxation T1 et mesurer le temps de relaxation T1 du cancer ORL ; calculer le taux de détection des nodules pulmonaires par la séquence IRM à temps d’écho zéro (ZTE) et évaluer la précision de la mesure de la taille des nodules pulmonaires ; Comparer les valeurs des indices de texture de la radiomique à 3 Tesla et 1,5 Tesla. L’étude du phénomène d’entrée de coupe et de sa correction a été effectuée avec un imageur 3 Tesla et un fantôme de flux puis chez l’homme. L’étude de la cartographie T1 a été effectuée avec un imageur 3 Tesla et des fantômes de calibration, la mesure du T1 du cancer ORL a été effectuée chez 10 patients. L’étude de la séquence ZTE a été effectué par deux lecteurs avec imageur 3 Tesla en comparaison de la tomodensitométrie (gold standard) chez 12 patients. L’étude des indices de texture a été effectuée avec des imageurs 3 Tesla et 1,5 Tesla et des fantômes faits « maison » avec un logiciel de texture en accès libre et chez 10 volontaires sains. La méthode IRM de présaturation du flux artériel carotidien corrige efficacement l’altération du signal de la fonction d’entrée artérielle liée au phénomène d’entrée de coupe. Son application permet d’envisager de réaliser des acquisitions IRM de perfusion / perméabilité répondant aux recommandations des sociétés savantes en terme de résolution temporelle (inférieure à 5 secondes) tout en étant adaptée à l’anatomie ORL et à la combinaison des imagerie paramétriques. La valeur du temps de relaxation T1 des carcinomes épidermoïdes des VADS est calculée à 1314,5 ms (± 246,1). La réalisation d’une cartographie T1 nécessite la calibration des séquences cliniques à l’aide d’un fantôme et de séquences IRM de référence. Le taux de détection des nodules pulmonaire par ZTE est des 53% (IC95% [48-58]), et de 85% (IC95% [78-92]) pour les nodules de plus de 9 mm. La corrélation entre la taille des nodules avec la séquence ZTE et la taille au scanner est excellente. Les voies d’amélioration de la séquence se portent sur l’augmentation de la résolution spatiale et l’optimisation du contrôle du mouvement respiratoire. Les valeurs des indices de texture en IRM varient avec l’intensité du champ magnétique (3 Tesla versus 1.5 Tesla). Ces résultats contribuent à l’élaboration d’un protocole d’acquisition d’image TEP-IRM en cancérologie ORL. Deux études cliniques loi Jardé 3 sont en cours et utilisent ces résultats. Ces études permettront d’évaluer les performances de l’appareil TEP-IRM et de la combinaison des imageries paramétriques IRM et TEP en carcinologie ORL, ceci avec un haut niveau de preuve histologiqueThe imaging workup for Head and Neck (ENT) cancers uses magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging. PET-MRI combines these two modalities and makes it possible to consider multiparametric exploration of ENT cancers. The implementation of a PET-MRI imaging protocol raises instrumentation questions.OjectivesThe objectives were to: quantify and correct arterial flow-related enhancement on dynamic contrast-enhanced MRI ; measure the precision of the T1 relaxation times maps and measure the T1 relaxation time of ENT cancer ; calculate the lung nodules detection rate by the MRI zero echo time sequence (ZTE) and evaluate the accuracy of lung nodules size measurement ; compare radiomic features values for different magnetic field strength (3 Tesla versus 1.5 Tesla). The study of the arterial flow-related enhancement and its correction was carried out with a 3 Tesla imager and a flow apparatus, then in humans. The T1 mapping study was performed with a 3 Tesla imager and calibration phantoms, the T1 measurement of ENT cancer was performed in 10 patients. The study of the ZTE sequence was performed by two readers with a 3 Tesla imager in comparison with the computed tomography (CTscan, gold standard) in 12 patients. The study of texture indices was performed with 3 Tesla and 1.5 Tesla imagers and “homemade phantoms”, with an open access texture software and then in 10 healthy volunteers. The MRI saturation method of the carotid arterial flow effectively corrects the alteration of the signal of the arterial input function related to the flow-related enhancement. Its application makes it possible to consider performing MRI perfusion / permeability acquisitions that meet the recommendations of learned societies in terms of temporal resolution (less than 5 seconds) while being adapted to ENT anatomy and to the combination of parametric imaging. The value of the relaxation time T1 of squamous cell carcinoma of the VADS is calculated at 1314.5 ms (± 246.1). Performing T1 mapping requires calibration of clinical MRI sequences using a phantom and reference MRI sequences.The detection rate of pulmonary nodules by ZTE is 53% (CI95% [48-58]), and 85% (CI95% [78-92]) for nodules of size more than 9 mm. The correlation between the size of the nodules with the ZTE sequence and the size on the CTscan is excellent. Areas for improvement of the sequence may focus on increasing spatial resolution and optimizing control of respiratory movement.The values of the texture indices in MRI vary with the intensity of the magnetic field (3 Tesla versus 1.5 Tesla). These results contribute to the development of a protocol for acquiring PET-MRI images in ENT oncology. Two clinical studies are in progress using these results. These studies will make it possible to evaluate the performance of the PET-MRI and of the combination of parametric MRI and PET imaging in ENT cancer, with a high level of histological evidence
25
Hey, Silke. "Thermothérapies guidées par IRM : développements méthodologiques en thermométrie par IRM et méthodes d’asservissement automatique." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14191/document.
Abstract:
Les ultrasons focalisés de haute intensité (HIFU) guidés par IRM et combinés à la thermométrie basée sur la fréquence de résonance du proton (PRF) sont une technique prometteuse pour l’ablation non invasive de tumeurs, le dépôt local de médicaments et l’activation des transgènes. Ce travail présente de nouveaux développements dans le domaine de la thermométrie PRF en présence de mouvement physiologique périodique associé aux variations du champ magnétique. De nouvelles stratégies de correction sont proposées et exploitent la méthode multi-baseline établie en incluant un modèle de variation de phase. Elles sont illustrées avec des exemples de thermométrie dans le sein et dans le cœur humain. De plus, d’autres facteurs influençant la thermométrie PRF, notamment la présence de graisse dans le sein et le flux sanguin dans le cœur, sont étudiés. Dans la seconde partie de ce travail a été abordée la problématique du contrôle précis de la température. Une première approche propose un algorithme de contrôle proportionel, intégral et dérivatif (PID) amélioré utilisant des paramétres de contrôle adaptatifs. En étendant ce concept à un contrôle 3D de la température, une implémentation de chauffage volumétrique est proposée. Par ailleurs, une nouvelle méthode de repositionnement dynamique de la coupe d’imagerie permet de fournir des informations volumétriques sur l’anatomie et la température en temps réel. La combinaison avec la compensation 2D de mouvement et l’adaptation du faisceau ultrasonore permet la réalisation d’un chauffage volumétrique suivant une courbe de température ou de dose thermique prédéfinie qui fonctionne même en présence de mouvementsMR-guided high-intensity focused ultrasound (HIFU) using proton resonance frequency (PRF) based thermometry is a promising technique for non-invasive ablations in tumor therapy as well as for targeted drug delivery and the activation of transgenes. This work presents further developments in the field of PRF thermometry in the presence of periodical physiological motion and the associated magnetic field variations. Using the examples of thermometry in the human breast and the human heart, new correction strategies are presented which extend the established multi-baseline phase correction to include a model of the phase variation and external sensor readings from a pencil-beam navigator. In addition further factors, namely the presence of fat in the breast and blood flow in the heart influencing the performance of MR thermometry in these organs are examined.In the second part of this work, the issue of precise temperature control has been approached in two ways. First, an improved proportional, integral and derivative (PID) controller using adaptive control parameters is developed. By expanding the concept of temperature control to 3D, an implementation of volumetric heating is presented. A novel slice sweep technique provides volumetric anatomic and temperature information in near-real time. The combination with 2D motion compensation and adaptation of the ultrasound beam position allows to achieve volumetric heating according to a pre-defined target temperature or thermal dose value even in the presence of motion
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Marques, Vagner Aparecido. "O irmão que virou irmão: rupturas e permanências na conversão de membros do PCC ao pentecostalismo na Vila Leste - SP." Pontifícia Universidade Católica de São Paulo, 2013. https://tede2.pucsp.br/handle/handle/1902.
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Previous issue date: 2013-10-21Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The present dissertation investigates the conversion process of current and former PCC members to the Pentecostalism, in the Eastern area of São Paulo City. Our approach is to analyze a case study, through the journey of Kadu , brother in the church and also brother in the PCC party. The conversion trajectory of Kadu to the Pentecostalism will be seen through a new religious conversion paradigm. In that approach, the conversion is the result of a slow, gradual and not-immediate process, accompanied by numbers of crisis, as shown by a great deal of the religious conversion writings. Kadu´s conversion was not followed by the rupture/asceticism binomial; on the opposite, we could verify continuities along the former network, the PCC. This dual brotherhood is the main focus point of the research. Kadu also open some doors for the analyses of engaging networks existing in the Vila Leste neighborhood and its moral entrepreneurs. In the region of Vila Leste, Pentecostalism and PCC are entangled, and this reality will be analyzed in this work
A presente dissertação investiga o processo de conversão de membros e ex-membros do PCC ao pentecostalismo, no extremo Leste de São Paulo. Nossa proposta é realizar um estudo de caso a partir da trajetória de Kadu, irmão da igreja e também irmão do PCC. A trajetória da conversão de Kadu ao pentecostalismo será observada a partir de um novo paradigma de conversão religiosa. Nesta, a conversão é resultado de um processo lento, gradual e não imediato, e acompanhado de crises conforme mostrará boa parte da literatura sobre sua conversão religiosa. A conversão de Kadu não foi acompanhada pelo binômio rupturas e ascetismo; pelo contrário, verificamos continuidades com a rede anterior, o PCC. Essa sua dupla irmandade é o objeto central desta pesquisa. Kadu também nos abre as portas para analisarmos as redes de engajamento existentes na Vila Leste e seus empreendedores morais. Na Vila Leste, pentecostais e PCC interpenetram-se, e essa realidade será analisada neste estudo
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MERINO, I. L. C. "Fenômenos de Exchange Bias e Exchange Spring em Tricamadas NiFe/IrMn/Co: A Influência da Textura Cristalográfica da camada IrMn." Universidade Federal do Espírito Santo, 2013. http://repositorio.ufes.br/handle/10/7484.
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Previous issue date: 2013-07-19Apresenta-se, no presente trabalho, uma investigação sistemática, através da caracterização estrutural e magnética, da infuência da textura cristalográfica sobre o efeito de Exchange Spring presente nas tricamadas NiFe/IrMn/Co depositadas, à temperatura ambiente, pelo método de Magnetron Sputtering. Usando a difração de Raios-X, demonstrou-se que as camadas de NiFe, IrMn e Co estão texturizadas com orientação [111]-fcc quando a deposição ocorre sobre a camada semente de Ta, não havendo constatação de outros tipos de orientações. Para as amostras crescidas sobre a camada semente de Cu, além da orientação majoritária [111]-fcc, orientações do tipo [200] e [220] encontram-se também presentes nos difratogramas das heteroestruturas NiFe/IrMn/Co. Deste modo, constata-se que o sistema com Ta possui um grau de textura [111] maior do que aquele do sistema com Cu. Da análise das curvas de difração de Raios-X em ângulos rasantes (refletividade) dos sistemas com Cu e Ta, verifica-se que o sistema com Cu possui uma elevada rugosidade na interface Si/Cu (2,8 nm), quando comparada com aquela da interface Si/Ta (0,2 nm) do sistema com Ta. A combinação das técnicas de magnetização DC e ressonância ferromagnética, à temperatura ambiente, nos proporcionou estudar a anisotropia magnética planar e os efeitos conjugados de Exchange Bias (acoplamento de troca unidirecional nas interfaces NiFe/IrMn e IrMn/Co) e Exchange Spring nas heteroestruturas NiFe/IrMn/Co. Os resultados de magnetização DC sugerem que o efeito de Exchange Spring existe mesmo antes da aplicação de um resfriamento com campo magnético (indução de anisotropia unidirecional). O fenômeno de Exchange Spring (consequentemente a estrutura de spins do IrMn) se mostrou fortemente dependente do grau de textura [111] da camada de IrMn que, por sua vez, é dependente da camada semente (Cu ou Ta) depositada sobre o substrato de Si(100). Verificou-se, a posteriori, que um campo magnético de resfriamento de 10 Oe (desde 400 K até 300 K) é suficiente para estabelecer o efeito de Exchange Bias em ambas as interfaces (NiFe/IrMn e IrMn/Co). Observou-se que os maiores valores do campo de Exchange Bias ocorrem quando se estabiliza a estrutura L12 do IrMn (intervalo 6-8 nm), a qual possui baixa tensão cristalográfica. Devido aos diferentes graus de textura (um efeito de rugosidade pode também estar presente), demonstra-se que o efeito de Exchange Bias da interface IrMn/Co é distinto para os sistemas com Ta e Cu. Para os sistemas com anisotropia unidirecional, comprovou-se que ao se aumentar a espessura da camada de IrMn (de 5 a 30 nm), o ângulo de acoplamento entre a camada de NiFe e a camada de Co aumentou no sistema com Cu e reduziu no sistema com Ta, apresentando comportamentos opostos. Explicaram-se estes resultados considerando: (i) diferentes anisotropias das camadas de Co e IrMn induzidas pelo grau de textura [111] e (ii) campos de Exchange Bias distintos nas interfaces NiFe/IrMn e IrMn/Co em ambos os sistemas. Comprovou-se que o ângulo de acoplamento encontra-se fortemente correlacionado com ambos os efeitos: Exchange Bias e Exchange Spring. Através de medidas de espalhamento magnético ressonante, constatou-se a presença de spins não-compensados reversíveis sob ação de campo magnético para ambos os sistemas com anisotropia unidirecional (efeito mais claro para o sistema com Cu). Além disso, através dos laços de histerese elemento seletivo obtidos por essa técnica, provou-se a presença do efeito de Exchange Spring no sistema com Cu, mesmo antes de se aplicar o resfriamento com campo magnético.
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Tretjakovas, Jurijus. "Diafragmos smūginiame dujų vamzdyje deformavimo ir irimo modeliavimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2007~D_20080108_110529-31551.
Abstract:
Išnagrinėjus ir palyginus įvairius skaičiuojamuosius baigtinių elementų modelius buvo ištirta ir nustatyta įpjovos geometrijos įtaka smūginio dujų vamzdžio liaunos diafragmos su kryžmine įpjova kritiniam slėgiui pagal ribinius deformavimo ir irimo kriterijus. Atlikti originalūs eksperimentiniai diafragmų deformavimo ir irimo tyrimai.Deformation and fracture behaviour of the slender diaphragm with cross incisions is simulated by the developed finite element model. The influence of incisions geometry on the critical pressure of diaphragms was examined by applying deformation and fracture criteria. Original experiments of diaphragms with incisions were performed.
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Barasuol, Rúbia Buêno. "O luto por um irmão: vivências da espiritualidade." Pontifícia Universidade Católica de São Paulo, 2012. https://tede2.pucsp.br/handle/handle/15150.
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Previous issue date: 2012-06-29Conselho Nacional de Desenvolvimento Científico e Tecnológico
The objective of this dissertation is to try to understand the lived experiences of spirituality of an adult person whose brother died of cancer, focusing on the period from the diagnosis of the disease to the present situation. This is a qualitative research based on the phenomenological approach. The research collaborator was intentionally chosen in order to apprehend the phenomenon, based on the following criteria: it should be a young adult (age between 25 and 35 years-old) that had experienced the illness process and the grief over a brother for approximately one year, and that was able to verbally express the loss and the spiritual experiences of that period. A semi-structured interview was used to conduct the research. Eight topics appeared, based on the narration, and they were grouped in four larger topics that guided the interview analysis: experiencing grief; experiencing spirituality; experiencing spirituality in the grief‟s context; and conceptions about life, death and spirituality. Through a bibliographic review that involved the two larger areas of this study grief and spirituality some considerations were made, as well as a dialog with the authors that study these areas, about the four topics chosen for analysis. It was concluded that the spirituality dimension is affected by the experience of losing a brother. The lived experience of faith and the relationship with God and the holy are shaken in this situation. The spiritual beliefs are questioned and evaluated, and spiritual transitions take place in the grieving process. New meanings are built so that the spiritual/religious beliefs can continue in the life of the bereaved, under new perspectives and meanings
O objetivo desta dissertação é buscar compreender as vivências da espiritualidade de uma pessoa adulta cujo irmão morreu com câncer, focando o período do diagnóstico da doença até a situação atual. Trata-se de uma pesquisa qualitativa baseada na abordagem fenomenológica. A colaboradora da pesquisa foi escolhida intencionalmente para a apreensão do fenômeno em questão, a partir dos seguintes critérios: ser um adulto jovem (entre 25 e 35 anos) que tenha vivenciado o processo de adoecimento e o luto por um irmão por aproximadamente um ano, e que tenha condições de expressar verbalmente as suas perdas e vivências espirituais deste período. O procedimento utilizado foi o da entrevista semidirigida. Oito temas emergiram do relato e foram agrupados em quatro grandes temas que nortearam a análise da entrevista: vivência do luto; vivência da espiritualidade; vivência da espiritualidade no contexto do luto; e concepções sobre a vida, a morte e a espiritualidade. A partir de um levantamento bibliográfico englobando as duas grandes áreas deste trabalho o luto e a espiritualidade foram tecidas considerações, e foi realizado um diálogo com os autores dessas áreas sobre os quatro temas definidos para a análise. Conclui-se que a dimensão da espiritualidade é afetada pela vivência da perda de um irmão. A vivência da fé, as relações com Deus e com o sagrado são abaladas nessa situação. As crenças espirituais foram questionadas e colocadas sob avaliação, e transições espirituais foram vivenciadas no processo do luto. Novas significações foram construídas para que as crenças espirituais/religiosas permanecessem na vida da enlutada, sob um novo olhar e novos significados
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Nicolodi, Sabrina. "Exchange Bias em filmes de IrMn/Cu/Co." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/10353.
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Medidas de magnetização (MAG) e de ressonância ferromagnética (FMR) foram usadas para estudar a interação de troca entre a camada antiferromagnética (AFM) de IrMn e a ferromagnética (FM) de Co no sistema IrMn/Cu/Co em função da espessura do Cu. Parâmetros importantes extraídos destas medidas foram comparados com os respectivos valores obtidos dos ajustes dos dados experimentais através de um modelo fenomenológico. Foi observada uma concordância muito boa entre os dados experimentais e os simulados numericamente. Os valores dos campos de anisotropia e de interação, obtidos pelas duas técnicas, MAG e FMR, foram comparados. Observou-se que, apesar das variações angulares experimentais dos campos de Exchange Bias coincidirem para todas as amostras, a intensidade de acoplamento J e os campos de anisotropia das camadas de Co (obtidos via simulação numérica) HU , são diferentes. Para todas as espessuras de Cu, vimos que J FMR > J MAG e FMR U H < MAG U H . Outro resultado importante é que J diminui exponencialmente com o aumento da espessura do espaçador, resultado de uma interação de curto alcance mediada por pinholes. Todas estas características foram explicadas através de um modelo que considera camadas magnéticas policristalinas com distribuições de eixos fáceis independentes, tomando em conta a anisotropia rodável. Conhecer o papel dos grãos AFM com diferentes tamanhos e diferentes estabilidades magnéticas também é essencial para entender as propriedades deste sistema. Os fatos dos HEB observados serem iguais (diferentemente dos resultados até agora conhecidos) e as interações assim como as anisotropias uniaxiais serem diferentes foram atribuídos ao fato de que as duas técnicas detectam processos diferentes. A medição estática, MAG, prioriza a amostra como um todo, enquanto a FMR (a qual depende da freqüência de oscilação da magnetização) detecta somente os momentos magnéticos cujos tempos de relaxação são menores do que o tempo de excitação da microonda. Quando não existe mais contato entre as camadas de IrMn e Co (e consequentemente, a interação), as diferenças entre as medidas não são mais observadas.Magnetization (MAG) and ferromagnetic resonance (FMR) measurements were used to study the exchange interaction between the IrMn (antiferromagnetic, AFM) and Co (ferromagnetic, FM) layers in an IrMn/Cu/Co system as a function of the Cu spacer thickness. Important parameters, extracted from these measurements, were compared with the respective values obtained from the experimental data fittings through a phenomenological model, and a very good agreement between experiment and model was observed. The comparison between the anisotropy and interaction fields obtained from both techniques, MAG and FMR, showed that although the experimental angular variations of the exchange-bias fields, FMR eb H and MAG eb H coincide, the coupling strengths, J and the Co layers' anisotropy fields, U H , obtained via numerical simulations, are different. For all Cu thicknesses, it was estimated that J FMR > J MAG e FMR U H < MAG . U H Another important result is that J decreases exponentially with the spacer thickness and is a short-range interaction mediated by pinholes. All these characteristics were explained in the framework of a model considering polycrystalline magnetic layers with independent easy axis distributions and taking into account the rotatable anisotropy. The role of antiferromagnetic grains at the interface with different sizes and different magnetic stability is essential for understanding the behavior of this exchange-biased system. The facts that the observed FMR eb H and MAG eb H are equal (differently from all results known till now) and that the interactions as well as the uniaxial anisotropies are different were attributed to the different processes detected by the techniques. While the static MAG measurement ‘senses’ the sample as a whole, the FMR (which depends on the frequency of the oscillation of the magnetization) detects only the magnetic moments with relaxation times less than the period of the microwave excitation. There are no differences observed between the measurements when there is no contact (and consequently, the interaction) between the IrMn and Co layers.
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KRÖHLING, A. C. "Anisotropia unidirecional anômala induzida em bicamadas NiFe/IrMn." Universidade Federal do Espírito Santo, 2015. http://repositorio.ufes.br/handle/10/7463.
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Previous issue date: 2015-08-31Nesta dissertação de mestrado a anisotropia unidirecional anômala e o efeito de Exchange Bias foram estudada na multicamada Si(100)/Ta(3nm)/NiFe(3nm)/ /IrMn(7nm)/Ta(1nm), depositada por sputtering DC, sistematicamente por difração de raios-X e medidas de magnetometria. Em particular, as amostras como-preparada e a aquecida a 600 K foram investigadas por difração de raios-X com as geometrias para baixo ângulo (refletividade) e alto ângulo (convencional) para caracterizar as propriedades estruturais e interfaciais do filme. Medidas de magnetização foram realizadas em uma ampla gama de temperatura (300 600 K), para estudar as propriedades magnéticas destas duas amostras (como-preparada e aquecida). As curvas de M(H) em temperatura ambiente tem mostrado um deslocamento horizontal do laço de histerese para a amostra como-preparada. Este efeito foi associado a uma anisotropia unidirecional anômala induzida durante a procedimento de preparação da amostra (propriedades intrínsecas), ou seja, um efeito que estava presente antes da realização do processo de field cooling necessário para induzir o efeito de Exchange Bias. Este comportamento anômalo, observado no filme da amostra como-preparada Si(100)/Ta(3nm)/NiFe(3nm)/IrMn(7nm)/Ta(1nm), pode ser explicado assumindo um efeito de interdifusão na interface Ta/NiFe sem a mudança estrutural. Este efeito de interdifusão que ocorre durante a preparação da amostra é devido a fase NiFeTa ser magneticamente dura (quando comparada com a fase do NiFe), consequentemente na amostra como preparada há duas contribuição magnéticas: (i) uma fase mole NiFe, magneticamente acoplada ao camada do IrMn, que é responsável pela visualização do deslocamento do laço horizontalmente (anisotropia unidirecional anômala) e (ii) uma fase NiFeTa dura que não influencia a anisotropia unidirecional anômala, mas que tem seus momentos magnéticos rotacinados incoerentemente com os spins da camada NiFe. A combinação das medidas em baixas e altas temperaturas e os dados estruturais indicam que é possível remover esta anisotropia anômala quando a amostra é aquecida em um intervalo de 520-570 K, que é o intervalo da temperatura de bloqueio deste efeito. Portanto os dados de medidas em altas temperaturas sugerem um aumento das interdifusões interfaciais atômicas do Ta/NiFe e NiFe/IrMn, levando a degradação da amostra assim como a formação de uma fase NiFeIrMnTa, com um completo desaparecimento da contribuição da camada NiFe.
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Makni, Salima. "Détection-estimation conjointe de l'activité cérébrale en imagerie par résonance magnétique fonctionnelle." Paris 11, 2006. http://www.theses.fr/2006PA112220.
Abstract:
Dans cette thèse, nous discutons et proposons un certain nombre de méthodes pour l'analyse intra-sujet de l'activité cérébrale en imagerie par résonance magnétique fonctionnelle (IRMf). L'IRMf est une modalité permettant d'explorer l'activité neuronale du cerveau. L'IRMf met en évidence l'activation de zones particulières du cortex cérébral en utilisant un agent de contraste endogène : la désoxyhémoglobine qui est paramagnétique et dont la concentration varie lors d'une activation neuronale. Dans ce manuscrit, nous commençons tout d'abord par présenter les différentes méthodes qui ont été proposées dans la littérature pour détecter les régions du cerveau qui sont activées par un paradigme expérimental. Cette analyse de détection nécessite une connaissance de la fonction de réponse hémodynamique (FRH). Nous présentons ensuite certaines approches utilisées en IRMf pour estimer la dynamique temporelle la FRH, nous décrivons notamment notre contribution à ce niveau. L'estimation de cette fonction se fait dans les régions du cerveau connues a priori comment étant activées. Généralement, détection et estimation sont faites séparément, alors qu'il est bien évident que les performances de chacune dépendent de la connaissance de l'autre. C'est pour cette raison que nous avons élaboré dans cette thèse une approche régionale où détection et estimation sont faites conjointement. Nous généralisons la méthode pour pouvoir utiliser cette technique pour tous les voxels du cerveau. Nos résultats offrent ainsi une description parcel par parcel du cerveau, pour chacune une forme spécifique de la FRH est fournie. La méthode fournie aussi une carte de classification des voxels en deux ou trois classes d'activitéIn this thesis, we discuss and propose methods for within-subject functional Magnetic Resonance Imaging (fMRI) data analysis. FMRI is a recently developed neuroimaging technique with the capacity to map neural activity with high spatial precision. To localize activated brain areas, the method utilizes local blood oxygenation changes which are reflected as small intensity changes in a special type of MR images. In the following manuscript, we first present the different approaches, proposed in the literature, to detect regions of the brain that are activated in a given experimental paradigm. Generally, such detection step needs to fix a model for the hemodynamic response function (HRF). We then describe some techniques used in fMRI to estimate the temporal dynamic of the HRF, we introduce our contribution among such techniques. Such estimation needs a prior knowledge of the localization of brain regions that are activated. Detection and estimation are generally performed separately, when it is well known that the performance of the one depends on the knowledge of the other. That's why, in this thesis we propose a regional approach where both detection and estimation are done at the same time. We extend our technique to deal with all brain voxels. Results give a parcel by parcel description of the brain, for every one, a specific HRF estimation is given. In addition, the method induces a spatial map of brain voxel classification in two or three activity classes
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Poulin, Éric. "Modélisation pharmacocinétique combinée IRM-TEP." Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6351.
Abstract:
Au cours des dernières années, des modalités d'imagerie comme la tomographie d'émission par positrons (TEP) et l'imagerie par résonance magnétique (IRM) ont été utilisées pour caractériser le microenvironnement tumoral et prédire la réponse au traitement durant la thérapie. La TEP est reconnue pour sa fonctionnalité et elle est utilisée avec une multitude de radiotraceurs. Par contre, sa résolution spatiale est limitée. L'IRM apporte une localisation anatomique précise et une information sur la perfusion des tissus. La modélisation pharmacocinétique augmente le potentiel de ces deux modalités en permettant des études quantitatives. Cependant, ces analyses quantitatives nécessitent l'acquisition de plusieurs images successives afin de suivre la distribution d'un agent de contraste (AC) en IRM et d'un radiotraceur en TEP. Plusieurs types d'analyse pharmacocinétique en IRM et en TEP requièrent la concentration de l'agent en fonction du temps dans le sang, nommée fonction d'entrée artérielle (AIF). Toutefois, cette dernière est difficile à mesurer. En IRM, pour la modélisation, il existe un compromis à faire entre la résolution spatiale et la résolution temporelle. Dans ce mémoire, une approche pour convertir l'AIF d'une modalité à l'autre est proposée pour le petit animal. L'AC gadolinium-acide diéthylène-triamine penta-acétique (Gd-DTPA) en IRM et le radiotraceur [indice supérieur 18] F-fluorodésoxyglucose (FDG) en TEP ont été utilisés. Un modèle mathématique a été développé pour effectuer la conversion et comparer les AIFs. Afin d'évaluer l'efficacité de la méthode, les paramètres pharmacocinétiques ont été calculés pour l'AIF obtenue par prélèvements sanguins et par notre méthode de conversion. Aucune différence statistique n'a été trouvée entre les paramètres des deux méthodes. Ces résultats suggèrent donc qu'une seule AIF serait nécessaire pour faire la modélisation dans les deux modalités. Une méthode qui optimise le temps d'acquisition d'images de même que la résolution spatiale en IRM a été proposée afin d'obtenir une quantification tumorale plus juste. Le temps d'acquisition a été réduit d'un facteur 3,2 avec une perte négligeable (1,5%) de résolution spatiale. Il a également été démontré qu'il est possible d'utiliser la méthode de région de référence combinée avec notre méthode de conversion d'AIF afin de faire la modélisation dans les deux modalités. Il s'agit, à notre connaissance, du premier travail évaluant la synergie entre les acquisitions IRM et TEP combinées. Ce travail pourrait donc avoir un impact significatif sur l'exploitation des deux modalités d'imagerie.
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Pieuchot, Pierre. "Angio-IRM du trépied jambier." Montpellier 1, 1995. http://www.theses.fr/1995MON11025.
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Martin, Françoise. "Irm et pathologie du genou." Nancy 1, 1990. http://www.theses.fr/1990NAN11135.
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André, Philippe. "Irm des neurinomes de l'acoustique." Aix-Marseille 2, 1993. http://www.theses.fr/1993AIX20817.
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Teissier, Jean-Marc. "Irm : l'image et ses conditions." Amiens, 1990. http://www.theses.fr/1990AMIEM078.
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Hamann, Christine. "Magnetische Hybridschichten - Magnetische Eigenschaften lokal austauschgekoppelter NiFe/IrMn-Schichten." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-64664.
Abstract:
Durch die laterale Modifizierung der magnetischen Eigenschaften von austauschgekoppelten NiFe/IrMn-Schichten wurden weichmagnetische Schichten geschaffen, die sowohl neue statische als auch dynamische hybride Eigenschaften zeigen. Als laterale Strukturierungsmethoden wurden hierbei die lokale Oxidation sowie Ionenimplantation verwendet. Mit Hilfe dieser Verfahren ist es gelungen spezifische magnetische Domänenkonfigurationen mit Streifenstrukturen nominell antiparalleler Magnetisierungsausrichtung in die Schichten einzuprägen. In Abhängigkeit der Strukturorientierung sowie Streifenperiode konnte direkt das Ummagnetisierungsverhalten sowie die magnetische Resonanzfrequenz und Dämpfung der Schichten modifiziert werden. Die neuen dynamischen Eigenschaften wie z.B. eine hybride Resonanzfrequenz werden hierbei im Rahmen der Kopplung über dynamische Ladungen und die direkte Beeinflussung des effektiven Feldes des künstlich eingebrachten Domänenzustandes diskutiert. Die vorgestellten Ergebnisse belegen somit das große Potential der lateralen Magneto-Strukturierung zur Einstellung spezifischer statischer wie auch dynamischer Eigenschaften magnetisch dünner Schichten.
39
Schwartz, Flora. "Raisonnement transitif et dyscalculie : étude par IRMf chez l’enfant." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1332/document.
Abstract:
Les dyscalculie se caractérise par d’importantes difficultés d’apprentissage des maths, malgré une scolarisation adéquat et des capacités intellectuelles dans la norme. Même si ce trouble affecte 3 à 7% des enfants d’âge scolaire, ses causes restent encore peu connues. Il a été proposé que la dyscalculie consiste en un déficit spécifique de représentation des quantités numériques, causé par des anomalies cérébrales au niveau du sillon intra-pariétal (IPS). Cependant, de plus en plus d’études suggèrent que la dyscalculie serait dûe à des atteintes cognitives générales. Cette thèse s’est intéressée au lien entre apprentissage des maths et une forme de raisonnement déductif, à savoir le raisonnement transitif (A>B, B>C donc A>C). Dans une première étude en Imagerie par Résonance Magnétique fonctionnelle (IRMf), nous avons comparé l’activité cérébrale d’enfants dyscalculiques de 9 à 12 ans à celle d’enfants neurotypiques de même âge pendant l’écoute d’histoires comprenant des problèmes transitifs. Dans une seconde étude, nous avons évalué l’amélioration en maths des enfants neurotypiques 1,5 an après la session IRMf. Nous avons déterminé si les mesures cérébrales associées au raisonnement transitif pouvaient prédire l’amélioration en maths. Nous avons mis en évidence l’implication de l’IPS gauche dans le raisonnement transitif chez les enfants neurotypiques mais pas chez les dyscalculiques, qui étaient moins précis pour évaluer les problèmes transitifs. Par ailleurs, les capacités de mémoire de travail étaient corrélées à la performance et à l’activité de l’IPS lors du raisonnement transitif. Enfin, l’activité cérébrale de l’IPS pendant le traitement des problèmes transitifs prédisait l’amélioration en maths chez les enfants neurotypiques. Ces résultats soulignent l’importance du raisonnement transitif pour l’apprentissage des maths et suggèrent qu’un déficit de traitement des problèmes transitifs dans l’IPS pourrait contribuer à la dyscalculieChildren who struggle to learn math despite normal intelligence and adequate schooling may suffer from dyscalculia. Although this learning disability may affect 3-7% of children worldwide, its causes remain poorly understood. Previous research has suggested that dyscalculia was due to a specific deficit in the processing of numerical magnitude that results from neural anomalies to the Intraparietal Sulcus (IPS). However, a growing body of studies has highlighted the domain-general deficits exhibited by children with dyscalculia. The goal of the present thesis was to investigate the neural relationship between math learning and a type of deductive reasoning, namely transitive reasoning (A>B, B>C, therefore A>C). In a first study, we used functional Magnetic Reasonance Imaging (fMRI) to measure brain activity in both typically developing (TD) children and chidren with dyscalculia while they listened to stories that included transitive relations. In a second study, we followed TD children longitudinally and to test whether brain measures of transitive reasoning could predict math improvement. First, the processing of transitive relations was associated with enhanced activity in the left IPS in TD children, but not in children with dyscalculia. Second, children with dyscalculia made more errors when processing transitive relations than TD peers. Third, IPS activity and behavioral performance was correlated with working-memory skill across all participants, suggesting that working memory impairments contribute to impaired transitive reasoning skills. Fourth, math gain in TD children was predicted by brain activity around the IPS during the processing of transitive relations. Therefore, the present findings show that measures of transitive reasoning are associated with math achievement. Our results further suggest that impaired neural processing of transitive relations in the IPS may contribute to math difficulties in dyscalculia
40
Stupak, Eugeniuš. "Dvimačių struktūrų irimo modeliavimas naudojant prisitaikančiuosius baigtinių elementų tinklus." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2004. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2004~D_20041111_085744-71834.
Abstract:
In this work the h-adaptive FE strategy for solving 2D problems of fracture mechanics is developed and applicated. The stress indicator employed in the adaptive analysis is able to capture high gradients of stress in the vicinity of the defect. Performance of this technique is checked against the defects of different geometry. Finally the above-mentioned technique exposes its suitability for solving fracture problems.
41
Querel, Richard Robert, and University of Lethbridge Faculty of Arts and Science. "IRMA calibrations and data analysis for telescope site selection." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2007, 2007. http://hdl.handle.net/10133/675.
Abstract:
Our group has developed a 20 μm passive atmospheric water vapour monitor.
The Infrared Radiometer for Millimetre Astronomy (IRMA) has been commissioned and
deployed for site testing for the Thirty Meter Telescope (TMT) and the Giant Magellan
Telescope (GMT). Measuring precipitable water vapour (PWV) requires both a sophisticated
atmospheric model (BTRAM) and an instrument (IRMA). Atmospheric models
depend on atmospheric profiles. Most profiles are generic in nature, representing only a
latitude in some cases. Site-specific atmospheric profiles are required to accurately simulate
the atmosphere above any location on Earth. These profiles can be created from publicly
available archives of radiosonde data, that offer nearly global coverage. Having created
a site-specific profile and model, it is necessary to determine the PWV sensitivity to the
input parameter uncertainties used in the model. The instrument must also be properly
calibrated. In this thesis, I describe the radiometric calibration of the IRMA instrument,
and the creation and analysis of site-specific atmospheric models for use with the IRMA
instrument in its capacity as an atmospheric water vapour monitor for site testing.xii, 135 leaves : ill. ; 28 cm. --
42
Mogicato, Giovanni. "Bases neurales de l'interaction temps-mouvement : étude en IRMf." Toulouse 3, 2007. http://www.theses.fr/2007TOU30336.
Abstract:
Notre capacité à percevoir la durée joue un rôle crucial dans notre vie, car elle permet l'anticipation des évènements dans le temps, ce qui constitue un gage d'adaptation à notre environnement. Dans la vie courante, le temps n'intervient jamais seul mais couplé à d'autres stimuli de l'environnement, notamment le mouvement. Ce travail de thèse a donc pour objectif de connaître l'influence de stimuli en mouvement sur le jugement des durées. Pour cela, nous avons présenté en IRMf, à douze sujets, des paires de stimuli visuels soit immobiles, soit pourvus d'un mouvement. Chaque paire de stimuli est constituée d'un stimulus de "référence" et d'un stimulus de "test", le sujet devait alors comparer les durées de ces deux stimuli. Nos résultats montrent que le traitement des durées est facilité pour des stimuli en mouvement et que ce traitement fait intervenir différemment les hémisphères cérébraux gauche et droitOur ability to perceive time plays a crucial role in our life, because it allows the anticipation of events in time, which is an adaptation to our environment pledge. In everyday life, time never comes alone, but coupled with other environmental stimuli, including movement. This thesis is therefore to know the influence of moving stimuli on judgment times. For this, we have presented at twelve subjects, using fMRI, pairs of visual either immobile or provided with a movement. Each pair of stimuli stimulus consists of a "reference" and a stimulus "test", the subject would then compare the durations of the two stimuli. Our results show that treatment durations is easy for moving stimuli and that treatment involvest the left and right cerebral hemispheres differently
43
Donnet, Sophie. "Inversion de données IRMf : estimation et sélection de modèles." Paris 11, 2006. http://www.theses.fr/2006PA112193.
Abstract:
Cette thèse est consacrée à l'analyse de données d'Imagerie par Résonance Magnétique fonctionnelle (IRMf). Dans le cadre du modèle classique de convolution, nous testons l'hypothèse de variabilité inter-occurrences des amplitudes des réponses hémodynamiques. L'estimation des paramètres de ce nouveau modèle requiert le recours à l'algorithme Expectation-Maximisation. Nous comparons ce modèle au modèle sans variabilité inter-occurrences par un test du rapport des vraisemblances, sur un grand nombre de jeu de données réelles. Le modèle linéaire souffrant d'un manque de fondement biologique, nous considérons un modèle physiologique aboutissant à l'écriture du signal IRMf comme la somme d'un terme de régression, solution d'une équation différentielle ordinaire (EDO), sans solution analytique dépendant d'un paramètre aléatoire, et d'un bruit de mesure gaussien. Nous proposons une méthode générale d'estimation paramétrique des modèles définis par EDO à données non-observées, intégrant une méthode de résolution numérique du système dynamique et reposant sur une version stochastique de l'algorithme EM. Nous montrons la convergence des estimateurs des paramètres produits par cet algorithme, et contrôlons l'erreur induite par l'approximation de la solution du système différentiel sur l'estimation des paramètres. Nous appliquons cette méthode à la fois sur données d'IRMf simulées et réelles. Enfin, nous considérons des modèles définis par équations différentielles stochastiques (EDS) dépendant d'un paramètre aléatoire. En approchant la diffusion par un schéma numérique, nous proposons une méthode d'estimation des paramètres du modèle. La précision de cette méthode est illustrée sur une étude sur données simulées dans le cadre d'un modèle à effets mixtes, issus de la pharmacocinétique. Une étude sur données réelle démontre la pertinence de l'approche stochastique. Finalement, nous nous intéressons à l'identifiabilité des modèles définis par EDS dépendant de paramètres aléatoiresThis thesis is devoted to the analysis of functional Magnetic Resonance Imaging data (fMRI). In the framework of standard convolution models, we test a model that allows for the variation of the magnitudes of the hemodynamic reponse. To estimate the parameters of this model, we have to resort to the Expectation-Maximisation algorithm. We test this model against the standard one --withconstant magnitudes-- on several real data, set by a likelihood ratio test. The linear model suffers from a lack of biological basis, hence we consider a physiological model. In this framework, we describe the data as the sum of a regression term, defined as the non-analytical solution of an ordinary differentiel equation (ODE) depending on random parameters, and a gaussian observation noise. We develop a general method to estimate the parameters of a statistical model defined by ODE with non-observed parameters. This method, integrating a numerical resolution of the ODE, relies on a stochastic version of the EM algorithm. The convergence of the algorithm is proved and the error induced by the numerical solving method is controlled. We apply this method on simulated and real data sets. Subsequently, we consider statistical models defined by stochastic differential equations (SDE) depending on random parameters. We approximate the diffusion process by a numerical scheme and propose a general estimation method. Results of a pharmacokineticmixed model study (on simulated and real data set) illustrate the accuracy of the estimation and the relevance of the SDE approach. Finally, the identifiability of statistical models defined by SDE with random parameters is studied
44
Henriques, Tiago Manuel de Sousa. "Implementação do TPM na empresa Oliveira & Irmão, S.A." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10360.
Abstract:
Mestrado em Engenharia e Gestão IndustrialNum mercado cada vez mais competitivo e industrializado, é essencial que as empresas se mentalizem que o caminho a seguir deve passar pela aposta da otimização dos seus processos produtivos, diminuição de custos e aumento da qualidade de produtos. A manutenção sofreu uma grande evolução na estrutura das empresas, e tem cada vez mais um papel determinante para o desempenho das mesmas. Foi essencialmente da aplicação e evolução de conceitos como a manutenção curativa, preventiva e preditiva que nasceu o conceito de TPM – Total Productive Maintenance. Implementada no Japão, é uma metodologia que se baseia em ações de eficiência global dos equipamentos, tirando destes o máximo desempenho. A aplicação do TPM requer um envolvimento de todos, desde a administração até aos operadores. Ao nível da utilização de ferramentas de apoio à implementação do TPM recorreu-se aos 5S’s, ciclo PDCA e Gestão Visual. Aplicação dos 5S’s na organização dos equipamentos e zonas de trabalho envolvente. Ciclo PDCA na definição de objetivos para a resolução de problemas tentando sempre procurar uma solução ideal. A Gestão Visual no apoio para aumentar a eficiência e eficácia de operações. O objetivo deste projeto passa por implementar e acompanhar a implementação do TPM na empresa Oliveira & Irmão, S.A..
In an more and more competitive and industrialized market, it is essential that companies realize that the way forward must pass through optimizing their production processes, reducing the costs and increasing product quality. The maintenance has suffered a great evolution in the structure of companies, and has an increasingly important role for the performance of them. Was essentially from the application and development of concepts such as maintenance curative, preventive and predictive that was born the concept of TPM - Total Productive Maintenance. Deployed in Japan, it’s an approach that relies on actions on overall efficiency of the equipment’s, getting from these the highest performance possible. The application of TPM requires the involvement of all employees, through all the company, from administration, to the different operators. Regarding the use of tools to support the implementation of TPM, it was used tools such as 5S, Visual Management and PDCA cycle. Application of 5S and in the equipment’s organization and work areas surrounding. PDCA cycle in setting goals for the resolution of problems, always trying to look for an optimal solution. The Visual Management as support to increase the efficiency and effectiveness of operations. The purpose of this project is to implement and monitoring TPM in the Portuguese company Oliveira & Irmão, S.A..
45
Curto, Bruno dos Santos. "Monitorização e racionalização energética na Oliveira & Irmão, S.A." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11576.
Abstract:
Mestrado em Engenharia e Gestão IndustrialDevido à grave crise política e económica sofrida no nosso país, aliado a ameaça de esgotamento dos combustíveis fosseis e aos crescentes problemas ambientais, o preço da energia tem vindo a aumentar nos últimos anos. Este misto de factores levou as empresas portuguesas a encarar a energia como um factor produtivo que necessita igualmente de ser gerido, em vez de um custo necessário para a realização do seu processo produtivo. A eficiência energética e a utilização racional de energia são consideradas como soluções para o aumento da competitividade, o combate aos problemas de cariz ambiental assim como para equilibrar a matriz energética mundial. Este documento contempla a problemática energética sofrida nas empresas atualmente, o estado da arte e realça a importância de uma gestão de energia nas empresas, abordando possíveis medidas de racionalização contempladas após a realização de um levantamento e de uma auditoria energética aos consumos elétricos e de ar comprimido da empresa em estudo, com os respetivos custos e payback. A preocupação e motivação da Oliveira & Irmão, S.A. em reduzir os seus custos energéticos, e otimizar os seus processos no que a energia diz respeito, de modo a manter a sua competitividade no mercado nacional e internacional e cumprir com as exigências impostas pelo Sistema de Gestão dos Consumos Intensivos levou à realização deste projeto. No decorrer deste projeto deu-se uma posição de realce à monitorização energética, devido ao facto de a Oliveira & Irmão, S.A. possuir um software para o devido efeito e este mesmo ser subaproveitado e em certos casos esquecido. Por esse motivo e tendo em conta o potencial daquele equipamento, conjuntamente com o novo gestor de energia, foi feita uma aposta em tornar aquele investimento uma real mais valia para a organização e que o mesmo nos ajude a sensibilizar tanto os colaboradores como a Administração para com a importância da gestão de energia. Conseguiu-se demonstrar que a sensibilização aos colaboradores pode trazer poupanças tão consideráveis como as medidas que necessitam de investimento e vivendo num momento económico tão critico qualquer redução de custos que não afecta o processo produtivo e não necessita de investimento é claramente bem vinda.
Due to the severe economic and political crisis in our country, allied to the threat of depletion of fossil fuels and to the growing environmental problems, energy prices have been rising te last years. This mix of factors led Portuguese companies to face energy as a productive factor that also needs to be managed rather than a cost necessary to carry out the production process. Energy efficiency and rational use of energy are considered as solutions to increase competitiveness, to fight environmental problems as well as to balance the global energy matrix. This document includes the energy problem suffered in companies today, the state of art and emphasizes the importance of energy management in companies, discussing possible rationalization measures contemplated after conducting a survey and an energy audit to electrical and compressed air consumption of the company under study, with their respective costs and payback The concern and motivation of Oliveira & Irmão, SA in reducing their energy costs, and optimizes their processes in the energy concerns, in order to maintain its competitiveness in the domestic and international market and comply with the requirements of the System Management of Intensive Consumption led to the realization of this project. During this project the position of monitoring energy has been enhanced due to the fact that Oliveira & Irmão, SA owns software for this purpose which is underutilized and, in some cases forgotten. For this reason and recognizing the potential of that equipment, in association with the new energy manager, was made a bet to make that investment an advantage to the organization and to help us raise awareness both employees and the top management to the importance of energy management. That sensibilization to employees can bring considerable savings as the measures that need investment. Due to the fact of living in a critical economic time as actually, any cost savings that do not affect the production process and requires no investment are clearly welcome.
46
Merlet, Sylvain. "Acquisition compressée en IRM de diffusion." Phd thesis, Université Nice Sophia Antipolis, 2013. http://tel.archives-ouvertes.fr/tel-00916582.
Abstract:
Cette thèse est consacrée à l'élaboration de nouvelles méthodes d'acquisition et de traitement de données en IRM de diffusion (IRMd) afin de caractériser la diffusion des molécules d'eau dans les fibres de matière blanche à l'échelle d'un voxel. Plus particulièrement, nous travaillons sur un moyen de reconstruction précis de l'Ensemble Average Propagator (EAP), qui représente la fonction de probabilité de diffusion des molécules d'eau. Plusieurs modèles de diffusion tels que le tenseur de diffusion ou la fonction de distribution d'orientation sont très utilisés dans la communauté de l'IRMd afin de quantifier la diffusion des molécules d'eau dans le cerveau. Ces modèles sont des représentations partielles de l'EAP et ont été développés en raison du petit nombre de mesures nécessaires à leurs estimations. Cependant, il est important de pouvoir reconstruire précisément l'EAP afin d'acquérir une meilleure compréhension des mécanismes du cerveau et d'améliorer le diagnostique des troubles neurologiques. Une estimation correcte de l'EAP nécessite l'acquisition de nombreuses images de diffusion sensibilisées à des orientations différentes dans le q-space. Ceci rend son estimation trop longue pour être utilisée dans la plupart des scanners cliniques. Dans cette thèse, nous utilisons des techniques de reconstruction parcimonieuses et en particulier la technique connue sous le nom de Compressive Sensing (CS) afin d'accélérer le calcul de l'EAP. Les multiples aspects de la théorie du CS et de son application à l'IRMd sont présentés dans cette thèse.
47
Alison, Marianne. "Imagerie fonctionnelle du placenta en IRM." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112329.
Abstract:
L’insuffisance placentaire par défaut de vascularisation est une pathologie fréquente de la grossesse, de diagnostic difficile, avec des complications potentiellement graves (retard de croissance intra utérin, prééclampsie). L’objectif de ce travail de Thèse a été de développer l’IRM fonctionnelle multiparamétrique pour l’exploration du placenta à 4.7 T chez la rate gestante. Matériel et méthode : L’IRM de diffusion (SE- EPI DWI) avec analyse IVIM et l’IRM dynamique avec injection de gadolinium (DCE) et haute résolution temporelle (< 1s) ont été développées puis étudiées sur un modèle murin contrôlé d’hypoperfusion placentaire par ligature du pédicule vasculaire utérin gauche au 17ème jour de gestation. Les paramètres obtenus sur les placentas hypoperfusés de la corne gauche ligaturée étaient comparés à ceux des placentas normaux de la corne droite. L’effet de l’hyperoxygénation maternelle était étudié en diffusion. Résultats : Ont été étudiés 73 placentas, dont 23 pathologiques (n= 10 rates) en diffusion et 53 placentas, dont 11 pathologiques (n=12 rates) en DCE. Les paramètres significativement diminués du côté hypoperfusé étaient le coefficient apparent de diffusion (ADC), la fraction de perfusion (f) en diffusion et le flux sanguin maternel (F) en DCE. Sous hyperoxygénation maternelle, l’ADC et le coefficient de diffusion (D) augmentaient et f diminuait. Les paramètres obtenus en diffusion et en DCE n’étaient pas nettement corrélés entre eux. Conclusion : Un outil d’IRM fonctionnelle placentaire multiparamétrique a été développé à 4.7 T chez la rate gestante. La DWI comme la DCE apparaissent complémentaires pour le diagnostic d’hypoperfusion placentairePlacental insufficiency caused by deficient vascularization is common during pregnancy, difficult to diagnose and can lead to severe materno-fetal complications (intrauterine growth restriction, preeclampsia). The aim of this work was to develop multi-parametric functional magnetic resonance imaging (MRI) to assess the placenta at 4.7 T on a murine model. Materials and methods : Diffusion-weighted imaging (SE-EPI-DWI) with the intravoxel incoherent motion (IVIM) analysis and dynamic contrast enhanced MRI (DCE) with a high-time resolution (<1 s) were developed and evaluated on a controlled rat model of reduced placental perfusion, achieved by ligation of the left uterine vascular pedicle on the 17th embryonic day. Parameters from the placentas in the left ligated horn were compared to those from the normal placentas in the non ligated horn. The effect of maternal hyperoxygenation on placental microvascularization was studied with DWI.Results: For DWI, 73 placentas were examined, 23 from the ligated side (n=10 rats). For DCE, 53 placentas were analysed, 11 from the ligated side (n=12 rats). In the uterine horn with reduced perfusion, the apparent diffusion coefficient (ADC), the perfusion fraction (f) obtained with DWI and the placental blood flow (F) obtained with DCE were significantly decreased. Under maternal hyperoxygenation, ADC and the diffusion coefficient (D) increased whereas f decreased. DWI and DCE parameters were not significantly correlated with each other. Conclusion: Multi-parametric MRI has been developed for murine placental analysis at 4.7T. DWI and DCE are complementary tools for the diagnosis of reduced placental perfusion
48
Sironneau, Sandrine. "Corrélation fibrose pancréatique et signal IRM." Bordeaux 2, 2000. http://www.theses.fr/2000BOR23043.
49
Teissier, Jean-Marc. "Rôle des protéines complexes en IRM." Compiègne, 1994. http://www.theses.fr/1994COMPD694.
Abstract:
Les variations d'intensité du signal IRM sont très largement influencées par la composition chimique des tissus humains ainsi que leur concentration. Les protéines complexes sont ainsi à l'origine de variations importantes du signal dans tous les types de pondération de l'image. Une étude in vitro puis in vivo de ces comportements tissulaires en IRM nous montre que ces variations sont prévisibles, analysables et peuvent donc participer au raisonnement diagnostique et à l'élaboration d'une caractérisation tissulaire.
50
Contreras, Meca Carlos. "IRM de diffusion de haute résolution." Paris 11, 2004. http://www.theses.fr/2004PA112298.
Abstract:
L'IRM de diffusion permet de caractériser la structure dynamique des tissus biologiques à l'échelon microscopique. L'objectif de cette thèse a été de développer des outils méthodologiques pour étudier les différences microstructurales du cortex " in vivo " chez l'homme. Un ajustement biexponentiel de la diffusion a été privilégié étant donnée sa sensibilité pour decrire le signal de diffusion. Une technique SENSE a été implémentée sur une séquence de diffusion à 1. 5T et nous avons conçu et développé une bobine parallèle basée sur le concept d'acquisition localisée. En parallèle, nous avons développé une méthode statistique pour déterminer la significativité du signal par rapport au bruit, ainsi que des ajustements du signal avec l'hypothèse de bruit ricien. Ces développements ont étés intégrés dans un logiciel présentant une plateforme graphique. Des différences subtiles, mais significatives, dans les paramètres de diffusion d'aires corticales, notamment dans les aires temporales et pariétales ont été observées. Si les résultats ont souligné la sensitivité au bruit à 1. 5T et 3T, l'IRM de diffusion se apparaît comme technique prometteuse pour l'étude de la cyto-architectonie corticaleDiffusion MRI allows characterizing the dynamical structure of biological tissue at the microscopic level. The purpose of this thesis was the development of methodological tools to study the micro-structural differences of cortex, in vivo in human. A bi-exponential fit was used for its sensibility to describe the diffusion signal. SENSE technique was implemented at 1. 5T and a phase array coil was designed for localized acquisition. We have also developed a statistical method to determine the significance of signal and correction schemes to fit rician distributed data. These developments were integrated on a graphical platform. Subtle, but significant, differences in diffusion parameters were found in cortical areas, namely between temporal and frontal and parietal areas. Although the results have shown important sensibility to noise at 1. 5 and 3\unit{T}, diffusion MRI appears as a promising technique for the study of cortical cyto-architecture