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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Avaliação do dano miocárdico e inervação autonômatica do ventrículo esquerdo por imagens de ressonância magnética e medicina nuclear, em pacientes com doença de Chagas / -

Oliveira, Paulo Fabiani de 05 August 2005 (has links)
A fibrose miocárdica (FM) secundária à doença isquêmica pode ser observada por imagens de ressonância magnética (RM) com a técnica de realce tardio miocárdico (RTM). A função autonômica cardíaca pode ser avaliada através da medicina nuclear (MN). A doença cardíaca chagásica (DCC) caracteriza-se por fibrose miocárdica (FM) e desautonomia cardíaca (DC) progressivas, podendo refletir na gravidade e no prognóstico da doença. Avaliamos a presença, localização e freqüência de FM, sua relação com a função e com a inervação autonômica simpática do ventrículo esquerdo (VE), em pacientes (pts) com DCC, nos diversos graus de gravidade da doença. Trinta e seis pts foram divididos em 3 grupos: 1 - assintomáticos; 2 - com eletrocardiograma (ECG) alterado e função do VE normal; 3 - com alteração do ECG e disfunção de VE. Todos realizaram estudo de ressonância magnética cardiovascular (RMC) para avaliar a função do VE e, após uso de meio de contraste à base de Gadolínio, a FM. Foi realizado ainda estudo de medicina nuclear (MN) para avaliar a DC com metaiodobenzilguanidina (MIBG). A FM esteve presente em 68,6% dos pacientes (25% - grupo1; 81,8% - grupo2; 100% - grupo3; p<0,001). A DC esteve presente em 83,3% dos pacientes (58,3% - grupo1; 75% - grupo2; 91,6% - grupo 3; p<0,001). Os segmentos apical e ínfero-lateral são os locais mais freqüentes de FM (66,6%;p<0,001) e de DC (65,7%; p<0,001). A quantidade de FM aumenta quanto maior a gravidade da doença (p>0,001). A função do VE piora com o aumento da porcentagem de FM (r= -0,74, p<0,001). Quanto maior a extensão de defeitos de captação de MIBG, maior é a presença de FM no VE (r=-0,56, p<0,001). Em concluão, a RMC mostra FM em pacientes chagásicos e, quanto maior a gravidade da doença, mais FM está presente, pior é a função do VE e maior é a DC / Myocardial fibrosis (MF) secondary to ischemic disease can be imaged by magnetic resonance images (MRI) myocardial delayed enhancement (MDE). The cardiac autonomy function can be assessed by nuclear medicine (MN). Advanced Chagas\' heart disease (CHD) is characterized by MF and heart autonomic dysfunction (HAD), and may reflect severity and prognosis. Objective: We evaluated the relationship of MF, left ventricular function (LVF) and HAD in Chagas\' patients, over several degrees of desease severity. Methods: Thirth six patients divided in 3 groups: 1 - asymptomatic; 2 - arrythmia and normal LVF; 3 - arrythmia and LV dysfunction. MRI evaluated MF and nuclear medicine (metaiodobenzylguanidine) HAD. Results: We found MF in 68.6% and HAD in 83.3% of all pts (p<0.001). MF and HAD were more frequent in apical and inferolateral segments (66.6% and 65.7%, p<0.001). The amount of MF increased with the severity of CHD (r=-0.74, p<0.001) and also increased whith a longer extension of MIBG LV defects (r=-0.56, p<0.001). Conclusions: MRI demonstrates MF in pts with Chagas\' disease, and the more MF, the worse LVF, and the greater HAD
312

Optimisation de l'utilisation du gadolinium comme poison consommable dans le combustible nucléaire : Vers un REP sans bore

Dario, Pieck 22 October 2013 (has links) (PDF)
L'excès de réactivité neutronique dans les centrales nucléaires est compensé par des sys-tèmes actifs de contrôle du réacteur : acide borique et barres de contrôle. L'apport d'antiréactivité peut se faire passivement avec des poisons consommables, c'est-à-dire des absorbants de neutrons, en particulier avec du gadolinium (Gd). Dans le cadre d'une augmentation de l'enrichissement en U²³⁵ et de réduction de l'utilisation d'acide borique, cette thèse a pour objectif d'optimiser la distribution du ga-dolinium dans des céramiques d'UO₂ afin d'obtenir un apport optimisé d'antiréactivité dans un Réacteur à Eau sous Pression. Dans ce sens, le travail est orienté à trouver des nouveaux matériaux riches en gadoli-nium. Le diagramme de phase U-O-Gd a donc été exploré dans le domaine des fortes teneurs en Gd. Deux phases cubiques ont été trouvées et caractérisées : les phases C1 et C2. En vue d'une application industrielle, la phase C1 a été retenue comme candidate pour l'ajout du Gd dans les pastilles d'UO₂. La distribution optimale de cette phase C1 dans les assemblages de combustible nucléaire a été étudiée avec le code de calcul neutronique APOLLO2.8. Des études paramétriques ont été réalisées. Ces études neutroniques ont aboutit à un concept performant de pas-tille empoisonnée. Finalement, des pastilles prototype ont été fabriquées en laboratoire suivant ce concept. L'ensemble des résultats obtenus montre qu'un concept de pastille avec un dépôt super-ficiel neutrophage de phase C1 est une manière d'apporter de l'antiréactivité de manière optimisée dans le cadre de cycles longs. Ceci pourrait potentiellement être appliquée à l'échelle industrielle. Un brevet a été déposé en ce sens.
313

Nanoparticles for Bio-Imaging : Magnetic Resonance Imaging and Fluorescence Imaging

Venkatesha, N January 2015 (has links) (PDF)
This thesis provides several nanomaterial systems that can be used as contrast agents in magnetic resonance imaging (MRI) and for optical fluorescence imaging. Nanoparticle systems described in this thesis fall under three categories: (a) graphene oxide-nanoparticle composites for MRI contrast agent application, (b) core-shell nanoparticles for MRI contrast agent application and (c) nanoparticle systems for both MRI and optical fluorescence imaging. In the case of graphene oxide based nano-composites, the following observations were made: (i) in the case of graphene oxide-Fe3O4 nanoparticle composite, it was observed that high extent of oxidation of the graphene oxide and large spacing between the graphene oxide sheets containing Fe3O4 nanoparticles provides the optimum structure for yielding a very high transverse proton relaxivity value, (ii) in the case of graphene oxide-Gd2O3 nanoparticle composite, it was observed that this composite exhibits high value for both longitudinal and transverse relaxivity values making it a potential materials for multi-contrast study of pathologies with a single agent, (iii) in the case of graphene oxide-CoFe2O4 nanoparticle composites, it was observed that an increase in the reflux time of the reaction mixture containing this composite led to appreciable variations in the proton relaxivity values. Transverse relaxivity value of the water protons increased monotonically with increase in the reflux time. Whereas, the longitudinal relaxivity value initially increased and then decreased with increase in the reflux time. In the case of coreshell nanoparticles for MRI contrast agent application two different core-shell systems were investigated. They are MnFe2O3-Fe3O4 core-shell nanoparticles and CoFe2O4-MnFe2O4 coreshell nanoparticles. Investigations of both the core-shell nanoparticle systems revealed that the proton relaxivity value obtained in the dispersion of the core-shell nanoparticles was considerably greater than the proton relaxivity value obtained in the presence of single phase nanoparticles of the core and shell phases. Very high value of transverse relaxivity in the case core-shell nanoparticles was due to the large magnetic inhomogeneity created by the core-shell nanoparticles in the water medium surrounding it. In the case of nanoparticle systems for both MRI and optical fluorescence imaging, two different systems were investigated. They were CoFe2O4-ZnO core-shell nanoparticles and Gd doped ZnS nanoparticles [Zn1-xGdxS, x= 0.1, 0.2 and 0.3] formed on graphene oxide sheets or coated with chitosan. In the case of CoFe2O4-ZnO core-shell nanoparticles it was observed that fluorescent CoFe2O4-ZnO core-shell nanoparticles with the unique geometry in which CoFe2O4 ferrite nanoparticles agglomerates were present within larger sized hollow ZnO capsules yields very high value of transverse proton relaxivity when compared to the proton relaxivity value exhibited by the individual CoFe2O4-ZnO coreshell nanoparticles. In the case of Gd doped ZnS nanoparticles, two different systems were synthesized and the values of the longitudinal and transverse proton relaxivity obtained were compared. These systems were (i) graphene oxide- Zn1-xGdxS (x= 0.1, 0.2 and 0.3) nanoparticle composites and (ii) chitosan coated Zn1-xGdxS (x= 0.1, 0.2 and 0.3) nanoparticles. It was observed that Gd doped ZnS nanoparticles in both cases exhibit both longitudinal and transverse relaxivity values. The relaxivity values showed a clear dependence on the composition of the nanoparticles and the nanoparticle environment (presence and absence of graphene oxide). It was also observed that Gd doped ZnS nanoparticle can be used for florescence imaging.
314

Avaliação do dano miocárdico e inervação autonômatica do ventrículo esquerdo por imagens de ressonância magnética e medicina nuclear, em pacientes com doença de Chagas / -

Paulo Fabiani de Oliveira 05 August 2005 (has links)
A fibrose miocárdica (FM) secundária à doença isquêmica pode ser observada por imagens de ressonância magnética (RM) com a técnica de realce tardio miocárdico (RTM). A função autonômica cardíaca pode ser avaliada através da medicina nuclear (MN). A doença cardíaca chagásica (DCC) caracteriza-se por fibrose miocárdica (FM) e desautonomia cardíaca (DC) progressivas, podendo refletir na gravidade e no prognóstico da doença. Avaliamos a presença, localização e freqüência de FM, sua relação com a função e com a inervação autonômica simpática do ventrículo esquerdo (VE), em pacientes (pts) com DCC, nos diversos graus de gravidade da doença. Trinta e seis pts foram divididos em 3 grupos: 1 - assintomáticos; 2 - com eletrocardiograma (ECG) alterado e função do VE normal; 3 - com alteração do ECG e disfunção de VE. Todos realizaram estudo de ressonância magnética cardiovascular (RMC) para avaliar a função do VE e, após uso de meio de contraste à base de Gadolínio, a FM. Foi realizado ainda estudo de medicina nuclear (MN) para avaliar a DC com metaiodobenzilguanidina (MIBG). A FM esteve presente em 68,6% dos pacientes (25% - grupo1; 81,8% - grupo2; 100% - grupo3; p<0,001). A DC esteve presente em 83,3% dos pacientes (58,3% - grupo1; 75% - grupo2; 91,6% - grupo 3; p<0,001). Os segmentos apical e ínfero-lateral são os locais mais freqüentes de FM (66,6%;p<0,001) e de DC (65,7%; p<0,001). A quantidade de FM aumenta quanto maior a gravidade da doença (p>0,001). A função do VE piora com o aumento da porcentagem de FM (r= -0,74, p<0,001). Quanto maior a extensão de defeitos de captação de MIBG, maior é a presença de FM no VE (r=-0,56, p<0,001). Em concluão, a RMC mostra FM em pacientes chagásicos e, quanto maior a gravidade da doença, mais FM está presente, pior é a função do VE e maior é a DC / Myocardial fibrosis (MF) secondary to ischemic disease can be imaged by magnetic resonance images (MRI) myocardial delayed enhancement (MDE). The cardiac autonomy function can be assessed by nuclear medicine (MN). Advanced Chagas\' heart disease (CHD) is characterized by MF and heart autonomic dysfunction (HAD), and may reflect severity and prognosis. Objective: We evaluated the relationship of MF, left ventricular function (LVF) and HAD in Chagas\' patients, over several degrees of desease severity. Methods: Thirth six patients divided in 3 groups: 1 - asymptomatic; 2 - arrythmia and normal LVF; 3 - arrythmia and LV dysfunction. MRI evaluated MF and nuclear medicine (metaiodobenzylguanidine) HAD. Results: We found MF in 68.6% and HAD in 83.3% of all pts (p<0.001). MF and HAD were more frequent in apical and inferolateral segments (66.6% and 65.7%, p<0.001). The amount of MF increased with the severity of CHD (r=-0.74, p<0.001) and also increased whith a longer extension of MIBG LV defects (r=-0.56, p<0.001). Conclusions: MRI demonstrates MF in pts with Chagas\' disease, and the more MF, the worse LVF, and the greater HAD
315

Intégration d'images multimodales pour la caractérisation de cardiomyopathies hypertrophiques et d'asynchronismes cardiaques / Multimodal image registration for the characterization of the hypertrophic cardiomyopathy and the cardiac asynchronism

Betancur Acevedo, Julian Andrés 27 May 2014 (has links)
Cette thèse porte sur la caractérisation cardiaque, qui représente un enjeu méthodologique et clinique important, à la fois pour améliorer le diagnostic des pathologies et optimiser les moyens de traitement. Des méthodes de recalage et de fusion de données sont proposées pour amener dans un même référentiel des images IRM, scanner, échographiques et électro-anatomiques et ainsi décrire le cœur suivant des caractéristiques anatomiques, électriques, mécaniques et tissulaires. Les méthodes proposées pour recaler des données multimodales reposent sur deux processus principaux : l'alignement temporel et le recalage spatial. Les dimensions temporelles des images considérées sont mises en synchronisées par une méthode de déformation temporelle dynamique adaptative. Celle-ci permet de compenser les modifications temporelles non-linéaires entre les différentes acquisitions. Pour le recalage spatial, des méthodes iconiques ont été développées pour corriger les artefacts de mouvements dans les séquences ciné-IRM, pour recaler les séquences ciné-IRM avec les séquences d'IRM de rehaussement tardif et pour recaler les ciné-IRM avec les images scanner. D'autre part, une méthode basée contours, développée dans un précédent travail, a été améliorée pour prendre en compte des acquisitions échographiques multi-vues. Ces méthodes ont été évaluées sur données réelles pour sélectionner les métriques les plus adaptées et pour quantifier les performances des approches iconiques et pour estimer la précision du recalage entre échographies et ciné-IRM. Ces méthodes sont appliquées à la caractérisation de cardiomyopathies hypertrophiques (CMH) et d'asynchronismes cardiaques. Pour la CMH, l'objectif était de mieux interpréter les données échographiques par la fusion de l'information de fibrose issue de l'IRM de rehaussement tardif avec l'information mécanique issue de l'échographie de speckle tracking. Cette analyse a permis d'évaluer le strain régional en tant qu'indicateur de la présence locale de fibrose. Concernant l'asynchronisme cardiaque, nous avons établi une description du couplage électromécanique local du ventricule gauche par la fusion de données échographiques, électro-anatomiques, scanner et, dans les cas appropriés, d'IRM de rehaussement tardif. Cette étude de faisabilité ouvre des perspectives pour l'utilisation de nouveaux descripteurs pour la sélection des sites de stimulation optimaux pour la thérapie de resynchronisation cardiaque. / This work concerns cardiac characterization, a major methodological and clinical issue, both to improve disease diagnostic and to optimize its treatment. Multisensor registration and fusion methods are proposed to bring into a common referential data from cardiac magnetic resonance (CMRI), dynamic cardiac X-ray computed tomography (CT), speckle tracking echocardiography (STE) and electro-anatomical mappings of the inner left ventricular chamber (EAM). These data is used to describe the heart by its anatomy, electrical and mechanical function, and the state of the myocardial tissue. The methods proposed to register the multimodal datasets rely on two main processes: temporal registration and spatial registration. The temporal dimensions of input data (images) are warped with an adaptive dynamic time warping (ADTW) method. This method allowed to handle the nonlinear temporal relationship between the different acquisitions. Concerning the spatial registration, iconic methods were developed, on the one hand, to correct for motion artifacts in cine acquisition, to register cine-CMRI and late gadolinium CMRI (LGE-CMRI), and to register cine-CMRI with dynamic CT. On the other hand, a contour-based method developed in a previous work was enhanced to account for multiview STE acquisitions. These methods were evaluated on real data in terms of the best metrics to use and of the accuracy of the iconic methods, and to assess the STE to cine-CMRI registration. The fusion of these multisensor data enabled to get insights about the diseased heart in the context of hypertrophic cardiomyopathy (HCM) and cardiac asynchronism. For HCM, we aimed to improve the understanding of STE by fusing fibrosis from LGE-CMRI with strain from multiview 2D STE. This analysis allowed to assess the significance of regional STE strain as a surrogate of the presence of regional myocardial fibrosis. Concerning cardiac asynchronism, we aimed to describe the intra-segment electro-mechanical coupling of the left ventricle using fused data from STE, EAM, CT and, if relevant, from LGE-CMRI. This feasibility study provided new elements to select the optimal sites for LV stimulation.
316

Synthesis and Characterization of Metal Complexes for Thin Film Formation via Spin-Coating or Chemical Vapor Deposition

Pousaneh, Elaheh 29 October 2020 (has links)
The present thesis describes the synthesis and characterization of magnesium, copper, and iron complexes and their application in the MOCVD (Metal-Organic Chemical Vapor Deposition) process, as well as the synthesis and characterization of yttrium and gadolinium complexes and their use as spin-coating precursors for metal oxide thin layer formation. The objective of this scientific work is the development of the family of bis(β-ketoiminato) magnesium(II) complexes and a series of heteroleptic β-ketoiminato copper(II) precursors for the formation of magnesium oxide and copper/copper oxide layers by using the MOCVD process. Modifications of the ketoiminato ligands affect the physical and chemical properties of the respective complexes. Another central theme of this work is the development of β-diketonato iron(III) complexes for the deposition of carbon-free gamma- and alpha-Fe2O3 layers via MOCVD. The thermal behavior and vapor pressure of the precursors could be influenced by the variation of the β-diketonate ligands. In addition, the synthesis and characterization of yttrium and gadolinium β-diketonates and their use as spin-coating precursors are described. Field-effect transistors were successfully fabricated by the deposition of carbon nanotubes on top of the Y2O3 films.
317

The Influence of Alloying Additions on Diffusion and Strengthening of Magnesium

Kammerer, Catherine 01 January 2015 (has links)
Magnesium alloys are being developed as advanced materials for structural applications where reduced weight is a primary motivator. Alloying can enhance the properties of magnesium without significantly affecting its density. Essential to alloy development, inclusive of processing parameters, is knowledge of thermodynamic, kinetic, and mechanical behavior of the alloy and its constituents. Appreciable progress has been made through conventional development processes, but to accelerate development of suitable wrought Mg alloys, an integrated Materials Genomic approach must be taken where thermodynamics and diffusion kinetic parameters form the basis of alloy design, process development, and properties-driven applications. The objective of this research effort is twofold: first, to codify the relationship between diffusion behavior, crystal structure, and mechanical properties; second, to provide fundamental data for the purpose of wrought Mg alloy development. Together, the principal deliverable of this work is an advanced understanding of Mg systems. To that end, the objective is accomplished through an aggregate of studies. The solid-to-solid diffusion bonding technique is used to fabricate combinatorial samples of Mg-Al-Zn ternary and Mg-Al, Mg-Zn, Mg-Y, Mg-Gd, and Mg-Nd binary systems. The combinatorial samples are subjected to structural and compositional characterization via Scanning Electron Microscopy with X-ray Energy Dispersive Spectroscopy, Electron Probe Microanalysis, and analytical Transmission Electron Microscopy. Interdiffusion in binary Mg systems is determined by Sauer-Freise and Boltzmann-Matano methods. Kirkaldy*s extension of the Boltzmann-Matano method, on the basis of Onsager*s formalism, is employed to quantify the main- and cross-interdiffusion coefficients in ternary Mg solid solutions. Impurity diffusion coefficients are determined by way of the Hall method. The intermetallic compounds and solid solutions formed during diffusion bonding of the combinatorial samples are subjected to nanoindentation tests, and the nominal and compositionally dependent mechanical properties are extracted by the Oliver-Pharr method. In addition to bolstering the scantly available experimental data and first-principles computations, this work delivers several original contributions to the state of Mg alloy knowledge. The influence of Zn concentration on Al impurity diffusion in binary Mg(Zn) solid solution is quantified to impact both the pre-exponential factor and activation energy. The main- and cross-interdiffusion coefficients in the ternary Mg solid solution of Mg-Al-Zn are reported wherein the interdiffusion of Zn is shown to strongly influence the interdiffusion of Mg and Al. A critical examination of rare earth element additions to Mg is reported, and a new phase in thermodynamic equilibrium with Mg-solid solution is identified in the Mg-Gd binary system. It is also demonstrated that Mg atoms move faster than Y atoms. For the first time the mechanical properties of intermetallic compounds in several binary Mg systems are quantified in terms of hardness and elastic modulus, and the influence of solute concentration on solid solution strengthening in binary Mg alloys is reported. The most significant and efficient solid solution strengthening is achieved by alloying Mg with Gd. The Mg-Nd and Mg-Gd intermetallic compounds exhibited better room temperature creep resistance than intermetallic compounds of Mg-Al. The correlation between the concentration dependence of mechanical properties and atomic diffusion is deliberated in terms of electronic nature of the atomic structure.
318

Akvizice a předzpracování MRI obrazových sekvencí pro klinické perfusní zobrazování / MRI Acquisition and Preprocessing of Image Sequences for Clinical Perfusion Imaging

Krchňavý, Jan January 2012 (has links)
This thesis describes the theory for static and dynamic magnetic-resonance imaging using contrast agents affecting T1 relaxation time. The available acquisition methods in the specified facility of Masaryk Oncological Institute in Brno are described. The sequences for subsequent experimental measurements are selected. The used phantoms are described. Acquisition protocol for measuring is described briefly and the evaluation method for the measured data is suggested. The best acquisition sequence and a method of measurements is chosen influenced by estimation of relaxation time T1, sensitivity and signal to noise ratio. Perfusion analysis is executed and perfusion parameters are calculated. The work was supported by the European Regional Development Fund and the State Budget of the Czech Republic (RECAMO, CZ.1.05/2.1.00/03.0101).
319

Lanthanide Doped Wide Band Gap Semiconductors: Intra-4f Luminescence and Lattice Location Studies / Lanthanid-dotierte Halbleiter mit großer Bandlücke: Intra-4f Lumineszenz- und Gitterplatzuntersuchungen

Vetter, Ulrich 15 July 2003 (has links)
No description available.

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