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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.
91

Strong-Field QED Processes in Short Laser Pulses

Seipt, Daniel 18 February 2013 (has links) (PDF)
The purpose of this thesis is to advance the understanding of strong-field QED processes in short laser pulses. The processes of non-linear one-photon and two-photon Compton scattering are studied, that is the scattering of photons in the interaction of relativistic electrons with ultra-short high-intensity laser pulses. These investigations are done in view of the present and next generation of ultra-high intensity optical lasers which are supposed to achieve unprecedented intensities of the order of 10^24 W/cm^2 and beyond, with pulse lengths in the order of some femtoseconds. The ultra-high laser intensity requires a non-perturbative description of the interaction of charged particles with the laser field to allow for multi-photon interactions, which is beyond the usual perturbative expansion of QED organized in powers of the fine structure constant. This is achieved in strong-field QED by employing the Furry picture and non-perturbative solutions of the Dirac equation in the presence of a background laser field as initial and final state wave functions, as well as the laser dressed Dirac-Volkov propagator. The primary objective is a realistic description of scattering processes with regard to the finite laser pulse duration beyond the common approximation of infinite plane waves, which is made necessary by the ultra-short pulse length of modern high-intensity lasers. Non-linear finite size effects are identified, which are a result of the interplay between the ultra-high intensity and the ultra-short pulse length. In particular, the frequency spectra and azimuthal photon emission spectra are studied emphasizing the differences between pulsed and infinite laser fields. The proper description of the finite temporal duration of the laser pulse leads to a regularization of unphysical infinities (due to the infinite plane-wave description) of the laser-dressed Dirac-Volkov propagator and in the second-order strong-field process of two-photon Compton scattering. An enhancement of the two-photon process is found in strong laser pulses as compared to the corresponding weak-field process in perturbative QED.
92

Um estudo sobre feixes intensos e não-contínuos de partículas carregadas / A study of intense bunched charged particle beams

Silva, Thales Marques Corrêa da January 2016 (has links)
Nesta tese, estudamos feixes intensos não-contínuos de partículas carregadas. Na primeira parte, analisamos um feixe com simetria esférica e a sua relaxação para um estado quase-estacionário. Por ser um sistema com interação de longo alcance, a evolução do feixe e dominado pela dinâmica de Vlasov-Maxwell. Mostramos que o mecanismo de relaxação e a ressonância entre o movimento coletivo e o individual de algumas partículas. Fazemos uma analogia entre a dinâmica de Vlasov e um gás de férmions para modelar o estado quase estacionário. Os parâmetros do modelo são calculados usando princípios básicos, como os de conservação de energia e de partículas no transporte. Os resultados quando comparados com simulação mostram uma boa concordância. Na segunda parte, verificamos a estabilidade do modo de oscilação simétrico para um feixe esférico. Argumentamos que, quando esse modo for estável, o modelo para o estado quase-estacionário pode descrever feixes levemente anisotrópicos, o que e uma situação mais realista em experimentos. Constatamos que, num regime de interesse prático, esse modo e sempre estável. Por fim, estudamos um caso em que as forças focalizadoras externas são anisotrópicas, e o feixe tem simetria elipsoidal. Mostramos que, para certos valores dos parâmetros, há um forte acoplamento entre a dinâmica não-linear dos envelopes, o que causa uma troca de energia entre os graus de liberdade. Os resultados quando comparados com dinâmica molecular mostraram uma boa concordância. / In this thesis, we study intense bunched charged particle beams. In the rst part, we analyze a beam with spherical symmetry and its relaxation to a stationary state. The beam evolution follows the Vlasov-Maxwell dynamics since it is a system of long range interaction. We show that the main mechanism for the beam relaxation is a resonance between the collective beam motion and individual particle motion. We make an analogy between Vlasov dynamics and a Fermi gas to model the beam quasistationary state. The parameters of the model are calculated using basic principles, such as energy and particle conservation in the beam transport. The results compared with simulation showed a good agreement. In the second part, we verify the symmetric oscillation mode stability for a spherical beam. We argue that when this mode is stable, our model for the quasistationary state can also describe slightly anisotropic beams, a situation more realistic in experiments. We nd out that in situations of practical interest the mode is always stable. Finally, we study a situation in which the external focusing forces are anisotropic, and the beam has ellipsoidal symmetry. We show that, for certain values of the parameters, there is a strong coupling between the nonlinear envelopes dynamics, which causes exchange of energy between the degrees of freedom. The results compared with molecular dynamics showed a good agreement.
93

ADAPTAÇÕES FUNCIONAIS E BIOQUÍMICAS DE JOGADORES DE FUTSAL DE ALTO NÍVEL EM DIFERENTES PERÍODOS DA TEMPORADA / FUNCTIONAL AND BIOCHEMICALS ADPTATIONS IN TOP LEVEL FUTSAL PLAYERS IN DIFFERENTS SEASON PERIODS

Tocchetto, Guilherme Lopes 23 March 2015 (has links)
The high-level sport requires a routine of intense training, high-levels players are exposed to various situations that may cause decline in their performance over a season. Therefore, the aim of this study was to verify functional and biochemical markers on elite level futsal players throughout a competition season. Eight players were analyzed statistically after being submitted to three maximal tests during the year: preseason (T1), competitive period (T2), and at the end of the season (T3). Functional parameters were assessed and blood sampling for cell count, lipid profile, inflammation, injury-related, and oxidative stress markers were performed before and after an maximum VO₂ test each time point. No differences were found for functional and lipid profile measurements. However, differences for total number of neutrophlis, monocytes, hemoglobin, creatine kinase, C-reactive protein, ischemia modified albumin, and advanced oxidation protein products between time points throughout the season were found. Blood lactate and lactate dehydrogenase levels showed differences within pre x post tests. Lower levels of inflammation, oxidative stress, and injury-related markers were found on T2 compared to T1 and T3, indicating that players were adapted to the training load. Although complementary studies are needed, it seems that routine-based biochemical markers may be used as training control means in this population. / O esporte de alto nível exige uma rotina de treinamento intenso, jogadores de futsal de alto nível são expostos a diversas situações que podem provocar declínio na sua performance ao longo de uma temporada. Portanto, o objetivo desse estudo foi verificar marcadores funcionais e bioquímicos ao longo de uma temporada de competição. Foram estudados oito jogadores de futsal submetidos a três testes de esforço máximo durante o ano competitivo: Pré temporada (T1), Período Competitivo (T2) e Final de Período Competitivo (T3). Foram mensurados parâmetros funcionais e, também, amostras de sangue para contagem de células, perfil lipídico, marcadores de inflamação, dano muscular e estresse oxidativo realizados antes e depois um teste máximo de VO₂ em cada período. Não foram encontradas diferenças significativas nos parâmetros funcionais, nem no perfil lipídico. No entanto, foram encontradas diferenças relativas ao número de neutrófilos, monócitos, hemoglobina, creatina quinase, proteína c-reativa, albumina modificada por isquemia e produto proteico de oxidação avançada nos diferentes períodos da temporada. Lactato sanguíneo e lactato desidrogenase mostraram diferenças dentro dos testes pré x pós. Os menores níveis de inflamação, estresse oxidativo e marcadores de dano muscular foram encontrados no T2 em relação ao T1 e T3, indicando que os jogadores se adaptaram as cargas de treinamento. Embora sejam necessários estudos complementares, parece que uma rotina de análises de marcadores bioquímicos pode ser utilizada para um controle dessa população.
94

ANÁLISE DE CONSISTÊNCIA E REGIONALIZAÇÃO DAS PRECIPITAÇÕES MÁXIMAS OCORRIDAS NO RIO GRANDE DO SUL ENTRE 1912-2014 / CONSISTENCY ANALYSIS AND REGIONALIZATION OF MAXIMUM PRECIPITATION OCCURED IN RIO GRANDE DO SUL BETWEEN 1912 2014.

Favaretto, Jean Ricardo 12 September 2016 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / The knowledge of intense precipitation is primordial in hydraulic structures design. However, the determination of this variable stumbles on its monitoring deficiency. Thus, the use of statistical methods, such as regional frequency analysis, aims to support the determination or caracterization of these precipitation. The purpose of this study was to identify behavioral patterns of daily intense precipitation that allows the estimative of design storm in ungauged basins. The study was directed to the southernmost state of Brazil, Rio Grande do Sul (RS), a region with one of the world highest intense precipitation events. The hydrometeorological monitoring of the region is accomplished mainly by the National Water Agency (ANA). In this study were analyzed 1070 rain gauges, containing records between 1912 and 2014. Firstly, the consistency procedure was performed, by pre-analyzing and classifying the precipitation events (adapted Z score), selection of annual maximum series of continuous periods, and punctual validation. In the second stage, the maximum events were submitted to a regional frequency analysis, based on the regionalization method of Hoskins e Wallis. Finally, was demonstrated a precipitation estimative method for ungauged basins. The results of the pre-analysis characterized the periods of greatest temporal and spatial continuity from the available records, which occurred in the decade of 1970. On the other hand, this period has the greatest number of monitoring inconsistencies. The classification of the precipitation records indicated possible inconsistent data. Parallel to this, the selection process allowed the elaboration of maximum series of 15 and 30 years, uninterrupted, which occurred between 1963 and 1977, and between 1971 and 2000, with 91 and 40 gauges, respectively. Among the series, 163 events were indicated as possibly inconsistent data, which then were analyzed by the punctual validation, resulting in more trustworthy maximum series. The results of the maximum series regionalization indicated that RS has from two to three regions of homogenous behavior. The estimative from the 15 years series generated the most accurate values for Return Periods (T) lower than ten years. In opposite, the 30 years series resulted in better approximations for T greater than 20 years. Nevertheless, the quality of the estimates is prejudiced in the regions with a low density of gauges. The processes applied to the consistency analysis were effective, and the suggested methodology demonstrated to be appropriate and flexible. / O conhecimento das precipitações intensas é primordial no projeto de estruturas hidráulicas. No entanto, a determinação desta variável esbarra nas deficiências do seu monitoramento. Assim, o emprego de métodos estatísticos, como análise de frequência regional visa auxiliar na determinação ou caracterização dessas precipitações. O objetivo deste estudo foi identificar padrões comportamentais das precipitações intensas diárias que possibilitem estimar chuvas de projetos em locais sem informações. O estudo foi direcionado ao estado do Rio Grande do Sul, Brasil, cujas precipitações intensas estão entre as maiores do mundo. Seu monitoramento hidrometeorológico é efetuado, principalmente, pela Agência Nacional de Águas (ANA). Foram analisadas 1070 estações pluviométricas, com registros entre os anos de 1912 a 2014. Foi realizado, primeiramente, o processo de consistência, que contou com: pré-análise e classificação dos eventos de precipitação (Z-score adaptado), seleção de séries de máximos anuais de períodos contínuos, e validação pontual. Na segunda etapa, os eventos de máximos foram submetidos a uma análise regional de frequências, baseada no método de regionalização de Hosking e Wallis, em seguida, foi demostrada uma forma de estimar as precipitações em locais sem dados. Os resultados da pré-análise caracterizaram os momentos de maior continuidade temporal e espacial dos registros disponíveis, os quais ocorreram em meados da década de 70. Por outro lado, este período também foi o com maior número de inconsciências no monitoramento. A classificação dos registros de precipitação indicou possíveis dados inconsistentes. Paralelo a isto, o processo de seleção permitiu a construção de séries de máximos de 15 e 30 anos, ininterruptos, os quais ocorreram entre 1963 a 1977 e, 1971 a 2000, com 91 e 40 estações, respectivamente. Dentre estas séries, 163 eventos foram indicados como possíveis dados inconsistentes, os quais passaram pelo processo de validação pontual, resultando em séries de máximos de maior confiabilidade. O resultado da regionalização das séries de máximos demonstrou que o Estado possui de duas a três regiões de comportamento homogêneo. As estimativas produzidas pelas regiões formadas pelas séries de 15 anos produziram valores mais precisos para tempos de retorno (Tr) inferior a dez anos. Já as séries de 30 anos resultaram numa melhor precisão nas estimativas com Tr superior a 20 anos. Contudo, a qualidade das estimativas é prejudicada nas regiões em que a densidade de estações é baixa. Os processos empregados na análise de consistência foram eficientes, e a metodologia sugerida demonstrou ser flexível e aplicável.
95

Um estudo sobre feixes intensos e não-contínuos de partículas carregadas / A study of intense bunched charged particle beams

Silva, Thales Marques Corrêa da January 2016 (has links)
Nesta tese, estudamos feixes intensos não-contínuos de partículas carregadas. Na primeira parte, analisamos um feixe com simetria esférica e a sua relaxação para um estado quase-estacionário. Por ser um sistema com interação de longo alcance, a evolução do feixe e dominado pela dinâmica de Vlasov-Maxwell. Mostramos que o mecanismo de relaxação e a ressonância entre o movimento coletivo e o individual de algumas partículas. Fazemos uma analogia entre a dinâmica de Vlasov e um gás de férmions para modelar o estado quase estacionário. Os parâmetros do modelo são calculados usando princípios básicos, como os de conservação de energia e de partículas no transporte. Os resultados quando comparados com simulação mostram uma boa concordância. Na segunda parte, verificamos a estabilidade do modo de oscilação simétrico para um feixe esférico. Argumentamos que, quando esse modo for estável, o modelo para o estado quase-estacionário pode descrever feixes levemente anisotrópicos, o que e uma situação mais realista em experimentos. Constatamos que, num regime de interesse prático, esse modo e sempre estável. Por fim, estudamos um caso em que as forças focalizadoras externas são anisotrópicas, e o feixe tem simetria elipsoidal. Mostramos que, para certos valores dos parâmetros, há um forte acoplamento entre a dinâmica não-linear dos envelopes, o que causa uma troca de energia entre os graus de liberdade. Os resultados quando comparados com dinâmica molecular mostraram uma boa concordância. / In this thesis, we study intense bunched charged particle beams. In the rst part, we analyze a beam with spherical symmetry and its relaxation to a stationary state. The beam evolution follows the Vlasov-Maxwell dynamics since it is a system of long range interaction. We show that the main mechanism for the beam relaxation is a resonance between the collective beam motion and individual particle motion. We make an analogy between Vlasov dynamics and a Fermi gas to model the beam quasistationary state. The parameters of the model are calculated using basic principles, such as energy and particle conservation in the beam transport. The results compared with simulation showed a good agreement. In the second part, we verify the symmetric oscillation mode stability for a spherical beam. We argue that when this mode is stable, our model for the quasistationary state can also describe slightly anisotropic beams, a situation more realistic in experiments. We nd out that in situations of practical interest the mode is always stable. Finally, we study a situation in which the external focusing forces are anisotropic, and the beam has ellipsoidal symmetry. We show that, for certain values of the parameters, there is a strong coupling between the nonlinear envelopes dynamics, which causes exchange of energy between the degrees of freedom. The results compared with molecular dynamics showed a good agreement.
96

Avaliação dos efeitos proliferativos e de síntese induzidos pela luz intensa pulsada em fibroblastos e células endoteliais humanas / Evaluation of the proliferative and synthesis effects induced by intense pulsed light in human fibroblasts and endothelial cells

Luciana Rodrigues Lisboa Faucz 25 March 2011 (has links)
A luz intensa pulsada é amplamente utilizada para o tratamento do fotoenvelhecimento e de lesões vasculares congênitas e adquiridas, porém, seus efeitos biológicos ainda não são completamente esclarecidos. Neste estudo, foram avaliadas as respostas proliferativas e de síntese em fibroblastos e células endoteliais humanas após a irradiação com a luz intensa pulsada. As culturas de fibroblastos e células endoteliais foram irradiadas com luz intensa pulsada com variação de comprimento de onda entre 420 e 1110 nm e fluências de 10, 16 e 20 J/cm2. Os experimentos foram realizados após 24 e 48 horas da irradiação e analisados os seguintes parâmetros: 1-alterações morfológicas; 2- determinação da capacidade proliferativa e citotóxica; 3- produção de radicais livres; 4- fases do ciclo celular; 5- expressão dos marcadores do ciclo celular e apoptose; 6- avaliação do potencial elétrico da membrana mitocondrial; 7- análise da atividade mitocondrial por microscopia confocal; 8- biossíntese de colágeno e 9- microscopia eletrônica de varredura dos fibroblastos e matriz extracelular. Os resultados demonstraram que, nos fibroblastos, a luz intensa pulsada promoveu aumento da densidade celular e da capacidade proliferativa; aumento na produção de radicais livres diretamente proporcional à intensidade de energia; estímulo na fase de síntese; estímulo na síntese de colágeno mais significativo em 10 e 16 J/cm²; induziu apoptose pela via extrínseca, dependente da intensidade de energia; a microscopia eletrônica de varredura demonstrou detalhes da organização e síntese da matriz extracelular, bem como o colágeno recém sintetizado. Nas células endoteliais a luz intensa pulsada não provocou mudanças morfológicas; promoveu aumento na produção de radicais livres, induziu citotoxicidade e apoptose pela via extrínseca e diminuiu a capacidade proliferativa, proporcional à intensidade de energia. Este estudo permitiu a determinação in vitro dos mecanismos biológicos envolvidos após a interação da luz intensa pulsada com os fibroblastos e células endoteliais humanas / Intense pulsed light is widespread used in the treatment of intrinsic and extrinsic photo damaged skin and congenital or acquired vascular diseases but its biological effects have not yet been clearly demonstrated. This study assessed the proliferative and synthesis responses of fibroblasts and endothelial cells. The fibroblasts and endothelial cells cultures were irradiated with intense pulsed light, with wavelength ranging from 420 to 1110 nm, fluencies of 10, 16 e 20 J/cm2 and pulse delay 10 ms. Experiments were performed 24 and 48 hours after irradiation and the following parameters were analyzed: 1- morphological changes; 2- measurement of proliferative capacity and citotoxicity; 3- free radical production; 4- cell cycle phases; 5- expression of cell cycle and apoptosis markers; 6- electrical potential of mitochondrial membrane; 7- mitochondrial activity by confocal microscopy; 8- collagen synthesis; 9- Scanning electron microscopy of fibroblasts and extracellular matrix. The results evidenced that intense pulsed light on fibroblasts increased cell density and proliferative capacity; stimulus on synthesis phase and collagen synthesis more significant at fluences of in 10 and 16 J/cm²; increase of free radical formation, citotoxicity and apoptosis through the extrinsic pathway proportional to the energy intensity. The scanning electron microscopy evidenced the organization details of extracellular matrix and new collagen fibers. Regarding the endothelial cells, intense pulsed light did not cause morphological changes; increased free radicals formation, induced citotoxicity and apoptosis through the extrinsic pathway and decreased the proliferative capacity proportionally to the intensity of energy. This study allowed the in vitro determination of the biological mechanisms involved after the interaction of intense pulsed light and human fibroblasts and endothelial cells
97

Creation and study of matter in extreme conditions by high-intensity free-electron laser radiation

Vinko, Sam M. January 2011 (has links)
The recent development of free-electron lasers operating at XUV and X-ray wavelengths are proving vital for the exploration of matter in extreme conditions. The ultra-short pulse length and high peak brightness these light sources provide, combined with a tunable X-ray wavelength range, makes them ideally suited both for creating high energy density samples and for their subsequent study. In this thesis I describe the work done on the XUV free-electron laser FLASH in Hamburg, aimed at creating homogeneous samples of warm dense matter through the process of volumetric XUV photo-absorption, and the theoretical work undertaken to understand the process of high-intensity laser-matter interactions. As a first step, we have successfully demonstrated intensities above 10<sup>17</sup> Wcm-2 at a wavelength of 13.5 nm, by focusing the FEL beam to micron and sub-micron spot sizes by means of a multilayer-coated off-axis parabolic mirror. Using these record high intensities, we have demonstrated for the first time saturable absorption in the XUV. The effect was observed in aluminium and magnesium samples and is due to the bleaching of a core-state absorption channel by the intense radiation field. This result has major implications for the creation of homogeneous high energy density systems, as a saturable absorption channel allows for a more homogeneous heating mechanism than previously thought possible. Further, we have conducted soft X-ray emission spectroscopy measurements which have delivered a wealth of information on the highly photo-excited system under irradiation, immediately after the excitation pulse, yet before the system evolves into the warm dense matter state. Such strongly photo-excited samples have also been studied theoretically, by means of density functional theory coupled to molecular dynamics calculations, yielding detailed electronic structure information. The use of emission spectroscopy as a probe for solid-density and finite-temperature systems is discussed in light of these results. Theoretical efforts have further been made in the study of the free-free absorption of aluminium as the system evolves from the solid state to warm dense matter. We predict an absorption peak in temperature as the system heats and forms a dense plasma. The physical significance of this effect is discussed in terms of intense light-matter interactions on both femtosecond and picosecond time-scales.
98

An evaluation of the influence of Basic Military Training on the visual skills of recruits

Fourie, Jacques January 2013 (has links)
Most sport coaches are under the impression that if their athletes have 20/20 vision, nothing more is needed to be done in the visual arena. This is a common misconception in youth sport and professional sport. Every sport involves the visual system in one way or another, yet very few coaches or athletes spend any time training the visual system to perform optimally during competition. To perform at the highest level of competition, athletes have to be in tune with their visual motor and visual perceptual system. Participants consisted of 200 male and female recruits enrolled for Basic Military Training (BMT) at the training academy in Ellisras, South Africa. Only recruits who completed the informed consent and adhere to the inclusion exclusion criteria participated in the study. The primary purpose of this study was to see how the recruits improve their visual skills after intense training which included cardio-respiratory endurance, muscular strength (upper body and abdominal), muscular endurance, speed, power, agility and flexibility. The training intensity of the sessions exceeded 6 metabolic equivalents (METs). Data sampling was completed over a period of one week during weeks 1, 12 and 20. The proposed schedule for the data gathering is suggested to ensure the special requirements demanded by the different tests and to see at what rate their visual skill improve. Results in this study suggests that a Basic Military Training (BMT) programme, focusing on intense physical training, enhances hand-eye co-ordination, visual response speed, accuracy, anticipation, visual concentration and short term visual memory. The improvement of various visual skills observed in this research provides evidence that physical exercise, along with an enhanced state of physical fitness, does have a positive effect on visual proficiency. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Physiology / unrestricted
99

Spectroscopie et Imagerie RMN multi-noyaux à très haut champ magnétique / Multi-nuclear RMN in Spectroscopy and Imagery at very high magnetic fields

Stout, Jacques 09 October 2019 (has links)
Le trouble bipolaire est un trouble de l'humeur récurrent affectant de 1 à 3% de la population adulte à travers le monde et ayant une comorbidité importante avec une hausse du taux de suicides, l'abus de drogues et d'autres troubles médicaux. Ce trouble semble avoir plusieurs liens avec la schizophrénie et une vulnérabilité au trouble est souvent héréditaire dans une famille. Même si les causes biologiques n'ont pas encore été établies, de nombreuses anomalies dans le système limbique sous-cortical et la zone préfrontal ont été observés.Depuis sa découverte il y a plus d'un demi-siècle, une prise de sels de Lithium a été le traitement le plus fiable, mais l'action biochimique du Lithium sur le cerveau et le pourquoi de l'efficacité du traitement reste un mystère. Afin de pouvoir mieux comprendre cet effet, nous avons développé des séquences d'imagerie du Lithium-7 via résonance magnétique à 7 et 17 Tesla afin de pouvoir établir sa distribution et concentration cérébrale. Spécifiquement, j'ai travaillé sur le développement et la validation des méthodes d'acquisition, de reconstruction et de quantification de notre protocole. Ces méthodes ont d'abord été appliqués afin d'étudier la distribution cérébrale du Lithium sur des cerveaux de rats ex-vivo. Ces rats étés traités pendant 28 jours avec du Li2CO3, sacrifiés et leurs têtes fixés avec du PFA. En utilisant une antenne surfacique double canaux 1H/7Li fait maison, une acquisition 7Li Turbo Spin echo et une méthode de remplacement par fantôme pour la quantification, nous avons pu mesurer les cartes de concentration du Lithium. Les concentrations moyennes obtenus dans des régions d’intérêt prédéfinis ont été mesurés afin de les comparer avec les résultats obtenus par spectrométrie de masse.Après cette étude préclinique qui a permis de valider notre approche, un protocole similaire fut créé pour une étude in-vivo 7Li d'imagerie par résonance magnétique chez des patients bipolaires euthymiques sur un scanner 7T. Ces individus ont tous suivis un traitement régulier de Lithium. Pour cette étude, nous avons utilisé une séquence Steady State Free Precession à TE ultra-court et avec un échantillonnage du k-space non-cartésien. Un pipeline de quantification et d'analyse similaire à celle utilisé pour notre étude préclinique fut appliqué pour cette étude, avec l'ajout d'une étape de correction pour les inhomogénéités de B0. Après avoir fait une analyse statistique au niveau de toute la cohorte par régions d'intérêt, il a été observé que l'hippocampe gauche, une part majeur du système limbique associé au trouble bipolaire à de multiples occasions, possède systématiquement une haute concentration de Lithium. Finalement, la méthode de quantification fut modifiée en quantification bi-compartimentale afin de prendre en compte les différences dans les taux de relaxation du Lithium dans le CSF et dans le parenchyme du cerveau. Cette méthode fut appliqué afin de pouvoir quantifier le Lithium à 7T dans un sous-groupe des patients bipolaires et radicalement réduire les différences initialement observés entre les séquences SSFP et bSSFP. / Bipolar disorder is a chronic affective disorder affecting 1 to 3% of the adult population worldwide and has a high level of comorbidity with suicide rates, substance abuse and other harmful conditions. The disorder has possible ties to schizophrenia and has been observed to have a strong genetic component. The exact biological underpinnings have not been firmly established, however abnormalities in limbic subcortical and prefrontal areas have been observed.Ever since its discovery more than half a century ago, a daily intake of Lithium salts has arguably become the most reliable treatment of the disorder, despite us possessing little to no understanding of its biochemical action. In order to shed some light on the effect of Lithium in the brain, we have developed Lithium-7 MR imaging at 7 and 17 Tesla in order to assess its cerebral concentration and distribution. Specifically, I worked on developing and validating several acquisition, reconstruction and quantification methods dedicated to 7Li MRI and MRS. Those methods were first applied to study ex vivo the cerebral distribution of lithium in rats. These rats were pretreated for 28 days with Li2CO3, sacrificed and their head fixated with PFA. Using a home-made 1H/7Li radiofrequency surface coil and a 7Li Turbo Spin echo acquisition and a modified phantom replacement method for quantification, we were able to measure Li concentration maps. Regional Li concentration values were then compared with those obtained with mass spectrometry.After this preclinical proof-of-concept study, an in vivo 7Li MRI protocol was designed to map the cerebral Li concentration in euthymic bipolar subjects at 7T. These individuals all followed a regular lithium treatment. For this study, we chose to use an ultra-short echo-time Steady State Free Precession sequence with non-Cartesian k-space sampling. A quantification and analysis pipeline similar to the one used for our preclinical study was applied for this study, with the addition of a correction step for B0 inhomogeneities. After conducting a statistical analysis at the cohort level, it was assessed that the left hippocampus, a major part of the limbic system that has been associated with BD on multiple occasions, exhibited systematically a high level of lithium. Finally, I developed a quantification method accounting for the different relaxation times of 7Li in the CSF and in the brain parenchyma. This method was applied to image lithium at 7T in a subset of bipolar patients reducing drastically the differences initially observed between the SSFP and bSSFP sequences.
100

Dům krátké cesty v Brně / 5-Minutes Neighbourhood

Šimberová, Iva January 2014 (has links)
Subject of the thesis is the architecture study of multifunctional architectural object based on the principle of creating intensive urban structures. Design area is located on the riverside Svitava, in the neighborhood the street Zvonařka . The aim of the project was to design an intensive structure that will meet the combination of features in order to achieve independence from the surrounding area and shorten the walking distance. The proposal itself, the principle of porosity. This generates a set of objects fulfilling different functions, public, semi-public and private spaces - atrium terraces, green roofs and balconies. The building has nine floors above ground and two underground floors used for parking. On the first floor there is a bank and retail space, the other floors are then situated administration, library, fitness, health center and on the top two floors of living. Construction of the building is designed as a reinforced concrete frame, sits on the pilots. The facade is solved soberly with regard to function, the main expressive elements are white façade,gray facing and glazing surface of the first two floors

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