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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.
261

線型モデルによる砕屑性堆積物形成過程の解析

水谷, 伸治郎 03 1900 (has links)
科学研究費補助金 研究種目:一般研究(C) 課題番号:03640640 研究代表者:水谷 伸治郎 研究期間:1991-1992年度
262

Epidemic models and inference for the transmission of hospital pathogens

Forrester, Marie Leanne January 2006 (has links)
The primary objective of this dissertation is to utilise, adapt and extend current stochastic models and statistical inference techniques to describe the transmission of nosocomial pathogens, i.e. hospital-acquired pathogens, and multiply-resistant organisms within the hospital setting. The emergence of higher levels of antibiotic resistance is threatening the long term viability of current treatment options and placing greater emphasis on the use of infection control procedures. The relative importance and value of various infection control practices is often debated and there is a lack of quantitative evidence concerning their effectiveness. The methods developed in this dissertation are applied to data of methicillin-resistant Staphylococcus aureus occurrence in intensive care units to quantify the effectiveness of infection control procedures. Analysis of infectious disease or carriage data is complicated by dependencies within the data and partial observation of the transmission process. Dependencies within the data are inherent because the risk of colonisation depends on the number of other colonised individuals. The colonisation times, chain and duration are often not visible to the human eye making only partial observation of the transmission process possible. Within a hospital setting, routine surveillance monitoring permits knowledge of interval-censored colonisation times. However, consideration needs to be given to the possibility of false negative outcomes when relying on observations from routine surveillance monitoring. SI (Susceptible, Infected) models are commonly used to describe community epidemic processes and allow for any inherent dependencies. Statistical inference techniques, such as the expectation-maximisation (EM) algorithm and Markov chain Monte Carlo (MCMC) can be used to estimate the model parameters when only partial observation of the epidemic process is possible. These methods appear well suited for the analysis of hospital infectious disease data but need to be adapted for short patient stays through migration. This thesis focuses on the use of Bayesian statistics to explore the posterior distributions of the unknown parameters. MCMC techniques are introduced to overcome analytical intractability caused by partial observation of the epidemic process. Statistical issues such as model adequacy and MCMC convergence assessment are discussed throughout the thesis. The new methodology allows the quantification of the relative importance of different transmission routes and the benefits of hospital practices, in terms of changed transmission rates. Evidence-based decisions can therefore be made on the impact of infection control procedures which is otherwise difficult on the basis of clinical studies alone. The methods are applied to data describing the occurrence of methicillin-resistant Staphylococcus aureus within intensive care units in hospitals in Brisbane and London
263

Widening the applicability of permutation inference

Winkler, Anderson M. January 2016 (has links)
This thesis is divided into three main parts. In the first, we discuss that, although permutation tests can provide exact control of false positives under the reasonable assumption of exchangeability, there are common examples in which global exchangeability does not hold, such as in experiments with repeated measurements or tests in which subjects are related to each other. To allow permutation inference in such cases, we propose an extension of the well known concept of exchangeability blocks, allowing these to be nested in a hierarchical, multi-level definition. This definition allows permutations that retain the original joint distribution unaltered, thus preserving exchangeability. The null hypothesis is tested using only a subset of all otherwise possible permutations. We do not need to explicitly model the degree of dependence between observations; rather the use of such permutation scheme leaves any dependence intact. The strategy is compatible with heteroscedasticity and can be used with permutations, sign flippings, or both combined. In the second part, we exploit properties of test statistics to obtain accelerations irrespective of generic software or hardware improvements. We compare six different approaches using synthetic and real data, assessing the methods in terms of their error rates, power, agreement with a reference result, and the risk of taking a different decision regarding the rejection of the null hypotheses (known as the resampling risk). In the third part, we investigate and compare the different methods for assessment of cortical volume and area from magnetic resonance images using surface-based methods. Using data from young adults born with very low birth weight and coetaneous controls, we show that instead of volume, the permutation-based non-parametric combination (NPC) of thickness and area is a more sensitive option for studying joint effects on these two quantities, giving equal weight to variation in both, and allowing a better characterisation of biological processes that can affect brain morphology.
264

[en] BAYESIAN STOCHASTIC EXTENSION OF DETERMINISTIC BOTTOM-UP APPROACH FOR THE LONG TERM FORECASTING OF ENERGY CONSUMPTION / [pt] EXTENSÃO ESTOCÁSTICA BAYESIANA DA ABORDAGEM BOTTOM-UP DETERMINÍSTICA PARA A PREVISÃO DE LONGO PRAZO DO CONSUMO DE ENERGIA

FELIPE LEITE COELHO DA SILVA 16 February 2018 (has links)
[pt] O comportamento do consumo de energia elétrica do setor industrial tem sido amplamente investigado ao longo dos últimos anos, devido a sua importância econômica, social e ambiental. Mais especificamente, o consumo de eletricidade dos subsetores da indústria brasileira exerce grande importância para o sistema energético brasileiro. Neste contexto, as projeções de longo prazo do seu consumo de energia elétrica para um país ou uma região são informações de grande relevância na tomada de decisão de órgãos e entidades que atuam no setor energético. A abordagem bottom-up determinística tem sido utilizada para obter a previsão de longo prazo em diversas áreas de pesquisa. Neste trabalho, propõe-se uma metodologia que combina a abordagem bottom-up com os modelos lineares hierárquicos para a previsão de longo prazo considerando os cenários de eficiência energética. Além disso, foi utilizada a inferência bayesiana para a estimação dos parâmetros do modelo, permitindo a incorporação de incerteza nessas previsões. Os resultados utilizando os dados de consumo de eletricidade de subsetores da indústria brasileira mostraram que a metodologia proposta consegue capturar a tajetória do consumo de eletricidade, em particular, dos subsetores de papel e celulose, e de metais não-ferrosos e outros de metalurgia. Por exemplo, os intervalos de credibilidade de 95 por cento construídos a partir do modelo estocástico contemplam os valores reais observados nos anos de 2015 e 2016. / [en] The electricity consumption behaviour in the Brazilian industry has been extensively investigated over the past years due to its economic, social and environmental importance. Specifically, the electricity consumption of the subsectors of Brazilian industry have great importance for the Brazilian energy system. In this context, the long-term projections of energy consumption of a country or region are highly relevant information to decision-making of organs and entities operating in the energy sector. The deterministic bottom-up approach has been used for the long-term forecast in several areas of research. In this paper, we propose a methodology that combines the bottom-up approach with hierarchical linear models for long-term forecasting considering energy efficiency scenarios. In addition, Bayesian inference was used to estimate the parameters of the model, allowing the uncertainty incorporation in these forecasts. The results using the electricity consumption data from subsectors of the Brazilian industry showed that the proposed methodology is able to capture the trajectory of their electricity consumption, in particular of the pulp and paper, and of non-ferrous metals and other metallurgical subsectors. For example, the 95 percent credibility intervals constructed from the stochastic model contemplate the actual values observed in the years 2015 and 2016.
265

Plans d'expérience optimaux en régression appliquée à la pharmacocinétique / Optimal sampling designs for regression applied to pharmacokinetic

Belouni, Mohamad 09 October 2013 (has links)
Le problème d'intérêt est d'estimer la fonction de concentration et l'aire sous la courbe (AUC) à travers l'estimation des paramètres d'un modèle de régression linéaire avec un processus d'erreur autocorrélé. On construit un estimateur linéaire sans biais simple de la courbe de concentration et de l'AUC. On montre que cet estimateur construit à partir d'un plan d'échantillonnage régulier approprié est asymptotiquement optimal dans le sens où il a exactement la même performance asymptotique que le meilleur estimateur linéaire sans biais (BLUE). De plus, on montre que le plan d'échantillonnage optimal est robuste par rapport à la misspecification de la fonction d'autocovariance suivant le critère du minimax. Lorsque des observations répétées sont disponibles, cet estimateur est consistant et a une distribution asymptotique normale. Les résultats obtenus sont généralisés au processus d'erreur de Hölder d'indice compris entre 0 et 2. Enfin, pour des tailles d'échantillonnage petites, un algorithme de recuit simulé est appliqué à un modèle pharmacocinétique avec des erreurs corrélées. / The problem of interest is to estimate the concentration curve and the area under the curve (AUC) by estimating the parameters of a linear regression model with autocorrelated error process. We construct a simple linear unbiased estimator of the concentration curve and the AUC. We show that this estimator constructed from a sampling design generated by an appropriate density is asymptotically optimal in the sense that it has exactly the same asymptotic performance as the best linear unbiased estimator (BLUE). Moreover, we prove that the optimal design is robust with respect to a misspecification of the autocovariance function according to a minimax criterion. When repeated observations are available, this estimator is consistent and has an asymptotic normal distribution. All those results are extended to the error process of Hölder with index including between 0 and 2. Finally, for small sample sizes, a simulated annealing algorithm is applied to a pharmacokinetic model with correlated errors.
266

Caracterização agronômica e molecular da coleção nuclear de arroz da Embrapa / Agronomic and molecular characterization of Embrapa Rice Core Collection

BUENO, Luíce Gomes 31 August 2010 (has links)
Made available in DSpace on 2014-07-29T14:52:04Z (GMT). No. of bitstreams: 1 TESE LUICE gomes.pdf: 3188724 bytes, checksum: c4156187d61efe808b3d021846f674dd (MD5) Previous issue date: 2010-08-31 / The plant genetic resources stored ex situ are considered as a genetic repository, and are raw material for the development of the world agriculture. In rice, despite its high genetic variability, the lack of information of accessions to compose a databank prevents its use to help the choice of genitors for the breeding programs. The Embrapa Rice Core Collection (ERiCC) was developed from 10,000 accessions from Embrapa GeneBank, and it was set up by 550 accessions, divided in three subsets: 1) 94 lines and cultivars from Brazil (LCB); 2) 148 lines and cultivars from abroad (LCI); and 3) 308 traditional varieties (VT), obtained from germplasm collection expeditions in Brazil. This work aimed: 1) to evaluate the extension of genetic variability of 550 accessions from ERiCC by means of agronomic traits characterization using mixed models and multivariate statistics; 2) to perform a comparative analysis of the genetic divergence considering the agronomical and SSR markers characterizations; and 3) to identify the genotypes with higher genetic diversity and with the best agronomic performances, aiming to promote the most efficient use of such germplasm in breeding programs. The agronomic characterization of 550 accessions was performed in nine field experiments, evaluating 18 phenological-agronomic traits. The data were analyzed using the mixed linear and AMMI models. There was wide variation range of genotypical values for most evaluated traits. In different environments, it was observed VT accessions among the high-yielding materials, demonstrating the potential of this group of germplasm, particularly important due to its high genetic variability, to contribute to the development of cultivars regionally adapted. The AMMI approach allowed a good discrimination of ERiCC rice genotypes in relation to the adaptive performance, identifying the accessions CA880078, CA990001, CA870071 (subset VT), and CNA0009113 (LCI) as having good yield and broad adaptation to distinct environments. The comparative analysis of genetic diversity between agronomic and molecular data was performed using the 242 lines and cultivars accessions from ERiCC, which were characterized by 86 fluorescent SSR markers, and five agronomic traits with genotypic values predicted (values without from the effects of interaction genotypes x environment, from a joint analysis of nine experiments. The genetic divergence among accessions was estimated by the average Euclidian distance for phenotypical data, and by the Rogers modified by Wright (RW) genetic distance. The datasets were jointly analyzed by descriptive and multivariate statistics, using correlation analyses from hierarchical grouping of Ward and UPGMA methods. The phenotypical and molecular data showed a broad distribution of dissimilarity indexes, despite they showed different patterns of variation between them. Low molecular distances were associated to low phenotypical distances, however to high molecular distances, occurred a high broad range of phenotypical variation. The correlation between genetical and phenotypical dissimilarities was significant for both lowland and upland accessions, despite with different values (r=0.156 and r=0.409, respectively). Due to the low relation between phenotypical and molecular data, the analysis of genotypes to be used in breeding programs must include both evaluations to a better accession characterization. Considering the high yielding accessions, the higher molecular distances were identified among the accessions from lowland system of cultivation, among which BR IRGA 413 and CNA0005014, BR IRGA 413 and CNA0005853, and CNA0004552 and CNA0005014. Considering the upland accessions, maximum genetic distances were identified in CNA0000482 and CNA0006422, CNA0001006 and CNA0006422, and CNA0001006 and CNA0003490. The molecular analysis was able to identify accessions with reduced genetic relationship, that if used as genitors, will result in a progeny with a high probability to find new allelic combinations. On the other hand, the phenotypical characterization is important to identify accessions not just genetically divergent, but with superior agronomic trait performances for breeding programs. The results of this work will permit to increase the activities related to the characterization of accessions from rice Genebank, giving support of breeding programs to choose the best accessions to obtain new cultivars, with favorable traits, and broad genetic basis. In addition, a continuous program of phenotypical and molecular characterization of germplasm will be able to identify accessions to increase the genetic variability of ERiCC. / Os recursos genéticos vegetais armazenados ex situ são considerados reservatórios de genes e funcionam como matéria-prima para o desenvolvimento da agricultura mundial. Na cultura do arroz, apesar da extensa variabilidade genética existente, a deficiência de informações que integrem dados que possam efetivamente auxiliar na escolha de genótipos importantes para os programas de melhoramento constitui o principal fator que limita a utilização mais ampla dos acessos armazenados nos bancos de germoplasma. A Coleção Nuclear de Arroz da Embrapa (CNAE) representa a variabilidade genética de mais de 10 mil acessos constituintes do Banco Ativo de Germoplasma (BAG) da Embrapa Arroz e Feijão, e é composta por 550 acessos subdivididos em três estratos: 1) 94 Linhagens e Cultivares Brasileiras (LCB), provenientes de programas de melhoramento de instituições brasileiras; 2) 148 Linhagens e Cultivares Introduzidas (LCI), provenientes de programas de melhoramento de outros países; e 3) 308 Variedades Tradicionais (VT), que reúne acessos obtidos por expedições de coleta de germoplasma realizadas em vários estados do Brasil. Este trabalho teve como principais objetivos: 1) avaliar a extensão da variabilidade genética dos 550 acessos pertencentes à CNAE por meio da caracterização agronômica via metodologias de modelos mistos e estatísticas multivariadas; 2) realizar a análise comparativa da divergência genética entre acessos, determinada pela avaliação de caracteres agronômicos e marcadores moleculares SSR; e 3) identificar os genótipos com maior diversidade genética e com melhores atributos agronômicos, a fim de indicar uma melhor utilização destes recursos genéticos em programas de melhoramento. Na caracterização agronômica foram avaliados 550 acessos em experimentos conduzidos em nove locais no Brasil, envolvendo um total de 18 caracteres fenológico-agronômicos. Os dados foram analisados empregando-se a abordagem de modelos lineares mistos e modelo AMMI de análise. Verificou-se grande amplitude de variação dos valores genotípicos para a maioria dos caracteres avaliados. Nos diferentes ambientes, houve ocorrência de genótipos do estrato VT entre os mais produtivos, o que demonstra o potencial deste grupo de germoplasma, particularmente importante por sua grande variabilidade genética, em contribuir para o desenvolvimento de cultivares regionalmente adaptadas. A abordagem AMMI permitiu uma boa discriminação dos genótipos de arroz da CNAE quanto ao seu comportamento adaptativo, identificando os acessos CA880078, CA990001, CA870071 (do estrato VT), e CNA0009113 (LCI) com estabilidade, produtividade satisfatória e ampla adaptação à diferentes ambientes. Para a análise comparativa da diversidade genética entre dados agronômicos e moleculares foram considerados 242 acessos da CNAE, os quais foram caracterizados utilizando-se 86 marcadores SSR fluorescentes, sendo que para os dados agronômicos, foram realizadas análises conjuntas dos experimentos e considerados os valores genotípicos preditos de cinco caracteres (valores livres dos efeitos de interação genótipos x ambientes). A divergência genética entre os acessos foi estimada pelo procedimento de distância Euclidiana média para os dados fenotípicos, e por meio da distância de Rogers modificada por Wright (RW) para os dados moleculares, analisando-se os conjuntos de dados por meio de estatísticas descritivas e multivariadas, empregando-se análises de correlação entre matrizes de dissimilaridade e análises de agrupamento hierárquico de Ward e UPGMA. Os dados fenotípicos e moleculares apresentaram uma ampla distribuição dos índices de dissimilaridade, embora tenham apresentado diferentes padrões dessa variação. Baixas distâncias moleculares estiveram associadas a baixas distâncias baseada nos valores genotípicos, no entanto para elevadas distâncias moleculares houve ocorrência de ampla escala de variação fenotípica. A correlação entre as dissimilaridades genéticas e valores genotípicos foi significativa tanto no conjunto de acessos irrigados quanto no de sequeiro, porém, com diferentes magnitudes (r=0,156 e r=0,409, respectivamente). Devido esta baixa relação entre os dados fenotípicos e moleculares, o estudo de genótipos para fins de uso no melhoramento genético deve incluir ambas avaliações para a melhor caracterização dos acessos. Entre os materiais mais produtivos, as maiores distâncias moleculares foram identificadas entre os genótipos do sistema de cultivo irrigado, dentre eles BR IRGA 413 e CNA0005014, BR IRGA 413 e CNA0005853, e CNA0004552 e CNA0005014. Entre os materiais de sequeiro, máximas distâncias genéticas foram identificadas entre os acessos CNA0000482 e CNA0006422, CNA0001006 e CNA0006422, e CNA0001006 e CNA0003490. A análise molecular permitiu que fossem identificados genótipos de vínculo genético reduzido, que quando utilizados como parentais em cruzamentos, possibilitarão que as progênies obtidas apresentem maiores chances de combinações alélicas inéditas. Por sua vez, a caracterização fenotípica tem papel fundamental na identificação de materiais que além de divergentes, apresentem desempenho agronômico superior para os programas de melhoramento. Os resultados deste trabalho permitirão aumentar eficazmente as atividades relacionadas à caracterização de acessos do Banco Ativo de Germoplasma de arroz, subsidiando os programas de melhoramento na escolha de genótipos a serem utilizados para a obtenção de novas cultivares, com características favoráveis, de ampla base genética. Em adição, um programa contínuo de caracterização fenotípica e molecular de germoplasma permitirá ainda a escolha de acessos para a ampliação da variabilidade genética da CNAE.
267

Estimation de synchrones de consommation électrique par sondage et prise en compte d'information auxiliaire / Estimate the mean electricity consumption curve by survey and take auxiliary information into account

Lardin, Pauline 26 November 2012 (has links)
Dans cette thèse, nous nous intéressons à l'estimation de la synchrone de consommation électrique (courbe moyenne). Etant donné que les variables étudiées sont fonctionnelles et que les capacités de stockage sont limitées et les coûts de transmission élevés, nous nous sommes intéressés à des méthodes d'estimation par sondage, alternatives intéressantes aux techniques de compression du signal. Nous étendons au cadre fonctionnel des méthodes d'estimation qui prennent en compte l'information auxiliaire disponible afin d'améliorer la précision de l'estimateur de Horvitz-Thompson de la courbe moyenne de consommation électrique. La première méthode fait intervenir l'information auxiliaire au niveau de l'estimation, la courbe moyenne est estimée à l'aide d'un estimateur basé sur un modèle de régression fonctionnelle. La deuxième l'utilise au niveau du plan de sondage, nous utilisons un plan à probabilités inégales à forte entropie puis l'estimateur de Horvitz-Thompson fonctionnel. Une estimation de la fonction de covariance est donnée par l'extension au cadre fonctionnel de l'approximation de la covariance donnée par Hájek. Nous justifions de manière rigoureuse leur utilisation par une étude asymptotique. Pour chacune de ces méthodes, nous donnons, sous de faibles hypothèses sur les probabilités d'inclusion et sur la régularité des trajectoires, les propriétés de convergence de l'estimateur de la courbe moyenne ainsi que de sa fonction de covariance. Nous établissons également un théorème central limite fonctionnel. Afin de contrôler la qualité de nos estimateurs, nous comparons deux méthodes de construction de bande de confiance sur un jeu de données de courbes de charge réelles. La première repose sur la simulation de processus gaussiens. Une justification asymptotique de cette méthode sera donnée pour chacun des estimateurs proposés. La deuxième utilise des techniques de bootstrap qui ont été adaptées afin de tenir compte du caractère fonctionnel des données / In this thesis, we are interested in estimating the mean electricity consumption curve. Since the study variable is functional and storage capacities are limited or transmission cost are high survey sampling techniques are interesting alternatives to signal compression techniques. We extend, in this functional framework, estimation methods that take into account available auxiliary information and that can improve the accuracy of the Horvitz-Thompson estimator of the mean trajectory. The first approach uses the auxiliary information at the estimation stage, the mean curve is estimated using model-assisted estimators with functional linear regression models. The second method involves the auxiliary information at the sampling stage, considering πps (unequal probability) sampling designs and the functional Horvitz-Thompson estimator. Under conditions on the entropy of the sampling design the covariance function of the Horvitz-Thompson estimator can be estimated with the Hájek approximation extended to the functional framework. For each method, we show, under weak hypotheses on the sampling design and the regularity of the trajectories, some asymptotic properties of the estimator of the mean curve and of its covariance function. We also establish a functional central limit theorem.Next, we compare two methods that can be used to build confidence bands. The first one is based on simulations of Gaussian processes and is assessed rigorously. The second one uses bootstrap techniques in a finite population framework which have been adapted to take into account the functional nature of the data
268

State and trait predictors of negatively toned dreams in women : a prospective investigation

Banu, Cristina 09 1900 (has links)
Bien que les rêves dysphoriques, comme les mauvais rêves et les cauchemars, surviennent du moins occasionnellement chez la majorité des adultes, les facteurs impliqués dans l’occurrence de ces rêves, d’une nuit à l’autre, demeurent incertains. Par le biais d’un devis prospectif multiniveaux, nous avons étudié l’impact interactif des facteurs d’état et de trait sur l’occurrence de rêves dysphoriques d’une nuit à l’autre. Nous avons également exploré dans quelle mesure le contenu affectif et négatif des rêves de tous les jours était affecté par les mêmes facteurs. Des femmes adultes ont complété des mesures de trait de personnalité et de psychopathologie suivies de jusqu’à quatre semaines de journaux quotidiens de rêves et d’anxiété avant le coucher, ainsi que d’inventaires hebdomadaires de stress perçu. En contrôlant pour le rappel de rêve, une hausse hebdomadaire du stress perçu a significativement augmenté la probabilité d’avoir un rêve dysphorique une nuit donnée, alors que la psychopathologie a modéré positivement cette relation. Ces résultats suggèrent que les femmes adultes ayant un niveau plus élevé de psychopathologie seraient particulièrement sensibles au stress quotidien et donc plus susceptibles de faire des mauvais rêves ou cauchemars les nuits suivantes. Les analyses ont aussi révélé des effets positifs différentiels des variables d’état et de trait sur le contenu émotionnel et négatif des rêves de tous les jours. Ces résultats concordent avec le modèle neurocognitif des rêves dysphoriques proposé récemment et l’hypothèse de continuité des rêves. Les implications de cette étude et des recommandations futures sont émises. / Although disturbing dreams, such as bad dreams and nightmares, are experienced at least occasionally by a majority of adults, the factors involved in the night-by-night occurrence of these dreams remain unclear. Using a prospective design and multilevel modeling, we investigated the interactive impact of state and trait factors on the nightly occurrence of disturbing dreams. We further explored the extent to which emotionally intense and negative everyday dream content was affected by the same variables. Adult women completed measures of personality and psychopathology followed by up to four weeks of daily dream logs, daily pre-sleep anxiety logs, and weekly perceived stress inventories. After controlling for dream recall, upsurges in weekly perceived stress significantly increased the likelihood of having a disturbing dream on a given night, whereas psychopathology positively moderated that relationship. These results suggest that adult women reporting higher levels of psychopathology are particularly sensitive to everyday stress and thus more likely to experience bad dreams or nightmares on subsequent nights. Analyses also revealed differential positive effects of state and trait variables on the emotional and negative content of everyday dreams. These findings are in line with a recently proposed neurocognitive model of disturbed dreaming and the continuity hypothesis of dreaming. The implications of this study and future recommendations are emitted.
269

Fúze simultánních EEG-FMRI dat za pomoci zobecněných spektrálních vzorců / Simultanneous EEG-FMRI Data Fusion with Generalized Spectral Patterns

Labounek, René January 2018 (has links)
Mnoho rozdílných strategií fúze bylo vyvinuto během posledních 15 let výzkumu simultánního EEG-fMRI. Aktuální dizertační práce shrnuje aktuální současný stav v oblasti výzkumu fúze simultánních EEG-fMRI dat a pokládá si za cíl vylepšit vizualizaci úkolem evokovaných mozkových sítí slepou analýzou přímo z nasnímaných dat. Dva rozdílné modely, které by to měly vylepšit, byly navrhnuty v předložené práci (tj. zobecněný spektrální heuristický model a zobecněný prostorovo-frekvenční heuristický model). Zobecněný frekvenční heuristický model využívá fluktuace relativního EEG výkonu v určitých frekvenčních pásmech zprůměrovaných přes elektrody zájmu a srovnává je se zpožděnými fluktuacemi BOLD signálů pomocí obecného lineárního modelu. Získané výsledky ukazují, že model zobrazuje několik na frekvenci závislých rozdílných úkolem evokovaných EEG-fMRI sítí. Model překonává přístup fluktuací absolutního EEG výkonu i klasický (povodní) heuristický přístup. Absolutní výkon vizualizoval s úkolem nesouvisející širokospektrální EEG-fMRI komponentu a klasický heuristický přístup nebyl senzitivní k vizualizaci s úkolem spřažené vizuální sítě, která byla pozorována pro relativní pásmo pro data vizuálního oddball experimentu. Pro EEG-fMRI data s úkolem sémantického rozhodování, frekvenční závislost nebyla ve finálních výsledcích tak evidentní, neboť všechna pásma zobrazily vizuální síť a nezobrazily aktivace v řečových centrech. Tyto výsledky byly pravděpodobně poškozeny artefaktem mrkání v EEG datech. Koeficienty vzájemné informace mezi rozdílnými EEG-fMRI statistickými parametrickými mapami ukázaly, že podobnosti napříč různými frekvenčními pásmy jsou obdobné napříč různými úkoly (tj. vizuální oddball a sémantické rozhodování). Navíc, koeficienty prokázaly, že průměrování napříč různými elektrodami zájmu nepřináší žádnou novou informaci do společné analýzy, tj. signál na jednom svodu je velmi rozmazaný signál z celého skalpu. Z těchto důvodů začalo být třeba lépe zakomponovat informace ze svodů do EEG-fMRI analýzy, a proto jsme navrhli více obecný prostorovo-frekvenční heuristický model a také jak ho odhadnout za pomoci prostorovo-frekvenční skupinové analýzy nezávislých komponent relativního výkonu EEG spektra. Získané výsledky ukazují, že prostorovo-frekvenční heuristický model vizualizuje statisticky nejvíce signifikantní s úkolem spřažené mozkové sítě (srovnáno s výsledky prostorovo-frekvenčních vzorů absolutního výkonu a s výsledky zobecněného frekvenčního heuristického modelu). Prostorovo-frekvenční heuristický model byl jediný, který zaznamenal s úkolem spřažené aktivace v řečových centrech na datech sémantického rozhodování. Mimo fúzi prostorovo-frekvenčních vzorů s fMRI daty, jsme testovali stabilitu odhadů prostorovo-frekvenčních vzorů napříč různými paradigmaty (tj. vizuální oddball, semantické rozhodování a resting-state) za pomoci k-means shlukovacího algoritmu. Dostali jsme 14 stabilních vzorů pro absolutní EEG výkon a 12 stabilních vzorů pro relativní EEG výkon. Ačkoliv 10 z těchto vzorů vypadají podobně napříč výkonovými typy, prostorovo-frekvenční vzory relativního výkonu (tj. vzory prostorovo-frekvenčního heuristického modelu) mají vyšší evidenci k úkolům.
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Analýza souvislostí mezi simultánně měřenými EEG a fMRI daty / Analysis of connections between simultaneous EEG and fMRI data

Labounek, René January 2012 (has links)
Electroencephalography and functional magnetic resonance are two different methods for measuring of neural activity. EEG signals have excellent time resolution, fMRI scans capture records of brain activity in excellent spatial resolution. It is assumed that the joint analysis can take advantage of both methods simultaneously. Statistical Parametric Mapping (SPM8) is freely available software which serves to automatic analysis of fMRI data estimated with general linear model. It is not possible to estimate automatic EEG–fMRI analysis with it. Therefore software EEG Regressor Builder was created during master thesis. It preprocesses EEG signals into EEG regressors which are loaded with program SPM8 where joint EEG–fMRI analysis is estimated in general linear model. EEG regressors consist of vectors of temporal changes in absolute or relative power values of EEG signal in the specified frequency bands from selected electrodes due to periods of fMRI acquisition of individual images. The software is tested on the simultaneous EEG-fMRI data of a visual oddball experiment. EEG regressors are calculated for temporal changes in absolute and relative EEG power values in three frequency bands of interest ( 8-12Hz, 12-20Hz a 20-30Hz) from the occipital electrodes (O1, O2 and Oz). Three types of test analyzes is performed. Data from three individuals is examined in the first. Accuracy of results is evaluated due to the possibilities of setting of calculation method of regressor. Group analysis of data from twenty-two healthy patients is performed in the second. Group EEG regressors analysis is realized in the third through the correlation matrix due to the specified type of power and frequency band outside of the general linear model.

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