En IRMf, les conclusions de paradigmes expérimentaux restent encore sujettes à caution dans la mesure où elles supposent une connaissance a priori du couplage neuro-vasculaire, c’est-à- dire de la fonction de réponse hémodynamique qui modélise le lien entre la stimulation et le signal mesuré. Afin de mieux appréhender les changements neuronaux et vasculaires induits par la réalisation d’une tâche cognitive en IRMf, il apparaît donc indispensable d’étudier de manière approfondie les caractéristiques de la réponse hémodynamique. Cette thèse apporte un nouvel éclairage sur cette étude, en s’appuyant sur une méthode originale d’analyse intra-sujet des données d’IRMf : la Détection-Estimation Conjointe (« Joint Detection-Estimation » en anglais, ou JDE). L’approche JDE modélise de façon non paramétrique et multivariée la réponse hémodynamique, tout en détectant conjointement les aires cérébrales activées en réponse aux stimulations d’un paradigme expérimental. La première contribution de cette thèse a été centrée sur l’analyse approfondie de la variabilité hémodynamique, tant inter-individuelle qu’inter-régionale, au niveau d’un groupe de jeunes adultes sains. Ce travail a permis de valider la méthode JDE au niveau d’une population et de mettre en évidence la variabilité hémodynamique importante apparaissant dans certaines régions cérébrales : lobes pariétal, temporal, occipital, cortex moteur. Cette variabilité est d’autant plus importante que la région est impliquée dans des processus cognitifs plus complexes.Un deuxième axe de recherche a consisté à se focaliser sur l’étude de l’organisation hémodynamique d’une aire cérébrale particulièrement importante chez les êtres humains, la région du langage. Cette fonction étant liée à la capacité d’apprentissage de la lecture, deux groupes d’enfants sains, âgés respectivement de 6 et 9 ans, en cours d’apprentissage ou de consolidation de la lecture, ont été choisis pour mener cette étude. Deux apports méthodologiques importants ont été proposés. Tout d’abord, une extension multi-sessions de l’approche JDE (jusqu’alors limitée au traitement de données mono-session en IRMf) a été mise au point afin d’améliorer la robustesse et la reproductibilité des résultats. Cette extension a permis de mettre en évidence, au sein de la population d’enfants, l’évolution de la réponse hémodynamique avec l’âge, au sein de la région du sillon temporal supérieur. Ensuite, un nouveau cadre a été développé pour contourner l’une des limitations de l’approche JDE « standard », à savoir la parcellisation a priori des données en régions fonctionnellement homogènes. Cette parcellisation est déterminante pour la suite de l’analyse et a un impact sur les résultats hémodynamiques. Afin de s’affranchir d’un tel choix, l’alternative mise au point combine les résultats issus de différentes parcellisations aléatoires des données en utilisant des techniques de «consensus clustering». Enfin, une deuxième extension de l’approche JDE a été mise en place pour estimer la forme de la réponse hémodynamique au niveau d’un groupe de sujets. Ce modèle a pour l’instant été validé sur simulations, et nous prévoyons de l’appliquer sur les données d’enfant pour améliorer l’étude des caractéristiques temporelles de la réponse BOLD dans les réseaux du langage.Ce travail de thèse propose ainsi d’une part des contributions méthodologiques nouvelles pour caractériser la réponse hémodynamique en IRMf, et d’autre part une validation et une application des approches développées sous un éclairage neuroscientifique. / In fMRI, the conclusions of experimental paradigms remain unreliable as far as they supposesome a priori knowledge on the neuro-vascular coupling which is characterized by thehemodynamic response function modeling the link between the stimulus input and the fMRIsignal as output. To improve our understanding of the neuronal and vascular changes inducedby the realization of a cognitive task given in fMRI, it seems thus critical to study thecharacteristics of the hemodynamic response in depth.This thesis gives a new perspective on this topic, supported by an original method for intra-subjectanalysis of fMRI data : the Joint Detection-Estimation (or JDE). The JDE approachmodels the hemodynamic response in a not parametric and multivariate manner, while itjointly detects the cerebral areas which are activated in response to stimulations deliveredalong an experimental paradigm.The first contribution of this thesis is centered on the thorough analysis of the interindividualand inter-regiona hemodynamic variability from a population of young healthyadults. This work has allowed to validate the JDE method at the group level and to highlightthe striking hemodynamic variability in some cerebral regions : parietal, temporal, occipitallobes, motor cortex. This variability is much more important as the region is involved in morecomplex cognitive processes.The second research axis has consisted in focusing on the study of the hemodynamic orga-nizationof a particularly important cerebral area in Humans, the language system. Becausethis function embeds the reading learning ability, groups of healthy children of 6 and 9 yearsold respectively, who were in the process of learning or of strenghting reading, were chosen forthis study. Two important methodological contributions have been proposed. First, a multi-sessionsextension of the JDE approach (until now limited to the processing of mono-sessiondata in fMRI) was worked out in order to improve the robustness and the reproducibility ofthe results. Then, a new framework was developed to overcome the main shortcoming of theJDE approach. The latter indeed relies on a prior parcellation of the data in functionally ho-mogeneousregions, the choice of which is critical for the subsequent inference and impacts thehemodynamic results. In order to avoid this a priori choice, the finalized alternative combinesthe results from various random data fragmentations by using “consensus clustering”.Finally, a second extension of the JDE approach was developed in order to robustly estimatethe shape of the hemodynamic response at the group level. So far, this model was validatedon simulations, and we plan to apply it on children data to improve the study of the BOLDresponse temporal characteristics in the language areas. Thus, this PhD work proposes onone hand new methodological contributions to characterize the hemodynamic response infMRI, and on the other hand a validation and a neuroscientific application of the proposedapproaches.

Submitted by (ana.araujo@ufrpe.br) on 2017-02-20T17:20:01Z No. of bitstreams: 1 Marcelo de Ataide Silva Filho.pdf: 290490 bytes, checksum: c973572d5c431d1b89267bcfca5d5b34 (MD5) / Made available in DSpace on 2017-02-20T17:20:01Z (GMT). No. of bitstreams: 1 Marcelo de Ataide Silva Filho.pdf: 290490 bytes, checksum: c973572d5c431d1b89267bcfca5d5b34 (MD5) Previous issue date: 2006-02-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The international market of the floriculture is presented in constant growth. In Brazil the branch of the floriculture grows to each year. One of the impediments of this expansion is the commercialization of dumb with illnesses. The embryo culture makes possible the production of free vegetal parts of illnesses, with plantations more uniforms and bigger precocity. The objective of this work was to analyze the genetic variability of changes of Heliconia bihai proceeding from culture embryos (CE) compared with the changes of vegetative propagation (PV), using the molecular marker of type RAPD. The DNA was extracted of 19 different individuals, having been ten proceeding ones from vegetative propagation and nine of embryo culture. These had been analyzed and amplified with six oligonucleotídeos of RAPD. The oligonucleotídeos of RAPD, used had demonstrated efficient in the study of the variability in H. bihai, therefore they had amplified with effectiveness and they had detected polymorphism sufficiently. The dendrograma showed that it had the formation of two groups, being in the one of this separation of two sub-groups for the type of propagation. The groupings had revealed sufficiently next when the coefficients of genetic similarity are considered. The data generated by means of RAPD had vegetative demonstrated one high similarity of the materials propagated for culture of embryo with the propagated individuals (81%), not making impracticable the propagation for culture of embryos in vitro. Our results suggest that for study of genetic variability in H. bihai, data generated through technique RAPD had been sufficiently satisfactory. The coefficient of this genetic variation is essential for the development of strategies of propagation in commercial scale of the studied vegetal material. / O mercado internacional da floricultura apresenta-se em constante crescimento. No Brasil o ramo da floricultura cresce a cada ano. Um dos entraves desta expansão é a comercialização de mudas com patógenos. O cultivo de embrião possibilita a produção de propágulos vegetais livres de doenças, com plantios mais uniformes e com maior precocidade. O objetivo deste trabalho foi analisar a variabilidade genética de mudas de Heliconia bihai provenientes de cultivo embriões (CE) comparadas às mudas de propagação vegetativa (PV), utilizando o marcador molecular do tipo RAPD. O DNA foi extraído de 19 diferentes indivíduos, sendo dez provenientes de propagação vegetativa e nove de cultivo de embrião. Estes foram analisados e amplificados com seis oligoinucleotíodeos de RAPD. Os oligonucleotídeos de RAPD utilizados demonstraram-se eficientes no estuda da variabilidade em H. bihai pois amplificaram com eficácia e detectaram bastante polimorfismo. O dendrograma mostrou que houve a formação de dois grupos, sendo em um destes a separação de dois subgrupos pelo tipo de propagação. Os agrupamentos mostraram-se bastante próximos quando considerados os coeficientes de similaridade genética. Os dados gerados por meio de RAPD demonstraram uma alta similaridade dos materiais propagados por cultivo de embrião com os indivíduos propagados vegetativamente (81%), não inviabilizando a propagação por cultivo de embriões in vitro. Nossos resultados sugerem que para estudo de variabilidade genética em H. bihai. dados gerados através da técnica RAPD foram bastante satisfatórios. O coeficiente desta variação genética é essencial para o desenvolvimento de estratégias de propagação em escala comercial do material vegetal estudado.

Se describe la composición de especies, distribución, abundancia y frecuencia de paralarvas de cefalópodos en el mar peruano. Se determinó un total de 14 familias, 8 géneros, 4 especies en un total de 1109 muestras de zooplancton colectadas con red Hensen a 50 metros de profundidad desde la superficie, proveniente de 8 cruceros de investigación ejecutados durante los años 2013 y 2014; siendo las especies más dominantes Argonauta spp. (41.4%) y Abraliopsis sp. (6.4%); y las familias Ommastrephidae (13%), Octopodidae (9.1%), Gonatidae (3.9%) y Pyroteuthidae (3.7%). Las paralarvas mostraron una distribución espacial y una relación especie-específica con las masas de agua. Las especies de Argonauta spp. estuvieron relacionadas con ASS, ACF y AES/ATS, y el aumento de sus abundancias relacionadas con el aumento de temperatura; la familia Ommastrephidae relacionadas con ASS y ACF, con una distribución oceánica; la familia Octopodidae distribuida solo en el norte-centro dentro de la plataforma continental; la familia Gonatidae asociadas únicamente a ACF; mientras que las familias Onychoteuthidae y Pyroteuthidae no mostraron patrón de distribución ni preferencia por alguna masa de agua específica. Species composition, distribution, abundance and frequency of paralarvae in Peruvian sea are described. It was determined a total of 14 families, 8 genera and 4 species were determined in a total of 1109 zooplankton samples collected with Hensen net to 50m deep from the surface from 8 vessel research carried out during 2013 and 2014; being the most dominant the species Argonauta spp. (41.4%) y Abraliopsis sp. (6.4%); and families Ommastrephidae (13%), Octopodidae (9.1%), Gonatidae (3.9%) and Pyroteuthidae (3.7%). Paralarvae showed a spatial distribution and species-specific relationship with water masses. The species Argonauta spp. was related with SSW, CCS and ESW/TSW, and increased their abundances related to the temperature rise; la family Ommastrephidae related with SSW and CCW, with an oceanic distribution; the family Octopodidae distributed only in the north-center within the continental shelf; the family Gonatidae associated only with CCW; while the families Onychoteuthidae and Pyroteuthidae didn´t show distribution pattern or preference for any specific water masses.

Noise, vibration and harshness (NVH)levels in the luxury automotive industry are used by customers as a subjective method of determining the vehicle quality. This can be achieved by adjusting the vehicle design, where simulations are used to predict the NVH behaviour. Changes can be expensive and time consuming when made after the design stage has been completed, so it is important to produce accurate simulations of the product. Variability exists to some extent in all products, even those just off the production line, however, if a high level of variability exists then only a small portion of products will meet the predicted behaviour. The aim of the project is to provide information that may lead to the reduction of variability in an automotive vehicle. This is achieved by quantifying the statistical spread of FRFs (frequency response function) in a set of nominally identical vehicles. Once overall levels have been calculated, the location of the most variable sources can be identified. Project also seeks to develop new methods of analysis for the system phase response to determine whether further information may be extracted compared to the magnitude response. There are three main themes that run throughout this thesis, with the first being the quantification of variability due to the measurement taking process which is covered in chapter 3. A novel application of a method to separate the measurement variability from the overall system uncertainty was achieved as well as the quantification of the vehicle to- vehicle variability. The second theme that runs through the study concerns the identification of variability sources. This is realised in chapter 4 and chapter 6 as a set of structural and acoustic tests on a luxury sedan door. The trim was found to be held to the door panel by a series of 11 polymer clips and 4 metal screws. The variability of small changes to a significant boundary condition at the door trim was quantified, showing that the removal of rigid clips had a more significant effect on the overall variability that if a loose clip has been removed. It was also found that clips at the corners were the most sensitive to change. The final theme outlines and tests new analysis methods on the phase and compares the statistical spread of the phase with the equivalent spread of the magnitude. Data taken from the same tests was used and for most of the cases the two results were found to be approximately the same.

O objetivo deste estudo foi investigar os efeitos de diferentes estruturas de prática sobre a organização hierárquica de habilidades motoras no processo adaptativo. Dois experimentos foram conduzidos, cada um com a participação de 40 adultos jovens de ambos os sexos. O delineamento de ambos os experimentos contou com duas fases (estabilização e adaptação) e quatro grupos de prática: constante, constante-aleatória, aleatória e aleatória-constante. No experimento 1, os participantes executaram 240 tentativas de rebatida forehand do tênis de campo na fase de estabilização e 60 tentativas na fase de adaptação. As medidas de macro e microestrutura referiram-se, respectivamente, aos timings relativos e o tempo total de movimento. E, o desempenho foi analisado por meio de um índice de desempenho (ID) e coeficiente de variação. No experimento 2, os participantes realizaram 90 tacadas putting do golfe na fase de estabilização e 30 na fase de adaptação. As medidas utilizadas foram os deslocamentos e os timings relativos (macroestrutura) e deslocamento e tempo totais de movimento (microestrutura). Análises de clusters foram conduzidas para inferir a emergência de padrões de movimento ao longo da prática. O desempenho foi analisado por meio de ANOVAs. Os resultados do experimento 1 mostraram que a macro e microestruturas tornaram-se mais consistentes na fase de estabilização, mas isso não foi acompanhado de melhora no desempenho. Verificou-se que em todo experimento a variabilidade da macroestrutura foi superior àquela da microestrutura. No experimento 2, os grupos de prática constante, aleatória e aleatória-constante alteraram macro e microestruturas e melhoraram o desempenho na fase de estabilização. Porém, com a modificação da tarefa, não suportaram a perturbação e pioraram o desempenho. Associado aos resultados de desempenho esteve o fato de a consistência da macroestrutura ter sido menor que a da microestrutura, inferindo-se assim, não ter ocorrido estabilização funcional / The aim of this study was to investigate the effects of different practice schedules on the hierarchical organization of motor skills in the adaptive process. Two experiments were conducted, each with the participation of 40 young adults of both sexes. The design of both experiments consisted of two phases (stabilization and adaptation) and four practice groups: constant, constant-random, random and random-constant. In experiment 1, participants performed 240 trials of field tennis forehand in the stabilization phase, and 60 trials in the adaptation phase. The macro- and microstructure measures referred to relative timing and total movement time, respectively. In addition, the performance was analyzed through a performance index (ID) and coefficient of variation. In Experiment 2, participants performed 90 trials of golf putting strokes in the stabilization phase, and 30 trials in the adaptation phase. The measures were relative displacement and timing (macrostructure) and total displacement and time (microstructure). Cluster analyzes were run for inferring the emergence of movement patterns over practice. The performances were analyzed through ANOVAs. The results of experiment 1 showed that showed that the macro and microstructures became more consistent in the stabilization phase, but this was not accompanied by an improvement in performance. It was verified that in all experiment the variability of the macrostructure was superior to that of the microstructure. In experiment 2, constant, random and random-constant groups altered macro and microstructure and improved performance in the stabilization phase. However, with task modification they did not support the perturbation and worsened the performance. Associated with the performance results was the fact that the consistency of the macrostructure was lower than that of the microstructure, thus inferring that functional stabilization had not occurred

A variabilidade da força muscular, geralmente em uma tarefa de força constante e isométrica, tem sido estudada tanto de forma experimental quanto com o uso de ferramentas computacionais. No entanto, a maioria dos estudos utilizando simulações computacionais tem sido feita em tarefas que utilizam apenas um músculo, geralmente da mão. Até onde se tem conhecimento, não foi feito um estudo, nem experimental nem teórico, abrangendo o comportamento da variabilidade do torque durante a flexão plantar de uma forma geral. Considerando isso, esse trabalho tem como objetivo estudar a variabilidade do torque de flexão plantar por meio de simulações e de modelos matemáticos, comparando os resultados com os obtidos em experimentos realizados localmente. Uma primeira tentativa foi feita utilizando um modelo de contração muscular do tipo Hill ativado pela envoltória dos sinais de eletromiograma captados de cada um dos três músculos do tríceps sural. Essa abordagem não foi bem sucedida em termos da reprodução dos resultados experimentais obtidos de variabilidade do torque em humanos, embora tenha reproduzido bem o valor médio do torque da flexão plantar. Essa impossibilidade em reproduzir os dados experimentais de variabilidade do torque com um modelo ativado por envoltória do eletromiograma provavelmente deveu-se à perda de informação no eletromiograma sobre os disparos dos motoneurônios. Em uma segunda tentativa, os disparos individuais dos motoneurônios foram obtidos de um simulador desenvolvido localmente, chamado de ReMoto, capaz de fornecer os instantes de disparos de todos os modelos de motoneurônios que ativam cada músculo, além de ser capaz de fornecer a força produzida por esse músculo, calculada a partir da força produzida pelas unidades motoras individualmente. No entanto, a versão original do ReMoto foi parametrizada quase que totalmente utilizando dados de gatos e, por isso, foi necessário modificar diversos parâmetros (como amplitude dos abalos e amplitude do potencial de ação da unidade motora) e modelos (como limiar de recrutamento e saturação da força) antes de utilizar o simulador para o estudo da variabilidade do torque. Também foi adicionado um segundo modelo de gerador de força, que consegue reproduzir melhor as características temporais dos abalos das unidades motoras. Adicionalmente, um modelo do tipo Hill também foi modificado para ser ativado pelo conjunto de motoneurônios do simulador ReMoto. Novas simulações foram feitas com a nova versão do simulador (adaptada a dados de humanos) e os resultados foram condizentes com os dados experimentais (variabilidade do torque e do eletromiograma), indicando que os modelos no simulador são uma representação razoável do que acontece no ser humano. / The muscle force variability, usually in a constant and isometric force task, has been studied both experimentally and using computational tools. However, most studies using computer simulations have been made on tasks that use only one muscle, usually in the hand. As far as is known, no study has analyzed, either theoretically or experimentally, the overall behavior of the torque variability during plantar flexion. Therefore, this work aims to study the plantar flexion torque variability by means of mathematical models and simulations, comparing the results with those obtained in human experiments carried out locally. A first attempt was made using a Hill-type muscle contraction model activated by the electromyogram obtained from each of the three triceps surae muscles. This approach was not successful in terms of reproducing the torque variability results obtained from humans, although it estimated well the average value of plantar flexion torque. This inability to reproduce the torque variability found in experimental data was probably due to the information loss in the electromyogram of the spike times of motoneurons. In a second approach, the firing of individual motoneuron were obtained from a neuromuscular simulator developed locally, called ReMoto, capable of providing the spike times of all motoneuron models that activate each muscle and the respective muscle force. The latter is generated in the simulator from the forces generated by each motor unit that composes the muscle. However, the ReMoto original version was almost completely parameterized using data from cats and, hence, it was necessary to modify various parameter values (such as motor unit twitchs and action potential amplitudes) and models (such as the recruitment threshold and force saturation) before using the simulator to study torque variability in humans. Besides the second order twitch model already implemented in the original version of the simulator, two other models were implemented in this work. One was a more refined twitch model and the second was a Hill-type model modified to be activated by the ReMoto simulator motoneuron pool. New simulations were run with the new version of the simulator (adapted to human data) and the fittings to the experimental data (torque and electomyogram envelope variability) were good, suggesting that the models in the simulator are a reasonable representation of what occurs in the living human being.

BACKGROUND: Adjudication is a standardized, objective, and often blinded mechanism designed to assess clinical events with increased accuracy. It is performed by a centralized committee of independent reviewers, who are specialized, expert physicians who have no involvement with either the treatment of study subjects or the trial sponsor. Adjudication can decrease variability and bias in study results and increase the likelihood of correct identification, assessment, and categorization of clinical events such as potential malignancies diagnosed through histopathology. Histopathology is highly variable due to the subjective nature of the assessments. THESIS: If it is the case that there are clinically significant discrepancies between local and central diagnoses and that central adjudication yields more accurate diagnoses than a local pathologist, then it should be accepted that adjudication ought to be more widely used in clinical trials to assess histopathology-related safety outcomes and endpoints. METHODS AND STATISTICS: This is a retrospective cross-sectional study assessing interrater variability between local and central diagnoses of biopsy samples in a clinical trial setting using kappa scores and percent agreement. Certified Professional Coders (CPC) and central pathologists used the International Classification of Diseases for Oncology revision 3 (ICD-O 3) to codify the local and central assessments to permit comparison. Three statistical groups (group A: the full dataset, group B: pathology sub-specialty reading groups, and group C: non-melanoma skin cancers versus all other malignancies) were assessed for interrater variability in seven separate analyses: neoplasm versus non-neoplasm (analysis 1), benign versus malignant including non-neoplasms (analysis 2.1), benign versus malignant excluding non-neoplasms (analysis 2.2), discrepancies in morphology and/or behavior including non-neoplasms (analysis 3.1), discrepancies in morphology and/or behavior excluding non-neoplasms (analysis 3.2), all discrepancies leading to differences in treatment (analysis 4.1), and all discrepancies leading to difference in treatment with round 1 matches removed (analysis 4.2). RESULTS: 602 cases comprised the dataset. Based on kappa scores, there is near perfect agreement between the central and local lab diagnoses in analyses 1, 2.1, and 2.2 in group A (all cases in the dataset). The percent agreement for these analyses is above 90%. The group A (full dataset) kappa score and percent agreement decreased to 0.59 and 68.3%, respectively, in analysis 3.1 (discrepancies in morphology and/or behavior codes, including non-neoplasms). When non-neoplasms were removed (analysis 3.2), the kappa score and percent agreement were 0.52 and 57.0%, respectively. In group C, NMSC had substantial kappa agreement in analyses 1, 2.1, and 2.2, whereas all other malignancies had near perfect kappa agreement. All percent agreements were above 88% and surpassed the minimally acceptable threshold for interrater percent agreement in healthcare (80%). Group B divided the data set into 10 sub-specialty reading groups. Kappa scores ranged from 0.66 (GYN) to 1.00 (lung) in analysis 1; the analysis 1 kappa score for lymphoma was 0.55, but this was not statistically significant. In analysis 2.1, lung and sarcoma had the highest kappa scores (1.00) and dermatology and GYN had the lowest (0.71). As in analysis 1, the kappa score for lymphoma was 0.55 but was not statistically significant. When non-neoplasms were removed from analysis 2.2, 6 of the 10 sub-groups had kappa scores of 1.00, but all 6 had sample sizes less than 10. Percent agreement ranged from 80 to 100 percent. When all cases were considered regardless of number of rounds of review (analysis 4.1), about 90% of diagnoses would have similar courses of treatment. All sub-groups except sarcoma reached the minimally acceptable agreement rate in healthcare (80%). In the remaining 33% of cases that did not have matching diagnoses in round 1 (analysis 4.2), 34% may have different courses of treatment depending on whether the local or central diagnoses was used. Mid-study updates to the charter and CPC/reviewer manuals and processing of specimens did not have a significant impact on results. CONCLUSION: Although there is little discrepancy between local and central pathologists on whether malignancies exist among samples, there is discord regarding specific diagnoses and their associated treatments. Adjudication can assist in decreasing this discordance in order to develop the most specific and accurate safety profile for a compound.

The central United States is a region of the country plagued by frequent catastrophic flooding (e.g., flood events of 1993, 2008, 2011, 2013, and 2014). In the twentieth and twenty-first centuries, flooding has taken a devastating societal and economic toll on the central United States, contributing to dozens of fatalities and causing billions of dollars in damage. Moreover, previous studies have shown that flood damage has been increasing over the past century across this region, and seems to foreshadow a future increase in flood activity. Despite these large repercussions, the use of historical records to ascertain the changes over time in flooding has thus far proved inconclusive. It is therefore of paramount importance to examine whether the characters (i.e., magnitude and frequency) of recent flooding are different from the long-term averages over the central United States. The results of this thesis are based on long-term discharge records at 774 U.S. Geological Survey sites and show limited evidence suggesting increasing or decreasing trends in the magnitude of flood peaks over the study region. In contrast, there is much stronger evidence of increasing frequency of flood events. While the detection of changes in flood characteristics is essential, it is also of critical importance to start exploring what caused these changes. Therefore, in addition to the aforementioned investigation on the stream flow records, precipitation records were used to inspect whether possible changes in flood characteristics can be linked to the changes in heavy precipitation characteristics. The results indicate that there is a stronger signal of change in the frequency rather than in the magnitude of heavy precipitation events, similar to what found for the discharge records. Given that heavy precipitation is responsible for the observed changes in flooding, further analyses were performed to examine the climatic driving forces that are responsible for the observed changes in the frequency of precipitation, and consequently flooding at the seasonal scale; particular emphasis was paid to the role played by the Atlantic and Pacific Oceans. The results of this dissertation indicate that changes in the climate system play a significant role in explaining the variations in the frequency of heavy precipitation and flooding over the central United States at both the seasonal and sub-seasonal scales. The Pacific North American (PNA) teleconnection pattern was found to play a particularly prominent role. Therefore, these results suggest that recent observed changes in the frequency of flood events over the central United States can be largely attributed to changes in the frequency of heavy precipitation events, which were in turn driven by changes in the climate system.

Les recherches sur le vieillissement ont montré que la variabilité intra-individuelle (VII) du fonctionnement cognitif (dispersion et inconsistance) augmente avec l’âge. La VII pourrait jouer un rôle central dans la compréhension des changements cognitifs observés chez la personne âgée. Le but de cette recherche a été d’évaluer l’apport de la VII pour expliquer les différences d’efficience cognitive entre personnes âgées. Les relations entre deux formes de VII, dispersion (VII des scores entre plusieurs tests cognitifs) et inconsistance (VII des temps de réponse (TR) entre les essais à une tâche de contrôle cognitif), et l’efficience cognitive, ont été évaluées auprès d’un groupe d’adultes âgés de 61 ans et plus. La tâche de contrôle AX-cpt utilisée dans cette étude permet l’évaluation de processus de contrôle cognitif distincts (contrôle réactif et contrôle proactif). L’augmentation de la dispersion était associée à une diminution de la vitesse de traitement, de la capacité de la mémoire épisodique et de l’état cognitif plus général. L’augmentation de l’inconsistance semble traduire une difficulté supérieure associée à des capacités de maintien de l’information contextuelle et de résistance à l’interférence moins préservées. Toutefois, l’inconsistance pourrait exprimer une évolution positive de la cognition. Les fluctuations intra-individuelles du comportement paraissent être les caractéristiques d’un fonctionnement normal. L’irrégularité de l’instabilité temporelle des TR aux essais successifs d’une même tâche semble être un indicateur pertinent dans l’étude de la VII pour rendre compte d’une diminution de l’efficience cognitive. L’étude de la VII de la performance semble donc être une approche fructueuse pour expliquer la variabilité interindividuelle chez la personne âgée et prédire d’éventuels changements cognitifs / Aging research shows an age-related increase in intraindividual variability in cognitive functioning (dispersion and inconsistency). Intraindividual variability would play a central role in understanding cognitive changes in older adults. The purpose of the present research was to examine the contribution of the intraindividual variability study, in order to explain differences in cognitive efficiency between older adults. The relationship between two forms of intraindividual variability, dispersion (variability in scores across several cognitive tests) and inconsistency (variability in response time (RT) across trials in a cognitive control task), and the cognitive efficiency, was estimated in a sample of adults aged from 61 years and older. The control task AX-cpt used in this study allows the evaluation of distinct cognitive control process (proactive and reactive control). The increase in dispersion was associated with a decrease in processing speed, episodic memory ability and the more general cognitive state. The increase in inconsistency seems related to a difficulty of a cognitive system whose capacities of context information maintenance, and resistance to interference, are less preserved. However, the inconsistency could also reveal a positive evolution of cognition. Intraindividual fluctuations in behavior appear to be the characteristics of normal functioning. The irregularity of temporal instability of successive trials response times, seems to be a valid cue of the decrease in cognitive efficiency. The study of intraindividual variability in performance seems to be a fruitful approach to explain the variability between individuals observed in the elderly, and to predict possible cognitive changes.

Global mean surface temperatures (GMST) warmed in the early 20th century, experienced a mid-century lull, and warmed again steadily until 1997. Observations at the turn of the 21st century have revealed another period of quiescent warming of GMSTs from 1998 to 2012, thus prompting the notion of a global warming “hiatus”. The warming hiatus occurred concurrently with steadily increasing atmospheric greenhouse gas concentrations, sea level rise, and retreating arctic sea ice. The occurrence of the warming hiatus suggests that natural variability continues to be a sizable contributor to modern climate change and implies that energy is rearranged or changed within the climate system. Much of the scientific research conducted over the last decade has attempted to identify which modes of natural variability may be contributing to the GMST signal in the presence of anthropogenic warming. Many of these studies concluded that natural variability, operating in the global oceans were the largest contributors to GMST. What remains unclear is how oceanic variability and its contribution to GMST may change on a warmer globe as greenhouse gas concentrations continue to rise. Our research includes diagnostic analyses of the available observational surface temperature estimates and novel state-of-the-art climate model experiments from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Our analyses seek to understand how the natural modes of variability within the ocean will change under different warming scenarios. Utilizing simulations forced with observed pre-industrial and historical greenhouse gas emissions in combination with several future warming simulations, we quantify the probability of similar “hiatus-like” periods occurring on a warmer globe. To that end employ various metrics and detrending techniques including EOF decomposition, running climatologies, along with linear and nonlinear trends to elucidate how natural variability changes over time. We also examine the changing influence of natural modes of variability with respect to the anthropogenic radiative forcing over different regions on the globe.Results suggest that natural variability for much of the global oceans decreases as the radiative forcing increases in the future warming scenarios.