Teses / dissertações sobre o tema "Modèle en masses neurales"
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Kuchenbuch, Mathieu. "Modélisation computationelle de l'épilepsie avec crises focales migrantes du nourrisson". Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1B062.
Texto completo da fonteEpilepsy in infancy with migrating focal seizures is characterized by focal seizures beginning before 6 months that intensify to a stormy phase where so-called migrating focal seizures appear. The gain-of-function mutations of the KCNT1 gene are the main causes of this epilepsy. We focused on a cohort of patients with a KCNT1 mutations and this epilepsy to better understand this syndrome in order to model it. First, we specified the clinic for these patients, including long-term poor outcomes, high mortality, microcephaly and the presence of extra-neurological symptoms. Then, we determined, through the study of ictal EEGs, that migrating seizures were not chaotic but rather corresponded to a type of propagation and we have identified specific markers of this epilepsy. Then, we showed that the majority of KCNT1 mutations appeared to cluster in "hot spots" and that there was no strict genotypephenotype correlation. Finally, we modelled this epilepsy at microscopic and mesoscopic levels. Preliminary results showed a decrease in excitation, a fall in inhibition and involvement of depolarizing GABA. We then discuss the different aspects of our work in the light of the literature and describe the perspectives opened by this thesis from a fundamental, clinical and physiological point of views
Condy, Carine. "La distractibilité : bases neurales, pharmacologie et modèles expérimentaux". Paris 6, 2007. https://tel.archives-ouvertes.fr/tel-00808982.
Texto completo da fonteCondy, Carine. "LA DISTRACTIBILITE : BASES NEURALES, PHARMACOLOGIE ET MODELES EXPERIMENTAUX". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00808982.
Texto completo da fonteNugroho, Dwiyoga. "La marée dans un modèle de circulation générale dans les mers indonésiennes". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30089/document.
Texto completo da fonteIn the Indonesian seas, large tidal currents interact with the rough topography and create strong internal waves at the tidal frequency, called internal tides. Part of them will eventually propagate and dissipate far away from generation sites. Their associated mixing upwells cold and nutrient-rich water that prove to be critical for climate system and for marine resources. This thesis uses the physical ocean general circulation model, NEMO, as part of the INDESO project that aims at monitoring the Indonesian marine living resources. Models not taking into account tidal missing are unable to correctly reproduce the vertical structure of watermasses in Indonesian seas. However, taking into account this mixing is no simple task as the phenomena involved in tidal mixing cover a wide spectrum of spatial scales. Internal tides indeed propagate over thousands of kilometres while dissipation and mixing occurs at centimetric to millimetric scales. A model capable of resolving all these processes at the same time does not exist. Until now scientists either parameterised the tidal mixing or used models which only partly resolve internal tides. More and more scientists introduce explicit tidal forcing in their models but without knowing where the energy is going and how the internal tides are dissipated. This thesis intends to quantify energy dissipation in NEMO forced with explicit tidal forcing and compares it to the dissipation induced by the currently used parameterization. This thesis also provides new results about the quantification of the tidal energy budget in NEMO. I first contributed to an INDESO study that aimed at validating the model against several observation data sets. In a second and third study, I investigated the mixing produced in the model by explicit tidal forcing and its impact on water mass. Explicit tides forcing proves to produce a mixing comparable to the one produced by the parameterization. It also produces a significant cooling of 0.3 °C with maxima reaching 0.8°C in the areas of internal tide generation. The cooling is stronger on austral winter. The spring tides and neap tides modulate this impact by 0.1°C to 0.3°C. The model generates 75% of the expected internal tides energy, in good agreement with other previous studies. In the ocean interior, most of it is dissipated by horizontal momentum dissipation (19 GW), while in reality one would expect dissipation through vertical possesses. This value is close to the dissipation induced by the parameterization (16 GW). The mixing is strong over generation sites, and only 20% remains for far field dissipation mainly in the Banda and Sulawesi Seas. The model and the recent INDOMIX cruise [Koch-Larrouy et al. (2015)], which provided direct estimates of the mixing, are surprisingly in good agreement mainly above straits. However, in regions far away from the energy generation sites where INDOMIX found NO evidence of intensified mixing, the model produces too strong mixing. The bias comes from the lack of specific set up of internal tides in the model. More work is thus needed to improve the modeled dissipation, which is a theme of active research for the scientific community. I dedicated the last part of my thesis to the quantification of tidal energy sinks in NEMO. I first worked on a simple academic case: the COMODO internal tides test case, which analyses the behaviour of a vertically stratified fluid forced by a barotropic flow interacting over an idealized abyssal plain/slope/shelf topography without bottom friction. The results of the finite element T-UGOm hydrodynamic model are compared with those of NEMO. The central issue in calculating tidal energy budget is the separation of barotropic and baroclinic precesses
Koch-Larrouy, Ariane. "Transformation des masses d'eau dans les mers indonésiennes". Paris 6, 2007. http://www.theses.fr/2007PA066621.
Texto completo da fonteKalantari, Saman. "Introduction de fonctionnalités de changements d'états topologiques dans le formalisme de modélisation et de simulation CORDIS-ANIMA". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENS004.
Texto completo da fonteL'auteur n'a pas fourni de résumé en anglais
Pla, Patrick. "Les cellules embryonnaires souches sauvages et mutantes : un nouveau modèle de la migration et de la différenciation de crêtes neurales". Paris 11, 2003. http://www.theses.fr/2003PA112124.
Texto completo da fonteTruncal neural crest cells (NCC) that migrate along the dorsoventral pathway give rise to neurons and glial cells of the peripheral nervous system. NCC that migrate along the dorsolateral pathway are called melanoblasts and give rise to melanocytes. To better determine the molecular mechanisms that determine the orientation towards the dorsolateral pathway, we developped a cellular model using mouse embryonic stem cells (ES cells). These cells are able to migrate on both NCC pathways, when they are grafted in the chicken embryo. Using this model, we found that integrin beta1, a protein linking the extracellular matrix with the cytoskeleton, and Ednrb2 have a crucial role in the dorsolateral migration. Ednrb2 is able to stimulate the activity of FAK and paxillin, two tyrosine kinases involved in migration. Moreover, we differentiated ES cells into melanocytes in vitro. ES expressing a reporter gene under the control of a melanoblast-specific promoter (Dct : :lacZ) were established and the cellular events such as determination, proliferation and differentiation were observed during their differentiation in vitro. ES cells expressing Ednrb2 are more easily recruited to the melanoçyte lineage. The addition of the ligand endothelin stimulated also the proliferation of ES-cell derived melanoblasts. Altogether, this work show the development and the application of novel model of NCC development
Dugault, Edouard. "Etude du transport et de l'évolution physico-chimique de masses d'air européennes au-dessus de l'Atlantique Nord sous des conditions anticycloniques". Paris 6, 2002. http://www.theses.fr/2002PA066518.
Texto completo da fonteVallet, Anais. "Etude de la balance Excitatiοn/Ιnhibitiοn de régiοns cérébrales impliquées dans une tâche de cοntrôle inhibiteur : mοdélisatiοn de dοnnées οbtenues en Ιmagerie par Résοnance Μagnétique fοnctiοnnelle et inversiοn". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMC014.
Texto completo da fonteIn psychology, inhibitory control is a cognitive mechanism that stops a motor, emotional orcognitive response from achieving a desired goal. At cerebral level, inhibitory control is associatedwith a network of brain regions, whose function may be measured using BOLD signals from fMRI.Prefrontal control regions lower the BOLD activity of target regions. fMRI provides an indirectmeasure of the activity of neurons. How can we then infer from fMRI data, neural excitatory andinhibitory (E/I) properties of brain regions involved in an inhibitory control task ?We start with a non-linear biophysical model that describes by region the temporal evolutionof neural excitatory and inhibitory activities (Naskar et al., 2021). These variations in activityproduce BOLD changes in each brain region. Analysis of this model enables us to : 1) identifyneural parameters of the E/I balance ; 2) show that increasing the BOLD activity of a controlregion does not lower the BOLD activity of a target region, since these regions are connected bytheir excitatory neurons only ; 3) propose a new connectivity architecture to enable this ; 4) studyhow the lowering of activity in the target region depends on the E/I balance in the target region.We then propose a new inversion procedure. We check its reliability through simulations, beforepresenting a proof-of-concept using real data from a subject during a Think/No-Think task, aparadigm used for studying the inhibitory control of memory intrusions (Mary et al., 2020)
Maire, Cecile. "Fonction des facteurs de transcription Olig1 et Olig2 dans les cellules souches neurales du système nerveux central : Etude d'un modèle de souris transgéniques d'expression inductible". Paris 5, 2007. http://www.theses.fr/2007PA05D030.
Texto completo da fonteOlig1 and Olig2 are b-HLH transcription factors involved in oligodendrocyte development in the central nervous system. My project aims to analyse the effect of Olig gene over-expression in neural stem cells. Therefore, I designed and analyzed transgenic mice models with inducible expression of Olig genes in nestin+ neural stem/progenitor cells (Tet-On system). At embryonic stages, forced expression of Olig1 and Olig2 leads to ectopic expression of oligodendrocyte markers. Moreover, Olig2 over-expression decreased V3 interneuron specification. At postnatal stage Olig2 over-expression in germinative area induced earlier myelination and astrocyte specification in corpus callosum. These transgenic mice provide a useful model to test whether forced expression of Olig genes represents a possible strategy to enhance remyelination in demyelinating disease such as multiple sclerosis
Bozokalfa, Gökhan Akkurt Sedat. ""Ann" artifical neural networks and fuzzy logic models for cooling load prediction/". [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezlerengelli/master/makinamuh/T000372.pdf.
Texto completo da fonteKeywords: Artificial neural networks, fuzzy logic, modeling, cooling load, prediction. Includes bibliographical references (leaves. 44-45).
Bouissac, Julien. "Rôle de la voie Notch dans la spécification des cellules souches neurales et dans la différenciation des précurseurs neuraux : Utilisation du système modèle des neurosphères". Université Louis Pasteur (Strasbourg) (1971-2008), 2005. https://publication-theses.unistra.fr/public/theses_doctorat/2005/BOUISSAC_Julien_2005.pdf.
Texto completo da fonteIn our laboratory we are interested in the role of the Notch pathway on cell fate decision of neural stem cells and on their differentiation into neurons and glia in the model system of neurospheres. Neurospheres derive clonally for neural stem cells and proliferate in suspension in the adapted cell culture medium. Neurospheres prepared from Dll1 mutant embryos segregate more neurons at the expense of both oligodendrocytes and astrocytes, compared to the wild-type ones. Our results indicate that the Notch pathway is acting in two steps: (i) in a first step it inhibits the neuronal fate while promoting glial fate, (ii) in a second step Notch promotes the differentiation of astrocytes while inhibiting the differentiation of both neurons and oligodendrocytes. In parallel to this work we have tested the effects of small non peptidic molecules on the cell fate decision of neural stem cells. One of these molecules, referred to as tCFA15, increases the number of neurons at the expense of glial cells, in a manner reminiscent of that resulting from the inactivation of Notch through the Dll1 mutation. Molecular analysis has shown that tCFA15 consistently decreases the expression of Notch1 gene, and subsequently of Hes5, a downstream target gene of Notch activation. In addition, we have shown that tCFA15 causes a diminution of the tyr705 phosphorylation of STAT3, thereby suggesting a link between both Notch and STAT3 signalings. We established a functionnal hierarchy between Notch and STAT3 by experiments combining gain and loss of functions for these two pathways and we found that in the system of neurospheres STAT3 is an upstream regulator of Notch1. These results have been confirmed by molecular analysis. In parallel to this work we have also tested the neurotrophic effect of other non peptidic small molecules in the system of neurospheres
Vescovi, Christophe. "Inversion d'un modèle des cordes vocales pour un robot parlant". Grenoble INPG, 1996. http://www.theses.fr/1996INPG0214.
Texto completo da fontePoulhet, Guillaume. "Développement et applications de capteurs passifs pour la mesure in situ des émissions de composés organiques volatils dans les environnements intérieurs". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10168/document.
Texto completo da fonteIndoor atmospheres are rich in volatile organic compounds (VOC), with indoor concentrations 2 to 10 times higher than outdoor concentrations. Even though indoor pollution is a sanitary topical issue, the wide diversity of VOC sources and the lack of tools for the measurement in-situ of the emissions from materials make difficult the application of strategies of VOC concentration reduction.The main objectives of this thesis were to develop, to qualify and to use passive samplers into different type of buildings in order to demonstrate the potential of these cheap tools for (i) the measurement in-situ of VOC emissions and (ii) the evaluation of strategies of VOC concentration reduction. The first part of this work allowed the development and the qualification of three passives samplers for the measurement of the emissions of aldehydes (formaldehyde and acetaldehyde) and aromatic compounds (BTEX, styrene and 1,2,4-trimethylbenzene). Analytical performances are adequate for a in-situ application. In a second part, the deployment of these samplers in accommodations and schools allowed to show the potential and limits of these tools for emissions sources diagnosis in indoor environments
Martin, Antoine. "Circulation et transport des masses d'eau sur le plateau Est-Antarctique au large de la Terre Adélie". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066188/document.
Texto completo da fonteIn this thesis, we study the Antarctic shelf ocean dynamics using in situ observation. We study the circulation of the Modified Circumpolar Deep Water (MCDW) on the East Antarctic shelf off Adélie Land presently recognized as the second major source of AntArctic Bottom Water (AABW). The MCDW is a source of heat, salt and nutrients for the Antarctic shelf. Improved knowledge of the circulation of the MCDW and the associated heat transport on the Antarctic shelf is very important to better understand the AABW formation, the role of the oceanic ice shelf, glacier melting and the biological activity. Thanks to the inverse model implemented on the Adélie Land shelf, we propose a comprehensive scheme of the mean circulation in summer 2008 and we estimate the associated heat and freshwater transports through the shelf break and farther on the shelf toward the Mertz Glacier. We present evidences of ocean induced glacial melt involving interaction of the dense shelf water and the MCDW with the glacier. A second part of this work focuses on the variability of the current from the inertial to the seasonal time scale using mooring observations collected in the AD, we show that a strong seasonal cycle exists in the current heading and vertical structure, in agreement with earlier model results, which implies that the seasonal cycle should be properly taken into account to correctly understand shelf-ocean processes in this region
Martin, Antoine. "Circulation et transport des masses d'eau sur le plateau Est-Antarctique au large de la Terre Adélie". Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066188.pdf.
Texto completo da fonteIn this thesis, we study the Antarctic shelf ocean dynamics using in situ observation. We study the circulation of the Modified Circumpolar Deep Water (MCDW) on the East Antarctic shelf off Adélie Land presently recognized as the second major source of AntArctic Bottom Water (AABW). The MCDW is a source of heat, salt and nutrients for the Antarctic shelf. Improved knowledge of the circulation of the MCDW and the associated heat transport on the Antarctic shelf is very important to better understand the AABW formation, the role of the oceanic ice shelf, glacier melting and the biological activity. Thanks to the inverse model implemented on the Adélie Land shelf, we propose a comprehensive scheme of the mean circulation in summer 2008 and we estimate the associated heat and freshwater transports through the shelf break and farther on the shelf toward the Mertz Glacier. We present evidences of ocean induced glacial melt involving interaction of the dense shelf water and the MCDW with the glacier. A second part of this work focuses on the variability of the current from the inertial to the seasonal time scale using mooring observations collected in the AD, we show that a strong seasonal cycle exists in the current heading and vertical structure, in agreement with earlier model results, which implies that the seasonal cycle should be properly taken into account to correctly understand shelf-ocean processes in this region
Fléchon, Elsa. "Définition d'un modèle unifié pour la simulation physique adaptative avec changements topologiques". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10284/document.
Texto completo da fonteThe work made during my PhD, respond to the problematic of physical simulation of the behavior of deformable objects subject to topological changes in interactive time. My work resulted in the definition of a new unified model coupling a complete topological model and a physical model for physical simulation of deformable objects decomposed in surface as volume elements, while performing during this simulation topological changes such as cutting or subdivision local of a mesh element. This operation allowed us to propose an adaptive method where mesh elements are refined during the simulation according to a geometric criterion. For the topological model of our unified model, we made the choice of combinatorial maps and more particularly linear cellular complexes. Their main advantage of the latter is the simplicity of its equations, its intuitive implementation, its interactivity and its ease to handle topological changes. Finally, the definition of a unified model allowed us to propose a model avoiding duplication of information and facilitate the update after topological changes
Botella, Christophe. "Méthodes statistiques pour la modélisation de la distribution spatiale des espèces végétales à partir de grandes masses d’observations incertaines issues de programmes de sciences citoyennes". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS135.
Texto completo da fonteHuman botanical expertise is becoming too scarce to provide the field data needed to monitor plant biodiversity. The use of geolocated botanical observations from major citizen science projects, such as Pl@ntNet, opens interesting paths for a temporal monitoring of plant species distribution. Pl@ntNet provides automatically identified flora observations, a confidence score, and can thus be used for species distribution models (SDM). They enable to monitor the distribution of invasive or rare plants, as well as the effects of global changes on species, if we can (i) take into account identification uncertainty, (ii) correct for spatial sampling bias, and (iii) predict species abundances accurately at a fine spatial grain.First, we ask ourselves if we can estimate realistic distributions of invasive plant species on automatically identified occurrences of Pl@ntNet, and what is the effect of filtering with a confidence score threshold. Filtering improves predictions when the confidence level increases until the sample size is limiting. The predicted distributions are generally consistent with expert data, but also indicate urban areas of abundance due to ornamental cultivation and new areas of presence.Next, we studied the correction of spatial sampling bias in SDMs based on presences only. We first mathematically analyzed the bias when the occurrences of a target group of species (Target Group Background, TGB) are used as background points, and compared this bias with that of a spatially uniform selection of base points. We then show that the bias of TGB is due to the variation in the cumulative abundance of target group species in the environmental space, which is difficult to control. We can alternatively jointly model the global observation effort with the abundances of several species. We model the observation effort as a step spatial function defined on a mesh of geographical cells. The addition of massively observed species to the model then reduces the variance in the estimation of the observation effort and thus on the models of the other species.Finally, we propose a new type of SDM based on convolutional neural networks using environmental images as input variables. These models can capture complex spatial patterns of several environmental variables. We propose to share the architecture of the neural network between several species in order to extract common high-level predictors and regularize the model. Our results show that this model outperforms existing SDMs, that performance is improved by simultaneously predicting many species, and this is confirmed by two cooperative SDM evaluation campaigns conducted on independent data sets. This supports the hypothesis that there are common environmental models describing the distribution of many species.Our results support the use of Pl@ntnet occurrences for monitoring plant invasions. Joint modelling of multiple species and observation effort is a promising strategy that transforms the bias problem into a more controllable estimation variance problem. However, the effect of certain factors, such as the level of anthropization, on species abundance is difficult to separate from the effect on observation effort with occurrence data. This can be solved by additional protocolled data collection. The deep learning methods developed show good performance and could be used to deploy spatial species prediction services
Gasparin, Florent. "Caractéristiques des Masses d'Eau, Transport de masse et Variabilité de la circulation océanique en mer de Corail". Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00840821.
Texto completo da fonteGasparin, Florent. "Caractéristiques des masses d'eau, transport de masse et variabilité de la circulation océanique en mer de corail (Pacifique sud-ouest)". Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1986/.
Texto completo da fonteWaters from the South Equatorial Current, the northern branch of the South Pacific subtropical gyre, have been identified as having an important contribution to climate variability and El Niño-Southern Oscillation. Initially a broad westward current extending from 2°S to 30°S, the South Equatorial Current splits upon the major archipelagos of Fiji (18°S, 180°E), Vanuatu (16°S, 168°E), New Caledonia (22°S, 165°E) and Australian coasts resulting in two main zonal jets entering the Coral Sea: the North Caledonian Jet (18°S, 180°E) and the North Vanuatu Jet (16°S, 168°E). In this work, we focus on the oceanic circulation using hydrographic data from sea cruises and we apply two inverse methods: the "inverse box model" and the "optimal multi-parametric analysis". Then, we report interannunal variability and its impacts on the Coral Sea circulation. We first study the East Caledonian Current which runs along the east coast of New Caledonia and feeds the North Caledonian Jet. Both currents extend about 100 km horizontally, to at least 1000 m depth vertically and transport 15 Sv (1 Sv = 106 m3. S-1). In the northern part, the North Vanuatu Jet is larger (~300 km) and shallower (0-500 m) and transports around 20 Sv. A part of these waters reaches Australia and supplies the Solomon Sea via its western boundary current, the New Guinea Coastal Undercurrent estimated at 30 Sv. These structures are characterized by water mass properties. Secondly, we emphasize the thermocline and intermediate waters to depict water mass pathways and mixing. In the thermocline, the New Guinea Coastal Undercurrent is mainly supplied by North Vanuatu Jet waters at the thermocline level while in the intermediate level, waters come from the North Caledonian Jet. This complementary approach shows that intermediate waters are mainly carried by deep currents and subsurface waters by the North Vanuatu Jet. In the last part, interannual variability is analyzed on the 1993-2010 period with a 1/10° numerical simulation and a proxy method based on altimetric data. Interannual variability of the South Equatorial Current mass transport follows the El Niño-Southern Oscillation with a 3-months lag. The North Vanuatu Jet leads this variability. Controlled by winds, the South Equatorial Current variability is associated with thermocline depth modulation, which involves intensification after an El Niño event (6 ±4 Sv) and a decrease after La Niña (4 ±4 Sv). We also show that temperature and salinity anomalies are the result of thermocline depth modulation
Thiéblemont, Rémi. "Dynamique de la stratosphère au printemps et en été : étude des couplages tropiques/pôles". Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00801758.
Texto completo da fonteFeat, Justyne. "Toxicité cellulaire d’un herbicide organophosphoré, le glufosinate d’ammonium, et de son principal métabolite : Induction d’un stress oxydatif et modifications des voies de différenciation sur un modèle murin in vitro de culture primaire de cellules souches neurales". Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2035/document.
Texto completo da fonteThe glufosinate-ammonium (GLA) is an organophosphorus herbicide commonly used in agriculture. Many cases of intentional ingestions have highlighted its neurotoxicity. However, its effects on neurodevelopment are not well studied. Indeed, the brain is an important target of GLA due to its structural homology with glutamate, the main excitatory neurotransmitter of the central nervous system. Our previous data are shown that a perinatal exposure to low doses of GLA induces disturbances in neurogenesis and in neuroblasts migration from the subventricular zone to the olfactory bulbs. These changes are associated with the development of autism spectrum disorders in the offspring. My thesis is in the continuity of his work and addresses the cellular and molecular aspects involved in early exposure to GLA. Since we are continuously exposed to pesticides, but also to their metabolites, I studied in parallel the effects of the main metabolite of GLA, the 4 methylphosphinyl-2-oxo-butanoic acid (PPO).The first work of my thesis was to develop an in vitro protocol for the primary culture of neural stem cells from the subventricular zone of mice, for the analysis of the neurotoxic effects of GLA and PPO. The results of the first study of my thesis showed an induction of related oxidative stress involving the glutamatergic system, and associated with a disruption of calcium homeostasis. Since neural stem cells are sensitive to the effects of oxidative stress, in a second study, I studied the impact of these effects on the cellular differentiation mechanisms of neural stem cells. My results indicated a significant effect of exposure to GLA and PPO on the formation and maintenance of the subventricular neurogenic niche in vitro. GLA and PPO interfere with the formation of ependyma and induce a disruption in the neuroglial differentiation of neural stem cells, without influencing their growth or proliferation capacity.All these data highlight on the interest of studying the cellular and molecular mechanisms linked to the neurotoxicity of the active substances of pesticides, the metabolites of these same pesticides, but also the mixtures of active substances and metabolites to which we are continuously exposed in our environment
Hansen, Enrique carlos. "Modeling non-stationary resting-state dynamics in large-scale brain models". Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4011/document.
Texto completo da fonteThe complexity of human cognition is revealed in the spatio-temporal organization of brain dynamics. We can gain insight into this organization through the analysis of blood oxygenation-level dependent (BOLD) signals, which are obtained from functional magnetic resonance imaging (fMRI). In BOLD data we can observe statistical dependencies between brain regions. This phenomenon is known as functional connectivity (FC). Computational models are being developed to reproduce the FC of the brain. As in previous empirical studies, these models assume that FC is stationary, i.e. the mean and the covariance of the BOLD time series used for the FC are constant over time. Nevertheless, recent empirical studies focusing on the dynamics of FC at different time scales show that FC is variable in time. This feature is not reproduced in the simulated data generated by some previous computational models. Here we have enhanced the non-linearity of local dynamics in a large-scale computational model. By enhancing this non-linearity, our model is able to reproduce the variability of the FC found in empirical data
Ricci, Sophie. "Assimilation variationnelle océanique : modélisation multivariée de la matrice de covariance d'erreur d'ébauche". Toulouse 3, 2004. http://www.theses.fr/2004TOU30048.
Texto completo da fontePoulhet, Guillaume. "Développement et applications de capteurs passifs pour la mesure in situ des émissions de composés organiques volatils dans les environnements intérieurs". Electronic Thesis or Diss., Lille 1, 2014. http://www.theses.fr/2014LIL10168.
Texto completo da fonteIndoor atmospheres are rich in volatile organic compounds (VOC), with indoor concentrations 2 to 10 times higher than outdoor concentrations. Even though indoor pollution is a sanitary topical issue, the wide diversity of VOC sources and the lack of tools for the measurement in-situ of the emissions from materials make difficult the application of strategies of VOC concentration reduction.The main objectives of this thesis were to develop, to qualify and to use passive samplers into different type of buildings in order to demonstrate the potential of these cheap tools for (i) the measurement in-situ of VOC emissions and (ii) the evaluation of strategies of VOC concentration reduction. The first part of this work allowed the development and the qualification of three passives samplers for the measurement of the emissions of aldehydes (formaldehyde and acetaldehyde) and aromatic compounds (BTEX, styrene and 1,2,4-trimethylbenzene). Analytical performances are adequate for a in-situ application. In a second part, the deployment of these samplers in accommodations and schools allowed to show the potential and limits of these tools for emissions sources diagnosis in indoor environments
Lemaréchal, Jean-Didier. "Estimation des propriétés dynamiques des réseaux cérébraux à large échelle par modèles de masse neurale de potentiels évoqués cortico-corticaux Comparison of two integration methods for dynamic causal modeling of electrophysiological data. NeuroImage An atlas of neural parameters based on dynamic causal modeling of cortico-cortical evoked potentials". Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALS007.
Texto completo da fonteThis thesis work aims at modeling cortico-cortical evoked potentials (CCEPs) induced by intracortical direct electrical stimulation in epileptic patients being recorded with stereo-electroencephalography during epilepsy surgery. Neural mass models implemented within the dynamic causal modeling (DCM) framework are used for this purpose.We first demonstrate the importance of using an accurate integration scheme to solve the system of differential equations governing the global dynamics of the model, in particular to obtain precise estimates of the neuronal parameters of the model (Lemaréchal et al., 2018).In a second study, this methodology is applied to a large dataset from the F-TRACT project. The axonal conduction delays and speeds between brain regions, as well as the local synaptic time constants are estimated and their spatial mapping is obtained based on validated cortical parcellation schemes. Interestingly, the large amount of data included in this study allow to highlight brain dynamics differences between the young and the older populations (Lemaréchal et al., submitted).Finally, in the Bayesian context of DCM, we show that an atlas of connectivity can improve the specification and the estimation of a neural mass model, for electroencephalographic and magnetoencephalographic studies, by providing a priori distributions on the connectivity parameters of the model.To sum up, this work provides novel insights on dynamical properties of cortico-cortical interactions. The publication of our results in the form of an atlas of neuronal properties already provides an effective tool for a better specification of whole brain neuronal models
Mollet, Simon. "Exploration of 6-dimensional models with non trivial topology and their predictions for fermions masses and mixings, neutrino physics, flavour changing interactions and CP violation". Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/230863.
Texto completo da fonteDoctorat en Sciences
info:eu-repo/semantics/nonPublished
Mainsant, Gildas. "Réponse des masses d'eau intermédiaires et modales de l'océan Austral au mode annulaire austral : les processus en jeu et rôle de la glace de mer". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU060/document.
Texto completo da fonteRecent climate trends show a warming and freshening of the surface layers in the region of the Antarctic Circumpolar Current (ACC). Over the same period, the westerlies driving the circulation of the Southern Ocean have significantly increased. This increase is partly due to the intensification of the Southern Annular Mode (SAM), the main mode of atmospheric variability south of 20°S. In this thesis, we are interested in understanding the effects of the positive trend of the SAM onto the properties of water masses formed in the region of the ACC. To do so, we implement a strategy of regional coupled ocean-sea ice simulations forced by a series of atmospheric disturbance scenarios.These scenarios are constructed from atmospheric reanalyses in order to describe the various components (dynamic and thermodynamic) of the changes related to the SAM. In response to the increase of the SAM, the simulations show a significant salinification of the ocean mixed layer and of the mode water (SAMW) and intermediate water (AAIW).Most of these changes can be attributed to the dynamic components of the SAM. In Seasonal Ice Zone, the thermodynamic components of the SAM can play an important part (especially in Amundsen Sea and Weddell Sea). The simulations also show the key role played by sea ice in mediating atmospheric changes toward the interior ocean.These simulation results suggest that SAM is not the only driver of recent climate trends in the Southern Ocean
Jaboviste, Kévin. "Caractérisation expérimentale et modélisation de solutions amortissantes pour la réduction des transferts vibratoires et la stabilisation de systèmes embarqués". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD068/document.
Texto completo da fonteThe work carried out during this thesis deals with the study of the dynamic mechanical behavior of passive damping solutions used for the reduction of vibration levels and the stabilization of embedded optronic systems within Thales LAS France company. These solutions integrate elastomer materials with high dissipative power, whose behavior must be perfectly controlled for a good mechanical dimensioning of vibration isolation, despite their dependence on temperature and frequency. The general objective is to improve the knowledge of these material behavior, the characterization techniques, and the method taking into account this behavior in the numerical simulations in order to improve the practices used in the engineering department that design the structures hosting these systems.In this context, the work presented first focuses on the characterization, the modeling and the identification of the viscoelastic behavior of elastomers used in Thales LAS France damping devices. A Generalized Maxwell Model (GMM) is used to describe this behavior, and is introduced into a finite element model of the damper to obtain a satisfactory physical representation of its dynamic mechanical behavior. The problem is rewritten as an original state space representation that is associated with a model reduction strategy to reduce computation times. Various simulations are moreover performed to illustrate the potential of the proposed approach, such as complex modal analysis, frequency response and temporal response. Since temperature has a major influence on the mechanical behavior of elastomers, a specific thermomechanical material model is proposed by identifying the temperature evolution of GMM parameters, and a robustness analysis on the dissipation ability of the damper in the presence of a lack-of-knowledge on this variable is carried out based on the Info-Gap theory.Experimental test results showed the appearance of a softening of the structure under heavy load, suggesting the presence of non-linearities. Another aspect of this thesis deals with the characterization, the modeling and the identification of non-linear phenomena that can impact the dynamic behavior of the damper. Two sources have been highlighted: a material non-linearity related to the dependence of the mechanical characteristics of the elastomers to the rate of deformation (Payne effect), and a contact non-linearity related to the presence of mechanical stops. These behaviors were implemented in a reduced representation of the damper to explain the nonlinear phenomena observed experimentally during the damping device qualification campaigns.Finally, the last part of this thesis deals with the design of a network of tuned mass absorbers (MTMD) in order to reduce the vibratory level of a structural part supporting optical systems. After a formulation of the finite element problem, a procedure for optimizing the parameters of the MTMD is implemented and a robustness analysis of the optimal solution in the presence of uncertainties on the specific eigenfrequency to be controlled is performed. This study is carried out for different sets of parameters and a robust design optimization method is proposed by combining the optimization procedure and the Info-Gap theory. Finally, a model of the studied system is realized as well as a simplified version of its associated MTMD in order to test the tuning rules resulting from numerical studies thanks to a series of experimental tests
Faure, Xavier. "Approche formelle pour la simulation interactive de modèles mixtes". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10177/document.
Texto completo da fonteInteractive simulation of the human body is a crucial issue in medical computer sciences. There are many approaches to reach this goal. Reducing the computation time is the leitmotiv of a large number of efforts in recent years. For researches which use physical models derived from continuum mechanics for the simulation of deformable objects, it is primarily the internal forces and their derivatives which are the subject of study for improving computation time. We chose to develop the Tensor Mass Method, a physical model often used for its good computation time vs accuracy trade-off. Our first contribution is the use of computer algebra to generate the internal forces and their derivatives. Our second contribution is the parallelization of this physical model by computing the generated equations on the GPU. Our third contribution is an extension of this physical model to other elements : triangle, quandrangle , hexahedron, prism and pyramid. Considering deformations to use the most effective constitutive law in terms of computation time whenever possible is a good strategy that we started developing. In the same idea, we take the geometry of the simulated model into account to introduce more complex elements, albeit in reduced numbers. To use these strategies, we have developed mixed models in constitutive laws and elements. Our research was performed in the framework of the ETOILE project, to develop a biomechanical model of the respiratory system
Sauvage, Stéphane. "Origine et comportement des composés hydrocarbonés non méthaniques (HCMN) en zone rurale". Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10098/document.
Texto completo da fonteNon-methane hydrocarbons (HCNM) play a key role in atmosphere chemistry as precursors of secondary pollutants formation like ozone or secondary organic aerosols. This works presents the analysis of an important datas et of 46 HCNM measured in three rural sites belonging to the French network (MERA). Statistical tools are used and adapted in order to study the spatial and temporal behaviour ofthese species in rural area. The research approach combined three steps: (1) univariate and bivariate analysis to a spatial and a temporal studies of the concentrations, (2) the used of the source receptor model PMF (Positive Matrix Factorization) to identity and apport ion the source of HCNM in rural area, (3) the adaptation of the oriented receptor model CF (Concentration Fields) in order to localise the main areas which influence the studied sites. Five common profiles have been identified for the three sites: "residential heating", "vehicle exhaust"; "fuel evaporation", "biogenic", and "remote sources". The relative contributions are in good accordance with the emissions inventory data and with results of other studies. These contributions allowed distinguishing local and remote influences. The ozone formation contributions of the modelled factors show that biogenic sources trend to significantly increase while anthropogenic sources decrease. That may explain that background levels of ozone do not decrease in Europe despite the anthropogenic emission reduction. Large urban areas (South of Germany and North of Italy) have been identitied as potentially at the origin of anthropogenic NMHC measured on the three French sites
Dribek, Abderraouf. "Vers un tourisme durable en Tunisie : le cas de l'ile de Djerba". Phd thesis, Université de Bretagne occidentale - Brest, 2012. http://tel.archives-ouvertes.fr/tel-00781871.
Texto completo da fonteAnton, Aurore. "Identification et caractérisation de gènes candidats pour la découverte de nouveaux mécanismes physiopathologiques à l'origine de l'anémie de Blackfan-Diamond". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30267.
Texto completo da fonteMutations in genes encoding proteins involved in ribosome biogenesis cause specific diseases in humans, called ribosomopathies. One of these, Diamond-Blackfan Anaemia (DBA), is characterized by a significant loss of erythroid cells in the bone marrow leading to severe anaemia and in some cases other abnormalities such as cranio-facial malformations. Until now, mutations are known for about 20 genes representing about 3/4 of patients with DBA, identifying the mutated genes in the remaining cases presents a major challenge in order to improve the diagnosis of the disease and discover new therapeutic targets. The aim of my thesis was to generate DBA models in zebrafish using the CRISPR/Cas9 genome editing technique on the basis of new candidate genes recently identified by exome sequencing in French DBA patients. My results show that homozygous embryos mutant for only one of these genes develop phenotypes that begin to resemble DBA, including severe anaemia associated with general developmental defects including growth retardation, microcephaly and lack of jaw; for the other two genes homozygous mutant embryos show developmental phenotypes unrelated to the pathology. The molecular mechanisms at the origin of the symptoms observed in the patients remain to be completely understood. The literature and my results show that the current integrated models of DBA do not satifyingly reproduce the physiopathology of patients. Indeed, in zebrafish, mutants in the DBA genes develop phenotypes that are not limited to the tissues affected in human pathology. This can be explained by the fact that in humans the genes responsible for DBA are haploinsufficient, whereas in zebrafish they have a recessive Mendelian behaviour. Thus, in parallel with my work to validate new DBA genes, I have established an integrated vertebrate model based on a previously identified causal gene: TSR2 (20S rRNA maturation factor). This gene is localized on the X chromosome and the missense mutation identified in patients behaves as a recessive allele since only male patients are affected. This particularity allows this gene to be an ideal candidate to generate an animal model that best reflects the genetics of DBA patients. I generated a tsr2 mutant in which the homozygous mutant embryos develop defects observed in patients: late anaemia and jaw bone placement defects. We also observed that, as described in DBA patients, adult heterozygous fish mutant for tsr2 are predisposed to developing cancers. This model could not only be used to understand how the dysfunction of a ubiquitous process such as ribosome biogenesis leads to specific defects, but also to explain the paradox of the transition from a hypo-proliferative state with phenotypes of bone marrow failure and anaemia, to a hyper-proliferative state leading to high cancer risks later in life. In the future, this model may improve the diagnosis of patients and lead to the emergence of new therapeutic targets by offering the possibility of performing pharmacological screening for the development of new treatments
Bertosio, Cécilia. "On the evolution of the halocline in the upper Arctic Ocean since 2007". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS423.
Texto completo da fonteIn the Arctic Ocean, stratification is determined by salinity, unlike the mid-latitude oceans which are stratified by temperature. In other words, in the Arctic, salty water ends up at the bottom, even if it is warmer. The halocline of the Arctic Ocean is a 100-200m thick layer with strong vertical salinity gradients and is located between 100 and 350m depth. The halocline lies between the sea ice at the surface and the relatively warm Atlantic water. The halocline thus insulates the ice from the heat reservoir contained in the underlying Atlantic layer, and is a key element for the maintenance of the sea ice cover. During this thesis, we studied the evolution of the Arctic Ocean halocline since 2007, using several tools: hydrographic measurements obtained from autonomous drifting platforms or from sea campaigns, and high spatial resolution numerical model simulations ("PSY4")
Sauvage, Stéphane. "Origine et comportement des composés hydrocarbonés non méthaniques (HCMN) en zone rurale". Electronic Thesis or Diss., Lille 1, 2008. http://www.theses.fr/2008LIL10098.
Texto completo da fonteNon-methane hydrocarbons (HCNM) play a key role in atmosphere chemistry as precursors of secondary pollutants formation like ozone or secondary organic aerosols. This works presents the analysis of an important datas et of 46 HCNM measured in three rural sites belonging to the French network (MERA). Statistical tools are used and adapted in order to study the spatial and temporal behaviour ofthese species in rural area. The research approach combined three steps: (1) univariate and bivariate analysis to a spatial and a temporal studies of the concentrations, (2) the used of the source receptor model PMF (Positive Matrix Factorization) to identity and apport ion the source of HCNM in rural area, (3) the adaptation of the oriented receptor model CF (Concentration Fields) in order to localise the main areas which influence the studied sites. Five common profiles have been identified for the three sites: "residential heating", "vehicle exhaust"; "fuel evaporation", "biogenic", and "remote sources". The relative contributions are in good accordance with the emissions inventory data and with results of other studies. These contributions allowed distinguishing local and remote influences. The ozone formation contributions of the modelled factors show that biogenic sources trend to significantly increase while anthropogenic sources decrease. That may explain that background levels of ozone do not decrease in Europe despite the anthropogenic emission reduction. Large urban areas (South of Germany and North of Italy) have been identitied as potentially at the origin of anthropogenic NMHC measured on the three French sites
Dribek, Abderraouf. "Vers un tourisme durable en Tunisie : le cas de l'île de Djerba". Thesis, Brest, 2012. http://www.theses.fr/2012BRES0080/document.
Texto completo da fonteTourism is a significant resource for Tunisia. Its economic impacts on the country are considerable (6% of GDP and over 386 000 direct and indirect jobs in 2009). But today, the tourism sector is facing many difficulties. This thesis is part of a plan to boost tourism in Tunisia. It is structured in two parts. The first diagnosis of the Tunisian tourism sector shows that it suffers on two levels: strategic (management is left to the private sector without government intervention, which leads to low profitability of some hotels, a high debt because of the pricing practice and the family business model) and qualitative (over-reliance on the Fordist model). The thesis discusses the limitations of Fordism quantitative, and demonstrates that a new reading of the tourism market is needed to achieve sustainable economic performance. From this perspective, the implementation of economic and environmental assessments is required. In the second part on the thesis, envisions a new trajectory for a specific territory (Djerba Island), it is to think of new trajectories. The work demands the search of relevant indicators of economic and environmental quality in order to assess the best methodologies to improve the assessment of the profitability of the tourism sector. Economically, the study proposes a new method for assessing the economic impact of tourism on the island of Djerba. This method called "method of the masses", builds on the theory of growth or development. It requires the determination of direct, indirect and induced activities. The indicators measured are: Value Added (VA), Earnings Before Interests, Taxes, Depreciation and Amortization (EBITDA) and Employment (E). The results show that the most direct activities that generate wealth and jobs are hotels. For indirect activities, it is the consumption of food products, agricultural products and fisheries. These results may provide a basis upon which for policy-makers may evaluate future tourism development projects. In terms of assessing the importance of the environment, it allows the Djerbian tourism to defend its future. This evaluation will also examine the environmental dimension and provides an analysis of regulatory instruments in place in Djerba and seeks to integrate new instruments proposed by the World Tourism Organization which objective is to search for sustainable development of tourism activity to conserve the natural wealth of the island
Abdallah, Ghassan. "La convection thermique dans les milieux fracturés : modélisation avec la méthode des éléments distincts". Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL126N.
Texto completo da fonteVilain, Coriandre Emmanuel. "Contribution à la synthèse de parole par modèle physique. Application à l'étude des voix pathologiques". Phd thesis, 2002. http://tel.archives-ouvertes.fr/tel-00003358.
Texto completo da fonteRuty, Nicolas. "Modèles d'interactions fluide/parois dans le conduit vocal. Applications aux voix et aux pathologies". Phd thesis, 2007. http://tel.archives-ouvertes.fr/tel-00370316.
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