Commande par platitude. Equations différentielles ordinaires et aux dérivées partielles

DEACommande par platitude. Equations différentielles ordinaires et aux dérivées partielle

Codage par compétition des vecteurs mouvements : que doit-on vraiment transmettre ?

Le standard de compression vidéo H.264/AVC obtient des gains significatifs par rapport à ses prédécesseurs en diminuant fortement l’entropie des résiduels de texture à l’aide, notamment, d’une augmentation du nombre de possibilités de codage. Les travaux pour une future norme ont déjà commencé au sein de chacun des deux groupes à l’origine de la norme H.264/AVC. La méthode de codage de l’information de mouvement par compétition de prédiction de vecteurs a été proposée dans le cadre des travaux exploratoires du groupe VCEG. Cette méthode visant à réduire la quantité d’information de mouvement a été intégrée dans le logiciel JM-KTA visant à préparer le nouveau standard. Dans cet article, une amélioration de cette méthode est proposée, permettant de limiter le débit des indices de prédicteurs. Elle est basée sur les caractéristiques de la fonction de sélection du meilleur prédicteur qui est reproduite au décodeur. Cette méthode, testée dans le JM-KTA, élimine 10 % des indices de prédicteurs et réduit ainsi le débit de l’information de mouvement.The H.264/AVC video coding standard obtains significative compression gains compared to its predecessors. These gains come from a reduction of the texture residual entropy by, notably, increasing the amount of coding possibilities. The work for the future standard have already started in both groups that normalized H.264/AVC. The competition based scheme for motion vectors prediction has been proposed for the exploratory work of VCEG. This scheme dedicated to the reduction of the motion information was also integrated in the JM-KTA software. In this paper, an improvement of the motion vector competition scheme is proposed to reduce the bitrate of the predictors indexes. This scheme is based on the properties of the best predictors selection function which is used at the decoder side. This scheme, tested in the JM-KTA, removes 10% of the predictor indexes and thus reduces the bitrate dedicated to the motion information

A mathematical model of the cell cycle and its control

Projet SOSSOWe consider mathematical models for the cell cycle, i.e. the sequence of events that leads to mitosis, at the level of a population of cells. These are structured population Partial Differential Equations that describe the evolution of the population along each phase of the cycle and the transition to the next phase. These models allow several types of controls such as therapeutic control in case of cancer therapy (some chemotherapies are known to act on specific phases of the cycle or on the transitions between phases) or circadian control by the central nervous system (in the suprachiasmatic nuclei). We study the long time behaviour of this system of PDEs using an entropy method and exhibit, by numerical simulations, the action of the circadian control

A multi-scale epidemic model of Salmonella infection with heterogeneous shedding∗

Salmonella strains colonize the digestive tract of farm livestock, such as chickens or pigs, without affecting them, and potentially infect food products, representing a threat for human health ranging from food poisoning to typhoid fever. It has been shown that the ability to excrete the pathogen in the environment and contaminate other animals is variable. This heterogeneity in pathogen carriage and shedding results from interactions between the host’s immune response, the pathogen and the commensal intestinal microbiota. In this paper we propose a novel generic multiscale modeling framework of heterogeneous pathogen transmission in an animal population. At the intra-host level, the model describes the interaction between the commensal microbiota, the pathogen and the inflammatory response. Random fluctuations in the ecological dynamics of the individual microbiota and transmission at between-host scale are added to obtain a drift-diffusion PDE model of the pathogen distribution at the population level. The model is further extended to represent transmission between several populations. The asymptotic behavior as well as the impact of control strategies including cleaning and antimicrobial administration are investigated through numerical simulation

Challenges in microbial ecology: building predictive understanding of community function and dynamics.

The importance of microbial communities (MCs) cannot be overstated. MCs underpin the biogeochemical cycles of the earth's soil, oceans and the atmosphere, and perform ecosystem functions that impact plants, animals and humans. Yet our ability to predict and manage the function of these highly complex, dynamically changing communities is limited. Building predictive models that link MC composition to function is a key emerging challenge in microbial ecology. Here, we argue that addressing this challenge requires close coordination of experimental data collection and method development with mathematical model building. We discuss specific examples where model-experiment integration has already resulted in important insights into MC function and structure. We also highlight key research questions that still demand better integration of experiments and models. We argue that such integration is needed to achieve significant progress in our understanding of MC dynamics and function, and we make specific practical suggestions as to how this could be achieved

Metagenomic data analysis and integration in a functional population model of fiber degradation by the human intestinal microbiota

International audienceThe human intestinal microbiota is a complex microbial ecosystem that plays a crucial role in several aspects of human health. It is particularly involved in the metabolism of residual fibers, through anaerobic digestion, thus providing significant energy (Short Chain Fatty Acids, simple sugars) and vitamins to the host. Whole Genome Sequencing (WGS) data from metagenomic analyses give an insight of the content in terms of genes of an entire microbial community, even if the organisms that compose it cannot be cultivated. In addition to the potential of conventional molecular inventory techniques (such as targeting ADNr16s), which allows an analysis of diversity, WGS approaches provide an access to the functions. We show how these data can be used to analyse the structure of carbohydrates degradation-related functions. We show how the information obtained can be integrated in a high level mechanistic in silico model of the microbiota carbohydrate trophic chain

Host microbiota interactions and barrier effect: some examples of modeling and data analysis for the gut microbiota

International audienc

A model coupling microbial physiology, spatial heterogeneity and fluid mechanics to investigate factors impacting the microbiota spatial organization in the human colon.

International audienc

Interactions hôte microbiote et dynamique écologique du microbiote intestinal humain et animal: quelques exemple de modélisation et d’analyse de données.

International audienc