Quand des sociologues rencontrent des informaticiens : essai de formalisation, méta-modélisation, modélisation et simulation des systèmes d’action concrets

Le texte résulte d’une collaboration inédite entre sociologues et informaticiens. Il présente un travail de formalisation de la sociologie de l’action organisée qui a abouti à l’élaboration d’un méta-modèle de cette théorie. Ce méta-modèle permet de modéliser des systèmes d’action concrets et de simuler leur fonctionnement. A travers l’exposition des résultats théoriques et leur application à un cas simple, nous souhaitons montrer que cette démarche présente un intérêt théorique et méthodologique pour la sociologie. Elle permet de préciser des concepts sociologiques initialement exprimés en langage naturel afin de pouvoir les évaluer de manière quantitative. Elle rend possible la simulation de situations organisationnelles et ouvre ainsi la voie à une exploration des états possibles d’un système d’action concret. Ces éléments constituent, à nos yeux, un enrichissement de la pratique sociologique.The text results from a new collaboration between sociologists and data processing specialists. It presents a work of formalization of the sociology of organized action which led to the development of a meta-model of this theory. This meta-model makes it possible to model concrete systems of action and to simulate their operation. Through the exposure of the theoretical results and their application to a simple case, we wish to show that this step is of theoretical and methodological interest for sociology. It makes it possible to specify sociological concepts initially expressed in natural language in order to be able to evaluate them in a quantitative way. It makes possible the simulation of organisational situations and thus opens the way with an exploration of the possible states of a concrete system of action. These elements constitute, from our point of view, an enrichment of the sociological practice

Optimized Adaptive Streaming Representations based on System Dynamics

Adaptive streaming addresses the increasing and heterogenous demand of multimedia content over the Internet by offering several encoded versions for each video sequence. Each version (or representation) has a different resolution and bit rate, aimed at a specific set of users, like TV or mobile phone clients. While most existing works on adaptive streaming deal with effective playout-control strategies at the client side, we take in this paper a providers' perspective and propose solutions to improve user satisfaction by optimizing the encoding rates of the video sequences. We formulate an integer linear program that maximizes users' average satisfaction, taking into account the network dynamics, the video content information, and the user population characteristics. The solution of the optimization is a set of encoding parameters that permit to create different streams to robustly satisfy users' requests over time. We simulate multiple adaptive streaming sessions characterized by realistic network connections models, where the proposed solution outperforms commonly used vendor recommendations, in terms of user satisfaction but also in terms of fairness and outage probability. The simulation results further show that video content information as well as network constraints and users' statistics play a crucial role in selecting proper encoding parameters to provide fairness a mong users and to reduce network resource usage. We finally propose a few practical guidelines that can be used to choose the encoding parameters based on the user base characteristics, the network capacity and the type of video content

Expression et fonction du récepteur antigénique B membranaire sur les plasmocytes médullaires producteurs d'IgM

Plasma cells (PC) represent the terminal differentiation stage of B lymphocytes. Their canonical function is to secrete antibodies (Abs). PC differentiation is driven by remodeling of the B cell transcriptional program, highlighted by the induction of the transcriptional repressor Blimp-1 and repression of Pax5, considered as the guardian of B cell identity. The dogma holds that PC, as opposed to B cells, have lost the Ag recognition capacity because they have switched from expression of a membrane-bound Ag receptor (mBCR) to production of the secreted form of the BCR (Abs). Here, we have compared the phenotypical and functional attributes of memory PC generated by the T cell-dependent (TD) and T-cell independent (TI) forms of the hapten NP. Our data show that TI NP-specific bone marrow (BM) PC generated by NP-dextran retain an Ag-binding capacity comparable to that of B cells long after immunization while TD NP-specific BM PC do not. We found that this difference is not imputable to the structure of the immunogen but is a specific feature of IgM-expressing PC, which are prominent in response to TI Ag. Upon Ag recognition in vitro, the mBCR of IgM+ BM PC promotes: i) Ca++ mobilization, ii) phosphorylation of Syk and Blnk, iii) Ag internalization and phosphorylation of the late endosomal kinase Erk. Finally, we demonstrate that Ag recall in vivo induces significant changes in the gene expression profile of NP-specific IgM+ BM PC with evidence for activation of a cytokine production program characterized in particular by up-regulation of the CCL5 and IL10 transcripts. In conclusion, our data show that IgM-expressing BM PC can sense Ag and may be driven to express a regulatory function upon Ag recallLe plasmocyte (PC), stade terminal de la différenciation du lymphocyte B induite par l'antigène, est la cellule effectrice de l'immunité humorale responsable de la production des anticorps. La population plasmocytaire se divise en deux grands sous-types différant par leur durée de vie et par leur localisation anatomique. On distingue ainsi les PC à durée de vie courte ou PC effecteurs (dans les tissus lymphoïdes secondaires) et les PC à longue durée de vi (LLPC ou PC à mémoire) localisés principalement dans la moelle osseuse. Ces derniers contribuent à la mémoire humorale en continuant à sécréter des anticorps protecteurs après résolution de l'infection. Nos résultats expérimentaux montrent que les Ags thymo-dépendants (TD) et les Ag thymo-indépendants (TI) induisent des PC médullaires exprimant des caractéristiques phénotypiques et fonctionnelles différentes. Ainsi, l'expression d'une forme membranaire fonctionnelle du récepteur antigénique (BCR) persiste sur les LLPC TI alors qu'elle est perdue sur les LLPC TD. Cette fonctionnalité nouvelle portée par les PC médullaires TI n'est pas dépendante de la sous population lymphocytaire B recrutée ni de la nature de l'Ag, mais de l'isotype IgM. Nos résultats montrent également que cette population de PC médullaires a les caractéristiques des LLPC : ces PC sont quiescents, ils demeurent dans la moelle osseuse jusqu'à 180 jours et sont phénotypiquement semblables aux LLPC. Nos travaux ont permis de montrer que les LLPC à IgM sont capables de reconnaître l'Ag et que l'engagement de leur BCR par l'Ag conduit à la production d'IL1

Resolution enhancement of input parameters in a demand side management model

©2010 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.International audienceDemand side management (DSM) and distributed generation (DG) introduce into power systems new dynamics and behaviors which must be taken into account in the planning and operation of the system. This paper presents a model that aims to simulate the spread out effects of DSM actions in a region. This model is suitable designed to represent the territorial or local specificities of each studied area where the DSM actions apply. The model involves a large number of input data. The main question is what should be the optimal level of detail this data has to be collected in terms of spatial resolution so that meaningful results are obtained. The paper presents a method to define the input data which are critical to collect with a higher spatial resolution. Results for a case study in France are presented