Vue de l'évolution centrée sur les gènes

Résumé

vignette|Richard Dawkins La vue de l'évolution centrée sur les gènes, théorie de la sélection par les gènes ou du gène égoïste (en) est une conséquence de la théorie de l’évolution par sélection naturelle de Charles Darwin. Elle s’appuie sur le résultat de différentes recherches visant à expliquer l’apparition de traits altruistes chez les êtres vivants. Les contributeurs à ces recherches sont J. B. S. Haldane qui a étudié l’altruisme dans les populations, des biologistes de l’évolution et des sociobiologistes comme Robert Trivers. Le pionnier en matière de recherche sur l'altruisme animal est W. D. Hamilton, qui a effectué une mathématisation de la théorie de la sélection de parentèle, vulgarisée ensuite par E. Wilson. Le biologiste et éthologue Richard Dawkins reprendra ces différentes théories dans son ouvrage Le Gène égoïste. Le livre Le Gène égoïste Le Gène égoïste est un ouvrage de R. Dawkins publié en 1976, destiné selon lui à trois catégories de personnes : le

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Multiview video has recently emerged as a means to improve user experience in novel multimedia services. We propose a new stochastic model to characterize the traffic generated by a Multiview Video Coding (MVC) variable bit-rate source. To this aim, we resort to a Poisson hidden Markov model (P-HMM), in which the first (hidden) layer represents the evolution of the video activity and the second layer represents the frame sizes of the multiple encoded views. We propose a method for estimating the model parameters in long MVC sequences. We then present extensive numerical simulations assessing the model's ability to produce traffic with realistic characteristics for a general class of MVC sequences. We then extend our framework to network applications where we show that our model is able to accurately describe the sender and receiver buffers behavior in MVC transmission. Finally, we derive a model of user behavior for interactive view selection, which, in conjunction with our traffic model, is able to accurately predict actual network load in interactive multiview services.

2015

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Drosophila melanogaster is one of the most important genetic models and techniques such as reverse transcription quantitative real-time PCR (RT-qPCR) are being employed extensively for deciphering the genetics basis of physiological functions. In RT-qPCR, the expression levels of target genes are estimated on the basis of endogenous controls. The purpose of these reference genes is to control for variations in RNA quantity and quality. Although determination of suitable reference genes is essential to RT-qPCR studies, reports on the evaluation of reference genes in D. melanogaster studies are lacking. We analyzed the expression levels of seven candidate reference genes (Actin, EF1, Mnf, Rps20, Rpl32, Tubulin and 18S) in flies that were injured, heat-stressed, or fed different diets. Statistical analyses of variation were determined using three established software programs for reference gene selection, geNorm, NormFinder and BestKeeper. Best-ranked references genes differed across the treatments. Normalization candidacy of the selected candidate reference genes was supported by an analysis of gene expression values obtained from microarray datasets available online. The differences between the experimental treatments suggest that assessing the stability of reference gene expression patterns, determining candidates and testing their suitability is required for each experimental investigation. © 2011.

Elsevier2011

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Augmented reality, interactive navigation in 3D scenes, multiview video, and other emerging multimedia applications require large sets of images, hence larger data volumes and increased resources compared with traditional video services. The significant increase in the number of images in multiview systems leads to new challenging problems in data representation and data transmission to provide high quality of experience on resource-constrained environments. In order to reduce the size of the data, different multiview video compression strategies have been proposed recently. Most of them use the concept of reference or key views that are used to estimate other images when there is high correlation in the data set. In such coding schemes, the two following questions become fundamental: 1) how many reference views have to be chosen for keeping a good reconstruction quality under coding cost constraints? And 2) where to place these key views in the multiview data set? As these questions are largely overlooked in the literature, we study the reference view selection problem and propose an algorithm for the optimal selection of reference views in multiview coding systems. Based on a novel metric that measures the similarity between the views, we formulate an optimization problem for the positioning of the reference views, such that both the distortion of the view reconstruction and the coding rate cost are minimized. We solve this new problem with a shortest path algorithm that determines both the optimal number of reference views and their positions in the image set. We experimentally validate our solution in a practical multiview distributed coding system and in the standardized 3D-HEVC multiview coding scheme. We show that considering the 3D scene geometry in the reference view, positioning problem brings significant rate-distortion improvements and outperforms the traditional coding strategy that simply selects key frames based on the distance between cameras.

Institute of Electrical and Electronics Engineers2016

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Institute of Electrical and Electronics Engineers2016