748 research outputs found
Minimax representation of nonexpansive functions and application to zero-sum recursive games
We show that a real-valued function on a topological vector space is
positively homogeneous of degree one and nonexpansive with respect to a weak
Minkowski norm if and only if it can be written as a minimax of linear forms
that are nonexpansive with respect to the same norm. We derive a representation
of monotone, additively and positively homogeneous functions on
spaces and on , which extend results of Kolokoltsov, Rubinov,
Singer, and others. We apply this representation to nonconvex risk measures and
to zero-sum games. We derive in particular results of representation and
polyhedral approximation for the class of Shapley operators arising from games
without instantaneous payments (Everett's recursive games)
Hypergraph conditions for the solvability of the ergodic equation for zero-sum games
The ergodic equation is a basic tool in the study of mean-payoff stochastic
games. Its solvability entails that the mean payoff is independent of the
initial state. Moreover, optimal stationary strategies are readily obtained
from its solution. In this paper, we give a general sufficient condition for
the solvability of the ergodic equation, for a game with finite state space but
arbitrary action spaces. This condition involves a pair of directed hypergraphs
depending only on the ``growth at infinity'' of the Shapley operator of the
game. This refines a recent result of the authors which only applied to games
with bounded payments, as well as earlier nonlinear fixed point results for
order preserving maps, involving graph conditions.Comment: 6 pages, 1 figure, to appear in Proc. 54th IEEE Conference on
Decision and Control (CDC 2015
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Exploring the latitude of attitude: Intentions to breastfeed among adolescents in Lebanese schools.
School-based breastfeeding education (SBBE) may help improve breastfeeding rates in the long-term by targeting children and adolescents' knowledge, attitudes, skills, and intentions. Breastfeeding rates in Lebanon are suboptimal. Psychosocial drivers of breastfeeding intention among the youth are unknown. We administered a survey to 658 high school students (448 females; 210 males) at two large Lebanese schools to understand intentions, intention drivers, and views on SBBE as means to guide SBBE programme design on the basis of the theory of planned behaviour. We collected information on demographics, intention to breastfeed/support wife to breastfeed future. Intention was predicted by attitude related to breastfeeding health outcomes and family normative beliefs-χ2 (25) = 115, P < .001 for males, and χ2 (39.3) = 186, P < .001 for females. Among females, intention was also positively associated with being breastfed, higher socio-economic status, and being more accepting of public breastfeeding. Seventy-eight per cent of students felt they were not learning enough about breastfeeding in school but were interested in SBBE through didactic teaching methods and interactive experiences. Findings indicate that breastfeeding intention among adolescent students is not merely influenced by the extent of knowledge but by more complicated psychosocial drivers that may differ by gender. Our findings also suggest a misalignment exists between what schools are providing with what students feel they need, thereby opening up a potential space for intervention
Mapping the energy and diffusion landscapes of membrane proteins at the cell surface using high-density single-molecule imaging and Bayesian inference: application to the multi-scale dynamics of glycine receptors in the neuronal membrane
Protein mobility is conventionally analyzed in terms of an effective
diffusion. Yet, this description often fails to properly distinguish and
evaluate the physical parameters (such as the membrane friction) and the
biochemical interactions governing the motion. Here, we present a method
combining high-density single-molecule imaging and statistical inference to
separately map the diffusion and energy landscapes of membrane proteins across
the cell surface at ~100 nm resolution (with acquisition of a few minutes).
When applying these analytical tools to glycine neurotransmitter receptors
(GlyRs) at inhibitory synapses, we find that gephyrin scaffolds act as shallow
energy traps (~3 kBT) for GlyRs, with a depth modulated by the biochemical
properties of the receptor-gephyrin interaction loop. In turn, the inferred
maps can be used to simulate the dynamics of proteins in the membrane, from the
level of individual receptors to that of the population, and thereby, to model
the stochastic fluctuations of physiological parameters (such as the number of
receptors at synapses). Overall, our approach provides a powerful and
comprehensive framework with which to analyze biochemical interactions in
living cells and to decipher the multi-scale dynamics of biomolecules in
complex cellular environments.Comment: 23 pages, 4 figure
Regards sur les quartiers parisiens. Contextes spatiaux, usages politiques et pratiques citadines
Rapport de rechercheLe débat scientifique que suscite le quartier est aujourd'hui à la hauteur de l'engouement dont il bénéficie dans la société. En effet, alors que les scientifiques se sont emparés du quartier, se demandant notamment si ces espaces continus de la proximité ont encore un sens, le local fait un retour en force dans le débat public. Face à la crise supposée d'une urbanité éclatée, beaucoup d'acteurs métropolitains tentent de peser sur les pratiques citadines, de redéfinir des espaces locaux de vie quotidienne, des espaces d'ancrage et d'identification commune. C'est cet enjeu territorial essentiel qui est placé au cœur de l'étude. Combinant plusieurs approches de l'échelon local à Paris, cette dernière s'appuie à la fois sur des analyses de données (logements, structures socio-démographiques, activités commerciales), sur une enquête par questionnaires, ainsi que sur de nombreux entretiens (habitants, commerçants, élus et techniciens, etc.) et sur une pratique assidue du terrain. Ce faisant, elle permet d'approfondir la connaissance de l'espace parisien à une échelle fine, tout en proposant une critique de la notion de quartier et de ses usages dans un contexte métropolitain
Entre banalité et exotisme, le panel individuel des destinations touristiques
International audienceThe globalization of the tourism expresses at the same time by the emergence of new markets and the dilation of the tourist space. Numerous questioning remain on the way this second process is embodied in the individual practices. How are articulated close and distant movements? What are the relations between spatial pattern of the tourist mobilities and profile of the mobile persons? The analysis proposed aims at lighting these questions by exploiting the data of a survey from ANR-Merev on the temporary mobilities realized in 2008-2009, with more than 1800 persons living in Berlin, Brussels, London or Paris. In this way, it confronts two contrasted visions of the spatial pattern of tourist practices, the one advancing the segmentation of the practices of mobility according to the personalities, the other one suggesting a generalized hybridization of these practices. The obtained results show that within mobile populations, the spatial pattern of the destinations remains very segmented, according to the socioeconomic characteristics of the individuals.La mondialisation du tourisme s'exprime à la fois par l'émergence de nouveaux foyers émetteurs et la dilatation de l'oekoumène touristique. De nombreuses interrogations subsistent sur la manière dont ce second processus s'incarne dans les pratiques individuelles. Comment s'articulent déplacements proches et lointains ? Quelles sont les relations entre canevas spatiaux des mobilités touristiques et profil des personnes mobiles ? L'analyse proposée vise à éclairer ces questions en exploitant les données d'une enquête de l'ANR-Merev sur les mobilités temporaires, réalisée en 2008-2009 auprès de plus de 1800 personnes résidant à Berlin, Bruxelles, Londres ou Paris. Dans cette optique, elle confronte deux visions contrastées du rapport à l'altérité, l'une mettant en avant la segmentation des pratiques de mobilité selon les personnalités, l'autre suggérant une hybridation généralisée de ces pratiques. Les résultats obtenus montrent qu'au sein même de populations mobiles, le canevas spatial des destinations reste très segmenté, selon les caractéristiques socio-économiques et socio-professionnelles des individus
Présentation : Aspects de comme
Ce numéro, intitulé « Aspects de comme », est issu de travaux menés dans le cadre du projet Gram-m. L’objectif initial de ce groupe de recherche fut double. Ce fut, d’une part, d’établir un état des connaissances sur comme afin d’obtenir une vue globale de ce terme si labile, en confrontant à la fois différentes études descriptives existantes, et en produisant un certain nombre d’études originales visant à éclairer des aspects moins bien repérés dans la littérature. D’autre part, l’originalit..
Présentation : Aspects de comme
Ce numéro, intitulé « Aspects de comme », est issu de travaux menés dans le cadre du projet Gram-m. L’objectif initial de ce groupe de recherche fut double. Ce fut, d’une part, d’établir un état des connaissances sur comme afin d’obtenir une vue globale de ce terme si labile, en confrontant à la fois différentes études descriptives existantes, et en produisant un certain nombre d’études originales visant à éclairer des aspects moins bien repérés dans la littérature. D’autre part, l’originalit..
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