54 research outputs found
Algorithme exact pour le problème de l'indépendant faiblement connexe de cardinalité minimum.
International audienceLa gestion des communications radios entre des capteurs sans fil dépend de la topologie mise en place sur le réseau. Généralement, on utilise des architectures basées sur des objets combinatoires issus de la théorie des graphes comme les arbres, les ensembles dominants connexes ou faiblement connexes. Dans cet exposé, nous étudions la structure alternative d'indépendant faiblement connexe (\emph{weakly connected independent set} ou ) et précisons ses propriétés. Nous décrivons une heuristique qui permet de trouver un rapidement dans un graphe des communications connexe, ainsi qu'un algorithme d'énumération pour la recherche d'un de cardinalité minimum. Nous donnons enfin des résultats d'expérimentations numériques
The k-edge connected subgraph problem: Valid inequalities and Branch-and-Cut
International audienceIn this paper we consider the k-edge connected subgraph problem from a polyhedral point of view. We introduce further classes of valid inequalities for the associated polytope, and describe sufficient conditions for these inequalities to be facet defining. We also devise separation routines for these inequalities, and discuss some reduction operations that can be used in a preprocessing phase for the separation. Using these results, we develop a Branch-and-Cut algorithm and present some computational results
Physiological Epidermal Growth Factor Concentrations Activate High Affinity Receptors to Elicit Calcium Oscillations
International audienceSignaling mediated by the epidermal growth factor (EGF) is crucial in tissue development, homeostasis and tumorigenesis. EGF is mitogenic at picomolar concentrations and is known to bind its receptor on high affinity binding sites depending of the oligomerization state of the receptor (monomer or dimer). In spite of these observations, the cellular response induced by EGF has been mainly characterized for nanomolar concentrations of the growth factor, and a clear definition of the cellular response to circulating (picomolar) concentrations is still lacking. We investigated Ca 2+ signaling, an early event in EGF responses, in response to picomolar doses in COS-7 cells where the monomer/dimer equilibrium is unaltered by the synthesis of exogenous EGFR. Using the fluo5F Ca 2+ indicator, we found that picomolar concentrations of EGF induced in 50% of the cells a robust oscillatory Ca 2+ signal quantitatively similar to the Ca 2+ signal induced by nanomolar concentrations. However, responses to nanomolar and picomolar concentrations differed in their underlying mechanisms as the picomolar EGF response involved essentially plasma membrane Ca 2+ channels that are not activated by internal Ca 2+ store depletion, while the nanomolar EGF response involved internal Ca 2+ release. Moreover, while the picomolar EGF response was modulated by charybdotoxin-sensitive K + channels, the nanomolar response was insensitive to the blockade of these ion channels
Methodes de decomposition et d'agregation pour le traitement de problemes de multiflots
Half integer extreme points in the linear relaxation of the 2-edge-connected subgraph polyhedron
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Composition of graphs and the polytope of weakly connected independent sets
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The weakly connected independent set polytope in corona and join of graphs
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Parallel annealing by partitioning of configurations: an application to optimal 3D triangulation
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A new polyhedral approach for the minimum energy symmetric network connectivity problem
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