945 research outputs found
Fisher-information condition for enhanced signal detection via stochastic resonance
Various situations where a signal is enhanced by noise through stochastic resonance are now known. This paper contributes to determining general conditions under which improvement by noise can be a priori decided as feasible or not. We focus on the detection of a known signal in additive white noise. Under the assumptions of a weak signal and a sufficiently large sample size, it is proved, with an inequality based on the Fisher information, that improvement by adding noise is never possible, generically, in these conditions. However, under less restrictive conditions, an example of signal detection is shown with favorable action of adding noise.Fabing Duan, François Chapeau-Blondeau, Derek Abbot
Rho-ROCK and Rac-PAK signaling pathways have opposing effects on the cell-to-cell spread of Marek's Disease Virus.
Marek's Disease Virus (MDV) is an avian alpha-herpesvirus that only spreads from cell-to-cell in cell culture. While its cell-to-cell spread has been shown to be dependent on actin filament dynamics, the mechanisms regulating this spread remain largely unknown. Using a recombinant BAC20 virus expressing an EGFPVP22 tegument protein, we found that the actin cytoskeleton arrangements and cell-cell contacts differ in the center and periphery of MDV infection plaques, with cells in the latter areas showing stress fibers and rare cellular projections. Using specific inhibitors and activators, we determined that Rho-ROCK pathway, known to regulate stress fiber formation, and Rac-PAK, known to promote lamellipodia formation and destabilize stress fibers, had strong contrasting effects on MDV cell-to-cell spread in primary chicken embryo skin cells (CESCs). Inhibition of Rho and its ROCKs effectors led to reduced plaque sizes whereas inhibition of Rac or its group I-PAKs effectors had the adverse effect. Importantly, we observed that the shape of MDV plaques is related to the semi-ordered arrangement of the elongated cells, at the monolayer level in the vicinity of the plaques. Inhibition of Rho-ROCK signaling also resulted in a perturbation of the cell arrangement and a rounding of plaques. These opposing effects of Rho and Rac pathways in MDV cell-to-cell spread were validated for two parental MDV recombinant viruses with different ex vivo spread efficiencies. Finally, we demonstrated that Rho/Rac pathways have opposing effects on the accumulation of N-cadherin at cell-cell contact regions between CESCs, and defined these contacts as adherens junctions. Considering the importance of adherens junctions in HSV-1 cell-to-cell spread in some cell types, this result makes of adherens junctions maintenance one potential and attractive hypothesis to explain the Rho/Rac effects on MDV cell-to-cell spread. Our study provides the first evidence that MDV cell-to-cell spread is regulated by Rho/Rac signaling
Computer-Assisted Generation of Patterns and Virtual Reality Techniques for Fashion Design
We present a methodology for the design of aesthetic patterns and their visualization on virtual clothes. Generated patterns are directly mapped on the dress of a virtual mannequin. Furthermore, patterns sets may be interactively mapped on the virtual dress using a specific 3D interaction technique called Back-and-Forth. Pattern generation involves different mathematical approaches such as iterated function systems (IFS) and nonlinear trajectory models. Both model parameters and color space exploration is performed through a simple user interface. This work contributes to promote both computer assistance in the context of mass customization for fashion design
ElonCam : SystÚme de vision pour mesurer la croissance des plantules en phase hétérotrophe
SystÚme de vision pour mesurer la croissance des plantules en phase hétérotrophe
ElonCam : instrumentation et analyse d'images pour le suivi automatisé individualisé du développement de semences et de plantules
Le systĂšme ElonCam est en cours de dĂ©veloppement dans le cadre d\u27une collaboration entre le LARIS, le GEVES-SNES et l\u27INRA d\u27Angers - IRHS. Il sâagit dâun systĂšme de vision, constituĂ© dâun systĂšme dâacquisition dâimages pilotĂ© par ordinateur, et dâun logiciel de traitement et d\u27analyse d\u27images couleur RVB, qui permet de rĂ©aliser des mesures automatisĂ©es sur les semences et les plantules au cours de leur dĂ©veloppement. Le systĂšme dâacquisition peut incorporer diffĂ©rentes modalitĂ©s d\u27imagerie, et il est actuellement employĂ© en imagerie visible (voir Fig. 1). L\u27acquisition des images est effectuĂ©e en lumiĂšre verte inactinique (censĂ©e simuler l\u27obscuritĂ© et ne pas influencer le dĂ©veloppement des plantules). Afin de minimiser l\u27apport d\u27Ă©nergie lumineuse l\u27Ă©clairage intermittent est synchronisĂ© avec la prise de vue. Les graines sont semĂ©es dans une boĂźte de PĂ©tri contenant de la gĂ©lose (milieu de culture transparent) placĂ©e Ă la verticale afin de respecter le gĂ©otropisme. Le logiciel de traitement d\u27images dĂ©tecte, isole, labellise puis mesure les semences et les plantules. L\u27analyse numĂ©rique des images permet d\u27aboutir Ă la mesure individuelle automatisĂ©e des semences au cours de la germination puis des plantules et de leurs organes d\u27intĂ©rĂȘt en fonction du temps, selon les conditions de la croissance. Afin de gĂ©rer les croisements de plantules, un algorithme de suivi de structures arborescentes a Ă©tĂ© dĂ©veloppĂ©. Le systĂšme de vision vise Ă contribuer au phĂ©notypage automatisĂ© haut-dĂ©bit des semences et plantules, afin de tester la capacitĂ© Ă germer et la vitesse de croissance pour diffĂ©rentes espĂšces et diffĂ©rents gĂ©notypes, et en vue d\u27amĂ©liorer leurs propriĂ©tĂ©s et rendement. Le systĂšme a Ă©tĂ© testĂ© pour la caractĂ©risation de diffĂ©rentes espĂšces comme Medicago truncatula, colza, blĂ©, tournesol, et Ă©galement la betterave dans le cadre du programme ANR Investissements d\u27Avenir AKER oĂč les coauteurs sont impliquĂ©s et qui concerne l\u27amĂ©lioration de la betterave sucriĂšre pour laquelle la France est l\u27un des premiers producteurs mondiaux. Ce travail a bĂ©nĂ©ficiĂ© d\u27une aide de l\u27Ătat gĂ©rĂ©e par l\u27Agence Nationale de la Recherche au titre du programme "Investissements d\u27Avenir" portant la rĂ©fĂ©rence ANR-11-BTBR-0007 (programme AKER)
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NonâLinear Thresholds Characterize the Relationship Between Reef Fishes and Mangrove Habitat
A significant obstacle to evaluating the importance of mangrove habitat to coral reef fishes has been the difficulty of disentangling its effects from other subtidal/nearshore habitats or human population pressures. Florida\u27s seascape, unlike most others, has been extensively surveyed and mapped, and there are reliable estimates of human population density. Despite many studies that have correlated reef fish abundance with nearby mangrove habitat, some researchers continue to question the importance of mangroves to reef fishes. Previous studies that have investigated the mangroveâreef fish subsidy effect have applied methods that either compared averages or examined linear relationships; yet there is a body of literature that indicates that the effects of habitat are characterized by thresholds and limiting functions. Here, we employed a generalized additive model to investigate whether species richness of 106 mangroveâassociated reef fishes is related to thresholds in the extent of nearby mangrove forests along the Florida Keys Reef Tract. In addition, we used linear discriminant analyses (LDAs) to examine the relationships between the occurrence of 77 reef fish species and extent of Florida mangrove forests. We found that after accounting for confounding factors, at scales \u3c20 km2, species richness declines with decreasing mangrove extent, whereas richness increases with increasing mangrove extent at scales \u3e80 km2. Results of our LDA suggested that at least 49 reef fish species (64% of focal species) were associated with higher nearby mangrove forest extent. Our results indicate that of all habitat attributes considered, mangroves played the most substantial role in the diversity of nearby reef fish populations. These apparent thresholds (i.e., nonâlinearities) in the extent of mangrove forests should be incorporated into fisheries critical habitat management and emphasize the need to consider nonâlinear relationships between fishes and their habitat
Différentes modalités d'imagerie (visible, thermographie, hyperspectrale) pour le phénotypage des semences et plantules
Différentes modalités d\u27imagerie (visible, thermographie, hyperspectrale) pour le phénotypage des semences et plantules
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