Contrôle de l'équilibre des humains virtuels

Ce chapitre aborde le problème de l'analyse de l'équilibre et de la synthèse par la ommande de la coordination des mouvements d'humains virtuels pour la simulation réaliste d'activités physiques quotidiennes ou professionnelles. nous discutons dans un premier temps les notions d'équilibre postural et de stabilité de cet équilibre dans le cadre particulier des mannequins numériques. Nous introduisons un modèle mécanique pour des mannequins en interaction physique avec l'environnement. À partir d'une formulation générale du problème de l'équilibre, nous examinons un certain nombre de moyens proposés pour caractériser et quantifier la stabilité de l'équilibre des systèmes mécaniques contraints. Nous introduisons la notion de perturbation admissible pour la dynamique posturale vis-à-vis des contraintes de persistance et de non-glissement des appuis. Enfin, nous proposons des techniques de synthèse par la commande de fonctions motrices pour une coordination de l'ensemble du système postural et de manipulation satisfaisant explicitement les contraintes d'équilibre des appuis

Qu’est-ce que le vivant ? Matières inanimées, avez-vous donc une âme ?

Depuis toujours, l’homme cherche à définir, explorer et utiliser le vivant, cette chose, cette substance, cette force vitale… En réalité, la vie n’est pas une entité mais une somme de processus complexes, dépendants de l’organisation de la matière. Dans cette contribution, nous effeuillons d’abord les visions de différentes civilisations anciennes concernant cette question. Une confrontation de ces représentations issues du passé avec les approches scientifiques actuelles est ensuite présentée. Une discussion autour d’une vision actuelle du vivant et la présentation de résultats préliminaires expérimentaux, obtenus au sein du laboratoire, terminent ce texte.Historically, men have sought to define, explore and use life, this thing, this substance, this strength… In fact, life is not an entity but an addition of complex processes, which depends on the organization of the matter at the molecular level. In this contribution, we first present several descriptions and representations of life coming from old civilizations. These ancient descriptions are compared with current scientific approaches. A discussion about a current representation of the living and some preliminary experimental results obtained in the laboratory, complete the text

Efficiency of dispersive wave generation in dual concentric core microstructured fiber

We describe the generation of powerful dispersive waves that are observed when pumping a dual concentric core microstructured fiber by means of a sub-nanosecond laser emitting at the wavelength of~1064 nm. The presence of three zeros in the dispersion curve, their spectral separation from the pump wavelength, and the complex dynamics of solitons originated by the pump pulse break-up, all contribute to boost the amplitude of the dispersive wave on the long-wavelength side of the pump. The measured conversion efficiency towards the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of the output spectra is completed by the acquisition of the time delays of the different spectral components. Numerical simulations and an analytical perturbative analysis identify the central wavelength of the red-shifted pump solitons and the dispersion profile of the fiber as the key parameters for determining the efficiency of the dispersive wave generation process.Comment: 11 pages, 12 figure

Visible supercontinuum generation controlled by intermodal four-wave mixing in micro-structured fibre

International audienceWe present an experimental and numerical study of supercontinuum generation extended in the visible part of the spectrum by using a selective optical coupling of the pump wave in the largely anomalous dispersion regime. The broadband frequency generation is induced by an initial four-wave mixing process that converts the pump wave at 1064 nm into 831 nm anti-Stokes and 1478 nm Stokes wavelengths. Phase matching is ensured on such a large frequency shift thanks to a microstructured multimodal fiber with a specific design. Continuum generation is therefore enhanced around the two generated sideband

A functional model of tree growth and tree architecture.

A new approach for modelling plant growth using the software AMAPpara is presented. This software takes into consideration knowledge about plant architecture which has been accumulated at the Plant Modelling Unit of CIRAD for several years, and introduces physiological concepts in order to simulate the dynamic functioning of trees. The plant is considered as a serial connection of vegetative organs which conduct water from the roots to the leaves. Another simple description of the plant as a network of parallel pipes is also presented which allows an analytical formulation of growth to be written. This recurring formula is used for very simple architectures and is useful to understand the role of each organ in water transport and assimilate production. Growth simulations are presented which show the influence of modifications in architecture on plant development

Efficacy and safety of enoxaparin versus unfractionated heparin during percutaneous coronary intervention: systematic review and meta-analysis

Objective To determine the efficacy and safety of enoxaparin compared with unfractionated heparin during percutaneous coronary intervention

A Note on Encodings of Phylogenetic Networks of Bounded Level

Driven by the need for better models that allow one to shed light into the question how life's diversity has evolved, phylogenetic networks have now joined phylogenetic trees in the center of phylogenetics research. Like phylogenetic trees, such networks canonically induce collections of phylogenetic trees, clusters, and triplets, respectively. Thus it is not surprising that many network approaches aim to reconstruct a phylogenetic network from such collections. Related to the well-studied perfect phylogeny problem, the following question is of fundamental importance in this context: When does one of the above collections encode (i.e. uniquely describe) the network that induces it? In this note, we present a complete answer to this question for the special case of a level-1 (phylogenetic) network by characterizing those level-1 networks for which an encoding in terms of one (or equivalently all) of the above collections exists. Given that this type of network forms the first layer of the rich hierarchy of level-k networks, k a non-negative integer, it is natural to wonder whether our arguments could be extended to members of that hierarchy for higher values for k. By giving examples, we show that this is not the case

Effects of passive smoking on heart rate variability, heart rate and blood pressure: an observational study

Background Exposure to environmental tobacco smoke (ETS) has been shown to increase the risk for cardiovascular diseases and death, and autonomic dysfunction (specifically, reduced heart rate variability (HRV)) is a predictor of increased cardiac risk. This study tests the hypothesis that ETS exposure reduces HRV in the general population and discusses possible pathways. Methods This cross-sectional study was conducted between 2001 and 2003 and is part of the SAPALDIA (Swiss Cohort Study on Air Pollution and Lung Diseases in Adults) study. The analysis included 1218 randomly selected non-smokers aged 50 and above who participated in 24-h electrocardiogram recordings. Other examinations included an interview, investigating health status (especially respiratory and cardiovascular health and health relevant behaviours and exposure to ETS) and measurements of blood pressure, body height and weight. Results Subjects exposed to ETS at home or at work for more than 2 h/day had a difference of −15% in total power (95%CI: −26 to −3%), low frequency power (−28 to −1%), low/high frequency ratio (−26 to −3%) and −18% (−29 to −4%) in ultralow frequency power of HRV compared with subjects not exposed to ETS at home or work. We also found a 2.7% (−0.01 to 5.34%) higher heart rate during the recording in exposed subjects. Conclusions Exposure to ETS at home and work is associated with lower HRV and with higher heart rate in an ageing population. Our findings suggest that exposure to ETS increases cardiac risk through disturbances in the autonomic nervous syste

The tumoral A genotype of the MGMT rs34180180 single-nucleotide polymorphism in aggressive gliomas is associated with shorter patients' survival

Malignant gliomas are the most common primary brain tumors. Grade III and IV gliomas harboring wild-type IDH1/2 are the most aggressive. In addition to surgery and radiotherapy, concomitant and adjuvant chemotherapy with temozolomide (TMZ) significantly improves overall survival (OS). The methylation status of the O-6-methylguanine-DNA methyltransferase (MGMT) promoter is predictive of TMZ response and a prognostic marker of cancer outcome. However, the promoter regions the methylation of which correlates best with survival in aggressive glioma and whether the promoter methylation status predictive value could be refined or improved by other MGMT-associated molecular markers are not precisely known. In a cohort of 87 malignant gliomas treated with radiotherapy and TMZ-based chemotherapy, we retrospectively determined the MGMT promoter methylation status, genotyped single nucleotide polymorphisms (SNPs) in the promoter region and quantified MGMT mRNA expression level. Each of these variables was correlated with each other and with the patients' OS. We found that methylation of the CpG sites within MGMT exon 1 best correlated with OS and MGMT expression levels, and confirmed MGMT methylation as a stronger independent prognostic factor compared to MGMT transcription levels. Our main finding is that the presence of only the A allele at the rs34180180 SNP in the tumor was significantly associated with shorter OS, independently of the MGMT methylation status. In conclusion, in the clinic, rs34180180 SNP genotyping could improve the prognostic value of the MGMT promoter methylation assay in patients with aggressive glioma treated with TMZ.ARC -Fondation ARC pour la Recherche sur le Cancer(EML20120904843