Contribution à la modélisation cinématique et dynamique d'un geste sportif :\ud le pas de patineur

Le mouvement du pas de patineur est utilisé en skating, pratique moderne du ski de fond. Il\ud résulte de l'association d'un geste technique et d'une évolution technologique. Le geste étudié :\ud le décalé, est une des techniques qui correspond à une poussée latérale alternative des jambes\ud associée à une poussée décalée des bras. Pour rendre compte de sa complexité gestuelle et\ud pouvoir l'analyser au niveau mécanique, notre but est de construire un modèle dynamique en\ud trois dimensions. Ce modèle est réalisé grâce au logiciel de biomécanique LifeModeler,\ud module intégré du logiciel ADAMS. Outil de modélisation et de simulation cinématique et\ud dynamique, il permet de modéliser le corps humain comme un robot anthropomorphe.\ud La première étape consiste à construire un modèle humain, reproduisant la technique du\ud décalé sur un sol dur. Pour valider ce modèle, nous analysons finement la cinématique en la\ud comparant aux données recueillies dans la littérature.\ud Dans un second temps, le modèle est équipé. Les paramètres de contact sont élaborés de\ud manière à rendre l’effet d’un sol enneigé.\ud Nous procédons à une simulation dynamique inverse puis directe. La simulation inverse rend\ud assez bien compte de la réalité d’un point de vue cinématique, l’ordre de grandeur des forces\ud de contact est bon. Pour la simulation dynamique directe nous utilisons l’ensemble des\ud muscles disponibles dans le logiciel. Le modèle est stable, mais tous les problèmes n’ont pu\ud être réglés notamment au niveau de la préhension des bâtons.\ud Ce travail permet de montrer la méthodologie de modélisation d’un skieur équipé de bâtons et\ud de skis souples. Le modèle permet d’accéder aux efforts musculaires lors d'un cycle de décalé.---------------------------------------------------------------------------------The skating movement is used in the modern practical of cross-country skiing. It results from\ud the association of a technical motion and a technological development. The technical motion\ud studied is the offset. It is one of the techniques, it corresponds to an alternative lateral thrust of\ud the legs associated with a push shifted with the arms. To give an account of its gestural\ud complexity and to be able to analyze it at the mechanical level, our goal is to build a threedimensional\ud dynamic model. This model is carried out thanks to the biomechanics software\ud LifeModeler, plug in of ADAMS software. Dynamic simulation and numerical model tool,\ud LifeModeler makes it possible to model the human body like an anthropomorphic robot.\ud The first stage consists in building a human model, reproducing the movements of the offset\ud on a hard ground. To validate this model, we finely analyze kinematics by comparing it with\ud the data collected in a thesis.\ud In the second time, the model is equipped. We elaborate the contact parameters so as to\ud simulate the effect of a snow-covered ground.\ud We carry out an inverse dynamic simulation then a forward dynamic simulation.\ud The inverse simulation gives rather well an account of the reality from a kinematic point of\ud view, the order of magnitude contact forces is good. For forward dynamic simulation we use\ud the whole of the muscles available in the software. The stability of the model is correct, but\ud not all the problems could be regulated particularly the gripping of the poles.\ud This work makes possible to show the modelling method of a cross-country skier equipped\ud with poles and flexible skis. The model gives access to the skier muscular efforts

Nanocrystalline apatites: From powders to biomaterials

Non-stoichiometric nanocrystalline apatite powders are used to elaborate highly-bioactive biomaterials. Their exceptional surface reactivity arises from a structured but rather unstable hydrated layer involving ions in nonapatitic chemical environments, like in bone mineral. The initial powder characteristics can be tailored through precipitation parameters (pH, temperature, maturation time in solution). The drying of nanocrystalline apatite suspensions at very low temperature (4 °C) leads to ceramic-like materials exhibiting average mechanical properties (compressive strength 54 MPa) and a high porosity which could be exploited to entrap active organic compounds (e.g. growth factors). The consolidation at 150–200 °C of nanocrystalline apatite powders has also been studied using uni-axial pressing and spark plasma sintering (SPS). The results indicate only a limited alteration of the initial nanocrystals, and the bioceramics obtained show mechanical properties close to those reached with sintered stoichiometric HA. The high ion mobility in the hydrated layer of the nanocrystals can lead to “crystal fusion” processes. This capability to favor crystal–crystal interactions at low temperature, while preserving the non-stoichiometry and nanometer dimensions of apatite crystals, opens interesting perspectives for the elaboration of new resorbable and highly-bioactive bioceramics

Télétravail à domicile et nouveaux rapports au travail

Le travail à domicile est une organisation ancienne. Il se décline dans une série d’activités salariées ou indépendantes, réalisées pour partie ou en totalité dans l’espace domestique. Le télétravail à domicile, basé sur l’utilisation de l’informatique et des technologies de l’information et de la communication, en représente un aspect moderne. Il redéfinit les frontières spatio-temporelles qui ont fortement structuré le monde du travail. Obligeant souvent à une forte implication, valorisé pour la liberté et la créativité, questionnant la séparation des sphères professionnelle et privée, le télétravail à domicile, lorsqu’il est pratiqué par des populations qualifiées et amatrices d’autonomie, peut être considéré comme emblématique des transformations contemporaines du rapport au travail et du rapport à l’emploi. Cette thématique mêle des enjeux transversaux et nous interroge sur l’évolution des modes de vie, sur de nouvelles figures de l’autorité et sur de nouvelles formes de recherche du bonheur au travail.Home work is an old type of organization. It corresponds to many activities which are salaried or independent and which are realized partially or entirely in domestic space. Home telework, using ICT, represents a modern form of home work. It changes space-time frontiers which have traditionally characterized work organization. It can require a strong implication, it can bring freedom and creativity, it questions the frontiers between work and non work: home telework, concerning qualified people who want autonomy, can be regarded as a symbol of contemporary transformations of work and employment. Theses themes question us about new ways of life, about the evolution of authority, and about happiness in working life

Use of nicotine substitute prescribed at hourly plus ab libitum intake or ad libitum for heavy smokers willing to quit: a randomized controlled trial

OBJECTIVE: To assess the impact of instructional guidance in the regular use of use nicotine nasal spray (NNS) on the true use of NNS during the first three weeks of smoking cessation for heavy smokers who are willing to quit. METHODS: This randomized, open, controlled trial included 50 patients who were heavy smokers, were willing to quit, and attending an academic outpatient clinic in Western Switzerland. Patients were randomised to instruction on NNS use as "ad libitum" (administration whenever cravings appear; control group) or to use NNS when craving appears and at least every hour when awake (intervention group). Intakes were monitored using an electronic device fixed in the spray unit (MDILog) during the first three weeks of use. Self reported abstinence from smoking at six months was confirmed by expired-air carbon monoxide. Using intention-to-treat analysis, random-effect GLS regression was used to calculate the mean difference of daily doses between groups controlling for lack of independence between measures from the same individual. RESULTS: One patient was lost to follow-up. At baseline randomization, the group receiving instruction to use NNS hourly included more women, patients with previous desires to quit, and patients with more psychiatric comorbidities and less somatic complaints compared to the group instructed to use NNS with cravings (group imbalance). Both groups self-administered more than the daily recommended dosage of 8 uses. Mean daily usage was 13.6 dose/day and 11.1 dose/day for the group instructed to use NNS hourly and with cravings, respectively. Adjusting for baseline imbalance, the increased daily doses in the intervention group (hourly use) remained nonsignificant compared to ad libitum use (-0.5 dose/day; CI 95% -6.2; 5.3, from day 1 to day 7; and 2.3 dose/day; CI 95% -5.4; 10.0, from day 8 to day 21). Instructing patients to use the NNS daily had no effect on smoking cessation at six months (RR = 0.69; CI 95% 0.34; 1.39). CONCLUSION: Heavy smokers willing to quit use NNS frequently, regardless of the instructions given. Recommending the use of NNS only when craving appears for heavy smokers willing to quit seems acceptable compared to prescribing hourly administration. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00861276

Hepatitis C Virus Is a Weak Inducer of Interferon Alpha in Plasmacytoid Dendritic Cells in Comparison with Influenza and Human Herpesvirus Type-1

Plasmacytoid dendritic cells (pDCs) are responsible for the production of type I IFN during viral infection. Viral elimination by IFN-α-based therapy in more than 50% of patients chronically infected with hepatitis C virus (HCV) suggests a possible impairment of production of endogenous IFN-α by pDCs in infected individuals. In this study, we investigated the impact of HCV on pDC function. We show that exposure of pDCs to patient serum- and cell culture-derived HCV resulted in production of IFN-α by pDCs isolated from some donors, although this production was significantly lower than that induced by influenza and human herpesvirus type 1 (HHV-1). Using specific inhibitors we demonstrate that endocytosis and endosomal acidification were required for IFN-α production by pDCs in response to cell culture-derived HCV. HCV and noninfectious HCV-like particles inhibited pDC-associated production of IFN-α stimulated with Toll-like receptor 9 (TLR9) agonists (CpG-A or HHV-1) but not that of IFN-α stimulated with TLR7 agonists (resiquimod or influenza virus). The blockade of TLR9-mediated production of IFN-α, effective only when pDCs were exposed to virus prior to or shortly after CpG-A stimulation, was already detectable at the IFN-α transcription level 2 h after stimulation with CpG-A and correlated with down-regulation of the transcription factor IRF7 expression and of TLR9 expression. In conclusion, rapidly and early occurring particle–host cell protein interaction during particle internalization and endocytosis followed by blockade of TLR9 function could result in less efficient sensing of HCV RNA by TLR7, with impaired production of IFN-α. This finding is important for our understanding of HCV-DC interaction and immunopathogenesis of HCV infection

Excess mortality related to the August 2003 heat wave in France.

Objectives: From August 1st to 20th, 2003, the mean maximum temperature in France exceeded the seasonal norm by 11-12 degrees C on nine consecutive days. A major increase in mortality was then observed, which main epidemiological features are described herein. Methods: The number of deaths observed from August to November 2003 in France was compared to those expected on the basis of the mortality rates observed from 2000 to 2002 and the 2003 population estimates. Results: From August 1st to 20th, 2003, 15,000 excess deaths were observed. From 35 years age, the excess mortality was marked and increased with age. It was 15% higher in women than in men of comparable age as of age 45 years. Excess mortality at home and in retirement institutions was greater than that in hospitals. The mortality of widowed, single and divorced subjects was greater than that of married people. Deaths directly related to heat, heatstroke, hyperthermia and dehydration increased massively. Cardiovascular diseases, ill-defined morbid disorders, respiratory diseases and nervous system diseases also markedly contributed to the excess mortality. The geographic variations in mortality showed a clear age-dependent relationship with the number of very hot days. No harvesting effect was observed. Conclusions: Heat waves must be considered as a threat to European populations living in climates that are currently temperate. While the elderly and people living alone are particularly vulnerable to heat waves, no segment of the population may be considered protected from the risks associated with heat waves