Nonlinear dynamical analysis for coupled fluid-structure systems

International audienceThe present research concerns the numerical dynamical analysis in elasto-acoustics, taking into account the geometrical non-linearities induced by the large displacements/deformations of the structure and assuming the internal acoustic fluid occupying an internal cavity coupled to the structure to remain in a linear range of vibration. More particularly, the modeling includes sloshing and capillarity effects on the free surface. A numerical application is presented

Une procédure de cartographie automatique: UNISAS

Un nouveau logiciel de cartographie automatique, UNISAS, combinant les avantages des logiciels SAS et UNIRAS, a été développé à la Maison de la Géographie

Epidemiological situation of Lyme borreliosis in Belgium, 2003 to 2012.

BACKGROUND: Some studies show that the incidence of Lyme borreliosis is increasing in different European countries. In order to evaluate if this is also the case in Belgium, different data sources were consulted to describe the epidemiology of Lyme borreliosis in the country during the last decade. METHODS: Data from two databases were analyzed for the time period 2003-2010 and 2003-2012 for respectively: the registration of minimal clinical data from Belgian hospitals (principal and secondary diagnosis), and a sentinel laboratory network reporting positive laboratory results. RESULTS: The number of hospitalized cases per year remained stable between 2003 and 2010, ranging from 970 (in 2008) to 1453 (in 2006), with a median of 1132.5 cases per year. Between 2003 and 2012, yearly fluctuations in the number of positive tests were reported by the sentinel laboratory network (with a minimum of 996 positive tests in 2007 and a maximum of 1651 positive tests in 2005), but there is no increasing trend over the study period (median = 1200.5 positive tests per year). The highest incidence rates of hospitalization and the highest reported incidence of positive laboratory results are registered in the provinces of Luxemburg, Limburg, Flemish Brabant and Antwerp, with a typical seasonal pattern (peak in September). The age groups affected most are those from 5 to 14 years and 45 to 69. CONCLUSION: Based on hospital records and laboratory results, no increasing trend in Lyme disease was observed over the 2003-2012 period in Belgium. These results are in line with the stable incidence of erythema migrans reported by a sentinel network of general practitionners between 2003 and 2009. Multi-source surveillance of vector-borne diseases should be further implemented

Pediatric Pneumococcal Serotypes in 4 European Countries

TOC Summary: Non–heptavalent pneumococcal conjugate vaccine serotypes have increased in Spain, France, Belgium, and England and Wales

Nonlinear geometric analysis of a mistuned bladed disk

This paper deals with the dynamical analysis and uncertainty quantification of a mistuned industrial rotating integrally bladed disk, for which the operating regime under consideration takes into account the nonlinear geometric effects induced by large displacements and deformations. First, a dedicated mean nonlinear reduced-order model of the tuned structure is explicitly constructed using three-dimensional solid finite elements. The random nature of the mistuning is then modeled by using the onparametric probabilistic approach extended to the nonlinear geometric context. Such a computational strategy provides an efficient tool, which is applied to a computational model of an industrial centrifugal compressor with a large number of degrees of freedom. This allows for putting in evidence some new complex dynamical behaviors

Seroepidemiology of Dengue Virus in Mayotte, Indian Ocean, 2006

BACKGROUND: Although Dengue virus (DENV) circulation had been documented in neighbouring South-western Indian Ocean Islands, its presence in Mayotte is poorly characterised. To address this issue, we aimed to assess the seroprevalence of dengue IgG antibodies (DENV-IgG Ab) among the population and to investigate potential associations with individual and household characteristics. METHODS/PRINCIPAL FINDINGS: In November-December 2006 we conducted a cross-sectional serologic survey in Mayotte among 1,154 inhabitants aged≥2 years by using a multistage cluster random sampling method. The overall prevalence of DENV-specific IgG antibodies (ELISA) was 22.73% (95% CI, 18.16-27.31). The age-specific seroprevalence increased with age (χ2 for trend=11.86, P<0.0006), and was linked with previous known outbreaks in this region. In multivariate analysis, older age, being born in the Comoros and living in a household with a low socioeconomic index were positively associated with DENV IgG antibody positivity. CONCLUSIONS: These findings document substantial prior exposure of the population of Mayotte to DENV and highlight the risk of severe illness due to the possibility of sequential DENV infections. Further investigations characterizing current DENV circulation patterns and associated serotypes are needed

Analyse d'une expérimentation exhibant une instabilité dans un liquide avec un modèle réduit non linéaire fluide-structure

National audienceCet article propose de revisiter et d’expliquer, au travers d’un modèle réduit numérique fluide-structure, une observation expérimentale d’un phénomène de résonance de la surface libre d’un liquide dans un réservoir cylindrique. Le système expérimental a été simulé par un modèle numérique du cylindre élastique en présence de non-linéarités géométriques, partiellement rempli d’un liquide acoustique prenant en compte les effets de ballottement. Les résultats obtenus montrent qu’une excitation inattendue de grande amplitude des modes de ballottement a lieu lorsque la structure est excitée sur certaines de ses résonances

Properties of water confined in hydroxyapatite nanopores as derived from molecular dynamics simulations

Bone tissue is characterized by nanopores inside the collagen-apatite matrix where fluid can exist and flow. The description of the fluid flow within the bone has however mostly relied on a macroscopic continuum mechanical treatment of the system, and, for this reason, the role of these nanopores has been largely overlooked. However, neglecting the nanoscopic behaviour of fluid within the bone volume could result in large errors in the overall description of the dynamics of fluid. In this work, we have investigated the nanoscopic origin of fluid motion by conducting atomistic molecular dynamics simulations of water confined between two parallel surfaces of hydroxyapatite (HAP), which is the main mineral phase of mammalian bone. The polarizable core–shell interatomic potential model used in this work to simulate the HAP–water system has been extensively assessed with respect to ab initio calculations and experimental data. The structural (pair distribution functions), dynamical (self-diffusion coefficients) and transport (shear viscosity coefficients) properties of confined water have been computed as a function of the size of the nanopore and the temperature of the system. Analysis of the results shows that the dynamical and transport properties of water are significantly affected by the confinement, which is explained in terms of the layering of water on the surface of HAP as a consequence of the molecular interactions between the water molecules and the calcium and phosphate ions at the surface. Using molecular dynamics simulations, we have also computed the slip length of water on the surface of HAP, the value of which has never been reported before