Monitoring the orientation of rare-earth-doped nanorods for flow shear tomography

Rare-earth phosphors exhibit unique luminescence polarization features originating from the anisotropic symmetry of the emitter ion's chemical environment. However, to take advantage of this peculiar property, it is necessary to control and measure the ensemble orientation of the host particles with a high degree of precision. Here, we show a methodology to obtain the photoluminescence polarization of Eu-doped LaPO4 nano rods assembled in an electrically modulated liquid-crystalline phase. We measure Eu3+ emission spectra for the three main optimal configurations ({\sigma}, {\pi} and {\alpha}, depending on the direction of observation and the polarization axes) and use them as a reference for the nano rod orientation analysis. Based on the fact that flowing nano rods tend to orient along the shear strain profile, we use this orientation analysis to measure the local shear rate in a flowing liquid. The potential of this approach is then demonstrated through tomographic imaging of the shear rate distribution in a microfluidic system.Comment: 8 pages, 3 figures + supplementary files for experimental and numerical method

Des étoiles de très faibles masses aux planètes: contraintes des modèles d'évolution par analyse combinée de vitesses radiales et d'imagerie à haut contraste

Formation and evolution of stars and substellar objects (brown dwarfs and planets) are described by theoretical models. Observers can use these models to determine several parameters of an object taken observables. However, these models still need to be properly tested and calibrated with observations. The purpose of this thesis is to bring some constrain to stellar and substellar formation and evolutionary models. I combined the high contrast imaging and radial-velocity methods to study substellar objects at wide separation and stellar systems of very low mass stars. This combination of techniques allow to determine the dynamical masses of the objects inside a system. Thanks to the high contrast imaging, photons coming directly from the objects can be collected which allowed me to characterize the atmosphere of substellar objects with a spectral analyze. These informations allow to put some constrain to evolutionary models of substellar objects

Effective crisis management requires close monitoring of public reactions. The case of international travelers from South-Eastern France

International audienc

Would we recover better sleep at the end of Covid-19 ? A relative improvement observed at the population level with the end of the lockdown in France

Background: The outbreak of the Covid-19 pandemic and the accompanying lockdown measures have had a major impact on societies around the world, leading to sleep problems for a large part of the population. In order to assess the sustainability of sleeping troubles related to the sanitary crisis, it was crucial to measure its prevalence after the end of the Covid-19 confinement. Methods: As part of an epidemiological survey on Covid and Confinement (COCONEL), we enquired on sleep disorders using two items in 4 repetitive cross-sectional surveys. The first took place during the first week of the French confinement (March 31 to April 2; N = 1005 participants). The second took place in the middle of this period (April 15-17; N = 1005). The two last surveys were held at the end of the confinement (May 7-10; N = 2003) and one month after the end (June 10-12; N = 1736). Using a random constant, the mixed model took into account the longitudinal character of the last two waves (intra-individual correlations for individuals surveyed in waves 3 and 4). Results: The prevalence of sleep problems significantly decreased during the last weeks of the confinement, and this trend was confirmed one month after the end of confinement. One quarter of the population reported that their sleep was better one month after the end of the confinement. Sleep improvement was reported more often by women and people aged less than 65. Such improvement was less frequent among those who were still highly exposed to the pandemic's media coverage after the end of the confinement. Conclusion: The possibility of recovering a good sleep largely depends on the type of sleep disorder. The decrease in sleep problems occurred mainly among people with mild sleep problems during the confinement. Further research is needed to assess the long-term effects of the Covid-19 pandemic and its confinement period on sleep quality in the general population

L’hésitation vaccinale en France: Prévalence et variation selon le statut socio-économique des parents

International audienceNo abstract availabl

Determinants of childhood immunizations in Senegal : adding previous shots to sociodemographic background

Introduction. Today, in Sub-Saharan Africa, vaccine-preventable diseases still contribute heavily to high child mortality. Maintaining high coverage rates for childhood vaccines and reducing related social inequalities are public health priorities in Senegal. Our aim was to investigate the determinants of childhood vaccination, including sociodemographic factors and previous vaccine-related decision-making. Methods. Data come from the 2016 Senegalese Demographic and Health Survey, a nationally representative household survey targeting women aged 15?49, with a questionnaire focusing on health and reproductive issues, including their children?s health. We restricted the analysis to children aged 12?23?months (n?=?1,143). We used bivariate and multivariate analyses for investigating the determinants of several childhood vaccinations (Bacillus Calmette-Gu?rin, pentavalent, polio, measles and yellow fever vaccines), including sociodemographic factors and previous shots. Results. We identified two main sociodemographic predictors of childhood vaccination in Senegal: the mother?s education level, which was strongly and positively correlated to every vaccination considered, except from the BCG vaccination, and the region of residence, with higher vaccination coverage rates in the Centre and West of Senegal. Moreover, previous shots were also strongly predictive of subsequent shots. Conclusion. The positive impact of mother?s education on child vaccination illustrates the wide-ranging benefits of educating girls, while the regional variability of immunization rates requires more research to be better understood. Previous shots are probably a proxy variable for unobservable factors strongly correlated to vaccinations, but beyond this ?proxy effect?, they may also have their own specific effect on following shots. We believe this topic deserves further research

Determinants of childhood immunizations in Senegal: Adding previous shots to sociodemographic background

International audienc

Risk perceptions of infectious diseases at the Grand Magal of Touba. A pilot study in two senegalese villages

International audienc