Interplay between Polymer Chain Conformation and Nanoparticles Assembly in Model Industrial Silica/Rubber Nanocomposites

International audienceThe question of the influence of nanoparticles (NP) on chain dimensions in polymer nanocomposites(PNC) has been treated mainly through the fundamental way using theoretical or simulation tools andexperiments on well-defined model PNC. Here we present the first experimental study about theinfluence of NP on the polymer chain conformation for PNC designed to be as close as possible toindustrial systems employed in tire industry. PNC are silica nanoparticles dispersed into a Styrene-Butadiene-Rubber (SBR) matrix whose NP dispersion can be managed by NP loading with interfacialcoating or coupling additives usually employed in the manufacturing mixing process. We associatedspecific chain (d) labeling, and the so-called Zero Average Contrast (ZAC) method, with SANS, in-situSANS and SAXS/TEM experiments to extract the polymer chain scattering signal at rest for non-crosslinked and under stretching for cross-linked PNCs. NP loading, individual clusters or connectednetwork, as well as the influence of the type, the quantity of interfacial agent and the influence of theelongation rate have been evaluated on the chain conformation and on its related deformation. Weclearly distinguish the situations where the silica is perfectly matched from the unperfected matching bydirect comparison of SANS and SAXS structure factor. Whatever the silica matching situation, theadditive type and quantity and the filler content, there is no thus significant change in the polymerdimension for NP loading up to 15% v/v within a range of 5%. One can see an extra scatteringcontribution at low Q, as often encountered, enhanced for non-perfect silica matching but also visiblefor perfect filler matching. This contribution can be qualitatively attributed to specific h or d chainsadsorption onto the NP surface inside the NP cluster that modifying the average scattering neutroncontrast of the silica cluster. Under elongation, NP act as additional cross-linking junction preventingchain relaxation giving a deformation of the chain with NP closer to theoretical phantom networkprediction than for pure matrix

Detection of the amoeba Entamoeba gingivalis in periodontal pockets

Periodontitis is a public health issue, being one of the most prevalent diseases worldwide. However, the aetiology of the disease is still unclear: genetics of patients cannot explain the dispersed or isolated localisation of gingival pockets, while bacteria-based models are insufficient to distinguish gingivitis and periodontitis. The possible role of parasites in the establishment of periodontitis has been poorly studied until now. The aim of this project was to study a potential link between colonisation of gingival crevices by the amoeba Entamoeba gingivalis and periodontitis. In eight different dental clinics in France, samples were taken in periodontal pockets (72) or healthy sites (33), and submitted to microscopic observation and molecular identification by PCR with a new set of primers designed to specifically detect E. gingivalis. This blind sample analysis showed the strong sensitivity of PCR compared with clinical diagnosis (58/72 = 81%), and microscopy (51/65 = 78%). The results of this work show that the parasites detected by microscopy mainly – if not exclusively – belong to the species E. gingivalis and that the presence of the parasite is correlated with periodontitis

Detection of the amoeba

Periodontitis is a public health issue, being one of the most prevalent diseases worldwide. However, the aetiology of the disease is still unclear: genetics of patients cannot explain the dispersed or isolated localisation of gingival pockets, while bacteria-based models are insufficient to distinguish gingivitis and periodontitis. The possible role of parasites in the establishment of periodontitis has been poorly studied until now. The aim of this project was to study a potential link between colonisation of gingival crevices by the amoeba Entamoeba gingivalis and periodontitis. In eight different dental clinics in France, samples were taken in periodontal pockets (72) or healthy sites (33), and submitted to microscopic observation and molecular identification by PCR with a new set of primers designed to specifically detect E. gingivalis. This blind sample analysis showed the strong sensitivity of PCR compared with clinical diagnosis (58/72 = 81%), and microscopy (51/65 = 78%). The results of this work show that the parasites detected by microscopy mainly – if not exclusively – belong to the species E. gingivalis and that the presence of the parasite is correlated with periodontitis

PHARAO : le premier étalon primaire de fréquence, à atomes froids, spatial

International audienc

PHARAO flight model : Integration and "on ground" performances tests

International audiencePHARAO (Projet d'Horloge Atomique par Refroidissement d'Atomes en Orbite), which is being developed by the French space agency CNES, is the first primary frequency standard specially designed for operation in space. PHARAO is the main instrument of the ESA mission ACES (Atomic Clock Ensemble in Space) [1]. ACES payload will be installed on-board the International Space Station to perform fundamental physics experiments. Last year [2], some results on two flight model (FM) sub-systems have been presented: Microwave Source performances and Cesium Tube operating as a cold atom clock by using the other engineering model sub-systems. All the FM sub-systems have now passed the qualification process and the whole FM of the cold cesium clock, PHARAO, has been assembled and will undergo extensive tests during the first semester of 2014. The results on the cold atoms manipulation and the metrological evaluation are presented