Intervertebral disc characterization by shear wave elastography: an in-vitro preliminary study

Patient-specific numerical simulation of the spine is a useful tool both in clinic and research. While geometrical personalization of the spine is no more an issue, thanks to recent technological advances, non-invasive personalization of soft tissue’s mechanical properties remains a challenge. Ultrasound elastography is a relatively recent measurement technique allowing the evaluation of soft tissue’s elastic modulus through the measurement of shear wave speed (SWS). The aim of this study was to determine the feasibility of elastographic measurements in intervertebral disc (IVD). An in-vitro approach was chosen to test the hypothesis that SWS can be used to evaluate IVD mechanical properties and to assess measurement repeatability. Eleven oxtail IVDs were tested in compression to determine their stiffness and apparent elastic modulus at rest and at 400 N. Elastographic measurements were performed in these two conditions and compared to these mechanical parameters. The protocol was repeated six times to determine elastographic measurement repeatability. Average SWS over all samples was 5.3 ± 1.0 m/s, with a repeatability of 7 % at rest and 4.6 % at 400 N; stiffness and apparent elastic modulus were 266.3 ± 70.5 N/mm and 5.4 ± 1.1 MPa at rest, respectively, while at 400 N they were 781.0 ± 153.8 N/mm and 13.2 ± 2.4 MPa. Correlations were found between elastographic measurements and IVD mechanical properties; these preliminary results are promising for further in-vivo application.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling for funding (with the support of Proteor, ParisTech and Yves Cotrel Foundations)

Friction properties of fluorinated carbons

In boundary lubrication regime, friction reduction and antiwear processes are associated to the presence of additives in the lubricating oils or greases. These processes are due to the formation of protective tribofilms resulting from chemical reactions between the additives and the sliding surfaces, in the physico-chemical conditions of the sliding contact. Conventional antiwear additives mainly consist of transition metal organo phosphate or thiophosphates which present a remarkable efficiency in the case of contacts between ferrous alloys. In the case of non reacting surfaces, these additives become inactive. Recently developped lubrication strategies consist in the use of dispersion in oils of nano additives able to build the protective tribofilm in the sliding contact without reaction with the surfaces. Carbon fluorinated phases, due to their lamellar structure and their high chemical stability even at relatively high temperature (400°C) represent interesting candidates as lubricant nano-additives subjected to present friction reduction, anti wear and anti corrosion actions. This work presents the tribologic behaviour of some carbon fluorinated derivatives such as graphite fluorides, fluorinated carbon nanofibers, fluorinated carbon nanodiscs and fluorinated carbon blacks. The influence, on the tribologic performances, of the structure of the initial carbon phases, of the fluorination rate (0<F/C<1) and the structure of the fluorinated compounds is discussed

Déterminants structuro-pédagogiques de l'implantation du programme ESPAR

Le programme d'éducation sexuelle fondé sur le pouvoir d'agir et de réfléchir (ESPAR) vise à réduire l'incidence des' grossesses non planifiées chez les adolescentes de première secondaire de quatre écoles de Québec-Centre, milieu où l'indice de défavorisation est élevé. L'objectif de l'étude est de vérifier les déterminants structuro-pédagogiques qui affectent l'implantation du programme dans les écoles. Une analyse de contenu a été exécutée à partir d'entrevues semi-structurées menées auprès de 4 directeurs d'établissement et de 7 enseignants ayant dispensé ESPAR. Suite à l'investigation, le climat de l'établissement, le style de gestion, les personnes-ressources ainsi que les procédures disciplinaires sont des caractéristiques identifiées comme ayant influencé l'implantation du programme ESPA

Esvres-sur-Indre, de la Protohistoire récente au début du Moyen Âge

National audienceLe territoire d'Esvres-sur-Indre (Indre-et-Loire) a livré de nombreux vestiges archéologiques. Sur le site du bourg, on suppose l'existence d'une agglomération antique, sans doute d'origine gauloise. Cette hypothèse se fonde essentiellement sur deux éléments : la présence d'une ou plusieurs nécropoles utilisées de la fin du 2e siècle avant notre ère jusqu'au 2e siècle, et la mention du site comme vicus par Grégoire de Tours. Les informations issues des recherches les plus récentes permettent une première cartographie du site et de son territoire

Apodized Lyot Coronagraph for VLT-SPHERE: Laboratory tests and performances of a first prototype in the visible

We present some of the High Dynamic Range Imaging activities developed around the coronagraphic test-bench of the Laboratoire A. H. Fizeau (Nice). They concern research and development of an Apodized Lyot Coronagraph (ALC) for the VLT-SPHERE instrument and experimental results from our testbed working in the visible domain. We determined by numerical simulations the specifications of the apodizing filter and searched the best technological process to manufacture it. We present the results of the experimental tests on the first apodizer prototype in the visible and the resulting ALC nulling performances. The tests concern particularly the apodizer characterization (average transmission radial profile, global reflectivity and transmittivity in the visible), ALC nulling performances compared with expectations, sensitivity of the ALC performances to misalignments of its components

Trust in MDE Components: the DOMINO Experiment

International audienceA large number of modeling activities can be automatic or computer assisted. This automation ensures a more rapid and robust software development. However, engineers must ensure that the models have the properties required for the application. In order to tend towards this requirement, the DOMINO project (DOMaINs and methodological prOcess) proposes to use the socalled trustworthy Model-Driven Engineering (MDE) components and aims to provide a methodology for the validation and qualification of such components