Introduction à la résistance des matériaux

1 - Généralités Concepts généraux Représentation et repère Description lagrangienne 2 - Petites déformations d'un milieu continu Déplacement et transformation Interprétation géométrique de la transformation Déformation autour d'un point Variation d'angle entre deux axes de référence Variation angulaire de deux directions quelconques Dilatation cubique Éléments propres de la matrice des déformations Invariants du tenseur des déformations Conditions d'intégrabilité Représentation de Mohr 3 - Contraintes dans un milieu continu Équilibre d'un domaine solide Notion de contraintes État de contrainte en un point Propriétés de la matrice des contraintes Représentation géométrique des contraintes 4 - Relation de comportement en élastostatique Coefficients élastiques Essai de torsion Critères limites de dimensionnement 5 - Énergie de déformation d'un milieu continu élastique Énergie de déformation Potentiel élastique 6 - Élasticité linéaire Position du problème Résolution Principe de Saint-Venant Applications 7 - Introduction à la théorie des poutres Introduction Problème de Saint-Venant Une théorie approchée des poutres 8 - Treillis Définition Effort normal Contraintes et déformations Équations cinématiques Énergie de déformation Résolution 9 - Théorèmes énergétiques Théorème de réciprocité de Maxwell-Betti Théorème de Castigliano 10 - Flexion des poutres droites Poutre droite et notations générales Équations locales Flexion plane 11 - Assemblages hyperstatiques de poutres Hyperstaticité des systèmes plans Applications Poutre sur appuis dénivelables Méthode des trois moments 12 - Effort tranchant Position du problème Contraintes de cisaillement et effort tranchant dans une section droite Solution approchée et formule de Bredt Centre de cisaillement 13 - Torsion des poutres Centres de torsion et de cisaillement Poutres de section pleine Section pleine admettant un centre de symétrie Poutres de section à paroi mince fermée 14 - Stabilité de l'équilibre des poutres élastiques longues Formulation du problème Modélisation linéaire du flambement Flambement des pièces longues Influence de l'effort tranchant Calcul de la charge critique d'Euler Déversement des poutres en flexion simple Torsion et traction/compression Stabilité des arcs et anneaux A - Problème de Saint-Venant Méthode des déplacements Méthode des contraintes Comparaison des deux méthodes Engineering schoolLa résistance des matériaux, appelée également mécanique des corps déformables, fait appel aux notions d'équilibre de la mécanique statique, aux notions de déplacements étudiées en cinématique et aux propriétés des matériaux, auxquelles on a recours pour évaluer les dimensions de pièces structurales ou d'éléments de machines. L'objet de cet enseignement est l'étude statique des milieux continus déformables

C-fos and c-jun Proto-Oncogene Expression Is Decreased in Psoriasis: an In Situ Quantitative Analysis

Psoriasis is a common, sometimes sevcre, non-malignant skin disease characterized by hyperproliferation and abnormal differentiation of keratinocytes. Because proto-oncogenes are implicated in both cell proliferation and differentiation, their expression could be modified in skin diseases such as psoriasis. The c-fos and c-jun proto-oncogenes, whose products associate to form a heterodimeric transcription factor, are among the first genes to be expressed when certain cells are stimulated to either proliferate or differentiate. Recent studies in our laboratory have shown that the c-fos protooncogene is highly expressed in normal human adult skin. In the present study, we used in situ hybridization with RNA to compare the expression and localization of c-fos and c-jun transcripts in 15 lesional and non-lesional psoriatic skin samples. Two clinical variants of psoriasis were studied: the most severe and chronic form or plaque-type psoriasis (N = 10) and rapidly resolutive guttate-type psoriasis (N = 5). Quantitative analysis was performed using a semi-automatic image analyzer and the “Starwise grain” software program. Our control samples included 10 normal skins and eight specimens from other benign hyperproliferative non-psoriatic skin diseases, consisting of three with inflammation (seborrheic dermatitis and atopic dermatitis), and 5 without inflammation (seborrheic keratoses). Control genes we used for in situ hybridization and RNA integrity were keratin 14, which is expressed in the epidermis and was normally expressed in all tissue analyzed, and ribosomal RNA. Our data showed that c-fos and c-jun were expressed to an equivalent extent, both spatially and quantitatively, in all specimens tested. Expression was significantly decreased in plaque-type but not in guttate-type psoriasis. It was also decreased in the three other benign inflammatory cutaneous hyperproliferative disorders, but not in the five non-inflammatory cases. These results were surprising because hyperproliferation was here associated with a decrease in proto-oncogene expression, thus suggesting that c-fos and c-jun do not play a crucial role in the control of keratinocyte proliferation in vivo. However, their reduced expression in some abnormally differentiated skins indicates that both c-fos and c-jun proto-oncogenes may play a key role in keratinocyte differentiation. Their altered expression correlated with severity of the disease and the presence of an inflammatory infiltrate. These data offer a new insight into the role and regulation of these proto-oncogenes in vivo in humans

LCA of perennial crops: implications of modeling choices through two contrasted case studies

International audienceAs highlighted in several recent reviews, there is a need to harmonize the way LCA of perennial crops is conducted (Bessou et al. 2013; Cerutti et al. 2013). In most published LCA on perennial crops, the agricultural production is based on data sets for just one productive year. This may be misleading since performances and impacts of the system may greatly vary year by year and the evolution of the stand over the cycle induces specific mechanisms (nutrient re-mobilization, yield alternating, resistance etc.) that must be included. Without a proper mechanistic model, the only way to account for such phenomena is to wider the data sets to at least account for each stage of the stand development and, if possible, all years of the crop cycle. Three modeling choices for the perennial crop cycle were tested in parallel in two contrasted LCA case studies: oil palm fruits from Indonesia, and small citrus from Morocco. Modeling choices tested were: i) a chronological modeling over the complete crop cycle of orchards (Bessou et al. 2013), ii) a three years average from the productive phase and iii) a selection of different single years from the productive phase. In both case studies, the system boundary included all processes from the seed production until the harvested fruits at farm-gate. The functional unit was 1 kg of fresh fruits. The chosen approach to model the perennial cycle influences the final results and deserves specific attention

RESTAURATION DES LESIONS OCCLUSALES POSTERIEURES A L'AIDE DE RESINE COMPOSITE (PROPOSITION D'UN PROTOCOLE DE MISE EN OEUVRE)

MONTROUGE-BUFR Odontol.PARIS5 (920492101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Interactive Art-Directable Smear Frame Stylization

International audienceSmear frames are used by artists to expressively convey motion in an animation. In this paper, we present a method to generate elongated inbetweens, i.e., smear frames created by stretching an object along its space-time trajectory. Our method takes as input the mesh of an animated character, with or without a skeleton, and outputs a deformed version of the mesh for each frame of the animation, that can still be refined by an artist before rendering. We first compute spatially and temporally coherent displacement weights that correspond to the direction and intensity of stretching of each vertex of the mesh. We then describe a framework to stylize these displacement weights, customizing elongated inbetweens at interactive rates. We propose built-in stylization functions that can be used by novice users for simple and fast smear frame generation, but our Blender “Geometry node” implementation allows easy integration of custom-made stylization functions designed by more expert artists

SELECTIVE HYDROGENATION ON PLATINUM NANOPARTICLES STABILIZED BY ORGANOSILANES

Nanoparticles are widely used in heterogeneous catalysis and generally, they are supported on oxides such as silica or alumina. Unfortunately, strong interactions between support and particles exist and lead to the modification of the particles’ properties which means that no unique active sites are obtained. Other side phenomena like diffusion or migration of adsorbed atoms towards the support surface are observed and undesired reactions (isomerization, cyclization,…) with the acid sites take place. Unsupported metal nanoparticles do not interact with a support. Their properties can be modified depending on their size especially in the order of magnitude between 1 and 10 nm. This makes unsupported nanoparticles interesting candidates for fine chemical catalytic applications since no side phenomena occur and active sites are well defined. Surface Organometallic Chemistry on Metals allows controlling the coordination sphere of the active metal by an organometallic fragment. By changing “at will” the steric and electronic properties of the organometallic fragment, it is possible to influence the chemio- , stereo- and regio-selectivity of reactions catalyzed by metallic surfaces. Pt is considered to be a very good catalyst for selective hydrogenation; in particular for enantioselective hydrogenation of alpha ketoesters and it is believed to be less hydrolyzing than Ru. Unsupported Pt nanoparticles were prepared following the procedure already described for Ru, using Pt(dba)2 as precursor and octylsilane (C8SiH3) or vinylphenylmethylsilane (VPMSiH) as stabilizer. The size and the structure of the nanoparticles were determined by TEM and the grafted organometallic fragments were characterized by solid state 1H and 13C CP-MAS NMR, IR and elementary analysis. Crystalline Pt nanoparticles (see Figure) of about 2 nm corresponding to a cubo-octahedron with 3 edge atoms, covered by organosilane fragments were obtained. These nanoparticles are active and chemio-selective in the hydrogenation of cetopentoylactone into the corresponding alcohol and their properties were compared to silica supported Pt