Prédiction du grade d'un cancer du sein par la découverte de motifs séquentiels contextuels dans des puces à ADN

National audienceLe cancer du sein reste de nos jours un problème de santé majeur et un véritable défi pour les biologistes et les professionnels de santé. Les puces à ADN permettent aujourd'hui d'étudier selon un jour nouveau les problématiques associées à cette maladie. Dans cet article, nous proposons de traiter les données issues des puces à ADN par le biais de l'extraction de motifs séquentiels contextuels (séquences de gènes ordonnés selon leur niveau d'expression associées à un contexte). L'objectif est de proposer une aide au diagnostic du grade d'une tumeur. Notre approche tient à la fois compte de l'information contenue dans les puces à ADN (exprimée par le biais de motifs séquentiels), mais également d'informations additionnelles d'ordre contextuel (e.g., âge du patient, taille de la tumeur, etc.) et qui sont associées aux données de puces à ADN lorsque celles-ci sont publiées en ligne. L'approche proposée a été évaluée sur des données réelles

Modelling of delta ferrite to austenite phase transformation kinetics in martensitic steels: application to rapid cooling in additive manufacturing

International audienceIn this paper, the high temperature transformation kinetics of delta ferrite to austenite (δ → γ) phase transformation is modeled by thermodynamic and diffusion calculations. It appears that, in martensitic steels, the δ → γ transformation is very fast (a few nanoseconds) as soon as the first austenite nuclei appears. Classically the austenitic phase will thus systematically be observed in the material during conventional elaboration processes. However, in powder metallurgy and additive manufacturing, it is possible to obtain sufficiently high quenching rates (up to 106 °C/s) so that the γ phase does not have time to appear. The calculations presented here allow to rationalize the understanding of the microstructures of powders and different additive manufacturing materials. They enable to understand why ferrite or martensite is sometimes obtained in the final microstructure. From the calculations made, an original CCT (Continuous Cooling Transformations) diagram starting from the δ phase is proposed. It allows to set up a strategy of grade design or process definition according to the final microstructure targeted

Fatigue mechanisms of brazed al-mn alloys used in heat exchangers

International audienceThe ratio of aluminium alloys used in the automotive industry tends to increase as a consequence of the enforcement of tougher environmental regulation (minimization of vehicles weight). For example, thanks to their good thermal, corrosion and mechanical properties, aluminium alloys have steadily replaced copper alloys and brass for manufacturing heat exchangers in cars or trucks. Such components have been constantly optimized in terms of exchange surface area and, nowadays, this has led to Al components in heat exchangers with a typical thickness of the order of 0.2 to 1.5 mm. With such small thicknesses, the load levels experienced by heat exchangers components has drastically increased leading to an important research effort in order to improve the resistance to damage development during service life.This paper focuses on the resistance to fatigue damage of thin sheets of brazed co-rolled aluminium alloys used for manufacturing heat exchangers and particularly on the mechanisms of fatigue cracks initiation. Digital Image Correlation (DIC) has been used to monitor damage development during constant amplitude fatigue tests of thin (0.27 mm) samples. Fatigue cracks have been found to initiate from deformation bands which presence can be correlated with solidification drops at the sample’s surface resulting from the brazing process. X-ray tomography has been used to obtain the spatial distribution of drops as well as their characteristics (height, surface...), on the sample gauge length. Those 3D data have been used to produce finite element meshes of the samples in order to assess the influence of the drops on fatigue crack initiation

Bottom-up assembly of cells in flow with dielectrophoresis

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Développement de microsystèmes utilisant des champs électriques pour la création et la caractérisation d'agrégats de cellules

International audienceLes agrégats de cellules peuvent avantageusement être employés en guise de modèles intermédiaires entre la cellule unique et le tissu dans le cadre de l’étude multi-échelle du phénomène d’électroporation. De tels assemblages peuvent être obtenus sur puce par diélectrophorèse (DEP)suivant une approche ascendante. Une interface graphique utilisateur a été développée pour faciliter le choix des paramètres expérimentaux. Des simulations multiphysiques ont été réalisées pour déterminer les configurations d’électrodes favorables au piégeage diélectrophorétique des cellules sous flux au sein d’une puce microfluidique. Après fabrication de la puce, des agrégats de cellules HEK (Human Embryonic Kidney )ont pu ainsi être obtenus par diélectrophorèse.Un dispositif expérimental pour la caractérisation électrique des cellules individuelles et des agrégats par spectroscopie d’impédance a également été développ

Towards DEP-assisted creation of cell aggregates mimicking tumor

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Microstructure Evolution during Multiaxial Processing of TA6V

International audienceSubtransus multiaxial hot forging of α+β Ti-6Al-4V (TA6V) titanium alloy with a β-transformed microstructure aims at obtaining an equiaxed microstructure through α phase globularization. The activation of mechanisms involved in microstructural evolution, such as globularization, depends on parameters such as time, temperature, strain and strain rate. It is also sensitive to the crystallographic orientation of α-lamellae. As a result, multiaxial processing of titanium alloys leads to significant microstructural gradients depending on thermomechanical conditions and initial microstructure. In this study, we focused on the effect of complex thermomechanical paths on microstructural evolutions. Thanks to the MaxStrain Gleeble device, we were able to reproduce such thermomechanical treatments to β-transformed TA6V samples. Stress strain fields obtained with finite element modelling of the MaxStrain test were compared to experimental microstructure gradients. This experimental method offers the opportunity to get closer to industrial open die forging conditions

Parent beta grain reconstruction of globularized Ti-6Al-4V alloy

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The Role of γ-Secretase Activating Protein (GSAP) and Imatinib in the Regulation of γ-Secretase Activity and Amyloid-β Generation

gamma-Secretase is a large enzyme complex comprising presenilin, nicastrin, presenilin enhancer 2, and anterior pharynx-defective 1 that mediates the intramembrane proteolysis of a large number of proteins including amyloid precursor protein and Notch. Recently, a novel gamma-secretase activating protein (GSAP) was identified that interacts with gamma-secretase and the C-terminal fragment of amyloid precursor protein to selectively increase amyloid-beta production. In this study we have further characterized the role of endogenous and exogenous GSAP in the regulation of gamma-secretase activity and amyloid-beta production in vitro. Knockdown of GSAP expression in N2a cells decreased amyloid-beta levels. In contrast, overexpression of GSAP in HEK cells expressing amyloid precursor protein or in N2a cells had no overt effect on amyloid-beta generation. Likewise, purified recombinant GSAP had no effect on amyloid-beta generation in two distinct in vitro gamma-secretase assays. In subsequent cellular studies with imatinib, a kinase inhibitor that reportedly prevents the interaction of GSAP with the C-terminal fragment of amyloid precursor protein, a concentration-dependent decrease in amyloid-beta levels was observed. However, no interaction between GSAP and the C-terminal fragment of amyloid precursor protein was evident in co-immunoprecipitation studies. In addition, subchronic administration of imatinib to rats had no effect on brain amyloid-beta levels. In summary, these findings suggest the roles of GSAP and imatinib in the regulation of gamma-secretase activity and amyloid-beta generation are uncertain