Evaluation de l'amorçage de l'endommagement par fatigue des tubes d'acier utilisés pour l'exploitation pétrolière

L'étude a pour but de proposer un critère de «micro-amorçage» que doit permettre de faire une bonne prédiction de la durée de vie résiduelle des tubes en aciers utilisés pour l'exploitation pétrolière soumis à des sollicitations cycliques afin d'augmenter la fiabilité des ces structures. Essais de fatigue sont réalisés en pour évaluer les mécanismes microstructuraux associés à l'amorçage de l'endommagement à partir de mesures des microdéformations et contraintes résiduelles en temps réel par diffraction des rayons X. Un modèle en éléments finis simule les observations expérimentales

Ultimate strength

Concern for the ductile behaviour of ships and offshore structures and their structural components under ultimate conditions. Attention shall be given to the influence of fabrication imperfections and in-service damage and degradation on reserve strength

Freeze-Dried Somatic Cells Direct Embryonic Development after Nuclear Transfer

The natural capacity of simple organisms to survive in a dehydrated state has long been exploited by man, with lyophylization the method of choice for the long term storage of bacterial and yeast cells. More recently, attempts have been made to apply this procedure to the long term storage of blood cells. However, despite significant progress, practical application in a clinical setting is still some way off. Conversely, to date there are no reports of attempts to lyophilize nucleated somatic cells for possible downstream applications. Here we demonstrate that lyophilised somatic cells stored for 3 years at room temperature are able to direct embryonic development following injection into enucleated oocytes. These remarkable results demonstrate that alternative systems for the long-term storage of cell lines are now possible, and open unprecedented opportunities in the fields of biomedicine and for conservation strategies

Detection of erbB2 copy number variations in plasma of patients with esophageal carcinoma

<p>Abstract</p> <p>Background</p> <p>Mortality is high in patients with esophageal carcinoma as tumors are rarely detected before the disease has progressed to an advanced stage. Here, we sought to isolate cell-free DNA released into the plasma of patients with esophageal carcinoma, to analyze copy number variations of marker genes in the search for early detection of tumor progression.</p> <p>Methods</p> <p>Plasma of 41 patients with esophageal carcinoma was prospectively collected before tumor resection and chemotherapy. Our dataset resulted heterogeneous for clinical data, resembling the characteristics of the tumor. DNA from the plasma was extracted to analyze copy number variations of the <it>erbB2 </it>gene using real-time PCR assays.</p> <p>Results</p> <p>The real-time PCR assays for <it>erbB2 </it>gene showed significant (<it>P </it>= 0.001) copy number variations in the plasma of patients with esophageal carcinoma, as compared to healthy controls with high sensitivity (80%) and specificity (95%). These variations in <it>erbB2 </it>were negatively correlated to the progression free survival of these patients (<it>P </it>= 0.03), and revealed a further risk category stratification of patients with low VEGF expression levels.</p> <p>Conclusion</p> <p>The copy number variation of <it>erbB2 </it>gene from plasma can be used as prognostic marker for early detection of patients at risk of worse clinical outcome in esophageal cancer.</p

X-ray diffraction study of microstructural changes during fatigue damage initiation in steel pipes

Steel pipes used in the oil and gas industry undergo the action of cyclic loads that can cause their failure by fatigue. A consistent evaluation of the fatigue damage during the initiation phase should fundamentally be based on a nanoscale approach, i.e., at the scale of the dislocation network, in order to take into account the micromechanisms of fatigue damage that precede macrocrack initiation and propagation until the final fracture. In this work, microstructural changes related to fatigue damage initiation are investigated in the API 5L X60 grade steel, used in pipe manufacturing. Microdeformations and macro residual stress are evaluated using X-ray diffraction in real time during alternating bending fatigue tests performed on samples cut off from an X60 steel pipe. The aim of this ongoing work is to provide ground for further development of an indicator of fatigue damage initiation in X60 steel. This damage indicator could allow a good residual life prediction of steel pipes previously submitted to fatigue loading, before macroscopic cracking, and help to increase the reliability of these structures. (C) 2011 Elsevier By. All rights reserved