Mesure des modules viscoélastiques d'un polypropylène lors d'un refroidissement et d'un changement de phase

International audienceLa rhéologie d'un polypropylène de grade injection a été mesurée sur un rhéomètre plan - plan lors d'un refroidissement depuis l'état fondu jusqu'au début de la solidification. Ce type de donnée est important en particulier lorsque l'on s'intéresse aux contraintes résiduelles prenant naissance à la solidification. Un outillage plan - plan rainuré a été monté sur un rhéomètre asservi en contrainte. Le rainurage limite le phénomène de glissement qui interviendrait sur un matériau solidifié. On a ainsi pu mesurer les températures de transition lors de la cristallisation. Un point de gel a pu être mis en évidence au début de la cristallisation pour des vitesses de refroidissement de 2°C par minute. Le dispositif a également pu être évalué dans le sens de la fusion du matériau solidifié. Des expériences complémentaires ont été conduites en calorimétrie pour valider les températures de transitions obtenues.Des vitesses de refroidissement plus élevées ont permis de mesurer l'évolution des modules en fonction des conditions de refroidissement = The rheology of an injection grade polypropylene was measured in a plate plate rheometer during cooling from the melt to the beginning of solidification. These results are particularly important when we are interested by the construction of residual stresses during solidification. A grooved tool was mounted on a tresscontrolled rheometer. The grooves limit the slippage which happened on a solid. We measured the transition temperature during crystallisation. A gel point is observed for a cooling rate of 2°C by minute. The fixture is also evaluated for melting. Differential Scanning Calorimetry was also used for validation of the transition temperatures. Higher cooling rates permitted the measurement of modulus versus cooling conditions

Early cardiovascular events in women with a history of gestational diabetes mellitus

International audienceBackground: The effect of gestational diabetes mellitus (GDM) on cardiovascular diseases (CVD) is not assessed within the first 10 years postpartum, regardless of subsequent diabetes. The aim of this study was to determine the risk of CVD events related to GDM within 7 years of postpartum.Methods: This nationwide population-based study of deliveries in 2007 and 2008 with a follow-up of 7 years was based on data from the French medico-administrative database. Two groups were formed: women with a history of GDM and women without GDM or previous diabetes. CVD included angina pectoris, myocardial infarction, stroke, heart bypass surgery, coronary angioplasty, carotid endarterectomy and fibrinolysis. Hypertensive disease was assessed separately. Determinants studied included age, obesity, subsequent diabetes mellitus and hypertensive diseases during pregnancy. Adjusted odds ratios for outcomes were calculated using multiple logistic regressions.Results: The hospital database recorded 1,518,990 deliveries in 2007 and 2008. Among these, 62,958 women had a history of GDM. After adjusting for age, DM, obesity and hypertensive disorders in pregnancy, GDM was significantly associated with a higher risk of CVD (adjusted Odds Ratio aOR = 1.25 [1.09-1.43]). Considering each variable in a separate model, GDM was associated with angina pectoris (aOR = 1.68 [1.29-2.20]), myocardial infarction (aOR = 1.92 [1.36-2.71]) and hypertension (aOR = 2.72 [2.58-2.88]) but not with stroke.Conclusions: A history of GDM was identified as a risk factor of CVD, especially coronary vascular diseases, within the 7 years postpartum. A lifestyle changes from postpartum onwards can be recommended and supported

Lipidomics reveals seasonal shifts in a large-bodied hibernator, the brown bear

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Hibernating brown bears are protected against atherogenic dyslipidemia

publishedVersio

Lipidomics Reveals Seasonal Shifts in a Large-Bodied Hibernator, the Brown Bear

Prior to winter, heterotherms retain polyunsaturated fatty acids (“PUFA”), resulting in enhanced energy savings during hibernation, through deeper and longer torpor bouts. Hibernating bears exhibit a less dramatic reduction (2–5°C) in body temperature, but lower their metabolism to a degree close to that of small hibernators. We determined the lipid composition, via lipidomics, in skeletal muscle and white adipose tissues (“WAT”), to assess lipid retention, and in blood plasma, to reflect lipid trafficking, of winter hibernating and summer active wild Scandinavian brown bears (Ursus arctos). We found that the proportion of monounsaturated fatty acids in muscle of bears was significantly higher during winter. During hibernation, omega-3 PUFAs were retained in WAT and short-length fatty acids were released into the plasma. The analysis of individual lipid moieties indicated significant changes of specific fatty acids, which are in line with the observed seasonal shift in the major lipid categories and can be involved in specific regulations of metabolisms. These results strongly suggest that the shift in lipid composition is well conserved among hibernators, independent of body mass and of the animals’ body temperature