Comportement mécanique par homogénéisation de la dynamique des disclocations

La plasticité des métaux est principalement due à la présence de lignes de défauts appelées dislocations. En ce qui concerne la déformation plastique des cristaux, elle résulte principalement du déplacement de ces dislocations, dont l'ordre de longueur typique dans les métaux est 10^-6 m et l'épaisseur 10^-9 m. Dans cette étude, on considère la dynamique collective des dislocations en interactions. Dans ces conditions, les dislocations se regroupent en « murs » pour former des structures ordonnées à longue distance

Multi-references shape constraint for snakes

In this research, we intend to present a new method of snakes with an invariant shape prior. We consider the general case where different templates are available and we have to choose the most suitable ones to define the shape constraint. A new external force is then proposed which is able to take into account several references at the same time with proportional weighting factors. Both a Fourier based shape alignment method and a complete and stable set of shape descriptors are used to ensure invariance and robustness of the prior knowledge to Euclidean transformations. To illustrate the efficiency of our approach, a set of experiments are applied on synthetic and real data. Promising results are obtained and commented

Changes in contractile protein expression are linked to ventricular stiffness in infants with pulmonary hypertension or right ventricular hypertrophy due to congenital heart disease

Background The right ventricle (RV) is not designed to sustain high pressure leading to failure. There are no current medications to help RV contraction, so further information is required on adaption of the RV to such hypertension. Methods The Right Ventricle in Children (RVENCH) study assessed infants with congenital heart disease undergoing cardiac surgery with hypertensive RV. Clinical and echocardiographic data were recorded, and samples of RV were taken from matched infants, analysed for proteomics and compared between pathologies and with clinical and echocardiographic outcome data. Results Those with tetralogy of Fallot (TOF) were significantly more cyanosed than those with ventricular septal defect (median oxygen saturation 83% vs 98%, P=0.0038), had significantly stiffer RV (tricuspid E wave/A wave ratio 1.95 vs 0.84, P=0.009) and had most had restrictive physiology. Gene ontology in TOF, with enrichment analysis, demonstrated significant increase in proteins of contractile mechanisms and those of calmodulin, actin binding and others associated with contractility than inventricular septal defect. Structural proteins were also found to be higher in association with sarcomeric function: Z-disc, M-Band and thin-filament proteins. Remaining proteins associated with actin binding, calcium signalling and myocyte cytoskeletal development. Phosphopeptide enrichment led to higher levels of calcium signalling proteins in TOF. Conclusion This is the first demonstration that those with an RV, which is stiff and hypertensive in TOF, have a range of altered proteins, often in calcium signalling pathways. Information about these alterations might guide treatment options both in terms of individualised therapy or inotropic support for the Right ventricle when hypertensive due to pulmoanry hypertension or congenital heart disease

Changes in contractile protein expression are linked to ventricular stiffness in infants with pulmonary hypertension or right ventricular hypertrophy due to congenital heart disease

Background The right ventricle (RV) is not designed to sustain high pressure leading to failure. There are no current medications to help RV contraction, so further information is required on adaption of the RV to such hypertension. Methods The Right Ventricle in Children (RVENCH) study assessed infants with congenital heart disease undergoing cardiac surgery with hypertensive RV. Clinical and echocardiographic data were recorded, and samples of RV were taken from matched infants, analysed for proteomics and compared between pathologies and with clinical and echocardiographic outcome data. Results Those with tetralogy of Fallot (TOF) were significantly more cyanosed than those with ventricular septal defect (median oxygen saturation 83% vs 98%, P=0.0038), had significantly stiffer RV (tricuspid E wave/A wave ratio 1.95 vs 0.84, P=0.009) and had most had restrictive physiology. Gene ontology in TOF, with enrichment analysis, demonstrated significant increase in proteins of contractile mechanisms and those of calmodulin, actin binding and others associated with contractility than inventricular septal defect. Structural proteins were also found to be higher in association with sarcomeric function: Z-disc, M-Band and thin-filament proteins. Remaining proteins associated with actin binding, calcium signalling and myocyte cytoskeletal development. Phosphopeptide enrichment led to higher levels of calcium signalling proteins in TOF. Conclusion This is the first demonstration that those with an RV, which is stiff and hypertensive in TOF, have a range of altered proteins, often in calcium signalling pathways. Information about these alterations might guide treatment options both in terms of individualised therapy or inotropic support for the Right ventricle when hypertensive due to pulmoanry hypertension or congenital heart disease

On the use of excavated earth hemp mortars as thermal insulation materials

International audienc

Characterization of tunnel excavated earth-based mortars for rammed earth repair

The aim of this work is to study the possibility to reuse the tunnel excavated earth in order to elaborate earth-based mortar for rammed earth reparation. The tunnel excavated earth-based mortars were compared with raw earth based-mortars, largely used in practice. The cement was used as stabilizer and the hemp fibers were used to diminish the cracking due to shrinkage. The mechanical, thermal and hydric properties of mortars were characterized after 28 days. The mortars were maintained in hydrothermal chamber at controlled conditions, 20 ± 2 °C and 50 ± 5 HR. The obtained results show that the mechanical performances increase with the increase of cement by earth ratio. While, the increase of cement content affects negatively the thermal conductivity of earth-based mortars. Whereas, the thermal properties were improved with the addition of natural fiber. The excavated earth-based mortars show higher mechanical performances and good thermal properties compared to raw earth-based mortars

Recovery of excavated materials as an alternative solution to earth building materials

International audienc

Effect of Used Engine Oil Addition on the Rheological Properties of a Plastic Bag Waste–Modified 40/50 Grade Bitumen

International audienc

Multi-references shape constraint for snakes

In this research, we intend to present a new method of snakes with an invariant shape prior. We consider the general case where different templates are available and we have to choose the most suitable ones to define the shape constraint. A new external force is then proposed which is able to take into account several references at the same time with proportional weighting factors. Both a Fourier based shape alignment method and a complete and stable set of shape descriptors are used to ensure invariance and robustness of the prior knowledge to Euclidean transformations. To illustrate the efficiency of our approach, a set of experiments are applied on synthetic and real data. Promising results are obtained and commented