École normale supérieure de Cachan

About: École normale supérieure de Cachan is a education organization based out in Cachan, Île-de-France, France. It is known for research contribution in the topics: Decidability & Finite element method. The organization has 2717 authors who have published 5585 publications receiving 175925 citations.

Bioinformatic prediction, deep sequencing of microRNAs and expression analysis during phenotypic plasticity in the pea aphid, Acyrthosiphon pisum

Abstract: Background Post-transcriptional regulation in eukaryotes can be operated through microRNA (miRNAs) mediated gene silencing. MiRNAs are small (18-25 nucleotides) non-coding RNAs that play crucial role in regulation of gene expression in eukaryotes. In insects, miRNAs have been shown to be involved in multiple mechanisms such as embryonic development, tissue differentiation, metamorphosis or circadian rhythm. Insect miRNAs have been identified in different species belonging to five orders: Coleoptera, Diptera, Hymenoptera, Lepidoptera and Orthoptera.

Submicrometer 3D structures fabrication enabled by one-photon absorption direct laser writing

Abstract: We demonstrate a new 3D fabrication method to achieve the same results as those obtained by the two-photon excitation technique, by using a simple one-photon elaboration method in a very low absorption regime. Desirable 2D and 3D submicrometric structures, such as spiral, chiral, and woodpile architectures, with feature size as small as 190 nm have been fabricated, by using just a few milliwatts of a continuous-wave laser at 532 nm and a commercial SU8 photoresist. Different aspects of the direct laser writing based on ultralow one-photon absorption (LOPA) technique are investigated and compared with the TPA technique, showing several advantages, such as simplicity and low cost.

Analysis of microcracking induced by differential drying shrinkage

Abstract: The drying of concrete induces surface microcracking. Because drying is, especially, a slow process, differential drying between the surface and the core induces shrinkage, which provokes an increase of the tensile stresses on the surface and of the compressive stresses in the core (the resultant is zero if there are no external forces or external restraints). Often, the tensile stresses obtained by elastic finite element analysis exceed the tensile strength. Numerical simulations show that if creep strains are taken into account the damage due to differential drying shrinkage is less important (compared to the case if creep is not considered in the numerical analysis). Therefore, a little drop of mechanical properties is predicted due to drying, for the studied concrete. Therefore, one may assume that microcracking and the associated drop in the Young’s modulus as the concrete dries are due mainly to aggregate restraint. Besides, an elastic damage model for prediction of cracking is found to be sufficient to retrieve evolution of drying shrinkage and damage fields (but not the orientation).

Quasispecies variant dynamics during emergence of resistance to raltegravir in HIV-1-infected patients

Abstract: Received 9 October 2008; returned 21 November 2008; revised 12 December 2008; accepted 8 January 2009 Objectives: Raltegravir is the first approved inhibitor of HIV-1 integrase (IN). In most patients, raltegravir failure is associated with mutations in the IN gene, through two different genetic pathways: 155 (N155H) or 148 (Q148K/R/H). The objective of this study was to characterize the dynamics of HIV-1 quasispecies variant populations in patients who failed to respond to raltegravir treatment. Patients and methods: Bulk genotyping and clonal analysis were performed during the follow-up of 10 patients who failed to respond to raltegravir treatment. Results: Treatment failed through the 155 pathway in six patients and through the 148 pathway in two patients; two further patients switched from the 155 to the 148 pathway. In the two patients switching from the 155 to the 148 pathway, clonal analysis showed that Q148R/H and N155H mutations were present on different strands, suggesting that these two pathways are independent. This was consistent with our finding that each genetic profile was associated with different secondary mutations. We observed a greater variability among quasispecies associated with the 155 pathway, and IC50 determinations showed that the fold resistance to raltegravir, relative to wild-type, was 10 for the N155H mutant and 50 for the G140S1Q148H mutant. Conclusions: Clonal analysis strongly suggests that the two main genetic pathways, 155 and 148, involved in the development of resistance to raltegravir are independent and exclusive. Moreover, the switch of the resistance profile from 155 to 148 may be related to the higher level of resistance to raltegravir conferred by the 148 pathway and also to the higher instability of the 155 pathway.