Short time growth of a KPZ interface with flat initial conditions

The short time behavior of the 1+1 dimensional KPZ growth equation with a flat initial condition is obtained from the exact expressions of the moments of the partition function of a directed polymer with one endpoint free and the other fixed. From these expressions, the short time expansions of the lowest cumulants of the KPZ height field are exactly derived. The results for these two classes of cumulants are checked in high precision lattice numerical simulations. The short time limit considered here is relevant for the study of the interface growth in the large diffusivity/weak noise limit, and describes the universal crossover between the Edwards-Wilkinson and KPZ universality classes for an initially flat interface.Comment: 9 pages, 7 figure

To be or not to be a piRNA: genomic origin and processing of piRNAs

Piwi-interacting RNAs (piRNAs) originate from genomic regions dubbed piRNA clusters. How cluster transcripts are selected for processing into piRNAs is not understood. We discuss evidence for the involvement of chromatin structure and maternally inherited piRNAs in determining their fate

Transferts de chaleur et de masse dans de ecoulements turbulents de Taylor-Couette avec flux axial

International audienceNous nous intéressons ici aux transferts de chaleur et de masse dans unsys eme de Taylor-Couette avec flux axial. Un dispositif permettant des mesures de vitesse et de coefficients de transferts á eté développé. Les régime etudiés sont turbulents : nombre de Reynolds axial entre 5600 et 11200 et entre 7900 et 79 millios pour le nombre de Taylor. Nous reportons le nombre de Nusselt en fonction du nombre de Reynolds axial et du nombre de Taylor ainsi que des mesures de vitesse. La présence de structures organisées proche du rotor á eté observée, ce qui est confirmé par un calcul DNS

Les 100 médicaments essentiels. Une approche de médecine interne = 100 essential drugs. An internal medicine approach

Déclaration d'intérêts : B. Grosbois : expert pour Actélion, Celgene, Octapharma, Shire. Recherche subventionnée par LFB, Janssen, Genzyme. L. Guillevin : conseiller scientifique Actélion, expert pour (et conférences rémunérées par) GSK, CSL, Roche. L. Guillevin estime cependant n'avoir pas de conflit d'intérêt concernant le présent travail. C. Le Jeunne : expert pour Roche, Sanofi, Novartis, BSM, UCB. Essais thérapeutiques en cours pour Bayer, Pfizer, BMS. P. Morlat : expert pour Gilead, ViiV Health Care, BMS, Abbott, MSD. Ph. Morlat estime cependant n'avoir pas de conflit d'intérêt concernant le présent travail. P. Arlet, O. Aumaitre, J. Cosserat, A. Kettaneh, C. Massot et M. Thomas : aucun conflit d'intérêt.International audiencePURPOSE: Up to 4600 drugs in about 15,000 pharmaceutical forms are available in France which may be a source of misuse with increased occurrence of side effects and costs. While the World Health Organization is encouraging each developed country to work out its own list of essential drugs. The list provided in 2008 by the French Office for the safety of health products has had so far limited impact on practice, so it became obvious to a group of internists to work out a "wise list" of 100 essential medicines covering 95% of the disorders observed in France. METHODS: In June 2011, 10 internists agreed to each provide a list of 100 essential medicines, according to individual experience. In December 2011, a meeting of the participants provided a list as initial consensus and mandated five among them to make proposals for those areas neglected by too many participants or in which needless dispersion of medicines was stated. After internet-facilitated exchanges, an additional list was validated in mild-January 2012. RESULTS: Fifty-four drugs were included in the list of initial consensus (including nine selected by all 10 participants), and 46 in the additional list. So the final "wise list" included 100 drugs. In June 2012, 56 of these drugs were available as generics. This list was compared to those lists set out by five countries in the European Union. CONCLUSION: Generating such a list is feasible. Undoubtedly still non-comprehensive, this list will benefit from the expertise of 14 general practitioners who are currently working out a similar list across France. The final list will be submitted for validation by the French associations of generalist teachers and Internists

Piwi induces piRNA-guided transcriptional silencing and establishment of a repressive chromatin state

In the metazoan germline, piwi proteins and associated piwi-interacting RNAs (piRNAs) provide a defense system against the expression of transposable elements. In the cytoplasm, piRNA sequences guide piwi complexes to destroy complementary transposon transcripts by endonucleolytic cleavage. However, some piwi family members are nuclear, raising the possibility of alternative pathways for piRNA-mediated regulation of gene expression. We found that Drosophila Piwi is recruited to chromatin, colocalizing with RNA polymerase II (Pol II) on polytene chromosomes. Knockdown of Piwi in the germline increases expression of transposable elements that are targeted by piRNAs, whereas protein-coding genes remain largely unaffected. Derepression of transposons upon Piwi depletion correlates with increased occupancy of Pol II on their promoters. Expression of piRNAs that target a reporter construct results in a decrease in Pol II occupancy and an increase in repressive H3K9me3 marks and heterochromatin protein 1 (HP1) on the reporter locus. Our results indicate that Piwi identifies targets complementary to the associated piRNA and induces transcriptional repression by establishing a repressive chromatin state when correct targets are found

Cutoff Suppresses RNA Polymerase II Termination to Ensure Expression of piRNA Precursors

Small non-coding RNAs called piRNAs serve as guides for an adaptable immune system that represses transposable elements in germ cells of Metazoa. In Drosophila the RDC complex, composed of Rhino, Deadlock and Cutoff (Cuff) bind chromatin of dual-strand piRNA clusters, special genomic regions, which encode piRNA precursors. The RDC complex is required for transcription of piRNA precursors, though the mechanism by which it licenses transcription remained unknown. Here, we show that Cuff prevents premature termination of RNA polymerase II. Cuff prevents cleavage of nascent RNA at poly(A) sites by interfering with recruitment of the cleavage and polyadenylation specificity factor (CPSF) complex. Cuff also protects processed transcripts from degradation by the exonuclease Rat1. Our work reveals a conceptually different mechanism of transcriptional enhancement. In contrast to other factors that regulate termination by binding to specific signals on nascent RNA, the RDC complex inhibits termination in a chromatin-dependent and sequence-independent manner

Cutoff Suppresses RNA Polymerase II Termination to Ensure Expression of piRNA Precursors

Small non-coding RNAs called piRNAs serve as guides for an adaptable immune system that represses transposable elements in germ cells of Metazoa. In Drosophila the RDC complex, composed of Rhino, Deadlock and Cutoff (Cuff) bind chromatin of dual-strand piRNA clusters, special genomic regions, which encode piRNA precursors. The RDC complex is required for transcription of piRNA precursors, though the mechanism by which it licenses transcription remained unknown. Here, we show that Cuff prevents premature termination of RNA polymerase II. Cuff prevents cleavage of nascent RNA at poly(A) sites by interfering with recruitment of the cleavage and polyadenylation specificity factor (CPSF) complex. Cuff also protects processed transcripts from degradation by the exonuclease Rat1. Our work reveals a conceptually different mechanism of transcriptional enhancement. In contrast to other factors that regulate termination by binding to specific signals on nascent RNA, the RDC complex inhibits termination in a chromatin-dependent and sequence-independent manner

The interplay of landscape composition and configuration: new pathways to manage functional biodiversity and agroecosystem services across Europe

Managing agricultural landscapes to support biodiversity and ecosystem services is a key aim of a sustainable agriculture. However, how the spatial arrangement of crop fields and other habitats in landscapes impacts arthropods and their functions is poorly known. Synthesising data from 49 studies (1515 landscapes) across Europe, we examined effects of landscape composition (% habitats) and configuration (edge density) on arthropods in fields and their margins, pest control, pollination and yields. Configuration effects interacted with the proportions of crop and non‐crop habitats, and species’ dietary, dispersal and overwintering traits led to contrasting responses to landscape variables. Overall, however, in landscapes with high edge density, 70% of pollinator and 44% of natural enemy species reached highest abundances and pollination and pest control improved 1.7‐ and 1.4‐fold respectively. Arable‐dominated landscapes with high edge densities achieved high yields. This suggests that enhancing edge density in European agroecosystems can promote functional biodiversity and yield‐enhancing ecosystem services