Hydrostatic and osmotic pressure study of the hairpin ribozyme.

The recent discovery of numerous catalytically active RNAs in various living species as well as the in vitro selection of a large series of RNA aptamers able to bind specifically various molecules such as metabolites and co-factors, emphasize the adaptability of RNAs through the plasticity of their secondary structure. Furthermore, all these observations give support to the “RNA world” hypothesis as a step in the primitive development of life on Earth. On this background, we used high pressure to study the mechanism of action of a model hairpin ribozyme which exhibits self-cleavage and ligation. The activation volume (ΔV≠) of the cleavage reaction (34 ± 4 ml/mol) indicates that an important compaction of the RNA molecule occurs during the reaction and must be accompanied by a significant movement of water molecules . Indeed, such a release of 78 ± 4 water molecules per RNA molecule could be measured by complementary osmotic shock experiments. These results are consistent with the information provided by the structural studies which indicate that two loops of the RNA molecule should come into contact for the reaction to occur .The high pressure study of a modified form of the ribozyme whose activity is strictly dependent on the presence of adenine as a co-factor should bring some information about the structural significance of this important ΔV≠ of activation

Estimation du comportement thermo-viscoélastique effectif des pièces composites obtenues par impression 3D-FDM

peer reviewedDans le but d’estimer le comportement effectif des pièces obtenues par le procédé de fabrication FDM pour le cas des matériaux composites à fibres courtes on a visé une méthodologie permettant la mise en place d’une procédure d'homogénéisation analytique en thermo-viscoélasticité de façon analogue à celle des matériaux élastiques linéaires ; la prise en compte de la variation des paramètres qui déterminent l’état particulier des fibres dans le filament est achevé grâce à l’introduction des fonctions de distribution obtenues via l’analyse statistique de la microstructure. La procédure d'homogénéisation a été évaluée en comparant ses prédictions aux calculs basés sur la FFT en champ complet et des résultats des essais pour des échantillons traités en autoclave, pour enlever les porosités à l'échelle des couches du filament imprimé

ESTIMATING THERMOMECHANICAL RESIDUAL STRESSES IN FDM 3D PRINTED COMPOSITE PARTS

peer reviewedWe implemented a two-step methodology to estimate the residual stresses induced by the FDM manufacturing process in 3D printed composite parts. The first step consisted in an analytical thermo-viscoelastic homogenization procedure to derive the effective behavior of the filament. The second step consisted in a coupled thermomechanical structural analysis of the part. The homogenization procedure was assessed by comparing its predictions to full-field FFT-based computations. The structural analysis was assessed by comparing its predictions to experimental results

Histoire des sociétés européennes, XIXe-XXe siècles. Liens, réseaux, configurations

Maurizio Gribaudi, directeur d’étudesMichèle Riot-Sarcey, professeur à l’Université Paris-VIII/Vincennes-Saint-Denis Repenser le XIXe siècle Depuis plusieurs années nous animons notre séminaire à deux voix, ce qui permet des échanges fructueux. Après avoir travaillé deux années durant sur le Livre des Passages, Paris capitale du XIXe siècle de Walter Benjamin, en présence de philosophes (Irving Wollfarth, philologues (Nathalie Raoux), littéraires, historiens, nous avons trouvé la voie d’accès..

Mean-Field Approximations in Effective Thermo-viscoelastic Behavior for Composite Parts Obtained via Fused Deposition Modeling Technology

editorial reviewedAiming to estimate the effective behavior of the parts obtained by fused deposition modeling (FDM) in the case of short fiber composite materials, the Mean-field homogenization procedure, introduced in linear elasticity, is here extended to linear thermo-viscoelasticity. The variation of the parameters describing the state of the fibers inside the printing filament is represented by introducing appropriate distribution functions obtained through the statistical analysis of the microstructure. The validation of the procedure is achieved by comparing its predictions with calculations based on full-field Fast-Fourier-Transform homogenization and experiments results from samples treated in autoclave to remove layer-scale porosities from the printed filament

Projet INCOME : INfrastructure de gestion de COntexte Multi-Echelle pour l'Internet des Objets

International audienceCet article donne un aperçu du projet de recherche INCOME financé par l'Agence Nationale de la Recherche française en décrivant la fiche d'identité du projet, ses principaux enjeux scientifiques ainsi que les premiers résultats obtenus

The effect of a crisis context on French wine exports: Comparison of independent wineries and wine cooperatives

International audienceIn this paper, we aim at assessing the effects of the 2019-2020 context (Covid 19, Brexit, Trump Taxes) on exporting activities of wine companies, distinguishing independent wine growers and cooperatives cellars. We rely on a survey carried out on French exporting wine companies. Our empirical investigation is based on a qualitative approach through the combination of a collection of secondary data and the results of a questionnaire survey conducted among 21 French exporting companies. On a theoretical level, we adopt the institutional approach often used in the field of international business, supplemented by recent work on the effects of disturbances in the institutional context and crisis management. Five main results were obtained: (1) effects that were generally mastered by both independent wine growers and cooperative cellars; (2) additional pressure on exports from the domestic market; (3) contrasting effects of changes in the institutional environment, with marked importance for disruptions due to the health crisis; (4) significant and differentiated adaptations of companies, and finally, (5) a distinct resilience according to territorial roots and export strategies with marked differences between independent wine growers and wine cooperatives

Ribozyme Chemistry: to be or not to be under high pressure

International audienceThe use of high hydrostatic pressure to investigate structure-function relationships in biomacromolecules in solution provides precise information about conformational changes and variations of the interactions between these macromolecules and the solvent , as well as the volume changes associated with their activity. The complementary use of osmotic pressure reveals quantitatively the extent and direction of the water exchanges between the macromolecules and the solvent and the number of water molecules involved in these exchanges. In this review, the chemistry of ribozymes and the influence of pressure is described. In the case of the hairpin ribozyme, pressure slowed down the self-cleavage reaction on the basis that the formation of the transition state involves a positive ∆V = of activation and the release of 78±4 water molecules. The self-cleaving activity of the hammerhead ribozyme is also slowed down by pressure on the basis of kinetic parameters and ∆Vs comparable to those of the hairpin ribozymes

Management et marketing du vin 2 : comprendre les enjeux et les nouvelles opportunités pour la filière vigne et vin

National audienceConcurrence accrue des nouveaux pays producteurs et des produits de substitution, déconsommation de vin, changement climatique, crise sanitaire ou contextes géopolitiques, la filière viticole se retrouve depuis quelques années confrontée à de graves difficultés. Pour autant, cette période récente offre paradoxalement de nouvelles opportunités.À travers la présentation de résultats de recherches originales, des grilles de lecture, des illustrations et des études de cas, ***Management et Marketing du vin 2*** analyse les principaux enjeux des filières vitivinicoles et envisage les opportunités nouvelles : un dynamisme renouvelé d'innovations techniques, organisationnelles et commerciales, des capacités d’adaptation des acteurs, une introduction plus importante des nouvelles technologies, etc. L’approche plurielle, mise en place par les différents auteurs et experts, propose une réflexion enrichie qui permet de mieux comprendre l’actualité de la filière vitivinicole et présente les leviers d’adaptation aux nouvelles attentes commerciales, sociétales et environnementales

Construire un avenir pour la filière vitivinicole [Conclusion]

International audienc