The effect of the G-Layer on the viscoelastic properties of tropical hardwoods

International audienceContext and aim : This study aimed to examine the effect of the tension wood G‐layer on the viscoelastic properties of wood. Methods : Tension wood and opposite wood samples were obtained from six French Guianese tropical rainforest species (Sextonia rubra, Ocotea guyanensis, Inga alba, Tachigali melinoni, Iyranthera sagotiana and Virola michelii); the tension wood of the former three of these species had a Glayer, whilst the tension wood from the latter three had no Glayer. Tensile dynamic mechanical analysis (DMA) was performed on green never dried wood samples in the longitudinal direction with samples submerged in a water bath at a temperature (30°C) and frequency (1 Hz) representative of the conditions experienced by wood within a living tree. Then, DMA was repeated with samples conditioned to an air-dried state. Finally, samples were oven-dried to measure longitudinal shrinkage. Results : Tension wood did not always have a higher longitudinal storage (elastic) modulus than opposite wood from the same tree regardless of the presence or absence of a G‐layer. For the species containing a G‐layer, tension wood had a higher damping coefficient and experienced a greater longitudinal shrinkage upon drying than opposite wood from the same species. No difference was found in damping coefficients between tension wood and opposite wood for the species that had no G‐layer. Conclusion : It is proposed that the different molecular composition of the G-layer matrix has an influence on the viscoelasticity of wood, even if a biomechanical gain is not yet clear. This study shows that rheological properties and longitudinal shrinkage can be used to detect the presence of a G‐layer in tension wood

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Hubert Curien à la présidence du Cnes

Président du Centre national d’études spatiales (Cnes) de juillet 1976 à juillet 1984, Hubert Curien a soutenu le programme du lanceur Ariane, avec le succès inaugural de décembre 1979, puis la création de la société Arianespace. Il est aussi à l’origine du programme d’observation spatiale Spot (Système probatoire d’observation de la Terre puis Satellite pour l’observation de la Terre). Au Cnes comme à l’Agence spatiale européenne (ESA) qu’il a présidée avec une grande diplomatie, puis au ministère de la Recherche, il a eu à cœur de mettre la science au centre de programmes spatiaux internationaux ambitieux (avec les USA et l’URSS en particulier), sans jamais oublier la dimension éducative de l’espace.As President of the CNES from July 1976 to July 1984, Hubert Curien supported the Ariane Space programme, starting with the first launch in 1979 and followed by the creation of Arianespace. He also initiated the Spot Space observation programme. Successively at the head of the CNES then of the ESA, both of which he led with great diplomacy, ending with the Ministry of Research, he made a point of putting science at the centre of ambitious Space programmes (involving both the USA and the USSR) without ever forgetting the educational role of Space

It was tomorrow, or humankind, from one frontier to the other

During the Jewish celebration of Passover, the youngest of the assembly has to request: “When these events did take place? ” The oldest one answers: “It was tomorrow.” A manner of affirming the singularity of the human being which, to survive and grow, must unceasingly cross new passages, without disavowing its past. But is a future still possible, when reality was désacralisée, when the threats are increasingly precise, when also we think of being able to create a new humanity? We should not hesitate to pose the thresholds of sacred where our ignorance starts, in order to reserve a space of freedom to us. Without it, our humanity would be likely to disappear, without a future