Contribution à l'étude des propriétés d'un composite PP/lin mis en oeuvre par extrusion

International audienceLe comportement mécanique d'un composite polypropylène (PP) renforcé avec des fibres de lin extrudé sous forme de bande plate a été étudié et comparé à celui du PP/talc. Ces mêmes matériaux ont aussi été injectés et leur propriétés comparées à celles des pièces extrudées. Les propriétés mécaniques et leur microstructure ont été étudiées après transformation. L'utilisation des fibres de lin comme renfort permet de dépasser les propriétés mécaniques du PP/talc tout en permettant une diminution du retrait et de la masse volumique. L'ajout d'anhydride maléique a permis une nette amélioration des performances grâce à l'amélioration de l'interface fibres/matrice. Les matériaux injectés présentent de meilleures caractéristiques mécaniques que ceux extrudés grâce à une meilleure orientation des fibres et une plus faible porosité

Purification and characterisation of the yeast plasma membrane ATP binding cassette transporter Pdr11p.

The ATP binding cassette (ABC) transporters Pdr11p and its paralog Aus1p are expressed under anaerobic growth conditions at the plasma membrane of the yeast Saccharomyces cerevisiae and are required for sterol uptake. However, the precise mechanism by which these ABC transporters facilitate sterol movement is unknown. In this study, an overexpression and purification procedure was developed with the aim to characterise the Pdr11p transporter. Engineering of Pdr11p variants fused at the C terminus with green fluorescent protein (Pdr11p-GFP) and containing a FLAG tag at the N terminus facilitated expression analysis and one-step purification, respectively. The detergent-solubilised and purified protein displayed a stable ATPase activity with a broad pH optimum near 7.4. Mutagenesis of the conserved lysine to methionine (K788M) in the Walker A motif abolished ATP hydrolysis. Remarkably, and in contrast to Aus1p, ATPase activity of Pdr11p was insensitive to orthovanadate and not specifically stimulated by phosphatidylserine upon reconstitution into liposomes. Our results highlight distinct differences between Pdr11p and Aus1p and create an experimental basis for further biochemical studies of both ABC transporters to elucidate their function

Study of the fibre morphology stability in polypropylene-flax composites

International audienc

Observation of the structure of a polypropylene flax composite and damage mechanism under stress

International audienc

The flax in the "Flora's image" in the Ariadne House (Pompeian area, Italy) as a symbol of feminine in a wedding sacred to the afterlife

In ancient time, life elements, like plants and animals, and unanimated forces of nature were usually associated with specific meanings related to deities and sacred rituals. In Roman archeology, the strong symbolic value of plants represented in wall paintings and artifacts was proved by several contributions, but this topic is often neglected. In this paper, for the first time, an interpretation is proposed for the plant represented in one of the most iconic paintings in Pompeii, the so-called "Flora" in Ariadne's house. Here, the analyzed plant is picked by a girl turned away and holding a floral cornucopia, and it plays a relevant role in the scene. Through the analysis of its morphological elements, and comparing them with other ancient representations, we suggest its identification as flax (Linum usitatissimum L.). Flax was an economically and culturally very important plant, widely represented in objects and paintings in the Mesopotamian and Egyptian area. We also suggest that the meaning behind the choice of depict flax was also related to its classical attribution as a symbol of fertility and afterlife as well as linked to the "feminine" sphere. This interpretation, together with other elements of the images, strengthens the already proposed interpretation of the yellow-dressed girl a wife, which is let to go this life for an afterlife, in the figure of Persephone

Observation of the structure of a polypropylene flax composite and damage mechanism under stress

International audienc

Observation of the structure of a composite polypropylene/flax and damage mechanisms under stress

International audienc

Contribution à l'étude des propriétés d'un composite PP/lin mis en oeuvre par extrusion

International audienceLe comportement mécanique d'un composite polypropylène (PP) renforcé avec des fibres de lin extrudé sous forme de bande plate a été étudié et comparé à celui du PP/talc. Ces mêmes matériaux ont aussi été injectés et leur propriétés comparées à celles des pièces extrudées. Les propriétés mécaniques et leur microstructure ont été étudiées après transformation. L'utilisation des fibres de lin comme renfort permet de dépasser les propriétés mécaniques du PP/talc tout en permettant une diminution du retrait et de la masse volumique. L'ajout d'anhydride maléique a permis une nette amélioration des performances grâce à l'amélioration de l'interface fibres/matrice. Les matériaux injectés présentent de meilleures caractéristiques mécaniques que ceux extrudés grâce à une meilleure orientation des fibres et une plus faible porosité