Caractérisation mécanique dynamique de matériaux poro-visco-élastiques

Poro-viscoelastic materials are well modelled with Biot-Allard equations. This model needs a number of geometrical parameters in order to describe the macroscopic geometry of the material and elastic parameters in order to describe the elastic properties of the material skeleton. Several characterisation methods of viscoelastic parameters of porous materials are studied in this thesis. Firstly, quasistatic and resonant characterization methods are described and analyzed. Secondly, a new inverse dynamic characterization of the same modulus is developed. The latter involves a two layers metal-porous beam, which is excited at the center. The input mobility is measured. The set-up is simplified compared to previous methods. The parameters are obtained via an inversion procedure based on the minimisation of the cost function comparing the measured and calculated frequency response functions (FRF). The calculation is done with a general laminate model. A parametric study identifies the optimal beam dimensions for maximum sensitivity of the inversion model. The advantage of using a code which is not taking into account fluid-structure interactions is the low computation time. For most materials, the effect of this interaction on the elastic properties is negligible. Several materials are tested to demonstrate the performance of the method compared to the classical quasi-static approaches, and set its limitations and range of validity. Finally, conclusions about their utilisation are given

Influence de la prédéformation sur la mesure des propriétés mécaniques de matériaux poreux acoustiques

Une étude de l'influence de la précontrainte sur l'estimation des paramètres élastiques de matériaux poreux acoustiques est réalisée. Le dispositif expérimental utilisé pour cette étude, dérivant d'un système masse de précontrainte-ressort, est celui décrit par. Deux classes de comportement de la rigidité en fonction de la précontrainte sont identifiées : une pour les matériaux cellulaires (ou mousses), une seconde pour les matériaux fibreux ou agglomérés. Enfin, des indications quant au choix de la masse permettant d'atteindre le comportement élastique linéaire d'un matériau poreux quelconque, en compression unixiale, sont données

Autophagy plays an important role in protecting Pacific oysters from OsHV-1 and Vibrio aestuarianus infections.

Recent mass mortality outbreaks around the world in Pacific oysters, Crassostrea gigas, have seriously affected the aquaculture economy. Although the causes for these mortality outbreaks appear complex, infectious agents are involved. Two pathogens are associated with mass mortality outbreaks, the virus ostreid herpesvirus 1 (OsHV-1) and the bacterium Vibrio aestuarianus. Here we describe the interactions between these 2 pathogens and autophagy, a conserved intracellular pathway playing a key role in innate immunity. We show for the first time that autophagy pathway is present and functional in Pacific oysters and plays an important role to protect animals from infections. This study contributes to better understand the innate immune system of Pacific oysters.This work was partially funded through the EU project Bivalife (FP7 KBBE, contract n 266157), the Poitou Charentes Region and DPMA (Direction des p^eches maritimes et de l’aquaculture, AESTU project). David Rubinsztein is aWellcome Trust Prinicipal Research Fellow.This is the final published version. It first appeared at http://www.tandfonline.com/doi/full/10.1080/15548627.2015.1017188

Type 1 interferons and Foxo1 down-regulation play a key role in age-related T-cell exhaustion in mice

Foxo family transcription factors are critically involved in multiple processes, such as metabolism, quiescence, cell survival and cell differentiation. Although continuous, high activity of Foxo transcription factors extends the life span of some species, the involvement of Foxo proteins in mammalian aging remains to be determined. Here, we show that Foxo1 is down-regulated with age in mouse T cells. This down-regulation of Foxo1 in T cells may contribute to the disruption of naive T-cell homeostasis with age, leading to an increase in the number of memory T cells. Foxo1 down-regulation is also associated with the up-regulation of co-inhibitory receptors by memory T cells and exhaustion in aged mice. Using adoptive transfer experiments, we show that the age-dependent down-regulation of Foxo1 in T cells is mediated by T-cell-extrinsic cues, including type 1 interferons. Taken together, our data suggest that type 1 interferon-induced Foxo1 down-regulation is likely to contribute significantly to T-cell dysfunction in aged mice

Caractérisation mécanique dynamique de matériaux poro-visco-élastiques

Poro-viscoelastic materials are well modelled with Biot-Allard equations. This model needs a number of geometrical parameters in order to describe the macroscopic geometry of the material and elastic parameters in order to describe the elastic properties of the material skeleton. Several characterisation methods of viscoelastic parameters of porous materials are studied in this thesis. Firstly, quasistatic and resonant characterization methods are described and analyzed. Secondly, a new inverse dynamic characterization of the same modulus is developed. The latter involves a two layers metal-porous beam, which is excited at the center. The input mobility is measured. The set-up is simplified compared to previous methods. The parameters are obtained via an inversion procedure based on the minimisation of the cost function comparing the measured and calculated frequency response functions (FRF). The calculation is done with a general laminate model. A parametric study identifies the optimal beam dimensions for maximum sensitivity of the inversion model. The advantage of using a code which is not taking into account fluid-structure interactions is the low computation time. For most materials, the effect of this interaction on the elastic properties is negligible. Several materials are tested to demonstrate the performance of the method compared to the classical quasi-static approaches, and set its limitations and range of validity. Finally, conclusions about their utilisation are given

Caractérisation mécanique dynamique de matériaux poro-visco-élastiques

Les matériaux poreux visco-élastiques peuvent être modélisés par le biais du modèle de Biot-Allard. Ce modèle requiert la connaissance d'une série de paramètres macroscopiques décrivant la géométrie des pores du matériau d'une part et les propriétés élastiques du squelette du matériau d'autre part. Différentes méthodes de caractérisation des paramètres visco-élastiques de ces matériaux poreux sont étudiées dans cette thèse. Dans un premier temps, les méthodes quasistatique et résonante existantes sont décrites et analysées. Dans un second temps, une nouvelle méthode dynamique de caractérisation par inversion est développée. Cette dernière met en jeu une poutre bicouche, de type métal-poreux, qui est excitée en son centre et dont la réponse fréquentielle est mesurée. Le principe de mesure est simplifié par rapport aux méthodes existantes. L'obtention des paramètres se fait par un processus d'inversion, qui est la minimisation d'une fonction coût calculée à partir de la différence des fonctions de réponses en fréquences (FRF) mesurée et prédite, grâce à un modèle de stratifié. Une étude paramétrique donne les dimensions de poutre permettant de se placer dans le cas où le modèle est le plus sensible. L'avantage de l'utilisation d'un code ne prenant pas en compte les phénomènes d'interaction fluide-structure est la rapidité de l'inversion. Pour la plupart des matériaux cette interaction est négligeable en ce qui concerne les propriétés élastiques. Les méthodes sont appliquées sur plusieurs matériaux et les résultats sont comparés. Les limitations des méthodes sont ainsi fixées et des conclu sions, quant à leur utilisation, sont tirées.Poro-viscoelastic materials are well modelled with Biot-Allard equations. This model needs a number of geometrical parameters in order to describe the macroscopic geometry of the material and elastic parameters in order to describe the elastic properties of the material skeleton. Several characterisation methods of viscoelastic parameters of porous materials are studied in this thesis. Firstly, quasistatics and resonant characterization me- thods are described and analyzed. Secondly, a new inverse dynamic characterization of the same modulus is developed. The latter involves a two layers metal-porous beam, which is excited at the center. The input mobility is measured. The set-up is simpli ed compared to previous methods. The parameters are obtained via an inversion procedure based on the minimisation of the cost function comparing the measured and calculated frequency response functions (FRF). The calculation is done with a general laminate model. A pa- rametric study identi es the optimal beam dimensions for maximum sensitivity of the inversion model. The advantage of using a code which is not taking into account uid- structure interaction is the low computation time. For most materials, the e®ect of this interaction on the elastic properties is negligible. Several materials are tested to demons- trate the performance of the method compared to the classical quasi-static approaches, and set its limitations and range of validity. Finally, conclusions about their utilisation are given.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

Sensitivity of Alphitobius diaperinus (Coleoptera : tenebrionidae) continuously exposed to one or multiple abiotic constraints

International audienc

Detection and tissue distribution of Ostreid herpesvirus 1 proteins in infected pacific oyster, Crassostrea gigas.

International audienc

Visualization of the 3D structure of the graft union of grapevine using X-ray tomography

International audienceSuccessful grafting in plants requires the development of a functional vascular system between the scion and the rootstock. Understanding the spatial organization of the graft interface is important to the evaluation of new rootstock genotypes and to the development of new grafting technologies. Until now the graft interface has only been studied using 2D classical histology and low resolution 3D magnetic resonance imaging. Here we investigate the ability of X-ray tomography to examine the graft interface of Vitis vinifera in high resolution and in 3D. Data were collected using a Skyscan 1076, scanning parameters, such as. X-ray energy, filter selection, pixel size and rotation angles, were optimized to study the particularities of the graft interface. The X-ray tomography technique was then used to evaluate graft quality. Two young vines were compared; one graft was classified as of 'good' quality, whereas the other was classified as of 'bad' quality. We were able to distinguish the "omega cut", the pith, the phloem and the xylem vessels in the images. The analysis shows several differences between the two vines. In the good graft, tissues appear well-connected in the wood and phloem, and had a regular structure; the wood appears homogenous with a lot of vessels that form a compact mass. By contrast, in the bad graft, the structures appear disorganized and not completely connected. Numerous new vessels, continuous between the scion and the rootstock, are visible in the "good graft" whereas only few ones are visible in the "bad one". It is the first time, to our knowledge, that 3D imaging of the graft interface and the vascular connections across it have been reported, opening new avenues for graft quality assessment in woody plants

Ostreid herpesvirus type 1 replication and host response in adult Pacific oysters, Crassostrea gigas

International audienceSince 2008, massive mortality outbreaks associated with OsHV-1 detection have been reported in Crassostrea gigas spat and juveniles in several countries. Nevertheless, adult oysters do not demonstrate mortality in the field related to OsHV-1 detection and were thus assumed to be more resistant to viral infection. Determining how virus and adult oyster interact is a major goal in understanding why mortality events are not reported among adult Pacific oysters. Dual transcriptomics of virus-host interactions were explored by real-time PCR in adult oysters after a virus injection. Thirty-nine viral genes and five host genes including MyD88, IFI44, IkB2, IAP and Gly were measured at 0.5, 10, 26, 72 and 144 hours post infection (hpi). No viral RNA among the 39 genes was detected at 144 hpi suggesting the adult oysters are able to inhibit viral replication. Moreover, the IAP gene (oyster gene) shows significant up-regulation in infected adults compared to control adults. This result suggests that over-expression of IAP could be a reaction to OsHV-1 infection, which may induce the apoptotic process. Apoptosis could be a main mechanism involved in disease resistance in adults. Antiviral activity of haemolymph against herpes simplex virus (HSV-1) was not significantly different between infected adults versus control