Modèles d'acoustique phénoménologiques - Application à la conception de matériaux sur mesure

Les modèles d'acoustique phénoménologique permettent, à partir de la description géométrique d'un matériau poreux, d'obtenir sa courbe d'absorption en fonction de la fréquence d'une onde le traversant. Faciles à programmer et à calculer, ces modèles permettent lors de la phase de conception d'une architecture poreuse d'accorder la structure aux exigences d'un cahier des charges. Nous présenterons une utilisation de ces modèles dans le cadre d'une approche Material-by-design

Representation graphique des coefficients d'anisotropies des milieux élastiques généralisés

On s'intéressera à des modèles d’élasticité généralisé : modèles se caractérisant par la prise en compte de longueurs internes. Nous introduirons une méthode graphique permettant de savoir, a priori, pour un modèle généralisé quelconque et pour un groupe de symétrie quelconque, le nombre de coefficients définissant l'opérateur de comportement associé. Cette approche permet d’obtenir les informations nécessaires pour dériver l’expression analytique de l’opérateur concerné

Etude de l'interdiffusion dans les revêtements protecteurs à haute température

Cette étude a pour but de mieux comprendre les phénomènes d'interdiffusion dans les revêtements protecteurs à haute température. La complexité des systèmes réels la rend difficile et nous avons travaillé sur des systèmes modèles B2-NiAl, B2-Ni-Pt-Al et B2-Ni-Pd-Al. Une méthode originale a été proposée pour calculer les coefficients d'interdiffusion fonction de la composition sur tout un chemin de diffusion dans les systèmes ternaires.Dans NiAl l'énergie d'activation expérimentale de la diffusion est maximum pour la composition Ni50,2Al49,8 , elle décroît lorsqu'on s'en éloigne. Des simulations ont permis de calculer les énergies de : formation des défauts ; migration de divers mécanismes de diffusion, dont un que nous avons proposé. Un choix de mécanismes a été fait, leurs énergies d'activation sont en bon accord avec l'énergie expérimentale.Dans les ternaires, le coefficient d'interdiffusion de Al croît lorsque la concentration en Pt ou Pd croît. Le gradient de Pt ou Pd n'influence pas la diffusion de Al. Le gradient de Al n'influence pas la diffusion de Pt ou de Pt dans les alliages pauvres en Al mais il la ralentit dans les alliages riches si le gradient de Al, Pt ou Pd sont de même signe. Ceci a été corrélé aux mécanismes de diffusion probables dans NiAl.L'oxydation isotherme d'alliages NiAl, Ni-Pt-Al et Ni-Pd-Al a été simulée, montrant l'intérêt d'interposer une barrière de diffusion entre substrat et revêtement. Une explication reliant la formation de cavités à l'interface métal-oxyde aux défauts structurels et aux mécanismes de diffusion dans NiAl a été proposée. A partir des couples de diffusion une barrière de diffusion a été proposée pour les systèmes réelsThis study aims at understanding interdiffusion phenomena in high temperature protective coatings. Since real systems are complex we have worked on model systems B2-NiAl, B2-Ni-Pt-Al and B2-Ni-Pd-Al.For these systems diffusion couples have been assembled. An original method for calculating composition-dependent interdiffusion coefficients along a diffusion path in ternary systems has been proposed.In B2-NiAl the experimental activation energy for diffusion is maximum at the composition Ni50.2Al49.8 and it decreases when moving away from it. Simulations have made possible to calculate the effective formation energies of defects and the migration energy associated with various diffusion mechanisms including one that we proposed. Diffusion mechanisms were selected, their activation energies are in good agreement with the experimental one.In B2-Ni-Pt-Al and B2-Ni-Pd-Al the Al direct interdiffusion coefficient increases when increasing Pt or Pd content; Pt or Pd gradient does not influence Al diffusion; Pt or Pd diffusion is not influenced by the Al gradient in Al-poor alloys but it is slowed down in Al-rich alloys if the sign of Pt or Pd gradient is the same as the one of Al gradient.These results have been correlated with the most-likely mechanisms in B2-NiAl.Isothermal oxidation of alloys B2-NiAl, B2-Ni-Pt-Al and B2-Ni-Pd-Al have been simulated showing the necessity of a diffusion barrier. An explanation has been suggested for the cavity formation at the metal-oxyde interface which takes into account both defects and diffusion mechanisms in these materials. From the results obtained with the diffusion couples a diffusion barrier in real systems has been suggested.LIMOGES-ENSCI (870852305) / SudocORSAY-PARIS 11-BU Sciences (914712101) / SudocPARIS12-THIAIS CNRS ICMPE (940732301) / SudocSudocFranceF

Fatigue of metal hollow spheres structures

International audienceA study was conducted to examine and formulate the effect of the microstructure of metal hollow spheres structures (MHSS) on their fatigue properties. Standard compression/compression fatigue tests were conducted to measure the macroscopic properties of microstructures with different structural parameters. The stress concentration inside the complex microstructure was measured to develop a model that shows properties of the materials. X-ray tomographic images were obtained to study their three-dimensional (3D) architecture. The tomography was also used to determine the morphological parameters. The 3D images were processed and analyzed using a granulometry procedure based on sequential opening operations. A hydraulic fatigue machine (MTS) at a frequency of 10 Hz was used to perform all the fatigue tests. Results show that the ratio of the fatigue limit to the yield stress is about 0.5 in each condition, providing a useful design rule for microstructure

Characterization of Rat ILCs Reveals ILC2 as the Dominant Intestinal Subset

International audienceInnate lymphoid cells (ILCs) are tissue-resident lymphocytes that lack antigen-specific receptors and exhibit innate effector functions such as cytokine production that play an important role in immediate responses to pathogens especially at mucosal sites. Mouse and human ILC subsets have been extensively characterized in various tissues and in blood. In this study, we present the first characterization of ILCs and ILC subsets in rat gut and secondary lymphoid organs using flow cytometry and single cell RNA sequencing. Our results show that phenotype and function of rat ILC subsets are conserved as compared to human and mouse ILCs. However, and in contrast to human and mouse, our study unexpectedly revealed that ILC2 and not ILC3 was the dominant ILC subset in the rat intestinal lamina propria. ILC2 predominance in the gut was independent of rat strain, sex or housing facility. In contrast, ILC3 was the predominant ILC subset in mesenteric lymph nodes and Peyer patches. In conclusion, our study demonstrates that in spite of highly conserved phenotype and function between mice, rat and humans, the distribution of ILC subsets in the intestinal mucosa is dependent on the species likely in response to both genetic and environmental factors

Preclinical Assessment of Autologous Tolerogenic Dendritic Cells From End-stage Renal Disease Patients

International audienceBackground: Kidney transplantation is the therapeutic of choice for patients with kidney failure. While immunosuppressive drugs can control graft rejection, their use is associated with increased infections and cancer, and they do not effectively control chronic graft rejection. Cell therapy is an attractive strategy to minimize the use of pharmacological drugs.Methods: We recently developed a protocol to generate human monocyte-derived autologous tolerogenic dendritic cells (ATDCs) from healthy volunteers. Herein, we transferred the ATDC manufacturing protocol to a Good Manufacturing Practice (GMP)-compliant facility. Furthermore, we compared the phenotype and in vitro functions of ATDCs generated from patients with end-stage renal disease to those generated from healthy volunteers.Results: We describe the critical steps for GMP-compliant production of ATDCs and define the quality criteria required to allow release of the cell products. Furthermore, we showed that ATDCs generated from healthy volunteers and patients with kidney failure display the same tolerogenic profile based on their phenotype, resistance to maturation, and ability to modulate T-cell responses.Conclusions: Together, these results allowed us to define the production process and the quality criteria for the release of ATDCs before their administration in patients receiving a kidney transplant

Comparative Study of the Immunoregulatory Capacity of In Vitro Generated Tolerogenic Dendritic Cells, Suppressor Macrophages, and Myeloid-Derived Suppressor Cells

International audienceBackground. Regulatory myeloid cell (RMC) therapy is a promising strategy for the treatment of immunological disorders such as autoimmune disease and allograft transplant rejection. Various RMC subsets can be derived from total bone marrow using different protocols, but their phenotypes often overlap, raising questions about whether they are truly distinct.Methods. In this study, we directly compared the phenotype and function of 3 types of RMCs, tolerogenic dendritic cells, suppressor macrophages, and myeloid-derived suppressor cells, generated in vitro from the same mouse strain in a single laboratory.Results. We show that the 3 RMC subsets tested in this study share some phenotypic markers, suppress T cell proliferation in vitro and were all able to prolong allograft survival in a model of skin transplantation. However, our results highlight distinct mechanisms of action that are specific to each cell population.Conclusions. This study shows for the first time a side-by-side comparison of 3 types of RMCs using the same phenotypic and functional assays, thus providing a robust analysis of their similarities and differences

Dans les marges. Trente ans du fonds Michel Chomarat à la bibliothèque de Lyon

International audienceCatalogue de l'exposition "Dans les marges. Trente ans du fonds Michel Chomarat à la bibliothèque de Lyon", exposition présentée à la Bibliothèque municipale de la Part-Dieu, 15 septembre 2022-28 janvier 2023. cf. https://www.bm-lyon.fr/expositions-en-ligne/dans-les-marges-30-ans-du-fonds-michel-chomarat