Adaptation of Phase-Lagged Boundary Conditions to Large-Eddy Simulation in Turbomachinery Configurations

With the increase in computing power, large eddy simulation (LES) emerges as a promising technique to improve both knowledge of complex physics and reliability of turbomachinery flow predictions. However, these simulations are very expensive for industrial applications, especially when a 360 degrees configuration should be considered. The objective of this paper is thus to adapt the well-known phase-lagged conditions to the LES approach by replacing the traditional Fourier series decomposition (FSD) with a compression method that does not make any assumptions on the spectrum of the flow. Several methods are reviewed and the proper orthogonal decomposition (POD) is retained. This new method is first validated on a flow around a circular cylinder with rotating downstream blocks. The results show significant improvements with respect to the FSD. It is then applied to unsteady Reynolds-Averaged Navier–Stokes (URANS) simulations of a single stage compressor in 2.5D and 3D as a first validation step toward single-passage LES of turbomachinery configuration

Utilisation de la décomposition orthogonale aux valeurs propres pour les conditions aux limites chorochroniques

Cette étude porte sur l'adaptation des conditions aux limites chorochroniques pour des simulations aux grandes échelles. Pour cela, la décomposition en séries de Fourier traditionnellement utilisée est remplacée par une décomposition orthogonale en modes propres. Les deux méthodes sont ensuite appliquées à la simulation URANS d'un étage de turbomachine

Culture tridimensionnelle de cellules épithéliales respiratoires humaines (applications à la thérapie génique et cellulaire)

@Nous avons pu mettre en évidence que des cellules épithéliales respiratoires humaines cultivées sous forme de sphéroïdes pouvaient mimer, à long terme, la structure et la fonctionnalité d'un épithélium respiratoire de surface. Nous avons étudié la capacité de ces structures 3-D à recoloniser un épithélium respiratoire dénudé. Par utilisation d'un vecteur lentiviral, codant la protéine GFP, nous avons également étudier la capacité de ces sphéroïdes polarisés et différenciés à être transduits. Notre étude a pu montrer que ces structures 3-D pouvaient rége nérer un épithélium respiratoire pseudostratifié et pouvaient être transduites par un vecteur lentiviral avec une expression à long terme de la protéine GFP et un maintien de la fonctionnalité épithéliale (fréquence ciliaire, sécrétion de chlore). Ces sphéroïdes pourraient ainsi être un outil potentiel de thérapie génique et cellulaire dans la régénération d'un épithélium respiratoire mucoviscidosique@We have shown that human airway epithelial cells cultured as 3-D spheroid could mimic for a long term an airway surface epithelium structure and functionality. We analyzed the potential capacity of these 3-D structures to regenerate an airway epithelium and to be transduced using a pseudotyped lentiviral vector encoding GFP. Our results demonstrate that the spheroids can regenerate a well-differentiated human airway epithelium and can be efficiently transduced by a pseudotyped lentiviral vector with a sustained and long-term expression of the GFP, without any alteration of the spheroid structure and functionality (ciliary beating frequency and CFTR Cl- channel activity). The spheroids could be proposed as a potential tool for gene and cell therapy in order to repopulate a denuded airway epithelium in cystic fibrosis.REIMS-BU Santé (514542104) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Multiple-frequency phase-lagged unsteady simulations of experimental axial compressor

International audienceno abstrac

A Novel approach to evaluate the benefits of casing treatment in axial compressors

International audiencePassive control devices based on casing treatments have already shown their capability to improve the flow stability in axial compressors. However, their optimization remains complex due to a partial understanding of the related physical mechanisms. In order to quantitatively assess the interaction between slots and the blade tip flow, the present paper develops a novel analysis methodology based on a control-volume approach located in the rotor tip region. This methodology may be used for analyzing the casing treatment based on both axi- and non-axisymmetric slots design. The second issue of the paper focuses on the application of the current approach to better understand the effects of axi- and non-axisymmetric grooves in three different axial compressors which differ by the flow regime (subsonic/transonic) and the smooth casing shape (cylindrical/concave). Numerical simulations are performed, and results of the current approach with and without casing treatments are compared

Aquaporin-3 expression in human fetal airway epithelial progenitor cells.

Airway epithelium stem cells have not yet been prospectively identified, but it is generally assumed that both secretory and basal cells have the capacity to divide and differentiate. Previously, we developed a test for progenitor cells of the human airway epithelium, relying on the transplantation of fetal respiratory tissues into immunodeficient mice. In this study, we hypothesized that airway-repopulating epithelial progenitors can be marked with surface antigens, and we screened an array of such candidate markers, including lectin ligands, the CD44 and CD166 adhesion molecules, and the aquaporin-3 (AQP3) water channel. We observed that AQP3 is selectively expressed on the surface of basal cells, allowing the separation by flow cytometry of AQP3+ basal cells and AQP3- ciliated and secretory cells. Functional evaluation of sorted cells in vivo showed that AQP3+ cells can restore a normal pseudostratified, mucociliary epithelium as well as submucosal glands. AQP3- cells are also endowed with a similar potential, although faster engraftment suggests their inclusion of more committed progenitors. These results show that stem cell candidates in the human tracheo-bronchial mucosa can be positively selected with a novel marker but also, for the first time, that epithelial progenitors exist among both basal and suprabasal cell subsets within the human airway

Regeneration of a well-differentiated human airway surface epithelium by spheroid and lentivirus vector-transduced airway cells.

BACKGROUND: Following injury to the airway epithelium, rapid regeneration of a functional epithelium is necessary in order to restore the epithelial barrier integrity. In the perspective of airway gene/cell therapy, we analyzed the capacity of human airway epithelial cells cultured as three-dimensional (3-D) spheroid structures to be efficiently transduced on long term by a pseudotyped lentiviral vector. The capacity of the 3-D spheroid structures to repopulate a denuded tracheal basement membrane and regenerate a well-differentiated airway epithelium was also analyzed. METHODS: An HIV-1-derived VSV-G pseudotyped lentiviral vector encoding the enhanced green fluorescent protein (eGFP) was used. Airway epithelial cells were isolated from mature human fetal tracheas and airway xenografts, cultured as 3-D spheroid structures, and either transduced at multiplicity of infection (MOI) 10 and 100 or assayed in an ex vivo and in vivo model to evaluate their regeneration capacity. RESULTS: An in vivo repopulation assay in SCID-hu mice with transduced isolated fetal airway epithelial cells shows that lentiviral transduction does not alter the airway reconstitution. Transduction of the 3-D spheroid structures shows that 12% of cells were eGFP-positive for up to 80 days. In ex vivo and in vivo assays (NUDE-hu mice), the 3-D spheroid structures are able to repopulate denuded basement membrane and reconstitute a well-differentiated human airway surface epithelium. CONCLUSIONS: The efficient and long-term lentiviral transduction of 3-D spheroid structures together with their capacity to regenerate a well-differentiated mucociliary epithelium demonstrate the potential relevance of these 3-D structures in human airway gene/cell therapy

Wealth and poverty in the rhizosphere – sharing a scarce resource: soil P

International audienceAims and Background Plant nutrition models assume that phosphorus is depleted in the rhizosphere, due to root uptake. These models adequately predict P acquisition in P-rich soils but most often underestimate it in P- poor soils. We aimed at challenging the hypothesis of P depletion as the driving force of P acquisition in the rhizosphere. Methods The rhizosphere of various crops, either grown alone or intercropped, was sampled in rhizobox, pot and field experiments conducted in soils of contrasting P-status (the P-poor soil did not receive any fertilizer- P for 40 years, while the P-rich soil received excess P), in order to measure changes in P availability relative to bulk soil. Geochemical modelling w as used to understand the underlying processes. Results Phosphorus availability (water and Olsen extracts) almost systematically increased in the rhizosphere, for both the P-poor and P-rich soils. The absence of P depletion suggested that P bioavailability was ruled by another process than P uptake. Geochemical modelling helped eluc idating the contribution of root-induced pH changes and uptake of calcium. Conclusion The rhizosphere can be P-enriched rather than becoming P-impoverished, which contradicts common know ledge. Biogeoche mical processes other than P uptake have to be accounted for to adequately predict P nutrition in crops

Polarized expression of cystic fibrosis transmembrane conductance regulator and associated epithelial proteins during the regeneration of human airway surface epithelium in three-dimensional culture.

We have previously shown that, in normal human airway tissue, localization of the cystic fibrosis transmembrane conductance regulator (CFTR) can be affected by epithelial maturation, polarity, and differentiation and that CFTR trafficking and apical localization depend on the integrity of the airway epithelium. In this study, we addressed the question of whether the three-dimensional (3-D) organization of adult human airway epithelial cells in suspension culture under rotation, leading to spheroid-like structures, could mimic the in vivo phenomenon of differentiation and polarization. The kinetics of the differentiation, polarity, and formation of the CFTR-ZO-1-ezrin complex was analyzed by transmission, scanning, and immunofluorescence microscopy. Functional activity of the airway surface epithelium was assessed by monitoring the degree of cAMP-stimulated chloride efflux from cultured cells. Our results show that after the initial step of dedifferentiation, characterized by a loss of ciliated cells and disappearance of epithelial subapical CFTR-ezrin-ZO-1 complex, the isolated cells formed 3-D spheroid structures within 24 hours. After 15 days, progressive ciliogenesis was observed and secretory cells could be identified. After 35 days of 3-D culture, ZO-1, CFTR, ezrin, and CD59 were apically or subapically located, and well-differentiated secretory and ciliated cells were identified. CFTR functionality was assessed by analyzing the Cl(-) secretion after amiloride and forskolin perfusion. After 35 days of culture of spheroids in suspension, a significant increase in Cl(-) efflux was observed in well-differentiated ciliated cells