72 research outputs found
Simulation of turbulent flows out of spectral equilibrium using the PITM method
The two main approaches to numerical prediction of turbulent flows that are the RANS method and the LES method have long been developed independently from each other and there is a need in practice to bridge these apparently different approaches. Relying upon the spectral theory background, it has been possible to develop continuous hybrid methods that allow seamless coupling between RANS and LES. The derivation of the PITM method is based on the dynamic equation of the two-point fluctuating velocity correlations with extension to nonhomogeneous turbulence. Indeed, the two-point velocity correlation equation embodies a detailed description of the turbulence field. Then, using Fourier transform and performing averaging on spherical shells on the dynamic equation, leads formally to the evolution equation of the one-dimensional spectral velocity correlation tensor. Exiled in one-dimensional space, the turbulence quantities are represented by functions of the scalar wave number rather than the wave vector. These spectral equations have also been the basis for developing one-dimensional non-isotropic spectral models [1, 2]. A partial integration over a split spectrum, with a given partitioning understood as spectral filtering, yields the partial integrated transport modeling (PITM) method that can be used for practical simulations of turbulent flows [3, 4]. As a result, new transport equations for the subfilter scale stresses and dissipation-rate have been obtained. In this formulation, the model is governed by a dimensionless parameter which involves the cutoff wave number and the turbulence length-scale. Previous simulations have shown that the PITM method is able to reproduce fairly well a large variety of internal and external flows out of spectral equilibrium in the energetic sense and spectral anisotropy sense. Because advanced closures can be used to model the subfilter range, then, large filter widths can be used without prejudice and as a result the computing time can be fairly reduced. The present paper considers various applications such as rotating flows encountered in turbomachinery [6], pulsed turbulent flows [3], flows with wall mass injection [4], flows with separation and reattachment of the boundary layer [7, 8] a mixing of two turbulent flows of different scales [9], airfoil flows [10], and a flow in a small axisymmetric contraction [11], while allowing a drastic reduction of the computational resources in comparison with the one required for highly resolved LES. [1] Cambon, C., Jeandel, D., Mathieu, J. 104, 247-262 (1981). [2] Chaouat, B., Schiestel, R. Theor. Comput. Fluid Dyn. 21, 201-229 (2007). [3] Schiestel, R., Dejoan, A. Theor. Comput. Fluid Dyn. 18, 443-468 (2005). [4] Chaouat, B., Schiestel, R. Phys. Fluids 17, 065106, 1-19 (2005). [5] Chaouat, B., Schiestel, R. Phys. Fluids 24, 085106, 1-34 (2012). [6] Chaouat, B. Phys. Fluids 24, 045108,1-35 (2012). [7] Chaouat, B. J. Turbul. 11, 1-30 (2010). [8] Chaouat, B., Schiestel, R. Computers and Fluids 84, 279-300 (2013). [9] Befeno, I., Schiestel, R. Flow, Turbul. Combust. 78, 129-151 (2007). [10] Stoellinger, M., Roy, R., Heinz, S. in Proceedings of the 9th Symposium on Turbulence Shear Flow Phenomena, edited by the University of Melbourne, 7B5, 1-6 (2015). [11] B. Chaouat. Flow, Turbul. Combust. In press (2016). [12] Uberoi M.S., Wallis, S. J. Fluid Mech. 24, 539-543 (1966)
Generation of a Novel Regulatory NK Cell Subset from Peripheral Blood CD34+ Progenitors Promoted by Membrane-Bound IL-15
BACKGROUND: NK cells have been long time considered as cytotoxic lymphocytes competent in killing virus-infected cells and tumors. However, NK cells may also play essential immuno-regulatory functions. In this context, the real existence of a defined NK subset with negative regulatory properties has been hypothesized but never clearly demonstrated. METHODOLOGY/PRINCIPAL FINDINGS: Herein, we show the in vitro generation from human peripheral blood haematopoietic progenitors (PB-HP), of a novel subset of non-cytolytic NK cells displaying a mature phenotype and remarkable immuno-regulatory functions (NK-ireg). The main functional hallmark of these NK-ireg cells is represented by the surface expression/release of HLA-G, a major immunosuppressive molecule. In addition, NK-ireg cells secrete two powerful immuno-regulatory factors: IL-10 and IL-21. Through these factors, NK-ireg cells act as effectors of the down-regulation of the immune response: reconverting mature myeloid DC (mDC) into immature/tolerogenic DC, blocking cytolytic functions on conventional NK cells and inducing HLA-G membrane expression on PB-derived monocytes. The generation of "NK-ireg" cells is obtained, by default, in culture conditions favouring cell-to-cell contacts, and it is strictly dependent on reciprocal trans-presentation of membrane-bound IL-15 forms constitutively and selectively expressed by human CD34(+) PB-HP. Finally, a small subset of NKp46(+) HLA-G(+) IL-10(+) is detected within freshly isolated decidual NK cells, suggesting that these cells could represent an in vivo counterpart of the NK-ireg cells. CONCLUSIONS/SIGNIFICANCE: In conclusion, NK-ireg cells represent a novel truly differentiated non-cytolytic NK subset with a self-sustainable phenotype (CD56(+) CD16(+) NKp30(+) NKp44(+) NKp46(+) CD94(+) CD69(+) CCR7(+)) generated from specific pSTAT6(+) GATA3(+) precursors. NK-ireg cells could be employed to develop new immuno-suppressive strategies in autoimmune diseases, transplant rejection or graft versus host diseases. In addition, NK-ireg cells can be easily derived from peripheral blood of the patients and could constitute an autologous biotherapic tool to be used combined or in alternative to other immuno-regulatory cells
A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)
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LâOmbre pour la proie
Lâhomme sans ombre est un moi sans Autre, monade solipsiste. InquiĂ©tante Ă©trangetĂ© de ce moi inaltĂ©rĂ©, Ă©gal Ă lui-mĂȘme, sans diffĂ©rence. Cette vie sans ombre, exposĂ©e Ă la lumiĂšre du jour, ce MĂȘme sans Autre, ne serait quâexpĂ©rience mutilĂ©e, umbra vitae, ombre de la vie. LâĂ©trange histoire de Peter Schlemihl, fable morale et mĂ©taphysique, plane sur les pages de ce livre comme une allĂ©gorie de lâhistoire de la pensĂ©e française aprĂšs la guerre froide. ProcĂ©dant par micrologies, LâOmbre pour la proie suggĂšre, en sâĂ©tayant dâun vaste corpus de textes polĂ©miques, philosophiques et littĂ©raires contemporains, que lâhomme postmoderne, nouveau Peter Schlemihl, aurait ainsi aliĂ©nĂ© son ombre (lâAutre, la Loi, le Symbolique) Ă la jouissance immĂ©diate et sans entraves quâoffre une sociĂ©tĂ© hyper-individualiste et festive. « Je sais que lâombre nâexiste plus dans notre monde, câest un accessoire dĂ©modĂ© de romans gothiques », Ă©crivait le romancier Pierre Jourde. Peut-ĂȘtre lâĂ©crivain survit-il littĂ©rairement dans un univers post-littĂ©raire, dernier tĂ©moin dâune civilisation crĂ©pusculair
Non-lieux de mémoire
Je suggĂšre, afin de poursuivre cette interminable anamnĂšse vers un non-lieu de la mĂ©moire et des MĂ©moires qui en marquerait le point asymptotique, dâentendre dans cet Ă©vĂ©nement sans tĂ©moin un Ă©cho de la chute dans lâhistoire ou de lâhistoire comme chute, comme lapsus, dans une perspective spĂ©cifiquement thĂ©ologique. Rappelons que le terme consacrĂ© par la Vulgate pour dĂ©signer la chute est lapsus, comme si la chute faisait dĂ©jĂ trou dans le texte, glissement ou saut inhĂ©rent Ă toute mise en rĂ©..
Ăpilogue De lâombre du moi Ă lâombre du roi
Risquons une synthĂšse de ces discours hĂ©tĂ©rogĂšnes, en revenant Ă notre allĂ©gorie de lâhomme qui a perdu son ombre. Nous avons vu quâun courant non nĂ©gligeable de la pensĂ©e française, dans lâaprĂšs-coup de la guerre froide, allĂšgue que lâAutre sâest comme volatilisĂ©. Cette volatilisation est imputĂ©e, de maniĂšre constante, Ă un nouvel ordre mondial, caractĂ©risĂ© par un processus infini « dâamĂ©ricanisation », de dĂ©socialisation, dâhĂ©donisme effrĂ©nĂ© et dâhyperconsommation (la maladie congĂ©nitale de..
III. La grande désaltération
Seigneur innommable du monde, donne-moi lâAutre !Victor Segalen La dialectique liquidĂ©e Dans son Court traitĂ© dâaltĂ©ricide, le jeune philosophe Dominique Quessada annonce la volatilisation pure et simple de « lâAutre » et lâapparition concomitante dâun « nouvel ordre mondial ». Cette spĂ©culation drolatique, nouvelle fable postmoderne, peut se lire comme lâautopsie du cadavre de la dialectique. Comme lâinsensĂ© du Gai savoir, messager de la mort de Dieu, contre-Ă©vangĂ©liste dĂ©sorientĂ©, « lâEscla..
I. Morosités postmodernes
Mais on ne gouverne pas. La roue du gouvernail est folle, libre, elle ne pĂšse pas un gramme, elle ne peut pas agir, ni sur la droite, ni sur la gauche, elle roule. Ce quâon fait nâest pas une route, câest une immobilitĂ© qui emporte sans mouvements ; on ne peut pas agir.Jean Giono, Fragments dâun paradis Une maladie de lâOccident Tenir la morositĂ© pour lâhumeur fondamentale du prĂ©sent nâest pas une coquetterie dâenfant du siĂšcle. Une crise inĂ©dite quant Ă ses causes et Ă ses modalitĂ©s sinon qu..
LâOmbre pour la proie
Lâhomme sans ombre est un moi sans Autre, monade solipsiste. InquiĂ©tante Ă©trangetĂ© de ce moi inaltĂ©rĂ©, Ă©gal Ă lui-mĂȘme, sans diffĂ©rence. Cette vie sans ombre, exposĂ©e Ă la lumiĂšre du jour, ce MĂȘme sans Autre, ne serait quâexpĂ©rience mutilĂ©e, umbra vitae, ombre de la vie. LâĂ©trange histoire de Peter Schlemihl, fable morale et mĂ©taphysique, plane sur les pages de ce livre comme une allĂ©gorie de lâhistoire de la pensĂ©e française aprĂšs la guerre froide. ProcĂ©dant par micrologies, LâOmbre pour la proie suggĂšre, en sâĂ©tayant dâun vaste corpus de textes polĂ©miques, philosophiques et littĂ©raires contemporains, que lâhomme postmoderne, nouveau Peter Schlemihl, aurait ainsi aliĂ©nĂ© son ombre (lâAutre, la Loi, le Symbolique) Ă la jouissance immĂ©diate et sans entraves quâoffre une sociĂ©tĂ© hyper-individualiste et festive. « Je sais que lâombre nâexiste plus dans notre monde, câest un accessoire dĂ©modĂ© de romans gothiques », Ă©crivait le romancier Pierre Jourde. Peut-ĂȘtre lâĂ©crivain survit-il littĂ©rairement dans un univers post-littĂ©raire, dernier tĂ©moin dâune civilisation crĂ©pusculair
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