Analysis of a turbulence model related to that of k-epsilon for stationary and compressible flows

We shall study a turbulence model arising in compressible fluid mechanics. The model called $\theta - \phi$ we study is closely related to the k-epsilon model. We shall establish existence, positivity and regularity results in a very general framework

Optimized Schwarz waveform relaxation for Primitive Equations of the ocean

In this article we are interested in the derivation of efficient domain decomposition methods for the viscous primitive equations of the ocean. We consider the rotating 3d incompressible hydrostatic Navier-Stokes equations with free surface. Performing an asymptotic analysis of the system with respect to the Rossby number, we compute an approximated Dirichlet to Neumann operator and build an optimized Schwarz waveform relaxation algorithm. We establish the well-posedness of this algorithm and present some numerical results to illustrate the method

Uniqueness result for the 3-D Navier-Stokes-Boussinesq equations with horizontal dissipation

In this paper, for the 3-D Navier-Stokes-Boussinesq system with horizontal dissipation, where there is no smoothing effect on the vertical derivatives, we prove a uniqueness result of solutions (u, ρ) ∈ L ∞ T H 0,s × H 0,1−s with (h u, h ρ) ∈ L 2 T H 0,s × H 0,1−s and s ∈ [1/2, 1]. As a consequence, we improve the conditions stated in the paper [13] in order to obtain a global well-posedness result in the case of axisymmetric initial data

higher integrability of the gradient in degenerate elliptic equations

accepte pour publication dans Potential Analysis (2006)International audienceWe prove that under some global conditions on the maximum and the minimum eigenvalue of the matrix of the coefficients, the gradient of the (weak) solution of some degenerate elliptic equations has higher integrability than expected. Technically we adapt the Giaquinta-Modica regularity method in some degenerate cases. When the dimension is two, a consequence of our result is a new Holder continuity result for the weak solutio

Biogenesis of cytochrome b6 in photosynthetic membranes

In chloroplasts, binding of a c′-heme to cytochrome b6 on the stromal side of the thylakoid membranes requires a specific mechanism distinct from the one at work for c-heme binding to cytochromes f and c6 on the lumenal side of membranes. Here, we show that the major protein components of this pathway, the CCBs, are bona fide transmembrane proteins. We demonstrate their association in a series of hetero-oligomeric complexes, some of which interact transiently with cytochrome b6 in the process of heme delivery to the apoprotein. In addition, we provide preliminary evidence for functional assembly of cytochrome b6f complexes even in the absence of c′-heme binding to cytochrome b6. Finally, we present a sequential model for apo- to holo-cytochrome b6 maturation integrated within the assembly pathway of b6f complexes in the thylakoid membranes

Deregulation of TDP-43 in amyotrophic lateral sclerosis triggers nuclear factor κB–mediated pathogenic pathways

TDP-43 interacts with and coactivates NF-κB p65 in the spinal cord of amyotrophic lateral sclerosis (ALS) patients, and an NF-κB inhibitor suppresses ALS disease symptoms and neuromuscular junction denervation in an ALS mouse model

CDX2 regulation by the RNA-binding protein MEX3A: impact on intestinal differentiation and stemness

The homeobox transcription factor CDX2 plays a crucial role in intestinal cell fate specification, both during normal development and in tumorigenic processes involving intestinal reprogramming. The CDX2 regulatory network is intricate, but it has not yet been fully uncovered. Through genome-wide screening of a 3D culture system, the RNA-binding protein MEX3A was identified as putatively involved in CDX2 regulation; therefore, its biological relevance was addressed by setting up cell-based assays together with expression studies in murine intestine. We demonstrate here that MEX3A has a repressive function by controlling CDX2 levels in gastric and colorectal cellular models. This is dependent on the interaction with a specific binding determinant present in CDX2 mRNA 3'untranslated region. We have further determined that MEX3A impairs intestinal differentiation and cellular polarization, affects cell cycle progression and promotes increased expression of intestinal stem cell markers, namely LGR5, BMI1 and MSI1. Finally, we show that MEX3A is expressed in mouse intestine, supporting an in vivo context for interaction with CDX2 and modulation of stem cell properties. Therefore, we describe a novel CDX2 post-transcriptional regulatory mechanism, through the RNA-binding protein MEX3A, with a major impact in intestinal differentiation, polarity and stemness, likely contributing to intestinal homeostasis and carcinogenesis

Navier-Stokes systems with quasimonotone viscosity tensor.

We (Dreyfuss P., Hungerbühler, N., 2004, Int. J. of Pure and Appl.Math. 14(2): 241– 271) investigated a class of Navier-Stokes systems which is motivated by models for electrorheological fluids. We obtained an existence result for a weak solution under mild monotonicity assumptions for the viscosity tensor. In this article, we continue the analysis of such systems, but with various notions of quasimonotonicity instead of classical pointwise monotonicity assumptions. Moreover we allow the external force to be of a more general form

Results on a Navier-Stokes system with applications to electrorheological fluid flow

We study a Navier-Stokes system which is motivated by models for electrorheological fluids. Its principal features are the weak monotonicity assumptions we impose on the viscosity tensor. Moreover we allow the viscosity to depend on the velocity in order to cover some of the models in electrorheological theory. We establish existence of a weak solution of the corresponding Navier-Stokes system