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In binary mixtures, the lifetimes of surface bubbles can be five orders of magnitude longer than those in pure liquids because of slightly different compositions of the bulk and the surfaces, leading to a thickness-dependent surface tension of thin films. Taking profit of the resulting simple surface rheology, we derive the equations describing the thickness, flow velocity and surface tension of a single liquid film. Numerical resolution shows that, after a first step of tension equilibration, a parabolic flow with mobile interfaces is associated with film pinching in a further drainage step. Our model paves the way for a better understanding of the rupture dynamics of liquid films., Comment: 21 pages, 6 figures

For partially wetting fluids, previous results suggest that the thickness and the dewetting velocity of gravity driven films are uniquely determined by the triple line dynamics. In contrast, when flushing aqueous liquids through polymer tubes, our measurements show that the dewetting velocity and thickness can be selected. The control parameter is pressure, i.e. the macroscopic curvature of the meniscus. Our results demonstrate directly the major role played by the macroscopic geometry in the stability of the triple line in a dynamic meniscus as predicted by Eggers (Phys. Rev. Lett. 93, 094502 (2004)).

We present here a microscopic study of the effect of shear on a dense purely repulsive colloidal suspension. We use Multispeckle Diffusing Wave Spectroscopy to monitor the transient motions of colloidal particles after being submitted to an oscillatory strain. This technique proves efficient to record the time evolution of the relaxation times distribution. After a high oscillatory shear, we show that this distribution displays a full aging behavior. Oppositely, when a moderate shear is applied the distribution is modified in a non trivial way. Whereas high shear is able to erase all the sample history and rejuvenate it, a moderate shear helps it to age. We call this phenomena overaging. We demonstrate that overaging can be understood if the complete shape of the relaxation time distribution is taken into account. We finally report how the Soft Glassy Rheology model accounts for this effect., Comment: 9 pages 10 figures to appear in Faraday Discussion 123

Various experiments evidence spatial heterogeneities in sheared yield stress fluids. To account for heterogeneities in the velocity gradient direction, we use a simple model corresponding to a non-monotonous local constitutive curve and study a simple shear geometry. Different types of boundary conditions are considered. Under controlled macroscopic shear stress $\Sigma$, we find homogeneous flow in the bulk and a hysteretic macroscopic stress - shear rate curve. Under controlled macroscopic shear rate $\dot{\Gamma}$, shear banding is predicted within a range of values of $\dot{\Gamma}$. For small shear rates, stick slip can also be observed. These qualitative behaviours are robust when changing the boundary conditions., Comment: 13 pages, 13 figures

In this paper, we introduce a simple mode-coupling model for concentrated suspensions under flow . This model exhibits a jamming transition, and stress vs shear rate relations which are very similar to experimental results. Namely newtonian regime or yield stress are followed by a slow variation of the stress for higher shear rates, and by an apparent newtonian regime for very large shear rates. Another striking result is that under oscillating strain, even in the jammed state, the system exhibits a relaxation time which depends on the strain amplitude., Comment: 9 pages, including 4 figures