Experimental observations of confined granular materials in the presence of an electric field that induces cohesive forces are reported. The angle of repose is found to increase with the cohesive force. A theoretical model for the stability of a granular heap, including both the effect of the sidewalls and cohesion is proposed. A good agreement between this model and the experimental results is found. The steady-state flow angle is practically unaffected by the electric field except for high field strengths and low flow rates.
We present a new full-field strain measurement method based on diffusing-wave spectroscopy. Our technique makes it possible to measure strains in the vicinity of the surface of highly light-scattering materials. Its main feature is an extreme sensitivity: the range of deformations measured is 10 )5 -10 )3 . To validate the measurements, experimental results from several plane stress configurations are compared with theoretical and numerical calculations. Furthermore, we propose an extension of the method for non-scattering materials.
International audienceWe have studied single curved films stabilized by globular proteins, using small angle scattering. By combining both the use of in-house X-ray and synchrotron radiation, we have measured the structural properties of films (thickness, electronic density) by controlling the physicochemical properties of protein (ovalbumin, pH 7, bulk concentration 10 g L−1). For each experiment, solutions of highly purified protein were freshly prepared to eliminate any problem of aging. The observation of Kiessig fringes shows that the films are thin with an average thickness of 60 nm. Benefiting from the fine angular resolution and the short acquisition time of a synchrotron source, we have highlighted a stratification formation inside the films. This phenomenon suggests protein structural reorganization under confinement, possibly driven by high osmotic pressure
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