Interaction between two large particles in a dry granular shear flow.

The interaction between two large spherical particles, called intruders, in a dry granular flow down an incline is brought to light and studied experimentally and numerically. Several parameters are varied, namely, the size ratio between the intruders and the small flowing particles, the thickness of the granular flow, the incline slope and roughness, and the densities of the intruders with respect to the small-particle density. In all cases, intruders get aligned with the flow.

Melde's Experiment on a Vibrating Liquid Foam Microchannel.

We subject a single Plateau border channel to a transverse harmonic excitation, in an experiment reminiscent of the historical one by Melde on vibrating strings, to study foam stability and wave properties. At low driving amplitudes, the liquid string exhibits regular oscillations. At large ones, a nonlinear regime appears and the acoustic radiation splits the channel into two zones of different cross section area, vibration amplitude, and phase difference with the neighboring soap films.

Drop coalescence and liquid flow in a single Plateau border.

We report a comprehensive study of the flow of liquid triggered by injecting a droplet into a liquid foam microchannel, also called a Plateau border. This drop-injected experiment reveals an intricate dynamics for the liquid redistribution, with two contrasting regimes observed, ruled either by inertia or viscosity. We devoted a previous study [A.

Response of a noncohesive packing of grains to a localized force: deviation from continuum elasticity.

In order to characterize the mechanical behavior of grain piles, we investigate the response of a noncohesive two-dimensional packing of cylinders submitted to a localized force. By means of image processing, we obtain an accurate measurement of the individual grain displacements in the reversible regime of deformation. The measured displacement field deviates unambiguously from the predictions of linear elasticity and of other theoretical descriptions commonly used to model the behavior of cohesionless soils in civil engineering or in soil mechanics.

Overproduction and increased molecular weight account for the symbiotic activity of the rkpZ-modified K polysaccharide from Sinorhizobium meliloti Rm1021.

K polysaccharides (KPSs) of Sinorhizobium meliloti strains are strain-specific surface polysaccharides analogous to the group II K antigens of Escherichia coli. The K(R)5 antigen of strain AK631 is a highly polymerized disaccharide of pseudaminic and glucuronic acids. During invasion of host plants, this K antigen is able to replace the structurally different exopolysaccharide succinoglycan (EPS I) and promotes the formation of a nitrogen-fixing (Fix(+)) symbiosis.