We have measured the spectrum of velocity fluctuations in a granular system confined to a vertical plane and driven into a homogeneous, steady state by strong vertical vibration. The distribution of horizontal velocities is not Maxwell-Boltzmann and is given by P(v) = Cexp[-beta(|v|/sigma)(alpha)] where alpha = 1.55+/-0.1 at all frequencies and amplitudes investigated, and also for varying boundary conditions. The deviation from Maxwell-Boltzmann statistics occurs in the absence of spatial clustering and does not result from an inhomogeneous average over regions of varying local density. Surprisingly, P(v) has the same shape over a wide range of densities.

Aqueous foams are studied both as materials with many applications, and as model systems for fields ranging from metallurgy to mathematics to biology. They are complex fluids with unique and unusual properties, exemplified as much by their multiscale structure as by the dynamical processes through which they evolve and even their dual liquid-like and solid-like behaviour. In this book, readers can easily find clear, up-to-date answers to their questions regarding the physical and physico-chemical properties of aqueous foams, explained using current knowledge of their structure, their stability, and their rheology. Newcomers to the field will find descriptions of numerous applications of foams in daily life and in industrial processes, the definition of basic concepts, hundreds of figures, and simple experiments to perform at home. Those who want to proceed further will find updated references, exercises with solutions, appendices with experimental and numerical techniques, and boxed text with the further mathematical detail.

At the end of their life, surface bubbles burst and emit aerosols, which drastically impact exchanges in liquid as well as in pathogens or flavors with the surrounding atmosphere. This exchange depends on the thickness of the liquid film and is thus linked to the bubble drainage dynamics and to their lifetime. In this article, we propose to explore both feature for big surface bubbles depending on their size. We also explore the impact of atmospheric humidity by a careful control and systematic variation of the relative humidity. We show that a model including both capillary and gravity driven drainage gives a prediction of the bubble lifetime in line with experiments provided convection is taken into account to calculate the evaporation rate. arXiv:1907.09734v1 [cond-mat.soft]