Air entrainment through free-surface cusps

In many industrial processes, such as pouring a liquid or coating a rotating cylinder, air bubbles are entrapped inside the liquid. We propose a novel mechanism for this phenomenon, based on the instability of cusp singularities that generically form on free surfaces. The air being drawn into the narrow space inside the cusp destroys its stationary shape when the walls of the cusp come too close. Instead, a sheet emanates from the cusp's tip, through which air is entrained. Our analytical theory of this instability is confirmed by experimental observation and quantitative comparison with numerical simulations of the flow equations

Synthesis and Crystal Structure of α,α′-dihydroxydi(perfluorocyclohexyl)peroxide

Reaction of stoichiometric quantities of perfluorocyclohexanone and 98% H2O2 in neutral media quantitatively forms α,α′-dihydroxydi(perfluorohexyl)peroxide, for which the main crystal and molecular structural parameters were determined by x-ray analysis