Relaxing in foam
  We investigate the mechanical response of an aqueous foam, and its relation to the microscopic rearrangement dynamics of the bubble-packing structure. At rest, even though the foam is coarsening, the rheology is demonstrated to be linear. Under flow, shear-induced rearrangements compete with coarsening-induced rearrangements. The macroscopic consequences are captured by a novel rheological method in which a step-strain is superposed on an otherwise steady flow. 
A. D. Gopal and D. J. Durian