Oscillatory settling in wormlike-micelle solutions: bursts and a long   time scale
  We study the dynamics of a spherical steel ball falling freely through a solution of entangled wormlike-micelles. If the sphere diameter is larger than a threshold value, the settling velocity shows repeated short oscillatory bursts separated by long periods of relative quiescence. We propose a model incorporating the interplay of settling-induced flow, viscoelastic stress and, as in M. E. Cates, D. A. Head and A. Ajdari, Phys. Rev. E, 2002, 66, 025202(R) and A. Aradian and M. E. Cates, Phys. Rev. E, 2006, 73, 041508, a slow structural variable for which our experiments offer independent evidence. 
Nitin Kumar, Sayantan Majumdar, Aditya Sood, Rama Govindarajan, Sriram   Ramaswamy and A.K. Sood
cond-mat.soft cond-mat.stat-mech