Callen's Adiabatic Piston and the Limits of the Second Law of   Thermodynamics
  The limits of the Second Law of Thermodynamics, which reigns undisputed in the macroscopic world, are investigated at the mesoscopic level, corresponding to spatial dimensions of a few microns. An extremely simple isolated system, modeled after Callen's adiabatic piston, [1] can, under appropriate conditions, be described as a self-organizing Brownian motor and shown to exhibit a perpetuum mobile behavior. 
Bruno Crosignani, Paolo Di Porto, Claudio Conti