Negative superdiffusion due to the inhomogeneous convection
  Fractional transport of particles on a comb structure in the presence of an inhomogeneous convection flow is studied. The large scale asymptotics is considered. It is shown that a contaminant spreads superdiffusively in the direction opposite to the convection flow. Conditions for the realization of this new effect is discussed in detail. 
A. Iomin and E. Baskin