  The propagation of the heavy quarks produced in relativistic nucleus-nucleus
collisions at RHIC and LHC is studied within the framework of Langevin dynamics
in the background of an expanding deconfined medium described by ideal and
viscous hydrodynamics. The transport coefficients entering into the
relativistic Langevin equation are evaluated by matching the hard-thermal-loop
result for soft collisions with a perturbative QCD calculation for hard
scatterings. The heavy-quark spectra thus obtained are employed to compute the
differential cross sections, the nuclear modification factors R_AA and the
elliptic flow coefficients v_2 of electrons from heavy-flavour decay.
