  Heavy quarks are a unique probe to study the medium produced in
ultra-relativistic heavy ion collisions. Within the partonic transport model
Boltzmann approach to multi-parton scatterings (BAMPS) the production, energy
loss and elliptic flow of heavy quarks are investigated in 3+1 dimensional
simulations of the quark gluon plasma evolution. With only binary interactions
between heavy quarks and particles from the medium calculated within
perturbative QCD, the results on elliptic flow and the nuclear modification
factor are not compatible with experimental data from RHIC and LHC. However, if
the binary cross section is multiplied with K=4 both the elliptic flow and the
nuclear modification factor are simultaneously described at RHIC and also LHC.
Furthermore, preliminary results are presented that the implementation of
radiative processes leads to a stronger suppression which agrees well with the
measured nuclear modification factor at RHIC without the need of any K factor.
