  The transition from hadronic to partonic degrees of freedom in the course of
a relativistic heavy-ion collision is described by the microscopic covariant
Parton-Hadron-String Dynamics (PHSD) transport approach. Studying Pb+Pb
reactions from 40 to 158 AGeV and comparing the PHSD results to those of the
Hadron-String Dynamics (HSD) approach without a phase transition to the QGP, we
observe that the existence of the partonic phase has a sizable influence on the
transverse mass distribution of final kaons due to the repulsive partonic mean
fields. Furthermore, we find a significant effect of the QGP on the production
of multi-strange antibaryons due to a slightly enhanced ssbar pair production
in the partonic phase from massive time-like gluon decay and to a more abundant
formation of strange antibaryons in the hadronization process. Another evidence
for pre-hadronization dynamics is gained from a study of di-jet correlations in
Au+Au collisions at the top RHIC energy of sqrt(S)=200 GeV. Within the HSD
transport approach, the reaction of the hadronic medium to the jet energy loss
is calculated. In comparison with the data of the STAR, PHOBOS and PHENIX
Collaborations differentially in azimuthal angle and pseudorapidity, the HSD
results do not show enough suppression for the `away-side' jet. In addition,
the HSD results exhibit neither a `Mach-cone' structure for the angular
distribution in the away-side jet nor the `ridge' long-range rapidity
correlations for the near-side jet as observed by the STAR and PHOBOS
Collaborations, thus suggesting a partonic origin of these structures.
