  Here we present several remarkable irregularities at chemical freeze-out
which are found using an advanced version of the hadron resonance gas model.
The most prominent of them are the sharp peak of the trace anomaly existing at
chemical freeze-out at the center of mass energy 4.9 GeV and two sets of highly
correlated quasi-plateaus in the collision energy dependence of the entropy per
baryon, total pion number per baryon, and thermal pion number per baryon which
we found at the center of mass energies 3.8-4.9 GeV and 7.6-10 GeV. The low
energy set of quasi-plateaus was predicted a long time ago. On the basis of the
generalized shock-adiabat model we demonstrate that the low energy correlated
quasi-plateaus give evidence for the anomalous thermodynamic properties inside
the quark-gluon-hadron mixed phase. It is also shown that the trace anomaly
sharp peak at chemical freeze-out corresponds to the trace anomaly peak at the
boundary between the mixed phase and quark gluon plasma. We argue that the high
energy correlated quasi-plateaus may correspond to a second phase transition
and discuss its possible origin and location. Besides we suggest two new
observables which may serve as clear signals of these phase transformations.
