  The quenching of jets (particles with $p_T>>T, \Lambda_{QCD}$) in
ultra-relativistic heavy-ion collisions has been one of the main prediction and
discovery at RHIC. We have studied, by a simple jet quenching modeling, the
correlation between different observables like the nuclear modification factor
$\Rapt$, the elliptic flow $v_2$ and the ratio of quark to gluon suppression
$R_{AA}(quark)/R_{AA}(gluon)$. We show that the relation among these
observables is strongly affected by the temperature dependence of the energy
loss. In particular the large $v_2$ and and the nearly equal $\Rapt$ of quarks
and gluons can be accounted for only if the energy loss occurs mainly around
the temperature $T_c$ and the flavour conversion is significant.Finally we
point out that the efficency in the conversion of the space eccentricity into
the momentum one ($v_2$) results to be quite smaller respect to the one coming
from elastic scatterings in a fluid with a viscosity to entropy density ratio
$4\pi\eta/s=1$.
