A Dynamical Evolution Study of 40 2MASS Open Clusters
  We investigate the dynamical evolution of 40 open clusters (OCs) by means of
their astrophysical parameters derived from field-decontaminated 2MASS
photometry. We find a bifurcation in the planes core radius vs. age and cluster
radius vs. age, in which part of the clusters appear to expand with time
probably due to the presence of stellar black holes while others seem to shrink
due to dynamical relaxation. Mass functions (MFs) are built for 3$/$4 of the
sample (31 OCs), which are used to search for indications of mass segregation
and external dynamical processes by means of relations among astrophysical,
structural and evolutionary parameters. We detect a flattening of MF slopes
ocurring at the evolutionary parameters $\tau_{core}\leq 32$ and
$\tau_{overall}\leq 30$, respectively. Within the uncertainties involved, the
overall MF slopes of 14 out of 31 OCs with $m_{overall} > 500~M_{\odot}$ are
consistent with Kroupa's initial mass function, implying little or no dynamical
evolution for these clusters. The remaining 17 OCs with MF slopes departing
from that of Kroupa show mild/large scale mass segregation due to dynamical
evolution.
