Peculiarities of the abundances of neutron-capture elements in Galactic
  open clusters
  The properties of the relative abundances of rapid and slow neutron-capture
elements are studied using a catalog containing spectroscopic abundance
determinations for 14~elements produced in various nuclear-synthesis processes
for 90~open clusters. The catalog also contains the positions, ages,
velocities, and elements of the Galactic orbits of the clusters. The relative
abundances of both $r$-elements (Eu) and $s$-elements (Y, Ba, La, and Ce) in
clusters with high, elongated orbits and in field stars of the Galactic thin
disk display different dependences on metallicity, age, Galactocentric
distance, and the elements of the Galactic orbits, supporting the view that
these objects have different natures. In young clusters, not only barium, but
also the three other studied $s$-elements display significantly higher relative
abundances than field stars of the same metallicity. The relative abundances of
Eu are lower in high-metallicity clusters (${\rm [Fe/H]} > -0.1$) with high,
elongated orbits than in field giants, on average, while the [Eu/Fe] ratios in
lower-metallicity clusters are the same as those in field stars, on average,
although with a large scatter. The metallicity dependence of the [O, Mg/Eu]
ratios in clusters with high, elongated orbits and in field stars are
substantially different. These and other described properties of the Eu
abundances, together with the properties of the abundances of primary
$\alpha$-elements, can be understood in a natural way if clusters with high,
elongated orbits with different metallicities formed as a result of
interactions of two types of high-velocity clouds with the interstellar medium
of the Galactic disk: low-metallicity high-velocity clouds that formed from
"primordial" gas, and high-metallicity clouds with intermediate velocities that
formed in "Galactic fountains".
