  Results for the $\pi + N \to \Lambda, \Sigma + K$ reactions in nuclear matter
of Ref. nucl-th/0004011 are presented. To evaluate the in-medium modification
of the reaction amplitude as a function of the baryonic density we introduce
relativistic, mean-field potentials for the initial, final and intermediate
mesonic and baryonic states in the resonance model. These vector and scalar
potentials were calculated using the quark meson coupling model. Contrary to
earlier work which has not allowed for the change of the cross section in
medium, we find that the data for kaon production at SIS energies are
consistent with a repulsive $K^+$-nucleus potential.
