New integrable boundary conditions for integrable quantum systems can be
constructed by tuning of scattering phases due to reflection at a boundary and
an adjacent impurity and subsequent projection onto sub-spaces. We illustrate
this mechanism by considering a gl(m<n)-impurity attached to an open
gl(n)-invariant quantum chain and a Kondo spin S coupled to the supersymmetric
t-J model.Comment: Latex2e, no figure