The XXX spin s quantum chain and the alternating s1s^{1}, s2s^{2} chain with boundaries

The integrable XXX spin s quantum chain and the alternating $s^{1}$, $s^{2}$ ($s^{1}-s^{2}={1\over 2}$) chain with boundaries are considered. The scattering of their excitations with the boundaries via the Bethe ansatz method is studied, and the exact boundary S matrices are computed in the limit $s, s^{1, 2} \to \infty$. Moreover, the connection of these models with the SU(2) Principal Chiral, WZW and the RSOS models is discussed.Comment: 21 pages Latex, one reference added, minor revisions in the title and the text, to appear in Nucl. Phys.