  A general class of solutions of string background equations is studied and
its physical interpretations are presented. These solutions correspond to
generalizations of the standard black p-brane solutions to surfaces with
curvature k=-1,0. The relation with the recently introduced S-branes is
provided. The mass, charge, entropy and Hawking temperature are computed,
illustrating the interpretation in terms of negative tension branes. Their
cosmological interpretation is discussed as well as their potential instability
under small perturbations.
