We analyze the Drude weight for both spin and thermal transport of
one-dimensional spin-1/2 systems by means of exact diagonalization at finite
temperatures. While the Drude weights are non-zero for finite systems, we find
indications of a vanishing of the Drude weights in the thermodynamic limit for
non-integrable models implying normal transport behavior.Comment: 2 pages, 1 figure. Proceedings of the ICM 2003, Rom