Transient evolution of C-type shocks in dusty regions of varying density I. Ashmore, S. Van Loo, P. Caselli, S. A. E. G. Falle and T. W. Hartquist A&A, 511 (2010) A41 Published online: 04 March 2010 DOI: 10.1051/0004-6361/200913277