Heat flow and efficiency in a microscopic engine B.-Q. Ai, H.-Z. Xie, D.-H. Wen, X.-M. Liu and L.-G. Liu Eur. Phys. J. B, 48 1 (2005) 101-106 Published online: 09 December 2005 DOI: 10.1140/epjb/e2005-00383-0