Cycling patterns in cerebral blood flow velocity waveforms in preterm and term neonates : M.Y. Anthonya, D.H. Evansb and M.I. Levenea, aUniversity Department of Paediatrics, University of Leeds, D floor, Clarendon Wing, The General Infirmary, Leeds LS2 9NS and bLeicester University School of Medicine, Department of Medical Physics, Leicester, U.K.