Pierre Magal is an Associate Professor of Mathematics at the University of Le Havre, France. He received the Ph.D. degree (1996) in applied mathematics from the University of Pau, France and the HDR (2003) in applied mathematics from the University of Le Havre, France. His research interests include semigroup theory, population dynamics, and mathematical biology. Shigui Ruan is a Professor of Mathematics at the University of Miami, Coral Gables, USA. He received the Ph.D. degree (1992) in applied mathematics from the University of Alberta, Edmonton, Canada. He was a Junior Fellow at the Fields Institute, Toronto, Canada in1992-1993 and a postdoctoral fellow at McMaster University, Hamilton, Canada in 1993-1994. From 1994 to 2002, he was an Assistant and Associate Professor at Dalhousie University, Halifax, Canada. His research interests are Differential Equations, Dynamical Systems, and Mathematical Biology.