Professor Paolo Secchi is visiting the Dynamical Systems and PDEs group in the department for two weeks, arriving on Wednesday 29th April, supported by a grant from the London Mathematical Society.  He is a Professor of Mathematical Analysis at the University of Brescia in Italy.  His co-hosts are Michele Bartuccelli and Bin Cheng.  The research to be carried out at Surrey will be focused on the following topic: when some dimensionless parameters in a fluid model approach zero or infinity, can we rigorously justify the limiting/reduced system, and what should be the correct convergence rate? Although extensively studied since the 1980′s, some crucial questions remain largely open.  Professor Secchi and his collaborators have made important recent contributions in this area, notably in compressible fluid dynamics. Another aspect of this research that will be addressed is in obtaining sharp estimates in the functional inequalities used to analyze the solutions of PDEs.  Indeed such estimates are still largely missing from the study of singular limit problems, but play a key role in bridging PDEs analysis to scientific computing.