Science cannot develop in an environment of isolation. The development of science always depends not only on the joint efforts of scientists at home, but also on the co-operation and discussion with scientists abroad. This series of scientific publications aims to provide a wider forum for academic discussions and might be helpful to the international scientific communities in assessing the progress of science in China. The series is divided into five different disciplines: Physics, Mathematics, Chemistry, Biology and Earth Sciences; each discipline has one volume published annually.