Sri Krishnadevaraya University organized a National Symposium on Science in '21 si century' and Annual convention of Andhra Pradesh Akademi of Sciences during February, 2008. About 100 delegates participated in the symposium. The present book is a collection of some of the papers presented during the symposium. Only some authors have responded to our invitation. Apart from the symposium articles a few invited articles have also been included in the book. We thank Andhra Pradesh Akademi of Sciences for the support. .