This volume is intended to coverthe presentstatus of the
mathematicaltools used to deal with problems related to slow rare?ed
?ows. The meaning and usefulness of the subject, and the extent to which
it is covered in the book, are discussed in some detail in the
introduction. In short, I tried to present the basic concepts and the
techniques used in probing mathematical questions and problems which
arise when studying slow rare?ed ?ows in environmental sciences and
micromachines. For the book to be up-to-date without being excessively
large, it was necessary to omit some topics, which are treated
elsewhere, as indicated in the introd- tion and, whenever the need
arises, in the various chapters of this volume. Their omission does not
alter the aim of the book, to provide an understanding of the essential
mathematical tools required to deal with slow rare?ed ?ows and give the
background for a study of the original literature. Although I have tried
to give a rather complete bibliographical coverage, the choice of the
topics and of the references certainly re?ects a personal bias and I
apologize in advance for any omission. I wish to thank Lorenzo
Valdettaro, Antonella Abb` a, Silva Lorenzani and Paolo Barbante for
their help with pictures and especially Professor Ching Shen for his
permission to reproduce his pictures on microchannel ?ows.