\chapter*{Preface} \normalsize \noindent

This thesis presents the results of studies of the circumstellar
medium around stars on the Asymptotic Giant Branch based in novel
imaging techniques of scattered stellar light, and modelling of
molecular radio line emission. The first pages of this thesis set a
background to the paper publications, which represent the back-bone of
the thesis work. An Appendix containing non-published observational
data is enclosed at the end.

The four included publications are:

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  \item \label{paper1} {\bf Imaging of detached shells around the carbon stars R Scl and U Ant through scattered stellar light} \\
 Gonz\'alez Delgado D., Olofsson H., Schwarz H., Eriksson K., Gustafsson B., 2001, A\&A {\bf 372}, 885
  
  \item \label{paper2} {\bf Imaging polarimetry of stellar light scattered in detached shells around the carbon stars R~Scl and U~Ant} \\
 Gonz\'alez Delgado D., Olofsson H., Schwarz H., Eriksson K., Gustafsson B., Gledhill T., 2002, A\&A, accepted 

  \item \label{paper3} {\bf Mass loss rates of a sample of irregular and semiregular M-type AGB-variables} \\
   Olofsson H., Gonz\'alez Delgado D., Kerschbaum F., Sch\"oier F.L., 2002, A\&A {\bf 391}, 1053 

  \item \label{paper4} {\bf 'Thermal' SiO radial line emission towards M-type AGB stars: a probe of circumstellar dust formation and dynamics} \\
  Gonz\'alez Delgado D., Olofsson H., Kerschbaum F., Sch\"oier F.L., 2003, submitted


\end{list}
