Edith Alicia Müller (1918-1995) was the IAU General Secretary from 1976 to 1979, the first woman to have this responsibility. Many friends, students and colleagues, and others who have met Edith at different occasions, give in this book their memories of her. Her fundamental work in solar physics concerned the

Proceedings of the Joint Discussion-17 at the 23rd IAU General Assembly, organised by the Commission 41, held in Kyoto, Japan, August 25-26, 1997

Proceedings of the second Hellenic Cosmology Meeting, held in the National Observatory of Athens (Penteli, 19-20 April 2001)

Space exploration and advanced astronomy have dramatically expanded our knowledge of outer space and made it possible to study the indepth mechanisms underlying various natural phenomena caused by complex interaction of physical-chemical and dynamical processes in the universe. Huge breakthroughs in astrophysics and the planetary s- ences have led to

Mergers are the mechanisms by which galaxy clusters are assembled through the hierarchical growth of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Many of the observed properties of clusters depend on the physics of the merging process. These