内容简介：
The topic of diffuse astrophysical media ranges over circumstellar to extragalactic scales. The physical conditions in these media can vary from cool, dusty gases to assemblies of relativistic particles. Flows can be set up by momentum and energy injection from radiation fields, winds, jets and explosions. Their observational study involves practically all wavelengths, their theoretical understanding involves physics, chemistry and, inevitably, hydrodynamics. The hydrodynamical aspect of this meeting is particularly emphasised since it was held to mark the retirement of Professor Franz Kahn FRS, who has made many distinguished contributions in this area. The book features invited reviews and contributed papers. After a historical introduction, they progress from circumstellar matter to active galactic nuclei and, throughout, emphasis is placed on the overlap between observation and theory.