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Picture on the cover: The MAGIC telescopes at the Observatory of Roque de los Muchachos in 2009. MEN WANTED for hazardous journey, low wages, bitter cold, long months of complete darkness, constant danger, safe return doubtful, honour and recognition in case of success.

The properties of Compton–thick AGN are reviewed, with particular emphasis on BeppoSAX hard X–ray observations. I also discuss evidence for the presence of Compton–thick, circumnuclear matter in unobscured AGN, and I briefly introduce the hellas2xmm 5–10 keV survey, discussed in more details in other contributions to this volume.

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1. Introduction Recently a method based on the emission Mössbauer spectroscopy of radioisotope nuclei inserted in grain boundaries worked out by Klotsman and Kaigorodov [1] was successfully employed in a number of studies of grain boundaries in transition and noble metals. In the present investigation this method is used to study the diffusion mechanism and grain boundary segregation in polycry...

We discuss the compact radio sources associated with quasars and AGN with particular emphasis on the implications of their structure and kinematics for relativistic beaming models.