It is known that nuclear shells play a particularly important role in the collective motion of nuclear matter and, as a consequence, determine the structure of nuclei, nuclear dynamics, nuclear decay models, etc.In 1999 the nuclear shell model turned fifty, and the 49th meeting on Nuclear Spectroscopy and Nuclear Structure was devoted to nuclear shells in their various manifestations. The talks presented at the conference covered a wide range of experimental and theoretical studies.

To overcome the problems of system theory and network theory over real field, this book uses matrices over the field F(z) of rational functions in multi-parameters describing coefficient matrices of systems and networks and makes systems and network description over F(z) and researches their structural properties: reducible condition of a class of matrices over F(z) and their characteristic polynomial; type-1 matrix and two basic properties; variable replacement conditions for independent parameters; structural controllability and observability of linear systems over F(z); separability, reducibility, controllability, observability and structural conditions of networks over F(z), and so on. This book involves three subjects: systems, networks and matrices over F(z), which is an achievement of interdisciplinary research.

The ENAM2001 Conference was held on July 2-7, 2001 at the Rantasipi Aulanko Hotel in Hameenlinna in southern Finland. The conference was organized by the Department of Physics and the Accelerator Laboratory of the University of Jyvaskyla with support from the Physics Departments of the Universities of Helsinki and Turku. This conference, Exotic Nuclei and Atomic Masses has now gained the status of a major nuclear physics serial conference. The previous conference was held in Bellaire, Michigan, USA. The conference was first held in 1967 in Lysekil, Sweden, then entitled Conference on Nuclei Far from Stability. ENAM2001 welcomed 270 participants from 34 countries, including 17 accompanying per sons. The content of the program was selected based on the advice of the International Advisory Committee. The Committee members read and considered 253 submitted abstracts in selecting oral contributions. During the conference week 76 invited and oral talks were given. The rest of the contributions were presented in dedicated poster sessions. Many thanks go to the speakers of oral and poster presentations for their enthusiasm and for the high quality of their work which demonstrated the liveliness of the field. Participation in the lectures was high and contributions from the audience were important towards the success of this conference. The organizers would like to especially thank Cary Davids of Argonne National Laboratory for his comprehensive summary talk, which is also included in these Proceedings.