This book reviews the current understanding of electronic, optical and magnetic properties of conjugated polymers in both the semiconducting and metallic states. It introduces in particular novel phenomena and concepts in these quasi one-dimensional materials that differ from the well-established concepts valid for crystalline semiconductors. After a brief introductory chapter, the second chapter presents basic theore tical concepts and treats in detail the various models for n-conjugated polymers and the computational methods required to derive observable quantities. Specific spatially localized structures, often referred to as solitons, polarons and bipolarons, result naturally from the interaction between n-electrons and lattice displacements. For a semi-quantitative understanding of the various measure ments, electron-electron interactions have to be incorporated in the models; this in turn makes the calculations rather complicated. The third chapter is devoted to the electrical properties of these materials. The high metallic conductivity achieved by doping gave rise to the expression conducting polymers, which is often used for such materials even when they are in their semiconducting or insulating state. Although conductivity is one of the most important features, the reader will learn how difficult it is to draw definite conclusions about the nature of the charge carriers and the microscopic transport mechanism solely from electrical measurements. Optical properties are discussed in the fourth chapter."

As the head of the theory group at Los Alamos, Hans A. Bethe played a central role in the dawn of the Nuclear Age. In the 50 years since, he has played an equally central role in the debate over the use and control of this new power. This volume collects together Bethe's best essays on the bomb, arms control, nuclear power and astrophysics. It also includes his reflections on science and morality and his comments on five fellow physicists. Of interest to physicists, particularly those working in nuclear physics and astrophysics, historians and philosophers of science, science policy makers, environmentalists, those concerned with disarmament and the role of science in society, and general science readers.