The interest in understanding the physical world that we live in, the origin of its formation and evolution, is reflected in the world-wide activities in Europe, the USA and Japan to set up powerful research facilities providing beams of radioactive nuclei of various kinds, and beams of extremely large energies. At the same time, complex and large detector arrays with improved technical capabilities are built either around these facilities or independently (dedicated to cosmic rays). Recently, spectacular progress has been made in superheavy nuclei, cold binary and ternary fission, nuclear shell structure and nuclear astrophysics, to mention only a few directions. The energy spectrum of cosmic rays exceeds the upper limits provided by artificial accelerators. An international collaboration has committed itself to the installation of an extremely large area detector array, AUGER, in order to study the highest particle energies in the Universe.

The two comprehensive reviews in this volume address two fundamental problems that have been of long-standing interest and are the focus of current effort in contemporary nuclear physics: exploring experimentally the density distributions of constituents within the nucleus and understand ing nuclear structure and interactions in terms of hadronic degrees of freedom. One of the major goals of experimental probes of atomic nuclei has been to discover the spatial distribution of the constituents within the nucleus. As the energy and specificity of probes have increased over the years, the degree of spatial resolution and ability to select specific charge, current, spin, and isospin densities have correspondingly increased. In the first chapter, Batty, Friedman, Gils, and Rebel provide a thorough review of what has been learned about nuclear density distributions using electrons, muons, nucleons, antinucleons, pions, alpha particles, and kaons as probes. This current understanding, and the limitations thereof, are crucial in framing the questions that motivate the next generation of experimental facilities to study atomic nuclei with electromagnetic and hadronic probes. The second chapter, by Machleidt, reviews our current understanding of nuclear forces and structure in terms of hadronic degrees of freedom, that is, in terms of mesons and nucleons. Such an understanding in terms of hadronic variables is crucial for two reasons. First, since effective hadronic theories are quite successful in describing a broad range of phenomena in low-energy nuclear physics, and there are clear experimental signatures of meson exchange currents in nuclei, we must understand their foundations.

The present volume reaffirms nuclear physics as an experimental science since the authors are primarily experimentalists and since the treatment of the topics might be said to be "experimental." (This is no reflection on the theoretical competence of any of the authors.) The subject of high-spin phenomena in heavy nuclei has grown much beyond the idea of "backbending" which gave such an impetus to its study five years ago. It is a rich, new field to which Lieder and Ryde have contributed greatly. The article "Valence and Doorway Mechanisms in Resonance Neutron Capture" is, in contradistinction, an article pertaining to one of the oldest branches of nuclear physics-and it brings back one of our previous authors. The Doppler-shift method, reviewed by Alexander and Forster, is one of the important new experimental techniques that emerged in the previous decade. This review is intended, deliberately, to describe thoroughly a classic technique whose elegance epitomizes much of the fascination which nuclear physics techniques have held for a generation of scientists. This volume concludes the work on the Advances in Nuclear Physics series of one of the editors (M. Baranger), whose judgment and style characterize that which is best in the first ten volumes. Many of our readers and most of our authors will be grateful for the high standards which marked his contributions and which often elicited extra labor from the many authors of the series.

The proceedings contain invited papers and contributions which capture the recent advances in technology (beams, detectors, electronics, computing) and emphasize the new frontiers opened up in Nuclear Physics. Results with most of the existing multidetectors, as well as the progress of new developments, were presented. The presentations of EUROGAM, GAMMASPHERE, GASP, DIAMANT, ORION, EDEN, DEMON, the Texas Neutron Ball, the DWARF Ball, INDRA, FOBOS, AMPHORA, MEDEA and the SIS/ESR Particle Ball will also be included. The progress in data collection with the new integrated electronics, as well as transputer farm and network distributed processing, is also presented. Experimental results cover superdeformation, multifragmentation, neutron-rich isotopes, dissipative collisions, cluster states and radioactive beam measurements.

Detection of Bulk Explosives: Advanced Techniques against Terrorism contains reviews of: existing and emerging bulk explosives detection techniques; scientific and technical policy of the Federal Border Service of the Russian Federation; challenges in application and evaluation of EDS systems for aviation security; multi-sensor approach to explosives detection. There are also reports devoted to the following individual explosive detection techniques: X-ray systems in airports; neutron in, gamma out techniques; neutron and gamma backscattering; nuclear quadruple resonance, including remote NQR; sub-surface radars; microwave scanners; laser-induced burst spectroscopy (LIBS); acoustic sensors; nonlinear location (NUD); systems for localization and destruction of explosive objects.