[en] Nuclei, like more familiar mechanical systems, undergo simple vibrational motion. Among these vibrations, sound modes are of particular interest since they reveal important information on the effective interactions among the constituents and, through extrapolation, on the bulk behaviour of nuclear and neutron matter. Sound wave propagation in nuclei shows strong quantum effects familiar from other quantum systems. Microscopic theory suggests that the restoring forces are caused by the complex structure of the many-Fermion wavefunction and, in some cases, have no classical analogue. The damping of the vibrational amplitude is strongly influenced by phase coherence among the particles participating in the motion. (author)

[en] Experimental particle physics relies heavily on charged particle detectors to observe collisions at high energies. Some of the most important detectors developed in recent years to meet the challenges of increasing particle energies, higher spatial resolution and faster rates of data acquisition are described. Many of them may be applicable in fields outside high energy physics. (author)

[en] The inverse square law of gravitation is very well established over the distances of celestial mechanics, while in electrostatics the law has been shown to be followed to very high precision. However, it is only within the last century that any laboratory experiments have been made to test the inverse square law for gravitation, and all but one has been carried out in the last ten years. At the same time, there has been considerable interest in the possibility of deviations from the inverse square law, either because of a possible bearing on unified theories of forces, including gravitation or, most recently, because of a possible additional fifth force of nature. In this article the various lines of evidence for the inverse square law are summarized, with emphasis upon the recent laboratory experiments. (author)

[en] An elementary introduction is given to the concept of anyons-quantum particles whose 'statistics' interpolate smoothly between those of bosons and fermions. Such particles - or quasi-particle excitations - can occur in two-dimensional systems in which the particles experience strong short-range mutual repulsions. These circumstances effectively mean that one has to apply quantum mechanics to a configuration space in which some points are excluded (i.e. it has 'holes') - namely, those points where two particles would coincide. The Aharonov-Bohm effect provides the simplest physical example of quantum mechanics in such a non-simply connected space, and is also fundamental to a simple model for anyons. A qualitative introduction is given to two currently proposed physical applications of anyons: high temperature superconductivity, and the (fractional) quantum Hall effect. (author)

[en] The use of materials with otherwise attractive properties is often limited by unacceptable mechanical performance. Fortunately, modern processing techniques are sometimes able to overcome such deficiencies, though a systematic and fundamental approach to materials development has yet to be devised. Recent advances in quantum-mechanical computational capabilities have fostered a growing number of applications that bear directly upon the mechanical properties of materials. After a brief discussion of the role of defect structures in mediating deformation behaviour, techniques for computing properties of solids within a quantum-mechanical framework are reviewed. Examples are cited where insight into macroscopic behaviour has been attained from the application of quantum-mechanical calculations to materials of technological importance. (author)

[en] Hypernuclei are exotic nuclei which contain, in addition to the usual neutrons and protons, at least one hyperon. Many species of Λ-hypernuclei, and more recently some Σ-hypernuclei, have been observed and determinations of their masses, excitation energies, lifetimes and modes of production and decay have been made. These results have then been used to elicit various features of the hyperon-nucleon interaction, a necessary procedure since, unlike the situation in the nucleon-nucleon case, the complementary information concerning hyperon-nucleon scattering processes is sparse indeed. (author)

[en] Accelerator based methods using ion beams form a valuable set of techniques for characterising, modifying and developing materials which complement and extend the technological uses of other energy beam methods involving lasers, synchrotron sources, neutrons and electron beams. Such methods, many first developed and increasingly used in the nuclear industry over the last decade, are currently being rapidly exploited in other high technology areas in the chemical, micro-electronics and biotechnology industries. These methods are based on the inherent atomic and nuclear properties of fast ion beams in materials; ions slow down and stop by atomic collision within well-defined depths which depend on the energy and species. By the suitable choice of these parameters, the depth of interaction can be precisely controlled over a very wide range from nanometres to centimetres, which covers the range of depths which exhibit material surface properties such as corrosion, oxidation, wear and catalysis. Nuclear interactions during the slowing down process produce primary and secondary radiations with predictable strength so that concentrations of the element isotopes can be determined. Microstructural and microanalytical information can often be obtained non-destructively and sometimes on-line to the working environment. The features underlying the increasing usefulness of these methods are discussed, examples of major application areas given and the considerable potential for these and related future developments explored. (author)

[en] A widespread interest has arisen in recent years in intermetallic compounds which show a variety of unusual properties. Prominent amongst these is a very large electronic contribution to the specific heat at low temperatures which can be parametrized in terms of an effective mass hundreds or thousands of times larger than those in normal metals. The background to this behaviour is outlined and some of the electrical, magnetic and superconducting properties of such materials, mainly alloys of Ce or U, are presented. (author)

[en] High-pressure nozzle sources yielding neutral particle beams with good monochromacy and high intensity have been combined in the last few years with ultra-high vacuum techniques to allow for atomic beam scattering experiments from solid surfaces which meet the purity requirements of modern surface science. Thus, experimental investigations even of very reactive surfaces have become possible. Beam techniques are presently being used in many branches of surface physics and chemistry, such as studies of the particle=surface physisorption potential, of surface structure, of surface phonons, of surface migration and diffusion, of the energy exchange upon collision of heavy particles and molecules with surfaces, and of substrate-mediated chemical reactions. (author)

[en] Hexagonal close-packed helium crystals in equilibrium with superfluid have been found to be one of the few systems in which an anisotropic solid comes into true thermodynamic equilibrium with its melt. The discovery of roughening transitions at the liquid-solid interface have shown this system to be ideal for the study of the statistical mechanics of interface structures. We describe the effect of roughening on the shape and growth of macroscopic crystals from both the theoretical and experimental points of view. (author)