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Supernovae have been expected to be X-ray sources for many years. This paper reviews the observations that have detected or placed upper limits on the emission of X-rays from supernovae. A firm upper limit exists on X-ray emission from Type Ia supernovae based upon an observation of SN 1992A (parent galaxy: NGC 1380) made with ROSAT. The type II supernovae detected include SN 1978K (NGC 1313), SN 1980K (NGC 6946), SN 1986J (NGC 891), SN 1987A (Large Magellanic Cloud), and, most recently, SN 1993J (NGC 3031). These supernovae emit X-rays by at least two different processes. The author briefly reviews the proposed emission mechanisms.

High-resolution measurements on gamma -rays from fission fragments have given a wealth of information on the structure of neutron-rich nuclei and on the mechanism of the fission process. Experiments to study prompt gamma -rays which deexcite secondary fragments have been greatly facilitated by the introduction of large arrays of Compton suppressed gamma -ray detectors. These have been used recently to give important data on new neutron-rich nuclei with up to ten more neutrons than the nearest stable isotope. High-resolution experiments have also been performed to study gamma -rays which follow the beta ^- decays of the ground states of secondary fragments, and extensive data now exist on decay properties of nuclei with up to twelve more neutrons than the nearest stable isotope. This paper reviews the scope of measurements which can be made on fission gamma -rays and the techniques used in the experiments. It also discusses some results recently obtained on nuclear structure of fragments and on beta ^- decays, and reviews information on fragment spins and other data relevant to fission dynamics.

Magnetic flux can penetrate a type-II superconductor in the form of Abrikosov vortices (also called flux lines, flux tubes, or fluxons) each carrying a quantum of magnetic flux phi ₀=h/2e. These tiny vortices of supercurrent tend to arrange themselves in a triangular flux-line lattice (FLL), which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-T_c superconductors (HTSCs) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSCs the FLL is very soft mainly because of the large magnetic penetration depth lambda . The shear modulus of the FLL is c₆₆~1/ lambda ², and the tilt modulus c₄₄(k)~(1+k² lambda ²)^-1 is dispersive and becomes very small for short distortion wavelengths 2 pi /k<< lambda . This softness is enhanced further by the pronounced anisotropy and layered structure of HTSCs, which strongly increases the penetration depth for currents along the c axis of these (nearly uniaxial) crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may `melt` the FLL and cause thermally activated depinning of the flux lines or ofthe two-dimensional `pancake vortices` in the layers. Various phase transitions are predicted for the FLL in layered HTSCs. Although large pinning forces and high critical currents have been achieved, the small depinning energy so far prevents the application of HTSCs as conductors at high temperatures except in cases when the applied current and the surrounding magnetic field are small.