New Approaches to Nonlinear Problems in Dynamics

charged dislocation resulting in relations between the occupation ration / (fraction of dislocation states occupied by electrons) and temperature or between the Fermi level and / are outlined and some important aspects in the application of these relations to experimental results are discussed. The problem of deriving the carrier density and / from Hall effect data is also discussed. Theoretical calculations of the free carrier mobility in deformed semiconductors are compared with experiments. F. R. N. Nabarro and A. T. Quintanilha. "Dislocations in Superconductors," pp. 192-242. In 1968, Kojima and Suzuki, conducting tensile tests at a constant rate of strain on the Type I superconductor lead and on the Type II superconductor niobium at 4.2 K, found that the flow stress increased when superconductivity was destroyed by a magnetic field. The electron drag on the moving dislocations was absent in the superconducting state and restored by the magnetic field. The first part of this chapter discusses the change in the mobility of ordinary dislocations of the crystal lattice of a metal when the metal becomes superconducting. The second part of this chapter is not very closely Telated to the first part. It is concerned with the magnetization of a superconductor of Type II, which occurs by the motion of a lattice of flux lines through the crystal. During this process, the authors postulate, the dislocations of the crystal lattice remain fixed, and act as moderatley effective obstacles to the motion of the flux-line lattice. The nature and effect of dislocations in the lattice of flux lines in a Type II superconductor are analyzed in the last section. M. Kleman. "The General Theory of Disclinations," pp. 243-297. The concept of disclinations (rotational dislocations) has recently found wide application in liquid crystals. Disclinations are the topoligical concepts which help in a description of broken sym-