Abstract: A substance which has a Cu--O plane containing crystal structure in its unit cell and which is called a Bi oxide superconductor consisting essentially of Bi, Sr, Ca, Cu, and O. Not only part of Bi but also part of Sr and/or Ca of the Bi oxide superconductor is substituted for Pb and rare earth elements (RE), respectively. The Pb substitution relaxes the structural modulation which is closely related to superconductivity of the Bi oxide superconductor and the RE substitution controls its carrier concentration. Accordingly, superconducting properties such as transition temperature and critical current density can be improved remarkably. In addition, not only oxide superconductors with excellent superconductivity can be prepared in a low oxygen content but also the surface condition of the prepared superconductors is stable.

Abstract: An insulating composition consisting of Bi, Sr, RE, Cu, O or of Tl, Ba, RE, Cu, O (wherein; RE is an element selected from a group consisting of Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) aligns properly with a crystal face of an oxide superconductor because its crystal structure is the same as or similar to that of the oxide superconductor. An insulating composition in which a part of Bi is replaced by Pb is further near the oxide superconductor its construction, and the modulation structure in this insulating composition is mitigated or disappears.

Abstract: An insulating composition consisting of Bi, Sr, RE, Cu, O or of Tl, Ba, RE, Cu, O (wherein; RE is an element selected from a group consisting of Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) aligns properly with a crystal face of an oxide superconductor because its crystal structure is the same as or similar to that of the oxide superconductor. An insulating composition in which a part of Bi is replaced by Pb is further near the oxide superconductor its construction, and the modulation structure in this insulating composition is mitigated or disappears.

Abstract: A protection circuit for a semiconductor device is disclosed. This circuit is connected in series with a power semiconductor device to be protected, and is comprised of a circuit breaker and current-limiting device. The current-limiting device limits the overcurrent, thereby providing a time allowance until the circuit breaker begins operate.

Abstract: A method for recording and reproducing information on or from an optical recording medium, which comprises:recording information by illuminating light to the optical recording medium which is equipped as a recording film with a thin film comprising dispersed fine grains of a material capable of showing a metal-insulator transition to cause the metal-insulator transition owing to the heating effect of the light; and reproducing the information by utilizing changes in optical characteristics owing to a plasma resonance absorption by the fine grains dispersed in the thin film. The method of this invention permits high-density recording with high sensitivity and upon reproduction, enables reproduction of record with a high signal/noise ratio. The recording medium obtained by this method is an erasable optical recording medium, which permits its reutilization for recording and reproduction after erasure of the previously-stored record.

Abstract: A PTC ceramic composition comprising a fundamental component represented by the formula:(V.sub.1-x A.sub.x).sub.2 O.sub.3wherein x is a value within the range of 0.ltoreq.x.ltoreq.0.02 and A is at least one of Cr and Al, and tin in an amount of 1 to 25 % by weight based on the total weight of the composition, has a small electric resistance in the low resistance state, good PTC properties, and a high density.