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The discovery of high-temperature superconductivity in the copper oxide perovskite [La.sub.2-x][Ba.sub.x]Cu[O.sub.4] (ref. 1) ranks among the major scientific events of the twentieth century. The superconducting transition temperatures in the copper [...], The discovery of high-temperature superconductivity in the copper oxides in 1986 triggered a huge amount of innovative scientific inquiry. In the almost three decades since, much has been learned about the novel forms of quantum matter that are exhibited in these strongly correlated electron systems. A qualitative understanding of the nature of the superconducting state itself has been achieved. However, unresolved issues include the astonishing complexity of the phase diagram, the unprecedented prominence of various forms of collective fluctuations, and the simplicity and insensitivity to material details of the 'normal' state at elevated temperatures.

Among toxic and explosive gases hydrogen sulfide occupies a leading position. It accompanies processes of methane recovery from gas wells on nonassociated gas fields (for example, Astrakhan and Orenburg) and [...], The sensitivity of semiconductor sensors based on tin (Sn[O.sub.2]), tungsten (W[O.sub.3]), and zinc (ZnO) oxides and Sn[O.sub.2] with catalytic admixtures of [La.sub.2][O.sub.3] and CuO to hydrogen sulfide is studied at [H.sub.2]S concentration 50 ppm in dry air in the temperature range 100-600°C. Concentration dependences for oxides are studied in the temperature range 350-450°C and [H.sub.2]S concentration range 0.5-100 ppm at the humidity of gas media 0-80 rel. %. It is shown that, under the specified conditions, the resistance and of sensors to [H.sub.2]S in air weakly depends on humidity. It was found that sensors based on Sn[O.sub.2] with an admixture of 3% [La.sub.2][O.sub.3] working at 350°C are the best for the registration of [H.sub.2]S by the set of performance and operation characteristics. A presumable mechanism of [H.sub.2]S interaction with oxide surfaces is considered, according to which each [H.sub.2]S molecule releases seven electrons to the conductivity zone of the oxide and molecules of metal oxides in the surface layer are, possibly, partially replaced by sulfide molecules. Keywords: gas sensitivity (response) to [H.sub.2]S, metal oxide, sensor, humidity DOI: 10.1134/S1061934814020105

The impact of heat treatment on the various structural and superconducting properties of [L.sub.n]SrBa[Cu.sub.3][O.sub.6Z] is being described in the study. A remarkable increase in their properties, including the cationic and chain oxygen ordering is observed.