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High Tc superconductivity has been observed in a new U-Y-Ba-Cu-O system at ambient pressure. The zero-resistance temperature in the sample with nominal composition of U0.1Y1.1Ba0.8CuO4−δ is 87K with a width of 2K. X-ray diffraction analysis shows that none of the peaks could be fitted to the uranium oxides and the other raw material structure, and its pattern might be attributed to new multiple phases with structure different from the known single-phase superconducting oxides.

Pulsed supersonic molecular beam scattering has been used to study the inelastic scattering, trapping ] desorption and reactive channels for the HCl ] GaAs(100) thermal etching reactions. Temperature proÐles of the reaction products GaCl, and Ga are reported in the range 600 to 883 K. Angular and As 2 time-of-Ñight (TOF) distributions of inelastically scattered and trapped ] desorbed HCl are also reported. Angular distribution of all reaction products are described by a cosn (h) form with 0.95 O n O 1.4. The TOF distribution of GaCl reveals rapid production but with measurable time delay (50 lsÈ10 ms). The signals As 2 are e †ectively demodulated and correspond to delayed production on the surface with a time constant [1 s. A kinetic model initially proposed by Bent and colleagues (C.