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Using the screen printing method, YBaCuO high T c superconducting films were fabricated. The thickness of the films was ≃30 µm and maximum grain size was ≃70 µm. T czero=90.7 K and J c=20 A/cm2 at 77 K were obtained. With a razor edge, the films were cut and formed to grain boundary bridges having a few grain boundaries in the bridge region. The devices showed clear Shapiro steps and SQUID patterns at 77 K.

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We study the covariant entropy bound in the context of gravitational collapse. First, we discuss critically the heuristic arguments advanced by Bousso. Then we solve the problem through an exact model: a Tolman-Bondi dust shell collapsing into a Schwarzschild black hole. After the collapse, a new black hole with a larger mass is formed. The horizon, L, of the old black hole then terminates at the singularity. We show that the entropy crossing L does not exceed a quarter of the area of the old horizon. Therefore, the covariant entropy bound is satisfied in this process.