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Preliminary microwave surface impedance measurements on this high-T c superconductor suggests that it consists mainly of grains separated by thin dielectric layers. A large proportion of the grains appear to be strongly superconducting at low temperatures. The continuous pathways that carry the DC supercurrent appear either to have very small volume or to involve very weak superconductivity at some points on their lengths.
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Cohen et al. (1987) studied this question.
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