{'fraction_non_alphanumeric': 0.02012072434607646, 'fraction_numerical': 0.03420523138832998, 'mean_word_length': 5.0, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Isotope Effect in Superconducting YBa2Cu3O7-δ System

An oxygen isotope effect is observed by a measurement of the resistivity when 16O is substituted for 18O in the YBa2Cu3O7-δ compound. The superconducting transition temperature Tc is lowered by 0.4 K upon substitution. The results suggest that the phonon related to oxygen in the two-dimensional CuO2 plane contributes to the mechanism of high-Tc superconductivity. When 63Cu is substituted for 65Cu, no appreciable isotope effect is observed.