{'fraction_non_alphanumeric': 0.02130681818181818, 'fraction_numerical': 0.02556818181818182, 'mean_word_length': 5.077586206896552, '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}}
Improvement of the Quality of Dark Field Images of Electron Microscope with the Increase of Accelerating Voltage

The dark field images of crystalline objects were taken at accelerating voltages, 50–1000 kV, with the incident beam parallel to the optic axis. Since the image forming ray makes a large angle, twice the Bragg angle, with the optic axis, the image quality is much lower than that of bright field images at ordinary accelerating voltages, 50–100 kV, due to the chromatic and spherical aberrations. It was shown experimentally that in high voltage electron microscopes (higher than 500 kV), both aberrations were much reduced and became almost negligible at 1000 kV for low order reflections.