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Modeling truncated pixel values of faint reflections in MicroED images
Author(s) -
Hattne Johan,
Shi Dan,
de la Cruz M. Jason,
Reyes Francis E.,
Gonen Tamir
Publication year - 2016
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576716007196
Subject(s) - pixel , diffraction , log normal distribution , optics , physics , truncation (statistics) , noise (video) , scattering , computational physics , amplitude , image (mathematics) , mathematics , computer science , statistics , artificial intelligence
The weak pixel counts surrounding the Bragg spots in a diffraction image are important for establishing a model of the background underneath the peak and estimating the reliability of the integrated intensities. Under certain circumstances, particularly with equipment not optimized for low‐intensity measurements, these pixel values may be corrupted by corrections applied to the raw image. This can lead to truncation of low pixel counts, resulting in anomalies in the integrated Bragg intensities, such as systematically higher signal‐to‐noise ratios. A correction for this effect can be approximated by a three‐parameter lognormal distribution fitted to the weakly positive‐valued pixels at similar scattering angles. The procedure is validated by the improved refinement of an atomic model against structure factor amplitudes derived from corrected micro‐electron diffraction (MicroED) images.