“Molecular Clusters” on the Surface of an Oxidizing Metal
FIELD ion microscopy, which holds the possibility of resolving the individual atoms in a metallic surface, should in principle be a powerful tool for the study of reactions on surfaces. As part of an extensive study of the mechanism of oxidation of several metals, we have recently observed the formation of characteristic, reproducible, small clusters of atoms of regular shape when a perfect iridium surface is exposed to oxygen.
Field ion microscope studies of the oxidation of iron
Abstract The oxidation of iron at temperatures from ambient to 800°C has been investigated by conventional field ion microscopy using hydrogen as the image gas. At room temperature and low oxygen exposures, no oxide layer was detected but preferential reaction was evident on the atomically rough regions of the surface. At higher temperatures, nucleation of oxide also appeared to occur in these areas although there was evidence of true oxide epitaxy above metal {110}. Results of the oxidation experiments, and of the effects of hydrogen on the imaging of iron, are discussed in terms of the structures exposed at the surface of hemispherical bcc specimens.
An automated retinal image quality grading algorithm
This paper introduces an algorithm for the automated assessment of retinal fundus image quality grade. Retinal image quality grading assesses whether the quality of the image is sufficient to allow diagnostic procedures to be applied. Automated quality analysis is an important preprocessing step in algorithmic diagnosis, as it is necessary to ensure that images are sufficiently clear to allow pathologies to be visible. The algorithm is based on standard recommendations for quality analysis by human screeners, examining the clarity of retinal vessels within the macula region. An evaluation against a reference standard data-set is given; it is shown that the algorithm's performance correlates closely with that of clinicians manually grading image quality.