Scanning transmission electron microscopy: A review of high angle annular dark field and annular bright field imaging and applications in lithium-ion batteries

Scanning transmission electron microscopy（STEM） has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field（HAADF） and annular bright field（ABF） imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries（LIBs）. The future prospects of the STEM are also discussed.

Optical coherence tomography evaluation of retinal nerve fiber layer thickness in non-arteritic anterior ischemic optic neuropathy and primary open angle glaucoma:a systematic review and Meta-analysis

AIM:To assess the differences in average and sectoral peripapillary retinal nerve fiber layer(p RNFL)thickness using spectral domain optical coherence tomography(SD-OCT)in patients with non-arteritic anterior ischemic neuropathy(NAION)compared with those with primary open angle glaucoma(POAG).METHODS:A comprehensive literature search of the Pub Med,Cochrane Library,and Embase databases were performed prior to October,2021.Studies that compared the p RNFL thickness in NAION eyes with that in POAG eyes with matched mean deviation of the visual fields were included.The weighted mean difference(WMD)with 95%confidence interval(CI)was used to pool continuous outcomes.RESULTS:Ten cross-sectional studies(11 datasets)comprising a total of 625 eyes(278 NAION eyes,347 POAG eyes)were included in the qualitative and quantitative analyses.The pooled results demonstrated that the superior p RNFL was significantly thinner in NAION eyes than in POAG eyes(WMD=-6.40,95%CI:-12.22 to-0.58,P=0.031),whereas the inferior p RNFL was significant thinner in POAG eyes than in NAION eyes(WMD=11.10,95%CI:7.06 to 15.14,P≤0.001).No difference was noted concerning the average,nasal,and temporal p RNFL thickness(average:WMD=1.45,95%CI:-0.75 to 3.66,P=0.196;nasal:WMD=-2.12,95%CI:-4.43 to 0.19,P=0.072;temporal:WMD=-1.24,95%CI:-3.96 to 1.47,P=0.370).CONCLUSION:SD-OCT based evaluation of inferior and superior p RNFL thickness can be potentially utilized to differentiate NAION from POAG,and help to understand the different pathophysiological mechanisms between these two diseases.Further longitudinal studies and studies using eight-quadrant or clock-hour classification method are required to validate the obtained findings.