Spin-dependent electronic transport properties in zigzag graphene nanoribbons ͑ZGNRs͒ are studied using first-principles quantum transport calculations. The effects of the symmetry and defect have been considered. The results show that when the spin polarization is considered, both symmetric and asymmetric ZGNRs present semiconductor behavior, which is different from spin-unpolarized result. The symmetry of ZGNRs plays an important role in electron transport behavior. Asymmetric ZGNR displays monotonic transport behavior. However, in symmetric ZGNRs systems, negative differential resistance is observed. The influence of defect is more obvious in symmetric ZGNRs than in asymmetric systems. A physical analysis of these results is given.

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Pre-treatment Eckardt score could be a predictive factor for failed POEM. Eckardt score ≥9 was associated with high sensitivity and specificity for predicting POEM failure.

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AimIn this retrospective review, we aimed to investigate the long-term efficacy and safety of POEM with follow-up period over 2 years.Materials and methodsA systematic review related to POEM for achalasia was conducted. A literature search was performed in Pubmed, Medline, Ovid, Cochrane and EBSCO databases on November 2017. The following postoperative outcomes were extracted: Eckardt score, lower esophageal sphincter pressure, complications and clinical success.ResultsThe total number of patients was 373. The mean operative time was 66.7 min and the overall rate of complications was 21.2%. The mean follow-up period was 30.0 months. The overall clinical success rate was 92.9% and the rate of gastroesophageal reflux disease was 10.2%. Rate of mortality after POEM was 0.ConclusionsOur study demonstrated that POEM is effective and safe for treating achalasia during the long-term followed up over 2 years.

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