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Two dimensional materials, befitting nanoscale electronics, can benefit strain-tunable applications due to their ultrathin and flexible nature. Based on the first-principles calculations within the generalized gradient approximation, GeSe monolayer with a distorted NaCl-type structure is predicted. The GeSe monolayer is found to be a direct semiconductor with a band gap of (1.16 ± 0.13) eV against the bulk counterpart. The electronic responses of the GeSe monolayer to strain are found to be sensitive and anisotropic, and the transitions between direct and indirect band gap are repeatedly met in the course of energy engineering by uniaxial and biaxial strains. The direct band gap of the GeSe monolayer is tunable by small strain within a large energy range (0.95–1.48 eV). The carrier effective masses in the GeSe monolayer are also tunable by strain in a low mass range (0.03–0.61 m0). These intriguing properties make GeSe monolayer a promising two-dimensional material for nanomechanics, thermoelectrics, and optoelectronics.

Background:Body mass index (BMI) has been associated with the risk of oesophageal cancer. But the influence of BMI on postoperative complication and prognosis has always been controversial.Methods:In total, 2031 consecutive patients who underwent oesophagectomy between 1998 and 2008 were classified according to Asian-specific BMI (kg m−2) cutoff values. The impact of BMI on overall survival (OS) was estimated using the Kaplan–Meier method and Cox proportional hazard models. We performed a meta-analysis to examine the association of BMI with OS and postoperative complication.Results:Patients with higher BMI had more postoperative complication (P=0.002), such as anastomotic leakage (P=0.016) and cardiovascular diseases (P<0.001), but less incidence of chylous leakage (P=0.010). Logistic regression analysis showed that BMI (P=0.005) was a confounding factor associated with postoperative complication. Multivariate analysis showed that overweight and obese patients had a more favourable survival than normal weight patients (HR (hazard ratio) = 0.80, 95% CI (confidence interval): 0.70–0.92, P=0.001). Subgroup analysis showed that the association with higher BMI and increased OS was observed in patients with oesophageal squamous cell carcinoma (ESCC) (P<0.001), oesophageal adenocarcinoma (EA) (P=0.034), never-smoking (P=0.035), ever-smoking (P=0.035), never alcohol consumption (P=0.005), weight loss (P=0.003) and advanced pathological stage (P<0.001). The meta-analysis further corroborated that higher BMI was associated with increased complication of anastomotic leakage (RR (risk ratio)=1.04, 95% CI: 1.02–1.06, P=0.001), wound infection (RR=1.03, 95% CI: 1.00–1.05, P=0.031) and cardiovascular diseases (RR=1.02, 95% CI: 1.00–1.05, P=0.039), but decreased incidence of chylous leakage (RR=0.98, 95% CI: 0.96–0.99, P<0.001). In addition, high BMI could significantly improved OS (HR=0.78, 95% CI: 0.71–0.85, P<0.001).Conclusion:Preoperative BMI was an independent prognostic factor for survival, and strongly associated with postoperative complications in oesophageal cancer.

Arsenene and antimonene are predicted to have 2.49 and 2.28 eV band gaps, which have aroused intense interest in the two-dimensional (2D) semiconductors for nanoelectronic and optoelectronic devices. Here, the hydrogenated arsenenes are reported to be planar magnet and 2D Dirac materials based on comprehensive first-principles calculations. The semi-hydrogenated (SH) arsenene is found to be a quasi-planar magnet, while the fully hydrogenated (FH) arsenene is a planar Dirac material. The buckling height of pristine arsenene is greatly decreased by the hydrogenation, resulting in a planar and relatively low-mass-density sheet. The electronic structures of arsenene are also evidently altered after hydrogenating from wide-band-gap semiconductor to metallic material for SH arsenene, and then to Dirac material for FH arsenene. The SH arsenene has an obvious magnetism, mainly contributed by the p orbital of the unsaturated As atom. Such magnetic and Dirac materials modified by hydrogenation of arsenene may have potential applications in future optoelectronic and spintronic devices.