Chemical effect on the Van Hove singularity in superconducting kagome metal AV3Sb5 (A = K, Rb, and Cs).

To understand the alkali-metal-dependent material properties of recently discovered AV3Sb5 (A = K, Rb, and Cs), we conducted a detailed electronic structure analysis based on first-principles density functional theory calculations. Contrary to the case of A = K and Rb, the energetic positions of the low-lying Van Hove singularities are reversed in CsV3Sb5, and the characteristic higher-order Van Hove point gets closer to the Fermi level. We found that this notable difference can be attributed to the chemical effect, apart from structural differences. Due to their different orbital compositions, Van Hove points show qualitatively different responses to the structure changes. A previously unnoticed highest lying point can be lowered, locating close to or even below the other ones in response to a reasonable range of bi- and uni-axial strain. Our results can be useful in better understanding the material-dependent features reported in this family and in realizing experimental control of exotic quantum phases.

Large-Gap and Topological Crystalline Insulating Phase in RbZnBi and CsZnBi.

Topological insulators (TIs) are a new class of materials with gapless boundary states inside the bulk insulating gap. This metallic boundary state hosts intriguing phenomena such as helical spin textures and Dirac crossing points. Here, we theoretically propose RbZnBi and CsZnBi as a new family of TIs exhibiting large bulk band gaps and unique gapless surface states. Our first-principles density functional calculations show that two materials can be stabilized in two different structures depending on the stacking order of hexagonal ZnBi layers. While both materials in the AA-stacked structure become TI, the AB-stacked RbZnBi and CsZnBi are topological crystalline insulators with hourglass-shaped Fermion surface states protected by nonsymmorphic glide symmetry. The calculated bulk gap is about 1.5-1.8 times larger than that of Bi2Se3, which makes RbZnBi and CsZnBi promising candidates for future applications.

Conversion of oximes to carbonyl compounds with 2-nitro-4,5-dichloropyridazin-3(2H)-one.

Conversion of oximes to the carbonyl compounds has been demonstrated with use of 2-nitro-4,5-dichloropyridazin-3(2H)-one (2) under microwave irradiated conditions. Fourteen aliphatic and aromatic oximes converted to their corresponding aldehydes and ketones in good to excellent yields. It is noteworthy that the reaction is conducted under neutral, mild, and eco-friendly condition.

TBAF-assisted copper-catalyzed N-arylation and benzylation of benzazoles with aryl and benzyl halides under the ligand/base/ solvent-free conditions.

TBAF-assisted N-arylation and benzylation of benzazoles such as 1H-benzimidazole, 1H-indole, and 1H-benzotriazole with aryl and benzyl halides have been demonstrated under the ligand/base/solvent-free conditions. In the presence of CuBr2 and TBAF (n-Bu4NF), the azoles underwent N-arylation and benzylation with aryl and benzyl halides smoothly in moderate to good yields. It is noteworthy that the reaction is conducted under the ligand/base/solvent-free conditions.

Comparison of different pancreatic anastomosis techniques using the definitions of the International Study Group of Pancreatic Surgery: a single surgeon's experience.

OBJECTIVES: We aimed to compare different techniques using the definitions of the International Study Group of Pancreatic Surgery for postoperative complications after pancreaticoduodenectomy. METHODS: The perioperative data of 119 patients that underwent pancreaticoduodenectomy by a single surgeon were retrospectively analyzed. Pancreaticojejunal anastomosis was performed using the dunking method (n = 39), the duct-to-mucosa anastomosis method (n = 40), and the duct-to-mucosa adaptation (n = 40). RESULTS: The most frequent complication was postoperative pancreatic fistula (POPF; grades A, 21%; B, 8%; and C, 3%), postpancreatectomy hemorrhage (PPH; grades B, 7% and C, 1%), and delayed gastric emptying (DGE; grades A, 1% and B, 6%). No significant differences in POPF were found between patients who underwent different types of pancreatic anastomoses. Only pancreatic ductal adenocarcinoma (P = 0.001) and pancreatic texture (P = 0.012) were potentially related to POPF. Patients with or without POPF grade A had shorter postoperative stays than patients with grade B or C POPF (P < 0.001), and similar findings were obtained for DGE and PPH. CONCLUSIONS: The successful management of pancreatic anastomoses depends more on a meticulous surgical technique and appropriate experience rather than on the type of technique. Furthermore, the International Study Group of Pancreatic Surgery definitions of POPF, DGE, and PPH seem objective and universally acceptable.

Carcinoma of the middle bile duct: is bile duct segmental resection appropriate?

AIM: To compare survival between bile duct segmental resection (BDSR) and pancreaticoduodenectomy (PD) for treating distal bile duct cancers. METHODS: Retrospective analysis was conducted for 45 patients in a BDSR group and for 149 patients in a PD group. RESULTS: The T-stage (P < 0.001), lymph node invasion (P = 0.010) and tumor differentiation (P = 0.005) were significant prognostic factors in the BDSR group. The 3- and 5-year overall survival rates for the BDSR group and PD group were 51.7% and 36.6%, respectively and 46.0% and 38.1%, respectively (P = 0.099). The BDSR group and PD group did not show any significant difference in survival when this was adjusted for the TNM stage. The 3- and 5-year survival rates were: stage Ia [BDSR (100.0% and 100.0%) vs PD (76.9% and 68.4%) (P = 0.226)]; stage Ib [BDSR (55.8% and 32.6%) vs PD (59.3% and 59.3%) (P = 0.942)]; stage IIb [BDSR (19.2% and 19.2%) vs PD (31.9% and 14.2%) (P = 0.669)]. CONCLUSION: BDSR can be justified as an alternative radical operation for patients with middle bile duct in selected patients with no adjacent organ invasion and resection margin is negative.