Doping Regulation Stabilizing δ-MnO2 Cathode for High-Performance Aqueous Aluminium-ion Batteries.

δ-MnO2 is a promising cathode material for aqueous aluminium-ion batteries (AAIBs) for its layered crystalline structure with large interlayer spacing. However, the excellent Al ion storage performance of δ-MnO2 cathode remains elusive due to the frustrating structural collapse during the intercalation of high ionic potential Al ion species. Here, it is discovered that introducing heterogeneous metal dopants with high bond dissociation energy when bonded to oxygen can significantly reinforce the structural stability of δ-MnO2 frameworks. This reinforcement translates to stable cycling properties and high specific capacity in AAIBs. Vanadium-doped δ-MnO2 (V-δ-MnO2 ) can deliver a high specific capacity of 518 mAh g-1 at 200 mA g-1 with remarkable cycling stability for 400 cycles and improved rate capabilities (468, 339, and 285 mAh g-1 at 0.5, 1, and 2 A g-1 , respectively), outperforming other doped δ-MnO2 materials and the reported AAIB cathodes. Theoretical and experimental studies indicate that V doping can substantially improve the cohesive energy of δ-MnO2 lattices, enhance their interaction with Al ion species, and increase electrical conductivity, collectively contributing to high ion storage performance. These findings provide inspiration for the development of high-performance cathodes for battery applications.

Low-temperature cluster spin glass transition in the single-domain NiCr2O4nanoparticles.

NiCr2O4nanoparticles with average particle size ∼15 nm, a single-domain size maintains the bulk canted antiferromagnetic ground state, were synthesized by a microwave combustion method. The magnetic behavior was carefully investigated by static and dynamic magnetic susceptibility measurements. In addition to a spin-glass-like behavior below paramagnetic-ferrimagnetic transition atTC, the NiCr2O4nanoparticles demonstrate a low-temperature cluster spin glass transition below the spin canting transitionTS, which manifests itself as a magnetic anomaly peak around ∼12 K (at 100 Oe) in the zero-field cooled magnetization with a relatively stronger field dependence in a 'de Almeida-Thouless' line for spin glasses. The AC susceptibility analyses in different approaches demonstrate a larger relative peak temperature variation per frequency decade and a longer characteristic relaxation time in the order of 0.04 and 10-7s, against 0.01 and 10-9s for the high-temperature blocking, indicating the slow spin dynamics for the low-temperature cluster glassy phase. A field-temperature magnetic phase diagram is proposed for the single-domain NiCr2O4nanoparticles.

Ursodeoxycholic acid for the prevention of gall stones after laparoscopic sleeve gastrectomy: a prospective controlled study.

BACKGROUND: Obesity is a risk factor for cholelithiasis. Besides, rapid weight loss after bariatric surgery upsurges the rate of cholelithiasis and acute cholecystitis. This study aimed to compare gallstone development frequency after LSG under ursodeoxycholic acid (UDCA) prophylaxis. METHODS: This prospective controlled study included 332 patients scheduled for LSG randomized to receive 500 mg UDCA daily for 12 months (UDCA Group) or no treatment (Control Group). Ultrasonography was done 6 and 12 months after surgery to detect gallstones. Cholecystectomy was done for complicated cases of cholelithiasis. RESULTS: Seventy-one patients were lost to follow-up, and 3 developed severe adverse effects of UDCA and excluded. Data are presented for 130 patients in the UDCA group and 128 in the Control group. Collectively, 11 patients (8.5%) of the UDCA group and 41 (32.0%) of the Control group developed gall stones during the first postoperative year (p < 0.001). Cholecystectomy was indicated in 3 patients (2.3%) of the UDCA group and 9 (7.0%) of the Control group (p = 0.072). On multivariate analysis, higher BMI, dyslipidemia, and lacking UDCA prophylaxis were the independent factors significantly associated with stone development. Also, stone development was associated with higher weight loss after 6 and 12 months. CONCLUSION: UDCA 500 mg once daily for 12 months after LSG is effective in reducing gallstone formation at 1 year. UDCA administration reduced the frequency of cholecystectomies from 7 to 2.3%. High BMI and dyslipidemia are the independent preoperative factors significantly associated with stone development.