Search

Spinel LiMn 2 O 4 (LMO) is a well-known cathode material for lithium-ion batteries. In order to elucidate the molecular mechanism of the solid electrolyte interface (SEI) formation and the effect of an additive, vinylene carbonate (VC), we systematically studied the spontaneous and electrochemical reactions of solvents and a salt (LiPF 6 ) in electrolytes with LMO in the absence and presence of VC. X-ray photoelectron spectroscopy (XPS) results of the LMO surfaces after soaking in the electrolyte solutions showed that the carbonate solvents as well as VC spontaneously decomposed on the LMO surfaces to form new compounds, such as alcohols, ethers, and carboxylates. The ratio of the produced LiF to MnF 2 was similar for both with and without VC. Considering these spontaneously formed initial SEI components, we then investigated the variation of the SEI compositions during the initial electrochemical process until 3.8 V vs. Li + /Li. The role of the additive was studied and found that the electrochemical reaction of VC produced more organic compounds and led to an increase in the LiF/MnF 2 ratio of the SEI layer. Based on the hard and soft acid and base theory, we proposed the mechanisms of the SEI formation via spontaneous and electrochemical reactions on the LMO thin film cathode with and without VC.

Objectives: We investigated the characteristics of prophylactic antimicrobial use in clean and clean-contaminated surgical procedures and assessed the efficacy of a prophylactic antimicrobial stewardship intervention at Thong Nhat Hospital, Ho Chi Minh City, Vietnam., Methods: A cross-sectional study was conducted on 354 patients who underwent either clean or clean-contaminated surgical procedures at Thong Nhat Hospital. Eligible patients were classified with respect to three periods of intervention from 2017 to 2020. Data collection included surgical procedures, patient characteristics, and prophylactic antimicrobial usage. We determined the efficacy of antimicrobial stewardship intervention based on comparisons among the primary outcome (the appropriateness of prophylactic antimicrobials) and secondary outcomes (postoperative antimicrobial prophylaxis (AP) prolongation, length of postoperative hospital stay, and cost of antimicrobials)., Results: The mean age of patients in periods 1, 2, and 3 was 54.5 ± 16.6, 50.2 ± 16.5, and 52.8 ± 17.3 years, respectively, with an overall male/female ratio of 1.1/1. No significant differences were detected in basic patient characteristics during the three periods. Majority of the surgical procedures were clean (56%-59%) and scheduled (85%-86%). Prophylactic antimicrobial stewardship intervention enhanced AP appropriateness (by 12.7%, 12.7%, and 39.0% in periods 1, 2, and 3, respectively, p < 0.001), decreased postoperative prophylactic antimicrobial duration [3.0 (0-6), 1.5 (0-5), and 0.0 (0-1) days, respectively, p < 0.001], and reduced average antimicrobial expenses (p < 0.001)., Conclusions: The prophylactic antimicrobial stewardship interventions introduced at Thong Nhat Hospital had several positive impacts on the appropriateness of prophylactic antimicrobial use and treatment costs., (© 2022 John Wiley & Sons Ltd.)

Crossover from an itinerant state to an isolated electronic state in electron-doped polycyclic aromatic hydrocarbon (PAH) was studied for the two smallest zigzag-type molecules of naphthalene (NN) and anthracene (AN) by focusing on their 1 : 1 stoichiometry, A 1 (NN) and A 1 (AN), with alkali metals (A = K and Rb). The competition between on-site Coulombic repulsion energy (U) and bandwidth (W) was argued in terms of their magnetic and electrical properties upon lattice expansion, when A varies from K, with a smaller ionic radius, to Rb, with a larger ionic radius. The temperature-dependence of magnetic susceptibility shows a pronounced hump associated with antiferromagnetic (AFM) interactions for Rb 1 (NN), being similar to those of K 1 (NN) and K 1 (AN) in the earlier report. On the other hand, Rb 1 (AN) intriguingly exhibits paramagnetic susceptibility, observed in a nearly localized electron system, being apart from an highly correlated Mott insulating state. Crystal structural analyses of the X-ray diffraction profiles show a small difference in lattice parameters of the ab plane among K 1 (NN), K 1 (AN), and Rb 1 (NN), whereas Rb 1 (AN) exhibits a significantly larger value than those of the others, being indicative of greatly modified interaction energies. The different magnetic properties observed in Rb 1 (AN) are interpreted from its modified intermolecular distance. The possibility of an emergent metallic state of K 1 (AN) under high pressure has also been described, referring to electrical transport measured under high pressure.