Respiratory illness caused by a novel coronavirus (COVID-19) appeared in China during December 2019. Attempting to contain infection, China banned travel to and from Wuhan city on 23 January and implemented a national emergency response. Here we evaluate the spread and control of the epidemic based on a unique synthesis of data including case reports, human movement and public health interventions. The Wuhan shutdown slowed the dispersal of infection to other cities by an estimated 2.91 days (95%CI: 2.54-3.29), delaying epidemic growth elsewhere in China. Other cities that implemented control measures pre-emptively reported 33.3% (11.1-44.4%) fewer cases in the first week of their outbreaks (13.0; 7.1-18.8) compared with cities that started control later (20.6; 14.5-26.8). Among interventions investigated here, the most effective were suspending intra-city public transport, closing entertainment venues and banning public gatherings. The national emergency response delayed the growth and limited the size of the COVID-19 epidemic and, by 19 February (day 50), had averted hundreds of thousands of cases across China.

Copper and its salts are abundant, inexpensive, and eco-friendly and have been used as the surrogates of noble metals to effect arene C-H bond activation and transformations. Despite of the recent significant progress of the study, syntheses of high-valent arylcopper(II-III) compounds are still very rare and mechanisms of copper(II)-catalyzed reactions remain elusive. With the use of azacalix[1]arene[3]pyridines as a platform, a number of arylcopper(II) compounds were synthesized efficiently from the reaction of Cu(ClO4)2 under ambient conditions. The resulting aryl-Cu(II) compounds, which contain an unprecedented (substituted) phenyl-Cu(II) σ-bond, were stable under atmospheric conditions and can undergo facile oxidation reaction by free copper(II) ions or oxone to afford arylcopper(III) compounds in good yields. Both arylcopper(II) and arylcopper(III) compounds were characterized unambiguously by means of XRD, XPS, and NMR methods. Experimental evidence including reaction kinetics, LFER and KIE, and theoretical calculations indicated that the Cu(ClO4)2-mediated arene C-H bond activation proceeds plausibly through an electrophilic aromatic metalation pathway. The synthesis of high-valent arylcopper compounds and the reaction mechanism reported here highlight the diversity and richness of organocopper chemistry.

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Flexible and rechargeable Zn−air batteries, because of their high energy density, low cost, and environmental and human benignity, are one kind of the most attractive energy systems for future wearable electronics. The development of high-performance rechargeable Zn−air batteries depends on the synthesis of highly efficient and highly stable electrocatalysts for the oxygen reduction reaction/oxygen evolution reaction (ORR/OER). Herein, a silk-derived defect-rich and nitrogen-doped nanocarbon electrocatalyst [SilkNC/Ketjenblack (KB)] is reported. The SilkNC/KB is synthesized by pyrolyzing commercially available porous KB carbon impregnated with silk fibroin. It exhibits remarkable electrocatalytic activities and long-term stability for the ORR/OER, enabling its applications in high-performance liquid and solid rechargeable Zn−air batteries. Particularly, the all-solid-state Zn−air battery based on SilkNC/KB exhibits good flexibility and remarkable charge/discharge stability, enabling its promising applications in wearable and energy-efficient batteries.