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This paper offers a unique perspective about the development of the online-to-offline (O2O) food delivery industry from 2017 to 2019 in China. This study demonstrates the latest transformation and improvements of the O2O market that address some common problems in the early stages of the development of this raising industry in China. New strategies and regulations from the O2O platforms, food providers, and national and local governments are discussed. In our view, the mission of the O2O industry in general has shifted from pursuing enormous quantity to ensuring high quality. China's O2O food delivery industry warrants further attention and studies as it grows and develops into the future. We suggest future studies to work on its economic, behavioral, and health impacts on population level as it encompasses both great risks and rewards., Author(s): Xueyin Zhao [sup.1] [sup.2] , Wenhui Lin [sup.1] [sup.2] [sup.3] , Shuyi Cen [sup.1] [sup.2] , Haoyu Zhu [sup.4] , Meng Duan [sup.1] [sup.2] , Wei Li [sup.1] [sup.5] [...]

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value‐added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br−/HOBr‐mediated method is developed to achieve a near‐quantitative selectivity and ≈100% FE of styrene oxide on α‐Fe2O3, in which low concentration of Br− as mediator and locally generated acidic micro‐environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH‐dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications. [ABSTRACT FROM AUTHOR]

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value‐added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br−/HOBr‐mediated method is developed to achieve a near‐quantitative selectivity and ≈100% FE of styrene oxide on α‐Fe2O3, in which low concentration of Br− as mediator and locally generated acidic micro‐environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH‐dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications. [ABSTRACT FROM AUTHOR]

Reasonable dense planting is an important measure to increase crop yield per unit area and save resources. However, there is no unified view of the competition for photosynthetic radiation in different stratification structures of maize plants due to different planting densities, as well as the internal mechanism of yield increase. In order to investigate these issues, field experiments were conducted from 2021 to 2022 in Daxing, Beijing, China (39°37′ N, 116°25′ E, altitude 31.3 m a.s.l.). Field plots were arranged in a randomized block design, with the main plot factor representing plant density. In each replicate, four densities were set, i.e., 33,000 (D1), 42,000 (D2), 55,000 (D3), and 83,000 (D4) plants·ha−1. Canopy stratification structure characteristics, including leaf area index, biomass, and photosynthetically active radiation (PAR), were measured in each stratification structure, and transmitted PAR, radiation use efficiency (RUE), and light extinction coefficient (K) were calculated. We found that increasing plant density significantly increased biomass, leaf area index (LAI), and precipitation use efficiency (PUE), but the light extinction coefficient (K) and harvest index (HI) showed opposite trends. Compared to the D1 treatment, the grain yield, precipitation use efficiency (PUE), radiation use efficiency (RUE), and LAI increased by 22.6–88.2%, 9.2–50.5%, 26.7–116.9%, and 27.7 to 150.6% in the D2, D3, and D4 treatments, and K and HI decreased by 19.7–50.3% and 4.2–11.5%, respectively. These showed that a density of 83,000 plants·ha−1 was effective in promoting maize growth in the Daxing area of Beijing, China. [ABSTRACT FROM AUTHOR]

A computational fluid dynamics coupled population balance model (CFD-PBM) was used to numerically simulate the fluid dynamics of bubble swarms in a bubble column containing non-Newtonian fluids. The effects of superficial gas velocity (Ug), the consistency index (K), and the flow index (n) on bubble size distribution (BSD), gas holdup, and fluid dynamic viscosity in a bubble column were analyzed at both local and overall scales. As Ug increases, the bubble breakup occurs excessively, the gas holdup increases, and the dynamic viscosity decreases. K and n were used to characterize the rheological properties of power law fluid. As K increases, fluid viscosity increases, bubble breakup rate decreases, gas holdup in the top zone is slightly lower than in the middle zone, and dynamic viscosity increases. Within the range of n from 0.45 to 1.07, when n is smallest, the relative frequency of bubbles smaller than the initial size is relatively large, and the overall and local gas holdup are the highest. When n = 1.07, the fluid exhibits shear-thickening properties, and the dynamic viscosity variations are significant. [ABSTRACT FROM AUTHOR]

Radical substitution is a useful method to functionalize heterocycles, as in the venerable Minisci reaction. Empirically observed regiochemistries indicate that the CF2H radical has a nucleophilic character similar to alkyl radicals, but the CF3 radical is electrophilic. While the difference between •CH3 and •CF3 is well understood, the reason that one and two Fs make little difference but the third has a large effect is puzzling. DFT calculations with M06-2X both reproduce experimental selectivities and also lead to an explanation of this difference. Theoretical methods reveal how the F inductive withdrawal and conjugative donation alter radical properties, but only CF3 becomes decidedly electrophilic toward heterocycles. Here, we show a simple model to explain the radical orbital energy trends and resulting nucleophilicity or electrophilicity of fluorinated radicals. Empirically observed regiochemistries indicate that the CF2H radical has a nucleophilic character similar to alkyl radicals, but the CF3 radical is electrophilic in reactions with heterocycles. Here, the authors report DFT calculations, reproducing experimental selectivities and leading to an explanation of this difference. [ABSTRACT FROM AUTHOR]