Early childhood learning patterns for a home visiting program in rural China.

This paper uses novel experimental data from a prototypical early childhood home visiting program in China with high-frequency measurements to investigate the growth of multiple skills. After identifying the presence of child skill development on multiple skills during the intervention, we further study the features of child learning patterns. We find that individual heterogeneity and previous task performance (state dependence) are key properties of the child's task performance during the intervention, consistent with models of reinforcement learning.

Insight into the Process and Mechanism of Water-Rock Interaction in Underground Coal Mine Reservoirs Based on Indoor Static Simulation Experiments.

During the storage of underground water reservoirs in coal mines, water-rock interaction occurred between mine water and collapsed rocks, resulting in improved mine water quality, but the water-rock process and mechanism have not been clarified. In this study, six sets of simulated experiments were designed to investigate the water-rock interaction between two types of roof collapse rocks and different water samples in the Daliuta coal mine. The ion ratio method and multivariate statistics are used to reveal the process and mechanism of water-rock interaction during the experimental process from the perspective of input and output water chemical characteristics and rock properties, respectively. The results show that the ion concentration of the effluent water is controlled by water-rock interaction, and the water-rock process mainly involves the dissolution of halite, silicate, pyrite, calcite, dolomite, magnesia chlorite, and gypsum precipitation and is accompanied by ion exchange. Mineral dissolution and precipitation are the most important factors affecting the ion abundance in the effluent. There are differences in the reaction rate, degree of reaction, and dissolution process during the experimental process of fine sandstone and mudstone. Fine sandstone is more reactive than mudstone in terms of reaction rate and degree of reaction, and fine sandstone is dissolved from surface pores to inside and around, while mudstone is generated in new dissolved pores. We found that rock type, ion concentration in the input water, and rock reaction period influence the water-rock interaction during the experiment. The results provide a reference for clarifying the water-rock interaction during the storage of underground water reservoirs in coal mines and predicting the water quality of the effluent.

Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism.

Classic, model-based theory of land-atmosphere interactions across the Sahel promote positive vegetation-rainfall feedbacks dominated by surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback nor its underlying albedo mechanism has been convincingly demonstrated using observational data. Here, we present observational evidence for the region's proposed positive vegetation-rainfall feedback on the seasonal to interannual time scale, and find that it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism. Positive anomalies of remotely sensed vegetation greenness across the Sahel during the late and post-monsoon periods favor enhanced evapotranspiration, precipitable water, convective activity and rainfall, indicative of amplified moisture recycling. The identified modest low-level cooling and anomalous atmospheric subsidence in response to positive vegetation greenness anomalies are counter to the responses expected through the classic vegetation-albedo feedback mechanism. The observational analysis further reveals enhanced dust emissions in response to diminished Sahel vegetation growth, potentially contributing to the positive vegetation-rainfall feedback.

Palladium-catalyzed direct and regioselective C-H acyloxylation of indolizines.

A direct and regioselective C1-acyloxylation of indolizines was developed via palladium-catalyzed C-H functionalization. A series of indolizines were successfully acyloxylated at the C1 position with the tolerance of a broad range of functional groups. In this reaction, high regioselectivity was achieved in the absence of a directing group. This work represents the first example of indolizine acyloxylation via C-H activation.

Copper(II)-catalyzed indolizines formation followed by dehydrogenative functionalization cascade to synthesize 1-bromoindolizines.

A one-pot, three-component cascade reaction between pyridine, α-acylmethylbromide, and maleic anhydride leading to direct access of 1-bromoindolizines in high yields has been developed. This protocol is accomplished via a reaction sequence of 1,3-dipolar cycloaddition of the pyridinium ylide with maleic anhydride, oxidative decarboxylation of the primary cycloadduct, and dehydrogenative bromination of the resulting 1-unsubstituted indolizine. Copper chloride was used as a catalyst and oxygen as the terminal oxidant. This reaction represents the first example of transition-metal-catalyzed direct dehydrogenative bromination of indolizine at the C-1 position. Moreover, the obtained 1-bromoindolizines can be transformed to other 1-substituted indolizines such as 1-arylindolizines via a simple reaction process.

Copper(II)-catalyzed carbon-carbon triple bond cleavage of internal alkynes for the synthesis of annulated indolizines.

Cleavage of C≡C bond in butynedioates via copper(II)-catalyzed reaction has been achieved, leading to the synthesis of benzo[f]pyrido[1,2-a]indole-6,11-diones in high yields by one-pot three-component reactions. In this unprecedented C≡C bond cleavage reaction of internal alkynes, both fragments from the alkyne are successively incorporated into the products.