Synthesis of Tetrahydro‑5<i>H</i>‑indolo[2,3‑<i>b</i>]quinolines through Copper-Catalyzed Cascade Reactions of Aza‑<i>o</i>‑quinone Methides with Indoles

A variety of tetrahydro-5H-indolo[2,3-b]quinolines were prepared in 40–97% yields through a copper(II)-catalyzed cascade reaction of aza-o-quinone methides generated in situ from 2-(chloromethyl)anilines and indoles. Experimental results showed that the reaction underwent double 1,4-additions and sequential intramolecular cyclization. The present method features broad substrate scope, good functional group tolerance, and easy gram scalable preparation of indolo[2,3-b]quinolines

Significant Reductions in Secondary Aerosols after the Three-Year Action Plan in Beijing Summer

Air quality in China has continuously improved during the Three-Year Action Plan (2018–2020); however, the changes in aerosol composition, properties, and sources in Beijing summer remain poorly understood. Here, we conducted real-time measurements of aerosol composition in five summers from 2018 to 2022 along with WRF-Community Multiscale Air Quality simulations to characterize the changes in aerosol chemistry and the roles of meteorology and emission reductions. Largely different from winter, secondary inorganic aerosol and photochemical-related secondary organic aerosol (SOA) showed significant decreases by 55–67% in summer, and the most decreases occurred in 2021. Comparatively, the decreases in the primary aerosol species and gaseous precursors were comparably small. While decreased atmospheric oxidation capacity as indicated by ozone changes played an important role in changing SOA composition, the large decrease in aerosol liquid water and small increase in particle acidity were critical for nitrate changes by decreasing gas-particle partitioning substantially (∼28%). Analysis of meteorological influences demonstrated clear and similar transitions in aerosol composition and formation mechanisms at a relative humidity of 50–60% in five summers. Model simulations revealed that emission controls played the decisive role in reducing sulfate, primary OA, and anthropogenic SOA during the Three-Year Action Plan, while meteorology affected more nitrate and biogenic SOA

Effects of reduced nitrogen inputs on crop yield and nitrogen use efficiency in a long-term maize-soybean relay strip intercropping system

<div><p>The blind pursuit of high yields via increased fertilizer inputs increases the environmental costs. Relay intercropping has advantages for yield, but a strategy for N management is urgently required to decrease N inputs without yield loss in maize-soybean relay intercropping systems (IMS). Experiments were conducted with three levels of N and three planting patterns, and dry matter accumulation, nitrogen uptake, nitrogen use efficiency (NUE), competition ratio (CR), system productivity index (SPI), land equivalent ratio (LER), and crop root distribution were investigated. Our results showed that the CR of soybean was greater than 1, and that the change in root distribution in space and time resulted in an interspecific facilitation in IMS. The maximum yield of maize under monoculture maize (MM) occurred with conventional nitrogen (CN), whereas under IMS, the maximum yield occurred with reduced nitrogen (RN). The yield of monoculture soybean (MS) and of soybean in IMS both reached a maximum under RN. The LER of IMS varied from 1.85 to 2.36, and the SPI peaked under RN. Additionally, the NUE of IMS increased by 103.7% under RN compared with that under CN. In conclusion, the separation of the root ecological niche contributed to a positive interspecific facilitation, which increased the land productivity. Thus, maize-soybean relay intercropping with reduced N input provides a very useful approach to increase land productivity and avert environmental pollution.</p></div

Effect of planting patterns and N application rates on nitrogen use efficiency (%) in the maize-soybean relay strip intercropping system.

<p>Effect of planting patterns and N application rates on nitrogen use efficiency (%) in the maize-soybean relay strip intercropping system.</p

N uptake of maize and soybean under different N levels and planting patterns (kg ha^-1).

<p>N uptake of maize and soybean under different N levels and planting patterns (kg ha^-1).</p

The temperature, daylight hour, precipitation and evapotranspiration during the cropping seasons from 2012 to 2014.

<p>The temperature, daylight hour, precipitation and evapotranspiration during the cropping seasons from 2012 to 2014.</p

Effect of planting patterns and N application rates on crop dry matter accumulation (Mg ha^-1).

<p>Effect of planting patterns and N application rates on crop dry matter accumulation (Mg ha^-1).</p

Maize-soybean relay intercropping system in August.

<p>Left side is RN treatment plot, right side is NN treatment, and the yellow line is the plot boundary.</p

Effect of different below-ground interactions and N application rates on soybean root distribution at the R2 stage of development in 2014.

<p>MS with different N application rates (A), IS with different N application rates (B), the coordinate axis and N application rates were same as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184503#pone.0184503.g004" target="_blank">Fig 4</a>.</p

Effects of N application rates on the land equivalent ratio (LER) of maize-soybean relay intercropping.

<p>Effects of N application rates on the land equivalent ratio (LER) of maize-soybean relay intercropping.</p