Article

Importance and vulnerability of lakes and reservoirs supporting drinking water in China

湖库是保障饮用水安全基石，但也面临脆弱性增加风险

Abstract

Drinking water is closely related to human health, disease and mortality, and contaminated drinking water causes 485,000 deaths from diarrhea each year worldwide. China has been facing increasingly severe water scarcity due to both water shortages and poor water quality. Ensuring safe and clean drinking water is a great challenge and top priority, especially for China with 1.4 billion people. In China, more than 4000 centralized drinking water sources including rivers, lakes and reservoirs, and groundwater have been established to serve urban residents. However, there is little knowledge on the percentage, serving population and water quality of three centralized drinking water source types. We collected nationwide centralized drinking water sources data and serving population data covering 395 prefecture-level and county-level cities and water quality data in the two most populous provinces (Guangdong and Shandong) to examine their contribution and importance. Geographically, the drinking water source types can be classified into three clear regions exhibiting apparent differences in the respective contributions of rivers, lakes and reservoirs, and groundwater. We further found that overall, lakes and reservoirs account for 40.6% of the centralized drinking water sources vs. river (30.8%) and groundwater (28.6%) in China. Lakes and reservoirs are particularly important in the densely populated eastern region, where they are used as drinking water sources by 51.0% of the population (318 million). Moreover, the contribution to the drinking water supply from lakes and reservoirs is increasing due to their better water quality and many cross-regional water transfer projects. These results will be useful for the government to improve and optimize the establishment of centralized drinking water sources, which provide safe and clean drinking water in China to safeguard people's lives and health and realize sustainable development goals.

Yunlin Zhang, Jianming Deng, Boqiang Qin, Guangwei Zhu, Yinjun Zhang, Erik Jeppesen, Yindong Tong

Article

Design and synthesis of axially chiral aryl-pyrroloindoles via the strategy of organocatalytic asymmetric (2 + 3) cyclization

轴手性芳基-吡咯并吲哚骨架的设计与构建

Abstract

The catalytic asymmetric construction of axially chiral indole-based frameworks is an important area of research due to the unique characteristics of such frameworks. Nevertheless, research in this area is still in its infancy and has some challenges, such as designing and constructing new classes of axially chiral indole-based scaffolds and developing their applications in chiral catalysts, ligands, etc. To overcome these challenges, we present herein the design and atroposelective synthesis of aryl-pyrroloindoles as a new class of axially chiral indole-based scaffolds via the strategy of organocatalytic asymmetric (2 + 3) cyclization between 3-arylindoles and propargylic alcohols. More importantly, this new class of axially chiral scaffolds was derived into phosphines, which served as efficient chiral ligands in palladium-catalyzed asymmetric reactions. Moreover, theoretical calculations provided an in-depth understanding of the reaction mechanism. This work offers a new strategy for constructing axially chiral indole-based scaffolds, which are promising for finding more applications in asymmetric catalysis.

Ping Wu, Lei Yu, Cong-Hui Gao, Qi Cheng, Shuang Deng, Yinchun Jiao, Wei Tan, Feng Shi

Article

Magnon squeezing enhanced ground-state cooling in cavity magnomechanics

腔磁力系统中磁振子压缩增强的基态冷却

Abstract

Cavity magnomechanics has recently become a new platform for studying macroscopic quantum phenomena. The magnetostriction induced vibration mode of a large-size ferromagnet or ferrimagnet reaching its ground state represents a genuine macroscopic quantum state. Here we study the ground-state cooling of the mechanical vibration mode in a cavity magnomechanical system, and focus on the role of magnon squeezing in improving the cooling efficiency. The magnon squeezing is obtained by exploiting the magnon self-Kerr nonlinearity. We find that the magnon squeezing can significantly and even completely suppress the magnomechanical Stokes scattering. It thus becomes particularly useful in realizing ground-state cooling in the unresolved-sideband regime, where the conventional sideband cooling protocols become inefficient. We also find that the coupling to the microwave cavity plays only an adverse effect in mechanical cooling. This makes essentially the two-mode magnomechanical system (without involving the microwave cavity) a preferred system for cooling the mechanical motion, in which the magnon mode is established by a uniform bias magnetic field and a microwave drive field.

M. Asjad, Jie Li, Shi-Yao Zhu, J.Q. You

Review

The grassland carbon cycle: Mechanisms, responses to global changes, and potential contribution to carbon neutrality

草地碳循环：机制、对全球变化的响应和对碳中和的潜在贡献

Abstract

Grassland is one of the largest terrestrial biomes, providing critical ecosystem services such as food production, biodiversity conservation, and climate change mitigation. Global climate change and land-use intensification have been causing grassland degradation and desertification worldwide. As one of the primary medium for ecosystem energy flow and biogeochemical cycling, grassland carbon (C) cycling is the most fundamental process for maintaining ecosystem services. In this review, we first summarize recent advances in our understanding of the mechanisms underpinning spatial and temporal patterns of the grassland C cycle, discuss the importance of grasslands in regulating inter- and intra-annual variations in global C fluxes, and explore the previously unappreciated complexity in abiotic processes controlling the grassland C balance, including soil inorganic C accumulation, photochemical and thermal degradation, and wind erosion. We also discuss how climate and land-use changes could alter the grassland C balance by modifying the water budget, nutrient cycling and additional plant and soil processes. Further, we examine why and how increasing aridity and improper land use may induce significant losses in grassland C stocks. Finally, we identify several priorities for future grassland C research, including improving understanding of abiotic processes in the grassland C cycle, strengthening monitoring of grassland C dynamics by integrating ground inventory, flux monitoring, and modern remote sensing techniques, and selecting appropriate plant species combinations with suitable traits and strong resistance to climate fluctuations, which would help design sustainable grassland restoration strategies in a changing climate.

Lingli Liu, Emma J. Sayer, Meifeng Deng, Ping Li, Weixing Liu, Xin Wang, Sen Yang, Junsheng Huang, Jie Luo, Yanjun Su, José M. Grünzweig, Lin Jiang, Shuijin Hu, Shilong Piao

朱军等：芳香性和反芳香性在反应机理中的应用

Review

The application of aromaticity and antiaromaticity to reaction mechanisms

芳香性和反芳香性在反应机理中的应用

Abstract

Aromaticity, in general, can promote a given reaction by stabilizing a transition state or a product via a mobility of π electrons in a cyclic structure. Similarly, such a promotion could be also achieved by destabilizing an antiaromatic reactant. However, both aromaticity and transition states cannot be directly measured in experiment. Thus, computational chemistry has been becoming a key tool to understand the aromaticity-driven reaction mechanisms. In this review, we will analyze the relationship between aromaticity and reaction mechanism to highlight the importance of density functional theory calculations and present it according to an approach via either aromatizing a transition state/product or destabilizing a reactant by antiaromaticity. Specifically, we will start with a particularly challenging example of dinitrogen activation followed by other small-molecule activation, Csingle bondF bond activation, rearrangement, as well as metathesis reactions. In addition, antiaromaticity-promoted dihydrogen activation, CO2 capture, and oxygen reduction reactions will be also briefly discussed. Finally, caution must be cast as the magnitude of the aromaticity in the transition states is not particularly high in most cases. Thus, a proof of an adequate electron delocalization rather than a complete ring current is recommended to support the relatively weak aromaticity in these transition states.

Qin Zhu, Shuwen Chen, Dandan Chen, Lu Lin, Kui Xiao, Liang Zhao, Miquel Solà, Jun Zhu