Spatiotemporal variation and driving factors of water yield services on the Qingzang Plateau

Water resources are a basic need for social sustainable development and human existence.As an important national strategy for water resources security,spatial and temporal patterns and driving mechanisms of water yield ecosystem services on the Qingzang Plateau(QP)are critical for water resources management,optimal water allocation and the improvement of ecological water protection efficiency.However,only a few relevant studies are currently available.In this study,we simulated the water yield(WY)of the QP over 34 years,from 1982 to 2015,using the InVEST model and analyzed the spatiotemporal dynamic relationships between WY and climate change as well as between WY and vegetation change,using geographically weighted regression(GWR)models.The results showed that:1)from 1982 to 2015,the WY of the QP increased at an average rate of 3.8 mm/yr;2)WY presented a reduced spatial pattern from southeast to northwest;and 3)the WY driving factors have individual and spatial differences.In terms of the area percentage in promoting WY when analyzing each driving factor,precipitation(99.8%)and air pressure(53.3%)played the major roles in promoting WY,while temperature(71.9%),wind speed(57.2%),net primary productivity(87.2%),radiation(68.3%)and lake(87.7%)played negative roles.The areas where WY are dominated by temperature are the largest(41.1%),and followed by areas dominated by pressure(19.7%)and precipitation(18.5%).The results of this study provide scientific support for formulating regional water resources policy,social and economic development planning and other macro decisions for the QP.

Grid Integration of Wind Generation Considering Remote Wind Farms:Hybrid Markovian and Interval Unit Commitment

Grid integration of wind power is essential to reduce fossil fuel usage but challenging in view of the intermittent nature of wind.Recently,we developed a hybrid Markovian and interval approach for the unit commitment and economic dispatch problem where power generation of conventional units is linked to local wind states to dampen the effects of wind uncertainties.Also,to reduce complexity,extreme and expected states are considered as interval modeling.Although this approach is effective,the fact that major wind farms are often located in remote locations and not accompanied by conventional units leads to conservative results.Furthermore,weights of extreme and expected states in the objective function are difficult to tune,resulting in significant differences between optimization and simulation costs.In this paper,each remote wind farm is paired with a conventional unit to dampen the effects of wind uncertainties without using expensive utility-scaled battery storage,and extra constraints are innovatively established to model pairing.Additionally,proper weights are derived through a novel quadratic fit of cost functions.The problem is solved by using a creative integration of our recent surrogate Lagrangian relaxation and branch-and-cut.Results demonstrate modeling accuracy,computational efficiency,and significant reduction of conservativeness of the previous approach.

Regioselective and asymmetric allylic alkylation of vinyl epoxides for the construction of allylic alcohols via synergistic catalysis

A highly efficient asymmetric allylic alkylation of cyclic and acyclic carbon nucleophiles with vinyl epoxides has been developed,which exhibits good functional group compatibility,high atomic and step economy.This protocol utilizes a strategy of synergistic catalysis with a chiral N,N'-dioxide/Ni~Ⅱ complex and an achiral Pd~0 catalyst,generating a series of multisubstituted allylic alcohols with a quaternary carbon stereocenter in high yield and excellent regio-,Z/E-and enantioselectivity under mild conditions.Further transformations of the product demonstrate the potential utility of this protocol in the synthesis of allyl alcohol derivatives and natural product analogues.Experimental studies revealed that the N,N′-dioxide/metal complexes play an important role in controlling the Z/E-and enantioselectivity.The density functional theory(DFT) calculations further demonstrated that multiple C–H···π interactions between the aromatic rings of the two substrates and the amide moiety in the ligand stabilized the dominant transition state.

Copper-catalyzed asymmetric dearomatizing amination of 2-naphthols:Csp^(2)–N coupling via 1,3-reductive elimination

An efficient catalytic asymmetric dearomatizing amination of 2-naphthols and phenols catalyzed by N,N′-dioxide-copper(I)complex as a chiral catalyst was presented.A variety of optically activeβ-naphthalenone compounds with a nitrogen-containing quaternary carbon stereocenter were obtained with high yield and enantioselectivity under mild reaction conditions.Mechanistic studies indicated that this Csp^(2)–N dearomatizing coupling proceeds via 1,3-reductive elimination of phenolate-Cu~Ⅲ-amino intermediate in five-membered ring transition states.The origin of enantioselectivity has also been elucidated based on density functional theory calculations.

Spatiotemporal drivers of Nature's contributions to people:A countylevel study

Nature's contributions to people(NCP)encompass both the beneficial and detrimental effects of living nature on human quality of life,including regulatory,material,and non-material contributions.Globally,vital NCPs have been deteriorating,accelerated by changes in both natural and anthropogenic drivers over recent decades.Despite the often inevitable trade-offs between NCPs due to their spatially and temporally uneven distributions,few studies have quantitatively assessed the impacts of different drivers on the spatial and temporal changes in multiple NCPs and their interrelationships.Here we evaluate the effects of precipitation,temperature,population,gross domestic product,vegetation restoration,and urban expansion on four key regulatory NCPs-habitat maintenance,climate regulation,water quantity regulation,and soil protection-in Nei Mongol at the county level.We observe increasing trends in climate regulation and soil protection from 2000 to 2019,contrasted with declining trends in habitat maintenance and water quantity regulation.We have identified the dominant positive and negative drivers influencing each NCP across individual counties,finding that natural drivers predominantly overpowered anthropogenic drivers.Furthermore,we discover significant spatial disparities in the tradeoff or synergy relationships between NCPs across the counties.Our findings illustrate how the impacts of various drivers on NCPs and their interrelationships can be quantitatively evaluated,offering significant potential for application in various spatial scales.With an understanding of trade-offs and scale effects,these insights are expected to support and inform policymaking at both county and provincial levels.

Divergent driving mechanisms of community temporal stability in China's drylands

Climate change and anthropogenic activities are reshaping dryland ecosystems globally at an unprecedented pace,jeopardizing their stability.The stability of these ecosystems is crucial for maintaining ecological balance and supporting local communities.Yet,the mechanisms governing their stability are poorly understood,largely due to the scarcity of comprehensive field data.Here we show the patterns of community temporal stability and its determinants across an aridity spectrum by integrating a transect survey across China's drylands with remote sensing.Our results revealed a U-shaped relationship between community temporal stability and aridity,with a pivotal shift occurring around an aridity level of 0.88.In less arid areas(aridity level below 0.88),enhanced precipitation and biodiversity were associated with increased community productivity and stability.Conversely,in more arid zones(aridity level above 0.88),elevated soil organic carbon and biodiversity were linked to greater fluctuations in community productivity and reduced stability.Our study identifies a critical aridity threshold that precipitates significant changes in community stability in China's drylands,underscoring the importance of distinct mechanisms driving ecosystem stability in varying aridity contexts.These insights are pivotal for developing informed ecosystem management and policy strategies tailored to the unique challenges of dryland conservation.

Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects

The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective.

Chiral Amino Acids-Derived Catalysts and Ligands

Transforming amino acids into novel catalysts and ligands is a remarkable subset of new catalyst development in order to imitate enzymatic efficiencies. Their ability to perform a variety of asymmetric catalytic reactions is complimented by their ready availability, rich transformations, stability and easy＇procedure. Herein, we focused-on describing our endeavoT ofdeveloping new catalysts and ligands from primary and secondary amino acids. It includes C2-symmetric N,N＇-dioxides, guanidine-amides, bispidine-based diamines, and other organic salts. The account covered a brief introduction about their discovery, representative applications and related mechanisms.

Does Experience Facilitate Entry into New Export Destinations?

Using a large panel dataset that covers 116 countries and 5013products over the period 1998-2010, this study evaluates the effects of export experience on the geographic expansion of China ＂s exports. The results suggest that past export experience in geographically close and culturally similar markets plays a crucial role in.facilitating new market entry, and the positive spillover effects are more pronounced for incumbent and successful products. The results also indicate that spillovers from export experience are market-specific and product- specific, and they are limited to within the same product class and the same market, with little cross-group effects. Finally, there is no strong evidence that export experience is more important for differentiated products than for homogeneous products, and the positive spillover effects are remarkable for both categories of products.

Recent leveling off of vegetation greenness and primary production reveals the increasing soil water limitations on the greening Earth

Global vegetation photosynthesis and productivity have increased substantially since the 1980s,but this trend is heterogeneous in both time and space.Here,we categorize the secular trend in global vegetation greenness into sustained greening,sustained browning and greening-to-browning.We found that by 2016,increased global vegetation greenness had begun to level off,with the area of browning increasing in the last decade,reaching 39.0 million km^(2)(35.9%of the world’s vegetated area).This area is larger than the area with sustained increasing growth(27.8 million km^(2),26.4%);thus,12.0%±3.1%(0.019±0.004 NDVI a^(-1))of the previous earlier increase has been offset since 2010(2010–2016,P<0.05).Global gross primary production also leveled off,following the trend in vegetation greenness in time and space.This leveling off was caused by increasing soil water limitations due to the spatial expansion of drought,whose impact dominated over the impacts of temperature and solar radiation.This response of global gross primary production to soil water limitation was not identified by land submodels within Earth system models.Our results provide empirical evidence that global vegetation greenness and primary production are offset by water stress and suggest that as global warming continues,land submodels may overestimate the world’s capacity to take up carbon with global vegetation greening.

Rapid Fabrication of Bio-inspired Antireflection Film Replicating From Cicada Wings

Inspired by cicada wings,a flexible film with self-cleaning and broadband antireflection properties was fabricated with a rapid,straightforward and cost-effective method.The cicada wing was selected as the original template,and a polymethyl methacrylate (PMMA) negative replica was obtained by evaporation solvent process.The original template was directly peeled off.Subsequently,the polydimethylsiloxane (PDMS) was spread in the as-prepared PMMA negative replica.After curing and peeling processes,the PDMS positive replica was manufactured successfully.The morphologies and performances of cicada wings were perfectly inherited by the PDMS positive replica.What is more,the excellent optical property of cicada wing was investigated experimentally and theoretically.Compared with fiat PDMS film,the average reflectivity of structural PDMS film was reduced from 9% to 3.5% in the wavelength range of 500 nm-900 nm.These excellent antireflection properties of bio-inspired antireflection film can be attributed to the nanostructures which achieve a gradient refractive index between air and the materials,and the mechanism of the antireflection properties was revealed via effective medium theory.Besides,the bio-inspired broadband antireflective film exhibited superhydrophobic property after the surface treatment (a 152.1° water contact angle),and it also displayed satisfactory flexibility.This work provided a universal method to fabricate the exquisite biological structures,realizing the transfer of structure and function.Moreover,the multifunctional antireflection film exhibited the potential value for applications in optical communications,flexible display screens,and anti-dazzle glasses.

Loss of Lkb1 impairs Treg function and stability to aggravate graft-versus-host disease after bone marrow transplantation

Accumulating evidence suggests that a reduction in the number of Foxp3^(+) regulatory T cells(Tregs)contributes to the pathogenesis of acute graft-versus-host disease(aGVHD),which is a major adverse complication that can occur after allogeneic hematopoietic stem cell transplantation(allo-HSCT).However,the precise features and mechanism underlying the defects in Tregs remain largely unknown.In this study,we demonstrated that Tregs were more dramatically decreased in bone marrow compared with those in peripheral blood from aGVHD patients and that bone marrow Treg defects were negatively associated with hematopoietic reconstitution.Tregs from aGVHD patients exhibited multiple defects,including the instability of Foxp3 expression,especially in response to IL-12,impaired suppressor function,decreased migratory capacity,and increased apoptosis.Transcriptional profiling revealed the downregulation of Lkb1,a previously identified critical regulator of murine Treg identity and metabolism,and murine Lkb1-regulated genes in Tregs from aGVHD patients.Foxp3 expression in human Tregs could be decreased and increased by the knockdown and overexpression of the Lkb1 gene,respectively.Furthermore,a loss-of-function assay in an aGVHD murine model confirmed that Lkb1 deficiency could impair Tregs and aggravate disease severity.These findings reveal that Lkb1 downregulation contributes to multiple defects in Tregs in human aGVHD and highlight the Lkb1-related pathways that could serve as therapeutic targets that may potentially be manipulated to mitigate aGVHD.

C–H alkylation of pyridines with olefins catalyzed by imidazolin-2-iminato-ligated rare-earth alkyl complexes

An array of rare-earth bis(aminobenzyl)complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized.These complexes showed high activity towards ortho-Csp^(2)–H alkylation of 2-alkylpyridines and benzylic Csp^(3)–H alkylation of 2,6-dialkylpyridines with alkenes.A wide range of alkyl or aryl substituted olefin substrates are compatible,providing an atom-economical route to linear or branched alkylated pyridine derivatives in moderate to high yields(45 examples,up to 99%yield).The primary study suggested that the asymmetric version of Csp^(3)–H alkylation of 2,4,6-collidine with allylbenzene was feasible with chiral imidazolin-2-iminato-ligated scandium(III)complexes,and good yield with moderate enantioselectivity was obtained(84%yield,84:16 er).Mechanistic investigations including kinetic isotope effect(KIE)experiments and density functional theory(DFT)calculations shed light on the catalytic cycle and the origin of enantiocontrol.

Asymmetric Catalytic α-Selective Allylation of Ketones with Allyltrifluoroborates Using Dual-Functional Chiral In^(Ⅲ)/N,N'-Dioxide Complex

Comprehensive Summary Asymmetric catalytic allylation of halo-substituted ketones and ketoesters was accomplished to yield a number of homoallylic tertiary alcohols in excellent reactivity and enantioselectivity.In the presence of chiral In^(Ⅲ)/N,N-dioxide catalyst,unusual α-selective allylation ofγ-substituted potassium allyltrifluoroborates to ketones was demonstrated.The control experiments and DFT calculation reveal that chiral In^(Ⅲ)/N,N'-dioxide catalyst plays dual-tasking roles:the formation of allylindium species via transmetalation and Lewis acid activation.Apossiblereaction pathwaywas provided tounderstandα-selectivity overy-selectivity.

20世纪后期气候加速变暖促进了北半球树木径向生长

20世纪后期全球加速变暖导致北半球森林衰退事件频发,并增加了树木生长-气候关系的复杂性。然而,关于气候加速变暖前后北半球不同地区树木生长对气候因子响应的异质性研究仍较为缺乏。本研究利用北半球3大洲9个地区共计229条温度敏感型树轮宽度年表分析了气候加速变暖前后不同地区树木生长趋势和气候响应的异质性表现。结果表明:(i)1977–2000年期间,气候加速变暖显著促进了北半球不同地区树木的径向生长,但在1950–2000年期间,不同地区的树木径向生长表现出异质性特征。(ii)1976年后,除北美中部和欧洲北部,北半球树木生长和温度的相关性均显著增加,亚洲地区最为明显。(iii)在1977–2000年期间,9个地区的树木年轮指数与温度均出现了短暂的分离(2–5年)。在1950–2000年期间,各地区树木生长能够更好地追踪到北半球平均温度的变化趋势而不是区域温度。

Asymmetric annulations based on cycloisomerization of cyclopropyl tethered allenyl ketones by bimetallic relay catalysis

The diastereo-and enantioselective tandem cycloisomerization/[4+2]-cycloaddition reaction of cyclopropyl tethered allenyl ketones withα,β-unsaturated carbonyl compounds was realized firstly under mild reaction conditions by using bimetallic silver(I)/chiral metal-N,N′-dioxide catalysts,providing a facile and atom-economic route to enantioenriched polysubstituted furopyran derivatives with good results.Possible transition state models were proposed to explain the stereoinduction.

Regio-and enantioselective conjugate addition ofβ-nitroα,β-unsaturated carbonyls to construct 3-alkenyl disubstituted oxindoles

Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction of functionalized 3,3-disubstituted oxindoles,including terminal and internal vinyl groups in excellent yields and ee values.

Catalytic asymmetric synthesis of chiral azo compounds via interrupted Japp-Klingemann reaction with aryldiazonium salts

Asymmetric synthesis of enantioenriched azo compounds bearing tetrasubstituted stereocenter was achieved through chiral N,N′-dioxide/metal Lewis acid promoted interrupted Japp-Klingemann reaction of aryldiazonium tetrafluoroborate salts with nucleophiles under mild conditions. This protocol features wide substrate scope and good functional group compatibility.Azaarene-containing chiral azo compounds were stable enough in Japp-Klingemann reaction condition. The key to success of the reaction was the employment of metal salt/N,N′-dioxide ligand and the dual-task roles of the base. Moreover, the X-ray crystal structure of Ni(II)/N,N′-dioxide/substrate complex confirmed that the substrate was activated by bidentate coordination, which shed light on the origin of chiral control of the reaction.

Multisubstituted pyrazole synthesis via[3+2]cycloaddition/rearrangement/N-H insertion cascade reaction of α-diazoesters and ynones

The cascade reactions of alkyl α-diazoesters and ynones using Al(OTf)_(3) as the catalyst are described.A series of 4-substituted pyrazoles were obtained via [3+2] cycloaddition,1,5-ester shift,1,3-H shift,and N-H insertion process.Deuterium labelling experiments,kinetic studies and control experiments were carried out for the rationalization of the mechanism.

Chiral organobases: Properties and applications in asymmetric catalysis

Chiral organobases occupy a significant position in asymmetric organocatalysis. The general types of chiral organobases include tertiary amines, amidines, guanidines, cyclopropenimines, and iminophosphoranes, etc. These organobases are demonstrated to be effective organocatalysts to promote divers kinds of base-initiated reactions in excellent yields and stereoselectivities. In previous reports, several groups have summarized each kind of chiral organobases in different reviews. To the aim of understanding the whole of them in one review, herein, we provide a brief introduction of these chiral organobases in asymmetric catalysis.