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First Enantioselective Synthesis of Daphneticin

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Chinese Chemical Letters 2003年第6期14卷 551-554页

作者： xin feng ren Kun PENG Xiao Chuan CHEN xin Gang XIE Ya Mu XIA xin Fu PAN Department of Chemistry National Laboratory of Applied Organic ChemistryLanzhou UniversityLanzhou 730000

An enantioselective total synthesis of chiral daphneticin is reported firstly.

关键词： Synthesis enantioselective coumarinolignoids daphneticin.

High summer background O_(3)levels in the desert of northwest China

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Journal of Environmental Sciences 2025年第5期151卷 516-528页

作者： xinbing ren Fang Wang Bayi Wu Shaoting Zhang Lei Zhang xingjun Zhou Yuanzhe ren Yongjing Ma feng Hao Yongli Tian Jinyuan xin Key Laboratory of Atmospheric Environment and Extreme Meteorology Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry(LAPC) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Inner Mongolia Environmental Monitoring Center Alashan Substation 750300China Inner Mongolia Environmental Monitoring Center Hohhot 010011China Laboratory for Supervision and Evaluation of Pollution Reduction and Carbon Reduction in Arid and Semi-Arid Regions Inner Mongolia Environmental Monitoring CenterHohhot 010011China

Generally speaking,the precursors of ozone(O_(3)),nitrogen oxides and volatile organic compounds are very low in desert areas due to the lack of anthropogenic emissions and natural emissions,and thus O_(3)concentrations are relatively ***,high summer background concentrations of about 100μg/m^(3)or 60 ppb were found in the Alxa Desert in the highland of northwest China based on continuous summer observations from 2019 to 2021,which was higher than the most of natural background areas or clean areas in world for summer O_(3)background *** high O_(3)background concentrations were related to surface features and ***-intensity anthropogenic activity areas in desert areas can cause increased O_(3)concentrations or pollution,but also generated O_(3)depleting substances such as nitrous oxide,which eventually reduced the regional O_(3)baseline *** dioxide(NO2)also had a dual effect on O_(3)generation,showing promotion at low concentrations and inhibition at high *** addition,sand-dust weather reduced O_(3)clearly,but O_(3)eventually stabilized around the background concentration values and did not vary with sand-dust particulate matter.

关键词： Alxa Desert O_(3)background concentration Anthropogenic effect Sand-dust weather Northwest China

A Multi-faceted View of the X-Ray Spectral Variability in Seyfert Galaxy Ark 120

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Research in Astronomy and Astrophysics 2025年第1期25卷 228-239页

作者： Lu-xin ren Jun-Xian Wang Jia-Lai Kang CAS Key Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of China School of Astronomy and Space Science University of Science and Technology of China

Utilizing a range of techniques including multi-band light curves,softness ratio analysis,structure functions,rms spectra,cross-correlation functions,and ratios of spectra from different intervals,we present a comprehensive study of the complex X-ray spectral variability in Seyfert 1 galaxy Ark 120,through re-analyzing its six XMM-Newton observations taken between 2003 and *** find a clear“softer-when-brighter”trend in the 2–10 ke V power-law component over long timescales,with this trend being timescale dependent,as it is much weaker on shorter timescales,similar to that previously detected in NGC ***,a rare“harder-when-brighter”trend is observed during one exposure,indicating dynamic changes in the spectral variability behavior of the power-law *** exceptional exposure,with the spectral variability indeed marked by a power-law pivoting at an unusually low energy of～2 ke V,suggests intricate variations in the thermal Comptonization processes within the ***,when the data below 2 ke V are included,we identify that the soft excess component adds significant complexity to the spectral variability,such as evidenced by a transition from“harder-when-brighter”to“softer-when-brighter”during another single *** extra complexity arises because the variability of the soft excess sometimes follows and sometimes does not follow the changes in the power-law *** findings underscore the necessity of applying multiple analytic techniques to fully capture the multifaceted spectral variability of AGNs.

关键词： galaxies: active galaxies: Seyfert X-rays: galaxies

Spatiotemporal variations of tenebrionid beetles(Coleoptera:Tenebrionidae)in the Gobi desert,Northwest China

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Journal of Arid Land 2025年第1期17卷 112-129页

作者： ren Jialong ZHAO Wenzhi HE Zhibin WANG Yongzhen feng Yilin NIU Yiping xin Weidong PAN Chengchen LIU Jiliang College of Geographic Sciences Shanxi Normal UniversityTaiyuan 030031China Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands Linze Inland River Basin Research StationNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Chengdu Institute of Biology Chinese Academy of SciencesChengdu 610213China Plant Protection Institute Hebei Academy of Agriculture and Forestry SciencesBaoding 071002China

Tenebrionid beetles represent a crucial arthropod taxon in the Gobi desert ecosystems owing to their species richness and high biomass,both of which are essential for maintaining ecosystem health and ***,the spatiotemporal variations of tenebrionid beetle assemblages in the Gobi desert remain poorly *** this study,the monthly dynamics of tenebrionid beetles in the central part of the Hexi Corridor,Northwest China,a representative area of the Gobi desert ecosystems,were monitored using pitfall trapping during *** following results were showed:(1)monthly activity of tenebrionid beetles was observed from March to October,with monthly activity peaking in spring and summer,and monthly activity periods and peak of tenebrionid beetle species exhibited interspecific differences that varied from year to year;(2)spatial distribution of tenebrionid beetle community was influenced by structural ***,at a spatial scale of 24.00 m,tenebrionid beetle community was strongly and positively correlated with the dominant species,with distinct spatial distribution patterns observed for Blaps gobiensis and Microdera kraatzi alashanica;(3)abundance of tenebrionid beetles was positively correlated with monthly mean precipitation and monthly mean temperature,whereas monthly abundance of *** and *** alashanica was positively correlated with monthly mean precipitation;and(4)the cover of Reaumuria soongarica(Pall.)*** Nitraria sphaerocarpa *** a positive influence on the number of tenebrionid beetles *** conclusion,monthly variation in precipitation significantly influences the community dynamic of tenebrionid beetles,with precipitation and shrub cover jointly determining the spatial distribution pattern of these beetles in the Gobi desert ecosystems.

关键词： Gobi desert precipitation change tenebrionid beetles temporal dynamics spatial pattern

Carbody sway behaviour of railway vehicles due to track irregularity from rail alternate side wear

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Railway Engineering Science 2025年第1期33卷 27-42页

作者： Lai Wei Jing Zeng ren Luo feng Gan Jijun Gong Jun Jiang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China China Railway Materials Operation and Maintenance Technology Co.Ltd. Beijing 100071China

Track irregularity from rail alternate side wear is manifested as uneven rail wear waveforms alternating in the left and right rails with equal intervals,which will cause carbody sway behaviour of railway vehicles and greatly influences the passenger *** this work,the carbody sway behaviour and mechanism due to track irregularity from rail alternate side wear and possible solutions to this issue were studied by the field testing and numerical calculation ***,the carbody sway of an urban rail transit train is introduced with full-scale field tests,through which the rail alternate side wear is characterized and the formatted track irregularity are ***,multibody vehicle dynamic models are developed to reproduce the carbody sway behaviour induced by the track irregularity from the rail alternate side *** creep forces acting on the wheel and rail are preliminarily discussed to study the influence of the carbody sway on the wear of the wheel flange and the rail ***,some potential solutions,*** the damping ratio of carbody rigid mode and rail grinding,are proposed to relieve this *** is concluded that an increased damping ratio of the carbody mode can alleviate the carbody sway and wheel–rail interactions,while properly maintaining track conditions can improve the vehicle performance.

关键词： Carbody sway Track irregularity Rail wear Creep force Carbody mode

Effect of Cu/HZSM-5 sorbents with different Si/Al ratios on the adsorption and oxidation performance of H_(2)S

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Journal of Environmental Sciences 2025年第5期151卷 161-173页

作者： Kaini Ma Kai Li Ping Ning Jiayu feng Jiacheng Bao Lei Shi Xiangyu Wang xin Sun Faculty of Environmental Science and Engineering Kunming University of Science and TechnologyKunming 650500China National-Regional Engineering Center for Recovery of Waste Gases from Metallurgical and Chemical Industries Kunming University of Science and TechnologyKunming 650500China

This study employed a wet impregnation method to synthesize five types of Cu/HZSM-5 adsorbents with Si/Al ratios of 25,50,85,200,and 300,used for the removal of H_(2)S in lowtemperature,low-oxygen *** impact of different Si/Al ratios on the adsorption oxidative performance of Cu_(30)/HZSM-5–85 adsorbents was *** to the performance test results,Cu_(30)/HZSM-5–85 exhibited the highest breakthrough capacity,reaching 231.75 mg H_(2)S/g_(sorbent).Cu/HZSM-5 sorbent maintains a strong ability to remove H_(2)S even under humid conditions and shows excellent water ***,BET,and XPS results revealed that CuO is the primary active species,with Cu_(30)/HZSM-5–85 having the largest surface area and highest CuO content,providing more active sites for H_(2)S adsorption.H_(2)-TPR and O_(2)-TPD results confirmed that Cu_(30)/HZSM-5–85 sorbent exhibits outstanding redox properties and oxygen storage capacity,contributing to excellent oxygen transferability in the molecular sieve adsorption-oxidation *** notable characteristics such as a large surface area,high desulfurization efficiency,and water resistance,Cu_(30)/HZSM-5–85 sorbents hold significant importance for industrial applications.

关键词： H_(2)S Si/Al ratio Adoration-oxidation Cu/HZSM-5-85(HZSM-5 with Si/Al ratio of 85 loaded Cu)

Distribution and mapping of temperate savanna in the sandy lands of eastern China

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Science China Earth Sciences 2025年第1期68卷 128-141页

作者： Xiaoya LI feng WANG Tao DUAN Kaijie YANG Bin YANG Chunmei WANG xin TIAN Qi LU Institute of Ecological Conservation and Restoration Institute of Desertification StudiesChinese Academy of ForestryBeijing100091China Institute of Desertification Institute of Desertification StudiesChinese Academy of ForestryBeijing100091China Institute of Great Green Wall Bayan Nur015200China Satellite Application Centre for Ecology and Environment MEEBeijing100094China Institute of Microelectronics Chinese Academy of SciencesBeijing100029China Aerospace Information Research Institute Chinese Academy of SciencesBeijing100094China Institute of Forest Resource Information Techniques Chinese Academy of ForestryBeijing100091China

Savannas are distributed globally across various *** perform a significant socioeconomic role in regulating net primary productivity and the terrestrial carbon *** to the high spatial heterogeneity induced by the mixed distribution of trees and grasses,current global land-cover classification maps often classify savannas as forests or grasslands Temperate savannas in China cover a vast area,yet their spatial patterns and extent remain poorly *** study developed a novel remote sensing temperate savannas mapping method by integrating very high-resolution(VHR)unmanned aerial vehicle(UAV)and GF-6 satellite imagery based on the vegetation structure characteristics of temperate savannas using the FAO definition of *** and validation datasets were collected from VHR UAV imagery covering the main temperate savannah types with a ground area of 1818 *** fractional woody vegetation cover(FWVC)and fractional herbaceous vegetation cover(FHVC)in temperate savannas were estimated by integrating Classification and Regression Tree and Random Forest *** current distribution of temperate savannas in the Horqin and Otindag Sandy Lands of Eastern China was mapped to a unit area of 0.5 *** root-mean-square error(RMSE)values for the FWVC and FHVC models were 10.69%and 11.67%,and the R^(2)values were 0.66 and 0.63,*** assessment indicated that the new temperate savanna map had high identification accuracy,with a Kappa coefficient of 0.70,overall accuracy of 0.88,and average accuracy of *** savannas in the sandy lands of eastern China were primarily distributed in the northern Horqin Sandy Land the central and eastern regions of the Otindag Sandy Land,and the transition zone from the southern slopes of the Greater Khingan Mountains to the plains,covering a total area of 3.27×10^(6)*** main savannah types were elm,oak/maple,and shrub *** savannas were widely distributed in the Otindag Sandy Land a

关键词： Temperate savanna UAV imagery GF-6 Fractional woody vegetation cover Fractional herbaceous vegetation cover Machine learning

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Effect of graphene addition on activation and kinetic properties of La-Mg-Ni-based hydrogen storage alloys

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Journal of Iron and Steel Research International 2025年第1期32卷 227-238页

作者： Dian-chen feng Chun-ling Zheng Zhi-yuan Zhao Dong-sheng Zhou Hui-ping ren Yang-huan Zhang School of Materials and Metallurgy Inner Mongolia University of Science and TechnologyBaotou014010Inner MongoliaChina Collaborative Innovation Center of Integrated Exploitation of Bayan Obo Multi-Metal Resources Inner Mongolia University of Science and TechnologyBaotou014010Inner MongoliaChina Department of Functional Material Research China Iron and Steel Research Institute GroupBeijing100081China

The La_(1.7)Pr_(0.3)Mg_(16)Ni hydrogen storage alloy was prepared by medium-frequency induction melting,and then the composite hydrogen storage alloy powder of La_(1.7)Pr_(0.3)Mg_(16)Ni+x wt.%(x=0,2,4,and 6)graphene was prepared by ball milling for 10 *** effect of the addition of graphene on the activation and hydrogen de/absorption properties of La_(1.7)Pr_(0.3)Mg_(16)Ni alloy was *** result demonstrated that these composite alloys were composed of La_(2)Mg_(17),La_(2)Ni_(3),and Mg_(2)Ni *** saturated hydrogen absorption,it was composed of LaH_(3),Mg_(2)NiH_(4),and MgH_(2)phases,while during the dehydrogenation process,it was composed of LaH_(3),Mg,and Mg_(2)Ni *** addition of graphene can help get a more homogeneous granule after ball milling and accelerate the first activation of dehydrogenation/hydrogen *** hydrogen release activation energy of the alloys first decreases and then increases as the graphene content increases from x=0 wt.%to x=6 wt.%.The minimum activation energy of the composite hydrogen storage alloy is 51.22 kJ mol^(-1) when x=4 wt.%.

关键词： La-Mg-Ni alloy Graphene Mechanical ball milling Activation property Dynamic performance

Metal-organic frameworks with dinuclear metal centers for synergistically boosting CO_(2) photoreduction

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Science China Chemistry 2025年第1期68卷 201-208页

作者： Hui-feng Wang Wen-Jie Shi Yu-xin Yang Bao-Xia Dong Tong-Bu Lu Di-Chang Zhong School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225002China Institute for New Energy Materials and Low Carbon Technologies School of Materials Science and EngineeringTianjin University of TechnologyTianjin 300384China

Dinuclear metal synergistic catalysis(DMSC)has been proved powerful in boosting CO_(2)reduction,while this has not been achieved in heterogeneous catalysts with long-range order *** this study,we,by introduction of metal catalytic centers into an indium-based metal-organic framework(MOF),obtained a series of isostructural In-MOFs,including three MOFs with mononuclear metal catalytic center(M-In),three MOFs with dinuclear homometallic catalytic centers(MM-In),and three MOFs with dinuclear heterometallic catalytic centers(MM’-In,M/M’=Co(II),Ni(II),Zn(II)).It was found that all these MOFs can serve as catalysts for photochemical CO_(2)reduction to *** with M-In,the catalytic activities of MM-In were obviously enhanced,and that of MM’-In was further significantly *** example,the CO yield of Co Zn-In reaches a record value of 12,700μmol g^(-1)h^(-1),which is 4.0,8.1,9.4,and 18.6-fold higher than that of Co Co-In,Zn Zn-In,Co-In,and Zn-In,***,the catalytic activities of Co Ni-In and Ni Zn-In also show different fold increase than those of corresponding dinuclear homometallic and mononuclear metallic *** results of control experiments and theoretical calculation reveal that the higher catalytic activities of MM-In over M-In can be ascribed to the DMSC effect,and the higher catalytic activity of MM’-In over MM-In can be ascribed to the strengthened DMSC *** work reveals the relationship between DMSC effect and bimetal centers in CO_(2)reduction,which provides new insights into the DMSC and paves a new way to design highly active catalysts for photochemical CO_(2)reduction.

关键词： metal-organic frameworks dinuclear metal centers synergistic catalysis CO_(2)reduction photocatalysis