Two distinctive rearranged 19-nor-7,8-seco-labdane diterpenoids(1 and 2)with a novel tetracyclo[5.2.1.0^(2,5.)0^(4,10)]decane skeleton,a derivative of the open tetrahydrofuran ring(7),three dimeric compounds(8-10),and...Two distinctive rearranged 19-nor-7,8-seco-labdane diterpenoids(1 and 2)with a novel tetracyclo[5.2.1.0^(2,5.)0^(4,10)]decane skeleton,a derivative of the open tetrahydrofuran ring(7),three dimeric compounds(8-10),and four revised homologs(3-6)were obtained from Chinese liverwort Pallavicinia ambigua.Their structures were identified via combined analysis of their spectroscopic data,single-crystal X-ray diffraction patterns,and ECD calculations.The light-driven conversion of compound 5 to compounds 1-4 demonstrated that photochemically induced postmodification involved in biosynthesis is an important way to diversify natural structures.A preliminary cytotoxicity assay revealed that compound 5 showed significant inhibition in the human prostate cancer(PC-3)cell line via an apoptotic pathway.展开更多
Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can prov...Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.展开更多
Ecosystems are becoming damaged or degraded as a result of stresses especially associated with human activities.A healthy ecosystem is essential to provide the services that humans and the natural environment require ...Ecosystems are becoming damaged or degraded as a result of stresses especially associated with human activities.A healthy ecosystem is essential to provide the services that humans and the natural environment require and has tremendous social and economic value.Exploration of the definition of ecosystem health includes what constitutes health and what it means to be healthy.To evaluate ecosystem health,it is necessary to quantify ecosystem conditions using a variety of indicators.In this paper,the main principles and criteria for indicator selection,classification of indicators for different kinds of ecosystems,the most appropriate indicators for measuring ecosystem sustainability,and various methods and models for the assessment of ecosystem health are presented.Drivers,sustainability,and resilience are considered to be critical factors for ecosystem health and its assessment.Effective integration of ecological understanding with socioeconomic,biophysical,biogeochemical,and public-policy dimensions is still the primary challenge in this field,and devising workable strategies to achieve and maintain ecosystem health is a key future challenge.展开更多
Urban areas are generally regarded as major sources of some semivolatile organic compounds and other persistent organic pollutants（POPs） to the surrounding regions. Huge differences in contaminant emissions between ...Urban areas are generally regarded as major sources of some semivolatile organic compounds and other persistent organic pollutants（POPs） to the surrounding regions. Huge differences in contaminant emissions between urban and rural areas directly affect their fate in environmental media. Little is known about POPs behavior between urban and rural areas at a regional scale. A spatially resolved Berkeley-Trent-Urban-Rural Fate Model（BETR-UR） was designed by coupling land cover information to simulate the transport of POPs between urban and rural areas, and the Bohai Rim was used as a case study to estimate Polycyclic Aromatic Hydrocarbon（PAH） fate. The processes of contaminant fate including emission, inter-compartmental transfer, advection and degradation in urban and rural areas were simulated in the model. Simulated PAH concentrations in environmental media of urban and rural areas were very close to measured values. The model accuracy was highly improved, with the average absolute relative error for PAH concentrations reduced from 37% to 3% compared with unimproved model results. PAH concentrations in urban soil and air were considerably higher than those in rural areas. Sensitivity analysis showed temperature was the most influential parameter for Phen rather than for Bap, whose fate was more influenced by emission rate, compartment dimension, transport velocity and chemical persistence. Uncertainty analysis indicated modeled results in urban media had higher uncertainty than those in rural areas due to larger variations of emissions in urban areas. The differences in urban and rural areas provided us with valuable guidance on policy setting for urban–rural POP control.展开更多
Metals discharged from industrial effluents,agricultural wastewater,and sewage runoff by rapid urbanization are of concern as contaminants of freshwater ecosystem because of their persistence and high toxicity to aqua...Metals discharged from industrial effluents,agricultural wastewater,and sewage runoff by rapid urbanization are of concern as contaminants of freshwater ecosystem because of their persistence and high toxicity to aquatic organisms.This study attempted to identify which metal posed the greatest risk to freshwater ecosystem in the Bohai Region,China.The metals arsenic(As),cadmium(Cd),chromium(Cr),copper(Cu),zinc(Zn),lead(Pb),nickel(Ni),mercury(Hg),iron(Fe),and manganese(Mn)were compared against norfloxacin and gamma-hexachlorocyclohexane(lindane).By comparing the median reported environmental and ecotoxicity concentrations,it showed that Cu,Fe,Zn,Mn,and Cr were the top five metals of concern.Of these,Cu was deemed to represent the highest risk and Hg the lowest risk.The risks for all metals were higher than those for norfloxacin and lindane.Almost all the metals except Hg had water concentrations that exceeded levels where ecotoxicity effects had been recorded in the literature.A comparison with the measurements across the UK rivers suggested that all metals examined had water concentrations about 5-to 10-fold higher than the UK median values except for Cu,Fe,Cd,and Pb.The Fuyang River,a tributary of the Haihe River Basin,seemed to be the location with the highest metal concentrations.However,comparing the post-2010 period to 2000-2009,concentrations of all the metals had fallen except for Fe and Mn,so risks have decreased over the last 7 yr with the greatest improvements for Cd and Pb.While metals still pose high risks to freshwater ecosystem in this region,there is encouragement that some control measures are taken into effect.展开更多
基金national financial support from the National Key R&D Program of China(No.2019YFA0905700)the National Natural Science Foundation of China(Nos.82173703 and 81874293)the Major Basic Research Program of Shandong Provincial Natural Science Foundation(No.ZR2019ZD26)。
文摘Two distinctive rearranged 19-nor-7,8-seco-labdane diterpenoids(1 and 2)with a novel tetracyclo[5.2.1.0^(2,5.)0^(4,10)]decane skeleton,a derivative of the open tetrahydrofuran ring(7),three dimeric compounds(8-10),and four revised homologs(3-6)were obtained from Chinese liverwort Pallavicinia ambigua.Their structures were identified via combined analysis of their spectroscopic data,single-crystal X-ray diffraction patterns,and ECD calculations.The light-driven conversion of compound 5 to compounds 1-4 demonstrated that photochemically induced postmodification involved in biosynthesis is an important way to diversify natural structures.A preliminary cytotoxicity assay revealed that compound 5 showed significant inhibition in the human prostate cancer(PC-3)cell line via an apoptotic pathway.
基金supported by the National Natural Sci-ence Foundation of China(No.22174135,No.21790352)the National Key R&D Program of China(No.2021YFA1500500,No.2016YFA0200600)+4 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Anhui Initiative in Quantum Information Technologies(No.AHY090100)CAS Project for Young Scientists in Basic Research(No.YSBR-054)Innovation Program for Quantum Science and Technology(No.2021ZD0303301)the Fundamental Research Funds for the Central Universities.
文摘Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.
基金This work was supported by the National Natural Science Foundation of China(41371488,41420104004)the International Scientific Cooperation Program with Grant No.2012DFA91150)the Key Research Program of the Chinese Academy of Sciences(No.KZZD-EW-TZ-12).
文摘Ecosystems are becoming damaged or degraded as a result of stresses especially associated with human activities.A healthy ecosystem is essential to provide the services that humans and the natural environment require and has tremendous social and economic value.Exploration of the definition of ecosystem health includes what constitutes health and what it means to be healthy.To evaluate ecosystem health,it is necessary to quantify ecosystem conditions using a variety of indicators.In this paper,the main principles and criteria for indicator selection,classification of indicators for different kinds of ecosystems,the most appropriate indicators for measuring ecosystem sustainability,and various methods and models for the assessment of ecosystem health are presented.Drivers,sustainability,and resilience are considered to be critical factors for ecosystem health and its assessment.Effective integration of ecological understanding with socioeconomic,biophysical,biogeochemical,and public-policy dimensions is still the primary challenge in this field,and devising workable strategies to achieve and maintain ecosystem health is a key future challenge.
基金supported by the International Scientific Cooperation Program (No. 2012DFA91150)the Chinese Academy of Sciences (No. KZZD-EW-TZ-12)the National Natural Science Foundation of China under Grants (Nos. 414201040045, 41501539)
文摘Urban areas are generally regarded as major sources of some semivolatile organic compounds and other persistent organic pollutants（POPs） to the surrounding regions. Huge differences in contaminant emissions between urban and rural areas directly affect their fate in environmental media. Little is known about POPs behavior between urban and rural areas at a regional scale. A spatially resolved Berkeley-Trent-Urban-Rural Fate Model（BETR-UR） was designed by coupling land cover information to simulate the transport of POPs between urban and rural areas, and the Bohai Rim was used as a case study to estimate Polycyclic Aromatic Hydrocarbon（PAH） fate. The processes of contaminant fate including emission, inter-compartmental transfer, advection and degradation in urban and rural areas were simulated in the model. Simulated PAH concentrations in environmental media of urban and rural areas were very close to measured values. The model accuracy was highly improved, with the average absolute relative error for PAH concentrations reduced from 37% to 3% compared with unimproved model results. PAH concentrations in urban soil and air were considerably higher than those in rural areas. Sensitivity analysis showed temperature was the most influential parameter for Phen rather than for Bap, whose fate was more influenced by emission rate, compartment dimension, transport velocity and chemical persistence. Uncertainty analysis indicated modeled results in urban media had higher uncertainty than those in rural areas due to larger variations of emissions in urban areas. The differences in urban and rural areas provided us with valuable guidance on policy setting for urban–rural POP control.
基金This study was supported by the National Natural Science Foundation of China under grant nos.41371488 and 414201040045the International Scientific Cooperation Program with grant no.2012DFA91150+1 种基金the Key Project of the Chinese Academy of Sciences under grant no.KZZD-EW-TZ-12The UK authors are grateful to the NERC Newton Fund NEC05951 for support.
文摘Metals discharged from industrial effluents,agricultural wastewater,and sewage runoff by rapid urbanization are of concern as contaminants of freshwater ecosystem because of their persistence and high toxicity to aquatic organisms.This study attempted to identify which metal posed the greatest risk to freshwater ecosystem in the Bohai Region,China.The metals arsenic(As),cadmium(Cd),chromium(Cr),copper(Cu),zinc(Zn),lead(Pb),nickel(Ni),mercury(Hg),iron(Fe),and manganese(Mn)were compared against norfloxacin and gamma-hexachlorocyclohexane(lindane).By comparing the median reported environmental and ecotoxicity concentrations,it showed that Cu,Fe,Zn,Mn,and Cr were the top five metals of concern.Of these,Cu was deemed to represent the highest risk and Hg the lowest risk.The risks for all metals were higher than those for norfloxacin and lindane.Almost all the metals except Hg had water concentrations that exceeded levels where ecotoxicity effects had been recorded in the literature.A comparison with the measurements across the UK rivers suggested that all metals examined had water concentrations about 5-to 10-fold higher than the UK median values except for Cu,Fe,Cd,and Pb.The Fuyang River,a tributary of the Haihe River Basin,seemed to be the location with the highest metal concentrations.However,comparing the post-2010 period to 2000-2009,concentrations of all the metals had fallen except for Fe and Mn,so risks have decreased over the last 7 yr with the greatest improvements for Cd and Pb.While metals still pose high risks to freshwater ecosystem in this region,there is encouragement that some control measures are taken into effect.
