Over the past century, transition metal-catalyzed crosscoupling reactions have evolved to be among the most used C-C bond forming reactions in chemical synthesis. An important remaining challenge is to synthesis with ...Over the past century, transition metal-catalyzed crosscoupling reactions have evolved to be among the most used C-C bond forming reactions in chemical synthesis. An important remaining challenge is to synthesis with heightened levels of efficiency by new method. A powerful new class of reactions that introduce oxidized functionality directly into sp3 C-H bonds of hydrocarbons is emerging [1, 2]. Despite important advances in the aliphatic C-H bond activations, selective functionalization with complex substrates has only been demonstrated for activated C-H bonds such as location adjacent to a heteroatom or substrate with directing groups [3]. High-efficient oxidations of isolated, unactivated sp3 C-H bonds are rare. The challenge to solve this problem lies in discovering new methodology that is both highly efficient and predictably selective for oxidizing these inert C-H bonds.展开更多
Introduction:Payment for watershed ecosystem services(PWES),a policy instrument for compensating for the externality of watershed ecosystem/environmental services,has gained in policy importance in China over the past...Introduction:Payment for watershed ecosystem services(PWES),a policy instrument for compensating for the externality of watershed ecosystem/environmental services,has gained in policy importance in China over the past two decades.Many scholars and researchers have contributed to the conceptualization of this policy framework by developing operational mechanisms as well as compensation standards for PWES.Outcomes:This article reviews 27 PWES schemes piloted in China and in 10 other countries,with a particular emphasis on successful cases of land-use conversion programs,such as the Paddy Land to Dry Land Program and Sloping Land Conversion Program that have been implemented in China.Discussion:By comparing different cases,the authors attempt to answer the following questions:what were the ecological and institutional contexts in which these schemes were established and how did they work?What were the actual efficiencies and impacts of these piloted schemes?Which scheme worked better in certain ecological,socio-economic,and institutional contexts?Conclusion:Based on case studies,the authors draw the following conclusions about Chinese PWES:(1)to establish an acceptable standard for a PWES program,it is necessary to estimate the economic and social costs regarding the livelihoods of households;(2)multistakeholder negotiation mechanism for PWES,including intermediaries,such as the local government,NGO/NPOs,village committees,and user associations,should be used;(3)ES,non-market services,should acquire positive externalities to accomplish an optimal win–win pattern concerning both environmental goals and the livelihoods of local resource users.展开更多
Digital cartoon production requires extensive manual labor to colorize sketches with visually pleasant color composition and color shading.During colorization,the artist usually takes an existing cartoon image as colo...Digital cartoon production requires extensive manual labor to colorize sketches with visually pleasant color composition and color shading.During colorization,the artist usually takes an existing cartoon image as color guidance,particularly when colorizing related characters or an animation sequence.Reference-guided colorization is more intuitive than colorization with other hints,such as color points or scribbles,or text-based hints.Unfortunately,reference-guided colorization is challenging since the style of the colorized image should match the style of the reference image in terms of both global color composition and local color shading.In this paper,we propose a novel learning-based framework which colorizes a sketch based on a color style feature extracted from a reference color image.Our framework contains a color style extractor to extract the color feature from a color image,a colorization network to generate multi-scale output images by combining a sketch and a color feature,and a multi-scale discriminator to improve the reality of the output image.Extensive qualitative and quantitative evaluations show that our method outperforms existing methods,providing both superior visual quality and style reference consistency in the task of reference-based colorization.展开更多
The accurate quantification and source partitioning of CO_(2)emitted from carbonate(i.e.,Haplustalf)and non-carbonate(i.e.,Hapludult)soils are critically important for understanding terrestrial carbon(C)cycling.The tw...The accurate quantification and source partitioning of CO_(2)emitted from carbonate(i.e.,Haplustalf)and non-carbonate(i.e.,Hapludult)soils are critically important for understanding terrestrial carbon(C)cycling.The two main methods to capture CO_(2)released from soils are the alkali trap method and the direct gas sampling method.A 25-d laboratory incubation experiment was conducted to compare the efficacies of these two methods to analyze CO_(2)emissions from the non-carbonate and carbonate-rich soils.An isotopic fraction was introduced into the calculations to determine the impacts on partitioning of the sources of CO_(2)into soil organic carbon(SOC)and soil inorganic carbon(SIC)and into C3 and/or C4 plant-derived SOC.The results indicated that CO_(2)emissions from the non-carbonate soil measured using the alkali trap and gas sampling methods were not significantly different.For the carbonate-rich soil,the CO_(2)emission measured using the alkali trap method was significantly higher than that measured using the gas sampling method from the 14 th day of incubation onwards.Although SOC and SIC each accounted for about 50%of total soil C in the carbonate-rich soil,SOC decomposition contributed 57%–72%of the total CO_(2)emitted.For both non-carbonate and carbonate-rich soils,the SOC derived from C4 plants decomposed faster than that originated from C3 plants.We propose that for carbonate soil,CO_(2)emission may be overestimated using the alkali trap method because of decreasing CO_(2)pressure within the incubation jar,but underestimated using the direct gas sampling method.The gas sampling interval and ambient air may be important sources of error,and steps should be taken to mitigate errors related to these factors in soil incubation and CO_(2)quantification studies.展开更多
基金supported by Natural Science Foundation of Fujian Province(2013J05035)
文摘Over the past century, transition metal-catalyzed crosscoupling reactions have evolved to be among the most used C-C bond forming reactions in chemical synthesis. An important remaining challenge is to synthesis with heightened levels of efficiency by new method. A powerful new class of reactions that introduce oxidized functionality directly into sp3 C-H bonds of hydrocarbons is emerging [1, 2]. Despite important advances in the aliphatic C-H bond activations, selective functionalization with complex substrates has only been demonstrated for activated C-H bonds such as location adjacent to a heteroatom or substrate with directing groups [3]. High-efficient oxidations of isolated, unactivated sp3 C-H bonds are rare. The challenge to solve this problem lies in discovering new methodology that is both highly efficient and predictably selective for oxidizing these inert C-H bonds.
基金National Natural Science Foundation of China(No:5157421521436010+3 种基金21646011U1662122)Key Research and Development Program of Shanxi Province in China(No:201603D312003)Beijing Hundreds of Leading Talents Training Project of Science and Technology(No:Z171100001117154)
基金This work was financially supported by the Program of“The strategic research for water safety and ecological compensation program in the Jing-Jin-Ji region of China”[No.2015TC035]the Fundamental Research Funds of the National Basic Research Program of China’University.
文摘Introduction:Payment for watershed ecosystem services(PWES),a policy instrument for compensating for the externality of watershed ecosystem/environmental services,has gained in policy importance in China over the past two decades.Many scholars and researchers have contributed to the conceptualization of this policy framework by developing operational mechanisms as well as compensation standards for PWES.Outcomes:This article reviews 27 PWES schemes piloted in China and in 10 other countries,with a particular emphasis on successful cases of land-use conversion programs,such as the Paddy Land to Dry Land Program and Sloping Land Conversion Program that have been implemented in China.Discussion:By comparing different cases,the authors attempt to answer the following questions:what were the ecological and institutional contexts in which these schemes were established and how did they work?What were the actual efficiencies and impacts of these piloted schemes?Which scheme worked better in certain ecological,socio-economic,and institutional contexts?Conclusion:Based on case studies,the authors draw the following conclusions about Chinese PWES:(1)to establish an acceptable standard for a PWES program,it is necessary to estimate the economic and social costs regarding the livelihoods of households;(2)multistakeholder negotiation mechanism for PWES,including intermediaries,such as the local government,NGO/NPOs,village committees,and user associations,should be used;(3)ES,non-market services,should acquire positive externalities to accomplish an optimal win–win pattern concerning both environmental goals and the livelihoods of local resource users.
基金supported in part by a CIHE Institutional Development Grant No.IDG200107the National Natural Science Foundation of China under Grant No.61973221the Natural Science Foundation of Guangdong Province of China under Grant Nos.2018A030313381 and 2019A1515011165.
文摘Digital cartoon production requires extensive manual labor to colorize sketches with visually pleasant color composition and color shading.During colorization,the artist usually takes an existing cartoon image as color guidance,particularly when colorizing related characters or an animation sequence.Reference-guided colorization is more intuitive than colorization with other hints,such as color points or scribbles,or text-based hints.Unfortunately,reference-guided colorization is challenging since the style of the colorized image should match the style of the reference image in terms of both global color composition and local color shading.In this paper,we propose a novel learning-based framework which colorizes a sketch based on a color style feature extracted from a reference color image.Our framework contains a color style extractor to extract the color feature from a color image,a colorization network to generate multi-scale output images by combining a sketch and a color feature,and a multi-scale discriminator to improve the reality of the output image.Extensive qualitative and quantitative evaluations show that our method outperforms existing methods,providing both superior visual quality and style reference consistency in the task of reference-based colorization.
基金supported by the National Key Research and Development Program of China(No.2016YFD0201200)the National Natural Science Foundation of China(Nos.31370527,31261140367,and 30870414)the Chinese Scholarship Council(No.201706350210)for the support of the work。
文摘The accurate quantification and source partitioning of CO_(2)emitted from carbonate(i.e.,Haplustalf)and non-carbonate(i.e.,Hapludult)soils are critically important for understanding terrestrial carbon(C)cycling.The two main methods to capture CO_(2)released from soils are the alkali trap method and the direct gas sampling method.A 25-d laboratory incubation experiment was conducted to compare the efficacies of these two methods to analyze CO_(2)emissions from the non-carbonate and carbonate-rich soils.An isotopic fraction was introduced into the calculations to determine the impacts on partitioning of the sources of CO_(2)into soil organic carbon(SOC)and soil inorganic carbon(SIC)and into C3 and/or C4 plant-derived SOC.The results indicated that CO_(2)emissions from the non-carbonate soil measured using the alkali trap and gas sampling methods were not significantly different.For the carbonate-rich soil,the CO_(2)emission measured using the alkali trap method was significantly higher than that measured using the gas sampling method from the 14 th day of incubation onwards.Although SOC and SIC each accounted for about 50%of total soil C in the carbonate-rich soil,SOC decomposition contributed 57%–72%of the total CO_(2)emitted.For both non-carbonate and carbonate-rich soils,the SOC derived from C4 plants decomposed faster than that originated from C3 plants.We propose that for carbonate soil,CO_(2)emission may be overestimated using the alkali trap method because of decreasing CO_(2)pressure within the incubation jar,but underestimated using the direct gas sampling method.The gas sampling interval and ambient air may be important sources of error,and steps should be taken to mitigate errors related to these factors in soil incubation and CO_(2)quantification studies.
