As the main form of new urbanization in China,urban agglomerations are an important platform to support national economic growth,promote coordinated regional development,and participate in international competition an...As the main form of new urbanization in China,urban agglomerations are an important platform to support national economic growth,promote coordinated regional development,and participate in international competition and cooperation.However,they have become core areas for air pollution.This study used PM_(2.5)data from NASA atmospheric remote sensing image inversion from 2000 to 2015 and spatial analysis including a spatial Durbin model to reveal the spatio-temporal evolution characteristics and main factors controlling PM_(2.5)in China's urban agglomerations.The main conclusions are as follows:(1)From 2000 to 2015,the PM_(2.5)concentrations of China's urban agglomerations showed a growing trend with some volatility.In 2007,there was an inflection point.The number of low-concentration cities decreased,while the number of high-concentration cities increased.(2)The concentrations of PM_(2.5)in urban agglomerations were high in the west and low in the east,with the"Hu Line"as the boundary.The spatial differences were significant and increasing.The concentration of PM_(2.5)grew faster in urban agglomerations in the eastern and northeastern regions.(3)The urban agglomeration of PM_(2.5)had significant spatial concentrations.The hot spots were concentrated to the east of the Hu Line,and the number of hot-spot cities continued to rise.The cold spots were concentrated to the west of the Hu Line,and the number of cold-spot cities continued to decline.(4)There was a significant spatial spillover effect of PM_(2.5)pollution among cities within urban agglomerations.The main factors controlling PM_(2.5)pollution in different urban agglomerations had significant differences.Industrialization and energy consumption had a significant positive impact on PM_(2.5)pollution.Foreign direct investment had a significant negative impact on PM_(2.5)pollution in the southeast coastal and border urban agglomerations.Population density had a significant positive impact on PM_(2.5)pollution in a particular region,but this had the opposite effect in neighboring areas.Urbanization rate had a negative impact on PM_(2.5)pollution in national-level urban agglomerations,but this had the opposite effect in regional and local urban agglomerations.A high degree of industrial structure had a significant negative impact on PM_(2.5)pollution in a region,but this had an opposite effect in neighboring regions.Technical support level had a significant impact on PM_(2.5)pollution,but there were lag effects and rebound effects.展开更多
A mutagenesis library was constructed using GPS-LS system to insert a random 5 aa into the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) encoded by aroA gene. Active EPSPS pro- teins were identified by the abili...A mutagenesis library was constructed using GPS-LS system to insert a random 5 aa into the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) encoded by aroA gene. Active EPSPS pro- teins were identified by the ability to rescue growth of aroA-deleted mutant ER2799 on M9 minimal media. 12 unique sites, which can tolerate a 5-aa insertion, were identified. In all of the 12 sites, only F295/T296 site was found to split the G2-EPSPS properly by co-transformation of plasmids into E. coli ER2799. The G2-EPSPS gene was then divided into N-termi- nal and C-terminal from F295/T296 site which were fused to the N-terminal and C-terminal of Ssp.DnaE intein, respectively, creating two plasmids pMEPS- N295IN and pKEPSc296Ic. Co-transformation of plasmids, pMEPSN295IN and pKEPSc296Ic, rescu- ed growth of ER2799 in M9 minimal media, indicating that the intein splicing domains were bringing the EPSPS fragments together to generate activity. Re- consituted activity of splitted G2-EPSPS enzyme was 4.48 U/mg.展开更多
基金National Natural Science Foundation of China,No.41771181National Key Research and Development Plan,No.2017YFC0505702Open Fund Project of New Urbanization Research Institute of Tsinghua University,No.TUCSU-K-17015-01。
文摘As the main form of new urbanization in China,urban agglomerations are an important platform to support national economic growth,promote coordinated regional development,and participate in international competition and cooperation.However,they have become core areas for air pollution.This study used PM_(2.5)data from NASA atmospheric remote sensing image inversion from 2000 to 2015 and spatial analysis including a spatial Durbin model to reveal the spatio-temporal evolution characteristics and main factors controlling PM_(2.5)in China's urban agglomerations.The main conclusions are as follows:(1)From 2000 to 2015,the PM_(2.5)concentrations of China's urban agglomerations showed a growing trend with some volatility.In 2007,there was an inflection point.The number of low-concentration cities decreased,while the number of high-concentration cities increased.(2)The concentrations of PM_(2.5)in urban agglomerations were high in the west and low in the east,with the"Hu Line"as the boundary.The spatial differences were significant and increasing.The concentration of PM_(2.5)grew faster in urban agglomerations in the eastern and northeastern regions.(3)The urban agglomeration of PM_(2.5)had significant spatial concentrations.The hot spots were concentrated to the east of the Hu Line,and the number of hot-spot cities continued to rise.The cold spots were concentrated to the west of the Hu Line,and the number of cold-spot cities continued to decline.(4)There was a significant spatial spillover effect of PM_(2.5)pollution among cities within urban agglomerations.The main factors controlling PM_(2.5)pollution in different urban agglomerations had significant differences.Industrialization and energy consumption had a significant positive impact on PM_(2.5)pollution.Foreign direct investment had a significant negative impact on PM_(2.5)pollution in the southeast coastal and border urban agglomerations.Population density had a significant positive impact on PM_(2.5)pollution in a particular region,but this had the opposite effect in neighboring areas.Urbanization rate had a negative impact on PM_(2.5)pollution in national-level urban agglomerations,but this had the opposite effect in regional and local urban agglomerations.A high degree of industrial structure had a significant negative impact on PM_(2.5)pollution in a region,but this had an opposite effect in neighboring regions.Technical support level had a significant impact on PM_(2.5)pollution,but there were lag effects and rebound effects.
文摘A mutagenesis library was constructed using GPS-LS system to insert a random 5 aa into the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) encoded by aroA gene. Active EPSPS pro- teins were identified by the ability to rescue growth of aroA-deleted mutant ER2799 on M9 minimal media. 12 unique sites, which can tolerate a 5-aa insertion, were identified. In all of the 12 sites, only F295/T296 site was found to split the G2-EPSPS properly by co-transformation of plasmids into E. coli ER2799. The G2-EPSPS gene was then divided into N-termi- nal and C-terminal from F295/T296 site which were fused to the N-terminal and C-terminal of Ssp.DnaE intein, respectively, creating two plasmids pMEPS- N295IN and pKEPSc296Ic. Co-transformation of plasmids, pMEPSN295IN and pKEPSc296Ic, rescu- ed growth of ER2799 in M9 minimal media, indicating that the intein splicing domains were bringing the EPSPS fragments together to generate activity. Re- consituted activity of splitted G2-EPSPS enzyme was 4.48 U/mg.
