Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitat...Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.展开更多
N-Acetylneuraminic acid(Neu5Ac),the most common type of Sia,generally acts as the terminal sugar in cell surface glycans,glycoconjugates,oligosaccharides,lipo-oligosaccharides,and polysaccharides,thus exerting numerou...N-Acetylneuraminic acid(Neu5Ac),the most common type of Sia,generally acts as the terminal sugar in cell surface glycans,glycoconjugates,oligosaccharides,lipo-oligosaccharides,and polysaccharides,thus exerting numerous physiological functions.The extensive applications of Neu5Ac in the food,cosmetic,and pharmaceutical industries make large-scale production of this chemical desirable.Biosynthesis which is associated with important application potential and environmental friendliness has become an indispensable approach for large-scale synthesis of Neu5Ac.In this review,the physiological roles of Neu5Ac was first summarized in detail.Second,the safety evaluation,regulatory status,and applications of Neu5Ac were discussed.Third,enzyme-catalyzed preparation,whole-cell biocatalysis,and microbial de novo synthesis of Neu5Ac were comprehensively reviewed.In addition,we discussed the main challenges of Neu5Ac de novo biosynthesis,such as screening and engineering of key enzymes,identifying exporters of intermediates and Neu5Ac,and balancing cell growth and biosynthesis.The corresponding strategies and systematic strategies were proposed to overcome these challenges and facilitate Neu5Ac industrial-scale production.展开更多
基金The National 973 Project of China, No.2001CB309404 O versea O utstanding Youth Cooperation Project, N o. 40128001/D 05N ationalN aturalScience Foundation ofChina,N o.49375248 Zhejiang Province Science Research (C33)Project,N o.2004C33082
文摘Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.
基金the National Key R&D Program of China(No.2022YFC2104900)the National Natural Science Foundation of China(No.31922073).
文摘N-Acetylneuraminic acid(Neu5Ac),the most common type of Sia,generally acts as the terminal sugar in cell surface glycans,glycoconjugates,oligosaccharides,lipo-oligosaccharides,and polysaccharides,thus exerting numerous physiological functions.The extensive applications of Neu5Ac in the food,cosmetic,and pharmaceutical industries make large-scale production of this chemical desirable.Biosynthesis which is associated with important application potential and environmental friendliness has become an indispensable approach for large-scale synthesis of Neu5Ac.In this review,the physiological roles of Neu5Ac was first summarized in detail.Second,the safety evaluation,regulatory status,and applications of Neu5Ac were discussed.Third,enzyme-catalyzed preparation,whole-cell biocatalysis,and microbial de novo synthesis of Neu5Ac were comprehensively reviewed.In addition,we discussed the main challenges of Neu5Ac de novo biosynthesis,such as screening and engineering of key enzymes,identifying exporters of intermediates and Neu5Ac,and balancing cell growth and biosynthesis.The corresponding strategies and systematic strategies were proposed to overcome these challenges and facilitate Neu5Ac industrial-scale production.
