Changing characteristics and spatial differentiation of spring precipitation in Southwest China during 1961-2012

In this study,we analyze spring precipitation from 92 meteorological stations spanning between 1961 and 2012 to understand temporal-spatial variability and change of spring precipitation over Southwest China.Various analysis methods are used for different purposes,including empirical orthogonal function(EOF) analysis and rotated EOF(REOF) for analyzing spatial structure change of precipitation anomaly,and the Mann-Kendall testing method to determine whether there were abrupt changes during the analyzed time span.We find that the first spatial mode of the precipitation has a domain uniform structure;the second is dominated by a spatial dipole;and the third contains five variability centers.The 2000 s is the decade with the largest amount of precipitation while the 1990 s is the decade with the smallest amount of precipitation.The year-to-year difference of that region is large:the amount of the largest precipitation year doubles that of the smallest precipitation year.We also find that spring precipitation in Southwest China experienced a few abrupt changes:a sudden increase at 1966,a sudden decrease at 1979,and a sudden increase at 1995.We speculate that the spring precipitation will increase gradually in the next two decades.     

西红花有效成分合成研究进展

西红花主要有效成分为西红花酸和西红花糖苷,论文综述西红花酸和西红花糖苷生物合成和化学合成方法.在生物合成中最关键的是用葡萄糖糖基转移酶作催化剂将西红花酸转化为西红花糖苷;共轭多烯链化合物是合成西红花有效成分的起始物,在论文中概述了几种通过Wittig和Wittig-Horner 反应合成共轭多烯链化合物的路线.     

西红花酸的合成

以E-1,4-二溴-2-丁烯和亚磷酸三乙酯为起始物, 通过Wittig-Horner反应合成化合物2,7-二甲基-2,4,6-辛三烯-1,8-二醛; 然后以E-2-甲基-2-丁烯酸为起始物经过溴代、酯化合成E-2-甲基-2-丁烯酸甲酯-4-膦酸二乙酯. 两化合物通过Wittig-Horner反应生成西红花酸二甲酯. 西红花酸二甲酯水解得西红花酸.