Small-scale turbulent fluctuations beyond Taylor's frozen-flow hypothesis

The space-time cross-correlation function C-T(r, tau) of local temperature fluctuations in turbulent Rayleigh-Benard convection is obtained from simultaneous two-point time series measurements. The obtained C-T(r, tau) is found to have the scaling form C-T(r(E), 0) with r(E)=[(r-U tau)(2)+ V-2 tau(2)](1/2), where U and V are two characteristic velocities associated with the mean and rms velocities of the flow. The experiment verifies the theory and demonstrates its applications to a class of turbulent flows in which the requirement of Taylor's frozen flow hypothesis is not met.

油菜与诸葛菜的几种分子标记比较研究

利用分子标记（随机引物、简单重复序列、微卫星DNA重复序列\rDNA–ITS ）比较研究了白菜型油菜与诸葛菜亲缘关系。RAPD分析表明，诸葛菜与白菜型油菜PCD产物相似性只有10%左右；简单重复序列（SSRS）标记中引物B.N 12A 的PCR 产物相似表明诸葛与白菜型油菜有明显差异，诸葛菜没有扩增产物，白菜型油菜具有明显的扩增产物；引物ITS4-IT5的PCR产物也有明显的差异。这些结果说明白菜型油菜与诸葛菜亲缘关系不是很近。结合其他学者的工作，讨论了甘蓝型油菜、芥菜型油菜与诸葛菜的亲缘关系。