高效液相色谱/质谱法测定4个玉米品种幼苗中丁布含量

丁布是植物中一种重要的组成型抗菌、抗虫活性物质。采用HPLC和HPLCMS方法对我国主栽的农大80、农大108、农大115和农大368等4个玉米品种幼苗中的丁布进行了定性和定量研究。结果证实,供试的4个玉米品种培育7d的正常幼苗和黄化幼苗中均含有丁布;不同品种之间丁布含量具有显著差异,由高到低依次为农大368>农大80>农大108>农大115,其中农大368整株正常幼苗和黄化幼苗中丁布含量分别达到0.441和1.220mg/fwg,而农大115整株正常幼苗和黄化幼苗中丁布含量仅分别为0.111和0.314mg/fwg;供试玉米品种的黄化幼苗整株和地上部中的丁布含量分别显著高于对应品种的正常幼苗整株和地上部中丁布的含量,提高幅度分别为74.0%～182.9%和19.7%～40.7%;正常幼苗和黄化幼苗地上部中丁布的含量明显高于其根部。综合分析认为,供试的4个玉米品种中农大368的黄化幼苗地上部器官是提取丁布的优选材料。     

Influence of resonator shape on nonlinear acoustic field in a thermoacoustic engine

The influence of the resonator shape on nonlinear acoustic field in a thermoacoustic engine is studied.The resonator of themoacoustic engine is boundary driving by a piston at one end,and the other end of it is rigid closed.A one-dimensional wave equation that accounts for gas dynamic nonlinearities and viscous dissipation in the resonator is established based on the governing equations of viscous hydromechanics.The nonlinear wave equation is solved using approximate Galerkin method.The nonlinear acoustic field in four different types of shaped resonators including hyperbolical,exponential,conical and sinusoidal are obtained and compared with that of a cylindrical resonator.It is found that the amplitude and waveform of the pressure are strongly affected by the resonator shape,the driving amplitude and the oscillation frequency of the piston.Waveform distortion,resonance frequency shift and hysteresis are observed,when the piston oscillation amplitude is large enough.The advantages of shaped resonator for thermoacoustic engine lie in inhibition of higher order harmonics and improvement of pressure ratio,etc.