Spectroscopic Measurement of Shock Waves in an Arcjet Plasma Expanding Through a Conical Nozzle

A diamond-shaped shock wave was created in a helium arcjet plasma. Visi- ble/ultraviolet emission spectroscopy was used to investigate the condition for the formation of stable shocks and to determine characteristics of the plasma. Dependence of the position of the shock front on the gas pressure in the expansion region was investigated. It was found that the shock wave arises from the collision of plasma particles and residual neutral atoms in that region. Continuum and line spectra of neutral helium were measured, from which the electron temper- atures were derived. The electron density was deduced from the Inglis-Teller limit of the He I 2p3p-3d3D series. The temperature and density were found to have almost constant values of 0.2 eV and 8.5x 1013 cm-3, respectively, across the shock front.

NC-311对水稻的安全性

NC—311(Pyrazosulfuron—ethyl,吡嘧黄隆)是日本日产化学公司研制的稻田新除草剂,在亚洲几个国家测试了单用或与其它除草剂混用的效果,20～30克有效成分/公顷的NC—311对阔叶杂草和莎草科杂草(包括多年生杂草),表现出良好的防效。NC—311在某些剂量下也能有效控制稗草。一些研究报道了作物对磺酰脲类除草剂耐性的机理,本文探讨NC—311在杂草和水稻间的选择作用及影响水稻生长的因素。