On the green aurora emission of Ar atmospheric pressure plasma

The Ar atmospheric pressure plasma was found to be an excellent laboratorial source for green aurora emission.However,the characteristic and production mechanism of the green aurora emission of the Ar atmospheric pressure plasma are still not clear.In this work,an Ar plasma in a long glass tube which emits intense green aurora light is investigated.With the long glass tube,it can be concluded that the green aurora emission in the Ar plasma is not owing to the mixture of Ar plasma plume with the surrounding air.It is also found that the green aurora emission often appeared beyond the active electrode when the active electrode is placed at the downstream of the gas flow.The green emission disappears when the traces amount of O_(2) or N_(2)(about 0.05%–0.07%)is added to Ar.This is because the O_(2) molecules deactivate the upper state O(^(1)S),which results in the decrease of the green emission.On the other hand,when N_(2) is added,Ar metastable atoms are quenched by N_(2),which results in the decrease of O atoms and eventually leads to the decrease of the green emission intensity.The intensity of the green aurora emission increases when the driving voltage frequency increases from 1 to 10 k Hz.More importantly,it is found that the green aurora emission is not affected when a grounded stainless steel needle is in contact with the plasma plume.Thus,the green emission is not driven electrically.All these findings are helpful for the understanding of the physics and its applications of atmospheric pressure plasma jet in space physics,laser physics and other application areas.

Asymmetric Synthesis and Antitumor Activity of Spiro- Oxadiazole Derivatives from 1,4：3,6-Dianhydro-D-fructose

A series of spiro-oxadiazoles were synthesized from 1,4：3,6-dianhydro-D-fructose and hydrazides via a stereoselective two-step reaction sequence. The structures of newly synthesized compounds were established by spectral analysis. The absolute configuration of compound 2a was further confirmed by single crystal X-ray analysis. All the synthesized compounds were screened for their in vitro antitumor activity, showing that these compounds have poor inhibitory activities against A549, MGC-803 tumor cells.