Ion trap performances are investigated based on digital ion trap technique with different collision gases at different pressures. Collision gases of helium (4 amu), nitrogen (28 amu) and argon (40 amu) with various pressures are adopted in ion excitation and dissociation stages to investigate the ion trap performances, including mass resolution, signal intensity, tandem mass spectrometric analysis ability and low-mass cut off (LMCO) effect. It is found that when heavy gas of argon is used, energy can be efficiently transferred and LMCO effect is decreased with higher ion capture and dissociation efficiencies but with low mass resolution. Higher mass resolution is realized with helium as collision gas. Furthermore, at the same gas pressure, heavy gas is beneficial to abundant fragment ions and structural information of precursor ion.

Objective To discuss the mass transfer of low temperature gas in the lung bronchus, so as to provide a theoretical basis for the implementation of hypothermic ventilation cooling non-heart-beating donor (NHBD) lung program. Methods A real airway model was reconstructed based on human lung CT images, and the computational fluid dynamics (CFD) method was used to investigate the airflow characteristics inside the airway during reciprocating ventilation. The effect of ventilation frequency (0.5, 0.25, 0.125 Hz) on bronchial flow was also studied. Results The flow in the airway showed complex three-dimensional （3D） flow characteristics during reciprocating ventilation. The flow in different areas of the airway was different during inhaling and exhaling; the irregular bronchial geometry had an important effect on its internal flow; when the ventilation frequency decreased from 0.5 Hz to 0.125 Hz, the thickness of flow boundary layer would increase, and the mainstream velocity in different areas of the airway was enhanced to different degrees. Conclusions The real airway model based on CT 3D reconstruction was more accurate than the ideal circularity tube model in showing the bronchial flow. The research findings have an important guiding significance to optimize the hypothermic ventilation cooling NHBD lung technique.