ABSTRACT
We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.
ABSTRACT
BACKGROUND: The system for treating waste anesthetic gases, Anesclean, has been developed recently. This system can collect volatile anesthetics from waste anesthetic gases, and then decompose nitrous oxide (N2O) into N2 and O2 immediately. The purpose of this study was to investigate the efficacy of this treating system, Anesclean, on removal of greenhouse effect gases in our university hospital. METHODS: The concentrations of sevoflurane and N2O from an outlet of the system were measured using gas-chromatography. The total amount of sevoflurane consumed in the past two years and the amount of sevoflurane collected by Anesclean in the same period were measured to calculate collection rate. RESULTS: The concentrations of anesthetics in the outlet were very low, suggesting that the system works effectively. The amount of sevoflurane consumed was 606.51, and 245.31 was collected. Thus, calculated collection rate was 40.4%, indicating that approximately 60% of sevoflurane is not collected in our current situation. CONCLUSIONS: The waste anesthetic gas treating system, Anesclean, was effective to some degree in collection of sevoflurane and decomposition of N2O. However, in order to increase collection rate of sevoflurane, we need to pay more attention to minimize gas leak during anesthetic procedure.
