The influence of solvent (in its gaseous state) on the stability of crystallized organic compounds was investigated. Through two examples of studies on the solid/vapour equilibria made in our lab, several behaviors we...The influence of solvent (in its gaseous state) on the stability of crystallized organic compounds was investigated. Through two examples of studies on the solid/vapour equilibria made in our lab, several behaviors were highlighted: (i) a new hydrated phase (thermodynamically stable) of an active pharmaceutical ingredient (API) was detected after the recrystallization starting from a deliquescent state, (ii) a spontaneous resolution of a hydrated racemic compound towards an anhydrous conglomerate can occur during the desolvation under the precise conditions of temperature and humidity. This study illustrates that knowledge about solid/vapour equilibrium is a crucial step during the complete characterization of solid organic compounds.展开更多
In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed ...In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed by the ＂Forming Mechanism and Con- trol Strategies of Haze in China＂ group using an intensive aerosol and trace gases campaign that simultaneously obtained data at 11 ground-based observing sites in the CARE-China network. The characteristics and formation mechanism of haze pollu- tion episodes were discussed. Five haze pollution episodes were identified in the Beijing-Tianjin-Hebei （Jing-Jin-Ji） area; the two most severe episodes occurred during 9-15 January and 25-31 January. During these two haze pollution episodes, the maximum hourly PMz5 mass concentrations in Beijing were 680 and 530 ~tg m-3, respectively. The process and evolution of haze pollution episodes in other major cities in the Jing-Jin-Ji area, such as Shijiazhuang and Tianjin were almost the same as those observed in Beijing. The external cause of the severe haze episodes was the unusual atmospheric circulation, the depres- sion of strong cold air activities and the very unfavorable dispersion due to geographical and meteorological conditions. How- ever, the internal cause was the quick secondary transformation of primary gaseous pollutants to secondary aerosols, which contributed to the ＂explosive growth＂ and ＂sustained growth＂ of PM2.5. Particularly, the abnormally high amount of nitric ox- ide （NOx） in the haze episodes, produced by fossil fuel combustion and vehicle emissions, played a direct or indirect role in the quick secondary transformation of coal-burning sulphur dioxide （SO2） to sulphate aerosols. Furthermore, gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of fine particles, which can change the particle＇s size and chemical composition. Consequently, the proportion of secondary inorganic ions, such as sulphate and nitrate, gradually increased, which enhances particle hygroscopicity and thereby accelerating formation of the haze pollution.展开更多
Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction.In this work,the ignition and combustion characteristics of a...Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction.In this work,the ignition and combustion characteristics of an individual millimeter-sized magnesium particle in water vapor were studied.In order to build an atmosphere of water vapor,an experiment system was established and validated by the experiments of magnesium particle in air.The ignition and combustion of a single magnesium particle were accomplished in a combustor filled with water vapor.The surface changes of the particle during the ignition and a steady-state vapor phase combustion were observed.Based on the data obtained,ignition mechanism was analyzed and ignition temperature was determined.The steady-state combustion of the sample was controlled by diffusion in gas phase,and a one-dimensional,spherically symmetric quasi-steady model was adopted to describe the process.The dependence of burning time on the diameter was investigated,and the conclusion that burning time is proportional to the square of the metal sample diameter was drawn.展开更多
文摘The influence of solvent (in its gaseous state) on the stability of crystallized organic compounds was investigated. Through two examples of studies on the solid/vapour equilibria made in our lab, several behaviors were highlighted: (i) a new hydrated phase (thermodynamically stable) of an active pharmaceutical ingredient (API) was detected after the recrystallization starting from a deliquescent state, (ii) a spontaneous resolution of a hydrated racemic compound towards an anhydrous conglomerate can occur during the desolvation under the precise conditions of temperature and humidity. This study illustrates that knowledge about solid/vapour equilibrium is a crucial step during the complete characterization of solid organic compounds.
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program(Grant Nos.XDB05020000 and XDA05100100)the National Natural Science Foundation of China(Grant Nos.41230642 and 41021004)
文摘In January 2013, a long-lasting episode of severe haze occurred in central and eastern China, and it attracted attention from all sectors of society. The process and evolution of haze pollution episodes were observed by the ＂Forming Mechanism and Con- trol Strategies of Haze in China＂ group using an intensive aerosol and trace gases campaign that simultaneously obtained data at 11 ground-based observing sites in the CARE-China network. The characteristics and formation mechanism of haze pollu- tion episodes were discussed. Five haze pollution episodes were identified in the Beijing-Tianjin-Hebei （Jing-Jin-Ji） area; the two most severe episodes occurred during 9-15 January and 25-31 January. During these two haze pollution episodes, the maximum hourly PMz5 mass concentrations in Beijing were 680 and 530 ~tg m-3, respectively. The process and evolution of haze pollution episodes in other major cities in the Jing-Jin-Ji area, such as Shijiazhuang and Tianjin were almost the same as those observed in Beijing. The external cause of the severe haze episodes was the unusual atmospheric circulation, the depres- sion of strong cold air activities and the very unfavorable dispersion due to geographical and meteorological conditions. How- ever, the internal cause was the quick secondary transformation of primary gaseous pollutants to secondary aerosols, which contributed to the ＂explosive growth＂ and ＂sustained growth＂ of PM2.5. Particularly, the abnormally high amount of nitric ox- ide （NOx） in the haze episodes, produced by fossil fuel combustion and vehicle emissions, played a direct or indirect role in the quick secondary transformation of coal-burning sulphur dioxide （SO2） to sulphate aerosols. Furthermore, gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of fine particles, which can change the particle＇s size and chemical composition. Consequently, the proportion of secondary inorganic ions, such as sulphate and nitrate, gradually increased, which enhances particle hygroscopicity and thereby accelerating formation of the haze pollution.
基金supported by the National Natural Science Foundation of China (Grant No. 51006118)
文摘Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction.In this work,the ignition and combustion characteristics of an individual millimeter-sized magnesium particle in water vapor were studied.In order to build an atmosphere of water vapor,an experiment system was established and validated by the experiments of magnesium particle in air.The ignition and combustion of a single magnesium particle were accomplished in a combustor filled with water vapor.The surface changes of the particle during the ignition and a steady-state vapor phase combustion were observed.Based on the data obtained,ignition mechanism was analyzed and ignition temperature was determined.The steady-state combustion of the sample was controlled by diffusion in gas phase,and a one-dimensional,spherically symmetric quasi-steady model was adopted to describe the process.The dependence of burning time on the diameter was investigated,and the conclusion that burning time is proportional to the square of the metal sample diameter was drawn.
