This paper simulated the ultraviolet aging process of asphalt and used dynamic mechanic analysis （DMA） method to evaluate the effect of ultraviolet aging on the asphalt theological properties. After having experienc...This paper simulated the ultraviolet aging process of asphalt and used dynamic mechanic analysis （DMA） method to evaluate the effect of ultraviolet aging on the asphalt theological properties. After having experienced ultravio- let aging, the low temperature performance of asphalt binder decreased significantly, with its complex modulus increased and phase angle decreased along with changing rheological properties as compared to the performance of original asphalt binder. The ultraviolet aging process would make asphalt binder more sensitive to brittle and fatigue failure. On the basis of the time-temperature superposition principle （TTSP）, the viscoelastic transition frequency （coT） is proposed to evaluate the effect of ultraviolet aging. It is found that with the increase in ultraviolet aging time, the cox moves to the lower frequency range gradually. Since the viscoelastic transition frequency is sensitive to the effect of aging, it can be used as an indicator of ultraviolet aging.展开更多
Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtai...Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtained by supercooling of the melt in a DSC （differential scanning calorimetry） apparatus and then investigated, especially under the stability point of view. The average rate of molecular motions at any given temperature is probably the most important parameter to know for amorphous pharmaceutical materials, and it was used to explain and predict the stability of ketoprofen and flurbiprofen. A quantitative estimate of the product＇s behaviour upon storage is obtained with additional data, such as the heat capacity of crystalline and amorphous samples and the distribution of molecular relaxation times. Amorphous flurbiprofen demonstrated greater physical stability at any aging temperature tested, when compared to ketoprofen and a different dependence from aging temperature. Both amorphous drugs could he classified as ＂fragile＂ ones.展开更多
基金supported by the National Natural Science Foundation of China(NNSFC,Grant No.50808058)the New Century Excellent Talents in University,2007(NCETU)+1 种基金the National Science Foundation for Post-doctoral Scientists of China(NSFPSC,Grant No.20080430925)the Specialized Research Fund for the Doctoral Program of Higher Education of China(SRFDPHEC,Grant No.200902403)
文摘This paper simulated the ultraviolet aging process of asphalt and used dynamic mechanic analysis （DMA） method to evaluate the effect of ultraviolet aging on the asphalt theological properties. After having experienced ultravio- let aging, the low temperature performance of asphalt binder decreased significantly, with its complex modulus increased and phase angle decreased along with changing rheological properties as compared to the performance of original asphalt binder. The ultraviolet aging process would make asphalt binder more sensitive to brittle and fatigue failure. On the basis of the time-temperature superposition principle （TTSP）, the viscoelastic transition frequency （coT） is proposed to evaluate the effect of ultraviolet aging. It is found that with the increase in ultraviolet aging time, the cox moves to the lower frequency range gradually. Since the viscoelastic transition frequency is sensitive to the effect of aging, it can be used as an indicator of ultraviolet aging.
文摘Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtained by supercooling of the melt in a DSC （differential scanning calorimetry） apparatus and then investigated, especially under the stability point of view. The average rate of molecular motions at any given temperature is probably the most important parameter to know for amorphous pharmaceutical materials, and it was used to explain and predict the stability of ketoprofen and flurbiprofen. A quantitative estimate of the product＇s behaviour upon storage is obtained with additional data, such as the heat capacity of crystalline and amorphous samples and the distribution of molecular relaxation times. Amorphous flurbiprofen demonstrated greater physical stability at any aging temperature tested, when compared to ketoprofen and a different dependence from aging temperature. Both amorphous drugs could he classified as ＂fragile＂ ones.
