When manufacturing pharmaceutical tablets by direct compression, the relationship between powder flowability and packing fraction must be evaluated to ensure that an appropriate excipient is selected. In this study, three types of microcrystalline cellulose with different particle sizes and shapes were evaluated by using the vibration shear tube method, which characterizes static and dynamic friction properties. First, to obtain the flowability profiles under quasi-steady-state conditions, the effects of an increasing rate of vibration acceleration on the mass flow rate were studied. Next, to analyze the effects of the initial packing fraction on powder flowability, the powder samples were subjected to vibration for different periods; then, experiments to evaluate powder flowability were conducted. The results demonstrated that the flowability related to static friction was strongly correlated with compressibility; this was evidenced by the packing-fraction variation. Because pre-consolidation of the powder suppressed flushing, the mass flow rate was directly proportional to compressibility. The proportional coefficient was used to evaluate the flowability related to dynamic friction.
Mineral pigments which have been used since old times in Japanese paintings as coloring materials are different in color and texture depending on their particle size. Recently, there have been an increased scarcity of certain natural mineral pigments. In this research, we have pulverized these natural mineral pigments into submicron/nano particles. It is observed that they exhibit different characteristics and unique colors when compared to natural mineral pigments sold in the commercial market. We could consider the possibility of applying the use these finely pulverized natural mineral pigments to various disciplines of the Arts. Here, we will discuss the present state of mineral pigments and the research conducted on natural mineral pigments by Joshibi University of Art and Design.
Buddhist paintings symbolically represent the sacred teachings. For further reproduction of the painting, the colors were investigated through instrumental analysis and research into their corresponding symbolism. Regarding the colors of the chignon of Bodhisattva, the analysis showed the original color was blue as written in the scripts. Both indigo and azurite pigments expressed blue but were used differently, indicating a symbolic meaning. Regarding the colors of the face of Jikoku-ten, they should conform to the colors which symbolize the scripts. This study concludes that combining symbolism with instrumental analysis has brought us closer to determining the original colors.