No abstract

Poster Sessions which can monitor the rheological properties of liquids between two surfaces as a function of surface separation distance (D) from µm to contact with nm resolution. In this study, we investigated the rheological properties of a liquid crystal, 4-cyano-4'-hexylbiphenyl (6CB), under the electric field which induces the orientational change of 6CB. Resonance curves were obtained by measuring the amplitude of shear as a function of angular frequency. Polarizing microscopy confirmed that 6CB was in the planar orientation between mica surfaces without electric field, and in the homeotropic orientation under the electric field (28 V, 1 kHz). The viscosity of 6CB was larger for the case of 0 V than the case of 28 V at 370-14 nm, which agreed with Miesowicz viscosity. Below D=14 nm, the viscosity increased similarly both at 0 V and 28 V, indicating the same orientation of 6CB under confinement. 1) M. Mizukami, K. Kusakabe, and K. Kurihara, Prog. Colloid Polym. Sci., 128, 105, (2004) Pressure-induced structural transformations have recently been attracting a lots of attentions. For example, the finding of pressureinduced first-order phase transition in fluid Phosphorous is very interesting in that it showed a possibility of a novel border which separates one fluid phase from another. We investigated the structure of heavier group V elements As and Sb, and IV-VI compounds such as GeS, GeSe, GeTe, PbSe, PbTe, SnSe, SnTe, in liquid phase, by high-temperature high-pressure X-ray diffraction. The intermediaterange structure of liquid As and GeSe was found to change by pressure; we suggest a change from two-to three-dimensional structure. We also found that R2/R1 (the ratio of the second peak position to the first of the pair distribution function) approaches root two with compression. This result show that the bond angle 90 degree is preferred in a certain pressure range. Interestingly this ratio R2/ R1 was found to change its pressure dependence when it passes root two. This indicates that further compression causes another structure. For liquid Sb and SnTe, the structure at ambient pressure has been conventionally assigned to a SC-like structure. However we found that the structure is not SC-like in low pressures, and our results suggest a considerable covalency in the bonds. With compression, the structure factor S(Q) showed a similar change to each other for these two liquids, and we found a hump in S(Q) (which is next to the first peak) rapidly and sharply changes at a certain pressure range. The overview of the pressure-induced structural changes for liquid group-V (and IV-VI compounds) will be given in the presentation, and systematic results and differences from crystalline pressure sequences will be shown. In an effort to find out details of the melanin fundamental structural unit, a great amount of information has been gathered using several techniques. The local short range order of the melanin molecular clusters has been described as consisting of five to seven 5,6-indolequinone units, arranged ...