When pressure-oscillation is applied to a highly viscous solution containing a bubble, the bubble rising velocity is significantly enhanced compared to its natural bubble rising velocity. In this study, unsteady-state non-Newtonian finite element analysis is performed, in which the shape of the air-liquid interface can be determined by the force balance equation, considering inertia and the gravitational term. It was found that the alternative local flows near the bubble surface generated by pressure-oscillation give rise to lowered apparent viscosity for shear-thinning fluid, and enhancing the bubble rising velocity, as well. In addition, it was also found that the bubble rising velocity during contraction phase is faster than that during the expansion phase.

Microscopic deformation behavior of polyamide (PA) elastomers (PAE) with various PA contents has been elucidated using various structural analyses including in situ infrared spectroscopy under cycle tests. Below the glass transition temperature (T_g), the stress–strain curves showed an obvious yielding point irrespective of the soft-segment content. The plastic deformation under tension is interpreted by irreversible morphological transformation observed in semi-crystalline polymers, such as the collapse of the spherulites and the fragmentation of the lamellar crystals. Above T_g, whereas the stress–strain curve is dominated by the temperature distance from T_g, PAE with higher soft-segment contents shows more elastic deformation in its supermolecular structure, which is essentially reversible up to the highly-strained region. The microscopic origin of high tunability for the elasticity of PAE is assigned to the mobility of interlamellar amorphous chains dominated by T_g.

In slide-ring (SR) gels, polymer chains are cross-linked by rings and can slide through the cross-linking points. The high chain mobility in SR gels is responsible for their unique physical properties such as softness, high deformability, and crack resistance. In this study, the dynamics of the polymer network in SR gels was investigated by the microrheological technique. The diffusion coefficients of the silica nanoparticles in SR gels with different cross-linking densities were measured by dynamic light scattering (DLS). It was found that the diffusion coefficient of the probe particles in the SR gels does not decrease monotonically with increasing cross-linking density even though their mesh sizes are close to the particle size. This suggests that the slidability of the cross-linking points enhances fluctuation of the polymer networks in the SR gels.

The high amylose rice KITAMIZUHO developed in Hokkaido is expected to be applied to various foods because its rice flour paste shows high viscoelasticity. In order to systematically investigate the relationship between this characteristic rheological property and amylose content, the rheological properties of various rice flour pastes. For the rheological properties, the frequency dependence of the complex modulus of each rice flour paste was analyzed by a weak-gel model (WGM). We can obtain the coordination number (z) which shows the spatial density of the swollen starchy endosperm and starch granules in the rice flour paste using the model. KITAMIZUHO rice flour paste showed the higher z values than the middle and low amylose contents rice flours. It was expected that the higher the amylose content of rice starch, the larger the size of swollen starchy endosperm and starch granules. On the other hand, the observation using scanning electron microscopy revealed that the size of swollen starch granules of KITAMIZUHO was larger than the other rice flour paste. These results suggest that the characteristic rheological properties of the KITAMIZUHO rice flour paste, is due to the relatively large size of its swollen starchy endosperm and starch granules.