Fluid Mode Spectroscopy for measuring dynamic viscosity of fluids in open cylindrical containers

On a daily basis we stir tee or coffee with a spoon and leave it to rest. We know empirically the larger the stickiness, viscosity, of the fluid, more rapidly its velocity slows down. It is surprising, therefore, that the variation has not been utilized for measuring (dynamic) viscosity of fluids. This study shows that a spectroscopy decomposing a velocity field into fluid modes (Stokes eigenmodes) allows us to measure accurately the dynamic viscosity. The method, Fluid Mode Spectroscopy (FMS), is based on the fact that each Stokes eigenmode has its inherent decay rate of eigenvalue and that the dimensionless rate of the slowest decaying mode (SDM) is constant, dependent only on the normalized shape of a fluid container, obtained analytically for some shapes including cylindrical containers. The FMS supplements major conventional measuring methods with each other, particularly useful for measuring low dynamic viscosity.Comment: 18 pagese, 6 figure

Cavitation Bubble Behavior Near Solid Boundaries

In the present study the bubble behavior in the narrow space are experimentally and numerically examined as the gap between two parallel walls and the position of bubble induction were changed. The main results are as follows. (1) The effects of two parallel walls can be classified by the ratio of the gap between the walls to the maximum bubble radius. If the ratio>5.0 the bubble shape is almost sphere. The wall effect remarkably appears for the ratio<3.0 and the bubble deforms to be dumbbell- or cone-like shape. (2) When the gap between the walls is small, the single bubble is finally divided into two bubbles owing to the large lateral pressure. The rebound of each bubble causes impulsive pressure and damages the upper and lower wall surface. Especially, if the bubble is not created at the center between the walls, the collapse phase shift among the divided bubbles brings the further damage on the wall surface. (3) The computed motion of the bubble without non-condensable gases well explains the dumbbell- or cone-shaped bubble deformation

Symmetry-Based Balance Equation for Local Entropy Density in a Dissipative Multibaker Chain System

In this study, the balance equation for local entropy density defined on each partition is obtained by the decomposition of the time-evolution operator for local entropy density, on the level of the master equation, by using symmetric and antisymmetric properties for the inversion of partition, density pairs and a given drift velocity. The resultant equation includes the following terms: convection, diffusion, entropy flow due to a thermostat and entropy production. The averaging of the four terms recover the corresponding terms in a balance equation for the macroscopic entropy density of irreversible thermodynamics for a thermostated system. Moreover, an empirical law of order estimation is introduced to explain the limiting behavior of the averaged quantities in the macroscopic limit for the bulk system. The law makes it possible to separate some minor contributions from the major four terms and, for example, to explain the positive entropy production rate in a nonequilibrium state for volume-preserving systems, even if the state is far from steady state. They are numerically confirmed on an invertible, dissipative multibaker chain system, named a circuit model. These properties are independent of partitioning

Thermal Mode Spectroscopy for Thermal Diffusivity of Millimeter-Size Solids

Heat conduction possesses (thermal) modes in analogy with acoustics even without oscillation. Here, we establish thermal mode spectroscopy to measure the thermal diffusivity of small specimens. Local heating with a light pulse excites such modes that show antinodes at the heating point, and photothermal detection at another antinode spot allows measuring relaxation behavior of the desired mode selectively: The relaxation time yields thermal diffusivity. The Ritz method is proposed for arbitrary geometry specimens. This method is applicable even to a diamond crystal with ∼1 mm dimensions.Ogi H., Ishihara T., Ishida H., et al. Physical Review Letters, 117(19), 195901, 2016. Copyright 2016 by the American Physical Society

Vulnerability of Purkinje Cells Generated from Spinocerebellar Ataxia Type 6 Patient-Derived iPSCs

SummarySpinocerebellar ataxia type 6 (SCA6) is a dominantly inherited neurodegenerative disease characterized by loss of Purkinje cells in the cerebellum. SCA6 is caused by CAG trinucleotide repeat expansion in CACNA1A, which encodes Cav2.1, α1A subunit of P/Q-type calcium channel. However, the pathogenic mechanism and effective therapeutic treatments are still unknown. Here, we have succeeded in generating differentiated Purkinje cells that carry patient genes by combining disease-specific iPSCs and self-organizing culture technologies. Patient-derived Purkinje cells exhibit increased levels of full-length Cav2.1 protein but decreased levels of its C-terminal fragment and downregulation of the transcriptional targets TAF1 and BTG1. We further demonstrate that SCA6 Purkinje cells exhibit thyroid hormone depletion-dependent degeneration, which can be suppressed by two compounds, thyroid releasing hormone and Riluzole. Thus, we have constructed an in vitro disease model recapitulating both ontogenesis and pathogenesis. This model may be useful for pathogenic investigation and drug screening