Biomedical subjects

Nariya Uchida

Publications and source records attributed to Nariya Uchida.

4 recordsLinked to original sources

PubMed2006

Numerical simulation of the twist-grain-boundary phase of chiral liquid crystals.

We study the structure of the twist-grain-boundary phase of chiral liquid crystals by numerically minimizing the Landau-de Gennes free energy. We analyze the morphology of layers at the grain boundary, to better understand the mechanism of frustration between the smectic layer order and chirality. As the chirality increases, the layer compression energy strongly increases while the effective layer bending rigidity is reduced due to unlocking of the layer orientation and the director. This results in large deviation of the layer morphology from that of Scherk's first minimal surface and linear stack of screw dislocations.

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PubMed2005

Boundary conditions for equilibrating incommensurate periodic patterns.

Simulation of periodic patterns often suffer from artifacts due to incommensurability of the intrinsic length scale and the system size. We introduce a simple numerical scheme to avoid this problem in finding equilibrium domain morphologies from a Ginzburg-Landau-type free energy. In this scheme, the boundary values are determined only by the local equilibrium condition at the adjacent bulk sites. The scheme is especially advantageous in equilibrating patterns that have two or more characteristic lengths. We demonstrate it using a model of lamellar-lamellar coexistence in block copolymer blends.

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PubMed2002

Dynamics of orientational ordering in fluid membranes.

We study the dynamics of orientational phase ordering in fluid membranes. Through numerical simulation we find an unusually slow coarsening of topological texture, which is limited by subdiffusive propagation of membrane curvature. The growth of the orientational correlation length xi obeys a power law xi proportional, variant t(w) with w<1/4 in the late stage. We will also discuss defect profiles and correlation patterns in terms of long-range interaction mediated by curvature elasticity.

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PubMed2002

Pattern formation in phase-separating gels with spontaneous shear.

We study pattern formation in gels undergoing simultaneous phase separation and orientational ordering. A 2D numerical simulation is performed using a minimal model of nonlinear elasticity with density-anisotropy coupling. For strong positive coupling, the collapsed phase elongates along the phase boundary and buckle, creating a folded structure with paired topological defects. For negative coupling, soft elasticity of the swollen phase causes a droplet morphology as in liquid-liquid phase separation. Their possible realizations in nematic liquid-crystalline gels are discussed.

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