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## Full-Text Articles in Physics

Azimuthal Dependence Of Switching Field Strength For Nematic Liquid Crystal Bistability On Patterned Alignment Layers, Jun-Ichi Niitsuma, Makoto Yoneya, Hiroshi Yokoyama

#### Azimuthal Dependence Of Switching Field Strength For Nematic Liquid Crystal Bistability On Patterned Alignment Layers, Jun-Ichi Niitsuma, Makoto Yoneya, Hiroshi Yokoyama

*Chemical Physics Publications*

We investigate the azimuthal dependence of the switching field strength for nematic liquid crystal bistability on patterned alignment layers to determine the validity of a switching theory proposed by Kim et al. [Appl. Phys. Lett. 78, 3055 (2001)] and to evaluate higher-order azimuthal anchoring coefficients. Director behavior during switching is described in detail for general azimuthal directions of an applied electric field and the experimental results are explained on the basis of the theory. We obtain azimuthal anchoring coefficients up to the second higher-order term in an expansion of the anchoring energy function. Detailed analysis of the director behavior reveals ...

Effects Of Dielectric Relaxation On The Director Dynamics Of Uniaxial Nematic Liquid Crystals, Mingxia Gu, Ye Yin, Sergij V. Shiyanovskii, Oleg Lavrentovich

#### Effects Of Dielectric Relaxation On The Director Dynamics Of Uniaxial Nematic Liquid Crystals, Mingxia Gu, Ye Yin, Sergij V. Shiyanovskii, Oleg Lavrentovich

*Chemical Physics Publications*

The dielectric anisotropy of liquid crystals causes director reorientation in an applied electric field and is thus at the heart of electro-optic applications of these materials. The components of the dielectric tensor are frequency dependent. Until recently, this frequency dependence was not accounted for in a description of director dynamics in an electric field. We theoretically derive the reorienting dielectric torque acting on the director, taking into account the entire frequency spectrum of the dielectric tensor. The model allows one to include the effects of multiple relaxations in both parallel and perpendicular components of the dielectric tensor, thus generalizing a ...

Pattern Formation In Non-Newtonian Hele-Shaw Flow, P. Fast, L. Kondic, M. J. Shelley, Peter Palffy-Muhoray

#### Pattern Formation In Non-Newtonian Hele-Shaw Flow, P. Fast, L. Kondic, M. J. Shelley, Peter Palffy-Muhoray

*Chemical Physics Publications*

We study theoretically the Saffman-Taylor instability of an air bubble expanding into a non-Newtonian fluid in a Hele-Shaw cell, with the motivation of understanding suppression of tip-splitting and the formation of dendritic structures observed in the flow of complex fluids, such as polymeric liquids or liquid crystals. A standard visco-elastic flow model is simplified in the case of flow in a thin gap, and it is found that there is a distinguished limit where shear thinning and normal stress differences are apparent, but elastic response is negligible. This observation allows formulation of a generalized Darcy's law, where the pressure ...

Non-Newtonian Hele-Shaw Flow And The Saffman-Taylor Instability, Ljubinko Kondic, Michael J. Shelley, Peter Palffy-Muhoray

#### Non-Newtonian Hele-Shaw Flow And The Saffman-Taylor Instability, Ljubinko Kondic, Michael J. Shelley, Peter Palffy-Muhoray

*Chemical Physics Publications*

We explore the Saffman-Taylor instability of a gas bubble expanding into a shear thinning liquid in a radial Hele-Shaw cell. Using Darcy's law generalized for non-Newtonian fluids, we perform simulations of the full dynamical problem. The simulations show that shear thinning significantly influences the developing interfacial patterns. Shear thinning can suppress tip splitting, and produce fingers which oscillate during growth and shed side branches. Emergent length scales show reasonable agreement with a general linear stability analysis.