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We present an experimental and theoretical investigation of a variant of electroconvection using an unusual nematic liquid crystal in an isotropic configuration (homeotropic alignment). The significance of the system is a direct transition to the convecting state due to the negative conductivity anisotropy and positive dielectric anisotropy. We observe at onset rolls or squares depending on the frequency and amplitude of the applied ac voltage with a strong signature of the zigzag instability. Good agreement with calculations based on the underlying hydrodynamic theory is found. We also construct an extended Swift-Hohenberg model which allows us to capture complex patterns like squares with a quasiperiodic modulation. 相似文献
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A. S. Karsakevich S. N. Shulichenko M. R. Buka I. A. Vina A. P. Kashkin 《Chemistry of Natural Compounds》1986,22(6):712-717
The synthesis has been effected of immobilizedE. coli L-asparaginase on medical dextran — poliglyukin. The influence of the bound polymer on some physicochemical properties of the final products have been studied. An increased resistance to heat and stability on storage of the immobilized forms of L-asparagine in comparison with a native enzyme has been found. It has been shown that the polymer modification of L-asparaginase leads to a decrease in the antigenic affinity of the immobilized enzyme as compared with the native enzyme. 相似文献
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An operator splitting approach for the interaction between a fluid and a multilayered poroelastic structure 下载免费PDF全文
Martina Bukač Ivan Yotov Paolo Zunino 《Numerical Methods for Partial Differential Equations》2015,31(4):1054-1100
We develop a loosely coupled fluid‐structure interaction finite element solver based on the Lie operator splitting scheme. The scheme is applied to the interaction between an incompressible, viscous, Newtonian fluid, and a multilayered structure, which consists of a thin elastic layer and a thick poroelastic material. The thin layer is modeled using the linearly elastic Koiter membrane model, while the thick poroelastic layer is modeled as a Biot system. We prove a conditional stability of the scheme and derive error estimates. Theoretical results are supported with numerical examples. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 31: 1054–1100, 2015 相似文献
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Summary The heterogeneity of the electrophoretically homogeneous form of yeast enolase has been established by the isoelectric electrofocusing method.Institute of Organic Synthesis, Academy of Sciences of the LatvianSSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 98–100, January–February, 1971. 相似文献
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We study a new variant of electroconvection using a homeotropically aligned nematic liquid crystal. The novelty of this system is a direct transition to roll- or square-type patterns controlled by the frequency of the applied voltage with a rich crossover scenario and strong influence of the zigzag instability even at onset. From the weakly nonlinear theory and simulations of an adapted Swift-Hohenberg model one can understand essential features of the phase diagram. In particular we find a quasiperiodic pattern with square symmetry. 相似文献
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We describe an experimental situation with a looped line defect in nematic liquid crystals observed by polarizing optical microscopy. We measured the critical size of the loop below which it spontaneously shrinks and transforms into a point defect. The experiment was done with 5CB which gives rise to twist disclinations as do most of the usual nematics. For this kind of disclination an in-plane force due to the boundary conditions acts on the line and influences the critical radius. W e have constructed a model which is in good agreement with experimental measurements and deduced the line tension of the disclination. 相似文献
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The spontaneous polarization and tilt angle have been measured as a function of temperature and concentration in the SC* phase of four binary ferroelectric liquid crystal mixtures. The substances have been chosen in a way that different situations could be studied, for example mixtures of a chiral substance (Ps non-zero) with a non-chiral one (Ps = 0) and mixtures of chiral compounds with the same sign of Ps as well as with opposite signs. The results have been interpreted by means of a molecular rotational model and potentials associated with the tilt as well as with the chirality have been determined as a function of concentration. 相似文献
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In the paper the electric field induced reorientation of a nematic liquid crystal film is investigated theoretically and experimentally. Both alternating and static fields are considered. 相似文献
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Electroconvection is a classical example of pattern-forming phenomena in liquid crystals, typically observed in nematics with negative dielectric and positive conductivity anisotropies. This article focuses on how electroconvection in the homeotropic geometry differs from that in planar alignment. The influence of an additional magnetic field on the pattern characteristics and on secondary instabilities (the normal roll–abnormal roll transition) is discussed. The homeotropic alignment offers unique possibilities also for studying defect motion. Basic characteristics of some patterns of large wavelength are presented and compared with those of the classical Carr–Helfrich structures. Finally, electroconvection in substances with negative conductivity anisotropy is addressed. 相似文献