ALIGNMENT INSTABILITY INDUCED BY IRRADIATION OF VISIBLE LIGHT IN FRUSTOELECTRIC LIQUID CRYSTALLINE CELLS SHOWING THE V-SHAPED SWITCHING

Abstract

Irradiation of the powerful visible light from the laser expedites the deterioration of the frustoelectric liquid crystalline cells (Inui mixture) showing the V-shaped switching. This deterioration is caused by the light absorption in the aligning layer, which strongly influences the molecule-surface polar interaction; this cannot be observed in the cell with the transparent aligning material in the used visible light region. This is observed just in the tilted smectic X* phase, not in the SmA phase. Irradiation during the switching leads to hysteresis in the V-shaped pattern and changes even the surface molecular alignment. These results can be explained by the shielding of the surface charge due to the alignment of the spontaneous polarization and the disturbed polar anchoring.     

动态像面法测量水面落点位置及误差分析

为了测量弹丸水面落点的位置, 建立了基于CCD相机动态像面的测量模型。该模型通过CCD相机辅助采集相关点位的图像信息, 对水面落点的位置函数以及误差进行了研究。首先, 利用空间几何获得靶船上三定点相对于测量船的方位、俯仰信息。接着, 结合t时刻观测图像上定点的像面坐标, 运用底片常数模型建立像面坐标和角度信息两套参量之间的关系函数, 从而得到目标落点的方位、俯仰信息, 再利用异面交会法计算出目标落点位置。最后, 分析了目标落点位置的误差来源(质心误差, 位置误差)、误差以及各误差源与位置坐标之间的关系。实验结果表明:在测量船位置精度达到0.05 m, 图像质心定位精度达到0.5 pixel时, 在最小交会误差的情况下, 目标落点的位置测量误差分别为2.8, 4.9, 4.3 m。     

Asymptotic computation for transient heat conduction performance of periodic porous materials in curvilinear coordinates by the second‐order two‐scale method

A novel second‐order two‐scale (SOTS) analysis method is developed for predicting the transient heat conduction performance of porous materials with periodic configurations in curvilinear coordinates. Under proper coordinate transformations, some non‐periodic porous structures in Cartesian coordinates can be transformed into periodic structures in general curvilinear coordinates, which is our particular interest in this study. The SOTS asymptotic expansion formulas for computing the temperature field of transient heat conduction problem in curvilinear coordinates are constructed, some coordinate transformations are discussed, and the related SOTS formulas are given. The feature of this asymptotic model is that each of the cell functions defined in the periodic cell domain is associated with the macroscopic coordinates and the homogenized material coefficients varies continuously in the macroscopic domain behaving like the functional gradient material. Finally, the corresponding SOTS finite element algorithms are brought forward, and some numerical examples are given in detail. The numerical results demonstrate that the SOTS method proposed in this paper is valid to predict transient heat conduction performance of porous materials with periodicity in curvilinear coordinates. By proper coordinate transformations, the SOTS asymptotic analysis method can be extended to more general non‐periodic porous structures in Cartesian coordinates. Copyright © 2017 John Wiley & Sons, Ltd.     

A numerical solution of the pair equation of a model two‐electron diatomic system

It has been well‐documented that about 90% of the total correlation energy of atomic systems can be obtained by solving so‐called pair equations. For atoms, this approach requires solving partial differential equations (PDE) in two variables. In case of a diatomic molecule, we face devising a method for treating PDEs in five variables. This article shows how a well‐established finite difference method used to solve Hartree–Fock equations for diatomic molecules can be extended to solve numerically a model two‐electron Schrödinger equation for such systems. We show that using less than 100 grid points in each variable, it is possible to obtain the total energy of the helium atom and hydrogen molecule with a chemical accuracy and the S energy of the helium atom and hydride ion as accurately as the best results available. © 2015 Wiley Periodicals, Inc.     

On the choice of a reference state for one‐step perturbation calculations between polar and nonpolar molecules in a polar environment

One‐step perturbation is an efficient method to estimate free energy differences in molecular dynamics (MD) simulations, but its accuracy depends critically on the choice of an appropriate, possibly unphysical, reference state that optimizes the sampling of the physical end states. In particular, the perturbation from a polar moiety to a nonpolar one and vice versa in a polar environment such as water poses a challenge which is of importance when estimating free energy differences that involve entropy changes and the hydrophobic effect. In this work, we systematically study the performance of the one‐step perturbation method in the calculation of the free enthalpy difference between a polar water solute and a nonpolar “water” solute molecule solvated in a box of 999 polar water molecules. Both these polar and nonpolar physical reference states fail to predict the free enthalpy difference as obtained by thermodynamic integration, but the result is worse using the nonpolar physical reference state, because both a properly sized cavity and a favorable orientation of the polar solute in a polar environment are rarely, if ever, sampled in a simulation of the nonpolar solute in such an environment. Use of nonphysical soft‐core reference states helps to sample properly sized cavities, and post‐MD simulation rotational and translational sampling of the solute to be perturbed leads to much improved free enthalpy estimates from one‐step perturbation. © 2012 Wiley Periodicals, Inc.     

Internal‐to‐Cartesian back transformation of molecular geometry steps using high‐order geometric derivatives

In geometry optimizations and molecular dynamics calculations, it is often necessary to transform a geometry step that has been determined in internal coordinates to Cartesian coordinates. A new method for performing such transformations, the high‐order path‐expansion (HOPE) method, is here presented. The new method treats the nonlinear relation between internal and Cartesian coordinates by means of automatic differentiation. The method is reliable, applicable to any system of internal coordinates, and computationally more efficient than the traditional method of iterative back transformations. As a bonus, the HOPE method determines not just the Cartesian step vector but also a continuous step path expressed in the form of a polynomial, which is useful for determining reaction coordinates, for integrating trajectories, and for visualization. © 2013 Wiley Periodicals, Inc.     

Azomesogens with polar chloro,nitro and phenolic –OH substituents

Two new mesogenic homologous series containing chloro, nitro and phenolic hydroxy groups were synthesised and their molecular structures characterised by a combination of element analysis and standard spectroscopic methods. The mesomorphic behaviour of the compounds of both series was investigated by polarising optical microscopy and, in some cases, differential scanning calorimetry. All the compounds of both the series exhibit an enantiotropic nematic mesophase. In series I higher members also exhibit an enantiotropic smectic A (SmA) mesophase, whereas in series II the enantiotropic SmA mesophase commences somewhat earlier for the middle members. The mesomorphic properties of both series are compared with each other and also with the properties of other structurally related series to evaluate the effects of different polar substituents on mesomorphism.     

Synthesis of Hydroxymethyl Side-Chained α-Aminoxy Diamide

Unnatural polar α-aminoxy acid residue with proteingenous hydroxymethyl side chain, a building block of the peptidomimetic foldamer of α-aminoxy peptide, was synthesized starting from natural amino acid L-serine. The starting material, L-serine, undergoes a reaction sequence to produce compound 1 in three steps: (1) the neighboring carboxyl group participates in diazotization/bromination to transform the amino group to a bromo group, (2) the C-terminal carboxyl group is protected, and (3) bromide is S_N2-displaced by N-hydroxyl phthalimide to introduce a N?O bond. After several conventional deprotection/coupling reactions, compound 1 is easily transformed to an α-aminoxy diamide, which can be widely used in peptidomimetics design.