Helical twisting power and compatibility in twisted nematic phase of new chiral liquid crystalline dopants with various liquid crystalline matrices

ABSTRACT

Four chiral dopants exhibiting smectic LC phases themselves were prepared and their helical twisting power (HTP) and thermal phase behaviour in mixtures with four various LC hosts were studied. The influence of host liquid crystal on HTP was evaluated and generally higher values were found for hosts with high birefringence. Unexpectedly, high enhancement was found for an LC-chiral dopant pair, both having a similar aromatic core – biphenyl ring substituted with polar group. All studied chiral dopants exhibited limited compatibility with the LC hosts in twisted nematic phase at room temperature. For one of the studied mixtures, it was able to obtain single twisted nematic phase with selective light reflection band with maximum at wavelength about 1.0 µm. Carboxylic acid-type dopants exhibited total compatibility with the studied host in single twisted nematic phase at elevated temperatures, allowing preparation of mixtures with reflection band in the visible range. In case of the carboxylic acid dopants, blue phases for optimised compositions were observed. Intermolecular hydrogen bonding between carboxylic acid proton and pyridine nitrogen of chiral dopants was found. Doping the LC host with these dopants led to slight enhancement of HTP value and higher solubility in the LC host.     

The Linking Number of Link with Two Components

ＴｈｅＬｉｎｋｉｎｇＮｕｍｂｅｒｏｆＬｉｎｋｗｉｔｈＴｗｏＣｏｍｐｏｎｅｎｔｓ￥ＷｕＨｕａａｎ（吴华安）ＴｉａｎＬｉｑｉｎ（田利钦）（Ｅｄ．Ｄｅｐｔ．Ｊ．ｏｆＨｕｂｅｉＵｎｉｖｅｒｓｉｔｙ）（ＬｕｏｙａｎｇＡｇｒｉｃｕｌｔｕｒａｌＣｏｌｌｅｇｅ）Ａｂ...     

Optimal phase sensitivity of atomic Ramsey interferometers with coherent spin states

We present a detailed analysis of phase sensitivity for a nonlinear Ramsey interferometer, which utilize effective mean-field interaction of a two-component Bose–Einstein condensate in phase accumulation. For large enough particle number N and small phase shift ?, analytical results of the Ramsey signal and the phase sensitivity are derived for a product coherent state |θ,0?. When collisional dephasing is absent, we confirm that the optimal sensitivity scales as 2/N^3/2 for polar angle of the initial state θ = π/4 or 3π/4. The best-sensitivity phase satisfies different transcendental equations, depending upon the initial state and the observable being measured after the phase accumulation. In the presence of the collisional dephasing, we show that the N^-3/2-scaling rule of the sensitivity maintains with spin operators J^x and J^y measurements. A slightly better sensitivity is attainable for optimal coherent state with θ = π/6 or 5π/6.     

Fluorescence Quenching of Auramine in Fluid Solutions: A Femtosecond Spectroscopy Study

The quenching of Auramine fluorescence in ethanol is studied by two ultrafast spectroscopy techniques. The gain band, probed by transient absorption spectroscopy, vanishes in a few picoseconds, while a transient absorption band rises and the ground-state repopulation is delayed. In up-conversion experiments, nonexponential wavelength-dependent fluorescence decays are observed. The average decay times increase with the wavelength and the reconstructed instantaneous spectrum exhibits a few hundred-wavenumber red shift and a broadening while its intensity drops. The previously proposed relaxation model, involving a barrierless internal twisting motion toward a transient dark state, is further examined. In particular, the extinction coefficients of the transient state are extracted from the differential absorption spectra. The band is found to lie in the same wavelength range as the dimethylaniline cation radical. This result is discussed as a possible support for an internal twisting process involving a charge shift.     

焊接扭转变形分析方法研究

大型薄壁梁在焊接拼装过程中常常会出现扭转变形。本文采用二种不同的数值方法对焊接扭转变形的动态过程进行了分析，比较全面系统地论述了研究的方法，阐述了扭转变形的形成机制，它们无论对理论研究还是对工程中的实际应用均有重要意义     

A criterion for satellite 1-genus 1-bridge knots

Let be a knot in a closed orientable irreducible 3-manifold . Suppose admits a genus 1 Heegaard splitting and we denote by the splitting torus. We say is a -genus -bridge splitting of if intersects transversely in two points, and divides into two pairs of a solid torus and a boundary parallel arc in it. It is known that a -genus -bridge splitting of a satellite knot admits a satellite diagram disjoint from an essential loop on the splitting torus. If and the slope of the loop is longitudinal in one of the solid tori, then is obtained by twisting a component of a -bridge link along the other component. We give a criterion for determining whether a given -genus -bridge splitting of a knot admits a satellite diagram of a given slope or not. As an application, we show there exist counter examples for a conjecture of Ait Nouh and Yasuhara.

     

几类交叉余积的关系

该文引进了广义对角交叉余积, 广义 L-R smash 余积, 广义双边交叉余积和双边smash余积并研究它们的关系. 特别地, 给出了两种不同方法来解释广义对角交叉余积与广义L-R smash 余积之间的关系. 作为应用, 运用比较简单的证明给出关于iterated广义smash余积的一个重要的结论.     

Adsorption processes during the filling of a display with a smectic A LC mixture

The separation of a smectic A liquid crystal (LC) mixture during the filling of a large area display was studied. This process is governed by the selective adsorption of the mixture's ionic dopant on the surface of the display substrates, leading to a non-uniform distribution of the dopant in the LC over the display area and resulting in defective regions. Conductivity measurements were performed to indicate the distribution of the dopant concentration in the LC over the display area. The consequences of mixture separation on the structure of the LC and on the display's electro-optical properties are discussed. Factors to reduce the extent of separation of the mixture are revealed using a general theory of chromatography. Increasing the cell gap, decreasing the area of the glass surface by reducting the gap between the ITO electrodes, and increasing the back pressure during filling, effectively reduce the significance of the separation process. The results obtained can be used when designing and filling displays based on the electrically reversible memory effect in a smectic A LC or displays based on dynamic light scattering in a nematic LC.