Fluorides of ruthenium and chromium: Theoretical studies

The electronic and structural characteristics of CrF₅, CrF₄, RuF₅ and RuF₄ were studied. Ab initio (SCF-CI) calculations were performed with different structures and spin states for each complex. The favored conformation always corresponds to the highest multiplicity: doublet for CrF₅ in D_3h, triplet for CrF₄ in T_d, quadruplet for RuF₅ in C_4v and quintuplet for RuF₄ in D_4h symmetry.     

Interactions intramoléculaires en série cyclohexanique: Partie II. Spectres photoélectroniques de chloro-2 cyclohexanones

The photoelectronic spectra of cis-2-chloro, 4-tert-butylcyclohexanone and cis-2-methyl-2-chlorocyclohexanone have been analysed. These analyses have been used in an investigation into the nature of the orbital interactions in these molecules, and into the dependence of these interactions on the axial or equatorial position of the halogen atom. The preferential conformations of 2-chlorocyclohexanone and 4,4-dimethyl-2-chlorocyclo-hexanone have thus been obtained.     

Syntheses and spectroscopic properties of energy transfer systems based on squaraines

The purpose of this project was to prepare fluorescent dyes that could absorb energy at relatively short wavelengths, and fluoresce in the near-IR region. To achieve this, copper- and palladium-mediated C-N couplings were used to prepare the ‘cassettes’, i.e the carbazole derivative 3b and the carbazole-, phenothiazine-, and phenoazine-squaraines 4b-d. These compounds have carbazole, phenothiazine, and phenoazine donor-components that absorb around about 300-320 nm, and squaraine acceptor-parts that fluoresce in the range 650-700 nm. The efficiencies of energy transfer from the donor to the acceptor, and the overall quantum yields of the cassettes were determined.     

Liquid Crystal Emulsions

We review recent findings about the behavior of emulsions made of droplets suspended in liquid crystalline materials. By contrast to classical emulsions, which are usually made of isotropic oils and water, liquid crystal emulsions exhibit a variety of structures result in the ordering of the continuous phase. The droplets induce the formation of topological defects and distortions that lead to strong and anisotropic elastic forces between the particles. These elastic forces govern the stability and the ordering of the particles. This is observed in aqueous emulsions as well as in non-aqueous emulsions obtained from phase separation phenomena. It is shown that phase separations in liquid crystals can lead to the formation of highly ordered arrays of uniformly sized droplets. More generally, ordered structures seen in liquid crystal emulsions are of interest as examples of topologicallv-controlled organizations; they are also of potential practical importance as a novel way to control both the stability and the structures of colloidal particles.     

基于K图的函数RM展开式在固定极性下的最小化

分析了K图的性质，发现在K图中过某格的所有聚合圈相应的各乘积项所含变量与该格对应的最小项均有相同的极性，在此基础上提出了得到基于K图函数RM展开式在固定极性下的最小化的图形方法，该方法可以从K图直接得到函数的最小化的RM展开式，从而省略了传统的把K图转变为bj图再求最小化的步骤，它具有直观、简单、易于掌握等特点。此外，文中还提出了该方法的改进算法。     

Photonic control of surface anchoring on solid colloids dispersed in liquid crystals

The anchoring of liquid-crystal (LC) mesogens to the surfaces of colloids is an important factor in determining intercolloidal interactions and the symmetry of the ensuing colloidal assembly in nematic colloids. The dynamic control of surface anchoring could therefore provide a handle to tune the colloidal organization and resulting properties in these systems. In this article, we report our results on the study of thermotropic nematic LC (E7) dispersions of silica and glass microcolloids bearing photosensitive surface azobenzene groups. By the photoinduced modulation of the colloidal-LC interfacial properties, due to the trans-cis isomerization of azobenzene units, we tune the anchoring on silica colloids from homeotropic (trans-azobenzene) to homogeneous planar (cis-azobenzene) reversibly. In tune with the change in surface anchoring, the interparticle interactions were also dictated by dipolar and quadrupolar symmetries for homeotropic and homogeneous planar anchoring, respectively. In our experiments, we find that, in addition to the isomerization state of the surface-bound azobenzene units, the nature of the colloid plays a crucial role in determining the anchoring state obtained on applying photostimuli. We also study the LC anchoring on colloids as a function of the azobenzene surface density and find that beyond a threshold value the anchoring properties remain invariant.     

Stripe instabilities in the menisci of free-standing smectic films: influence of the phase sequence of the mesogenic material

We briefly report experimental observations of striped patterns in the menisci of free-standing smectic C films. The results were obtained with a mesogenic compound that transits directly from the nematic phase to the smectic C phase, without an intermediate smectic A phase. In this case, it is shown that stripes do not correspond to undulations of the smectic free surface and smectic layers, as was indeed evidenced in previous studies with other compounds and different phase sequences. Hence, our results show that the nature of striped patterns in free-standing films depends on the phase sequence of the considered materials. Further experimental and theoretical works are still required to fully elucidate the physical mechanisms that drive the onset of patterns in such systems.     

Gravitational Deflection of Massive Particles by a Schwarzschild Black Hole in Radiation Gauge*

The exact metric of a Schwarzschild black hole in the true radiation gauge was recently reported.In this work, we base on this gravity and calculate the gravitational deflection of relativistic massive particles up to the fourth post-Minkowskian order. It is found that the result is consistent with the previous formulations for both the case of dropping the fourth-order contribution and the case of light deflection. Our result might be helpful for future high-accuracy observations.     

The Exact Harmonic Metric for a Moving Reissner-Nordstrom Black Hole

The exact harmonic metric for a moving Reissner-Nordstr6m black hole with an arbitrarily constant speed is presented. As an application, the post-Newtonian dynamics of a non-relativistic particle in this field is calculated.     

T型微混合器混合特性的浓度分布评价法

提出一种微混合器混合性能的评价方法.在样品盒中注入不同浓度罗丹明B溶液并用体视显微镜观察捕获图像,通过Image J软件读取图像灰度值,建立不同深度下溶液的浓度-灰度值函数关系,运用此关系式将T型微混合器3种不同深度(0.1、 0.2和0.4 mm,质量浓度0.05 %的罗丹明B溶液和去离子水作为配对流体)混合实验中捕获的图像中各像素点上的灰度值转换为浓度值,绘制浓度等高线图及浓度频数分布图,分析各自混合情况,最后引入浓度混合指数概念及计算公式,分析3种深度混合器内不同截面上的混合程度.此方法从定性和定量两方面分析了微尺度下混合腔深度对微混合的影响程度,具有一定的应用价值.