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991.
The role of the linear elastic term in the spatial derivatives of the nematic director on the director field is analysed. We consider a nematic sample in the shape of a slab, confined by two surfaces treated to induce homeotropic alignment. It is shown that this term can be responsible for spontaneous Fréedericksz transitions. The connection between the linear term and the flexoelectric contribution, associated with a surface field, to the bulk energy density, is discussed. The importance of dielectric anisotropy on the spontaneous Fréedericksz transition is also investigated. 相似文献
992.
A mesoscopic, extended Doi theory for flows of nematic liquid crystals (LCs) has been successfully applied by Rey to study extensional flow-induced, homogeneous phase transitions both for rod-like and disc-like molecular geometry. Rey analysed the two order parameters (eigenvalues) of the orientation tensor. Recently the authors generalized the flow-phase diagram (nematic concentration vs. flow rate) for rod-like nematics by analysing all tensor degrees of freedom, i.e. by coupling the three director (eigenvector) degrees of freedom. Here we record and discuss subtleties of the corresponding diagram for discotic LCs in uniaxial extension and uniaxial compression. We focus here on the induced stable orientation configurations. Uniaxial extension (an idealization of fibre flow) yields a low concentration region of unique oblate uniaxial states at every flow rate; a very small finite region of bi-stable oblate and biaxial states; and the predominant region, encompassing all concentrations above the pure I-N transition and all flow rates, where the only stable steady state is a biaxial pattern. Furthermore, whereas uniaxial states are 'unique', all biaxial states occur in a continuous family, corresponding to an arbitrary positioning of the director pair in the plane transverse to the flow axis of symmetry. Uniaxial compression (an idealization of film stretching flow) of discotic LCs exclusively yields stable prolate uniaxial patterns. 相似文献
993.
We analyse the electrostatic properties of a set of cyano-containing mesogen molecules with different rigid cores and variable alkyl chain lengths, computing the molecular charge distributions. Using the simple prototype benzonitrile, we analyse the reliability of the quantum chemical methods used to estimate the electrostatic dipole moments of polar conjugated molecules. We show that the electronic properties of the long mesogenic molecules can be treated by combining HF geometry optimization procedures with single point MP2 calculations. We compare the results of these computations with the available experimental phase transition data of mesogens and discuss some examples of how the non-trivial mesomorphic behaviour, which is usually observed in these cyano compounds, can be qualitatively explained by the molecular electrostatic interaction potential. 相似文献
994.
Xiangfen Jiang Dr. Bishnu Prasad Bastakoti Dr. Wu Weng Dr. Tetsuya Higuchi Dr. Hamid Oveisi Dr. Norihiro Suzuki Wei‐Jung Chen Prof. Yu‐Tzu Huang Prof. Dr. Yusuke Yamauchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(33):10958-10964
Ordered mesoporous alumina‐doped titania thin films with anatase crystalline structure were prepared by using triblock copolymer Pluronic P123 as structure‐directing agent. Uniform Al doping was realized by using aluminum isopropoxide as a dopant source which can be hydrolyzed together with titanium tetraisopropoxide. Aluminum doping into the titania framework can prevent rapid crystallization to the anatase phase, thereby drastically increasing thermal stability. With increasing Al content, the crystallization temperatures tend to increase gradually. Even when the Al content doped into the framework was increased to 15 mol %, a well‐ordered mesoporous structure was obtained, and the mesostructural ordering was still maintained after calcination at 550 °C. During the calcination process, large uniaxial shrinkage occurred along the direction perpendicular to the substrate with retention of the horizontal mesoscale periodicity, whereby vertically oriented nanopillars were formed in the film. The resulting vertical porosity was successfully exploited to fabricate a high‐speed and high‐quality passive‐matrix electrochromic display by using a leuco dye. The vertical nanospace in the films can effectively prevent drifting of the leuco dye. 相似文献
995.
Zu-Quan Hu He-Ping Li Jing-Bo Zhang Tao Huang Jin-Long Liu Sheng Xue Ai-Bo Wu Yu-Cai Liao 《Analytica chimica acta》2013
Fusarium and its poisonous mycotoxins are distributed worldwide and are of particular interest in agriculture and food safety. A simple analytical method to detect pathogens is essential for forecasting diseases and controlling mycotoxins. This article describes a proposed method for convenient and sensitive detection of Fusarium pathogens that uses the fusion of single-chain variable fragment (scFv) and alkaline phosphatase (AP). A highly reactive scFv antibody specific to soluble cell wall-bound proteins (SCWPs) of F. verticillioides was selected from an immunized chicken phagemid library by phage display. The antibody was verified to bind on the surface of ungerminated conidiospores and mycelia of F. verticillioides. The scFv–AP fusion was constructed, and soluble expression in bacteria was confirmed. Both the antibody properties and enzymatic activity were retained, and the antigen-binding capacity of the fusion was enhanced by the addition of a linker. Surface plasmon resonance measurements confirmed that the fusion displayed 4-fold higher affinity compared with the fusion's parental scFv antibody. Immunoblot analyses showed that the fusion had good binding capacity to the components from SCWPs of F. verticillioides, and enzyme-linked immunosorbent assays revealed that the detection limit of the fungus was below 10−2 μg mL−1, superior to the scFv antibody. The fusion protein was able to detect fungal concentrations as low as 10−3 mg g−1 of maize grains in both naturally and artificially contaminated samples. Thus, the fusion can be applied in rapid and simple diagnosis of Fusarium contamination in field and stored grain or in food. 相似文献
996.
997.
The diffraction properties of reflection volume holographic gratings are studied when the gratings are illuminated by an ultrashort beam with arbitrary temporal profiles. The modified Kogelnik's theory of coupled waves is used. Simple analytical expressions for spectral and temporal distribution of the transmitted and diffracted are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the reflection volume grating on the temporal profiles of the input ultrashort pulse are investigated. Study shows that the bandwidth of the reflection volume holographic gratings varies with the grating parameters more slowly than the transmitting volume holographic gratings. For three different temporal profiles, numerical results about diffraction properties of the reflection volume holographic gratings are given and compared with the transmitting volume holographic gratings. 相似文献
998.
We report a method for fabricating a cholesteric liquid crystal capsule display wherein the red, green, and blue capsules are separated in the subpixels with a width of 200 μm. The mixture of a photo-isomerizable chiral dopant and a nematic liquid crystal was encapsulated by an emulsification technique, and then directly printed onto a plastic substrate. A UV light with different amount of energy was exposed through a shadow photomask, and consequently, the red, green, and blue colors were separately induced in each subpixels zone. 相似文献
999.
根据光在界面上反射时产生半波损失的条件,设计了一种利用激光产生的非定域干涉条纹来大幅面展示半波损失现象的实验装置。该实验装置思路清晰、操作简便、画面显示效果好。 相似文献
1000.
Anna Sobolewska Andrzej Miniewicz Eugenia Grabiec Danuta Sek 《Central European Journal of Chemistry》2006,4(2):266-284
A group of 22 polymers have been synthesized to test their suitability for recording holographic gratings. Polyamides, polyimides,
polyesters and their combinations were functionalized with pendant azobenzene groups containing single or double N=N. The
polymers were studied using a standard degenerate two-wave mixing technique, which enables measurement of light-induced periodic
modification of polymer refractive index and absorption coefficient by analysis of the diffracted light. Two qualitatively
different configurations of the holographic polarization recording were used, s-s and s-p. The relationship between structural properties of polymer matrix and azobenzene groups and the holographic grating recording
kinetics and light diffraction efficiency was investigated. 相似文献