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991.
992.
ABSTRACTWe have studied the properties of biaxial particles interacting via an anisotropic pair potential, involving second-rank quadrupolar and third-rank octupolar coupling terms, using Monte Carlo simulation. The particles occupy the sites of a 2D square lattice and the interactions are restricted to nearest neighbours. The system exhibits spontaneous chiral symmetry breaking from an isotropic phase to a chiral modulated nematic phase, composed of ambidextrous chiral domains. When twofold axes of quadrupolar and octupolar tensors coincide this modulated phase appears to be the ambidextrous cholesteric phase with pitch comparable to a few lattice spacings. The associated phase transition is first order. 相似文献
993.
Maja Trček George Cordoyiannis Brigita Rožič Vassilios Tzitzios George Nounesis Samo Kralj 《Liquid crystals》2017,44(10):1575-1581
We report on the stabilisation of the liquid-crystalline, twist-grain boundary A (TGBA) phase in mixtures of a chiral liquid crystal and surface-functionalised spherical Au nanoparticles (NPs) of 10 nm diameter. The results, obtained by calorimetric, optical, small-angle X-ray and plasmon resonance measurements, demonstrate that a TGBA phase, which is metastable for the pure liquid crystal host, can be effectively stabilised for a 3 K range in the presence of NPs. Moreover, the role of NPs size on the TGBA stabilisation is briefly discussed. 相似文献
994.
ABSTRACTA homologous series of new chiral liquid crystal compounds, MnBEB (n = 4–10), was prepared by covalently linking a chiral (–)-menthyl with biphenyl-benzoate via a dicarboxylic spacer of varying length and parity. A combination of analysis methods, such as FT-IR, 1H NMR spectra, differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction was carried out to systematically investigate their phase structures and phase transition behaviours. The length and parity of the flexible spacers has a profound influence on the Tm and Tc and a modest odd-even effect is observed for the chiral liquid crystal compounds MnBEB. Only compound M4BEB developed an N* phase with selectively reflection on heating and a blue phase on cooling process. In addition, increasing the length of the flexible spacers tends to narrow the temperature range of the N* phase and widen the smectic phase, moreover, the pitch becomes longer with the spacer increases. 相似文献
995.
We prepared some taper-shaped liquid-crystalline trimers in which two phenylpyrimidine units and a 1,4-diphenyl-2,3-difluorobenzene unit are connected to 2,4-dihdroxy benzoic acid via flexible spacers. We then investigated their liquid-crystalline properties using polarised optical microscopy, differential scanning microscopy and X-ray diffraction. 6-[4–(5-Octylpyrimidin-2-yl)phenyloxy]hexyl 2-{7-{4-[4–(4-hexylphenyl)-2,3-difluorophenyl]phenyloxy}heptanoyloxy}-4-{6-[4–(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy}benzoate (1) was found to exhibit a phase sequence of isotropic liquid – nematic – intercalated smectic A – intercalated anticlinic smectic C – modulated smectic C. The structure–property relation in the taper-shaped trimers reveals that the modulated phase is induced by competition between an intercalated structure stabilised by dipole–dipole interaction and a monolayer structure by packing entropy effects. Conformational change of compound 1 induced by intermolecular interactions plays an important role in the phase transition behaviour. 相似文献
996.
Xiaotian Li Baoluo Wan Tong Yu Linxi Wang Lianqi Hao Maowen Guo 《Biomedical chromatography : BMC》2013,27(12):1595-1602
A reversed‐phase ion pair chromatography method with liquid–liquid extraction analytical method was developed and validated for the determination of antazoline hydrochloride in plasma and excreta of rat. The aim of our study was to characterize the preclinical pharmacokinetics and excretion profiles of antazoline hydrochloride in rats after intravenous injection at the dose of 10 mg/kg. Plasma and excreta samples were extracted with ethyl acetate, and phenacetin was used as the internal standard. The result showed that the method is suitable for the quantification of antazoline hydrochloride in plasma and excreta samples. Analysis of accuracy (90.89–112.33%), imprecision (<7.1%) and recovery (>82.5%) showed adequate values. After a single intravenous administration at 10 mg/kg to rats, plasma concentration profile showed a relative fast elimination proceeding with a terminal elimination half‐life of 3.53 h. Approximately 61.8 and 14.2% of the administered dose were recovered in urine and bile after 72 and 24 h post‐dosing respectively; 5.9% of the administered dose was recovered in feces after 72 h post‐dosing. The above results show that the major elimination route is urinary excretion. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
997.
The problem of chemical order of polyamide-hydrazides prepared from terephthaloyl chloride with an unsymmetrical monomer, p-aminobenzhydrazide, is discussed. An NMR method for identifying the molecular structure of species formed in the early stages of poly condensation has enabled the course of a polymerization to be followed during this time and the final degree of order to be predicted qualitatively. These studies have provided a demonstration that the structure of these polymers can be controlled to a significant degree by appropriate variations in experimental conditions. But even under the most adverse conditions usually employed, poly amide-hydrazides are found to be at least “partially ordered” copolymers. The techniques developed for this study may find application in the study of other polymer forming reactions with monomers having two functional groups with dissimilar reactivities. 相似文献
998.
Interacting Boson Model-2(IBM-2)is used to determine the Hamiltonian for Er nuclei.Fit values of parameters are used to construct the Hamiltonian,energy levels and electromagnetic transitions(B(E2),B(M1))multipole mixing ratios(δ(E2/M1))for some even-even Er nuclei and monopole transition probability are estimated.New ideas are used for counting bosons number at N=64 and results are compared with previous works. 相似文献
999.
1000.
Optimization of solid phase dispersive field‐assisted ultrasonication for the extraction of auramine O and crystal violet dyes using central composite design 下载免费PDF全文
Faezeh Pourebrahim Mehrorang Ghaedi Kheibar Dashtian Shadi Kheirandish Alireza Goudarzi 《应用有机金属化学》2018,32(3)
Simultaneous preconcentration and determination of auramine o (AO) and crystal violet (CV) dyes from aqueous solution was conducted by ultrasound assisted (dispersive) solid phase microextraction (UASPME) based on SnO2/SnS composite loaded activated carbon (SnO2/SnS‐NCs‐AC). The prepared of SnO2/SnS‐NCs‐AC was characterized by FESEM and XRD analysis. Main and interaction influences of operational parameters such as pH, sonication time, amounts of sorbent, and type of eluent on extraction efficiency were investigated by central composite design and optimized with desirability function approach (DFA). ANOVA was conducted and shows that optimized values were found at 15.33 min sonication time, 0.019 g SnO2/SnS‐NCs‐AC mass, pH 5.46 and among different solvents, dimethyl formamide was selected as an efficient eluent. Under this conditions recoverees percentage were obtained 82.85% and 86.70% for AO and CV, respectively. Based on F‐test under ANOVA all main effect and interaction effect of understudy parameters has the significant effect on the responses. At optimum conditions, limit of detection (0.0015 and 0.001 mg/l), limit of quantitation (0.4 and 0.4 mg/l), limit of linearity (9.0 and 9.0 mg/l), enrichment factor (33.48 and 83.71) and percent relative standard deviation (3.44 and 4.20) were found to be for auramine o and crystal violet dyes, respectively. Finally, the method was successfully applied for the preconcentration and determination of AO and CV in water samples and ER% of 89.0‐97.0 and 96.2–98.0% as acceptable range were found to be for AO and CV samples, respectively. 相似文献