The SmCPA phase in five‐ring bent‐core compounds derived from 5‐methoxyisophthalic acid

The synthesis and mesophase characterization of a homologous series of five‐ring bent‐core compounds derived from 5‐methoxyisophthalic acid are described. Most of the compounds exhibit a polar antiferroelectric smectic C phase. Replacement of the terminal n‐alkoxy chains by n‐alkyl carboxylate groups, not only destabilizes the formation of mesophases but induces a calamitic mesophase. However, extension of the arms of the bent‐core molecule by a phenyl moiety stabilizes the switchable phase. The mesophases were investigated using a combination of polarizing optical microscopy, differential scanning calorimetry, X‐ray diffraction and electro‐optical methods.     

The SmCPA phase in five-ring bent-core compounds derived from 5-methoxyisophthalic acid

The synthesis and mesophase characterization of a homologous series of five-ring bent-core compounds derived from 5-methoxyisophthalic acid are described. Most of the compounds exhibit a polar antiferroelectric smectic C phase. Replacement of the terminal n-alkoxy chains by n-alkyl carboxylate groups, not only destabilizes the formation of mesophases but induces a calamitic mesophase. However, extension of the arms of the bent-core molecule by a phenyl moiety stabilizes the switchable phase. The mesophases were investigated using a combination of polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical methods.     

Oxidative decolorization of indigo caramine dye with chloramine-T catalyzed by cobalt(II)

Decolorization of indigo caramine dye by oxidation process using chloramine-T as oxidant and Co(II) as catalyst in acidic buffer media, pH 5.8 has been kinetically studied at 300 K. Decolorization of indigo caramine dye was followed spectrophotometrically. Decolorization and oxidation led to a decrease in Chemical Oxygen Demand of the dye. The Co(II)-catalyzed reaction shows first-order dependence of the rate on chloramine-T and indigo caramine concentrations. It also shows fractional order dependence on [Co(II)] and [H⁺]. Addition of halide ions or reduction product of chloramine-T toluenesulfonamide, and variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. Activation parameters are evaluated from the Arrhenius plot, and a mechanism is proposed for the reaction.     

Design of sampled data state estimator for Markovian jumping neural networks with leakage time-varying delays and discontinuous Lyapunov functional approach

This paper is concerned with the sampled-data state estimation problem for neural networks with both Markovian jumping parameters and leakage time-varying delays. Instead of the continuous measurement, the sampled measurement is used to estimate the neuron states, and a sampled-data estimator is constructed. In order to make full use of the sawtooth structure characteristic of the sampling input delay, a discontinuous Lyapunov functional is proposed based on the extended Wirtinger inequality. A less conservative delay dependent stability criterion is derived via constructing a new triple-integral Lyapunov–Krasovskii functional and the famous Jenson integral inequality. Based on the Lyapunov–Krasovskii functional approach, a state estimator of the considered neural networks has been achieved by solving some linear matrix inequalities, which can be easily facilitated by using the standard numerical software. Finally, two numerical examples are provided to show the effectiveness of the proposed methods.     

Dependence of Self-Assembled Peptide Hydrogel Network Structure on Local Fibril Nanostructure

Physically cross-linked, fibrillar hydrogel networks are formed by the self-assembly of β-hairpin peptide molecules with varying degrees of strand asymmetry. The peptide registry in the self-assembled state can be used as a design element to generate fibrils with twisting, nontwisting, or laminated morphology. The mass density of the networks varies significantly, and can be directly related to the local fibrillar morphology as evidenced by small angle neutron scattering (SANS) and in situ substantiation using cryogenic transmission electron microscopy (cryo-TEM) under identical concentrations and conditions. Similarly, the density of the network is dependent on changes in the peptide concentration. Bulk rheological properties of the hydrogels can be correlated to the fibrillar nanostructure, with the stiffer, laminated fibrils forming networks with a higher G' as compared to the flexible, singular fibrillar networks.     

Chemical constituents of a marine soft coral of the genus Lobophytum

Chemical investigations on the marine soft coral Lobophytum sp., collected from the Andaman and Nicobar Islands, yielded two new acyl glycerol monoalkyl ethers along with two known compounds of this series (1a-d), and a new ceramide (4a). The structures of the new and known compounds were elucidated on the basis of extensive spectroscopic studies and chemical reactions.     

Possible Influence of Layer Deformation and Chiral Segregation on Dielectric Modes in the Dark Conglomerate Liquid Crystal

Dielectric spectroscopy is used to investigate the structure, molecular dynamics, and relaxation phenomena in electric‐field‐induced switchable dark conglomerate (DC) phases in a bent‐core liquid crystal. The DC phases are obtained by applying a high‐frequency ac electric field in the B_1rev phase or by cooling under a dc or an ac field from the isotropic phase. Although the DC phases exhibit good electro‐optic switching properties, the dielectric parameters are different from those observed in typical lamellar SmCP phases and similar to those obtained in a non‐switchable DC phase. We therefore propose that the dielectric response and reduced intensity of the relaxation modes may be a general feature in DC phases and may owe its origin to the deformed layer structure in which certain molecular motions are impeded. Further, we find that in the field‐induced DC phases derived from the isotropic phase, the dielectric modes are affected by chiral segregation promoted by the applied field.