Formation of 2D spherulites in Langmuir films of amphiphilic T-shaped liquid crystals

Langmuir films of facial T-shaped amphiphilic liquid crystals were studied at the air-water interface. The liquid crystals were composed of three incompatible segments: a central rigid rodlike p-terphenyl (TP) group, two flexible hydrophobic n-alkyl terminal chains of identical length linked through ether bonds, and one hydrophilic lateral chain of three ethylene oxide units with a carboxyl end group. In order to determine the influence of the alkyl chain length on the characteristics of condensed films three TPs having n-alkyl chains with eight (TP8/3), ten (TP10/3) or 16 (TP16/3) carbon atoms were investigated. Surface pressure - mean molecular area isotherms revealed clear differences. TP8/3 and TP10/3 exhibit an extended plateau region where a phase transition from monolayer to multilayer takes place. On the other hand, the TP16/3 isotherm showed a distinct maximum ('spike') corresponding to a surprising surface crystallization process which is reported for the first time for a Langmuir film of a liquid crystal. Brewster angle microscopy clearly confirmed these differences: TP8/3 and TP10/3 formed circular domains with liquid crystalline order, while TP16/3 formed well-defined two-dimensional polycrystalline spherulites which are fractured after further compression. The film thickness determined by X-ray reflectivity measurements correlated with a multilayer formation for TP10/3. The morphology of Langmuir-Blodgett (LB) films transferred onto silicon wafers and studied by atomic force microscopy also confirmed the striking different behavior (multilayer formation vs. 2D crystallization) of the TPs under investigation.     

Electrochemical behavior of tungsten-containing nanocomposite with siloxane matrix

Electrochemical properties of a thin-film nanocomposite “silicon-carbon matrix-tungsten carbide” deposited onto pyroceramics (“sitall”) substrate are studied by potentiodynamic curves and electrochemical impedance spectroscopy. Transfer coefficients in model redox system [Fe(CN)₆]^3?/4? are measured. With the decreasing of the films’ electrical resistance, their experiment behavior gradually changed from that of “poor conductor” till nearly metal-like one. In particular, the electrode differential capacitance increases, which is explained by the increase in the number of conducting metal-containing clusters in the film bulk and at the film/electrolyte solution interface. Some specific features of the complex-plane plots of impedance spectra are tentatively explained by the adsorption at the nanocomposite surface elements.     

Low-Light Trees, and Tight Lower Bounds for Euclidean Spanners

We show that for every n-point metric space M and positive integer k, there exists a spanning tree T with unweighted diameter O(k) and weight w(T)=O(k⋅n ^1/k )⋅w(MST(M)), and a spanning tree T′ with weight w(T′)=O(k)⋅w(MST(M)) and unweighted diameter O(k⋅n ^1/k ). These trees also achieve an optimal maximum degree. Furthermore, we demonstrate that these trees can be constructed efficiently.     

Classification of Symmetric Circulants of Degree 4

4-tegular symmetric circulant digraphs and graphs are classified in this paper.     

Turbulent Electrochemical Noise: A Theoretical Analysis in the Frequency–Potential Coordinates

Spectral density of random alternating current, which is induced by turbulent pulsations of electrolyte velocity in a cell, is theoretically analyzed within the Ershler–Randles charge transfer model in the Nernst diffusion layer approximation. The effect of electrode potential on the spectral current density is analyzed at various frequencies of hydrodynamic pulsations.     

4度对称循环图的分类(英文)

本文刻划了所有4度有向和无内循环图．     

On the classification of nonlinear control systems

We study equivalence of nonlinear control systems and obtain a classification for some types of affine control systems.