A Method for Detecting and Localizing Inhomogeneities in Plates Using Lamb Waves

Acoustical Physics - The paper presents the results from a study of the interaction of Lamb waves with inhomogeneities in composite plates. It was found that waves of this type are diffracted by...     

On Diffraction of a Sawtooth Nonlinear Wave by a Narrow Circular Aperture in a Screen

Acoustical Physics - The paper presents the experimental and theoretical studies of diffraction effects in intense acoustic beams diffracted by a narrow circular aperture in a screen. The...     

Correlation between thermodynamic stability of zinc(II)tetraphenylporphyrine complexes with neutral molecules and physicochemical properties of the coordinated ligands

The heats of interactions of zinc(II)tetraphenylporphyrine with 30 types of neutral molecules in benzene and carbon tetrachloride were measured using the calorimetric titration method. The thermodynamic characteristics of complex formation were calculated. The satisfactory multiparameter correlation of thermodynamic stability of the molecular complexes formed with physicochemical properties of the neutral molecules (electron pair donor ability, volume, electronic and orientational polarization) was obtained.     

Crystal solvates of tetrakis(3,5-di-t-butylphenyl)-porphyrinates Mn(III), Ni(II) and Zn(II) with pyridine

The crystal solvates of complexes MP (P is the dianion of tetrakis(3,5-di-t-butylphenyl)porphin, M=Ni(II), Zn(II)) and (Ac)MnP with pyridine have been obtained by isothermal evaporation of corresponding solutions at 35°C. The formation and the decomposition temperatures of crystal solvates and enthalpies of evaporation pyridine molecules from those crystal solvates were received using thermogravimetric method. In addition to that, an influence of the type of metal on the compositions, the energetic and thermal stabilities of the received complexes were analyzed.     

The High Sensitive and Selective “Off-On” Fluorescent Zn2+ Sensor Based on the Bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)methane

A fluorescent chemosensor based on the 3,3′-bis(dipyrrin) bearing two chromophoric dipyrrin units was synthesized, which showed a strongly enhanced fluorescent intensity in the presence of Zn²⁺ ions and a high selectivity toward Zn²⁺ ions over a wide range of tested metal ions in organic solvents.     

Chitosans: Thermochemical Study

The physical and phase transitions of a series of chitosans differing in molecular weight and deacetylation degree have been revealed by means of differential scanning calorimetry, thermogravimetry, and mass spectrometry. The temperature ranges corresponding to the dehydration and thermolysis of the considered polymers have been determined. The devitrification temperature of the polymers has been recorded, and its two-parametric regression on the chitosans molecular weight and deacetylation degree has been found. The molecular weight of the polymer revealed stronger effect on the devitrification temperature in comparison with the deacetylation degree.     

Thermal and spectral analyses of complexes of zinc(II)tetra-tertbutylphthalocyanine with amines

Spectral and thermochemical studies of complexes of zinc(II)tetra-tertbutylphthalocyanine (Zn(t-Bu)₄Pc) with some amines have been carried out. Spectral effects of the complex formation of the metallophthalocyanine with amines have been established. It has been found that an ability of Zn(t-Bu)₄Pc to coordinate amines depends on both their nature and conditions of preparation. Similarity of the crystal structures of biligand and monoligand of Zn(t-Bu)₄Pc complexes to individual β- and α-polymorphs of Zn(t-Bu)₄Pc, respectively is proved by IR spectroscopy and X-ray diffraction method.     

Features of сhitosan interaction with copper(II) and cobalt(II) tetrasulfophthalocyanines

The interaction of chitosan with copper(II) and cobalt(II) tetrasulfophthalocyanines is studied by spectral methods. The main parameters of binding of chitosan to anionic metal phthalocyanines are determined by Scatchard analysis. It is found that the formation of the polymer complex is considerably contributed by donor?acceptor interactions between the coordinately unsaturated metal phthalocyanine and chitosan amino groups. Сhitosan reacts with a monomeric cobalt(II) tetrasulfophthalocyanine, whereas copper(II) tetrasulfophthalocyanine in its complex with chitosan remains in the dimeric state. The reaction centers responsible for the Cu(SO₃H)₄Pc)₂–chitosan and Co(SO₃H)₄Pc–chitosan complexes are revealed by means of IR spectroscopy.     

Kinetics of Alkylated Biladiene-a,c Deprotonation

The kinetics of deprotonation of 1,3,7,13,17,19-hexamethyl-2,8,12,18-tetrabutylbiladiene-a,c dyhydrobromide on treatment with nucleophilic reagents (pyridine, dimethylformamide, dimethyl sulfoxide) in carbon tetrachloride was measured by electron absorption spectroscopy in the temperature range of 293.15–303.15 K. The effects of the reactant concentrations, the temperature, and the electron-donor properties of the nucleophilic reagent on the kinetics of deprotonation of biladiene-a,c as the salt with HBr are discussed.