Raman spectra of various polymorphs of isotactic polypropylene

The Raman spectra of the α, γ, and smectic modifications of isotactic polypropylene (PP) are studied. The most significant spectral differences are observed in the frequency range around 2960 cm⁻¹ for the spectral doublet assigned to the asymmetric stretching vibrations of the CH₃ groups and in the frequency range around 800 cm⁻¹, which is used for analysis of the phase composition of isotactic PP. It is demonstrated that the peak positions and relative intensities of the doublet assigned to the asymmetric stretching vibrations of the CH₃ groups can be used to identify the polymorph modifications of isotactic PP.     

Geological and economic characteristics of the Russian mineral-resource base

Characteristics of the Russian mineral-resource base and its development under the current market conditions are given on the basis of the analysis of deposits accounting for 90% of reserves and extraction of 65 types of mineral resources. Statistical data on reserves of the deposits included into the State Register and the demanded component of the mineral-resource base are presented. The defining role of major deposits in the mineral-resource base development is demonstrated. The group of highly liquid minerals forming the domestic mineral-resource base is described. The reserves of these mineral raw materials are essential and sufficient to satisfy both the domestic needs and a considerable export component.     

Influence of chemical structure and chain length on conducting properties of dielectric polymers in metal/polymer/metal structures

The influence of weight-average molecular mass M _w on the maximal width of a conducting layer h _max of polysterene, polymethylmethacrylate, and polyamidine films was investigated. It was shown that h _max increases in proportion to M _w ^S for all investigated polymers. It points to the fact that the h _max value is defined by the macromolecular coil size.     

Phosphorylation of Dialkylaminomethylated Calix[4]-Resorcinarenes with Some P(III) and P(IV) Derivatives

Abstract

The phosphorylation of dialkylaminomethylated calix[4]resorcinarenes with P(m)-amides and P(TV)chlorides under various conditions results in the formation of different structures with phosphorus containing fragments fixed on the cavity rim. Hydrophosphoryl compounds based on dialkylaminomethylated calix[4]resorcinarenes have been synthesized and some of their properties investigated.     

Programming of temperature and flow rate of carrier gas in work with polycapillary columns for gas-liquid chromatography

Methods of programming temperature and flow rate of carrier gas for to reducing the time of analyte separation on polycapillary columns (PCC) are compared. As was shown, the programming of temperature is accompanied by a change of peak shape, associated with the irregular heating of PCC capillaries. The programming of carrier gas flow rate does not distort the shape of chromatography peaks and does not require long time to return the system to the starting conditions.     

Raman structural study of random copolymers of ethylene with 1-hexene

Ethylene/1-hexene copolymers, which differ significantly in 1-hexene content (from 1.9 to 37.0 mol %), are studied by Raman spectroscopy. The copolymer spectra are compared with the Raman spectra of polyethylene at elevated temperatures. We have found that the phase and conformational order of the copolymer macromolecules depends strongly on the 1-hexene content. In particular, an increase in 1-hexene content leads to a decrease in content of the PE-like orthorhombic crystalline phase and in content of trans-conformers in the amorphous phase. The Raman signature at about 800 cm^?1 provides information about the end conformers for the ethylene/1-hexene copolymers with high 1-hexene content.     

Cyclic Phosphorochloridites,Phosphorochloridates, and Phosphorochloridothioates Based on Calix[4]resorcinolarenes

Phosphorylation of calix[4]resorcinolarenes with PCl₃ yields cyclic phosphorochloridites. Cavitands containing cyclic phosphorochloridite fragments in the upper rim are readily oxidized with SO₂Cl₂ to the corresponding phosphorochloridates and take up four equivalents of sulfur on heating to form cyclic phosphorochloridothioates.     

Temperature behavior of the order parameter in Pb5Ge3O11

The temperature dependence of the spontaneous polarization in the Pb₅Ge₃O₁₁ lead germanate (PGO) is experimentally investigated using optical, magnetic resonance, and conventional electrical measurements. The deviations from the temperature dependence typical of second-order phase transitions at temperatures below 420 K are explained in terms of incomplete polarization switching and polarization induced by a residual depolarization field. The low-temperature anomalies are interpreted without consideration of additional structural transformations. The internal bias field is determined from the experimental temperature dependence of the perfect polarization of PGO single crystals in an electric field.     

Properties of the Likelihood Ratio for Counting Processes in the Problem of Estimation of Unknown Parameters

We obtain an asymptotic decomposition of the logarithm of the likelihood ratio for counting processes in the case of similar hypotheses. We establish the properties of the normalized likelihood ratio in the problem of estimation of an unknown parameter.     

Modification of the domain wall structure and generation of submicron magnetic formations by local optical irradiation

Experimental and theoretical investigations are made of the generation of vertical Bloch lines in a magnetic iron garnet film exposed to pulsed optical radiation. High-speed photography and anisotropic dark-field microscopy are used to study characteristic features of the generation of Bloch lines and domain structure relaxation processes after the local action of a laser pulse. Optimum optical irradiation parameters to ensure the controlled generation of Bloch lines are established. A theoretical model is developed which links the generation of Bloch lines to the migration of domain walls induced by local changes in the distribution of the degaussing fields caused by a reduction in magnetization with temperature at the optical radiation focusing point. The experimental results indicate that the controlled formation of magnetic structures smaller than or of the order of 0.1 μm by local optical irradiation is quite feasible.