Study of the conditions of formation of spectral and absorbption multidimensional images of motor fuels and liquid mineral technical oils

Effect of experimental conditions on the possibility of formation of multidimensional images of motor fuels and liquid mineral technical oils used for the classification and identification of these samples by the method of pattern recognition is studied. Transmission spectra are considered as primary images of the studied samples. Multidimensional statistical analysis of the results of spectroscopic measurements is performed by principal component analysis. A noticeable increase in the separation of spectroscopic images on the statistical plane in the optimization of the spectral range of the primary image and the thickness of the absorbing layer is shown.     

Parameterization of electrostatic interactions for molecular dynamics simulations of heterocyclic polymers

The paper focuses on the problem of electrostatic interactions in molecular dynamics simulations of thermal properties of heterocyclic polymers. The study focuses on three thermoplastic polyimides synthesized on the basis of 1,3‐bis‐(3′,4‐dicarboxyphenoxy)benzene (dianhydride R) and three diamines: 4,4′‐bis‐(4″‐aminophenoxy) diphenylsulfone (diamine BAPS), 4,4′‐bis‐(4″‐aminophenoxy) biphenyl (diamine BAPB), and 4,4′‐bis‐(4''‐aminophenoxy) diphenyloxide (diamine BAPO). In the molecular dynamics simulations these polyimides were described by the Gromos53a5 force field. To parameterize the electrostatic interactions four methods of calculating the partial atomic charges were chosen: B3LYP/6–31G*(Mulliken), AM1(Mulliken), HF/6–31G*(Mulliken), and HF/6–31G*(ChelpG). As our parameterization is targeted to reproduce thermal properties of the thermoplastic polyimides, the choice of proper partial charges was finalized on a basis of the closest match between computational and experimental data for the thermal expansion coefficients of the polyimides below glass transition temperatures. Our finding clearly show that the best agreement with experimental data is achieved with the Mulliken partial atomic charges calculated by the Hartree‐Fock method with 6–31G* basis set. Furthermore, in addition to the thermal expansion coefficients this set of partial atomic charges predicts an experimentally observed relationship between glass transition temperatures of the three polyimides under study: . A mechanism behind the change in thermal properties upon the change in the chemical structure in considered polyimides may be related to an additional spatial ordering of sulfone groups due to dipole‐dipole interactions. Overall, the modified force‐field is proved to be suitable for accurate prediction of thermal properties of thermoplastic polyimides and can serve as a basis for building up atomistic theoretical models for describing other heterocyclic polymers in bulk. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 912–923     

Unprecedented acid-catalyzed Wurtz-type coupling of meso-bromoindodicarbocyanine dyes

meso-Bromosubstituted indodicarbocyanine dyes produce dimeric molecules, together with the debrominated species, under acid catalysis. The relationship between the dimerization and hydrodebromination routes depends on the aryl substitution of the dyes. A possible reaction mechanism is also proposed.     

Kinetic Theory of Boson Gas

Theoretical and Mathematical Physics - We construct a quantum kinetic theory of a weakly interacting critical boson gas using the expectation values of products of Heisenberg field operators in the...     

Laser-induced continuous generation of Ni nanoparticles for organic synthesis

Russian Chemical Bulletin - The possibilities of laser-induced liquid phase chemical deposition (LCLD) of metal for continuous generation of nickel nanoparticles, the sizes of which allow their use...     

The thermal behavior of double complex compounds with the cation [Cr(ur)6]3+ in a reducing atmosphere

Journal of Thermal Analysis and Calorimetry - The thermal behavior of double complex compounds (DCC) [Cr(ur)6][Co(CN)6]·4H2O (I), [Cr(ur)6][Co(C2O4)3]·3.5H2O (II),...     

Computer simulation of the structure and raman spectra of GaAs polytypes

The structure, energy of formation, and Raman spectra of several polytypes (3C, 2H, 4H, and 8H) of gallium arsenide GaAs have been investigated using quantum mechanical calculations based on the local density functional theory. It has been found that the energy of the formation of hexagonal polytypes increases with an increase in the length of the periodicity and approaches the value corresponding to the ground state, i.e., to the structure of the 3C polytype. It has been shown that the calculated frequencies of normal vibrations of different polytypes are consistent, with good accuracy (±6 cm^?1), with the scheme of folding of the phonon branches. In the calculated Raman spectra of the polytypes, there are new lines (forbidden in the spectrum of the 3C polytype) which can serve as characteristic lines of other polytypes. Similar lines can be found in the Raman spectra of GaAs nanowhiskers. This result has opened up new prospects for the application of Raman spectroscopy to the characterization of the structure of these nano-objects.     

57Fe Mössbauer study of a secondary phase in FeSe1−x with a large quadrupole splitting

We have studied the hyperfine interactions in samples belonging to the Fe-Se system. Several samples with various concentrations of selenium were synthesized and investigated. The objective was to find synthesis conditions increasing the concentration of a secondary Fe-Se phase with a rather large quadrupole splitting of ~1.7 mm/s. At T _m ≈ 104 K this secondary phase undergoes a magnetic ordering.     

Low-temperature heat capacity and thermodynamic properties of layered perovskite-like oxides NaNdTiO4 and Na2Nd2Ti3O10

We report the results of the study of thermodynamic properties for layered perovskite-like oxides NaNdTiO₄ and Na₂Nd₂Ti₃O₁₀. Isobaric heat capacity of the compounds was measured in an adiabatic calorimeter in the range of 5–340 K. Low-temperature heat capacity anomaly was observed in the heat capacity curve of Na₂Nd₂Ti₃O₁₀. Standard thermodynamic properties of the oxides were evaluated from the experimental heat capacity temperature dependencies. Finally, on the basis of the experimental data obtained in this work, we tested applicability of the additivity principle for prediction of thermodynamic properties for layered compounds built of fragments of various structural types.