Reaction of 4-aryl-4-oxobutane-1,1,2,2-tetracarbonitriles with hydrochloric acid

Russian Journal of Organic Chemistry -     

Decidability of the interpolation problem and of related properties in tabular logics

Propositional modal and positive logics are considered as well as extensions of Johansson’s minimal logic. It is proved that basic versions of the interpolation property and of the Beth definability property, and also the Hallden property, are decidable on the class of tabular logics, i.e., logics given by finitely many finite algebras. Algorithms are described for constructing counterexamples to each of the properties mentioned in handling cases where the logic under consideration does not possess the required property.     

Electron paramagnetic resonance and optical spectroscopy of K3Na(CrO4)2 ferroelastics activated by MnO 4 2− molecular impurity ions

Crystals of a proper ferroelastic K₃Na(CrO₄)₂ containing molecular impurity ions MnO ₄ ^2? are studied using electron paramagnetic resonance (EPR) and optical spectroscopy. The EPR spectrum of the Mn⁶⁺ ion contained in the molecular impurity ion MnO ₄ ^2? is identified at low temperatures (T ≤ 20 K). The intensity of this spectrum decreases unusually fast as the temperature increases. A broad IR luminescence band with a vibronic structure well resolved at a temperature of 8 K is revealed. Theoretical treatment of the Mn⁶⁺ ion involved in the molecular impurity ions MnO ₄ ^2? of the K₃Na(CrO₄)₂ ferroelastic crystal suggests that an important role in this case is played by the pseudo-Jahn-Teller. The pseudo-Jahn-Teller effect offers an explanation for the appearance of a fine structure in the vibronic replicas in the luminescence spectrum, on the one hand, and accounts for the fast decrease in the intensity of the EPR spectrum of K₃Na(CrO₄)₂: MnO ₄ ^2? with increasing temperature, on the other.     

Structure and phase composition of thin a-C:H films modified by Ag and Ti

The structure and phase composition of thin a-C:H and a-C:H〈M〉 films (M = Ag, Ti, or Ag + Ti) have been studied by Raman and X-ray photoelectron spectroscopy. The a-C:H〈M〉 films were prepared by ion-plasma magnetron sputtering of a combined target of graphite and metal in an Ar–CH₄ gas mixture. The Raman spectra of these films indicate that their structure is amorphous. The a-C:H〈Ag + Ti〉 films have a more graphitized structure in comparison with pure a-C:H films and films containing only one metal. It is established that carbon in the a-C:H〈Ag + Ti〉 films is in the sp ², sp ³, and C=O states, which are characteristic of the a-C:H, a-C:H〈Ag〉, and a-C:H〈Ti〉 films. In addition, there are also ether (–C–O–C–) or epoxy (?C?O–) carbon groups in the a-C:H〈Ag + Ti〉 films. It has been revealed that silver atoms in the a-C:H〈Ag〉 and a-C:H〈Ag + Ti〉 films form no chemical bonds with carbon, oxygen, and titanium. Titanium in the a-C:H〈Ti〉 and a-C:H〈Ag + Ti〉 films exists in the form of titanium IV oxide (TiO₂).     

Magnetization reversal processes in layered high-temperature superconductors with ferromagnetic impurities

The self-consistent interaction of a vortex system of a high-temperature superconductor and ferromagnetic impurities, including single impurities and their clusters, has been considered in the model of a layered high-temperature superconductor. For different temperatures and concentrations of ferromagnetic impurities, the magnetization reversal loops have been calculated by the Monte Carlo method taking into account an ensemble of ferromagnetic particles with different orientations of their easy magnetization axes with respect to the direction of an external magnetic field and for different magnetic anisotropy energies. It has been demonstrated that there is a nonlinear interaction of the high-temperature superconductor with ferromagnetic impurities, in which the initially thermodynamically reversible character of the magnetization reversal of the ferromagnetic ensemble can become irreversible. For a periodic lattice of clusters of ferromagnetic impurities, the magnetization curves of the high-temperature superconductor have been calculated for different sizes and configurations of the clusters. It has been revealed that, when extended defects are oriented parallel to the direction of the entrance of vortices in the sample, the length of the defects does not affect the remanent magnetization. It has been shown that the inclusion of the interaction between the magnetic moments inside the impurity cluster leads to a decrease in the magnetization reversal loop, the coercivity, and, accordingly, the energy loss due to magnetization reversal.     

Electret processes in disordered systems based on liquid dispersion media

Electret-thermal analysis (ETA) of disordered systems based on dispersed media is carried out. It is shown that the method of thermally stimulated currents makes it possible to estimate the structural changes occurring in a liquid dispersion medium. It is found that liquid water in a free state exhibits the electret properties. The observed multiple peaks on the thermally stimulated current curve are the evidence of the multicomponent nature of the ??free water?? system. The mechanisms of processes leading to the formation of the electret state in such systems are considered.     

Mathematical Simulation of the Distribution of the Electron Beam Current during Pulsed Heating of a Metal Target

Journal of Applied and Industrial Mathematics - We study a model of the current distribution during heating of the surface of a tungsten sample under pulsed exposure to an electron beam. The model...