Highly efficient synthesis and solid-state characterization of 1,2,4,5-tetrakis(alkyl- and arylamino)benzenes and cyclization to their respective benzobis(imidazolium) salts

[reaction: see text] New synthetic methodology to a variety of 1,2,4,5-tetraaminobenzenes and their corresponding benzobis(imidazolium) salts has been accomplished. Palladium-catalyzed coupling of various 1,2,4,5-tetrabromo- or 1,2,4,5-tetrachlorobenzenes with aryl- or tert-alkylamines afforded the respective tetrakis(N-substituted)aminobenzenes in excellent yields. This enabled comparative solid-state structural analyses of this elusive class of electron-rich arenes with their oxidized derivatives. The tetraamines were found to undergo formylative cyclization to the corresponding benzobis(imidazolium) salts in good to excellent yields.     

The effect of temperature on the nonlinear dynamics of charge in a semiconductor superlattice in the presence of a magnetic field

The space-time dynamics of electron domains in a semiconductor superlattice is studied in a tilted magnetic field with regard to the effect of temperature. It is shown that an increase in temperature substantially changes the space-time dynamics of the system. This leads to a decrease in the frequency and amplitude of oscillations of a current flowing through the semiconductor superlattice. The quenching of oscillations is observed, which is attributed to the change in the drift velocity as a function of electric-field strength under the variation of temperature.     

Fractal model of magnetization reversal in a strained garnet ferrite film

The domain structure in strained garnet ferrite films and its behavior in an external magnetic field are studied using the Faraday effect. Based on the experimental results, a model of magnetization reversal in thin polycrystalline layers is proposed that describes the process of remagnetization as the development of fractal clusters. The model proposed is verified using a computer simulation of magnetization reversal.     

Synchronization in a Network of Spiking Neural Oscillators with Plastic Connectivity

Radiophysics and Quantum Electronics - Synchronization of neural activity plays an important role for processing of information in the brain. In this work, we study the dynamics of a neural network...     

Effect of the cationic composition of cryolite-alumina melts on the anodic overvoltage

Steady-state polarization of anodes prepared from platinum or glassy carbon is studied in a laboratory cell in a cryolite-alumina melt containing small amounts of potassium and lithium fluorides and various alumina amounts. The surface area of the anodes reaches a few centimeters squared. An insignificant depolarization of the anodic process is discovered following the replacement of a fraction of sodium ions in the electrolyte by potassium ions in an amount of ～3.9 mol % KF (～4.1 wt %) and a noticeable depolarization, following the substitution of K⁺ in an amount of ～7.1 mol % KF (～7.6 wt %). Substituting lithium ions in an amount of ～3.7 mol % LiF (～1.8 wt %) for a fraction of sodium ions leads to an insignificant polarization. A significant effect of a general cryolite ratio on polarization is discovered. A noticeable increase in the anodic polarization is fixed at an alumina concentration equal to 5–5.5 wt %.     

Catalytic systems for reduction of nitro compounds involving cerium complexes with organic ligands

Conclusions Effective catalytic systems were developed for the reduction of aromatic nitro compounds, which consist of a heterogeneous palladium catalyst and cerium complexes with organic ligands.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp.1104–1107, May, 1979.     

Absorption of Radiation by ITO Semiconductor Nanoparticles in Plasmon Resonance Region

The radiation absorption cross section of indium–tin oxide (ITO) semiconductor nanoparticles of various sizes placed in various media is calculated in the region of plasmon resonance. The photoabsorption cross sections calculated within the framework of the Mie theory and in the dipole approximation are compared with each other and with the available experimental data. The limits of applicability of the dipole approximation are determined. The prospects of using these nanoparticles as an active material in optical plasmon sensors are assessed.     

Scattering of Electromagnetic Radiation by ITO Nanoparticles with Various Doping Levels

The process of scattering of radiation by indium?tin oxide (ITO) nanoparticles is theoretically studied at various degrees of doping and for different radii of nanoparticles. Qualitative conclusions are made about the character of the dependence of the scattering cross section on the frequency with variation of the particle size and the percentage content of tin. The prospects of using ITO nanoparticles as an active substance in optical sensors are estimated.     

Stability of the synchronous state of an arbitrary network of coupled elements

We propose a method for determining the range of the coupling parameter for which the network of slightly nonidentical chaotic oscillators demonstrates stable synchronous behavior. As an example of using this method, we study the complete-synchronization regime of a network of nonidentical Rossler oscillators. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 10, pp. 917–924, October 2006.