Synthesis,structure, and phase behavior of carbosilane LC dendrimers with terminal butoxyphenylbenzoate mesogenic groups

Two series of carbosilane LC dendrimers with terminal protonated and deuterated butoxyphenylbenzoate mesogenic groups linked to carbosilane dendritic matrices of the first to fifth generations via an undecylene spacer have been synthesized. The chemical structure of new dendrimers has been studied by ¹H NMR spectroscopy and gel-permeation chromatography. The dendrimers of first-fourth generations are characterized by formation of the smectic C mesophase in a wide temperature range, whereas much more complex columnar supramolecular structures are formed in dendrimers of the fifth generation. Structural studied of mesophases by X-ray diffraction and small-angle neutron scattering show that segregation takes place in mixtures of deuterated and protonated LC dendrimers; as a result, huge aggregates composed of hundreds of chemically unbound molecules develop and the sizes of these aggregates reversibly change with temperature.     

Sura-wind radar: Studies of nonlinear effects using VHF-wave occultion of the ionosphere

We present experimental results on reception of VHF signals of the transmitting facility “Sura” of the Radiophysical Research Institute by the NASA spacecraft WIND. The experiments were performed during daytime during the summer seasons 1997–1998. The dependence of power and spectral characteristics of the VHF radio waves on the power of the sounding radiation is analyzed. We find that, in a wide range of effective powers of the VHF radiation from about 40 kW to 160 MW, the phenomena observed in the radiation received onboard WIND (such as focusing, scintillations, or frequency deviations of signals) does not usually depend on the operation mode of the “Sura” facility. At the same time, broadening of the radiation pattern of the facility and decrease of the mean level of the received signal by about 6 dB toward the direction of maximum of the radiation pattern were observed at the peak radiation power of the facility. The experimental results are compared to present concepts on effects of self-focusing instability and nonlinear defocusing of VHF radio waves in the ionospheric plasma. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 8, pp. 799–809, August 1999.     

Light-induced orientation of the molecules of nematic liquid crystals doped with comb-shaped polymers with different spatial distributions of chromophores

The orienting effect of light on nematic liquid crystals (NLCs) doped with comb-shaped polymers with different spatial distributions of side absorbing azobenzene fragments, i.e., a homopolymer (containing only azofragments), a block copolymer (containing additionally a block of non-absorbing fragments), and a statistical copolymer (containing randomly arranged absorbing and non-absorbing fragments) is experimentally studied. The light-induced Freedericksz transition threshold for the block copolymer is two times lower than that for the homopolymer. For NLC with statistical copolymer dopant, the first-order orientation transition with an extremely wide optical bistability region is observed.     

Effect of Confinement on Structural and Spectral Characteristics of Composites of CsPbX3 Halide Perovskite Nanoparticles with Zeolites of Faujasite Structure

Theoretical and Experimental Chemistry - CsPbBr3–zIz/Y(X) nanocomposites based on FAU (Y and X) zeolites and halide perovskite nanoparticles (HP NP) with CsPbBr3–zIz composition (z = 0...     

X-ray electronic spectra of certain tetraaza macrocyclic complexes of cobalt (III)

The electronic structure-Of several tetraaza macrocyclic complexes of cobalt (III), containing different axial acido ligands was studied using X-ray electron spectroscopy. The bond energies of electrons of nitrogen, cobalt, chlorine, bromide, and sulfur atoms were measured. It was shown that the bond energy of isoelectrons of the macrocyclic ligand nitrogen atoms is not a constant value, but depends on the nature of the additionally coordinated axial ligand, which reflects the cis-effect of the ligands in the macrocyclic complexes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 497–500, July–August, 1985.     

A kinetic model of thermochemical transformation of solid organic fuels

A kinetic model of thermochemical transformation of solid organic fuels was constructed. The mathematical model describes the kinetics of drying, release and combustion of volatiles, and combustion and gasification of the nonvolatile (coke) residue at linear heating. The kinetic curves of burn-out of Irsha-Borodino brown coal at various heating rates and model parameters were calculated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 9, 2004, pp. 1558–1567.Original Russian Text Copyright © 2004 by Boiko, Pachkovskii.