Circular Dichroism Spectra of DNA Dispersions and Textures of DNA Phases

Optics and Spectroscopy - Circular dichroism (CD) spectra of liquid crystalline dispersions formed as a result of phase exclusion of double-stranded DNA molecules from aqueous-salt-poly(ethylene...     

Long range correlations in DNA: scaling properties and charge transfer efficiency

We address the relation between long-range correlations and charge transfer efficiency in aperiodic artificial or genomic DNA sequences. Coherent charge transfer through the highest occupied molecular orbital states of the guanine nucleotide is studied using the transmission approach, and the focus is on how the sequence-dependent backscattering profile can be inferred from correlations between base pairs.     

Quadrupolar forces and aggregation of nematic droplets

The electrostatic quadrupolar interaction between spherical nematic droplets in an isotropic (and nonconducting) liquid is calculated. It is found to have an anisotropic form U _q ∝1/R ⁵, where R is the distance between droplets, with repulsion for droplets having parallel orientation of the quadrupole moments and attraction at oblique angles around the orthogonal orientation. In an external magnetic field aligning the orientations of the quadrupole moments, a competition of the quadrupolar repulsion and van der Waals attraction (U _vdW∝ 1/R ⁶) leads to a specific spatial organization of droplets which is in fact often reported in experimental observations (see the monograph by P. Drzaic, Liquid Crystal Dispersions, World Scientific, Singapore (1995) and references cited therein). Pis’ma Zh. éksp. Teor. Fiz. 68, No. 10, 747–752 (25 November 1998) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Collapse of islands in freely suspended smectic nanofilms

A time-nonlinear stage of the collapse of islands in freely suspended smectic nanofilms is observed and investigated. Islands thicker than a nanofilm are prepared and studied, which are unstable inside the dislocation loops, since they increase the energy of the film. Such instability leads to the decrease in the size of islands and is terminated by their collapse. The time dependence of the size of islands is measured experimentally. It is shown that the found dependence is in agreement with the theory of the dynamics of dislocation loops in smectic films developed earlier with allowance for the dissipation of energy in the film and in the meniscus. A nontrivial dynamic coupling between islands in a film resembling Ostwald ripening is also found, though the nonequilibrium kinetics of unstable islands, at which the hydrodynamic flow through a film leads to the decrease in sizes of one island and the increase in those of the other, rather than of the growth of the nucleation centers in the thermodynamically stable phase from the metastable state of the system (described by the Lifshitz–Slezov theory in films), is studied in our experiments.     

Toward a theory of diffraction by the boundary of a highly reflective medium with periodically modulated characteristics

The problem of diffraction by simultaneously existing surface-profile and impedance gratings in the presence of resonance with a surface electromagnetic wave is examined. The problem is solved in an impedance approximation (Leontovich boundary condition) using Rayleigh's hypothesis. The solution method is based on the distinguishing of resonance fields, for which a finite system of equations is constructed. A proposed regular procedure for exclusion of nonresonance fields makes it possible to obtain a solution with any accuracy for any polarization of the incident radiation and orientation of the gratings. Specific results are given in a principal approximation for the case of several resonances in the first-order spectra.Scientific-Industrial Organization Metrology. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, Nos. 3, 4, pp. 234–245, March–April, 1992.     

Possible use of a gas-discharge plasma in an oscillating field to modulate electromagnetic radiation

The conditions for resonance and signal cutoff are determined from the dispersion relation for the complex refractive index for a plane electromagnetic wave propagating in a gas-discharge plasma when a magnetic field H = H₀ + H₁e^jt is imposed on the plasma. The refractive index and absorption are calculated for circularly polarized waves as functions of the alternating magnetic field with _p, _b, andv as parameters. Possible observation of modulation of the transmitted signal is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 94–99, April, 1971.     

Ferrielectric smectic phase with a layer-by-layer change of the two-component order parameter

One of the most remarkable properties of smectics is the wide variety of possible equilibrium structures. In this paper, based on the Landau theory of the phase transitions, the transitions between ferroelectric and antiferroelectric phases and the structure formed by smectic layers with different azimuthal and polar orientations of the molecules were calculated. This unique structure has been predicted [P.V. Dolganov et al., JETP Lett. 76, 498 (2002)] using the minimization of the free energy with respect to the phase and modulus of the two-component order parameter, but never before detected. Recently, a nonresonant Bragg reflection, consistent with the predictions of the model, was found [P. Fernandes et al., Eur. Phys. J. E 20, 81 (2006)] in the ferrielectric smectic C* _FI1(SmC* _FI1) phase. In the three-layer ferrielectric structure with a macroscopic helical pitch, the modulus of the order parameter is larger in anticlinic-like layers and smaller in layers with mixed ordering. The values of the interlayer interactions were determined for smectic liquid-crystalline materials forming different polar structures. The text was submitted by the authors in English.     

Preparation of 8-(5-oxoindeno [3,2-b]-4-pyridyl)-1-naphthoic acids

The condensation of 1-(1,3-indanedion-2-ylidene)-2-acenaphthenone with imines of -dicarbonyl compounds gave 2,5-dioxospiro 1,4,acenaphthene-1,4-dihydroindeno-[3,2-b]pyridines. Oxidation of the pyridines with air oxygen at room temperature without catalysts brings about cleavage of the C-C bond to give 8-(5-oxoindeno[3,2-b]-4-pyridyl)-1-naphthoic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 210–212, February, 1972.