Radiation field of a dipole situated near an interface of two media

The electromagnetic-field distributions and angular and total radiation intensities of a point electric dipole situated near a semibounded plasmalike medium are obtained for specular diffuse, and random reflection of plasma charged particles from the interface. It is shown that the dipole's radiation field is completely determined by the Fresnel coefficient. of electromagnetic-wave reflection from a plasma half-space with allowance for mechanism of interaction of plasma-system charged particles with the boundary surface. The frequency spectra of the dipole's radiation intensity are studied in detail in a cold-plasma approximation.Institute of Theoretical Physics, Academy of Sciences of Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 6/7, pp. 540–567, June–July, 1992.     

Sulfolenyl and sulfolanyl sulfonates in the Friedel-Crafts reaction

The behavior of various sulfolenyl and sulfolanyl sulfonates in the Friedel-Crafts reaction was studied. The sulfolane ring undergoes both arylation and halogenation. The ratio of reaction products depends on the nature of the starting sulfonate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 746–748, June, 1973.     

Studies on arylhydrazones of ethyl arylsulfonylglyoxylates

The reaction of arylhydrazones of 4-arylthiosemicarbazides of arylsulfonylglyoxylic acid with ω-bromoacetophenone has given arylhydrazones of N-(3-aryl-4-phenyl-2-thiazolinylidene)hydrazides of arylsulfonylglyoxylic acids. The reaction of ethyl p-toluenesulfonate with o-aminothiophenol and o-phenylenediamine in polyphosphoric acid has given 2-(p-tolylsulfonyl)methylbenzothiazole and 2-(p-tolylsulfonyl)methylbenzimidazole. From 2-(p-tolylsulfonyl)methylbenzothiazole, a styryl and the corresponding carbocyanine with a substituted indoline have been obtained. The considerable hypsochromic shift of the absorption maxima of the latter is explained by the influence of the voluminous electronegative group SO₂R in the position α to the heterocyclic nuclei.     

Kinetics of the formation and structure of oligoperoxide nanolayers and grafted polymer brushes on glass plate surface

Functional oligoperoxide surfactants and coordinating oligoperoxide metal complexes were studied as modifiers of glass flat plates to provide the localization of radical forming sites and other functional fragments in adsorbed polymeric layers of a nanoscale thickness. Both the kinetics of the coating formation and properties of the nanolayers witness the dependence of the packing density of oligoperoxide molecules in the coatings on the oligoperoxide natures, concentrations and conditions of the sorption modification. The availability of definite amount of peroxide groups in formed nanolayer provides the possibility of controlled radical graft polymerization initiated from modified surface leading to reliable surface protection, functionality and targeted surface hydrophilic-hydrophobic properties.      

Bit threshold optimization for multiphoton communication in lossy channels

We address M-ary communication channels based on entangled two-mode states of radiation in the presence of losses. In particular we focus on channels build by two-mode coherently-correlated (TMC) or twin-beam (TWB) states. Optimized bit discrimination thresholds, as well as the corresponding maximized mutual information, are explicitly evaluated as a function of beam intensities and loss parameters for binary and quaternary alphabets. The evolution of the two entangled support states in lossy channels is analyzed and the joint photon number distribution is evaluated, showing that the beam statistics (either sub-Poissonian for TMC or super-Poissonian for TWB) is not altered by channel losses. The effects of losses on the channel security is discussed. The text was submitted by the authors in English.     

Nonlinear Dirac Operator and Quaternionic Analysis

Properties of the Cauchy–Riemann–Fueter equation for maps between quaternionic manifolds are studied. Spaces of solutions in case of maps from a K3–surface to the cotangent bundle of a complex projective space are computed. A relationship between harmonic spinors of a generalized nonlinear Dirac operator and solutions of the Cauchy–Riemann–Fueter equation are established.     

Gold coated metal nanostructures grown by glancing angle deposition and pulsed electroplating

Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.     

Molecular basis for water-promoted supramolecular chirality inversion in helical rosette nanotubes

Helical rosette nanotubes (RNTs) are obtained through the self-assembly of the GwedgeC motif, a self-complementary DNA base analogue featuring the complementary hydrogen bonding arrays of both guanine and cytosine. The first step of this process is the formation of a 6-membered supermacrocycle (rosette) maintained by 18 hydrogen bonds, which then self-organizes into a helical stack defining a supramolecular sextuple helix whose chirality and three-dimensional organization arise from the chirality, chemical structure, and conformational organization of the GwedgeC motif. Because a chiral GwedgeC motif is predisposed to express itself asymmetrically upon self-assembly, there is a natural tendency for it to form one chiral RNT over its mirror image. Here we describe the synthesis and characterization of a chiral GwedgeC motif that self-assembles into helical RNTs in methanol, but undergoes mirror image supramolecular chirality inversion upon the addition of very small amounts of water (<1% v/v). Extensive physical and computational studies established that the mirror-image RNTs obtained, referred to as chiromers, result from thermodynamic (in water) and kinetic (in methanol) self-assembly processes involving two conformational isomers of the parent GwedgeC motif. Although derived from conformational states, the chiromers are thermodynamically stable supramolecular species, they display dominant/recessive behavior, they memorize and amplify their chirality in an achiral environment, they change their chirality in response to solvent and temperature, and they catalytically transfer their chirality. On the basis of these studies, a detailed mechanism for supramolecular chirality inversion triggered by specific molecular interactions between water molecules and the GwedgeC motif is proposed.     

Mechanism of titanocene-mediated epoxide opening through homolytic substitution

The mechanism of titanocene-mediated epoxide opening was studied by a combination of voltammetric, kinetic, computational, and synthetic methods. With the aid of electrochemical investigations the nature of a number of Ti(III) complexes in solution was established. In particular, the distribution of monomeric and dimeric Ti(III) species was found to be strongly affected by the exact steric conditions. The overall rate constants of the reductive epoxide opening were determined for the first time. These data were employed as the basis for computational studies of the structure and energies of the epoxide-titanocene complexes, the transition states of epoxide opening, and the beta-titanoxy radicals formed. The results obtained provide a structural basis for the understanding of the factors determining the regioselectivity of ring opening and match the experimentally determined values. By employing substituted titanocenes even more selective epoxide openings could be realized. Moreover, by properly adjusting the steric demands of the catalysts and the substrates the first examples of reversible epoxide openings were designed.     

Theoretical analysis on changes in thermodynamic quantities upon protein folding: essential role of hydration

The free energy change associated with the coil-to-native structural transition of protein G in aqueous solution is calculated by using the molecular theory of solvation, also known as the three-dimensional reference interaction site model theory, to uncover the molecular mechanism of protein folding. The free energy is decomposed into the protein intramolecular energy, the hydration energy, and the hydration entropy. The folding is accompanied with a large gain in the protein intramolecular energy. However, it is almost canceled by the correspondingly large loss in the hydration energy due to the dehydration, resulting in the total energy gain about an order of magnitude smaller than might occur in vacuum. The hydration entropy gain is found to be a substantial driving force in protein folding. It is comparable with or even larger than the total energy gain. The total energy gain coupled with the hydration entropy gain is capable of suppressing the conformational entropy loss in the folding. Based on careful analysis of the theoretical results, the authors present a challenging physical picture of protein folding where the overall folding process is driven by the water entropy effect.