Dual reactivity of diazonium salts derived from 1-amino-2-ethynyl-9,10-anthraquinones

Diazotization of vicinal 1-amino-2-ethynyl-4-R-9,10-anthraquinones followed by a reaction with NaN₃ gave 5-hydroxy-3-R-1H-naphtho[2,3-g]indazole-6,11-diones or 3-ethynyl-5-R-6H-anthra[1,9-cd]isoxazol-6-ones, depending on the substituents at the triply bonded C atom and in position 4 of the anthraquinone framework.     

Terahertz emission from a metallic surface induced by a femtosecond optic pulse

Results of experimental and theoretical investigations on generation of terahertz radiation at the interaction of femtosecond laser pulses with a metal surface are presented. Investigations are performed with the laser pulse intensities higher compared with that used in papers [Opt. Lett.29, 2674 (2004); Opt. Lett.30, 1402 (2005)]. The most effective generation is observed for p-polarized optical pulses with incidence angles in the range 5°-10° (from the surface), depending on the kind of metal. For the copper, the exponential growth of terahertz pulse energy with the increase of optical pulse energy was registered. Theoretical interpretation for some of the experimental results is proposed based on the model of free electrons in metal.     

On the shift of a regulatory signal in models of matrix synthesis

The paper deals with the limiting properties of the matrix synthesis models that take into account the phenomenon of branching and an unspecified number of intermediate steps. Numerically, it is shown that with unlimited increase of the number of intermediate steps, there is observed a shift of the control signal along the chain synthesis. Also the shift causes the compression of the control function which is inversely proportional to the branching ratio. If branching is absent then the conjectures are proved by analogy with the available limit theorems.     

Toward describing one-nucleon exchange in nucleus-nucleus scattering

The effect of one-nucleon exchanges on the potential of nucleus-nucleus interaction is considered on the basis of the resonating-group method. Corrections to the folding-model potential are obtained in the semiclassical approximation. Neutron scattering on ⁴He nuclei is considered as a model example.     

Generation of terahertz radiation by the axicon focusing of ionizing laser pulses

JETP Letters - Experimental results on the generation of terahertz radiation in the gas breakdown by high-power quasi-monochromatic laser pulses focused by an axicon lens are presented. A...     

Steady streaming around a spherical drop displaced from the velocity antinode in an acoustic levitation field

The steady (acoustic) streaming associated with a sphericaldrop displaced from the velocity antinode of a standing waveis studied. The ratio of the particle size to the acoustic wavelengthis treated as small but non-zero, and the solution is developedin the form of a two-term expansion in terms of the correspondingsmallness parameter. The drop viscosity is assumed to be muchhigher than that of the surrounding fluid, which is the casefor a drop in a gas medium. There are essentially three distinctregions where the steady streaming flow is analysed: insidethe drop (internal circulation), in the Stokes shear-wave layerat the surface on the gas side, and the gas outside the Stokeslayer (the outer streaming region). Solutions for the internalcirculation and the outer streaming are obtained in the limitof small Reynolds number. Despite the gas-to-liquid viscosity ratio being small, the outerstreaming may be dramatically affected by the fact that thesphere is liquid as opposed to solid. The parameter that measuresthe effect of liquidity is essentially the viscosity ratio dividedby the relative (to the particle size) thickness of the Stokeslayer. The case of a solid sphere is recovered by letting thisparameter go to zero.     

Properties of the surface of silicas modified with bi-and trifunctional perfluorohexylsilanes: Adsorption of benzene

Diffuse reflection IR spectroscopy, static adsorption, and gas chromatography were used to study the chemistry and adsorption properties of the surface of silicas modified by chemically grafted bi-(C₆F₁₃(II)) and trifunctional (C₆F₁₃(III)) perfluorohexylsilanes. It was established that the modification of silica (SiO₂) results in a nearly complete screening of free silanols. At the same time, IR spectra featured absorption bands belonging to weakly perturbed OH groups capable of interacting with benzene molecules. The IR spectroscopy data on benzene adsorption were found to be in close agreement with the results of static adsorption and chromatographic measurements, according to which the specific amount of benzene adsorbed decreases in the series SiO₂ > C₆F₁₃(III) > C₆F₁₃(II). It was demonstrated that the heat of adsorption of benzene on the C₆F₁₃(III) sample is higher than that on the initial carrier. Grafted layers prepared from the trifunctional modifier exhibited higher efficiency in preventing benzene molecules from reaching the carrier surface.     

Synthesis of (Het)aryl 2-(2-hydroxyaryl)cyclopropyl Ketones

A simple general method for the synthesis of 1-acyl-2-(ortho-hydroxyaryl)cyclopropanes, which belong to the donor–acceptor cyclopropane family, has been developed. This method, based on the Corey–Chaykovsky cyclopropanation of 2-hydroxychalcones, allows for the preparation of a large diversity of hydroxy-substituted cyclopropanes, which can serve as promising building blocks for the synthesis of various bioactive compounds.     

Revelation of ion hydration in Raman scattering spectral bands of water

The influence of ions with different hydration properties on the stretching, bending, and low-frequency bands of water Raman scattering spectra has been investigated. The obtained results are explained using the ion hydration theory: from the point of view of the formation of hydration shells, ion pairs and complexes, and the migration of protons in water. Using the detected peculiarities of the dependences of spectra characteristics on the salt concentration for the determination of the parameters of long-range and short-range hydration is proposed.     

Bio-inspired synthesis of chiral silver nanoparticles in mucin glycoprotein--the natural choice

A method of synthesizing stable chiral Ag nanoparticles inside a natural mucin glycoprotein is demonstrated. The reaction is carried out without the help of an external reducing agent, by utilizing the reducing properties of the host mucin. A chiral spectrum is detected in the visible range, indicating the formation of a new type of chiral Ag nanoparticles-containing biomaterial.