Experimental investigation of nonstationary flow in cavities in a supersonic flow

An experimental investigation was made into the flow and pressure pulsations in cylindrical cavities open toward a supersonic flow and set up at zero angle of attack (i.e., the cavity axis and the direction of the flow coincide).Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 180–183, September–October, 1979.     

Effect of coagulating agent viscosity on the kinetics of formation,morphology, and transport properties of cellulose nanofiltration membranes

Low-viscous coagulating agents are tradionally used to precipitate polymers from their solutions and obtain films and fibers from them; they represent, as a rule, the combinations of solvent and nonsolvent of the polymer used. At the same time, since the structure of the precipitated polymer is formed under non-equilibrium conditions, the influence of the coagulant viscosity can be quite substantial. The influence of the viscosity of the medium on the formation of structure, morphology, and transport characteristics of the precipitated polymer is studied by example of forming of the cellulose membranes from solution in N-methyl-morpholine N-oxide using some proton-donor coagulants. In this regard, the interdiffusion processes proceeding at the contact of cellulose solutions and coagulating agents (water, propylene glycol, glycerin) are explored using the laser interferometry method. Varying the precipitator viscosity allows one to change the rate of formation and correspondingly the morphology of the cellulose films. In turn, the membrane structure determines its transport characteristics, which were assessed by the filtration of aprotic media with anionic dyes—Orange II and Remazol Brilliant Blue R. The application of the low-viscous precipitator provides the formation of a uniform film structure in the bulk, but leads to development of defects close to the surface, while a viscous medium promotes the formation of a relatively thin dense shell on the films.     

Toward the development of the direct and selective detection of nitrates by a bioinspired Mo-Cu system

The development of a new platform for the direct and selective detection of nitrates is described. Two thioether-based chemosensors and the corresponding sulfoxides and sulfones were prepared, and their photophysical properties were evaluated. Upon selective sulfoxidation of these thioethers with nitrates via an oxygen-transfer reaction promoted by a bioinspired Mo-Cu system, significant fluorescence shifts were measured. A selective response of these systems, discriminating between nitrate salts and H(2)O(2), was also shown.     

On the growth rate of arbitrary sequences of double rectangular Fourier sums

The theorem is proved that an arbitrary sequence \(\left\{ {S_{m_{k,} n_k } \left( {f,x,y} \right)} \right\}_{k = 1}^\infty\) of double rectangular Fourier sums of any function from the class L(ln⁺ L)²([0, 2π)²) satisfies the relation \(S_{m_k ,n_k } \left( {f,x,y} \right) = o\left( {\ln k} \right)\) almost everywhere.     

Synthesis of the N-terminal tripeptide of the oxytocin sequence

Two schemes for the synthesis of the hydrazide of the N-terminal tripeptide of the oxytocin sequence are considered. It is shown that the most rational is a 1 + 2 scheme.All-Union Scientific-Research Institute of the Technology of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 116–122, January–February, 1989.     

Longitudinal development of giant air showers and problem of estimating the energy of primary-cosmic-ray particles

The attenuation length for the charged-particle density at a distance of 600 m from the shower axis may differ from that adopted in experimental investigations by 40–50%. This casts some doubt on experimental estimates previously obtained for the energy of primary-cosmic-ray particles in the region of ultrahigh energies.     

A study of many-body phenomena in metal nanoclusters (Au, Cu) close to their transition to the nonmetallic state

The results of a study of many-body phenomena in gold and copper nanoclusters are presented. The measured conductivity as a function of nanocluster height h was found to have a minimum at h ≈ 0.6 nm. Conductivity was local in character at nanocluster sizes l ≤ l _c ≈ 2.5 nm. Changes in core hole screening and an anomalous increase in the Anderson singularity index α in gold and copper nanoclusters could be caused by changes in permittivity from metallic (? → ∞) to nonmetallic (? ∝ l ²). The many-body phenomenon characteristics observed in the X-ray photoelectron and tunnel spectra of gold and copper nanoclusters as the size of the nanoclusters changed led us to suggest changes in the band structure of the nanoclusters and, therefore, their possible transition from the metallic to nonmetallic state.     

Two-coordinate diffusion of optical beams by an acoustooptic Raman-Nath modulator based on a paratellurite crystal

Acoustooptic Raman-Nath diffraction by a standing acoustic wave in a paratellurite crystal is investigated. An acoustic line is made in the form of a polished cube and serves as a high-Q acoustic resonator. A slow shear wave is excited by a single piezoelectric transducer. Multiple lossless sound reflections lead to two-coordinate light diffusion. When the acoustic intensity introduced into the crystal is about 2 W/cm² at a sound frequency of 7 MHz, there appears a diffraction pattern in the form of a homogeneous light spot with a solid angle of about 0.5 sr. An explanation for the features of the acoustooptic interaction is given. It is shown that this type of diffraction is helpful in designing acoustooptic two-coordinate diffusers of light beams.     

Renormalization group in the theory of two-dimensional turbulence: Instability of the fixed point with respect to weak anisotropy

A statistical model of fully developed turbulence in two-dimensional space is considered by means of the renormalization group method in the weak anisotropy approximation. It is shown that the corresponding fixed point of the renormalization group equations is not infrared stable. Hence, the weak, anisotropy approximation is not valid for describing two-dimensional turbulence. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 112, No. 3, pp. 417–427, September, 1997.     

Catalytic properties of oligonuclear cobalt acetate complexes in oxidation of glutathione with hydrogen peroxide

Catalytic activity of oligonuclear cobalt(III) and cobalt(II, III) oxoacetate complexes in homogeneous oxidation of glutathione with hydrogen peroxide was studied.