Mechanochemical Modification of Activated Carbon in Air

Russian Journal of Applied Chemistry - The effect exerted on the chemical properties and structure of activated carbon by the mechanical treatment as a modification procedure was studied....     

Novel π-conjugated structures with fluorescent properties based on 4-alkoxytetrahydroquinazoline N-oxide

Russian Chemical Bulletin - Synthetic approaches to previously unknown 4-OR-2-methyltetrahydroquinazoline N-oxides were elaborated. 4-Alkoxy- and 4-aryloxy-2-methyltetrahydroquinazoline N-oxides...     

Interaction of amorphous and crystalline nickel nanoparticles with hydrogen

Nickel nanoparticles were deposited on the surface of highly oriented pyrolytical graphite by laser electrodispersion and precipitation from a solution of reverse micelles. The particles were studied using scanning tunneling microscopy and spectroscopy as well as Auger spectroscopy. The elemental composition of the nanoparticles and specific features of the electronic structure of their surface were determined. Adsorption of molecular hydrogen was also studied.     

Specific features of coupling reactions of polystyrene in the presence α-dinitrones based on glyoxal

Russian Chemical Bulletin - Bromine-containing polystyrene synthesized by atom transfer radical polymerization was used as a model to study coupling reactions in the presence of such free radical...     

Synthesis of novel non-natural spiro[2.3]hexane amino acids,the conformationally restricted analogs of γ-aminobutyric acid

3-Methylenecyclobutanecarboxylic acid and its methyl ester were used as the starting compounds for the synthesis of new spiro[2.3]hexane amino acids, the conformationally rigid analogs of γ-aminobutyric acid, namely, 5-aminospiro[2.3]hexanecarboxylic and 5-amino-spiro[2.3]hexanephosphonic acids, promising modulators of GABAergic cascades in the human central nervous system. The methods developed for the synthesis of the target amino acids are based on the reactions of catalytic [1+2] cycloaddition of diazoacetic and diazophosphonic esters to 3-substituted methylenecyclobutanes, as well as on a modified Curtius reaction for the transformation of a carboxy group to the amine one.     

Effect of angle of attack on supersonic flow past axisymmetric blunt bodies with surface injection

The effect of angles of attack in the interval 0 40° on the flow pattern and the aerodynamic characteristics of a body of power-law shape (equation of the generator in the cylindrical coordinate system r=zⁿ, n=0.125) is investigated for supersonic flow without injection and with intense subsonic localized injection from the surface. As a result of numerical calculations it is established that the use of Newton's theory for determining the coordinates of the gas stagnation point behind the shock in flow past an impermeable body of the shape in question leads to serious errors, and an expression for determining the location of this point is given. It is shown that for three-dimensional flow the flow pattern and the surface pressure distribution are sharply different from the case=0. It is established that on the parameter interval in question intense injection considerably reduces the aerodynamic drag without loss of static stability, which is important in connection with the solution of the problem of gas-stable aircraft control.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 95–101, September–October, 1987.     

Effect of viscosity on the autoignition of a reacting moving mixture

Ya. B. Zel'dovich has established [1] that in a continuous-flow reactor two ignition regimes are possible: forced ignition and autoignition.It is important to consider the special properties of the autoignition regime associated with the hydromechanics of laminar flow and heat transfer through the pipe wall. In [2, 3] it was shown that the effect of heat of friction on heat transfer in long pipes is qualitative in character. Moreover, according to Schlichting [4], in certain cases the temperature gradient for such flows due to the heat of friction may reach 10–30°, which is comparable with the preexplosion temperature rise in the stationary theory of thermal explosion [5]. In this connection it is clear that under certain conditions the heat of friction may considerably reduce the explosion limit.This paper is devoted to a study of the effect of heat of friction on the explosion limit of a reacting fluid in a long cylindrical pipe. The dynamic autoignition regime due to heat of friction is examined. In particular, it is established that, other things being equal, by increasing the pressure drop it is possible to obtain explosion of the reacting system.     

Investigation of supersonic viscous flow past a sphere in the presence of subsonic and sonic injection

Supersonic flow past a sphere with a given rate of gas injection along the generator is investigated numerically on the range Re=10²–10⁴. Calculations have been made on the interval 0 90°, where is the angle between the axis of symmetry and the normal to the surface. It is shown that for high subsonic and sonic injection rates it is possible to observe qualitatively new features in the flow structure and in the distribution of the local supersonic flow characteristics around the perimeter of the sphere not previously noted in [9]. In the case of sonic injection the changes in flow structure occur only in the supersonic zone. In the neighborhood of the transition from a subsonic to sonic injection velocity the heat flux has a local maximum, which in absolute value does not exceed the heat flux in the absence of injection. It is shown that there may be qualitative differences in the pressure distribution over the surface of the body with increase in the injection parameter depending on the distribution and value of the injected gas flow rate and, moreover, the number Re.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 83–89, January–February, 1988.     

Triple 13C-{1H, 2H} NMR: A precise quantitative method for study deuterated organic compounds

We have shown the advantages of quantitative ¹³C-{¹H, ²H} NMR spectroscopy in the study of deuterated organic compounds. The simultaneous use of two saturating fields at the resonance frequencies of protons and deuterons significantly simplifies NMR spectra and increases the sensitivity of the method. We tested the performance capabilities of triple resonance when analyzing the mixture of tetradecane isotopomers and precisely measuring the isotope shifts Δ(¹³C) for biphenyl-d₅.     

Visualization of IR radiation by fluoride ceramics

Ceramic luminophors based on YF₃ (Er, Yb) and LiYF₄ (Er, Yb) solid solutions were obtained in the form of tablets by the solid-phase synthesis in the temperature range 800–1000°C. The synthesized luminophors can be used in the form of thin-film lacquer coats phosphorescing under the action of IR radiation, for recording hidden information, for defense of goods and securities, and for adjustment of IR lasers.