Developing a moderating block for the NG-400 neutron generator

The results from developing and determining the optimal characteristics of a thermal neutron source using the NG-400 neutron generator are presented. The primary aims of this study were to achieve the maximum conversion of fast neutrons (14 MeV) into thermal neutrons and to investigate the current density distribution of fast and thermal neutrons inside the moderator cavity to determine the zone with maximum density of the flux of thermal neutrons.     

Photoreflectance Spectroscopy of Porous Silicon Photonic Crystals

Journal of Russian Laser Research - We study one-dimensional porous silicon photonic crystals by photoreflectance (PR) spectroscopy. We calculate the reflectance and PR spectra by transfer matrix...     

Synthesis and Properties of Ethyl [(Adamantan-1-yl)alkylene(phenylene)amino]oxoacetates and N1,N2-Bis[(adamantan-1-yl)alkylene(phenylene)]oxamides

Russian Journal of Organic Chemistry - Ethyl [(adamantan-1-yl)alkylene(phenylene)amino]oxoacetates and N1,N2-bis[(adamantan-1-yl)-alkylene(phenylene)oxamides were prepared in yields of 72–87...     

Synthesis and Properties of N,N′-Disubstituted Ureas and Their Isosteric Analogs Containing Polycyclic Fragments: XI. 1-[(Adamantan-1 yl)alkyl]-3-arylselenoureas

Russian Journal of Organic Chemistry - A series of N,N′-disubstituted selenoureas containing an adamantane fragment have been synthesized in 23–75% yields. Procedures for the isolation...     

Specific features of the formation of zinc and cadmium complexes with tetraphenylporphine in amphiprotic media

The kinetics of the complex formation reactions of tetraphenylporphine with zinc and cadmium acetates in mixed solvents containing alcohols and inert diluents was studied by electronic absorption spectroscopy. The dependences of the rate constant on the binary solvent composition have an extreme character, which is universal in the temperature range 298–313 K for different salts, alcohols, and weakly solvating diluents. The electric conductivity of zinc acetate solutions was measured in a wide range of compositions of alcohol-chloroform binary solvents. The electric conductivity increased with an increase in the content of alcohols.     

Possibility of determining microimpurities in materials using a activation measuring complex based on a photoneutron source

An activation measuring complex containing a W–Be photoneutron source of neutrons and a lowbackground gamma spectrometer is designed at the Russian Academy of Sciences Institute for Nuclear Research. The photoneutron source is mounted on the beam of a LUE-8 industrial electron linear accelerator with an electron energy of 7–8 MeV and contains a tungsten bremsstrahlung target, a photoneutron beryllium target, and a fast neutron moderator. The measuring component of the complex includes a detector made from high purity germanium, positioned inside a low-background chamber with active-passive protection. Neutron-activation analysis (NAA) is used to determine the content of microimpurities in a substance. A procedure for measuring ultralow contents of elements in aerosol filters is developed. Contents of Au, As, Sb, Mn, Fe, W, and other elements are measured in a variety of samples. The limits of detecting microimpurities in materials are estimated.     

Alkylation of aminothiazoles

The alkylation of 2-aminothiazole and 2-amino-4-methylthiazole with ten-butyl alcohol in sulfuric acid has been repeated. In correction of preceding information, it has been found that alkylation takes place in position 5 of the thiazole ring and not at the amino group. The presence of a primary amino group in the alkylation products was shown by the production of arylsulfonyl derivatives soluble in alkalies and of 2-halothiazoles by the Sandmeyer replacement of the amino group by halogen. Alkylation with alkyl halides yielded the corresponding thiazolone imides.For part VI, see [6].     

Investigation by dynamic NMR spectroscopy of the mechanism of rotation about the carbon?double bond in nitroenamines

Rapid Z,E-isomerization of nitroenamines R? NH? CH?C(NO₂)COOCH₃ in solutions was investigated by dynamic NMR spectroscopy. In weakly basic solvents all the studied nitroenamines isomerize by a thermal mechanism. In pyridine the isomerization proceeds by the thermal mechanism in aliphatic enamines with R?? CH₃, ? COCH₃ and H, but involves the formation of an intermediate mesomeric ion with kinetically controlled ionization of the N? H bond in the case of aromatic nitroenamines where R = X—Ph-.     

Crossover behavior of disordered interacting two-dimensional electron systems in a parallel magnetic field

The crossover behavior of disordered interacting two-dimensional electron systems in a parallel magnetic field is analyzed. Using the so-called crossover one-loop renormalization group equations for the resistance and electron-electron interaction amplitudes, experimentally observed transformation of the temperature dependence of the resistance from a reentrant (nonmonotonic) behavior in relatively weak fields to an insulating-type behavior in stronger fields is qualitatively explained. The text was submitted by the authors in English.     

Dynamic NMR study of rotation around carbon-carbon double bond in esters of α-nitro-β-arylaminoacrylic acids

Conclusions Employing dyanmic NMR, it was shown that the Z, E-isomerization of -arylaminoacrylic esters in nitrobenzene and o-dichlorobenzene is accomplished by the thermal mechanism of rotation around the C=C bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2820-2822, December, 1977.