A study of void size growth in nonequilibrium stochastic systems of point defects

We study properties of voids growth dynamics in a stochastic system of point defects insolids under nonequilibrium conditions (sustained irradiation). It is shown thatfluctuations of defect production rate (external noise) increase the critical void radiuscomparing to a deterministic system. An automodel regime of void size growth in astochastic system is studied in detail. Considering a homogeneous system, it is found thatexternal noise does not change the universality of the void size distribution function;the mean void size evolves according to classical nucleation theory. The noise increasesthe mean void size and spreads the void size distribution. Studying dynamics of spatiallyextended systems it was shown that vacancies remaining in a matrix phase are able toorganize into vacancy enriched domains due to an instability caused by an elastic latticedeformation. It is shown that dynamics of voids growth is defined by void sinks strengthwith void size growth exponent varying from 1/3 up to 1/2.     

Acoustic field structure in the first oceanic convergence zone for different frequencies in the audio range

Experimental data on the angular and energy structures of the acoustic field generated in the first convergence zone by a source of continuous pseudo-noise radiation in the frequency range 0.5–4.0 kHz are presented. The experiments are carried out in a tropical region of the Central Atlantic. The acoustic field characteristics are studied with the omnidirectional and highly directional (～2°) reception in the vertical plane. Particular attention is given to studying the field structure at the entrance to the convergence zone at frequencies of 1.25 and 3.15 kHz. The experimental data are compared with the ray calculations. In the experiments, the origin of the convergence zone, which is determined by a sharp increase in the received signal intensity, is found to be about 1.2 km nearer to the source than in the calculations. At a frequency of 1.25 kHz, the convergence zone begins 300 m nearer than at the higher frequency (3.15 kHz). At distances of several kilometers to the zone origin, weak signals that arrive at the same angles as the signals forming the origin of the convergence zone are detected.     

A quantum analog of the Poincare-Birkhoff-Witt theorem

We reduce the basis construction problem for character Hopf algebras to a study of special elements, called “super-letters,” which are defined by Shirshov standard words. It is shown that character Hopf algebras having not more than finitely many “hard” super-letters share some of the properties of universal envelopings of finite-dimensional lie algebras. The background for our proofs is the construction of a filtration such that the associated graded algebra is obtained by iterating the skew polynomials construction, possibly followed with factorization. Supported by the National Society of Researchers, México (SNI, exp. 18740, 1997–2000) Translated fromAlgebra i Logika, Vol. 38, No. 4, pp. 476–507, July–August, 1999.     

Evaluation of the possibilities of detecting ejections of nitrogen oxides by an airborne differential absorption lidar operating in the medium ir spectral region

Using numerical simulation, we evaluated the possibilities of detecting ejections of nitrogen oxides by an airborne differential absorption lidar operating in the medium IR spectral region at converted frequencies of CO- and CO₂-lasers. We present results of calculations of random errors in determining the integrated content of nitrogen oxide and dioxide depending on the amount of ejection and the flight altitude of an airplane. It is shown that the use of frequency-converted CO- and CO₂-laser radiation makes it possible to determine ground-level ejections of nitrogen oxides at a level of 0.01 MPC. Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences, I Akademicheskii Ave., Tomsk, 634055, Russia; e-mail: oleg@losa.iao.tomsk.ru. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 843–845, November–December, 1999.     

Advanced Mass Calibration and Visualization for FT-ICR Mass Spectrometry Imaging

Mass spectrometry imaging by Fourier transform ion cyclotron resonance (FT-ICR) yields hundreds of unique peaks, many of which cannot be resolved by lower performance mass spectrometers. The high mass accuracy and high mass resolving power allow confident identification of small molecules and lipids directly from biological tissue sections. Here, calibration strategies for FT-ICR MS imaging were investigated. Sub-parts-per-million mass accuracy is demonstrated over an entire tissue section. Ion abundance fluctuations are corrected by addition of total and relative ion abundances for a root-mean-square error of 0.158?ppm on 16,764 peaks. A new approach for visualization of FT-ICR MS imaging data at high resolution is presented. The ??Mosaic Datacube?? provides a flexible means to visualize the entire mass range at a mass spectral bin width of 0.001?Da. The high resolution Mosaic Datacube resolves spectral features not visible at lower bin widths, while retaining the high mass accuracy from the calibration methods discussed.     

Effect of substituents on the nature of the products of oxidation of 4H-thiopyrans

Depending on the degree of substitution of the thiopyran ring, either oxidation at the sulfur atom, which leads to the formation of the 1,1-dioxide, or dehydrogenation of the heteroring in the C₍₄₎ position may occur in the reaction of 4H-thiopyrans with hydrogen peroxide in acetic acid. In the case of dehydrogenation the composition of the products depends on the nature of the starting 4H-thiopyran. Some peculiarities of the structure of 4H-thiopyrans that promote their conversion to 1,1-dioxides were ascertained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1042–1046, August, 1985.     

Crystal and molecular structure of 2-benzoly-5-phenylpyrrole

An x-ray diffraction investigation of 2-benzoyl-5-phenylpyrrole, whose molecules are combined as dimers in the crystal, has been carried out. The bond lengths and angles have been presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1355–1358, October, 1984.     

Conversion of di(furyl-2)alkyl and di(furyl-2)arylmethanes to the thiophene analogs

On reaction with hydrogen sulfide in strongly acidic media, difurylalkyl-(aryl)methanes are converted to furylthienylalkyl(aryl)- or dithienylalkyl-(aryl)methanes, depending on the conditions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1046–1048, August, 1989.     

Mechanism of recyclization of furans to thiophenes and selenophenes under acid catalysis. 1. Kinetic studies of the reaction of 2,5-dialkylfurans with hydrogen sulfide in the presence of hydrochloric acid

The transformation of 2,5-dialkylfurans to thiophenes by reaction with hydrogen sulfide in the presence of hydrochloric acid was studied. The reaction was found to be first order with respect to the furan; the rate of consumption of the furan did not change with increasing length of one of the alkyl substituents. Recyclization in the presence of acid proceeds in two independent directions: through the formation of an intermediate dicarbonyl compound, and by direct conversion of the furan to a thiophene. Kinetic data showed that the reaction occurs mainly by the second route.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1333–1337, October, 1989.     

Cyclization of 2,4-dichloro-1,5-pentanediones with nucleophilic reagents

The mechanism of reaction of 2,4-dichloro-1,5-pentanediones with ammonia has been studied. Intramolecular cyclization of the intermediate resulting from nucleophilic attack at the carbonyl group can occur in two ways, depending on the reaction conditions, either at the -chloromethylene fragment or at the second carbonyl group, leading to the formation of 2-aroylpyrroles or 3-chloropyridines, respectively. In reactions with thio- and phenylthiourea both chlorophenacyl fragments are involved, resulting in the formation of di(2-amino-4-arylthiazolyl-5)methanes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1095–1099, August, 1991.