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V. A. Burov I. M. Grishina O. I. Lapshenkina S. A. Morozov O. D. Rumyantseva E. G. Sukhov 《Acoustical Physics》2003,49(6):627-637
In the ultrasonic diagnostics of small-size neoplasms of biological tissues at the earliest stage of their development, an efficient way to eliminate the distorting influence of high-contrast or large inhomogeneities of the biological medium is to apply the iterative technique. A simple approach is proposed, which makes it possible with only two iteration steps to achieve an efficient focusing of the tomograph array. At the first step, the unknown distribution of the large-scale inhomogeneities of sound velocity and absorption over the scatterer is reconstructed, where the large-scale inhomogeneities are those whose size exceeds several wavelengths. At the second step, the fine structure of the scatterer is reconstructed against the large-scale background, which can be performed with a high accuracy owing to the evaluation of the background at the first step. The possibility of simultaneous reconstruction of the large-scale and fine structures by the noniterative Grinevich-Novikov algorithm is considered as an alternative. This algorithm reconstructs in an explicit form two-dimensional refractive-absorbing acoustic scatterers of almost arbitrary shape and strength. Taking into account the effects of multiple scattering, this algorithm provides resolution of the fine structure almost as good as that achieved in reconstructing the same structure against an undistorting homogeneous background. The results of numerical simulations of both algorithms are presented. 相似文献
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A. Yu. Ershov A. D. Shashko O. V. Sizova N. V. Ivanova S. V. Burov A. V. Kuteikina-Teplyakova 《Russian Journal of General Chemistry》2003,73(1):135-140
The electronic absorption spectra and photochemical behavior of the complexes of cis-[Ru(bpy)2 · (L)(Cl)]+ (bpy is 2,2'-bipyridyl) with pyridine (L = py) and 4-substituted pyridines [L = methyl-, amino-, and cyanopyridine, and 4,4'-bipyridyl (bipy)]. Photoirradiation of acetonitrile solutions of the complexes results in substitution of ligand L by a solvent molecule. A correlation was revealed between the photolysis quantum yield and the coordination-induced ligand L-to-metal charge transfer. 相似文献
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The influence of the parameters and conditions of sodium sulfide-induced reaction of polyol synthesis of silver nanoparticles
on the yield of cube-shaped particles and the optical properties of colloids is studied. The protocol proposed by Skrabalak
et al. for the synthesis of nanocubes in small volumes (Nature Protocols, 2007, vol. 2, p. 2182) is taken as an initial variant
for optimization. The effects of the reagent concentrations, degree of ethylene glycol oxygenation, the presence of impurities,
reaction time, and temperature are studied. Suspensions containing nanoparticles with different shapes and sizes, including
polydisperse particles of irregular shapes, silver nanocubes with a yield of 0 to 97%, nanoprisms, and nanorods, can be produced
by varying the synthesis parameters. The key parameters controlling the yield of nanocubes are the degree of ethylene glycol
oxygenation and the presence of trace amounts of ions of other metals (not silver). It is established that variations in the
reaction time make it possible to vary the sizes of nanocubes in the range of 30–60 nm. Suspensions with high contents of
cube-shaped particles are shown to exhibit three maxima in the plasmon extinction resonance spectrum at wavelengths of 350,
390, and, depending on the particle size, 435–470 nm. 相似文献
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V. I. Minkin A. D. Dubonosov V. A. Bren’ O. G. Nikolaeva A. V. Tsukanov O. N. Burov A. Yu. Fedyanina 《Russian Journal of Organic Chemistry》2013,49(3):374-378
Schiff bases were synthesized from 3-hydroxy-6-oxo-6H-benzo[c]chromene-4-carbaldehyde, 5-hydroxy-4,7-dimethyl-2-oxo-2H-chromene-6-carbaldehyde, 6,7-dihydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde, 5,7-dihydroxy-4-methyl-2-oxo-2H-chromene-6,8-dicarbaldehyde, and 5-hydroxy-4,7-dimethyl-2-oxo-2H-chromene-6,8-dicarbaldehyde and (15N)aniline or aminobenzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-amine), and tautomeric equilibrium between the hydroxy enimino and keto enamino forms of the 4- and 8-iminomethyl derivatives in solution was revealed by 1H NMR and electronic spectroscopy. Addition of alkaline earth cations to their solutions in acetonitrile displaced the tautomeric equilibrium toward the hydroxy enimino structure due to complex formation with the crown ether fragment. 相似文献
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V. A. Burov O. V. Matveev D. I. Zotov O. D. Rumyantseva 《Physics of Wave Phenomena》2015,23(2):135-142
The possibility of simultaneous reconstruction of the blood flow velocity vector and spatial distributions of the speed of sound and absorption coefficient in a medical ultrasonic tomograph is discussed. The operating capacity of the proposed spatial-correlation method for determining the blood flow velocity vector is confirmed by experiments on a tomograph prototype. 相似文献
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