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91.
Pavlov SG Zhukavin RK Orlova EE Shastin VN Kirsanov AV Hubers H Auen K Riemann H 《Physical review letters》2000,84(22):5220-5223
The observation of far-infrared stimulated emission from shallow donor transitions in silicon is reported. Lasing with a wavelength of 59 &mgr;m due to the neutral donor intracenter 2p(0)-->1s(E) transition in Si:P pumped by CO2 laser radiation is obtained. Populations of D0 and D- center states and the balance of the radiation absorption and amplification are theoretically analyzed. 相似文献
92.
Elastic light scattering by low-dimensional quantum objects without a change in the frequency is theoretically investigated in terms of the quantum perturbation theory. The differential cross section of resonance light scattering from any excitons in any quantum dots is calculated. It is demonstrated that, when the light wavelengths considerably exceed the quantum-dot size, the polarization and angular distribution of the scattered light do not depend on the shape, the size, or the configuration of quantum dots. In this case, the total light scattering cross section is independent of the quantum-dot size. If the radiative damping of an exciton exceeds the nonradiative damping, the total light scattering cross section at resonance is of the order of the light wavelength squared. The radiative damping associated with the long-range exchange interaction between electrons and holes is calculated for any excitons and any quantum dots. 相似文献
93.
D. M. Podorozhnyi V. L. Bulatov N. V. Baranova A. V. Vlasov A. G. Voronin N. N. Egorov S. A. Golubkov V. M. Grebenyuk D. E. Karmanov M. G. Korolev N. A. Korotkova Z. V. Krumshtein E. G. Lyannoy M. M. Merkin A. Yu. Pavlov A. Yu. Pakhomov A. V. Romanov A. B. Sadovskii L. G. Sveshnikova L. G. Tkachev A. V. Tkachenko A. Turundaevskiy 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(4):500-502
The main purpose of the NUCLEON experiment is direct measurements of the energy spectra of cosmic rays in the range 1011–1015 eV with the use of the lightweight facility during a prolonged orbital flight. The energy is determined using a technique based on the measurement of the spatial density of secondary particles produced in the initial event of inelastic interaction. The schematic diagram of the NUCLEON facility, the current status of the project, the results of testing the prototype, and plans are presented. 相似文献
94.
Andrei V. Afonin Igor A. Ushakov Dmitry V. Pavlov Andrei V. Ivanov Al'bina I. Mikhaleva 《Magnetic resonance in chemistry : MRC》2010,48(9):685-692
The 1H, 13C and 15N NMR studies have shown that the E and Z isomers of pyrrole‐2‐carbaldehyde oxime adopt preferable conformation with the syn orientation of the oxime group with respect to the pyrrole ring. The syn conformation of E and Z isomers of pyrrole‐2‐carbaldehyde oxime is stabilized by the N? H···N and N? H···O intramolecular hydrogen bonds, respectively. The N? H···N hydrogen bond in the E isomer causes the high‐frequency shift of the bridge proton signal by about 1 ppm and increase the 1J(N, H) coupling by ~3 Hz. The bridge proton shows further deshielding and higher increase of the 1J(N, H) coupling constant due to the strengthening of the N? H···O hydrogen bond in the Z isomer. The MP2 calculations indicate that the syn conformation of E and Z isomers is by ~3.5 kcal/mol energetically less favorable than the anti conformation. The calculations of 1H shielding and 1J(N, H) coupling in the syn and anti conformations allow the contribution to these constants from the N? H···N and N? H···O hydrogen bondings to be estimated. The NBO analysis suggests that the N? H···N hydrogen bond in the E isomer is a pure electrostatic interaction while the charge transfer from the oxygen lone pair to the antibonding orbital of the N? H bond through the N? H···O hydrogen bond occurs in the Z isomer. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
95.
N. Tsibakhashvili L. Mosulishvili E. Kirkesali I. Murusidze M. V. Frontasyeva S. S. Pavlov I. I. Zinicovscaia P. Bode Th. G. van Meerten 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(2):533-537
Instrumental neutron activation analysis was used to study accumulation of Hg(II) and Cr(VI) ions in Arthrobacter globiformis 151B, a gram-positive, Cr(VI)-reducer aerobic bacterium isolated from basalt sample taken from the most polluted region in the Republic of Georgia (Kazreti). Experiments were focused on (1) accumulation of Hg(II) in bacterial cells; (2) accumulation of Cr(VI) in A. globiformis 151B in the presence of Hg(II) and (3) effects of Hg(II) and mixture of Cr(VI)–Hg(II) on the elemental composition of bacteria. It was shown that this bacterial strain possesses uptake mechanisms by which mercury toxicity can be reduced in environment and that accumulation of Cr(VI) in A. globiformis 151B is much higher in the presence of Hg(II) ions. Accumulation of Hg(II), similar to the Cr(VI) accumulation, follows well the Lengmuir–Freundlich model. NAA measurements showed increased content of Fe in bacteria under Hg and Cr action, suggesting that Fe-containing biomolecules play a decisive role in detoxifying of heavy metals by A. globiformis 151B. A concentration of 5000 μg/L of Hg(II) was found to be critical for A. globiformis 151B. At this concentration of Hg(II) the concentrations of both essential (Na, Mg, Al, Cl, K, Mn, Zn) and some non-essential elements (Rb, Sb, Sc, As) changed drastically along with a decrease of the biomass of bacteria by a factor of two. One may assume that under this high exposure to Hg(II) the structure of the bacterial cell wall was destroyed. 相似文献
96.
97.
P. A. Pavlov 《Chemistry of Heterocyclic Compounds》2002,38(5):524-529
A new method based on the Schmidt reaction was developed for the production of 5-R-2-cyanofurans from 5-R-furfurals. 相似文献
98.
A.N. Pavlov O.V. Semyachkina-Glushkovskaya O.N. Pavlova O.A. Bibikova J. Kurths 《The European physical journal. Special topics》2013,222(10):2705-2712
Nitric oxide (NO) plays an important role in regulation of central and peripheral circulation in normal state and during hemorrhagic stress. Because the impaired gastric mucosal blood flow is the major cause of gastroduodenal lesions including ulcer bleeding (UB), we study in this work the NO-ergic mechanism responsible for regulation of this blood flow. Our study is performed in rats with a model of stress-induced UB using laser Doppler flowmetry (LDF) that characterizes the rate of blood flow by measuring a Doppler shift of the laser beam scattered by the moving red blood cells. Numerical analysis of LDF-data is based on the discrete wavelet-transform (DWT) using Daubechies wavelets aiming to quantify influences of NO on the gastric microcirculation. We show that the stress-induced UB is associated with an increased level of NO in the gastric tissue and a stronger vascular sensitivity to pharmacological modulation of NO-production by L-NAME. We demonstrate that wavelet-based analyses of NO-dependent regulation of gastric microcirculation can provide an effective endoscopic diagnostics of a risk of UB. 相似文献
99.
Based on the Schmidt reaction, a new method has been developed for the preparation of nitriles in furan series from the corresponding furfural derivatives. Depending on conditions, the reaction of 5-substituted cyanofurans with hydrazine leads to amidrazones, N-aminotriazoles, or 1,2,4,5-dihydrotetrazines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 181–186, February, 1986. 相似文献
100.