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排序方式: 共有688条查询结果,搜索用时 15 毫秒
1.
O. P. Mikheeva A. I. Sidorov A. S. Khaiikina E. V. Chuguevets 《Technical Physics Letters》2002,28(1):48-49
Experimental data on the pulsed laser radiation confinement in compensated GaAs and ZnSe with deep impurity levels are reported for the laser wavelength λ=1.55 μm and a pulse repetition frequency of up to 100 kHz. It is demonstrated that an increase in the pulse repetition rate is accompanied by a decrease in the energy confinement threshold and by an increase in the radiation attenuation coefficient. These effects are explained by the accumulation of nonequilibrium charge carriers related to a dependence of the recombination time constant on the concentration of free impurity centers. 相似文献
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The following modes of isotope exchange of azidothymidine (3'-azido-3'-deoxythymidine) with tritium were studied: solid- and liquid-phase isotope exchange with gaseous tritium and isotope exchange in solution with tritium water. Catalytic reactions of azidothymidine with gaseous tritium in solution result in virtually complete reduction of the azido group to amino group. This reduction also occurs in the course of solid-phase catalytic hydrogenation; the yield of 3'-amino-3'-deoxythymidine ranges from 20 to 70%. The molar radioactivity of tritium-labeled azidothymidine prepared by solid-phase catalytic isotope exchange with gaseous tritium and by isotope exchange in solution with tritium water does not exceed 0.5 Ci mmol-
1. 相似文献
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L. A. Dombrovskii L. I. Zaichik Yu. A. Zeigarnik E. S. Mukhtarov A. S. Sidorov 《Thermal Engineering》2006,53(4):302-306
Quasi-steady-state thermal conditions of the corium bath found on a reactor vessel bottom is considered. Using approximate heat transfer models proposed earlier, a conjugate problem is solved with taking into account radiation heat transfer in the space above the bath surface. The results of calculations of heat flow-rates from the corium bath to the VVER-440 reactor vessel are presented. It is shown that water delivery to the bath surface leads to an essential decrease in the heat flowrate towards the wall in the most dangerous area, where a layer of melted steel contacts the reactor vessel, and retains a possibility of keeping the melt inside the reactor vessel under external cooling. 相似文献
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S.?A.?Dvoretskii A.?P.?Kovchavtsev I.?I.?LeeEmail author V.?G.?Polovinkin G.?Yu.?Sidorov M.?V.?Yakushev 《Optoelectronics, Instrumentation and Data Processing》2018,54(6):569-575
Modern designs of time delay and integration (TDI) IR linear scanning focal plane arrays (IR FPAs) are analyzed. Advanced designs of linear IR FPAs with increased sensitivity and spatial resolution are proposed. The analysis is based on Monte-Carlo simulation of the diffusion of photogenerated charge carriers in photodiode arrays based on mercury–cadmium–telluride epitaxial layers taking into account the main photoelectric and design parameters of the detectors and optical system. 相似文献
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Reaction between α-V2O5 and NaN3 has been studied at pressures from 5.0 to 6.0 GPa and temperatures from 600 to 800°C using Toroid high-pressure chambers. A new oxide, V3.047O7 (VO2.297), isostructural with simpsonite, Al4Ta3O13(OH), has been detected in samples with the initial composition 0.2NaN3 · V2O5 after high-temperature, high-pressure processing at p = 5.0 GPa and t = 800°C for 2 min. The crystal structure of the oxide has been refined by the Rietveld method using X-ray powder diffraction data: a = 7.35136(2) Å, c = 4.51462(2) Å, V = 211.294(1) Å3, Z = 2, sp. gr. P3. Each vanadium atom in this structure is coordinated by six oxygens in the form of a [VO6] octahedron. The synthesized oxide is a second compound with the simpsonite structure. We have measured the infrared transmission and Raman spectra of V3.047O7. Electrical measurements have demonstrated that the material is a semiconductor. 相似文献
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PURPOSE: To compare admission data and academic performances of medical students younger and older than 25, and to qualify older students' experiences and perceptions in medical school. METHOD: The authors reviewed 1988-1991 data for applications to the McGill University Faculty of Medicine. Data included GPAs and MCAT scores, as well as ratings for reference letters, autobiographical statements, and interviews. For those same years, the authors measured students' academic performances in the preclinical and clinical years. The authors compared the data by students' age: "younger" students, aged 17 to 24; and "older" students, aged 25 and above. All enrolled students took the Derogatis Stress Profile, and the older students participated in focus groups. RESULTS: The older applicants had lower GPAs and MCAT scores, but higher interview and reference letter ratings. For older accepted students, basic science course scores were lower than those of younger students, but clinical scores did not differ significantly between the groups. The two groups had similar stress levels, although older students tested lower in driven behavior, relaxation potential, attitude posture, and hostility. In focus groups, the older students spoke of learning style differences, loss of social support, and loss of professional identity. CONCLUSION: Different scores in admission criteria suggest that McGill uses different standards to select older medical students. Older students admitted under different criteria, however, do just as well as do younger students by their clinical years. A broad-based study of admission criteria and outcomes for the older student population is warranted. 相似文献
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I. Gurevich V. Beloozerov A. Myagkov Yu. Sidorov Yu. Trusova 《Pattern Recognition and Image Analysis》2011,21(3):392-397
The study of the functioning and development of the nervous system and its main structural-functional units, neurons, is a
critical direction in modern medicine and neurobiology. The key stage in this process is analysis of neurons in microscopic
images. The application of methods based on mathematical theory of pattern recognition and image analysis creates wide novel
possibilities for analyzing similar representations of experimental data. The question on creating reliable automated systems
for recognition and analysis of histological specumens remains, however, open. In the survey, we present results of an analysis
of the methods and systems meant for automated neuron image analysis based on studies published in leading scientific journals
within the past 25 years. 相似文献