排序方式: 共有32条查询结果,搜索用时 46 毫秒
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Wolfgang Oppolzer Giovanni Poli Arend J. Kingma Christian Starkemann Grald Bernardinelli 《Helvetica chimica acta》1987,70(8):2201-2214
The 1,4-addition of alkylmagnesium chlorides to conjugated N-enoylsultams and subsequent ‘enolate trapping’ with aq. NH4Cl or MeI/hexamethylphosphoric triamide generated centers of asymmetry at C(β) and/or at C(α) with good to excellent π-face defferentiation as demonstrated by the conversions 1 → 2 , 1 → 4 , and 8 → 9 . This holds also for the regioselective 1,4-addition of EtMgC1 to a dienoylsultam ( 15 → 16 ). Reactive conformations 1 ≠, 8 ≠, 13 , and 14 are postulated in agreement with X-ray evidence which also served for the structure determination of the product 9j . 相似文献
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We report six-dimensional quantum dynamics calculations of the dissociative scattering of molecular hydrogen from the copper111 surface. Two potential energy surfaces are investigated and the results are compared with experiment. Our study completes the preliminary work of Somers et al. [Chem. Phys. Lett. 360, 390 (2002)] and focuses on the role of initial vibrational excitation and on isotopic effects. None of the two investigated potential energy surfaces is found satisfactory: the use of neither potential yields reaction and vibrational excitation probabilities and vibrational efficacies that are in close agreement with experiment. In addition to showing the shortcomings of existing potential energy surfaces we point out an inconsistency in the experimental fits for D2. 相似文献
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Demkin V. P. Melnichuk S. V. Svetlik M. V. Shchetinin P. P. Kingma H. Van de Berg R. Demkin O. V. Udut E. V. 《Russian Physics Journal》2019,61(12):2264-2267
Russian Physics Journal - Experimental data on electric signal transmission through tissues of the vestibular organ of a guinea pig are presented. Stimulating electrodes are implanted in three... 相似文献
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Effect of Leakage Currents on the Formation of Electrical Pulse for the Vestibular Nerve Stimulation
Demkin V. P. Kingma G. Mel’nichuk S. V. Svetlik M. V. Rudenko T. V. Akinina M. D. Suyundukova A. T. 《Russian Physics Journal》2020,62(12):2228-2234
Russian Physics Journal - A theoretical and experimental study was performed of a frequency dependence of the amplitude-phase characteristics of the vestibular nerve stimulation signal and its... 相似文献
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A capillary gas chromatographic method with nitrogen-phosphorus detection is used to determine simultaneously 1,3-diaminopropane, putrescine, cadaverine, spermidine and spermine in human erythrocytes. The compounds are isolated by adsorption on silica and converted into their heptafluorobutyryl derivatives. We give quality-control data and (age-dependent) normal values for 48 apparently healthy controls. 相似文献
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Demkin V. P. Shchetinin P. P. Melnichuk S. V. Kingma H. Van de Berg R. Pleshkov M. O. Starkov D. N. 《Russian Physics Journal》2018,60(11):2019-2024
Russian Physics Journal - An electric model of current transmission through tissues of the vestibular labyrinth of a patient is suggested. To stimulate directly the vestibular nerve in surgical... 相似文献
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Simple Zeros of the Riemann Zeta-Function 总被引:1,自引:0,他引:1
Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26. 相似文献