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1.
3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3). 相似文献
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M.H. Majles Ara SR. Hosseini M.H. Rezvani M. Abolhassani 《Journal of Physics and Chemistry of Solids》2011,72(11):1367-1372
In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO3 photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering. 相似文献
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V. N. Shut I. F. Kashevich S. R. Syrtsov I. V. Shnaídshteín 《Crystallography Reports》2010,55(3):458-461
Some features of the ferroelectric behavior of triglycine sulphate crystals with a nonuniform distribution of chromium impurity
have been considered. The dielectric hysteresis loop of the samples is characterized by a large shift along both the polarization
axis and the electric field direction. The results are explained well within the phenomenological approach with allowance
for the gradient term in the expansion of free energy. It is established that the unipolarity coefficient and pyroelectric
signal of inhomogeneous crystals barely changes during multiple heating-cooling cycles. 相似文献
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The specific features of the ferroelectric behavior of triglycine sulfate crystals with a nonuniform distribution of chromium impurities are analyzed. It is demonstrated that the dielectric hysteresis loops of the samples exhibit large shifts both along the polarization and electric field directions. The results obtained are well explained within the phenomenological approach with due regard for the gradient term in the expansion of the free energy. It is established that the unipolarity coefficient and the pyroelectric signal of nonuniform crystals remain virtually unchanged in multiple heating-cooling cycles. 相似文献
6.
MA Freitas SR Dillon RC Dougherty AG Marshall 《Rapid communications in mass spectrometry : RCM》1999,13(15):1622-1625
The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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K. I. Arshinov O. N. Krapivnaya V. V. Nevdakh S. R. Syrtsov V. N. Shut 《Optics and Spectroscopy》2018,124(1):1-7
The spectrum of excitation of Rydberg states of thallium atoms has been investigated using a collimated atomic beam in a two-step isotope selective laser scheme 62P1/2 → 62D3/2 → Tl** in the presence of an electric field with a strength of up to 1.5 kV/cm near the level 16F5/2. The optical transitions 6D3/2 → 18D3/2 and 6D3/2 → 16G7/2, which were induced by an external electric field and dipole-forbidden, have been studied experimentally. The values for the scalar polarizabilities (in units сm–1/(kV/сm)2) α0(16F5/2) = 3.71 ± 0.3, α0(18D3/2) = 11.70 ± 0.25, and α0(16G7/2) = 44.1 ± 0.9, which are compared with the calculated one, have been obtained. The new values of energy parameters for the states 18D3/2 and 16G7/2 have been determined. 相似文献
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V. N. Shut V. M. Laletin S. R. Syrtsov V. L. Trublovsky Yu. V. Medvedeva K. I. Yanushkevich M. V. Bushinskii T. V. Petlitskaya 《Physics of the Solid State》2018,60(9):1744-1751
The phase composition, microstructure, and dielectric, ferroelectric, magnetic, and magnetoelectric properties of bulk ceramic (1 – x)PZT–xNiFe1.9Co0.02О4 – δ composites with 3–0 connectivity have been studied. Using X-ray diffraction and electron microscopy, it has been established that the ferrimagnetic (spinel- like) and ferroelectric (tetragonal perovskite-like) phases separately exist in the composites of all compositions. The simultaneous existence of ferroelectric and ferrimagnetic properties in the composites is confirmed by measuring their P(E) and σ(B) hysteresis loops and studying the temperature dependences of dielectric and magnetic properties. The synthesized composites have high magnetoelectric characteristics: their voltage coefficient at x = 0.4 is 215 mV/A at a frequency of 1 kHz and 130 V/A at an electromechanical resonance frequency of 380 kHz. 相似文献
10.
怀孕期头发中一些元素含量的变化趋势 总被引:5,自引:1,他引:4
用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。 相似文献