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41.
G. A. Zou S. Mansur S. C. Hu H. A. Aisa Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2012,48(4):635-637
The novel pyrrole alkaloid alhagifoline A (1) together with the two known analogs pyrrolezanthine (2) and pyrrolezanthine-6-methyl ether (3) were isolated from the aerial part of Alhagi sparsifolia. Their structures were established based on spectral (HR-ESI-MS, 1 H and 13C NMR, 1 H–1 H COSY, HSQC, HMBC) data. Compounds 2 and 3 were isolated from the genus Alhagi for the first time. 相似文献
42.
A novel approach to nanoscale broadband viscoelastic spectroscopy is presented. The proposed approach utilizes the recently developed modeling-free inversion-based iterative control (MIIC) technique to achieve accurate measurement of the material response to the applied excitation force over a broad frequency band. Scanning probe microscope (SPM) and nanoindenter have become enabling tools to quantitatively measure the mechanical properties of a wide variety of materials at nanoscale. Current nanomechanical measurement, however, is limited by the slow measurement speed: the nanomechanical measurement is slow and narrow-banded and thus not capable of measuring rate-dependent phenomena of materials. As a result, large measurement (temporal) errors are generated when material is undergoing dynamic evolution during the measurement. The low-speed operation of SPM is due to the inability of current approaches to (1) rapidly excite the broadband nanomechanical behavior of materials, and (2) compensate for the convolution of the hardware adverse effects with the material response during high-speed measurements. These adverse effects include the hysteresis of the piezo actuator (used to position the probe relative to the sample); the vibrational dynamics of the piezo actuator and the cantilever along with the related mechanical mounting; and the dynamics uncertainties caused by the probe variation and the operation condition. In the proposed approach, an input force signal with frequency characteristics of band-limited white-noise is utilized to rapidly excite the nanomechanical response of materials over a broad frequency range. The MIIC technique is used to compensate for the hardware adverse effects, thereby allowing the precise application of such an excitation force and measurement of the material response (to the applied force). The proposed approach is illustrated by implementing it to measure the frequency-dependent plane-strain modulus of poly(dimethylsiloxane) (PDMS) over a broad frequency range extending over 3 orders of magnitude (~1 Hz to 4.5 kHz). 相似文献
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Cascade reactions of nitroallylic acetates with methanesulfonyl 2-aminoethanones affords either the 3-pyrrolines or the pyrroles in one pot depending on reaction solvents and temperature. A possible mechanism for the entire sequence is proposed. 相似文献
45.
Chang Jun Zou Quan Wu Tang Gui Hong Lan Qiang Tian Tai Yu Wang 《Journal of inclusion phenomena and macrocyclic chemistry》2013,76(1-2):61-68
For the first time, hydroxypropyl-β-cyclodextrin (HP-β-CD) has been brought in to include 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) in order to enhance inhibition efficiency of PBTCA, which leads a new approach to study oil–gas field corrosion inhibition in the process of acid treatment. Based on the host–guest inclusion reaction, the inclusion complex of PBTCA with HP-β-CD has been prepared in the laboratory. UV–Vis absorption spectrum was applied to study the inclusion behavior of PBTCA with HP-β-CD. The results revealed that PBTCA with HP-β-CD can form a 1:1 stoichiometry inclusion complex. The 1:1 inclusion complex synthesized by using lyophilization was further characterized by Fourier transform infrared spectroscopy. Besides, inhibition effect of the inclusion complex on the corrosion inhibition of Q235 carbon steel has been investigated in 0.1 M sulfuric acid (H2SO4) solution using potentiodynamic polarization, electrochemical impedance spectroscopy techniques and scanning electron microscopy (SEM). It was found that the presence of the inclusion complex better achieved the anti-corrosion property in aggressive medium than was the case with alone PBTCA and the highest inhibition efficiency of the inclusion complex over 90 % was obtained, which are suggestive of the active effect of the inclusion complex for improving inhibition efficiency of PBTCA. Meanwhile, the results obtained from SEM further showed that the inclusion complex acts as a more efficient corrosion inhibitor for Q235 carbon steel in H2SO4 medium. 相似文献
46.
The research provides a novel approach for producing diarylmethane derivatives using CB[7]–NaCl–PdCl2 catalyzed Suzuki cross-coupling reaction of benzyl chloride derivatives and arylboronic acids in ethanol aqueous solution. 相似文献
47.
Shuanglong Chen Mingguang Yao Ye Yuan Fengxian Ma Zhaodong Liu Bing Li Ran Liu Quanjun Li Bo Zou Tian Cui Bingbing Liu 《Journal of Raman spectroscopy : JRS》2015,46(4):400-405
Raman spectra of iodine species confined in one‐dimensional elliptical channels of AlPO4‐11 (AEL) crystals have been studied from room temperature down to −196 °C. As temperature decreases, thermal fluctuations of individual iodine molecules confined in AEL channels are slowed down and they prefer to rotate to channel axis direction, which increases the population of iodine molecules along channel axis (i.e., lying molecules and chains). Such temperature‐driven orientation transformation of iodine molecules is found to be reversible upon heating up to room temperature. The experimental observations are in good agreement with our theoretical simulations by molecular dynamics on low density iodine‐filled AEL crystals. We thus provide a new way to modulate the orientation of iodine molecules in nanochannels, which may have implications in low‐temperature‐sensitive nanoscale devices. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
48.
Zhongzhi Zhang Shuigeng Zhou Tao Zou Lichao Chen Jihong Guan 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):259-264
We make a mapping from Sierpinski fractals to a new class
of networks, the incompatibility networks, which are scale-free,
small-world, disassortative, and maximal planar graphs. Some
relevant characteristics of the networks such as degree
distribution, clustering coefficient, average path length, and
degree correlations are computed analytically and found to be
peculiarly rich. The method of network representation can be applied
to some real-life systems making it possible to study the complexity
of real networked systems within the framework of complex network
theory. 相似文献
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