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861.
A palladium-based catalyst (Fe3O4/SiO2/HPG–OPPh2–PNP) supported on chlorodiphenylphosphine-functionalized magnetic nanoparticles was successfully prepared from Fe3O4/SiO2 with sequential attachment of glycerol and chlorodiphenylphosphine, followed by treatment of an ethanolic solution of palladium chloride with hydrazine. The as-prepared catalyst was characterized by ICP-AES, FTIR, XRD, SEM, and TEM. The Fe3O4/SiO2/HPG–OPPh2–PNP was found as a magnetically separable and highly active catalyst for Suzuki coupling reactions of aryl iodides, bromides, and chlorides as well as Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions afforded the desired products in moderate to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six cycles without significant loss of its activity. 相似文献
862.
863.
Inside Cover: Naphthalene‐Functionalized,Photoluminescent Room Temperature Ionic Liquids Bearing Small Counterions (Chem. Eur. J. 18/2016) 下载免费PDF全文
864.
Differences and Commonalities in the Gas‐Phase Reactions of Closed‐Shell Metal Dioxide Clusters [MO2]+ (M=V,Nb, and Ta) with Methane 下载免费PDF全文
Dr. Shaodong Zhou Dr. Jilai Li Dr. Maria Schlangen Prof. Dr. Helmut Schwarz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7225-7228
High‐level electronic structure calculations, in combination with Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometric studies, permit the mechanism by which closed‐shell, “naked” [TaO2]+ brings about C?H bond activation of methane to be revealed. These studies also help to understand why the lighter congeners of [MO2]+ (M=V, Nb) are unreactive under ambient conditions. 相似文献
865.
Dahai He Xuemin Xu Yan Zhou Wenlong Deng Bin Xia Lisheng Ding 《Helvetica chimica acta》2012,95(7):1136-1143
Two new diterpenoids, loxocalyxin A ( 1 ) and 13‐epiloxocalyxin A ( 2 ), and two new sesquiterpenoids, loxocalyxins B and C ( 3 and 4 , resp.), together with three known compounds, were isolated from the MeOH extract of the whole plant of Loxocalyx urticifolius Hemsl . The structures of the new compounds were established by means of spectroscopic analysis including one‐ and two‐dimensional NMR spectroscopy. All new structures were confirmed by X‐ray crystallographic analysis. Their absolute configurations were established. 相似文献
866.
Xiaochun Zhou Xiaojun Wang 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(13):2033-2036
A modified low temperature solid state process has been proposed to systematically synthesize europium-doped yttrium phosphate-vanadates with general formula Y0.48Li1.5V1 ? x P x O4:Eu3+ (x = 0.2, 0.4, 0.6). All the Y0.48Li1.5V1 ? x P x O4:Eu3+ products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The excitation and emission spectra were measured at room temperature. Y0.48Li1.5V1 ? x P x O4:Eu3+ show the characteristic missions of Eu3+ (5 D 0?7 F 1, 2, 3, 4 transitions dominated by 5 D 0?7 F 2), intensities of the products were sensitive to the x value, and the x value had an obvious influence on the (5 D 0?7 F 2)/(5 D)0?7 F 1) intensity ratio of Eu3+. In addition, incorporation of Li+ ions in the phosphors reduce the amount of Y2O3, lower the cost of production, and cause a new phase Li3VO4. 相似文献
867.
In the photoelectric tracking system, the detection of space multi-target is crucial for target localization and tracking. The difficulties include the interferences from CCD smear and strong noise, the few characteristics of spot-like targets and the challenge of multiple targets. In this paper, we propose a hybrid algorithm of joint decision and Naive Bayes (JD-NB) learning, and present the duty ratio feature to discriminate the target and smear blocks. Firstly, we extract the proper features and train the parameters of the Naive Bayes classifier. Secondly, target blocks are preliminarily estimated with the Naive Bayes. Lastly, the 4-adjacent blocks of the candidate target blocks are jointed to analyze the distribution pattern and the true target blocks are secondarily extracted by the method of pattern matching. Experimental results indicate that the proposed JD-NB algorithm not only possesses a high recognition rate of better than 90% for the target block, but also effectively overcomes the disturbance of the smear block. Moreover, it performs well in the detection of small and faint targets when the SNR of the block is higher than about 0.014. 相似文献
868.
Based on three-dimensional (3D) Lü chaotic system, we introduce a four-dimensional (4D) nonlinear system with infinitely many equilibrium points. The Lyapunov-exponent spectrum is obtained for the 4D chaotic system. A hyperchaotic attractor and a chaotic attractor are emerged in this 4D nonlinear system. Furthermore, to verify the existence of hyperchaos, the chaotic dynamics of this 4D nonlinear system is also studied by means of topological horseshoe theory and numerical computation. 相似文献
869.
870.