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81.
In this paper we consider the parabolic conservation law with large initial data which has a big perturbation. Using the method of Green function, we first obtain the decay rates of the derivatives of the solutions in L 2 and L ∞ spaces, and then the pointwise estimate of the solutions. 相似文献
82.
Optimal decay rates and global existence for a semilinear Timoshenko system with two damping effects
In this paper, we study a semilinear Timoshenko system having two damping effects. The observation that two damping effects might lead to smaller decay rates for solutions in comparison with one damping effect is rigorously proved here in providing optimality results. Moreover, the global well‐posedness for small data in a low regularity class is presented for a larger class of nonlinearities than previously known and proved by a simpler approach. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
83.
A chemo- and regioselective α-hydroxylation reaction of carbonyl compounds with molecular oxygen as oxidant is reported. The hydroxylation reaction is catalyzed by a dinuclear Pd(II) complex, which functions as an oxygen transfer catalyst, reminiscent of an oxygenase. The development of this oxidation reaction was inspired by discovery and mechanism evaluation of previously unknown Pd(III)-Pd(III) complexes. 相似文献
84.
In this paper, we consider the global existence as well as the optimal decay estimates of the Cauchy problem for the multi-dimensional Benjamin–Bona–Mahony–Burgers equation with large initial data in the whole-space. And these results are obtained by Green?s function method, Fourier analysis method, energy estimates method combined with the time-frequency decomposition method. 相似文献
85.
A simple and efficient one-pot synthesis of polyfunctionalized benzenes has been developed via cyclocondensation of activated α-methylene alkenes such as vinyl malononitriles and ethyl vinyl cyanoacetates with nitroolefins using Cu(OTf)2/Et3N as a novel catalytic system. 相似文献
86.
Thermoset Shape‐Memory Polyurethane with Intrinsic Plasticity Enabled by Transcarbamoylation 下载免费PDF全文
Ning Zheng Zizheng Fang Weike Zou Prof. Qian Zhao Prof. Tao Xie 《Angewandte Chemie (International ed. in English)》2016,55(38):11421-11425
Thermoset polymers are known for their superior thermomechanical properties, but the chemical crosslinking typically leads to intractability. This is reflected in the great differences between thermoset and thermoplastic shape‐memory polymers; the former exhibit a robust shape memory but are not capable of redefining the permanent shape. Contrary to current knowledge, we reveal here that a classical thermoset shape‐memory polyurethane is readily capable of permanent reshaping (plasticity) after a topological network rearrangement that is induced by transcarbamoylation. By employing the Jianzhi technique (also known as kirigami), unexpected shape‐shifting versatility was observed for this otherwise classical material. As the essential carbamate moiety in polyurethanes is one of the most common polymer building units, we anticipate that our finding will have significant benefits beyond shape shifting. 相似文献
87.
An efficient mechanically activated solvent‐free synthesis of (E)‐stilbene derivatives by high‐speed ball milling is described. This method has notable advantages in terms of good yield, short reaction time and high selectivity. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
88.
A novel and effective protocol has been developed for the Ullmann‐type C? N coupling reaction catalyzed by calix[4]arene supported amino acid ionic liquid and copper(I) iodide in water under microwave irradiation condition. The protocol uses calix[4]arene supported amino acid ionic liquid as double function of the ligand and phase‐transfer catalyst, and shows good tolerance in good to excellent yields. 相似文献
89.
Feng Su Lv Ye Zilin Zhou An Su Jinping Gu Zili Guo Peixi Zhu Weike Su 《Molecules (Basel, Switzerland)》2022,27(9)
Paris polyphylla var. chinensis (Franch.) Hara is a perennial herb belonging to the Trilliaceae family. Ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC/Q–TOF MS) was used to detect the composition of different fractions of Paris polyphylla var. chinensis leaves. Meanwhile, the extracts of different fractions were evaluated for their cytotoxic activities against four selected human cancer cell lines and one human normal epithelial cell line based on the MTT assay method. Multivariate statistical analysis was performed to screen differential compounds and to analyze the distributions between different fractions. Finally, more than 60 compounds were obtained and identified from the different fractions of Paris polyphylla var. chinensis leaves, and the chloroform and n−butanol extracts showed significant cytotoxic effects on these four cancer cells. Several compounds were preliminarily identified from different fractions, including 36 steroidal saponins, 11 flavonoids, 10 ceramides, 8 lipids, 6 organic acids, and 8 other compounds. Various compounds were screened out as different chemical components of different fractions, which were considered as a potential substance basis for the cytotoxicity of Paris polyphylla var. chinensis leaves. 相似文献
90.
Quantitative determination and validation of avermectin B1a in commercial products using quantitative nuclear magnetic resonance spectroscopy 总被引:1,自引:0,他引:1
Zhuoni Hou Xianrui Liang Liping Du Feng Su Weike Su 《Magnetic resonance in chemistry : MRC》2014,52(9):480-485
Nuclear magnetic resonance is defined as a quantitative spectroscopic tool that enables a precise determination of the number of substances in liquids as well as in solids. There is few report demonstrating the application of NMR in the quantification of avermectin B1a (AVB1a); here, a proton nuclear magnetic resonance spectroscopy (1H NMR) using benzene [1‐methoxy‐4‐(2‐nitroethyl) (PMN)] as an internal standard and deuterochloroform as an NMR solvent was tested for the quantitative determination of AVB1a. The integrated signal of AVB1a at 5.56 ppm and the signal of PMN at 8.14 ppm in the 1H NMR spectrum were used for quantification purposes. Parameters of specificity, linearity, accuracy, precision, intermediate precision, range, limit of detection (LOD), limit of quantification (LOQ), stability and robustness were validated. The established method was accurate and precise with good recovery (98.86%) and relative standard deviation (RSD) of assay (0.34%) within the linearity of the calibration curve ranging from 5.08 to 13.58 mg/ml (R2 = 0.9999). The LOD and LOQ were 0.009 and 0.029 mg/ml, which indicated the excellent sensitivity of the method. The stability of the method was testified by a calculated RSD of 0.11%. The robustness was testified by modification of four different parameters, and the differences among each parameter were all less than 0.1%. Comparing with the assay described by the manufacturer of avermectin tablets, there was no significant difference between the assay obtained by HPLC and quantitative NMR (qNMR), which indicated qNMR was a simple and efficient method for the determination of AVB1a in commercial formulation products. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献