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991.
The article describes an efficient, economical, and environmentally friendly approach for Michael addition of diethyl malonate to ferrocenyl substituted chalcones in the presence of microwave irradiation under solvent-free conditions, affording the corresponding Michael adducts in moderate to good yields of 53–94%.
992.
Ting Wu Hai-Ting Wang Bo Shen Yi-Ping Du Xuan Wang Zhen-Ping Wang Chuan-Jing Zhang Wen-Bin Miu 《中国化学快报》2016,27(5):745-748
Primary aromatic amines(PAAs) are substances with toxicity and suspected human carcinogenicity. A facile method for highly sensitive detection of PAAs using surface-enhanced Raman spectroscopy(SERS)is reported. The immobilization of Au nanoparticles(AuNPs) on the glycidyl methacrylate–ethylene dimethacrylate(GMA-EDMA) materials makes the substrate a closely packed but not aggregated AuNP arrays which provides a prominent SERS enhancement. Four PAAs with different substituent groups,namely, p-toluidine, p-nitroaniline, benzidine and 4,4-methylene-bis-(2-chloroaniline) have been successfully identified and quantified. High sensitivity and good linear relationship between SERS signals and concentrations of PAAs are obtained for all four PAAs. 相似文献
993.
It is demonstrated that many novel vacuum effects will be caused if an anisotropic electromagnetic environment, which can break the universal symmetry of vacuum, is achieved. It is thus possible for the momentum to be transferred from the vacuum zero-point field to the anisotropic electromagnetic media. In addition to the effect considered by Feigel more recently [A. Feigel, Phys. Rev. Lett. 92 (2004) 020404], there may exist another vacuum-fluctuation contribution to the momentum of a medium. Such an effect has a relativistic origin (resulting from the relativistic transformation of the optical constants), which, however, was not taken into account by Feigel. 相似文献
994.
The atomic structure of bulk metallic glasses has long been mysterious for the lack of long range order. Although the solute-centered cluster packing model has recently been proposed to disclose the nanoscale medium-range order (MRO), the atomic packing scheme in systems with large solute concentration remains obscure. In this work, the atomic structure of Cu60Zr40 metallic glass is investigated via molecular dynamics simulations with the Finnis–Sinclair potential. It is found that the fragments of icosahedra are dominant in the model metallic glass. The icosahedra are completely centered by solvent atoms. Extended clusters composed of two icosahedra interpenetrate and form MRO with 3–11 icosahedra. It is suggested that the structure of Cu60Zr40 metallic glass can be described by the aggregation of icosahedra. 相似文献
995.
996.
Yanfei Zhou Zhaoyang Shen Xiaojun Huang Jiong Wu Yujun Li Siqi Huang Helin Yang 《Physics letters. A》2019,383(23):2739-2743
The natural water has frequency dispersion and its permittivity is also related to temperature, which are important factors to design temperature insensitive absorber at microwave frequency. Here, a water-based metamaterial absorber which is fabricated by 3D-printing is proposed. The absorber can perform stably at different temperatures and it also shows 90% absorption in the frequency range of 7.9–21.7 GHz. The experiment proves that the absorber can work at a wide incident angle and is polarization insensitive. Based on these features, the water-based absorber could be applied to various electromagnetic scenarios such as stealth technology and electromagnetic compatibility in temperature-variable environment. 相似文献
997.
Preparation of single-crystalline platinum nanowires with small diameters under mild conditions 总被引:1,自引:0,他引:1
We report a convenient method to synthesize single-crystalline platinum nanowires with high aspect ratio of ca. 2.0 nm diameter by sophisticated and precise control of Pt(0) nuclei and their growth. 相似文献
998.
该文应用G -函数概念, 获得了迭代矩阵谱半径新的上、下界, 所得结果推广和改进了文献[1--6]中的相应结果.这些结果适合于更广泛的矩阵类, 数值结果也表明在相同的条件下这些新界优于文献[1--6]中的界. 相似文献
999.
提出了一种基于声光折射对聚焦超声焦点声压进行非侵入式检测的方法。当一束直径小于声波长的平行光束入射穿过聚焦超声的焦点时,通过研究焦点声压与光线偏转的具体关系,建立了光线最大偏转距离与焦点声压变化的关系模型,从而计算出焦点峰值声压。为了对理论模型进行验证,采用凹球面型聚焦换能器进行实验研究。通过与采用光纤水听器测量的结果进行对比,证明理论模型的可行性。结果表明实验得到的光斑图像与理论分析的结果一致,且用该方法测得的焦点峰值声压与光纤水听器测量的结果相比,相对误差小于15%,证明该方法具有可行性,能够定量检测焦点峰值声压。模型的提出也为将声光折射效应用于整个聚焦声场的定量检测提供了实验依据和理论依据。 相似文献
1000.