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排序方式: 共有694条查询结果,搜索用时 15 毫秒
1.
A highly efficient protocol for the synthesis of aminopropyl functionalized ganglioside GM1b has been described. The full protected ganglioside GM1b was obtained in 71% yield within 5 h. The key feature of the synthetic approach was the use of sialic acid donor that was with a C-5 trichloroacetamide moiety and with a dibenzyl phosphite residue as leaving group at the anomeric carbon. The sialyl donor gave high yields and excellent α-anomeric selectivities with a wide variety of glycosyl acceptors ranging from C-3 or C-6 hydroxyls of galactoside to C-6 hydroxyl of glucosaminoside by using TMSOTf as catalyst in a mixture solution of acetonitrile and methylene chloride. 相似文献
2.
In this paper, we propose a sinusoidal phase modulating (SPM) interferometer that is insensitive to external disturbances, and its measuring principle is analyzed theoretically. In the SPM interferometer, the interference signal is detected by a high-speed image sensor based on a low-speed CCD and a signal processing circuit is used to obtain the phase of each point on the surface. Therefore, the surface profile can be measured real-time. The experiments measuring the surface profile of a wedge-shaped optical flat show that the measurement time of the SPM interferometer is less than 10 ms, the repetitive measurement accuracy is 4.2 nm. The results show that the impacts of nonlinear distortion of the piezoelectric transducer (PZT) and part external disturbance are removed. 相似文献
3.
Yi-Wen Han Xiao-Xiong Zeng Shu-Zheng Yang 《International Journal of Theoretical Physics》2008,47(7):2011-2020
The recent work of Robinson and Wilczek that Hawking radiation can be determined by the compensating fluxes is extended to the charged and magnetized Reissner-Nordström de Sitter black hole. We reconstruct the electromagnetic field tensor and the Lagrangian of the field corresponding to the source with electric and magnetic charges to redefine an equivalent charge and gauge potential. We construct the effect field theory between the event horizon and cosmological horizon to respectively determine the compensating fluxes from them, which are shown to exactly equal to those of Hawking radiation, by the covariant anomaly cancellation conditions. 相似文献
4.
Li Jiaojiao Mohammadi Amin Maleki Akbar 《Journal of Thermal Analysis and Calorimetry》2020,139(4):2691-2703
Journal of Thermal Analysis and Calorimetry - Microgas turbines are one of the most well-known technologies for distributed generation. Unfortunately, their efficiency is not as high as it should... 相似文献
5.
Adsorption of ponceau 4R from aqueous solutions by polyamidoamine–cyclodextrin crosslinked copolymer
Batch adsorption experiments were carried out for the removal of ponceau 4R (P4R, C.I. 16255) from aqueous solutions using a novel polyamidoamine–cyclodextrin crosslinked copolymer (PAMAM-CD). The influence of several operating variables, such as contact time, initial concentration, pH, ionic strength, was investigated. Results showed that PAMAM-CD exhibited very high adsorption capacity toward P4R. The adsorption capacity of P4R was even up to 254.3?mg/g when the initial concentration of P4R solution was 340?mg/L at 288?K. The maximum adsorption capacity occured at below pH 5. The adsorption rate was fast and over 52% of the equilibrium adsorption value occurred in the first 15?min at 308?K. Adorption kinetics followed the Ho and McKay equation. Intraparticle diffusion was involved in the adsorption process but it is not the only rate-controlling step. Equilibrium isotherm data were precisely fitted by the Langmuir model. The negative values of Gibbs free energy change indicated the spontaneous nature of adsorption. The PAMAM-CD was easily recovered by 2?M HCl as washing solvent and it could be used as a promising alternative adsorbent. 相似文献
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8.
Peng Lu Xueli Hu Yujie Li Yazhou Peng Meng Zhang Xue Jiang Youzhou He Min Fu Fan Dong Zhi Zhang 《Journal of Saudi Chemical Society》2019,23(8):1109-1118
A novel CaCO3/graphitic carbon nitride (g-C3N4) photocatalyst was synthesized for the first time via a facile calcination method using CaCO3 and melamine as precursors. The as-prepared samples were characterized using various techniques, such as scanning and transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, as well as Fourier-transform infrared, X-ray photoelectron, photoluminescence, and UV–vis diffuse reflectance spectroscopy. The results of the experiments confirm the successful coupling of CaCO3 to g-C3N4. The photocatalytic activity of the synthesized CaCO3/g-C3N4 composites was evaluated by assessing their performance in the photocatalytic degradation of crystal violet (CV) in water under visible light irradiation. The analysis shows that CaCO3/g-C3N4 exhibits higher photocatalytic activity towards CV degradation (76.0%) than pristine g-C3N4 (21.6%) and CaCO3 (23.2%). Radical trapping and electron spin resonance experiments show that hydroxyl radicals (OH) and holes (h+) are the key reactive species in the photocatalytic process. The enhanced photocatalytic activity of the composite is mainly attributed to the efficient separation rate of electron-hole pairs achieved through the incorporation of CaCO3. 相似文献
9.
Two nickel(II) complexes [Ni(NIT-l′-MeBzlrn)2(Dca)2] (I, II) (NIT-l′-MeBzIm = 2-{2′-[(l′methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide) have been prepared and structurally characterized by single-crystal X-ray diffraction. They are structural epimers. The complexe crystallizes in monoclinic, space group P21/n, Z = 4. Crystal data: C34H38N14NiO4, M r = 765.49, a = 15.019(3), b = 18.803(4), c = 15.756(3) Å, β = 109.399(3)°, γ = 90° (I); a = 13.934(3), b = 11.046(2), c = 24.570(5) Å, β = 90.024(2)° (II). The X-ray analysis reveals that Ni2+ ion resides in a distorted octahedral center. The complex was linked by intermolecular hydrogen bonds, resulting in a ID chain structure for I and a 2D network configuration for II. 相似文献
10.
The organocatalytic sulfenylation of α-nitroesters mediated by diaryl-l-prolinols was developed. A range of α-sulfenylated α-nitroesters were obtained in good yields with moderate to good enantioselectivities. 相似文献