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961.
962.
Lei Li Hui Xu Lirong Yan Zhongyun Xu Zhi Ling Liangce Rong Shu-Jiang Tu 《Tetrahedron letters》2017,58(25):2468-2474
A simple and efficient tandem reaction approach was developed for the synthesis of 5-hydroxyhydantoins from one-pot reaction of isatins, phthalic anhydride or succinic anhydride, and 1,3-dimethylurea (1,3-diethylurea). The products were gained through the ring-opening of isatins process. The advantages of this report are simple operation, mild reaction conditions, good yields and easily available raw materials. It was very important for us to obtain the intermediate product and that provided a solid basis for the correct interpretation of the reaction mechanism. 相似文献
963.
A facile method for the determination of polycyclic aromatic hydrocarbons in mosses is reported using ultrasonic-assisted extraction and gas chromatography–tandem mass spectrometry. The efficiency of ultrasonic-assisted extraction and the reagents was optimized. Tandem mass spectrometry with selective reaction monitoring was used to enhance the selectivity to reduce matrix interferences and simplify the purification protocol. The detection limits were from 0.1 to 2.0?ng/mL. The linear calibration range was two orders of magnitude and the coefficients of linear correlation exceeded 0.9992 for all analytes. The relative standard deviations within 1 day and 3 days were less than 9.0%. Recoveries from 56.8 to 109.0% were obtained in fortified mosses. The rapid, low solvent gas chromatography–tandem mass spectrometry method was used to determine polycyclic aromatic hydrocarbons in mosses. 相似文献
964.
<正>Chelate tetra(acetylacetonato) tin(Ⅳ) was prepared and used as catalyst for polytrimethylene terephthalate synthesis.It exhibited higher catalytic activity than tetrabutyl titanate,butyltinhydroxide oxide and dibutyltin oxide.Decrease in reaction time, content of terminal carboxyl group,color intensity and increase in intrinsic viscosity were observed.The unique molecular structure can be considered as factor remarkably improving the catalytic activity of tetra(acetylacetonato) tin(Ⅳ). 相似文献
965.
Yuesheng Zheng Jinliang He Bo Zhang Wei Li Rong Zeng 《Plasma Chemistry and Plasma Processing》2010,30(1):55-73
Numerical simulations are presented for the ion flow effects on the negative direct current corona in air. One dimensional
equivalent steady corona model containing the continuity equations for electrons and ions on the basis of Townsend theory
coupled with Poisson’s equation is applied. The conductor radius and the electric field intensity on conductor surface keep
constant under the standard atmosphere condition in this paper. The results suggest that the space charges within the plasma
region have no influence on the electric field distribution throughout the interelectrode gap, which is only governed by the
ion flow. The influences of the gap distance and the corona current on the corona discharge within the plasma region have
been investigated. If the voltage-current characteristics of the negative corona discharge are measured, the ion flow region
and the plasma region can be investigated individually. Based on Kaptzov’s hypothesis, the plasma region can be investigated
solely. 相似文献
966.
A novel polymeric photoinitiator P(MPBP‐co‐DMAEMA), bearing side‐chain benzophenone (BP) and coinitiator amine, was synthesized through free radical copolymerization of a polymerizable photoinitiator, 4‐[(4‐maleimido)phenoxy]benzophenone (MPBP), and a polymerizable coinitiator amine, N, N‐dimethylaminoethyl methacrylate (DMAEMA). In order to find out the influences of coinitiator amine on photopolymerization, a polymeric coinitiator amine, P(DMAEMA), was also synthesized for comparison. FT‐IR, 1H NMR, and GPC analyses confirm the structures of polymers. The UV‐Vis spectra of polymeric photoinitiator P(MPBP‐co‐DMAEMA) and polymerizable photoinitiator MPBP are similar, and both exhibit high red‐shifted maximal absorption as compared with BP. The photopolymerization of 1,6‐hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA), initiated by MPBP/DMAEMA, MPBP/P(DMAEMA), and P(MPBP‐co‐DMAEMA) systems, was studied by photo‐DSC. The results indicate that P(MPBP‐co‐DMAEMA) is most efficient for the polymerization of both HDDA and TMPTA, and MPBP/P(DMAEMA) is the least efficient of the three photoinitiating systems. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
967.
Shu‐Wei Tang Jing‐Dong Feng Yong‐Qing Qiu Hao Sun Feng‐Di Wang Ying‐Fei Chang Rong‐Shun Wang 《Journal of computational chemistry》2010,31(14):2650-2657
Electronic structures and nonlinear optical properties of two highly deformed halofullerenes C3v C60F18 and D3d C60Cl30 have been systematically studied by means of density functional theory. The large energy gaps (3.62 and 2.61 eV) between the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs) and the strong aromatic character (with nucleus‐independent chemical shifts varying from ?15.08 to ?23.71 ppm) of C60F18 and C60Cl30 indicate their high stabilities. Further investigations of electronic property show that C60F18 and C60Cl30 could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states and frontier molecular orbitals are also calculated, which present that HOMOs and LUMOs are mainly distributed in the tortoise shell subunit of C60F18 and the aromatic [18] trannulene ring of C60Cl30, and the influence from halogen atoms is secondary. In addition, the static linear polarizability and second‐order hyperpolarizability of C60F18 and C60Cl30 are calculated using finite‐field approach. The values of and for C60F18 and C60Cl30 molecules are significantly larger than those of C60 because of their lower symmetric structures and high delocalization of π electrons. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010 相似文献
968.
微波辅助共沉淀法制备SrCO_3∶Eu~(3+)红色荧光粉 总被引:2,自引:2,他引:0
采用微波辅助共沉淀法制备SrCO3∶Eu3+红色荧光粉,并利用XRD、SEM和PL-PLE分别对样品SrCO3∶Eu3+的物相、形貌和发光性能进行表征。研究了激发波长以及Eu3+浓度对样品发光性能的影响。结果表明,掺杂Eu3+作为红色发光中心进入到文石型碳酸锶晶格中占据非中心对称的格位。不论是以284nm为中心的Eu3+-O2-电荷迁移带跃迁激发,还是以393nm、464nm的f-f跃迁激发,样品的发射光谱均以614nm为主,对应于Eu3+的电偶极跃迁5D0→7F2,属于红色发光。随着Eu3+掺杂浓度的增大,发光强度先增加后减小,其中在284nm激发下的猝灭浓度为3mol%;在393nm和464nm激发下的猝灭浓度为12mol%。根据Dexter理论,样品的浓度猝灭机理为电偶极-偶极跃迁。这种红色荧光粉SrCO3∶Eu3+有望应用于荧光灯和白光LED领域。 相似文献
969.
Syntheses,Structural Characterization and Thermoanalysis of Transition-Metal Compounds Derived from 3,5-Dinitropyridone 总被引:1,自引:0,他引:1
Rong Fan Qiu-Ping Zhou Guo-Fang Zhang Mei-Yu Cai Ping Li Li-Hua Gan Feng-Qi Zhao Ji-Zhen Li Xue-Zhong Fan Seik Weng Ng 《Journal of chemical crystallography》2010,40(3):266-271
Abstract
Nine metal compounds of Mn(II), Zn(II) and Cd(II) derived from dinitropyridone ligands (3,5-dinitropyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N- hydroxide, 4HDNPO) were characterized by elemental analysis, FT-IR and partly by TG-DSC. Three of which were further structurally characterized by X-ray single-crystal diffraction analysis. The structures of the three compounds, Mn(4DNP)2(H2O)4, 4, Zn(4DNPO)2(H2O)4, 8, and Cd(4DNPO)2(H2O)4, 9, crystallize in the monoclinic space group P2(1)/n and Z = 2, with a = 8.9281(9), b = 9.1053(9), c = 10.6881(11) Å, β = 97.9840(10)° for 4; a = 8.4154(7), b = 9.9806(8), c = 10.5695(8) Å, β = 97.3500(10)° for 8; a = 8.5072(7), b = 10.2254(8), c = 10.5075(8) Å, β = 96.6500(10)° for 9. All three complexes are octahedral consisting of four equatorial water molecules, and two nitrogen or oxygen donor ligands (DNP or DNPO). The abundant hydrogen-bonding and π-π stacking interactions seem to contribute to stabilization of the crystal structures of the compounds. The TG-DTG results revealed that the complexes showed a weight loss sequence corresponding to all coordinated water molecules, nitro groups, the breaking of the pyridine rings and finally the formation of metal oxides. 相似文献970.
The dynamic analysis of biological living samples is one of the particular interests in life sciences. An improved digital
holographic microscope for long-term quantitative phase-contrast imaging of living cells is presented in this paper. The optical
configuration is optimized in the form of a free-space-fiber hybrid system which promotes the flexibility of imaging in complex
or semi-enclosed experimental environment. Aberrations compensation is implemented taking into account the additional phase
aberration induced by liquid culture medium in long-term observation. The proposed approach is applied to investigate living
samples of MC3T3-E1 and MLO-Y4 cells. The experimental results demonstrate its availability in the analysis of cellular changes. 相似文献