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141.
A practical copper-catalyzed N-arylation of NH-containing heterocycles with arenediazonium tetrafluoroborates has been developed using CuCl as catalyst and K2CO3 as additive under ligand-free conditions. This reaction system has wide substrate scope including imides, 1H-pyrazole, 1H-tetrazoles, 1,2-benzisothiazol-3(2H)-one, and related sulfonamides and gives moderate to excellent yields (up to 95%) of the desired products. This strategy is very general, simple, environmentally friendly, and tolerant of oxygen. 相似文献
142.
本文应用弹塑性理论研究了被测试样的屈服强度、应力场对钻孔法测量残余应力过程中钻孔附加应变的影响,使用简化的理论模型推导了低速旋转钻头钻孔产生附加应变的一般表达式.结果表明钻孔引入的附加应变与被测试样的原始残余应力状态有关,随应力水平增加而增大,在压应力减小到某一临界值σ时,钻孔附加应变为零。在 Ly12铝合金上的实验测量结果与理论结果一致。 相似文献
143.
Xin Ping Ouyang Pan Zhang Chun Mei Tan Yong Hong Deng Dong Jie Yang Xue Qing Qiu 《中国化学快报》2010,21(12):1479-1481
<正>Lignosulfonate with low polydispersity index of 1.178-1.210 was isolated by gel column chromatography of Sephacryl S-100 eluted with 0.2 mol/L of NaNO_3 aqueous solution,whereas nearly monodisperse ligosulfonate fraction with polydispersity of 1.0(57 can be obtained after chromatographic separation twice.This method provides an available approach to investigate the structure and characteristics of lignosulfonate. 相似文献
144.
145.
Keller TF Müller M Ouyang W Zhang JT Jandt KD 《Langmuir : the ACS journal of surfaces and colloids》2010,26(24):18893-18901
We report a templating effect of uniaxially oriented melt-drawn polyethylene (MD-PE) films on α-helical poly(L-lysine)/poly(styrenesulfonate) (α-PLL/PSS) complexes deposited by the layer-by-layer (LBL) method. The melt-drawing process induced an MD-PE fiber texture consisting of nanoscale lamellar crystals embedded in amorphous regions on the MD-PE film surface whereby the common crystallographic c axis is the PE molecular chain direction parallel to the uniaxial melt-drawing direction. The MD-PE film and the α-PLL/PSS deposit were analyzed by atomic force microscopy (AFM) and in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) using polarized light as a complementary method. Both methods revealed that α-PLL/PSS complexes adsorbed at the MD-PE surface were anisotropic and preferentially oriented perpendicular to the crystallographic c direction of the MD-PE film. Quantitatively, from AFM image analysis and ATR-FTIR dichroism of the amide II band of the α-PLL, mean cone opening angles of 12-18° for both rodlike α-PLL and the anisotropic α-PLL/PSS complexes with respect to the PE lamellae width direction were obtained. A model for the preferred alignment of α-PLL along the protruding PE lamellae is discussed, which is based on possible hydrophobic driving forces for the minimization of surface free energy at molecular and supermolecular topographic steps of the PE surface followed by electrostatic interactions between the interconnecting PSS and the α-PLL during layer-by-layer adsorption. This study elucidates the requirements and mechanisms involved in orienting biomolecules and may open up a path for designing templates to induce directed protein adsorption and cell growth by oriented polypeptide- or protein-modified PE surfaces. 相似文献
146.
Jiang F Wang Y Hu X Shao N Na N Delanghe JR Ouyang J 《Journal of separation science》2010,33(21):3393-3399
The application of pore-gradient polyacrylamide gel electrophoresis (PG-PAGE) incorporated with carbon nanotube modified by Triton X-100 and carboxylation so as to improve the separation of human serum proteins is reported. The novel PG-PAGE was made by adding water-soluble single-walled carbon nanotubes (CNTs) when preparing the polyacrylamide gel. Significant improvements in separation of complement C3 protein and haptoglobin (Hp) in human serum were achieved. It was estimated that the interactions between the hydrophilic groups on the proteins and the surface of the CNTs result in different adsorption kinetics of complement C3 and Hp subtype on the nanoparticles incorporated in the gel, thus enhancing the separation of the two proteins in serum. This new CNT matrix-assisted PG-PAGE method for enhanced separation of complement C3 and Hp in human serum was successfully applied to distinguish the samples from liverish patients and healthy people. 相似文献
147.
In pH 1.99 sodium acetate-HCl buffer solutions at 60 °C, Rhodamine B exhibited a strong fluorescence peak at 584 nm using
an excitation wavelength of 548 nm. The fluorescence quenching occurred when Fe3O4 nanoparticles catalyzed H2O2 oxidation of Rhodamine B. Under the chosen conditions, the fluorescence intensity at 584 nm decreased when the concentration
of H2O2 increased. The fluorescence quenching intensity is linear with the concentration of H2O2 in the range of 10–200 nmol/L. Thus, a new and simple and sensitive nanocatalytic fluorescence method was proposed for the
determination of H2O2 in synthetic sample, with satisfactory results. 相似文献
148.
This article presents a technique for modelling the coupled dynamics of a railway vehicle and the track. The method is especially useful for simulating the dynamics of high speed trains running on nonlinear tracks. The main hypothesis is a cyclic system: an infinite track on which there is an infinite set of identical vehicles spaced at a regular interval of distance. Thus the main problems of the finite-length track models (e.g. the waves that reflect at the end of the track and interact with the vehicle; and the time interval of integration must be shorter than the track length divided by the velocity) are avoided. The flexibility of the method can be observed from the case studies presented in the present work: a vehicle passing over a hanging sleeper, and the vehicle-track dynamics for different ballast compaction cases. The results show the influence of the hanging sleeper gap on the wheel-rail contact forces, and the bending moment at the sleeper for different ballast compaction cases. 相似文献
149.
借鉴直流、交流的研究经验,比较了纳秒脉冲条件下几种不同的电树枝老化实验方法。对单针-板电极和多针-板电极在纳秒脉冲下实验结果的一致性进行考察,结果表明,多针-板电极系统可以在提高实验效率的同时保证结果的准确性。采用步进法和累加法进行了不同频率下聚苯乙烯电树枝引发实验,结果表明:两种方法得到的纳秒脉冲下聚苯乙烯电树枝引发电压-频率特性基本一致,在50~500 Hz范围内,引发电压随频率的升高而降低;在500~800 Hz范围内,引发电压随频率的升高而增加。最后讨论了对于不同脉冲功率装置中绝缘材料老化试验设计的方法。 相似文献
150.
适配体修饰金硒纳米合金共振散射光谱法检测痕量Hg2+ 总被引:1,自引:0,他引:1
用硼氢化钠还原法制备了金硒(AuSe)纳米合金.用单链核酸适配体(aptamer)修饰AuSe纳米合金制备了汞离子的核酸适配体纳米探针(Apta-AuSe).在pH 6.8 Na2HPO4-NaH2PO4缓冲溶液中及NaCl存在下,Apta-AuSe纳米探针亦不聚集;当Hg2+存在时,它可以稳定aptamer序列中的T... 相似文献