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141.
The decomposition of peroxynitrite at physiological pH yielded a hydroxyl radical, which reacted rapidly with dimethyl sulfoxide (DMSO) to produce a methyl radical (*CH3), which was then trapped by a spin-label fluorophore nitroxide-linked naphthalene (NTEMPO), a carbon-centered radical probe with a low fluorescence intensity, and transformed to a stable diamagnetic O-alkoxyamine, a high-fluorescence compound. The fluorescence increment was proportional to the concentration of the hydroxyl radical, and then to the concentration of peroxynitrite. NTEMPO therefore was demonstrated to be capable of detecting hydroxyl radicals generated from peroxynitrite, and the method was proved to be simple and sensitive. The hydroxyl radical-mediated reactivities of peroxynitrite to several amino acids, such as tyrosine, phenylalanine and histidine, were then evaluated by the spin-labeling fluorophore NTEMPO at pH 7.4 and, 37 degrees C. The obtained data were in good agreement with the reference values, respectively. 相似文献
142.
143.
144.
145.
Kejian Bian Michael F. Cunningham 《Journal of polymer science. Part A, Polymer chemistry》2005,43(10):2145-2154
Polymeric microspheres were prepared from a Merrifield resin via nitroxide‐mediated radical polymerization. Polystyrene, poly(acetoxystyrene), and poly[styrene‐b‐(methyl methacrylate‐co‐styrene)], poly(acetoxystyrene‐b‐styrene), and poly(styrene‐co‐2‐hydroxyethyl methacrylate) copolymers were demonstrated to graft onto 2,2,6,6‐tetramethyl‐1‐piperidinyloxy nitroxide bound Merrifield resins. The polymerization control was enhanced both on the surface and in solution by the addition of sacrificial nitroxide. The significant increase in the particle diameter (more than a fivefold volume increase for polystyrene brushes) showed that polymer growth was not only on the surface but also within the particles, and this diameter increase could be adjusted through changes in the molecular weight of the polymers. The microspheres were characterized by elemental analysis, IR spectroscopy, particle size analysis, and optical microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2145–2154, 2005 相似文献
146.
In this paper, we derived the Z-scan formula for a photorefractive crystal sample under an external applied electric field.
The far-field diffraction pattern of a Gaussian beam wavefront through a photorefractive crystal is calculated by considering
spatial-phase perturbation induced by the space-charge field. The photorefractive drift nonlinearities and correspondingly,
the electro-optic coefficients r
33, r
13, (r
23) and the characteristic ratio n
3
e
r
33/n
3
o
r
13 for a cerium-doped Sr0.61Ba0.39Nb2O6 crystal are determined from the Z-scan experiments. Z-scan with enhanced sensitivity is also realized by measuring the normalized
transmittance at the off-axis position in the far field. A deviation between the off-axis Z-scan experimental results and
the theoretical prediction is discussed too.
Received: 22 July 1996/Revised version: 7 October 1996 相似文献
147.
Zhaohui Tang Xuesi Chen Qizhi Liang Xinchao Bian Lixin Yang Longhai Piao Xiabin Jing 《Journal of polymer science. Part A, Polymer chemistry》2003,41(13):1934-1941
An amino isopropoxyl strontium (Sr‐PO) initiator, which was prepared by the reaction of propylene oxide with liquid strontium ammoniate solution, was used to carry out the ring‐opening polymerization (ROP) of cyclic esters to obtain aliphatic polyesters, such as poly(ε‐caprolactone) (PCL) and poly(L ‐lactide) (PLLA). The Sr‐PO initiator demonstrated an effective initiating activity for the ROP of ε‐caprolactone (ε‐CL) and L‐lactide (LLA) under mild conditions and adjusted the molecular weight by the ratio of monomer to Sr‐PO initiator. Block copolymer PCL‐b‐PLLA was prepared by sequential polymerization of ε‐CL and LLA, which was demonstrated by 1H NMR, 13C NMR, and gel permeation chromatography. The chemical structure of Sr‐PO initiator was confirmed by elemental analysis of Sr and N, 1H NMR analysis of the end groups in ε‐CL oligomer, and Fourier transform infrared (FTIR) spectroscopy. The end groups of PCL were hydroxyl and isopropoxycarbonyl, and FTIR spectroscopy showed the coordination between Sr‐PO initiator and model monomer γ‐butyrolactone. These experimental facts indicated that the ROP of cyclic esters followed a coordination‐insertion mechanism, and cyclic esters exclusively inserted into the Sr–O bond. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1934–1941, 2003 相似文献
148.
Jie Bian Sheng‐Rong Ye Lin‐Xian Feng 《Journal of Polymer Science.Polymer Physics》2003,41(18):2135-2144
The crystallization behavior of poly(ethylene terephthalate) (PET) with disodium terephthalate (DST) as nucleating agent was investigated. A detailed analysis of the crystallization course from the melt was made with the Avrami expression. The results demonstrated that DST additive can promote the PET crystallization rate in its entire crystallizable temperature range, and the acceleration degree of DST decreases with increasing temperature after a temperature higher than 180 °C. The values of the Avrami exponent indicated that the crystallization mode in Avrami theory is not suitable for the crystallization of these polymers, and the mechanism of the heterogeneous nucleation on PET crystallization is discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2135–2144, 2003 相似文献
149.
采用射频磁控溅射方法在纯N2气氛中沉积了非晶CNx薄膜样品,并 在真空中退火至900 ℃.对高温退火引起的CNx薄膜化学成分、键合结构及其场发射特性方面的变 化进行研究.用傅里叶变换红外光谱和x射线光电子能谱分析样品的内部成分及键合结构的变化,其中sp2键及薄膜中N的含量与薄膜的场发射特性密切相关.退火实验的结果表明 高温退火可以导致CNx薄膜中N含量大量损失,并在薄膜中形成大量sp2<
关键词:
x薄膜')" href="#">CNx薄膜
化学键合
退火温度
场致电子发射 相似文献
150.
W. Bian 《Journal of Optimization Theory and Applications》2006,129(2):277-292
Sufficient conditions are given for a mapping to be γ-G inverse differentiable. Constrained implicit function theorems for
γ-G inverse differentiable mappings are obtained, where the constraint is taken to be either a closed convex cone or a closed
subset. A theorem without assuming the γ-G inverse differentiability in a finite-dimensional space is also presented.
Communicated by F. A. Potra
The author thanks the referees for valuable suggestions concerning the presentation of this paper. He also thanks Professor
J. R. L. Webb and Dr. M. French for help. 相似文献