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91.
Improved reaction conditions for the preparation of poly(p‐phenylene sulfide) (PPS) directly from bis(4‐bromophenyl) disulfide (BBD) have been established. Heating BBD with magnesium metal afforded only a low molecular weight polymer. PPS with a melting temperature around 280 °C was obtained from BBD in the presence of sodium carbonate or zinc metal. The best results were obtained with the addition of a catalytic amount of KI to the zinc–BBD mixture. Polymers prepared by the above methods are semicrystalline and dissolve in 1‐chloronaphthalene and have properties comparable to commercial PPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 900–904, 2006 相似文献
92.
Toshiyuki Oyama Akira Kitamura Eiichi Sato Masao Tomoi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2694-2706
The factors affecting pattern‐forming properties in reaction development patterning were examined with polyarylates with various bisphenol moieties. The developability of the photosensitive polyarylates was dependent on the properties of the subtituent (R) in the bisphenol moieties. The development time decreased in the following order: R?C(CH3)2 > fluorenyl unit ? phenolphthalein unit > C(CF3)2 > SO2. This order agreed with that of the reactivity between the polyarylates and ethanolamine, and these orders can be explained by pKa of the bisphenol used to prepare the polyarylates. The development with NH2? R′? OH resulted in successful positive‐tone pattern formation. However, pattern formation with the developers containing NH2? R′? OCH3 was unsuccessful. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2694–2706, 2006 相似文献
93.
本文根据空心阴极放电中电子能量分布的物理图象,分析了原子从低激态向高激态弛豫的可能途径。建立高低激态集居数密度增量的关系。讨论高激态集居数密度增量获得可观量的条件。根据此条件分别选取钠原子的基态3s~2S_(1/2)和铜原子的亚稳态4s~2D_(3/2)为与激光共振的下能级,并激发具有较大自发发射几率的3s~2S_(1/2)→3p~2P°_(1/2)(和3p~2P°_(3/2))和4s~2D_(3/2)→4p~2P°_(1/2)跃迁,在远离上能级的高激态上观测到敏化荧光,并精确测得这些态的自发发射系数比值,而在更高激态上没有观测到敏化荧光,表明讨论中提出的条件是合理的。 相似文献
94.
95.
96.
Tom Kennedy 《Journal of statistical physics》1990,59(1-2):195-220
A fixed-point equation on an infinite-dimensional space is proposed as an alternative to the usual definition of the infinite-volume limit in discrete lattice spin systems in the high-temperature phase. It is argued heuristically that the free energy and correlation functions one obtains by solving this equation agree with the usual definitions of these quantities. A theorem is then proved that says that if a certain finite-volume condition is satisfied, then this fixed-point equation has a solution and the resulting free energy is analytic in the parameters in the Hamiltonian. For particular values of the temperature this finite-volume condition may be checked with the help of a computer. The two-dimensional Ising model is considered as a test case, and it is shown that the finite-volume condition is satisfied for0.77
critical. 相似文献
97.
本文研究了用电位滴定法测定模拟高放废液中游离酸的方法。用草酸钾做络合剂以消除Fe^3+、Al^3+、Nd^3+等多种水解离子的影响,用标准碱直接进行电位滴定,即可快速准确地测定模拟高放废液中游离酸的含量。方法的相对标准偏差为1.8%,标准加入回收率为100-101%,能为放射性废物固化试验提供可靠的分析数据。 相似文献
98.
兖州高硫煤的加氢热解脱硫及脱硫动力学 总被引:5,自引:1,他引:5
在加压热天平上,考察了氢气和氮扬气氛下高硫煤的热解脱硫。利用气相色谱在线分析研究了硫化氢氢气的逸出规律。结果表明,加氢热解比氮气下的热解有着更显著的脱友作用,脱硫率可达90%以上。而且加氢热解下65%的脱除硫转化为气相硫化氢,而氮气下热解是有80%的硫转化为液相。 相似文献
99.
Nanoscale organization of the pathogen receptor DC-SIGN mapped by single-molecule high-resolution fluorescence microscopy. 总被引:3,自引:0,他引:3
Bärbel I. de Bakker Dr. Frank de Lange Dr. Alessandra Cambi Dr. Jeroen P. Korterik Erik M. H. P. van Dijk Dr. Niek F. van Hulst Prof. Carl G. Figdor Prof. Maria F. Garcia‐Parajo Prof. 《Chemphyschem》2007,8(10):1473-1480
DC-SIGN, a C-type lectin exclusively expressed on dendritic cells (DCs), plays an important role in pathogen recognition by binding with high affinity to a large variety of microorganisms. Recent experimental evidence points to a direct relation between the function of DC-SIGN as a viral receptor and its spatial arrangement on the plasma membrane. We have investigated the nanoscale organization of fluorescently labeled DC-SIGN on intact isolated DCs by means of near-field scanning optical microscopy (NSOM) combined with single-molecule detection. Fluorescence spots of different intensity and size have been directly visualized by optical means with a spatial resolution of less than 100 nm. Intensity- and size-distribution histograms of the DC-SIGN fluorescent spots confirm that approximately 80 % of the receptors are organized in nanosized domains randomly distributed on the cell membrane. Intensity-size correlation analysis revealed remarkable heterogeneity in the molecular packing density of the domains. Furthermore, we have mapped the intermolecular organization within a dense cluster by means of sequential NSOM imaging combined with discrete single-molecule photobleaching. In this way we have determined the spatial coordinates of 13 different individual dyes, with a localization accuracy of 6 nm. Our experimental observations are all consistent with an arrangement of DC-SIGN designed to maximize its chances of binding to a wide range of microorganisms. Our data also illustrate the potential of NSOM as an ultrasensitive, high-resolution technique to probe nanometer-scale organization of molecules on the cell membrane. 相似文献
100.
高效液相色谱法测定花生中黄曲霉毒素 总被引:3,自引:0,他引:3
本文报导了用高效液相色谱-荧光检测法测定了花生中黄曲霉毒素的方法,并做了回收验证。实验证明本法具有灵敏度高,分离能力强,测试结果准确可靠,色谱条件,RP18柱,甲醇四氢呋喃水溶液作流动相,流速1mL/min。 相似文献