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41.
Frequency response to liquid density of a piezoelectric quartz crystal sensor with longitudinal wave
Elimination of longitudinal wave effect is an important aspect in the detection cell design, although such consideration is ignored in most of references. Three detection cells were designed to investigate the influence of longitudinal wave effect on the frequency response of a piezoelectric quartz crystal (PQC) to liquid density. In the cell with horizontally mounted quartz crystal, the air/liquid interface acts the reflection surface for the longitudinal wave. The variation in liquid height by regent addition or solvent evaporation can result in fluctuation in the oscillating frequency of the PQC. The influence of the longitudinal wave is more obvious in a test liquid of lower density. In the cell with perpendicularly mounted quartz crystal, the longitudinal wave is mainly reflected back by the inner wall body. The fine structure of plotting of frequency shift (Δf) versus (ρη)1/2 shows a wave shape, which is different from the well-known linear relationship between of Δf and (ρη)1/2, where ρ and η are the density and viscosity of the liquid, respectively. And wave-shaped frequency-temperature curves were observed. The longitudinal wave was a kind of potential error source in the PQC measurements. The longitudinal wave effect can be efficiently eliminated by using a rough reflection surface. After eliminating the influence of reflected longitudinal wave, the stability of the sensor PQC was much improved. 相似文献
42.
SMAI和CI法制备的Ni—Ag/SiO2催化剂的结构与催化性质研究 总被引:1,自引:0,他引:1
应用溶剂化金属原子浸渍(SMAI)法和普通浸渍(CI)法制备了金属含量相同的SiO2负载Ni-Ag双金属催化剂。XRD和磁测定结果表明SMAI催化剂中Ni和Ag的粒度均小于金属含量相同的CI催化剂,SMAI催化剂中Ni和Ag未形成合金,而CI催化剂中Ni和Ag形成了合金。SMAI和CI催化剂都具有超顺磁性。研究了这些催化剂在甲苯加氢反应的催化性质,结果表明与组成相同的普通浸渍法催化相比,SMAI催 相似文献
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Wu X Sun S Yang J Wang M Liu L Guo C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):896-901
At pH 9.75, the resonance light scattering (RLS) intensity of OA–Eu3+ system is greatly enhanced by nucleic acid. Based on this phenomenon, a new quantitative method for nucleic acid in aqueous solution has been developed. Under the optimum condition, the enhanced RLS is proportional to the concentration of nucleic acid in the range of 1.0 × 10−9 to 1.0 × 10−6 g/ml for herring sperm DNA, 8.0 × 10−10 to 1.0 × 10−6 g/ml for calf thymus DNA and 1.0 × 10−9 to 1.0 × 10−6 g/ml for yeast RNA, and their detection limits are 0.020, 0.011 and 0.010 ng/ml, respectively. Synthetic samples and actual samples were satisfactorily determined. In addition, the interaction mechanism between nucleic acid and OA–Eu3+ is also investigated. 相似文献
46.
A tandem Wittig-type reaction via allylgallation of magnesium acetylides to afford allyl allenes was reported. As a result of the ready availability of starting materials and the simple and convenient operation, this reaction would have potential utility in organic synthesis. 相似文献
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用Java Applet编写大学物理实验数据处理软件 总被引:2,自引:0,他引:2
本文介绍了用Java语言编写的大学物理实验数据处理软件,此软件实现简单、操作方便、人机交互界面友好,且程序容易实现Web化。 相似文献
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Xue C Yonet-Tanyeri N Brouette N Sferrazza M Braun PV Leckband DE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(14):8810-8818
The protein resistance of poly(N-isopropylacrylamide) brushes grafted from silicon wafers was investigated as a function of the chain molecular weight, grafting density, and temperature. Above the lower critical solution temperature (LCST) of 32 °C, the collapse of the water-swollen chains, determined by ellipsometry, depends on the grafting density and molecular weight. Ellipsometry, radio assay, and fluorescence imaging demonstrated that, below the lower critical solution temperature, the brushes repel protein as effectively as oligoethylene oxide-terminated monolayers. Above 32 °C, very low levels of protein adsorb on densely grafted brushes, and the amounts of adsorbed protein increase with decreasing brush-grafting-densities. Brushes that do not exhibit a collapse transition also bind protein, even though the chains remain extended above the LCST. These findings suggest possible mechanisms underlying protein interactions with end-grafted poly(N-isopropyl acrylamide) brushes. 相似文献
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