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排序方式: 共有450条查询结果,搜索用时 15 毫秒
391.
Xiang-Wu Zhang Chunsheng Wang A. John Appleby Frank E. Little 《Solid State Ionics》2002,150(3-4):383-389
Mixed-conducting lithium-ion doped emeraldine polyaniline (PAni)–polyethylene oxide (PEO) blends have been developed to achieve an optimal electronic–ionic conductivity balance in nano-tin composite anodes. Electrochemical evaluation was performed on the anodes with differing electrode preparation procedures, doping methods and PEO contents. Results indicate that both good electronic and ionic conductivity in the binder are required for rapid lithium insertion/extraction and low polarization. This doped PAni–PEO polymer blend is an attractive binder for high capacity composite anodes with low polarization. 相似文献
392.
Penney G.P. Weese J. Little J.A. Desmedt P. Hill D.L.G. hawkes D.J. 《IEEE transactions on medical imaging》1998,17(4):586-595
A comparison of six similarity measures for use in intensity-based two-dimensional-three-dimensional (2-D-3-D) image registration is presented. The accuracy of the similarity measures are compared to a “gold-standard” registration which has been accurately calculated using fiducial markers. The similarity measures are used to register a computed tomography (CT) scan of a spine phantom to a fluoroscopy image of the phantom. The registration is carried out within a region-of-interest in the fluoroscopy image which is user defined to contain a single vertebra. Many of the problems involved in this type of registration are caused by features which were not modeled by a phantom image alone. More realistic “gold-standard” data sets were simulated using the phantom image with clinical image features overlaid. Results show that the introduction of soft-tissue structures and interventional instruments into the phantom image can have a large effect on the performance of some similarity measures previously applied to 2-D-3-D image registration. Two measures were able to register accurately and robustly even when soft-tissue structures and interventional instruments were present as differences between the images. These measures were pattern intensity and gradient difference. Their registration accuracy, for all the rigid-body parameters except for the source to film translation, was within a root-mean-square (rms) error of 0.53 mm or degrees to the “gold-standard” values. No failures occurred while registering using these measures 相似文献
393.
The application of 1,3-diyl trapping reactions to the synthesis of commonly used prostanoid precursors is described. 相似文献
394.
N. C. Little L. J. Kosakowsky R. J. Speakman M. D. Glascock J. C. Lohse 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(1):103-110
A total of 81 pottery and 25 clay samples from the archaeological site and hinterland areas of Blue Creek in northwest Belize
were analyzed by instrumental neutron activation analysis and inductively-coupled-plasma mass-spectrometry at the University
of Missouri Research Reactor. Data generated for this study offers insight into local clay-resource variability and movement
of pottery in the transition from Early (A.D. 250–600) to Late Classic (A.D. 600–850) occupation. Comparison of data generated
by the two analytical techniques demonstrates the relative strengths and weaknesses of each method.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
395.
Matthew R. Dintzner Andrew J. Little Massimo Pacilli Dominic J. Pileggi Zachary R. Osner Thomas W. Lyons 《Tetrahedron letters》2007,48(9):1577-1579
Montmorillonite K10 clay was found to catalyze the hetero-Diels-Alder reaction of 2,3-dimethyl-1,3-butadiene with o-anisaldehyde and other benzaldehyde derivatives; a transition state involving chelation of the clay’s metal ions with the dienophile’s heteroatoms is proposed. 相似文献
396.
Giles K Pringle SD Worthington KR Little D Wildgoose JL Bateman RH 《Rapid communications in mass spectrometry : RCM》2004,18(20):2401-2414
The use of radio-frequency (RF)-only ion guides for efficient transport of ions through regions of a mass spectrometer where the background gas pressure is relatively high is widespread in present instrumentation. Whilst multiple collisions between ions and the background gas can be beneficial, for example in inducing fragmentation and/or decreasing the spread in ion energies, the resultant reduction of ion axial velocity can be detrimental in modes of operation where a rapidly changing influx of ions to the gas-filled ion guide needs to be reproduced at the exit. In general, the RF-only ion guides presently in use are based on multipole rod sets. Here we report investigations into a new mode of ion propulsion within an RF ion guide based on a stack of ring electrodes. Ion propulsion is produced by superimposing a voltage pulse on the confining RF of an electrode and then moving the pulse to an adjacent electrode and so on along the guide to provide a travelling voltage wave on which the ions can surf. Through appropriate choice of the travelling wave pulse height, velocity and gas pressure it will be shown that the stacked ring ion guide with the travelling wave is effective as a collision cell in a tandem mass spectrometer where fast mass scanning or switching is required, as an ion mobility separator at pressures around 0.2 mbar, as an ion delivery device for enhancement of duty cycle on an orthogonal acceleration time-of-flight (oa-TOF) mass analyser, and as an ion fragmentation device at higher wave velocities. 相似文献
397.
[reaction: see text]. A novel approach to simple C-glycosides is reported. Reductive ring opening of 1,2-anhydro sugars with titanocene(III) chloride produces an anomeric radical that can be trapped with a variety of agents. The reaction stereospecifically affords alpha-glycosides and produces a free C-2 hydroxyl group allowing for further elaboration. 相似文献
398.
399.
Summary The preparation of efficient chemically bonded phases based upon interaction of silica gel with trichlorosilanes is reported.
Chlorinated solvents are found to yield superior products whilst reaction at elevated temperatures is shown to be unnecessary.
A new capping procedure, involving methanolysis and subsequent reaction with trimethylchlorosilane, is shown to be more effective
than existing procedures. 相似文献
400.