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1.
A simple method was used to prepare a "switchable" electrode surface by using self-assembled monolayers of dodecanethiol on a gold electrode. The dodecane-modified electrode was electrochemically inactive until the monolayer was soaked in solutions of 1,10-phenanthroline or 2,2'-bipyridine. The electroactive form of the electrode could be reverted back to the nonelectroactive form by rinsing the electrode. Surface IR results showed that both dodecanethiol and 1,10-phenanthroline exist in the mixed monolayer. 相似文献
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Zero-valent palladium precatalysts containing rigid bidentate bis(arylimino)acenaphthene ligands (shown schematically) facilitate the highly stereoselective homogeneous catalytic hydrogenation of alkynes to (Z)-alkenes. Internal, terminal, aryl-substituted, and cyclic alkynes are suitable substrates, as are some enynes, which are chemoselectively hydrogenated to dienes. E=CO(2)Me; R(1), R(2)=4-OCH(3), 4-CH(3), 2,6-(CH(3))(2). 相似文献
3.
The sensitivity of all ion trap mass spectrometry (ITMS) methods is dependent on the trapping efficiency of the instrument. For ITMS instruments utilizing external ion sources, such as laser desorption, trapping efficiency is known to depend on the phase and amplitude of the radio frequency (RF) potential applied to the ring electrode at the time of ion introduction. It is remarkable that, in a considerable body of literature, no consensus exists regarding the effects of these parameters on the efficacy of trapping externally generated ions. In this paper, a summary of the literature is presented in order to highlight significant discrepancies. New laser desorption ion trap mass spectrometry (LD-ITMS) data are also presented, from which conclusions are drawn in our effort to clarify some of the confusion. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
4.
The design, fabrication, and testing of photoelastic models of double-lap, multiple-pin connectors are discussed. Interest
is in the stresses in the inner laps. These stresses are determined by constructing models with photoelastic inner laps and
transparent-acrylic outer laps. The connectors have two pins, in tandem, parallel to the load direction. A photoelastic-isotropic
point is shown to permit the evaluation of load sharing between the two pins. A numerical scheme, utilizing the isochromatic-
and isoclinic-photoelastic data and a finite-difference representation of the planestress equilibrium equations, is used to
compute the stresses around the two pins. Representative stress distributions and stress-concentration factors are shown. 相似文献
5.
The single component adsorption of alkanes in carbon slit pores was studied using configurational-biased grand canonical Monte Carlo simulations. Wide ranges of temperature, pressure, alkane chain length, and slit height were studied to evaluate their effects on adsorption. Adsorption isotherms and density and orientation profiles were calculated. The behavior of long alkanes at high temperatures was found to be similar to short alkanes at lower temperatures. This suggests that the isotherms may be related through the Polanyi potential theory. 相似文献
6.
A 32 x 32 microelectromechanical systems deformable mirror is controlled in closed loop with a spatially filtered Shack-Hartmann wavefront sensor and a Fourier-transform wavefront reconstruction algorithm. A phase plate based on atmospheric turbulence statistics is used to generate a 1 microm peak-valley static phase aberration. Far-field images and direct phase measurements of the residual are used to compare performance with and without the spatial filter. Use of the spatial filter reduces error in the controllable band from 20 to 6 nm rms. Residual phase power is reduced by more than a factor of 5 for all spatial frequencies up to 0.85 x 1/2d, with a maximum attenuation factor of 37. 相似文献
7.
Received October 11, 2005; accepted November 10, 2005; posted December 2, 2005 (Doc. ID 65234) We have measured a contrast of 6.5 x 10(-8) from 10 to 25 lambda/D in visible light on the Extreme Adaptive Optics testbed, using a shaped pupil for diffraction suppression. The testbed was designed with a minimal number of high-quality optics to ensure low wavefront error and uses a phase-shifting diffraction interferometer for metrology. This level of contrast is within the regime needed for imaging young Jupiter-like planets, a primary application of high-contrast imaging. We have concluded that wavefront error, not pupil quality, is the limiting error source for improved contrast in our system. 相似文献
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Two regular GC instruments were modified with injection port liners, split-mode injection systems, pressure regulators, effluent traps and needle valves to produce an all-glass GC-2 system. This simple and inexpensive system allows the quantitative analyses of phenols, hydrocarbons, acids, sterols, terpenoids, and alkaloids with excellent reproducibility and linear response. Even more impressive was its ability to analyze a C45-terpenoid alcohol, solanesol, as its TMS-derivative (M.W. 702). 相似文献
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