The adsorption, vibration, and diffusion of O atoms on Rh(100), Rh(111), Rh(110), and Rh(711) surfaces were studied using the 5-parameter Morse potential (5-MP) of interaction between an adatom and a metal surface cluster. Our theoretical calculations provide information about adsorption sites, adsorption geometry, binding energy, and eigenvibration. Our results agreed very well with experimental results. Four major results follow. First, the theoretical calculation showed that on the Rh(100) surface the 4-fold hollow site is the only adsorption site. Second, on the O-Rh(111) system, the 3-fold hollow site is the stable adsorption site. Third, on the Rh(110) surface at low coverage, the O atom is adsorbed preferably on the pseudo-3-fold site, while with increasing coverage, the O atom is adsorbed not only on the pseudo-3-fold site but also on the long bridge site. Last, as for the Rh(711) stepped surface, the 3-fold site on the (111) step is metastable, whereas the 4-fold sites on the (100) terrace are stable, which enables the O atoms to diffuse easily from the 3-fold to the 4-fold site at low coverage. Therefore, the O atoms are adsorbed preferrably on the stable 4-fold sites of the (100) terrace and then later as coverage increases on the metastable 3-fold site of the (110) step. 相似文献
An on-line wavelet transform algorithm and development of voltammetric analyzer with the on-line wavelet transform (WT-voltammetric analyzer) are described. Because the on-line wavelet transform decomposes the sampled signal simultaneously with the progress of sampling, the WT-voltammetric analyzer gives all the components contained in the sampled voltammogram. Applications of the WT-voltammetric analyzer in linear sweep voltammetric analysis of mixtures of Pb(II) and Tl(I) and in square wave voltammetric analysis of mixture of Cd(II) and In(III) were investigated. Results showed that the overlapping peaks of Pb(II) and Tl(I) can be separated easily, and the peak position after the on-line wavelet transform does not change. The linearity of the calibration curves for Cd(II) and In(III) in the overlapping square wave voltammetric curves were kept after the on-line wavelet transform. Quantitative determination of Cd(II) and In(III) in mixture samples were investigated. The recoveries are between 92.5 and 107.1%. 相似文献
An extremely efficient process has been developed for the synthesis of linear silylene-acetylene and disilylene-acetylene polymers. Trichloroethylene is quantitatively converted by n-butyllithium to dilithioacetylene. Quenching with dialkyl-or diaryldichlorosilanes affords high yields of the polymers, $ \rlap{--} [{\rm SiR}_{\rm 2} \hbox{---} {\rm C} \equiv {\rm C\rlap{--} ]}_n ,{\rm and }\rlap{--} [{\rm SiMe}_{\rm 2} {\rm SiMe}_{\rm 2} - {\rm C} \equiv {\rm C\rlap{--} ]}_n $ if ClMe2SiSiMe2Cl is employed. Molecular weights are much higher with this route than when acetylene is used as the dilithio- or dimagnesium acetylide precursor. Some of these polymers can be pulled into continuous fibers, and all can be cast into coherent films and thermally converted into silicon carbide. 相似文献
The soft rot disease caused by Rhizopus stolonifer is an important disease in cherry tomato fruit. In this study, the effect of iturin A on soft rot of cherry tomato and its influence on the storage quality of cherry tomato fruit were investigated. The results showed that 512 μg/mL of iturin A could effectively inhibit the incidence of soft rot of cherry tomato fruit. It was found that iturin A could induce the activity of resistance-related enzymes including phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), glucanase (GLU), and chitinase (CHI), and active oxygen-related enzymes including ascorbate peroxidases (APX), superoxide dismutases (SOD), catalases (CAT), and glutathione reductase (GR) of cherry tomato fruit. In addition, iturin A treatment could slow down the weight loss of cherry tomato and soften the fruit. These results indicated that iturin A could retard the decay and improve the quality of cherry tomato fruit by both the inhibition growth of R. stolonifera and the inducing the resistance. 相似文献
An eight-legged vibration isolation platform (ELVIP) with dual-pyramid-shape (DPS) struts is proposed in this paper to achieve six-degree-of-freedom vibration isolation. The DPS strut has higher static stiffness and lower dynamic stiffness than the equivalent linear strut due to geometric nonlinearity, and therefore the ELVIP with DPS struts possesses high-static–low-dynamic-stiffness characteristic which is desirable for widening the frequency range of isolation. The layout of the ELVIP legs is conducive to vibration decoupling and has higher reliability than six-legged platforms. Firstly, the stiffness characteristics of the DPS strut are derived; then the dynamic model of the ELVIP with DPS struts is established and the steady-state responses are obtained analytically; finally, the isolation performance is studied and the effects of damping and excitation amplitudes are investigated. It is shown that the ELVIP with DPS struts, as a passive approach, can achieve good isolation performance in all six directions with a small static deflection.
Ternary europium complexes with thenoyltrifluoroacetone (TTA) and phenanthroline (phen) were incorporated into SiO2/polymer matrix by a sol-gel method. The gels exhibit the characteristic emission bands of europium ion. In addition, Eu3+ presents a longer fluorescence lifetime in gel than in the corresponding pure complex powder. Concentration effects on the luminescence intensity were investigated. The reasons that are responsible for above results are also discussed in the context. 相似文献
The crystal structure of B-Si pentasil zeolite molecular sieve was determined by means of the x-ray diffraction for polycrystalline samples and refined by Rietveld method.The parameters of the unit cell are e=19.983(1)A;b=19.773(1)A;c=13.303(1)A.Its space group is D2h1G-Pnma The framework topology found agrees with reported Si-Al ZSM-5zeolite molecular sieves.It is concluded from the structural determination that B is introduced into the framework of this sample. 相似文献