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应用密度泛函理论(DFT)和B3LYP/6-31+G**方法,对金属Cr9团簇与DNA/RNA的碱基的相互作用规律进行了研究. 运用势能面扫描的方法和计算各种复合体的结合能, 得到了Cr9团簇在各碱基的不同的点附近与碱基形成复合体时,其复合体的稳定性大小的分布情况. 发现Cr9团簇通过接近碱基的环上氮原子及氧原子与其结合时,所构成的Cr9团簇-碱基复合体比较稳定. 通过对复合体的前线轨道的分析,找出了各种Cr9团簇-碱基复合体的结合能大小不同的原因.研究结果表明,结合能比较大的Cr9团簇-碱基复合体的最高占有轨道(HOMO)由Cr-d和N-p(或O-p)轨道杂化而成,共价相互作用为团簇与碱基结合的主要因素. 结合能较小的Cr9团簇-碱基复合体的HOMO中没有团簇与碱基的电子云的重叠,范德瓦尔斯力是两者结合的主要因素. 本文的研究对揭示金属铬团簇对生物体影响的规律,以及对探测和监控生物体中铬团簇的都有着要的意义. 相似文献
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Aiming at the dispersion stability of nanopartieles regarded as the guide of heat transfer enhancement, we investigate the viscosity and the thermal conductivity of Cu and Al2O3 nanoparticles in water under different pH values. The results show that there exists an optimal pH value for the lowest viscosity and the highest thermal conductivity, and that at the optimal pH value the nanofluids containing a small amount of nanoparticles have noticeably higher thermal conductivity than that of the base fluid without nanoparticles. For the two nanofluids the enhancements of thermal conductivity are observed up to 13% (Al2O3-water) or 15% (Cu-water) at 0.4 wt%, respectively. Therefore, adjusting the pH values is suggested to improve the stability and the thermal conductivity for practical applications of nanofluid. 相似文献
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Effect of Distribution Pattern of Molecular Dipoles on Microscopic Second-Harmonic Generation 总被引:1,自引:0,他引:1 下载免费PDF全文
We set up a model for dealing with the second-harmonic generation (SHG) from molecular dipoles in a line alignment pattern rather than a planar distribution under a microscope. Because of this model, it is possible to perform a flexibly quantitative investigation of SHG from collagen fibres at a molecular level The line alignment pattern induces more significant modifications in both the angular dipole distribution structure A(θ, φ) and the second-harmonic power structure θ(θ, φ), compared to a planar distribution. Also, the line Mignment angle t has strong effect on A(θ, φ) and θy(θ, φ), resulting in an irregular SHG angular power distribution. That is to say, it is unnecessary for SHG emission to present two well-defined off-axis lobes. The total SHG power shows two symmetrical peaks at angles of t = 50° and t - 130° while a drop at t = 90°. The weakest SHG signals can be measured at t = 0° and t = 180°. 相似文献
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We present a tumour cell growth process model including a multiplicative coloured noise and an additive coloured noise correlated. How the noise cross-correlation intensity λ and correlation time T can affect the steady state properties of tumour cell growth model are discussed by solving an approximative Fokker-Planck equation. It is found that the increase of noise correlation time T can cause the tumour cell number increasing, but the increase of multiplicative noise intensity can cause the tumour cell number extinction. We also find that the increase of cross-correlation intensity λ in the case of 0 〈 λ 〈 1 can cause the tumour cell number extinction, whereas increase of cross-correlation intensity λ in the case of λ 〈 0 can cause the tumour cell number increasing. 相似文献
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