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A hybrid particle–continuum method is used to study the shear flow confined between two opposing walls, one of which is coated with polymer chains. Molecular dynamics (MD) is used in the particle region near the brush and Navier–Stokes (NS) equations are applied in the remaining region where the continuum assumption holds. The information exchange from the continuum region to the particle region is implemented using the constrained particle dynamics. Both Couette shear flow and oscillatory flow are considered in the present work. The effect of the shear flow on the conformational characteristics of polymer brushes is analyzed. In the overlap region, the velocities obtained from MD simulations are smoothly connected with those from NS equations. Our investigations demonstrate that the hybrid particle–continuum model is valid in exploring the shear behavior of polymer brushes. 相似文献
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Qianqian Cao Chuncheng Zuo Lujuan Li Mingfeng Gao 《Colloid and polymer science》2011,289(10):1089-1102
Using Brownian dynamics simulations, we study the effect of the charge ratio, the surfactant length, and the grafting density
on the conformational behavior of the complex formed by the polyelectrolyte brush with oppositely charged surfactants. In
our simulations, the polyelectrolyte chains and surfactants are represented by a coarse-grained bead-spring model, and the
solvent is treated implicitly. It is found that varying the charge ratio induces different morphologies of surfactant aggregates
adsorbed onto the brush. At high charge ratios, the density profiles of surfactant monomers indicate that surfactant aggregates
exhibit a layer-by-layer arrangement. The surfactant length has a strong effect on the adsorption behavior of surfactants.
The lengthening of surfactant leads to a collapsed brush configuration, but a reswelling of the brush with further increasing
the surfactant length is observed. The collapse of the brush is attributed to the enhancement of surfactants binding to polyelectrolyte
chains. The reswelling is due to an increase in the volume of adsorbed surfactant aggregates. At the largest grafting density
investigated, enhanced excluded volume interactions limit the adsorption of surfactant within the polyelectrolyte brush. We
also find that end monomers in polyelectrolyte chains exhibit a bimodal distribution in cases of large surfactant lengths
and high charge ratios. 相似文献
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Two special classes of conserved densities involving arbitrary smooth functions are explicitly formulated for the generalized Riemann equation at arbitrary N. The particular case when N = 2 covers most of the known conserved densities of the equation, and the result is also extended to the famous Gurevich-Zybin, Monge-Ampere and two-component Hunter-Saxton equations by considering certain reductions. 相似文献
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Lujuan Liao Zhenjie Li Wei Hu Yan Huang Bu-min Liu Lisheng Wang Mian Wang Jianyi Wang 《Tetrahedron letters》2018,59(27):2683-2687
A novel H2S-responsive fluorescent probe Rh-Lyso-H2S has been designed and synthesized. The Rh-Lyso-H2S shows high sensitivity and selectivity toward H2S, with a limit of detection of 3.36?×?10?7?M. The reason is that Rh-Lyso-H2S changed from a stable non-conjugated closed-ring lactone conformation with weak fluorescence to a conjugated open-ring conformation with strong fluorescence in the presence of H2S. The Rh-Lyso-H2S has a good lysosome-targeting capacity and is used to detect lysosomal H2S in living cells, which is driven via the protonation of its basic morpholine moiety by acidic lysosomes. Rh-Lyso-H2S is triggered by H2S via removing the thiophenecarboxylate group, and the corresponding activated mechanism of Rh-Lyso-H2S toward H2S is proposed. 相似文献
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Mediterranean Journal of Mathematics - Let G be a locally compact Abelian (LCA) group which possesses a covering family. We define an atomic Hardy space $$H^1(G)$$ and $$\textrm{BMO}(G)$$ of... 相似文献
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自动化测试技术是软件测试未来的发展方向,自动化测试过程中会遇到测试脚本维护困难、脚本维护工作量大、重用性差、测试效率低的问题;怎样引入自动化测试框架技术解决上面的问题是测试工程师一直在探讨和研究的主流问题;探讨研究了在自动化测试框架技术应用过程中遇到的下列问题:脚本库中测试脚本存放技术;测试用例设计技术;测试数据的管理和分类技术;对象库共享技术等;初步达到了以下结果:提高了测试代码的可重用性和可维护性,测试执行更有效,从而降低了测试成本;最后使用了协同办公平台实例,从而证明了基于QTP的协同办公平台的自动化测试框架可以降低多余的代码量,加快代码生成速度,缩小测试周期等特点,从而提高代码的利用率和可维护性。 相似文献
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Qianqian Cao Chuncheng Zuo Lujuan Li Yinhe Zhang 《Macromolecular theory and simulations》2012,21(7):492-499
A molecular dynamics study of the electrophoresis of bottle‐brush polyelectrolytes (BPEs) through nanochannels is reported. The BPE molecules consist of a neutral backbone with charged side chains. For strong attractive interactions between the BPE and the wall, the BPE is being trapped on the channel surface. A stretching–shrinking migration of the BPE in a channel of radius 6σ is observed at relatively strong electric fields. The stretching–shrinking transition is periodic for intermediate electric fields but not for stronger electric fields. The BPE also shows a transverse migration toward the wall at weak electric fields, while toward the center with further enhancing the electric field. For a channel with larger radius 12σ, the BPE does not migrate in the stretching–shrinking manner.
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Qianqian Cao Chuncheng Zuo Yanhong Ma Lujuan Li Siyan Chen Zhangyou Hu 《Journal of Polymer Science.Polymer Physics》2011,49(12):882-889
We report molecular dynamics simulations on bottle‐brush polyelectrolytes end‐grafted to a planar surface. For each bottle‐brush polyelectrolyte, flexible charged side chains are anchored to one neutral main chain. The effects of the counterion valence and the grafting density on the density profiles and the structural characteristics of the brush were studied in this work. It is found that the electrostatic repulsion between charged monomers in the side chains leads an extended conformation of the brush in a solution containing monovalent counterions, while strong electrostatic binding of multivalent counterions to the side chains has a significant contribution to the collapse of the brush. For the trivalent case, the distribution of end monomers in the main chains becomes broader upon decreasing the grafting density, as compared with the monovalent case. However, the position of the distribution for the monovalent case is relatively insensitive to the change of the grafting density. Additionally, with increased counterion valence, enhanced electrostatic correlation between counterions and charged side chains also weakens the diffusive ability of counterions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献