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The structural and dynamic properties of nanoscale ethanol film on a mica surface are investigated via molecular dynamics simulations.We observe a dense,almost flat ethanol bilayer formed in the vicinity of the mica surface,with the hydrophobic alkyl groups pointing outward from the surface.Remarkably,such ethanol bilayer is laterally well-ordered with patterned adsorption sites.Each ethanol molecule in the first layer donates one hydrogen bond to the surface basal oxygen atoms and accepts one hydrogen bond from that in the second layer.The ethanol molecules within the bilayer exhibit constrained lateral mobility and delayed dynamics as compared with bulk ethanol,whereas those on top of the bilayer have bulk-like characteristics. 相似文献
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Peptide frictions in water nanofilms of various thicknesses on a mica surface are studied via molecular dynamics simulations. We find that the forced lateral motion of the peptide exhibits stick-slip behaviour at low water coverage; in contrast, the smooth gliding motion is observed at higher water coverage. The adsorbed peptide can form direct peptide-surface hydrogen bonds as well as indirect peptide-water-surface hydrogen bonds with the substrate. We propose that the stick-slip phenomenon is attributed to the overall effects of direct and indirect hydrogen bonds formed between the surface and the peptide. 相似文献
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以正硅酸乙酯(TEOS)为前驱体,采用酸碱两步催化法制备了SiO2醇凝胶。醇凝胶分别经过TEOS母液、甲基三乙氧基硅烷(MTEOS)处理后,以六甲基二硅胺烷(HMDSA)为疏水改性试剂,制备了改性SiO2醇凝胶,醇凝胶经溶剂交换后以CO2作为干燥介质,采用超临界干燥法制备了密度在30~100 mg/cm3的SiO2气凝胶。用傅里叶变换红外光谱仪(FTIR)对疏水性SiO2气凝胶进行了研究。研究结果表明,经过改性的气凝胶在潮湿环境中具有极好的尺寸稳定性和疏水性。采用精密车床加工得到了满足惯性约束聚变(ICF)物理试验要求的微柱。 相似文献
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High density gas state at water/graphite interface studied by molecular dynamics simulation 下载免费PDF全文
In this paper molecular dynamics simulations are performed to study the accumulation behaviour of N2 and H2 at water/graphite interface under ambient temperature and pressure. It finds that both N2 and H2 molecules can accumulate at the interface and form one of two states according to the ratio of gas molecules number to square of graphite surface from our simulation results: gas films (pancake-like) for a larger ratio and nanobubbles for a smaller ratio. In addition, we discuss the stabilities of nanobubbles at different environment temperatures. Surprisingly, it is found that the density of both kinds of gas states can be greatly increased, even comparable with that of the liquid N2 and liquid H2. The present results are expected to be helpful for the understanding of the stable existence of gas film (pancake-like) and nanobubbles. 相似文献
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Peptides/proteins aggregation can give rise to pathological conditions of many human diseases.Small partially ordered oligomers formed in the early stage of aggregation,rather than mature fibrils,are thought to be the main toxicity agent for the living cell.Thus,understanding the pathway and the underlying physical mechanism in the early stage of aggregation is very important for prevention and treatment of these protein functional diseases.Herein we use all-atom molecular dynamics simulations to study the aggregation of four NFGAIL hexapeptides(NFGAIL peptide is a core segment of human islet amyloid polypeptide and exhibits similar aggregation kinetics as the full-length polypeptide).We observe that the peptide monomers in water mainly adopt non-structural coil configurations;the four peptides which are randomly placed in water aggregate spontaneously to partially ordered oligomer(β-sheets)through dimerization or trimerization,with the dimerization predominated.Both parallel and anti-parallelβ-sheets are observed.The hydrophobic interactions drive the initial peptides associations,and the subsequent conformational fluctuations promote the formation of more hydrogen bonds between the dangling hydrogen sites in the main chains of peptides. 相似文献
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以三聚氰胺(M)和甲醛(F)为原料,经溶胶-凝胶和超临界干燥工艺制备出密度156.82 mg/cm3的MF气凝胶。通过X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)及比表面测定仪(BET)等测试手段研究了其结构和性能。XRD结果表明MF气凝胶是一种非晶材料;TEM和SEM结果表明MF气凝胶所有孔孔径均在10 nm左右;孔径分布及比表面积测试仪测得该气凝胶具有很高的比表面积(1 015.98 m2/g),孔径大小主要为5~30 nm。所得MF气凝胶是一种具有nm量级3维网络结构的轻质多孔材料,有望在ICF实验靶中得到应用。 相似文献
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