烷基芳基磺酸盐界面性质的分子动力学模拟

利用分子动力学方法模拟了阴离子表面活性剂在水/辛烷,水/甲苯,水/辛烷、甲苯混合油相时的动力学特点,结果很好地展示了体系静止时清楚的油水界面,并与无表面活性剂的油水界面进行了比较.利用密度剖面图可说明表面活性剂对不同油相的诱导作用.同时,模拟计算出烷基芳基磺酸盐表面活性剂在油水界面的界面张力、均方根偏差、接触面积等,由计算结果可知,油相为甲苯时能很好的降低其界面张力,油相为辛烷时更易于形成清楚的油水界面且界面强度较大.     

烯烃类分子的分子力学力场及热力学性质预测

高质量的分子力学力场是准确预测分子各种性质的前提。本文借助第一性原理计算开发了新的适用于烯烃类分子的全原子力场,将所得力场计算和预测不同的热力学性质、传递性质以及气液相平衡性质。该力场不但可以准确预测分子的气相性质,且可得到和实验值吻合较好的液相热力学性质。与已有力场相比,在应用范围和精度都有明显的改进。借助分子动力学和蒙特卡洛模拟,计算密度和实验值偏差±0.01g/ml左右,蒸发焓为±0.3 kcal/mol左右,热容为±1.0 cal/mo1·K左右,热胀系数为±10~(-4)K~(-1)左右,以及粘度为±0.02 centipoise左右。     

量子化学方法研究阴离子表面活性剂在气液界面上的吸附

用量子化学方法中的密度泛函理论,在B3LYP/6-3IG水平上,对十二烷基硫酸钠（SDS）阴离子表面活性剂与水分子形成的水合物CH₃（CH₂）₁₁OSO₃ˉ（H₂O）_n（n=0～7）进行结构优化和频率计算。从分子水平上研究了CH₃（CH₂）₁₁OSO₃ˉ在气液界面上与水分子的相互作用。计算结果表明:（1）7个水分子与极性头均采用1:1型和2:1型,即极性头中一个氧原子或2个氧原子与水分子以氢键形式构成水合层;（2）CH₃（CH₂）₁₁OSO₃中的氧原子与水分子中的氧原子最短氢键的键长（O-O键长）在0.27～0.31 nm之间,H…O键长在0.19～0.21 nm之间,O-H…O键角在140°～167°之间,均属于中强氢键:（3）水合物R（S-O）平均键长比表面活性剂单体分子分别增长了,说明形成水合物后S-O间的键减弱;（4）结合能D₀从64.04 kJ/mol增加到.428.29 kJ/mol,说明随着水分子数的增加,所获得的7种水合物的稳定性依次增强,表明最终形成的水合层是稳定的:（5）随着水分子数增加疏水基链长收缩,亲水基总电荷增加,C12-O13-S14的键角增大;（6）由于烷烃链带有了弱电荷,使胶束内核带有了部分极性,此种极性介于烷烃油相和水相的极性之间,利于表面活性剂在溶液中的聚集。     

多烷基苯的沸点与分子结构的拓扑化学研究

利用一种简单直观的一个改进的拓扑指数D,路径指数P2和位置指数S来表征多烷基苯的分子结构,并建立了多烷基苯的沸点与其分子结构之间的定量关系式。拓扑指数的相关性良好,对各种多烷基苯及其异构体的沸点的预测结果与文献值一致性令人满意。     

十二烷基磺丙基甜菜碱表面活性剂的气液界面聚集行为分子动力学模拟

采用分子动力学模拟方法对十二烷基磺丙基甜菜碱(SB12-3)在气/液界面微观聚集行为进行研究,模拟结果表明:SB12-3分子在气/液界面处紧密排列形成紧密单分子层界面膜,SB12-3亲水基团-N~+-(CH_2)_3-SO_3~--磺酸基与水分子间相互作用高于季氮离子与水分子间相互作用,水分子更易聚集与磺酸基周围,加入Ca~(2+)后磺酸基中SB12-3分子与水分子之间氢键数量基本保持不变,解释了SB12-3具有较强的耐盐性能;体系中加入Na~+和Ca~(2+)对亲水基团占有面积影响较小,SB12-3疏水链尾端碳原子灵活性与摆动空间序参数较小,有序性较好。     

混凝- 膜分离集成工艺处理表面活性剂废水的研究

废水中的表面活性剂成分复杂、分子量小,若不经处理直接排入水体,将造成水体的富营养化。膜分离法处理废水存在膜易污染、清洗困难的问题。针对上述问题,文章提出采用混凝-膜分离集成工艺处理表面活性剂废水。首先,采用相转化法自制二氧化钛改性聚偏氟乙烯超滤膜,并通过扫描电子显微镜、傅里叶红外光谱、接触角测量仪测试膜的结构和性能;然后以十二烷基苯磺酸钠配制表面活性剂废水,以聚合氯化铝作为混凝剂,研究紫外光照强度、进水流量,溶液 pH值对集成工艺处理效果的影响。研究结果表明,改性膜表面具有致密分离层,断面呈指状孔和海绵状结构;傅里叶红外光谱表明聚乙二醇和二氧化钛的加入掩盖了部分聚偏氟乙烯晶型的红外吸收;二氧化钛改性膜具有更小的接触角;紫外光照强度和进水流量对混凝-膜分离工艺影响较小,溶液酸碱性对工艺影响较大,并且当溶液 pH值为4.5时集成工艺对表面活性剂废水处理效果最佳。混凝-膜分离集成工艺作为一种新型解决方案,在大规模、高效、低成本处理生活和工业废水中有望发挥重要作用。     

表面改性四针状纳米ZnO结构与气敏性能研究

将4种质量分数(5%,10%,20%,30%)的Co(CH3COO)24H2O混合到四针状纳米ZnO原料里,采用超声化学浸泡法制备出表面改性四针状纳米ZnO颗粒。通过XRD和TEM分析了表面改性四针状纳米ZnO结构的物相和形貌特征。随着Co(CH3COO)24H2O质量分数增大,Co3O4相明显出现,Co3O4相沉积在ZnO表面上。研究表明:以表面改性四针状纳米ZnO粉末为原料制备的厚膜气敏元件,与纯ZnO气敏元件相比,Co(CH3COO)24H2O质量分数为5%的气敏元件对酒精和甲醇有较高的灵敏度,并讨论了表面改性对气敏性能的影响。     

密度泛函论1-乙基-3-甲基咪唑四氟硼酸盐离子液的结构和性质

离子液以其独特的性质广受关注,被誉为"绿色设计者溶剂",人们对其潜在的利用价值做了大量的研究.本文采用半经验PM3法和密度泛函(DFT)方法相结合,计算研究1-乙基-3-甲基咪唑四氟硼酸盐([EMIM][BF4])离子液的分子结构及其氢键作用.经PM3法预优化和在B3LYP/6-31G(d)水平上再优化得到离子对的最稳定结构,通过自然键轨道(NBO)分析阴阳离子间的电荷分布,经振动频率和强度分析得理论红外谱图.结果发现:[EMIM][BF4]离子液阴阳离子间有电荷转移,咪唑环上靠近阴离子的C-H键伸缩振动频率发生红移,且振动强度加强,阴阳离子间存在着弱氢键的作用.     

表面活性剂预报数据库(SIMS 2.0)的设计与研究

通过对现有数据库管理系统的分析,用Visual C#编写表面活性剂预报数据库的应用程序,建立了可供查询和数据输入的表面活性剂物化参数、分子结构信息以及农药配方数据库。另根据表面活性剂预报数据库中分子结构数据库的功能需要,在此工作的基础上,运用GMA算法,实现表面活性剂二维子结构检索。在预报模块中,运用多元线性回归方法建立了三种定量构效关系模型(QSPR)预报硫酸盐、磺酸盐、聚氧乙烯醚类表面活性剂的临界胶束浓度(CMC)值,以及一种预报硫酸盐类表面活性剂亲水亲油平衡值(HLB)的QSPR模型。     

中性载体K^＋与pH电极响应机理的液—液界面电化学研究

利用循环伏安法和循环线性电流扫描计时电位法，详细研究了在一系列中性载体化合物存在下钾离子和氢离子在水－硝基苯相界面上传输，描述了传输的可能机理，并计算了相应的热力学常数。电化学研究结果与基于上述中性载体的ｐＫ和ｐＨ电极的响应性能之间有良好的相关性，这表明液－液界面电化学的研究方法为液膜电极的机理研究提供了一种有价值的手段。     

氨水溶液汽液界面微观结构的分子模拟

为研究吸收式制冷机常用工质对氨水溶液的微观形态,采用分子动力学方法:蛙跳法积分运动方程,Ewald加和方法计算库仑相互作用,分别对不同摩尔浓度的氨水溶液的汽液界面的微观结构、密度分布、界面厚度、界面张力进行r分析与计算,并拟合出界面厚度随氨水溶液摩尔浓度变化的线性关系式.结果表明:氨分子比水分子更容易吸附于汽液界面处,随着氨水溶液摩尔浓度的增加,汽液界面厚度增加,汽液界面张力减小,变化趋势与实验一致.界面张力的计算值从计算结果的量级和数量上看,与实验值接近.     

高斯多峰拟合运用于十二烷基苯磺酸钠聚集状态的研究

分光光度法研究十二烷基苯磺酸钠(sodium dodecyl benzene sulfonate,SDBS)在水中的聚集行为,具体作法是测量一系列不同浓度的SDBS——碱性品红水溶液体系可见吸收光谱,其光谱特征是碱性品红(Fuchsine)单体吸收峰540-570nm和二聚体吸收峰490-530 nm叠合在一起,用Origin软件频谱分析软件包中的高斯多峰拟合法,实现了体系紫外可见光谱吸收叠合峰的分峰、峰面积(积分吸光度)、频移及半高宽计算;单体和二聚体峰面积比(相对积分吸光度A2/A1)、频移(△λ)及半高宽(w1,w2)对SDBS浓度敏感,转折点十分明显,且该转折点对应的浓度为SDBS的临界胶束浓度(critical micelle concentration, CMC)。其中体系紫外可见光谱的半高宽对表面活性剂浓度敏感是首次观察到。     

吐温-80和十二烷基苯磺酸钠混合溶液的可见吸收光谱特征及其高斯多峰拟合

报道可见吸收光谱线型的高斯多峰拟合计算,用于研究非离子表面活性剂吐温-80(Polysorbate 80,简称Tween80)和阴离子表面活性剂十二烷基苯磺酸钠(sodium dodecyl benzene sulfonate,SDBS)混合水溶液中的聚集行为。以孔雀石绿(malachite green,MG)为探针,测量一系列不同浓度的Tween80-SDBS-MG水溶液的可见吸收光谱,其特征是MG单体吸收峰(619～632)nm和二聚体吸收峰(590～606)nm叠合在一起。用Origin软件频谱分析软件包高斯多峰拟合法,计算出体系可见光谱吸收叠合峰的分峰、峰面积(积分吸光度)、频移及半高宽等光谱的线型参数;单体和二聚体峰面积比(相对积分吸光度A_2/A_1)、频移(Δλ)及半高宽(w_1,w_2)使Tween80或SDBS浓度图形,在临界胶束浓度cmc处发生突变。首次发现体系可见吸收光谱线型参数半高宽对吐温-80-十二烷基苯磺酸钠混合表面活性剂相互作用和聚集行为敏感,并成功用于研究该混合表面活性剂体系的聚集行为。     

Scalability study of molecular dynamics simulation on Godson-T many-core architecture

Molecular dynamics (MD) simulation has broad applications, and an increasing amount of computing power is needed to satisfy the large scale of the real world simulation. The advent of the many-core paradigm brings unprecedented computing power, but it remains a great challenge to harvest the computing power due to MD’s irregular memory-access pattern. To address this challenge, this paper presents a joint application/architecture study to enhance the scalability of MD on Godson-T-like many-core architecture. First, a preprocessing approach leveraging an adaptive divide-and-conquer framework is designed to exploit locality through memory hierarchy with software controlled memory. Then three incremental optimization strategies–a novel data-layout to improve data locality, an on-chip locality-aware parallel algorithm to enhance data reuse, and a pipelining algorithm to hide latency to shared memory–are proposed to enhance on-chip parallelism for Godson-T many-core processor. Experiments on Godson-T simulator exhibit strong-scaling parallel efficiency of 0.99 on 64 cores, which is confirmed by a field-programmable gate array emulator. Also the performance per watt of MD on Godson-T is much higher than MD on a 16-cores Intel core i7 symmetric multiprocessor (SMP) and 26 times higher than MD on an 8-core 64-thread Sun T2 processor. Detailed analysis shows that optimizations utilizing architectural features to maximize data locality and to enhance data reuse benefit scalability most. Furthermore, a hierarchical parallelization scheme is designed to map the MD algorithm to Godson-T many-core cluster and a simple performance model is derived, which suggests that the optimization scheme is likely to scale well toward exascale. Certain architectural features are found essential for these optimizations, which could guide future hardware developments.     

Adsorption and diffusion of benzene in the nanoporous catalysts FAU, ZSM-5 and MCM-22: a molecular dynamics study

Molecular dynamics (MD) simulations of benzene in siliceous zeolites (FAU, ZSM-5, and MCM-22) were performed at loadings of 1, 2, 4, 8, and 16 molecules per supercell. The potential energy functions for these simulations were constructed in a semi-empirical way from existing potentials and experimental energetic data. The MD simulations were employed to analyze the dynamic properties of the benzene-zeolite systems. The adsorption energies of benzene/siliceous zeolite complexes increase with increasing loading number, due to the intermolecular attraction between benzene molecules. The self-diffusion coefficient of benzene in siliceous zeolites decreases with increasing loading due to the steric hindrance between the sorbates passing each other. From the zeolite-benzene radial distribution functions it was found that the benzene molecules are relatively far from each other, about 5.2A for siliceous FAU, 5.2A for siliceous ZSM-5, and 4.8A for siliceous MCM-22. In the case of FAU, the benzene molecules prefer to be adsorbed parallel to the surface of the sodalite cage above the six-membered-ring. In ZSM-5, we found a T-structure of the benzene molecules at loadings 2, 4, and 8 molecules per supercell. At loadings of 16 molecules per supercell, the molecules are lined up along the straight channel and their movement is highly correlated. For MCM-22 we found adjacent benzene molecules at a loading of 4 molecules with an orientation similar to the stacked conformation of benzene dimer in the gas phase.     

Structure-guided cancer blockade between bioactive bursehernin and proteins: Molecular docking and molecular dynamics study

Bursehernin (5′-desmethoxyyatein) is a natural lignan, which has anti-tumor activity in vitro. In this study, the binding-inhibitory effects of bursehernin were screening on selected 80 proteins associated with cancer pathway. The computational analysis suggested inhibitory effect due to bursehernin towards proteins related to cancer proliferation, including FMS kinase receptor, heat shock protein 90-α (Hsp90-α), adenylate cyclase 10 (ADCY10), mitogen-activated protein kinase kinase (MEK1), and α-tubulin. Moreover, bursehernin could interfere with cell cycle progression via binding to cyclin B proteins. Among all screened proteins, the compound showed an interesting binding affinity to the FMS kinase receptor. The binding mode studies by molecular dynamic technique showed that aromatic ring of bursehernin compound was responsible for compound-protein interaction through pi-pi stacking with Tyr105 and Phe178 of the FMS kinase receptor. This study suggests that bursehernin has potential for development as an anti-tumor agent with an anti-proliferation, and cell cycle arrest inducing, although further studies are needed.     

Functionalized graphene as a nanostructured membrane for removal of copper and mercury from aqueous solution: A molecular dynamics simulation study

The purpose of the present study was to investigate the removal of copper and mercury using functionalized graphene as a nanostructured membrane. The molecular dynamics simulation method was used to investigate the removal ability of these ions from aqueous solution using functionalized graphene membrane. The studied systems included a functionalized graphene membrane which was placed in the aqueous ionic solution of CuCl₂ and HgCl₂. An external electrical field was applied along the z axis of the system. The results indicated that the application of electrical field on the system caused the desired ions to pass through the functionalized graphene membrane. The Fluorinated pore (F-pore) terminated graphene selectively conducted Cu²⁺ and Hg²⁺ ions. The calculation of the potential of mean force of ions revealed that Cu²⁺ and Hg²⁺ ions face a relatively small energy barrier and could not pass through the F-pore graphene unless an external electrical field was applied upon them. In contrast, the energy barrier for the Cl⁻ ion was large and it could not pass through the F-pore graphene. The findings of the study indicate that the permeation of ions across the graphene was a function of applied electrical fields. The findings of the present study are based on the detailed analysis and consideration of potential of mean force and radial distribution function curves.     

Motor adaptation with passive machines: A first study on the effect of real and virtual stiffness

Motor adaptation to novel force fields is considered as a key mechanism not only for the understanding of skills learning in healthy subjects but also for rehabilitation of neurological subjects. Several studies conducted over the last two decades used active robotic manipulanda to generate force fields capable of perturbing the baseline trajectories of both healthy and impaired subjects.