Bilayer swelling of nonionic surfactant and sodium dodecylsulfate mixed system by refractive-index matching

Bilayer swelling behavior of nonionic and anionic surfactant mixed aqueous solution induced by adding glycerin was studied. The phenomenon were performed on a system, polyethylene glycol ether of tridecyl alcohol with the average number of ethylene oxide of 5 (CH₃(CH₂)₁₂(OCH₂CH₂)₅OH; abbreviation IT5) and SDS mixed aqueous solution, with white cream of the upper phase and micelles (L₁) of the lower phase. White cream containing densely packed multilamellar vesicles was revealed by freeze-fracture transmission electron microscopy and polarized microscope observations. Phase transition from white cream/L₁, two-phase, to clear unique vesicle phase can be induced by adding glycerin to replace water. The addition of glycerin lowers the turbidity of the dispersion and swells the interlamellar distance between bilayers, which could be explained by refractive-index matching between solvent and bilayers.     

Effect of Modified Nano-Silica on the Reinforcement of Styrene Butadiene Rubber Composites

The performance of styrene butadiene rubber (SBR) composites filled with nano-silica has been improved by surface modification of the nano-silica using silane coupling agents. The dispersion of nano-silica in SBR rubber and the bonding force of nano-silica with SBR were significantly improved, and the physical and mechanical properties of the vulcanized rubber were greatly improved. The results showed Si69 (bis-(γ- triethoxysilylpropyl)-tetrasulfide) was the best modifier among the six silane coupling agents used in the experiments, and its optimum amount was 12% (wt) of nano-silica.     

Microsecond time-scale conformational exchange in proteins: using long molecular dynamics trajectory to simulate NMR relaxation dispersion data

With the advent of ultra-long MD simulations it becomes possible to model microsecond time-scale protein dynamics and, in particular, the exchange broadening effects (R(ex)) as probed by NMR relaxation dispersion measurements. This new approach allows one to identify the exchanging species, including the elusive "excited states". It further helps to map out the exchange network, which is potentially far more complex than the commonly assumed 2- or 3-site schemes. Under fast exchange conditions, this method can be useful for separating the populations of exchanging species from their respective chemical shift differences, thus paving the way for structural analyses. In this study, recent millisecond-long MD trajectory of protein BPTI (Shaw et al. Science 2010, 330, 341) is employed to simulate the time variation of amide (15)N chemical shifts. The results are used to predict the exchange broadening of (15)N lines and, more generally, the outcome of the relaxation dispersion measurements using Carr-Purcell-Meiboom-Gill sequence. The simulated R(ex) effect stems from the fast (~10-100 μs) isomerization of the C14-C38 disulfide bond, in agreement with the prior experimental findings (Grey et al. J. Am. Chem. Soc. 2003, 125, 14324).     

菲涅耳聚光系统下砷化镓电池输出特性研究

对理论聚光比为676的菲涅耳聚光系统下单片砷化镓太阳电池及由六片砷化镓电池的串联组件的输出特性进行分析。建立三结砷化镓电池输出特性的单指数数学模型,并与实验进行了对比。理论计算与实验吻合较好,误差在7.6%以内。实验结果表明,在相同理论聚光比下,单片电池系统能流聚光比为390,六片电池组件系统能流聚光比为281;聚光后单片电池的短路电流与峰值功率分别放大322倍与316倍,六片电池组件系统的短路电流与峰值功率分别放大275倍与272倍;电池表面能流密度为0.321MW/m2时电池的输出功率达到最大,电池表面温度高于323K将影响其工作稳定性;聚光系统的透射率每增加0.01系统效率升高约0.227%。全天累积直射辐照度为17.212MJ/m2条件下测得单片电池全天发电量为0.015kW.h,六片电池串联组件的全天发电量为0.076kW.h。     

Investigation of the characteristics of heat current in a nanofluid based on molecular dynamics simulation

Molecular dynamics simulation of nanofluid system composed of argon liquid and copper nanoparticle was carried out in this paper. To ensure the interatomic force gradually decreases to zero at the cut-off distance, Stoddard and Ford potential function was employed. Green–Kubo method was used to obtain the thermal conductivity. The characteristics of the heat current were measured by its mean value, variance, third moment, and the Shannon entropy. It was found that the thermal conductivity increases as the nanoparticle volume fraction increases, and so do the variance and the Shannon entropy of the heat current. The third moment of the heat current was almost zero, indicating that the probability distribution of the heat current is nearly symmetric about its mean value. Autocorrelation and partial autocorrelation functions of the heat current were used to investigate the correlation between the discrete heat current value and different lags.     

贻贝中有机氯农药和多氯联苯标准物质的研制及同位素稀释高分辨质谱法定值

建立了贻贝中有机氯农药(OCPs)和多氯联苯(PCBs)标准物质的研制和定值方法,该研究对我国开展环境生物标准物质的研制具有重要的方法学借鉴价值。该标准物质样品为采自大连湾海域的贻贝,其定值目标物包括18种OCPs和16种PCBs,采用的定值测量方法是目前世界上最权威、最准确的同位素稀释-高分辨气相色谱/高分辨质谱联用法(ID-HRGC/HRMS)。所研制的标准物质具有定值目标物种类多、不确定度较小(约10%)等特点。该标准物质是目前国际上唯一一种采用同位素稀释高分辨质谱法进行定值的底栖生物中OCPs标准物质,于2012年3月通过了国家一级标准物质的终审,并于2012年6月被国家质量监督检验检疫总局批准为国家一级标准物质(GBW10069)。该标准物质可用于食品安全控制、环境监测、质量检测等领域相关分析方法的评价、测量质量控制及技术仲裁检验等。     

基于分布布拉格反射光纤激光器的压力传感器

介绍了一种基于单纵模分布布拉格反射(DBR)光纤激光器的新型压力传感器.该传感器基于拍频检测原理,其解调方法与传统光波长解调相比成本低且易实现.激光器谐振腔的增益光纤在应力作用下感生双折射从而导致单纵模激光器原本简并的正交偏振模式分离,互相差拍,产生1 GHz左右的拍频.对这种新型传感器进行了理论分析和实验论证,通过对0～1.2 N范围内压力进行传感检测,测得拍频为800~1200 MHz,曲线拟合度达到99.76 %.结果表明,该压力传感器不仅延续了光纤光栅传感器高灵敏度等优点.还可以看作是在原有光纤Bragg光栅传感技术的升级,以分布布拉格反射(DBR)代替光纤光栅作为传感基元,将无源传感升级为有源传感,以提高信噪比和传输距离.     

Molecular dynamics simulation of effect of liquid layering around the nanoparticle on the enhanced thermal conductivity of nanofluids

The effect of the molecular layering at liquid–solid interface on the thermal conductivity of the nanofluid is investigated by an equilibrium molecular dynamics simulation. By tracking the position of the nanoparticle and the liquid atoms around the spherical nanoparticle, it was found that a thin layer of liquid is formed at the interface between the nanoparticle and liquid; this thin layer will move with the Brownian motion of the nanoparticle. Through the analysis of the density distribution of the liquid near the nanoparticle, it is found that more argon atoms are attracted to form the layer around the nanoparticle when the diameter of the nanoparticle is larger, and therefore lead to the more significant enhancement of the thermal conductivity of the nanofluid.     

钼酸铵溶液配制方法的探讨及优化

本文针对无机化学实验中钼酸铵溶液的配制方法及使用过程中存在的问题进行了理论分析与实验探究,提出了一种简便可行的钼酸铵溶液配制方法。磷酸根离子鉴定实验结果表明,新方法所配制的钼酸铵溶液检验现象明显且无干扰,在教学实践中取得了理想的效果。该溶液放置一定时间后,检验磷酸根现象与之前无异,便于实验室长期储备。     

超空泡航行器尾喷管实验研究

为了进一步研究尾喷管对航行器空泡形态及其力学特性的影响,在高速水洞中进行了尾喷管对超空泡形态、闭合性及其力学特性的系列实验研究.实验结果显示尾喷管长度对空泡形态和力学特性有较大影响.相同通气流量率下,尾喷管对超空泡具有拉伸效果,会改变通气空化数;并对空化阻力、升力和俯仰力矩都有较为明显的影响,且升力通道和俯仰力矩通道对尾喷管长度变化响应较为敏感.