In situ observations of unusual drop deformation and wobbling in simple shear flow

Deformation and wobbling of a liquid drop immersed in a liquid matrix were studied under mild shear conditions for various viscosity ratios. In situ visualization experiments were conducted on a homemade transparent Couette cell incorporated to the Paar Physica MCR500 shear rheometer. The effect of drop or matrix elasticity was examined and was found to play a major role in both deformation and wobbling processes. Experimental results were compared to Jackson and Tucker (J Rheol 47:659–682, 2003), Maffettone and Minale (J Non-Newton Fluid Mech 78:227–241, 1998) and Yu and Bousmina (J Rheol 47:1011–1039, 2003) ellipsoidal models. It was found that the agreement between the Newtonian models and the experimental results required an increase in the drop viscosity. Such increment in viscosity was found to scale with the first normal stress difference.     

Imaging and analysis of wave type interfacial instability in the coextrusion of low-density polyethylene melts

This report covers experimental studies and numerical modelling of interfacial instability in the bi-layer coextrusion flow of two low-density polyethylene melts. Melt streams are converged at an angle of 30° to a common die land. Melt stream confluence was observed in two coextrusion die arrangements. In one die design, which we term ‘bifurcated’ the melt stream is split by a divider plate in the die after being delivered from a single extruder. In the other design melt streams are delivered to a die from two separate extruders. In each die design melt flow in the confluent region and die land to the die exit was observed through side windows of a visualization cell. Velocity ratios of the two melt streams were varied and layer thickness ratios producing wave type interfacial instability determined for each melt for a variety of flow conditions. Stress and velocity fields in the coextrusion arrangements were quantified using stress birefringence and particle image velocimetry techniques.     

Rapid passive MR catheter visualization for endovascular therapy using nonsymmetric truncated k-space sampling strategies

Passive catheter tracking guidance by MRI is a promising approach for endovascular therapy that may have several clinical advantages over the more frequently employed active MR approaches. However, real-time MR passive tracking is problematic because it is difficult to have an image update rate >1 Hz and preserve adequate spatial and image contrast resolution. One solution for improving real-time temporal performance is the use of nonsymmetric truncated k-space sampling strategies, which acquire only a fraction of the data in both the readout and phase-encoding directions. This article investigated these acquisition strategies in combination with using (a) multicycle projection dephaser (mcPD) gradients for background suppression and (b) the projection-onto-convex sets (POCS) algorithm to reconstruct the images. The use of mcPD gradients allowed the data sampling strategies to exploit the k-space energy structure of the catheter, and POCS allowed reconstruction of high-quality MR images that were suitable for real-time passive catheter tracking and demonstrated improved geometric representations of catheter width and tip position compared to zero filling. The use of nonsymmetric truncated k-space reduced the total acquisition time.     

黄芩的13C NMR指纹图谱研究

利用PFT-NMR 核磁共振波谱仪测定了黄芩提取物的¹³C NMR图谱,对黄芩提取物的¹³C NMR指纹图谱进行了解析,并与黄芩素、千层纸素A、汉黄芩素和黄芩苷进行了比较,获得了黄芩提取物的特征峰,结果表明不同黄芩提取物的¹³C NMR指纹图谱都显示出黄酮类有效成分特征共振峰,并具有很好的重现性和高度的特征性,可以成为黄芩真伪鉴别的依据.     

基于双波长HPLC指纹谱的一级系统指纹定量法鉴定木香顺气丸质量

建立木香顺气丸(Muxiangshunqi pills, MXSQP)双波长HPLC指纹图谱, 用一级系统指纹定量法鉴定其质量. 采用RP-HPLC法, 以橙皮苷(HI)为参照物峰, 在265和326 nm下分别检测获得60和56个共有指纹峰. 以S_m和P_m为指标用系统聚类分析分别确定其中11批和12批样品指纹图谱生成265和326 nm对照指纹图谱(RFP), 并以此二个RFP为标准用一级系统指纹定量法分别评价16批样品. 分别用权重法、均值法和投影参数法整合双波长指纹谱的宏定性和宏定量信息, 用一级系统指纹定量法鉴定MXSQPs质量. 上述五种方法鉴别出12批质量基本合格, 4批含量明显不合格. 基于不同波长及双波长整合谱的一级系统指纹定量法能够对中药系统的化学指纹进行整体定性分析和整体定量分析, 是评价中药质量的便捷有效方法.     

化合物结构特征与其基因表达信息的互补性研究

化合物分子指纹在化合物相似性比较、生物芯片技术在分子标记识别中都有着重要的应用, 因而受到广泛的重视. 但是由于这两个研究对象依传统的观点, 分属于化学信息学和生物信息学两个不同的研究领域, 因此一直未能在同一研究对象中同时得到应用. 近年来, 小分子刺激的生物芯片数据的大量出现, 使得联合化合物的结构特征及其基因表达谱信息共同的用于药物筛选成为可能. 为此, 根据本质和外延互补的哲学思想, 提出了综合运用这两种数据来共同描述化合物的新方法. 通过(1)只利用化合物分子指纹, (2)只利用化合物基因表达谱信息和(3)前面两种方法互补等三种方法在化合物相似性比较的研究中, 发现本文提出的互补方法比前两种方法的查询结果更准确: (1)使结构和功能两方面均相似的化合物之间的相似性更高, (2)并且能有效使那些仅在某一方面表现非常特殊的化合物能够暴露出来, 而得到有效地排除. 本研究给化学信息者和生物信息者重新审视以往的数据, 联合致力于药物的筛选提供了线索. 化合物分子指纹(本质)和基因表达谱(外延)的互补原理则为药物的筛选提供更有效的依据, 并最终加快药物的研发进程.     

高效液相色谱指纹图谱法分析南方红豆杉药材的氯仿提取物

建立了南方红豆杉药材氯仿提取物的高效液相色谱(HPLC)指纹图谱分析方法。采用Eurospher 100 C18色谱柱(250 mm×4 mm, 5 μm),以甲醇和水为流动相进行梯度洗脱,流速为1 mL/min,检测波长为232 nm,柱温为30 ℃。以10-脱乙酰巴卡亭III(10-DABIII)为参照物,在相同的色谱条件下测定了10批不同产地的南方红豆杉药材氯仿提取物的指纹图谱,获得了11个共有指纹峰,并利用主成分分析法(PCA)对指纹图谱进行统计分析。结果表明南方红豆杉药材的质量与种植区域有关。该方法稳定、可靠,可用于南方红豆杉药材的质量控制。     

eSHAFTS: Integrated and graphical drug design software based on 3D molecular similarity

With the development of computer technology, computer-aided drug design (CADD) has become an important means for drug research and development, and its representative method is virtual screening. Various virtual screening platforms have emerged in an endless stream and play great roles in the field of drug discovery. With the increasing number of compound molecules, virtual screening platforms face two challenges: low fluency and low visibility of software operations. In this article, we present an integrated and graphical drug design software eSHAFTS based on three-dimensional (3D) molecular similarity to overcome these shortcomings. Compared with other software, eSHAFTS has four main advantages, which are integrated molecular editing and drawing, interactive loading and analysis of proteins, multithread and multimode 3D molecular similarity calculation, and multidimensional information visualization. Experiments have verified its convenience, usability, and reliability. By using eSHAFTS, various tasks can be submitted and visualized in one desktop software without locally installing any dependent plug-ins or software. The software installation package can be downloaded for free at http://lilab.ecust.edu.cn/home/resource.html . © 2019 Wiley Periodicals, Inc.     

太赫兹时域光谱在邮件隐匿危险品检测中的应用

随着电子商务的快速发展,邮件数量剧增,在邮件中隐匿危险品已经成为犯罪分子重要的犯罪手段,威胁公共安全和社会稳定。邮件的安全检查变得尤为重要,而常规的检测技术不能准确识别危险品。太赫兹波是介于红外和微波之间的电磁波,邮件中隐匿的爆炸物、毒品和有害生物因子等在太赫兹波段存在特征吸收光谱,而邮件常用的非极性包装材料可以被太赫兹波穿透。太赫兹波还具有低能性、相干性等特性,这些特性使得太赫兹技术可以实现邮件隐匿危险品高灵敏度的无损检测。文章介绍了太赫兹技术的特性,太赫兹时域光谱系统的组成和获取光学常数的菲涅尔公式解析法。该方法通过样品透射或反射信号和参考信号来获取包括吸收光谱在内的材料参数。将样品的太赫兹特征吸收光谱和已建立的各种危险品的光谱特征数据库进行比对,可以判断是否为危险品以及危险品种类。对爆炸物、毒品在太赫兹波段的特征吸收光谱的研究成果,及在各种非极性材料遮挡下吸收光谱的特异性的研究进展进行了总结。获取吸收光谱的解析法适用于较厚样品,针对薄样品,还介绍了一种P-谱法。该方法不需要参考信号就能准确获取覆盖物下样品的吸收光谱。除直接利用吸收光谱做检测外,近些年还提出了很多其他识别危险品的方法,如光谱动力学分析法,化学计量学方法和基于太赫兹时域光谱的成像分析法等。其中,光谱动力学分析法可以很好的区分吸收频率有重叠的物质;化学计量学方法可以对混合物进行成分的定性和定量分析;光谱成像法可以完成较大面积的隐匿危险品识别。分析了太赫兹时域光谱技术识别有害生物因子的可行性,以及针对有害生物因子携带量小的特点,总结了太赫兹时域光谱技术在提高生物因子检测灵敏度方面的研究进展。探讨了太赫兹技术在邮件安检应用中一些有待解决的问题,如太赫兹功率有限、受环境因素影响较大、缺乏统一的标准等,展望了未来的发展趋势。     

The art of shock waves and their flowfields

The visualization of compressible flows is a mature science that has significantly contributed to many advances in fluid mechanics. Numerous visualization records have been generated, many of which are not only noteworthy for their physical content, but also for their aesthetic appeal. Images of shock waves and their flowfields, primarily obtained with density-sensitive visualization methods, not only provide valuable information about the physical mechanisms of flows, but often have the qualities of works of art. This paper reviews briefly the role of these visualizations in science and their possible position in an art environment, while trying to establish a little-explored link between the elements of compressible fluid dynamics and some features found in various works of art.