Self-emulsification in chemical and pharmaceutical technologies

The interest in the low energy self-emulsification techniques has exploded in the recent years, driven by three main trends: by the transition to “greener” technologies in both its aspects—less energy consumption and replacement of the petrochemicals by natural ingredients; by the costly and maintenance demanding equipment for nanoemulsification; and by the quest for efficient and robust self-emulsifying formulations for oral drug delivery. Here, we first present a brief overview of the main known low-energy methods for nanoemulsion formation, focusing on their mechanistic understanding and discussing some recent advances in their development and applications. Next, we review three conceptually new approaches for self-emulsification in chemical technologies, discovered in the last several years. The colloidal features and the specific requirements of the self-emulsifying drug-delivery systems (SEDDS) are also discussed briefly. Finally, we summarize the current trends and the main challenges in this vivid research area.     

Force-field parametrization based on radial and energy distribution functions

We propose a novel force-field-parametrization procedure that fits the parameters of potential functions in a manner that the pair distribution function (DF) of molecules derived from candidate parameters can reproduce the given target DF. Conventionally, approaches to minimize the difference between the candidate and target DFs employ radial DFs (RDF). RDF itself has been reported to be insufficient for uniquely identifying the parameters of a molecule. To overcome the weakness, we introduce energy DF (EDF) as a target DF, which describes the distribution of the pairwise energy of molecules. We found that the EDF responds more sensitively to a small perturbation in the pairwise potential parameters and provides better fitting accuracy compared to that of RDF. These findings provide valuable insights into a wide range of coarse graining methods, which determine parameters using information obtained from a higher-level calculation than that of the developed force field. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.     

基于科赫曲线分形结构太赫兹带通滤波器

太赫兹滤波器是太赫兹通信、太赫兹成像和太赫兹检测等太赫兹应用系统中不可或缺的功能器件。按照不同的分类方式,滤波器有不同的种类,常见的按照选频功能可分为高通滤波器、低通滤波器、带阻滤波器和带通滤波器。为了实现在太赫兹波段的滤波效果,世界各地的研究人员利用不同的结构、材料和控制方式实现了功能各异的太赫兹滤波器,但是考虑到设计的器件要应用到太赫兹系统中,成本低廉、结构简单、性能优越的太赫兹滤波器一直是研究人员的追求。分形概念自提出以来在很多研究领域都有了快速发展,但是在太赫兹波段的应用还不是很常见,特别是应用于太赫兹功能器件的设计。引入分形中科赫曲线的概念设计并制备了一种新型的太赫兹带通滤波器,该滤波器是在金属薄膜上刻蚀出科赫曲线分形结构,当太赫兹波垂直入射到该滤波器时候实现了在太赫兹波段的窄带滤波。在滤波器的设计过程中,追求理论与实验相结合,首先在电磁仿真软件中建立科赫曲线分形结构滤波器模型进行计算,探究分形结构应用于太赫兹波段进行滤波的可行性,在进行多次计算之后得到优化后的尺寸和结构,然后根据优化后的尺寸加工出科赫曲线分形结构太赫兹滤波器样品,并且将样品放在太赫兹时域光谱系统中进行实验测量,得到实验数据后与仿真结果进行比较。在仿真中利用了时域有限差分法模拟科赫曲线分形结构太赫兹带通滤波器的传输特性,优化后的仿真结果表明:滤波器的谐振频率为0.715 THz,透射系数能够达到0.92,-3 dB带宽为21.9 GHz,将仿真得到的散射参数进行S参数反演得到了太赫兹滤波器样品的电磁参数,这在理论上分析了太赫兹波在谐振点处产生透射增强的原因。利用飞秒激光微加工系统制备了尺寸优化后的科赫曲线分形结构太赫兹带通滤波器样品,然后使用太赫兹时域光谱系统对样品的传输特性进行测试,对实验得到的时域数据进行快速傅里叶变换之后得到频域数据,再把频域数据进行归一化处理后与之前的电磁仿真结果进行对比,发现实验测得的结果与电磁软件仿真得到的结果较为吻合。     

基于连续量子级联激光器的1103.4cm–1处NH3混叠吸收光谱特性研究

由于NH3在大气气溶胶化学中具有重要作用,所以快速和精确反演NH3浓度对环境问题非常重要.本文以9.05μm的室温连续量子级联激光器(quantum cascade laser,QCL)作为光源,采用波长扫描直接吸收可调谐二极管激光吸收光谱(tunable diode laser absorption spectroscopy,TDLAS)技术,研究了QCL在1103.4 cm–1的光谱特性,获得了激光器控制的温度电流与波长的关系.设计了QCL二级温控的低压实验平台,测量氨气在1103.4 cm–1处的6条混叠吸收线,在降低压强的情况下谱线展宽变小,使混叠光谱分离,由此计算各条吸收线的线强,进一步对测量不确定度进行分析.针对混叠严重的光谱提出了低压分离单光谱精确反演气体浓度的方法,并进行了实验验证.通过与HITRAN数据库进行结果对比,得出氨气在1103.4 cm–1的实验测量线强值与数据库偏差为2.71%-4.71%,实验测量线强值的不确定度在2.42%-8.92%,极低压条件下反演浓度与实际值的偏差在1%-3%.     

Solvent- and Substrate-Induced Chiroptical Inversion in Amphiphilic,Biocompatible Glycoconjugate Supramolecules: Shape-Persistent Gelation,Self-Healing,and Antibacterial Activity

We have shown solvent- and substrate-dependent chiral inversion of a few glycoconjugate supramolecules. (Z)-F-Gluco, in which d -glucosamine has been attached chemically to Cbz-protected l -phenylalanine at the C terminus, forms a self-healing hydrogel through intertwining of the nanofibers wherein the gelators undergo lamellar packing in the β-sheet secondary structures with a single chiral handedness. Dihybrid (Z)-F-gluco nanocomposite gel was prepared by in-situ formation of silver nanoparticles AgNPs in the gel; this enhances the mechanical properties of the composite gel through physical crosslinking without altering the packing pattern. In contrast, (Z)-L-gluco bearing an l -leucine moiety does not form a hydrogel but an organogel. Interestingly, the chiral handedness of the aggregates of (Z)-L-gluco can be reversed by choosing suitable solvents. In addition to self-healing behavior, (Z)-L-gluco gel revealed shape persistency. Further, (Z)-F-gluco hydrogel is benign, nontoxic, non-immunogenic, and non-allergenic in animal cells. AgNP-loaded (Z)-F-gluco hydrogel showed antibacterial activity against both Gram-positive and Gram-negative bacteria.     

湍流大气传输中跟踪抖动对远场影响的仿真研究

分析了跟踪抖动对湍流大气传输远场光斑的影响。基于麦克斯韦电磁场理论,采用大气相干长度对大气湍流进行描述,推导了发射光束因跟踪抖动导致光轴偏离的远场表达式。在此基础上,利用相位屏法模拟抖动引起的倾斜相位和大气折射率起伏引起的相位调制,并采用低频补偿的功率谱反演法对传输过程进行了数值仿真。分析了不同跟踪抖动、湍流强度条件下远场光斑质心脱靶量的变化,以及不同尺寸模拟目标的回波概率。分析结果表明,在传输距离为10 km时,强湍流造成的远场光斑脱靶量可达几十μrad;当跟踪抖动较大时,湍流强弱对脱靶量影响差别很小。最后,对一定尺寸的模拟目标,从探测回波概率的角度给出了发射系统跟踪抖动量的控制范围。     

载机平台光电转塔目标定位的仿真算法

目标定位是光电转塔典型功能和任务之一，对其定位精度的考量也是转塔作战技术指标之一，针对该问题，从理论和仿真角度进行了分析。分析目标定位中用到的坐标系及其相互转换关系，给出光电转塔视轴反演、有源目标定位、无源目标定位的算法流程，通过仿真实验加以验证，考虑了定位过程中可能的随机误差来源，并分析是否采用均值滤波及其对定位结果的影响，最后通过Monte-Carlo分析计算了定位精度。分析结果表明:1）有源定位比无源定位的精度高，在仿真假设条件下，精度约提高1倍；2）均值滤波后，定位精度有较大提升（约提高15倍）；3）18 km距离时典型无源定位精度在80%置信度条件下约为39.4 m；4）统计直方图反映出80%置信度CEP半径及最大误差距离随载机位置、姿态、转塔视轴等（体现在目标载机距离上）不同参数的变化结果。     

Thermoelastic solutions for thermal distributions moving over thin slim rod under memory-dependent three-phase lag magneto-thermoelasticity

Abstract

Enlightened by the Caputo fractional derivative, the present study deals with a novel mathematical model of generalized thermoelasticity to investigate the transient phenomena due to the influence of magnetic field and moving heat source in a rod in the context of three-phase lag (TPL) theory of thermoelasticity. Both ends of the rod are fixed and heat insulated. Employing Laplace transform as a tool, the problem has been transformed into the space-domain and solved analytically. Finally, solutions in the real-time domain are obtained by applying the inverse Laplace transform. Numerical calculation for stress, displacement, and temperature within the rod is carried out and displayed graphically. The effect of moving heat source speed on temperature, stress, and temperature is studied. It is found from the distributions that the temperature, thermally induced displacement and stress of the rod are found to decrease at large source speed. For the better understanding of the effect of moving heat source on all the distributions, three animations are added.     

Photoinduced Pyramidal Inversion Behavior of Phosphanes Involved with Aggregation-Induced Emission Behavior

Aggregation-induced emission (AIE) is a fascinating phenomenon because of the applications of luminescent materials in the aggregated state, which exploit the large structural changes of the molecules in the excited state. Recently, it was reported that triphenylphosphane derivatives show AIE behavior in which they undergo potentially large structural changes in the excited state. Inspired by this report, photoinduced pyramidal inversion behavior of phosphanes was investigated. In photochemical experiments, the prepared P-stereogenic phosphanes exhibited photoracemization in dilute solution, and a negative correlation was observed between the photoracemization and the AIE phenomenon. Theoretical computations revealed that the inversion barrier in the excited state was much smaller than that in the ground state. This is the first report on the photoinduced pyramidal inversion behavior of phosphanes, which will provide new and unexplored applications.     

One Terminal Guanosine Flip of Intramolecular Parallel G-Quadruplex: Catalytic Enhancement of G-Quadruplex/Hemin DNAzymes

Numerous studies have shown compelling evidence that incorporation of an inversion of polarity site (IPS) in G-rich sequences can affect the topological and structural characteristics of G-quadruplexes (G4s). Herein, the influence of IPS on the formation of a previously studied intramolecular parallel G4 of d(G₃TG₃TG₃TG₃) (TTT) and its stacked higher-order structures is explored. Insertion of 3′–3′ or 5′–5′ IPS did not change the parallel folding pattern of TTT. However, both the species and position of the IPS in TTT have a significant impact on the G4 stability and end-stacking through the alteration of G4–G4 interfaces properties. The data demonstrate that one base flip in each terminal G-tetrad can stabilize parallel G4s and facilitate intermolecular packing of monomeric G4s. Such modifications can also enhance the fluorescence and enzymatic performances by promoting interactions between parallel G4s with N-methyl mesoporphyrin IX (NMM) and hemin, respectively.