Atomic Force Microscopy,Transmission Electron Microscopy,and Photon Correlation Spectroscopy: Three Techniques for Rapid Characterization of Optimized Self-Nanoemulsiying Drug Delivery System of Glibenclamide,Carvedilol, and Lovastatin

This article looks at atomic force microscopy as an important aid to characterize the self-nanoemulsifying formulation of glibenclamide, lovastatin, and carvedilol in conjunction with other sophisticated technique, viz., transmission electron microscopy and photon correlation spectroscopy. Sizes obtained by processing the atomic force microscopy (AFM) image are comparable with those obtained from transmission electron microscope. Although in the present study, the mean particle size obtained from photon correlation spectroscopy does not correlate to the findings of atomic force microscopy and transmission electron microscopy, but the poly-disperse index values correlate well with the findings of AFM and transmission electron microscopy where uniform particle size was observed in aqueous dispersion of self-nanoemulsifying formulation of glibenclamide, lovastatin, and carvedilol.     

Structural Transitions of Self-Nanoemulsifying Drug Delivery System of Glibenclamide,Carvedilol, and Lovastatin upon Progressive Aqueous Dilution

The dynamics of morphological transition in amphiphillic systems such as self-nanoemulsifying drug delivery system (SNEDDS) has become an increasingly active field of research in colloidal science. The present contribution deals with the morphological transition of selected optimized SNEDDS formulations of glibenclamide, carvedilol, and lovastatin on progressive aqueous dilution using transmission electron microscopy. The study emphasizes the structural aspects of the systems and stresses the effect of aqueous dilution under which the systems transform from water-in-oil (L₂) phase into bicontinuous structure and, finally, in oil-in-water (L₁) nanodroplets.     

Fast polarisation-insensitive optical shutter supported by backflow in dichroic dye-doped dual-frequency liquid crystal

This paper describes a novel implementation of a dual-frequency liquid crystal optical shutter of the guest–host type. The transmissive state of the filter is obtained by applying a low-frequency electric field that brings the dichroic dye in a homeotropic orientation. The light-absorbing state is realised by a twisted planar configuration for which the absorption is quasi-independent of the polarisation. Switching between the two states occurs in about 1 ms and the devices show no scattering for wavelengths inside or outside the absorption band of the dichroic dye. Simulations and experiments reveal how a twisted state is obtained through the backflow phenomenon.     

Polymerizable hexacatenar liquid crystals containing a luminescent oligo(p-phenylenevinylene) core

Polymerizable hexacatenar mesogens containing a photo-active oligo(p-phenylenevinylene) core were successfully synthesized by replacing the traditional n-alkoxy tails on the molecules with polymerizable hydrocarbon tails containing terminal isoprenyl or 1,3-dienyl units. It was found that for this particular liquid crystal (LC) platform, the incorporation of conventional radical polymerizable groups such as acrylates in the tails was not conducive to the formation of thermotropic LC phases, presumably due to their polar nature. The resulting photoluminescent isoprenyl and 1,3-dienyl hexacatenar monomers were found to form columnar hexagonal phases at elevated temperatures (c. 45–75°C), as determined by powder X-ray diffraction. Unfortunately, photoinitiated radical polymerization studies revealed that the mesogens are susceptible to photodegradation in the LC state at elevated temperatures, resulting in the loss of both LC order and emission properties during photopolymerization. Thermally initiated radical polymerization in the absence of light, however, afforded effective crosslinking with retention of both LC order and the desired emission properties. The resulting crosslinked columnar hexagonal phases were found to exhibit emission maxima at nearly identical wavelengths, with comparable intensities relative to the unpolymerized starting materials. The effect of the different polymerizable groups on the mesogenic behaviour, polymerization characteristics, and emission properties of the hexacatenar compounds is presented.     

基于ARM的嵌入式超声传播时间测量装置

应用超声波检测技术进行检测时,通常需对超声波在介质中的传播时间进行精准的测量,为精准测量超声波的传播时间,设计了一套基于ARM的嵌入式超声传播时间测量装置。该装置电路运行稳定,成本低廉,采用多次测量结果取算数平均值的方法以减小随机干扰,采用参比方法放置接收探头以消减电路中电子器件的延时。通过对实验结果进行分析,得出该装置可精准测量超声波在实验试块中的传播时间且满足设计要求,分辨率可达一纳秒。     

基于SEDRIS的虚拟试验合成环境建模技术研究

为解决合成环境的统一描述和可交互问题,在分析合成环境数据表示与转换标准SEDRIS基础上,提出了基于SEDRIS的虚拟试验合成环境建模方法,针对大气、红外、电磁等3类自然环境,给出了实现环境数据表示和转换的技术途径。通过系统开发,实现了4种试验环境条件下对产品性能的验证与评估,建立的环境模型具有良好的交互性,建模方法可应用于多种试验环境的描述,为虚拟试验合成环境模型体系、标准规范和辅助工具的形成打下了基础。     

由不同镍盐前体制备高分散Ni/SBA-15催化剂：活化氛围的影响

以硝酸镍和乙酸镍为镍前体,用浸渍法分别在空气和氢气氛围活化制得系列Ni/SBA-15催化剂,通过XRD、H₂-TPD、N₂物理吸附和在线质谱等物理化学手段对催化剂进行了表征,并结合微型高压反应釜萘加氢反应,评价了催化剂的加氢性能。结果表明,氢气氛围活化对硝酸镍为镍前体所制Ni/SBA-15催化剂的镍分散度和活性有显著促进作用,而空气氛围活化对乙酸镍为镍前体所制催化剂有明显促进作用。根据催化剂前体在不同氛围活化时的热分解产物,提出了活化氛围对不同镍前体制得Ni/SBA-15催化剂所产生的作用机理。     

Spatially‐resolved and polarized Raman scattering from a single Si nanowire

We report spatially‐resolved and polarized Raman scattering results from a single Si nanowire (NW). Transmission electron microscope images show that the surface morphology of the Si NW varies from smooth to rough along the long axis. As the NW grows, the smooth surface becomes rough because of Au diffusion to the surface, resulting in the formation of facets and stacking faults. Spatially‐resolved Raman spectra along the NW long axis reveal variations in tensile strain related to the morphological changes in NW surface. The tensile strain in the top segment of the NW with a smooth surface is greater than that in the bottom segment with a rough surface. Despite the formation of facets and stacking faults, polarized Raman scattering results both from the top and bottom segments of the NW are consistent with the Raman polarization selection rules expected for a cubic crystal. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of post-deposition annealing on chemical composition of SiNx film in SiO2/SiNx/SiO2/Si stacked structure

To systematically evaluate the quality of SiN_x films in multi-stacked structures, we investigated the effects of post-deposition annealing (PDA) on the film properties of SiN_x within the SiO₂/SiN_x/SiO₂/Si stacked structure by performing X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), Fourier transform infrared (FT-IR) spectroscopy, and scanning transmission electron microscope–electron energy loss spectroscopy (STEM-EELS) analyses. The XPS results showed that PDA induces the oxidation of the SiN_x layer. In particular, new finding is that Si-rich SiN_x in the SiN_x layer is preferentially oxidized by PDA even in multi-stacked structure. The XRR results showed that the SiN_x layer becomes thinner, whereas the interface layer between the SiN_x layer and Si becomes thicker. It is concluded by STEM-EELS and XPS that this interface layer is SiON layer. The density of N–H and Si–H bonding within the stacked structure strongly depends on the PDA temperature. Our study helps elucidate the properties of SiN_x films in stacked structures from various perspectives.