Urea-based hydrothermal growth, optical and photocatalytic properties of single-crystalline In(OH)3 nanocubes

Nearly monodisperse single-crystalline In(OH)(3) nanocubes were successfully synthesized using In(NO(3))(3) x 4.5 H(2)O as indium source in the presence of urea and cetyltrimethyl ammonium bromide (CTAB) by a two-step hydrothermal process: the stock solution was heated at 70 degrees C for 24 h and then at 120 degrees C for 12 h. The structure and morphology of the resultant In(OH)(3) samples were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed that most of as-synthesized In(OH)(3) nanocubes were uniform in size, with the average edge length of approximately 700 nm. The influences of the reaction temperature, the reaction time, the mineralizer, and the surfactant on the morphology of the obtained products were discussed in detail. Room-temperature photoluminescence (PL) spectrum of the In(OH)(3) nanocubes showed a peculiar strong emission peak centered at 480 nm. Furthermore, the photocatalytic properties of the In(OH)(3) nanocubes were tested. It was found that In(OH)(3) exhibited not only higher activity for benzene removal, but also better H(2) evolution from water than the commercial Degussa P25 TiO(2).     

Comparing the Contribution of Visible‐Light Irradiation,Gold Nanoparticles,and Titania Supports in Photocatalytic Nitroaromatic Coupling and Aromatic Alcohol Oxidation

Under visible‐light irradiation, gold nanoparticles (Au NPs) supported by titania (TiO₂) nanofibers show excellent activity and high selectivity for both reductive coupling of nitroaromatics to corresponding azobenzene or azoxylbenzene and selective oxidation of aromatic alcohols to corresponding aldehydes. The Au NPs act as active centers mainly due to their localized surface plasmon resonance (LSPR) effect. They can effectively couple the photonic energy and thermal energy to enhance reaction efficiency. Visible‐light irradiation has more influence on the reduction than on the oxidation, lowering the activation energy by 24.7 kJ mol^?1 and increasing the conversion rate by 88% for the reductive coupling, compared to merely 8.7 kJ mol^?1 and 46% for the oxidation. Furthermore, it is found that the conversion of nitroaromatics significantly depends on the particle size and specific surface area of supported Au NPs; and the catalyst on TiO₂(B) support outperforms that on anatase phase with preferable ability to activate oxygen. In contrast, for the selective oxidation, the effect of surface area is less prominent and Au NPs on anatase exhibit higher photo‐catalytic activity than other TiO₂ phases. The catalysts can be recovered efficiently because the Au NPs stably attach to TiO₂ supports by forming a well‐matched coherent interface observed via high‐resolution TEM.     

Finite Element Simulations with Adaptively Moving Mesh for the Reaction Diffusion System

A moving mesh method is proposed for solving reaction-diffusion equations. The finite element method is used to solving the partial different equation system, and an efficient scheme is applied to implement mesh moving. In the practical calculations, the moving mesh step and the problem equation solver are performed alternatively. Serveral numerical examples are presented, including the Gray-Scott, the Activator-Inhibitor and a case with a growing domain. It is illustrated numerically that the moving mesh method costs much lower, compared with the numerical schemes on a fixed mesh. Even in the case of complex pattern dynamics described by the reaction-diffusion systems, the adapted meshes can capture the details successfully.     

Preparation and evaluation of a mixed-bed immunoaffinity column for selective purification of sixteen sulfonamides in pork muscle

This paper describes the preparation of a novel mixed-bed immunoaffinity chromatography (IAC) column by coupling four monoclonal antibodies against different sulfonamides (SAs) to Sepharose 4B. The IAC column can be used to simultaneously extract and purify 16 SAs in pork muscle. The dynamic column capacities for all SAs in mixed standard solution were between 312 and 479 ng/mL gel. After simple extraction and IAC cleanup, the sample solution can be directly injected for liquid chromatography-ultraviolet analysis. The recoveries of SAs from spiked samples at levels of 25, 50 and 100 μg/kg ranged from 83.3 to 103.1% with variation coefficient less than 8.6%. The comparison of IAC with liquid-liquid extraction and solid phase extraction indicated that IAC has better purification effect and needs less organic solution than conventional methods, thus it would be an ideal method for selective purification of SAs in pork muscle.     

无模板剂条件下ZSM-5与丝光沸石之间的可控转晶

采用预晶化液添加法,即将高温(190oC)预晶化液添加到低温(150oC)晶化母液中合成沸石分子筛,考察了高温预晶化液的Na2O:SiO2比、预晶化时间以及低温晶化母液的Na2O:SiO2比对ZSM-5与丝光沸石之间转晶的影响,并采用X射线衍射和扫描电子显微镜对合成的产物进行了表征.研究发现,通过调节整体合成液的Na2O:SiO2比可有效控制ZSM-5沸石与丝光沸石之间的转晶.当整体合成液的组成为xNa2O:100SiO2:2.5Al2O3:12SO42?:4000H2O时,Na2O:SiO2=0.18是ZSM-5沸石和丝光沸石的一个分界线.通过调节母液的Na含量,使Na2O:SiO2>0.18时,高温预晶化过程中产生MFI结构的晶体在低温晶化时可向丝光沸石发生转晶;当Na2O:SiO2≤0.18时,具有MFI和丝光沸石结构共生的晶体在低温晶化时向MFI结构的ZSM-5沸石发生转晶.ZSM-5与丝光沸石之间转晶的前提条件是高温预晶化所形成晶体的结晶度不能太高(≤30%).另外,整体合成液中Na2O含量对生成晶体的形貌也有影响.     

高阶辛算法的稳定性与数值色散性分析

利用Maxwell方程的哈密尔顿函数,导出对应的欧拉-哈密尔顿方程.利用辛积分技术与高阶交错差分技术,建立求解三维时域Maxwell方程的高阶辛算法;结合电磁场中的物理概念,借助矩阵分析和张量分析理论,获得高阶时域方法及高阶辛算法的稳定性和数值色散性的统一处理新方法.用数值结果证实方法的正确性,与FDTD算法和其它时域高阶方法相比,高阶辛算法具有较大的计算优势,为电磁计算提供了新的途径.     

Affine frames, quasi-affine frames, and their duals

The notion of quasi-affine frame was recently introduced by Ron and Shen [9] in order to achieve shift-invariance of the discrete wavelet transform. In this paper, we establish a duality-preservation theorem for quasi-affine frames. Furthermore, the preservation of frame bounds when changing an affine frame to a quasi-affine frame is shown to hold without the decay assumptions in [9]. Our consideration leads naturally to the study of certain sesquilinear operators which are defined by two affine systems. The translation-invariance of such operators is characterized in terms of certain intrinsic properties of the two affine systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

纳米器件的非零点能Casimir排斥力

结合边界元方法,利用离散点表面电流及表面磁流的格林函数得到任意三维几何体及任意材料纳米器件互相作用离散点之间的Casimir力.给出浸泡在液体中纳米器件的"非零点能"Casimir效应,分析Casimir排斥力产生的条件,为实际纳米器件之间Casimir效应分析提供新的数值方法.     

Tight Multiwavelet Frames with Different Matrix Dilations and Matrix Translations

The characterization of tight multiwavelet frames with different matrix dilations and matrix translations for L ²(R ^d ) is established. The result contains and further extends the generalizations that have appeared in the literature. Two sufficient conditions for affine frames are also presented.     

Determination of jumps in terms of spectral data

Summary We discuss the concentration factor methods for determination of jumps in terms of spectral data. The results are relative to the classical Lukács Theorem and some recent results obtained by A. Gelb, E. Tadmor and F. Móricz.