The use of ethylene glycol solution as the running buffer for highly efficient microchip-based electrophoresis in unmodified cyclic olefin copolymer microchips

An ethylene glycol solution was used as the electrophoretic running buffer in unmodified cyclic olefin copolymer (COC) microchips to minimize the interactions between the analytes and the hydrophobic walls of the plastic microchannels, enhance the resolution of the analytes and eliminate the uncontrollable dispersion caused by uneven liquid levels and non-uniform surfaces of the separation channels. Five amino acids that were labeled with fluorescein isothiocyanate (FITC) were used as model analytes to examine the separation efficiency. The effects of ethylene glycol concentration, pH and sodium tetraborate concentration were systematically investigated. The five FITC-labeled amino acids were effectively resolved using a COC microchip with an effective length of 2.5 cm under optimum conditions, which included using a running buffer of 20 mmol/L sodium tetraborate in ethylene glycol:water (80:20, v/v), pH 6.7. A theoretical plate number of 4.8 × 10(5)/m was obtained for aspartic acid. The system exhibited good repeatability, and the relative standard deviations (n=5) of the peak areas and migration times were no more than 3.4% and 0.7%, respectively. Furthermore, the system was successfully applied to elucidate these five amino acids in human saliva.     

A carbon–LiFePO<Subscript>4</Subscript> nanocomposite as high-performance cathode material for lithium-ion batteries

A cathode material of an electrically conducting carbon–LiFePO₄ nanocomposite is synthesized by wet ball milling and spray drying of precursor powders prior to a solid-state reaction. The structural characterization shows that the composite is composed of LiFePO₄ crystals and 4.8 wt.% amorphous carbon. Galvanostatic charge/discharge measurements indicate that the composite exhibits a superior high energy and high cycling stability. This composite delivers a discharge capacity of 159.1 mAh g⁻¹ at 0.1 C, 150.8 mAh g⁻¹ at 1 C, and 140.1 mAh g⁻¹ at 2 C rate. The capacity retention of 99% is achieved after 200 cycles at 2 C. The 18,650 cylindrical batteries are assembled using the composite as cathode materials and demonstrate the capacity of 1,400 mAh and the capacity retention of 97% after 100 cycles at 1 C. These results reveal that the as-prepared LiFePO₄–carbon composite is one of the promising cathode materials for high-performance, advanced lithium-ion batteries directed to the hybrid electric vehicle and pure electric vehicle markets.     

Semi-classical theory of laser cooling in two dimensions

We present a semi-classical theory of the light pressure force for atoms interacting with a two-dimensional laser field. Unlike previous 2D theory, ours is valid for general atomic level and laser field configurations. We show that striking new features appear in the velocity-dependent force arising from the multi-dimensionality. Finally, we describe in detail the novel numerical technique used in the calculation. Received 4 December 1998 and Received in final form 13 February 1999     

Influence of the comatic aberration of an apertured lens on the focused polychromatic Gaussian beams

The focusing of polychromatic Gaussian beams by an apertured lens with comatic aberration is investigated in this paper. We study the influence of the comatic aberration and truncation parameter on the intensity distribution at the focal plane, and singularities and spectral behavior near the focal plane in detail. The simulation results show that the maximum intensity at the focal plane will shift and split with the gradual increment of comatic aberration. We also find that the decrease of truncation parameter will counteract the influence of comatic aberration, which leads to the intensity variation. Furthermore, the singularity transformation and spectral anomalies are discussed. It is found that with the increment of comatic aberration, some singularities are split into several new singularities, and by combining some of these new singularities with other singularities near the focal plane, they vanish or form new singularities with the continuing increase of comatic aberration. The decreasing value of truncation parameter will cause similar phenomena.     

Anti-Staphylococcus aureus evaluation of gallic acid by isothermal microcalorimetry and principle component analysis

Journal of Thermal Analysis and Calorimetry - The emergence of antibiotic-resistant Staphylococcus aureus requires new antibacterial drugs. In this study, using a thermal activity monitor air...     

光纤非相干合成光束在湍流大气中的传输实验研究

进行了六路100 W量级光纤非相干合成光束在实际大气湍流中的传输实验,将六路光斑直径为9 mm的单模光纤光束分别扩束,扩束后的光斑直径为90 mm。基于倾斜镜的合束系统来控制各路光束的指向,在不同强度的湍流条件中,通过主镜口径为440 mm的发射系统水平聚焦传输至470 m处。倾斜控制系统闭环工作时,一倍衍射极限内的桶中功率占目标处总功率的比值是开环工作时的1.7倍左右,随着大气湍流的强度变弱,此比值变大。     

声光调Q纳秒脉冲全光纤超连续谱光源

基于声光调Q技术的纳秒脉冲光纤激光超连续谱光源系统为全光纤结构,使用普通的传能光纤作为超连续谱的产生介质,通过改变泵浦功率和调制频率,可获得不同的超连续谱输出。实验结果表明：泵浦功率越大,调制频率越低,传能光纤越长,光谱展宽越宽。当传能光纤为200 m、调制频率为1 kHz、占空比为1.0%、泵浦功率为4.68 W时,获得谱线宽度超过700 nm的超连续谱输出。该系统可作为超连续谱光源的一种参考方案。     

Photochromism of new unsymmetrical isomeric diarylethenes bearing a methoxyl group

Three new unsymmetrical isomeric diarylethenes having a methoxyl substituent at ortho‐, meta‐, and para‐position of the terminal benzene ring, namely 1‐(2,5‐dimethyl‐3‐thienyl)‐2‐[2‐methyl‐5‐(2‐methoxylphenyl)‐3‐thienyl]perfluorocyclopentene ( 1o ), 1‐(2,5‐dimethyl‐3‐thienyl)‐2‐[2‐methyl‐5‐(3‐methoxylphenyl)‐3‐thienyl]perfluorocyclopentene ( 2o ), and 1‐(2,5‐dimethyl‐3‐ thienyl)‐2‐[2‐methyl‐5‐(4‐methoxylphenyl)‐3‐thienyl]perfluorocyclopentene ( 3o ), have been synthesized. The substituent position effect of methoxyl group on their properties, including photochromism and fluorescence both in hexane solution and in PMMA film, and their electrochemical properties, were investigated in detail. These diarylethenes showed good photochromism both in solution and in PMMA film. For the same photochromic diarylethene backbone, the electron‐ donating methoxyl substituent can effectively depress the cyclization quantum yields and increase the cycloreversion quantum yields compared to those of diarylethenes bearing chlorine atoms reported previously. Diarylethenes 1o – 3o showed clear fluorescent switches by photoirradiation both in hexane and in PMMA film. In addition, cyclic voltammetry tests showed that the electron‐donating methoxyl group at different position on the terminal benzene ring had a significant effect on the electrochemical properties of these isomeric diarylethenes. Copyright © 2009 John Wiley & Sons, Ltd.     

Engineering Heterogeneous Catalysis with Strong Metal–Support Interactions: Characterization,Theory and Manipulation

Strong metal–support interactions (SMSI) represent a classic yet fast-growing area in catalysis research. The SMSI phenomenon results in the encapsulation and stabilization of metal nanoparticles (NPs) with the support material that significantly impacts the catalytic performance through regulation of the interfacial interactions. Engineering SMSI provides a promising approach to steer catalytic performance in various chemical processes, which serves as an effective tool to tackle energy and environmental challenges. Our Minireview covers characterization, theory, catalytic activity, dependence on the catalytic structure and inducing environment of SMSI phenomena. By providing an overview and outlook on the cutting-edge techniques in this multidisciplinary research field, we not only want to provide insights into the further exploitation of SMSI in catalysis, but we also hope to inspire rational designs and characterization in the broad field of material science and physical chemistry.