Birefringent azopolymer long period fiber gratings induced by 532 nm polarized laser

Based on the photoinduced birefringence in azo materials, the model of the birefringent long period fiber gratings (BLPFGs) has been proposed and the transmission of such birefringent fiber gratings was further simulated by the coupled mode theory. In order to obtain the optimum condition for making birefringent azopolymer optical fiber (APOF) gratings the photoinduced birefringence of azo dye and methyl methacrylate (MMA) copolymers was systematically studied. After photosensitivity study of azo samples, using Teflon technique, azo dye containing single mode polymer optical fiber (POF) was fabricated. Finally, BLPFGs can be fabricated in azopolymer fiber using polarized 532 nm laser. A 120 μm LPFG with a 50% duty cycle has been successfully written within the core of the fiber with 532 nm laser by an amplitude mask method. Under polarized microphotography, the grating was observed when the optical axis was set at 45° with the direction of the first polarizing lens of the polarization microscope.     

Population of closed-channel molecules in trapped Fermi gases with broad Feshbach resonances

We compute the fraction of closed-channel molecules in trapped atomic Fermi gases, over the entire range of accessible fields and temperatures. We use a two-channel model of Bardeen-Cooper-Schrieffer-Bose-Einstein-condensation crossover theory at general temperature , and show that this fraction provides a measure of the T-dependent pairing gap. Our calculations, containing no free parameters, are in good quantitative agreement with recent low- measurements in (6)Li. We present readily testable predictions for the dependencies of the closed-channel fraction on temperature and Fermi momentum.     

Thermodynamics of interacting fermions in atomic traps

We calculate the entropy in a trapped, resonantly interacting Fermi gas as a function of temperature for a wide range of magnetic fields between the BCS and Bose-Einstein condensation end points. This provides a basis for the important technique of adiabatic sweep thermometry and serves to characterize quantitatively the evolution and nature of the excitations of the gas. The results are then used to calibrate the temperature in several ground breaking experiments on (6)Li and (40)K.     

Upper critical field of heavy fermion superconductors

The upper critical field in a model with dispersion in the f-band of a periodic Anderson model has been calculated.     

过氧化聚吡咯膜修饰微电极的制备及其电化学特性

用电聚合法在铂微盘电极上制备了聚吡咯膜，并将其在电解质水溶液中进行了过氧化处理。所得到的过氧化膜是非电子导体而为离子导体，膜具有多孔笥的特征。该膜具有排有离子的作用，而对大阳离子如多巴胺具有高度的选择性。     

侧链型偶氮聚合物液晶在不同温度条件下的光致取向

在高于和低于玻璃化转变温度 (Tg)的温度范围内 ,研究了聚甲基丙烯酸 ( 6 [4 ( 4 氰基偶氮苯 )苯氧基 ]己酯 ) (Poly( 6 [4 ( 4 cyanophenylazo)phenoxy]hexylmethacrylate) (PM6ABCN) )聚合物膜的光致取向行为 .实验结果表明 ,在温度低于Tg 时 ,实验温度对取向速率没有影响 ;高于Tg 温度时 ,取向的速率随温度升高而变大 ,取向过程的表观活化能为 3 2 76kJ mol.通过对Tg 温度以下的光致取向进行分析 ,对光致取向过程提出了一个新的微相模型 ,微相内的温度能够达到Tg 以上 ,而实验中控制的样品宏观温度不变 ;高于Tg 温度时的光致取向过程受到宏观温度的控制 ,其表观活化能远远小于热致的各向同性相I(Isotropicphase,I)到向列相N(Nematicphase,N)相转变表观活化能 ( 3 40 2kJ mol) ,表明光致取向过程对温度的依赖性较小     

Functional polythiophene nanoparticles: size-controlled electropolymerization and ion selective response

We have synthesized a thiophene derivative, (4-benzeno-15-crown-5 ether)-thiophene-3-methylene-amine (BTA), which was used as a monomer for electrochemical polymerization on metallic surfaces to prepare functional polymer films. Self-assembly of BTA monomers on Au(111) surfaces promotes ordered polymerization to form polymer nanoparticles or clusters by which the size of the polymer nanoparticles can further be controlled electrochemically. The electropolymerization was monitored in situ by scanning tunneling microscopy to unravel the dynamics of the process and possible mechanisms. These are further supported by calculations using a semiquantative model of polymer clusters and X-ray photoelectron spectroscopy analysis. On the basis of these observations, we have attempted to optimize the construction of BTA polymer based ion selective electrodes. The BTA based polymer films, prepared from both aqueous solution and organic phase on gold electrodes, displayed selective sensitivity to potassium ions with a linear dependence of ion concentration over 4 orders of magnitude.     

微模塑法制备PMMA/SiO2二氧化硅杂化材料微结构

PMMA/ SiO2 organic-inorganic hybrid sol was synthesized by monomer methyl methacrylate,3-（triethoxysilyl）propylmethacrylate（mol ration is 1: 1）,0.2%（total weight of monomers）initiator azodiisobutyronitrile,solvent tetrahydrofuran and 20%（total weight of the system）tetraethylorthosilicate. PDMS stamp with micropatterns was placed on the hybrid sol film prepared by spin-coating on the clean glass slides. Heat treatment under 120℃ for 2 h with a weak pressure of 1 N makes the sol convert to gel. PMMA/SiO2 hybrid material micropatterns remain on the substrate after being peeled off the stamp. Optical microscope images show stringent pattern fidelity using the micromolding method which also indicates the further application in the micropatterns fabrication.     

Handling and Sensing of Single Enzyme Molecules: From Fluorescence Detection towards Nanoscale Electrical Measurements

Classical methods to study single enzyme molecules have provided valuable information about the distribution of conformational heterogeneities, reaction mechanisms, and transients in enzymatic reactions when individual molecules instead of an averaging ensemble are studied. Here, we highlight major advances in all‐electrical single enzyme studies with a focus on recent micro‐ and nanofluidic tools, which offer new ways of handling and studying small numbers of molecules or even single enzyme molecules. We particularly emphasize nanofluidic devices, which enable the integration of electrochemical transduction and detection.     

Dynamic Temperature Distribution in Photo‐induced Alignment of Azobenzene Liquid Crystalline Polymer

A theoretical model has been established to describe the dynamic temperature distribution during the alignment of an azobenzene liquid crystalline polymer irradiated by a linearly polarized laser beam. The dynamic heat diffusion equations are used, and the relationship between heat source item and time is introduced, based on experimental results. With the model, the contours of the temperature distribution at different time have been worked out. It can be found from the theoretical model that there is a maximum temperature rise during the photo‐induced alignment, which is coincident with the analysis of experimental observations. The existence of a minimum laser power and an offset photo‐alignment temperature T_off required to carry on photo‐induce alignment are explained based on the theoretical model.

Temperature distribution after two minutes.