Fast Analytical Temperature Rising Elution Fractionation (ATREF) Method

Conventional analytical temperature rising elution fractionation (ATREF) is performed using slowly crystallized polymers in about 16 h. In this work, we developed a fast ATREF method in which the polymer sample is directly injected on the column at room temperature, thus reducing the analysis time to about 1 h. The method was tested using four metallocene polyethylenes with unimodal short chain branching distributions and different densities, previously analyzed by ATREF using a cooling rate of 0.1°C/min. The obtained results demonstrate that the fast ATREF method is very effective and accurate in evaluating short chain branching distribution for polyolefins having unimodal distributions.     

光子晶体光纤温度压力传感器

提出了一种在高温环境下同时测量温度和气压的光子晶体光纤温度压力传感器.在普通单模光纤和光子晶体光纤之间熔接一段空心光纤构成干涉结构.空心光纤段构成非本征法布里-珀罗干涉仪,利用光子晶体光纤的微孔与外界相通,通过气体折射率变化来测量环境中的气压变化;光子晶体光纤段构成本征法布里-珀罗干涉仪,利用热膨胀效应和热光效应来测量环境中的温度.传感器的解调通过自制的白光干涉解调仪实现,实验通过测量腔长得到被测环境的温度和气压.在不同温度和气压环境下,对腔长分别为306μm和1535μm的温度压力光纤传感器进行连续测量.实验结果表明,传感器能够在28~800℃的温度下和0~10 MPa的气压下稳定工作,测量范围内温度灵敏度可达17.4 nm/℃,压力灵敏度随温度增加而降低,在28℃时可达1460.5 nm/MPa.     

角锥棱镜谐振腔激光模式模拟研究

为了探究角锥棱镜谐振腔激光模式,以角锥-平面镜腔为例,将角锥棱镜等效为衍射光栅,考虑角锥镜棱宽在谐振腔中的衍射效应以及二面角误差引起的附加相位分布对谐振腔激光模式的影响,在光学谐振腔理论的基础上,建立了求解本征模式的理论分析模型.采用快速傅里叶法数值模拟不同腔长、角锥镜棱宽和二面角误差情况下该无源谐振腔激光输出模式分布情况.结果表明,在腔长30 cm、角锥镜棱宽小于75μm、二面角误差在-10′~5′之间时,可实现光斑完整的圆形分布输出模式,且有较好的光束质量;棱宽不小于0.4 mm,二面角误差在-40′~10′之间时,光斑为TEM 03阶横模,光场呈六瓣分布;当角锥镜棱宽为0.4 mm、二面角误差为3′,腔长从30~90 cm范围内增加时,该谐振腔输出的激光模式从TEM 03转换成TEM 10.     

在NaCl溶液中以海藻酸钠为致孔剂制备快速温度响应型多孔聚(N-异丙基丙烯酰胺)水凝胶

用海藻酸钠为致孔剂,在NaCl水溶液中制备了多孔聚(N-异丙基丙烯酰胺)(PNIPAAm)水凝胶,分别用扫描电镜(SEM)和小角X光散射(SAXS)对PNIPAAm水凝胶的多孔结构进行了表征.结果发现,PNIPAAm水凝胶网络中的孔洞相互贯通,随着反应介质中NaCl浓度的增加,孔洞尺寸逐渐增大,孔洞排列越来越有序.相应地,PNIPAAm水凝胶的消溶胀速率随着反应介质中NaCl浓度的增加而提高.当NaCl浓度为0.6 mol/L时制备的PNIPAAm水凝胶,从室温处于平衡溶胀状态快速转移到45℃水介质中,1 min后凝胶的水保留率不足15%,4 min后消溶胀就达到平衡状态.     

快原子轰击离子化质谱研究酚类化合物抗氧化作用

为了建立简便、快速筛选高效、低毒的新型抗氧化药物的方法,本研究采用快原子轰击离子化质谱( FAB-MS)对酚类化合物抗氧化作用强弱进行了研究。考察了基质、轰击时间和样本浓度对FAB-MS 谱中分子离子(M+·)相对强度的影响,研究了黄酮类化合物在FAB-MS谱中的I(M+·)/I([M+H]+)比值与其抗氧化活性的相关性。对12种酚类化合物的抗氧化活性进行了预测与评价,并与硫代巴比妥酸法( TBA)检测的脂质过氧化抑制率进行比较,验证 FAB-MS 方法的可靠性。结果表明,由 FAB-MS 获得的 I ( M+·)/I([ M+H]+)比值能较好地反映酚类化合物抗氧化作用的强弱,可以作为抗氧化剂的体外筛选或预测方法,有助于加速新型抗氧化药物的发现。     

A Conjugated Copolymer Bearing Imidazolium-based Ionic Liquid:Electrochemical Synthesis and Electrochromic Properties

An imidazolium-based ionic liquid(IL) modified triphenylamine derivative,namely 1-(4-((4-(diphenylamino)benzoyl) oxy)butyl)-3-methyl imidazole tetrafluoroborate(TPAC_6 IL-BF_4),was designed and synthesized,and further applied with 3,4-ethylene dioxythiophene(EDOT)to prepare conjugated copolymer P(EDOT:TPAC_6 IL-BF_4) via electrochemical polymerization.The cyclic voltammetry curves show that the copolymer P(EDOT:TPAC_6 IL-BF_4) possesses two pairs of redox peaks,which should be ascribed to the redox behaviors of EDOT and triphenylamine.The ultraviolet-visible(UV-Vis) absorption spectrum of P(EDOT:TPAC_6 IL-BF_4) exhibits one maximum absorption peak at 580 nm and a small shoulder characteristic peak at 385 nm under neutral state which are assigned to π-π~* conjugated structure of EDOT and triphenylamine.After being applied at the positive voltage,the copolymer color changes from dark blue to light blue,which is close to the color of poly(3,4-ethylenedioxythiophene)(PEDOT).Surprisingly,the copolymer P(EDOT:TPAC_6 IL-BF_4) shows shorter switching time of 0.37 s,0.30 s at 580 nm and 0.38 s,0.45 s at 1100 nm compared with PEDOT.It is more intriguing that the copolymer P(EDOT:TPAC_6 IL-BF_4) exhibits electrochromism even in free supporting electrolyte.The results confirm that the existence of imidazolium-based ionic liquid has an improvement on the ion diffusion properties and the switching time of conjugated polymer,which may provide a potential direction for the preparation of high-performance electrochromic materials.     

Characterization of patterns in rimming flow

Patterns were generated inside a horizontal cylinder rotating at low speeds. The cylinder was filled with a very low volume liquid fraction of 1.8% of Newtonian fluid and the rotation speed ranged between 0.08 and 5.2 s⁻¹. A novel laser-plane technique was utilized to obtain time series from each pattern. This enabled the characterization of fluid patterns using Fourier spectral (FS) and dynamical-systems (chaotic) techniques such as the recurrence map, correlation dimension (D₂) and Hurst exponent (H). Four patterns were found (fingers, furrows, waterfall and smooth tooth) before annular flow was reached. The results indicate that the FS technique not is suitable for flow pattern characterization; and H only has the ability to indicate a possible pattern change. The best tool for indicating the pattern transitions and the inner coat liquid evolution was found to be recurrence maps and D₂.     

Fast Gaussian wavepacket transforms and Gaussian beams for the Schrödinger equation

This paper introduces a wavepacket-transform-based Gaussian beam method for solving the Schrödinger equation. We focus on addressing two computational issues of the Gaussian beam method: how to generate a Gaussian beam representation for general initial conditions and how to perform long time propagation for any finite period of time. To address the first question, we introduce fast Gaussian wavepacket transforms and develop on top of them an efficient initialization algorithm for general initial conditions. Based on this new initialization algorithm, we address the second question by reinitializing the beam representation when the beams become too wide. Numerical examples in one, two, and three dimensions demonstrate the efficiency and accuracy of the proposed algorithms. The methodology can be readily generalized to deal with other semi-classical quantum mechanical problems.     

Polynomial factorization over

We describe algorithms for polynomial factorization over the binary field , and their implementation. They allow polynomials of degree up to to be factored in about one day of CPU time, distributing the work on two processors.