2-甲氧基-4-乙酰胺基苯甲酸甲酯合成方法的改进

以ＰＡＳ－ Ｎａ 为原料，经水溶液中酰化后，再经酯化与醚化一步反应制得２－ 甲氧基－ ４ － 乙酰胺基苯甲酸甲酯，总收率８１％ 。     

Determination of the Onset of Asphaltene Precipitation by Visible Ultraviolet Spectrometry and Spectrofluorimetry

Abstract

Asphaltene deposition is a problem for the petroleum industry, affecting the production, transport, and storage of crude oil. The aim of this work is to develop and compare different methods to determine asphaltene precipitation. Two asphaltene fractions, one extracted from a Brazilian crude oil sample and the other from petroleum distillation residue, were evaluated by using model systems constituted of toluene/n-heptane in different compositions, using visible ultraviolet spectrometry and spectrofluorimetry. The results of the precipitation tests carried out by these two methods agreed, indicating they are effective to analyze asphaltene deposition and the performance of chemicals as asphaltene stabilizers.     

N-辛基-β-D-吡喃葡萄糖苷与BSA相互作用的研究

通过稳态荧光法、紫外-可见光谱法和表面张力法研究了N-辛基-β-D-吡喃葡萄糖苷(OGP)与牛血清白蛋白(BSA)在缓冲液中的相互作用. 根据OGP溶液和OGP/BSA混合溶液的表面张力曲线可以看出, 蛋白质的加入改变了单一表面活性剂溶液的表面张力曲线. 蛋白质的加入还使混合体系的临界胶束浓度(cmc*)大于单一表面活性剂的临界胶束浓度(cmc), 这主要是由于OGP与蛋白质结合减少了单体OGP分子的浓度所致. 加入荧光探针芘测量了OGP和OGP/BSA溶液的I₁/I₃值, 结果也表明BSA的加入增大了OGP的聚集浓度, 其原因与表面张力的变化原因是相同的. 在OGP/BSA体系中, 随着OGP浓度的增大, 紫外吸收减弱、荧光强度有规律的降低, 而且荧光发射峰位发生蓝移, 说明它们的结合部位趋向于Trp残基上|同时通过同步荧光和I^－猝灭实验, 进一步证明了OGP与BSA的结合部位是在BSA的疏水空腔内的色氨酸残基上.     

深紫外激光光发射与热发射电子显微镜在热扩散阴极研究中的应用

对热扩散阴极表面微区发射状态进行原位观察和分析一直是热阴极研究的重要课题.本文着重介绍深紫外激光光发射电子/热发射电子显微镜的基本原理及其在热扩散阴极研究中的典型实例.系统配备了高温激活所用的加热装置,样品可被加热至1400℃.系统具有光发射电子、阴极热发射电子、光发射电子和阴极热发射电子联合三种电子成像模式.应用表明,对于热扩散阴极而言,深紫外激光光发射电子像适于呈现阴极表面的微观结构形貌;热发射电子像适于反映阴极表面的本征热电子发射及均匀性;光电子和热电子联合成像适于对阴极表面的有效发射点做出精确定位.     

6H-SiC衬底上AlGaN基垂直结构紫外LED的制备

利用金属有机物化学气相沉积方法,在n型6H-SiC衬底上制备了15对Si掺杂Al_(0.19)Ga_(0.81)N/Al_(0.37)Ga_(0.63)N DBR,并采用低温AlN缓冲层有效抑制了DBR结构中裂纹的产生,得到了表面均方根粗糙度仅为0.4 nm且导电性能良好的n型DBR,其在369 nm处峰值反射率为68%,阻带宽度为10 nm。在获得导电DBR的基础上,进一步在n型6H-SiC衬底上构建了有、无DBR的垂直结构紫外LED。对比两者电致发光光谱,发现DBR结构的引入有效增强了LED紫外发光强度。     

Electron localization of H_2~+ in a dc electric field

A dc electric field is utilized to steer the electron motion after the molecular ion H_2~+ is excited by an ultrashort ultraviolet laser pulse. The numerical simulation shows that the electron localization distribution and the dissociation control ratio are dependent on the polarization direction and amplitude of the dc electric field. Most electrons of the dissociation state move opposite to the dc electric field and stabilize at the dressed-up potential well, for the dressed-down well is occupied by the electrons of the 1 sσ_g state.     

A tunable XUV monochromatic light source based on the time preserving grating selection of high-order harmonic generation

We accomplish a laboratory facility for producing a femtosecond XUV coherent monochromatic radiation with a broad tunable spectral range of 20 eV-75 eV. It is based on spectral selected single-order harmonics from intense laser driven high harmonic generation in gas phase. The time preserving for the selected harmonic radiation is achieved by a Czerny-Turner type monochromator designed with a conical diffraction grating mount for minimizing the time broadening caused by grating diffraction and keeping a relatively high diffraction efficiency. Our measurement shows that the photon flux of the 23-order harmonic(H23) centered at 35.7 eV is 1×10~9 photons/s approximately with a resolving power E/?E ≈ 36.This source provides an ultrashort tunable monochromatic XUV beam for ultrafast studies of electronic and structural dynamics in a large variety of matters.     

Large-angle channeling radiation from relativistic electrons in optically transparent crystals

In the work within the frame of quantum electrodynamics are obtained new formulae describing the large-angle photon emission from channeled electrons with taking into account of the dispersion of refractive index. Calculations based on these formulae show that the spectral and angular distributions of large-angle optical and ultraviolet radiation from planar channeled sub-GeV electrons in optically transparent crystal reflect the band structure of transverse energy levels of channeled electrons. Comparison with ordinary Cherenkov radiation spectrum reveals that channeling (depending on the beam energy) leads to sufficient change of the large-angle emission spectrum.     

离子转换色谱-紫外检测法测定啤酒中的无机阴离子和有机酸

建立了离子转换色谱与紫外检测器联用检测啤酒中无机阴离子与有机酸的新方法。在传统的离子色谱基础上引入两根离子转换柱,无机阴离子与有机酸经过两步转换,定量转换成有相同紫外响应的碘酸盐,然后用紫外检测器代替电导检测器进行定量分析。在Dionex AS11-HC阴离子色谱柱上,采用KOH梯度淋洗方式实现了12种无机阴离子与有机酸的分离。结果表明,12种无机阴离子和有机酸检出限（S/N=3）与定量限（S/N=10）分别为6.168~29.01 μg/L与20.56~66.30 μg/L;线性关系良好（r在0.9994以上）,回收率为89.0%~117.0%,RSD均小于1.0%,该方法与传统的电导检测器检测结果相当。该方法简单快捷,只需采用少数标准曲线,就可以实现啤酒中无机离子与有机酸的定量测定。     

响应面法优化萃取条件用于高效液相色谱分析饮用水中痕量邻苯二甲酸二(2-乙基己基)酯及其迁移规律

应用响应面法辅助分析塑料瓶装饮用水中邻苯二甲酸二（2-乙基己基）酯（DEHP）的迁移,建立了一种快速、简便、环保的痕量塑化剂类污染物检测方法。在盐析作用下,使用正己烷涡旋萃取,经氮气浓缩后进行高效液相色谱-紫外检测。响应面最优分析法考察了盐量、涡旋时间和萃取液体积3个因素作为萃取条件对DEHP回收率的影响,得到最佳萃取条件：盐量为16 g/L、涡旋时间为90 s、萃取液体积为5.28 mL。在此实验条件下,DEHP的最大理论回收率为92.91%,实验验证值为92.97%,与理论值相差0.06%。本方法检出限为0.006 mg/L,满足中国国家标准规定的生活饮用水安全标准要求（0.008 mg/L）,在0.01~15 mg/L范围内线性关系良好（相关系数R=0.9996）。选取常见市售饮用水样品进行分析,研究了塑料包装饮用水中痕量DEHP迁移的规律。与传统的优化方法相比,响应面模型分析法综合考虑了各因素的影响,而且更加简便、低成本、对环境友好,是实现样品中微痕量污染物精准检测的重要辅助手段。