装置极化效率对极化中子成像质量的影响及修正分析

极化中子照相技术通过分析极化中子束的自旋相移对样品磁场进行成像, 自旋极化/分析装置是照相系统的主要组成部分. 引入中子自旋极化/分析装置的极化效率参数, 从中子极化矢量与磁场相互作用机理出发, 重新推导探测中子强度与磁场分布的定量关系, 利用谱仪模拟软件VITESS, 选取bender型超镜极化器和 ³He 自旋过滤器作为极化/分析装置, 对量化修正式进行验证, 并综合装置极化效率、单色器能量分辨精度和bender型极化器的几何结构等参数, 初步分析极化中子照相技术的磁场定量检测能力, 相关结果可为极化中子照相的实验数据处理技术研究及装置设计提供参考. 关键词： 极化效率 中子照相 磁场成像     

动荷载作用下高速铁路风积土地基动力特性试验研究

根据辽西地区的地震资料和波速测试资料,通过动三轴试验,进行了地震冲击荷载和列车振动荷载两种动荷载作用下辽西风积土地基的动力特性试验研究。研究结果表明,风积土的动强度、动变形和动模量等指标与荷载类型、持续时间、振动频率和动应力幅值等条件有关。在地震荷载作用下,动荷载频率和动应力幅值越大、震动持续时间越长,其产生的动应变越大;在高速列车振动荷载作用下,土的动强度和动抗剪强度随振动次数的增加而降低;固结比相同时,动弹性模量Ed和动剪切模量Gd随固结压力的增大而增大;随动应变εd的增大而减小,且初始时刻减小速度明显,之后逐渐变缓。     

大豆中二硝基苯胺类除草剂多残留的气相色谱法定量检测及质谱确证

建立以凝胶渗透色谱法（GPC）和固相萃取法（SPE）及气相色谱法（GC）联用技术测定大豆中10种二硝基苯胺类除草剂（氟乐灵、乙氟灵、环丙氟、氯乙氟灵、仲丁灵、异乐灵、二甲戊乐灵、二硝胺、氨基丙氟灵和磺乐灵）多残留检测方法。目标农药经正己烷饱和的乙腈提取，凝胶渗透色谱除去大豆中大部分油脂及色素，再经Florisil柱净化和富集，依次用6mL二氯甲烷和6mL二氯甲烷＋丙酮（99＋1）洗脱。目标农药采用电子捕获检测（GC／ECD），外标法定量，并经质谱（MS）确证。两个添加水平重复6次，回收率分别为74％～105％和59％～105％；相对标准偏差〈20％；检出限为1．8～7．6μg／kg；定量限为6～38μg/kg。     

Separation and identification of compounds in Adinandra nitida by comprehensive two-dimensional liquid chromatography coupled to atmospheric pressure chemical ionization source ion trap tandem mass spectrometry

A comprehensive two-dimensional liquid chromatographic (2D-LC) separation system based on the combination of a CN column and a Merck Chromolith Flash reversed-phase column was developed for the separation of components in Adinandra nitida, one type of traditional Chinese medicine (TCM). The two dimensions were connected by a ten-port, dual-position valve controlled automatically by software written in-house. The effluents were detected by both ultraviolet and atmospheric pressure chemical ionization source ion trap tandem mass spectrometry (MS). The calculated peak capacity of the 2D-LC–MS/MS system was above 1240. More than 57 components were resolved in the methanol extract from Adinandra nitida leaves, and five of these were identified based on their relative retention times, molecular weights and MS/MS spectra.     

Synthesis of new 2-aryl-6-styryl-2,3-dihydropyridin-4(1H)-one derivatives from curcuminoids

Series of new 2-aryl-6-styryl-2,3-dihydropyridin-4(1H)-one derivatives were synthesized in acceptable to good yields by treatment of the curcuminoids with aqueous ammonia,the mechanism was proposed.By modification of the primary products,total 13 new compounds were obtained.The structures of all products were elucidated by spectroscopy analysis including HR-MS,~1H NMR and ~(13)C NMR.     

Kinetics and mechanism of oxidation of <Emphasis Type="Italic">N</Emphasis>-methylethylamine by bis(hydrogenperiodato)argentate(III) complex anion

Oxidation of N-methylethylamine by bis(hydrogenperiodato)argentate(III) ([Ag(HIO₆)₂]⁵⁻) in alkaline medium results in demethylation, giving rise to formaldehyde and ethylamine as the oxidation products. The oxidation kinetics has been followed spectrophotometrically in the temperature range of 20.0–35.0 °C, and shows an overall second-order character: being first-order with respect to both Ag(III) and N-methylethylamine. The observed second-order rate constants k′ increase with increasing [OH⁻] of the reaction medium, but decrease with increasing the total concentration of periodate. An empirical rate expression for k′ has been derived as: k′ = (k _a + k _b[OH⁻])K ₁/{f([OH⁻])[IO₄ ⁻]_tot + K ₁}, where k _a and k _b are rate parameters, and K ₁ is an equilibrium constant. These parameters have been evaluated at all the temperatures studied, enabling calculation of activation parameters. A reaction mechanism is suggested to involve two pre-equilibria, leading to formation of an intermediate Ag(III) complex, namely [Ag(HIO₆)(OH)(MeNHEt)]²⁻. In the subsequent rate-determining steps, this intermediate undergoes inner-sphere electron transfer from the coordinated amine to the metal center via two distinct routes, one of which is spontaneous while the other is mediated by a hydroxide ion.     

Synthesis and characterization of novel conjugated polymers based on 3-cyclobutene-1,2-dione moiety

Three novel conjugated polymers bearing 3,4-bis（4-hexylthiophen-2-yl）-3-cyclobutene-1,2-dione unit in their main chain have been synthesized successfully in good yields through Suzuki or Stille coupling reaction.Their molecular structures have been confirmed by FT-IR,¹H NMR and ¹³C NMR.All these copolymers exhibit broad and strong absorption bands in UV-vis region,and their optical band gaps are calculated to be 1.6-2.0 eV.suggesting that they have good coverage with the solar spectrum.These polymers have good thermostability and solubility in common organic solvents.Moreover,all these objective macromolecules possess high electron affinity of～3.8 eV determined from cyclic voltammetry measurement,implying that they are potential n-type polymeric photovoltaic materials.     

Porous composite scaffolds of hydroxyapatite/silk fibroin via two‐step method

A two‐step method was used to fabricate the hydroxyapatite (HAP)/silk fibroin (SF) scaffolds, i.e. the nano‐sized HAP/SF composite powders were prepared by co‐precipitation, which were then blended with SF solution to fabricate the HAP/SF composite scaffolds. The obtained scaffolds showed a 3D porous structure. The porosity was higher than 90% with the average macropore size of 214.2 µm. Moreover, the nano‐sized HAP/SF composite powders were uniformly dispersed in the silk fibroin matrix, which provided the scaffolds enhanced compressive properties. The cell culture assay showed that the scaffolds fabricated by the two‐step method could improve the cell proliferation and osteogenic differentiation when compared with those prepared by the conventional one‐step blending method. The results suggested that the two‐step method could promote the uniform dispersion of HAP in the SF matrix and efficient combination between the HAP and the matrix, which may provide a potential application in the composite scaffold preparation for tissue engineering. Copyright © 2009 John Wiley & Sons, Ltd.     

Oxidative Dehydrogenative Silylation‐Alkenation Reaction of Alkyl Aromatics with Silanes

A Cu(OAc)₂/DDQ/DTBP/Py system catalyzed oxidative dehydrogenative silylation‐alkenation tandem reaction of readily available alkyl aromatic compounds with silanes was established. A variety of functionalized alkenyl organosilicon compounds were provided in good to high yields with a total β‐(E) selectivity. The control experiments revealed that the transformation might proceed through a radical pathway.