239,240Pu,241Am and137Cs in soils from several areas in China

This paper gives the first data on^239,240Pu and²⁴¹Am in Chinese soils. Surface soil samples with a set of 0–5 cm and 5–20 cm depth were collected from Beijing, Taiyuan, Shijiazhuang and Jinang of China in 1990, and^239,240Pu,²⁴¹Am and¹³⁷Cs, including naturally occurring radionuclides, in these samples were measured to evaluate their present levels and distributions. From these results, the average accumulated depositions were estimated roughly to be 24±13 MBq/km² for^239,240Pu, 10±5 MBq/km² for²⁴¹Am and 1.2±0.7 GBq/km² for¹³⁷Cs. The activity ratios of^239,240Pu/¹³⁷Cs and²⁴¹Am/^239,240Pu ranged from 0.016 to 0.026 with a mean value of 0.020±0.004 and 0.35 to 0.49 with a mean value of 0.43±0.05, respectively.     

全氟己酮中间体全氟丙酰氟及全氟环氧丙烷的合成研究进展

全氟己酮是优良的灭火剂和清洁剂,环境友好且性能优异。本文对其合成工艺进行探究,指出了以六氟丙烯为原料的合成工艺具有工业化的前景,并对六氟丙烯工艺中的重要中间体六氟丙酰氟及六氟环氧丙烷(HFPO)的合成方法进行了分析,指出分子氧液相氧化六氟丙烯制HFPO及使用鼓泡反应器将HFPO异构化成全氟丙酰氟是最有应用前途的工业合成方法。     

Cis-trans isomerization of chemically activated 1-methylallyl radical and fate of the resulting 2-buten-1-peroxy radical

The cis-trans isomerization of chemically activated 1-methylallyl is investigated using RRKM/Master Equation methods for a range of pressures and temperatures. This system is a prototype for a large range of allylic radicals formed from highly exothermic (～35 kcal/mol) OH + alkene reactions. Energies, vibrational frequencies, anharmonic constants, and the torsional potential of the methyl group are computed with density functional theory for both isomers and the transition state connecting them. Chemically activated radicals are found to undergo rapid cis-trans isomerization leading to stabilization of significant amounts of both isomers. In addition, the thermal rate constant for trans → cis isomerization of 1-methylallyl is computed to be high enough to dominate reaction with O(2) in 10 atm of air at 700 K, so models of the chemistry of the (more abundant and more commonly studied) trans-alkenes may need to be modified to include the cis isomers of the corresponding allylic radicals. Addition of molecular oxygen to 1-methylallyl radical can form 2-butene-1-peroxy radical (CH(3)CH═CHCH(2)OO(?)), and quantum chemistry is used to thoroughly explore the possible unimolecular reactions of the cis and trans isomers of this radical. The cis isomer of the 2-butene-1-peroxy radical has the lowest barrier (via 1,6 H-shift) to further reaction, but this barrier appears to be too high to compete with loss of O(2).     

Defect-less, layered organo-titanosilicate with superhydrophobicity and its catalytic activity in room-temperature olefin epoxidation

A new type of defect-less, layered organo-titanosilicate is synthesized using a simple, template-free, evaporation-induced self-assembly process. The obtained layered material has superhydrophobicity and exhibits promising catalytic activity in the epoxidation of olefins using 30% H(2)O(2) aqueous solution as oxidant at room temperature.     

原子吸收光谱法间接测定食品中甲醛含量

提出了原子吸收光谱法间接测定食品中甲醛含量的方法。甲醛与斐林溶液(含铜离子和酒石酸钾钠的碱性溶液)在沸水浴中反应30min生成氧化亚铜沉淀,或与银氨溶液(含银离子的氨性溶液)在50℃水浴中反应15min生成单质银沉淀。两种沉淀分别用6mol·L-1盐酸溶液和6mol·L-1硝酸溶液溶解,并用原子吸收光谱法测定反应中定量释出的铜量或银量,间接换算成甲醛含量。铜和银的质量浓度分别在7.000,6.000mg·L-1以内与吸光度呈线性关系。在试样溶液中加入1.000mg·L-1铜、银标准溶液并按所述方法进行分析,所得回收率在99.6%～101%之间(Cu)和81.9%～84.2%之间(Ag)。     

金催化的C—C偶联反应研究进展

近年来金催化剂作为一种温和的π路易斯酸展现了其独特的催化性能,已经成为有机化学研究的热点之一.综述了近年来金催化的碳碳偶联反应,并对其以后在氧化还原反应方面的应用进行探讨.     

Quantification of leonurine, a novel potential cardiovascular agent, in rat plasma by liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study in rats

Leonurine (SCM‐198), an alkaloid from Herba Leonuri, has been suggested as a novel cardiovascular agent by pharmacology studies in preclinical stage. In present study, we report a simple, rapid and sensitive high‐performance liquid chromatography–tandem mass spectrometry method (HPLC‐MS/MS) for determination of leonurine in rat plasma. Leonurine and its internal standard (IS) n‐benzoyl‐l ‐arginine ethyl ester (BAEE) were extracted from plasma samples by one‐step protein precipitation with perchloric acid. Chromatographic separation was performed on an Agilent Zorbax SB‐C₁₈ column (150 × 2.1 mm, 5 µm) using an isocratic elution with acetonitrile–ammonium acetate buffer (10 mm , pH 4.0; 25:75, v/v) as mobile phase at a flow rate of 0.2 mL/min. Analytes were detected by tandem mass spectrometry in positive electrospray ionization (ESI) mode using multiple reaction monitoring (MRM) with the transitions of m/z 312.3 → 181.1 for leonurine and m/z 307.2 → 104.6 for IS. The calibration curves were linear over the range of 4–256 ng/mL with a lower limit of quantitation (LLOQ) of 4 ng/mL. The intra‐ and inter‐day assay precision (as relative standard deviation) were <15%, except which at LLOQ were <20%, with accuracy in the range 98.73‐105.42%. The validated HPLC‐MS/MS method was successfully applied to the pharmacokinetic study in rats following oral administration of leonurine. Copyright © 2011 John Wiley & Sons, Ltd.     

Formation of N-heterocyclic diphosphine ligands from Ag(I)-assisted condensation reactions between bdppeda and formaldehyde and their binuclear silver(I) complexes

The reaction of [Ag(MeCN)(4)]ClO(4) with N,N,N',N'-tetra(diphenylphosphanylmethyl)ethylenediamine (dppeda) in CH(2)Cl(2)/MeOH afforded an unexpected cationic binuclear complex [Ag(2)(L(1))(2)(η,η-μ-ClO(4))(2)](ClO(4))(2) (L(1) = N,N'-bis(diphenylphosphanylmethyl)-3H-4,5-dihydroimidazole-1-ium) (1). Compound 1 was also prepared in high yield from reactions of [Ag(MeCN)(4)]ClO(4) with N,N'-bis(diphenylphosphanylmethyl)ethylenediamine (bdppeda) in the presence of formaldehyde (HCHO) or formic acid (HCOOH). Analogous reactions of AgCl with bdppeda and HCHO resulted in the formation a neutral binuclear complex [Ag(2)(L(2))(2)(μ-Cl)(2)] (L(2) = N,N-bis(diphenylphosphanylmethyl)-tetrahydroimidazole) (2). Treatment of 1 with concentrated HCl gave rise to a partially anion-exchanged product [Ag(2)(L(1))(2)(μ-Cl)(2)](ClO(4))(2) (3). Compounds 1 and 3 have a similar cationic binuclear structure, in which a [Ag(2)(η,η-μ-ClO(4))(2)] or [Ag(2)(μ-Cl)(2)] ring is sandwiched by two in situ-formed cationic L(1) ligands. The L(1) ligand may be generated by the Ag(I)-assisted condensation reaction between bdppeda and HCHO or HCOOH. Compound 2 holds a neutral binuclear structure, in which a [Ag(2)(μ-Cl)(2)] ring is connected by two in situ-formed L(2) ligands from its top and bottom sites. The neutral ligand L(2) may be produced from another Ag(I)-assisted condensation reaction between bdppeda and HCHO. The in situ formation of the L(1) and L(2) ligands provides a new route to the N-heterocyclic diphosphine ligands, and an interesting insight into the coordination chemistry of their metal complexes.     

325 MHz spoke腔的二次电子倍增效应

采用CST软件的粒子工作室模块, 对spoke超导腔中可能发生的二次电子倍增效应进行了分析研究,并采用二次电子倍增效应发生后形成稳定状态时的粒子数增长率来表征其强度。模拟计算表明:该腔存在两处二次电子倍增效应,spoke柱两端的两点一阶倍增; spoke腔两端侧壁与中心圆筒交界处的单点一阶倍增;二次电子倍增在加速腔压为0.65 MV时的增长率最高,而腔压大于1 MV时,增长率均为负,即无倍增发生。     

农村初中物理主题探究性学习的评价研究

分析了农村初中物理主题探究性学习与《全日制义务教育物理课程标准》内容的共同点与差异性,并在此基础上,设计了初中物理主题探究性学习中的评价标准．文章最后部分通过实践的反馈,对评价量表进行了改进,使评价表具有较好的可操作性．