6291型热变形温度和维卡软化温度测试仪的校准及故障排除

介绍6291型热变形温度和维卡软化温度测试仪的温度校准和位移校准方法，对测试仪的一些常见故障，例如电源故障，主温度传感器故障，电加热系统控制单元故障及测试站的温度偏差较大等进行了分析，并给出了排除故障的方法。     

Alkylation of ethylenethiourea with alcohols: a convenient synthesis of S-alkyl-isothioureas without toxic alkylating agents

The alkylation of ethylenethiourea with alcohols and aqueous acids (HCl, HBr, and HI) allows the synthesis of the respective S-alkyl-isothioureas in high yield and purity. Consistently high yields (91-98%) were obtained with 56% HI, the yields for 48% HBr (48-93%) and 37% HCl (36-85%) were lower and varied with the type of alcohol. The method is a convenient low-cost alternative to the use of alkyl iodides and an easy access to the S-tert-butyl isothiourea.     

Effect of subsurface oxygen on the reactivity of the Ag(111) surface

Periodic, self-consistent, density functional theory calculations have been performed to demonstrate that subsurface oxygen (O(sb)) dramatically increases the reactivity of the Ag(111) surface. O(sb) greatly facilitates the dissociation of H2, O2, and NO and enhances the binding of H, C, N, O, O2, CO, NO, C2H2, and C2H4 on the Ag(111) surface. This effect originates from an O(sb)-induced upshift of the d-band center of the Ag surface and becomes more pronounced at higher O(sb) coverage. Our findings point to the important role that near-surface impurities, such as O(sb), can play in determining the thermochemistry and kinetics of elementary steps catalyzed by transition metal surfaces.     

A Rapid and Convenient Synthesis of Derivatives of Imidazoles under Microwave Irradiation

An efficient and a quick microwave‐assisted synthesis of benzimidazoles and trisubstituted imidazoles was developed. Three benzimidazoles were obtained as a result of the condensation of 1,2‐phenylenediamine with carboxylic acids and acetoacetic ester without catalyst. A series of trisubstituted imidazoles were synthesized by condensation of benzil, aromatic aldehyde and ammonium acetate in the presence of glacial acetic acid.     

Quantitation of SU1 1248, an oral multi-target tyrosine kinase inhibitor, and its metabolite in monkey tissues by liquid chromatograph with tandem mass spectrometry following semi-automated liquid-liquid extraction

SU11248 is a potent inhibitor of PDGFR, VEGFR, KIT, and Flt3, and is currently under Phase I clinical evaluation as an anticancer drug. A sensitive and specific analytical method for the quantitation of SU11248 and its metabolite in several monkey tissues (liver, kidney, brain and white fat) using LC-MS-MS following semi-automated liquid-liquid extraction (LLE) was developed and validated. Amounts of 50 mg of tissue were homogenized using an ultrasonic processor. After addition of the stable labelled internal standard (IS) and ammonium hydroxide (0.3%), samples were extracted with 2.5 ml of tert-butyl methyl ether. Following centrifugation, aliquots of 1.8 ml of the organic phase were transferred into a 96-well plate. The Packard Multiprobe II robotic liquid handler was used to perform all steps mentioned above. The organic phase was dried and the residue was reconstituted with 800 microl of 15 mM ammonium formate buffer solution (pH 3.25) using a Tomtec Quadra 96 workstation. Aliquots of 10 microl of the resulting solution were injected into the LC-MS-MS system. A Symmetry Shield C8 column (50 mm x 2.1 mm, 3.5 microm) was used to perform the chromatographic analysis. The mobile phase was 15 mM ammonium formate buffer solution (pH 3.25)-acetonitrile (74:26 (v/v)) with a flow-rate of 0.35 ml/min. Retention times of the metabolite and SU11248 were about 2.5 and 3.5 min, respectively. Total cycle time was 5 min. MS detection used the Applied Biosystems-MDS Sciex API 3000 with TurbolonSpray interface and multiple reaction monitoring (MRM) operated in positive ion mode. The method was validated for both compounds over the calibration range of about 2 and 2000 ng/g. The suitability and robustness of the method for in vivo samples were confirmed by analysis of monkey tissues from animals dosed with SU11248.     

钒、铬、锰磷桥络合物中31P NMR化学位移的研究

ISSIe山和W6flSChllh山子1960年首次用pdCI。和二苯基磷合成出黄色的二聚络合物，后被H。yieY＊确认为具有pRZ的桥式结构．此后一系列该类结构的化合物被合成并引起了广泛的兴趣．磷可以和两个甚至多个金属原子络合构成多核金属络合物，在催化反应中有重要应用．磷原子存在多种电子态，其3d空轨道也能参与成键．P乃1的NMR谱是研究含磷化合物立体结构的有力工具．P－31与其它核素之间的耦合常数以及P－31的化学位移对阐明化合物的立体构象以及电子结构具有重要作用．近年来，West饲用计算机神经网络技术预测P－：if的化学位移，但仅…     

Optimization of the Conditions for the Cr (III) Adsorption on Activated Carbon

In order to understand the patterns of the adsorption equilibrium of Cr (III) on activated carbon, the adsorption process was studied by two different ways: classical batch experiments on commercial Norit and Merck activated carbons and their oxidized forms in a wide range of pHs; and extended time-based tests at the same pH values on the same adsorbents. This approach allowed us to understand the role of texture, chemical carbon surface functionality and experimental conditions (initial pH of the solution, contact time and adsorbate/adsorbent ratio) on the effectiveness of Cr (III) removal. The adsorption process of Cr (III) at (24 ± 1^∘C) on Merck and Norit activated carbons and their oxidized forms were studied at pH values between 1.5 and 5 (either adjusted or buffered). Chromium concentration was fixed at 200 ppm. The carbon loading ranged from 1.2 to 20 g/l. The carbon/Cr (III) solution contact time was varied from 0.5–1 month to 5 months, to ensure that the saturation of the carbon level was reached. According to the data obtained, the presence of carboxylic groups on carbon surface seems to enhance Cr (III) uptake at initial pH of the solution in the range between 2 and 4. Depending on the nature of the adsorbent surface chemistry, the contact time to reach equilibrium may range from 3 to 5 months. There is an optimum carbon loading which limits the Cr (III) uptake/removal at given pH value. In order to understand the adsorption process, an ion exchange, surface complex and surface precipitation were considered. This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18-21 July, 2004.     

Three-component one-pot total syntheses of glyantrypine, fumiquinazoline F, and fiscalin B promoted by microwave irradiation

A microwave-promoted three-component one-pot reaction has been developed to provide access to the core pyrazino[2,1-b]quinazoline-3,6-dione (1) scaffold, which is common to several families of alkaloids with significant biological activities. By adapting this synthetic strategy through the use of selected Boc-amino acids and amino acid esters, we have accomplished highly efficient and concise total syntheses of glyantrypine (2), fumiquinazoline F (3), and fiscalin B (5), achieving overall yields of 55, 39, and 20%, respectively.     

固相膜萃取与GC/MS联用测定地下水中痕量半挥发性有机物的野外采样方法研究

C18固相萃取膜适宜处理大体积地下水样现场采样而且易于运输、贮存。利用C18固相膜萃取以及GC／MS联用的方法对地下水中痕量半挥发性有机污染物进行了萃取以及定性、定量分析。优化了固相膜萃取的地下水采样量和浓缩体积。有机氯农药和多环芳烃的平均回收率分别为85％～110．1％、90．3％～115．1％；方法检出限达到10^-9g／L；相对标准偏差均小于15％。本方法用于北京地区地下水中的有机污染物分析，并给出地下水样C18固相膜萃取的GC／MS测定结果。     

Mass spectrometric study of μ4-oxohexa-μ-acetatotetrazinc,Zn4O(CH3CO2)6

The electron impact mass spectrum of Zn₄O(CH₃CO₂)₆ isostructural to Be₄O(CH₃CO₂)₆ studied earlier is reported. The principal fragmentation paths of both compounds involve the elimination of M(CH₃CO₂)₂ where M is Zn, Be, or (CH₃CO)₂O. Further fragmentations proceed by the losses of CH₂CO and H₂O. The spectrum of Zn₄O(CH₃CO₂)₆ contains intense doubly charged ions. The results obtained are interpreted in terms of stereochemical considerations.