Oscillatory Behavior during the Partial Oxidation of Methane

A simplified Monte Carlo model was proposed to simulate the oscillatory behavior during catalytic partial oxidation of methane. Using the Langmuir-Hinshelwood mechanism, the oscillatory behavior was observed in both reaction rates and coverages of adsorbed species. The influence of oxidation and reduction of the catalyst surface on the oscillations was investigated, and the analysis showed that the fast oxidation and slow reduction of the catalyst surface resulted in the oscillatory behavior.     

H2S对NiW/Al2O3和CoMo/Al2O3上二苯并噻吩和4,6-二甲基二苯并噻吩加氢脱硫反应的影响

 考察了H2S对NiW/Al2O3和CoMo/Al2O3上二苯并噻吩(DBT)和4,6-二甲基二苯并噻吩(DMDBT)加氢脱硫反应的影响. 结果表明,H2S同时抑制DBT和DMDBT两种硫化物的加氢脱硫反应,并且对DBT的抑制作用更为明显. 对于NiW/Al2O3和CoMo/Al2O3两种催化剂,H2S抑制了DBT和DMDBT的直接脱硫路径活性; 对于CoMo/Al2O3催化剂上DBT转化中的加氢反应也有抑制作用,但促进了DMDBT转化中加氢反应的进行. NiW/Al2O3催化剂更易受H2S的影响.     

Synthesis and biodistribution of the 99mTc nitrido complex with 2-(4-nitro-1H-imidazolyl)ethyl dithiocarbamate (NIET)

Sodium and chlorine measurements were made by instrumental neutron activation analysis (INAA) on stratigraphically dated ice core samples from Byrd Station, Antarctica, for the last three centuries. The time period between 1969 and 1989 showed an enhanced impact on the Antarctic ice sheets from oceans in the form of marine aerosols. A disturbed ocean-atmosphere interface due to El Niño Southern Oscillation (ENSO) events seems to be a candidate for this observation in Antarctica.     

关于序超半群的左超理想的研究

本文在序超半群中引入了极小左超理想和极大左超理想的概念, 并讨论了它们的一些相关性质. 进一步地, 引入了序超半群的弱素左超理想、拟素左超理想、拟半素左超理想及弱拟素左超理想的概念, 并讨论这四种素超理想之间的关系. 而且通过左超理想和弱~$m$-系刻画了序超半群的弱拟素左超理想. 同时, 借助于$m$-系对序超半群的拟素左超理想给出刻画. 尤其证明了序超半群$S$是强半单的当且仅当$S$的每个左超理想是$S$的包含它的所有拟素左超理想的交.     

序半群的一类正则同余

设S是有向序半群,本文给出了S上的一类正则同余,称为强序同余的定义及性质.证明了S的强序同余是强正则同余,但反之不成立.同时证明了强序同余格SOC(S)是S的同余格C(S)关于通常集合的交和传递积的V-完备的分配子格.     

Dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-diode array detection for the determination of N-methyl carbamate pesticides in vegetables

This paper described a simple, rapid and efficient method for the determination of N-methyl carbamate pesticides in tomato, cucumber, carrot and lettuce samples by dispersive liquid-liquid microextraction coupled with HPLC-diode array detection. Some experimental parameters that influenced the extraction efficiency, such as types and volumes of extraction and disperser solvents, extraction time and salt effect were examined and optimized. Under optimum conditions, the LOD of the method were 0.5-3.0 μg/kg depending on the compounds and the kind of vegetables. The linearities of the method were obtained in the range of 10.0-300 μg/kg for aldicarb, MTMC, carbofuran and carbaryl, and 20.0-600 μg/kg for isoprocarb, with the correlation coefficients ranging from 0.9921 to 0.9993. The RSD varied from 2.9 to 7.5% (n=5). The recoveries of the method for the five carbamates from vegetable samples at two different spiking levels were ranged from 77.8 to 98.2%. Results showed that the method we proposed can meet the requirements for the determination of N-methyl carbamate in vegetable samples and was finally applied to the analysis of target pesticides in vegetable samples taken from local markets.     

Stereoselective determination of famoxadone enantiomers with HPLC-MS/MS and evaluation of their dissipation process in spinach

A simple and enantioselective method for the determination of famoxadone enantiomers in spinach using reversed-phase HPLC-MS/MS is presented. Famoxadone residues in spinach were extracted with acetonitrile and an aliquot was cleaned up with PSA (primary and secondary amine, Si-(CH(2))(3)-NH-(CH(2))(2)-NH(2)) and C(18) sorbent, which were powder material. Chiral stationary phase (CSP), cellulose tris(3,5-dimethylphenylcarbamate), was successfully applied to separate two enantiomers using methanol/formic acid-ammonium acetate buffer as mobile phase. The MS/MS fragmentation pathway of ammonium adduct famoxadone molecules ion at m/z 392 was analyzed and an odd electron fragment ion at m/z 238 was observed. Excellent linearity was achieved for each enantiomer over a range of concentrations from 0.5 to 1500 μg/L with coefficients more than 0.99. Average recoveries at five different levels (1, 2.5, 12.5, 250 and 1250 μg/kg, for each enantiomer) ranged from 80.8 to 96.5% with RSD of 4.8-13.4%. The famoxadone enantiomers LODs in spinach were determined to be both 0.3 μg/kg with LOQs of 1 μg/kg. Based on this method, the dissipation process of famoxadone enantiomers in spinach under open field and greenhouse conditions was characterized, providing guidance to the proper and safe use of this fungicide in agriculture.     

Crystal structures and photoisomerization behaviors of five novel pyrazolone derivatives containing furoyl group

Five novel pyrazolone derivatives containing a furoyl group, 1-phenyl-3-furoyl-4-(4-chlorobenzal)-5-pyrazolone thiosemicarbazone (PF4ClBP-TSC) (1)/methylthiosemicarbazone (PF4ClBP-MTSC) (2)/ethylthiosemicarbazone (PF4ClBP-ETSC) (3), 1-phenyl-3-furoyl-4-(2-chlorobenzal)/(3-chlorobenzal)-5-pyrazolone methylthiosemicarbazone (PF2ClBP-MTSC) (4)/(PF3ClBP-MTSC) (5), have been synthesized and characterized by elemental analysis, IR, ¹H NMR spectra, and the molecular structures of 2 and 5 were determined by X-ray single crystal diffraction. Photoisomerization properties have been studied by UV–vis and fluorescence spectra. Based on theoretical calculation and crystal structural analysis, the compounds undergo photoisomerization from the enol form to the keto form through an intermolecular proton transfer upon UV light irradiation. Moreover, the photoisomerization rate decreases with the increase of volume of substituent groups on 4-position of thiosemicarbazide and the steric hindrance of Cl atom on benzal of 4-positon on the pyrazolone ring.     

Enantioselective determination of carboxyl acid amide fungicide mandipropamid in vegetables and fruits by chiral LC coupled with MS/MS

An efficient enantioselective method for the determination of mandipropamid in vegetables and fruits was presented by LC coupled with MS/MS. The mandipropamid residues in samples (potato, pepper, grape, and watermelon) were extracted with acetonitrile containing 1% acetic acid. An aliquot was cleaned up with primary and secondary amine and C₁₈ sorbent. Complete enantioseparation of mandipropamid enantiomers in <4 min was obtained on a Lux Cellulose‐2 column at 25°C using methanol with 0.1% formic acid/0.1% aqueous formic acid solution (85:15, v/v) as mobile phase. Good linearity was obtained over the concentration range of 0.5–250 μg/L for each enantiomer in the standard solution and sample matrix calibration curves. Quantification was achieved using matrix‐matched standard calibration curves. The interday mean recoveries, intraday repeatability, and inter‐day reproducibility varied from 76.4 to 97.1%, 3.4 to 9.4%, and 3.5 to 11.4%, respectively. The limits of quantification for mandipropamid enantiomers in vegetables and fruits were both 1 μg/kg. Moreover, the absolute configuration of mandipropamid enantiomers was determined by the combination of experimental and predicted electronic circular dichroism spectra, and the first eluted enantiomer was confirmed as (R)‐mandipropamid on five chiral columns.