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  • Author or Editor: Y. Xiang x
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Abstract  

Mn2O3/-Al2O3 catalysts were prepared by the impregnation method, and the maximum monolayer dispersion capacity or dispersion threshold value of Mn2O3 on the surface of -Al2O3 was determined to be 13.08% from the decomposition mass loss of supported Mn(NO3)2 in the monolayer state. This was compared with the values estimated from a close-packed monolayer model and an interaction model. It was confirmed that the high activities and selectivities of the catalysts for benzoic acid hydrogenation to benzaldehyde are due to the monolayer dispersion of the Mn2O3 on the surface of -Al2O3.

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Abstract  

Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)3 and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)2 and its adducts with pyridine, Ni(detp)2(py)2 or 4-methylpyridine, Ni(detp)(mpy)2 in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate. The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two ligands are of different type.

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Abstract  

The power-time curves of the growth of three strains of petroleum bacteria at different temperatures have been determined. A novel equation of a power-time curve has been proposed in this paper. The general formula to calculate the rate constant of the bacterial growth has been derived. The rate constants of the bacterial growth at different temperatures, the heat production per newly formed bacterium, the bacterial number at the end of the bacterial growth and the deceleration rate constant of the bacterial growth at 50.00°C, have been calculated. The optimum growth temperatures of the three strains have been obtained.

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Summary

A highly sensitive and reproducible isocratic liquid chromatographic method has been developed for the analysis of artemisinin and its three commonly used derivatives (artesunate, dihydroartemisinin, and artemether). The method involves a precolumn derivatization reaction with 4-carboxyl-2,6-dinitrobenzene diazonium ion to produce azo adducts that are UV-active. The critical parameters for the derivatization such as temperature, reaction time, and reagent concentrations were studied and optimized. The chromatographic separations were carried out on a C-18 column with mobile phase consisting of acetonitrile-0.1% acetic acid (60:40) at a flow rate of 1 mL min−1. UV detection was set at 254 nm. Dynamic linear calibration range was obtained at concentrations of artemisinins ranging from 0.26 to 1.44 μg mL−1. The low limits of detections of artemisinin, artesunate, dihydroartemisinin, and artemether were found to be 0.091, 0.0125, 0.0489, and 0.0128 ng μL−1, respectively. The developed methods were precise (RSD <3%) and accurate (% error < 5%). The developed methods may find application in dosage form analysis and pharmacokinetic studies.

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