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Leaf nitrogen and phosphorus stoichiometry of plants from natural and restorable communities at lands used for Qinghai-Tibet Highway Construction, China

Luo M. W., Mao L., Guo Z. G.

Polish Journal of Ecology

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2014

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Vol. 62, nr 2

227--238

EN

Highway network construction is one of common factors contributing to alpine grassland degradation in the Qinghai-Tibet Plateau as well as other regions, resulting in big area land used for highway construction by abruptly removing the vegetation and topsoil on both sides of roadbed. Taking the Land Used for Qinghai-Tibet Highway Construction (LUQHC) produced in 1994 as an example, a field survey was conducted to investigate the leaf N, P stoichiometry of plants from natural communities and restorable communities by using all plants and same pairwise of species, because the natural vegetation restoration at LUQHC is driven by element availability to some extent. This study showed that plants were probably P-limited in study region and the variation of N:P ratio was closely related to leaf P concentration. Results of same pairwise of species showed that the leaf N, P and N:P ratio of plants from restorable communities were higher than those of adjacent natural communities, indicating that leaf N and P were simultaneously affected by the environment circumstance of LUQHC. However, results of all species showed that the environment factors only impacted on leaf N concentration. These showed that the plant in restorable communities suffered from more intense P-limited conditions than those in natural communities, and that the same pairwise of species sampling was better to acquire the N- or P-limitation status for plant in restorable communities than all species. This study also showed that phylogenetic variation (family and genus identity) was key factor affecting the variations of N, P stoichiometry.

2

Simultaneous RP-LC analysis of 10-O-(N,N-dimethylaminoethyl)-ginkgolide B and three related impurities

Liu W.-Y, Yang X.-J, Li P., Feng F, Mao L.

Acta Chromatographica

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2011

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Vol. 23, no. 3

459--468

EN

10-O-(N,N-dimethylaminoethyl)-ginkgolide B (XQ-1) is an intermediate for synthesizing 10-O-(N,N-dimethylaminoethyl)-ginkgolide B methanesulfonate (XQ-1H), which is a novel ginkgolide B derivative and is being developed as a platelet-activating factor antagonist. A specific and rapid liquid chromatographic method was developed for the quantitative analysis of XQ-1 and its three related impurities, which were 10-O-(N,N-dimethylaminoethyl)-11,12-seco-ginkgolide B (imp-1), 10-O-(N,N-dimethylaminoethyl)-11,12-seco-3,14-dehydroginkgolide B (imp-2) and 10-O-(N,N-dimethylaminoethyl)-3,14-dehydroginkgolide B (imp-3) simultaneously in XQ-1 samples. Chromatographic separation was achieved on a CN band stationary phase, with the mobile phase consisting of methanol and 20 mM dipotassium hydrogen phosphate (pH 7.5) (50:50, υ/υ) in isocratic elution. The flow rate was 1.0 mL min-1 and detector was set at 220 nm. The method was optimized by the analysis of the samples generated during the forced degradation studies. The XQ-1, imp-1, imp-2, and imp-3 were completely separated within 15 min. The resolutions (Rs) amongst four target compounds were >2. The developed method was validated with respect to specificity, linearity, accuracy, precision, and robustness. The results indicated that the simultaneous LC determination method was readily utilized as a quality control method for XQ-1 sample.

3

Theoretical Study on the Chemical Reactions in the Cl-ClO Catalytic Cycle

Bing D., Mao L., Zhao Y., Li X., Hao F., Liu F.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 11

1857-1864

EN

One of the processes of ozone depletion in the polar stratosphere was investigated using ab initio calculations at the MP2, B3LYP, QCISD(T), G2, G2MP2 and CBS-Q levels. The reactional energy, the enthalpy of formation, and the relativeGibbs free energy of the reactions in the Cl-ClO catalytic cycle were calculated. The energies of the transition states of the reactions were calculated, followed by the calculations of the reaction barriers. The results support the mechanism of ozone deleption by the Cl-ClO catalytic cycle, and explain the basic reason of ozone depletion from the point of energy.