| 3 | Land cover dynamics of different topographic conditions in Beijing,China显示文摘Topographic conditions play an important role in controlling land cover dynamic processes.In this study,remotely sensed data and the geographic information system were applied to analyze the changes in land cover along topographic gradients from 1978 to 2001 in Beijing,a rapidly urbanized mega city in China.The study was based on five periods of land cover maps derived from remotely sensed data:Landsat MSS for 1978,Landsat TM for 1984,1992,1996 and 2001,and the digital elevation model(DEM)derived from 1:250,000 topographic map.The whole area was divided into ten land cover types:conifer forest,broadleaf forest,mixed forest,shrub,brushwood,meadow,farmland,built-up,water body and bare land.The results are summarized as follows.(1)Shrub,forest,farmland and built-up consist of the main land cover types of the Beijing area.The most significant land cover change from 1978 to 2001 was the decrease of the farmland and expansion of the built-up area.Farmland decreased from 6354 to 3813 km^(2)in the 23 years,while the built-up area increased from 421 to 2642 km^(2).Meanwhile,the coverage of forest increased from 17.2%to 24.7%of the total area.The conversion matrix analysis indicated that the transformation of farmland to the built-up area was the most significant process and afforesta-tion was the primary cause of the replacement of shrub to forest.(2)Topographic conditions are of great importance to the distribution of land cover types and the process of land cover changes.Elevation has an intensive impact on the dis-tribution of land cover types.The area below 100 m mostly consists of farmland and built-up areas,while the area above 100 m is mainly covered by shrub and forest.Shrub has the maximum frequency in areas between 100 and 1000 m,while forest has dominance in areas above 800 m.According to the analysis of land cover changes in different ranges of elevation,the greatest change below 100 m was the process of urbanization.The process of the main land cover change occurred above 100 m was the transformation from shrub to forest.This result was consistent with the vertical change of natural vegetation distribution in Beijing.(3)Slope has a great influence on the distribution of land cover.Farmland and built-up areas are mostly distributed in flat areas,while shrub and forest occupy steeper areas compared with other land cover types.Forest frequency increased with the increas-ing slope.Land cover changes differed from the slope gradients.In the plain area,the land cover change occurred as the result of urbanization.With the increasing of the slope gradient,afforestation,which converts shrub to forest,was the process of the primary land cover change. | WU Xiaopu TANG Zhiyao CUI Haiting FANG Jingyun | 2007 | Frontiers in Biology2007，2，4： | 1 |
| 4 | Short-form OPA1 is a molecular chaperone in mitochondrial intermembrane space显示文摘Mitochondria,double-membrane organelles,are known to participate in a variety of metabolic and signal transduction pathways.The intermembrane space(IMS)of mitochondria is proposed to subject to multiple damages emanating from the respiratory chain.The optic atrophy 1(OPA1),an important protein for mitochondrial fusion,is cleaved into soluble short-form(S-OPA1)under stresses.Here we report that S-OPA1 could function as a molecular chaperone in IMS.We purified the S-OPA1(amino acid sequence after OPA1 isoform 5 S1 site)protein and showed it protected substrate proteins from thermally and chemically induced aggregation and strengthened the thermotolerance of Escherichia coli(E.coli).We also showed that S-OPA1 conferred thermotolerance on IMS proteins,e.g.,neurolysin.The chaperone activity of S-OPA1 may be required for maintaining IMS homeostasis in mitochondria. | Deyang Yao Yukun Li Sheng Zeng Zhifan Li Zahir Shah Bigui Song Jinglei Liu Yi Wu Liang Yang Qi Long Wenqian Wang Zhijuan Hu Haite Tang Xingguo Liu | 2022 | Science China(Life Sciences)2022，65，2： | 1 |
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