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城中村的城市化与城市生态化的营力系统分析 被引量:2
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作者 李莉莉 高建军 《环境科学与技术》 CAS CSCD 北大核心 2010年第S2期678-681,共4页
城中村是伴随着我国城市化的加速发展而产生的一个特有的城市问题,已严重地影响着我国的城市化和城市生态化,影响着我国城市的可持续发展。在2000年左右,各大城市的城中村改造工程开始启动,在十几年的改造过程中,一些大城市取得了很大... 城中村是伴随着我国城市化的加速发展而产生的一个特有的城市问题,已严重地影响着我国的城市化和城市生态化,影响着我国城市的可持续发展。在2000年左右,各大城市的城中村改造工程开始启动,在十几年的改造过程中,一些大城市取得了很大的成就,但也存在着一些问题和不足,究其原因主要是对城中村形成、发展和改造的诸因子及其相互关系的认识不足。通过对我国城中村改造问题的深入研究,对城中村诸因子及其相互关系建立了力学模型并进行营力系统分析:城市化与城市生态化是城中村形成、演变、改造、发展并最终使城中村实现城市化与城市生态化相统一的主要驱动力;城市的经济功能、社会功能、环境功能及其生态功能是城中村的支撑力;城中村在体制、功能、生态上和城市体制、功能、生态的二元差异性所产生的粗糙度和压力构成了城中村形成、改造和发展的摩擦力。 展开更多
关键词 城中村 诸因子 营力系统分析
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PEG-mediated Gene Transfer into Orychophragmus Violaceus Cotyledon Protoplast and Regeneration of Transgenic Plants
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作者 周冀明 卫志明 +1 位作者 刘世贵 罗鹏 《Developmental and Reproductive Biology》 1994年第2期55-63,T001,共10页
Transgenic plants were obtained by PEG-mediated tranfer of foreign gene into cotyledon protoplasts of Orychophragums violaceus. Systematic study was carricd out on PEG-mediatcd transformation of cotyledon protoplast u... Transgenic plants were obtained by PEG-mediated tranfer of foreign gene into cotyledon protoplasts of Orychophragums violaceus. Systematic study was carricd out on PEG-mediatcd transformation of cotyledon protoplast using transient expression system, which showed 25-30 μg of pasmid, 15% PEG and a pH value of 8.0 as the optimal parameters contributing to the highest expression level. Using these parameters, cotyledon protoplasts were isolated, treated with bacterial plasmid DNA (pBI222 with HPT as selective marker) and PEG, and cultured at a density of 5×10 4/ml.After 10-15 days,they were selected by adding 25 μg/ml hygromycine. One month later, a few calli were observed, which were then transferred onto a solid medium with 50-100 μg/ml hygromycine for proliferation. Later they were transferred successively onto differentiation and rooting media and finally hygromycineresistant whole plants were obtaincd. The plants grew well in pots and a regeneration rate of 5 ×10(-5) was achieved. Then,excised leaves of the transgenic plants were used as explants for Southern blot analysis, which confirmed the stable integration of HPT gene into the chromosomal genome of Orychophragmus violaceus The transformation frequency was 10-5. 展开更多
关键词 Orychophragmus violaceus COTYLEDON Protoplast culture PEG transformation Transgenic plant.
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