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The rapid economic growth stimulates a surprising and uncontrolled urbanization wave in China, and necessarily brings about, in turn, poor environment quality and low life amenity. By what means the situation can be substantially transformed into a healthy track has been a puzzled and considerably difficult work challenging all Chinese. The article attempts to explore the conceptual model for establishing an ecological defense system in Yuelu District of Changsha, Hunan province, China, a rapid urbanized area, primarily focusing on its spatial pattern and adaptable scheme in order to control its continuing sprawl and improve local environment. For achieving the aim, authors first define the concept and its key qualities, then analyze and compare differing schemes with the principal purposes of defending urbanization and resolving prevailing urban ills, in terms of their principal goals, elements and spatial patterns. Finally, three elements are indentified, that is, the eco- base, eco-fortress and eco-corridor, and the skeleton and final scheme are set out, comprising 3 zones - enhancement zones, buffer zones and core conservation zones - and designing a web- like spatial pattern composing of urban green spaces, greenways, waterways, wetlands, forested hills and mountains, farmlands and villages. The system is designed as an eco-centric, forest- oriented, sustainable network of life support system. In order to accomplish its anticipated functions, it must make every efforts to obtain supports from legislation, administration, residents, enterprises and other institutions, to launch large-scale mass propagations and specific training, and ultimately to compete a high level priority over so called "gray" planning processes, at lest concurrently.

In this paper, ultrasound contrast agents based on a high molecular polymer-poly lactic acid (PLA) and loaded with hydroxycamptothecin (HCPT) were prepared by combining ultrasound method and a Shirasu porous glass (SPG) membrane emulsification technique. A special focus was on the optimization of production of HCPT-PLA microbubbles. Different factors, such as the power and the time of ultrasonic action, the ratio of inner aqueous phase against outer oil phase, and the concentration of PLA were evaluated, and the average size of HCPT-PLA microbubbles, the drug carrying efficiency, as well as the acoustically- triggered drug release at 3 kHz ultrasound were determined. The study showed that the HCPT-PLA microbubbles prepared using our optimized conditions, were sphere-like in shape with a mean diameter of 1-7 mum. The drug loading efficiency reached up to 56.48% In vitro, the drug release of HCPT-PLA microbubbles increased significantly at 3 kHz ultrasound for 30 s compared with that of ultrasound-free condition. In conclusion, the HCPT-PLA microbubbles has the characteristics desirable for an intravenously administered ultrasound contrast agent for further clinical use.