Group A streptococcus （GAS） causes a wide range of diseases in the human population. GAS diseases are more common in children than in adults, with clinical manifestations ranging from pharyngitis and impetigo to inv...Group A streptococcus （GAS） causes a wide range of diseases in the human population. GAS diseases are more common in children than in adults, with clinical manifestations ranging from pharyngitis and impetigo to invasive infections and post streptococcal sequelae, such as acute rheumatic fever and acute post-streptococcal glomerulonephritis[1]. GAS harbors a host of virulence factors that contribute to its complex pathogenicity and differences in the disease severity and frequency. M protein, one of the major virulence factors, is encoded by the emm gene induces a type of specific host immune response and confers antiphagocytic properties.展开更多
China is in the process of rapid urbanization,and wise land use is critical to the long-term sustainability of Chinese cities.Promotion of a compact city is typically believed to be helpful for sustainable land use ma...China is in the process of rapid urbanization,and wise land use is critical to the long-term sustainability of Chinese cities.Promotion of a compact city is typically believed to be helpful for sustainable land use management.However,given the fact that Chinese cities are characterized by high population densities,the applicability of a more compact solution to expand cities in China remains questionable;there is little evidence to support the many claims in its favor.In seeking to provide empirical data to explore the application of compact city theory in China,one of the key problems researchers face is the task of measuring the urban compactness,in order to objectively investigate the current characteristics of urban compactness.To meet this need,indices were developed for measuring the urban land use compactness,by which the spatial distribution characteristics of urban land use compactness were identified and applied to the Chaoyang District of Beijing.The conclusions can be made as follows:(1) comprehensive land use compactness in Chaoyang District has increased during the period of 2001-2007,especially the population density;(2) the spatial distribution of land use compactness has the characteristics of a ring structure,which shows a decreasing trend with its distance to the city center;(3) there is a strong positive correlation between urban land use compactness and location.The better the location is,the higher the land use compactness is.展开更多
Beijing's green belt policy is three-fold:fi rstly to protect farmers' interests during urbanization, secondly to control the urban expansion, and thirdly to improve the ecological environment. The planning of...Beijing's green belt policy is three-fold:fi rstly to protect farmers' interests during urbanization, secondly to control the urban expansion, and thirdly to improve the ecological environment. The planning of industrial land for green belts has thus emerged as a way to help achieve these goals during Beijing's urban growth from morphological, social, and economic perspectives. First of all, this paper introduces the implementation mechanisms of the planning of industrial land for green belts, from which it abstracts a model of land adjustment and urban-rural cooperation. Secondly, the paper analyzes the effects and current dilemmas during the implementation of the planning of industrial land for green belts. Thirdly, results are compared with other spontaneously developed industries in the rural-urban fringe area to illustrate the changes brought about by the planning. Finally, the paper proposes three measures for future improvement, including balancing the industrial land use quotas between different townships, conducting cooperative land adjustment, and encouraging spontaneously developed industrial projects.展开更多
【目的】生态网络作为整合景观斑块和廊道的有机结构,提升景观连通性是维持生态系统健康的重要途径。完善北京市朝阳区的城市生态网络,可推动生态文明战略背景下的城市绿色空间建设。【方法】以朝阳区为研究区域,选取2005、2010、2015、...【目的】生态网络作为整合景观斑块和廊道的有机结构,提升景观连通性是维持生态系统健康的重要途径。完善北京市朝阳区的城市生态网络,可推动生态文明战略背景下的城市绿色空间建设。【方法】以朝阳区为研究区域,选取2005、2010、2015、2020年4个时间节点,利用图论(graph theory)原理工具Graphab进行景观连通性分析,探讨生态网络的演变特征和图论在网络格局优化方面的应用。【结果】发现:2005—2020年,朝阳区绿色空间规模持续提升,斑块总数增加,但平均斑块面积缩减27.3%,网络趋于破碎化;生态网络整体水平上的景观连通性提高,连通概率指数(probability of connectivity, PC)提升35.4%;最大连通单元面积(size of the largest component, SLC)提高,平均连通单元面积(mean size of the components, MSC)下降,核心景观连通单元优势度增强,而平均景观连通单元退化,网络趋于两极化;个体水平上的景观连通性等级空间分布不均,呈现北高南低的格局。【结论】基于图论实现朝阳区生态网络的诊断和优化,识别出4个重要潜在生态斑块的位置,使PC提升11.9%。研究结果可为城市绿色空间的规划发展工作提供决策参考,体现图论在城市生态网络构建及优化中的应用价值。展开更多
文摘Group A streptococcus （GAS） causes a wide range of diseases in the human population. GAS diseases are more common in children than in adults, with clinical manifestations ranging from pharyngitis and impetigo to invasive infections and post streptococcal sequelae, such as acute rheumatic fever and acute post-streptococcal glomerulonephritis[1]. GAS harbors a host of virulence factors that contribute to its complex pathogenicity and differences in the disease severity and frequency. M protein, one of the major virulence factors, is encoded by the emm gene induces a type of specific host immune response and confers antiphagocytic properties.
基金financed by the National Natural Science Foundation of China(Grant nos.40635026and40901068)Special Fund from the Science and Technology Department of Beijing Municipality(Grant no.zz0922)the Postdoctoral Science Foundation of China(Grant no.200902133)
文摘China is in the process of rapid urbanization,and wise land use is critical to the long-term sustainability of Chinese cities.Promotion of a compact city is typically believed to be helpful for sustainable land use management.However,given the fact that Chinese cities are characterized by high population densities,the applicability of a more compact solution to expand cities in China remains questionable;there is little evidence to support the many claims in its favor.In seeking to provide empirical data to explore the application of compact city theory in China,one of the key problems researchers face is the task of measuring the urban compactness,in order to objectively investigate the current characteristics of urban compactness.To meet this need,indices were developed for measuring the urban land use compactness,by which the spatial distribution characteristics of urban land use compactness were identified and applied to the Chaoyang District of Beijing.The conclusions can be made as follows:(1) comprehensive land use compactness in Chaoyang District has increased during the period of 2001-2007,especially the population density;(2) the spatial distribution of land use compactness has the characteristics of a ring structure,which shows a decreasing trend with its distance to the city center;(3) there is a strong positive correlation between urban land use compactness and location.The better the location is,the higher the land use compactness is.
文摘Beijing's green belt policy is three-fold:fi rstly to protect farmers' interests during urbanization, secondly to control the urban expansion, and thirdly to improve the ecological environment. The planning of industrial land for green belts has thus emerged as a way to help achieve these goals during Beijing's urban growth from morphological, social, and economic perspectives. First of all, this paper introduces the implementation mechanisms of the planning of industrial land for green belts, from which it abstracts a model of land adjustment and urban-rural cooperation. Secondly, the paper analyzes the effects and current dilemmas during the implementation of the planning of industrial land for green belts. Thirdly, results are compared with other spontaneously developed industries in the rural-urban fringe area to illustrate the changes brought about by the planning. Finally, the paper proposes three measures for future improvement, including balancing the industrial land use quotas between different townships, conducting cooperative land adjustment, and encouraging spontaneously developed industrial projects.
文摘【目的】生态网络作为整合景观斑块和廊道的有机结构,提升景观连通性是维持生态系统健康的重要途径。完善北京市朝阳区的城市生态网络,可推动生态文明战略背景下的城市绿色空间建设。【方法】以朝阳区为研究区域,选取2005、2010、2015、2020年4个时间节点,利用图论(graph theory)原理工具Graphab进行景观连通性分析,探讨生态网络的演变特征和图论在网络格局优化方面的应用。【结果】发现:2005—2020年,朝阳区绿色空间规模持续提升,斑块总数增加,但平均斑块面积缩减27.3%,网络趋于破碎化;生态网络整体水平上的景观连通性提高,连通概率指数(probability of connectivity, PC)提升35.4%;最大连通单元面积(size of the largest component, SLC)提高,平均连通单元面积(mean size of the components, MSC)下降,核心景观连通单元优势度增强,而平均景观连通单元退化,网络趋于两极化;个体水平上的景观连通性等级空间分布不均,呈现北高南低的格局。【结论】基于图论实现朝阳区生态网络的诊断和优化,识别出4个重要潜在生态斑块的位置,使PC提升11.9%。研究结果可为城市绿色空间的规划发展工作提供决策参考,体现图论在城市生态网络构建及优化中的应用价值。
