机会移动社交网络(opportunistic mobile social networks,OMSNs)是一种利用节点的相遇机会进行端到端无线数据传输的网络.随着人们使用移动智能终端数量的剧增,为建立泛在的数据传输基础设施提供了机会,因此研究机会移动社交网络的数...机会移动社交网络(opportunistic mobile social networks,OMSNs)是一种利用节点的相遇机会进行端到端无线数据传输的网络.随着人们使用移动智能终端数量的剧增,为建立泛在的数据传输基础设施提供了机会,因此研究机会移动社交网络的数据传输机制具有重要意义.为了提高机会移动社交网络的数据传输性能,提出了一种基于群组构造的数据分发机制(data dissemination mechanism based on group structure,DDMGS).首先,基于用户的行为属性,即节点重要性、兴趣相似度和通信关系紧密度,设计关系度量模型.其次,依据不同的行为属性关系构成的网络拓扑特征设计群组构造算法:基于位置关系的拓扑结构具有周期稳定性,基于兴趣关系的拓扑结构具有长期稳定性,而基于通信关系的拓扑结构具有动态性.为进一步提高数据分发性能和网络的整体性能,还设计了节点缓冲区管理机制,引入了合作博弈理论加强节点之间的合作能力,规避节点的自私行为.仿真验证表明DDMGS与直接投递路由、先知路由以及Simbet路由和Epidemic路由相比具有较好的性能,提高了消息传输成功率,减少了平均跳数,该算法是可行的.展开更多
AIM: To studythe role of intestinal flora in inflammatory bowel disease (IBD).METHODS: The spatial organization of intestinal flora was investigated in normal mice and in two models of murine colitis using fluorescenc...AIM: To studythe role of intestinal flora in inflammatory bowel disease (IBD).METHODS: The spatial organization of intestinal flora was investigated in normal mice and in two models of murine colitis using fluorescence in situ hybridization.RESULTS: The murine small intestine was nearly bacteriafree. The normal colonic flora was organized in three distinct compartments (crypt, interlaced, and fecal), each with different bacterial compositions. Crypt bacteria were present in the cecum and proximal colon. The fecal compartment was composed of homogeneously mixed bacterial groups that directly contacted the colonic wall in the cecum but were separated from the proximal colonic wall by a dense interlaced layer. Beginning in the middle colon, a mucus gap of growing thickness physically separated all intestinal bacteria from contact with the epithelium. Colonic inflammation was accompanied with a depletion of bacteria within the fecal compartment, a reduced surface area in which feces had direct contact with the colonic wall, increased thickness and spread of the mucus gap, and massive increases of bacterial concentrations in the crypt and interlaced compartments. Adhesive and infiltrative bacteria were observed in inflamed colon only, with dominant Bacteroides species.CONCLUSION: The proximal and distal colons are functionally different organs with respect to the intestinal flora, representing a bioreactor and a Segregation device.The highly organized structure of the colonic flora, its specific arrangement in different colonic segments, and its specialized response to inflammatory stimuli indicate that the intestinal flora is an innate part of host immunity that is under complex control.展开更多
In this paper, we present a method for constructing a Dulac function for mathematical models in population biology, in the form of systems of ordinary differential equations in the plane.
文摘机会移动社交网络(opportunistic mobile social networks,OMSNs)是一种利用节点的相遇机会进行端到端无线数据传输的网络.随着人们使用移动智能终端数量的剧增,为建立泛在的数据传输基础设施提供了机会,因此研究机会移动社交网络的数据传输机制具有重要意义.为了提高机会移动社交网络的数据传输性能,提出了一种基于群组构造的数据分发机制(data dissemination mechanism based on group structure,DDMGS).首先,基于用户的行为属性,即节点重要性、兴趣相似度和通信关系紧密度,设计关系度量模型.其次,依据不同的行为属性关系构成的网络拓扑特征设计群组构造算法:基于位置关系的拓扑结构具有周期稳定性,基于兴趣关系的拓扑结构具有长期稳定性,而基于通信关系的拓扑结构具有动态性.为进一步提高数据分发性能和网络的整体性能,还设计了节点缓冲区管理机制,引入了合作博弈理论加强节点之间的合作能力,规避节点的自私行为.仿真验证表明DDMGS与直接投递路由、先知路由以及Simbet路由和Epidemic路由相比具有较好的性能,提高了消息传输成功率,减少了平均跳数,该算法是可行的.
基金Supported by Broad Medical Research Program of the Eli and Edy the L. Broad foundation
文摘AIM: To studythe role of intestinal flora in inflammatory bowel disease (IBD).METHODS: The spatial organization of intestinal flora was investigated in normal mice and in two models of murine colitis using fluorescence in situ hybridization.RESULTS: The murine small intestine was nearly bacteriafree. The normal colonic flora was organized in three distinct compartments (crypt, interlaced, and fecal), each with different bacterial compositions. Crypt bacteria were present in the cecum and proximal colon. The fecal compartment was composed of homogeneously mixed bacterial groups that directly contacted the colonic wall in the cecum but were separated from the proximal colonic wall by a dense interlaced layer. Beginning in the middle colon, a mucus gap of growing thickness physically separated all intestinal bacteria from contact with the epithelium. Colonic inflammation was accompanied with a depletion of bacteria within the fecal compartment, a reduced surface area in which feces had direct contact with the colonic wall, increased thickness and spread of the mucus gap, and massive increases of bacterial concentrations in the crypt and interlaced compartments. Adhesive and infiltrative bacteria were observed in inflamed colon only, with dominant Bacteroides species.CONCLUSION: The proximal and distal colons are functionally different organs with respect to the intestinal flora, representing a bioreactor and a Segregation device.The highly organized structure of the colonic flora, its specific arrangement in different colonic segments, and its specialized response to inflammatory stimuli indicate that the intestinal flora is an innate part of host immunity that is under complex control.
文摘In this paper, we present a method for constructing a Dulac function for mathematical models in population biology, in the form of systems of ordinary differential equations in the plane.
