The flourishing complex network theory has aroused increasing interest in studying the properties of real-world networks. Based on the traffic network of Chang-Zhu Tan urban agglomeration in central China, some basic ...The flourishing complex network theory has aroused increasing interest in studying the properties of real-world networks. Based on the traffic network of Chang-Zhu Tan urban agglomeration in central China, some basic network topological characteristics were computed with data collected from local traffic maps, which showed that the traffic networks were small-world networks with strong resilience against failure; more importantly, the investigations of as- sortativity coefficient and average nearestlneighbour degree implied the disassortativity of the traffic networks. Since traffic network hierarchy as an important basic property has been neither studied intensively nor proved quantitatively, the authors are inspired to analyse traffic network hierarchy with disassortativity and to finely characterize hierarchy in the traffic networks by using the n-degree-n-clustering coefficient relationship. Through numerical results and analyses an exciting conclusion is drawn that the traffic networks exhibit a significant hierarchy, that is, the traffic networks are proved to be hierarchically organized. The result provides important information and theoretical groundwork for optimal transport planning.展开更多
Duplication and divergence have been widely recognized as the two domi- nant evolutionary forces in shaping biological networks, e.g., gene regulatory networks and protein-protein interaction （PPI） networks. It has ...Duplication and divergence have been widely recognized as the two domi- nant evolutionary forces in shaping biological networks, e.g., gene regulatory networks and protein-protein interaction （PPI） networks. It has been shown that the network growth models constructed on the principle of duplication and divergence can recapture the topo- logical properties of real PPI networks. However, such network models only consider the evolution processes. How to select the model parameters with the real biological experi- mental data has not been presented. Therefore, based on the real PPI network statistical data, a yeast PPI network model is constructed. The simulation results indicate that the topological characteristics of the constructed network model are well consistent with those of real PPI networks, especially on sparseness, scale-free, small-world, hierarchical modularity, and disassortativity.展开更多
The floral morphology, breeding system and pollinators of four natural populations of Psychotria elata (Rubiaceae), found in tropical rainforests of Costa Rica, were examined. Anisoplethy and distylous morphology were...The floral morphology, breeding system and pollinators of four natural populations of Psychotria elata (Rubiaceae), found in tropical rainforests of Costa Rica, were examined. Anisoplethy and distylous morphology were observed in all studied populations. The number of flowers per inflorescence was significantly higher in the most abundant morph (p 0.05). Reciprocal herkogamy was detected in only one of the morphs in one population. Breakdown of the heteromorphic incompatibility system was observed in the populations Tirimbina and Rara Avis. Pollen production was significantly lower in thrum morphs of Tirimbina. Seedless fruits were formed in two of the four populations. One-seeded fruits were formed in all populations and were predominant in thrum morphs of Tirimbina (9.15%) and Zurqui (75%). According to our visitation records, hummingbirds, butterflies and moths are the main pollinators of P. elata flowers.展开更多
Mixing matrices are included in infectious disease models to reflect transmission opportunities between population strata.These matrices were originally constructed on the basis of theoretical considerations and most ...Mixing matrices are included in infectious disease models to reflect transmission opportunities between population strata.These matrices were originally constructed on the basis of theoretical considerations and most of the early work in this area originates from research on sexually transferred diseases in the 80s,in response to AIDS.Later work in the 90s populated these matrices on the basis of survey data gathered to capture transmission risks for respiratory diseases.We provide an overview of developments in the construction of matrices for capturing transmission opportunities in populations.Such transmission matrices are useful for epidemiologic modelling to capture within and between stratum transmission and can be informed from theoretical mixing assumptions,informed by empirical evidence gathered through investigation as well as generated on the basis of data.Links to summary measures and threshold conditions are also provided.展开更多
The highly polymorphic genes within the major histocompatibility complex(MHC)not only play a major role in immunity resistance,but also seem to provide hints for mate choice in some animal populations.In the pres...The highly polymorphic genes within the major histocompatibility complex(MHC)not only play a major role in immunity resistance,but also seem to provide hints for mate choice in some animal populations.In the present study we investigated MHC-related mate choice in a small natural population(group size 40-55 individuals)of a polygynous primate,the Sichuan snub-nosed monkey(Rhinopithecus roxellana).We found that there was no evidence either for MHC-disassortative mating,or for females to mate with males based on MHC heterozygosity or specific alleles.Nevertheless,of the 11 alleles identified,we found that the frequencies of 2 alleles,Rhro-DRB2(P<0.01)and Rhro-DRB5(P<0.05)were higher in offspring than in their parents.These findings suggest that MHC-DRB in this population of R.roxellana is unlikely to be associated with mating preferences.Limited female opportunities for mate choice are likely due,in part,to the harem breeding structure present in R.roxellana,and the relatively small number of resident adult males in our study band(N=4-6).In addition,we suggest that differences in the frequency of particular alleles across generations may be linked to parasite resistance in a fluctuating environment;however,confirmation of this finding requires further study.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60964006)the Scientific Research Innovation Fund Project for Graduate Student of Hunan,China (Grant No.3340-74236000003)the Open Program of State Key Laboratory of Rail Traffic Control and Safety (Beijing Jiaotong University),China (Grant No.2007K-0027)
文摘The flourishing complex network theory has aroused increasing interest in studying the properties of real-world networks. Based on the traffic network of Chang-Zhu Tan urban agglomeration in central China, some basic network topological characteristics were computed with data collected from local traffic maps, which showed that the traffic networks were small-world networks with strong resilience against failure; more importantly, the investigations of as- sortativity coefficient and average nearestlneighbour degree implied the disassortativity of the traffic networks. Since traffic network hierarchy as an important basic property has been neither studied intensively nor proved quantitatively, the authors are inspired to analyse traffic network hierarchy with disassortativity and to finely characterize hierarchy in the traffic networks by using the n-degree-n-clustering coefficient relationship. Through numerical results and analyses an exciting conclusion is drawn that the traffic networks exhibit a significant hierarchy, that is, the traffic networks are proved to be hierarchically organized. The result provides important information and theoretical groundwork for optimal transport planning.
基金Project supported by the National Natural Science Foundation of China(No.11172158)
文摘Duplication and divergence have been widely recognized as the two domi- nant evolutionary forces in shaping biological networks, e.g., gene regulatory networks and protein-protein interaction （PPI） networks. It has been shown that the network growth models constructed on the principle of duplication and divergence can recapture the topo- logical properties of real PPI networks. However, such network models only consider the evolution processes. How to select the model parameters with the real biological experi- mental data has not been presented. Therefore, based on the real PPI network statistical data, a yeast PPI network model is constructed. The simulation results indicate that the topological characteristics of the constructed network model are well consistent with those of real PPI networks, especially on sparseness, scale-free, small-world, hierarchical modularity, and disassortativity.
文摘The floral morphology, breeding system and pollinators of four natural populations of Psychotria elata (Rubiaceae), found in tropical rainforests of Costa Rica, were examined. Anisoplethy and distylous morphology were observed in all studied populations. The number of flowers per inflorescence was significantly higher in the most abundant morph (p 0.05). Reciprocal herkogamy was detected in only one of the morphs in one population. Breakdown of the heteromorphic incompatibility system was observed in the populations Tirimbina and Rara Avis. Pollen production was significantly lower in thrum morphs of Tirimbina. Seedless fruits were formed in two of the four populations. One-seeded fruits were formed in all populations and were predominant in thrum morphs of Tirimbina (9.15%) and Zurqui (75%). According to our visitation records, hummingbirds, butterflies and moths are the main pollinators of P. elata flowers.
文摘Mixing matrices are included in infectious disease models to reflect transmission opportunities between population strata.These matrices were originally constructed on the basis of theoretical considerations and most of the early work in this area originates from research on sexually transferred diseases in the 80s,in response to AIDS.Later work in the 90s populated these matrices on the basis of survey data gathered to capture transmission risks for respiratory diseases.We provide an overview of developments in the construction of matrices for capturing transmission opportunities in populations.Such transmission matrices are useful for epidemiologic modelling to capture within and between stratum transmission and can be informed from theoretical mixing assumptions,informed by empirical evidence gathered through investigation as well as generated on the basis of data.Links to summary measures and threshold conditions are also provided.
基金This project was supported by the Project of Public Benefit(No.201104073)the Natural Science Foundation of China(No.30970427,31130061)the National Key Technology R&D Program of China(2013BAD03B02).
文摘The highly polymorphic genes within the major histocompatibility complex(MHC)not only play a major role in immunity resistance,but also seem to provide hints for mate choice in some animal populations.In the present study we investigated MHC-related mate choice in a small natural population(group size 40-55 individuals)of a polygynous primate,the Sichuan snub-nosed monkey(Rhinopithecus roxellana).We found that there was no evidence either for MHC-disassortative mating,or for females to mate with males based on MHC heterozygosity or specific alleles.Nevertheless,of the 11 alleles identified,we found that the frequencies of 2 alleles,Rhro-DRB2(P<0.01)and Rhro-DRB5(P<0.05)were higher in offspring than in their parents.These findings suggest that MHC-DRB in this population of R.roxellana is unlikely to be associated with mating preferences.Limited female opportunities for mate choice are likely due,in part,to the harem breeding structure present in R.roxellana,and the relatively small number of resident adult males in our study band(N=4-6).In addition,we suggest that differences in the frequency of particular alleles across generations may be linked to parasite resistance in a fluctuating environment;however,confirmation of this finding requires further study.
