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Information spreading with aging in heterogeneous populations  [PDF]
Marlon Ramos,Nuno Crokidakis,Celia Anteneodo
Computer Science , 2012,
Abstract: We study the critical properties of a model of information spreading based on the SIS epidemic model. Spreading rates decay with time, as ruled by two parameters, $\epsilon$ and $l$, that can be either constant or randomly distributed in the population. The spreading dynamics is developed on top of Erd\"os-Renyi networks. We present the mean-field analytical solution of the model in its simplest formulation, and Monte Carlo simulations are performed for the more heterogeneous cases. The outcomes show that the system undergoes a nonequilibrium phase transition whose critical point depends on the parameters $\epsilon$ and $l$. In addition, we conclude that the more heterogeneous the population, the more favored the information spreading over the network.
Spreading of infectious diseases on heterogeneous populations: multi-type network approach  [PDF]
Alexei Vazquez
Physics , 2006, DOI: 10.1103/PhysRevE.74.066114
Abstract: I study the spreading of infectious diseases on heterogeneous populations. I represent the population structure by a contact-graph where vertices represent agents and edges represent disease transmission channels among them. The population heterogeneity is taken into account by the agent's subdivision in types and the mixing matrix among them. I introduce a type-network representation for the mixing matrix allowing an intuitive understanding of the mixing patterns and the analytical calculations. Using an iterative approach I obtain recursive equations for the probability distribution of the outbreak size as a function of time. I demonstrate that the expected outbreak size and its progression in time are determined by the largest eigenvalue of the reproductive number matrix and the characteristic distance between agents on the contact-graph. Finally, I discuss the impact of intervention strategies to halt epidemic outbreaks. This work provides both a qualitative understanding and tools to obtain quantitative predictions for the spreading dynamics on heterogeneous populations.
Spreading of sexually transmitted diseases in heterosexual populations  [PDF]
J. Gomez-Gardenes,V. Latora,Y. Moreno,E. V. Profumo
Physics , 2007, DOI: 10.1073/pnas.0707332105
Abstract: The spread of sexually transmitted diseases (e.g. Chlamydia, Syphilis, Gonorrhea, HIV) across populations is a major concern for scientists and health agencies. In this context, both data collection on sexual contact networks and the modeling of disease spreading, are intensively contributing to the search for effective immunization policies. Here, the spreading of sexually transmitted diseases on bipartite scale-free graphs, representing heterosexual contact networks, is considered. We analytically derive the expression for the epidemic threshold and its dependence with the system size in finite populations. We show that the epidemic outbreak in bipartite populations, with number of sexual partners distributed as in empirical observations from national sex surveys, takes place for larger spreading rates than for the case in which the bipartite nature of the network is not taken into account. Numerical simulations confirm the validity of the theoretical results. Our findings indicate that the restriction to crossed infections between the two classes of individuals (males and females) has to be taken into account in the design of efficient immunization strategies for sexually transmitted diseases.
Droplet spreading and pinning on heterogeneous substrates  [PDF]
Mikko J. Alava,Martin Dube
Physics , 2012, DOI: 10.1103/PhysRevE.86.011607
Abstract: The contact angle of a fluid droplet on an heterogeneous surface is analysed using the statistical dynamics of the spreading contact line. The statistical properties of the final droplet radius and contact angle are obtained through applications of depinning transitions of contact lines with non-local elasticity and features of pinning-depinning dynamics. Such properties not only depend on disorder strength and surface details, but also on the droplet volume and disorder correlation length. Deviations from Wenzel or Cassie/Baxter behaviour are particularly apparent in the case of small droplet volumes and small contact angles.
Evolutionary Dynamics for Persistent Cooperation in Structured Populations  [PDF]
Yan Li,Xinsheng Liu,Jens Christian Claussen,Wanlin Guo
Quantitative Biology , 2015,
Abstract: The emergence and maintenance of cooperative behavior is a fascinating topic in evolutionary biology and social science. The public goods game (PGG) is a paradigm for exploring cooperative behavior. In PGG, the total resulting payoff is divided equally among all participants. This feature still leads to the dominance of defection without substantially magnifying the public good by a multiplying factor. Much effort has been made to explain the evolution of cooperative strategies, including a recent model in which only a portion of the total benefit is shared by all the players through introducing a new strategy named persistent cooperation. A persistent cooperator is a contributor who is willing to pay a second cost to retrieve the remaining portion of the payoff contributed by themselves. In a previous study, this model was analyzed in the framework of well-mixed populations. This paper focuses on discussing the persistent cooperation in lattice-structured populations. The evolutionary dynamics of the structured populations consisting of three types of competing players (pure cooperators, defectors and persistent cooperators) are revealed by theoretical analysis and numerical simulations. In particular, the approximate expressions of fixation probabilities for strategies are derived on one-dimensional lattices. The phase diagrams of stationary states, the evolution of frequencies and spatial patterns for strategies are illustrated on both one-dimensional and square lattices by simulations. Our results are consistent with the general observation that, at least in most situations, a structured population facilitates the evolution of cooperation. Specifically, here we find that the existence of persistent cooperators greatly suppresses the spreading of defectors under more relaxed conditions in structured populations compared to that obtained in well-mixed population.
Impact of Heterogeneous Human Activities on Epidemic Spreading  [PDF]
Zimo Yang,Ai-Xiang Cui,Tao Zhou
Computer Science , 2011, DOI: 10.1016/j.physa.2011.06.068
Abstract: Recent empirical observations suggest a heterogeneous nature of human activities. The heavy-tailed inter-event time distribution at population level is well accepted, while whether the individual acts in a heterogeneous way is still under debate. Motivated by the impact of temporal heterogeneity of human activities on epidemic spreading, this paper studies the susceptible-infected model on a fully mixed population, where each individual acts in a completely homogeneous way but different individuals have different mean activities. Extensive simulations show that the heterogeneity of activities at population level remarkably affects the speed of spreading, even though each individual behaves regularly. Further more, the spreading speed of this model is more sensitive to the change of system heterogeneity compared with the model consisted of individuals acting with heavy-tailed inter-event time distribution. This work refines our understanding of the impact of heterogeneous human activities on epidemic spreading.
Range Expansion of Heterogeneous Populations  [PDF]
Matthias Reiter,Steffen Rulands,Erwin Frey
Quantitative Biology , 2014, DOI: 10.1103/PhysRevLett.112.148103
Abstract: Risk spreading in bacterial populations is generally regarded as a strategy to maximize survival. Here, we study its role during range expansion of a genetically diverse population where growth and motility are two alternative traits. We find that during the initial expansion phase fast growing cells do have a selective advantage. By contrast, asymptotically, generalists balancing motility and reproduction are evolutionarily most successful. These findings are rationalized by a set of coupled Fisher equations complemented by stochastic simulations.
Dynamic spreading behavior of homogeneous and heterogeneous networks
XIA Chengyi,LIU Zhongxin,CHEN Zengqiang,YUAN Zhuzhi,
XIA Chengyi
,LIU Zhongxin,CHEN Zengqiang,YUAN Zhuzhi

自然科学进展 , 2007,
Abstract: The detailed investigation of the dynamic epidemic spreading on homogeneous and heterogeneous networks was carried out. After the analysis of the basic epidemic models, the susceptible-infected-susceptible (SIS) model on homogenous and heterogeneous networks is established, and the dynamical evolution of the density of the infected individuals in these two different kinds of networks is analyzed theoretically. It indicates that heterogeneous networks are easier to propagate for the epidemics and the leading spreading behavior is dictated by the exponential increasing in the initial outbreaks. Large-scale simulations display that the infection is much faster on heterogeneous networks than that on homogeneous ones. It means that the network topology can have a significant effect on the epidemics taking place on complex networks. Some containment strategies of epidemic outbreaks are presented according to the theoretical analyses and numerical simulations.
Lymphocytes’ population profile of women with infringement of reproductive function and persistent infections
Nagima Mamedaliyeva,Almagul Kurmanova,Ludmila Dzoz
Medical and Health Science Journal , 2012,
Abstract: 164 women with inflammatory diseases of genitals were observed to study lymphocytes’ sub/population profile in peripheral blood in the background of persistent viral and bacterial infections depending on reproductive function condition. In patients with non-infringement reproductive function there were not expressed changes of lymphocytes’ population profile and activity CD25 lymphocytes increase was marked. In the women with pregnancy losses in anamnesis with a various degree of infringement the picture of differently directed changes of lymphocytes’ populations profile was observed. Infertile women had expressed depression of T-cellular link with decrease in the general maintenance of both T-cells and T-helpers; as well as increase of active lymphocytes with expressed apoptosis.
Monolayer Spreading on a Chemically Heterogeneous Substrate  [PDF]
N. Pesheva,G. Oshanin
Physics , 2002,
Abstract: We study the spreading kinetics of a monolayer of hard-core particles on a semi-infinite, chemically heterogeneous solid substrate, one side of which is coupled to a particle reservoir. The substrate is modeled as a square lattice containing two types of sites -- ordinary ones and special, chemically active sites placed at random positions with mean concentration $\alpha$. These special sites temporarily immobilize particles of the monolayer which then serve as impenetrable obstacles for the other particles. In terms of a mean-field-type theory, we show that the mean displacement $X_0(t)$ of the monolayer edge grows with time $t$ as $X_0(t) = \sqrt{2 D_{\alpha} t \ln(4 D_{\alpha} t/\pi a^2)}$, ($a$ being the lattice spacing). This time dependence is confirmed by numerical simulations; $D_{\alpha}$ is obtained numerically for a wide range of values of the parameter $\alpha$ and trapping times of the chemically active sites. We also study numerically the behavior of a stationary particle current in finite samples. The question of the influence of attractive particle-particle interactions on the spreading kinetics is also addressed.
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