1,132 research outputs found
Reaction-diffusion processes on correlated and uncorrelated scale-free networks
We compare reaction-diffusion processes of the type on scale-free
networks created with either the configuration model or the uncorrelated
configuration model. We show via simulations that except for the difference in
the behavior of the two models, different results are observed within the same
model when the minimum number of connections for a node varies from to . This difference is attributed to the varying local
properties of the two systems. In all cases we are able to identify a power law
behavior of the density decay with time with an exponent , considerably
larger than its lattice counterpart
Scale-free networks resistant to intentional attacks
We study the detailed mechanism of the failure of scale-free networks under
intentional attacks. Although it is generally accepted that such networks are
very sensitive to targeted attacks, we show that for a particular type of
structure such networks surprisingly remain very robust even under removal of a
large fraction of their nodes, which in some cases can be up to 70%. The degree
distribution of these structures is such that for small values of the
degree the distribution is constant with , up to a critical value ,
and thereafter it decays with with the usual power law. We describe in
detail a model for such a scale-free network with this modified degree
distribution, and we show both analytically and via simulations, that this
model can adequately describe all the features and breakdown characteristics of
these attacks. We have found several experimental networks with such features,
such as for example the IMDB actors collaboration network or the citations
network, whose resilience to attacks can be accurately described by our model.Comment: 5 pages, 4 figure
A Note on the Onset of Synchronous Egg Laying in a Seabird Behavior Model
Protection Island, Washington hosts a large colony of Glaucous-winged gulls (Larus glaucescens). These birds are known to exhibit every-other-day egg-laying synchrony in dense areas of the colony in response to egg cannibalism, which is the main source of egg loss. Here we present an equilibrium analysis of a discrete-time animal behavior model for egg laying. We use Jury Conditions to find the stability criteria for the equilibrium as a function of the colony density and show that a 2-cycle bifurcation occurs when the equilibrium loses stability. The 2-cycle pattern in egg laying becomes increasingly synchronous as the colony density increases. We also show that egg-laying synchrony benefits the colony by allowing more eggs to survive cannibalism
Self-organizing social hierarchies on scale-free networks
In this work we extend the model of Bonabeau et al. in the case of scale-free
networks. A sharp transition is observed from an egalitarian to an hierarchical
society, with a very low population density threshold. The exact threshold
value also depends on the network size. We find that in an hierarchical society
the number of individuals with strong winning attitude is much lower than the
number of the community members that have a low winning probability
Construction of embedded fMRI resting state functional connectivity networks using manifold learning
We construct embedded functional connectivity networks (FCN) from benchmark
resting-state functional magnetic resonance imaging (rsfMRI) data acquired from
patients with schizophrenia and healthy controls based on linear and nonlinear
manifold learning algorithms, namely, Multidimensional Scaling (MDS), Isometric
Feature Mapping (ISOMAP) and Diffusion Maps. Furthermore, based on key global
graph-theoretical properties of the embedded FCN, we compare their
classification potential using machine learning techniques. We also assess the
performance of two metrics that are widely used for the construction of FCN
from fMRI, namely the Euclidean distance and the lagged cross-correlation
metric. We show that the FCN constructed with Diffusion Maps and the lagged
cross-correlation metric outperform the other combinations
The Effect of Disease-induced Mortality on Structural Network Properties
As the understanding of the importance of social contact networks in the
spread of infectious diseases has increased, so has the interest in
understanding the feedback process of the disease altering the social network.
While many studies have explored the influence of individual epidemiological
parameters and/or underlying network topologies on the resulting disease
dynamics, we here provide a systematic overview of the interactions between
these two influences on population-level disease outcomes. We show that the
sensitivity of the population-level disease outcomes to the combination of
epidemiological parameters that describe the disease are critically dependent
on the topological structure of the population's contact network. We introduce
a new metric for assessing disease-driven structural damage to a network as a
population-level outcome. Lastly, we discuss how the expected individual-level
disease burden is influenced by the complete suite of epidemiological
characteristics for the circulating disease and the ongoing process of network
compromise. Our results have broad implications for prediction and mitigation
of outbreaks in both natural and human populations.Comment: 23 pages, 6 figure
P-08 Bifurcations in an Animal Behavior Model for Synchronous Egg Laying in a Seabird Colony
Glaucous-winged gulls (Larus glaucescens) breed on Protection Island, Washington. During years with high sea surface temperature (and hence low food resource), they exhibit egg cannibalism and every-other-day egg-laying synchrony in dense areas of the colony. Here we present a bifurcation analysis of a discrete-time model of egg-laying behavior. We use the Jury Conditions to find the stability criteria of the system as a function of the crowding factor. The equilibrium loses stability in a synchronous two-cycle bifurcation as the crowding factor increases beyond a critical value. We show that in the presence of egg cannibalism synchrony can increase population size
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