606 research outputs found
Community Structure in Time-Dependent, Multiscale, and Multiplex Networks
Network science is an interdisciplinary endeavor, with methods and
applications drawn from across the natural, social, and information sciences. A
prominent problem in network science is the algorithmic detection of
tightly-connected groups of nodes known as communities. We developed a
generalized framework of network quality functions that allowed us to study the
community structure of arbitrary multislice networks, which are combinations of
individual networks coupled through links that connect each node in one network
slice to itself in other slices. This framework allows one to study community
structure in a very general setting encompassing networks that evolve over
time, have multiple types of links (multiplexity), and have multiple scales.Comment: 31 pages, 3 figures, 1 table. Includes main text and supporting
material. This is the accepted version of the manuscript (the definitive
version appeared in Science), with typographical corrections included her
External Periodic Driving of Large Systems of Globally Coupled Phase Oscillators
Large systems of coupled oscillators subjected to a periodic external drive
occur in many situations in physics and biology. Here the simple, paradigmatic
case of equal-strength, all-to-all sine-coupling of phase oscillators subject
to a sinusoidal external drive is considered. The stationary states and their
stability are determined. Using the stability information and numerical
experiments, parameter space phase diagrams showing when different types of
system behavior apply are constructed, and the bifurcations marking transitions
between different types of behavior are delineated. The analysis is supported
by results of direct numerical simulation of an ensemble of oscillators
Restorative and conflict resolution interventions
20 pagesConflicts between peers are inevitable in schools, and schools must be equipped with strategies
to assist students in avoiding conflicts and engaging in problem-solving when conflicts occur.
Restorative practices and other conflict resolution interventions such as peer mediation are
gaining popularity, particularly as an alternate framework to the overutilization of disciplinary
punishment with ethnic minority students. This chapter discusses the effective use of restorative
practices and conflict resolution interventions, with an emphasis on establishing these types of
practices in schools using best practices.Preparation of this chapter was supported by the Institute of
Education Sciences, U.S. Department of Education, through Grant R305A180006 to University
of Oregon
Interplay between HIV/AIDS Epidemics and Demographic Structures Based on Sexual Contact Networks
In this article, we propose a network spread model for HIV epidemics, wherein
each individual is represented by a node of the transmission network and the
edges are the connections between individuals along which the infection may
spread. The sexual activity of each individual, measured by its degree, is not
homogeneous but obeys a power-law distribution. Due to the heterogeneity of
activity, the infection can persistently exist at a very low prevalence, which
has been observed in real data but can not be illuminated by previous models
with homogeneous mixing hypothesis. Furthermore, the model displays a clear
picture of hierarchical spread: In the early stage the infection is adhered to
these high-risk persons, and then, diffuses toward low-risk population. The
prediction results show that the development of epidemics can be roughly
categorized into three patterns for different countries, and the pattern of a
given country is mainly determined by the average sex-activity and transmission
probability per sexual partner. In most cases, the effect of HIV epidemics on
demographic structure is very small. However, for some extremely countries,
like Botswana, the number of sex-active people can be depressed to nearly a
half by AIDS.Comment: 23 pages, 12 figure
Community Structure Characterization
This entry discusses the problem of describing some communities identified in
a complex network of interest, in a way allowing to interpret them. We suppose
the community structure has already been detected through one of the many
methods proposed in the literature. The question is then to know how to extract
valuable information from this first result, in order to allow human
interpretation. This requires subsequent processing, which we describe in the
rest of this entry
On metastable configurations of small-world networks
We calculate the number of metastable configurations of Ising small-world
networks which are constructed upon superimposing sparse Poisson random graphs
onto a one-dimensional chain. Our solution is based on replicated
transfer-matrix techniques. We examine the denegeracy of the ground state and
we find a jump in the entropy of metastable configurations exactly at the
crossover between the small-world and the Poisson random graph structures. We
also examine the difference in entropy between metastable and all possible
configurations, for both ferromagnetic and bond-disordered long-range
couplings.Comment: 9 pages, 4 eps figure
Hierarchical information clustering by means of topologically embedded graphs
We introduce a graph-theoretic approach to extract clusters and hierarchies
in complex data-sets in an unsupervised and deterministic manner, without the
use of any prior information. This is achieved by building topologically
embedded networks containing the subset of most significant links and analyzing
the network structure. For a planar embedding, this method provides both the
intra-cluster hierarchy, which describes the way clusters are composed, and the
inter-cluster hierarchy which describes how clusters gather together. We
discuss performance, robustness and reliability of this method by first
investigating several artificial data-sets, finding that it can outperform
significantly other established approaches. Then we show that our method can
successfully differentiate meaningful clusters and hierarchies in a variety of
real data-sets. In particular, we find that the application to gene expression
patterns of lymphoma samples uncovers biologically significant groups of genes
which play key-roles in diagnosis, prognosis and treatment of some of the most
relevant human lymphoid malignancies.Comment: 33 Pages, 18 Figures, 5 Table
Community structure and ethnic preferences in school friendship networks
Recently developed concepts and techniques of analyzing complex systems
provide new insight into the structure of social networks. Uncovering recurrent
preferences and organizational principles in such networks is a key issue to
characterize them. We investigate school friendship networks from the Add
Health database. Applying threshold analysis, we find that the friendship
networks do not form a single connected component through mutual strong
nominations within a school, while under weaker conditions such
interconnectedness is present. We extract the networks of overlapping
communities at the schools (c-networks) and find that they are scale free and
disassortative in contrast to the direct friendship networks, which have an
exponential degree distribution and are assortative. Based on the network
analysis we study the ethnic preferences in friendship selection. The clique
percolation method we use reveals that when in minority, the students tend to
build more densely interconnected groups of friends. We also find an asymmetry
in the behavior of black minorities in a white majority as compared to that of
white minorities in a black majority.Comment: submitted to Physica
Uncovering the overlapping community structure of complex networks in nature and society
Many complex systems in nature and society can be described in terms of
networks capturing the intricate web of connections among the units they are
made of. A key question is how to interpret the global organization of such
networks as the coexistence of their structural subunits (communities)
associated with more highly interconnected parts. Identifying these a priori
unknown building blocks (such as functionally related proteins, industrial
sectors and groups of people) is crucial to the understanding of the structural
and functional properties of networks. The existing deterministic methods used
for large networks find separated communities, whereas most of the actual
networks are made of highly overlapping cohesive groups of nodes. Here we
introduce an approach to analysing the main statistical features of the
interwoven sets of overlapping communities that makes a step towards uncovering
the modular structure of complex systems. After defining a set of new
characteristic quantities for the statistics of communities, we apply an
efficient technique for exploring overlapping communities on a large scale. We
find that overlaps are significant, and the distributions we introduce reveal
universal features of networks. Our studies of collaboration, word-association
and protein interaction graphs show that the web of communities has non-trivial
correlations and specific scaling properties.Comment: The free academic research software, CFinder, used for the
publication is available at the website of the publication:
http://angel.elte.hu/clusterin
A shadowing problem in the detection of overlapping communities: lifting the resolution limit through a cascading procedure
Community detection is the process of assigning nodes and links in
significant communities (e.g. clusters, function modules) and its development
has led to a better understanding of complex networks. When applied to sizable
networks, we argue that most detection algorithms correctly identify prominent
communities, but fail to do so across multiple scales. As a result, a
significant fraction of the network is left uncharted. We show that this
problem stems from larger or denser communities overshadowing smaller or
sparser ones, and that this effect accounts for most of the undetected
communities and unassigned links. We propose a generic cascading approach to
community detection that circumvents the problem. Using real and artificial
network datasets with three widely used community detection algorithms, we show
how a simple cascading procedure allows for the detection of the missing
communities. This work highlights a new detection limit of community structure,
and we hope that our approach can inspire better community detection
algorithms.Comment: 14 pages, 12 figures + supporting information (5 pages, 6 tables, 3
figures
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