476,263 research outputs found
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
Deciphering Network Community Structure by Surprise
The analysis of complex networks permeates all sciences, from biology to
sociology. A fundamental, unsolved problem is how to characterize the community
structure of a network. Here, using both standard and novel benchmarks, we show
that maximization of a simple global parameter, which we call Surprise (S),
leads to a very efficient characterization of the community structure of
complex synthetic networks. Particularly, S qualitatively outperforms the most
commonly used criterion to define communities, Newman and Girvan's modularity
(Q). Applying S maximization to real networks often provides natural,
well-supported partitions, but also sometimes counterintuitive solutions that
expose the limitations of our previous knowledge. These results indicate that
it is possible to define an effective global criterion for community structure
and open new routes for the understanding of complex networks.Comment: 7 pages, 5 figure
Characterizing the dynamical importance of network nodes and links
The largest eigenvalue of the adjacency matrix of the networks is a key
quantity determining several important dynamical processes on complex networks.
Based on this fact, we present a quantitative, objective characterization of
the dynamical importance of network nodes and links in terms of their effect on
the largest eigenvalue. We show how our characterization of the dynamical
importance of nodes can be affected by degree-degree correlations and network
community structure. We discuss how our characterization can be used to
optimize techniques for controlling certain network dynamical processes and
apply our results to real networks.Comment: 4 pages, 4 figure
Diverse reductive dehalogenases are associated with Clostridiales-enriched microcosms dechlorinating 1,2-dichloroethane
The achievement of successful biostimulation of active microbiomes for the cleanup of a polluted site is strictly dependent on the knowledge of the key microorganisms equipped with the relevant catabolic genes responsible for the degradation process. In this work, we present the characterization of the bacterial community developed in anaerobic microcosms after biostimulation with the electron donor lactate of groundwater polluted with 1,2-dichloroethane (1,2-DCA). Through a multilevel analysis, we have assessed (i) the structural analysis of the bacterial community; (ii) the identification of putative dehalorespiring bacteria; (iii) the characterization of functional genes encoding for putative 1,2-DCA reductive dehalogenases (RDs). Following the biostimulation treatment, the structure of the bacterial community underwent a notable change of the main phylotypes, with the enrichment of representatives of the order Clostridiales. Through PCR targeting conserved regions within known RD genes, four novel variants of RDs previously associated with the reductive dechlorination of 1,2-DCA were identified in the metagenome of the Clostridiales-dominated bacterial community
Hierarchical mutual information for the comparison of hierarchical community structures in complex networks
The quest for a quantitative characterization of community and modular
structure of complex networks produced a variety of methods and algorithms to
classify different networks. However, it is not clear if such methods provide
consistent, robust and meaningful results when considering hierarchies as a
whole. Part of the problem is the lack of a similarity measure for the
comparison of hierarchical community structures. In this work we give a
contribution by introducing the {\it hierarchical mutual information}, which is
a generalization of the traditional mutual information, and allows to compare
hierarchical partitions and hierarchical community structures. The {\it
normalized} version of the hierarchical mutual information should behave
analogously to the traditional normalized mutual information. Here, the correct
behavior of the hierarchical mutual information is corroborated on an extensive
battery of numerical experiments. The experiments are performed on artificial
hierarchies, and on the hierarchical community structure of artificial and
empirical networks. Furthermore, the experiments illustrate some of the
practical applications of the hierarchical mutual information. Namely, the
comparison of different community detection methods, and the study of the
consistency, robustness and temporal evolution of the hierarchical modular
structure of networks.Comment: 14 pages and 12 figure
Accuracy and Precision of Methods for Community Identification in Weighted Networks
Based on brief review of approaches for community identification and
measurement for sensitivity characterization, the accuracy and precision of
several approaches for detecting communities in weighted networks are
investigated. In weighted networks, the community structure should take both
links and link weights into account and the partition of networks should be
evaluated by weighted modularity . The results reveal that link weight has
important effects on communities especially in dense networks. Potts model and
Weighted Extremal Optimization (WEO) algorithm work well on weighted networks.
Then Potts model and WEO algorithms are used to detect communities in Rhesus
monkey network. The results gives nice understanding for real community
structure.Comment: 14 pages, 15 figure
Closed benchmarks for network community structure characterization
Characterizing the community structure of complex networks is a key challenge
in many scientific fields. Very diverse algorithms and methods have been
proposed to this end, many working reasonably well in specific situations.
However, no consensus has emerged on which of these methods is the best to use
in practice. In part, this is due to the fact that testing their performance
requires the generation of a comprehensive, standard set of synthetic
benchmarks, a goal not yet fully achieved. Here, we present a type of benchmark
that we call "closed", in which an initial network of known community structure
is progressively converted into a second network whose communities are also
known. This approach differs from all previously published ones, in which
networks evolve toward randomness. The use of this type of benchmark allows us
to monitor the transformation of the community structure of a network.
Moreover, we can predict the optimal behavior of the variation of information,
a measure of the quality of the partitions obtained, at any moment of the
process. This enables us in many cases to determine the best partition among
those suggested by different algorithms. Also, since any network can be used as
a starting point, extensive studies and comparisons can be performed using a
heterogeneous set of structures, including random ones. These properties make
our benchmarks a general standard for comparing community detection algorithms.Comment: 18 pages, 5 figures. Available at
http://pre.aps.org/abstract/PRE/v85/i2/e02610
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