869 research outputs found
Uncovering nodes that spread information between communities in social networks
From many datasets gathered in online social networks, well defined community
structures have been observed. A large number of users participate in these
networks and the size of the resulting graphs poses computational challenges.
There is a particular demand in identifying the nodes responsible for
information flow between communities; for example, in temporal Twitter networks
edges between communities play a key role in propagating spikes of activity
when the connectivity between communities is sparse and few edges exist between
different clusters of nodes. The new algorithm proposed here is aimed at
revealing these key connections by measuring a node's vicinity to nodes of
another community. We look at the nodes which have edges in more than one
community and the locality of nodes around them which influence the information
received and broadcasted to them. The method relies on independent random walks
of a chosen fixed number of steps, originating from nodes with edges in more
than one community. For the large networks that we have in mind, existing
measures such as betweenness centrality are difficult to compute, even with
recent methods that approximate the large number of operations required. We
therefore design an algorithm that scales up to the demand of current big data
requirements and has the ability to harness parallel processing capabilities.
The new algorithm is illustrated on synthetic data, where results can be judged
carefully, and also on a real, large scale Twitter activity data, where new
insights can be gained
Infering and calibrating triadic closure in a dynamic network
In the social sciences, the hypothesis of triadic closure contends that new links in a social contact network arise preferentially between those who currently share neighbours. Here, in a proof-of-principle study, we show how to calibrate a recently proposed evolving network model to time-dependent connectivity data. The probabilistic edge birth rate in the model contains a triadic closure term, so we are also able to assess statistically the evidence for this effect. The approach is shown to work on data generated synthetically from the model. We then apply this methodology to some real, large-scale data that records the build up of connections in a business-related social networking site, and find evidence for triadic closure
Addressing the shortcomings of three recent bayesian methods for detecting interspecific recombination in DNA sequence alignments
We address a potential shortcoming of three probabilistic models for detecting interspecific recombination in DNA sequence alignments: the multiple change-point model (MCP) of Suchard et al. (2003), the dual multiple change-point model (DMCP) of Minin et al. (2005), and the phylogenetic factorial hidden Markov model (PFHMM) of Husmeier (2005). These models are based on the Bayesian paradigm, which requires the solution of an integral over the space of branch lengths. To render this integration analytically tractable, all three models make the same assumption that the vectors of branch lengths of the phylogenetic tree are independent among sites. While this approximation reduces the computational complexity considerably, we show that it leads to the systematic prediction of spurious topology changes in the Felsenstein zone, that is, the area in the branch lengths configuration space where maximum parsimony consistently infers the wrong topology due to long-branch attraction. We apply two Bayesian hypothesis tests, based on an inter- and an intra-model approach to estimating the marginal likelihood. We then propose a revised model that addresses these shortcomings, and compare it with the aforementioned models on a set of synthetic DNA sequence alignments systematically generated around the Felsenstein zone
Examining collusion and voting biases between countries during the Eurovision song contest since 1957
The Eurovision Song Contest (ESC) is an annual event which attracts millions
of viewers. It is an interesting activity to examine since the participants of
the competition represent a particular country's musical performance that will
be awarded a set of scores from other participating countries based upon a
quality assessment of a performance. There is a question of whether the
countries will vote exclusively according to the artistic merit of the song, or
if the vote will be a public signal of national support for another country.
Since the competition aims to bring people together, any consistent biases in
the awarding of scores would defeat the purpose of the celebration of
expression and this has attracted researchers to investigate the supporting
evidence for biases. This paper builds upon an approach which produces a set of
random samples from an unbiased distribution of score allocation, and extends
the methodology to use the full set of years of the competition's life span
which has seen fundamental changes to the voting schemes adopted.
By building up networks from statistically significant edge sets of vote
allocations during a set of years, the results display a plausible network for
the origins of the culture anchors for the preferences of the awarded votes.
With 60 years of data, the results support the hypothesis of regional collusion
and biases arising from proximity, culture and other irrelevant factors in
regards to the music which that alone is intended to affect the judgment of the
contest.Comment: to be published in JASS
Multimodal Literature in the Age of Covid-19
Multimodal literary works typically feature an array of verbal and non-verbal elements that operate collaboratively and, in addition to the materiality of the print book medium, create unique narrative experiences. The recent developments in relation to the Covid-19 pandemic have significantly impacted the availability of multimodal works and their access by readers and scholars. While institutions have responded to the changing environment with a surge of digital online material, experiencing multimodal literary works in digital format, when available, can compromise several facets of the reading experience. The complex physical format as well as the (occasionally) limited print run of such works makes libraries and other institutions reluctant to scan and disseminate them for public access.This article examines the contemporary challenges that multimodal print-based works are currently facing in relation to their distinctive composition and print run, suggesting that digital and audio formats can be partially effective when considered at the production stage of these literary works (rather than at earlier stages during the creative process). Moreover, the prominence of physicality in the narrative experience of multimodal literary works leads to a reconsideration of broader readerly experiences in the age of Covid-19 developments
Class, community, language and struggle: Hebrew against Yiddish in South Africa 1900-1914
Paper presented at the Wits History Workshop: The Making of Class, 9-14 February, 198
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