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Barry Wellman
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Faculty of Information (iSchool)
University of Toronto Toronto Canada M5S 3G6
http://www.chass.utoronto.ca/~wellman twitter: @barrywellman
NSA/CSEC: Canadian and American citizen
NETWORKED:The New Social Operating System. Lee Rainie & Barry Wellman
MIT Press http://amzn.to/zXZg39 Print $14 Kindle $16
Old/NewCyberTimes http://bit.ly/c8N9V8
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Date: Mon, 14 Jul 2014 13:15:26 -0500
From: Complexity Digest Administration <[log in to unmask]>
To: [log in to unmask]
Subject: [comdig] Latest Complexity Digest Posts
Connecting Core Percolation and Controllability of Complex Networks
Core percolation is a fundamental structural transition in complex networks related to a wide range of important problems. Recent advances have provided us an analytical framework of core percolation in uncorrelated random networks with arbitrary degree distributions. Here we apply the tools in analysis of network controllability. We confirm analytically that the emergence of the bifurcation in control coincides with the formation of the core and the structure of the core determines the control mode of the network. We also derive the analytical expression related to the controllability robustness by extending the deduction in core percolation. These findings help us better understand the interesting interplay between the structural and dynamical properties of complex networks.
Connecting Core Percolation and Controllability of Complex Networks
˙˙ Tao Jia & Mįrton Pósfai
Scientific Reports 4, Article number: 5379 http://dx.doi.org/10.1038/srep05379
See it on Scoop.it (http://www.scoop.it/t/papers/p/4024479340/2014/07/12/connecting-core-percolation-and-controllability-of-complex-networks) , via Papers (http://www.scoop.it/t/papers)
Coding Together at Scale: GitHub as a Collaborative Social Network
GitHub is the most popular repository for open source code. It has more than 3.5 million users, as the company declared in April 2013, and more than 10 million repositories, as of December 2013. It has a publicly accessible API and, since March 2012, it also publishes a stream of all the events occurring on public projects. Interactions among GitHub users are of a complex nature and take place in different forms. Developers create and fork repositories, push code, approve code pushed by others, bookmark their favorite projects and follow other developers to keep track of their activities.
In this paper we present a characterization of GitHub, as both a social network and a collaborative platform. To the best of our knowledge, this is the first quantitative study about the interactions happening on GitHub. We analyze the logs from the service over 18 months (between March 11, 2012 and September 11, 2013), describing 183.54 million events and we obtain information about 2.19 million users and 5.68 million repositories, both growing linearly in time. We show that the distributions of the number of contributors per project, watchers per project and followers per user show a power-law-like shape. We analyze social ties and repository-mediated collaboration patterns, and we observe a remarkably low level of reciprocity of the social connections. We also measure the activity of each user in terms of authored events and we observe that very active users do not necessarily have a large number of followers. Finally, we provide a geographic characterization of the
centers of activity and we investigate how distance influences collaboration.
Coding Together at Scale: GitHub as a Collaborative Social Network
Antonio Lima, Luca Rossi, Mirco Musolesi
http://arxiv.org/abs/1407.2535
See it on Scoop.it (http://www.scoop.it/t/papers/p/4024479296/2014/07/11/coding-together-at-scale-github-as-a-collaborative-social-network) , via Papers (http://www.scoop.it/t/papers)
On the Use of Human Mobility Proxies for Modeling Epidemics
The spatial dissemination of a directly transmitted infectious disease in a population is driven by population movements from one region to another allowing mixing and importation. Public health policy and planning may thus be more accurate if reliable descriptions of population movements can be considered in the epidemic evaluations. Next to census data, generally available in developed countries, alternative solutions can be found to describe population movements where official data is missing. These include mobility models, such as the radiation model, and the analysis of mobile phone activity records providing individual geo-temporal information. Here we explore to what extent mobility proxies, such as mobile phone data or mobility models, can effectively be used in epidemic models for influenza-like-illnesses and how they compare to official census data. By focusing on three European countries, we find that phone data matches the commuting patterns reported by census
well but tends to overestimate the number of commuters, leading to a faster diffusion of simulated epidemics. The order of infection of newly infected locations is however well preserved, whereas the pattern of epidemic invasion is captured with higher accuracy by the radiation model for centrally seeded epidemics and by phone proxy for peripherally seeded epidemics.
Tizzoni M, Bajardi P, Decuyper A, Kon Kam King G, Schneider CM, et al. (2014) On the Use of Human Mobility Proxies for Modeling Epidemics. PLoS Comput Biol 10(7): e1003716. http://dx.doi.org/10.1371/journal.pcbi.1003716
See it on Scoop.it (http://www.scoop.it/t/papers/p/4024479247/2014/07/11/on-the-use-of-human-mobility-proxies-for-modeling-epidemics) , via Papers (http://www.scoop.it/t/papers)
Patterns of collaboration in four scientific disciplines of the Turkish collaboration network
* We constructed a nationwide scientific collaboration network in four scientific subdisciplines.
* By the years pass, all the subsets display the tendency of co-authoring with more authors per paper.
* The perfect power-law consistence of the interdisciplinary network in degree distribution is best copied by the mathematics subset.
* The surgery subset tends to deviate from the exponential growth rate, while others are in good consistency with exponential fits.
* The Matthew Effect is observed in career longevity distributions.
Patterns of collaboration in four scientific disciplines of the Turkish collaboration network
Abdullah Ēavu˙˙o˙˙lu, ˙˙lker Türker
Physica A
http://dx.doi.org/10.1016/j.physa.2014.06.069
See it on Scoop.it (http://www.scoop.it/t/papers/p/4024354004/2014/07/09/patterns-of-collaboration-in-four-scientific-disciplines-of-the-turkish-collaboration-network) , via Papers (http://www.scoop.it/t/papers)
Collective motion in a minimal continuous model
The cohesive motion of autonomous agents is ubiquitous in natural, social and technological settings. Its current models are often discretized in time and include one or more of the following components: explicit velocity alignment (also called neighbor following), attraction/adhesion, inelastic collisions and friction. However, real moving agents (animals, humans, robots, etc.) are usually asynchronous and perceive the coordinates of others with higher precision than their velocities. Therefore, here we work with a minimal model that applies none of the listed components and is continuous in both time and space. The model contains (i) radial repulsion among the particles, (ii) self-propelling parallel to each particle's velocity and (iii) noise. First, we show that in this model two particles colliding symmetrically in 2 dimensions at a large angle leave at a smaller angle, i.e., their total momentum grows. For many particles we find that such local gains of momentum can
lead to stable global ordering. As a function of noise amplitudes we observe a critical slowing down at the order-disorder boundary, indicating a dynamical phase transition. Our current numerical results -- limited by the system's slowing down -- show that the transition is discontinuous.
Collective motion in a minimal continuous model
Illes J. Farkas, Jeromos Kun, Yi Jin, Gaoqi He, Mingliang Xu
http://arxiv.org/abs/1406.7679
See it on Scoop.it (http://www.scoop.it/t/papers/p/4024092035/2014/07/08/collective-motion-in-a-minimal-continuous-model) , via Papers (http://www.scoop.it/t/papers)
Co-Following on Twitter
We present an in-depth study of co-following on Twitter based on the observation that two Twitter users whose followers have similar friends are also similar, even though they might not share any direct links or a single mutual follower. We show how this observation contributes to (i) a better understanding of language-agnostic user classification on Twitter, (ii) eliciting opportunities for Computational Social Science, and (iii) improving online marketing by identifying cross-selling opportunities.
Co-Following on Twitter
Venkata Rama Kiran Garimella, Ingmar Weber
http://arxiv.org/abs/1407.0791
See it on Scoop.it (http://www.scoop.it/t/papers/p/4024092043/2014/07/08/co-following-on-twitter) , via Papers (http://www.scoop.it/t/papers)
Toward Analytical Chaos in Nonlinear Systems (by Albert C. J. Luo)
Exact analytical solutions to periodic motions in nonlinear dynamical systems are almost not possible. Since the 18th century, one has extensively used techniques such as perturbation methods to obtain approximate analytical solutions of periodic motions in nonlinear systems. However, the perturbation methods cannot provide the enough accuracy of analytical solutions of periodic motions in nonlinear dynamical systems. So the bifurcation trees of periodic motions to chaos cannot be achieved analytically. The author has developed an analytical technique that is more effective to achieve periodic motions and corresponding bifurcation trees to chaos analytically.
Toward Analytical Chaos in Nonlinear Systems systematically presents a new approach to analytically determine periodic flows to chaos or quasi-periodic flows in nonlinear dynamical systems with/without time-delay. It covers the mathematical theory and includes two examples of nonlinear systems with/without time-delay in engineering and physics. From the analytical solutions, the routes from periodic motions to chaos are developed analytically rather than the incomplete numerical routes to chaos. The analytical techniques presented will provide a better understanding of regularity and complexity of periodic motions and chaos in nonlinear dynamical systems.
See it on Scoop.it (http://www.scoop.it/t/cxbooks/p/4023556379/2014/07/07/toward-analytical-chaos-in-nonlinear-systems-by-albert-c-j-luo) , via CxBooks (http://www.scoop.it/t/cxbooks)
Quantum Field Theory for the Gifted Amateur (by Tom Lancaster & Stephen J. Blundell)
Quantum field theory is arguably the most far-reaching and beautiful physical theory ever constructed, with aspects more stringently tested and verified to greater precision than any other theory in physics. Unfortunately, the subject has gained a notorious reputation for difficulty, with forbidding looking mathematics and a peculiar diagrammatic language described in an array of unforgiving, weighty textbooks aimed firmly at aspiring professionals. However, quantum field theory is too important, too beautiful, and too engaging to be restricted to the professionals. This book on quantum field theory is designed to be different. It is written by experimental physicists and aims to provide the interested amateur with a bridge from undergraduate physics to quantum field theory. The imagined reader is a gifted amateur, possessing a curious and adaptable mind, looking to be told an entertaining and intellectually stimulating story, but who will not feel patronised if a few
mathematical niceties are spelled out in detail. Using numerous worked examples, diagrams, and careful physically motivated explanations, this book will smooth the path towards understanding the radically different and revolutionary view of the physical world that quantum field theory provides, and which all physicists should have the opportunity to experience.
See it on Scoop.it (http://www.scoop.it/t/cxbooks/p/4023556412/2014/07/07/quantum-field-theory-for-the-gifted-amateur-by-tom-lancaster-stephen-j-blundell) , via CxBooks (http://www.scoop.it/t/cxbooks)
Postdocs at the Institute for Analytical Sociology, Linköping University
The Institute for Analytical Sociology at Linköping University is looking for up to five highly qualified postdocs to be part of an ambitious interdisciplinary research program on modeling segregation processes. The program is directed by Peter Hedström and includes a group of researchers with variety of disciplinary backgrounds [see http://www.liu.se/ias?l=en ].˙˙˙˙In the research program, we use large-scale register data, selected field experiments, and the tools of analytical sociology and complexity science to better understand the processes through which schools, organizations, and neighborhoods become segregated. ˙˙˙˙We seek outstanding social scientists whose research interests and qualifications resonate well with the core themes of the research program, and whose research agendas have a high potential to contribute to the development of the methodological and theoretical foundations of the social sciences. The successful candidates are expected to work independently and
to collaborate with colleagues within the project. Experience in handling and analyzing large-scale micro-level data, experimental design, network analysis, and/or agent-based simulation modeling is a merit.˙˙˙˙We can offer a stimulating research environment, extraordinary data materials - including micro-level population register data for the years 1990 to 2012 - and competitive salaries. The position will initially be for two years, with a possible extension, and should preferably be taken up no later than January 2015. The position entails no teaching or supervision obligations.
See it on Scoop.it (http://www.scoop.it/t/cxannouncements/p/4024228078/2014/07/07/postdocs-at-the-institute-for-analytical-sociology-linkoping-university) , via CxAnnouncements (http://www.scoop.it/t/cxannouncements)
Chaotic Harmony: A Dialog about Physics, Complexity and Life (by Ali Sanayei & Otto E. Rössler)
This fascinating book written by Ali Sanayei and Otto E. Rössler is not a classic scientific publication, but a vivid dialogue on science, philosophy and the interdisciplinary intersections of science and technology with biographic elements. Chaotic Harmony: A Dialog about Physics, Complexity and Life represents a discussion between Otto Rössler and his colleague and student, focusing on the different areas of science and highlights their mutual relations. The book's concept of interdisciplinary dialogue is unusual nowadays although it has a long tradition in science. It provides insight not only into interesting topics that are often closely linked, but also into the mind of a prominent scientist in the field of physics, chaos and complexity in general. It allows a deep look into the fascinating process of scientific development and discovery and provides a very interesting background of known and unknown facts in the areas of complex processes in physics, cosmology,
biology, brains and systems in general. This book will be valuable to all who are interested in science, its evolution and in an unconventional and original look at various issues. Surely it can serve as an inspiration for students, explaining the often overlooked fact that science and philosophy enrich each other.
See it on Scoop.it (http://www.scoop.it/t/cxbooks/p/4023554455/2014/07/07/chaotic-harmony-a-dialog-about-physics-complexity-and-life-by-ali-sanayei-otto-e-rossler) , via CxBooks (http://www.scoop.it/t/cxbooks)
The thirteenth Mathematics of Networks meeting will take place on 10th September 2014 at Imperial College in London. The meeting is free to present and to attend. It is now accepting abstracts for potential talks. The deadline for abstracts is 1st August. The theme of this MoN is networks in the humanities, including research on spatial and temporal networks. As always, talks on any topic will be considered but talks related to the theme will be given preference. Our hosts this year are the Centre for Complexity science. Thanks to Tim Evans for acting as local organiser.
This MoN is being organised to coincide with The Connected Past. TCP is a one-and-a-half-day multi-disciplinary meeting to explore how concepts and techniques from network- and complexity science can be used to study archaeological data. It will be held on 8th and 9th September at Imperial college.
http://www.monmeetings.org/meeting13/
http://connectedpast.soton.ac.uk/london-2014/
See it on Scoop.it (http://www.scoop.it/t/cxconferences/p/4023973808/2014/07/07/mon13-2014-thirteenth-mathematics-of-networks-meeting) , via CxConferences (http://www.scoop.it/t/cxconferences)
The Fascinating World of Complex Systems
Part 1: http://www.multimedia.ethz.ch/campus/zurichmeetsny/?doi=10.3930/ETHZ/AV-80b92958-97b0-4ad7-b07f-b15192931efc&autostart=false
Part 2: http://www.multimedia.ethz.ch/campus/zurichmeetsny/?doi=10.3930/ETHZ/AV-1db36e67-b2d7-4229-8973-ef1bb54dde27&autostart=false
http://www.complexsys.org/publicprograms.html
See it on Scoop.it (http://www.scoop.it/t/talks/p/4024210551/2014/07/07/the-fascinating-world-of-complex-systems) , via Talks (http://www.scoop.it/t/talks)
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