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   Barry Wellman

    A vision is just a vision if it's only in your head
    Step by step, link by link, putting it together Streisand/Sondheim

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   NetLab Network                   FRSC                    INSNA Founder
   http://www.chass.utoronto.ca/~wellman           twitter: @barrywellman
   NETWORKED:The New Social Operating System   Lee Rainie & Barry Wellman
   MIT Press            http://amzn.to/zXZg39       Print $18  Kindle $11
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---------- Forwarded message ----------
Date: Mon, 11 Jan 2016 12:02:44 +0000
From: "[utf-8] Complexity Digest" <[log in to unmask]>
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To: "[utf-8] Barry" <[log in to unmask]>
Subject: [utf-8] Latest Complexity Digest Posts

Learn about the latest and greatest related to complex systems research. More at http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=1b9684c19c&e=55e25a0e3e


Faster Adaptation in Smaller Populations: Counterintuitive Evolution of HIV during Childhood Infection

    Since some common approaches to the study of molecular adaptation may not be optimal for answering questions regarding within-host virus evolution, we have developed an alternative approach that estimates an absolute rate of molecular adaptation from serially-sampled viral populations. Here, we extend this framework to include sampling error when estimating the rate of adaptation, which is an important addition when analyzing historical data sets obtained in the pre-HAART era, for which the number of sequences per time point is often limited. We applied this extended method to a cohort of 24 pediatric HIV-1 patients and discovered that viral adaptation is strongly associated with the rate of disease progression, which is in contrast to previous analyses of these data that did not find a significant association. Strikingly, this results in a negative relationship between the rate of viral adaptation and viral population size, which is unexpected under standard
micro-evolutionary models since larger populations are predicted to fix more mutations per unit time than smaller populations. Our findings indicate that the negative correlation is unlikely to be driven by relaxation of selective constraint, but instead by significant variation in host immune responses. Consequently, this supports a previously proposed non-linear model of viral adaptation in which host immunity imposes counteracting effects on population size and selection.

Raghwani J, Bhatt S, Pybus OG (2016) Faster Adaptation in Smaller Populations: Counterintuitive Evolution of HIV during Childhood Infection. PLoS Comput Biol 12(1): e1004694. http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=a6cb0ab373&e=55e25a0e3e  (http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=ba09379b11&e=55e25a0e3e) ;

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Tracking Urban Activity Growth Globally with Big Location Data

    In recent decades the world has experienced rates of urban growth unparalleled in any other period of history and this growth is shaping the environment in which an increasing proportion of us live. In this paper we use a longitudinal dataset from Foursquare, a location-based social network, to analyse urban growth across 100 major cities worldwide.
Initially we explore how urban growth differs in cities across the world. We show that there exists a strong spatial correlation, with nearby pairs of cities more likely to share similar growth profiles than remote pairs of cities. Subsequently we investigate how growth varies inside cities and demonstrate that, given the existing local density of places, higher-than-expected growth is highly localised while lower-than-expected growth is more diffuse. Finally we attempt to use the dataset to characterise competition between new and existing venues. By defining a measure based on the change in throughput of a venue before and after the opening of a new nearby venue, we demonstrate which venue types have a positive effect on venues of the same type and which have a negative effect. For example, our analysis confirms the hypothesis that there is large degree of competition between bookstores, in the sense that existing bookstores normally experience a notable drop in footfall
after a new bookstore opens nearby. Other place categories however, such as Airport Gates or Museums, have a cooperative effect and their presence fosters higher traffic volumes to nearby places of the same type.

Tracking Urban Activity Growth Globally with Big Location Data
Matthew Daggitt, Anastasios Noulas, Blake Shaw, Cecilia Mascolo

http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=84fa3c6ded&e=55e25a0e3e

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The angular nature of road networks

    Road networks are characterised by several structural and geometric properties. Their topological structure determines partially its hierarchical arrangement, but since these are networks that are spatially situated and, therefore, spatially constrained, to fully understand the role that each road plays in the system it is fundamental to characterize the influence that geometrical properties have over the network's behaviour. In this work, we percolate the UK's road network using the relative angle between street segments as the occupation probability. We argue that road networks undergo a non-equilibrium first-order phase transition at the moment the main roads start to interconnect forming the spanning percolation cluster. The percolation process uncovers the hierarchical structure of the roads in the network, and as such, its classification. Furthermore, this technique serves to extract the set of most important roads of the network and to create a hierarchical index !
 for
each road in the system.

The angular nature of road networks
Carlos Molinero, Roberto Murcio, Elsa Arcaute

http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=377b524b14&e=55e25a0e3e

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Understanding the group dynamics and success of teams

    Complex problems often require coordinated group effort and can consume significant resources, yet our understanding of how teams form and succeed has been limited by a lack of large-scale, quantitative data. We analyze activity traces and success levels for ~150,000 self-organized, online team projects. While larger teams tend to be more successful, workload is highly focused across the team, with only a few members performing most work. We find that highly successful teams are significantly more focused than average teams of the same size, that their members have worked on more diverse sets of projects, and the members of highly successful teams are more likely to be core members or 'leads' of other teams. The relations between team success and size, focus and especially team experience cannot be explained by confounding factors such as team age or external contributions from non-team members nor by group mechanisms such as social loafing. Taken together, these features
point to organizational principles that may maximize the success of collaborative endeavors.

Understanding the group dynamics and success of teams
Michael Klug, James P. Bagrow

http://unam.us4.list-manage1.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=4ba3d930f6&e=55e25a0e3e

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On the origin of burstiness in human behavior: The wikipedia edits case

    A number of human activities exhibit a bursty pattern, namely periods of very high activity that are followed by rest periods. Records of this process generate time series of events whose inter-event times follow a probability distribution that displays a fat tail. The grounds for such phenomenon are not yet clearly understood. In the present work we use the freely available Wikipedia's editing records to tackle this question by measuring the level of burstiness, as well as the memory effect of the editing tasks performed by different editors in different pages. Our main finding is that, even though the editing activity is conditioned by the circadian 24 hour cycle, the conditional probability of an activity of a given duration at a given time of the day is independent from the latter. This suggests that the human activity seems to be related to the high "cost" of starting an action as opposed to the much lower "cost" of continuing that action.

On the origin of burstiness in human behavior: The wikipedia edits case
Yerali Gandica, Joao Carvalho, Fernando Sampaio Dos Aidos, Renaud Lambiotte, and Timoteo Carletti

http://unam.us4.list-manage.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=4507cf2cd6&e=55e25a0e3e

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Interacting Behavior and Emerging Complexity

    Can we quantify the change of complexity throughout evolutionary processes? We attempt to address this question through an empirical approach. In very general terms, we simulate two simple organisms on a computer that compete over limited available resources. We implement Global Rules that determine the interaction between two Elementary Cellular Automata on the same grid. Global Rules change the complexity of the state evolution output which suggests that some complexity is intrinsic to the interaction rules themselves. The largest increases in complexity occurred when the interacting elementary rules had very little complexity, suggesting that they are able to accept complexity through interaction only. We also found that some Class 3 or 4 CA rules are more fragile than others to Global Rules, while others are more robust, hence suggesting some intrinsic properties of the rules independent of the Global Rule choice. We provide statistical mappings of Elementary Cellular
Automata exposed to Global Rules and different initial conditions onto different complexity classes.

Interacting Behavior and Emerging Complexity
Alyssa Adams, Hector Zenil, Eduardo Hermo Reyes, Joost Joosten

http://unam.us4.list-manage1.com/track/click?u=0eb0ac9b4e8565f2967a8304b&id=33d7b1837c&e=55e25a0e3e

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Founding Editor: Gottfried Mayer.
Editor-in-Chief: Carlos Gershenson.

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