复杂文摘翻译第四期－(摘自Complex Digest 2016.3月文章)

Fitness Landscape Epistasis And Recombination

March 1, 3:38 AM
From Complex Syst. 18, 1550026 (2015)
By MANUEL BELTRÁN DEL RÍO, CHRISTOPHER R. STEPHENS, and DAVID A. ROSENBLUETH
(Translated by -)

Homologous recombination is an important operator in the evolution of biological organisms. However, there is still no clear, generally accepted understanding of why it exists and under what circumstances it is useful. In this paper, we consider its utility in the context of an infinite population haploid model with selection and homologous recombination. We define utility in terms of two metrics — the increase in frequency of fit genotypes, and the increase in average population fitness, relative to those associated with selection only. Explicitly, we explore the full parameter space of a two-locus two-allele system, showing, as a function of the landscape and the initial population, that recombination is beneficial in terms of these metrics in two distinct regimes: a relatively landscape independent regime — the search regime — where recombination aids in the search for a fit genotype that is absent or at low frequency in the population; and the modular regime, where recombination allows for the juxtaposition of fit “modules” or Building Blocks (BBs). Thus, we conclude that the ubiquity and utility of recombination is intimately associated with the existence of modularity and redundancy in biological fitness landscapes.

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原文链接：http://dx.doi.org/10.1142/S0219525915500265

Relative Entropy in Biological Systems

March 1, 4:27 AM
From Entropy 2016, 18(2), 46
By John C. Baez and Blake S. Pollard
(Translated by -)

In this paper we review various information-theoretic characterizations of the approach to equilibrium in biological systems. The replicator equation, evolutionary game theory, Markov processes and chemical reaction networks all describe the dynamics of a population or probability distribution. Under suitable assumptions, the distribution will approach an equilibrium with the passage of time. Relative entropy—that is, the Kullback–Leibler divergence, or various generalizations of this—provides a quantitative measure of how far from equilibrium the system is. We explain various theorems that give conditions under which relative entropy is nonincreasing. In biochemical applications these results can be seen as versions of the Second Law of Thermodynamics, stating that free energy can never increase with the passage of time. In ecological applications, they make precise the notion that a population gains information from its environment as it approaches equilibrium.

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原文链接：http://dx.doi.org/10.3390/e18020046

An Experimental Study of Segregation Mechanisms

March 1, 5:32 AM
From EPJ Data Science 2016, 5 :4 (27 February 2016)
By Tsvetkova M, Nilsson O, Öhman C, Sumpter L, Sumpter D
(Translated by -)

Segregation is widespread in all realms of human society. Several influential studies have argued that intolerance is not a prerequisite for a segregated society, and that segregation can arise even when people generally prefer diversity. We investigated this paradox experimentally, by letting groups of high-school students play four different real-time interactive games. Incentives for neighbor similarity produced segregation, but incentives for neighbor dissimilarity and neighborhood diversity prevented it. The participants continued to move while their game scores were below optimal, but their individual moves did not consistently take them to the best alternative position. These small differences between human and simulated agents produced different segregation patterns than previously predicted, thus challenging conclusions about segregation arising from these models.

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原文链接：http://dx.doi.org/10.1140/epjds/s13688-016-0065-5

Temporal Network Analysis of Literary Texts

March 1, 5:08 PM
From arxiv.org
By Sandra D. Prado, Silvio R. Dahmen, Ana L.C. Bazzan, Padraig Mac Carron, Ralph Kenna
(Translated by -)

We study temporal networks of characters in literature focusing on "Alice's Adventures in Wonderland" (1865) by Lewis Carroll and the anonymous "La Chanson de Roland" (around 1100). The former, one of the most influential pieces of nonsense literature ever written, describes the adventures of Alice in a fantasy world with logic plays interspersed along the narrative. The latter, a song of heroic deeds, depicts the Battle of Roncevaux in 778 A.D. during Charlemagne's campaign on the Iberian Peninsula. We apply methods recently developed by Taylor and coworkers \cite{Taylor+2015} to find time-averaged eigenvector centralities, Freeman indices and vitalities of characters. We show that temporal networks are more appropriate than static ones for studying stories, as they capture features that the time-independent approaches fail to yield.

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原文链接：http://arxiv.org/abs/1602.07275

The Research Space: using the career paths of scholars to predict the evolution of the research output of individuals, institutions, and nations

March 1, 7:01 PM
From arxiv.org
By Miguel R. Guevara, Dominik Hartmann, Manuel Aristarán, Marcelo Mendoza, César A. Hidalgo
(Translated by -)

In recent years scholars have built maps of science by connecting the academic fields that cite each other, are cited together, or that cite a similar literature. But since scholars cannot always publish in the fields they cite, or that cite them, these science maps are only rough proxies for the potential of a scholar, organization, or country, to enter a new academic field. Here we use a large dataset of scholarly publications disambiguated at the individual level to create a map of science-or research space-where links connect pairs of fields based on the probability that an individual has published in both of them. We find that the research space is a significantly more accurate predictor of the fields that individuals and organizations will enter in the future than citation based science maps. At the country level, however, the research space and citations based science maps are equally accurate. These findings show that data on career trajectories-the set of fields that individuals have previously published in-provide more accurate predictors of future research output for more focalized units-such as individuals or organizations-than citation based science maps.

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原文链接：http://arxiv.org/abs/1602.08409

Rate or Trade? Identifying Winning Ideas in Open Idea Sourcing

March 3, 9:10 PM
From Information Systems Research
By Ivo Blohm, Christoph Riedl, Johann Füller, Jan Marco Leimeister
(Translated by -)

Information technology (IT) has created new patterns of digitally-mediated collaboration that allow open sourcing of ideas for new products and services. These novel sociotechnical arrangements afford finely-grained manipulation of how tasks can be represented and have changed the way organizations ideate. In this paper, we investigate differences in behavioral decision-making resulting from IT-based support of open idea evaluation. We report results from a randomized experiment of 120 participants comparing IT-based decision-making support using a rating scale (representing a judgment task) and a preference market (representing a choice task). We find that the rating scale-based task invokes significantly higher perceived ease of use than the preference market-based task and that perceived ease of use mediates the effect of the task representation treatment on the users’ decision quality. Furthermore, we find that the understandability of ideas being evaluated, which we assess through the ideas’ readability, and the perception of the task’s variability moderate the strength of this mediation effect, which becomes stronger with increasing perceived task variability and decreasing understandability of the ideas. We contribute to the literature by explaining how perceptual differences of task representations for open idea evaluation affect the decision quality of users and translate into differences in mechanism accuracy. These results enhance our understanding of how crowdsourcing as a novel mode of value creation may effectively complement traditional work structures.

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原文链接：http://pubsonline.informs.org/doi/abs/10.1287/isre.2015.0605

Living Cognitive Society: a 'digital' World of Views

March 3, 9:47 PM
From arxiv.org
By Viktoras Veitas, David Weinbaum (Weaver)
(Translated by -)

The current social reality is characterized by all-encompassing change, which disrupts existing social structures at all levels. Yet the prevailing view of society is based on the ontological primacy of stable hierarchical structures, which is no longer adequate.
We propose a conceptual framework for thinking about a dynamically changing social system: the Living Cognitive Society. Importantly, we show how it follows from a much broader philosophical framework, guided by the theory of individuation, which emphasizes the importance of relationships and interactive processes in the evolution of a system.
The framework addresses society as a living cognitive system -- an ecology of interacting social subsystems -- each of which is also a living cognitive system. We argue that this approach can help us to conceive sustainable social systems that will thrive in the circumstances of accelerating change. The Living Cognitive Society is explained in terms of its fluid structure, dynamics and the mechanisms at work. We then discuss the disruptive effects of Information and Communication Technologies on the mechanisms at work.
We conclude by delineating a major topic for future research -- distributed social governance -- which focuses on processes of coordination rather than on stable structures within global society.


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原文链接：http://arxiv.org/abs/1602.08388

From neurons to epidemics: How trophic coherence affects spreading processes

March 3, 10:48 PM
From arxiv.org
By Janis Klaise, Samuel Johnson
(Translated by -)

Trophic coherence, a measure of the extent to which the nodes of a directed network are organised in levels, has recently been shown to be closely related to many structural and dynamical aspects of complex systems, including graph eigenspectra, the prevalence or absence of feed-back cycles, and linear stability. Furthermore, non-trivial trophic structures have been observed in networks of neurons, species, genes, metabolites, cellular signalling, concatenated words, P2P users, and world trade. Here we consider two simple yet apparently quite different dynamical models -- one a Susceptible-Infected-Susceptible (SIS) epidemic model adapted to include complex contagion, the other an Amari-Hopfield neural network -- and show that in both cases the related spreading processes are modulated in similar ways by the trophic coherence of the underlying networks. To do this, we propose a network assembly model which can generate structures with tunable trophic coherence, limiting in either perfectly stratified networks or random graphs. We find that trophic coherence can exert a qualitative change in spreading behaviour, determining whether a pulse of activity will percolate through the entire network or remain confined to a subset of nodes, and whether such activity will quickly die out or endure indefinitely. These results could be important for our understanding of phenomena such as epidemics, rumours, shocks to ecosystems, neuronal avalanches, and many other spreading processes.

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原文链接：http://arxiv.org/abs/1603.00670

Estimation and monitoring of city-to-city travel times using call detail records

March 3, 11:26 PM
From EPJ Data Science 2016 5:6
By Rainer Kujala, Talayeh Aledavood and Jari Saramäki
(Translated by -)

Whenever someone makes or receives a call on a mobile telephone, a Call Detail Record (CDR) is automatically generated by the operator for billing purposes. CDRs have a wide range of applications beyond billing, from social science to data-driven development. Recently, CDRs have been increasingly used to study human mobility, whose understanding is crucial e.g. for planning efficient transportation infrastructure. A major difficulty in analyzing human mobility using CDR data is that the location of a cell phone user is not recorded continuously but typically only when a call is initiated or a text message is sent. In this paper we address this problem, and develop a method for estimating travel times between cities based on CDRs that relies not on individual trajectories of people, but their collective statistical properties. We apply our method to data from Senegal, released by Sonatel and Orange for the 2014 Data for Development Challenge. We turn CDR mobility traces to estimates on travel times between Senegalese cities, filling an existing gap in knowledge. Moreover, the proposed method is shown to be highly valuable for monitoring travel conditions and their changes in near real-time, as demonstrated by measuring the decrease in travel times due to the opening of the Dakar-Diamniadio highway. Overall, our results indicate that it is possible to extract reliable de facto information on typical travel times that is useful for a variety of audiences ranging from casual travelers to transport infrastructure planners.

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原文链接：http://dx.doi.org/10.1140/epjds/s13688-016-0067-3

Women through the glass ceiling: gender asymmetries in Wikipedia

March 4, 1:28 AM
From EPJ Data Science 2016 5:5
By Claudia Wagner, Eduardo Graells-Garrido, David Garcia and Filippo Menczer
(Translated by -)

Contributing to the writing of history has never been as easy as it is today thanks to Wikipedia, a community-created encyclopedia that aims to document the world’s knowledge from a neutral point of view. Though everyone can participate it is well known that the editor community has a narrow diversity, with a majority of white male editors. While this participatory gender gap has been studied extensively in the literature, this work sets out to assess potential gender inequalities in Wikipedia articles along different dimensions: notability, topical focus, linguistic bias, structural properties, and meta-data presentation.
We find that (i) women in Wikipedia are more notable than men, which we interpret as the outcome of a subtle glass ceiling effect; (ii) family-, gender-, and relationship-related topics are more present in biographies about women; (iii) linguistic bias manifests in Wikipedia since abstract terms tend to be used to describe positive aspects in the biographies of men and negative aspects in the biographies of women; and (iv) there are structural differences in terms of meta-data and hyperlinks, which have consequences for information-seeking activities. While some differences are expected, due to historical and social contexts, other differences are attributable to Wikipedia editors. The implications of such differences are discussed having Wikipedia contribution policies in mind. We hope that the present work will contribute to increased awareness about, first, gender issues in the content of Wikipedia, and second, the different levels on which gender biases can manifest on the Web.

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原文链接：http://dx.doi.org/10.1140/epjds/s13688-016-0066-4

Exploring the Space of Viable Configurations in a Model of Metabolism–Boundary Co-construction

March 4, 3:33 AM
From www.mitpressjournals.org
By Eran Agmon, Alexander J. Gates, Valentin Churavy, Randall D. Beer
(Translated by -)

We introduce a spatial model of concentration dynamics that supports the emergence of spatiotemporal inhomogeneities that engage in metabolism–boundary co-construction. These configurations exhibit disintegration following some perturbations, and self-repair in response to others. We define robustness as a viable configuration's tendency to return to its prior configuration in response to perturbations, and plasticity as a viable configuration's tendency to change to other viable configurations. These properties are demonstrated and quantified in the model, allowing us to map a space of viable configurations and their possible transitions. Combining robustness and plasticity provides a measure of viability as the average expected survival time under ongoing perturbation, and allows us to measure how viability is affected as the configuration undergoes transitions. The framework introduced here is independent of the specific model we used, and is applicable for quantifying robustness, plasticity, and viability in any computational model of artificial life that demonstrates the conditions for viability that we promote.

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原文链接：http://dx.doi.org/10.1140/epjds/s13688-016-0066-4

Flies as Ship Captains? Digital Evolution Unravels Selective Pressures to Avoid Collision in Drosophila

March 4, 5:45 AM
From arxiv.org
By Ali Tehrani-Saleh, Christoph Adami
(Translated by -)

Flies that walk in a covered planar arena on straight paths avoid colliding with each other, but which of the two flies stops is not random. High-throughput video observations, coupled with dedicated experiments with controlled robot flies have revealed that flies utilize the type of optic flow on their retina as a determinant of who should stop, a strategy also used by ship captains to determine which of two ships on a collision course should throw engines in reverse. We use digital evolution to test whether this strategy evolves when collision avoidance is the sole penalty. We find that the strategy does indeed evolve in a narrow range of cost/benefit ratios, for experiments in which the "regressive motion" cue is error free. We speculate that these stringent conditions may not be sufficient to evolve the strategy in real flies, pointing perhaps to auxiliary costs and benefits not modeled in our study.

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原文链接：http://arxiv.org/abs/1603.00802

Zika Virus: Endemic Versus Epidemic Dynamics and Implications for Disease Spread in the Americas

March 4, 7:42 AM
From biorxiv.org
By Sharon Bewick, William F Fagan, Justin M Calabrese, Folashade Agusto
(Translated by -)

Since being introduced into Brazil in 2014, Zika virus (ZIKV) has spread explosively across Central and South America. Although the symptoms of ZIKV are mild, recent evidence suggests a relationship between prenatal exposure to ZIKV and microcephaly. This has led to widespread panic, including travel alerts and warnings to avoid pregnancy. Because ZIKV is an emerging disease, response efforts are complicated by limited understanding of disease dynamics. To this end, we develop a novel state- and class-structured compartment model for ZIKV. Our model shows that the risk of prenatal ZIKV exposure should decrease dramatically following the initial wave of disease, reaching almost undetectable levels in endemic systems. Our model also suggests that efforts to reduce ZIKV prenatal exposures through mosquito management and avoidance may have minimal benefit, and may even result in increased risk of microcephaly in later years of an outbreak.

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原文链接：http://dx.doi.org/10.1101/041897

About 40% of economics experiments fail replication survey

March 5, 4:07 PM
From www.sciencemag.org
By John Bohannon
(Translated by -)

When a massive replicability study in psychology was published last year, the results were, to some, shocking: 60% of the 100 experimental results failed to replicate. Now, the latest attempt to verify findings in the social sciences—this time with a small batch from experimental economics—also finds a substantial number of failed replications. Following the exact same protocols of the original studies, the researchers failed to reproduce the results in about 40% of cases.

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原文链接：http://dx.doi.org/10.1126/science.aaf4141

Generalizing Moore

March 5, 5:45 PM
From Nature Physics 12, 200 (2016)
By Mark Buchanan
(Translated by -)

Over the past few years, several independent teams of researchers have noticed something surprising in historical data on a broad set of technologies. Everyone, of course, knows about Moore's Law — for decades, the density of transistors on integrated circuits has doubled every two years, with computational speed advancing even faster. This spectacular record of improvement shows up in just about any metric. Much less known, however, is that this pattern of exponential advance isn't actually limited to electronics; it applies just as well to technologies ranging from cars or batteries to beer or nuclear power.

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原文链接：http://dx.doi.org/10.1038/nphys3685

Keep-Left Behavior Induced by Asymmetrically Profiled Walls

March 5, 9:34 PM
From Phys. Rev. X 6, 011003 (2016)
By C. L. N. Oliveira, A. P. Vieira, D. Helbing, J. S. Andrade, Jr., and H. J. Herrmann
(Translated by -)

Ensuring efficient pedestrian streams through transit corridors such as subway hallways is a problem of significant relevance to many cities. By modeling self-driven particles, scientists show that modulating the shape of a hallway’s walls might help to separate opposite pedestrian flows.

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原文链接：http://dx.doi.org/10.1103/PhysRevX.6.011003

Complex Autocatalysis in Simple Chemistries

March 6, 9:31 PM
From www.mitpressjournals.org
By Nathaniel Virgo, Takashi Ikegami, Simon McGregor
(Translated by -)

Life on Earth must originally have arisen from abiotic chemistry. Since the details of this chemistry are unknown, we wish to understand, in general, which types of chemistry can lead to complex, lifelike behavior. Here we show that even very simple chemistries in the thermodynamically reversible regime can self-organize to form complex autocatalytic cycles, with the catalytic effects emerging from the network structure. We demonstrate this with a very simple but thermodynamically reasonable artificial chemistry model. By suppressing the direct reaction from reactants to products, we obtain the simplest kind of autocatalytic cycle, resulting in exponential growth. When these simple first-order cycles are prevented from forming, the system achieves superexponential growth through more complex, higher-order autocatalytic cycles. This leads to nonlinear phenomena such as oscillations and bistability, the latter of which is of particular interest regarding the origins of life.

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原文链接：http://dx.doi.org/10.1162/ARTL_a_00195

Zika and Other Potential Causes of Microcephaly in Brazil: Status March 8, 2016 | NECSI

March 8, 6:10 PM
From Status March 8, 2016, NECSI (2016)
By Raphael Parens, Yaneer Bar-Yam, Zika and other potential causes of microcephaly in Brazil
(Translated by -)

We review the current information about causes of microcephaly in Brazil in 2015-6, including speculative ones, in order to provide the best possible clarity about the information that is available as of the publication date in order to advance the rapid response efforts. We review the leading candidate, Zika virus infections, the second candidate, the pesticide pyriproxifen, as well as DPT immunizations, and GM mosquitoes. Each of these candidates has been considered because of an increase at very roughly the time of the increase in microcephaly cases. The strongest evidence is in favor of Zika, through the observation of Zika virus in neural tissue, though a key piece of evidence is missing in the expected rise of cases in other locations, specifically Colombia. Evaluation of the potential role of pyriproxifen is difficult due to the limited number and nature of available studies, which should be revisited as they include some evidence for neurodevelopmental toxicity. The possibility of DPT immunizations of pregnant women as a factor is largely ruled out by an increase in immunization in countries in which microcephaly cases are not being reported. There is no direct evidence for GM mosquitoes as a cause. If there is a dramatic increase in cases of microcephaly in Columbia in the next three months, the case for Zika will be dramatically strengthened, and the case for pyriproxyfen and GM mosquitoes will be essentially ruled out. On the other hand if the cases do not materialize, Zika will essentially be ruled out and pyriproxyfen would become the strongest case with GM mosquitoes a speculative alternative along with other environmental toxins.

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原文链接：http://necsi.edu/research/social/pandemics/zikacauses.html

Grand Challenges in Transportation and Transit Systems

March 8, 7:43 PM
From Front. Built Environ., 24 February 2016 |
Sakdirat Kaewunruen, Joseph M. Sussman and Akira Matsumoto
(Translated by -)

Transportation and transit systems draw upon broad spectra of research fields due to the diversity and interconnectivity of transport modes, including road, rail, aviation, pipeline, maritime, or even aerospace. These systems have evolved over centuries to be considerably more efficient and environment-friendly for a wide range of customers. The fundamental principle “safety first” is still the key priority in most research today. However, thanks to extensive interface with various customers; research and innovation in practices have shifted from optimizing functional purposes and targets through each stage of life cycle toward modernization, reliability, resilience, and better quality of life. These initiatives additionally coincide with the grand challenges for engineering proposed by the National Academy of Engineering and the United Nations’ Millennium Development Goals

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原文链接：http://dx.doi.org/10.3389/fbuil.2016.00004

Rhetoric of Effortlessness in Science

March 10, 7:01 PM
From Science March-April 2016 Volume: 24, Number: 2 March-April 2016: 145-166.
By James W. McAllister
(Translated by -)

Scientists use several rhetorical strategies to heighten the objectivity and credibility of their findings. Examples are the rhetoric of effort, which involves emphasizing the amount of effort expended in research, and the rhetoric of self-effacement, which involves suggesting that the facts have manifested themselves without input from the researcher. In this article, I present a further, hitherto unrecognized rhetorical strategy that scientists use for the same aims: the rhetoric of effortlessness, which consists in conveying the impression that establishing a result has cost the investigator little effort. This rhetorical strategy heightens the credibility of individual scientific findings, raises the reputation of individual scientists, and propagates an attractive view of science as a whole. I outline the epistemology underpinning the rhetoric of effortlessness and give examples of its use in modern science.

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原文链接：http://dx.doi.org/10.1162/POSC_a_00198

Hoaxy: A Platform for Tracking Online Misinformation

March 10, 9:31 PM
From arxiv.org
By Chengcheng Shao, Giovanni Luca Ciampaglia, Alessandro Flammini, Filippo Menczer
(Translated by -)

Massive amounts of misinformation have been observed to spread in uncontrolled fashion across social media. Examples include rumors, hoaxes, fake news, and conspiracy theories. At the same time, several journalistic organizations devote significant efforts to high-quality fact checking of online claims. The resulting information cascades contain instances of both accurate and inaccurate information, unfold over multiple time scales, and often reach audiences of considerable size. All these factors pose challenges for the study of the social dynamics of online news sharing. Here we introduce Hoaxy, a platform for the collection, detection, and analysis of online misinformation and its related fact-checking efforts. We discuss the design of the platform and present a preliminary analysis of a sample of public tweets containing both fake news and fact checking. We find that, in the aggregate, the sharing of fact-checking content typically lags that of misinformation by 10--20 hours. Moreover, fake news are dominated by very active users, while fact checking is a more grass-roots activity. With the increasing risks connected to massive online misinformation, social news observatories have the potential to help researchers, journalists, and the general public understand the dynamics of real and fake news sharing.

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原文链接：http://arxiv.org/abs/1603.01511

Statisticians issue warning over misuse of P values

March March 11, 4:29 PM
From www.nature.com
By
(Translated by -)

Misuse of the P value — a common test for judging the strength of scientific evidence — is contributing to the number of research findings that cannot be reproduced, the American Statistical Association (ASA) warns in a statement released today. The group has taken the unusual step of issuing principles to guide use of the P value, which it says cannot determine whether a hypothesis is true or whether results are important.

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原文链接：http://www.nature.com/news/statisticians-issue-warning-over-misuse-of-p-values-1.19503

A bacterium that degrades and assimilates poly(ethylene terephthalate)

March 11, 6:47 PM
From Science  11 Mar 2016: Vol. 351, Issue 6278, pp. 1196-1199
By Shosuke Yoshida, et al.
(Translated by -)

Poly(ethylene terephthalate) (PET) is used extensively worldwide in plastic products, and its accumulation in the environment has become a global concern. Because the ability to enzymatically degrade PET has been thought to be limited to a few fungal species, biodegradation is not yet a viable remediation or recycling strategy. By screening natural microbial communities exposed to PET in the environment, we isolated a novel bacterium, Ideonella sakaiensis 201-F6, that is able to use PET as its major energy and carbon source. When grown on PET, this strain produces two enzymes capable of hydrolyzing PET and the reaction intermediate, mono(2-hydroxyethyl) terephthalic acid. Both enzymes are required to enzymatically convert PET efficiently into its two environmentally benign monomers, terephthalic acid and ethylene glycol.

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原文链接：http://dx.doi.org/10.1126/science.aad6359

Sensitivity of global terrestrial ecosystems to climate variability

March 12, 4:39 PM
From Nature 531, 229–232 (10 March 2016)
By Shosuke Yoshida, et al.
(Translated by -)

Using satellite data and a novel analytical approach, a new index of the sensitivity of vegetation to climate variability is developed, revealing areas of high sensitivity that include tundra, boreal forest, tropical forest and temperate grasslands.

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原文链接：http://dx.doi.org/10.1038/nature16986

Social Evolution Selects for Redundancy in Bacterial Quorum Sensing

March 12, 5:31 PM
From Social Evolution Selects for Redundancy in Bacterial Quorum Sensing. PLoS Biol 14(2): e1002386
By Even-Tov E, Omer Bendori S, Valastyan J, Ke X, Pollak S, Bareia T, et al.
(Translated by -)

Quorum sensing is a mechanism through which bacteria communicate by producing, releasing, and detecting signal molecules encoding information about cell population density. Quorum sensing allows bacteria to synchronize their behaviors and act as collectives. Often, quorum sensing controls cooperative behaviors that benefit the entire community, such as the production and secretion of costly metabolites. Some bacteria release multiple signal molecules which, once detected, funnel information into the same cellular response. Thus, the benefit of using multiple rather than a single signal is mysterious since the signals seem redundant. Here, we combine modeling and experiments to show that the evolutionary accumulation of multiple quorum-sensing systems can be attributed to social exploitation and kin recognition. When in low abundance, a strain that has acquired an additional quorum-sensing system can avoid cooperating and can exploit its ancestor strain, which contains one less quorum-sensing system. The cheater containing the additional system returns to a cooperative behavior when it is abundant. We also identify the molecular mechanisms necessary for the acquisition of an additional signaling system. Our work demonstrates that increased complexity in bacterial social signaling circuits can evolve without providing an adaptive advantage in a clonal population.

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原文链接：http://dx.doi.org/10.1371/journal.pbio.1002386

Major transitions in evolution and in technology: What they have in common and where they differ

March 12, 7:05 PM
From Complexity
By Peter Schuster
(Translated by -)

What have technological and biological evolution in common? One feature has been mentioned just above: Technologies and the professions related to them have finite lifetimes like biological species. Efficiency and other economic criteria are crucial for the survival of technologies and play the same role as fitness does in biological evolution. Technologies form complex networks of mutual dependences just as the different species do in the food webs of ecosystems. One less obvious feature is the tinkering principle. Innovation builds upon already existing technologies and only rarely—in exceptional cases—starts from scratch. One of these exceptions, perhaps, was the introduction of electricity into society. Pre-human nature is an obligatory tinkerer and the tinkering principle was indeed formulated first in the context of biological evolution: Nature does not design with the eyes of an engineer, she works like a tinkerer. Biological evolution can only make use of entities that are already present in the population. Biological evolution does never start from scratch but existing functions are used in different combinations and in a different context. Common to technology and biological evolution is an optimization principle that concerns economic efficiency in the former and fitness in the sense of the number of progeny in the latter case: In case a technology produces the same goods more expensively it will run out of business as a variant within a population does when it has less offspring.

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原文链接：http://dx.doi.org/10.1002/cplx.21773

The Enlightenment is Dead, Long Live the Entanglement

March 14 8:38 PM
From Journal of Design and Science
By Danny Hillis
(Translated by -)

We humans are changing. We have become so intertwined with what we have created that we are no longer separate from it. We have outgrown the distinction between the natural and the artificial. We are what we make. We are our thoughts, whether they are created by our neurons, by our electronically augmented minds, by our technologically mediated social interactions, or by our machines themselves. We are our bodies, whether they are born in womb or test tube, our genes inherited or designed, organs augmented, repaired, transplanted, or manufactured. Our prosthetic enhancements are as simple as contact lenses and tattoos and as complex as robotic limbs and search engines. They are both functional and aesthetic. We are our perceptions, whether they are through our eyes and ears or our sensory-fused hyper-spectral sensors, processed as much by computers as by our own cortex. We are our institutions, cooperating super-organisms, entangled amalgams of people and machines with super-human intelligence, processing, sensing, deciding, acting. Our home planet is inhabited by both engineered organisms and evolved machines. Our very atmosphere is the emergent creation of forests, farms and factories. Empowered by the tools of the Enlightenment, connected by networked flows of freight and fuel and finance, by information and ideas, we are becoming something new. We are at the dawn of the Age of Entanglement.

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原文链接：http://jods.mitpress.mit.edu/pub/enlightenment-to-entanglement

Epistemological Odyssey: Introduction to Special Issue on the Diversity of Enactivism and Neurophenomenology

March 15, 5:06 PM
From Constructuvist Foundations Volume 11 · Number 2 · Pages 189–204
By Sebastjan Vörös, Tom Froese & Alexander Riegler
(Translated by -)

Context: In the past two decades, the so-called 4E approaches to the mind and cognition have been rapidly gaining in recognition and have become an integral part of various disciplines. Problem: Recently, however, questions have been raised as to whether, and to what degree, these different approaches actually cohere with one another. Specifically, it seems that many of them endorse mutually incompatible, perhaps even contradictory, epistemological and metaphysical presuppositions. Method: By retracing the roots of an alternative conception of mind and cognition, as propounded by Varela, Thompson & Rosch, we provide an outline of the original philosophical framework of enactivism and neurophenomenology. We focus on its three central tenets - reflexivity, subject-world co-determination, and the construal of cognition as situated, skillful and embodied action - and show how they collectively add up to a radical change in attitude towards the age-old philosophical dilemmas. Results: We show how contemporary enactivist and embodied approaches relate to the original Varelian conception, and argue that many of them, despite frequent claims to the contrary, adopt significantly less radical philosophical positions. Further, we provide some tentative suggestions as to why this dilution of the original impetus might have occurred, paying special attention to the deep-rooted disparities that span the field. Implications: It is argued that more attention should be paid to epistemological and metaphysical tenets of different proposals within the 4E movement in general and enactivism in particular. Additionally, in emphasizing the inescapable multilayeredness and contextuality of scientific knowledge, enactivism and neurophenomenology accord with pluralist accounts of science and might provide important contributions to contemporary debates in the field. Constructivist content: The epistemological odyssey, construed as a journey to find a middle way between realism and idealism, is a central tenet of anti-representationalist, non-dualist constructivist approaches aimed at avoiding age-old philosophical traps.

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原文链接：http://www.univie.ac.at/constructivism/journal/11/2/189.editorial

Improving Urban Mobility by Understanding its Complexity

March 15, 7:12 PM
From arxiv.org
By Carlos Gershenson
(Translated by -)

Urban mobility systems are composed multiple elements with strong interactions, i.e. their future is co-determined by the state of other elements. Thus, studying components in isolation, i.e. using a reductionist approach, is inappropriate. I propose five recommendations to improve urban mobility based on insights from the scientific study of complex systems: use adaptation over prediction, regulate interactions to avoid friction, use sensors to recover real time information, develop adaptive algorithms to exploit that information, and deploy agents to act on the urban environment.

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原文链接：http://arxiv.org/abs/1603.04267

Design as Participation

March 16, 8:40 PM
From Journal of Design and Science
By Kevin Slavin
(Translated by -)

The hypothesis is that most designers that are deliberately working with complex adaptive systems cannot help but be humbled by them. Maybe those who really design systems-interacting-with-systems approach their relationships to said systems with the daunting complexity of influence, rather than the hubris of definition or control. The designers of complex adaptive systems are not strictly designing systems themselves. They are hinting those systems towards anticipated outcomes, from an array of existing interrelated systems. These are designers that do not understand themselves to be in the center of the system. Rather, they understand themselves to be participants, shaping the systems that interact with other forces, ideas, events and other designers. This essay is an exploration of what it means to participate.

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原文链接：http://jods.mitpress.mit.edu/pub/design-as-participation

Discovery of fairy circles in Australia supports self-organization theory

March 17, 11:08 AM
From www.pnas.org
By Stephan Getzin, et al.
(Translated by -)

Pattern-formation theory predicts that vegetation gap patterns, such as the fairy circles of Namibia, emerge through the action of pattern-forming biomass–water feedbacks and that such patterns should be found elsewhere in water-limited systems around the world. We report here the exciting discovery of fairy-circle patterns in the remote outback of Australia. Using fieldwork, remote sensing, spatial pattern analysis, mathematical modeling, and pattern-formation theory we show that the Australian gap patterns share with their Namibian counterparts the same characteristics but are driven by a different biomass–water feedback. These observations are in line with a central universality principle of pattern-formation theory and support the applicability of this theory to wider contexts of spatial self-organization in ecology.

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原文链接：http://dx.doi.org/10.1073/pnas.1522130113

Do jobs run in families?

March 17, 11:08 AM
From research.facebook.com
By Ismail Onur Filiz, Lada Adamic
(Translated by -)

How much of our choice of profession depends on who our parents are? Parents pass on their genes, set an example, provide opportunities, and give advice to either aim for or steer clear of their own lines of work. In the end, do their children end up in the same type of job? Do siblings choose the same occupation? And is this more or less true for different professions? To study these questions, we analyzed in aggregate two related sets of de-identified Facebook data: one a sample of siblings' choices of profession, and the other of parent-child choices. The sample included those pairs of individuals in English-speaking locales who specified a sibling or parent-child relationship on Facebook, along with filling in their occupations. The occupations were mapped to major occupation categories 1. The military occupation category is over-represented because it is mapped based on both employer and stated occupation and past military service, whereas other job categories were mapped based on stated occupation only. Since the data excludes those not specifying an occupation on Facebook, it may not be representative of the population overall, but is interesting to study nonetheless.

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原文链接：https://research.facebook.com/blog/do-jobs-run-in-families-/

Revisiting Street Intersections Using Slot-Based Systems

March 17, 1:05 PM
From Revisiting Street Intersections Using Slot-Based Systems. PLoS ONE 11(3): e0149607.
By Tachet R, Santi P, Sobolevsky S, Reyes-Castro LI, Frazzoli E, Helbing D, et al.
(Translated by -)

Since their appearance at the end of the 19th century, traffic lights have been the primary mode of granting access to road intersections. Today, this centuries-old technology is challenged by advances in intelligent transportation, which are opening the way to new solutions built upon slot-based systems similar to those commonly used in aerial traffic: what we call Slot-based Intersections (SIs). Despite simulation-based evidence of the potential benefits of SIs, a comprehensive, analytical framework to compare their relative performance with traffic lights is still lacking. Here, we develop such a framework. We approach the problem in a novel way, by generalizing classical queuing theory. Having defined safety conditions, we characterize capacity and delay of SIs. In the 2-road crossing configuration, we provide a capacity-optimal SI management system. For arbitrary intersection configurations, near-optimal solutions are developed. Results theoretically show that transitioning from a traffic light system to SI has the potential of doubling capacity and significantly reducing delays. This suggests a reduction of non-linear dynamics induced by intersection bottlenecks, with positive impact on the road network. Such findings can provide transportation engineers and planners with crucial insights as they prepare to manage the transition towards a more intelligent transportation infrastructure in cities.

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原文链接：http://dx.doi.org/10.1371/journal.pone.0149607 Complexity Digest's insight: See Also: http://senseable.mit.edu/light-traffic/

Policy:urban physics

March 18, 10:10 AM
From Nature 531, S64–S66 (17 March 2016)
By Kevin Pollock
(Translated by -)

Cities are complex environments. Planning interventions that borrow principles from theoretical physics could help to improve peoples' lives.

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原文链接：http://dx.doi.org/10.1038/531S64a

Living factories of the future

March 18, 6:01 PM
From Nature 531, 401–403 (17 March 2016)
By Michael Eisenstein
(Translated by -)

Scientists are designing cells that can manufacture drugs, food and materials — and even act as diagnostic biosensors. But first they must agree on a set of engineering tools.

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原文链接：http://dx.doi.org/10.1038/531401a

Age of Entanglement

March 18, 8:42 PM
From jods.mitpress.mit.edu
By Neri Oxman
(Translated by -)

This essay proposes a map for four domains of creative exploration—Science, Engineering, Design and Art—in an attempt to represent the antidisciplinary hypothesis: that knowledge can no longer be ascribed to, or produced within, disciplinary boundaries, but is entirely entangled. The goal is to establish a tentative, yet holistic, cartography of the interrelation between these domains, where one realm can incite ®evolution inside another; and where a single individual or project can reside in multiple dominions. Mostly, this is an invitation to question and to amend what is being proposed.

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原文链接：http://jods.mitpress.mit.edu/pub/AgeOfEntanglement

If the World Began Again, Would Life as We Know It Exist?

March 18, 12:13 PM
From nautil.us
By
(Translated by -)

Experiments in evolution are exploring what would happen if we rewound the tape of life.

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原文链接：http://nautil.us/issue/34/adaptation/if-the-world-began-again-would-life-as-we-know-it-exist-rp

How Do You Say “Life” in Physics?

March 19, 10:29 AM
From nautil.us
By
(Translated by -)

We think we know life when we see it. Darwin’s theory even explains how one form of life evolves into another. But what is the difference between a robin and a rock, when both obey the same physical laws? In other words, how do you say “life” in physics? Some have argued that the word is untranslatable. But maybe it simply needed the right translator.

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原文链接：http://nautil.us/issue/34/adaptation/how-do-you-say-life-in-physics

Design and Science

March 20, 8:44 PM
From jods.mitpress.mit.edu
By Joichi Ito
(Translated by -)

For me, antidisciplinary research is akin to mathematician Stanislaw Ulam’s famous observation that the study of nonlinear physics is like the study of “non-elephant animals.” Antidisciplinary is all about the non-elephant animals.I believe that by bringing together design and science we can produce a rigorous but flexible approach that will allow us to explore, understand and contribute to science in an antidisciplinary way.

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原文链接：http://jods.mitpress.mit.edu/pub/designandscience

Cell Fate Reprogramming by Control of Intracellular Network Dynamics

March 22, 6:07 PM
From PLoS Comput Biol 11(4): e1004193.
By Zañudo JGT, Albert R
(Translated by -)

Practical applications in modern molecular and systems biology such as the search for new therapeutic targets for diseases and stem cell reprogramming have generated a great interest in controlling the internal dynamics of a cell. Here we present a network control approach that integrates the structural and functional information of the network. We show that stabilizing the expression or activity of a few select components can drive the cell towards a desired fate or away from an undesired fate. We demonstrate our method’s effectiveness by applying it to a type of blood cell cancer and to the differentiation of a type of immune cell. Overall, our approach provides new insights into how to control the dynamics of intracellular networks.

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原文链接：http://dx.doi.org/10.1371/journal.pcbi.1004193

Military Strategy in a Complex World

March 23, 12:29 PM
From www.necsi.edu
By Dominic K. Albino, Katriel Friedman, Yaneer Bar-Yam, William Glenney
(Translated by -)

A strategy is a plan, method, or series of actions for obtaining a specified goal. A military strategy typically employs the threat or use of military force to advance goals in opposition to an adversary, and is called upon where large scale force is viewed as the way to achieve such goals. Strategic thinking is traditionally focused on which part or combination of land, air, and naval forces is most effective. This may be too narrow an approach to accomplishing the ultimate end, which is generally political influence or control—or preventing influence or control by others—and almost never consists of physical destruction itself. In order to broaden the discussion of military strategy, we consider here three distinct effects of inflicting stress on an opponent: a) A fragile system is damaged—possibly catastrophically, b) A robust system is largely unaffected, retaining much or all of its prior strength, c) Some systems actually gain strength, a property which has recently been termed antifragility. Traditional perspectives of military strategy implicitly assume fragility, limiting their validity and resulting in surprise, and assume a specific end state rather than an overall condition of the system as a goal. Robustness and antifragility are relevant both to offense, in attacks against the enemy, and defense, in meeting attacks against one’s own forces. While robustness and antifragility are desirable in friendly systems, an enemy possessing these characteristics undermines the premise that an attack will achieve a desired increase in control. Historical and contemporary examples demonstrate the failure of traditional strategies against antifragile enemies—even devastating damage inflicted upon nations or other organizations did not weaken and defeat them, but rather strengthened them, resulting in their victory. Underlying such successful responses are socio-economic or political strengths. Our discussion is a basis for scientific analysis of the historical and contemporary conditions under which distinct types of strategies will be successful and provides guidance to improved strategic thinking.

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原文链接：http://www.necsi.edu/research/military/strategy.html

How Diversity Makes Us Smarter

March 23, 2:34 PM
From www.scientificamerican.com
By Katherine W. Phillips
(Translated by -)

Decades of research by organizational scientists, psychologists, sociologists, economists and demographers show that socially diverse groups (that is, those with a diversity of race, ethnicity, gender and sexual orientation) are more innovative than homogeneous groups.It seems obvious that a group of people with diverse individual expertise would be better than a homogeneous group at solving complex, nonroutine problems. It is less obvious that social diversity should work in the same way—yet the science shows that it does.This is not only because people with different backgrounds bring new information. Simply interacting with individuals who are different forces group members to prepare better, to anticipate alternative viewpoints and to expect that reaching consensus will take effort.

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原文链接：http://www.scientificamerican.com/article/how-diversity-makes-us-smarter/

The impact of social networks on leadership behaviour

March 23, 12:37 PM
From mio.sagepub.com
By
(Translated by -)

Dominant streams in leadership literature conceptualise it either as a role within sociopolitical structure or as a behavioural predisposition of agents. In this article, a number of hypotheses are tested via an empirical case study where interaction and affiliation networks across multiple decision experiments are coupled with attribute and psychometric data of the actors.  Findings suggest that in egalitarian political systems, centrality in social networks is directly associated with political success, while in political systems imbued with power inequalities successful actors are idiocentric brokers. The use of attitudinal micro-surveys, psychometric tests, observation and relational surveys is combined for a comprehensive mapping of group dynamics suited to questions of agency.

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原文链接：http://mio.sagepub.com/content/9/2059799116630649.full

Unveiling causal activity of complex networks

March 23, 6:34 PM
From arxiv.org
By Rashid V. Williams-Garcia, John M. Beggs, Gerardo Ortiz
(Translated by -)

We introduce a novel tool for analyzing complex network dynamics, allowing for cascades of causally-related events, which we call causal webs (c-webs for short), to be separated from other activity. In the context of neural networks, c-webs represent a new, emergent dynamical degree of freedom which highlights the effective network connectivity, in contrast with the oft-used degrees of freedom, neuronal avalanches. By identifying non-causal activity, our method can also be used to characterize dynamical disorder in complex networks. Using this method, we reveal causally-related activity from experimental data with statistics which may support quasicriticality in the brain.

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原文链接：http://arxiv.org/abs/1603.05659

Human judgment vs. theoretical models for the management of ecological resources

From arxiv.org
March 24, 6:39 PM
By Matthew Holden, Stephen Ellner
(Translated by -)

Despite major advances in quantitative approaches to natural resource management, there has been resistance to using these tools in the actual practice of managing ecological populations. Given a managed system and a set of assumptions, translated into a model, optimization methods can be used to solve for the most cost effective management actions. However, when the underlying assumptions are not met, such methods can potentially lead to poor decisions. Managers who develop decisions based on past experience and judgment, without the aid of mathematical models, can potentially learn about the system and develop flexible management strategies. However, these strategies are often based on subjective criteria and equally invalid and often unstated assumptions. Given the drawbacks of both methods, it is unclear whether simple quantitative models improve environmental decision making over expert opinion. In this paper, we explore how well students, using their experience and judgment, manage simulated fishery populations in an online computer game and compare their management outcomes to the performance of model-based decisions. We consider harvest decisions generated using four different quantitative models: 1. the model used to produce the simulated population dynamics observed in the game, with all underlying parameter values known [a control], 2. the same model, but with unknown parameter values that must be estimated during the game from observed data, 3. models that are structurally different from those used to simulate the population dynamics and 4. a model that ignores age structure. Humans on average performed much worse than the models in cases 1 - 3. When the models ignored age structure, they generated poorly performing management decisions, but still outperformed students using experience and judgment 66 percent of the time.

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原文链接：http://arxiv.org/abs/1603.04518

Fetishizing Food in Digital Age: #foodporn Around the World

From arxiv.org
March 23, 8:31 PM
By Yelena Mejova, Sofiane Abbar, Hamed Haddadi

What food is so good as to be considered pornographic? Worldwide, the popular #foodporn hashtag has been used to share appetizing pictures of peoples' favorite culinary experiences. But social scientists ask whether #foodporn promotes an unhealthy relationship with food, as pornography would contribute to an unrealistic view of sexuality. In this study, we examine nearly 10 million Instagram posts by 1.7 million users worldwide. An overwhelming (and uniform across the nations) obsession with chocolate and cake shows the domination of sugary dessert over local cuisines. Yet, we find encouraging traits in the association of emotion and health-related topics with #foodporn, suggesting food can serve as motivation for a healthy lifestyle. Social approval also favors the healthy posts, with users posting with healthy hashtags having an average of 1,000 more followers than those with unhealthy ones. Finally, we perform a demographic analysis which shows nation-wide trends of behavior, such as a strong relationship (r=0.51) between the GDP per capita and the attention to healthiness of their favorite food. Our results expose a new facet of food "pornography", revealing potential avenues for utilizing this precarious notion for promoting healthy lifestyles.

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原文链接： http://arxiv.org/abs/1603.00229

Homophily, influence and the decay of segregation in self-organizing networks

From Network Science / Volume 4 / Issue 01 / March 2016, pp 81-116
March 24, 6:56 PM
By ADAM DOUGLAS HENRY, DIETER MITSCHE and PAWEŁ PRAŁAT

We study the persistence of network segregation in networks characterized by the co-evolution of vertex attributes and link structures, in particular where individual vertices form linkages on the basis of similarity with other network vertices (homophily), and where vertex attributes diffuse across linkages, making connected vertices more similar over time (influence). A general mathematical model of these processes is used to examine the relative influence of homophily and influence in the maintenance and decay of network segregation in self-organizing networks. While prior work has shown that homophily is capable of producing strong network segregation when attributes are fixed, we show that adding even minute levels of influence is sufficient to overcome the tendency towards segregation even in the presence of relatively strong homophily processes. This result is proven mathematically for all large networks and illustrated through a series of computational simulations that account for additional network evolution processes. This research contributes to a better theoretical understanding of the conditions under which network segregation and related phenomenon—such as community structure—may emerge, which has implications for the design of interventions that may promote more efficient network structures.

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原文链接： http://dx.doi.org/10.1017/nws.2016.1

Fetishizing Food in Digital Age: #foodporn Around the World

From arxiv.org
March 23, 8:31 PM
By Yelena Mejova, Sofiane Abbar, Hamed Haddadi

What food is so good as to be considered pornographic? Worldwide, the popular #foodporn hashtag has been used to share appetizing pictures of peoples' favorite culinary experiences. But social scientists ask whether #foodporn promotes an unhealthy relationship with food, as pornography would contribute to an unrealistic view of sexuality. In this study, we examine nearly 10 million Instagram posts by 1.7 million users worldwide. An overwhelming (and uniform across the nations) obsession with chocolate and cake shows the domination of sugary dessert over local cuisines. Yet, we find encouraging traits in the association of emotion and health-related topics with #foodporn, suggesting food can serve as motivation for a healthy lifestyle. Social approval also favors the healthy posts, with users posting with healthy hashtags having an average of 1,000 more followers than those with unhealthy ones. Finally, we perform a demographic analysis which shows nation-wide trends of behavior, such as a strong relationship (r=0.51) between the GDP per capita and the attention to healthiness of their favorite food. Our results expose a new facet of food "pornography", revealing potential avenues for utilizing this precarious notion for promoting healthy lifestyles.

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原文链接：http://dx.doi.org/10.1017/nws.2016.1

Selection and influence in cultural dynamics

From Network Science / Volume 4 / Issue 01 / March 2016, pp 1-27
March 24, 8:58 PM
By DAVID KEMPE, JON KLEINBERG, SIGAL OREN and ALEKSANDRS SLIVKINS

One of the fundamental principles driving diversity or homogeneity in domains such as cultural differentiation, political affiliation, and product adoption is the tension between two forces: influence (the tendency of people to become similar to others they interact with) and selection (the tendency to be affected most by the behavior of others who are already similar). Influence tends to promote homogeneity within a society, while selection frequently causes fragmentation. When both forces act simultaneously, it becomes an interesting question to analyze which societal outcomes should be expected. To study this issue more formally, we analyze a natural stylized model built upon active lines of work in political opinion formation, cultural diversity, and language evolution. We assume that the population is partitioned into “types” according to some traits (such as language spoken or political affiliation). While all types of people interact with one another, only people with sufficiently similar types can possibly influence one another. The “similarity” is captured by a graph on types in which individuals of the same or adjacent types can influence one another. We achieve an essentially complete characterization of (stable) equilibrium outcomes and prove convergence from all starting states. We also consider generalizations of this model.

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原文链接：http://dx.doi.org/10.1017/nws.2015.36

Fetishizing Food in Digital Age: #foodporn Around the World

From arxiv.org
March 23, 8:31 PM
By Yelena Mejova, Sofiane Abbar, Hamed Haddadi

What food is so good as to be considered pornographic? Worldwide, the popular #foodporn hashtag has been used to share appetizing pictures of peoples' favorite culinary experiences. But social scientists ask whether #foodporn promotes an unhealthy relationship with food, as pornography would contribute to an unrealistic view of sexuality. In this study, we examine nearly 10 million Instagram posts by 1.7 million users worldwide. An overwhelming (and uniform across the nations) obsession with chocolate and cake shows the domination of sugary dessert over local cuisines. Yet, we find encouraging traits in the association of emotion and health-related topics with #foodporn, suggesting food can serve as motivation for a healthy lifestyle. Social approval also favors the healthy posts, with users posting with healthy hashtags having an average of 1,000 more followers than those with unhealthy ones. Finally, we perform a demographic analysis which shows nation-wide trends of behavior, such as a strong relationship (r=0.51) between the GDP per capita and the attention to healthiness of their favorite food. Our results expose a new facet of food "pornography", revealing potential avenues for utilizing this precarious notion for promoting healthy lifestyles.

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原文链接： http://dx.doi.org/10.1017/nws.2015.36

The classical origin of modern mathematics

From arxiv.org
March 25, 6:36 PM
By Floriana Gargiulo, Auguste Caen, Renaud Lambiotte, Timoteo Carletti

The aim of this paper is to study the historical evolution of mathematical thinking and its spatial spreading. To do so, we have collected and integrated data from different online academic datasets. In its final stage, the database includes a large number (N~200K) of advisor-student relationships, with affiliations and keywords on their research topic, over several centuries, from the 14th century until today. We focus on two different topics, the evolving importance of countries and of the research disciplines over time. Moreover we study the database at three levels, its global statistics, the mesoscale networks connecting countries and disciplines, and the genealogical level.

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原文链接：http://arxiv.org/abs/1603.06371

Special Operations Forces

From arXiv:1602.05474v2 (February 18, 2016).
March 25, 12:30 PM
By Joseph Norman, Yaneer Bar-Yam

The use of special operations forces (SOF) in war fighting and peace keeping efforts has increased dramatically in recent decades. A scientific understanding of the reason for this increase would provide guidance as to the contexts in which SOF can be used to their best effect. Ashby's law of requisite variety provides a scientific framework for understanding and analyzing a system's ability to survive and prosper in the face of environmental challenges. We have developed a generalization of this law to extend the analysis to systems that must respond to disturbances at multiple scales. This analysis identifies a necessary tradeoff between scale and complexity in a multiscale control system. As with Ashby's law, the framework applies to the characterization of successful biological and social systems in the context of complex environmental challenges. Here we apply this multiscale framework to provide a control theoretic understanding of the historical and increasing need for SOF, as well as conventional military forces. We propose that the essential role distinction is in the separation between high complexity fine scale challenges as opposed to large scale challenges. This leads to a correspondence between the role SOF can best serve and that of the immune system in complex organisms--namely, the ability to respond to fine-grained, high-complexity disruptors and preserve tissue health. Much like a multicellular organism, human civilization is composed of a set of distinct and heterogeneous social tissues. Responding to disruption and restoring health in a system with highly diverse local social conditions is an essentially complex task. SOF have the potential to mitigate against harm without disrupting normal social tissue behavior. This analysis suggests how SOF might be leveraged to support global stability and mitigate against cascading crises.

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原文链接：http://www.necsi.edu/research/military/sof.html

Corruption corrupts

From Nature 531, 456–457 (24 March 2016)
March 26, 7:00 AM
By Shaul Shalvi

A cross-cultural experiment involving thousands of people worldwide shows that the prevalence of rule violations in a society, such as tax evasion and fraudulent politics, is detrimental to individuals' intrinsic honesty.

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原文链接：http://dx.doi.org/10.1038/nature17307

Design and synthesis of a minimal bacterial genome

From Science 25 Mar 2016:Vol. 351, Issue 6280
March 27, 12:24 PM
By Clyde A. Hutchison III, et al.

The minimal cell concept appears simple at first glance but becomes more complex upon close inspection. In addition to essential and nonessential genes, there are many quasi-essential genes, which are not absolutely critical for viability but are nevertheless required for robust growth. Consequently, during the process of genome minimization, there is a trade-off between genome size and growth rate. JCVI-syn3.0 is a working approximation of a minimal cellular genome, a compromise between small genome size and a workable growth rate for an experimental organism. It retains almost all the genes that are involved in the synthesis and processing of macromolecules. Unexpectedly, it also contains 149 genes with unknown biological functions, suggesting the presence of undiscovered functions that are essential for life. JCVI-syn3.0 is a versatile platform for investigating the core functions of life and for exploring whole-genome design.

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原文链接：DOI: 10.1126/science.aad6253

Analysis and valuation of the health and climate change cobenefits of dietary change

From www.pnas.org
March 28, 8:06 PM
By Marco Springmann, H. Charles J. Godfray, Mike Rayner, and Peter Scarborough

The food system is responsible for more than a quarter of all greenhouse gas emissions while unhealthy diets and high body weight are among the greatest contributors to premature mortality. Our study provides a comparative analysis of the health and climate change benefits of global dietary changes for all major world regions. We project that health and climate change benefits will both be greater the lower the fraction of animal-sourced foods in our diets. Three quarters of all benefits occur in developing countries although the per capita impacts of dietary change would be greatest in developed countries. The monetized value of health improvements could be comparable with, and possibly larger than, the environmental benefits of the avoided damages from climate change.

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原文链接：http://dx.doi.org/ 10.1073/pnas.1523119113

The standard map: From Boltzmann-Gibbs statistics to Tsallis statistics

From Scientific Reports 6, Article number: 23644 (2016)
March 29, 5:52 PM
By Ugur Tirnakli & Ernesto P. Borges

As well known, Boltzmann-Gibbs statistics is the correct way of thermostatistically approaching ergodic systems. On the other hand, nontrivial ergodicity breakdown and strong correlations typically drag the system into out-of-equilibrium states where Boltzmann-Gibbs statistics fails. For a wide class of such systems, it has been shown in recent years that the correct approach is to use Tsallis statistics instead. Here we show how the dynamics of the paradigmatic conservative (area-preserving) stan-dard map exhibits, in an exceptionally clear manner, the crossing from one statistics to the other. Our results unambiguously illustrate the domains of validity of both Boltzmann-Gibbs and Tsallis statistical distributions. Since various important physical systems from particle confinement in magnetic traps to autoionization of molecular Rydberg states, through particle dynamics in accelerators and comet dynamics, can be reduced to the standard map, our results are expected to enlighten and enable an improved interpretation of diverse experimental and observational results.

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原文链接：http://dx.doi.org/10.1038/srep23644

Heterogeneity of Global and Local Connectivity in Spatial Network Structures of World Migration

From arxiv.org
March 31, 3:04 PM
By Valentin Danchev, Mason A. Porter

We examine world migration as a social-spatial network of countries connected via movements of people. We assess how multilateral migratory relationships at global, regional, and local scales coexist ("glocalization"), divide ("polarization"), or form an interconnected global system ("globalization"). To do this, we decompose the world migration network (WMN) into communities---sets of countries with denser than expected migration connections---and characterize their pattern of local (i.e., intracommunity) and global (i.e., intercommunity) connectivity. We distinguish community signatures---"cave", "biregional", and "bridging"---with distinct migration patterns, spatial network structures, temporal dynamics, and underlying antecedents. Cave communities are tightly-knit, enduring structures that tend to channel local migration between contiguous countries; biregional communities are likely to merge migration between two distinct geographic regions (e.g., North Africa and Europe); and bridging communities have hub-and-spoke structures that tend to emerge dynamically from globe-spanning movements. We find that world migration is neither globally interconnected nor reproduces the geographic boundaries as drawn on a world map but involves a heterogeneous interplay of global and local tendencies in different network regions. We discuss the implications of our results for the understating of variability in today's transnational mobility patterns and migration opportunities across the globe.

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原文链接：http://arxiv.org/abs/1603.09313

Dynamics of a population of oscillatory and excitable elements

From arxiv.org
March 31, 4:30 PM
By Kevin P. O'Keeffe, Steven H. Strogatz

We analyze a variant of a model proposed by Kuramoto, Shinomoto, and Sakaguchi for a large population of coupled oscillatory and excitable elements. Using the Ott-Antonsen ansatz, we reduce the behavior of the population to a two-dimensional dynamical system with three parameters. We present the stability diagram and calculate several of its bifurcation curves analytically, for both excitatory and inhibitory coupling. Our main result is that when the coupling function is broad, the system can display bistability between steady states of constant high and low activity, whereas when the coupling function is narrow and inhibitory, one of the states in the bistable regime can show persistent pulsations in activity.

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原文链接：http://arxiv.org/abs/1603.08803

The Death and Life of Great Italian Cities: A Mobile Phone Data Perspective

From arxiv.org
March 31, 8:36 PM
By Marco De Nadai, Jacopo Staiano, Roberto Larcher, Nicu Sebe, Daniele Quercia, Bruno Lepri

The Death and Life of Great American Cities was written in 1961 and is now one of the most influential book in city planning. In it, Jane Jacobs proposed four conditions that promote life in a city. However, these conditions have not been empirically tested until recently. This is mainly because it is hard to collect data about "city life". The city of Seoul recently collected pedestrian activity through surveys at an unprecedented scale, with an effort spanning more than a decade, allowing researchers to conduct the first study successfully testing Jacobs's conditions. In this paper, we identify a valuable alternative to the lengthy and costly collection of activity survey data: mobile phone data. We extract human activity from such data, collect land use and socio-demographic information from the Italian Census and Open Street Map, and test the four conditions in six Italian cities. Although these cities are very different from the places for which Jacobs's conditions were spelled out (i.e., great American cities) and from the places in which they were recently tested (i.e., the Asian city of Seoul), we find those conditions to be indeed associated with urban life in Italy as well. Our methodology promises to have a great impact on urban studies, not least because, if replicated, it will make it possible to test Jacobs's theories at scale.

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原文链接：http://arxiv.org/abs/1603.04012

Phase transitions and hysteresis of cooperative contagion processes

From arxiv.org
March 31, 6:33 PM
By Li Chen, Fakhteh Ghanbarnejad, Dirk Brockmann
We investigate the effects of cooperation between two interacting infectious diseases that spread and stabilize in a host population. We propose a model in which individuals that are infected with one disease are more likely to acquire the second disease, both diseases following the susceptible-infected-susceptible reaction scheme. We analyze cooperative coinfection in stochastic network models as well as the idealized, well-mixed mean field system and show that cooperative mechanisms dramatically change the nature of phase transitions compared to single disease dynamics. We show that, generically, cooperative coinfection exhibits discontinuous transitions from the disease free to high prevalence state when a critical transmission rate is crossed. Furthermore, cooperative coinfection exhibits two distinct critical points, one for outbreaks the second one for eradication that can be substantially lower. This implies that cooperative coinfection exhibits hysteresis in its response to changing effective transmission rates or equivalently the basic reproduction number. We compute these critical parameters as a function of a cooperativity coefficient in the well-mixed mean field system. We finally investigate a spatially extended version of the model and show that cooperative interactions between diseases change the general wave propagation properties of conventional spreading phenomena of single diseases. The presented work may serve as a starting and reference point for a more comprehensive understanding of interacting diseases that spread in populations.

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原文链接：http://arxiv.org/abs/1603.09082

Can a video game company tame toxic behaviour?

From www.nature.com
March 31, 10:11 PM
By
Scientists are helping to stop antisocial behaviour in the world's most popular online game. The next stop could be a kinder Internet.

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原文链接：http://www.nature.com/news/can-a-video-game-company-tame-toxic-behaviour-1.19647