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Issue linkage is often advocated as a powerful mechanism to encourage cooperation on issues where free-riding incentives are significant. The basic idea is to link cooperation on such issues with cooperation on issues that provide (partially) excludable benefits and are therefore less susceptible to free-riding. In this paper, we take a coalition formation approach and study the effects of issue linkage on overall cooperation levels and welfare. We show that, when the linked issues are independent, issue linkage is not necessarily welfare improving; in fact, unless the less critical issue is almost perfectly excludable, issue linkage leads to a welfare loss. By contrast, a generalized enlargement of cooperation and an increase in welfare are obtainable when the linked issues are "complements". Using concepts from network theory, we further provide insights into the design of cost-effective (minimally connected) linkage architectures when more than two issues are at stake. [ABSTRACT FROM AUTHOR]

This paper examines experimentally how reputational uncertainty and the rate of change of the social environment determine cooperation. Reputational uncertainty significantly decreases cooperation, while a fast-changing social environment only causes a second-order qualitative increase in cooperation. At the individual level, reputational uncertainty induces more leniency and forgiveness in imposing network punishment through the link proposal and removal processes, inhibiting the formation of cooperative clusters. However, this effect is significant only in the fast-changing environment and not in the slow-changing environment. A substitution pattern between network punishment and action punishment (retaliatory defection) explains this discrepancy across the two social environments. [ABSTRACT FROM AUTHOR]

We consider a fixed network of players endowed with idiosyncratic preferences over actions and involved in interactions of various types. The aim is to investigate the interplay between idiosyncratic preferences and interactional incentives on a network. The earlier literature demonstrated the conflict between players' intrinsic preferences and coordination incentives. This paper shows that such a conflict is also present in contexts in which players do not necessarily aim at coordination with their peers. The introduction of action preferences changes equilibrium outcomes in a non-trivial fashion: some equilibria disappear, while other, qualitatively new ones, appear. We characterize equilibria for a large class of games, including games of strategic complements and strategic substitutes, and outline a subclass with a unique equilibrium in which all players follow their idiosyncratic action preferences. This equilibrium is Pareto optimal and for many games is also a unique efficient profile. [ABSTRACT FROM AUTHOR]

Several approaches and techniques exist to resolve load balancing problem in general and torus topology networks. Graph methods are natural ways to perform balancing of routing paths. A routing balancing algorithm must operate within the constraints of the underlying network architecture that limits several parameters, such as the number of logical paths in the network. In this paper, we consider a torus topology that is one of the common topologies that are used in high performance computing systems. We introduce a routing graph that corresponds to a interconnect topology, abstracts interconnect routing rules, providing one-to-one correspondence of network routes and graph paths. We propose a deadlock-free routing algorithm based on a fast single-source shortest path algorithm in a routing graph for the deterministic routing of a torus topology interconnect with a single virtual channel. The proposed algorithm is a tradeoff between two existing routing algorithms, also the algorithm is optimized for multidimensional torus topology and can be applied to any torus topology HPC system. We present a complete description of a routing graph that abstracts the Angara interconnect with 4D torus topology. We evaluated the proposed routing algorithm and benchmarked the maximum performance improvement of 71% for the Alltoall pattern for torus topology systems up to 432 nodes on the Angara interconnect simulator. The performance improvement of more than 5% was obtained for the NPB FT and IS application kernels on a 32-node supercomputer. • A routing graph abstracts network routing rules. • A deadlock-free routing algorithm is based on a fast single-source shortest path algorithm and optimized for a torus topology. • A routing graph for the Angara network reflects the restrictions on a further packet route with the previous route steps in mind. • The maximum performance improvement is 71% for the Alltoall pattern on the simulated torus topology systems up to 432 nodes. • The performance improvement on the 32-node Angara based cluster is 5% for the NPB FT and IS application kernels. [ABSTRACT FROM AUTHOR]

This research explores the networks of technological knowledge that influenced changes in the iron production practices of western Uganda in the second half of the second millennium AD. Temporal and spatial variability in technological processes were observed within the research area, in terms of the style and construction of the furnaces, the use of a manganese-rich flux, and the configuration of tuyères. These shifts were considered in relation to the social dimensions of iron production, specifically the protection of technical knowledge. Informed by ethnographic data from the study area, variations were noted in the participation in, or exclusion from, iron production activity on the basis of gender and clan affiliation. This stands in contrast to ethno-historic accounts that speak of a strongly regulated production environment. This paper considers that an uncritical emphasis on conservatism provides an inadequate framework for addressing long-term change in iron production technologies. It suggests that constellations of knowledge in western Uganda fostered the potential for innovation and experimentation, resulting in dynamic technological practice. This paper urges a more nuanced discussion of how complex metallurgical technologies transform and move within cultural and physical landscapes, with ramifications for how we conceptualize the emergence and adoption of early technologies. [ABSTRACT FROM AUTHOR]

How does the structure of an organization affect corruption? This paper analyzes a model that views organizations as networks on which coalitions of corrupt accomplices may form. This network approach to corruption provides new insights into the problem: (i) corruption will arise in enclaves, i.e. coalitions that minimize joint exposure to witnesses, (ii) making the organization more connected may increase corruption, and (iii) corruption will involve larger coalitions under better monitoring. Simulation results also suggest that more hierarchical organizations are more corrupt than flatter organizations. I test these predictions in the lab. Results confirm the predictions and reveal a systematic deviation that has implications for why better monitoring reduces corruption: participants disproportionately fail to realize larger coalitions, which are more necessary under good monitoring. Results suggest it would be sensible to redesign public agencies to puncture the isolation of enclaves. [ABSTRACT FROM AUTHOR]

This paper studies fictitious play in networks of noncooperative two-person games. We show that continuous-time fictitious play converges to the set of Nash equilibria if the overall n -person game is zero-sum. Moreover, the rate of convergence is 1 / τ , regardless of the size of the network. In contrast, arbitrary n -person zero-sum games with bilinear payoff functions do not possess the continuous-time fictitious-play property. As extensions, we consider networks in which each bilateral game is either strategically zero-sum, a weighted potential game, or a two-by-two game. In those cases, convergence requires a condition on bilateral payoffs or, alternatively, that the network is acyclic. Our results hold also for the discrete-time variant of fictitious play, which implies, in particular, a generalization of Robinson's theorem to arbitrary zero-sum networks. Applications include security games, conflict networks, and decentralized wireless channel selection. [ABSTRACT FROM AUTHOR]

This paper provides an in-depth understanding of social dynamics in the form of kinship ties in matrilineal societies. It unpacks gender roles and relationships at the community level to understand how social structures, created by the pattern of relations, enhance or hinder coping initiatives during lake recessions in the Lake Chilwa socio-ecological system. Using qualitative and quantitative methods including in-depth interviews, Focus Group Discussions (FGD) and household questionnaires, this paper provides insights into how people in the Lake Chilwa social-ecological system prepare for and cope with Lake Chilwa water recessions by capitalising on their social networks. The findings have shown that during lake recessions poor households in the Lake Chilwa socio-ecological system are cushioned by fellow households through lineage networks. There is strong tradition secured through kinship ties where the generic term ‘mwambo wathu’ (our tradition) embraces a group of formative norms enforced via a series of rules and rituals. Based in a matrilineal system, women have strong rights over land allocation and use in which the female sorority group ‘mbumba’ is very stable. There is a great deal of reciprocity and food redistribution among the households. This self-organization provides deeper meaning about how people assimilate the dynamics affecting their social and natural environments. Specifically the findings provide evidence on how households, communities and their livelihoods in Africa are reconstructed as natural resources fluctuate. [ABSTRACT FROM AUTHOR]

Abstract Geometric gradient flows for elastic energies of Willmore type play an important role in mathematics and in many applications. The evolution of elastic curves has been studied in detail both for closed as well as for open curves. Although elastic flows for networks also have many interesting features, they have not been studied so far from the point of view of mathematical analysis. So far it was not even clear what are appropriate boundary conditions at junctions. In this paper we give a well-posedness result for Willmore flow of networks in different geometric settings and hence lay a foundation for further mathematical analysis. A main point in the proof is to check whether different proposed boundary conditions lead to a well posed problem. In this context one has to check the Lopatinskii–Shapiro condition in order to apply the Solonnikov theory for linear parabolic systems in Hölder spaces which is needed in a fixed point argument. We also show that the solution we get is unique in a purely geometric sense. [ABSTRACT FROM AUTHOR]

Abstract In this paper two cost sharing solutions for minimum cost spanning tree problems are introduced, the degree adjusted folk solution and the cost adjusted folk solution. These solutions overcome the problem of the classical reductionist folk solution as they have considerable strict ranking power, without breaking established axioms. As such they provide an affirmative answer to an open question, put forward in Bogomolnaia and Moulin (2010). [ABSTRACT FROM AUTHOR]

This paper investigates the welfare effect of income redistribution in the private provision of public goods on networks. We first show that the welfare effect of income redistribution is determined by Bonacich centrality. Then we develop an index based on the network structure of interactions, which, roughly speaking, measures the welfare effect of income redistribution confined to a component of contributors. The proposed index vanishes when applied to large components of contributors that display special segregated interactions, which suggests an “asymptotic neutrality” of redistributive policies. [ABSTRACT FROM AUTHOR]

The paper analyzes the optimal targeting strategies of a planner (a governmental agency, a firm) who aims to increase the aggregate action of a population. The agents interact through a social network and react to their exposure to neighbors' actions. The reaction function describes, for example, the best response in a strategic game, a mechanical influence in a contagion disease or a mimetic behavior. The reaction is assumed to be increasing in exposure, resulting in complementarity in actions. When it is linear, the optimal planner's strategies are explicit, characterized by well-known centralities indices computed on the bilateral impacts. When the reaction function is concave or convex, the optimal strategies depend not only on the impacts but also on the pattern of agents' attentions. The value of information on the interaction structure is shown to be (almost always) positive and related to some form of heterogeneity between agents. [ABSTRACT FROM AUTHOR]

The study of functional connectivity using magnetoencephalography (MEG) is an expanding area of neuroimaging, and adds an extra dimension to the more common assessments made using fMRI. The importance of such metrics is growing, with recent demonstrations of their utility in clinical research, however previous reports suggest that whilst group level resting state connectivity is robust, single session recordings lack repeatability. Such robustness is critical if MEG measures in individual subjects are to prove clinically valuable. In the present paper, we test how practical aspects of experimental design affect the intra-subject repeatability of MEG findings; specifically we assess the effect of co-registration method and data recording duration. We show that the use of a foam head-cast, which is known to improve co-registration accuracy, increased significantly the between session repeatability of both beamformer reconstruction and connectivity estimation. We also show that recording duration is a critical parameter, with large improvements in repeatability apparent when using ten minute, compared to five minute recordings. Further analyses suggest that the origin of this latter effect is not underpinned by technical aspects of source reconstruction, but rather by a genuine effect of brain state; short recordings are simply inefficient at capturing the canonical MEG network in a single subject. Our results provide important insights on experimental design and will prove valuable for future MEG connectivity studies. [ABSTRACT FROM AUTHOR]

While, in theory, the school matching problem is a static non-cooperative one-shot game, in reality the “matching game” is played by parents who choose their strategies after consulting or chatting with other parents in their social networks. In this paper we compare the performance of the Boston and the Gale–Shapley mechanisms in the presence of chatting through social networks. Our results indicate that allowing subjects to chat has an important impact on the likelihood that subjects change their strategies and also on the welfare and stability of the outcomes determined by the mechanism. [ABSTRACT FROM AUTHOR]

Increasing concerns about climate change have given rise to the formation of International Environmental Agreements (IEAs) as a possible solution to limit global pollution effects. In this paper, we study the stability of IEAs in a repeated game framework where we restrict to strategies which are simple and invariant to renegotiation. Our main contribution is that we characterize necessary and sufficient conditions for stability of an IEA when pollution has both a global and local effect. Local pollution spillovers are represented by a network structure. We find that stable IEAs exist if the network structure is balanced. Too large asymmetries in the degree of local spillovers may, however, lead to non-existence of stable structures. We also discuss the implications of our results for welfare. The generality of our approach allows for several applications, in particular the provision of public goods. [ABSTRACT FROM AUTHOR]

Markov dynamics constitute one of the most fundamental models of random motion between the states of a system of interest. Markov dynamics have diverse applications in many fields of science and engineering, and are particularly applicable in the context of random motion in networks. In this paper we present a two-dimensional gauging method of the randomness of Markov dynamics. The method–termed Markov Stochasticity Coordinates –is established, discussed, and exemplified. Also, the method is tweaked to quantify the stochasticity of the first-passage-times of Markov dynamics, and the socioeconomic equality and mobility in human societies. [ABSTRACT FROM AUTHOR]

In this paper we construct high order finite volume schemes on networks of hyperbolic conservation laws with coupling conditions involving ODEs. We consider two generalized Riemann solvers at the junction, one of Toro–Castro type and a solver of Harten, Enquist, Osher, Chakravarthy type. The ODE is treated with a Taylor method or an explicit Runge–Kutta scheme, respectively. Both resulting high order methods conserve quantities exactly if the conservation is part of the coupling conditions. Furthermore we present a technique to incorporate lumped parameter models, which arise from simplifying parts of a network. The high order convergence and the robust capturing of shocks are investigated numerically in several test cases. [ABSTRACT FROM AUTHOR]

The new approach to classification of the epilepsies emphasizes the role of dysfunction in networks in defining types of epilepsies. This paper reviews the structural and neuropsychological deficits in two types of childhood epilepsy: frontal lobe and temporal lobe epilepsy. The evidence for and against a pattern of specificity of deficits in executive function and memory associated with these two types of epilepsies is presented. The evidence varies with the methodologies used in the studies, but direct comparison of the two types of epilepsies does not suggest a clear-cut mapping of function onto structure. These findings are discussed in light of the concept of network dysfunction. The evidence supports the conceptualization of epilepsy as a network disease. Implications for future work in the neuropsychology of pediatric epilepsy are suggested. This article is part of a Special Issue entitled “The new approach to classification: Rethinking cognition and behavior in epilepsy”. [ABSTRACT FROM AUTHOR]

Information on which weed species are present within agricultural fields is important for site specific weed management. This paper presents a method that is capable of recognising plant species in colour images by using a convolutional neural network. The network is built from scratch trained and tested on a total of 10,413 images containing 22 weed and crop species at early growth stages. These images originate from six different data sets, which have variations with respect to lighting, resolution, and soil type. This includes images taken under controlled conditions with regard to camera stabilisation and illumination, and images shot with hand-held mobile phones in fields with changing lighting conditions and different soil types. For these 22 species, the network is able to achieve a classification accuracy of 86.2%. [ABSTRACT FROM AUTHOR]

This paper describes and validates a novel framework using the Approximate Bayesian Computation (ABC) algorithm for parameter estimation and model selection in models of mesoscale brain network activity. We provide a proof of principle, first pass validation of this framework using a set of neural mass models of the cortico-basal ganglia thalamic circuit inverted upon spectral features from experimental, in vivo recordings. This optimization scheme relaxes an assumption of fixed-form posteriors (i.e. the Laplace approximation) taken in previous approaches to inverse modelling of spectral features. This enables the exploration of model dynamics beyond that approximated from local linearity assumptions and so fit to explicit, numerical solutions of the underlying non-linear system of equations. In this first paper, we establish a face validation of the optimization procedures in terms of: (i) the ability to approximate posterior densities over parameters that are plausible given the known causes of the data; (ii) the ability of the model comparison procedures to yield posterior model probabilities that can identify the model structure known to generate the data; and (iii) the robustness of these procedures to local minima in the face of different starting conditions. Finally, as an illustrative application we show (iv) that model comparison can yield plausible conclusions given the known neurobiology of the cortico-basal ganglia-thalamic circuit in Parkinsonism. These results lay the groundwork for future studies utilizing highly nonlinear or brittle models that can explain time dependant dynamics, such as oscillatory bursts, in terms of the underlying neural circuits. [ABSTRACT FROM AUTHOR]

In finite populations the action of neutral mutations is balanced by genetic drift, leading to a stationary distribution of alleles that displays a transition between two different behaviors. For small mutation rates most individuals will carry the same allele at equilibrium, whereas for high mutation rates of the alleles will be randomly distributed with frequencies close to one half for a biallelic gene. For well-mixed haploid populations the mutation threshold is μ c = 1 / 2 N , where N is the population size. In this paper we study how spatial structure affects this mutation threshold. Specifically, we study the stationary allele distribution for populations placed on regular networks where connected nodes represent potential mating partners. We show that the mutation threshold is sensitive to spatial structure only if the number of potential mates is very small. In this limit, the mutation threshold decreases substantially, increasing the diversity of the population at considerably low mutation rates. Defining k c as the degree of the network for which the mutation threshold drops to half of its value in well-mixed populations we show that k c grows slowly as a function of the population size, following a power law. Our calculations and simulations are based on the Moran model and on a mapping between the Moran model with mutations and the voter model with opinion makers. [ABSTRACT FROM AUTHOR]

Simulations of spatial interaction in archaeology have been successful in predicting the emergence of central sites, and political and economic hierarchies that match observed long-term settlement patterns. It still remains unclear, however, to what degree such models can effectively allow for uncertainty in the archaeological record, especially when it comes to incomplete and unevenly distributed settlement data, and how best they might incorporate artefact-scale evidence. This paper aims to address these issues, while attempting to tackle widely debated aspects of socio-political organisation and cultural interaction in the prehistoric Cretan landscape at the period immediately before and after the foundation of the first palace of Phaistos, one of the less well documented Bronze Age phases. We employ a simulation of spatial interaction inspired by approaches first developed in urban geography and combine this with regression-based predictive modelling to address the uncertainty introduced by missing settlements. We use evidence from artefact analysis partly to calibrate and partly to validate our model. We conclude that such an approach can contribute to more convincing archaeological theories about socio-political organisation, cultural affinity and regional identity by providing new evidence even in the presence of very fragmented data. [ABSTRACT FROM AUTHOR]

The extensive literature on sanctions has mainly focused on a dyadic interaction between sender and target. In contrast, this paper examines sanctions when the sender and target are embedded in a network of linkages to other agents. The sender can assemble a sanctioning coalition of neighbors to sever their links (execute multi-link cuts) to the target and her allies. Efficacy of sanctions is now crucially dependent on the network architecture. We characterize the structural properties of networks in which a sender can effectively sanction a target in the short run (when links can only be deleted) and the long run (when links can be both deleted and added). [ABSTRACT FROM AUTHOR]

Bibliometric indicators are used to characterize the research activity of institutions worldwide with production in the period 2003–2013 in journals that are indexed in Scopus's Food Science thematic category. Basic, normalized indicators were used to compare the institutions' performances, together with highly cited papers (top-10% and top-1%). An interactive map was generated, displaying the 645 institutions with at least 100 documents produced during this period. The greatest numbers of those institutions are in the United States, South Korea, Spain, and China. National collaboration networks were detected on the East and West Coasts of the United States, and in Canada, Ireland, France, Spain, Holland, Denmark, China, South Korea, Malaysia, Brazil, India, Argentina, and Nigeria. There was no significant research activity in many developing and food exporting countries located in sub-Saharan Africa, North and East Africa, the Middle East, Latin America, the Caribbean, Eastern Europe, Central Asia, and South East Asia. The need to take into account other criteria based on qualitative attributes and the inherent limitations in the bibliometric indicators are discussed. [ABSTRACT FROM AUTHOR]

Epilepsy is both a disease of the brain and the mind. Here, we present the first of two papers with extended summaries of selected presentations of the Third International Congress on Epilepsy, Brain and Mind (April 3–5, 2014; Brno, Czech Republic). Epilepsy in history and the arts and its relationships with religion were discussed, as were overviews of epilepsy and relevant aspects of social cognition, handedness, accelerated forgetting and autobiographical amnesia, and large-scale brain networks. [ABSTRACT FROM AUTHOR]

This paper explores how unequal resources and social and economic polarization affects the size of social networks and their use to access resources. We argue that individual resource position generates divergent expectations with regard to the impact of polarization on the size of networks on one hand, and their usefulness for accessing resources on the other. Social and economic polarization encourages reliance on informal networks, but those at the bottom of the social structure are forced to rely on more extensive networks than the wealthy to compensate for their isolated and underprivileged position. At the same time, social and economic polarization limits the resources the poor can access through their networks. We provide evidence consistent with these propositions, based on data derived from the International Social Survey Programme 2001 “Social Networks” dataset combined with contextual information on the levels of economic inequality in particular countries along with whether they experienced postcommunism. [ABSTRACT FROM AUTHOR]

• Moment-closure methods can be used to approximate the spread of epidemics on networks. • In pairwise models, triples are typically approximated using the standard pairwise approximation. • For diseases with SIS-dynamics, this approximation is not exact, due to dynamic build-up of correlations. • We improve the pairwise model by tracking the errors between triples and their approximation. • We demonstrate this improvement through comparison with higher-order models and simulation. Network models of disease spread play an important role in elucidating the impact of long-lasting infectious contacts on the dynamics of epidemics. Moment-closure approximation is a common method of generating low-dimensional deterministic models of epidemics on networks, which has found particular success for diseases with susceptible-infected-recovered (SIR) dynamics. However, the effect of network structure is arguably more important for sexually transmitted infections, where epidemiologically relevant contacts are comparatively rare and longstanding, and which are in general modelled via the susceptible-infected-susceptible (SIS)-paradigm. In this paper, we introduce an improvement to the standard pairwise approximation for network models with SIS-dynamics for two different network structures: the isolated open triple (three connected individuals in a line) and the k -regular network. This improvement is achieved by tracking the rate of change of errors between triple values and their standard pairwise approximation. For the isolated open triple, this improved pairwise model is exact, while for k -regular networks a closure is made at the level of triples to obtain a closed set of equations. This improved pairwise approximation provides an insight into the errors introduced by the standard pairwise approximation, and more closely matches both higher-order moment-closure approximations and explicit stochastic simulations with only a modest increase in dimensionality to the standard pairwise approximation. [ABSTRACT FROM AUTHOR]

Line of Sight (LoS) networks were designed to model wireless communication in settings which may contain obstacles. For fixed positive integer d , and positive integer ω , a graph G = (V , E) is a (d -dimensional) LoS network with range parameter ω if it can be embedded in a finite cube of the d -dimensional integer grid so that each pair of vertices in V are adjacent if and only if their embedding coordinates differ only in one position and such difference is less than ω. In this paper we investigate a dynamic programming (DP) approach which can be used to obtain efficient algorithmic solutions for various combinatorial problems in LoS networks. In particular DP solves the Maximum Independent Set (MIS) problem in LoS networks optimally, for any ω , on narrow LoS networks (i.e. networks which can be embedded in a k × k ... × k × n region, for some fixed k independent of n). In the unrestricted case it has been shown that the (decision version of the) problem is NP-hard when 2 < ω = O (n 1 − δ) , for fixed 0 < δ < 1. We describe how DP can be used as a building block in the design of good approximation algorithms in this case. In particular we present a semi-online polynomial-time approximation scheme for the MIS problem in narrow d -dimensional LoS networks, as well as a polynomial-time 2-approximation algorithm and a fast polynomial time approximation scheme for the MIS problem in arbitrary d -dimensional LoS networks. Finally we comment on how the approach can be adapted to prove similar results for a number of important optimization problems in LoS networks. [ABSTRACT FROM AUTHOR]