Leader Election for Anonymous Asynchronous Agents in Arbitrary Networks

We study the problem of leader election among mobile agents operating in an arbitrary network modeled as an undirected graph. Nodes of the network are unlabeled and all agents are identical. Hence the only way to elect a leader among agents is by exploiting asymmetries in their initial positions in the graph. Agents do not know the graph or their positions in it, hence they must gain this knowledge by navigating in the graph and share it with other agents to accomplish leader election. This can be done using meetings of agents, which is difficult because of their asynchronous nature: an adversary has total control over the speed of agents. When can a leader be elected in this adversarial scenario and how to do it? We give a complete answer to this question by characterizing all initial configurations for which leader election is possible and by constructing an algorithm that accomplishes leader election for all configurations for which this can be done

Virtual Radicalisation: Challenges for Police

Recent advances in communications technology are providing a medium for individuals or groups to subscribe to extremist worldviews and form networks, access training and obtain information, whilst remaining virtually undetected in the online world. Whilst the Internet is facilitating global virtual communities like Second Life, MySpace and Facebook it is also providing an anonymous meeting place for disenfranchised individuals to gather, share ideas, post and exchange information regarding their particular ideology. This virtual community provides a sense of belonging to a global cause in which the actions of an individual can be aligned to, and seen to contribute towards something more significant than their own lives. Membership of this virtual community can facilitate the indoctrination of individuals, thereby negating psychological barriers that would normally inhibit particular types of behaviour. Terrorist groups operate as amorphous, fluid networks providing them significant advantages over rigidly structured state and nation based law enforcement agencies. In addition terrorist groups are exploiting the combination of rapidly evolving technology and incommodious legislation to prevent detection

Sexual networks and the transmission of HIV in London

Copyright @ 1998 Cambridge University Press.This paper discusses ways in which empirical research investigating sexual networks can further understanding of the transmission of HIV in London, using information from a 24-month period of participant observation and 53 open-ended, in-depth interviews with eighteen men and one woman who have direct and indirect sexual links with each other. These interviews enabled the identification of a wider sexual network between 154 participants and contacts during the year August 1994-July 1995. The linked network data help to identify pathways of transmission between individuals who are HIV + and those who are HIV -, as well as sexual links between 'older' and 'younger' men, and with male prostitutes. There appears to be considerable on-going transmission of HIV in London. The majority of participants reported having had unprotected anal and/or vaginal sex within a variety of relationships. The implications of these findings for policies designed to prevent the transmission of HIV are discussed.The Wellcome Trust and The Health Education Authority

Foucault, exhibitionism and voyeurism on chatroulette

Sexuality, understood as a Foucauldian discourse that expresses itself through our passions and pursuits and contributes massively to our socially- constructed identity formation, has from the outset been a major factor in the growth of the internet. As the ultimate look-but-don‘t-touch medium, the computer screen has offered us a pornographic emporium in the privacy of our homes, fed first by the producers of material in the standard broadcast mode, then more and more by ourselves, to each other, in the social media context of online sexual social networking. The recent shift of sexual video material from broadcast to social media mode highlights the fundamental exhibitionism/voyeurism dyad at the core of all this activity, and finds its most impersonal, anonymous apotheosis in the phenomenon that is ChatRoulette, where visual discourse-objects are deployed in a nexus of online sexual power relations

Is there more than one linkage between Social Network and Inequality?

The paper aims to analyse how income inequality affects social networks strength in fourteen European Countries. We introduce some new evidences by using the ECHP for testing the networks-inequality nexus and being able to construct directly inequality indices from the microdata as well their decomposition. In particular, we focus on two main point: firstly, we analyse how total income inequality could be related to social network; secondly, we introduce the "clustered network" definition, by decomposing total income inequality based on the education level. We test the existence of a pluralism linkage between Social Network and Inequality and many results confirm that the linkage is neither unambiguous nor unidirectional. We introduce and stress some important issue. First, we use dierent levels of social network: narrow, wide and anonymous; second, we use different inequality indexes (different sensitiveness to changes at different part of the income distribution); third, the ambiguous linkage could be explained on one hand by the positive role of emulation and reciprocity behaviors and on the other hand by negative ones of the envy, amoral familism and keeping up with the Joneses mechanisms. Finally, we stress the different roles of within and between components of inequality. Our idea is that higher income inequality - related to the changing education premia - could affect social network formation among individuals through two different channels: higher inequality among dierent educated ind ividuals could raise (clustered networks), while higher inequality among similars could halt the social networks.Social Network ; Inequality ; Clustered Network ; Envy ; Emulation

Gathering in Dynamic Rings

The gathering problem requires a set of mobile agents, arbitrarily positioned at different nodes of a network to group within finite time at the same location, not fixed in advanced. The extensive existing literature on this problem shares the same fundamental assumption: the topological structure does not change during the rendezvous or the gathering; this is true also for those investigations that consider faulty nodes. In other words, they only consider static graphs. In this paper we start the investigation of gathering in dynamic graphs, that is networks where the topology changes continuously and at unpredictable locations. We study the feasibility of gathering mobile agents, identical and without explicit communication capabilities, in a dynamic ring of anonymous nodes; the class of dynamics we consider is the classic 1-interval-connectivity. We focus on the impact that factors such as chirality (i.e., a common sense of orientation) and cross detection (i.e., the ability to detect, when traversing an edge, whether some agent is traversing it in the other direction), have on the solvability of the problem. We provide a complete characterization of the classes of initial configurations from which the gathering problem is solvable in presence and in absence of cross detection and of chirality. The feasibility results of the characterization are all constructive: we provide distributed algorithms that allow the agents to gather. In particular, the protocols for gathering with cross detection are time optimal. We also show that cross detection is a powerful computational element. We prove that, without chirality, knowledge of the ring size is strictly more powerful than knowledge of the number of agents; on the other hand, with chirality, knowledge of n can be substituted by knowledge of k, yielding the same classes of feasible initial configurations