Showing papers by "Vito Latora published in 2009"
TL;DR: In this article, the authors examined the relationship between street centrality and densities of commercial and service activities in the city of Bologna, northern Italy and found that the distribution of these activities correlates highly with the global betweenness of the street network, and also, to a slightly lesser extent, with global closeness.
Abstract: This paper examines the relationship between street centrality and densities of commercial and service activities in the city of Bologna, northern Italy. Street centrality is calibrated in a multiple centrality assessment model composed of multiple measures such as closeness, betweenness, and straightness. Kernel density estimation is used to transform datasets of centrality and activities to one scale unit for analysis of correlation between them. Results indicate that retail and service activities in Bologna tend to concentrate in areas with better centralities. The distribution of these activities correlates highly with the global betweenness of the street network, and also, to a slightly lesser extent, with the global closeness. This confirms the hypothesis that street centrality plays a crucial role in shaping the formation of urban structure and land uses.
348 citations
TL;DR: This work studies a model in which prisoner's dilemma players are allowed to move in a two-dimensional plane and shows that cooperation can survive in such a system provided that both the temptation to defect and the velocity at which agents move are not too high.
Abstract: We address the problem of how the survival of cooperation in a social system depends on the motion of the individuals. Specifically, we study a model in which prisoner's dilemma players are allowed to move in a two-dimensional plane. Our results show that cooperation can survive in such a system provided that both the temptation to defect and the velocity at which agents move are not too high. Moreover, we show that when these conditions are fulfilled, the only asymptotic state of the system is that in which all players are cooperators. Our results might have implications for the design of cooperative strategies in motion coordination and other applications including wireless networks.
245 citations
17 Aug 2009
TL;DR: New temporal distance metrics to quantify and compare the speed (delay) of information diffusion processes taking into account the evolution of a network from a local and global view are proposed and shown how these metrics are able to capture the temporal characteristics of time-varying graphs.
Abstract: The analysis of social and technological networks has attracted a lot of attention as social networking applications and mobile sensing devices have given us a wealth of real data. Classic studies looked at analysing static or aggregated networks, i.e., networks that do not change over time or built as the results of aggregation of information over a certain period of time. Given the soaring collections of measurements related to very large, real network traces, researchers are quickly starting to realise that connections are inherently varying over time and exhibit more dimensionality than static analysis can capture.In this paper we propose new temporal distance metrics to quantify and compare the speed (delay) of information diffusion processes taking into account the evolution of a network from a local and global view. We show how these metrics are able to capture the temporal characteristics of time-varying graphs, such as delay, duration and time order of contacts (interactions), compared to the metrics used in the past on static graphs. As a proof of concept we apply these techniques to two classes of time-varying networks, namely connectivity of mobile devices and e-mail exchanges.
185 citations
19 Apr 2009
TL;DR: It is found that mobile social networks are very robust to the distributions of altruism due to the nature of multiple paths, including the impact of topologies and traffic patterns.
Abstract: Many kinds of communication networks, in particular social and opportunistic networks, rely at least partly on on humans to help move data across the network. Human altruistic behavior is an important factor determining the feasibility of such a system. In this paper, we study the impact of different distributions of altruism on the throughput and delay of mobile social communication system. We evaluate the system performance using four experimental human mobility traces with uniform and community-biased traffic patterns. We found that mobile social networks are very robust to the distributions of altruism due to the nature of multiple paths. We further confirm the results by simulations on two popular social network models. To the best of our knowledge, this is the first complete study of the impact of altruism on mobile social networks, including the impact of topologies and traffic patterns.
99 citations
TL;DR: This work addresses the problem of how cooperative (altruistic-like) behavior arises in natural and social systems by analyzing an Ultimatum Game in complex networks and discusses the emergence of fairness in the different settings and network topologies.
Abstract: We address the problem of how cooperative (altruistic-like) behavior arises in natural and social systems by analyzing an Ultimatum Game in complex networks. Specifically, players of three types are considered: (a) empathetic, whose aspiration levels, and offers, are equal, (b) pragmatic, who do not distinguish between the different roles and aim to obtain the same benefit, and (c) agents whose aspiration levels, and offers, are independent. We analyze the asymptotic behavior of pure populations with different topologies using two kinds of strategic update rules: natural selection, which relies on replicator dynamics, and social penalty, inspired by the Bak–Sneppen dynamics, in which players are subject to a social selection rule penalizing not only the less fit individuals, but also their first neighbors. We discuss the emergence of fairness in the different settings and network topologies.
72 citations
07 Jun 2009
TL;DR: This is the first study of the impact of altruism on opportunistic communications and evaluates the system performance by utilizing social network topological models and experimental human mobility traces with different communication patterns.
Abstract: Opportunistic networking largely relies on human-carried devices as relays to move data across the network. Human altruistic behavior is an important factor in the feasibility and performance of such a system. In this paper, we study the impact of different altruism distributions on the system throughput and delay of opportunistic communications. We evaluate the system performance by utilizing social network topological models and experimental human mobility traces with different communication patterns. We also discuss several observations from the result of the study. To the best of our knowledge, this is the first study of the impact of altruism on opportunistic communications.
39 citations
01 Dec 2009
TL;DR: Cortical and Neural Networks Cultured Neural Networks Functional Connectivity in Complex Brain Networks Boolean Dynamics Gene Circuits Metabolic Networks Folding Landscapes and Networks Evolutionary Dynamics Motion Coordination Ecosystems.
Abstract: Cortical and Neural Networks Cultured Neural Networks Functional Connectivity in Complex Brain Networks Boolean Dynamics Gene Circuits Metabolic Networks Folding Landscapes and Networks Evolutionary Dynamics Motion Coordination Ecosystems.
24 citations
TL;DR: In this paper, the topological properties of functional connectivity patterns among cortical areas in the frequency domain were studied using high-resolution EEG recordings in a group of spinal cord injured patients and healthy subjects, during the preparation of a limb movement.
Abstract: We study the topological properties of functional connectivity patterns among cortical areas in the frequency domain. The cortical networks were estimated from high-resolution EEG recordings in a group of spinal cord injured patients and in a group of healthy subjects, during the preparation of a limb movement. We first evaluate global and local efficiency, as indicators of the structural connectivity respectively at a global and local scale. Then, we use the Markov Clustering method to analyze the division of the network into community structures. The results indicate large differences between the injured patients and the healthy subjects. In particular, the networks of spinal cord injured patient exhibited a higher density of efficient clusters. In the Alpha (7–12 Hz) frequency band, the two observed largest communities were mainly composed of the cingulate motor areas with the supplementary motor areas, and of the premotor areas with the right primary motor area of the foot. This functional separation ...
9 citations
Book Chapter•
01 Jan 2009
TL;DR: In this article, the authors examined the relationship between street centrality and densities of commercial and service activities in cities and found that secondary activities exhibit a higher correlation with centrality.
Abstract: This paper examines the relationship between street centrality and densities of commercial and service activities in cities. The aim is to verify whether a correlation exists and whether some 'secondary' activities, i.e. those scarcely specialized oriented to the general public and ordinary daily life, are more linked to street centrality than others. The metropolitan area of Barcelona (Spain) is investigated, and results are compared with those found in a previous work on the city of Bologna (Italy). Street centrality is calibrated in a multiple centrality assessment (MCA) model composed of multiple measures such as closeness, betweenness and straightness. Kernel density estimation (KDE) is used to transform data sets of centrality and activities to one scale unit for correlation analysis between them. Results indicate that retail and service activities in both Bologna and Barcelona tend to concentrate in areas with better centralities, and that secondary activities exhibit a higher correlation.
7 citations
TL;DR: In this article, the authors use a cellular automata model to simulate the motion of vehicles along streets, coupled with a congestion-aware routing at street crossings, allowing the vehicles to dynamically update the routes towards their destinations.
Abstract: Congestion in transport networks is a topic of theoretical interest and practical importance. In this paper we study the flow of vehicles in urban street networks. In particular, we use a cellular automata model to simulate the motion of vehicles along streets, coupled with a congestion-aware routing at street crossings. Such routing makes use of the knowledge of agents about traffic in nearby roads and allows the vehicles to dynamically update the routes towards their destinations. By implementing the model in real urban street patterns of various cities, we show that it is possible to achieve a global traffic optimization based on local agent decisions.
1 citations
01 Jan 2009
TL;DR: The results suggest that modularity plays a role for the functional organization of brain areas durin g spontaneous neural organization in healthy subjects and epileptic patients.
Abstract: We analyze the modular structure of weighted brain networks extracted from spontaneous magnetoencephalographic (MEG ) signals of healthy subjects and epileptic patients recorded at rest . We find that, healthy brains exhibit a modular organization characterized by a weak connectivity between the modules, whereas in the cortical c onnectivity of epileptic patients, nodes are interconnect ed with different modules of the network. Our results suggest that modularity plays a k ey role for the functional organization of brain areas durin g spontaneous neural
01 Jan 2009
TL;DR: In this paper, the authors examined the relationship between street centrality and densities of commercial and service activities in the city of Bologna, northern Italy, and found that retail and service acti- vities tend to concentrate in areas with better centralities.
Abstract: This paper examines the relationship between street centrality and densities of commercial and service activities in the city of Bologna, northern Italy. Street centrality is calibrated in a multiple centrality assessment model composed of multiple measures such as closeness, betweenness, and straightness. Kernel density estimation is used to transform datasets of centrality and activities to one scale unit for analysis of correlation between them. Results indicate that retail and service acti- vities in Bologna tend to concentrate in areas with better centralities. The distribution of these activities correlates highly with the global betweenness of the street network, and also, to a slightly lesser extent, with the global closeness. This confirms the hypothesis that street centrality plays a crucial role in shaping the formation of urban structure and land uses.