Raissa M. D’Souza

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This paper reports preliminary results of a survey designed to quantify how social networks influence travel behavior. Using a three-day activity diary, we simultaneously measured social interactions and travel behavior. Respondents were asked to record all trips, as well as all social interactions with friends and family for three days. We use a novel(More)
Commercial software project managers design project organizational structure carefully, mindful of available skills, division of labour, geographical boundaries, etc. These organizational “cathedrals” are to be contrasted with the “bazaarlike” nature of Open Source Software (OSS) Projects, which have no pre-designed organizational structure. Any structure(More)
The emergence of large-scale connectivity on an underlying network or lattice, the so-called percolation transition, has a profound impact on the system’s macroscopic behaviours. There is thus great interest in controlling the location of the percolation transition to either enhance or delay its onset and, more generally, in understanding the consequences(More)
Our modern infrastructure relies increasingly on computation and computers. Accompanying this is a rise in the prevalence and complexity of computer programs. Current software systems (composed of an interacting collection of programs, functions, classes, etc.) implement a tremendous range of functionality, from simple mathematical operations to intricate(More)
1 Bell Laboratories, Murray Hill, New Jersey 07974; e-mail: raissa@bell-labs.com 2 Center for Computational Science, Boston University, Boston, Massachusetts 02215, Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; e-mail: nhm@mit.edu 3 Department of Molecular and Cellular Biology, Harvard University,(More)
The Biham–Middleton–Levine (BML) model is simple lattice model of traffic flow, selforganization and jamming. Rather than a sharp phase transition between free-flow and jammed, itwas recently shown that there is a regionwhere stable intermediate states exist, with details dependent on the aspect ratio of the underlying lattice. Here we investigate square(More)
We introduce a lattice gas model of cluster growth via the diffusive aggregation of particles in a closed system obeying a local, deterministic, microscopically reversible dynamics. This model roughly corresponds to placing the irreversible Diffusion Limited Aggregation model (DLA) in contact with a heat bath. Particles release latent heat when aggregating,(More)
Understanding what types of phenomena lead to discontinuous phase transitions in the connectivity of random networks is an outstanding challenge. Here we show that a simple stochastic model of graph evolution leads to a discontinuous percolation transition and we derive the underlying mechanism responsible: growth by overtaking. Starting from a collection(More)
Idealized models of interconnected networks can provide a laboratory for studying the consequences of interdependence in real-world networks, in particular those networks constituting society’s critical infrastructure. Here we show how random graph models of connectivity between networks can provide insights into shifts in percolation properties and into(More)
Could surgery be the gold standard in moderate and severe ischaemic colitis? Atypical case description and review of literature Dear Editor, Ischaemic colitis (IC) is a rare condition caused by an inadequate perfusion leading to colonic inflammation. This condition has an incidence of 4.5–9.9 per 100,000 population/year [1]. The exact pathophysiology is(More)