Exploring digital encounters in the city

In this paper we explore the types of encounters that technology enables. We consider the differences between digital and non-digital encounters, and investigate how technology can be appropriated for shared interactions that support conscious (or unconscious) social encounters. Finally, we describe two prototypes that generate different types of digital encounters in a city context, and we discuss our initial results

Dynamics of direct inter-pack encounters in endangered African wild dogs

Aggressive encounters may have important life history consequences due to the potential for injury and death, disease transmission, dispersal opportunities or exclusion from key areas of the home range. Despite this, little is known of their detailed dynamics, mainly due to the difficulties of directly observing encounters in detail. Here, we describe detailed spatial dynamics of inter-pack encounters in African wild dogs (Lycaon pictus), using data from custom-built high-resolution GPS collars in 11 free-ranging packs. On average, each pack encountered another pack approximately every 7 weeks and met each neighbour twice each year. Surprisingly, intruders were more likely to win encounters (winning 78.6% of encounters by remaining closer to the site in the short term). However, intruders did tend to move farther than residents toward their own range core in the short-term (1 h) post-encounter, and if this were used to indicate losing an encounter, then the majority (73.3%) of encounters were won by residents. Surprisingly, relative pack size had little effect on encounter outcome, and injuries were rare (<15% of encounters). These results highlight the difficulty of remotely scoring encounters involving mobile participants away from static defendable food resources. Although inter-pack range overlap was reduced following an encounter, encounter outcome did not seem to drive this, as both packs shifted their ranges post-encounter. Our results indicate that inter-pack encounters may be lower risk than previously suggested and do not appear to influence long-term movement and ranging

Does the mass distribution in discs influence encounter-induced losses in young star clusters?

One mechanism for the external destruction of protoplanetary discs in young dense clusters is tidal disruption during the flyby of another cluster member. The degree of mass loss in such an encounter depends, among other parameters, on the distribution of the material within the disc. Previous work showed that this is especially so in encounters that truncate large parts of the outer disc. The expectation is that the number of completely destroyed discs in a cluster depends also on the mass distribution within the discs. Here we test this hypothesis by determining the influence of encounters on the disc fraction and average disc mass in clusters of various stellar densities for different mass distributions in the discs. This is done by performing Nbody6 simulation of a variety of cluster environments, where we track the encounter dynamics and determine the mass loss due to these encounters for different disc-mass distributions. We find that although the disc mass distribution has a significant impact on the disc losses for specific star-disc encounters, the overall disc frequency generally remains rather unaffected. The reason is that in single encounters the dependence on the mass distribution is strongest if both stars have very different masses. Such encounters are rather infrequent in sparse clusters. In dense clusters such encounters are more common, however, here the disc frequency is largely determined by encounters between low-mass stars such that the overall disc frequency does not change significantly. For tidal disruption the disc destruction in clusters is fairly independent of the actual distribution of the material in the disc. The all determining factor remains the cluster density.Comment: 7pages, 4 figures, accepted by A&

Living with difference in hyper-diverse areas: how important are encounters in semi-public spaces?

Urban populations increasingly diversify in their socio-economic, cultural, religious and linguistic profiles as well as in their lifestyles, attitudes and activity patterns. This hyper-diversification can complicate feelings of belonging and community. Since diversity is negotiated at the neighbourhood level, micro spaces are central in building communities. Micro spaces tend to be semi-public and stimulate diverse groups to intermingle, which results in on–off as well as repetitive and structural interactions. Understanding the creation and impact of encounters is central to capturing contemporary notions of belonging and living with difference. This paper compares encounters experienced in two semi-public spaces in the hyper-diverse neighbourhood of Feyenoord in Rotterdam, the Netherlands. Although encounters at the library were lighter and shorter than at the community-centre, all positively impact collective life in the neighbourhood. At the community-centre, encounters result in light as well as deeper relationships, making visitors feel more at ‘home’ because they recognize others elsewhere in the neighbourhood. At the library, encounters are lighter but visitors become familiar with diversity, making them feel more at ‘home’ and safe in their neighbourhood as well. The study suggests that fleeting encounters require more serious attention within the context of negotiating diversity

Aggressive Encounters & White Fragility: Deconstructing the Trope of the Angry Black Woman

Black women in the United States are the frequent targets of bias-filled interactions in which aggressors: (1) denigrate Black women; and (2) blame those women who elect to challenge the aggressor’s acts and the bias that fuels them. This Article seeks to raise awareness of these “aggressive encounters” and to challenge a prevailing narrative about Black women and anger. It examines the myriad circumstances (both professional and social) in which aggressive encounters occur and the ways in which these encounters expose gender and racial hierarchies. It then explores how the intersectional nature of Black women’s identities triggers a particularized stereotype or trope of the “Angry Black Woman” and explains how this trope is often invoked in aggressive encounters to deflect attention from the aggressor and to project blame onto the target. After discussing the harmful effects of aggressive encounters and the absence of effective legal mechanisms to address them, the Article sets forth tangible steps that individuals can take to minimize their incidence

High-velocity runaway stars from three-body encounters

We performed numerical simulations of dynamical encounters between hard massive binaries and a very massive star (VMS; formed through runaway mergers of ordinary stars in the dense core of a young massive star cluster), in order to explore the hypothesis that this dynamical process could be responsible for the origin of high-velocity (\geq 200-400 km/s) early or late B-type stars. We estimated the typical velocities produced in encounters between very tight massive binaries and VMSs (of mass of \geq 200 Msun) and found that about 3-4 per cent of all encounters produce velocities of \geq 400 km/s, while in about 2 per cent of encounters the escapers attain velocities exceeding the Milky Ways's escape velocity. We therefore argue that the origin of high-velocity (\geq 200-400 km/s) runaway stars and at least some so-called hypervelocity stars could be associated with dynamical encounters between the tightest massive binaries and VMSs formed in the cores of star clusters. We also simulated dynamical encounters between tight massive binaries and single ordinary 50-100 Msun stars. We found that from 1 to \simeq 4 per cent of these encounters can produce runaway stars with velocities of \geq 300-400 km/s (typical of the bound population of high-velocity halo B-type stars) and occasionally (in less than 1 per cent of encounters) produce hypervelocity (\geq 700 km/s) late B-type escapers.Comment: 4 pages, 2 figure, to appear in Star Clusters -- Basic Galactic Building Blocks throughout Time and Space, Proceed. of the IAU Symp. 266, eds. R. de Grijs and J. Lepin

Orbital Perturbations of the Galilean Satellites During Planetary Encounters

The Nice model of the dynamical instability and migration of the giant planets can explain many properties of the present Solar System, and can be used to constrain its early architecture. In the jumping-Jupiter version of the Nice model, required from the terrestrial planet constraint and dynamical structure of the asteroid belt, Jupiter has encounters with an ice giant. Here we study the survival of the Galilean satellites in the jumping-Jupiter model. This is an important concern because the ice-giant encounters, if deep enough, could dynamically perturb the orbits of the Galilean satellites, and lead to implausible results. We performed numerical integrations where we tracked the effect of planetary encounters on the Galilean moons. We considered three instability cases from Nesvorny & Morbidelli (2012) that differed in the number and distribution of encounters. We found that in one case, where the number of close encounters was relatively small, the Galilean satellite orbits were not significantly affected. In the other two, the orbital eccentricities of all moons were excited by encounters, Callisto's semimajor axis changed, and, in a large fraction of trials, the Laplace resonance of the inner three moons was disrupted. The subsequent evolution by tides damps eccentricities and can recapture the moons in the Laplace resonance. A more important constraint is represented by the orbital inclinations of the moons, which can be excited during the encounters and not appreciably damped by tides. We find that one instability case taken from Nesvorny & Morbidelli (2012) clearly fails this constraint. This shows how the regular satellites of Jupiter can be used to set limits on the properties of encounters in the jumping-Jupiter model, and help us to better understand how the early Solar System evolved.Comment: The Astronomical Journal, in pres