High-resolution simulations of stellar collisions between equal-mass main-sequence stars in globular clusters

We performed high-resolution simulations of two stellar collisions relevant for stars in globular clusters. We considered one head-on collision and one off-axis collision between two 0.6 M_sun main sequence stars. We show that a resolution of about 100 000 particles is sufficient for most studies of the structure and evolution of blue stragglers. We demonstrate conclusively that collision products between main-sequence stars in globular clusters do not have surface convection zones larger than 0.004 M_sun after the collision, nor do they develop convection zones during the `pre-main-sequence' thermal relaxation phase of their post-collision evolution. Therefore, any mechanism which requires a surface convection zone (i.e. chemical mixing or angular momentum loss via a magnetic wind) cannot operate in these stars. We show that no disk of material surrounding the collision product is produced in off-axis collisions. The lack of both a convection zone and a disk proves a continuing problem for the angular momentum evolution of blue stragglers in globular clusters.Comment: 7 pages, 5 figures, accepted by MNRA

Brown dwarf populations in open clusters

We present the results of multiple simulations of open clusters, modelling the dynamics of a population of brown dwarf members. We consider the effects of a large range of primordial binary populations, including the possibilities of having brown dwarf members contained within a binary system. We also examine the effects of various cluster diameters and masses. Our examination of a population of wide binary systems containing brown dwarfs, reveals evidence for exchange reactions whereby the brown dwarf is ejected from the system and replaced by a heavier main-sequence star. We find that there exists the possibility of hiding a large fraction of the brown dwarfs contained within the primordial binary population. We conclude that it is probable that the majority of brown dwarfs are contained within primordial binary systems which then hides a large proportion of them from detection.Comment: 16 pages, 8 figures; to appear in MNRA

The Daily Shaping of State Transparency: Standards, Machine-Readability and the Configuration of Open Government Data Policies

International audienceWhile many governments are now committed to release Open Government Data under non-proprietary standardized formats, less attention has been given to the actual consequences of these standards for knowledge workers. Unpacking the history of three open data standards (CSV, GTFS, IATI), this paper shows what is actually happening when these standards are enacted in the work practices of bureaucracies. It is built on participant-observer enquiry and interviews focussed on the back rooms of open data, and looking specifi cally at the invisible work necessary to construct open datasets. It shows that the adoption of open standards is increasingly becoming an indicator of the advancement of open data programmes. Enacting open standards involves much more than simple technical operations, it operates a quiet and localised transformation of bureaucracies, in which the decisions of data workers have substantive consequences for how the open government data and transparency agendas are performed

Researching the emerging impacts of open data: revisiting the ODDC conceptual framework

Open data has rapidly moved from being a niche interest, to being part of the global policy mainstream. Government-led open data initiatives have spread across the globe, and civil society or technologist experiments using data to improve governance have been spreading organically, from budget monitoring in Nigeria, to court transparency projects in Argentina. It is increasingly seen as enabler of a “data revolution” in the process of decision-making and accountability.  However, understanding how experience of open data will vary from country to country and context to context, and, understanding the common features of open data that are shaping its implementation in these diverse settings, requires broad-based research framework. It requires research that can engage with both existing realities of decision-making in sectors, acknowledging the growing complexity of this process in an increasingly networked society. In this paper we have reviewed the framework of the “Open Data in Developing Countries”(ODDC) project, the largest research project on the impact of open data in developing countries to date.  The framework was designed to help explore the link between openness in the data ecosystem, decentralized changes in decision-making, and positive and negative emerging impacts such as transparency and accountability, inclusion and empowerment as well as innovation and economic development.  It was tested to generate cross-learning from 17 in-depth cases studies in 14 countries, as well as generate policy-relevant findings.  This paper reviews and updates the original framework based on the findings and reflections developed during the research project

Fisheries and Aquaculture and Their Potential Roles in Development: An Assessment of the Current Evidence

Commissioned by the International Sustainability Unity, this report investigates a number of innovative solutions that have been developed to deal with five key challenges that are impeding progress in achieving sustainable fisheries: overcapacity; perverse subsidies; poor governance; lack of data; and by-catch and discards. These key challenges are interlinked and affect the sustainability of fisheries both directly as well as indirectly by undermining instances of good management. Through 22 case studies demonstrating good practice, we explore how these challenges have been addressed around the world and how these approaches might be scaled up and applied in other fisheries. Each case study draws on published material and interviews with key people involved in the fishery. The main report draws lessons from these case studies

CATASTROPHIC FLANK COLLAPSE ON TA’U ISLAND AND SUBSEQUENT TSUNAMI: HAS THIS OCCURRED DURING THE LAST 170 YEARS?

Ta’u, the easternmost inhabited island in the Samoan Islands archipelago, exhibits a series of down-faulted benches on its southern flank, believed to be the remnant of ~30 km3 catastrophic collapse. A historical map of Ta’u charted in 1839 during the United States Exploring Expedition, which did not show the benches, suggests that the event occurred less than 170 years ago. A collapse event of this magnitude would have generated a locally devastating tsunami, with possible impacts experienced at the regional level. However, no written or oral records of such an event exist. A number of key questions thus emerge, and formed the basis for this study. Did this event actually happen within the last 170 years, and if so, how and why could it have gone unnoticed? Or, is the event much older than the impression obtained from the literature? The catastrophic flank collapse was modeled using 100 m contour-resolution bathymetry data of the Ta’u region, coupled with rational assumptions made on the geometry of the failed mass. This enabled numerical landslide- tsunami simulation in the Cornell Multigrid Coupled Tsunami Model (COMCOT). The results indicate that if an event of this magnitude occurred in the last 170 years, it could not have gone unnoticed by local inhabitants. It thus seems likely that the initial survey conducted during the Exploring Expedition was inaccurate. Nevertheless, the well-preserved nature of the benches indicates collapse relatively recently and raises the possibility of future collapse