Rapid variability at very high energies in Mrk 501

A major flaring state of the BL Lac object Mrk 501 was observed by the High Energy Stereoscopic System (H.E.S.S.) in June, 2014. Flux levels higher than one Crab unit were recorded and rapid variability at very high energies ($\sim$2-20 TeV) was revealed. The high statistics afforded by the flares allowed us to probe the presence of minutes timescale variability and study its statistical characteristics exclusively at TeV energies owing to the high energy threshold of approximately 2 TeV. Doubling times of a few minutes are estimated for fluxes greater than 2 TeV. Statistical tests on the light curves show interesting temporal structure in the variations including deviations from a normal flux distribution similar to those found in the PKS 2155-304 flare of July 2006, at nearly an order of magnitude higher threshold energy. Rapid variations at such high energies put strong constraints on the physical mechanisms in the blazar jet.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherland

Social Navigation of Food Recipes

The term Social Navigation captures every-day behaviour used to find information, people, and places – namely through watching, following, and talking to people. We discuss how to design information spaces to allow for social navigation. We applied our ideas in a recipe recommendation system. In a follow-up user study, subjects state that social navigation adds value to the service: it provides for social affordance, and it helps turning a space into a social place. The study also reveals some unresolved design issues, such as the snowball effect where more and more users follow each other down the wrong path, and privacy issues

Do cyber-birds flock together? Comparing deviance among social network members of cyber-dependent offenders and traditional offenders

The distinct setting in which cyber-dependent crime takes place may reduce the similarity in the deviance of social network members. We test this assumption by analysing the deviance of the most important social contacts of cyber-dependent offenders and traditional offenders in the Netherlands (N = 344 offenders; N = 1131 social contacts). As expected, similarity in deviance is weaker for cyber-dependent crime. Because this is a strong predictor of traditional offending, this has important implications for criminological research and practice. Additionally, for both crime types the offending behaviour of a person is more strongly linked to the deviance of social ties if those ties are of the same gender and age, and if the offender has daily contact with them. Implications and future criminological research suggestions are discussed

The Geographical and Institutional Proximity of Scientific Collaboration Networks

The geography of innovation has established itself as a central subject in economic geography. Geographical proximity to firms and organizations like universities is supposed to have a positive effect on a firms’ innovative performance. One of the reasons causing these positive agglomeration effects is the fact that collaboration is eased by geographical proximity. Although the role of proximity for collaboration is a well researched theme with regard to innovation, less is known about the role of proximity in scientific collaboration and how this affects the probability and nature of networking among research institutions. This is surprising given the fact that collaboration in science has become a central policy issue. In this paper we set out a number of theoretical considerations about the role of geography for innovation and see whether these apply for science as well. The empirical part will focus on the geography of collaboration in scientific knowledge production, testing the hypothesis that collaboration between different kinds of organizations is geographically more localized than collaboration between the same kinds of organizations due to institutional or organizational proximity. Besides this we will analyze the importance of spatial proximity for various forms of collaboration (such as university-university and university-firm collaboration) using the concept of the gravity model. Finally we will look at the spatial structure of these collaboration networks using insights from social network methodology. Based on co-publications, central nodes of collaborative interaction and network structures are analysed over time. On the network-level we conclude on differences in the fields of life- and physical sciences and on differences on the type of relations according to university-firm, university-university and university-governmental institution linkages. On the regional level we conclude on the centrality and spatial extent of scientific collaboration hubs over time

Testing Porter's Hypothesis: A Stochastic Frontier Panel Data Analysis of Dutch Horticulture

We propose a test of the Porter hypothesis for the Dutch horticulture sector, using a stochastic production frontier analysis allowing for an inclusion of policy variables to account for the effect of environmental policy of firm performance. We find considerable heterogeneity in the way firms react to environmental policy measures. Our estimation results indicate, for example, that a 1997 voluntary agreement covering energy, nutrient and pesticides use enhances technical efficiency of vegetable and plants growers, contrary to specialised flower growers. Specialised flower growers, however, did react to the 1993 multi-year agreement on energy reduction, contrary to vegetable and plant growers. Summarising, our findings are mixed but do not seem to reject the anecdotal evidence mentioned by Porter and Van der Linde (1995b) that Dutch horticulture firms' performance increased due to increased environmental stringency.firm performance, environmental stringency, technical efficiency, Environmental Economics and Policy, Production Economics, D24, Q12, Q50,

Liberalisation, care and the struggle for women's social citizenship in Vietnam

social policy;subsidies;Viet Nam;economic liberalization;care work;women workers;women's rights