Astrophysical signatures of leptonium

More than 10^43 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries. However, these models are difficult to reconcile with the distribution of positrons, which are highly concentrated in the Galactic bulge, and therefore require specific propagation of the positrons through the interstellar medium. Alternative sources include dark matter decay, or the supermassive black hole, both of which would have a naturally high bulge-to-disc ratio. The chief difficulty in reconciling models with the observations is the intrinsically poor angular resolution of gamma-ray observations, which cannot resolve point sources. Essentially all of the positrons annihilate via the formation of positronium. This gives rise to the possibility of observing recombination lines of positronium emitted before the atom annihilates. These emission lines would be in the UV and the NIR, giving an increase in angular resolution of a factor of 10^4 compared to gamma ray observations, and allowing the discrimination between point sources and truly diffuse emission. Analogously to the formation of positronium, it is possible to form atoms of true muonium and true tauonium. Since muons and tauons are intrinsically unstable, the formation of such leptonium atoms will be localised to their places of origin. Thus observations of true muonium or true tauonium can provide another way to distinguish between truly diffuse sources such as dark matter decay, and an unresolved distribution of point sources.Comment: Accepted for publication in EPJ-D, 9 pages, 4 figure

An upper limit to the dry merger rate at <z> ~ 0.55

We measure the fraction of Luminous Red Galaxies (LRGs) in dynamically close pairs (with projected separation less than 20 $h^{-1}$ kpc and velocity difference less than 500 km s$^{-1}$) to estimate the dry merger rate for galaxies with $-23 < M(r)_{k+e,z=0.2} +5 \log h < -21.5$ and $0.45 < z < 0.65$ in the 2dF-SDSS LRG and QSO (2SLAQ) redshift survey. For galaxies with a luminosity ratio of $1:4$ or greater we determine a $5\sigma$ upper limit to the merger fraction of 1.0% and a merger rate of $< 0.8 \times 10^{-5}$ Mpc$^{-3}$ Gyr$^{-1}$ (assuming that all pairs merge on the shortest possible timescale set by dynamical friction). This is significantly smaller than predicted by theoretical models and suggests that major dry mergers do not contribute to the formation of the red sequence at $z < 0.7$.Comment: 8 pages emulateapj style, 3 figures, accepted by AJ (March 2010

Eco-neighborhoods and the question of locational advantage: a socio-spatial analysis of French ‘ÉcoQuartiers’

In response to the need for ecological transition, a multitude of eco-city and eco-neighborhood initiatives have been instigated around the world. A major challenge has been the charge, captured by terms such as ‘eco enclaves’ and ‘environmental gentrification’, that these initiatives poorly attend to questions of social diversity and spatial equity. In France, too, where since 2008 a major national ÉcoQuartier initiative has been underway with close to 500 projects launched, some have warned against creating ‘écoquartiers bobo’ – urban development catering for a mainly ‘bourgeois-bohemian’ clientele. Consequently, this article investigates whether there may be selectivity at work in the placement of ÉcoQuartiers that favours advantageous locations. To this end, a detailed socio-spatial analysis was carried out with a sample of 214 implemented ÉcoQuartiers. Using exploratory factor analysis (EFA), eight factors were extracted from a comprehensive set of 53 socio-economic and geospatial variables. These were used to compare the sampled ÉcoQuartiers with the overall territory (mainland France and Corsica) as well as with a parallel national urban policy initiative, the ‘Quartiers Prioritaires de la Ville’ (‘urban priority neighborhoods’) which expressly focuses on areas of social disadvantage. As a result, this study reveals several dimensions of locational selectivity, which are discussed in terms of their policy and practice implications as well as their significance for conceptualizing eco-neighborhoods as socio-spatially inclusive places

Dynamic optimization of the transmission efficiency between the solid state microwave sources and the microwave applicator

[EN] Microwaves are a fast way to dry moist goods through volumetric heating. During the drying process, materials change their electrical properties. As a result, the impedances at the feed port of the applicator will change and the microwave source is not matched anymore. The amount of reflected power increases and the process efficiency reduces. New semiconductor high power sources can perform a dynamic impedance matching. A lab scaled functional model with two sources was designed and realized. For measuring the scattering parameters during the process run, an embedded two-port vector network analyzer was added. Measurement results confirm the feasibility of the concept.Zuber, S.; Joss, M.; Tresch, S.; Kleingries, M. (2018). Dynamic optimization of the transmission efficiency between the solid state microwave sources and the microwave applicator. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 291-298. https://doi.org/10.4995/IDS2018.2018.7412OCS29129

Smart Cities: Towards a New Citizenship Regime? A Discourse Analysis of the British Smart City Standard

Growing practice interest in smart cities has led to calls for a less technology-oriented and more citizen-centric approach. In response, this articles investigates the citizenship mode promulgated by the smart city standard of the British Standards Institution. The analysis uses the concept of citizenship regime and a mixture of quantitative and qualitative methods to discern key discursive frames defining the smart city and the particular citizenship dimensions brought into play. The results confirm an explicit citizenship rationale guiding the smart city (standard), although this displays some substantive shortcomings and contradictions. The article concludes with recommendations for both further theory and practice development

Seeking celestial Positronium with an OH-suppressed diffraction-limited spectrograph

Celestially, Positronium (Ps), has only been observed through gamma-ray emission produced by its annihilation. However, in its triplet state, a Ps atom has a mean lifetime long enough for electronic transitions to occur between quantum states. This produces a recombination spectrum observable in principle at near IR wavelengths, where angular resolution greatly exceeding that of the gamma-ray observations is possible. However, the background in the NIR is dominated by extremely bright atmospheric hydroxyl (OH) emission lines. In this paper we present the design of a diffraction-limited spectroscopic system using novel photonic components - a photonic lantern, OH Fiber Bragg Grating filters, and a photonic TIGER 2-dimensional pseudo-slit - to observe the Ps Balmer alpha line at 1.3122 microns for the first time.Comment: 6 pages, 9 Figures, 2 Tables. Accepted to Applied Optics feature issue on Astrophotonic

Sustainability Indicators Past and Present: What Next?

This paper discusses the current state of thought amongst the Sustainability Indicator (SI) community, what has been achieved and where we are succeeding and failing. Recent years have witnessed the rise of “alternative facts” and “fake news” and this paper discusses how SIs fit into this maelstrom, especially as they are themselves designed to encapsulate complexity into condensed signals and it has long been known that SIs can be selectively used to support polarized sides of a debate. This paper draws from chapters in a new edited volume, the “Routledge Handbook of Sustainability Indicators and Indices”, edited by the authors. The book has 34 chapters written by a total of 59 SI experts from a wide range of backgrounds, and attempts to provide a picture of the past and present, strengths and weaknesses of SI development today. This paper is an “analysis of those analyses”—a mindful reflection on reflection, and an assessment of the malign and benign forces at work in 2018 within the SI arena. Finally, we seek to identify where SIs may be going over the coming, unpredictable years

The New Urban Agenda: key opportunities and challenges for policy and practice

The UN-HABITAT III conference held in Quito in late 2016 enshrined the first Sustainable Development Goal (SDG) with an exclusively urban focus. SDG 11, as it became known, aims to make cities more inclusive, safe, resilient and sustainable through a range of metrics, indicators, and evaluation systems. It also became part of a post-Quito ‘New Urban Agenda’ that is still taking shape. This paper raises questions around the potential for reductionism in this new agenda, and argues for the reflexive need to be aware of the types of urban space that are potentially sidelined by the new trends in global urban policy