The two uniform infinite quadrangulations of the plane have the same law

We prove that the uniform infinite random quadrangulations defined respectively by Chassaing-Durhuus and Krikun have the same distribution.Comment: English version of arXiv:0805.4687, with various improvement

Improved high-performance shock tube

Mylar diaphragms in shock tubes are a major improvement over steel diaphragms. Other improvements include: better electrode design; improved flow by opening the throat and removing all constrictions; and improved driver geometry by optimizing volume and shape

Spectra of large diluted but bushy random graphs

We compute an asymptotic expansion in $1/c$ of the limit in $n$ of the empirical spectral measure of the adjacency matrix of an Erd\H{o}s-R\'enyi random graph with $n$ vertices and parameter $c/n$. We present two different methods, one of which is valid for the more general setting of locally tree-like graphs. The second order in the expansion gives some information about the edge.Comment: 24 pages, 5 figure

A transitory regime : water supply in Conakry, Guinea

Both consumers and the government benefited from reform of the water system in Conakry, Guinea, whose deterioration since independence had become critical by the mid-1980s. Less than 40 percent of Conakry's population had access to piped water - low even by regional standards - and service was intermittent, at best, for the few who had connections. The public agency in charge of the sector was inefficient, overstaffed, and virtually insolvent. In several ways, the reform introduced to the sector in 1989 under a World Bank-led project was remarkable. It showed that even in a weak institutional environment, where contracts are hard to enforce and political interference is common, private sector participation can improve sector performance. The authors discuss the mechanismsthat made progress possible and identify factors that inhibit the positive effects of reform. Water has become very expensive, the number of connections has increased very slowly, and conflicts have developed between SEEG (the private operator) and SONEG (the state agency). Among the underlying problems: a) The lack of strong, stable institutions. b) The lack of an independent agency capable of restraining arbitrary government action, regulating the private operator, and enforcing contractual arrangements. c) The lack of adequate conflict resolution mechanisms for contract disputes. d) Weak administrative capacity.Environmental Economics&Policies,Water and Industry,Water Conservation,Decentralization,Water Supply and Systems,Town Water Supply and Sanitation,Water and Industry,Water Supply and Sanitation Governance and Institutions,Environmental Economics&Policies,Water Conservation

One School: Using Teach-Throughs to Ensure Consistency

Presented as a Poster Presentation at 2020 IUSM Education Day

On the polarization mechanism in the R Mon/NGC 2261 complex

The detection of circular polarization in R Mon and NGC 2261 is reported. This detection implies that the mechanism responsible for the linear and circular polarization is most likely multiple scattering in a flattened distribution. It replaces the previously suggested scenario where dichroic extinction by elongated dust grains aligned by a toroidal magnetic field was producing the polarization. The multiple scattering interpretation of linear polarization maps also means that these maps now provide direct evidence for a circumstellar disk around R Mon and possibly around many other young stellar objects

Weak lensing study of Abell 2029

Abell 2029 is one of the most studied clusters due to its proximity (z=0.07), its strong X-ray brightness and its giant cD galaxy which is one of the biggest stellar aggregates we know. We present here the first weak lensing mass reconstruction of this cluster made from a deep I-band image of 28.5'x28.5' centered on the cluster cD galaxy. This preliminary result allows us already to show the shape similarities between the cD galaxy and the cluster itself, suggesting that they form actually a single structure. We find a lower estimate of the total mass of 1.8 10^14 h^-1 solar masses within a radius of 0.3 h^-1 Mpc. We finally compute the mass-to-cD-light ratio and its evolution as a function of scale.Comment: 5 pages, to appear in the proceedings of "Matter and Energy in Clusters of Galaxies", ASP Conference Serie

A program for computing shock-tube gas dynamic properties

Computer program calculates thermodynamic properties from basic spectroscopic data. Program capacity is a mixture of 100 different species composed of ten different elements. The output is a complete thermodynamic and chemical description of the gas

Clustering of MgII absorption line systems around massive galaxies: an important constraint on feedback processes in galaxy formation

We use the latest version of the metal line absorption catalogue of Zhu & M\'enard (2013) to study the clustering of MgII absorbers around massive galaxies (~10^11.5 M_sun), quasars and radio-loud AGN with redshifts between 0.4 and 0.75. Clustering is evaluated in two dimensions, by binning absorbers both in projected radius and in velocity separation. Excess MgII is detected around massive galaxies out to R_p=20 Mpc. At projected radii less than 800 kpc, the excess extends out to velocity separations of 10,000 km/s. The extent of the high velocity tail within this radius is independent of the mean stellar age of the galaxy and whether or not it harbours an active galactic nucleus. We interpret our results using the publicly available Illustris and Millennium simulations. Models where the MgII absorbers trace the dark matter particle or subhalo distributions do not fit the data. They overpredict the clustering on small scales and do not reproduce the excess high velocity separation MgII absorbers seen within the virial radius of the halo. The Illustris simulations which include thermal, but not mechanical feedback from AGN, also do not provide an adequate fit to the properties of the cool halo gas within the virial radius. We propose that the large velocity separation MgII absorbers trace gas that has been pushed out of the dark matter halos, possibly by multiple episodes of AGN-driven mechanical feedback acting over long timescales.Comment: 10 pages, 11 figures, accepted in MNRA