The Choice of Ignorance: The Debate on Ethnic and Racial Statistics in France

A researcher or a journalist trying to compare the situation of ethnic and racial minorities in the United States and in France immediately confronts a crippling obstacle. The concept of ‘ethnic and racial minority’ as such is not used in France. This is not simply a matter of vocabulary –something the French typically like to argue about; the problem rather lies in the very incomparability of populations that one is talking about. Many of the categories that do exist in political discourse and public debate can of course be found in statistics. But there are no data describing the situation of minorities in France that could be compared with those produced in the United States. This state of affairs in French statistics – gathering has been the subject of major criticism for some 20 years now; it has gotten to the point that it has triggered a controversy of rare violence between those that would like to see statistics take into account the diversity of the population and those who denounce the danger that such statistics might pose of ethnicizing or racializing society. The media focus on the contentiousness of this debate has been such as to sometimes lose sight of the very existence of discrimination and the flaws of the Republican model that are at the root of the controversy in the first place

New evidence for the origin of the Porcupine Median Volcanic Ridge: Early Cretaceous volcanism in the Porcupine Basin, Atlantic margin of Ireland

International audienceTwo-dimensional pre-stack depth migrated seismic reflection data, gravity and velocity models are used to assess the nature and origin of a prominent, buried ridge, the Porcupine Median Volcanic Ridge (PMVR) within the Porcupine Basin, offshore Ireland. The debate on the origin of the PMVR during the past 30 years has followed the evolution of the concept of continental margin genesis. In this paper, the origin of the ridge is evaluated on the basis of the internal geometry and velocity structure, revealed by the seismic data. Implication of the presence of these type of ridges in hyper-extensional rifted margins is discussed and compared with other margins. The analysis indicates that the ridge is an extrusive volcanic ridge, probably tholeiitic in composition, constructed by stacked hyaloclastite deltas and topped by carbonate platforms. The results invalidate previously proposed models involving highly rotated fault blocks and the serpentinite mud volcanism. The extension magnitude analysis suggests a highly stretched setting where limited mantle serpentinization may have occurred, but the architecture and velocity of the PMVR demonstrates that it is made of lower velocity materials than serpentinite. During the opening of the North Atlantic, the PMVR represents the northern time-equivalent magmatic event expressed along the Newfoundland-Iberia-Galicia, recorded by the J anomaly that originate from Cretaceous volcanic deposits

Mouvements verticaux de la marge NO africaine

National audienc

Mouvements verticaux de la marge NO africaine

National audienc

Direct VLBI observations of Global Navigation Satellite System signals

We describe an experiment carried out to observe signals emitted by GLONASS (GLObal NAvigation Satellite System) satellites using the Very Long Baseline Interferometry (VLBI) technique. This test was performed on a single baseline and had as its primary goal to evaluate the capability of the VLBI system to observe GNSS (Global Navigation Satellite System) signals in terms of scheduling, tracking, acquisition, recording, correlation and processing of data. The general aim of such observations is to contribute to the connection of the reference frames for GNSS and VLBI by so-called co-location in space, or space-ties, as a complement to the existing so-called local-ties on the Earth’s surface. In our experiment we found an interferometric response from both signals emitted by GLONASS satellites and a natural radio source that was observed as a calibrator, using the same VLBI equipment. The derived fringe phase scatters were 80 ps (2.5 cm) and 1.3 ns (39 cm) in 1 second for the GLONASS satellite and the calibrator signals, respectively. This indicates that the accuracy is not limited by GLONASS signals, but by the calibrator. Our results show that VLBI observations of GNSS signals are possible and have the potential to derive the satellite positions on a centimetre level for observing times of just a few minutes. Future experiments should include several baselines and a larger number of calibrators in close angular distance to the satellite tracks to allow frequent switching between calibrator and satellite signals