Implosion Symmetry of Laser-Irradiated Cylindrical Targets

We consider the symmetry of cylindrical implosions of laser targets with parameters corresponding to experiments proposed for the LIL laser facility at Bordeaux: eight laser beams in octahedrical configuration, delivering a total of 50 kJ of 0.35 (xm laser light in 5 ns, impinging on 1.26 mm diameter polystyrene cylindrical shells filled with deuterium at 30 bar and 5.35 mg cm"3; this configuration allows to place diagnostics along the symmetry axis to evaluate directly the uniformity of implosion. Numerical studies have been carried out by using the hydrodynamic computer codes MULTI and CHIC, including one-dimensional, and two-dimensional R-Z and R-6 simulations. Deuterium is compressed into a 1 mm long and 50 |xm diameter filament, with density ranging from 2 to 6 g cm-3 and temperatures above 1000 eV. In spite of the reduced numbers of beams, a good symmetry can be achieved with a careful choice of the irradiation pattern. The heat transport smoothing between laser absorption zone and ablation layer plays a fundamental role in the attenuation of residual non-uniformities. Also, it has been found that the radiation transport determines the radial structure of the compressed filament

Proceedings of the international colloquium photosynthesis and remote sensing

The in vivo specific absorption coefficient of phytoplankton a*ph (lambda) was measured along an equatorial transect in the Pacific Ocean during the JGOFS-cruise in Octobre 1994 in order to validate bio-optical models of primary production. The fiber filter technique was used on board, as well as spectrofluorometry for pigment determination and flow cytometry for cells counting. The a*ph (435-441 nm) walues strongly decreased from oligotrophic to mesotrophic waters (between 170°E and 153°W). This zonal variation reflected a change in phytoplankton composition, dominated by #Prochlorococcus$ in the oligotrophic zone and by picoeucaryotes in the mesotrophic one. Such variations in a*ph have to be taken into account for estimating primary production of the equatorial Pacific Ocean from ocean colour imagery. (Résumé d'auteur

‘Mind the gap’: Responding to the indeterminable in migration

Prompted by the paper by Miriam Tedeschi, this commentary attempts to unsettle the dominant understanding of a relation in migration research that prioritises linkages between people, places and organisations while treating boundaries as limits to overcome. Building on geographers’ earlier engagements with Adorno, Levinas and extending this conversation to include Blanchot, the analysis attempts to move beyond the hold of mastery on a relation with alterity. The paper argues for an interruptive non-relation that resists the appropriation and affirms the dispersion of the self by the alterity it cannot internalise. It offers an alternative response to difference in migration that avoids bringing it to unifying continuity. Instead of treating interruptions in migration as gaps to be resolved through language, the paper considers the possibility of a neutral writing that reflects the powerlessness to say the unspeakable. In a movement of inscription and effacement, neutral writing invokes the unspeakable pain and affliction that exceeds the concepts to which it gives rise. The neuter answers for the non-subject of loss and trauma, the nothing often haunting international migrants

Electromagnetic Compatibility of a Low Voltage Power Supply for the ATLAS Tile Calorimeter Front-End Electronics

The front-end electronics of the ATLAS Tile Calorimeter is powered by DC/DC converters that sit close to it. The performance of the detector electronics is constrained by the conducted noise emissions of its power supply. A compatibility limit is defined for the system. The noise susceptibility of the front-end electronics is evaluated, and different solutions to reduce the front-end electronics noise are discussed and tested

Rapport de la campagne PROPPAC 04 à bord du N.O. Le Suroît (30 octobre au 26 novembre 1989)

La campagne PROPPAC 4, dont l'ORSTOM était maître d'oeuvre, s'est déroulée du 30 octobre au 26 novembre 1989 entre 20°S (nord de la Nouvelle-Calédonie) et 5°S le long de 165°E. L'objectif était de décrire en deux points fixes de 8 jours la variabilité à court terme des paramètres hydrologiques et planctoniques, leur répartition le long de la colonne d'eau, la distribution des différentes classes d'organismes et de mesurer l'intensité des flux : advection et mélanges, taux de sédimentation, production primaire et secondaire. Ces informations, recueillies dans deux situations oligotrophes considérées comme typiques, doivent permettre de compléter les données rudimentaires de biologie qui sont collectées au cours des stations de courte durée des radiales bi-annuelles SURTROPAC depuis 1984 et servir à la définition de la relation production-hydrologie dans le Pacifique occidental. La première station de 8 jours, dont la position a été choisie à l'issue d'une radiale préliminaire, était située à 7-8°S et caractérisée par une pycnocline profonde (75 m) et marquée, avec un maximum de chlorophylle vers 80-100 m. La seconde, située à 16°S, correspondrait à une structure hydrologique avec un faible gradient et des sels nutritifs vers 140 m, le maximum de chlorophylle se situant à 120-140 m. (Résumé d'auteur

Passive education

This paper does not present an advocacy of a passive education as opposed to an active education nor does it propose that passive education is in any way ‘better’ or more important than active education. Through readings of Maurice Blanchot, Jacques Derrida and B.S. Johnson, and gentle critiques of Jacques Rancière and John Dewey, passive education is instead described and outlined as an education which occurs whether we attempt it or not. As such, the object of critique for this essay are forms of educational thought which, through fate or design, exclude the passive dimension, either within or outside of formal educational settings. An underlying component of this argument is therefore also that education does occur outside of formal educational settings and that, contra Gert Biesta and his critique of ‘learnification’, we may gain rather than lose something by attending to it as education

The ATLAS SCT grounding and shielding concept and implementation

This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is a very large Michelson interferometer, with 3 km-long arms. In this paper, following a presentation of the physics requirements, leading to the specifications for the construction of the detector, a detailed description of all its different elements is given. These include civil engineering infrastructures, a huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), all of the optical components, including high quality mirrors and their seismic isolating suspensions, all of the electronics required to control the interferometer and for signal detection. The expected performances of these different elements are given, leading to an overall sensitivity curve as a function of the incoming gravitational wave frequency. This description represents the detector as built and used in the first data-taking runs. Improvements in different parts have been and continue to be performed, leading to better sensitivities. These will be detailed in a forthcoming paper