Development of an empirical chart datum model for a region of the Southwest Atlantic Ocean

The datum for sounding reduction is a permanently fixed surface, to which the depths displayed on the nautical charts and the tide tables heights refer. The International Hydrographic Organization recommends adopting the lowest astronomical tide as a chart datum, although its calculation can be complex because it varies both spatially and temporally. The ever increasing accuracy of 3D positioning with Global Navigation Satellite Systems requires that the chart datum is referenced to the ellipsoid WGS84. The aims of this paper are to calculate the lowest astronomical tide and to develop an empirical model to determine the distance between the lowest astronomical tide and the WGS84 ellipsoid, for a region of the Southwest Atlantic Ocean between latitudes 36°S and 54°S and longitude 54°W, on a 5km x 5km grid. Harmonic constants from the Centre for Topographic studies of the Oceans and Hydrosphere are used to calculate the lowest astronomical tide. To refer it to the WGS84 ellipsoid, results from mean sea level models and along-track sea level heights provided by Archiving, Validation and Interpretation of Satellite Oceanographic data are utilized. The final product has been designed for open waters and will be useful both for the development of relevant marine activities in the area, as well as to increase the efficiency of hydrographic surveys while contributing to more precise navigation in critical areas

Autour de Lucien Sebag

Ce numéro présente un dossier intitulé « Autour de Lucien Sebag », établi et présenté par Salvatore D’Onofrio, Professeur à l’université de Palerme. Ce dossier se propose de revenir sur le parcours de Lucien Sebag, ethnologue élève de Claude Lévi-Strauss. Un article de Bruno Karsenti aborde le rapport au structuralisme de Lucien Sebag, auteur de l’ouvrage Marxisme et Structuralisme, publié en 1964, un an avant sa disparition prématurée à l’âge de trente et un ans. Salvatore D’Onofrio et John Leavitt reviennent, quant à eux, sur l’analyse structurale des mythes et des rêves que poursuivait Lucien Sebag et telle qu’elle apparaît dans ses articles et son livre posthume L’ Invention du Monde chez les Indiens pueblos. Les documents et matériaux de ce dossier – photographies de terrain, extraits de manuscrits et correspondances – font revivre les recherches que cet ethnologue a menées chez les Guayaki et les Ayoré en Bolivie et au Paraguay. Au sommaire de ce numéro figurent également des articles sur la relation entre les populations et les ethnologues et sur la vie des objets dans les musées d’ethnographie. Acheter ce numéro en lign

Design and commissioning of the FASER trigger and data acquisition system

The FASER experiment is a new small and inexpensive experiment that is located 480 meters downstream of the ATLAS experiment at the CERN LHC. The experiment will shed light on currently unexplored phenomena, having the potential to make a revolutionary discovery. FASER is designed to capture decays of exotic particles, produced in the very forward region, beyond the ATLAS detector acceptance. The experiment installation was completed at the end of March 2021 and the experiment is now getting ready for the LHC Run 3 data-taking. This presentation will focus mostly on the trigger and data acquisition (TDAQ) system of the experiment. The TDAQ system is going to combine information from the tracker, scintillators, and calorimeter and will send them to the PC that is going to be located on the ground at the expected physics trigger rate of 650 Hz. The presentation will include information about the commissioning of the system on the ground and in the LHC tunnel as well as it will be presenting various tests performed during the commissioning phase including first test runs using cosmic particles