Cometary topography and phase darkening

Cometary surfaces can change significantly and rapidly due to the sublimation of their volatile material. Many authors have investigated this evolution; Vincent et al. (2017) have used topographic data from all comets visited by spacecrafts to derive a quantitative model which relates large scale roughness (i.e. topography) with the evolution state of the nucleus for Jupiter Family Comets (JFCs). Meanwhile, ground based observers have published measurements of the phase functions of many JFCs and reported a trend in the phase darkening, with primitive objects showing a stronger darkening than evolved ones). In this paper, we use a numerical implementation of the topographic description by Vincent et al. (2017) to build virtual comets and measure the phase darkening induced by the different levels of macro-roughness. We then compare our model with the values published by Kokotanekova et al. (2018) We find that pure geometric effects like self-shadowing can represent up to 22% of the darkening observed for more primitive objects, and 15% for evolved surfaces. This shows that although physical and chemical properties remain the major contributor to the phase darkening, the additional effect of the topography cannot be neglected

La Hoguette – Abbaye de Saint-André-en-Gouffern

Le monastère de Saint-André-en-Gouffern se trouve en limite sud de la Plaine de Caen, à proximité de Falaise. L’abbaye est fondée en 1130 par Guillaume III Talvas, sous la filiation de Savigny, chef d’ordre anglo-normand qui intègre Cîteaux en 1147, comme la totalité de ses filles. Aujourd’hui, le visage de l’abbaye médiévale est partiellement sauvegardé : au centre de l’enceinte monastique, l’aile ouest du cloître dédiée aux convers est encore debout mais a perdu sa configuration d’origine e..

Caen – Collège Pasteur

En 2015, le service d’archéologie du Calvados a conduit un diagnostic d’archéologie préventive motivé par des travaux de restauration sur les vestiges de l’enceinte urbaine de Bourg-le-Roi, situés dans le collège Pasteur. Au milieu du xie s., dès lors que Guillaume le Conquérant établit son pouvoir à Caen, la ville connaît un essor structurel important réparti dans un premier temps entre le château et les abbayes de Saint-Etienne et de la Sainte-Trinité. Ainsi, différentes enceintes urbaines ..

Comparison of local electrochemical impedance measurements derived frombi-electrode and microcapillary techniques

In the present paper, local electrochemical impedance spectrawere obtained on a 316L stainless steel from two configurations: a dual microelectrode (bi-electrode) and microcapillaries. With the bi-electrode, the local impedance measurements were made from the ratio of the applied voltage to the local current density calculated from the application of the ohm’s law. With the use of microelectrochemical cells, the specimen surface area in contact with the electrolyte is limited by the use of glass microcapillaries and the local impedance was defined fromthe ratio of the local potential to the local current restricted to the analysed surface area. Differences and similarities observed in local impedance spectra obtained with the two configurations were describe

Pont-de-l’Arche – Abbaye de Bonport : tour d’enceinte

L’abbaye cistercienne de Bonport est fondée sur la rive gauche de la Seine, en aval du bourg médiéval de Pont-de-l’Arche, par Richard Cœur-de-Lion entre 1189 et 1190. Son implantation est singulière puisqu’elle est la seule abbaye construite sur une terrasse alluviale surplombant le fleuve, tout en ayant les pieds dans l’eau. La conservation presque intégrale de deux ailes du carré claustral (aile des moines, aile du réfectoire et vestiges de l’abbatiale), est inégalée dans la Normandie ciste..

Bose-Einstein condensates in fast rotation

In this short review we present our recent results concerning the rotation of atomic Bose-Einstein condensates confined in quadratic or quartic potentials, and give an overview of the field. We first describe the procedure used to set an atomic gas in rotation and briefly discuss the physics of condensates containing a single vortex line. We then address the regime of fast rotation in harmonic traps, where the rotation frequency is close to the trapping frequency. In this limit the Landau Level formalism is well suited to describe the system. The problem of the condensation temperature of a fast rotating gas is discussed, as well as the equilibrium shape of the cloud and the structure of the vortex lattice. Finally we review results obtained with a quadratic + quartic potential, which allows to study a regime where the rotation frequency is equal to or larger than the harmonic trapping frequency.Comment: Laser Physics Letters 2, 275 (2005

La Hoguette – Abbaye de Saint-André-en-Gouffern

Durant le printemps 2013 dans le cadre du chantier-école de l’Université de Caen de 4 semaines, des sondages archéologiques ont été ouverts dans le carré claustral de l’abbaye savignio-cistercienne de Saint-André-en-Gouffern (commune de La Hoguette), à environ 5 km au sud-ouest de Falaise. Cette abbaye d’hommes est fondée en 1131 par Guillaume III Talvas, dans l’ancien diocèse de Sées. Le site monastique conserve encore certains bâtiments à l’intérieur d’une enceinte de 8,4 ha, tels que l’ail..

Galvanic Coupling Between Pure Copper and Pure Aluminum Experimental Approach and Mathematical Model

The corrosion behavior of a pure aluminum/pure copper couple in a weakly conductive sulfate solution was investigated. Potential and current distributions on the surface of the model couple at the beginning of immersion were obtained by solving the Laplace equation using a finite element method (FEM) algorithm. The potential distribution predicted by the calculations was checked using a Ag/AgCl microreference electrode. A good agreement was found between experimental and theoretical results. It was shown that the reaction occurring at the copper electrode was oxygen reduction, while aluminum remote from the Al/Cu interface remained in the passive state. Moreover, calculations predicted a large cathodic current, related to an increase in oxygen reduction, restricted to copper at the Al/Cu interface. This led to a local pH increase reaching values higher than 9, allowing the dissolution of aluminum to occur close to the interface. Combining these data with optical and scanning electron microscope observations after 24 h of immersion in the sodium sulfate solution allowed a three-step mechanism to be proposed to explain the corrosion damage, and particularly the presence of a copper deposit on the aluminum surface, some distance from the Al/Cu interface, a phenomenon currently observed in commercial copper-rich aluminum alloys

Interference of an array of independent Bose-Einstein condensates

We have observed high-contrast matter wave interference between 30 Bose-Einstein condensates with uncorrelated phases. Interference patterns were observed after independent condensates were released from a one-dimensional optical lattice and allowed to expand and overlap. This initially surprising phenomenon is explained with a simple theoretical model which generalizes the analysis of the interference of two independent condensates

Savigny-le-Vieux – Abbaye de Savigny

La fondation de l’abbaye Savigny en 1112 est un acte majeur du monachisme réformé du nord-ouest de la France au xiie s. Cette abbaye originellement bénédictine recrute massivement dans les familles seigneuriales locales, lesquelles favorisent l’essaimage d’environ 32 maisons dans l’ouest de la France et en Angleterre. Toutefois, l’ampleur du réseau savignien et les problèmes de gestion des abbayes filles font que l’abbé de Savigny décide d’intégrer l’ordre cistercien en 1147. Forte de son rés..