129 research outputs found
Dirac Point and Edge States in a Microwave Realization of Tight-Binding Graphene-like Structures
We present a microwave realization of finite tight-binding graphene-like
structures. The structures are realized using discs with a high index of
refraction. The discs are placed on a metallic surface while a second surface
is adjusted atop the discs, such that the waves coupling the discs in the air
are evanescent, leading to the tight-binding behavior. In reflection
measurements the Dirac point and a linear increase close to the Dirac point is
observed, if the measurement is performed inside the sample. Resonances due to
edge states are found close to the Dirac point if the measurements are
performed at the zigzag-edge or at the corner in case of a broken benzene ring.Comment: 4 pages, 6 figure
Un Spongiaire Sphinctozoaire colonial apparenté aux constructeurs de récifs triasiques survivant dans le bathyal de Nouvelle-Calédonie
Un second représentant actuel des Sphinctozoaires, importants constructeurs de récifs au Permo-Trias, a été découvert dans la zone bathyale de la NouvelleCalédonie. Contrairement au survivant déjà connu, #Valecetia crypta$, il a conservé le mode de croissance colonial et les capacités constructrices de ses analogues fossiles. Sa croissance est bien plus lente que celle des coraux récifaux actuels. La base d'une construction de 10 cm d'épaisseur a été datée de 700 ans. (Résumé d'auteur
Séance spécialisée : géodynamique des bassins océaniques et des marges continentales
Une morphologie de fonds sous-marins bathyaux comportant des indurations liées à des dépôts ferro-manganésifères inclus dans des sédiments hémipélagiques peu ou pas cimentés a été découverte sur une ride volcanique tertiaire au large de la Nouvelle-Calédonie (SW Pacifique). Elle semble être en relation avec des circulations hydrothermales au travers de la couverture sédimentaire pendant l'activité volcanique miocène de la ride des Loyauté. (Résumé d'auteur
Case studies on decapod crustaceans from the Philippines reveal deep, steep underwater slopes as prime habitats for 'rare' species
10.1007/s10531-009-9744-xBiodiversity and Conservation192575-586BONS
Disappearance of Acropora from the Marquesas (French Polynesia) during the last deglacial period
International audienceThe major reef-building coral genus Acropora has never been recorded, living or fossil, from the Marquesas Islands in the central Pacific Ocean, which are characterized by limited modern reef formations. During the "Musorstom 9" cruise in 1997, investigations of marine platforms representing drowned reef systems revealed for the first time the presence of two Acropora species as fossils at seven Marquesas islands. The predominant species was Acropora valida, which was widespread in the archipelago and dated between 7.4 and 48.6 ka, providing evidence of an earlier Pacific distribution pattern broader than previously observed. It is proposed that disappearance of Acropora after 7.4 ka was linked to climatic events probably ENSO events controlling the distribution of corals and coral reefs in the eastern Pacific without excluding alternatively the effects of an increase in sea-level rise
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