Search results for "Universe"
showing 10 items of 2171 documents
Late decaying 2-component dark matter scenario as an explanation of the AMS-02 positron excess
2016
The long standing anomaly in the positron flux as measured by the PAMELA and AMS-02 experiments could potentially be explained by dark matter (DM) annihilations. This scenario typically requires a large "boost factor" to be consistent with a thermal relic dark matter candidate produced via freeze-out. However, such an explanation is disfavored by constraints from CMB observations on energy deposition during the epoch of recombination. We discuss a scenario called late-decaying two-component dark matter (LD2DM), where the entire DM consists of two semi-degenerate species. Within this framework, the heavier species is produced as a thermal relic in the early universe and decays to the lighter…
Los Subalternos en las ficciones de apropiación de menores
2013
the rol of the subordinates in the appropriation of children during the Argentinian Dictatorship has been questioned in several disciplines. However, are the works of the writer Martín Kohan which have managed to tell the untold history in a very effective way by condensing it in the creation of a credible fictional world and, because of that, grinding. In Dos veces junio, as well as in Cuentas pendientes, the consequences of the banality of evil are obvious, since it represents the consensus set within the different levels of the repressive State machinery and glipmse the consequences of all this in the life of future generations.
Porewater pressure control on subglacial soft sediment remobilization and tunnel valley formation: A case study from the Alnif tunnel valley (Morocco)
2014
25 pages; International audience; In the eastern part of the Moroccan Anti-Atlas Mountains, the Alnif area exposes a buried Ordovician glacial tunnel valley (5 km wide, 180 m deep) cut into preglacial marine sediments. The preglacial sedimentary sequence, deposited in a marine environment, is characterized by a typical "layer-cake" configuration of permeable (sand) and impermeable (clays and early-cemented sandstones) layers. At the base of the tunnel valley, a discontinuous and fan-shaped glacial conglomeratic unit 10 to 15 m thick occurs, erosively deposited over preglacial marine sediments. The conglomeratic unit is composed of preglacial intraclasts embedded within a sandy matrix. Both …
Compared regimes of NDVI and Rainfall in semi-arid regions of Africa
2006
International audience; Bi-monthly normalized difference vegetation index (NDVI) at an 8km spatial resolution from the advanced very high resolution radiometers (AVHRR) was used from 1981 to 1995 to analyse the vegetation response to rainfall supply in semi-arid regions of Africa. Within the 200-600 mm annual rainfall belt, for which the apparent NDVI response to rainfall was the strongest, three regions were selected which exhibited different patterns in their NDVI regimes and/or relationships with rainfall. The regions, located in western, southern and eastern Africa, were split into coherent sub-regions in terms of mean regime of photosynthetic activity through a cluster analysis. Overal…
Sea surges at Monaco and Nice: present-day and future variability (1998-2100).
2018
Sea surges arerapid increase of the level of the sea under atmospheric conditions that could lead to coastal submersion havingstrong impacts especially for coastal towns of the French Riviera such as Nice and the principality of Monaco.Interannual variability of the highest surges at Monaco is robustly simulates by a linear regression usingbarometric conditions over [3-10°E]-[40-45°N] as a predictor. According to 15 global circulation models,highest surges at Monaco could stay stationary for two different climate change scenarios (RCP4.5 andRCP8.5).
Adsorption of organic compounds at the surface of Enceladus' ice grains. A grand canonical Monte Carlo simulation study
2021
International audience; In this paper, we characterise the adsorption of ethylene, propanol and hexanal molecules on crystalline ice by grand canonical Monte Carlo simulations performed at 236 K, a temperature which is typical of some Enceladus’ environments. We show that at low coverage of the ice surface, the adsorption of propanol and hexanal is driven by the interaction of these molecules with the ice phase and, as a consequence, the adsorbed molecules lie more or less parallel to the ice surface. On the other hand, upon saturation, the adsorbate–adsorbate interactions become more and more important and the molecules tend to become tilted with respect to the surface, the aliphatic chain…
Phylogeny and origin of Jurassic irregular echinoids (Echinodermata: Echinoidea).
2006
27 pages; International audience; A phylogenetic analysis of Jurassic irregular echinoids is realized to explore the origin and early evolution of this important subset of echinoids. The phylogeny is based on 39 characters and considers data from apical system architecture, the corona including tuberculation and spines, Aristotle's lantern, and general test shape. Results corroborate the monophyly of Irregularia, and clarify the phylogenetic interrelationships existing between the main groups of irregular echinoids. Specializations of the Aristotle's lantern, spines, tubercles and phyllodes constitute the apomorphies for different taxa, as for the whole of Irregularia. The phylogenetic sign…
Les reptiles et synapsides fossiles de Bourgogne.
2012
65 pages; National audience; L'inventaire actuel des Amniotes (Synapsida et Reptiles) fossiles à partir des collections bourguignonnes est présenté dans l'ordre stratigraphique. Il montre que les Synapsida (Reptiles Mammaliens) sont représentés au Carbonifère et au Permien inférieur par quelques squelettes. Dans le reste du Permien (moyen ou moyen à supérieur) ) puis au Trias, c'est la palichnofaune qui prend le relai avec quelques empreintes de pas permiennes attribuées à des Capthorinomorpha et avec celles beaucoup plus nombreuses du Trias laissées par une faune très variée. Celle-ci comportait le groupe souche des Crurotarsi d'où sont issus les Crocodylomorpha et les Dinosauria via les D…
Early–middle Jurassic lytoceratid ammonites with constrictions from Morocco: palaeobiogeographical and evolutionary implications.
2008
13 pages; International audience; The ammonite genus Alocolytoceras Hyatt, 1900 is an uncommon lytoceratid with distinctive shell ornament. A set of 58 specimens, recently collected at Amellago in the central High Atlas (Morocco), has enabled us to trace a succession of three species over eight biozones from the Toarcian to the Aalenian. Two specimens from the Lusitanian Basin are added for comparison. Following a review of the genus, based on original specimens and data from the literature, seven species are considered valid. A palaeobiogeographical synthesis of 13 regions demonstrates irregular distribution patterns over time, with a constant presence in the south-west Tethys and an insta…
New specimens of Lingulocystis Thoral, 1935 (Eocrinoidea, Blastozoa) from the Arenig (Lower Ordovician) of Montagne noire (southern France): Intraspe…
2007
16 pages; The genus Lingulocystis Thoral, 1935 is a preponderant component of the echinoderm fauna of the Lower Ordovician of Montagne noire (France), as suggested by its abundant remains. Its morphology is characterized by a flattened theca, composed of a frame enclosing numerous small polygonal central plates. The new specimens have been determined partly as Lingulocystis elongata Thoral, 1935 and partly as Lingulocystis aff. deani Ubaghs, 1994. This study is the first report of Lingulocystis in the Foulon Formation. New stratigraphic ranges have been defined for both species: L. elongata from the early Tremadoc (Saint- Chinian Formation) to the middle Arenig (lower part of the Landeyran …