Search results for "star"
showing 10 items of 4285 documents
GRB 050904 at redshift 6.3: observations of the oldest cosmic explosion after the Big Bang
2005
We present optical and near-infrared observations of the afterglow of the gamma-ray burst GRB 050904. We derive a photometric redshift z = 6.3, estimated from the presence of the Lyman break falling between the I and J filters. This is by far the most distant GRB known to date. Its isotropic-equivalent energy is 3.4x10^53 erg in the rest-frame 110-1100 keV energy band. Despite the high redshift, both the prompt and the afterglow emission are not peculiar with respect to other GRBs. We find a break in the J-band light curve at t_b = 2.6 +- 1.0 d (observer frame). If we assume this is the jet break, we derive a beaming-corrected energy E_gamma = (4-12)x10^51 erg. This limit shows that GRB 050…
The XMM-Newton Optical Monitor survey of the Taurus molecular cloud
2007
The Optical Monitor (OM) on-board XMM-Newton obtained optical/ultraviolet data for the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), simultaneously with the X-ray detectors. With the XEST OM data, we aim to study the optical and ultraviolet properties of TMC members, and to do correlative studies between the X-ray and OM light curves. In particular, we aim to determine whether accretion plays a significant role in the optical/ultraviolet and X-ray emissions. The Neupert effect in stellar flares is also investigated. Coordinates, average count rates and magnitudes were extracted from OM images, together with light curves with low time resolution (a few kiloseconds). For a …
Preliminary report on new echinoderm Lagerstatten from the Upper Ordovician of the eastern Anti-Atlas, Morocco.
2006
8 pages (p.23-30); International audience; Four distinct echinoderm Lagerstatten have recently been discovered in the Upper Ordovician of the eastern Anti-Atlas, Morocco. They have yielded hundreds of exquisitely preserved specimens. Their taphonomy and associated lithology both suggest rapid, in situ burial. Here we discuss the diverse range of assemblages represented and their significance to the diversity of echinoderms in the Lower Palaeozoic. The oldest assemblage (Izegguirene Formation, lowermost Caradoc) is dominated by eocrinoids, large ophiuroids, and mitrate stylophorans associated with rare crinoids. It shows strong similarities with slightly older faunas described from the under…
Regional coherency of boreal forest growth defines Arctic driftwood provenancing
2016
Arctic driftwood represents a unique proxy archive at the interface of marine and terrestrial environments. Combined wood anatomical and dendrochronological analyses have been used to detect the origin of driftwood and may allow past timber floating activities, as well as past sea ice and ocean current dynamics to be reconstructed. However, the success of driftwood provenancing studies depends on the length, number, and quality of circumpolar boreal reference chronologies. Here, we introduce a Eurasian-wide high-latitude network of 286 ring width chronologies from the International Tree Ring Data Bank (ITRDB) and 160 additional sites comprising the three main boreal conifers Pinus, Larix, a…
Diverse growth trends and climate responses across Eurasia’s boreal forest
2016
The area covered by boreal forests accounts for similar to 16% of the global and 22% of the Northern Hemisphere landmass. Changes in the productivity and functioning of this circumpolar biome not o ...
Lowering histamine formation in a red Ribera del Duero wine (Spain) by using an indigenous O. oeni strain as a malolactic starter
2016
This study demonstrates for the first time that a non-commercial selected autochthonous O. oeni strain has been used to conduct malolactic fermentation (MLF) while lowering histamine formation in the same winery. Lactic acid bacteria (LAB) were isolated from 13 vats before and after spontaneous MLF at the Pago de Carraovejas winery from the Ribera del Duero region (Spain). Only O. oeni were present, typed and characterized, and both histamine producer and non-producers existed. From the non-producers, one strain was selected to become a starter according to its genetic profile, prevalence in the different wines in the winery, resistance to alcoholic degree, resistance to high polyphenolic c…
Deimatism: a neglected component of antipredator defence
2017
Deimatic or ‘startle’ displays cause a receiver to recoil reflexively in response to a sudden change in sensory input. Deimatism is sometimes implicitly treated as a form of aposematism (unprofitability associated with a signal). However, the fundamental difference is, in order to provide protection, deimatism does not require a predator to have any learned or innate aversion. Instead, deimatism can confer a survival advantage by exploiting existing neural mechanisms in a way that releases a reflexive response in the predator. We discuss the differences among deimatism, aposematism, and forms of mimicry, and their ecological and evolutionary implications. We highlight outstanding questions …
Leaf starch and nutrient responses to stem girdling and drought stress with respect to understanding HLB (greening) symptoms in citrus
2016
The most important problem in world citrus production is the bacterial disease Huanglongbing (HLB; greening) which is caused by a phloem-limited bacterium that is vectored by a phloem-feeding psyllid. The earliest visible symptoms of HLB in leaves are an asymmetrical chlorosis referred to as "blotchy mottle", thought to be from starch accumulation from a phloem dysfunction and a decline in root health. We tested the hypothesis that such visible symptoms are not unique to HLB by stemgirdling two year-old seedling trees of 'Cleopatra' mandarin and 'Swingle' citrumelo rootstocks in the greenhouse. Girdling induced a 4-fold greater starch concentration in leaves on well-watered trees while star…
Following the Antarctic Circumpolar Current: patterns and processes in the biogeography of the limpet Nacella (Mollusca: Patellogastropoda) across th…
2017
14 pages; International audience; AimWe use an integrative biogeographical approach to further understand the evolution of an important Southern Ocean marine benthic element, the limpet genus Nacella (Mollusca: Patellogastropoda).LocationSouthern Ocean.MethodsWe used multi-locus time-calibrated phylogeny of Nacella at the scale of the whole Southern Ocean to elucidate the underlying processes involved in the origin and diversification of the genus.ResultsDivergence-time estimates suggest that soon after its origin during the mid-Miocene (c. 12.5 Ma), Nacella separated into two main lineages currently distributed in (1) South America and (2) Antarctica and the sub-Antarctic islands. We ident…
Transcriptome analysis of the Populus trichocarpa–Rhizophagus irregularis Mycorrhizal Symbiosis: Regulation of Plant and Fungal Transportomes under N…
2017
Nutrient transfer is a key feature of the arbuscular mycorrhizal (AM) symbiosis. Valuable mineral nutrients are transferred from the AM fungus to the plant, increasing its fitness and productivity, and, in exchange, the AM fungus receives carbohydrates as an energy source from the plant. Here, we analyzed the transcriptome of the Populus trichocarpa-Rhizophagus irregularis symbiosis using RNA-sequencing of non-mycorrhizal or mycorrhizal fine roots, with a focus on the effect of nitrogen (N) starvation. In R. irregularis, we identified 1,015 differentially expressed genes, whereby N starvation led to a general induction of gene expression. Genes of the functional classes of cell growth, memb…