1,721,150 research outputs found
Solar incubation cuts down parenmtal care in a burrow nesting tropical shorebird, the crab plover Dromas ardeola
No full textCrystal chemistry of a clinopyroxene series in ultrafemic xenoliths from North-Eastern Brazil
No full textA series of clinopyroxenes (Cpx) in peridotitic
spinel nodules from Rio Grande do Norte, North-Eastern
Brazil, was investigated by X-ray diffraction and electron
microprobe analyses and compared with an analogous series
from spinel peridotite nodules from Mt. Leura, Victoria,
Australia. The examined Cpx series is mainly characterized
by increasing Mg/(Mg+Fe 2+) ratio (i.e. increase of
refractory character of the host nodules), by the substitutions
of A1 vi vs Mg in the MI site and Navs (Ca+Mg)
in the M2 site, whereas A1 iv in the T site remains substantially
constant. The strong Na depletion in the Brazilian
Cpx causes a different charge balance from that in the Australian
Cpx, in which Na remains quite constant. This feature,
associated with the differences in polyhedral and cell
volumes which are significantly higher in the Brazilian Cpx
than in those of the Australian Cpx, suggests that the Brazilian
Cpx crystal chemistry may be related to a lower pressure
regime, compared with that of the Australian Cpx series
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Discovery of 15 Myr Old pre-Main Sequence Stars with Active Accretion and Sizeable Discs in NGC 6611
No full textAttention is given to a population of 110 stars with prominent near-infrared (NIR) excess in the NGC 6611 cluster of the Eagle Nebula that have optical colours typical of pre-main sequence (PMS) stars older than 10 Myr. In principle, their V-I colours would be consistent with those of young PMS objects (< 1 Myr), whose radiation is heavily obscured by a circumstellar disc seen at high inclination and in small part scattered towards the observer by the back side of the disc. However, using theoretical models it is shown here that objects of this type can only account for a few percent of this population. In fact, the spatial distribution of these objects, their X-ray luminosities, their optical brightness and their positions in the colour-magnitude diagram unambiguously indicate that most of these stars are intrinsically older than 10 Myr. Ages range from 8 to 30 Myr with a median value of 15 Myr. This is the largest homogeneous sample to date of Galactic PMS stars considerably older than 10 Myr that are still actively accreting from a circumstellar disc and it allows us to set a lower limit of 5% to the disc frequency at 15 Myr in NGC 6611. These values imply a characteristic exponential lifetime of 5 Myr for disc dissipation
Development of type II mixed cryoglobulinaemic syndrome after effective and persistent hepatitis C virus eradication.
No full text
Fibronectin gene polymorphisms influence type II mixed cryoglobulinemia clinical manifestations.
No full textExtinction in the Large Magellanic Cloud Bar around NGC 1854, NGC 1856, and NGC 1858
No full textWe report on the extinction properties in the fields around the clusters NGC 1854, NGC 1856, and NGC 1858 in the bar of the Large Magellanic Cloud. The color-magnitude diagrams of the stars in all these regions show an elongated red giant clump that reveals a variable amount of extinction across these fields, ranging from A ( V ) similar or equal to 0.2 to A ( V ) similar or equal to 1.9, including Galactic foreground extinction. The extinction properties nonetheless are remarkably uniform. The slope of the reddening vectors measured in the (V - I, V) and (B - I, B) color-magnitude planes is fully in line with the A ( V )/E(B - V) similar or equal to 5.5 value found in the outskirts of 30 Dor. This indicates the presence of an additional gray extinction component in the optical requiring big grains to be about twice as abundant as in the diffuse Galactic interstellar medium (ISM). Areas of higher extinction appear to be systematically associated with regions of more intense star formation, as measured by the larger number of stars more massive than 8 M (circle dot), thus making injection of big grains into the ISM by a SNII explosion the likely mechanism at the origin of the observed gray extinction component
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