143 research outputs found
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues â a realisation of the Tycho-Gaia Astrometric Solution (TGAS) â and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of âŒ3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yrâ1 for the proper motions. A systematic component of âŒ0.3 mas should be added to the parallax uncertainties. For the subset of âŒ94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yrâ1. For the secondary astrometric data set, the typical uncertainty of the positions is âŒ10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to âŒ0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
A new Late Agenian (MN2a, Early Miocene) fossil assemblage from Wallenried (Molasse Basin, Canton Fribourg, Switzerland)
Excavations of two fossiliferous layers in the Wallenried sand- and marl pit produced a very diversified vertebrate fauna. New material allows the reassessment of the taxonomic position of the ruminant taxa Andegameryx andegaviensis and endemic Friburgomeryx wallenriedensis. An emended diagnosis for the second species is provided and additional material of large and small mammals, as well as ectothermic vertebrates, is described. The recorded Lagomorpha show interesting morphological deviations from other Central European material, and probably represent a unique transitional assemblage with a co-occurrence of Titanomys, Lagopsis and Prolagus. Rodentia and Eulipotyphla belong to typical and well-known species of the Agenian of the Swiss Molasse Basin. Abundant small mammal teeth have allowed us to pinpoint the biostratigraphic age of Wallenried to late MN2a. The biostratigraphic age conforms to data derived from the charophyte assemblages and confirms the oldest occurrence of venomous snake fangs. The palaeoenvironmental context is quite complex. Sedimentary structures and fauna (fishes, frogs, salamanders, ostracods) are characteristic for a humid, lacustrine environment within a flood plain system
Survival and long-term maintenance of tertiary trees in the Iberian Peninsula during the Pleistocene. First record of Aesculus L.
The Italian and Balkan peninsulas have been places traditionally highlighted as Pleistocene glacial refuges. The Iberian Peninsula, however, has been a focus of controversy between geobotanists and palaeobotanists as a result of its exclusion from this category on different occasions. In the current paper, we synthesise geological, molecular, palaeobotanical and geobotanical data that show the importance of the Iberian Peninsula in the Western Mediterranean as a refugium area. The presence of Aesculus aff. hippocastanum L. at the Iberian site at Cal Guardiola (Tarrasa, Barcelona, NE Spain) in the Lowerâ Middle Pleistocene transition helps to consolidate the remarkable role of the Iberian Peninsula in the survival of tertiary species during the Pleistocene. The palaeodistribution of the genus in Europe highlights a model of area abandonment for a widely-distributed species in the Miocene and Pliocene, leading to a diminished and fragmentary presence in the Pleistocene and Holocene on the southern Mediterranean peninsulas. Aesculus fossils are not uncommon within the series of Tertiary taxa. Many appear in the Pliocene and suffer a radical impoverishment in the LowerâMiddle Pleistocene transition. Nonetheless some of these tertiary taxa persisted throughout the Pleistocene and Holocene up to the present in the Iberian Peninsula. Locating these refuge areas on the Peninsula is not an easy task, although areas characterised by a sustained level of humidity must have played an predominant role
Real-Time NanoparticleâCell Interactions in Physiological Media by Atomic Force Microscopy
Particleâcell interactions in physiological media are important in determining the fate and transport of nanoparticles and biological responses to them. In this work, these interactions are assessed in real time using a novel atomic force microscopy (AFM) based platform. Industry-relevant CeO2 and Fe2O3 engineered nanoparticles (ENPs) of two primary particle sizes were synthesized by the flame spray pyrolysis (FSP) based Harvard Versatile Engineering Nanomaterials Generation System (Harvard VENGES) and used in this study. The ENPs were attached on AFM tips, and the atomic force between the tip and lung epithelia cells (A549), adhered on a substrate, was measured in biological media, with and without the presence of serum proteins. Two metrics were used to assess the nanoparticle cell: the detachment force required to separate the ENP from the cell and the number of bonds formed between the cell and the ENPs. The results indicate that these atomic level ENPâcell interaction forces strongly depend on the physiological media. The presence of serum proteins reduced both the detachment force and the number of bonds by approximately 50% indicating the important role of the protein corona on the particle cell interactions. Additionally, it was shown that particle to cell interactions were size and material dependent
Comparing MRI metrics to quantify white matter microstructural damage in multiple sclerosis
Quantifying white matter damage in vivo is becoming increasingly important for investigating the effects of neuroprotective and repair strategies in multiple sclerosis (MS). While various approaches are available, the relationship between MRIâbased metrics of white matter microstructure in the disease, that is, to what extent the metrics provide complementary versus redundant information, remains largely unexplored. We obtained four microstructural metrics from 123 MS patients: fractional anisotropy (FA), radial diffusivity (RD), myelin water fraction (MWF), and magnetisation transfer ratio (MTR). Coregistration of maps of these four indices allowed quantification of microstructural damage through voxelâwise damage scores relative to healthy tissue, as assessed in a group of 27 controls. We considered three white matter tissueâstates, which were expected to vary in microstructural damage: normal appearing white matter (NAWM), T2âweighted hyperintense lesional tissue without T1âweighted hypointensity (T2L), and T1âweighted hypointense lesional tissue with corresponding T2âweighted hyperintensity (T1L). All MRI indices suggested significant damage in all three tissueâstates, the greatest damage being in T1L. The correlations between indices ranged from r = 0.18 to r = 0.87. MWF was most sensitive when differentiating T2L from NAWM, while MTR was most sensitive when differentiating T1L from NAWM and from T2L. Combining the four metrics into one, through a principal component analysis, did not yield a measure more sensitive to damage than any single measure. Our findings suggest that the metrics are (at least partially) correlated with each other, but sensitive to the different aspects of pathology. Leveraging these differences could be beneficial in clinical trials testing the effects of therapeutic interventions
Synthesis of ZnO nanoparticles by flame spray pyrolysis and characterisation protocol
There is uncertainty concerning the potential toxicity of zinc oxide (ZnO) nanoparticles, which may be attributed in part to a lack of understanding with regard to the physiochemical properties of the nanoparticles used in toxicological investigations. This paper reports the synthesis of a ZnO nanopowder by flame spray pyrolysis and demonstrates that the typically employed characterisation techniques such as specific surface area measurement and X-ray diffraction provide insufficient information on the sample, especially if it is intended for use in toxicity studies. Instead, a more elaborate characterisation protocol is proposed that includes particle morphology as well as detailed compositional analysis of the nanoparticle surface. Detailed transmission electron microscopy analysis illustrated the polydispersity within the sample: particles were elongated in the c-crystallographic direction, with average Ferret length âŒ23 nm and Ferret width âŒ14 nm. Dynamic light scattering (0.1 w/v% in deionised water, pH 7.4) revealed the particles were agglomerated with a modal secondary particle size of âŒ1.5 ÎŒm. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated the presence of carbonate and hydroxide impurities on the surface of the ZnO nanoparticles and an increase of such impurities was observed as the sample was aged, which might influence the nanoparticle dissolution and/or cellular uptake behaviour. These data will be utilised, in order to facilitate the interpretation and understanding of results from toxicological investigations using in vitro cell lines
Megaspore and microfossil assemblages reveal diverse herbaceous lycophytes in the Australian Early Jurassic flora
The high pressure behaviour of the cubic phase of KPF6 an X ray single crystal and entropy maximization study
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