Endogenous mammalian lectin localized extracellularly in lung elastic fibers.

An affinity-purified antibody preparation raised against a beta-galactoside-binding lectin from bovine lung was used to localize a similar lectin in rat lung by immunofluorescence and by electron microscopy after on-grid staining visualized with colloidal gold conjugated second antibody. The endogenous mammalian lectin was found in smooth muscle cells and squamous alveolar epithelial (type I) cells and was concentrated extracellularly in elastic fibers of pulmonary parenchyma and blood vessels. The extracellular localization of this lectin suggests that it, like others, functions by interaction with extracellular glycoconjugates

On the metallicity of the Milky Way thin disc and photometric abundance scales

The mean metallicity of the Milky Way thin disc in the solar neighbourhood is still a matter of debate, and has recently been subject to upward revision (Haywood, 2001). Our star sample was drawn from a set of solar neighbourhood dwarfs with photometric metallicities. In a recent study, Reid (2002) suggests that our metallicity calibration, based on Geneva photometry, is biased. We show here that the effect detected by Reid is not a consequence of our adopted metallicity scale, and we confirm that our findings are robust. On the contrary, the application to Stromgren photometry of the Schuster & Nissen metallicity scale is problematic. Systematic discrepancies of about 0.1 to 0.3 dex affect the photometric metallicity determination of metal rich stars, on the colour interval 0.22< b-y <0.59, i.e including F and G stars. For F stars, it is shown that this is a consequence of a mismatch between the standard sequence m_1(b-y) of the Hyades used by Schuster & Nissen to calibrate their metallicity scale, and the system of Olsen (1993, 1994ab). It means that although Schuster & Nissen calibration and Olsen photometry are intrinsically correct, there are mutually incompatible for metal rich, F-type stars. For G stars, the discrepancy is most probably the continuation of the same problem, albeit worthen by the lack of spectroscopic calibrating stars. A corrected calibration is proposed which renders the calibration of Schuster & Nissen applicable to the catalogues of Olsen. We also give a simpler calibration referenced to the Hyades sequence, valid over the same color and metallicity ranges.Comment: 11 pages, 11 figures, accepted in MNRA

On the kinematic deconvolution of the local neighbourhood luminosity function

A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three r\'egimes: the singular ellipsoid, the constant ratio Schwarzschild ellipsoid plane parallel models and the epicyclic model. This more realistic model is taylored to account for local neighbourhood density and velocity distribution. The first model is fully investigated both analytically and via means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated via a 5D+2D non-parametric inversion technique where positivity of the underlying luminosity function is explicitely accounted for. It is argued that its future application to data such as the Tycho catalogue (and in the upcoming satellite GAIA) could lead -- provided the vertical potential, and/or the asymmetric drift or w_0 are known -- to a non-parametric determination of the local neighbourhood luminosity function without any reference to stellar evolution tracks. It should also yield the proportion of stars for each kinematic component and a kinematic diagnostic to split the thin disk from the thick disk or the halo.Comment: 18 pages, LateX (or Latex, etc), mnras, accepted for publicatio

Cool White Dwarfs Identified in the Second Data Release of the UKIRT Infrared Deep Sky Survey

We have paired the Second Data Release of the Large Area Survey of the UKIRT Infrared Deep Sky Survey with the Fifth Data Release of the Sloan Digital Sky Survey to identify ten cool white dwarf candidates, from their photometry and astrometry. Of these ten, one was previously known to be a very cool white dwarf. We have obtained optical spectroscopy for seven of the candidates using the GMOS-N spectrograph on Gemini North, and have confirmed all seven as white dwarfs. Our photometry and astrometry indicates that the remaining two objects are also white dwarfs. Model analysis of the photometry and available spectroscopy shows that the seven confirmed new white dwarfs, and the two new likely white dwarfs, have effective temperatures in the range Teff = 5400-6600 K. Our analysis of the previously known white dwarf confirms that it is cool, with Teff = 3800 K. The cooling age for this dwarf is 8.7 Gyr, while that of the nine ~6000 K white dwarfs is 1.8-3.6 Gyr. We are unable to determine the masses of the white dwarfs from the existing data, and therefore we cannot constrain the total ages of the white dwarfs. The large cooling age for the coolest white dwarf in the sample, combined with its low estimated tangential velocity, suggests that it is an old member of the thin disk, or a member of the thick disk of the Galaxy, with an age 10-11 Gyr. The warmer white dwarfs appear to have velocities typical of the thick disk or even halo; these may be very old remnants of low-mass stars, or they may be relatively young thin disk objects with unusually high space motion.Comment: 37 pages (referee format), 4 tables, 7 figures, accepted to Ap

Galactic structure studies with BATC star counts

We report the first results of star counts carried out with the National Astronomical Observatories (NAOC) 60/90 cm Schmidt Telescope in 15 intermediate-band filters from 3000 to 10000 {\AA} in the BATC survey. We analyze a sample of over 1400 main sequence stars ($14\le$V$\le21$), which lie in the field with central coordinates R.A.=$09^h53^m13^s.30$ and DEC=47$^\circ49^{\prime}00^{\prime\prime}.0$ (J2000). The field of view is 0.95 deg$^{2}$, and the spatial scale was 1\arcsec.67. In our model, the distribution of stars perpendicular to the plane of the Galaxy is given by two exponential disks (thin disk plus thick disk) and a de Vaucouleurs halo. Based on star counts, we derive the scale heights of the thin disk to be $320^{+14}_{-15}$ pc and of the thick disk to be $640^{+30}_{-32}$ pc, respectively, with a local density of $7.0\pm1$ of the thin disk. We find that the observed counts support an axial ratio of $c/a\le0.6$ for a de Vaucouleurs $r^{1/4}$ law, implying a more flattened halo. We also derive the stellar luminosity function (SLF) for the thin disk, and it partly agrees with the Hipparcos luminosity function.Comment: 17pages,9 figure

Individual aerosol particles from biomass burning in southern Africa: 1. Compositions and size distributions of carbonaceous particles

Individual aerosol particles in smoke plumes from biomass fires and in regional hazes in southern Africa were studied using analytical transmission electron microscopy ( TEM), which allowed detailed characterization of carbonaceous particle types in smoke and determination of changes in particle properties and concentrations during smoke aging. Based on composition, morphology, and microstructure, three distinct types of carbonaceous particles were present in the smoke: organic particles with inorganic ( K- salt) inclusions, " tar ball'' particles, and soot. The relative number concentrations of organic particles were largest in young smoke, whereas tar balls were dominant in a slightly aged ( similar to 1 hour) smoke from a smoldering fire. Flaming fires emitted relatively more soot particles than smoldering fires, but soot was a minor constituent of all studied plumes. Further aging caused the accumulation of sulfate on organic and soot particles, as indicated by the large number of internally mixed organic/ sulfate and soot/ sulfate particles in the regional haze. Externally mixed ammonium sulfate particles dominated in the boundary layer hazes, whereas organic/ sulfate particles were the most abundant type in the upper hazes. Apparently, elevated haze layers were more strongly affected by biomass smoke than those within the boundary layer. Based on size distributions and the observed patterns of internal mixing, we hypothesize that organic and soot particles are the cloud-nucleating constituents of biomass smoke aerosols. Sea- salt particles dominated in the samples taken in stratus clouds over the Atlantic Ocean, off the coast of Namibia, whereas a distinct haze layer above the clouds consisted of aged biomass smoke particles

Characterisation of the Galactic thin disc with Corot targets

We use kinematical and chemical properties of 754 Corot stars to characterise the stellar populations of the Milky Way disc in three beams close the Galactic plane. From the atmospheric parameters derived in Gazzano et al. (2010) with the Matisse algorithm, we derived stellar distances using isochrones. Combining these data with proper motions, we provide the complete kinematical description of stars in three Corot fields. Finally, we used kinematical criteria to identify the Galactic populations in our sample and study their characteristics, particularly their chemistry. Comparing our kinematics with the Besancon Galactic model, we show that, within 3-sigma, simulated and observed kinematical distributions are in good agreement. We study the characteristics of the thin disc, finding a correlation that is significant at a value of 2-sigma between the V-velocity component and the metallicity for two different radial distance bins (8-9kpc and 9-10kpc; but not for the most inner bin 7-8kpc, probably because of the uncertainties in the abundances) which could be interpreted as radial migration evidence. We also measured a radial metallicity gradient value of -0.097+/-0.015dex/kpc with giant stars, and -0.053+/-0.015dex/kpc with dwarfs. Finally, we identified metal-rich stars with peculiar high [alpha/Fe] values in the directions pointing to the inner part of the Galaxy. Applying the same methodology to the planet-hosting stars detected by Corot shows that they mainly belong to the thin disc population with normal chemical and kinematical properties.Comment: Astronomy & Astrophysics, in pres

Atmospheric tar balls: Particles from biomass and biofuel burning

"Tar balls'' are amorphous, carbonaceous spherules that occur in the tropospheric aerosol as a result of biomass and biofuel burning. They form a distinct group of particles with diameters typically between 30 and 500 nm and readily identifiable with electron microscopy. Their lack of a turbostratic microstructure distinguishes them from soot, and their morphology and composition (similar to90 mol % carbon) renders them distinct from other carbonaceous particles. Tar balls are particularly abundant in slightly aged (minutes to hours old) biomass smoke, indicating that they likely form by gas-to-particle conversion within smoke plumes. The material of tar balls is initially hygroscopic; however, the particles become largely insoluble as a result of free radical polymerization of their organic molecules. Consequently, tar balls are primarily externally mixed with other particle types, and they do not appreciably increase in size during aging. When tar balls coagulate with water-bearing particles, their material may partly dissolve and no longer be recognizable as distinct particles. Tar balls may contain organic compounds that absorb sunlight. They are an important, previously unrecognized type of carbonaceous (organic) atmospheric particle

Overabundance of alpha-elements in exoplanet host stars

We present the results for a chemical abundance analysis between planet-hosting and stars without planets for 12 refractory elements for a total of 1111 nearby FGK dwarf stars observed within the context of the HARPS GTO programs. Of these stars, 109 are known to harbour high-mass planetary companions and 26 stars are hosting exclusively Neptunians and super-Earths. We found that the [X/Fe] ratios for Mg, Al, Si, Sc, and Ti both for giant and low-mass planet hosts are systematically higher than those of comparison stars at low metallicities ([Fe/H] < from -0.2 to 0.1 dex depending on the element). The most evident discrepancy between planet-hosting and stars without planets is observed for Mg. Our data suggest that the planet incidence is greater among the thick disk population than among the thin disk for mettallicities bellow -0.3 dex. After examining the [alpha/Fe] trends of the planet host and non-host samples we conclude that a certain chemical composition, and not the Galactic birth place of the stars, is the determinating factor for that. The inspection of the Galactic orbital parameters and kinematics of the planet-hosting stars shows that Neptunian hosts tend to belong to the "thicker" disk compared to their high-mass planet-hosting counterparts.We also found that Neptunian hosts follow the distribution of high-alpha stars in the UW vs V velocities space, but they are more enhanced in Mg than high-alpha stars without planetary companions. Our results indicate that some metals other than iron may also have an important contribution to planet formation if the amount of iron is low. These results may provide strong constraints for the models of planet formation, especially for planets with low mass.Comment: 10 pages, 8 figures, 3 tables, accepted for publication in Astronomy & Astrophysic