2,641 research outputs found
Consumption of Metallic Lead and its Effects on Tissue Lead Levels of Urban Eastern Gray Squirrels (Sciurus carolinensis)
Starcounts Redivivus. IV. Density Laws Through Photometric Parallaxes
In an effort to more precisely define the spatial distribution of Galactic
field stars, we present an analysis of the photometric parallaxes of 70,000
stars covering nearly 15 square degrees in seven Kapteyn Selected Areas. We
address the affects of Malmquist Bias, subgiant/giant contamination,
metallicity and binary stars upon the derived density laws. The affect of
binary stars is the most significant. We find that while the disk-like
populations of the Milky Way are easily constrained in a simultaneous analysis
of all seven fields, no good simultaneous solution for the halo is found. We
have applied halo density laws taken from other studies and find that the
Besancon flattened power law halo model (c/a=0.6, r^-2.75) produces the best
fit to our data. With this halo, the thick disk has a scale height of 750 pc
with an 8.5% normalization to the old disk. The old disk scale height is
280-300 pc. Corrected for a binary fraction of 50%, these scale heights are 940
pc and 350-375 pc, respectively. Even with this model, there are systematic
discrepancies between the observed and predicted density distributions. Our
model produces density overpredictions in the inner Galaxy and density
underpredictions in the outer Galaxy. A possible solution is modeling the
stellar halo as a two-component system in which the halo has a flattened inner
distribution and a roughly spherical, but substructured outer distribution.
Further reconciliation could be provided by a flared thick disk, a structure
consistent with a merger origin for that population. (Abridged)Comment: 66 pages, accepted to Astrophysical journal, some figures compresse
Maternal urinary iodine concentration in pregnancy and children's cognition: Results from a population-based birth cohort in an iodine-sufficient area
OBJECTIVE: Reports from populations with an insufficient iodine intake suggest that children of mothers with mild iodine deficiency during pregnancy are at risk for cognitive impairments. However, it is unknown whether, even in iodine-sufficient areas, low levels of iodine intake occur that influence cognitive development in the offspring. This study investigated the association between maternal low urinary iodine concentration (UIC) in pregnancy and children's cognition in a population-based sample from a country with an optimal iodine status (the Netherlands). SETTING AND PARTICIPANTS: In 1525 mother–child pairs in a Dutch multiethnic birth cohort, we investigated the relation between maternal UIC<150 μg/g creatinine, assessed <18 weeks gestation and children's cognition. OUTCOMES MEASURES: Non-verbal IQ and language comprehension were assessed during a visit to the research centre using Dutch test batteries when the children were 6 years. RESULTS: In total, 188 (12.3%) pregnant women had UIC<150 μg/g creatinine, with a median UIC equal to 119.3 μg/g creatinine. The median UIC in the group with UIC>150 μg/g creatinine was 322.9 μg/g and in the whole sample 296.5 μg/g creatinine. There was a univariate association between maternal low UIC and children's suboptimum non-verbal IQ (unadjusted OR=1.44, 95% CI 1.02 to 2.02). However, after adjustment for confounders, maternal low UIC was not associated with children's non-verbal IQ (adjusted OR=1.33, 95% CI 0.92 to 1.93). There was no relation between maternal UIC in early pregnancy and children's language comprehension at 6 years. CONCLUSIONS: The lack of a clear association between maternal low UIC and children's cognition probably reflects that low levels of iodine were not frequent and severe enough to affect neurodevelopment. This may result from the Dutch iodine fortification policy, which allows iodised salt to be added to almost all processed food and emphasises the monitoring of iodine intake in the population
The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo
We present a complete spectroscopic survey of 2414 2MASS-selected blue
horizontal branch (BHB) candidates selected over 4300 deg^2 of the sky. We
identify 655 BHB stars in this non-kinematically selected sample. We calculate
the luminosity function of field BHB stars and find evidence for very few hot
BHB stars in the field. The BHB stars located at a distance from the Galactic
plane |Z|<4 kpc trace what is clearly a metal-weak thick disk population, with
a mean metallicity of [Fe/H]= -1.7, a rotation velocity gradient of
dv_{rot}/d|Z|= -28+-3.4 km/s in the region |Z|<6 kpc, and a density scale
height of h_Z= 1.26+-0.1 kpc. The BHB stars located at 5<|Z|<9 kpc are a
predominantly inner-halo population, with a mean metallicity of [Fe/H]= -2.0
and a mean Galactic rotation of -4+-31 km/s. We infer the density of halo and
thick disk BHB stars is 104+-37 kpc^-3 near the Sun, and the relative
normalization of halo to thick-disk BHB stars is 4+-1% near the Sun.Comment: 12 pages in emulateapj format, accepted for publication in February
A
A systematic genetic screen identifies new factors influencing centromeric heterochromatin integrity in fission yeast
BACKGROUND: Heterochromatin plays important roles in the regulation and stability of eukaryotic genomes. Both heterochromatin components and pathways that promote heterochromatin assembly, including RNA interference, RNAi, are broadly conserved between the fission yeast Schizosaccharomyces pombe and humans. As a result, fission yeast has emerged as an important model system for dissecting mechanisms governing heterochromatin integrity. Thus far, over 50 proteins have been found to contribute to heterochromatin assembly at fission yeast centromeres. However, previous studies have not been exhaustive, and it is therefore likely that further factors remain to be identified. RESULTS: To gain a more complete understanding of heterochromatin assembly pathways, we have performed a systematic genetic screen for factors required for centromeric heterochromatin integrity. In addition to known RNAi and chromatin modification components, we identified several proteins with previously undescribed roles in heterochromatin regulation. These included both known and newly characterised splicing-associated proteins, which are required for proper processing of centromeric transcripts by the RNAi pathway, and COP9 signalosome components Csn1 and Csn2, whose role in heterochromatin assembly can be explained at least in part by a role in the Ddb1-dependent degradation of the heterochromatin regulator Epe1. CONCLUSIONS: This work has revealed new factors involved in RNAi-directed heterochromatin assembly in fission yeast. Our findings support and extend previous observations that implicate components of the splicing machinery as a platform for RNAi, and demonstrate a novel role for the COP9 signalosome in heterochromatin regulation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13059-014-0481-4) contains supplementary material, which is available to authorized users
Rothamsted Research willow (Salix spp.) breeding programme: multi-site yield trial results 2014
The Distribution Of Heavy Elements In Spiral And Elliptical Galaxies
This review recaps significant results as they apply to non-dwarf galaxies,
including the Milky Way, spiral disks and bulges, and elliptical and lenticular
galaxies. Conclusions that span the galaxy types treated here are as follows.
All galaxies, on average, have heavy element abundances (metallicities) that
systematically decrease outward from their galactic centers while their global
metallicities increase with galaxy mass. Abundance gradients are steepest in
normal spirals and are seen to be progressively flatter going in order from
barred spirals, lenticulars, and ellipticals. For spiral galaxies, local
metallicity appears to be correlated with total (disk plus bulge) surface
density. Observed abundance patterns indicate that N production is dominated by
primary processes at low metallicity and secondary processes at high
metallicity; C production increases with increasing metallicity; and O, Ne, S,
and Ar are produced in lockstep independent of metallicity. In elliptical
galaxies, nuclear abundances are in the range [Z/H] = 0.0 to 0.4, but the
element mixture is not scaled-solar. In large elliptical galaxies [Mg/Fe] is in
the range 0.3 to 0.5, decreasing to ~0 in smaller elliptical galaxies. Other
light elements track the Mg enhancement, but the heavier Ca tracks Fe. Velocity
dispersion appears to be a key parameter in the modulation of [Mg/Fe], but the
cause of the connection is unclear.Comment: 55-page manuscript plus 16 figures. Invited review to appear in the
Publications Of The Astronomical Society Of The Pacifi
The INT/WFC survey of the Monoceros Ring: Accretion origin or Galactic Anomaly?
We present the results of a wide-field camera survey of the stars in the
Monoceros Ring, thought to be an additional structure in the Milky Way of
unknown origin. Lying roughly in the plane of the Milky Way, this may represent
a unique equatorial accretion event which is contributing to the Thick Disk of
the Galaxy. Alternatively, the Monoceros Ring may be a natural part of the Disk
formation process. With ten pointings in symmetric pairs above and below the
plane of the Galaxy, this survey spans 90 degrees about the Milky Way's
equator. Signatures of the stream of stars were detected in three fields, ({\it
l},{\it b}) = (118,+16) and (150,+15) plus a more tentative
detection at (150,-15). Galactocentric distance estimates to these
structures gave 17, 17, and 13 kpc respectively. The
Monoceros Ring seems to be present on both sides of the Galactic plane, in a
form different to that of the Galactic suggestive of a tidal origin with
streams multiply wrapping the Galaxy. A new model of the stream has shown a
strong coincidence with our results and has also provided the opportunity to
make several more detections in fields in which the stream is less significant.
The confirmed detection at ({\it l},{\it b}) = (123,-19) at 14,
kpc from the Galactic centre allows a re-examination revealing a tentative new
detection with a Galactocentric distance of 21 kpc. (Abridged)Comment: 14 pages, figure resolution reduced. Accepted for publication in
MNRA
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