428 research outputs found
Photometric redshift galaxies as tracers of the filamentary network
Galaxy filaments are the dominant feature in the overall structure of the
cosmic web. The study of the filamentary web is an important aspect in
understanding galaxy evolution and the evolution of matter in the Universe. A
map of the filamentary structure is an adequate probe of the web. We propose
that photometric redshift galaxies are significantly positively associated with
the filamentary structure detected from the spatial distribution of
spectroscopic redshift galaxies. The catalogues of spectroscopic and
photometric galaxies are seen as point-process realisations in a sphere, and
the catalogue of filamentary spines is proposed to be a realisation of a random
set in a sphere. The positive association between these sets was studied using
a bivariate function, which is a summary statistics studying clustering. A
quotient was built to estimate the distance distribution of the filamentary
spine to galaxies in comparison to the distance distribution of the filamentary
spine to random points in dimensional Euclidean space. This measure gives a
physical distance scale to the distances between filamentary spines and the
studied sets of galaxies. The bivariate function shows a statistically
significant clustering effect in between filamentary spines and photometric
redshift galaxies. The quotient confirms the previous result that smaller
distances exist with higher probability between the photometric galaxies and
filaments. The trend of smaller distances between the objects grows stronger at
higher redshift. Additionally, the quotient for photometric galaxies gives
a rough estimate for the filamentary spine width of about ~Mpc. Photometric
redshift galaxies are positively associated with filamentary spines detected
from the spatial distribution of spectroscopic galaxies.Comment: Accepted to Astronomy & Astrophysics. 13 pages and 9 figure
Chemical evolution of the metal poor Globular Cluster NGC 6809
We present the abundances analysis for a sample of 11 red giant branch stars
in the metal-poor globular cluster NGC 6809 based on high-resolution spectra.
Our main goals are to characterize its chemical composition and analyze this
cluster's behavior associated with the Multiple Population (MPs) phenomenon. In
our work we obtained the stellar parameters and chemical abundances of 24
elements (O, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Sc, Ni, Cu, Zn, Y, Zr,
Ba, La, Ce, Eu, Nd and Dy). We found a radial velocity of 174.7 3.2 km
and a mean iron content of [Fe/H]=-2.01 0.02 in good agreement
with other studies. Moreover, we found a large spread in the abundances of the
light elements O, Na and Al confirming the presence of a Na-O anti-correlation
a Na-Al correlation. The Mg-Al anti-correlation is also present in our cluster.
The and iron-peak elements show good agreement with the halo field
star trend. The heavy elements are dominated by the r-process.Comment: 13 pages, 11 figures, 3 tables, accepted for publication in MNRA
The blue straggler population of the open clusters Trumpler 5, Trumpler 20, and NGC 2477
We present a study, based on Gaia DR2, of the population of blue straggler
stars (BSS) in the open clusters Trumpler 5, Trumpler 20, and NGC 2477. All
candidates were selected according to their position in the color-magnitude
diagram, to their proper motion components, and to their parallax. We also
looked for yellow stragglers, i.e., possible evolved blue stragglers. We found
that Trumpler 5 hosts a large BSS population, which allowed us to analyze their
radial distribution as a probe of the cluster's dynamical status. The BSS
distribution was compared with that of red giant branch stars (RGB) to evaluate
mass segregation. Our results indicate that blue straggler stars are not more
centrally concentrated than RGB stars in any of the clusters. The radial
distribution of BSS in Trumpler 5 is flat. Additionally, using a multi-epoch
radial velocity survey conducted with the high-resolution spectrograph
FLAMES/GIRAFFE at VLT, we measured the radial velocities of a sample of
stragglers, for the sake of comparison with the mean radial velocity and the
velocity dispersion of the clusters. Based on the radial velocity variations
for different epochs, we roughly classified these stars as possible close-or
long-period binaries.Comment: 20 pages, 5 figures, accepted for publication in A
Recommended from our members
Space charge behaviour in epoxy laminates under high constant electric field
The development of space charge in insulating materials is one of the main causes of their electrical ageing. The pulsed electro-acoustic method is often used to determine space charge distribution, but the signal analysis in the case of laminate structures is much more complex to analyse. In this paper the authors describe and use a simulated signal in order to study laminates made of epoxy resin and fibre mat. The relatively large conductivity of the fibres compared with that of the resin seems to produce a rapid charge dissociation and recombination in the fibres. Under voltage the presence of fibres close to an electrode seems to promote charge injection
Infinite-Order Percolation and Giant Fluctuations in a Protein Interaction Network
We investigate a model protein interaction network whose links represent
interactions between individual proteins. This network evolves by the
functional duplication of proteins, supplemented by random link addition to
account for mutations. When link addition is dominant, an infinite-order
percolation transition arises as a function of the addition rate. In the
opposite limit of high duplication rate, the network exhibits giant structural
fluctuations in different realizations. For biologically-relevant growth rates,
the node degree distribution has an algebraic tail with a peculiar rate
dependence for the associated exponent.Comment: 4 pages, 2 figures, 2 column revtex format, to be submitted to PRL 1;
reference added and minor rewording of the first paragraph; Title change and
major reorganization (but no result changes) in response to referee comments;
to be published in PR
In vitro antiplasmodial properties of selected plants of Sabah
The antiplasmodial activity of the crude extracts of thirty plant species collected from Sabah was evaluated using chloroquine-sensitive strain (D10) and chloroquine-resistant strain (Gombak A) of Plasmodium falciparum. Significant activities were observed for the bark extract of Polyalthia insignis (IC50 3.89 and 11.89 µg/ml against Gombak A and D10, respectively), the leaf extracts of Kopsia dasyrachis (4.62 µg/ml against Gombak A) and Litsea elliptibacea (IC50 8.88 µg/ml against Gombak A), as well as the leaf and bark extracts of Neouvaria acuminatissima (IC50 6.90-10.08 and 0.69 µg/ml against Gombak A and D10, respectively), and the bark extract of Polyalthia microtus (IC50 9.0 and 12.12 µg/ml against Gombak A and D10, respectively)
Functional Genomics Highlights Differential Induction of Antiviral Pathways in the Lungs of SARS-CoV–Infected Macaques
The pathogenesis of severe acute respiratory syndrome coronavirus (SARS-CoV) is likely mediated by disproportional immune responses and the ability of the virus to circumvent innate immunity. Using functional genomics, we analyzed early host responses to SARS-CoV infection in the lungs of adolescent cynomolgus macaques (Macaca fascicularis) that show lung pathology similar to that observed in human adults with SARS. Analysis of gene signatures revealed induction of a strong innate immune response characterized by the stimulation of various cytokine and chemokine genes, including interleukin (IL)-6, IL-8, and IP-10, which corresponds to the host response seen in acute respiratory distress syndrome. As opposed to many in vitro experiments, SARS-CoV induced a wide range of type I interferons (IFNs) and nuclear translocation of phosphorylated signal transducer and activator of transcription 1 in the lungs of macaques. Using immunohistochemistry, we revealed that these antiviral signaling pathways were differentially regulated in distinctive subsets of cells. Our studies emphasize that the induction of early IFN signaling may be critical to confer protection against SARS-CoV infection and highlight the strength of combining functional genomics with immunohistochemistry to further unravel the pathogenesis of SARS
- …