443 research outputs found
Highly absorbed X-ray binaries in the Small Magellanic Cloud
Many of the high mass X-ray binaries (HMXRBs) discovered in recent years in
our Galaxy are characterized by a high absorption, most likely intrinsic to the
system, which hampers their detection at the softest X-ray energies. We have
undertaken a search for highly-absorbed X-ray sources in the Small Magellanic
Cloud (SMC) with a systematic analysis of 62 XMM-Newton SMC observations. We
obtained a sample of 30 sources showing evidence for an equivalent hydrogen
column density larger than 3x10^23 cm^-2. Five of these sources are clearly
identified as HMXRBs: four were already known (including three X-ray pulsars)
and one, XMM J005605.8-720012, reported here for the first time. For the
latter, we present optical spectroscopy confirming the association with a Be
star in the SMC. The other sources in our sample have optical counterparts
fainter than magnitude ~16 in the V band, and many of them have possible NIR
counterparts consistent with highly reddened early type stars in the SMC. While
their number is broadly consistent with the expected population of background
highly-absorbed active galactic nuclei, a few of them could be HMXRBs in which
an early type companion is severely reddened by local material.Comment: 10 pages, 4 figures, 4 tables. Accepted for publication by Astronomy
& Astrophysic
Electrochemically dealloyed platinum with hierarchical pore structure as highly active catalytic coating
Electrochemical dealloying of PtâSi produces Pt films with hierarchical pore structure and superior performance in butadiene hydrogenation.</p
The XMM-Newton survey of the Small Magellanic Cloud: XMMUJ005011.2-730026 = SXP214, a Be/X-ray binary pulsar
In the course of the XMM-Newton survey of the Small Magellanic Cloud (SMC), a
region to the east of the emission nebula N19 was observed in November 2009. To
search for new candidates for high mass X-ray binaries the EPIC PN and MOS data
of the detected point sources were investigated and their spectral and temporal
characteristics identified. A new transient (XMMUJ005011.2-730026= SXP214) with
a pulse period of 214.05 s was discovered; the source had a hard X-ray spectrum
with power-law index of ~0.65. The accurate X-ray source location permits the
identification of the X-ray source with a ~15th magnitude Be star, thereby
confirming this system as a new Be/X-ray binary.Comment: 8 pages 11 figures. Accepted for publication in MNRA
The Search for High-Mass X-ray Binaries in the Phoenix Dwarf Galaxy
We report on the first X-ray images of the Phoenix dwarf galaxy, taken with
\emph{XMM-Newton} in July 2009. This local group dwarf galaxy shares
similarities with the Small Magellanic Cloud (SMC) including a burst of star
formation 50 Myr ago. The SMC has an abundance of High Mass X-ray
Binaries (HMXBs) and so we have investigated the possibility of an HMXB
population in Phoenix with the intention of furthering the understanding of the
HMXB-star formation rate relation. The data from the combined European Photon
Imaging Cameras (EPIC) were used to distinguish between different source
classes (foreground stars, background galaxies, AGN and supernova remnants)
using EPIC hardness ratios and correlations with optical and radio catalogues.
Of the 81 X-ray sources in the field of view, six are foreground stars, four
are galaxies and one is an AGN. The remaining sources with optical counterparts
have log() consistent with AGN in the local universe.
Further investigation of five sources in the field of view suggests they are
all background AGN. Their position behind the gas cloud associated with Phoenix
makes them a possible tool for further probing the metallicity of this region.
We find no evidence for any HMXBs in Phoenix at this time. This rules out the
existence of the X-ray persistent supergiant X-ray binary systems. However the
transient nature of the Be/X-ray binaries means we cannot rule out a population
of these sources but can conclude that it is not extensive.Comment: 13 pages, 4 figures, 4 tables, Accepted for publication in MNRA
Allele-specific miRNA-binding analysis identifies candidate target genes for breast cancer risk
Most breast cancer (BC) risk-associated single-nucleotide polymorphisms (raSNPs) identified in genome-wide association studies (GWAS) are believed to cis-regulate the expression of genes. We hypothesise that cis-regulatory variants contributing to disease risk may be affecting microRNA (miRNA) genes and/or miRNA binding. To test this, we adapted two miRNA-binding prediction algorithms-TargetScan and miRanda-to perform allele-specific queries, and integrated differential allelic expression (DAE) and expression quantitative trait loci (eQTL) data, to query 150 genome-wide significant ( Pâ€5Ă10-8 ) raSNPs, plus proxies. We found that no raSNP mapped to a miRNA gene, suggesting that altered miRNA targeting is an unlikely mechanism involved in BC risk. Also, 11.5% (6 out of 52) raSNPs located in 3'-untranslated regions of putative miRNA target genes were predicted to alter miRNA::mRNA (messenger RNA) pair binding stability in five candidate target genes. Of these, we propose RNF115, at locus 1q21.1, as a strong novel target gene associated with BC risk, and reinforce the role of miRNA-mediated cis-regulation at locus 19p13.11. We believe that integrating allele-specific querying in miRNA-binding prediction, and data supporting cis-regulation of expression, improves the identification of candidate target genes in BC risk, as well as in other common cancers and complex diseases.Funding Agency
Portuguese Foundation for Science and Technology
CRESC ALGARVE 2020
European Union (EU)
303745
Maratona da Saude Award
DL 57/2016/CP1361/CT0042
SFRH/BPD/99502/2014
CBMR-UID/BIM/04773/2013
POCI-01-0145-FEDER-022184info:eu-repo/semantics/publishedVersio
The CLIC positron source based on compton schemes
The CLIC polarized positron source is based on a positron production scheme in which polarized photons are produced by a Compton process. In one option, Compton backscattering takes place in a so-called âCompton ringâ, where an electron beam of 1 GeV interacts with circularly-polarized photons in an optical resonator. The resulting circularly-polarized gamma photons are sent on to an amorphous target, producing pairs of longitudinally polarized electrons and positrons. The nominal CLIC bunch population is 4.2x109 particles per bunch at the exit of the Pre-Damping Ring (PDR). Since the photon flux coming out from a "Compton ring" is not sufficient to obtain the requested charge, a stacking process is required in the PDR. Another option is to use a Compton Energy Recovery Linac (ERL) where a quasicontinual stacking in the PDR could be achieved. A third option is to use a "Compton Linac" which would not require stacking. We describe the overall scheme as well as advantages and constraints of the three options
The CLIC Positron Sources Based on Compton Schemes
International audienceThe CLIC polarized positron source is based on a positron production scheme in which polarized photons are produced by Compton process. Compton backscattering happens in a so-called "Compton ring" where an electron beam of 1.06 GeV interacts with a powerful laser beam amplified in an optical resonator. The circularly-polarized gamma rays are sent on to a target, producing pairs of longitudinally polarized electrons and positrons. An Adiabatic Matching Device maximizes the capture of the positrons. A normal-conducting 2 GHz Linac accelerates the beam up to 2.424 GeV before injection into the Pre-Damping Ring (PDR). The nominal CLIC bunch population is 4.4x10**9 particles per bunch. Since the photon flux coming out from a "Compton ring" is not sufficient to obtain the requested charge, a stacking process is required in the PDR. Another option is to use a "Compton Energy Recovery Linac" where a quasi-continual stacking in the PDR could be achieved. A third option is to use a "Compton Linac" which would not require stacking. We describe the overall scheme as well as advantages and constraints of the three different options
LEM-3 is a midbody-tethered DNA nuclease that resolves chromatin bridges during late mitosis
Chromosome segregation and genome maintenance require the removal of DNA bridges that link chromosomes just before cells divide. Here the authors show that the LEM-3/Ankle1 nuclease processes DNA bridges before cells divide and define a previously undescribed genome integrity mechanism
An evaluation of the polymorphisms Ins16bp and Arg72Pro in p53 as breast cancer risk modifiers in BRCA1 and BRCA2 mutation carriers
The close functional relationship between p53 and the breast cancer susceptibility genes BRCA1 and BRCA2 has promoted the investigation of various polymorphisms in the p53 gene as possible risk modifiers in BRCA1/2 mutation carriers. Specifically, two polymorphisms in p53, c.97-147ins16bp and p.Arg72Pro have been analysed as putative breast cancer susceptibility variants, and it has been recently reported that a p53 haplotype combining the absence of the 16-bp insertion and the presence of proline at codon 72 (No Ins-72Pro) was associated with an earlier age at the onset of the first primary tumour in BRCA2 mutation carriers in the Spanish population. In this study, we have evaluated this association in a series of 2932 BRCA1/2 mutation carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2
The XMM-Newton survey of the Small Magellanic Cloud: XMMUJ010633.1-731543 and XMMUJ010743.1-715953, two new Be/X-ray binary systems
In the course of the XMM-Newton survey of the Small Magellanic Cloud (SMC),
two new bright X-ray sources were discovered exhibiting the spectral
characteris- tics of High Mass X-ray Binaries - but revealing only weak
evidence for pulsations in just one of the objects(at 153s in
XMMUJ010743.1-715953). The accurate X- ray source locations permit the
identification of these X-ray source with Be stars, thereby strongly suggesting
these systems are new Be/X-ray binaries. From blue spectra the proposed
classification for XMMUJ010633.1-731543 is B0.5-1Ve and for
XMMUJ010743.1-715953 it is B2IV-Ve.Comment: MNRAS (accepted), 12 pages, 17 figures, 4 table
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