15 research outputs found
Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope
SS433, located at the center of the supernova remnant W50, is a close
proximity binary system consisting of a compact star and a normal star. Jets of
material are directed outwards from the vicinity of the compact star
symmetrically to the east and west. Non-thermal hard X-ray emission is detected
from lobes lying on both sides. Shock accelerated electrons are expected to
generate sub-TeV gamma rays through the inverse-Compton process in the lobes.
Observations of the western X-ray lobe region of SS433/W50 system have been
performed to detect sub-TeV gamma-rays using the 10m CANGAROO-II telescope in
August and September, 2001, and July and September, 2002. The total observation
times are 85.2 hours for ON source, and 80.8 hours for OFF source data. No
significant excess of sub-TeV gamma rays has been found at 3 regions of the
western X-ray lobe of SS433/W50 system. We have derived 99% confidence level
upper limits to the fluxes of gamma rays and have set constraints on the
strengths of the magnetic fields assuming the synchrotron/inverse-Compton model
for the wide energy range of photon spectrum from radio to TeV. The derived
lower limits are 4.3 microgauss for the center of the brightest X-ray emission
region and 6.3 microgauss for the far end from SS433 in the western X-ray lobe.
In addition, we suggest that the spot-like X-ray emission may provide a major
contribution to the hardest X-ray spectrum in the lobe.Comment: 7 pages, 8 figures, to be published in Astroparticle Physic
Extragalactic jets on subpc and large scales
Jets can be probed in their innermost regions (d~0.1 pc) through the study of
the relativistically-boosted emission of blazars. On the other extreme of
spatial scales, the study of structure and dynamics of extragalactic
relativistic jets received renewed impulse after the discovery, made by
Chandra, of bright X-ray emission from regions at distances larger than
hundreds of kpc from the central engine. At both scales it is thus possible to
infer some of the basic parameters of the flow (speed, density, magnetic field
intensity, power). After a brief review of the available observational
evidence, I discuss how the comparison between the physical quantities
independently derived at the two scales can be used to shed light on the global
dynamics of the jet, from the innermost regions to the hundreds of kpc scale.Comment: Proceedings of the 5th Stromlo Symposium: Disks, Winds, and Jets -
from Planets to Quasars. Accepted, to be published in Astrophysics & Space
Scienc
Searches for very high energy gamma rays from blazars with CANGAROO-III telescope in 2005-2009
We have searched for very high energy (VHE) gamma rays from four blazars
using the CANGAROO-III imaging atmospheric Cherenkov telescope. We report the
results of the observations of H 2356-309, PKS 2155-304, PKS 0537-441, and 3C
279, performed from 2005 to 2009, applying a new analysis to suppress the
effects of the position dependence of Cherenkov images in the field of view. No
significant VHE gamma ray emission was detected from any of the four blazars.
The GeV gamma-ray spectra of these objects were obtained by analyzing Fermi/LAT
archival data. Non-simultaneous wide range (radio to VHE gamma-ray bands)
spectral energy distributions (SEDs) including CANGAROO-III upper limits, GeV
gamma-ray spectra, and archival data are discussed using a one-zone synchrotron
self-Compton (SSC) model in combination with a external Compton (EC) radiation.
The HBLs (H 2356-309 and PKS 2155-304) can be explained by a simple SSC model,
and PKS 0537-441 and 3C 279 are well modeled by a combination of SSC and EC
model. We find a consistency with the blazar sequence in terms of strength of
magnetic field and component size.Comment: 11 pages, 8 figures, Accepted for publication in Astroparticle
Physic
Sphingosine-1-phosphate signalling drives an angiogenic transcriptional programme in diffuse large B cell lymphoma
Although the over-expression of angiogenic factors is reported in diffuse large B-cell lymphoma (DLBCL), the poor response to anti-VEGF drugs observed in clinical trials suggests that angiogenesis in these tumours might be driven by VEGF-independent pathways. We show that sphingosine kinase-1 (SPHK1), which generates the potent bioactive sphingolipid sphingosine-1-phosphate (S1P), is over-expressed in DLBCL. A meta-analysis of over 2000 cases revealed that genes correlated with SPHK1 mRNA expression in DLBCL were significantly enriched for tumour angiogenesis meta-signature genes; an effect evident in both major cell of origin (COO) and stromal subtypes. Moreover, we found that S1P induces angiogenic signalling and a gene expression programme that is present within the tumour vasculature of SPHK1-expressing DLBCL. Importantly, S1PR1 functional antagonists, including Siponimod, and the S1P neutralising antibody, Sphingomab, inhibited S1P signalling in DLBCL cells in vitro. Furthermore, Siponimod, also reduced angiogenesis and tumour growth in an S1P-producing mouse model of angiogenic DLBCL. Our data define a potential role for S1P signalling in driving an angiogenic gene expression programme in the tumour vasculature of DLBCL and suggest novel opportunities to target S1P-mediated angiogenesis in patients with DLBCL
Bivariate genome-wide association meta-analysis of pediatric musculoskeletal traits reveals pleiotropic effects at the SREBF1/TOM1L2 locus
Bone mineral density is known to be a heritable, polygenic trait whereas genetic variants contributing to lean mass variation remain largely unknown. We estimated the shared SNP heritability and performed a bivariate GWAS meta-analysis of total-body lean mass (TB-LM) and total-body less head bone mineral density (TBLH-BMD) regions in 10,414 children. The estimated SNP heritability is 43% for TBLH-BMD, and 39% for TB-LM, with a shared genetic component of 43%. We identify variants with pleiotropic effects in eight loci, including seven established bone mineral density loci: _WNT4, GALNT3, MEPE, CPED1/WNT16, TNFSF11, RIN3, and PPP6R3/LRP5_. Variants in the _TOM1L2/SREBF1_ locus exert opposing effects TB-LM and TBLH-BMD, and have a stronger association with the former trait. We show that _SREBF1_ is expressed in murine and human osteoblasts, as well as in human muscle tissue. This is the first bivariate GWAS meta-analysis to demonstrate genetic factors with pleiotropic effects on bone mineral density and lean mass
Bivariate genome-wide association meta-analysis of pediatric musculoskeletal traits reveals pleiotropic effects at the SREBF1/TOM1L2 locus
Bone mineral density is known to be a heritable, polygenic trait whereas genetic variants contributing to lean mass variation remain largely unknown. We estimated the shared SNP heritability and performed a bivariate GWAS meta-analysis of total-body lean mass (TB-LM) and total-body less head bone mineral density (TBLH-BMD) regions in 10,414 children. The estimated SNP heritability is 43% (95% CI: 34-52%) for TBLH-BMD, and 39% (95% CI: 30-48%) for TB-LM, with a shared genetic component of 43% (95% CI: 29-56%). We identify variants with pleiotropic effects in eight loci, including seven established bone mineral density loci: WNT4, GALNT3, MEPE, CPED1/WNT16, TNFSF11, RIN3, and PPP6R3/LRP5. Variants in the TOM1L2/SREBF1 locus exert opposing effects TB-LM and TBLH-BMD, and have a stronger association with the former trait. We show that SREBF1 is expressed in murine and human osteoblasts, as well as in human muscle tissue. This is the first bivariate GWAS meta-analysis to demonstrate genetic factors with pleiotropic effects on bone mineral density and lean mass. © 2017 The Author(s)
Erratum: Evidence of TeV gamma-ray emission from the nearby starburst galaxy NGC 253
TeV gamma-rays were recently detected from the nearby normal spiral galaxy NGC 253 (Itoh et al. 2002). Observations to detect the Cherenkov light images initiated by gamma-rays from the direction of NGC 253 were carried out in 2000 and 2001 over a total period of ∼150 hours. The orientation of images in gamma-ray-like events is not consistent with emission from a point source, and the emission region corresponds to a size greater than 10 kpc in radius. Here, detailed descriptions of the analysis procedures and techniques are given