50 research outputs found
Initial low/hard state, multiple jet ejections and X-ray/radio correlations during the outburst of XTE J1859+226
We have studied the 1999 soft X-ray transient outburst of XTE J1859+226 at
radio and X-ray wavelengths. The event was characterised by strong variability
in the disc, corona and jet - in particular, a number of radio flares
(ejections) took place and seemed well-correlated with hard X-ray events.
Apparently unusual for the `canonical soft' X-ray transient, there was an
initial period of low/hard state behaviour during the rise from quiescence but
prior to the peak of the main outburst - we show that not only could this
initial low/hard state be an ubiquitous feature of soft X-ray transient
outbursts but that it could also be extremely important in our study of
outburst mechanisms.Comment: 12 pages, Accepted for publication in MNRA
Fermi Large Area Telescope Bright Gamma-ray Source List
Following its launch in June 2008, the Fermi Gamma-ray Space Telescope
(Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi
in 3 months produced a deeper and better-resolved map of the gamma-ray sky than
any previous space mission. We present here initial results for energies above
100 MeV for the 205 most significant (statistical significance greater than
~10-sigma) gamma-ray sources in these data. These are the best-characterized
and best-localized point-like (i.e., spatially unresolved) gamma-ray sources in
the early-mission data.Comment: Accepted by ApJS. Many helpful comments by referee incorporated 57
pages, 12 figure
All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe
The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class
mission concept that will provide essential contributions to multimessenger
astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in
the 200 keV to 10 GeV energy range with a wide field of view, good spectral
resolution, and polarization sensitivity. Therefore, AMEGO is key in the study
of multimessenger astrophysical objects that have unique signatures in the
gamma-ray regime, such as neutron star mergers, supernovae, and flaring active
galactic nuclei. The order-of-magnitude improvement compared to previous MeV
missions also enables discoveries of a wide range of phenomena whose energy
output peaks in the relatively unexplored medium-energy gamma-ray band
Genome-wide association identifies nine common variants associated with fasting proinsulin levels and provides new insights into the pathophysiology of type 2 diabetes.
OBJECTIVE: Proinsulin is a precursor of mature insulin and C-peptide. Higher circulating proinsulin levels are associated with impaired β-cell function, raised glucose levels, insulin resistance, and type 2 diabetes (T2D). Studies of the insulin processing pathway could provide new insights about T2D pathophysiology. RESEARCH DESIGN AND METHODS: We have conducted a meta-analysis of genome-wide association tests of ∼2.5 million genotyped or imputed single nucleotide polymorphisms (SNPs) and fasting proinsulin levels in 10,701 nondiabetic adults of European ancestry, with follow-up of 23 loci in up to 16,378 individuals, using additive genetic models adjusted for age, sex, fasting insulin, and study-specific covariates. RESULTS: Nine SNPs at eight loci were associated with proinsulin levels (P < 5 × 10(-8)). Two loci (LARP6 and SGSM2) have not been previously related to metabolic traits, one (MADD) has been associated with fasting glucose, one (PCSK1) has been implicated in obesity, and four (TCF7L2, SLC30A8, VPS13C/C2CD4A/B, and ARAP1, formerly CENTD2) increase T2D risk. The proinsulin-raising allele of ARAP1 was associated with a lower fasting glucose (P = 1.7 × 10(-4)), improved β-cell function (P = 1.1 × 10(-5)), and lower risk of T2D (odds ratio 0.88; P = 7.8 × 10(-6)). Notably, PCSK1 encodes the protein prohormone convertase 1/3, the first enzyme in the insulin processing pathway. A genotype score composed of the nine proinsulin-raising alleles was not associated with coronary disease in two large case-control datasets. CONCLUSIONS: We have identified nine genetic variants associated with fasting proinsulin. Our findings illuminate the biology underlying glucose homeostasis and T2D development in humans and argue against a direct role of proinsulin in coronary artery disease pathogenesis
A genome-wide association search for type 2 diabetes genes in African Americans.
African Americans are disproportionately affected by type 2 diabetes (T2DM) yet few studies have examined T2DM using genome-wide association approaches in this ethnicity. The aim of this study was to identify genes associated with T2DM in the African American population. We performed a Genome Wide Association Study (GWAS) using the Affymetrix 6.0 array in 965 African-American cases with T2DM and end-stage renal disease (T2DM-ESRD) and 1029 population-based controls. The most significant SNPs (n = 550 independent loci) were genotyped in a replication cohort and 122 SNPs (n = 98 independent loci) were further tested through genotyping three additional validation cohorts followed by meta-analysis in all five cohorts totaling 3,132 cases and 3,317 controls. Twelve SNPs had evidence of association in the GWAS (P<0.0071), were directionally consistent in the Replication cohort and were associated with T2DM in subjects without nephropathy (P<0.05). Meta-analysis in all cases and controls revealed a single SNP reaching genome-wide significance (P<2.5×10(-8)). SNP rs7560163 (P = 7.0×10(-9), OR (95% CI) = 0.75 (0.67-0.84)) is located intergenically between RND3 and RBM43. Four additional loci (rs7542900, rs4659485, rs2722769 and rs7107217) were associated with T2DM (P<0.05) and reached more nominal levels of significance (P<2.5×10(-5)) in the overall analysis and may represent novel loci that contribute to T2DM. We have identified novel T2DM-susceptibility variants in the African-American population. Notably, T2DM risk was associated with the major allele and implies an interesting genetic architecture in this population. These results suggest that multiple loci underlie T2DM susceptibility in the African-American population and that these loci are distinct from those identified in other ethnic populations