3 research outputs found
First Results from Fermi GBM Earth Occultation Monitoring: Observations of Soft Gamma-Ray Sources Above 100 keV
The NaI and BGO detectors on the Gamma-ray Burst Monitor (GBM) on Fermi are
now being used for long-term monitoring of the hard X-ray/low energy gamma-ray
sky. Using the Earth occultation technique as demonstrated previously by the
BATSE instrument on the Compton Gamma-Ray Observatory, GBM can be used to
produce multiband light curves and spectra for known sources and transient
outbursts in the 8 keV to 1 MeV energy range with its NaI detectors and up to
40 MeV with its BGO detectors. Over 85% of the sky is viewed every orbit, and
the precession of the Fermi orbit allows the entire sky to be viewed every ~26
days with sensitivity exceeding that of BATSE at energies below ~25 keV and
above ~1.5 MeV. We briefly describe the technique and present preliminary
results using the NaI detectors after the first two years of observations at
energies above 100 keV. Eight sources are detected with a significance greater
than 7 sigma: the Crab, Cyg X-1, SWIFT J1753.5-0127, 1E 1740-29, Cen A, GRS
1915+105, and the transient sources XTE J1752-223 and GX 339-4. Two of the
sources, the Crab and Cyg X-1, have also been detected above 300 keV.Comment: 13 pages, 9 figures, submitted to Ap
Assimilation of surface-sensitive infrared radiances over land: Estimation of land surface temperature and emissivity
Heart Rate Variability, Ambient Particulate Matter Air Pollution, and Glucose Homeostasis: The Environmental Epidemiology of Arrhythmogenesis in the Women's Health Initiative
Metabolic neuropathophysiology underlying the prediabetic state may confer susceptibility to the adverse health effects of ambient particulate matter <10 μm in diameter (PM10). The authors therefore examined whether impaired glucose homeostasis modifies the effect of PM10 on heart rate variability in a stratified, random sample of 4,295 Women's Health Initiative clinical trial participants, among whom electrocardiograms and fasting blood draws were repeated at 3-year intervals from 1993 to 2004. In multilevel, mixed models weighted for sampling design and adjusted for clinical and environmental covariables, PM10 exposure was inversely associated with heart rate variability. Inverse PM10–heart rate variability associations were strongest for the root mean square of successive differences in normal-to-normal RR intervals (RMSSD). Among participants with impaired fasting glucose, there were −8.3% (95% confidence interval: −13.9, −2.4) versus −0.6% (95% confidence interval: −2.4, 1.3), −8.4% (95% confidence interval: −13.8, −2.7) versus −0.3% (95% confidence interval: −2.1, 1.6), and −4.3% (95% confidence interval: −9.4, 1.0) versus −0.8% (95% confidence interval: −2.7, 1.0) decreases in the RMSSD per 10-μg/m3 increase in PM10 at high versus low levels of insulin (P < 0.01), insulin resistance (P < 0.01), and glucose (P = 0.16), respectively. These associations were stronger among participants with diabetes and weaker among those without diabetes or impaired fasting glucose. The findings suggest that insulin and insulin resistance exacerbate the adverse effect of PM10 on cardiac autonomic control and thus risk of coronary heart disease among nondiabetic, postmenopausal women with impaired fasting glucose