125 research outputs found
Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)
The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in
March-April 2013 and January 2015, combined with the improved observational
capabilities of submillimeter facilities, offered an opportunity to carry out
sensitive compositional and isotopic studies of the volatiles in their coma. We
observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January
2015, and with the Odin submillimeter space observatory on 29 January - 3
February 2015. We detected 22 molecules and several isotopologues. The
HO and HO production rates measured with Odin follow a
periodic pattern with a period of 0.94 days and an amplitude of ~25%. The
inferred isotope ratios in comet Lovejoy are O/O = 499 24
and D/H = 1.4 0.4 in water, S/S = 24.7
3.5 in CS, all compatible with terrestrial values. The ratio
C/C = 109 14 in HCN is marginally higher than terrestrial
and N/N = 145 12 in HCN is half the Earth ratio. Several
upper limits for D/H or 12C/13C in other molecules are reported. From our
observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio
in an Oort Cloud comet that is not larger than the terrestrial value. On the
other hand, the observation of the same HDO line in the other Oort-cloud comet,
C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous
measurements of D/H in cometary water, this illustrates that a diversity in the
D/H ratio and in the chemical composition, is present even within the same
dynamical group of comets, suggesting that current dynamical groups contain
comets formed at very different places or times in the early solar system.Comment: Accepted for publication in Astronomy and Astrophysic
Mixed-Meal Tolerance Test Versus Glucagon Stimulation Test for the Assessment of ÎČ-Cell Function in Therapeutic Trials in Type 1 Diabetes
OBJECTIVEâÎČ-Cell function in type 1 diabetes clinical trials is commonly measured by C-peptide response to a secretagogue in either a mixed-meal tolerance test (MMTT) or a glucagon stimulation test (GST). The Type 1 Diabetes TrialNet Research Group and the European C-peptide Trial (ECPT) Study Group conducted parallel randomized studies to compare the sensitivity, reproducibility, and tolerability of these procedures
Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C 454.3
This is the first report of Fermi Gamma-ray Space Telescope observations of
the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts
since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7
- October 6, indicate strong, highly variable gamma-ray emission with an
average flux of ~3 x 10^{-6} photons cm^{-2} s^{-1}, for energies above 100
MeV. The gamma-ray flux is variable, with strong, distinct,
symmetrically-shaped flares for which the flux increases by a factor of several
on a time scale of about three days. This variability indicates a compact
emission region, and the requirement that the source is optically thin to
pair-production implies relativistic beaming with Doppler factor delta > 8,
consistent with the values inferred from VLBI observations of superluminal
expansion (delta ~ 25). The observed gamma-ray spectrum is not consistent with
a simple power-law, but instead steepens strongly above ~2 GeV, and is well
described by a broken power-law with photon indices of ~2.3 and ~3.5 below and
above the break, respectively. This is the first direct observation of a break
in the spectrum of a high luminosity blazar above 100 MeV, and it is likely
direct evidence for an intrinsic break in the energy distribution of the
radiating particles. Alternatively, the spectral softening above 2 GeV could be
due to gamma-ray absorption via photon-photon pair production on the soft X-ray
photon field of the host AGN, but such an interpretation would require the
dissipation region to be located very close (less than 100 gravitational radii)
to the black hole, which would be inconsistent with the X-ray spectrum of the
source.Comment: Accepted by the Astrophysical Journal; corresponding authors: Greg
Madejski ([email protected]) and Benoit Lott ([email protected]
Fermi/LAT discovery of gamma-ray emission from a relativistic jet in the narrow-line quasar PMN J0948+0022
We report the discovery by the Large Area Telescope (LAT) onboard the Fermi
Gamma-ray Space Telescope of high-energy gamma-ray emission from the peculiar
quasar PMN J0948+0022 (z=0.5846). The optical spectrum of this object exhibits
rather narrow Hbeta (FWHM(Hbeta) ~ 1500 km s^-1), weak forbidden lines and is
therefore classified as a narrow-line type I quasar. This class of objects is
thought to have relatively small black hole mass and to accrete at high
Eddington ratio. The radio loudness and variability of the compact radio core
indicates the presence of a relativistic jet. Quasi simultaneous
radio-optical-X-ray and gamma-ray observations are presented. Both radio and
gamma-ray emission (observed over 5-months) are strongly variable. The
simultaneous optical and X-ray data from Swift show a blue continuum attributed
to the accretion disk and a hard X-ray spectrum attributed to the jet. The
resulting broad band spectral energy distribution (SED) and, in particular, the
gamma-ray spectrum measured by Fermi are similar to those of more powerful
FSRQ. A comparison of the radio and gamma-ray characteristics of PMN J0948+0022
with the other blazars detected by LAT shows that this source has a relatively
low radio and gamma-ray power, with respect to other FSRQ. The physical
parameters obtained from modelling the SED also fall at the low power end of
the FSRQ parameter region discussed in Celotti & Ghisellini (2008). We suggest
that the similarity of the SED of PMN J0948+0022 to that of more massive and
more powerful quasars can be understood in a scenario in which the SED
properties depend on the Eddington ratio rather than on the absolute power.Comment: 10 pages, 5 figures, accepted for publication on ApJ Main Journal.
Corresponding author: L. Foschin
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
Establishing glycaemic control with continuous subcutaneous insulin infusion in children and adolescents with type 1 diabetes: experience of the PedPump Study in 17 countries
AIMS/HYPOTHESIS: To assess the use of paediatric continuous subcutaneous infusion (CSII) under real-life conditions by analysing data recorded for up to 90 days and relating them to outcome. METHODS: Pump programming data from patients aged 0-18 years treated with CSII in 30 centres from 16 European countries and Israel were recorded during routine clinical visits. HbA(1c) was measured centrally. RESULTS: A total of 1,041 patients (age: 11.8 +/- 4.2 years; diabetes duration: 6.0 +/- 3.6 years; average CSII duration: 2.0 +/- 1.3 years; HbA(1c): 8.0 +/- 1.3% [means +/- SD]) participated. Glycaemic control was better in preschool (n = 142; 7.5 +/- 0.9%) and pre-adolescent (6-11 years, n = 321; 7.7 +/- 1.0%) children than in adolescent patients (12-18 years, n = 578; 8.3 +/- 1.4%). There was a significant negative correlation between HbA(1c) and daily bolus number, but not between HbA(1c) and total daily insulin dose. The use of 7.5%. The incidence of severe hypoglycaemia and ketoacidosis was 6.63 and 6.26 events per 100 patient-years, respectively. CONCLUSIONS/INTERPRETATION: This large paediatric survey of CSII shows that glycaemic targets can be frequently achieved, particularly in young children, and the incidence of acute complications is low. Adequate substitution of basal and prandial insulin is associated with a better HbA(1c)
Glucose management for exercise using continuous glucose monitoring (CGM) and intermittently scanned CGM (isCGM) systems in type 1 diabetes: position statement of the European Association for the Study of Diabetes (EASD) and of the International Society for Pediatric and Adolescent Diabetes (ISPAD) endorsed by JDRF and supported by the American Diabetes Association (ADA)
Physical exercise is an important component in the management of type 1 diabetes across the lifespan. Yet, acute exercise increases the risk of dysglycaemia, and the direction of glycaemic excursions depends, to some extent, on the intensity and duration of the type of exercise. Understandably, fear of hypoglycaemia is one of the strongest barriers to incorporating exercise into daily life. Risk of hypoglycaemia during and after exercise can be lowered when insulinâdose adjustments are made and/or additional carbohydrates are consumed. Glycaemic management during exercise has been made easier with continuous glucose monitoring (CGM) and intermittently scanned continuous glucose monitoring (isCGM) systems; however, because of the complexity of CGM and isCGM systems, both individuals with type 1 diabetes and their healthcare professionals may struggle with the interpretation of given information to maximise the technological potential for effective use around exercise (ie, before, during and after). This position statement highlights the recent advancements in CGM and isCGM technology, with a focus on the evidence base for their efficacy to sense glucose around exercise and adaptations in the use of these emerging tools, and updates the guidance for exercise in adults, children and adolescents with type 1 diabetes
Prospects for GRB Science with the Fermi Large Area Telescope
The LAT instrument on the Fermi mission will reveal the rich spectral and
temporal gamma-ray burst phenomena in the > 100 MeV band. The synergy with
Fermi's GBM detectors will link these observations to those in the well
explored 10-1000 keV range; the addition of the > 100 MeV band observations
will resolve theoretical uncertainties about burst emission in both the prompt
and afterglow phases. Trigger algorithms will be applied to the LAT data both
onboard the spacecraft and on the ground. The sensitivity of these triggers
will differ because of the available computing resources onboard and on the
ground. Here we present the LAT's burst detection methodologies and the
instrument's GRB capabilities.Comment: Accepted by Ap
Report from the CVOT Summit 2021: new cardiovascular, renal, and glycemic outcomes.
The 7th Cardiovascular Outcome Trial (CVOT) Summit on Cardiovascular, Renal, and Glycemic Outcomes, was held virtually on November 18-19, 2021. Pursuing the tradition of the previous summits, this reference congress served as a platform for in-depth discussion and exchange on recently completed CVOTs. This year's focus was placed on the outcomes of EMPEROR-Preserved, FIGARO-DKD, AMPLITUDE-O, SURPASS 1-5, and STEP 1-5. Trial implications for diabetes and obesity management and the impact on new treatment algorithms were highlighted for endocrinologists, diabetologists, cardiologists, nephrologists, and general practitioners. Discussions evolved from outcome trials using SGLT2 inhibitors as therapy for heart failure, to CVOTs with nonsteroidal mineralocorticoid receptor antagonists and GLP-1 receptor agonists. Furthermore, trials for glycemic and overweight/obesity management, challenges in diabetes management in COVID-19, and novel guidelines and treatment strategies were discussed.Trial registration The 8th Cardiovascular Outcome Trial Summit will be held virtually on November 10-11, 2022 ( http://www.cvot.org )
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