| 1. |
- Acharya, B. S., et al.
(författare)
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Introducing the CTA concept
- 2013
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Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 43, s. 3-18
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Actis, M., et al.
(författare)
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Design concepts for the Cherenkov Telescope Array CTA : an advanced facility for ground-based high-energy gamma-ray astronomy
- 2011
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Ingår i: Experimental astronomy. - : Springer. - 0922-6435 .- 1572-9508. ; 32:3, s. 193-316
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.
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| 3. |
- O'Connor, C. M., et al.
(författare)
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Effect of nesiritide in patients with acute decompensated heart failure
- 2011
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Ingår i: The New England journal of medicine. - : Massachusetts Medical Society. - 0028-4793 .- 1533-4406. ; 365:1, s. 32-43
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Nesiritide is approved in the United States for early relief of dyspnea in patients with acute heart failure. Previous meta-analyses have raised questions regarding renal toxicity and the mortality associated with this agent. METHODS: We randomly assigned 7141 patients who were hospitalized with acute heart failure to receive either nesiritide or placebo for 24 to 168 hours in addition to standard care. Coprimary end points were the change in dyspnea at 6 and 24 hours, as measured on a 7-point Likert scale, and the composite end point of rehospitalization for heart failure or death within 30 days. RESULTS: Patients randomly assigned to nesiritide, as compared with those assigned to placebo, more frequently reported markedly or moderately improved dyspnea at 6 hours (44.5% vs. 42.1%, P=0.03) and 24 hours (68.2% vs. 66.1%, P=0.007), but the prespecified level for significance (P
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| 4. |
- Eapen, Z. J., et al.
(författare)
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Do Countries or Hospitals With Longer Hospital Stays for Acute Heart Failure Have Lower Readmission Rates?: Findings From ASCEND-HF
- 2013
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Ingår i: Circulation Heart Failure. - 1941-3289 .- 1941-3297. ; 6:4, s. 727-32
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Tidskriftsartikel (refereegranskat)abstract
- Background- Hospital readmission is an important clinical outcome of patients with heart failure. Its relation to length of stay for the initial hospitalization is not clear. Methods and Results- We used hierarchical modeling of data from a clinical trial to examine variations in length of stay across countries and across hospitals in the United States and its association with readmission within 30 days of randomization. Main outcomes included associations between country-level length of stay and readmission rates, after adjustment for patient-level case mix; and associations between length of stay and readmission rates across sites in the United States. Across 27 countries with 389 sites and 6848 patients, mean length of stay ranged from 4.9 to 14.6 days (6.1 days in the United States). Rates of all-cause readmission ranged from 2.5% to 25.0% (17.8% in the United States). There was an inverse correlation between country-level mean length of stay and readmission (r=-0.52; P<0.01). After multivariable adjustment, each additional inpatient day across countries was associated with significantly lower risk of all-cause readmission (odds ratio, 0.86; 95% confidence interval, 0.75-0.98; P=0.02) and heart failure readmission (odds ratio, 0.79; 95% confidence interval, 0.69-0.99; P=0.03). Similar trends were observed across US study sites concerning readmission for any cause (odds ratio, 0.92; 95% confidence interval, 0.85-1.00; P=0.06) and readmission for heart failure (odds ratio, 0.90; 95% confidence interval, 0.80-1.01; P=0.07). Across countries and across US sites, longer median length of stay was independently associated with lower risk of readmission. Conclusions- Countries with longer length of stay for heart failure hospitalizations had significantly lower rates of readmission within 30 days of randomization. These findings may have implications for developing strategies to prevent readmission, defining quality measures, and designing clinical trials in acute heart failure. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00475852.
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| 5. |
- Starling, R. L. C., et al.
(författare)
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Discovery of the nearby long, soft GRB 100316D with an associated supernova
- 2011
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 411:4, s. 2792-2803
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Tidskriftsartikel (refereegranskat)abstract
- We report the Swift discovery of the nearby long, soft gamma-ray burst GRB 100316D, and the subsequent unveiling of its low-redshift host galaxy and associated supernova. We derive the redshift of the event to be z = 0.0591 +/- 0.0001 and provide accurate astrometry for the gamma-ray burst (GRB) supernova (SN). We study the extremely unusual prompt emission with time-resolved gamma-ray to X-ray spectroscopy and find that the spectrum is best modelled with a thermal component in addition to a synchrotron emission component with a low peak energy. The X-ray light curve has a remarkably shallow decay out to at least 800 s. The host is a bright, blue galaxy with a highly disturbed morphology and we use Gemini-South, Very Large Telescope and Hubble Space Telescope observations to measure some of the basic host galaxy properties. We compare and contrast the X-ray emission and host galaxy of GRB 100316D to a subsample of GRB-SNe. GRB 100316D is unlike the majority of GRB-SNe in its X-ray evolution, but resembles rather GRB 060218, and we find that these two events have remarkably similar high energy prompt emission properties. Comparison of the host galaxies of GRB-SNe demonstrates, however, that there is a great diversity in the environments in which GRB-SNe can be found. GRB 100316D is an important addition to the currently sparse sample of spectroscopically confirmed GRB-SNe, from which a better understanding of long GRB progenitors and the GRB-SN connection can be gleaned.
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| 6. |
- Toma, M., et al.
(författare)
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The relationship between left ventricular ejection fraction and mortality in patients with acute heart failure: insights from the ASCEND-HF Trial
- 2014
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Ingår i: European Journal of Heart Failure. - : Wiley. - 1388-9842. ; 16:3, s. 334-41
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Tidskriftsartikel (refereegranskat)abstract
- AIM: Acute decompensated heart failure (ADHF) is associated with significant morbidity and mortality but the relationship between LVEF and outcomes is unclear. We explored the association between LVEF and 30 and 180 day mortality in 7007 ADHF patients enrolled in the Acute Studies of Nesiritide in Decompensated Heart Failure (ASCEND-HF) trial. METHODS AND RESULTS: We explored the association between LVEF and 30 and 180 day mortality in 7007 ADHF patients enrolled in the Acute Studies of Nesiritide in Decompensated Heart Failure (ASCEND-HF) trial. LVEF was analysed both as a continuous variable and according to three categories: < 40% (LowEF), 40-50% [intermediate EF (IntEF)], and > 50% [preserved ejection fraction (PresEF)]. Of the patients in the trial, 4474 (78.7%) had LowEF, 674 (11.9%) had IntEF, and 539 (9.5%) had PresEF. The unadjusted 30 and 180 day mortality was similar for LowEF (3.7%, 12.3%), IntEF (3.4%, 13.1%), and PresEF (4.3%, 14.1%), respectively (P > 0.05). After multivariable adjustment, the hazard ratio (HR) for 180 day mortality remained similar for the LowEF [HR 0.96, 95% confidence interval (CI) 0.75-1.24; P = 0.77] and IntEF (0.91, 95% CI 0.66-1.3; P = 0.58) compared to PresEF patients. By contrast, when LVEF was evaluated as a continuous measure, it exhibited a U-shaped pattern with mortality. After matching for age and sex, the mortality risk attributed to LVEF was attenuated, as the LVEF increased as a continuous variable over 35%. However, in patients with EF < 35%, the mortality risk continue to increase as the LVEF declined. CONCLUSIONS: Among patients with ADHF, the unadjusted mortality rates are similar across LVEF strata. However, after accounting for key patient variables, the mortality risk increases as EF falls below 35%. These data will be useful in planning future studies of ADHF. CLINICAL TRIAL REGISTRATION: www.clinicaltrials.gov identifier: NCT00475852.
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| 7. |
- van der Horst, A. J., et al.
(författare)
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A comprehensive radio view of the extremely bright gamma-ray burst 130427A
- 2014
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 444:4, s. 3151-3163
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Tidskriftsartikel (refereegranskat)abstract
- GRB130427A was extremely bright as a result of occurring at low redshift whilst the energetics were more typical of high-redshift gamma-ray bursts (GRBs). We collected well-sampled light curves at 1.4 and 4.8 GHz of GRB 130427A with the Westerbork Synthesis Radio Telescope (WSRT); and we obtained its most accurate position with the European Very Long Baseline Interferometry Network (EVN). Our flux density measurements are combined with all the data available at radio, optical and X-ray frequencies to perform broad-band modelling in the framework of a reverse-forward shock model and a two-component jet model, and we discuss the implications and limitations of both models. The low density inferred from the modelling implies that the GRB 130427A progenitor is either a very low metallicity Wolf-Rayet star, or a rapidly rotating, low-metallicity O star. We also find that the fraction of the energy in electrons is evolving over time, and that the fraction of electrons participating in a relativistic power-law energy distribution is less than 15 per cent. We observed intraday variability during the earliest WSRT observations, and the source sizes inferred from our modelling are consistent with this variability being due to interstellar scintillation effects. Finally, we present and discuss our limits on the linear and circular polarization, which are among the deepest limits of GRB radio polarization to date.
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| 8. |
- Bufano, Filomena, et al.
(författare)
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THE HIGHLY ENERGETIC EXPANSION OF SN 2010bh ASSOCIATED WITH GRB 100316D
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 753:1, s. 67-
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Tidskriftsartikel (refereegranskat)abstract
- We present the spectroscopic and photometric evolution of the nearby (z = 0.059) spectroscopically confirmed Type Ic supernova, SN 2010bh, associated with the soft, long-duration gamma-ray burst (X-ray flash) GRB 100316D. Intensive follow-up observations of SN 2010bh were performed at the ESO Very Large Telescope (VLT) using the X-shooter and FORS2 instruments. Thanks to the detailed temporal coverage and the extended wavelength range (3000-24800 angstrom), we obtained an unprecedentedly rich spectral sequence among the hypernovae, making SN 2010bh one of the best studied representatives of this SN class. We find that SN 2010bh has a more rapid rise to maximum brightness (8.0 +/- 1.0 rest-frame days) and a fainter absolute peak luminosity (L-bol approximate to 3 x 10(42) erg s(-1)) than previously observed SN events associated with GRBs. Our estimate of the ejected Ni-56 mass is 0.12 +/- 0.02 M-circle dot. From the broad spectral features, we measure expansion velocities up to 47,000 km s(-1), higher than those of SNe 1998bw (GRB 980425) and 2006aj (GRB 060218). Helium absorption lines He I lambda 5876 and He I 1.083 mu m, blueshifted by similar to 20,000-30,000 km s(-1) and similar to 28,000-38,000 km s(-1), respectively, may be present in the optical spectra. However, the lack of coverage of the He I 2.058 mu m line prevents us from confirming such identifications. The nebular spectrum, taken at similar to 186 days after the explosion, shows a broad but faint [O I] emission at 6340 angstrom. The light curve shape and photospheric expansion velocities of SN 2010bh suggest that we witnessed a highly energetic explosion with a small ejected mass (E-k approximate to 10(52) erg and M-ej approximate to 3 M-circle dot). The observed properties of SN 2010bh further extend the heterogeneity of the class of GRB SNe.
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