| 1. |
- Burgess, J. Michael, et al.
(författare)
-
AN OBSERVED CORRELATION BETWEEN THERMAL AND NON-THERMAL EMISSION IN GAMMA-RAY BURSTS
- 2014
-
Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 784:2
-
Tidskriftsartikel (refereegranskat)abstract
- Recent observations by the Fermi Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal gamma-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, E-p and kT, of these two components are correlated via the relation E-p proportional to T-alpha which varies from GRB to GRB. We present an interpretation in which the value of the index alpha indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.
|
|
| 2. |
- Guiriec, Sylvain, et al.
(författare)
-
Detection of a thermal spectral component in the prompt emission of GRB 100724B
- 2011
-
Ingår i: ASTROPHYSICAL JOURNAL LETTERS. - 2041-8205. ; 727:2, s. L33-
-
Tidskriftsartikel (refereegranskat)abstract
- Observations of GRB 100724B with the Fermi Gamma-Ray Burst Monitor find that the spectrum is dominated by the typical Band functional form, which is usually taken to represent a non-thermal emission component, but also includes a statistically highly significant thermal spectral contribution. The simultaneous observation of the thermal and non-thermal components allows us to confidently identify the two emission components. The fact that these seem to vary independently favors the idea that the thermal component is of photospheric origin while the dominant non-thermal emission occurs at larger radii. Our results imply either a very high efficiency for the non-thermal process or a very small size of the region at the base of the flow, both quite challenging for the standard fireball model. These problems are resolved if the jet is initially highly magnetized and has a substantial Poynting flux.
|
|
| 3. |
- Haverd, Vanessa, et al.
(författare)
-
A stand-alone tree demography and landscape structure module for Earth system models
- 2013
-
Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 1944-8007 .- 0094-8276. ; 40:19, s. 5234-5239
-
Tidskriftsartikel (refereegranskat)abstract
- We propose and demonstrate a new approach for the simulation of woody ecosystem stand dynamics, demography, and disturbance-mediated heterogeneity suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any earth system model. The approach is encoded in a model called Populations-Order-Physiology (POP). We demonstrate the behavior and performance of POP coupled to the Community Atmosphere Biosphere Land Exchange model (CABLE) applied along the Northern Australian Tropical Transect, featuring gradients in rainfall and fire disturbance. The model is able to simultaneously reproduce observation-based estimates of key functional and structural variables along the transect, namely gross primary production, tree foliage projective cover, basal area, and maximum tree height. Prospects for the use of POP to address current vegetation dynamic deficiencies in earth system modeling are discussed.
|
|
| 4. |
- Lorgelly, Paula K, et al.
(författare)
-
An economic evaluation of rosuvastatin treatment in systolic heart failure: evidence from the CORONA trial.
- 2010
-
Ingår i: European journal of heart failure. - : Wiley. - 1879-0844 .- 1388-9842. ; 12:1, s. 66-74
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: To estimate the cost-effectiveness of 10 mg rosuvastatin daily for older patients with systolic heart failure in the Controlled Rosuvastatin Multinational Study in Heart Failure (CORONA) trial. METHODS AND RESULTS: This within trial analysis of CORONA used major cardiovascular (CV) events as the outcome measure. Resource use was valued and the costs of hospitalizations, procedures, and statin use compared. Cost-effectiveness was estimated as cost per major CV event avoided. There were significantly fewer major CV events in the rosuvastatin group compared with the placebo group (1.04 vs. 1.20 per patient; difference 0.164; 95% CI: 0.075-0.254, P < 0.001). The average cost of CV hospitalizations and procedures was significantly lower for those receiving rosuvastatin ( pound1531 vs. pound1769; difference pound238; 95% CI: pound73-403, P = 0.005); the additional cost of the statin resulted in significantly higher total costs for the rosuvastatin group ( pound1769 vs. pound2072; difference pound303; 95% CI: pound138-468, P < 0.001). Overall, rosuvastatin was found to cost pound1840 (95% CI: pound562-6028) per major CV event avoided. CONCLUSION: This economic analysis showed that a significant reduction in major CV events with rosuvastatin led to significantly reduced costs of CV hospitalizations and procedures. The reduction in associated costs for major CV events was found to offset partially (by 44%) the cost of rosuvastatin treatment in patients with systolic heart failure.
|
|
