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- Salafia, Om Sharan, et al.
(författare)
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Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 931:2
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Tidskriftsartikel (refereegranskat)abstract
- We monitored the position of the close-by (about 370 Mpc) gamma-ray burst GRB 190829A, which originated from a massive star collapse, through very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very Long Baseline Array, carrying out a total of nine observations between 9 and 117 days after the gamma-ray burst at 5 and 15 GHz, with a typical resolution of a few milliarcseconds. From a state-of-the art analysis of these data, we obtained valuable limits on the source size and expansion rate. The limits are in agreement with the size evolution entailed by a detailed modeling of the multiwavelength light curves with a forward-plus-reverse shock model, which agrees with the observations across almost 18 orders of magnitude in frequency (including the HESS data at TeV photon energies) and more than 4 orders of magnitude in time. Thanks to the multiwavelength, high-cadence coverage of the afterglow, inherent degeneracies in the afterglow model are broken to a large extent, allowing us to capture some unique physical insights; we find a low prompt emission efficiency of less than or similar to 10(-3), a low fraction of relativistic electrons in the forward shock downstream chi ( e ) < 13% (90% credible level), and a rapid decay of the magnetic field in the reverse shock downstream after the shock crossing. While our model assumes an on-axis jet, our VLBI astrometry is not sufficiently tight as to exclude any off-axis viewing angle, but we can exclude the line of sight to have been more than similar to 2 degrees away from the border of the gamma-ray-producing region based on compactness arguments.
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| 2. |
- Terenziani, Monica, et al.
(författare)
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Practices of Pediatric Oncology and Hematology Providers Regarding Fertility Issues: A European Survey
- 2014
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Ingår i: Pediatric Blood & Cancer. - : Wiley. - 1545-5017 .- 1545-5009. ; 61:11, s. 2054-2058
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundFertility is impaired in many survivors of childhood cancer following treatment. Preservation of fertility after cancer has become a central survivorship concern. Nevertheless, several doctors, patients, and families do not discuss fertility and recommendations for fertility preservation in pediatrics are still lacking. Recommendations based on scientific evidence are needed and before their development we wanted to assess the practice patterns of fertility preservation in Europe. ProceduresOn behalf of the PanCare network, we sent a questionnaire to pediatric onco-hematology institutions across Europe. The survey consisted of 21 questions assessing their usual practices around fertility preservation. ResultsOne hundred ninety-eight institutional representatives across Europe received the survey and 68 (response rate 34.3%) responded. Pre-treatment fertility counseling was offered by 64 institutions. Counseling was done by a pediatric onco-hematologist in 52% (33/64) and in 32% (20/64) by a team. The majority of institutions (53%) lacked recommendations for fertility preservation. All 64 centers offered sperm banking; eight offered testicular tissue cryopreservation for pre-pubertal males. For females, the possibility of preserving ovarian tissue was offered by 40 institutions. ConclusionsThere is a high level of interest in fertility preservation among European centers responding to our survey. However, while most recommended sperm cryopreservation, many also recommended technologies whose efficacy has not been shown. There is an urgent need for evidence-based European recommendations for fertility preservation to help survivors deal with the stressful topic of fertility. Pediatr Blood Cancer 2014;61:2054-2058. (c) 2014 Wiley Periodicals, Inc.
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