| 1. |
- Dornelas, M., et al.
(author)
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BioTIME: A database of biodiversity time series for the Anthropocene
- 2018
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In: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 27:7, s. 760-786
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Journal article (peer-reviewed)abstract
- Motivation: The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene. Main types of variables included: The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record. Spatial location and grain: BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km(2) (158 cm(2)) to 100 km(2) (1,000,000,000,000 cm(2)). Time period and grainBio: TIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year. Major taxa and level of measurement: BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.
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| 2. |
- Feroci, M., et al.
(author)
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The large observatory for x-ray timing
- 2014
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9780819496126
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Conference paper (peer-reviewed)abstract
- The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m2 effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.
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| 3. |
- Feroci, M., et al.
(author)
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LOFT - The large observatory for x-ray timing
- 2012
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. - 9780819491442 ; , s. 84432D-
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Conference paper (peer-reviewed)abstract
- The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m2 peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO's to yearlong transient outbursts. In this paper we report the current status of the project.
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| 4. |
- Feroci, M., et al.
(author)
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The Large Observatory for X-ray Timing (LOFT)
- 2012
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In: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 34:2, s. 415-444
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Journal article (peer-reviewed)abstract
- High-time-resolution X-ray observations of compact objects provide direct access to strong-field gravity, to the equation of state of ultradense matter and to black hole masses and spins. A 10 m(2)-class instrument in combination with good spectral resolution is required to exploit the relevant diagnostics and answer two of the fundamental questions of the European Space Agency (ESA) Cosmic Vision Theme "Matter under extreme conditions", namely: does matter orbiting close to the event horizon follow the predictions of general relativity? What is the equation of state of matter in neutron stars? The Large Observatory For X-ray Timing (LOFT), selected by ESA as one of the four Cosmic Vision M3 candidate missions to undergo an assessment phase, will revolutionise the study of collapsed objects in our galaxy and of the brightest supermassive black holes in active galactic nuclei. Thanks to an innovative design and the development of large-area monolithic silicon drift detectors, the Large Area Detector (LAD) on board LOFT will achieve an effective area of similar to 12 m(2) (more than an order of magnitude larger than any spaceborne predecessor) in the 2-30 keV range (up to 50 keV in expanded mode), yet still fits a conventional platform and small/medium-class launcher. With this large area and a spectral resolution of < 260 eV, LOFT will yield unprecedented information on strongly curved spacetimes and matter under extreme conditions of pressure and magnetic field strength.
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| 5. |
- Cannizzaro, G., et al.
(author)
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Accretion disc cooling and narrow absorption lines in the tidal disruption event AT2019dsg
- 2021
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 504:1, s. 792-815
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Journal article (peer-reviewed)abstract
- We present the results of a large multiwavelength follow-up campaign of the tidal disruption event (TDE) AT 2019dsg, focusing on low to high resolution optical spectroscopy, X-ray, and radio observations. The galaxy hosts a super massive black hole of mass (5.4±3.2)×106M⊙ and careful analysis finds no evidence for the presence of an active galactic nucleus, instead the TDE host galaxy shows narrow optical emission lines that likely arise from star formation activity. The transient is luminous in the X-rays, radio, UV, and optical. The X-ray emission becomes undetected after ∼100 d, and the radio luminosity density starts to decay at frequencies above 5.4 GHz by ∼160 d. Optical emission line signatures of the TDE are present up to ∼200 d after the light-curve peak. The medium to high resolution spectra show traces of absorption lines that we propose originate in the self-gravitating debris streams. At late times, after ∼200 d, narrow Fe lines appear in the spectra. The TDE was previously classified as N-strong, but after careful subtraction of the host galaxy’s stellar contribution, we find no evidence for these N lines in the TDE spectrum, even though O Bowen lines are detected. The observed properties of the X-ray emission are fully consistent with the detection of the inner regions of a cooling accretion disc. The optical and radio properties are consistent with this central engine seen at a low inclination (i.e. seen from the poles).
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| 6. |
- Wang, Yanan, et al.
(author)
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Rapid Dimming Followed by a State Transition: A Study of the Highly Variable Nuclear Transient AT 2019avd over 1000+ Days
- 2024
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In: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 962:1
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Journal article (peer-reviewed)abstract
- The tidal disruption of a star around a supermassive black hole (SMBH) offers a unique opportunity to study accretion onto an SMBH on a human timescale. We present results from our 1000+ days monitoring campaign of AT 2019avd, a nuclear transient with tidal-disruption-event-like properties, with NICER, Swift, and Chandra. Our primary finding is that approximately 225 days following the peak of the X-ray emission, there is a rapid drop in luminosity exceeding 2 orders of magnitude. This X-ray dropoff is accompanied by X-ray spectral hardening, followed by a plateau phase of 740 days. During this phase, the spectral index decreases from 6.2 ± 1.1 to 2.3 ± 0.4, while the disk temperature remains constant. Additionally, we detect pronounced X-ray variability, with an average fractional rms amplitude of 47%, manifesting over timescales of a few dozen minutes. We propose that this phenomenon may be attributed to intervening clumpy outflows. The overall properties of AT 2019avd suggest that the accretion disk evolves from a super-Eddington to a sub-Eddington luminosity state, possibly associated with a compact jet. This evolution follows a pattern in the hardness-intensity diagram similar to that observed in stellar-mass BHs, supporting the mass invariance of accretion-ejection processes around BHs
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| 7. |
- Acciarresi, M., et al.
(author)
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Prestroke CHA(2)DS(2)-VASc Score and Severity of Acute Stroke in Patients with Atrial Fibrillation: Findings from RAF Study
- 2017
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In: Journal of Stroke & Cerebrovascular Diseases. - : Elsevier BV. - 1052-3057. ; 26:6, s. 1363-1368
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Journal article (peer-reviewed)abstract
- Background and Purpose: The aim of this study was to investigate for a possible association between both prestroke CHA(2)DS(2)-VASc score and the severity of stroke at presentation, as well as disability and mortality at 90 days, in patients with acute stroke and atrial fibrillation (AF). Methods: This prospective study enrolled consecutive patients with acute ischemic stroke, AF, and assessment of prestroke CHA2DS2-VASc score. Severity of stroke was assessed on admission using the National Institutes of Health Stroke Scale (NIHSS) score (severe stroke: NIHSS >= 10). Disability and mortality at 90 days were assessed by the modified Rankin Scale (mRS < 3 or >= 3). Multiple logistic regression was used to correlate prestroke CHA(2)DS(2)-VASc and severity of stroke, as well as disability and mortality at 90 days. Results: Of the 1020 patients included in the analysis, 606 patients had an admission NIHSS score lower and 414 patients higher than 10. At 90 days, 510 patients had mRS >= 3. A linear correlation was found between the prestroke CHA(2)DS(2)-VASc score and severity of stroke (P = .001). On multivariate analysis, CHA(2)DS(2)-VASc score correlated with severity of stroke (P = .041) and adverse functional outcome (mRS = 3) (P = .001). A logistic regression with the receiver operating characteristic graph procedure (C-statistics) evidenced an area under the curve of .60 (P = .0001) for severe stroke. Furthermore, a correlation was found between prestroke CHA(2)DS(2)-VASc score and lesion size. Conclusions: In patients with AF, in addition to the risk of stroke, a high CHA(2)DS(2)-VASc score was independently associated with both stroke severity at onset and disability and mortality at 90 days.
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| 8. |
- Antonenko, Kateryna, et al.
(author)
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Sex-related differences in risk factors, type of treatment received and outcomes in patients with atrial fibrillation and acute stroke: Results from the RAF-study (Early Recurrence and Cerebral Bleeding in Patients with Acute Ischemic Stroke and Atrial Fibrillation)
- 2017
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In: European Stroke Journal. - : SAGE Publications. - 2396-9873 .- 2396-9881. ; 2:1, s. 46-53
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Journal article (peer-reviewed)abstract
- Introduction: Atrial fibrillation is an independent risk factor of thromboembolism. Women with atrial fibrillation are at a higher overall risk for stroke compared to men with atrial fibrillation. The aim of this study was to evaluate for sex differences in patients with acute stroke and atrial fibrillation, regarding risk factors, treatments received and outcomes. Methods: Data were analyzed from the ‘‘Recurrence and Cerebral Bleeding in Patients with Acute Ischemic Stroke and Atrial Fibrillation’’ (RAF-study), a prospective, multicenter, international study including only patients with acute stroke and atrial fibrillation. Patients were followed up for 90 days. Disability was measured by the modified Rankin Scale (0–2 favorable outcome, 3–6 unfavorable outcome). Results: Of the 1029 patients enrolled, 561 were women (54.5%) (p<0.001) and younger (p<0.001) compared to men. In patients with known atrial fibrillation, women were less likely to receive oral anticoagulants before index stroke (p¼0.026) and were less likely to receive anticoagulants after stroke (71.3% versus 78.4%, p¼0.01). There was no observed sex difference regarding the time of starting anticoagulant therapy between the two groups (6.411.7 days for men versus 6.512.4 days for women, p¼0.902). Men presented with more severe strokes at onset (mean NIHSS 9.26.9 versus 8.17.5, p<0.001). Within 90 days, 46 (8.2%) recurrent ischemic events (stroke/TIA/systemic embolism) and 19 (3.4%) symptomatic cerebral bleedings were found in women compared to 30 (6.4%) and 18 (3.8%) in men (p¼0.28 and p¼0.74). At 90 days, 57.7% of women were disabled or deceased, compared to 41.1% of the men (p<0.001). Multivariate analysis did not confirm this significance. Conclusions: Women with atrial fibrillation were less likely to receive oral anticoagulants prior to and after stroke compared to men with atrial fibrillation, and when stroke occurred, regardless of the fact that in our study women were younger and with less severe stroke, outcomes did not differ between the sexes.
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| 9. |
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| 10. |
- Vincentelli, Federico M., et al.
(author)
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A shared accretion instability for black holes and neutron stars
- 2023
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 615:7950, s. 45-49
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Journal article (peer-reviewed)abstract
- Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales2. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole3-5. Although there are hints of these cycles in a few isolated cases6-10, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle11. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrum-from radio to X-ray-of both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.
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