To assess incidence and predictors of acute symptomatic seizures in a prospective cohort of patients with first stroke.
Patients with first stroke hospitalized in 31 Italian centers were recruited. ...Relevant demographic data, disease characteristics, and risk factors were collected. Acute symptomatic seizures (≤7 days) were recorded and correlated to age, gender, family history of epilepsy, and vascular risk factors.
A total of 714 patients (315 women, 399 men; age 27-97 years) were enrolled. A total of 609 (85.3%) had cerebral infarction (32 cerebral infarction with hemorrhagic transformation CIHT) and 105 (14.7%) primary intracerebral hemorrhage (PIH). A total of 141 (19.7%) had a large lesion (>3 cm) and 296 (41.5%) cortical involvement. Twelve patients reported family history of seizures. Forty-five patients (6.3%) presented acute symptomatic seizures, 24 with cerebral infarction (4.2%), 4 with CIHT (12.5%), and 17 (16.2%) with PIH. In multivariate analysis, compared to cerebral infarction, PIH carried the highest risk (odds ratio OR 7.2; 95% confidence interval CI 3.5-14.9) followed by CIHT (OR 2.7; 95% CI 0.8-9.6). Cortical involvement was a risk factor for PIH (OR 6.0; 95% CI 1.8-20.8) and for CI (OR 3.1; 95% CI 1.3-7.8). Hyperlipidemia (OR 0.2; 95% CI 0.03-0.8) was a protective factor for IPH.
The incidence of acute symptomatic seizures is the highest reported in patients with first stroke with prospective follow-up. Hemorrhagic stroke and cortical lesion were independent predictors of acute symptomatic seizures. Hyperlipidemia was a protective factor for hemorrhagic stroke.
Long-term variability of AGN at hard X-rays Soldi, S.; Beckmann, V.; Baumgartner, W. H. ...
Astronomy and astrophysics (Berlin),
03/2014, Letnik:
563, Številka:
A57
Journal Article
Recenzirano
Odprti dostop
Aims. Variability at all observed wavelengths is a distinctive property of active galactic nuclei (AGN). Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by ...absorption along the line of sight. Characterizing the intrinsic hard X-ray variability of a large AGN sample and comparing it to the results obtained at lower X-ray energies can significantly contribute to our understanding of the mechanisms underlying the high-energy radiation. Methods. Swift/BAT provides us with the unique opportunity to follow, on time scales of days to years and with regular sampling, the 14–195 keV emission of the largest AGN sample available up to date for this kind of investigation. As a continuation of an early work using the first 9 months of BAT data, we study the amplitude of the variations and their dependence on subclass and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. Results. About 80% of the AGN in the sample are found to exhibit significant variability on month-to-year time scales. In particular, radio loud sources are the most variable, and Seyfert 1.5−2 galaxies are slightly more variable than Seyfert 1, while absorbed and unabsorbed objects show similar timing properties. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes in the absorption column density. In general, the variations in the 14–24 and 35–100 keV bands are correlated well, suggesting a common origin to the variability across the BAT energy band. However, radio quiet AGN display on average 10% larger variations at 14–24 keV than at 35–100 keV, and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on a time scale of a month. In addition, sources with harder spectra are found to be more variable than softer ones, unlike what it is observed below 10 keV. These properties are generally consistent with a variable, in flux and shape, power law continuum, pivoting at energies ≳ 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at hard X-rays are comparable to those at lower energies, with at least some of the differences possibly ascribable to components contributing differently in the two energy domains (e.g., reflection, absorption).
Emission of two short hard X-ray bursts on 2009 June 5 disclosed the existence of a new soft gamma-ray repeater, now catalogued as SGR 0418+5729. After a few days, X-ray pulsations at a period of 9.1 ...s were discovered in its persistent emission. SGR 0418+5729 was monitored almost since its discovery with the Rossi X-ray Timing Explorer (2–10 keV energy range) and observed many times with Swift (0.2–10 keV). The source persistent X-ray emission faded by a factor of ∼10 in about 160 d, with a steepening in the decay about 19 d after the activation. The X-ray spectrum is well described by a simple absorbed blackbody, with a temperature decreasing in time. A phase-coherent timing solution over the ∼160 d time-span yielded no evidence for any significant evolution of the spin period, implying a 3σ upper limit of 1.1 × 10−13 s s−1 on the period derivative and of ∼3 × 1013 G on the surface dipole magnetic field. Phase-resolved spectroscopy provided evidence for a significant variation of the spectrum as a function of the stellar rotation, pointing to the presence of two emitting caps, one of which became hotter during the outburst. Finally, a deep observation of the field of SGR 0418+5729 with the new Gran Telescopio Canarias 10.4-m telescope allowed us to set an upper limit on the source optical flux of i′ > 25.1 mag, corresponding to an X-ray-to-optical flux ratio exceeding 104, consistent with the characteristics of other magnetars.
Aims. We attempt to determine the nature of the high energy emission of the radio galaxy 3C 111, by distinguishing between the effects of the thermal and non-thermal processes. Methods. We study the ...X-ray spectrum of 3C 111 between 0.4 keV and 200 keV, and its spectral energy distribution, using data from the Suzaku satellite combined with INTEGRAL, Swift/BAT data, and Fermi/LAT data. We then model the overall spectral energy distribution by including radio and infrared data. Results. The combined Suzaku, Swift and INTEGRAL data are represented by an absorbed exponentially cut-off power-law with reflection from neutral material with a photon index Γ = 1.68 ± 0.03, a high-energy cut-off Ecut = 227-67+143 keV, a reflection component with R = 0.7 ± 0.3 and a Gaussian component to account for the iron emission-line at 6.4 keV with an equivalent width of EW = 85 ± 11 eV. The X-ray spectrum appears dominated by thermal, Seyfert-like processes, but there are also indications of non-thermal processes. The radio to γ-ray spectral energy distribution can be fit with a single-zone synchrotron-self Compton model, with no need for an additional thermal component. Conclusions. We suggest a hybrid scenario to explain the broad-band emission, including a thermal component (iron line, reflection) that dominates in the X-ray regime and a non-thermal one to explain the spectral energy distribution.
Pulsar wind nebulae are a prominent class of very high energy (E > 0.1 TeV) Galactic sources. Their Gamma-ray spectra are interpreted as due to inverse Compton scattering of ultrarelativistic ...electrons on the ambient photons, whereas the X-ray spectra are due to synchrotron emission. We investigate the relation between the Gamma- and-X-ray emission and the pulsars' spin-down luminosity and characteristic age. We find that the distance-independent Gamma- to X-ray flux ratio of the nebulae is inversely proportional to the spin-down luminosity, (\propto \dot{E}^-1.9), while it appears proportional to the characteristic age, (\propto tau_c^2.2), of the parent pulsar. We interpret these results as due to the evolution of the electron energy distribution and the nebular dynamics, supporting the idea of so-called relic pulsar wind nebulae. These empirical relations provide a new tool to classify unidentified diffuse Gamma-ray sources and to estimate the spin-down luminosity and characteristic age of rotation powered pulsars with no detected pulsation from the X- and Gamma-ray properties of the associated pulsar wind nebulae. We apply these relations to predict the spin-down luminosity and characteristic age of four (so far unpulsing) candidate pulsars associated to wind nebulae.
SGR 1833−0832 was discovered on 2010 March 19, thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, Rossi ...X-ray Timing Explorer and XMM-Newton. Using these data, which span about 225 d, we studied the long-term spectral and timing characteristics of SGR 1833−0832. We found evidence for diffuse emission surrounding SGR 1833−0832, which is most likely a halo produced by the scattering of the point-source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT∼ 1.2 keV and absorbing column N
H= (10.4 ± 0.2) × 1022 cm−2, while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at ∼3.7 × 10−12 erg cm−2 s−1 for the first ∼20 d after the onset of the bursting episode, then it faded by a factor of ∼40 in the subsequent ∼140 d, following a power-law trend with index α≃−0.5. We obtained a phase-coherent timing solution with the longest baseline (∼225 d) to date for this source which, besides period P= 7.565 4084(4) s and period derivative
s s−1, includes higher order period derivatives. We also report on our search of the counterpart to the soft gamma-ray repeater (SGR) at radio frequencies using the Australia Telescope Compact Array and the Parkes Radio Telescope. No evidence for radio emission was found, down to flux densities of 0.9 mJy (at 1.5 GHz) and 0.09 mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs. Finally, the analysis of the field of PSR B1830−08 (J1833−0827), which was serendipitously imaged by the XMM-Newton observations, led to the discovery of the X-ray pulsar wind nebula generated by this 85-ms radio pulsar. We discuss its possible association with the unidentified TeV source HESS J1834−087.
We report the discovery of a 38.5 ms X-ray pulsar in observations of the soft Delta *g-ray source IGR J18490--0000 with the Rossi X-ray Timing Explorer (RXTE). PSR J1849--0001 is spinning down ...rapidly with period derivative 1.42 X 10--14 s s--1, yielding a spin-down luminosity 9.8 X 1036 erg s--1, characteristic age 42.9 kyr, and surface dipole magnetic field strength Bs = 7.5 X 1011 G. Within the INTEGRAL/IBIS error circle lies a point-like XMM-Newton and Chandra X-ray source that shows evidence of faint extended emission consistent with a pulsar wind nebula (PWN). The XMM-Newton spectrum of the point source is well fitted by an absorbed power-law model with photon index Delta *GPSR = 1.1 ? 0.2, N H = (4.3 ? 0.6) X 1022 cm--2, and F PSR(2-10 keV) = (3.8 ? 0.3) X 10--12 erg cm--2 s--1, while the spectral parameters of the extended emission are roughly Delta *GPWN 2.1 and F PWN(2-10 keV) 9 X 10--13 erg cm--2 s--1. IGR J18490--0000 is also coincident with the compact TeV source HESS J1849--000. For an assumed distance of 7 kpc in the Scutum arm tangent region, the 0.35-10 TeV luminosity of HESS J1849--000 is 0.13% of the pulsar's spin-down energy, while the ratio F(0.35-10 TeV)/F PWN(2-10 keV) 2. These properties are consistent with leptonic models of TeV emission from PWNe, with PSR J1849--0001 in a stage of transition from a synchrotron X-ray source to an inverse Compton Delta *g-ray source.
Despite it being well known that anaphylaxis is a severe life-threatening reaction requiring prompt management and treatment, this entity is still under-recognized and not correctly managed, above ...all in children. The aim of this study was to analyze the most frequent features of anaphylaxis in a pediatric population (n=65 patients) and to identify factors predicting more severe reactions. Among the 70 recorded episodes, food was the main culprit of anaphylaxis, and patients with a positive history for allergic asthma had more severe episodes (P=0.008). A self-injectable adrenaline was used only in 2 of the 70 episodes and none of the 50 episodes managed in the Emergency Department was treated with intramuscular adrenaline. Only 10/65 patients (15%) had a prescription for an auto-injector prior to the first episode of anaphylaxis. The retrospective analysis of the risk factors potentially requiring an epinephrine auto-injector prescription before the first anaphylactic episode, showed that of the 55 patients without prescription, at least 10 (18%) should have been provided with a device, according to the most recent guidelines. In conclusion, notwithstanding intramuscular adrenaline being the first-line treatment of anaphylaxis, many episodes are still undertreated and the risk of anaphylaxis is still underestimated. More efforts should be made to promote the correct management of anaphylaxis among both healthcare-providers and patients.
We report the discovery of 31.18 ms pulsations from the INTEGRAL source IGR J14003-6326 using the Rossi X-ray Timing Explorer (RXTE). This pulsar is most likely associated with the bright Chandra ...X-ray point source lying at the center of G310.6-1.6, a previously unrecognized Galactic composite supernova remnant (SNR) with a bright central non-thermal radio and X-ray nebula, taken to be the pulsar wind nebula (PWN). PSR J1400-6325 is amongst the most energetic rotation-powered pulsars in the Galaxy, with a spin-down luminosity of \dot{E} = 5.1 × 10^{37} erg s-1. In the rotating dipole model, the surface dipole magnetic field strength is Bs = 1.1 × 1012 G and the characteristic age τ_c ≡ P/2\dot{P} = 12.7 kyr. The high spin-down power is consistent with the hard spectral indices of the pulsar and the nebula of 1.22 ± 0.15 and 1.83 ± 0.08, respectively, and a 2-10 keV flux ratio F PWN/F PSR ~ 8. Follow-up Parkes observations resulted in the detection of radio emission at 10 and 20 cm from PSR J1400-6325 at a dispersion measure of ~560 cm-3 pc, which implies a relatively large distance of 10 ± 3 kpc. However, the resulting location off the Galactic plane of ~280 pc would be much larger than the typical thickness of the molecular disk, and we argue that G310.6-1.6 lies at a distance of ~7 kpc. There is no gamma-ray counterpart to the nebula or pulsar in the Fermi data published so far. A multi-wavelength study of this new composite SNR, from radio to very high-energy gamma rays, suggests a young (lsim103 yr) system formed by a sub-energetic (lsim1050 erg), low ejecta mass (M ej ~ 3 M sun) supernova explosion that occurred in a low-density environment (n 0~ 0.01 cm-3).
ABSTRACT SGR1833-0832 was discovered on 2010 March 19, thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, ...Rossi X-ray Timing Explorer and XMM-Newton. Using these data, which span about 225d, we studied the long-term spectral and timing characteristics of SGR1833-0832. We found evidence for diffuse emission surrounding SGR1833-0832, which is most likely a halo produced by the scattering of the point-source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT 1.2keV and absorbing column NH= (10.4 ± 0.2) × 1022cm-2, while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at 3.7 × 10-12 erg cm-2s-1 for the first 20d after the onset of the bursting episode, then it faded by a factor of 40 in the subsequent 140d, following a power-law trend with index α-0.5. We obtained a phase-coherent timing solution with the longest baseline (225d) to date for this source which, besides period P= 7.5654084(4)s and period derivative ss-1, includes higher order period derivatives. We also report on our search of the counterpart to the soft gamma-ray repeater (SGR) at radio frequencies using the Australia Telescope Compact Array and the Parkes Radio Telescope. No evidence for radio emission was found, down to flux densities of 0.9mJy (at 1.5 GHz) and 0.09mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs. Finally, the analysis of the field of PSRB1830-08 (J1833-0827), which was serendipitously imaged by the XMM-Newton observations, led to the discovery of the X-ray pulsar wind nebula generated by this 85-ms radio pulsar. We discuss its possible association with the unidentified TeV source HESSJ1834-087. PUBLICATION ABSTRACT
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