Randomized clinical trials in non-critically ill COVID-19 patients showed that therapeutic-dose heparin increased survival with reduced organ support as compared with usual-care thromboprophylaxis, ...albeit with increased bleeding risk. The purpose of the study is to assess the safety of intermediate dose enoxaparin in hospitalized patients with moderate to severe COVID-19. A phase II single-arm interventional prospective study including patients receiving intermediate dose enoxaparin once daily according to body weight: 60 mg for 45-60 kg, 80 mg for 61-100 kg or 100 mg for > 100 kg for 14 days, with dose adjustment according to anti-factor Xa activity (target range: 0.4-0.6 UI/ml); an observational cohort (OC) included patients receiving enoxaparin 40 mg day for comparison. Follow-up was 90 days. Primary outcome was major bleeding within 30 and 90 days after treatment onset. Secondary outcome was the composite of all-cause 30 and 90-day mortality rates, disease severity at the end of treatment, intensive care unit (ICU) admission and length of ICU stay, length of hospitalization. All outcomes were adjudicated by an independent committee and analyzed before and after propensity score matching (PSm). Major bleeding was similar in IC (1/98 1.02%) and in the OC (none), with only one event observed in a patient receiving concomitantly anti-platelet therapy. The composite outcome was observed in 53/98 patients (54%) in the IC and 132/203 (65%) patients in the OC (p = 0.07) before PSm, while it was observed in 50/90 patients (55.6%) in the IC and in 56/90 patients (62.2%) in the OC after PSm (p = 0.45). Length of hospitalization was lower in the IC than in OC median 13 (IQR 8-16) vs 14 (11-21) days, p = 0.001, however it lost statistical significance after PSm (p = 0.08). At 30 days, two patients had venous thrombosis and two pulmonary embolism in the OC. Time to first negative RT-PCR were similar in the two groups. Weight adjusted intermediate dose heparin with anti-FXa monitoring is safe with potential positive impact on clinical course in COVID-19 non-critically ill patients.
A comparison of a 1992 optical image of Geminga with previous data from 1984 and 1987 is presented. The proper motion is consistent with the identification of G" as a neutron star at a distance of ...about 100 parsec, thus confirming it as the optical counterpart of Geminga.
We present numerical calculations of the photon-light-pseudoscalar-boson (LPB) production in the recently discovered binary pulsar system J0737-3039. Light pseudoscalar bosons oscillate into photons ...in the presence of strong magnetic fields. In the context of this binary pulsar system, this phenomenon attenuates the light beam emitted by one of the pulsars, when the light ray goes through the magnetosphere of the companion pulsar. We show that such an effect is observable in the gamma-ray band since the binary pulsar is seen almost edge-on, depending on the values of the LPB mass and on the strength of its two-photon coupling. Our results are surprising in that they show a very sharp and significant (up to 50%) transition probability in the gamma-ray (> tens of MeV) domain. The observations can be performed by the upcoming NASA GLAST mission.
ABSTRACT
RX J0822−4300 is the central compact object associated with the Puppis A supernova remnant. Previous X‐ray observations suggested RX J0822−4300 to be a young neutron star with a weak dipole ...field and a peculiar surface temperature distribution dominated by two antipodal spots with different temperatures and sizes. An emission line at 0.8 keV was also detected. We performed a very deep (130‐ks) observation with XMM–Newton, which allowed us to study in detail the phase‐resolved properties of RX J0822−4300. Our new data confirm the existence of a narrow spectral feature, best modelled as an emission line, only seen in the ‘soft’‐phase interval – when the cooler region is best aligned to the line of sight. Surprisingly, comparison of our recent observations to the older ones yields evidence for a variation in the emission‐line component, which can be modelled as a decrease in the central energy from ∼0.80 keV in 2001 to ∼0.73 keV in 2009–10. The line could be generated via cyclotron scattering of thermal photons in an optically‐thin layer of gas, or, alternatively, it could originate in low‐rate accretion by a debris disc. In any case, a variation in energy, pointing to a variation of the magnetic field in the line‐emitting region, cannot be easily accounted for.
The peculiar central compact object 1E 1207.4−5209 in the G296.5+10.0 supernova remnant has been proposed to be an “anti-magnetar” – a young neutron star born with a weak dipole field. Accretion, ...possibly of supernova fallback material, has also been invoked to explain a large surface temperature anisotropy as well as the generation of peculiar cyclotron absorption features superimposed on its thermal spectrum. Interestingly enough, a faint optical/infrared source was proposed as a possible counterpart to 1E 1207.4−5209, but later questioned, based on coarse positional coincidence. On the basis of the large offset of 1E 1207.4−5209 with respect to the center of its host supernova remnant, the source should move at ~70 mas yr-1. Thus, we tested the association by measuring the proper motion of the proposed optical counterpart. Using Hubble Space Telescope (HST) observations spanning 3.75 years, we computed a 3σ upper limit of 7 mas yr-1. Absolute astrometry on the same HST data set also places the optical source significantly off the 99% confidence Chandra position. This allows us to safely rule out the association. Using the HST data set, coupled to ground-based observations collected at the ESO/Very Large Telescope (VLT), we set the deepest limits ever obtained on the optical/infrared emission from 1E 1207.4−5209. By combining these limits with the constraints derived from X-ray timing, we rule out accretion as the source of the thermal anisotropy of the neutron star.
We present the AGILE gamma-ray observations in the energy range 50 MeV-10 GeV of the supernova remnant (SNR) W44, one of the most interesting systems for studying cosmic-ray production. W44 is an ...intermediate-age SNR (~2,000 years) and its ejecta expand in a dense medium as shown by a prominent radio shell, nearby molecular clouds, and bright S II emitting regions. We extend our gamma-ray analysis to energies substantially lower than previous measurements which could not conclusively establish the nature of the radiation. We find that gamma-ray emission matches remarkably well both the position and shape of the inner SNR shocked plasma. Furthermore, the gamma-ray spectrum shows a prominent peak near 1 GeV with a clear decrement at energies below a few hundreds of MeV as expected from neutral pion decay. Here we demonstrate that (1) hadron-dominated models are consistent with all W44 multiwavelength constraints derived from radio, optical, X-ray, and gamma-ray observations; (2) ad hoc lepton-dominated models fail to explain simultaneously the well-constrained gamma-ray and radio spectra, and require a circumstellar density much larger than the value derived from observations; and (3) the hadron energy spectrum is well described by a power law (with index s = 3.0 ? 0.1) and a low-energy cut-off at Ec = 6 ? 1 GeV. Direct evidence for pion emission is then established in an SNR for the first time.
We present the results of new AGILE observations of PSR B1509 -- 58 performed over a period of ~2.5 years following the detection obtained with a subset of the present data. The modulation ...significance of the light curve above 30 MeV is at a 5 Delta *s confidence level and the light curve is similar to those found earlier by COMPTEL up to 30 MeV: a broad asymmetric first peak reaching its maximum 0.39 ? 0.02 cycles after the radio peak plus a second peak at 0.94 ? 0.03. The gamma-ray spectral energy distribution of the pulsed flux detected by COMPTEL and AGILE is well described by a power law (photon index Delta *a = 1.87 ? 0.09) with a remarkable cutoff at Ec = 81 ? 20 MeV, representing the softest spectrum observed among gamma-ray pulsars so far. The pulsar luminosity at E > 1 MeV is L Delta *g = 4.2+0.5 --0.2 X 1035 erg s--1, assuming a distance of 5.2 kpc, which implies a spin-down conversion efficiency to gamma rays of ~0.03. The unusual soft break in the spectrum of PSR B1509 -- 58 has been interpreted in the framework of polar cap models as a signature of the exotic photon-splitting process in the strong magnetic field of this pulsar. In this interpretation, our spectrum constrains the magnetic altitude of the emission point(s) at 3 km above the neutron star surface, implying that the attenuation may not be as strong as formerly suggested because pair production can substitute photon splitting into regions of the magnetosphere where the magnetic field becomes too low to sustain photon splitting. In the case of an outer-gap scenario or the two-pole caustic model, better constraints on the geometry of the emission would be needed from the radio band in order to establish whether the conditions required by the models to reproduce AGILE light curves and spectra match the polarization measurements.
The Italian program for small satellites Bignami, G.F.; Palumbo, G.G.C.
Advances in space research,
2003, 2003-1-00, 20030101, Letnik:
31, Številka:
2
Journal Article
Recenzirano
In the framework of a five year plan the Italian Space Agency has started a national program of small scientific satellites. The first two, AGILE and DAVID are already at an advanced stage of ...development. The former is dedicated to Gamma Ray Astrophysics, the latter to communication technology and engineering development. A third mission, to be devoted to Earth Science and exploration is in the process of being defined. A general view of the program and some specific features of the missions selected so far are given
A 1,000-year chain of thinkers Bignami, Giovanni F
Nature (London),
03/2000, Letnik:
404, Številka:
6775
Journal Article
Recenzirano
Odprti dostop
Bignami connects the last 1,000 years of scientific thinkers. Avicenna opened the millennium with his first philosophical work in 1001, and the millennium chain ends with mathematician Andrew Wiles.
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