26 research outputs found
The XMM-Newton view of GRS1915+105 during a "plateau"
Two XMM-Newton observations of the black-hole binary GRS1915+105 were
triggered in 2004 (April 17 and 21), during a long "plateau" state of the
source. We analyzed the data collected with EPIC-pn in Timing and Burst modes,
respectively. No thermal disc emission is required by the data; the spectrum is
well fitted by four components: a primary component (either a simple power law
or thermal Comptonization) absorbed by cold matter with abundances different
than those of standard ISM; reprocessing from an ionized disc; emission and
absorption lines; and a soft X-ray excess around 1 keV. The latter is not
confirmed by RGS (which were used in the second observation only); if real, the
excess could be due to reflection from the optically thin, photoionized plasma
of a disc wind, in which case it may provide a way to disentangle intrinsic
from interstellar absorption. Indeed, the former is best traced by the higher
abundances of heavier elements, while an independent estimate of the latter may
be given by the value we get for the disc wind component only, which roughly
coincides with what is found for lower-Z species.Comment: 5 pages, 3 figures, 1 table. Submitte
The XMM-Newton View of GRS1915+105
(abridged) Two XMM-Newton observations of the black-hole binary GRS1915+105
were triggered in 2004, during a long "plateau" state of the source. (...)
While the light curves show just small amplitude variations (a few percent) at
timescales longer than a few seconds, a QPO is seen at about 0.6 Hz (...). The
pn spectrum is well fitted without invoking thermal disk emission, on the base
of four main components: a primary one (...), absorbed by cold matter with
abundances different than those of standard ISM; reprocessing from an ionized
disk; emission and absorption lines; and a soft X-ray excess around 1 keV.
However, the latter is not confirmed by the RGS spectra, whose difference from
the EPIC-pn ones actually lacks of a fully satisfactory explanation. If real,
the soft X-ray excess may be due to reflection from an optically thin,
photoionized disk wind; in this case it may yield a way to disentangle
intrinsic from interstellar absorption.Comment: 11 pages, 7 figures. Accepted for publication on Astronomy and
Astrophysic
Does the continuation of low-dose acetylsalicylic acid during the perioperative period of thyroidectomy increase the risk of cervical haematoma? A 1-year experience of two Italian centers
Background: A growing number of patients taking antiplatelet drugs, mainly low-dose acetylsalicylic acid (ASA) (75–150 mg/day), for primary or secondary prevention of thrombotic events, are encountered in every field of surgery. While the bleeding risk due to the continuation of these medications during the perioperative period has been adequately investigated in several surgical specialties, in thyroid surgery it still needs to be clarified. The main aim of this study was to assess the occurrence of cervical haematoma in patients receiving low-dose acetylsalicylic acid, specifically ASA 100 mg/day, during the perioperative period of thyroidectomy.
Methods: Patients undergoing thyroidectomy in two high-volume thyroid surgery centers in Italy, between January 2021 and December 2021, were retrospectively analysed. Enrolled patients were divided into two groups: those not taking ASA were included in Group A, while those receiving this drug in Group B. Univariate analysis was performed to compare these two groups. Moreover, multivariate analysis was employed to evaluate the use of low-dose ASA as independent risk factor for cervical haematoma.
Results: A total of 412 patients underwent thyroidectomy during the study period. Among them, 29 (7.04%) were taking ASA. Based on the inclusion criteria, 351 patients were enrolled: 322 were included in Group A and 29 in Group B. In Group A, there were 4 (1.24%) cervical haematomas not requiring surgical revision of haemostasis and 4 (1.24%) cervical haematomas requiring surgical revision of haemostasis. In Group B, there was 1 (3.45%) cervical haematoma requiring surgical revision of haemostasis. At univariate analysis, no statistically significant difference was found between the two groups in terms of occurrence of cervical haematoma, nor of the other early complications of thyroidectomy. At multivariate analysis, the use of low-dose ASA did not prove to be an independent risk factor for cervical haematoma.
Conclusions: Based on our findings, we believe that in patients receiving this drug, either for primary or secondary prevention of thrombotic events, its discontinuation during the perioperative period of thyroidectomy is not necessary
An X-ray polarimeter for hard X-ray optics
Development of multi-layer optics makes feasible the use of X-ray telescope
at energy up to 60-80 keV: in this paper we discuss the extension of
photoelectric polarimeter based on Micro Pattern Gas Chamber to high energy
X-rays. We calculated the sensitivity with Neon and Argon based mixtures at
high pressure with thick absorption gap: placing the MPGC at focus of a next
generation multi-layer optics, galatic and extragalactic X-ray polarimetry can
be done up till 30 keV.Comment: 12 pages, 7 figure
POLARIX: a pathfinder mission of X-ray polarimetry
Since the birth of X-ray astronomy, spectral, spatial and timing observation
improved dramatically, procuring a wealth of information on the majority of the
classes of the celestial sources. Polarimetry, instead, remained basically
unprobed. X-ray polarimetry promises to provide additional information
procuring two new observable quantities, the degree and the angle of
polarization. POLARIX is a mission dedicated to X-ray polarimetry. It exploits
the polarimetric response of a Gas Pixel Detector, combined with position
sensitivity, that, at the focus of a telescope, results in a huge increase of
sensitivity. Three Gas Pixel Detectors are coupled with three X-ray optics
which are the heritage of JET-X mission. POLARIX will measure time resolved
X-ray polarization with an angular resolution of about 20 arcsec in a field of
view of 15 arcmin 15 arcmin and with an energy resolution of 20 % at 6
keV. The Minimum Detectable Polarization is 12 % for a source having a flux of
1 mCrab and 10^5 s of observing time. The satellite will be placed in an
equatorial orbit of 505 km of altitude by a Vega launcher.The telemetry
down-link station will be Malindi. The pointing of POLARIX satellite will be
gyroless and it will perform a double pointing during the earth occultation of
one source, so maximizing the scientific return. POLARIX data are for 75 % open
to the community while 25 % + SVP (Science Verification Phase, 1 month of
operation) is dedicated to a core program activity open to the contribution of
associated scientists. The planned duration of the mission is one year plus
three months of commissioning and SVP, suitable to perform most of the basic
science within the reach of this instrument.Comment: 42 pages, 28 figure
A photoelectric polarimeter for XEUS: a new window in x-ray sky
XEUS is a large area telescope aiming to rise X-ray Astronomy to the level of
Optical Astronomy in terms of collecting areas. It will be based on two
satellites, locked on a formation flight, one with the optics, one with the
focal plane. The present design of the focal plane foresees, as an auxiliary
instrument, the inclusion of a Polarimeter based on a Micropattern Chamber. We
show how such a device is capable to solve open problems on many classes of
High Energy Astrophysics objects and to use X-ray sources as a laboratory for a
substantial progress on Fundamental Physics.Comment: 12 pages, 7 figure
Risk factors for postoperative cervical haematoma in patients undergoing thyroidectomy: a retrospective, multicenter, international analysis (REDHOT study)
Background Postoperative cervical haematoma represents an infrequent but potentially life-threatening complication of thyroidectomy. Since this complication is uncommon, the assessment of risk factors associated with its development is challenging. The main aim of this study was to identify the risk factors for its occurrence.Methods Patients undergoing thyroidectomy in seven high-volume thyroid surgery centers in Europe, between January 2020 and December 2022, were retrospectively analysed. Based on the onset of cervical haematoma, two groups were identified: Cervical Haematoma (CH) Group and No Cervical Haematoma (NoCH) Group. Univariate analysis was performed to compare these two groups. Moreover, employing multivariate analysis, all potential independent risk factors for the development of this complication were assessed.Results Eight thousand eight hundred and thirty-nine patients were enrolled: 8,561 were included in NoCH Group and 278 in CH Group. Surgical revision of haemostasis was performed in 70 (25.18%) patients. The overall incidence of postoperative cervical haematoma was 3.15% (0.79% for cervical haematomas requiring surgical revision of haemostasis, and 2.35% for those managed conservatively). The timing of onset of cervical haematomas requiring surgical revision of haemostasis was within six hours after the end of the operation in 52 (74.28%) patients. Readmission was necessary in 3 (1.08%) cases. At multivariate analysis, male sex (P < 0.001), older age (P < 0.001), higher BMI (P = 0.021), unilateral lateral neck dissection (P < 0.001), drain placement (P = 0.007), and shorter operative times (P < 0.001) were found to be independent risk factors for cervical haematoma.Conclusions Based on our findings, we believe that patients with the identified risk factors should be closely monitored in the postoperative period, particularly during the first six hours after the operation, and excluded from outpatient surgery
POLARIX: a small mission of x-ray polarimetry
X-Ray Polarimetry can be now performed by using a Micro Pattern Gas Chamber
in the focus of a telescope. It requires large area optics for most important
scientific targets. But since the technique is additive a dedicated mission
with a cluster of small telescopes can perform many important measurements and
bridge the 40 year gap between OSO-8 data and future big telescopes such as
XEUS. POLARIX has been conceived as such a pathfinder. It is a Small Satellite
based on the optics of JET-X. Two telescopes are available in flight
configuration and three more can be easily produced starting from the available
superpolished mandrels. We show the capabilities of such a cluster of
telescopes each equipped with a focal plane photoelectric polarimeter and
discuss a few alternative solutions.Comment: 9 pages, 5 figure
An atlas of X- and gamma-ray pulse profiles of the Crab pulsar (PSR 0531+21): An analysis of energy and time variations
We present an atlas of X and gamma-ray pulse profiles of PSR 0531+21 (Crab pulsar) measured since 1967. This atlas, containing 250 profiles, is useful to study in detail the behaviour with time and energy of this important source and to test models of the emission geometrical pattern. The atlas database is also accessible from Mosaic. An analysis of the energy dependence and time changes of the Crab pulsar light curve (and in particular of the P2/P1 ratio), based on the atlas database, is presented
DESIGN OF A SCATTERING POLARIMETER FOR HARD X-RAY ASTRONOMY
The design of a new hard X-ray Compton scattering polarimeter based on scintillating fibres technology is presented and studied in detail by means of Monte Carlo calculations. Several different configurations and materials have been tested in order to optimise the sensitivity in the medium/high energy X-ray band. A high sensitivity over the energy band 20-200 keV is obtained for a two material configuration. The advantages deriving from employing a new scintillating material, the YAP (YAlO3), are also discussed