16 research outputs found
XMM-Newton observations of MR Vel/RX J0925.7-4758
We report on XMM-Newton observations of the galactic supersoft X-ray source
RX J0925.7-4758. The RGS spectrum exhibits a wealth of spectral features from
iron and oxygen. XMM-Newton data confirm the finding of previous Chandra
HETGS/MEG observations that NLTE models of hot white dwarf atmospheres fail to
represent the complex spectrum. There are clear evidences for P Cygni profiles
with wind velocities of up to 2000 km/s. Small flux variations with time scales
larger than 1000s are present. The strongest power is at ~ 0.21d, a period
close to that seen in V band optical light curves. A detailed analysis of the
associated changes in the RGS and EPIC pn spectra hint at a mostly grey
mechanism suggesting a variation of the visibility of the white dwarf due to
occulting material in the accretion disk. Finally, we detect radial velocity
changes of 173 +/- 47 km/s between two RGS observations obtained half an
orbital cycle apart. The amplitude of the RGS velocity shift is consistent with
that of the optical He II 4686 and thus supports the idea that most of the He
II optical line emission arises from the accretion disk.Comment: Accepted for publication in A&A (8 pages and 9 figures
The X-ray emission from Nova V382 Velorum: II. The super-soft component observed with BeppoSAX
Nova Velorum 1999 (V382 Vel) was observed by BeppoSAX 6 months after optical
maximum and was detected as a bright X-ray supersoft source, with a count rate
3.454+-0.002 cts/s in the LECS. It was the softest and most luminous supersoft
source observed with this instrument. The flux in the 0.1-0.7 keV range was not
constant during the observation. It dropped by a factor of 2 in less than 1.5
hour and then was faint for at least 15 minutes, without significant spectral
changes.
The observed spectrum is not well fit with atmospheric models of a hot,
hydrogen burning white dwarf. This is due mainly to a supersoft excess in the
range 0.1-0.2 keV, but the fit can be significantly improved at higher energy
if at least one emission feature is superimposed. We suggest that a
``pseudocontinuum'' was detected, consisting of emission lines in the supersoft
X-ray range superimposed on the thermal continuum of a white dwarf atmosphere.
As a result, an accurate determination of the effective temperature and gravity
of the white dwarf at this post-outburst stage is not possible.Comment: To appear in MNRA
Charge transport after hard breakdown in gate oxides
We show measurement results and simulations of current�voltage characteristics of Metal-Oxide-Semiconductor capacitors after hard breakdown. The devices exhibit either point contact or diode behaviour, depending on electrode and substrate characteristics and the bias regime. The charge transport characteristics were reproduced in device simulations, including the dependence on the gate dimensions and breakdown spot size
Wet chemical treatment of boron doped emitters on n-type (100) c-Si prior to amorphous silicon passivation
10.1016/j.apsusc.2014.11.180APPLIED SURFACE SCIENCE328140-14
Complex clinical scenarios with the use of direct oral anticoagulants in patients with atrial fibrillation: a multidisciplinary expert advisory board
The risk of developing atrial fibrillation (AF) and the risk of stroke both increase with advancing age. As such, many individuals have, or will develop, an indication for oral anticoagulation to reduce the risk of stroke. Currently, a large number of anticoagulants are available, including vitamin K antagonists, direct thrombin or factor Xa inhibitors (the last two also referred to as direct oral anticoagulants or DOACs), and different dosages are available. Of the DOACs, rivaroxaban can be obtained in the most different doses: 2.5 mg, 5 mg, 15 mg and 20 mg. Many patients develop co-morbidities and/or undergo procedures that may require the temporary combination of anticoagulation with antiplatelet therapy. In daily practice, clinicians encounter complex scenarios that are not always described in the treatment guidelines, and clear recommendations are lacking. Here, we report the outcomes of a multidisciplinary advisory board meeting, held in Utrecht (The Netherlands) on 3 June 2019, on decision making in complex clinical situations regarding the use of DOACs. The advisory board consisted of Dutch cardiovascular specialists: (interventional) cardiologist, internist, neurologist, vascular surgeon and general practitioners invited according to personal title and specific field of expertise