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Plasma Model (plasma + model)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

The use of desflurane or propofol in combination with remifentanil in myasthenic patients undergoing a video-assisted thoracoscopic-extended thymectomy

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 3 2009
P. GRITTI
Background: Although several studies of the use of desflurane in anesthesia have revealed many desirable qualities, there are no data on the use and effects especially on the neuromuscular function of desflurane on myasthenia gravis (MG) patients. The purpose of this study was to evaluate the use of either desflurane or propofol, both combined with remifentanil, in patients with MG undergoing a video-assisted thoracoscopic-extended thymectomy (VATET). Methods: Thirty-six MG patients who underwent VATET were enrolled. Nineteen patients were anesthetized with remifentanil and propofol infused with a target-controlled infusion plasma model, and 17 patients with desflurane and remifentanil. No muscle relaxant was used. The intubating conditions, hemodynamic and respiratory changes, neuromuscular transmission and post-operative complications were evaluated. Results: Neuromuscular transmission was significantly decreased in the desflurane group (6.7%, from 3% to 9% during anesthesia P=<0.05). The intubating conditions were good in all 36 patients and 35 patients were successfully extubated in the operating room. The time-to-awakening, post-operatory pH and base excess were significantly different in the two groups, with a decreasing mean arterial pressure in the group administered with desflurane. No patients required reintubation due to myasthenic or cholinergic crisis, or respiratory failure. No other significant differences between the two groups studied were observed. Conclusion: Our experience indicates that anesthesia with desflurane plus remifentanil in patients with MG could determine a reversible muscle relaxation effect, but with no clinical implication, allowing a faster recovery with no difference in extubation time and post-operative complications in the two groups. [source]

X-ray colour maps of the cores of galaxy clusters

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000
J. S. Sanders
We present an analysis of X-ray colour maps of the cores of clusters of galaxies, formed from the ratios of counts in different X-ray bands. Our technique groups pixels lying between contours in an adaptively smoothed image of a cluster. We select the contour levels to minimize the uncertainties in the colour ratios, whilst preserving the structure of the object. We extend the work of Allen & Fabian by investigating the spatial distributions of cooling gas and absorbing material in cluster cores. Their sample is almost doubled: we analyse archive ROSAT Position Sensitive Proportional Counter (PSPC) data for 33 clusters from the sample of the 55 brightest X-ray clusters in the sky. Many of our clusters contain strong cooling flows. We present colour maps of a sample of the clusters, in addition to adaptively smoothed images in different bands. Most of the cooling flow clusters display little substructure, unlike several of the non-cooling-flow clusters. We fitted an isothermal plasma model with galactic absorption and constant metallicity to the mid-over-high energy colours in our clusters. Those clusters with known strong cooling flows have inner contours which fit a significantly lower temperature than the outer contours. Clusters in the sample without strong cooling flows show no significant temperature variation. The inclusion of a metallicity gradient alone was not sufficient to explain the observations. A cooling flow component plus a constant temperature phase did account for the colour profiles in clusters with known strong cooling flow components. We also had to increase the levels of absorbing material to fit the low-over-high colours at the cluster centres. Our results provide more evidence that cooling flows accumulate absorbing material. No evidence for increased absorption was found for the non-cooling-flow clusters. [source]

Beginning of the super-soft phase of the classical nova V2491 Cygni

ASTRONOMISCHE NACHRICHTEN, Issue 2 2010
D. Takei
Abstract We present the results of soft X-ray studies of the classical nova V2491 Cygni using the Suzaku observatory. On day 29 after outburst, a soft X-ray component with a peak at ,0.5 keV has appeared, which is tantalising evidence for the beginning of the super-soft X-ray emission phase. We show that an absorbed blackbody model can describe the observed spectra, yielding a temperature of 57 eV, neutral hydrogen column density of 2 × 1021 cm,2, and a bolometric luminosity of ,1036 erg s,1. However, at the same time, we also found a good fit with an absorbed thin-thermal plasma model, yielding a temperature of 0.1 keV, neutral hydrogen column density of 4 × 1021 cm,2, and a volume emission measure of ,1058 cm,3. Owing to low spectral resolution and low signal-to-noise ratio below 0.6 keV, the statistical parameter uncertainties are large, but the ambiguity of the two very different models demonstrates that the systematic errors are the main point of concern. The thin-thermal plasma model implies that the soft emission originates from optically thin ejecta, while the blackbody model suggests that we are seeing optically thick emission from the white dwarf (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Sgr A East and its surroundings , a view with XMM-Newton

ASTRONOMISCHE NACHRICHTEN, Issue S1 2003
Masaaki Sakano
Abstract We present an X-ray study of the Sgr A East region based on recent XMM-Newton observations. The spectrum of Sgr A East can be represented by a two-component thin thermal plasma model with temperatures of 1 and 4 keV, both of which have reached ionization equilibrium state. The abundance of iron is found to be higher in the central region of the nebula, with Z , 3,4 solar, than in the outer area for which Z , 0.5 solar. On the other hand, the abundances of other elements appear uniformly distributed with Z , 1. We also detect a weak fluorescent K, line from neutral iron in the outer region of source. We discuss the nature of Sgr A East on the basis of these new X-ray results. [source]

Chandra ACIS Imaging Spectroscopy of Sgr A East

ASTRONOMISCHE NACHRICHTEN, Issue S1 2003
Y. Maeda
Abstract We report on the X-ray emission from the shell-like, non-thermal radio source Sgr A East located in the inner few parsecs of the Galaxy based on observations made with the ACIS detector on board the Chandra X-ray Observatory. The X-ray emission from Sgr A East is concentrated within the central ,2 pc of the larger radio shell. The spectrum shows strong K, lines from highly ionized ions of S, Ar, Ca, and Fe. A simple isothermal plasma model gives electron temperature ,2 keV, absorption column ,1 × 1023 H cm,2, luminosity ,8 × 1034 ergs s,1 in the 2,10 keV band, and gas mass ,2,½ M, with a filling factor ,. The plasma appears to be rich in heavy elements, over-abundant by roughly a factor of four with respect to solar abundances. Accompanied with filamentary or blob-like structures, the plasma shows a spatial gradient of elemental abundance: the spatial distribution of iron is more compact than that of the lighter elements. These Chandra results strongly support the long-standing hypothesis that Sgr A East is a supernova remnant (SNR). Since Sgr A East surrounds Sgr A* in projection, it is possible that the dust ridge compressed by the forward shock of Sgr A East hit Sgr A* in the past, and the passage of the ridge may have supplied material to accrete onto the black hole in the past, and may have removed material from the black hole vicinity, leading to its present quiescent state. [source]