| 1. |
- Gustafsson, Bengt, et al.
(författare)
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A grid of MARCS model atmospheres for late-type stars
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 486:3, s. 951-970
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Forskningsöversikt (refereegranskat)abstract
- Context. In analyses of stellar spectra and colours, and for the analysis of integrated light from galaxies, a homogeneous grid of model atmospheres of late-type stars and corresponding flux spectra is needed. Aims. We construct an extensive grid of spherically-symmetric models (supplemented with plane-parallel ones for the highest surface gravities), built on up-to-date atomic and molecular data, and make it available for public use. Methods. The most recent version of the MARCS program is used. Results. We present a grid of about 104 model atmospheres for stars with 2500K <= T-eff <= 8000 K, -1 <= log g = log (GM/R-2) <= 5 (cgs) with various masses and radii, -5 <= [Me/H] <= + 1, with [alpha/Fe] = 0.0 and 0.4 and different choices of C and N abundances. This includes "CN-cycled" models with C/N=4.07 (solar), 1.5 and 0.5, C/O ranging from 0.09 to (normally) 5.0 to also represent stars of spectral types R, S and N, and with 1.0 <= xi(t) = 5km s(-1). We also list thermodynamic quantities (T, P-g, P-e, rho, partial pressures of molecules, etc.) and provide them on the World Wide Web, as well as calculated fluxes in approximately 108 000 wavelength points. Underlying assumptions in addition to 1D stratification (spherical or plane-parallel) include hydrostatic equilibrium, mixing-length convection and local thermodynamic equilibrium. We discuss a number of general properties of the models, in particular in relation to the effects of changing abundances, of blanketing, and of sphericity. We illustrate positive and negative feedbacks between sphericity and molecular blanketing. We compare the models with those of other available grids and find excellent agreement with planeparallel models of Castelli & Kurucz (if convection is treated consistently) within the overlapping parameter range. Although there are considerable departures from the spherically-symmetric NextGen models, the agreement with more recent PHOENIX models is gratifying. Conclusions. The models of the grid show considerable regularities, but some interesting departures from general patterns occur for the coolest models due to the molecular opacities. We have tested a number of approximate "rules of thumb" concerning effects of blanketing and sphericity and often found them to be astonishingly accurate. Some interesting new phenomena have been discovered and explored, such as the intricate coupling between blanketing and sphericity, and the strong effects of carbon enhancement on metal-poor models. We give further details of line absorption data for molecules, as well as details of models and comparisons with observations in subsequent papers.
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| 2. |
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| 3. |
- Jonsell, Karin, 1970-
(författare)
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Chemical Abundance Analysis of Population II Stars : The Summary Includes a Background in General Astronomy
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. I have done two such investigations. A vigourous debate is going on whether the oxygen-to-iron ratio varies strongly with the general metal-content of halo stars. In my first study, I made an abundance analysis of 43 halo stars, and found no support for such a variation. I have also found that there probably is a cosmic spread in the abundances of oxygen, magnesium, silicon, and calcium relative to iron for halo stars. This may be an indication that the halo was built up by subsystems with differences in the star formation rate. In my second study, I performed a thorough abundance analysis of the star HE0338-3945, which is strangely overabundant in both r- and s-elements. Several other stars have been found with abundance patterns curiously similar to this star, and I define new criteria for the class r+s stars. The abundance similarities among the r+s stars suggest a common formation scenario. However, as the s-elements usually are considered to be produced in binary systems of low mass, and r-elements in supernovae of Type II, this scenario is not obvious. In the article I discuss seven hypotheses, and several of them are dismissed.
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| 4. |
- Jonsell, Karin, et al.
(författare)
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Chemical abundances in 43 metal-poor stars
- 2005
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 440:1, s. 321-343
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Tidskriftsartikel (refereegranskat)abstract
- We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni, and Ba for 43 metal-poor field stars in the solar neighbourhood, most of them subgiants or turn-off-point stars with iron abundances [Fe/H] ranging from -0.4 to -3.0. About half of this sample has not been spectroscopically analysed in detail before. Effective temperatures were estimated from uvby photometry, and surface gravities primarily from Hipparcos parallaxes. The analysis is differential relative to the Sun, and was carried out with plane-parallel MARCS models. Various sources of error are discussed and found to contribute a total error of about 0.1-0.2 dex for most elements, while relative abundances, such as [Ca/Fe], are most probably more accurate. For the oxygen abundances, determined in an NLTE analysis of the 7774 Å triplet lines, the errors may be somewhat larger. We made a detailed comparison with similar studies and traced the reasons for the, in most cases, relatively small differences. Among the results we find that [O/Fe] possibly increases beyond [Fe/H] = -1.0, though considerably less so than in results obtained by others from abundances based on OH lines. We did not trace any tendency toward strong overionization of iron, and find the excesses, relative to Fe and the Sun, of the α elements Mg, Si, and Ca to be smaller than those of O. We discuss some indications that also the abundances of different α elements relative to Fe vary and the possibility that some of the scatter around the trends in abundances relative to iron may be real. This may support the idea that the formation of Halo stars occurred in smaller systems with different star formation rates. We verify the finding by Gratton et al. (2003b, A&A, 406, 131) that stars that do not participate in the rotation of the galactic disk show a lower mean and larger spread in [ α/Fe] than stars participating in the general rotation. The latter stars also seem to show some correlation between [ α/Fe] and rotation speed. We trace some stars with peculiar abundances, among these two Ba stars, HD 17072 and HD 196944, the second already known to be rich in s elements. Finally we advocate that a spectroscopic study of a larger sample of halo stars with well-defined selection criteria is very important, in order to add to the very considerable efforts that various groups have already made.
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| 5. |
- Ryde, Nils, et al.
(författare)
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A First Study of Giant Stars in the Galactic Bulge based on Crires spectra
- 2007
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Ingår i: Stellar Populations as Building Blocks of Galaxies. ; , s. 260-261
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present our on-going work on the determination of elemental abundances of giants in the Galactic Bulge by means of infrared spectroscopy. We show a preliminarily reduced spectrum and a synthetic spectrum fit of the Bulge giant Arp 4203 recorded with the near-infrared, high-resolution Crires spectrograph mounted on the VLT during its science verification run in August 2006. Abundances derived from this spectrum are discussed.
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| 6. |
- VandenBerg, Don A., et al.
(författare)
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A Constraint on Zsolar from Fits of Isochrones to the Color-Magnitude Diagram of M67
- 2007
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 666:2, s. L105-L108
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Tidskriftsartikel (refereegranskat)abstract
- The mass at which a transition is made between stars that have radiative or convective cores throughout the core H burning phase is a fairly sensitive function of Z (particularly, the CNO abundances). As a consequence, the ~4 Gyr, open cluster M67 provides a constraint on Zsolar (and the solar heavy-element mixture) because (1) high-resolution spectroscopy indicates that this system has virtually the same metal abundances as the Sun, and (2) its turnoff stars have masses just above the lower limit for sustained core convection on the main sequence. In this study, evolutionary tracks and isochrones using the latest MARCS model atmospheres as boundary conditions have been computed for 0.6-1.4 Msolar on the assumption of a metals mix (implying Zsolar~0.0125) based on the solar abundances derived by M. Asplund and collaborators using 3D model atmospheres. These calculations do not predict a turnoff gap where one is observed in M67. No such difficulty is found if the analysis uses isochrones for Zsolar=0.0165, assuming the Grevesse and Sauval mix of heavy elements. Our findings, like the inferences from helioseismology, indicate a problem with the abundances of Asplund and collaborators. However, it is possible that low-Z models with diffusive processes taken into account will be less problematic.
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| 7. |
- Vandenberg, Don A., et al.
(författare)
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On Stellar Models with Blanketed Atmospheres as Boundary Conditions
- 2007
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Ingår i: Stellar Populations as Building Blocks of Galaxies. ; , s. 23-27
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The impact on the predicted Teff scale of using the latest MARCS model atmospheres, instead of a fixed atmospheric structure (e.g., the gray T–τ relation) is examined. The former were fitted to stellar interior models at both the photosphere and at τ = 100 to determine the sensitivity of evolutionary tracks and isochrones for [Fe/H] = 0.0 and −2.0 to the chosen fitting point. In the case of solar abundances, the Teff of the giant branch varied by up to 100–150 K, depending on how the outer layers were treated. Much smaller variations were found for metal-poor giants (or main-sequence stars). Interestingly, models for the low solar Z favored by Asplund et al. (Z=0.0125) were unable to reproduce the gap near the turnoff in the C-M diagram of the old open cluster M 67, in contrast to models that assume Z=0.0188.
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| 8. |
- VandenBerg, Don A., et al.
(författare)
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On the use of blanketed atmospheres as boundary conditions for stellar evolutionary models
- 2008
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 675:1, s. 746-763
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Tidskriftsartikel (refereegranskat)abstract
- Stellarmodels have been computed for stars having [Fe/H] = 0.0 (assuming both the Grevesse & Sauval and Asplund et al. heavy-element mixtures) and -2.0 to determine the effects on the predicted T-eff scale of using boundary conditions derived from the latest MARCS model atmospheres. The latter were fitted in a fully consistent way to the interior models at the photosphere and at tau = 100: the resultant evolutionary sequences on the H-R diagram were found to be nearly independent of the chosen fitting point. Tracks were also computed in which the pressure at T = T-eff was obtained by integrating the hydrostatic equation together with either the classical gray T(tau, T-eff) relation or that derived by Krishna Swamy from an empirical solar atmosphere. Due to the effects of differences in the solar-calibrated values of the mixing-length parameter, alpha(MLT), very similar tracks were obtained for the different treatments of the atmosphere, except at solar abundances, where the models based on the Krishna Swamy T(tau, T-eff) relationship predicted similar to 150 K hotter giant branches than the others, in good agreement with the inferred temperatures of giants in the open cluster M67 from recent (V - K) -T-eff relations. Tracks that used new "scaled solar, differentially corrected'' MARCS atmospheres were found to agree well with those that employed the Krishna Swamy T(tau, T-eff) relationship, independently of the assumed metal abundance. (Gray atmospheres are quite different from MARCS models.) Fits of isochrones for [Fe/H] = -2.0 to the CMD of the globular cluster M68, as well as the possibility that alpha(MLT) varies with stellar parameters, are also discussed.
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| 9. |
- Önehag, Anna, et al.
(författare)
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Calibration of Stromgren uvby-H beta photometry for late-type stars - a model atmosphere approach
- 2009
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 498:2, s. 527-542
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Tidskriftsartikel (refereegranskat)abstract
- Context. The use of model atmospheres for deriving stellar fundamental parameters, such as T-eff, log g, and [Fe/H], will increase as we find and explore extreme stellar populations where empirical calibrations are not yet available. Moreover, calibrations for upcoming large satellite missions of new spectrophotometric indices, similar to the uvby-H beta system, will be needed. Aims. We aim to test the power of theoretical calibrations based on a new generation of MARCS models by comparisons with observational photomteric data. Methods. We calculated synthetic uvby-H beta colour indices from synthetic spectra. A sample of 367 field stars, as well as stars in globular clusters, is used for a direct comparison of the synthetic indices versus empirical data and for scrutinizing the possibilities of theoretical calibrations for temperature, metallicity, and gravity. Results. We show that the temperature sensitivity of the synthetic (b-y) colour is very close to its empirical counterpart, whereas the temperature scale based upon H beta shows a slight offset. The theoretical metallicity sensitivity of the m(1) index (and for G-type stars its combination with c(1)) is somewhat higher than the empirical one, based upon spectroscopic determinations. The gravity sensitivity of the synthetic c(1) index shows satisfactory behaviour when compared to obervations of F stars. For stars cooler than the sun, a deviation is significant in the c(1)-(b-y) diagram. The theoretical calibrations of (b-y), (v-y), and c(1) seem to work well for Pop II stars and lead to effective temperatures for globular cluster stars supporting recent claims that atomic diffusion occurs in stars near the turnoff point of NGC 6397. Conclusions. Synthetic colours of stellar atmospheres can indeed be used, in many cases, to derive reliable fundamental stellar parameters. The deviations seen when compared to observational data could be due to incomplete linelists but are possibly also due to the effects of assuming plane-parallell or spherical geometry and LTE.
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| 10. |
- Edvardsson, Bengt, et al.
(författare)
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Cerebral infarct presenting with thunderclap headache.
- 2009
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Ingår i: Journal of Headache and Pain. - : Springer Science and Business Media LLC. - 1129-2369 .- 1129-2377. ; 10, s. 207-209
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Tidskriftsartikel (refereegranskat)abstract
- A 73-year-old man presented with a thunderclap headache (TCH), suggesting a subarachnoid haemorrhage. Neurological examination, computer tomography of the head, and cerebrospinal fluid examination were normal. Magnetic resonance imaging of the brain revealed a supratentorial cerebral infarct. No cerebral aneurysm could be detected. A TCH can be the presenting feature of many conditions. A formula for the diagnostic assessment of TCH should be established. The management of this type of headache is controversial. Articles differ in their conclusions and recommendations. An expansion of routine investigations should be performed in cases where the neurological examination, cerebrospinal fluid analysis, and computer tomography are normal. A TCH can be the primary clinical feature of a supratentorial cerebral infarct.
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| 11. |
- Edvardsson, Bengt
(författare)
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Observed versus predicted stellar flux distributions of solar-type stars
- 2008
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T133, s. 014011-
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Tidskriftsartikel (refereegranskat)abstract
- I have compared the low-resolution spectrophotometric fluxes in the visible spectral region of F- and G-type MARCS 2008 model atmospheres to six spectrophotometric databases of the Sun and stars. These observational databases disagree with each other concerning the overall red/blue flux balances on the several percent scale for the same objects. There is, however, no systematic overall trend between MARCS model fluxes and these observations taken together and therefore no reason to suspect any problem with the MARCS overall spectrum balance. The results strongly suggest, however, that there are systematic errors in the ultraviolet and blue opacities used in the construction of the model atmospheres. These errors appear in wavelength regions with widths of some 50-150 angstrom. Similar uncertainties are found also in other independent libraries of synthetic model atmosphere fluxes. I also highlight a number of unidentified spectral features with unusual shapes in spectra of the Sun and solar-type stars.
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| 12. |
- Edvardsson, Bengt, et al.
(författare)
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Polyneuritis cranialis presenting with anti-GQ1b IgG antibody.
- 2009
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Ingår i: Journal of the Neurological Sciences. - : Elsevier BV. - 1878-5883 .- 0022-510X. ; 281, s. 125-126
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Tidskriftsartikel (refereegranskat)abstract
- A 52-year-old man developed diplopia, a nasal voice, dysphagia, hoarseness and slight bilateral facial palsies. There was no ataxia, areflexia, limb weakness or sensory involvement. Serum anti-GQ1b IgG antibody was present. Treatment with intravenous immunoglobulin started, and the patient responded with a rapid resolution of symptoms. The diagnosis is consistent with polyneuritis cranialis which is considered to be a Guillain-Barre syndrome variant, a forme fruste, but very rare. The diagnosis can be difficult and a thorough investigation is required. Electrophysiological examination, laboratory evaluations, imaging and cerebrospinal fluid examination are often required in the investigations. Cranial neuropathy can be the presentation of many disorders. Determination of anti-ganglioside antibodies as anti-GQ1b is valuable to the diagnosis, and shows the association with the Guillain-Barre syndrome.
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| 13. |
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| 14. |
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| 15. |
- Edvardsson, David, et al.
(författare)
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Person-centred care of people with severe Alzheimer's disease : current status and ways forward
- 2008
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Ingår i: Lancet Neurology. - New York : Elsevier. - 1474-4422 .- 1474-4465. ; 7:4, s. 362-367
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Tidskriftsartikel (refereegranskat)abstract
- When caring for people with severe Alzheimer's disease (AD), the concept of the person being central is increasingly advocated in clinical practice and academia as an approach to deliver high-quality care. The aim of person-centred care, which emanates from phenomological perspectives on AD, is to acknowledge the personhood of people with AD in all aspects of their care. It generally includes the recognition that the personality of the person with AD is increasingly concealed rather than lost; personalisation of the person's care and their environment; offering shared decision-making; interpretation of behaviour from the viewpoint of the person; and prioritising the relationship as much as the care tasks. However, questions remain about how to provide, measure, and explore clinical outcomes of person-centred care. In this Review, we summarise the current knowledge about person-centred care for people with severe AD and highlight the areas in need of further research.
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| 16. |
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| 17. |
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| 18. |
- Flemme, Inger, et al.
(författare)
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Long-term quality of life and uncertainty in patients living with an implantable cardioverter defibrillator.
- 2005
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Ingår i: Heart & lung : the journal of critical care. - St. Louis, MO : Elsevier BV. - 0147-9563 .- 1527-3288. ; 34:6, s. 386-92
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: This study describes the quality of life (QOL) and uncertainty in patients who have an implantable cardioverter defibrillator (ICD) and predicts QOL at long-term follow-up. METHODS: Long-term follow-up was defined as 6.9 years +/- 1 year (range 4.11-8.7 years). QOL was measured with the Quality of Life Index, and uncertainty was measured with the Mishel Uncertainty in Illness Scale. RESULTS: The overall QOL and health/functioning were unchanged over time. QOL in the socioeconomic (P = .002) and psychologic/spiritual domains (P = .012) decreased in the first year. From baseline to long-term follow-up, the QOL in the family domain (P = .011) and uncertainty (P = .002) decreased. Uncertainty was a predictor of low QOL. CONCLUSION: QOL was reasonably good 6.9 years post-ICD implantation. Patients felt less uncertain once they had passed the first year of their illness.
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| 19. |
- Flemme, Inger, 1947-, et al.
(författare)
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Quality of life related to shocks in ICD-recipients : a 5-year follow-up
- 2006
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Ingår i: 6th Annual Spring Meeting of the Working Group on Cardiovascular Nursing of the European Society of Cardiology and the Spring Meeting of the Norwegian National Society of Cardiovascular Nurses Bergen, Norway 5–6 May 2006. - London : Sage Publications. ; , s. S20-S20
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Konferensbidrag (refereegranskat)abstract
- Purpose: The purpose of this study was to describe QoL in relation to shocks and uncertainty in ICD-recipients and to identify predictors of QoL over a 5-year period. Methods: The design was prospective and longitudinal. Thirty-five patients who had lived with the ICD for at least five years had taken part in the study. All recipients had received their ICD as a form of secondary prevention. The questionnaires Mishel Uncertainty in Illness Scale – community version (MUIS-C), Quality of Life Index – cardiac version (QLI-CV) were completed on three occasions: before implantation, at year 1 and at year 5 after implantation. Self-reported number of shocks between the implantation and year 1 and between year 1 and year 5 were described. Data were analyzed by descriptive as well as analytical statistics. Results: In general, QoL was lower at year 1 than before implantation (p = 0.033). A decrease in the socio-economic domain was observed at year 1 (p = 0.006) but improved again at year 5 (p = 0.027) although it remained below the value before implantation. ICD recipient’s satisfaction with the family domain decreased from the time before ICD implantation (p = < 0.001) and from year 1 (p = 0.039) to year 5 after implantation. A decrease in overall uncertainty was observed at year 5 in relation to year 1 (p = 0.009). The longer the ICD recipient had lived with the device, the greater the risk of receiving a shock. However, ICD recipients who received shocks reported being less troubled by them over time. Uncertainty was identified as a predictor of low QoL. Conclusion: The recipients reported a higher level of QoL at year 5 than at year 1. QoL was reasonably good 5 years after implantation and the ICD recipient felt more secure and perceived their ICD as a lifesaver.
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| 20. |
- Larsson, Elin Maria Kristina, 1979, et al.
(författare)
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A combined nanoplasmonic and electrodeless quartz crystal microbalance setup
- 2009
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 80:12, s. 125105-
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an instrument combining localized surface plasmon resonance (LSPR) sensing with electrodeless quartz crystal microbalance with dissipation monitoring (QCM-D). The two techniques can be run simultaneously, on the same sensor surface, and with the same time resolution and sensitivity as for the individual techniques. The electrodeless QCM eliminates the need to fabricate electrodes on the quartz crystal and gives a large flexibility in choosing the surface structure and coating for both QCM-D and LSPR. The performance is demonstrated for liquid phase measurements of lipid bilayer formation and biorecognition events, and for gas phase measurements of hydrogen uptake/release by palladium nanoparticles. Advantages of using the combined equipment for biomolecular adsorption studies include synchronized information about structural transformations and extraction of molecular (dry) mass and degree of hydration of the adlayer, which cannot be obtained with the individual techniques. In hydrogen storage studies the combined equipment, allows for synchronized measurements of uptake/release kinetics and quantification of stored hydrogen amounts in nanoparticles and films at practically interesting hydrogen pressures and temperatures.
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| 21. |
- Ljungman, Petter L S, et al.
(författare)
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Rapid effects of air pollution on ventricular arrhythmias.
- 2008
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Ingår i: European heart journal. - : Oxford University Press (OUP). - 1522-9645 .- 0195-668X. ; 29:23, s. 2894-901
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: Air pollution has been associated with ventricular arrhythmias in patients with implantable cardioverter defibrillators (ICDs) for exposure periods of 24-48 h. Only two studies have investigated exposure periods <24 h. We aimed to explore such effects during the 2 and 24 preceding hours as well as in relation to distance from the place of the event to the air pollution monitor. METHODS AND RESULTS: We used a case-crossover design to investigate the effects of particulate matter <10 microm in diameter (PM10) and nitrogen dioxide (NO2) in 211 patients with ICD devices in Gothenburg and Stockholm, Sweden. Events interpreted as ventricular arrhythmias were downloaded from the ICDs, and air pollution data were collected from urban background monitors. We found an association between 2 h moving averages of PM10 and ventricular arrhythmia [odds ratio (OR) 1.31, 95% confidence interval (CI) 1.00-1.72], whereas the OR for 24 h moving averages was 1.24 (95% CI 0.87-1.76). Corresponding ORs for events occurring closest to the air pollution monitor were 1.76 (95% CI 1.18-2.61) and 1.74 (95% CI 1.07-2.84), respectively. Events occurring in Gothenburg showed stronger associations than in Stockholm. CONCLUSION: Moderate increases in air pollution appear to be associated with ventricular arrhythmias in ICD patients already after 2 h, although future studies including larger numbers of events are required to confirm these findings. Representative geographical exposure classification seems important in studies of these effects.
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| 22. |
- Sandstedt, Bengt, 1951, et al.
(författare)
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Testing the implantable cardioverter-defibrillator after implantation--is it necessary?
- 2007
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Ingår i: Pacing Clin Electrophysiol. - 0147-8389. ; 30:8, s. 985-91
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Tidskriftsartikel (refereegranskat)abstract
- The results of intraoperative and postoperative predischarge implantable cardioverter-defibrillator (ICD) testing of 211 consecutive patients, starting at 15 J and requiring two successful terminations of induced VT/VF with a relative defibrillation safety margin (DSM) of >10 J, were reviewed. The aim was to define the type of intraoperative response that would make postoperative predischarge testing unnecessary. The intraoperative responses were divided into three types: A, a DSM > or =10 J and an absolute energy level of < or =20 J; B, a DSM of > or =10 J and an absolute energy level of >20 J; and C, a DSM <10 J and an absolute energy level of >20 J. At operation, the responses to defibrillation were A, 88.6%; B, 7.1%; and C, 4.3%. Accepting an A response only would leave 11.4% of the patients for postoperative testing. The positive and negative predictive values for diagnosing a postoperative C response were 0.78 and 0.97, respectively. Similarly, the predictive values for diagnosing a postoperative B or C response were 0.71 and 0.97, respectively. The postoperative testing responses were A, 89.1%; B, 4.3%; and C, 6.6%. In summary, an intraoperative A response was sufficient to make a postoperative defibrillation testing unnecessary, while it was found that intraoperative B and C responders should undergo postoperative testing. Applying these criteria, approximately 90% of the patients could be discharged without any postoperative induction test.
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| 23. |
- Tautvaisiene, Grazina, et al.
(författare)
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Abundances of C, N and O as Probes of Mixing in Low-Mass Helium-Core Burning Stars
- 2006
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Ingår i: Convection in Astrophysics. - 1886733953 ; , s. 66-
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the standard stellar theory and observational data for stars of different masses and metallicity. Abundances of 12C, 13C, N and O chemical elements in atmospheres of 17 low-mass helium-core burning stars were determined from the high-resolution spectra obtained on the Nordic Optical Telescope with the SOFIN spectrograph. The stars belong to the red clump of the Galaxy and according to the analysis are in the metallicity range of ‑0.28 < [Fe/H] < 0.14 and mass range 1.2 < M /M[Sun]< 2.3. Abundances of carbon were studied using the C[2 ]Swan (0,1) band head at 5635.5 Å. The wavelength interval 7980-8130 Å with strong CN features was analysed in order to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 Å. In comparison to the chemical composition in field dwarfs, the results show that carbon abundance is depleted and [C/H] is lowered in all the star by about 0.2 dex which is in agreement with results for other stars of this type and the theory of the 1st dredge-up. The results of C/N quite closely follow the C/N vs. mass trend predicted by the 1st dredge-up models. The extra-mixing model by Boothroyd & Sackmann (1999, ApJ, 510, 232) does not predict C/N changes to be noticeable at this metallicity and mass as well. Comparing the results with the same theoretical study by Boothroyd & Sackmann (1999) in the 12C/13C, mass plot the stars separate into two groups, one of which follow the trend of 1st dredge-up with 12C/13C ratio being in the range of 20-30, depending of mass. The 12C/13C ratios of the other group of stars is equal to about 15 which show the evidence of extra-mixing. The analysis of a larger sample of Galaxy red clump stars as well as of metal deficient horizontal branch stars is needed for further progress in revealing of extent of mixing in atmospheres of low mass stars.
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| 24. |
- Tautvaisiene, Grazina, et al.
(författare)
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Abundances of C, N and O as probes of mixing in low-mass helium-core burning stars
- 2007
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Ingår i: Convection in Astrophysics. ; , s. 301-303
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A large population of helium-core-burning clump stars of the Galactic field, revealed by the Hipparcos orbiting observatory, is an excellent target for the analysis of mixing processes in evolved low-mass metal-abundant stars. In this contribution we overview first result of 12C, 13C, N and O abundance determinations in our extensive project which we started with the aim at deriving the fundamental parameters and abundances of more than 20 chemical elements in a large sample of Galactic clump stars.
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| 25. |
- Tautvaisiene, Grazina, et al.
(författare)
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Chemical composition of evolved stars in the open Cluster NGC 7789
- 2005
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 431:3, s. 933-942
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution spectra of six giants and three core-helium-burning “clump” stars in the open cluster NGC 7789 have been obtained with the SOFIN spectrograph on the Nordic Optical Telescope to investigate abundances of up to 20 chemical elements. Abundances of carbon were studied using the C2 Swan (0, 1) band head at 5635.5 Å. The wavelength interval 7980 8130 Å with strong CN features was analysed in order to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 Å. The overall metallicity of evolved stars in the cluster was found to be close to solar ([Fe/H]=-0.04±0.05). Compared with the Sun and other dwarf stars of the Galactic disk, mean abundances in the investigated giant stars suggest that carbon is depleted by about 0.2 dex, and nitrogen and oxygen are close to solar. In the clump stars investigated, carbon is depleted by about 0.2 dex, the mean abundance of nitrogen is enhanced by 0.26 dex and oxygen is lower by 0.14 dex. This has the effect of lowering the mean C/N ratios to the value of 1.9±0.5 in the giant stars and to the value of 1.3±0.2 in the clump stars. The mean 12C/13C ratios are lowered to about the same value of 9±1 in the giants and clump stars investigated. Concerning other chemical elements an overabundance of sodium is noticeable and of silicon and calcium one is suspected. Abundances of iron-group and heavier chemical elements in all nine stars were found to be close to solar.
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| 26. |
- Vallenari, A., et al.
(författare)
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Synthetic stellar libraries and SSP simulations in the Gaia Era
- 2009
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Ingår i: Proceedings of the International Astronomical Union. ; , s. 444-445
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Konferensbidrag (refereegranskat)abstract
- The Gaia mission will obtain accurate positions, parallaxes and proper motions for 109 object all over the sky. In addition, it will collect low resolution spectroscopy in the optical range for ∼ 109 objects, stars, galaxies, and QSOs. Parameters of those objects are expected to be part of the final Catalog. Complete and up-to-date libraries of synthetic stellar spectra are needed to train the algorithms to classify this huge amount of data. Here we focus on the use of the synthetic libraries of spectra calculated by the Gaia community to derive grids of Single Stellar Populations as building blocks of population synthesis models. © International Astronomical Union 2010.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Zhdanov, Vladimir, 1952, et al.
(författare)
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Suppression of binding events via external perturbation with emphasis on QCM
- 2006
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 424:1-3, s. 214-217
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Tidskriftsartikel (refereegranskat)abstract
- Recent experiments indicate that the external perturbations, related e.g. to high-amplitude shear oscillations of the surface of a quartz crystal microbalance sensor, may suppress binding of mesoscopic aggregates (e.g., polystyrene spheres, vesicles, large proteins, etc.) to the surface. Using a simple kinetic model, we derive equations making it possible to conceptually understand and to mathematically describe what may happen in such experiments.
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