13 research outputs found
The solar photospheric abundance of carbon.Analysis of atomic carbon lines with the CO5BOLD solar model
The use of hydrodynamical simulations, the selection of atomic data, and the
computation of deviations from local thermodynamical equilibrium for the
analysis of the solar spectra have implied a downward revision of the solar
metallicity. We are in the process of using the latest simulations computed
with the CO5BOLD code to reassess the solar chemical composition. We determine
the solar photospheric carbon abundance by using a radiation-hydrodynamical
CO5BOLD model, and compute the departures from local thermodynamical
equilibrium by using the Kiel code. We measure equivalent widths of atomic CI
lines on high resolution, high signal-to-noise ratio solar atlases. Deviations
from local thermodynamic equilibrium are computed in 1D with the Kiel code. Our
recommended value for the solar carbon abundance, relies on 98 independent
measurements of observed lines and is A(C)=8.50+-0.06, the quoted error is the
sum of statistical and systematic error. Combined with our recent results for
the solar oxygen and nitrogen abundances this implies a solar metallicity of
Z=0.0154 and Z/X=0.0211. Our analysis implies a solar carbon abundance which is
about 0.1 dex higher than what was found in previous analysis based on
different 3D hydrodynamical computations. The difference is partly driven by
our equivalent width measurements (we measure, on average, larger equivalent
widths with respect to the other work based on a 3D model), in part it is
likely due to the different properties of the hydrodynamical simulations and
the spectrum synthesis code. The solar metallicity we obtain from the CO5BOLD
analyses is in slightly better agreement with the constraints of
helioseismology than the previous 3D abundance results. (Abridged)Comment: Astronomy and Astrophysics, accepte
Do dusty A stars exhibit accretion signatures in their photospheres?
We determined abundances of O, Ca, Fe, Ba and Y for a sample of dusty and
dust-free A stars, taken from the list of Cheng et al. (1992). Five of the
stars have an infrared-excess due to circumstellar dust. Ongoing accretion from
their circumstellar surroundings might have modified the abundances in the
photospheres of these stars, but our results clearly show, that there is no
difference in the photospheric composition of the dusty and dust-free stars.
Instead all of them show the typical diffusion pattern which diminishes towards
larger rotational velocities.Comment: 8 pages, 3 figures, accepted for publication in A&
A study of lambda Bootis type stars in the wavelength region beyond 7000A
The group of lambda Bootis type stars comprises late B- to early F-type,
Population I objects which are basically metal weak, in particular the Fe group
elements, but with the clear exception of C, N, O and S. One of the theories to
explain the abundance pattern of these stars involves circumstellar or
interstellar matter around the objects. Hence, we have compiled all available
data from the literature of well established members of the lambda Bootis group
redward of 7000A in order to find evidence for matter around these objects.
Furthermore, we present unpublished ISO as well as submillimeter continuum and
CO (2-1) line measurements to complete the data set. In total, measurements for
34 (26 with data redward of 20 mu m) well established lambda Bootis stars are
available. There is evidence for an infrared excesses in six stars (HD 31295,
HD 74873, HD 110411, HD 125162, HD 198160/1 and HD 210111) and two are doubtful
cases (HD 11413 and HD 192640) resulting in a percentage of 23% (excluding the
two doubtful cases). Dust models for these objects show fractional dust
luminosities comparable to the Vega-type stars and slightly higher dust
temperatures. ISO-SWS spectroscopy for HD 125162 and HD 192640 resulted in the
detection of pure stellar HI lines ruling out an active accretion disk (as
found for several Herbig Ae/Be stars) around these objects. The submillimeter
measurements gave only upper limits for the line and continuum fluxes.Comment: 16 pages, 5 figures, accepted by A&
Performance on the Frontal Assessment Battery is sensitive to frontal lobe damage in stroke patients
Background: The Frontal Assessment Battery (FAB) is a brief battery of six neuropsychological tasks designed to assess frontal lobe function at bedside [Neurology 55:1621-1626, 2000]. The six FAB tasks explore cognitive and behavioral domains that are thought to be under the control of the frontal lobes, most notably conceptualization and abstract reasoning, lexical verbal fluency and mental flexibility, motor programming and executive control of action, self-regulation and resistance to interference, inhibitory control, and environmental autonomy. Methods: We examined the sensitivity of performance on the FAB to frontal lobe damage in right-hemisphere-damaged first-ever stroke patients based on voxel-based lesion-behavior mapping.
Results: Voxel-based lesion-behavior mapping of FAB performance revealed that the integrity of the right anterior insula (BA13) is crucial for the FAB global composite score, for the FAB conceptualization score, as well as for the FAB inhibitory control score. Furthermore, the FAB conceptualization and mental flexibility scores were sensitive to damage of the right middle frontal gyrus (MFG; BA9). Finally, the FAB inhibitory control score was sensitive to damage of the right inferior frontal gyrus (IFG; BA44/45).
Conclusions: These findings indicate that several FAB scores (including composite and item scores) provide valid measures of right hemispheric lateral frontal lobe dysfunction, specifically of focal lesions near the anterior insula, in the MFG and in the IFG
Clinical manifestations, diagnosis, and treatment of Mycobacterium haemophilum infections.
Item does not contain fulltextMycobacterium haemophilum is a slowly growing acid-fast bacillus (AFB) belonging to the group of nontuberculous mycobacteria (NTM) frequently found in environmental habitats, which can colonize and occasionally infect humans and animals. Several findings suggest that water reservoirs are a likely source of M. haemophilum infections. M. haemophilum causes mainly ulcerating skin infections and arthritis in persons who are severely immunocompromised. Disseminated and pulmonary infections occasionally occur. The second at-risk group is otherwise healthy children, who typically develop cervical and perihilar lymphadenitis. A full diagnostic regimen for the optimal detection of M. haemophilum includes acid-fast staining, culturing at two temperatures with iron-supplemented media, and molecular detection. The most preferable molecular assay is a real-time PCR targeting an M. haemophilum-specific internal transcribed spacer (ITS), but another approach is the application of a generic PCR for a mycobacterium-specific fragment with subsequent sequencing to identify M. haemophilum. No standard treatment guidelines are available, but published literature agrees that immunocompromised patients should be treated with multiple antibiotics, tailored to the disease presentation and underlying degree of immune suppression. The outcome of M. haemophilum cervicofacial lymphadenitis in immunocompetent patients favors surgical intervention rather than antibiotic treatment.1 oktober 201