96 research outputs found
Rapid detection of methicillin-resistant Staphylococcus aureus directly from clinical samples: methods, effectiveness and cost considerations
Methicillin-resistant Staphylococcus aureus (MRSA) isolates is a serious public health problem whose ever-increasing rate is commensurate with the pressure it is exerting on the healthcare system. At present, more than 20% of clinical S. aureus isolates in German hospitals are methicillin resistant. Strategies from low-prevalence countries show that this development is not necessarily inevitable. In the Scandinavian countries and the Netherlands, thanks to a rigorous prevention programme, MRSA prevalence has been kept at an acceptably low level (<1–3%). Central to these ‘search and destroy’ control strategies is an admission screening using several MRSA swabs taken from mucocutaneous colonisation sites of high-risk patients (‘MRSA surveillance’)
Spectral analysis of the sdO K 648, the exciting star of the planetary nebula Ps 1 in the globular cluster M 15 (NGC 7078)
We present a spectral analysis of the sdO central star K 648 based on
medium-resolution optical and high-resolution UV spectra. The photospheric
parameters are determined by means of state-of-the-art NLTE model atmosphere
techniques.
We found Teff = 39 +/- 2 kK and log g = 3.9 +/- 0.2. The helium (He/H=0.08)
and oxygen (O/H=0.001) abundances are about solar while carbon is enriched by a
factor of 2.5 (C/H=0.001). Nitrogen (N/H = 10**(-6), [N/H] = -2.0) appears at a
sub-solar value. However, these metal abundances are much higher than the
cluster's metallicity M 15: [Fe/H] = -2.25).
The surface composition appears to be a mixture of the original hydrogen-rich
material and products of helium burning (3 alpha process) which have been mixed
up to the surface. The abundances of He, C, and N are consistent with the
nebular abundance, while O is considerably more abundant in the photosphere
than in the nebula.
From a comparison of its position in the log Teff - log g plane with
evolutionary calculations a mass of 0.57 (+0.02, -0.01) Msun and a luminosity
of 3810 +/- 1200 Lsun are deduced.
Our spectroscopic distance d = 11.1 (+2.4, -2.9) kpc is in agreement with the
distance of M 15 as determined by Alves et al. (2000).
From the GHRS spectra we measure a radial velocity of vrad = -130 km/sec.Comment: 8 pages, 13 figure
Abundances of lithium, sodium, and potassium in Vega
Vega's photospheric abundances of Li, Na, and K were determined by using
considerably weak lines measured on the very high-S/N spectrum, while the
non-LTE correction and the gravity-darkening correction were adequately taken
into account. It was confirmed that these alkali elements are mildly
underabundant ([Li/H] ~ -0.6, [Na/H] ~ -0.3, and [K/H] ~ -0.2) compared to the
solar system values, as generally seen also in other metals. Since the tendency
of Li being more deficient than Na and K is qualitatively similar to what is
seen in typical interstellar cloud, the process of interstellar gas accretion
may be related with the abundance anomaly of Vega, as suspected in the case of
lambda Boo stars.Comment: Accepted for publication in MNRAS; 8 pages, 9 figure
Antisemitismus in der Popkultur
ANTISEMITISMUS IN DER POPKULTUR
Antisemitismus in der Popkultur / Kappl, Eva (Rights reserved) ( -
Stellar Nucleosynthesis in the Hyades Open Cluster
We report a comprehensive light element (Li, C, N, O, Na, Mg, and Al)
abundance analysis of three solar-type main sequence (MS) dwarfs and three red
giant branch (RGB) clump stars in the Hyades open cluster using high-resolution
and high signal-to-noise spectroscopy. For each group (MS or RGB), the CNO
abundances are found to be in excellent star-to-star agreement. Our results
confirm that the giants have undergone the first dredge-up and that material
processed by the CN cycle has been mixed to the surface layers. The observed
abundances are compared to predictions of a standard stellar model based on the
Clemson-American University of Beirut (CAUB) stellar evolution code. The model
reproduces the observed evolution of the N and O abundances, as well as the
previously derived 12C/13C ratio, but it fails to predict by a factor of 1.5
the observed level of 12C depletion. Li abundances are derived to determine if
non-canonical extra mixing has occurred in the Hyades giants. The Li abundance
of the giant gamma Tau is in good accord with the predicted level of surface Li
dilution, but a ~0.35 dex spread in the giant Li abundances is found and cannot
be explained by the stellar model. Possible sources of the spread are
discussed; however, it is apparent that the differential mechanism responsible
for the Li dispersion must be unrelated to the uniformly low 12C abundances of
the giants. Na, Mg, and Al abundances are derived as an additional test of our
stellar model. All three elements are found to be overabundant by 0.2-0.5 dex
in the giants relative to the dwarfs. Such large enhancements of these elements
are not predicted by the stellar model, and non-LTE effects significantly
larger (and, in some cases, of opposite sign) than those implied by extant
literature calculations are the most likely cause.Comment: 40 pages, 6 figures, 6 tables; accepted by Ap
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
Lambda Boo stars with composite spectra
We examine the large sample of lambda Boo candidates collected in Table 1 of
Gerbaldi et al. (2003) to see how many of them show composite spectra. Of the
132 lambda Boo candidates we identify 22 which definitely show composite
spectra and 15 more for which there are good reasons to suspect a composite
spectrum. The percentage of lambda Boo candidates with composite spectra is
therefore > 17 and possibly considerably higher. For such stars the lambda Boo
classification should be reconsidered taking into account the fact that their
spectra are composite. We argue that some of the underabundances reported in
the literature may simply be the result of the failure to consider the
composite nature of the spectra. This leads to the legitimate suspicion that
some, if not all, the lambda Boo candidates are not chemically peculiar at all.
A thorough analysis of even a single one of the lambda Boo candidates with
composite spectra, in which the composite nature of the spectrum is duly
considered, which would demonstrate that the chemical peculiarities persist,
would clear the doubt we presently have that the stars with composite spectra
may not be lambda Boo at all.Comment: Accepted for publication by A&A on June 3rd 200
Carbon Abundances of Three Carbon-Enhanced Metal-Poor Stars from High-Resolution Gemini-S/bHROS Spectra of the 8727A [C I] Line
We present the results from an analysis of the 8727ang forbidden [C I] line
in high-resolution Gemini-S/bHROS spectra of three CEMP stars. We find the
[C/Fe] ratios based on the [C I] abundances of the two most Fe-rich stars in
our sample (HIP 0507-1653: [Fe/H] = -1.42 and HIP 0054-2542: [Fe/H] = -2.66) to
be in good agreement with previously determined CH and C_2 line-based values.
For the most Fe-deficient star in our sample (HIP 1005-1439: [Fe/H] = -3.08),
however, the [C/Fe] ratio is found to be 0.34 dex lower than the published
molecular-based value. We have carried out 3D local thermodynamic equilibrium
(LTE) calculations for [C I], and the resulting corrections are found to be
modest for all three stars, suggesting that the discrepancy between the [C I]
and molecular-based C abundances of HIP 1005-1439 is due to more severe 3D
effects on the molecular lines. Carbon abundances are also derived from C I
high-excitation lines and are found to be 0.45-0.64 dex higher than the [C
I]-based abundances. Previously published non-LTE C I abundance corrections
bring the [C I] and C I abundances into better agreement; however, targeted
NLTE calculations for CEMP stars are clearly needed. We have also derived the
abundances of N, K, and Fe for each star. The Fe abundances agree well with
previously derived values, and the K abundances are similar to those of
C-normal metal-poor stars. Nitrogen abundances have been derived from resolved
lines of the CN red system. The abundances are found to be approximately 0.44
dex larger than literature values, which have been derived from CN blue bands
near 3880 and 4215 ang. We discuss evidence that suggests that analyses of the
CN blue system bands underestimate the N abundances of metal-poor giants.Comment: Accepted for publication in AJ; 42 pages, 6 figures, 7 table
Errors on the Trail Making Test Are Associated with Right Hemispheric Frontal Lobe Damage in Stroke Patients
Measures of performance on the Trail Making Test (TMT) are among the most popular neuropsychological assessment techniques. Completion time on TMT-A is considered to provide a measure of processing speed, whereas completion time on TMT-B is considered to constitute a behavioral measure of the ability to shift between cognitive sets (cognitive flexibility), commonly attributed to the frontal lobes. However, empirical evidence linking performance on the TMT-B to localized frontal lesions is mostly lacking. Here, we examined the association of frontal lesions following stroke with TMT-B performance measures (i.e., completion time and completion accuracy measures) using voxel-based lesion-behavior mapping, with a focus on right hemispheric frontal lobe lesions. Our results suggest that the number of errors, but not completion time on the TMT-B, is associated with right hemispheric frontal lesions. This finding contradicts common clinical practice-the use of completion time on the TMT-B to measure cognitive flexibility, and it underscores the need for additional research on the association between cognitive flexibility and the frontal lobes. Further work in a larger sample, including left frontal lobe damage and with more power to detect effects of right posterior brain injury, is necessary to determine whether our observation is specific for right frontal lesions
HD 210111: a new lambda Bootis type SB system
The small group of lambda Bootis stars comprises late B to early F-type
stars, with moderate to extreme (up to a factor 100) surface underabundances of
most Fe-peak elements and solar abundances of lighter elements (C, N, O, and
S). The main mechanisms responsible for this phenomenon are atmospheric
diffusion, meridional mixing and accretion of material from their surroundings.
Especially spectroscopic binary (SB) systems with lambda Bootis type components
are very important to investigate the evolutionary status and accretion process
in more details. For HD 210111, also delta Scuti type pulsation was found which
gives the opportunity to use the tools of asteroseismology for further
investigations. The latter could result in strict constraints for the amount of
diffusion for this star. Together with models for the accretion and its source
this provides a unique opportunity to shed more light on these important
processes. We present classification and high resolution spectra for HD 210111.
A detailed investigation of the most likely combinations of single star
components was performed. For this, composite spectra with different stellar
astrophysical parameters were calculated and compared to the observations to
find the best fitting combination. HD 210111 comprises two equal (within the
estimated errors) stars with T(eff)=7400K, logg=3.8dex, [M/H]=-1.0dex and
vsini=30km/s. This result is in line with other strict observational facts
published so far for this object. It is only the third detailed investigated
lambda Bootis type SB system, but the first one with a known IR-excess.Comment: 5 pages, 2 figure
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