86 research outputs found
A census with ROSAT of low-luminosity X-ray sources in globular clusters
I analyze 101 observations from the ROSAT archive to search for X-ray sources
in or near 55 globular clusters. New sources are found in the cores of NGC362
(a double source), NGC6121 (marginally significant), NGC6139, and NGC6266; and
outside the cores of NGC6205, NGC6352 and NGC6388. More accurate positions are
determined for the X-ray sources in some ten clusters. The improved position
for the source in NGC6341 excludes the suggested ultraviolet counterpart. It is
shown that one of the two sources reported near the core NGC6626 is spurious,
as is the detection of a pulsar period in the PSPC data of this cluster; the
central source is resolved in three sources. One source reported previously in
NGC6304 is demoted to an upper limit. For 20 cluster cores better upper limits
to the X-ray luminosity are obtained.
From a statistical analysis I argue that several sources outside the cluster
cores may well belong to the clusters. All spectral energy distributions
observed so far are relatively soft, with bremsstrahlung temperatures =~0.9keV;
there is evidence however that bremsstrahlung spectra do not correctly describe
the spectra. The X-ray luminosity per unit mass for the cluster as a whole does
not depend on the concentration; the luminosity per unit mass for the core may
increase with the cluster concentration.Comment: 24 pages, 8 figures, 5 tables, accepted for publication in Astronomy
and Astrophysic
The C-type lectin receptor CLEC12A recognizes plasmodial hemozoin and contributes to cerebral malaria development
Virtual-pion and two-photon production in pp scattering
Two-photon production in pp scattering is proposed as a means of studying
virtual-pion emission. Such a process is complementary to real-pion emission in
pp scattering. The virtual-pion signal is embedded in a background of
double-photon bremsstrahlung. We have developed a model to describe this
background process and show that in certain parts of phase space the
virtual-pion signal gives significant contribution. In addition, through
interference with the two-photon bremsstrahlung background, one can determine
the relative phase of the virtual-pion process
Isoscalar off-shell effects in threshold pion production from pd collisions
We test the presence of pion-nucleon isoscalar off-shell effects in the
reaction around the threshold region. We find that these
effects significantly modify the production cross section and that they may
provide the missing strength needed to reproduce the data at threshold.Comment: 6 pages, REVTeX, twocolumn, including 3 figures (Postscript), uses
psfig, updated and extended versio
A unitary model for meson-nucleon scattering
In an effective Lagrangian model employing the K-matrix approximation we
extract nucleon resonance parameters. To this end we analyze simultaneously all
available data for reactions involving the final states , ,
and in the energy range GeV. The background contributions are generated consistently from the
relevant Feynman amplitudes, thus significantly reducing the number of free
parameters.Comment: Revised version. 60 pages, 17 figures. Two figures and a short
discussion (\pi N \to \eta N, K \Lambda amplitudes) added, typos and minor
errors in the citations correcte
On the Predicted and Observed Color Boundaries of the RR Lyrae Instability Strip as a Function of Metallicity
The purpose of the paper is to predict the temperature at the fundamental
blue edge (FBE) of the instability strip for RR Lyrae (RRL) variables from the
pulsation equation that relates temperature to period, luminosity, and mass.
Modern data for the correlations between period, luminosity, and metallicity at
the FBE for field and cluster RRL are used for the temperature calculation. The
predicted temperatures are changed to B-V colors using an adopted color
transformation. The predicted temperatures at the FBE become hotter as [Fe/H]
changes from 0 to -1.5, and thereafter cooler as the metallicity decreases to
-2.5 and beyond. The temperature range over this interval of metallicity is
log = 0.04, or 640 K at 6900K. The predicted color variation is
at the level of 0.03 mag in B-V. The predictions are compared with the observed
RRL colors at the FBE for both the field and cluster variables, showing general
agreement at the level of 0.02 mag in (B-V), which, however, is the
uncertainty of the reddening corrections.
The focus of the problem is then reversed by fitting a better envelope to the
observed FBE relation between color and metallicity for metallicities smaller
than -1.8 which, when inserted in the pulsation equation, gives a non-linear
calibration ....Comment: 34 pages, 11 figures, 2 tables. To appear in March 2006 A
Isocalar Roper excitation in the pp --> pp pi0 reaction close to threshold
A new mechanism for the pp --> pp pi0 reaction close to threshold is
suggested coming from the isoscalar excitation of the Roper and its decay into
N(pi pi)S-wave, with one of the pi0 emitted and the other one reabsorbed on the
second nucleon. The mechanism can lead to important interference with other
mechanisms and, together with experiment, serves to exclude large ranges of the
2pi N* decay parameters allowed by the N* partial decay widths.Comment: 11 LaTeX pages, 4 postscript figure
Perioperative fluid and volume management: physiological basis, tools and strategies
Fluid and volume therapy is an important cornerstone of treating critically ill patients in the intensive care unit and in the operating room. New findings concerning the vascular barrier, its physiological functions, and its role regarding vascular leakage have lead to a new view of fluid and volume administration. Avoiding hypervolemia, as well as hypovolemia, plays a pivotal role when treating patients both perioperatively and in the intensive care unit. The various studies comparing restrictive vs. liberal fluid and volume management are not directly comparable, do not differ (in most instances) between colloid and crystalloid administration, and mostly do not refer to the vascular barrier's physiologic basis. In addition, very few studies have analyzed the use of advanced hemodynamic monitoring for volume management
Extracellular micronutrient levels and pro-/antioxidant status in trauma patients with wound healing disorders: results of a cross-sectional study
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