93 research outputs found
A Spectroscopic Reconnaissance of UV-Bright Stars
We have carried out spectroscopic observations and made preliminary
classifications of 62 UV-bright stars identified by Lanning on plates taken by
A. Sandage. The goal was to search for "interesting" objects, such as
emission-line stars, hot sub-dwarfs, and high-gravity stars. Our targets were
grouped into two samples, a bright, B < 13, sample of 35 stars observed with
the Kitt Peak 2.1m telescope and a faint, 13< B < 16, sample of 27 stars
observed with the Hobby-Eberly Telescope. We find 39% fairly normal O-mid B
stars, 15% late ~B-late A stars and 32% F-G stars, with 13% of the stars being
high gravity objects, composite, or otherwise peculiar. Included are four
emission-line stars, three composite systems. Thus one out of every ten Lanning
stars is "interesting" and may deserve individual study. Stars in the bright
sample are often found to be late F or early G stars, although this sample does
include interesting stars as well. No such large contamination occurs among the
fainter stars, however, owing to "deselection" of these stars by interstellar
reddening in the low-latitude fields of the survey.Comment: 9 pages in total, to appear in February 2002 issue of P.A.S.
Discovery of a Hard X-Ray Source, SAX J0635+0533, in the Error Box of the Gamma-Ray Source 2EG 0635+0521
We have discovered an x-ray source, SAX J0635+0533, with a hard spectrum
within the error box of the GeV gamma-ray source in Monoceros, 2EG J0635+0521.
The unabsorbed x-ray flux is 1.2*10^-11 erg cm^-2 s^-1 in the 2-10 keV band.
The x-ray spectrum is consistent with a simple powerlaw model with absorption.
The photon index is 1.50 +/- 0.08 and we detect emission out to 40 keV. Optical
observations identify a counterpart with a V-magnitude of 12.8. The counterpart
has broad emission lines and the colors of an early B type star. If the
identification of the x-ray/optical source with the gamma-ray source is
correct, then the source would be a gamma-ray emitting x-ray binary.Comment: Accepted to the Astrophysical Journal, 8 page
A Study of the B-V Colour Temperature Relation
We attempt to construct a B-V colour temperature relation for stars in the
least model dependent way employing the best modern data. The fit we obtained
with the form Teff = Teff((B-V)0,[Fe/H],log g) is well constrained and a number
of tests show the consistency of the procedures for the fit. Our relation
covers from F0 to K5 stars with metallicity [Fe/H] = -1.5 to +0.3 for both
dwarfs and giants. The residual of the fit is 66 K, which is consistent with
what are expected from the quality of the present data. Metallicity and surface
gravity effects are well separated from the colour dependence. Dwarfs and
giants match well in a single family of fit, differing only in log g. The fit
also detects the Galactic extinction correction for nearby stars with the
amount E(B-V) = 0.26 +/-0.03 mag/kpc. Taking the newly obtained relation as a
reference we examine a number of B-V colour temperature relations and
atmosphere models available in the literature. We show the presence of a
systematic error in the colour temperature relation from synthetic calculations
of model atmospheres; the systematic error across K0 to K5 dwarfs is 0.04-0.05
mag in B-V, which means 0.25-0.3 mag in Mv for the K star range. We also argue
for the error in the temperature scale used in currently popular stellar
population synthesis models; synthetic colours from these models are somewhat
too blue for aged elliptical galaxies. We derive the colour index of the sun
(B-V)sun = 0.627 +/-0.018, and discuss that redder colours (e.g., 0.66-0.67)
often quoted in the literature are incompatible with the colour-temperature
relation.Comment: AASLaTeX (aaspp4.sty),36 pages (13 figures included), submitted to
Astronomical Journal, replaced (typo in author name
The night-sky at the Calar Alto Observatory
We present a characterization of the main properties of the night-sky at the
Calar Alto observatory for the time period between 2004 and 2007. We use
optical spectrophotometric data, photometric calibrated images taken in
moonless observing periods, together with the observing conditions regularly
monitored at the observatory, such as atmospheric extinction and seeing. We
derive, for the first time, the typical moonless night-sky optical spectrum for
the observatory. The spectrum shows a strong contamination by different
pollution lines, in particular from Mercury lines, which contribution to the
sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag
and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the
moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25
mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a
particularly dark site for optical observations up to the I-band. The fraction
of astronomical useful nights at the observatory is ~70%, with a ~30% of
photometric nights. The typical extinction at the observatory is k_V~0.15 mag
in the Winter season, with little dispersion. In summer the extinction has a
wider range of values, although it does not reach the extreme peaks observed at
other sites. The median seeing for the last two years (2005-6) was ~0.90",
being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude
in general that after 26 years of operations Calar Alto is still a good
astronomical site, being a natural candidate for future large aperture optical
telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of
Astronomical Society of the Pacific (PASP
Bi-allelic JAM2 Variants Lead to Early-Onset Recessive Primary Familial Brain Calcification.
Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder characterized by a combination of neurological, psychiatric, and cognitive decline associated with calcium deposition on brain imaging. To date, mutations in five genes have been linked to PFBC. However, more than 50% of individuals affected by PFBC have no molecular diagnosis. We report four unrelated families presenting with initial learning difficulties and seizures and later psychiatric symptoms, cerebellar ataxia, extrapyramidal signs, and extensive calcifications on brain imaging. Through a combination of homozygosity mapping and exome sequencing, we mapped this phenotype to chromosome 21q21.3 and identified bi-allelic variants in JAM2. JAM2 encodes for the junctional-adhesion-molecule-2, a key tight-junction protein in blood-brain-barrier permeability. We show that JAM2 variants lead to reduction of JAM2 mRNA expression and absence of JAM2 protein in patient's fibroblasts, consistent with a loss-of-function mechanism. We show that the human phenotype is replicated in the jam2 complete knockout mouse (jam2 KO). Furthermore, neuropathology of jam2 KO mouse showed prominent vacuolation in the cerebral cortex, thalamus, and cerebellum and particularly widespread vacuolation in the midbrain with reactive astrogliosis and neuronal density reduction. The regions of the human brain affected on neuroimaging are similar to the affected brain areas in the myorg PFBC null mouse. Along with JAM3 and OCLN, JAM2 is the third tight-junction gene in which bi-allelic variants are associated with brain calcification, suggesting that defective cell-to-cell adhesion and dysfunction of the movement of solutes through the paracellular spaces in the neurovascular unit is a key mechanism in CNS calcification
Detection of Extended Red Emisson in the Diffuse Interstellar Medium
Extended Red Emission (ERE) has been detected in many dusty astrophysical
objects and this raises the question: Is ERE present only in discrete objects
or is it an observational feature of all dust, i.e. present in the diffuse
interstellar medium? In order to answer this question, we determined the blue
and red intensities of the radiation from the diffuse interstellar medium (ISM)
and examined the red intensity for the presence of an excess above that
expected for scattered light. The diffuse ISM blue and red intensities were
obtained by subtracting the integrated star and galaxy intensities from the
blue and red measurements made by the Imaging Photopolarimeter (IPP) aboard the
Pioneer 10 and 11 spacecraft. The color of the diffuse ISM was found to be
redder than the Pioneer intensities, contrary to that expected for scattered
light (Diffuse Galactic Light [DGL]). The red DGL was calculated using the blue
diffuse ISM intensities and the approximately invariant color of the DGL
calculated with the DGL model. Subtracting the calculated red DGL from the red
diffuse ISM intensities resulted in the detection of an excess red intensity.
This represents the likely detection of ERE in the diffuse ISM since H-alpha
emission cannot account for the strength of this excess and the only other
known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears
to be a general characteristic of dust. From the correlation between N_HI and
ERE intensity the ERE photon conversion efficiency was estimated at 10 +/- 3%.Comment: 44 pages (41 figures included), to be published in the ApJ, new
version corrected for small error in fig. 2
Diet supplementation for 5 weeks with polyphenol-rich cereals improves several functions and the redox state of mouse leucocytes
BACKGROUND: Cereals naturally contain a great variety of polyphenols, which exert a wide range of physiological effects both in vitro and in vivo. Many of their protective effects, including an improvement of the function and redox state of immune cells in unhealthy or aged subjects come from their properties as powerful antioxidant compounds. However, whether cereal-based dietary supplementation positively affects the immune function and cellular redox state of healthy subjects remains unclear. AIM OF THE STUDY: To investigate the effects of supplementation (20% wt/wt) for 5 weeks with four different cereal fractions on healthy mice. METHODS: Several parameters of function and redox state of peritoneal leukocytes were measured. The cereals, named B (wheat germ), C (buckwheat flour), D (fine rice bran) and E (wheat middlings) contained different amounts of gallic acid, p-hydroxybenzoic acid, vanillic acid, sinapic acid, p-coumaric acid, ferulic acid, quercetin, catechin, rutin and oryzanol as major polyphenols. RESULTS: In general, all cereal fractions caused an improvement of the leukocyte parameters studied such as chemotaxis capacity, microbicidal activity, lymphoproliferative response to mitogens, interleukin-2 (IL-2) and tumor necrosis factor (TNFα) release, as well as oxidized glutathione (GSSG), GSSG/GSH ratio, catalase (CAT) activity and lipid oxidative damage. We observed similar effects among the cereal fractions. CONCLUSIONS: The results suggest that some of these effects may due, at least partially, to the antioxidant activity of the polyphenols naturally present in cereals. Since an appropriate function of the leukocytes has been proposed as marker of the health state, a short-term intake of cereals seems to be sufficient to exert a benefit in the health of the general population. However, further studies are needed to assess the optimal doses and to find out which active polyphenols are able to mediate the observed physiological effects before recommending their regular consumption
Analysis of IL12B Gene Variants in Inflammatory Bowel Disease
IL12B encodes the p40 subunit of IL-12, which is also part of IL-23. Recent genome-wide association studies identified IL12B and IL23R as susceptibility genes for inflammatory bowel disease (IBD). However, the phenotypic effects and potential gene-gene interactions of IL12B variants are largely unknow
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