3,016 research outputs found
The subdwarf B star SB 290 - A fast rotator on the extreme horizontal branch
Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very
thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose
almost all of its hydrogen envelope right at the tip of the red giant branch.
In close binary systems, mass transfer to the companion provides the
extraordinary mass loss required for their formation. However, apparently
single sdBs exist as well and their formation is unclear since decades. The
merger of helium white dwarfs leading to an ignition of core helium-burning or
the merger of a helium core and a low mass star during the common envelope
phase have been proposed. Here we report the discovery of SB 290 as the first
apparently single fast rotating sdB star located on the extreme horizontal
branch indicating that those stars may form from mergers.Comment: 5 pages, 4 figures, A&A letters, accepte
The population of white dwarf binaries with hot subdwarf companions
Hot subdwarfs (sdBs) are core helium-burning stars, which lost almost their
entire hydrogen envelope in the red-giant phase. Since a high fraction of those
stars are in close binary systems, common envelope ejection is an important
formation channel. We identified a total population of 51 close sdB+WD binaries
based on time-resolved spectroscopy and multi-band photometry, derive the WD
mass distribution and constrain the future evolution of these systems. Most WDs
in those binaries have masses significantly below the average mass of single
WDs and a high fraction of them might therefore have helium cores. We found 12
systems that will merge in less than a Hubble time and evolve to become either
massive C/O WDs, AM\,CVn systems, RCrB stars or even explode as supernovae type
Ia.Comment: 5 pages, 2 figures, to appear in the proceedings of the 19th European
White Dwarf Workshop, ASP Conf. Se
The C/EBPβ LIP isoform rescues loss of C/EBPβ function in the mouse
The transcription factor C/EBPβ regulates hematopoiesis, bone, liver, fat, and skin homeostasis, and female reproduction. C/EBPβ protein expression from its single transcript occurs by alternative in-frame translation initiation at consecutive start sites to generate three isoforms, two long (LAP*, LAP) and one truncated (LIP), with the same C-terminal bZip dimerization domain. The long C/EBPβ isoforms are considered gene activators, whereas the LIP isoform reportedly acts as a dominant-negative repressor. Here, we tested the putative repressor functions of the C/EBPβ LIP isoform in mice by comparing monoallelic WT or LIP knockin mice with Cebpb knockout mice, in combination with monoallelic Cebpa mice. The C/EBPβ LIP isoform was sufficient to function in coordination with C/EBPα in murine development, adipose tissue and sebocyte differentiation, and female fertility. Thus, the C/EBPβ LIP isoform likely has more physiological functions than its currently known role as a dominant-negative inhibitor, which are more complex than anticipated
Magnetic-Field Induced Quantum Critical Point in YbRhSi
We report low-temperature calorimetric, magnetic and resistivity measurements
on the antiferromagnetic (AF) heavy-fermion metal YbRhSi ( 70
mK) as a function of magnetic field . While for fields exceeding the
critical value at which the low temperature resistivity
shows an dependence, a divergence of upon
reducing to suggests singular scattering at the whole Fermi
surface and a divergence of the heavy quasiparticle mass. The observations are
interpreted in terms of a new type of quantum critical point separating a
weakly AF ordered from a weakly polarized heavy Landau-Fermi liquid state.Comment: accepted for publication in Phys. Rev. Let
Induction of the pro-myelocytic leukaemia gene by type I and type II interferons.
The physiological role of the pro-myelocytic leukaemia (PML) gene product is poorly defined. Among other functions, PML is involved in haematopoietic differentiation and in control of cell growth and tumorigenesis. We investigated the regulation of human PML expression by interferons (IFNs) and IL-1 in various human haematopoietic lines (U937, THP1, HL60, NB4), in human diploid fibroblasts and in human peripheral blood leukocytes. Cytokine-induced modulation of PML expression was assessed by Northern blot analyses, flow cytometry studies and in situ immunolabelling. Our data show that IFNs and IL-1 upregulate PML transcript and protein expression in a time and dose-dependent manner. In situ immunolabelling revealed that upregulation of protein expression by IFN-alpha is a consequence of a marked increase in both the number and the intensity of the staining of so-called PML nuclear bodies. Our data suggest that stimulation of PML expression by interferons and IL-1 may account for upregulation of PML proteins observed in inflammatory tissues and in proliferative states
Logical Rules and a Preliminary Prototype for Translating Mortality Coding Rules from ICD-10 to ICD-11
Iris is a system for coding multiple causes of death in ICD-10 and for the selection of the underlying cause of death, based on a knowledge base composed by a large number of rules. With the adoption of ICD-11, those rules need translation to ICD-11. A pre-project has been carried out to evaluate feasibility of transition to ICD-11, which included the analysis of the logical meta-rules needed for rule translation and development of a prototype support system for the expert that will translate the coding rules
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