3,281 research outputs found
Photometric Variability in the Faint Sky Variability Survey
The Faint Sky Variability Survey (FSVS) is aimed at finding photometric
and/or astrometric variable objects between 16th and 24th mag on time-scales
between tens of minutes and years with photometric precisions ranging from 3
millimag to 0.2 mag. An area of 23 deg, located at mid and high Galactic
latitudes, was covered using the Wide Field Camera (WFC) on the 2.5-m Isaac
Newton Telescope (INT) on La Palma. Here we present some preliminary results on
the variability of sources in the FSVS.Comment: 4 pages, 3 figures, to appear in 14th European Workshop on White
Dwarfs, ASP Conference Series, eds. D. Koester, S. Moehle
A white dwarf merger as progenitor of the anomalous X-ray pulsar 4U 0142+61?
It has been recently proposed that massive fast-rotating highly-magnetized
white dwarfs could describe the observational properties of some of Soft
Gamma-Ray Repeaters (SGRs) and Anomalous X-Ray Pulsars (AXPs). Moreover, it has
also been shown that high-field magnetic (HFMWDs) can be the outcome of white
dwarf binary mergers. The products of these mergers consist of a hot central
white dwarf surrounded by a rapidly rotating disk. Here we show that the merger
of a double degenerate system can explain the characteristics of the peculiar
AXP 4U 0142+61. This scenario accounts for the observed infrared excess. We
also show that the observed properties of 4U 0142+6 are consistent with an
approximately 1.2 M_{\sun} white dwarf, remnant of the coalescence of an
original system made of two white dwarfs of masses 0.6\, M_{\sun} and 1.0\,
M_{\sun}. Finally, we infer a post-merging age kyr,
and a magnetic field G. Evidence for such a magnetic
field may come from the possible detection of the electron cyclotron absorption
feature observed between the and bands at Hz in the
spectrum of 4U 0142+61.Comment: to appear in ApJ Letter
The Spin Evolution of Fast-Rotating, Magnetized Super-Chandrasekhar White Dwarfs in the Aftermath of White Dwarf Mergers
The evolution of the remnant of the merger of two white dwarfs is still an
open problem. Furthermore, few studies have addressed the case in which the
remnant is a magnetic white dwarf with a mass larger than the Chandrasekhar
limiting mass. Angular momentum losses might bring the remnant of the merger to
the physical conditions suitable for developing a thermonuclear explosion.
Alternatively, the remnant may be prone to gravitational or rotational
instabilities, depending on the initial conditions reached after the
coalescence. Dipole magnetic braking is one of the mechanisms that can drive
such losses of angular momentum. However, the timescale on which these losses
occur depend on several parameters, like the strength of the magnetic field. In
addition, the coalescence leaves a surrounding Keplerian disk that can be
accreted by the newly formed white dwarf. Here we compute the post-merger
evolution of a super-Chandrasekhar magnetized white dwarf taking into account
all the relevant physical processes. These include magnetic torques acting on
the star, accretion from the Keplerian disk, the threading of the magnetic
field lines through the disk, as well as the thermal evolution of the white
dwarf core. We find that the central remnant can reach the conditions suitable
to develop a thermonuclear explosion before other instabilities (such as the
inverse beta-decay instability or the secular axisymmetric instability) are
reached, which would instead lead to gravitational collapse of the magnetized
remnant.Comment: Accepted for publication in The Astrophysical Journa
Differential expression of the FAK family kinases in rheumatoid arthritis and osteoarthritis synovial tissues
The focal adhesion kinase (FAK) family kinases, including FAK and proline-rich kinase 2 (Pyk)2, are the predominant mediators of integrin αvβ3 signaling events that play an important role in cell adhesion, osteoclast pathology, and angiogenesis, all processes important in rheumatoid arthritis (RA). Using immunohistochemical and western blot analysis, we studied the distribution of phospho (p)FAK, pPyk2, pSrc, pPaxillin and pPLCγ in the synovial tissue (ST) from patients with RA, osteoarthritis (OA) and normal donors (NDs) as well as in RA ST fibroblasts and peripheral blood differentiated macrophages (PB MΦs) treated with tumor necrosis factor-α (TNFα) or interleukin-1β (IL1β). RA and OA STs showed a greater percentage of pFAK on lining cells and MΦs compared with ND ST. RA ST fibroblasts expressed pFAK at baseline, which increased with TNFα or IL1β stimulation. Pyk2 and Src were phosphorylated more on RA versus OA and ND lining cells and MΦs. pPyk2 was expressed on RA ST fibrobasts but not in MΦs at baseline, however it was upregulated upon TNFα or IL1β activation in both cell types. pSrc was expressed in RA ST fibroblasts and MΦs at baseline and was further increased by TNFα or IL1β stimulation. pPaxillin and pPLCγ were upregulated in RA versus OA and ND lining cells and sublining MΦs. Activation of the FAK family signaling cascade on RA and OA lining cells may be responsible for cell adhesion and migration into the diseased STs. Therapies targeting this novel signaling pathway may be beneficial in RA
Systematic review of fatty acid composition of human milk from mothers of preterm compared to full-term infants
Background: Fatty acid composition of human milk serves as guidance for the composition of infant formulae. The aim of the study was to systematically review data on the fatty acid composition of human milk of mothers of preterm compared to full-term infants. Methods: An electronic literature search was performed in English (Medline and Medscape) and German (SpringerLink) databases and via the Google utility. Fatty acid compositional data for preterm and fullterm human milk were converted to differences between means and 95% confidence intervals. Results: We identified five relevant studies publishing direct comparison of fatty acid composition of preterm versus full-term human milk. There were no significant differences between the values of the principal saturated and monounsaturated fatty acids. In three independent studies covering three different time points of lactation, however, docosahexaenoic acid (DHA) values were significantly higher in milk of mothers of preterm as compared to those of full-term infants, with an extent of difference considered nutritionally relevant. Conclusion: Higher DHA values in preterm than in full-term human milk underlines the importance of using own mother's milk for feeding preterm babies and raises the question whether DHA contents in preterm formulae should be higher than in formulae for full-term infants. Copyright (c) 2008 S. Karger AG, Basel
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