551 research outputs found
On the Wilson-Bappu relationship in the Mg II k line
An investigation is carried out on the Wilson-Bappu effect in the Mg II k
line at 2796.34 A. The work is based on a selection of 230 stars observed by
both the IUE and HIPPARCOS satellites, covering a wide range of spectral type
and absolute visual magnitudes. The Wilson-Bappu relationship here provided is
considered to represent an improvement over previous recent results for the
considerably larger data sample used as well as for a proper consideration of
the measurement errors. No evidence has been found for a possible dependence of
the WB effect on stellar metallicity and effective temperature.Comment: 8 pages, 8 figures Accepted for publication on A&
A study of the Mg II 2796.34 A emission line in late--type normal, and RS CVn stars
We carry out an analysis of the Mg II 2796.34 A emission line in RS CVn stars
and make a comparison with the normal stars studied in a previous paper (Paper
I). The sample of RS CVn stars consists of 34 objects with known HIPPARCOS
parallaxes and observed at high resolution with IUE. We confirm that RS CVn
stars tend to possess wider Mg II lines than normal stars having the same
absolute visual magnitude. However, we could not find any correlation between
the logarithmic line width log Wo and the absolute visual magnitude Mv (the
Wilson--Bappu relationship) for these active stars, contrary to the case of
normal stars addressed in Paper I. On the contrary, we find that a strong
correlation exists in the (Mv, log L) plane (L is the absolute flux in the
line). In this plane, normal and RS CVn stars are distributed along two nearly
parallel straight lines with RS CVn stars being systematically brighter by
about 1 dex. Such a diagram provides an interesting tool to discriminate active
from normal stars. We finally analyse the distribution of RS CVn and of normal
stars in the (log L, log Wo) plane, and find a strong linear correlation for
normal stars, which can be used for distance determinations.Comment: 10 pages, 7 figures, latex, to be published in A&
The evolution of ultraviolet emission lines from the circumstellar material surrounding SN 1987A
The presence of narrow high-temperature emission lines from nitrogen-rich gas
close to SN 1987A has been the principal observational constraint on the evolu-
tionary status of the supernova's progenitor. A new analysis of the complete
five-year set of low and high resolution IUE ultraviolet spectra of SN 1987A
(1987.2--1992.3) provide fluxes for the N V 1240, N IV] 1486, He II 1640, OIII]
1665, NIII] 1751, and CIII] 1908 lines with significantly reduced random and
systematic errors and reveals significant short-term fluctuations in the light
curves. The N V, N IV] and N III] lines turn on sequentially over 15 to 20 days
and show a progression from high to low ionization potential, implying an ioni-
zation gradient in the emitting region. The line emission turns on suddenly at
83+/-4 days after the explosion, as defined by N IV]. The N III] line reaches
peak luminosity at 399+/-15 days. A ring radius of (6.24+/-0.20)E{17} cm and
inclination of 41.0+/-3.9 is derived from these times, assuming a circular
ring. The probable role of resonant scattering in the N V light curve
introduces systematic errors that leads us to exclude this line from the timing
analysis. A new nebular analysis yields improved CNO abundance ratios
N/C=6.1+/-1.1 and N/O=1.7+/-0.5, confirming the nitrogen enrichment found in
our previous paper. From the late-time behavior of the light curves we find
that the emission origi- nates from progressively lower density gas. We
estimate the emitting mass near maximum (roughly 400 days) to be roughly
4.7E{-2} solar masses, assuming a filling factor of unity and an electron
density of 2.6E4 cm^{-3}. These results are discussed in the context of current
models for the emission and hydrodynamics of the ring.Comment: 38 pages, AASTeX v.4.0, 13 Postscript figures; ApJ, in pres
A study of the expanding envelope of Nova V1974 Cyg 1992 based on IUE high resolution spectroscopy
We have carried out a detailed analysis of the IUE archival high resolution
spectra of the classical nova V1974 Cyg 1992. In addition to the P Cygni and
emission lines, two shortward shifted absorption systems are present. Evidence
is given that these absorptions originate in two separate expanding shells,
outside the wind layers where the emission lines are formed. The outer main
shell, containing most of the matter ejected at outburst, produces the
so-called ``principal absorption line system'', and the inner faster moving
second shell produces the so-called ``diffuse--enhanced absorption line
system''. The outflow velocity of the two shells increases exponentially with
time reaching a value of about 1750 km/s and 2900 km/s, respectively. We
suggest that the acceleration of the shells is the result of increasing
line-radiation pressure due to the UV-brightening of the star as the effective
radius decreases. Around day 60 the second shell has overtaken the slower
moving principal system shell, and merged with it. This explains: the sudden
disappearance of the diffuse line system near that date, the upward jump of 240
km/s in velocity of the principal system and the first detection of hard X-ray
emission on day 63. This velocity jump indicates that the main shell is about 4
times more massive than the second shell. The deceleration suffered by the
diffuse-enhanced system after the shock provides a shock temperature of about
1.6 KeV, in fairly good agreement with the temperature of the observed hard
X-ray emission.Comment: 19 pages, 11 figure
Male infertility and copy number variants (CNVs) in the dog: a two-pronged approach using Computer Assisted Sperm Analysis (CASA) and Fluorescent In Situ Hybridization (FISH)
Tumour-infiltrating lymphocytes bear the 75 kDa tumour necrosis factor receptor.
Tumour necrosis factor alpha (TNF-alpha) is a cytokine with a variety of immunological properties. The identification of two receptors for this molecule, i.e. the 75 kDa and the 55 kDa TNF receptors (TNF-R), recently clarified the mechanisms through which this cytokine provides its wide range of immunomodulatory activities. In this study we have investigated the expression and the functional properties of these receptors on tumour-infiltrating lymphocytes (TILs) recovered from 17 patients with solid cancers (melanoma, colorectal carcinoma and lung cancer). To this end, TIL lines and freshly isolated TILs were evaluated for (a) the expression and the functional role of TNF receptors following culture in the presence of interleukin 2 (IL-2) and (b) the production of TNF-alpha following culture with IL-2 and the role of this cytokine in IL-2-driven TIL proliferation. Flow cytometry analysis demonstrated that TILs bear the 75 kDa TNF-R. Moreover, TIL lines express detectable messages for TNF-alpha and release this cytokine. Functional in vitro studies have shown that anti-TNF-alpha, as well as anti-75 kDa TNF-R antibodies, are able to inhibit the IL-2-induced TIL proliferation. These data demonstrate that TILs are equipped with a fully functional TNF-R system and suggest a putative role for this receptor and its ligand in the activation and expression of TILs following immunotherapy with IL-2
TL1A/DR3 axis involvement in the inflammatory cytokine network during pulmonary sarcoidosis
BACKGROUND:
TNF-like ligand 1A (TL1A), a recently recognized member of the TNF superfamily, and its death domain receptor 3 (DR3), firstly identified for their relevant role in T lymphocyte homeostasis, are now well-known mediators of several immune-inflammatory diseases, ranging from rheumatoid arthritis to inflammatory bowel diseases to psoriasis, whereas no data are available on their involvement in sarcoidosis, a multisystemic granulomatous disease where a deregulated T helper (Th)1/Th17 response takes place.
METHODS:
In this study, by flow cytometry, real-time PCR, confocal microscopy and immunohistochemistry analyses, TL1A and DR3 were investigated in the pulmonary cells and the peripheral blood of 43 patients affected by sarcoidosis in different phases of the disease (29 patients with active sarcoidosis, 14 with the inactive form) and in 8 control subjects.
RESULTS:
Our results demonstrated a significant higher expression, both at protein and mRNA levels, of TL1A and DR3 in pulmonary T cells and alveolar macrophages of patients with active sarcoidosis as compared to patients with the inactive form of the disease and to controls. In patients with sarcoidosis TL1A was strongly more expressed in the lung than the blood, i.e., at the site of the involved organ. Additionally, zymography assays showed that TL1A is able to increase the production of matrix metalloproteinase 9 by sarcoid alveolar macrophages characterized, in patients with the active form of the disease, by reduced mRNA levels of the tissue inhibitor of metalloproteinase (TIMP)-1.
CONCLUSIONS:
These data suggest that TL1A/DR3 interactions are part of the extended and complex immune-inflammatory network that characterizes sarcoidosis during its active phase and may contribute to the pathogenesis and to the progression of the disease
Helicobacter pylori-derived neutrophil-activating protein increases the lifespan of monocytes and neutrophils
P>An invariable feature of Helicobacter pylori-infected gastric mucosa is the persistent infiltration of inflammatory cells. The neutrophil-activating protein (HP-NAP) has a pivotal role in triggering and orchestrating the phlogistic process associated with H. pylori infection. Aim of this study was to address whether HP-NAP might further contribute to the inflammation by increasing the lifespan of inflammatory cells. We report that HP-NAP is able to prolong the lifespan of monocytes, in parallel with the induction of the anti-apoptotic proteins A1, Mcl-1, Bcl-2 and Bcl-X(L). This effect does not result from a direct action on the apoptotic machinery, but rather it requires the release of endogenous pro-survival factors, such as interleukin-1 beta, which probably acts in synergy with other unidentified mediators. We also report that HP-NAP promotes the survival of Ficoll-purified neutrophils in a monocyte-dependent fashion: indeed, mononuclear cell depletion of Ficoll-purified neutrophils completely abolished the pro-survival effect by HP-NAP. In conclusion, our data reinforce the notion that HP-NAP has a pivotal role in sustaining a prolonged activation of myeloid cells
X-ray and UV observations of nova V598 Puppis between 147 and 255 days after outburst
Aims: The launch of Swift has allowed many more novae to be observed
regularly over the X-ray band. Such X-ray observations of novae can reveal
ejecta shocks and the nuclear burning white dwarf, allowing estimates to be
made of the ejecta velocity. Methods: We analyse XMM-Newton and Swift X-ray and
UV observations of the nova V598 Pup, which was initially discovered in the
XMM-Newton slew survey. These data were obtained between 147 and 255 days after
the nova outburst, and are compared with the earlier, brighter slew detection.
Results: The X-ray spectrum consists of a super-soft source, with the soft
emission becoming hotter and much fainter between days ~147 and ~172 after the
outburst, and a more slowly declining optically thin component, formed by
shocks with kT ~ 200-800 eV (corresponding to velocities of 400-800 km s^-1).
The main super-soft phase had a duration of less than 130 days. The Reflection
Grating Spectrometer data show evidence of emission lines consistent with
optically thin emission of kT ~100 eV and place a limit on the density of the
surrounding medium of log(n_e/cm^-3) < 10.4 at the 90 % level. The UV emission
is variable over short timescales and fades by at least one magnitude (at
lambda ~ 2246-2600 angstrom) between days 169 and 255.Comment: 6 pages, 5 figures, accepted for publication in A&
Five-Year Optical and Near Infrared Observations of the Extremely Slow Nova V1280 Scorpii
We present optical (, , , and ) and near
infrared (, and ) photometric and spectroscopic observations
of a classical nova V1280 Scorpii for five years from 2007 to 2011. Our
photometric observations show a declining event in optical bands shortly after
the maximum light which continues 250 days. The event is most probably
caused by a dust formation. The event is accompanied by a short ( 30
days) re-brightening episode ( 2.5 mag in ), which suggests a
re-ignition of the surface nuclear burning. After 2008, the band
observations show a very long plateau at around = 10.5 for more than 1000
days until April 2011 ( 1500 days after the maximum light). The nova had
taken a very long time ( 50 months) before entering the nebular phase
(clear detection of both [\ion{O}{iii}] 4959 and 5007) and is still continuing
to generate the wind caused by H-burning. The finding suggests that V1280 Sco
is going through the historically slowest evolution. The interval from the
maximum light (2007 February 16) to the beginning of the nebular phase is
longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10
months), or HR Del (8 months). It suggests that the mass of a white dwarf in
the V1280 Sco system might be 0.6 M_\mathrm{\sun} or smaller. The distance,
based on our measurements of the expansion velocity combined with the directly
measured size of the dust shell, is estimated to be 1.1 0.5 kpc.Comment: 17 pages, 14 figures, accepted for publication in A&
- …