858 research outputs found
The Tip of the Red Giant Branch and Distance of the Magellanic Clouds: results from the DENIS survey
We present a precise determination of the apparent magnitude of the tip of
the red giant branch (TRGB) in the I (0.8 micron), J (1.25 micron), and K_S
(2.15 micron) bands from the luminosity function of a sample of data extracted
from the DENIS catalogue towards the Magellanic Clouds (Cioni et al. 2000).
From the J and Ks magnitudes we derive bolometric magnitudes m_bol. We
present a new algorithm for the determination of the TRGB magnitude, which we
describe in detail and test extensively using Monte-Carlo simulations. We note
that any method that searches for a peak in the first derivative (used by most
authors) or the second derivative (used by us) of the observed luminosity
function does not yield an unbiased estimate for the actual magnitude of the
TRGB discontinuity. We stress the importance of correcting for this bias, which
is not generally done. We combine the results of our algorithm with theoretical
predictions to derive the distance modulus of the Magellanic Clouds. We obtain
m-M = 18.55 (0.04 formal, 0.08 systematic) for the Large Magellanic Cloud
(LMC), and m-M = 18.99 (0.03 formal, 0.08 systematic) for the Small Magellanic
Cloud (SMC). These are among the most accurate determinations of these
quantities currently available, which is a direct consequence of the large size
of our sample and the insensitivity of near infrared observations to dust
extinction.Comment: 16 pages, 8 figures, revised version, accepted for publication in A&
On The 5D Extra-Force according to Basini-Capozziello-Leon Formalism and five important features: Kar-Sinha Gravitational Bending of Light, Chung-Freese Superluminal Behaviour, Maartens-Clarkson Black Strings, Experimental measures of Extra Dimensions on board International Space Station(ISS) and the existence of the Particle due to a Higher Dimensional spacetime
We use the Conformal Metric as described in Kar-Sinha work on Gravitational
Bending of Light in a 5D Spacetime to recompute the equations of the 5D Force
in Basini-Capozziello-Leon Formalism and we arrive at a result that possesses
some advantages. The equations of the Extra Force as proposed by Leon are now
more elegant in Conformal Formalism and many algebraic terms can be simplified
or even suppressed. Also we recompute the Kar-Sinha Gravitational Bending of
Light affected by the presence of the Extra Dimension and analyze the
Superluminal Chung-Freese Features of this Formalism describing the advantages
of the Chung-Freese BraneWorld when compared to other Superluminal spacetime
metrics(eg:Warp Drive) and we describe why the Extra Dimension is invisible and
how the Extra Dimension could be made visible at least in theory.We also
examine the Maartens-Clarkson Black Holes in 5D(Black Strings) coupled to
massive Kaluza-Klein graviton modes predicted by Extra Dimensions theories and
we study experimental detection of Extra Dimensions on-board LIGO and LISA
Space Telescopes.We also propose the use of International Space Station(ISS) to
measure the additional terms(resulting from the presence of Extra Dimensions)
in the Kar-Sinha Gravitational Bending of Light in Outer Space to verify if we
really lives in a Higher Dimensional Spacetime.Also we demonstrate that
Particle can only exists if the 5D spacetime exists.Comment: Withdrawn: author no longer wishes to post work on arXi
Magnetic Flares on Asymptotic Giant Branch Stars
We investigate the consequences of magnetic flares on the surface of
asymptotic giant branch (AGB) and similar stars. In contrast to the solar wind,
in the winds of AGB stars the gas cooling time is much shorter than the outflow
time. As a result, we predict that energetic flaring will not inhibit, and may
even enhance, dust formation around AGB stars. If magnetic flares do occur
around such stars, we expect some AGB stars to exhibit X-ray emission; indeed
certain systems including AGB stars, such as Mira, have been detected in
X-rays. However, in these cases, it is difficult to distinguish between
potential AGB star X-ray emission and, e.g., X-ray emission from the vicinity
of a binary companion. Analysis of an archival ROSAT X-ray spectrum of the Mira
system suggests an intrinsic X-ray luminosity 2x10^{29} erg/sec and temperature
10^7 K. These modeling results suggest that magnetic activity, either on the
AGB star (Mira A) or on its nearby companion (Mira B), is the source of the
X-rays, but do not rule out the possibility that the X-rays are generated by an
accretion disk around Mira B.Comment: ApJ, Accepted; revised version of astro-ph/020923
Difficultés de la surveillance épidémiologique de la rougeole en Afrique : exemple de la Côte d'Ivoire
En zone tropicale, les cas de rougeole sont souvent sous-déclarés mais les auteurs exposent deux épidémies qui ont été considérées au début comme des manifestations de rougeole. La première épidémie s'est manifestée comme une épidémie de viroses à Chikungunya avec éruptions, hyperthermie et algies importantes, elle était due à un arbovirus Igbo-Ora. Dans l'autre cas il s'agissait d'enfants atteints d'éruptions avec hyperthermie et adénopathies évoquant la rubéole. Les auteurs évoquent la possibilité de diagnostic par excès dans le cadre de la surveillance de cette maladie-cible du PEV (Programme Elargi de Vaccination), hypothèse confirmée par la répartition des cas déclarés au niveau national avec une fréquence élevée des cas en contre-saison et chez certains adultes. (Résumé d'auteur
Urinary peptidomics provides a noninvasive humanized readout of diabetic nephropathy in mice
Nephropathy is among the most frequent complications of diabetes and the leading cause of end-stage renal disease. Despite the success of novel drugs in animal models, the majority of the subsequent clinical trials employing those drugs targeting diabetic nephropathy failed. This lack of translational value may in part be due to an inadequate comparability of human disease and animal models that often capture only a few aspects of disease. Here we overcome this limitation by developing a multimolecular noninvasive humanized readout of diabetic nephropathy based on urinary peptidomics. The disease-modified urinary peptides of 2 type 2 diabetic nephropathy mouse models were identified and compared with previously validated urinary peptide markers of diabetic nephropathy in humans to generate a classifier composed of 21 ortholog peptides. This classifier predicted the response to disease and treatment with inhibitors of the renin-angiotensin system in mice. The humanized classifier was significantly correlated with glomerular lesions. Using a human type 2 diabetic validation cohort of 207 patients, the classifier also distinguished between patients with and without diabetic nephropathy, and their response to renin-angiotensin system inhibition. Thus, a combination of multiple molecular features common to both human and murine disease could provide a significant change in translational drug discovery research in type 2 diabetic nephropathy
Circulating antibodies directed against tryptophan-like epitopes in sera of patients with human African trypanosomiasis
Mid Infrared Photometry of Mass-Losing AGB Stars
We present ground-based mid-infrared imaging for 27 M-, S- and C-type
Asymptotic Giant Branch (AGB) stars. The data are compared with those of the
database available thanks to the IRAS, ISO, MSX and 2MASS catalogues. Our goal
is to establish relations between the IR colors, the effective temperature
, the luminosity and the mass loss rate , for improving
the effectiveness of AGB modelling. Bolometric (absolute) magnitudes are
obtained through distance compilations, and by applying previously-derived
bolometric corrections; the variability is also studied, using data accumulated
since the IRAS epoch. The main results are: i) Values of and for C
stars fit relations previously established by us, with Miras being on average
more evolved and mass losing than Semiregulars. ii) Moderate IR excesses (as
compared to evolutionary tracks) are found for S and M stars in our sample:
they are confirmed to originate from the dusty circumstellar environment. iii)
A larger reddening characterizes C-rich Miras and post-AGBs. In this case, part
of the excess is due to AGB models overestimating for C-stars, as a
consequence of the lack of suitable molecular opacities. This has a large
effect on the colors of C-rich sources and sometimes disentangling the
photospheric and circumstellar contributions is difficult; better model
atmospheres should be used in stellar evolutionary codes for C stars. iv) The
presence of a long-term variability at mid-IR wavelengths seems to be limited
to sources with maximum emission in the 8 -- 20 m region, usually Mira
variables (1/3 of our sample). Most Semiregular and post-AGB stars studied here
remained remarkably constant in mid-IR over the last twenty years.Comment: Accepted for publication in the Astronomical Journal - 35 pages (in
preprint), 9 figures, 5 table
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