13,488 research outputs found
Nous avanços en la guerra contra els fongs
La esporotricosi és un malaltia causada pel fong Sporothix schenckii. El fong penetra en la pell a través de petites ferides i pot arribar a estendre's des de la pell als ganglis linfáticos o a les vísceres. Encara que aquest fong existeix en tot el món, la malaltia que provoca és més freqüent en Centre i Suramérica i a Àfrica. Un nou estudi permet conèixer millor l'efectivitat dels antifúngicos disponibles en la lluita contra aquesta malaltia.La esporotricosis es un enfermedad causada por el hongo Sporothix schenckii. El hongo penetra en la piel a través de pequeñas heridas y puede llegar a extenderse desde la piel a los ganglios linfáticos o a las vísceras. Aunque este hongo existe en todo el mundo, la enfermedad que provoca es más frecuente en Centro y Suramérica y en África. Un nuevo estudio permite conocer mejor la efectividad de los antifúngicos disponibles en la lucha contra esta enfermedad
The Gould's Belt distance survey
Very Long Baseline Interferometry (VLBI) observations can provide the
position of compact radio sources with an accuracy of order 50
micro-arcseconds. This is sufficient to measure the trigonometric parallax and
proper motions of any object within 500 pc of the Sun to better than a few
percent. Because they are magnetically active, young stars are often associated
with compact radio emission detectable using VLBI techniques. Here we will show
how VLBI observations have already constrained the distance to the most often
studied nearby regions of star-formation (Taurus, Ophiuchus, Orion, etc.) and
have started to provide information on their internal structure and kinematics.
We will then briefly describe a large project (called The Gould's Belt Distance
Survey) designed to provide a detailed view of star-formation in the Solar
neighborhood using VLBI observations.Comment: To be published in the Revista Mexicana de Astronomia y Astrofisica
(Serie de Conferencias
A Chandra observation of the millisecond X-ray pulsar IGR J17511-3057
IGR J17511-3057 is a low mass X-ray binary hosting a neutron star and is one
of the few accreting millisecond X-ray pulsars with X-ray bursts. We report on
a 20ksec Chandra grating observation of IGR J17511-3057, performed on 2009
September 22. We determine the most accurate X-ray position of IGR J17511-3057,
alpha(J2000) = 17h 51m 08.66s, delta(J2000) = -30deg 57' 41.0" (90% uncertainty
of 0.6"). During the observation, a ~54sec long type-I X-ray burst is detected.
The persistent (non-burst) emission has an absorbed 0.5-8keV luminosity of 1.7
x 10^36 erg/sec (at 6.9kpc) and can be well described by a thermal
Comptonization model of soft, ~0.6keV, seed photons up-scattered by a hot
corona. The type-I X-ray burst spectrum, with average luminosity over the 54sec
duration L(0.5-8keV)=1.6 x 10^37 erg/sec, can be well described by a blackbody
with kT_(bb)~1.6keV and R_(bb)~5km. While an evolution in temperature of the
blackbody can be appreciated throughout the burst (average peak
kT_(bb)=2.5(+0.8/-0.4)keV to tail kT_(bb)=1.3(+0.2/-0.1)keV), the relative
emitting surface shows no evolution. The overall persistent and type-I burst
properties observed during the Chandra observation are consistent with what was
previously reported during the 2009 outburst of IGR J17511-3057.Comment: 6 pages, 4 figures, accepted for publication in ApJ (2012-06-08
VLBA determination of the distance to nearby star-forming regions II. Hubble 4 and HDE 283572 in Taurus
The non-thermal 3.6 cm radio continuum emission from the naked T Tauri stars
Hubble 4 and HDE 283572 in Taurus has been observed with the Very Long Baseline
Array (VLBA) at 6 epochs between September 2004 and December 2005 with a
typical separation between successive observations of 3 months. Thanks to the
remarkably accurate astrometry delivered by the VLBA, the trajectory described
by both stars on the plane of the sky could be traced very precisely, and
modeled as the superposition of their trigonometric parallax and uniform proper
motion. The best fits yield distances to Hubble 4 and HDE 283572 of 132.8 +/-
0.5 and 128.5 +/- 0.6 pc, respectively. Combining these results with the other
two existing VLBI distance determinations in Taurus, we estimate the mean
distance to the Taurus association to be 137 pc with a dispersion (most
probably reflecting the depth of the complex) of about 20 pc.Comment: 21 pages, 4 figues, accepted in ApJ (Dec 20, 2007 issue
The largest oxigen bearing organic molecule repository
We present the first detection of complex aldehydes and isomers in three
typical molecular clouds located within 200pc of the center of our Galaxy.
We find very large abundances of these complex organic molecules (COMs) in
the central molecular zone (CMZ), which we attribute to the ejection of COMs
from grain mantles by shocks. The relative abundances of the different COMs
with respect to that of CH3OH are strikingly similar for the three sources,
located in very different environments in the CMZ. The similar relative
abundances point toward a unique grain mantle composition in the CMZ. Studying
the Galactic center clouds and objects in the Galactic disk having large
abundances of COMs, we find that more saturated molecules are more abundant
than the non-saturated ones. We also find differences between the relative
abundance between COMs in the CMZ and the Galactic disk, suggesting different
chemical histories of the grain mantles between the two regions in the Galaxy
for the complex aldehydes. Different possibilities for the grain chemistry on
the icy mantles in the GC clouds are briefly discussed. Cosmic rays can play an
important role in the grain chemistry. With these new detections, the molecular
clouds in the Galactic center appear to be one of the best laboratories for
studying the formation of COMs in the Galaxy.Comment: 20 pages, 4 figures, accepted in Ap
The dust-enshrouded microquasar candidate AX J1639.0-4642 = IGR J16393-4643
We present a multiwavelength study of the field containing the unidentified
X-ray source AX J1639.0-4642, discovered with the ASCA observatory and recently
detected with the IBIS telescope, onboard the INTEGRAL satellite, dubbed IGR
J16393-4643. The huge hydrogen column density towards the source, the hard
spectral index in the 0.7-10 keV band and its flux variability suggest that the
source is a High Mass X-ray Binary (HMXB) enshrouded by dust. Our search
reveals the presence of a non-thermal radio counterpart within the X-ray error
box. After a study of the broadband emission from X-rays to the radio domain,
we propose that AX J1639.0-4642 is a dust-enshrouded Microquasar (MQ)
candidate. In addition, the X-ray source is well within the 95% location
contour of the unidentified gamma-ray source 3EG J1639-4702. The main
properties of AX J1639.0-4642/3EG J1639-4702 are consistent with those of two
other MQs previously proposed to display high-energy gamma-ray emission.Comment: 7 pages, 5 figures. Accepted for publication in A&A. Title and
discussion on the possible NIR counterpart have been modifie
- …