257 research outputs found
The isolated interacting galaxy pair NGC 5426/27 (Arp 271)
We present H alpha observations of the isolated interacting galaxy pair NGC
5426/27 using the scanning Fabry-Perot interferometer PUMA. The velocity field,
various kinematical parameters and rotation curve for each galaxy were derived.
The FWHM map and the residual velocities map were also computed to study the
role of non-circular motions of the gas. Most of these motions can be
associated with the presence of spiral arms and structure such as central bars.
We found a small bar-like structure in NGC 5426, a distorted velocity field for
NGC 5427 and a bridge-like feature between both galaxies which seems to be
associated with NGC 5426. Using the observed rotation curves, a range of
possible masses was computed for each galaxy. These were compared with the
orbital mass of the pair derived from the relative motion of the participants.
The rotation curve of each galaxy was also used to fit different mass
distribution models considering the most common theoretical dark halo models.
An analysis of the interaction process is presented and a possible 3D scenario
for this encounter is also suggested.Comment: 27 pages, 15 figures, to be published in Astronomy & Astrophysic
The Interaction of Supernova Remnant G357.7+0.3 with the Interstellar Medium
The supernova remnant (SNR) G357.7+0.3 appears to have caused considerable
shredding of the local interstellar medium (ISM), leading to the formation of
multiple cloud fragments having bright rims and cometary structures. We
investigate five of these regions using mid-infrared (MIR) imaging and
photometry deriving from the Spitzer Space Telescope (SST), as well as
photometry deriving from the 2MASS near-infrared all sky survey, the Mid-Course
Science Experiment (MSX), and the Multiband Imaging Photometer for Spitzer
(MIPSGAL) survey of the Galactic plane. It is noted that two of the rims show
evidence for emission by shock excited H2 transitions, whilst the centres of
the clouds also show evidence for dark extinction cores, observed in silhouette
against the bright emission rims. Levels of extinction for these cores are
determined to be of order AV ~ 17-26 mag, whilst densities n(HI) are of order ~
10^4 cm^(-3), and masses in the region of ~40-100 Msun. It is shown that the
wavelength dependence of extinction is probably similar to that of Cardelli et
al. and Martin & Whittet, but differs from the MIR extinction trends of
Indebetouw et al. The distributions of Class I young stellar objects (YSOs)
implies that many of them are physically associated with the clouds, and were
likely formed as a result of interaction between the clouds and SN winds. A
determination of the spectral energy distributions (SEDs) of these stars,
together with 2-D radiative transfer modelling of their continua is used to
place constraints upon their properties.Comment: The paper contains 18 figures and 2 table
Sensibilización a hongos anemófilos en trabajadores del Archivo y Biblioteca de la Universidad de La Habana
Introducción: En Cuba no se conoce la prevalencia de sensibilización a hongos anemófilos en trabajadores(as) de archivos y bibliotecas. Objetivo: Determinar la frecuencia de sensibilización a aeroalérgenos micóticos y la prevalencia de enfermedades alérgicas en trabajadores(as) del Archivo y la Biblioteca de la Universidad de La Habana. Métodos: Estudio observacional, y transversal, que incluyó 53 trabajadores(as). Se les realizó historia clínica y pruebas cutáneas por punción (PCP) con extractos de hongos anemófilos. Se analizó: edad, sexo, resultados de PCP, tamaño del habón y área de trabajo. Se empleó X2 para comparar frecuencias de sensibilización y t de student para el tamaño del habón, con significación estadística si p < 0,05. Resultados: El 64 % de los trabajadores(as) del archivo y el 33 % de la biblioteca estuvieron al menos sensibilizados a un hongo. La especie Aspergillus níger predominó con el mayor porcentaje de sensibilización (20,4 %). La rinitis alérgica fue la enfermedad más frecuente en estos trabajadores(as), 23 casos (43,3 %). La combinación de asma y rinitis se encontró en 9 trabajadores(as). En el 32,1 % de los casos (9) con enfermedad alérgica respiratoria se encontró positividad, al menos a un hongo anemófilo. Los mayores tamaños del habón se encontraron en los trabajadores(as) del archivo, especialmente para Alternaria alternata (3,46 mm) y Penicillium notatum (3,43 mm). Conclusiones: Existe elevada prevalencia de sensibilización a hongos anemófilos en los trabajadores(as) investigados. Son necesarios más estudios que investiguen la sensibilización a estas y otras especies fúngicas en este entorno laboral
Reduced levels of intracellular calcium releasing in spermatozoa from asthenozoospermic patients
<p>Abstract</p> <p>Background</p> <p>Asthenozoospermia is one of the most common findings present in infertile males characterized by reduced or absent sperm motility, but its aetiology remains unknown in most cases. In addition, calcium is one of the most important ions regulating sperm motility. In this study we have investigated the progesterone-evoked intracellular calcium signal in ejaculated spermatozoa from men with normospermia or asthenozoospermia.</p> <p>Methods</p> <p>Human ejaculates were obtained from healthy volunteers and asthenospermic men by masturbation after 4–5 days of abstinence. For determination of cytosolic free calcium concentration, spermatozoa were loaded with the fluorescent ratiometric calcium indicator Fura-2.</p> <p>Results</p> <p>Treatment of spermatozoa from normospermic men with 20 micromolar progesterone plus 1 micromolar thapsigargin in a calcium free medium induced a typical transient increase in cytosolic free calcium concentration due to calcium release from internal stores. Similar results were obtained when spermatozoa were stimulated with progesterone alone. Subsequent addition of calcium to the external medium evoked a sustained elevation in cytosolic free calcium concentration indicative of capacitative calcium entry. However, when progesterone plus thapsigargin were administered to spermatozoa from patients with asthenozoospermia, calcium signal and subsequent calcium entry was much smaller compared to normospermic patients. As expected, pretreatment of normospermic spermatozoa with both the anti-progesterone receptor c262 antibody and with progesterone receptor antagonist RU-38486 decreased the calcium release induced by progesterone. Treatment of spermatozoa with cytochalasin D or jasplakinolide decreased the calcium entry evoked by depletion of internal calcium stores in normospermic patients, whereas these treatments proved to be ineffective at modifying the calcium entry in patients with asthenozoospermia.</p> <p>Conclusion</p> <p>Our results suggest that spermatozoa from asthenozoospermic patients present a reduced responsiveness to progesterone.</p
Operations of and Future Plans for the Pierre Auger Observatory
Technical reports on operations and features of the Pierre Auger Observatory,
including ongoing and planned enhancements and the status of the future
northern hemisphere portion of the Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand events above 10^18 eV observed by the fluorescence detector of the
Pierre Auger Observatory in coincidence with at least one surface detector
station are selected for the analysis. The average shower maximum was found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
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