5,661 research outputs found
On the bar pattern speed determination of NGC 3367
An important dynamic parameter of barred galaxies is the bar pattern speed.
Among several methods that are used for the determination of the pattern speed
the Tremaine-Weinberg method has the advantage of model independency and
accuracy. In this work we apply the method to a simulated bar including gas
dynamics and study the effect of 2D spectroscopy data quality on robustness of
the method. We added a white noise and a Gaussian random field to the data and
measured the corresponding errors in the pattern speed. We found that a signal
to noise ratio in surface density ~5 introduces errors of ~20% for the Gaussian
noise, while for the white noise the corresponding errors reach ~50%. At the
same time the velocity field is less sensitive to contamination. On the basis
of the performed study we applied the method to the NGC 3367 spiral galaxy
using H{\alpha} Fabry-Perot interferometry data. We found for the pattern speed
43 \pm 6 km/s/kpc for this galaxy.Comment: Accepted for publication in ApJ. 16 pages, 16 figure
Double Inverse Stochastic Resonance with Dynamic Synapses
We investigate the behavior of a model neuron that receives a
biophysically-realistic noisy post-synaptic current based on uncorrelated
spiking activity from a large number of afferents. We show that, with static
synapses, such noise can give rise to inverse stochastic resonance (ISR) as a
function of the presynaptic firing rate. We compare this to the case with
dynamic synapses that feature short-term synaptic plasticity, and show that the
interval of presynaptic firing rate over which ISR exists can be extended or
diminished. We consider both short-term depression and facilitation.
Interestingly, we find that a double inverse stochastic resonance (DISR), with
two distinct wells centered at different presynaptic firing rates, can appear.Comment: 12 pages, 7 figure
Salmonella enterica: a review or the trilogy agent, host and environment and its importance in Chile
Indexación: Web of Science; Scopus; Scielo.Salmonella enterica es uno de los principales patógenos transmitidos por los alimentos en el mundo, siendo la primera causa de brotes de intoxicación alimentaria en Chile. A pesar de todos los esfuerzos de control y prevención desplegados, la incidencia en las personas se ha mantenido alta, por lo que diversos factores podrían estar influenciando el comportamiento epidemiológico de esta infección. El objetivo de esta revisión es describir factores referidos tanto al agente biológico, al hospedero humano y al medio ambiente, que podrían tener mayor trascendencia en Chile. De esta forma, se infieren ámbitos prioritarios para la investigación de S. enterica, que permitan entender su dispersión en la naturaleza y su éxito como patógeno de un amplio rango de hospederos. A futuro, el mayor conocimiento de estos determinantes facilitará la implementación de estrategias de bioseguridad y vigilancia para la prevención de la enfermedad en las personas y en los animales.Salmonella enterica is a major foodborne pathogen worldwide, being the main cause of outbreaks by food consumption in Chile. Despite all efforts deployed for control and prevention, the high incidence in people still persists, with several factors that could be influencing the epidemiological behavior of this infection. The objective of this review is to identify these factors belonging to the biological agent, the human host and the environment, which probably have a greater importance in Chile. Thus, priority areas for research of S. enterica are inferred, which hopefully will help to understand its spread in nature and its success as a wide host range pathogen. In the future, increased understanding of these determinants will facilitate the implementation of biosecurity and surveillance strategies for the prevention of disease in people and animals.http://ref.scielo.org/kz75k
Fabry Perot Halpha Observations of the Barred Spiral NGC 3367
We report the gross properties of the velocity field of the barred spiral
galaxy NGC 3367. The following values were found: inclination with respect to
the plane of the sky, i=30 deg; position angle (PA) of receding semi major axis
PA=51 and systemic velocity V(sys)=3032 km/s. Large velocity dispersion are
observed of upt o 120 km/s in the nuclear region, of up to 70 km/s near the
eastern bright sources just beyond the edge of the stellar bar where three
spiral arms seem to start and in the western bright sources at about 10 kpc.
Deviations from normal circular velocities are observed from all the disk but
mainly from the semi circle formed by the string of south western Halpha
sources. An estimate of the dynamical mass is M(dyn)=2x10^11 Msolar.Comment: Accepted to be published in May 2001 issue in the A.J. 19 pages, 7
figure
U B V R I Photometry of Stellar Structures throughout the Disk of the Barred Galaxy NGC 3367
We report new detailed surface U, B, V, R, and I photometry of 81 stellar
structures in the disk of the barred galaxy NGC 3367. The images show many
different structures indicating that star formation is going on in the most
part of the disk. NGC 3367 is known to have a very high concentration of
molecular gas distribution in the central regions of the galaxy and bipolar
synchrotron emission from the nucleus with two lobes (at 6 kpc) forming a
triple structure similar to a radio galaxy. We have determined the U, B, V, R,
and I magnitudes and U - B, B - V, U - V, and V - I colors for the central
region (nucleus), a region which includes supernovae 2003 AA, and 79 star
associations throughout NGC 3367. Estimation of ages of star associations is
very difficult due to several factors, among them: filling factor, metallicity,
spatial distribution of each structure and the fact that we estimated the
magnitudes with a circular aperture of 16 pixels in diameter, equivalent to
kpc. However, if the colors derived for NGC 3367 were similar to
the colors expected of star clusters with theoretical evolutionary star tracks
developed for the LMC and had a similar metallicity, NGC 3367 show 51 percent
of the observed structures with age type SWB I (few tens of Myrs), with seven
sources outside the bright surface brightness visible disk of NGC 3367.Comment: Accepted for publication (abr 2007) in The Astronomical Journal (July
2007 issue
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