1,967 research outputs found
Searching and fixating: scale-invariance vs. characteristic timescales in attentional processes
In an experiment involving semantic search, the visual movements of sample
populations subjected to visual and aural input were tracked in a taskless
paradigm. The probability distributions of saccades and fixations were obtained
and analyzed. Scale-invariance was observed in the saccadic distributions,
while the fixation distributions revealed the presence of a characteristic
(attentional) time scale for literate subjects. A detailed analysis of our
results suggests that saccadic eye motions are an example of Levy, rather than
Brownian, dynamics.Comment: Accepted to Europhysics Letters (2011
Near-infrared photometry of isolated spirals with and without an AGN. I: The Data
We present infrared imaging data in the J and K' bands obtained for 18 active
spiral galaxies, together with 11 non active galaxies taken as a control
sample. All of them were chosen to satisfy well defined isolation criteria so
that the observed properties are not related to gravitational interaction. For
each object we give: the image in the K' band, the sharp-divided image
(obtained by dividing the observed image by a filtered one), the difference
image (obtained by subtracting a model to the observed one), the color J-K'
image, the ellipticity and position angle profiles, the surface brightness
profiles in J and K', their fits by bulge+disk models and the color gradient.
We have found that four (one) active (control) galaxies previously classified
as non-barred turn out to have bars when observed in the near-infrared. One of
these four galaxies (UGC 1395) also harbours a secondary bar. For 15 (9 active,
6 control) out of 24 (14 active, 10 control) of the optically classified barred
galaxies (SB or SX) we find that a secondary bar (or a disk, a lense or an
elongated ring) is present. The work presented here is part of a large program
(DEGAS) aimed at finding whether there are differences between active and non
active galaxies in the properties of their central regions that could be
connected with the onset of nuclear activity.Comment: Accepted for publication in Astronomy & Astrophysics Supplement
Serie
Circumnuclear structure and kinematics in the active galaxy NGC 6951
A study is presented of the central structure and kinematics of the galaxy
NGC 6951, by means of broad band B'IJK images and high resolution high
dispersion longslit spectroscopy, together with archival HST WFPC2 V and
NICMOS2 J and H images. We find that there is evidence of two modes of star
formation, in bursts and continuously. The equivalent width of the CaII triplet
absorption lines show that, in the metal rich central region, the continuum is
dominated by a population of red supergiants. The gaseous and stellar
kinematics along three slit position angles, suggest the existence of a
hierarchy of disks within disks, whose dynamics are decoupled at the two ILRs,
that we find at 180 pc and at 1100 pc. This is supported by the structure seen
in the high resolution HST images. The nucleus is spatially resolved within a
radius of 1.5 arcsec, just inside the innermost ILR. Outside the iILR, the
stellar CaT velocity profile is resolved into two components, associated with
the bar and the disk. Several results indicate that this is a dynamically old
system. It is thus possible that a nuclear bar has existed in NGC 6951 that
drove the gas towards the nucleus, as in the bars within bars scenario, but
that this bar has already dissolved by the gas accumulated within the
circumnuclear region. We discuss the possibility that the kinematical component
inside the iILR could be due to a nuclear outflow produced by the combined
effects of SN and SN remnants, or to a nuclear disk, as in the disk within disk
scenario that we propose for the fueling of the AGN in NGC 6951.Comment: 14 pages, 16 figures. Accepted for publication in Astronomy and
Astrophysics. High resolution images in
http://www.iaa.es/~eperez/research/degas.htm
Active galactic nuclei synapses: X-ray versus optical classifications using artificial neural networks
(Abridged) Many classes of active galactic nuclei (AGN) have been defined
entirely throughout optical wavelengths while the X-ray spectra have been very
useful to investigate their inner regions. However, optical and X-ray results
show many discrepancies that have not been fully understood yet. The aim of
this paper is to study the "synapses" between the X-ray and optical
classifications.
For the first time, the new EFLUXER task allowed us to analyse broad band
X-ray spectra of emission line nuclei (ELN) without any prior spectral fitting
using artificial neural networks (ANNs). Our sample comprises 162 XMM-Newton/pn
spectra of 90 local ELN in the Palomar sample. It includes starbursts (SB),
transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2).
The ANNs are 90% efficient at classifying the trained classes S1, S1.8, and
SB. The S1 and S1.8 classes show a wide range of S1- and S1.8-like components.
We suggest that this is related to a large degree of obscuration at X-rays. The
S1, S1.8, S2, L1.8, L2/T2/SB-AGN (SB with indications of AGN), and SB classes
have similar average X-ray spectra within each class, but these average spectra
can be distinguished from class to class. The S2 (L1.8) class is linked to the
S1.8 (S1) class with larger SB-like component than the S1.8 (S1) class. The L2,
T2, and SB-AGN classes conform a class in the X-rays similar to the S2 class
albeit with larger fractions of SB-like component. This SB-like component is
the contribution of the star-formation in the host galaxy, which is large when
the AGN is weak. An AGN-like component seems to be present in the vast majority
of the ELN, attending to the non-negligible fraction of S1-like or S1.8-like
component. This trained ANN could be used to infer optical properties from
X-ray spectra in surveys like eRosita.Comment: 15 pages, 7 figures, accepted for publication in A&A. Appendix B only
in the full version of the paper here:
https://dl.dropboxusercontent.com/u/3484086/AGNSynapsis_OGM_online.pd
Lineamiento estategico para la formulacion de un plan de desarrollo turistico para la comuna de Curepto, Region del Maule
184 p.El propósito de esta investigación es diseñar lineamientos estratégicos para la formulación de un Plan de Desarrollo Turístico, para permitir a la comunidad mostrar todos sus atributos turísticos (Atractivos, Actividades, Planta, Infraestructura, entre otros) a nivel comunal, regional y nacional, a fin de aumentar el flujo de turistas que recibe la comuna cada año, logrando impactos positivos tanto a nivel económico como sociocultural. Para lograr este propósito, la información se recabó tanto de fuentes primarias como secundarias. Se realizó una revisión bibliográfica sobre todos los temas relacionados con un Plan de Desarrollo Turístico, de Curepto, y con el tema turismo en general. Esta revisión bibliográfica ayudó a determinar el público objetivo, identificando la demanda potencial en términos cualitativos, obteniendo conclusiones importantes sobre todo de los distintos gustos y preferencias que tienen las personas de los distintos estratos socioeconómicos al momento de vacacionar. En tanto las fuentes primarias fueron compuestas por las siguientes actividades: grupos foco, entrevistas en profundidad, entrevistas con informantes claves, observación directa y encuestas. La información que se obtuvo permitió conocer lo que piensan los cureptanos sobre el pueblo y cuales son sus proyecciones en el tema del turismo. Se entrevistaron actores como las autoridades locales, microempresarios de la comuna y a residentes, además de una entrevista con la encargada del Departamento de Planificación de la oficina de Sernatur de la Región del Maule, y con el Director Regional de Sernatur. Así se estableció la realidad que vive Curepto en el tema Turismo, sus principales falencias, limitaciones, fortalezas y oportunidades. Las principales conclusiones sobre el estudio, apuntan a que Curepto posee un potencial turístico que está en desarrollo en el turismo. Pero existe un gran déficit en la planta turística, por lo que se deben hacer muchos esfuerzos para introducir y mejorar el servicio y ofrecer lugares atractivos para el visitante, más cómodos, acogedores y con sólida infraestructura vial. Dado lo anterior se formula un lineamiento estratégico de Pladetur que servirá de gran apoyo para el municipio y la comunidad en general. Finalmente, y como resultado de todos los estudios realizados, se concluye que el turismo forma parte importante y fundamental de una futura gran actividad económica para la comuna de Curepto
The X-ray nature of the LINER nuclear sources
The analysis of the X-ray data for a sample of 51 LINER nuclei with available
X-ray Chandra imaging is reported. Our aim was to investigate the physical
mechanisms which power LINER nuclear activity. The use of multiwavelenght
information at radio, UV, optical HST and X-ray lead us to conclude that at
least 60% of the LINERs are hosting a low luminosity AGN in their nuclei. This
percentage may be even higher if the Compton-thickness of some nuclei (mostly
with SB-like hard X-ray morphology) is confirmed.Comment: Conference proceedings to appear in "The Central Engine of Active
Galactic Nuclei", ed. L.C. Ho and J.-M. Wang (San Francisco: ASP
Intracellular trafficking and cellular uptake mechanism of PHBV nanoparticles for targeted delivery in epithelial cell lines
Indexación: Web of Science; Scopus; Scielo.Background: Nanotechnology is a science that involves imaging, measurement, modeling and a manipulation of matter at the nanometric scale. One application of this technology is drug delivery systems based on nanoparticles obtained from natural or synthetic sources. An example of these systems is synthetized from poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which is a biodegradable, biocompatible and a low production cost polymer. The aim of this work was to investigate the uptake mechanism of PHBV nanoparticles in two different epithelial cell lines (HeLa and SKOV-3).
Results: As a first step, we characterized size, shape and surface charge of nanoparticles using dynamic light scattering and transmission electron microscopy. Intracellular incorporation was evaluated through flow cytometry and fluorescence microscopy using intracellular markers. We concluded that cellular uptake mechanism is carried out in a time, concentration and energy dependent way. Our results showed that nanoparticle uptake displays a cell-specific pattern, since we have observed different colocalization in two different cell lines. In HeLa (Cervical cancer cells) this process may occur via classical endocytosis pathway and some internalization via caveolin-dependent was also observed, whereas in SKOV-3 (Ovarian cancer cells) these patterns were not observed. Rearrangement of actin filaments showed differential nanoparticle internalization patterns for HeLa and SKOV-3. Additionally, final fate of nanoparticles was also determined, showing that in both cell lines, nanoparticles ended up in lysosomes but at different times, where they are finally degraded, thereby releasing their contents.
Conclusions: Our results, provide novel insight about PHBV nanoparticles internalization suggesting that for develop a proper drug delivery system is critical understand the uptake mechanism.https://jnanobiotechnology.biomedcentral.com/articles/10.1186/s12951-016-0241-
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