1,725 research outputs found
Structure and assembly of desmosome junctions - biosynthesis, processing, and transport of the major protein and glycoprotein components in cultured epithelial-cells
A direct image of the obscuring disk surrounding an active galactic nucleus
Active galactic nuclei (AGN) are generally accepted to be powered by the
release of gravitational energy in a compact accretion disk surrounding a
massive black hole. Such disks are also necessary to collimate powerful radio
jets seen in some AGN. The unifying classification schemes for AGN further
propose that differences in their appearance can be attributed to the opacity
of the accreting material, which may obstruct our view of the central region of
some systems. The popular model for the obscuring medium is a parsec-scale disk
of dense molecular gas, although evidence for such disks has been mostly
indirect, as their angular size is much smaller than the resolution of
conventional telescopes. Here we report the first direct images of a pc-scale
disk of ionised gas within the nucleus of NGC 1068, the archetype of obscured
AGN. The disk is viewed nearly edge-on, and individual clouds within the
ionised disk are opaque to high-energy radiation, consistent with the unifying
classification scheme. In projection, the disk and AGN axes align, from which
we infer that the ionised gas disk traces the outer regions of the long-sought
inner accretion disk.Comment: 14 pages, LaTeX, PSfig, to appear in Nature. also available at
http://hethp.mpe-garching.mpg.de/Preprint
Monte Carlo Simulations of Star Clusters - VII. The globular cluster 47 Tuc
We describe Monte Carlo models for the dynamical evolution of the massive
globular cluster 47 Tuc (NGC 104). The code includes treatments of two-body
relaxation, most kinds of three- and four-body interactions involving
primordial binaries and those formed dynamically, the Galactic tide, and the
internal evolution of both single and binary stars. We arrive at a set of
initial parameters for the cluster which, after 12Gyr of evolution, gives a
model with a fairly satisfactory match to surface brightness and density
profiles, the velocity dispersion profile, the luminosity function in two
fields, and the acceleration of pulsars. Our models appear to require a
relatively steep initial mass function for stars above about turnoff, with an
index of about 2.8 (where the Salpeter mass function has an index of 2.35), and
a relatively flat initial mass function (index about 0.4) for the lower main
sequence. According to the model, the current mass is estimated at 0.9 million
solar masses, of which about 34% consists of remnants. We find that primordial
binaries are gradually taking over from mass loss by stellar evolution as the
main dynamical driver of the core. Despite the high concentration of the
cluster, core collapse will take at least another 20Gyr.Comment: 16 pages, 16 figures, revised version submitted to MNRA
Physical activity attitudes, intentions and behaviour among 18-25 year olds: a mixed method study
Peer reviewedPublisher PD
Visual perceptual load induces inattentional deafness
In this article, we establish a new phenomenon of “inattentional deafness” and highlight the level of load on visual attention as a critical determinant of this phenomenon. In three experiments, we modified an inattentional blindness paradigm to assess inattentional deafness. Participants made either a low- or high-load visual discrimination concerning a cross shape (respectively, a discrimination of line color or of line length with a subtle length difference). A brief pure tone was presented simultaneously with the visual task display on a final trial. Failures to notice the presence of this tone (i.e., inattentional deafness) reached a rate of 79% in the high-visual-load condition, significantly more than in the low-load condition. These findings establish the phenomenon of inattentional deafness under visual load, thereby extending the load theory of attention (e.g., Lavie, Journal of Experimental Psychology. Human Perception and Performance, 25, 596–616, 1995) to address the cross-modal effects of visual perceptual load
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