203 research outputs found
Age, puberty and attractiveness judgments in adolescents
Previous work has suggested that judgments of the attractiveness of some facial and vocal features change during adolescence. Here, over 70 Czech adolescents aged 12–14 made forced-choice attractivenessjudgments on adolescent faces manipulated in symmetry, averageness and femininity, and on adolescent opposite-sex voices manipulated in fundamental frequency (perceived as pitch), and completed questionnaires on pubertal development. Consistent with typical adult judgments, adolescents selected the symmetric, average and feminine male and female faces as more attractive significantly more often than the asymmetric, non-average and masculine faces respectively. Moreover, preferences for symmetric faces were positively associated with adolescents’ age and stage of pubertal development. Unexpectedly, voice pitch did not significantly influence adolescents’ attractivenessjudgments. Collectively, these findings present new evidence using refined methodology that adolescent development is related to variation in attractivenessjudgments
Size of the Vela Pulsar's Radio Emission Region: 500 km
We use interstellar scattering of the Vela pulsar to determine the size of
its emission region. From interferometric phase variations on short baselines,
we find that radio-wave scattering broadens the source by 3.4+/-0.3
milliarcseconds along the major axis at position angle 81+/-3 degrees. The
ratio of minor axis to major axis is 0.51+/-0.03. Comparison of angular and
temporal broadening indicates that the scattering material lies in the Vela-X
supernova remnant surrounding the pulsar. From the modulation of the pulsar's
scintillation on very short baselines, we infer a size of 500 km for the
pulsar's emission region. We suggest that radio-wave refraction within the
pulsar's magnetosphere may plausibly explain this size.Comment: 14 pages, includes 2 figures. Also available at:
http://charm.physics.ucsb.edu:80/people/cgwinn/cgwinn_group/cgwinn_group.htm
The Pearson-Readhead Survey of Compact Extragalactic Radio Sources From Space. I. The Images
We present images from a space-VLBI survey using the facilities of the VLBI
Space Observatory Programme (VSOP), drawing our sample from the well-studied
Pearson-Readhead survey of extragalactic radio sources. Our survey has taken
advantage of long space-VLBI baselines and large arrays of ground antennas,
such as the Very Long Baseline Array and European VLBI Network, to obtain high
resolution images of 27 active galactic nuclei, and to measure the core
brightness temperatures of these sources more accurately than is possible from
the ground. A detailed analysis of the source properties is given in
accompanying papers. We have also performed an extensive series of simulations
to investigate the errors in VSOP images caused by the relatively large holes
in the (u,v) plane when sources are observed near the orbit normal direction.
We find that while the nominal dynamic range (defined as the ratio of map peak
to off-source error) often exceeds 1000:1, the true dynamic range (map peak to
on-source error) is only about 30:1 for relatively complex core-jet sources.
For sources dominated by a strong point source, this value rises to
approximately 100:1. We find the true dynamic range to be a relatively weak
function of the difference in position angle (PA) between the jet PA and (u,v)
coverage major axis PA. For low signal-to-noise regions typically located down
the jet away from the core, large errors can occur, causing spurious features
in VSOP images that should be interpreted with caution.Comment: 26 pages, 16 figures. Accepted for publication in the Astrophysical
Journal. A version with higher resolution figures (7 Mb) can be found at
http://sgra.jpl.nasa.gov/html_lister/pr_papers/map_paper.p
A note on graded Yang-Baxter solutions as braid-monoid invariants
We construct two solutions of the graded Yang-Baxter equation by
using the algebraic braid-monoid approach. The factorizable S-matrix
interpretation of these solutions is also discussed.Comment: 7 pages, UFSCARF-TH-94-1
A longitudinal study of adolescents’ judgments of the attractiveness of facial symmetry, averageness and sexual dimorphism
Adolescents have been found to differ by age in their attraction to facial symmetry, averageness, and sexual dimorphism. However, it has not been demonstrated that attraction to these facial characters changes over time as a consequence of age-linked development. We aimed to extend previous cross-sectional findings by examining whether facial attractiveness judgments change over time during adolescence as a consequence of increasing age, in a within-subjects study of two cohorts of adolescents aged 11–16. Consistent with previous findings, we find that adolescents (often particularly females) judged faces with increased averageness, symmetry and femininity to be more attractive than original, asymmetric and masculine faces, respectively. However, we do not find longitudinal changes in face preference judgments across the course of a year, leading us to question the extent to which some of the previously reported differences in facial attractiveness judgments between younger and older adolescents were due to age-linked changes
Decoherence-Free Subspaces for Multiple-Qubit Errors: (I) Characterization
Coherence in an open quantum system is degraded through its interaction with
a bath. This decoherence can be avoided by restricting the dynamics of the
system to special decoherence-free subspaces. These subspaces are usually
constructed under the assumption of spatially symmetric system-bath coupling.
Here we show that decoherence-free subspaces may appear without spatial
symmetry. Instead, we consider a model of system-bath interactions in which to
first order only multiple-qubit coupling to the bath is present, with
single-qubit system-bath coupling absent. We derive necessary and sufficient
conditions for the appearance of decoherence-free states in this model, and
give a number of examples. In a sequel paper we show how to perform universal
and fault tolerant quantum computation on the decoherence-free subspaces
considered in this paper.Comment: 18 pages, no figures. Major changes. Section on universal fault
tolerant computation removed. This section contained a crucial error. A new
paper [quant-ph/0007013] presents the correct analysi
The 74MHz System on the Very Large Array
The Naval Research Laboratory and the National Radio Astronomy Observatory
completed implementation of a low frequency capability on the VLA at 73.8 MHz
in 1998. This frequency band offers unprecedented sensitivity (~25 mJy/beam)
and resolution (~25 arcsec) for low-frequency observations. We review the
hardware, the calibration and imaging strategies, comparing them to those at
higher frequencies, including aspects of interference excision and wide-field
imaging. Ionospheric phase fluctuations pose the major difficulty in
calibrating the array. Over restricted fields of view or at times of extremely
quiescent ionospheric ``weather'', an angle-invariant calibration strategy can
be used. In this approach a single phase correction is devised for each
antenna, typically via self-calibration. Over larger fields of view or at times
of more normal ionospheric ``weather'' when the ionospheric isoplanatic patch
size is smaller than the field of view, we adopt a field-based strategy in
which the phase correction depends upon location within the field of view. This
second calibration strategy was implemented by modeling the ionosphere above
the array using Zernike polynomials. Images of 3C sources of moderate strength
are provided as examples of routine, angle-invariant calibration and imaging.
Flux density measurements indicate that the 74 MHz flux scale at the VLA is
stable to a few percent, and tied to the Baars et al. value of Cygnus A at the
5 percent level. We also present an example of a wide-field image, devoid of
bright objects and containing hundreds of weaker sources, constructed from the
field-based calibration. We close with a summary of lessons the 74 MHz system
offers as a model for new and developing low-frequency telescopes. (Abridged)Comment: 73 pages, 46 jpeg figures, to appear in ApJ
GASKAP -- The Galactic ASKAP Survey
A survey of the Milky Way disk and the Magellanic System at the wavelengths
of the 21-cm atomic hydrogen (HI) line and three 18-cm lines of the OH molecule
will be carried out with the Australian Square Kilometre Array Pathfinder
telescope. The survey will study the distribution of HI emission and absorption
with unprecedented angular and velocity resolution, as well as molecular line
thermal emission, absorption, and maser lines. The area to be covered includes
the Galactic plane (|b|< 10deg) at all declinations south of delta = +40deg,
spanning longitudes 167deg through 360deg to 79deg at b=0deg, plus the entire
area of the Magellanic Stream and Clouds, a total of 13,020 square degrees. The
brightness temperature sensitivity will be very good, typically sigma_T ~ 1 K
at resolution 30arcsec and 1 km/s. The survey has a wide spectrum of scientific
goals, from studies of galaxy evolution to star formation, with particular
contributions to understanding stellar wind kinematics, the thermal phases of
the interstellar medium, the interaction between gas in the disk and halo, and
the dynamical and thermal states of gas at various positions along the
Magellanic Stream.Comment: 45 pages, 8 figures, Pub. Astron. Soc. Australia (in press
The low frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz
We present new Very Large Array (VLA) radio images at 74 and 324 MHz of the
SNR W44. The VLA images, obtained with unprecedented angular resolution and
sensitivity for such low frequencies have been used in combination with
existing 1442 MHz radio data, Spitzer IR data, and ROSAT and Chandra X-ray data
to investigate morphological and spectral properties of this SNR. The spatially
resolved spectral index study revealed that the bright filaments, both around
and across the SNR, have a straight spectrum between 74 and 1442 MHz, with
alpha ~ -0.5, with two clear exceptions: a short portion of the SNR limb to the
southeast, with alpha varying between 0 and +0.4 and a bright arc to the west
where the spectrum breaks around 300 MHz and looks concave down. We conclude
that at the shell and along the internal filaments, the electrons responsible
for the synchrotron emission were accelerated at the shock according to a
simple diffusive shock model; the positive spectrum corresponds to a location
where the SN shock is running into a molecular cloud and where the line of
sight intersects the photo dissociation region of an HII region and a young
stellar object is present. The curved spectrum on the westernmost bright arc is
explained as the consequence of strong post-shock densities and enhanced
magnetic fields after the interaction of the SN shock with a collindant
molecular cloud.Comment: After language edited, 16 pages, 12 figures (3 in color). Figures
degraded to reduce file size. Accepted 01/03/2007 for publicaion in A&
LOFAR, VLA, AND CHANDRA observations of the Toothbrush galaxy cluster
We present deep LOFAR observations between 120 and 181 MHz of the "Toothbrush" (RX J0603.3+4214), a cluster that contains one of the brightest radio relic sources known. Our LOFAR observations exploit a new and novel calibration scheme to probe 10 times deeper than any previous study in this relatively unexplored part of the spectrum. The LOFAR observations, when combined with VLA, GMRT, and Chandra X-ray data, provide new information about the nature of cluster merger shocks and their role in re-accelerating relativistic particles. We derive a spectral index of at the northern edge of the main radio relic, steepening toward the south to . The spectral index of the radio halo is remarkably uniform (, with an intrinsic scatter of ). The observed radio relic spectral index gives a Mach number of , assuming diffusive shock acceleration. However, the gas density jump at the northern edge of the large radio relic implies a much weaker shock (, with an upper limit of ). The discrepancy between the Mach numbers calculated from the radio and X-rays can be explained if either (i) the relic traces a complex shock surface along the line of sight, or (ii) if the radio relic emission is produced by a re-accelerated population of fossil particles from a radio galaxy. Our results highlight the need for additional theoretical work and numerical simulations of particle acceleration and re-acceleration at cluster merger shocks
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