16,912 research outputs found
Task constraints distinguish perspective inferences from perspective use during discourse interpretation in a false belief task
Interpreting other peoplesâ actions relies on an understanding of their current mental states (e.g. beliefs, desires and intentions). In this paper, we distinguish between listenersâ ability to infer othersâ perspectives and their explicit use of this knowledge to predict subsequent actions. In a visual-world study, two groups of participants (passive observers vs. active participants) watched short videos, depicting transfer events, where one character (âJaneâ) either held a true or false belief about an objectâs location. We tracked participantsâ eye-movements around the final visual scene, time-locked to related auditory descriptions (e.g. âJane will look for the chocolates in the container on the leftâ.). Results showed that active participants had already inferred the characterâs belief in the 1 s preview period prior to auditory onset, before it was possible to use this information to predict an outcome. Moreover, they used this inference to correctly anticipate reference to the objectâs initial location on false belief trials at the earliest possible point (i.e. from âJaneâ onwards). In contrast, passive observers only showed evidence of a belief inference from the onset of âJaneâ, and did not show reliable use of this inference to predict Janeâs behaviour on false belief trials until much later, when the location (âleft/rightâ) was auditorily available. These results show that active engagement in a task activates earlier inferences about othersâ perspectives, and drives immediate use of this information to anticipate othersâ actions, compared to passive observers, who are susceptible to influences from egocentric or reality biases. Finally, we review evidence that using other peoplesâ perspectives to predict their behaviour is more cognitively effortful than simply using oneâs own
Strain-stress study of AlxGa1-xN/AlN heterostructures on c-plane sapphire and related optical properties
This work presents a systematic study of stress and strain of AlxGa1-xN/AlN
with composition ranging from GaN to AlN, grown on a c-plane sapphire by
metal-organic chemical vapor deposition, using synchrotron radiation
high-resolution X-ray diffraction and reciprocal space mapping. The c-plane of
the AlxGa1-xN epitaxial layers exhibits compressive strain, while the a-plane
exhibits tensile strain. The biaxial stress and strain are found to increase
with increasing Al composition, although the lattice mismatch between the
AlxGa1-xN and the buffer layer AlN gets smaller. A reduction in the lateral
coherence lengths and an increase in the edge and screw dislocations are seen
as the AlxGa1-xN composition is varied from GaN to AlN, exhibiting a clear
dependence of the crystal properties of AlxGa1-xN on the Al content. The
bandgap of the epitaxial layers is slightly lower than predicted value due to a
larger tensile strain effect on the a-axis compared to the compressive strain
on the c-axis. Raman characteristics of the AlxGa1-xN samples exhibit a shift
in the phonon peaks with the Al composition. The effect of strain is also
discussed on the optical phonon energies of the epitaxial layers. The
techniques discussed here can be used to study other similar materials.Comment: 14 pages, 5 figures, 2 table
The Dust Content of Galaxy Clusters
We report on the detection of reddening toward z ~ 0.2 galaxy clusters. This
is measured by correlating the Sloan Digital Sky Survey cluster and quasar
catalogs and by comparing the photometric and spectroscopic properties of
quasars behind the clusters to those in the field. We find mean E(B-V) values
of a few times 10^-3 mag for sight lines passing ~Mpc from the clusters'
center. The reddening curve is typical of dust but cannot be used to
distinguish between different dust types. The radial dependence of the
extinction is shallow near the cluster center suggesting that most of the
detected dust lies at the outskirts of the clusters. Gravitational
magnification of background z ~ 1.7 sources seen on Mpc (projected) scales
around the clusters is found to be of order a few per cent, in qualitative
agreement with theoretical predictions. Contamination by different spectral
properties of the lensed quasar population is unlikely but cannot be excluded.Comment: 4 pages, 3 figure
Mission-oriented requirements for updating MIL-H-8501. Volume 1: STI proposed structure
The structure of a new flying and ground handling qualities specification for military rotorcraft is presented. This preliminary specification structure is intended to evolve into a replacement for specification MIL-H-8501A. The new structure is designed to accommodate a variety of rotorcraft types, mission flight phases, flight envelopes, and flight environmental characteristics and to provide criteria for three levels of flying qualities, a systematic treatment of failures and reliability, both conventional and multiaxis controllers, and external vision aids which may also incorporate synthetic display content. Existing and new criteria were incorporated into the new structure wherever they could be substantiated
Far-ultraviolet imaging of the Hubble Deep Field-North: Star formation in normal galaxies at z < 1
We present far-ultraviolet (FUV) imaging of the Hubble Deep Field-North (HDF-N) taken with the Solar Blind Channel of the Advanced Camera for Surveys (ACS SBC) and the FUV MAMA detector of the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The full WFPC2 deep field has been observed at 1600 Ă
. We detect 134 galaxies and one star down to a limit of FUV_(AB) ~ 29. All sources have counterparts in the WFPC2 image. Redshifts (spectroscopic or photometric) for the detected sources are in the range 0 < z < 1. We find that the FUV galaxy number counts are higher than those reported by GALEX, which we attribute at least in part to cosmic variance in the small HDF-N field of view. Six of the 13 Chandra sources at z < 0.85 in the HDF-N are detected in the FUV, and those are consistent with starbursts rather than active galactic nuclei. Cross-correlating with Spitzer sources in the field, we find that the FUV detections show general agreement with the expected L_(IR)/L_(UV) versus ÎČ relationship. We infer star formation rates (SFRs), corrected for extinction using the UV slope, and find a median value of 0.3 M_â yr^(-1) for FUV-detected galaxies, with 75% of detected sources having SFR < 1 M_â yr^(-1). Examining the morphological distribution of sources, we find that about half of all FUV-detected sources are identified as spiral galaxies. Half of morphologically selected spheroid galaxies at z < 0.85 are detected in the FUV, suggesting that such sources have had significant ongoing star formation in the epoch since z ~ 1
The Luminosity Function of Galaxies in Compact Groups
From R-band images of 39 Hickson compact groups (HCGs), we use galaxy counts
to determine a luminosity function extending to M_R=-14.0, approximately two
magnitudes deeper than previous compact group luminosity functions. We find
that a single Schechter function is a poor fit to the data, so we fit a
composite function consisting of separate Schechter functions for the bright
and faint galaxies. The bright end is best fit with M^*=-21.6 and alpha=-0.52
and the faint end with M^*=-16.1 and alpha=-1.17. The decreasing bright end
slope implies a deficit of intermediate luminosity galaxies in our sample of
HCGs and the faint end slope is slightly steeper than that reported for earlier
HCG luminosity functions. Furthermore, luminosity functions of subsets of our
sample reveal more substantial dwarf populations for groups with x-ray halos,
groups with tidal dwarf candidates, and groups with a dominant elliptical or
lenticular galaxy. Collectively, these results support the hypothesis that
within compact groups, the initial dwarf galaxy population is replenished by
"subsequent generations" formed in the tidal debris of giant galaxy
interactions.Comment: 26 pages, to be published in The Astrophysical Journal, 8 greyscale
plates (figures 1 and 2) can be retrieved at
http://www.astro.psu.edu/users/sdh/pubs.htm
A Theory for Rapid Charging Events on the International Space Station
The Floating Potential Measurement Unit (FPMU) has detected high negative amplitude rapid charging events (RCEs) on the International Space Station (ISS) at the morning terminator. These events are larger and more rapid than the ISS morning charging events first seen by the Floating Potential Probe (FPP) on ISS in 2001. In this paper, we describe a theory for the RCEs that further elucidates the nature of spacecraft charging in low Earth orbit (LEO) in a non-equilibrium situation. The model accounts for all essential aspects of the newly discovered phenomenon, and is amenable to testing on-orbit. Predictions of the model for the amplitude of the ISS RCEs for the full set of ISS solar arrays and for the coming solar cycle are given, and the results of modeling by the Environments WorkBench (EWB) are compared to the observed events to show that the phenomenon can be explained by solar array driven charging. The situation is unique because the coverglasses have not yet reached equilibrium with the surrounding plasma during the RCEs. Finally, a prescription for further use of the ISS for investigating fundamental plasma physics in LEO is given. Already, plasma and charging monitoring instruments on ISS have taught us much about spacecraft interactions with the dense LEO plasma, and we expect they will continue to yield more valuable science when the Japanese Experiment Module (JEM) is in place
Infrared luminosities of galaxies in the Local Volume
Near-infrared properties of 451 galaxies with distances D \leq 10 Mpc are
considered basing on the all-sky two micron survey (2MASS). A luminosity
function of the galaxies in the K-band is derived within [-25,-11] mag. The
local (D < 8 Mpc) luminosity density is estimated to be 6.8*10^8 L_sun/Mpc^3
that exceeds (1.5+-0.1) times the global cosmic density in the K-band. Virial
mass-to-K-luminosity ratios are determined for nearby groups and clusters. In
the luminosity range of (5*10^{10} - 2*10^{13})L_sun, the groups and clusters
follow the relation \lg(M/L_K) propto (0.27+-0.03) lg(L_K) with a scatter of
\~0.1 comparable to errors of the observables. The mean ratio ~=
(20-25) M_sun/L_sun for the galaxy systems turns out to be significantly lower
than the global ratio, (80-90)M_sun/L_sun, expected in the standard
cosmological model with the matter density of Omega_m =0.27. This discrepancy
can be resolved if most of dark matter in the universe is not associated with
galaxies and their systems.Comment: 15 pages, 7 figures. Astronomy Letters, submitte
Limits on Dust in Rich Clusters of Galaxies from the Color of Background Quasars
I measure the V-I color distribution of two samples of radio-selected
quasars. Quasars from one sample are projected on the sky within 1 degree of a
rich foreground Abell cluster of galaxies, while quasars from the other sample
are more than 3 degrees from any such cluster . There is no significant
difference between the color distributions of the two samples. The 90\% upper
limit on the relative reddening between the two samples is E(B-V)=0.05 mag.
This result limits the allowed quantity of smoothly distributed dust in rich
clusters, and contradicts previous indications for the existence of such a
component.Comment: Submitted to ApJ Letters. 14 pages incl. 2 figures, uuencoded,
compressed postscript. Also available by anonymous ftp to
ftp://wise3.tau.ac.il/pub/dani/dust.ps.
Temperature perturbation model of the opto-galvanic effect in CO2-laser discharges
A detailed discharge model of the opto-galvanic effect in molecular laser gas mixtures is developed based on the temperature perturbation or discharge cooling mechanism of Smith and Brooks (1979). Excellent agreement between the model and experimental results in CO2 laser gas mixtures is obtained. The model should be applicable to other molecular systems where the OGE is being used for laser stabilisation and as a spectroscopic tool
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