8,533 research outputs found
Concordant cues in faces and voices: testing the backup signal hypothesis
Information from faces and voices combines to provide multimodal signals about a person. Faces and voices may offer redundant, overlapping (backup signals), or complementary information (multiple messages). This article reports two experiments which investigated the extent to which faces and voices deliver concordant information about dimensions of fitness and quality. In Experiment 1, participants rated faces and voices on scales for masculinity/femininity, age, health, height, and weight. The results showed that people make similar judgments from faces and voices, with particularly strong correlations for masculinity/femininity, health, and height. If, as these results suggest, faces and voices constitute backup signals for various dimensions, it is hypothetically possible that people would be able to accurately match novel faces and voices for identity. However, previous investigations into novel face–voice matching offer contradictory results. In Experiment 2, participants saw a face and heard a voice and were required to decide whether the face and voice belonged to the same person. Matching accuracy was significantly above chance level, suggesting that judgments made independently from faces and voices are sufficiently similar that people can match the two. Both sets of results were analyzed using multilevel modeling and are interpreted as being consistent with the backup signal hypothesis
Measuring Column Densities in Quasar Outflows: VLT Observations of QSO 2359-1241
We present high resolution spectroscopic VLT observations of the outflow seen
in QSO 2359-1241. These data contain absorption troughs from five resonance Fe
II lines with a resolution of ~7 km/s and signal-to-noise ratio per resolution
element of order 100. We use this unprecedented high quality data set to
investigate the physical distribution of the material in front of the source,
and by that determine the column densities of the absorbed troughs. We find
that the apparent optical depth model gives a very poor fit to the data and
greatly underestimates the column density measurements. Power-law distributions
and partial covering models give much better fits with some advantage to
power-law models, while both models yield similar column density estimates. The
better fit of the power-law model solves a long standing problem plaguing the
partial covering model when applied to large distance scale outflow: How to
obtain a velocity dependent covering factor for an outflow situated at
distances thousands of time greater than the size of the AGN emission source.
This problem does not affect power-law models. Therefore, based on the better
fit and plausibility of the physical model, we conclude that in QSO 2359-1241,
the outflow covers the full extent of the emission source but in a
non-homogeneous way.Comment: 27 pages, 6 figures, to appear on ApJ Jul 10. The full (online)
version of figure 2 can be obtained here:
http://www.phys.vt.edu/~arav/f2_online_version.p
Galactic Cosmic Rays from Supernova Remnants: II Shock Acceleration of Gas and Dust
This is the second paper (the first was astro-ph/9704267) of a series
analysing the Galactic Cosmic Ray (GCR) composition and origin. In this we
present a quantitative model of GCR origin and acceleration based on the
acceleration of a mixture of interstellar and/or circumstellar gas and dust by
supernova remnant blast waves. We present results from a nonlinear shock model
which includes (i) the direct acceleration of interstellar gas-phase ions, (ii)
a simplified model for the direct acceleration of weakly charged dust grains to
energies of order 100keV/amu simultaneously with the gas ions, (iii) frictional
energy losses of the grains colliding with the gas, (iv) sputtering of ions of
refractory elements from the accelerated grains and (v) the further shock
acceleration of the sputtered ions to cosmic ray energies. The calculated GCR
composition and spectra are in good agreement with observations.Comment: to appear in ApJ, 51 pages, LaTeX with AAS macros, 9 postscript
figures, also available from ftp://wonka.physics.ncsu.edu/pub/elliso
Charge-coupled devices with fast timing for astrophysics and space physics research
A charge coupled device is under development with fast timing capability (15 millisecond full frame readout, 30 microsecond resolution for measuring the time of individual pixel hits). The fast timing CCD will be used in conjunction with a CsI microfiber array or segmented scintillator matrix detector to detect x rays and gamma rays with submillimeter position resolution. The initial application will be in conjunction with a coded aperture hard x ray/gamma ray astronomy instrument. We describe the concept and the readout architecture of the device
The Investigation of Space Charge Dominated Beams in a Synchrotron
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Dust-driven Dynamos in Accretion Disks
Magnetically driven astrophysical jets are related to accretion and involve
toroidal magnetic field pressure inflating poloidal magnetic field flux
surfaces. Examination of particle motion in combined gravitational and magnetic
fields shows that these astrophysical jet toroidal and poloidal magnetic fields
can be powered by the gravitational energy liberated by accreting dust grains
that have become positively charged by emitting photo-electrons. Because a dust
grain experiences magnetic forces after becoming charged, but not before,
charging can cause irreversible trapping of the grain so dust accretion is a
consequence of charging. Furthermore, charging causes canonical angular
momentum to replace mechanical angular momentum as the relevant constant of the
motion. The resulting effective potential has three distinct classes of
accreting particles distinguished by canonical angular momentum, namely (i)
"cyclotron-orbit", (ii) "Speiser-orbit", and (iii) "zero canonical angular
momentum" particles. Electrons and ions are of class (i) but depending on mass
and initial orbit inclination, dust grains can be of any class. Light-weight
dust grains develop class (i) orbits such that the grains are confined to
nested poloidal flux surfaces, whereas grains with a critical weight such that
they experience comparable gravitational and magnetic forces can develop class
(ii) or class (iii) orbits, respectively producing poloidal and toroidal field
dynamos.Comment: 70 pages, 16 figure
Clustering of vacancy defects in high-purity semi-insulating SiC
Positron lifetime spectroscopy was used to study native vacancy defects in
semi-insulating silicon carbide. The material is shown to contain (i) vacancy
clusters consisting of 4--5 missing atoms and (ii) Si vacancy related
negatively charged defects. The total open volume bound to the clusters
anticorrelates with the electrical resistivity both in as-grown and annealed
material. Our results suggest that Si vacancy related complexes compensate
electrically the as-grown material, but migrate to increase the size of the
clusters during annealing, leading to loss of resistivity.Comment: 8 pages, 5 figure
Metabolism of profenofos to 4-bromo-2-chlorophenol, a specific and sensitive exposure biomarker.
Profenofos is a direct acting phosphorothioate organophosphorus (OP) pesticide capable of inhibiting β-esterases such as acetylcholinesterase, butyrylcholinesterase, and carboxylesterase. Profenofos is known to be detoxified to the biologically inactive metabolite, 4-bromo-2-chlorophenol (BCP); however, limited data are available regarding the use of urinary BCP as an exposure biomarker in humans. A pilot study conducted in Egyptian agriculture workers, demonstrated that urinary BCP levels prior to application (3.3-30.0 μg/g creatinine) were elevated to 34.5-3,566 μg/g creatinine during the time workers were applying profenofos to cotton fields. Subsequently, the in vitro enzymatic formation of BCP was examined using pooled human liver microsomes and recombinant human cytochrome P-450s (CYPs) incubated with profenofos. Of the nine human CYPs studied, only CYPs 3A4, 2B6, and 2C19 were able to metabolize profenofos to BCP. Kinetic studies indicated that CYP 2C19 has the lowest Km, 0.516 μM followed by 2B6 (Km=1.02 μM) and 3A4 (Km=18.9μM). The Vmax for BCP formation was 47.9, 25.1, and 19.2 nmol/min/nmol CYP for CYP2B6, 2C19, and 3A4, respectively. Intrinsic clearance (Vmax/Km) values of 48.8, 46.9, and 1.02 ml/min/nmol CYP 2C19, 2B6, and 3A4, respectively, indicate that CYP2C19 and CYP2B6 are primarily responsible for the detoxification of profenofos. These findings support the use of urinary BCP as a biomarker of exposure to profenofos in humans and suggest polymorphisms in CYP 2C19 and CYP 2B6 as potential biomarkers of susceptibility
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