1,897 research outputs found
Integration of identity and emotion information in faces: fMRI evidence.
Separate neural systems have been implicated in the recognition of facial identity and emotional expression. A growing number of studies now provide evidence against this modular view by demonstrating that integration of identity and emotion information enhances face processing. Yet, the neural mechanisms that shape this integration remain largely unknown. We hypothesize that the presence of both personal and emotional expression target information triggers changes in functional connectivity between frontal and extrastriate areas in the brain. We report and discuss three important findings. First, the presence of target identity and emotional expression in the same face was associated with super capacity and violations of the independent processing of identity and expression cues. Second, activity in the orbitofrontal cortex (OFC) was associated with the presence of redundant targets and changes in functional connectivity between a particular region of the right OFC (BA11/47) and bilateral visual brain regions (the inferior occipital gyrus (IOG)). Third, these changes in connectivity showed a strong link to behavioural measures of capacity processing. We suggest that the changes in functional connectivity between the right OFC and IOG reduce variability of BOLD responses in the IOG, enhancing integration of identity and emotional expression cues in faces
HST/NICMOS Paschen-alpha Survey of the Galactic Center: Overview
We have recently carried out the first wide-field hydrogen Paschen-alpha line
imaging survey of the Galactic Center (GC), using the NICMOS instrument aboard
the Hubble Space Telescope. The survey maps out a region of 2253 pc^2 around
the central supermassive black hole (Sgr A*) in the 1.87 and 1.90 Micron narrow
bands with a spatial resolution of 0.01 pc at a distance of 8 kpc. Here we
present an overview of the observations, data reduction, preliminary results,
and potential scientific implications, as well as a description of the
rationale and design of the survey. We have produced mosaic maps of the
Paschen-alpha line and continuum emission, giving an unprecedentedly high
resolution and high sensitivity panoramic view of stars and photo-ionized gas
in the nuclear environment of the Galaxy. We detect a significant number of
previously undetected stars with Paschen-alpha in emission. They are most
likely massive stars with strong winds, as confirmed by our initial follow-up
spectroscopic observations. About half of the newly detected massive stars are
found outside the known clusters (Arches, Quintuplet, and Central). Many
previously known diffuse thermal features are now resolved into arrays of
intriguingly fine linear filaments indicating a profound role of magnetic
fields in sculpting the gas. The bright spiral-like Paschen-alpha emission
around Sgr A* is seen to be well confined within the known dusty torus. In the
directions roughly perpendicular to it, we further detect faint, diffuse
Paschen-alpha emission features, which, like earlier radio images, suggest an
outflow from the structure. In addition, we detect various compact
Paschen-alpha nebulae, probably tracing the accretion and/or ejection of stars
at various evolutionary stages.Comment: accepted for publication in MNRAS; a version of higher resolution
images may be found at http://www.astro.umass.edu/~wqd/papers/hst/paper1.pd
Adiabatic orientation of rotating dipole molecules in an external field
The induced polarization of a beam of polar clusters or molecules passing
through an electric or magnetic field region differs from the textbook
Langevin-Debye susceptibility. This distinction, which is important for the
interpretation of deflection and focusing experiments, arises because instead
of acquiring thermal equilibrium in the field region, the beam ensemble
typically enters the field adiabatically, i.e., with a previously fixed
distribution of rotational states. We discuss the orientation of rigid
symmetric-top systems with a body-fixed electric or magnetic dipole moment. The
analytical expression for their "adiabatic-entry" orientation is elucidated and
compared with exact numerical results for a range of parameters. The
differences between the polarization of thermodynamic and "adiabatic-entry"
ensembles, of prolate and oblate tops, and of symmetric-top and linear rotators
are illustrated and identified.Comment: 18 pages, 4 figure
Intermediate to low-mass stellar content of Westerlund 1
We have analysed near-infrared NTT/SofI observations of the starburst cluster
Westerlund 1, which is among the most massive young clusters in the Milky Way.
A comparison of colour-magnitude diagrams with theoretical main-sequence and
pre-main sequence evolutionary tracks yields improved extinction and distance
estimates of A_Ks = 1.13+-0.03 mag and d = 3.55+-0.17 kpc (DM = 12.75+-0.10
mag). The pre-main sequence population is best fit by a Palla & Stahler
isochrone for an age of 3.2 Myr, while the main sequence population is in
agreement with a cluster age of 3 to 5 Myr. An analysis of the structural
parameters of the cluster yields that the half-mass radius of the cluster
population increases towards lower mass, indicative of the presence of mass
segregation. The cluster is clearly elongated with an eccentricity of 0.20 for
stars with masses between 10 and 32 Msun, and 0.15 for stars with masses in the
range 3 to 10 Msun. We derive the slope of the stellar mass function for stars
with masses between 3.4 and 27 Msun. In an annulus with radii between 0.75 and
1.5 pc from the cluster centre, we obtain a slope of Gamma = -1.3. Closer in,
the mass function of Westerlund 1 is shallower with Gamma = -0.6. The
extrapolation of the mass function for stars with masses from 0.08 to 120 Msun
yields an initial total stellar mass of ~52,000 Msun, and a present-day mass of
20,000 to 45,000 Msun (about 10 times the stellar mass of the Orion Nebula
Cluster, and 2 to 4 times the mass of the NGC 3603 young cluster), indicating
that Westerlund 1 is the most massive starburst cluster identified to date in
the Milky Way.Comment: 15 pages, jpg figures, uses aa.cls and graphicx, accepted for
publication in A&
Direct determination of the sign of the NO dipole moment.
We report a novel approach for determining the sign of permanent dipole moments, using nitric oxide [NO(v=0)] as an example. State-selected NO (j=|m|=|Ω=1/2) molecules are focused using a hexapole and oriented in a strong dc electric field. The angular distributions of ionic fragments resulting from extreme ultraviolet single-photon and multiphoton dissociative ionization at 400 and 800 nm are measured and indicate that the dipole moment is negative (corresponding to N-O+). The experiments thus rule out an error in the sign of the dipole of NO as the possible source of a remarkable discrepancy between previous theoretical and experimental work on orientation effects in bimolecular collisions involving oriented NO. © 2007 The American Physical Society
Extreme Cosmic-Ray-Dominated-Regions: a new paradigm for high star formation density events in the Universe
We examine in detail the recent proposal that extreme
Cosmic-Ray-Dominated-Regions (CRDRs) characterize the ISM of galaxies during
events of high-density star formation, fundamentally altering its initial
conditions (Papadopoulos 2010). Solving the coupled chemical and thermal state
equations for dense UV-shielded gas reveals that the large cosmic ray energy
densities in such systems (U_{CR} (few)x(10^3-10^4) U_{CR,Gal}) will indeed
raise the minimum temperature of this phase (where the initial conditions of
star formation are set) from ~10K (as in the Milky Way) to (50-100)K. Moreover
in such extreme CRDRs the gas temperature remains fully decoupled from that of
the dust, with T_{kin} >> T_{dust}, even at high densities (n(H_2)~10^5--10^6
cm^{-3}), quite unlike CRDRs in the Milky Way where T_k T_{dust} when n(H_2) >=
10^5 cm^{-3}.
These dramatically different star formation initial conditions will: a) boost
the Jeans mass of UV-shielded gas regions by factors of ~10--100 with respect
to those in quiescent or less extreme star forming systems, and b) "erase" the
so-called inflection point of the effective equation of state (EOS) of
molecular gas. Both these effects occur across the entire density range of
typical molecular clouds, and may represent {\it a new paradigm for all
high-density star formation in the Universe}, with cosmic rays as the key
driving mechanism, operating efficiently even in the high dust extinction
environments of extreme starbursts...Comment: 10 pages, 5 figures, accepted with minor modifications for
publication in the MNRAS (the follow-up paper to Papadopoulos 2010, ApJ, 720,
226
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