395 research outputs found
Adaptive neural reward processing during anticipation and receipt of monetary rewards in mindfulness meditators
Reward seeking is ubiquitous and adaptive in humans. But excessive reward seeking behavior, such as chasing monetary rewards, may lead to diminished subjective well-being. This study examined whether individuals trained in mindfulness meditation show neural evidence of lower susceptibility to monetary rewards. Seventy-eight participants (34 meditators, 44 matched controls) completed the monetary incentive delay task while undergoing functional magnetic resonance imaging. The groups performed equally on the task, but meditators showed lower neural activations in the caudate nucleus during reward anticipation, and elevated bilateral posterior insula activation during reward anticipation. Meditators also evidenced reduced activations in the ventromedial prefrontal cortex during reward receipt compared with controls. Connectivity parameters between the right caudate and bilateral anterior insula were attenuated in meditators during incentive anticipation. In summary, brain regions involved in reward processingboth during reward anticipation and receipt of rewardresponded differently in mindfulness meditators than in nonmeditators, indicating that the former are less susceptible to monetary incentives
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Contextual bias and insulation against bias during aesthetic rating. The roles of VMPFC and DLPFC in neural valuation
The scientific study of aesthetic experience through the examination of the neural correlates of sensory and motor responses works of art and to other visual images has thrived during the last decade. The neural substrate of embodied responses to works of art, and to visual images more generally, has been the object of much attention. This research, however, has tended to sidestep the question of aesthetic preference and rating, and the neural correlates of contextual influences on such ratings. Responses in the domain of perception–action coupling have provided useful and important evidence for the role of somatic and emotional responses in viewers’ engagement with works of art. Nevertheless, the degree to which they form the basis of evaluation, ranking, and even judgment remains unclear. In this chapter we concentrate on the respective roles of the ventromedial prefrontal cortex (VMPFC) and the dorsolateral prefrontal cortex (DLPFC) during aesthetic evaluation, particularly the aesthetic evaluation of visual works of art. Activity in these areas is modulated by external contextual pressures on viewing. The roles of ACC, hippocampal and striatal connections in the process of rating and evaluating works of visual art, and the relationship between expert and non-expert responses, are also discussed
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Cognitive framing modulates emotional processing through dorsolateral prefrontal cortex and ventrolateral prefrontal cortex networks: A functional magnetic resonance imaging study
Introduction: In this study, we show new evidence for the role of ventrolateral prefrontal cortex-dorsolateral prefrontal cortex (VLPFC-DLPFC) networks in the cognitive framing of emotional processing. Method: We displayed neutral and aversive images described as having been sourced from artistic material to one cohort of subjects (i.e., the art-frame group; n = 19), while identical images, this time identified as having been sourced from documentary material (i.e., the doc-frame group; n = 20) were shown to a separate cohort.
Results: Using functional magnetic resonance imaging (fMRI), we employed a linear parametric model showing that relative to the doc-frame group the art-frame group exhibited a modulation of amygdala activity in response to aversive images. The attenuated amygdala activity in the art-frame group supported our hypothesis that reduced amygdala activity was driven by top-down DLPFC inhibition of limbic responses. A psychophysiological interaction (PPI) analysis demonstrated that VLPFC activity correlated with amygdala activity in the art-frame group, but not in the docframe group for the contrast [Aversive > Neutral].
Conclusion: The role of the VLPFC in cognitive control suggests the hypothesis that it alongside DLPFC insulates against embodied emotional responses by inhibiting automatic affective responses
Dynamics of Warm-Absorbing Gas in Seyfert Galaxies: NGC 5548
A hydromagnetic (MHD) wind from a clumpy molecular accretion disk is invoked
to explain observations of warm absorbing (WA) gas in UVX from Sy galaxies.
This paper focuses on two issues: (1) compatibility of kinematics and dynamics
of MHD wind with the observed properties of WAs; and (2) relationship between
the UVX absorptions. We provide an in-depth comparison between the MHD model
and the Sy 1 galaxy NGC 5548, which at high spectral resolution exhibits a
number of discrete UV absorption components. We find that: (1) the total column
densities of Ovii, Oviii and H, are reproduced by constraining the UV ion
column densities of Civ and Nv in each component to lie within a factor of 2 of
their observed values and optimizing over the possible sets of component
ionization states and Civ column densities; (2) the WA exists in the outer part
of the wind and is not a continuation of the flow in the BLR; and (3) the WA
extends in radial and polar directions and is ionization-stratified. X-ray
absorption is found to be heavily biased towards smaller r, and UV absorption
originates at larger distances from the central continuum source. We show that
the discrete absorption components along the line-of-sight are intrinsically
clumpy. Density differences between kinematic components result in a range of
ionization and recombination timescales. We further test the applicability of
the MHD wind to WAs in general, by constructing a quasi-continuous flow model,
and extending it to arbitrary aspect angles. We estimate the fraction of Sy 1s
having detectable WAs with larger Ovii column density than Oviii, and the range
of total H column densities. We also find that the ratio of Ovii to Oviii
optical depths can serve as a new diagnostic of AGN aspect angle.Comment: Latex, 8 postscript figures. Astrophysical Journal, 536, June 10, in
pres
Progress in understanding Blazars from BeppoSAX observations
Results obtained with BeppoSAX observations of blazars within various
collaborative programs are presented. The spectral similarity "paradigm",
whereby the spectral energy distributions of blazars follow a sequence, leading
to a unified view of the whole population, is briefly illustrated. We
concentrate on recent observations of flares and associated spectral
variability for three objects at the "blue" end of the spectral sequence,
namely PKS 2155-304, Mkn 421 and Mkn 501. The results are discussed in terms of
a general analytic synchrotron self-Compton interpretation of the overall
spectrum. The physical parameters of the quasi-stationary emission region can
be derived with some confidence, while the variability mechanism(s) must be
complex.Comment: 10 pages, 8 figures, to be published in the Proceedings of the 32nd
COSPAR Meeting, Nagoya, 12-19 July 199
Observing the gas temperature drop in the high-density nucleus of L 1544
Abridged: The thermal structure of a starless core is crucial for our
understanding of the physics in these objects and hence for our understanding
of star formation. Theory predicts a gas temperature drop in the inner 5000 AU
of these objects, but there has been little observational proof of this. We
performed VLA observations of the NH3 (1,1) and (2,2) transitions towards the
pre-stellar core L 1544 in order to measure the temperature gradient between
the high density core nucleus and the surrounding core envelope. Our VLA
observation for the first time provide measurements of gas temperature in a
core with a resolution smaller than 1000 AU. We have also obtained high
resolution Plateau de Bure observations of the 110 GHz 111-101 para-NH2D line
in order to further constrain the physical parameters of the high density
nucleus. We have estimated the temperature gradient using a model of the source
to fit our data in the u,v plane. We find that indeed the temperature decreases
toward the core nucleus from 12 K down to 5.5 K resulting in an increase of a
factor of 50% in the estimated density of the core from the dust continuum if
compared with the estimates done with constant temperature of 8.75 K. We also
found a remarkably high abundance of deuterated ammonia with respect to the
ammonia abundance (50%+-20%), which proves the persistence of nitrogen bearing
molecules at very high densities (2e6 cm-3) and shows that high-resolution
observations yield higher deuteration values than single-dish observations. Our
analysis of the NH3 and NH2D kinematic fields shows a decrease of specific
angular momentum from the large scales to the small scales.Comment: 12 pages, 6 figures. Accepted for publication by A&
Synchrotron and inverse-Compton emission from blazar jets I: a uniform conical jet model
In the first of a series of papers investigating emission from blazar jets
from radio to high-energy {\gamma}-rays, we revisit the class of models where
the jet has a uniform conical ballistic structure. We argue that by using
simple developments of these models, in the context of new multi-frequency data
extending to gamma-ray energies, valuable insights may be obtained into the
properties that fully realistic models must ultimately have. In this paper we
consider the synchrotron and synchrotron-self-Compton emission from the jet,
modelling the recent simultaneous multi-wavelength observations of BL Lac. This
is the first time these components have been fitted simultaneously for a blazar
using a conical jet model.
In the model we evolve the electron population dynamically along the jet
taking into account the synchrotron and inverse-Compton losses. The
inverse-Compton emission is calculated using the Klein-Nishina cross section
and a relativistic transformation into the jet frame, and we explicitly show
the seed photon population. We integrate synchrotron opacity along the line of
sight through the jet plasma, taking into account the emission and opacity of
each section of the jet. In agreement with previous studies of radio emission,
we find that a conical jet model which conserves magnetic energy produces the
characteristic blazar flat radio spectrum, however, we do not require any
fine-tuning of the model to achieve this. Of particular note, in our model fit
to BL Lac--which at ~10^37W is a relatively low jet-power source--we find no
requirement for significant re-acceleration within the jet to explain the
observed spectrum.Comment: 11 pages, 6 figures, accepted for publication in MNRA
TetraphenylÂarsonium cis-bisÂ[1,2-bisÂ(triÂfluoroÂmethÂyl)ethene-1,2-dithiolÂato]platinate(II)
In the title compound, (C24H20As)[Pt(C4F6S2)2], the cation lies on a twofold rotation axis while the anion has crystallographic inversion symmetry. The PtII ion is in a slightly distorted square-planar coordination environment. The F atoms of both unique –CF3 groups are disordered over two sets of sites, the ratios of refined occupancies being 0.677 (15):0.323 (15) and 0.640 (16):0.360 (16). The crystal structure is the first to date of a monoanionic [Pt(tfd)2]− species [tfd is 1,2-bisÂ(trifluoroÂmethÂyl)ethene-1,2-dithiolÂate] with a non-redox-active cation
Research and Education in Computational Science and Engineering
Over the past two decades the field of computational science and engineering
(CSE) has penetrated both basic and applied research in academia, industry, and
laboratories to advance discovery, optimize systems, support decision-makers,
and educate the scientific and engineering workforce. Informed by centuries of
theory and experiment, CSE performs computational experiments to answer
questions that neither theory nor experiment alone is equipped to answer. CSE
provides scientists and engineers of all persuasions with algorithmic
inventions and software systems that transcend disciplines and scales. Carried
on a wave of digital technology, CSE brings the power of parallelism to bear on
troves of data. Mathematics-based advanced computing has become a prevalent
means of discovery and innovation in essentially all areas of science,
engineering, technology, and society; and the CSE community is at the core of
this transformation. However, a combination of disruptive
developments---including the architectural complexity of extreme-scale
computing, the data revolution that engulfs the planet, and the specialization
required to follow the applications to new frontiers---is redefining the scope
and reach of the CSE endeavor. This report describes the rapid expansion of CSE
and the challenges to sustaining its bold advances. The report also presents
strategies and directions for CSE research and education for the next decade.Comment: Major revision, to appear in SIAM Revie
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