38,793 research outputs found
Beta event-related desynchronization as an index of individual differences in processing human facial expression: further investigations of autistic traits in typically developing adults
The human mirror neuron system (hMNS) has been associated with various forms of social cognition and affective processing including vicarious experience. It has also been proposed that a faulty hMNS may underlie some of the deficits seen in the autism spectrum disorders (ASDs). In the present study we set out to investigate whether emotional facial expressions could modulate a putative EEG index of hMNS activation (mu suppression) and if so, would this differ according to the individual level of autistic traits [high versus low Autism Spectrum Quotient (AQ) score]. Participants were presented with 3 s films of actors opening and closing their hands (classic hMNS mu-suppression protocol) while simultaneously wearing happy, angry, or neutral expressions. Mu-suppression was measured in the alpha and low beta bands. The low AQ group displayed greater low beta event-related desynchronization (ERD) to both angry and neutral expressions. The high AQ group displayed greater low beta ERD to angry than to happy expressions. There was also significantly more low beta ERD to happy faces for the low than for the high AQ group. In conclusion, an interesting interaction between AQ group and emotional expression revealed that hMNS activation can be modulated by emotional facial expressions and that this is differentiated according to individual differences in the level of autistic traits. The EEG index of hMNS activation (mu suppression) seems to be a sensitive measure of the variability in facial processing in typically developing individuals with high and low self-reported traits of autism
Investigation of the Coupling Potential by means of S-matrix Inversion
We investigate the inelastic coupling interaction by studying its effect on
the elastic scattering potential as determined by inverting the elastic
scattering -matrix. We first address the effect upon the real and imaginary
elastic potentials of including excited states of the target nucleus. We then
investigate the effect of a recently introduced novel coupling potential which
has been remarkably successful in reproducing the experimental data for the
C+C, C+Mg and O+Si reactions over a
wide range of energies. This coupling potential has the effect of deepening the
real elastic potential in the surface region, thereby explaining a common
feature of many phenomenological potentials. It is suggested that one can
relate this deepening to the super-deformed state of the compound nucleus,
Mg.Comment: 12 pages with 3 figure
Spin 1 inversion: a Majorana tensor force for deuteron alpha scattering
We demonstrate, for the first time, successful S-matrix to potential
inversion for spin one projectiles with non-diagonal yielding a
interaction. The method is a generalization of the
iterative-perturbative, IP, method. We present a test case indicating the
degree of uniqueness of the potential. The method is adapted, using established
procedures, into direct observable to potential inversion, fitting ,
, , and for d + alpha scattering over
a range of energies near 10 MeV. The interaction which we find is
very different from that proposed elsewhere, both real and imaginary parts
being very different for odd and even parity channels.Comment: 7 pages Revtex, 4 ps figure
Dual Response Models for the Fractional Quantum Hall Effect
It is shown that the Jain mapping between states of integer and fractional
quantum Hall systems can be described dynamically as a perturbative
renormalization of an effective Chern-Simons field theory. The effects of
mirror duality symmetries of toroidally compactified string theory on this
system are studied and it is shown that, when the gauge group is compact, the
mirror map has the same effect as the Jain map. The extrinsic ingredients of
the Jain construction appear naturally as topologically non-trivial field
configurations of the compact gauge theory giving a dynamical origin for the
Jain hierarchy of fractional quantum Hall states.Comment: 8 pages LaTe
Nuclear magnetic resonance probes for the Kondo scenario for the 0.7 feature in semiconductor quantum point contact devices
We propose a probe based on nuclear relaxation and Knight shift measurements
for the Kondo scenario for the "0.7 feature" in semiconductor quantum point
contact (QPC) devices. We show that the presence of a bound electron in the QPC
would lead to a much higher rate of nuclear relaxation compared to nuclear
relaxation through exchange of spin with conduction electrons. Furthermore, we
show that the temperature dependence of this nuclear relaxation is very
non-monotonic as opposed to the linear-T relaxation from coupling with
conduction electrons. We present a qualitative analysis for the additional
relaxation due to nuclear spin diffusion (NSD) and study the extent to which
NSD affects the range of validity of our method. The conclusion is that nuclear
relaxation, in combination with Knight shift measurements, can be used to
verify whether the 0.7 feature is indeed due to the presence of a bound
electron in the QPC.Comment: Published version. Appears in a Special Section on the 0.7 Feature
and Interactions in One-Dimensional Systems. 16 page
Pauli equation and the method of supersymmetric factorization
We consider different variants of factorization of a 2x2 matrix
Schroedinger/Pauli operator in two spatial dimensions. They allow to relate its
spectrum to the sum of spectra of two scalar Schroedinger operators, in a
manner similar to one-dimensional Darboux transformations. We consider both the
case when such factorization is reduced to the ordinary 2-dimensional SUSY QM
quasifactorization and a more general case which involves covariant
derivatives. The admissible classes of electromagnetic fields are described and
some illustrative examples are given.Comment: 18 pages, Late
Modeling the Formation of Clouds in Brown Dwarf Atmospheres
Because the opacity of clouds in substellar mass object (SMO) atmospheres
depends on the composition and distribution of particle sizes within the cloud,
a credible cloud model is essential for accurately modeling SMO spectra and
colors. We present a one--dimensional model of cloud particle formation and
subsequent growth based on a consideration of basic cloud microphysics. We
apply this microphysical cloud model to a set of synthetic brown dwarf
atmospheres spanning a broad range of surface gravities and effective
temperatures (g_surf = 1.78 * 10^3 -- 3 * 10^5 cm/s^2 and T_eff = 600 -- 1600
K) to obtain plausible particle sizes for several abundant species (Fe,
Mg2SiO4, and Ca2Al2SiO7). At the base of the clouds, where the particles are
largest, the particle sizes thus computed range from ~5 microns to over 300
microns in radius over the full range of atmospheric conditions considered. We
show that average particle sizes decrease significantly with increasing brown
dwarf surface gravity. We also find that brown dwarfs with higher effective
temperatures have characteristically larger cloud particles than those with
lower effective temperatures. We therefore conclude that it is unrealistic when
modeling SMO spectra to apply a single particle size distribution to the entire
class of objects.Comment: 25 pages; 8 figures. We have added considerable detail describing the
physics of the cloud model. We have also added discussions of the issues of
rainout and the self-consistent coupling of clouds with brown dwarf
atmospheric models. We have updated figures 1, 3, and 4 with new vertical
axis labels and new particle sizes for forsterite and gehlenite. Accepted to
the Astrophysical Journal, Dec. 2, 200
Quantum and classical surface acoustic wave induced magnetoresistance oscillations in a 2D electron gas
We study theoretically the geometrical and temporal commensurability
oscillations induced in the resistivity of 2D electrons in a perpendicular
magnetic field by surface acoustic waves (SAWs). We show that there is a
positive anisotropic dynamical classical contribution and an isotropic
non-equilibrium quantum contribution to the resistivity. We describe how the
commensurability oscillations modulate the resonances in the SAW-induced
resistivity at multiples of the cyclotron frequency. We study the effects of
both short-range and long-range disorder on the resistivity corrections for
both the classical and quantum non-equilibrium cases. We predict that the
quantum correction will give rise to zero-resistance states with associated
geometrical commensurability oscillations at large SAW amplitude for
sufficiently large inelastic scattering times. These zero resistance states are
qualitatively similar to those observed under microwave illumination, and their
nature depends crucially on whether the disorder is short- or long-range.
Finally, we discuss the implications of our results for current and future
experiments on two dimensional electron gases.Comment: 16 pages, 8 figure
Investigation into the limits of perturbation theory at low Q^2 using HERA deep inelastic scattering data
A phenomenological study of the final combined HERA data on inclusive deep
inelastic scattering (DIS) has been performed. The data are presented and
investigated for a kinematic range extending from values of the four-momentum
transfer, , above 10 GeV down to the lowest values observable at
HERA of = 0.045 GeV and Bjorken , = 6
10. The data are well described by fits based on perturbative quantum
chromodynamics (QCD) using collinear factorisation and evolution of the parton
densities encompassed in the DGLAP formalism from the highest down to
of a few GeV. The Regge formalism can describe the data up to 0.65 GeV. The complete data set can be described by a new fit
using the ALLM parameterisation. The region between the Regge and the
perturbative QCD regimes is of particular interest.Comment: 38 pages, 13 figure
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An on-going investigation into the ecological determinants of Lyme disease in the South Downs National Park, South East England: the potential for 'One Health' based interventions
Lyme borreliosis (LB) is a tick-borne infectious disease, with UK annual diagnoses trebling over the last two decades. The widening UK distribution of the main LB tick vector (Ixodes ricinus) has been linked to deer population expansion. However, the wider ecological determinants that affect the density of infected ticks are poorly understood. Deer have key roles in most, but not all, UK LB disease systems, but they are non-competent hosts for the pathogen itself, and small mammals or birds are usually obligatory disease reservoirs. In addition, the relapsing fever spirochete Borrelia miyomotoi was detected in the UK in 2014, but the spread and extent of this emerging human pathogen is still unknown. To date, five sites have been drag-sampled across the South Downs National Park (SDNP); with ticks being successfully obtained from all sites. In addition, ticks have been collected from a further sixteen sites where individual or multiple deer were sampled. Currently, ticks are undergoing genetic analysis to determine the host animals involved in the disease cycle, and the presence of Borrelia sp. The study aims to provide a mapped assessment of LB risk across the South Downs National Park, and identify the disease reservoir community composition. The results will help elucidate the causal factors in the SDNP, and support development of policies that avoid or minimise conflicts between public and ecosystem health
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