7,600 research outputs found
Recommended from our members
A physiological marker of recognition memory in adults with autism spectrum disorder? The Pupil Old/New Effect
This study investigated the pupil Old/New effect in individuals with Autism Spectrum Disorder (ASD) and typical development (TD). Participants studied verbal and visual meaningful and meaningless materials in black and white on a computer screen. Pupil sizes were measured while participants performed a Remember (episodic memory with context) /Know (semantic memory, no context) recognition memory test. ASD compared to TD individuals showed significantly reduced recognition rates for all materials. Both groups showed better memory for visual compared to verbal (picture superiority effect) and meaningful compared to meaningless materials. A pupil size ratio (pupil size for test item divided by baseline) for old (studied) and new (unstudied) materials indicated larger pupils for old compared to new materials only for the TD but not the ASD group. Pupil size in response to old versus new items was positively related to recognition accuracy, confirming that the pupil Old/New effect reflects a memory phenomenon in the ASD group. In addition, this study suggests an involvement of the noradrenergic neurotransmitter system in the abnormal hippocampal functioning in ASD. Implications of these findings as well as their underlying neurophysiology will be discussed in relation to current theories of memory in ASD
Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions. II. Microscopic analysis of low-lying states in magnesium isotopes
The recently developed structure model that uses the generator coordinate
method to perform configuration mixing of angular-momentum projected wave
functions, generated by constrained self-consistent relativistic mean-field
calculations for triaxial shapes (3DAMP+GCM), is applied in a systematic study
of ground states and low-energy collective states in the even-even magnesium
isotopes Mg. Results obtained using a relativistic point-coupling
nucleon-nucleon effective interaction in the particle-hole channel, and a
density-independent -interaction in the pairing channel, are compared
to data and with previous axial 1DAMP+GCM calculations, both with a
relativistic density functional and the non-relativistic Gogny force. The
effects of the inclusion of triaxial degrees of freedom on the low-energy
spectra and E2 transitions of magnesium isotopes are examined.Comment: 28 pages, 11 figures and 1 tabl
Remarks on the use of projected densities in the density dependent part of Skyrme or Gogny functionals
I discuss the inadequacy of the "projected density" prescription to be used
in density dependent forces/functionals when calculations beyond mean field are
pursued. The case of calculations aimed at the symmetry restoration of mean
fields obtained with effective realistic forces of the Skyrme or Gogny type is
considered in detail. It is shown that at least for the restoration of spatial
symmetries like rotations, translations or parity the above prescription yields
catastrophic results for the energy that drive the intrinsic wave function to
configurations with infinite deformation, preventing thereby its use both in
projection after and before variation.Comment: To be published as a contribution to J. Phys G, Special Issue, Focus
Section: Open Problems in Nuclear Structur
Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions
The framework of relativistic energy density functionals is extended to
include correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. The generator coordinate method is used
to perform configuration mixing of angular-momentum projected wave functions,
generated by constrained self-consistent relativistic mean-field calculations
for triaxial shapes. The effects of triaxial deformation and of -mixing is
illustrated in a study of spectroscopic properties of low-spin states in
Mg.Comment: 15 pages, 11 figures, 4 tables, accepted for publication in Phys.
Rev.
Axially deformed relativistic Hartree Bogoliubov with separable pairing force
A separable form of pairing interaction in the channel has been
introduced and successfully applied in the description of both static and
dynamic properties of superfluid nuclei. By adjusting the parameters to
reproduce the pairing properties of the Gogny force in nuclear matter, this
separable pairing force is successful in depicting the pairing properties of
ground states and vibrational excitations of spherical nuclei on almost the
same footing as the original Gogny force. In this article, we extend these
investigations for Relativistic Hartree Bogoliubov theory in deformed nuclei
with axial symmetry (RHBZ) using the same separable pairing interaction. In
order to preserve translational invariance we construct one- and
two-dimensional Talmi-Moshinsky brackets for the cylindrical harmonic
oscillator basis. We show that the matrix elements of this force can then be
expanded in a series of separable terms. The convergence of this expansion is
investigated for various deformations. We observe a relatively fast
convergence. This allows for a considerable reduction in computing time as
compared to RHBZ-calculations with the full Gogny force in the pairing channel.
As an example we solve the RHBZ equations with this separable pairing force for
the ground states of the chain of Sm-isotopes. Good agreement with the
experimental data as well as with other theoretical results is achieved.Comment: 8 pages, 5 figures. accepted by Phys. Rev.
Avoiding Wireheading with Value Reinforcement Learning
How can we design good goals for arbitrarily intelligent agents?
Reinforcement learning (RL) is a natural approach. Unfortunately, RL does not
work well for generally intelligent agents, as RL agents are incentivised to
shortcut the reward sensor for maximum reward -- the so-called wireheading
problem. In this paper we suggest an alternative to RL called value
reinforcement learning (VRL). In VRL, agents use the reward signal to learn a
utility function. The VRL setup allows us to remove the incentive to wirehead
by placing a constraint on the agent's actions. The constraint is defined in
terms of the agent's belief distributions, and does not require an explicit
specification of which actions constitute wireheading.Comment: Artificial General Intelligence (AGI) 201
Athletes' perceptions of coaching effectiveness and athlete-related outcomes in rugby union: An investigation based on the coaching efficacy model
This study examined the relationships between athletes' perceptions of coaching effectiveness, based on the coaching efficacy model, and their effort, commitment, enjoyment, self-efficacy, and prosocial and antisocial behavior in rugby union. Participants were 166 adult male rugby-union players (M age = 26.5, SD = 8.5 years), who completed questionnaires measuring their perceptions of four dimensions of coaching effectiveness as well as their effort, commitment, enjoyment, self-efficacy, and prosocial and antisocial behavior. Regression analyses, controlling for rugby experience, revealed that athletes' perceptions of motivation effectiveness predicted effort, commitment, and enjoyment. Further, perceptions of technique effectiveness predicted self-efficacy, while perceptions of character-building effectiveness predicted prosocial behavior. None of the perceived coaching effectiveness dimensions were related to antisocial behavior. In conclusion, athletes' evaluations of their coach's ability to motivate, provide instruction, and instill an attitude of fair play in his athletes have important implications for the variables measured in this study
Application of the gradient method to Hartree-Fock-Bogoliubov theory
A computer code is presented for solving the equations of
Hartree-Fock-Bogoliubov (HFB) theory by the gradient method, motivated by the
need for efficient and robust codes to calculate the configurations required by
extensions of HFB such as the generator coordinate method. The code is
organized with a separation between the parts that are specific to the details
of the Hamiltonian and the parts that are generic to the gradient method. This
permits total flexibility in choosing the symmetries to be imposed on the HFB
solutions. The code solves for both even and odd particle number ground states,
the choice determined by the input data stream. Application is made to the
nuclei in the -shell using the USDB shell-model Hamiltonian.Comment: 20 pages, 5 figures, 3 table
- …