631 research outputs found
Spin-isospin nuclear response using the existing microscopic Skyrme functionals
Our paper aims at providing an answer to the question whether one can
reliably describe the properties of the most important spin-isospin nuclear
excitations, by using the available non-relativistic Skyrme energy functionals.
Our method, which has been introduced in a previous publication devoted to the
Isobaric Analog states, is the self-consistent Quasiparticle Random Phase
Approximation (QRPA). The inclusion of pairing is instrumental for describing a
number of experimentally measured spherical systems which are characterized by
open shells. We discuss the effect of isoscalar and isovector pairing
correlations. Based on the results for the Gamow-Teller resonance in Zr,
in Pb and in few Sn isotopes, we draw definite conclusions on the
performance of different Skyrme parametrizations, and we suggest improvements
for future fits. We also use the spin-dipole resonance as a benchmark of our
statements.Comment: Submitted to Phys. Rev.
Fooling the eyes: the influence of a sound-induced visual motion illusion on eye movements
The question of whether perceptual illusions influence eye movements is critical for the long-standing debate regarding the separation between action and perception. To test the role of auditory context on a visual illusion and on eye movements, we took advantage of the fact that the presence of an auditory cue can successfully modulate illusory motion perception of an otherwise static flickering object (sound-induced visual motion effect). We found that illusory motion perception modulated by an auditory context consistently affected saccadic eye movements. Specifically, the landing positions of saccades performed towards flickering static bars in the periphery were biased in the direction of illusory motion. Moreover, the magnitude of this bias was strongly correlated with the effect size of the perceptual illusion. These results show that both an audio-visual and a purely visual illusion can significantly affect visuo-motor behavior. Our findings are consistent with arguments for a tight link between perception and action in localization tasks
The fully self-consistent quasiparticle random phase approximation and its application to the isobaric analog resonances
A microscopic model aimed at the description of charge-exchange nuclear
excitations along isotopic chains which include open-shell systems, is
developed. It consists of quasiparticle random phase approximation (QRPA) made
on top of Hartree-Fock-Bardeen-Cooper-Schrieffer (HF-BCS). The calculations are
performed by using the Skyrme interaction in the particle-hole channel and a
zero-range, density-dependent pairing force in the particle-particle channel.
At variance with the (many) versions of QRPA which are available in literature,
in our work special emphasis is put on the full self-consistency. Its
importance, as well as the role played by the charge-breaking terms of the
nuclear Hamiltonian, like the Coulomb interaction, the charge symmetry and
charge independence breaking (CSB-CIB) forces and the electromagnetic
spin-orbit, are elucidated by means of numerical calculations of the isobaric
analog resonances (IAR). The theoretical energies of these states along the
chain of the Sn isotopes agree well with the experimental data in the stable
isotopes. Predictions for unstable systems are presented.Comment: 15 pages, 6 figure
Can Euroscepticism Contribute to a European Public Sphere? The Europeanization of Media Discourses about Euroscepticism across Six Countries
This study compares the media discourses about Euroscepticism in 2014 across
six countries (United Kingdom, Ireland, France, Spain, Sweden, and Denmark). We
assess the extent to which the mass media's reporting of Euroscepticism
indicates the Europeanization of public spheres. Using a mixed-methods approach
combining LDA topic modeling and qualitative coding, we find that approximately
70 per cent of print articles mentioning "Euroscepticism" or "Eurosceptic" are
framed in a non-domestic (i.e. European) context. In five of the six cases
studied, articles exhibiting a European context are strikingly similar in
content, with the British case as the exception. However, coverage of British
Euroscepticism drives Europeanization in other Member States. Bivariate
logistic regressions further reveal three macro-level structural variables that
significantly correlate with a Europeanized media discourse: newspaper type
(tabloid or broadsheet), presence of a strong Eurosceptic party, and
relationship to the EU budget (net contributor or receiver of EU funds).Comment: 29 pages, 2 figures, 4 tables, 2 appendice
Spin-orbit splitting and the tensor component of the Skyrme interaction
We study the role of the tensor term of the Skyrme effective interactions on
the spin-orbit splittings in the N=82 isotones and Z=50 isotopes. The different
role of the triplet-even and triplet-odd tensor forces is pointed out by
analyzing the spin-orbit splittings in these nuclei. The experimental isospin
dependence of these splittings cannot be described by Hartree-Fock calculations
employing the usual Skyrme parametrizations, but is very well accounted for
when the tensor interaction is introduced. The capability of the Skyrme forces
to reproduce binding energies and charge radii in heavy nuclei is not destroyed
by the introduction of the tensor term. Finally, we also discuss the effect of
the tensor force on the centroid of the Gamow-Teller states.Comment: Submitted to Phys. Lett.
A forensic case of hydranencephaly in a preterm neonate fully documented by postmortem imaging techniques.
The authors present a medico-legal autopsy case of hydranencephaly in a male preterm newborn, fully documented by postmortem unenhanced and enhanced imaging techniques (postmortem computed tomography and postmortem magnetic resonance imaging). Hydranencephaly is a congenital anomaly of the central nervous system, consisting in almost complete absence of the cerebral hemispheres and replacement of the cerebral parenchyma by cerebrospinal fluid, rarely encountered in forensic medical practice. A premature baby was born during the supposed 22nd and 24th week of pregnancy in the context of a denial of pregnancy without any follow-up. The newborn died a few hours after birth and medico-legal investigations were requested to determine the cause of death and exclude the intervention of a third person in the lethal process. The external examination revealed neither traumatic nor malformative lesions. Postmortem imaging investigations were typical of hydranencephaly, and conventional medico-legal autopsy, neuropathological examination, and histological examination confirmed a massive necrotic-haemorrhagic hydranencephaly. This case represents in itself an association of out-of-the-ordinary elements making it worthy of interest.
Postmortem unenhanced and enhanced imaging techniques (computed tomography and magnetic resonance imaging) were performed as complementary examination to conventional medico-legal investigations.Postmortem angiography of a preterm newborn is possible with catheterization of the umbilical blood vessels.Hydranencephaly is a congenital anomaly of the central nervous system, consisting in almost complete absence of the cerebral hemispheres and replacement of the brain by cerebrospinal fluid, for which several aetiologies have been postulated
The Influence of Vicarious Fear-Learning in “Infecting” Reactive Action Inhibition
Since the dawn of cognitive neuroscience, emotions have been recognized to impact on several executive processes, such as action inhibition. However, the complex interplay between emotional stimuli and action control is not yet fully understood. One way to measure inhibitory control is the stop-signal task (SST), which estimates the ability to cancel outright an action to the presentation of a stop signal by means of the stop-signal reaction times (SSRTs). Impaired as well as facilitated action control has been found when faced with intrinsic emotional stimuli as stop signals in SSTs. Here, we aimed at investigating more deeply the power of negative stimuli to influence our action control, testing the hypothesis that a previously neutral stimulus [i.e., the image of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)], which has been conditioned through vicarious fear learning, has the same impact on reactive action inhibition performance as an intrinsically negative stimulus (i.e., a fearful face or body). Action control capabilities were tested in 90 participants by means of a SST, in which the stop signals were represented by different negative stimuli. Results showed that the SARS-CoV-2 image enhanced the ability to suppress an ongoing action similarly to observing fearful facial expressions or fearful body postures. Interestingly, we found that this effect was predicted by impulsivity traits: for example, the less self-control the participants had, the less they showed emotional facilitation for inhibitory performance. These results demonstrated that vicarious fear learning has a critical impact on cognitive abilities, making a neutral image as threatening as phylogenetically innate negative stimuli and able to impact on our behavioral control
The role of primary auditory and visual cortices in temporal processing: A tDCS approach
Aim: Many studies showed that visual stimuli are frequently experienced as shorter than equivalent auditory stimuli. These findings suggest that timing is distributed across many brain areas and that "different clocks" might be involved in temporal processing. The aim of this study is to investigate, with the application of tDCS over V1 and A1, the specific role of primary sensory cortices (either visual or auditory) in temporal processing.
Method: Forty-eight University students were included in the study. Twenty-four participants were stimulated over A1 and 24 participants were stimulated over VI. Participants performed time bisection tasks, in the visual and the auditory modalities, involving standard durations lasting 300 ms (short) and 900 ms (long).
Results: When tDCS was delivered over A1, no effect of stimulation was observed on perceived duration but we observed higher temporal variability under anodic stimulation compared to sham and higher variability in the visual compared to the auditory modality. When tDCS was delivered over V1, an underestimation of perceived duration and higher variability was observed in the visual compared to the auditory modality.
Conclusion: Our results showed more variability of visual temporal processing under tDCS stimulation. These results suggest a modality independent role of A1 in temporal processing and a modality specific role of V1 in the processing of temporal intervals in the visual modality. (C) 2016 Elsevier B.V. All rights reserved
The unrestricted Skyrme-tensor time-dependent Hartree-Fock and its application to the nuclear response from spherical to triaxial nuclei
The nuclear time-dependent Hartree-Fock model formulated in the
three-dimensional space,based on the full Skyrme energy density functional and
complemented with the tensor force,is presented for the first time. Full
self-consistency is achieved by the model. The application to the isovector
giant dipole resonance is discussed in the linear limit, ranging from spherical
nuclei (16O, 120Sn) to systems displaying axial or triaxial deformation (24Mg,
28Si, 178Os, 190W, 238U).
Particular attention is paid to the spin-dependent terms from the central
sector of the functional, recently included together with the tensor. They turn
out to be capable of producing a qualitative change on the strength
distribution in this channel. The effect on the deformation properties is also
discussed. The quantitative effects on the linear response are small and,
overall, the giant dipole energy remains unaffected.
Calculations are compared to predictions from the (quasi)-particle random
phase approximation and experimental data where available, finding good
agreement
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