12,395 research outputs found
Spatial Social Networks
social networks;implementation;spatial cost topologies
From glass formation to icosahedral ordering by curving three-dimensional space
Geometric frustration describes the inability of a local molecular
arrangement, such as icosahedra found in metallic glasses and in model atomic
glass-formers, to tile space. Local icosahedral order however is strongly
frustrated in Euclidean space, which obscures any causal relationship with the
observed dynamical slowdown. Here we relieve frustration in a model
glass-forming liquid by curving 3-dimensional space onto the surface of a
4-dimensional hypersphere. For sufficient curvature, frustration vanishes and
the liquid freezes in a fully icosahedral structure via a sharp `transition'.
Frustration increases upon reducing the curvature, and the transition to the
icosahedral state smoothens while glassy dynamics emerges. Decreasing the
curvature leads to decoupling between dynamical and structural length scales
and the decrease of kinetic fragility. This sheds light on the observed
glass-forming behavior in the Euclidean space.Comment: 5 pages + supplementary materia
Non-Langevin behaviour of the uncompensated magnetisation in nanoparticles of artificial ferritin
The magnetic behaviour of nanoparticles of antiferromagnetic ferritin has
been investigated by 57Fe Mossbauer absorption spectroscopy and magnetisation
measurements, in the temperature range 2.5K-250K and with magnetic fields up to
7T. Samples containing nanoparticles with an average number of Fe atoms ranging
from 400 to 2500 were studied. The value of the anisotropy energy per unit
volume was determined and found to be in the range 3-6 10**5 ergs/cm3, which is
a value typical for ferric oxides. By comparing the results of the two
experimental methods at large field, we show that, contratry to what is
currently assumed, the uncompensated magnetisation of the feritin cores in the
superparamagnetic regime does not follow a Langevin law. For magnetic fields
below the spin-flop field, we propose an approximate law for the field and
temperature variation of the uncompensated magnetisation which has so far never
been applied in antiferromagnetic systems. This approach should more generally
hold for randomly oriented antiferro- magnetic nanoparticles systems with weak
uncompensated moments.Comment: 11 pages, 11 figure
How does visual context influence recognition of facial emotion in people with traumatic brain injury?
OBJECTIVE:
The current study assessed recognition of facial emotional stimuli following traumatic brain injury (TBI) and examined whether performance may be influenced by emotional visual scenes.
METHODS:
Thirty-five patients with moderate-to-severe TBI and 55 matched controls completed the novel Angers Facial Expression in Context Task (AFECT), designed to examine recognition of facial expressions of basic emotions in both congruent and incongruent emotional visual contexts.
RESULTS:
In comparison with non-brain damaged adults, patients with TBI performed more poorly and slowly on both contextual conditions (congruent vs. incongruent) of the AFECT.
CONCLUSION:
Taken together, these results raise the possibility that adults with TBI may not fully benefit from supportive contextual cues. Also, they stress the importance of using emotional stimuli that better capture affect processing in real-world contexts and open up new avenues to better understand negative social outcomes in patients with TBI
From Classical State-Swapping to Quantum Teleportation
The quantum teleportation protocol is extracted directly out of a standard
classical circuit that exchanges the states of two qubits using only
controlled-NOT gates. This construction of teleportation from a classically
transparent circuit generalizes straightforwardly to d-state systems.Comment: Missing daggers added to Figures 13, 14, and 15. Otherwise this is
the version that appeared in Physical Revie
Time-dependent spherically symmetric covariant Galileons
We study spherically symmetric solutions of the cubic covariant Galileon
model in curved spacetime in presence of a matter source, in the test scalar
field approximation. We show that a cosmological time evolution of the Galileon
field gives rise to an induced matter-scalar coupling, due to the
Galileon-graviton kinetic braiding, therefore the solution for the Galileon
field is non trivial even if the bare matter-scalar coupling constant is set to
zero. The local solution crucially depends on the asymptotic boundary
conditions, and in particular, Minkowski and de Sitter asymptotics correspond
to different branches of the solution. We study the stability of these
solutions, namely, the well-posedness of the Cauchy problem and the positivity
of energy for scalar and tensor perturbations, by diagonalizing the kinetic
terms of the spin-2 and spin-0 degrees of freedom. In addition, we find that in
presence of a cosmological time evolution of the Galileon field, its kinetic
mixing with the graviton leads to a friction force, resulting to efficient
damping of scalar perturbations within matter.Comment: 20 pages, no figure, RevTeX4 format; v2: minor changes reflecting the
published version in PR
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