1,582 research outputs found
Theta synchronization over occipito‐temporal cortices during visual perception of body parts
Categorical clustering in the visual system is thought to have evolved as a function of intrinsic (intra-areal) and extrinsic (interareal) connectivity and experience. In the visual system, the extrastriate body area (EBA), an occipito-temporal region, responds to full body and body part images under the organizational principle of their functional/semantic meaning. Although frequency-specific modulations of neural activity associated with perceptive and cognitive functions are increasingly attracting the interest of neurophysiologists and cognitive neuroscientists, perceiving single body parts with different functional meaning and full body images induces time-frequency modulations over occipito-temporal electrodes are yet to be described. Here, we studied this issue by measuring EEG in participants who passively observed fingers, hands, arms and faceless full body images with four control plant stimuli, each bearing hierarchical analogy with the body stimuli. We confirmed that occipito-temporal electrodes (compatible with the location of EBA) show a larger event-related potential (ERP, N190) for body-related images. Furthermore, we identified a body part-specific (i.e. selective for hands and arms) theta event-related synchronization increase under the same electrodes. This frequency modulation associated with the perception of body effectors over occipito-temporal cortices is in line with recent findings of categorical organization of neural responses to human effectors in the visual system
Active primate simulator Final report
Systems engineering data and design specifications for Biosatellite active primate simulato
A clinical review on megalencephaly: A large brain as a possible sign of cerebral impairment.
Megalencephaly and macrocephaly present with a head circumference measurement 2 standard deviations above the age-related mean. However, even if pathologic events resulting in both megalencephaly and macrocephaly may coexist, a distinction between these two entities is appropriate, as they represent clinical expression of different disorders with a different approach in clinical work-up, overall prognosis, and treatment. Megalencephaly defines an increased growth of cerebral structures related to dysfunctional anomalies during the various steps of brain development in the neuronal proliferation and/or migration phases or as a consequence of postnatal abnormal events. The disorders associated with megalencephaly are classically defined into 3 groups: idiopathic or benign, metabolic, and anatomic. In this article, we seek to underline the clinical aspect of megalencephaly, emphasizing the main disorders that manifest with this anomaly in an attempt to properly categorize these disorders within the megalencephaly group
Congenital muscular dystrophy: from muscle to brain.
Congenital muscular dystrophies (CMDs) are a wide group of muscular disorders that manifest with very early onset of muscular weakness, sometime associated to severe brain involvement.The histologic pattern of muscle anomalies is typical of dystrophic lesions but quite variable depending on the different stages and on the severity of the disorder.Recent classification of CMDs have been reported most of which based on the combination of clinical, biochemical, molecular and genetic findings, but genotype/phenotype correlation are in constant progression due to more diffuse utilization of the molecular analysis.In this article, the Authors report on CMDs belonging to the group of dystroglycanopathies and in particular on the most severe forms represented by the Fukuyama CMD, Muscle-Eye-Brain disease and Walker Walburg syndrome.Clinical diagnosis of infantile hypotonia is particularly difficult considering the different etiologic factors causing the lesions, the difficulty in localizing the involved CNS area (central vs. peripheral) and the limited role of the diagnostic procedures at this early age.The diagnostic evaluation is not easy mainly in differentiating the various types of CMDs, and represents a challenge for the neonatologists and pediatricians. Suggestions are reported on the way to reach a correct diagnosis with the appropriate use of the diagnostic means
Slow Light amplification in a non-inverted gain medium
We investigate the propagation of a coherent probe light pulse through a
three-level atomic medium (in the --configuration) in the presence of
a pump laser under the conditions for gain without inversion. When the carrier
frequency of the probe pulse and the pump laser are in a Raman configuration,
we show that it is possible to amplify a slow propagating pulse. We also
analyze the regime in which the probe pulse is slightly detuned from resonance
where we observe anomalous light propagation.Comment: 7 pages, 10 figures. To be published in Europhysics Letter
Vibrational modes and low-temperature thermal properties of graphene and carbon nanotubes: A minimal force-constant model
We present a phenomenological force-constant model developed for the
description of lattice dynamics of sp2 hybridized carbon networks. Within this
model approach, we introduce a new set of parameters to calculate the phonon
dispersion of graphene by fitting the ab initio dispersion. Vibrational modes
of carbon nanotubes are obtained by folding the 2D dispersion of graphene and
applying special corrections for the low-frequency modes. Particular attention
is paid to the exact dispersion law of the acoustic modes, which determine the
low-frequency thermal properties and reveal quantum size effects in carbon
nanotubes. On the basis of the resulting phonon spectra, we calculate the
specific heat and the thermal conductance for several achiral nanotubes of
different diameter. Through the temperature dependence of the specific heat we
demonstrate that phonon spectra of carbon nanotubes show one-dimensional
behavior and that the phonon subbands are quantized at low temperatures.
Consequently, we prove the quantization of the phonon thermal conductance by
means of an analysis based on the Landauer theory of heat transport.Comment: 14 pages, 12 figure
A Copositive Framework for Analysis of Hybrid Ising-Classical Algorithms
Recent years have seen significant advances in quantum/quantum-inspired
technologies capable of approximately searching for the ground state of Ising
spin Hamiltonians. The promise of leveraging such technologies to accelerate
the solution of difficult optimization problems has spurred an increased
interest in exploring methods to integrate Ising problems as part of their
solution process, with existing approaches ranging from direct transcription to
hybrid quantum-classical approaches rooted in existing optimization algorithms.
While it is widely acknowledged that quantum computers should augment classical
computers, rather than replace them entirely, comparatively little attention
has been directed toward deriving analytical characterizations of their
interactions. In this paper, we present a formal analysis of hybrid algorithms
in the context of solving mixed-binary quadratic programs (MBQP) via Ising
solvers. We show the exactness of a convex copositive reformulation of MBQPs,
allowing the resulting reformulation to inherit the straightforward analysis of
convex optimization. We propose to solve this reformulation with a hybrid
quantum-classical cutting-plane algorithm. Using existing complexity results
for convex cutting-plane algorithms, we deduce that the classical portion of
this hybrid framework is guaranteed to be polynomial time. This suggests that
when applied to NP-hard problems, the complexity of the solution is shifted
onto the subroutine handled by the Ising solver
Penning collisions of laser-cooled metastable helium atoms
We present experimental results on the two-body loss rates in a
magneto-optical trap of metastable helium atoms. Absolute rates are measured in
a systematic way for several laser detunings ranging from -5 to -30 MHz and at
different intensities, by monitoring the decay of the trap fluorescence. The
dependence of the two-body loss rate coefficient on the excited state
() and metastable state () populations is also investigated.
From these results we infer a rather uniform rate constant
cm/s.Comment: 8 pages, 9 figures, Revte
Efficient magneto-optical trapping of a metastable helium gas
This article presents a new experiment aiming at BEC of metastable helium
atoms. It describes the design of a high flux discharge source of atoms and a
robust laser system using a DBR diode coupled with a high power Yb doped fiber
amplifier for manipulating the beam of metastable atoms. The atoms are trapped
in a small quartz cell in an extreme high vacuum. The trapping design uses an
additional laser (repumper) and allows the capture of a large number of
metastable helium atoms (approximately ) in a geometry favorable for
loading a tight magnetostatic trap.Comment: 12 pages, 7 figures, Late
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