1,575 research outputs found
Anxious to see you: Neuroendocrine mechanisms of social vigilance and anxiety during adolescence.
Social vigilance is a behavioral strategy commonly used in adverse or changing social environments. In animals, a combination of avoidance and vigilance allows an individual to evade potentially dangerous confrontations while monitoring the social environment to identify favorable changes. However, prolonged use of this behavioral strategy in humans is associated with increased risk of anxiety disorders, a major burden for human health. Elucidating the mechanisms of social vigilance in animals could provide important clues for new treatment strategies for social anxiety. Importantly, during adolescence the prevalence of social anxiety increases significantly. We hypothesize that many of the actions typically characterized as anxiety behaviors begin to emerge during this time as strategies for navigating more complex social structures. Here, we consider how the social environment and the pubertal transition shape neural circuits that modulate social vigilance, focusing on the bed nucleus of the stria terminalis and prefrontal cortex. The emergence of gonadal hormone secretion during adolescence has important effects on the function and structure of these circuits, and may play a role in the emergence of a notable sex difference in anxiety rates across adolescence. However, the significance of these changes in the context of anxiety is still uncertain, as not enough studies are sufficiently powered to evaluate sex as a biological variable. We conclude that greater integration between human and animal models will aid the development of more effective strategies for treating social anxiety
The connection between radio halos and cluster mergers and the statistical properties of the radio halo population
We discuss the statistical properties of the radio halo population in galaxy
clusters. Radio bi-modality is observed in galaxy clusters: a fraction of
clusters host giant radio halos while the majority of clusters do not show
evidence of diffuse cluster-scale radio emission. The radio bi-modality has a
correspondence in terms of dynamical state of the hosting clusters showing that
merging clusters host radio halos and follow the well known radio--X-ray
correlation, while more relaxed clusters do not host radio halos and populate a
region well separated from that correlation. These evidences can be understood
in the framework of a scenario where merger-driven turbulence re-accelerate the
radio emitting electrons. We discuss the main statistical expectations of this
scenario underlining the important role of upcoming LOFAR surveys to test
present models.Comment: 11 pages, 2 figures, Invited talk at the conference "Diffuse
Relativistic Plasmas", Bangalore, 1-4 March 2011; accepted for publication in
the Journal of Astrophysics and Astronom
Harnack inequality and regularity for degenerate quasilinear elliptic equations
We prove Harnack inequality and local regularity results for weak solutions
of a quasilinear degenerate equation in divergence form under natural growth
conditions. The degeneracy is given by a suitable power of a strong
weight. Regularity results are achieved under minimal assumptions on the
coefficients and, as an application, we prove local estimates
for solutions of a degenerate equation in non divergence form
Comparative analysis of the diffuse radio emission in the galaxy clusters A1835, A2029, and Ophiuchus
We recently performed a study of a sample of relaxed, cooling core galaxy
clusters with deep Very Large Array observations at 1.4 GHz. We find that in
the central regions of A1835, A2029, and Ophiuchus the dominant radio galaxy is
surrounded by a diffuse low-brightness radio emission that takes the form of a
mini-halo. Here we present the results of the analysis of the extended diffuse
radio emission in these mini-halos. In order to investigate the morphological
properties of the diffuse radio emission in clusters of galaxies we propose to
fit their azimuthally averaged brightness profile with an exponential,
obtaining the central brightness and the e-folding radius from which the radio
emissivity can be calculated. We investigate the radio properties of the
mini-halos in A1835, A2029, and Ophiuchus in comparison with the radio
properties of a representative sample of mini-halos and halos already known in
the literature. We find that radio halos can have quite different length-scales
but their emissivity is remarkably similar from one halo to the other. In
contrast, mini-halos span a wide range of radio emissivity. Some of them, like
the Perseus mini-halos, are characterized by a radio emissivity which is more
than 100 times greater than that of radio halos. On the other hand, the new
mini-halos in cooling core clusters analyzed in this work, namely A2029,
Ophiuchus, and A1835, have a radio emissivity which is much more typical of
halos in merging clusters rather than similar to that of the other mini-halos
previously known.Comment: 17 pages, 11 figures, A&A in press. For a version with high quality
figures, see http://erg.ca.astro.it/preprints/mini_halo_2
Revealing the magnetic field in a distant galaxy cluster: discovery of the complex radio emission from MACS J0717.5 +3745
Aims. To study at multiple frequencies the radio emission arising from the
massive galaxy cluster MACS J0717.5+3745 (z=0.55). Known to be an extremely
complex cluster merger, the system is uniquely suited for an investigation of
the phenomena at work in the intra-cluster medium (ICM) during cluster
collisions. Methods. We use multi-frequency and multi-resolution data obtained
with the Very Large Array radio telescope, and X-ray features revealed by
Chandra, to probe the non-thermal and thermal components of the ICM, their
relations and interactions. Results. The cluster shows highly complex radio
emission. A bright, giant radio halo is detected at frequencies as high as 4.8
GHz. MACS J0717.5+3745 is the most distant cluster currently known to host a
radio halo. This radio halo is also the most powerful ever observed, and the
second case for which polarized radio emission has been detected, indicating
that the magnetic field is ordered on large scales.Comment: 14 pages, 13 figures, Astronomy and Astrophysics, accepte
Dependability of Alternative Computing Paradigms for Machine Learning: hype or hope?
Today we observe amazing performance achieved by Machine Learning (ML); for specific tasks it even surpasses human capabilities. Unfortunately, nothing comes for free: the hidden cost behind ML performance stems from its high complexity in terms of operations to be computed and the involved amount of data. For this reasons, custom Artificial Intelligence hardware accelerators based on alternative computing paradigms are attracting large interest. Such dedicated devices support the energy-hungry data movement, speed of computation, and memory resources that MLs require to realize their full potential. However, when ML is deployed on safety-/mission-critical applications, dependability becomes a concern. This paper presents the state of the art of custom Artificial Intelligence hardware architectures for ML, here Spiking and Convolutional Neural Networks, and shows the best practices to evaluate their dependability
A low-frequency radio halo associated with a cluster of galaxies
Clusters of galaxies are the largest gravitationally bound objects in the
Universe, containing about 10^15 solar masses of hot (10^8 K) gas, galaxies and
dark matter in a typical volume of about 10 Mpc^3. Magnetic fields and
relativistic particles are mixed with the gas as revealed by giant radio
haloes, which arise from diffuse, megaparsec-scale synchrotron radiation at
cluster center. Radio haloes require that the emitting electrons are
accelerated in situ (by turbulence), or are injected (as secondary particles)
by proton collisions into the intergalactic medium. They are found only in a
fraction of massive clusters that have complex dynamics, which suggests a
connection between these mechanisms and cluster mergers. Here we report a radio
halo at low frequencies associated with the merging cluster Abell 521. This
halo has an extremely steep radio spectrum, which implies a high frequency
cut-off; this makes the halo difficult to detect with observations at 1.4 GHz
(the frequency at which all other known radio haloes have been best studied).
The spectrum of the halo is inconsistent with a secondary origin of the
relativistic electrons, but instead supports turbulent acceleration, which
suggests that many radio haloes in the Universe should emit mainly at low
frequencies.Comment: 18 pages, 4 figures, Nature 455, 94
Depressive-like behavior is paired to monoaminergic alteration in a murine model of Alzheimer's disease
Background: Neuropsychiatric signs are critical in primary caregiving of Alzheimer patients and have not yet been fully investigated in murine models. Methods: 18-month-old 3.Tg-AD Male mice and their wild-type Male littermates (non-Tg) were used. The open field test and the elevated plus maze test were used to evaluate anxiety-like behaviors, whereas the Porsolt forced swim test, the tail suspension test, and the sucrose preference test for antidepressant/depression-coping behaviors. Neurochemical study was conducted by microdialysis in freely-moving mice, analyzing the basal and K+-stimulated monoamine output in the frontal cortex and ventral hippocampus. Moreover by immunohistochemistry, we analysed the expression of Tyrosin hydroxylase and Tryptophan hydroxylase, which play a key role in the synthesis of monoamines. Results: Aged 3.Tg-AD mice exhibited a higher duration of immobility in the forced swim and tail suspension tests (predictors of depression-like behavior) which was not attenuated by a noradrenaline reuptake inhibitor, desipramine. In the sucrose preference test, 3.Tg-AD mice showed a significantly lower sucrose preference compared to the non-Tg group, without any difference in total fluid intake. In contrast, the motor functions and anxiety-related emotional responses of 3.Tg-AD mice were normal, as detected by the open-field and elevated plus-maze tests. To strengthen these results, we then evaluated the monoaminergic neurotransmissions by in vivo microdialysis and immunohistochemistry. In particular, with the exception of the basal hippocampal dopamine levels, 3.Tg-AD mice exhibited a lower basal extracellular output of amines in the frontal cortex and ventral hippocampus and also a decreased extracellular response to K+ stimulation. Such alterations occur with obvious local amyloid-β and tau pathologies and without gross alterations in the expression of Tyrosin and Tryptophan hydroxylase. Conclusions: These results suggest that 3.Tg-AD mice exhibit changes in depression-related behavior involving aminergic neurotrasmitters and provide an animal model for investigating AD with depression
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