7,157 research outputs found
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
Cell Ultrastructure in Disease
The doctor of today must adopt the \u27cellular way of thinking\u27 in the evaluation of diseases. This ultrastructural outlook provides him with much indispensable information that also serves a practical purpose. A diseased cell organelle is at the basis of every clinical sign and any attempt of therapy must be aimed at that specific point of lesion. We intend, in the light of a long experience, to propose to clinicians a new way of thinking in which a precise correlation between symptoms and sub-microscopic changes of the cell is considered. Many different examples amply justify this proposal. Electron microscopy can contribute by enabling a) identification of structural sub-cellular modifications suitable for the finest differential diagnosis, b) more and more complete understanding of pathogenic pathways of various diseases, c) the establishment of guidelines for precise pharmacological interventions at the molecular level
The intracluster magnetic field power spectrum in Abell 665
The goal of this work is to investigate the power spectrum of the magnetic
field associated with the giant radio halo in the galaxy cluster A665. For
this, we present new deep Very Large Array total intensity and polarization
observations at 1.4 GHz. We simulated Gaussian random three-dimensional
turbulent magnetic field models to reproduce the observed radio halo emission.
By comparing observed and synthetic radio halo images we constrained the
strength and structure of the intracluster magnetic field. We assumed that the
magnetic field power spectrum is a power law with a Kolmogorov index and we
imposed a local equipartition of energy density between relativistic particles
and field. Under these assumptions, we find that the radio halo emission in
A665 is consistent with a central magnetic field strength of about 1.3 micro-G.
To explain the azimuthally averaged radio brightness profile, the magnetic
field energy density should decrease following the thermal gas density, leading
to an averaged magnetic field strength over the central 1 Mpc^3 of about 0.75
micro-G. From the observed brightness fluctuations of the radio halo, we infer
that the outer scale of the magnetic field power spectrum is ~450 kpc, and the
corresponding magnetic field auto-correlation length is ~100 kpc.Comment: 12 pages, 6 figures, accepted for publication on A&A, language
editing. For a high quality version see
http://erg.ca.astro.it/preprints/a665_halo
Testing the radio halo-cluster merger scenario. The case of RXCJ2003.5-2323
We present a combined radio, X-ray and optical study of the galaxy cluster
RXCJ2003.5-2323. The cluster hosts one of the largest, most powerful and
distant giant radio halos known to date, suggesting that it may be undergoing a
strong merger process. The aim of our multiwavelength study is to investigate
the radio-halo cluster merger scenario. We studied the radio properties of the
giant radio halo in RXCJ2003.5-2323 by means of new radio data obtained at 1.4
GHz with the Very Large Array, and at 240 MHz with the Giant Metrewave Radio
Telescope, in combination with previously published GMRT data at 610 MHz. The
dynamical state of the cluster was investigated by means of X-ray Chandra
observations and optical ESO--NTT observations. Our study confirms that
RXCJ2003.5-2323 is an unrelaxed cluster. The unusual filamentary and clumpy
morphology of the radio halo could be due to a combination of the filamentary
structure of the magnetic field and turbulence in the inital stage of a cluster
merger.Comment: 10 page, 10 figures, accepted for publication on A&
The spectral index image of the radio halo in the cluster Abell 520 hosting a famous bow shock
Synchrotron radio emission is being detected from an increasing number of
galaxy clusters. Spectral index images are a powerful tool to investigate the
origin, nature, and connection of these sources with the dynamical state of the
cluster. The aim of this work is to investigate the spectral index distribution
of the radio halo in the galaxy cluster A520, a complex system from an optical,
radio, and X-ray point of view. We present deep Very Large Array observations
in total intensity at 325 and 1400 MHz. We produced and analyzed spectral index
images of the radio halo in this frequency range at a resolution of 39" and 60"
and looked for possible correlations with the thermal properties of the
cluster. We find an integrated radio halo spectral index alpha(325-1400) ~
1.12. No strong radial steepening is present and the spectral index
distribution is intrinsically complex with fluctuations only partially due to
measurement errors. The radio halo integrated spectral index and the cluster
temperature follow the global trend observed in other galaxy clusters although
a strong point-to-point correlation between the spectral index and the thermal
gas temperature has not been observed. The complex morphology in the spectral
index image of the radio halo in A520 is in agreement with the primary models
for radio halo formation. The flatness of the radial profile suggests that the
merger is still ongoing and is uniformly and continuously (re-) accelerating
the population of relativistic electrons responsible of the radio emission even
at large (~ 1 Mpc) distances from the cluster center.Comment: 12 pages, 10 figures, A&A accepte
Potential Predation On Fish Eggs By The Lobate Ctenophore Mnemiopsis-Leidyi Within And Outside The Chesapeake Bay Plume
In Chesapeake Bay in June, the predatory lobate ctenophore Mnemiopsis leidyi and the eggs of the bay anchovy Anchoa mitchilli typically reach seasonal and localized abundance together. When examined at small vertical (1-3m), horizontal (10-50m), and temporal (6-hour) scales, the co-occurrence of M. leidyi and fish eggs (32.3-74.2% of which were A. mitchilli) was greatest in the northern reaches of the mouth of Chesapeake Bay, where the water column was stratified. Stratification to the south was effected by the Chesapeake Bay plume. With estimates of ctenophore clearance rate reported elsewhere and observed densities of ctenophores and fish eggs, potential predation was judged to be greatest in the northern reaches of the Bay mouth. The observation that co-occurrence and potential predation are greatest in areas where Chesapeake Bay water mixes with coastal shelf water implies that those fishes that spawn in low-salinity surface waters of well-stratified water columns may afford protection of their eggs from ctenophore predation
Unravelling the origin of large-scale magnetic fields in galaxy clusters and beyond through Faraday Rotation Measures with the SKA
We investigate the possibility for the SKA to detect and study the magnetic
fields in galaxy clusters and in the less dense environments surrounding them
using Faraday Rotation Measures. To this end, we produce 3-dimensional magnetic
field models for galaxy clusters of different masses and in different stages of
their evolution, and derive mock rotation measure observations of background
radiogalaxies. According to our results, already in phase I, we will be able to
infer the magnetic field properties in galaxy clusters as a function of the
cluster mass, down to solar-masses. Moreover, using cosmological
simulations to model the gas density, we have computed the expected rotation
measure through shock-fronts that occur in the intra-cluster medium during
cluster mergers. The enhancement in the rotation measure due to the density
jump will permit to constraint the magnetic field strength and structure after
the shock passage. SKA observations of polarised sources located behind galaxy
clusters will answer several questions about the magnetic field strength and
structure in galaxy clusters, and its evolution with cosmic time.Comment: 9 pages, 4 Figures, to appear as part of 'Cosmic Magnetism' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14
Cluster Magnetic Fields from Galactic Outflows
We performed cosmological, magneto-hydrodynamical simulations to follow the
evolution of magnetic fields in galaxy clusters, exploring the possibility that
the origin of the magnetic seed fields are galactic outflows during the
star-burst phase of galactic evolution. To do this we coupled a semi-analytical
model for magnetized galactic winds as suggested by \citet{2006MNRAS.370..319B}
to our cosmological simulation. We find that the strength and structure of
magnetic fields observed in galaxy clusters are well reproduced for a wide
range of model parameters for the magnetized, galactic winds and do only weakly
depend on the exact magnetic structure within the assumed galactic outflows.
Although the evolution of a primordial magnetic seed field shows no significant
differences to that of galaxy clusters fields from previous studies, we find
that the magnetic field pollution in the diffuse medium within filaments is
below the level predicted by scenarios with pure primordial magnetic seed
field. We therefore conclude that magnetized galactic outflows and their
subsequent evolution within the intra-cluster medium can fully account for the
observed magnetic fields in galaxy clusters. Our findings also suggest that
measuring cosmological magnetic fields in low-density environments such as
filaments is much more useful than observing cluster magnetic fields to infer
their possible origin.Comment: Minor revision for publication in MNRA
Hyaluronan and cardiac regeneration
Hyaluronan (HA) is abundantly expressed in several human tissues and a variety of roles for HA has been highlighted. Particularly relevant for tissue repair, HA is actively produced during tissue injury, as widely evidenced in wound healing investigations. In the heart HA is involved in physiological functions, such as cardiac development during embryogenesis, and in pathological conditions including atherosclerosis and myocardial infarction. Moreover, owing to its relevant biological properties, HA has been widely used as a biomaterial for heart regeneration after a myocardial infarction. Indeed, HA and its derivatives are biodegradable and biocompatible, promote faster healing of injured tissues, and support cells in relevant processes including survival, proliferation, and differentiation. Injectable HA-based therapies for cardiovascular disease are gaining growing attention because of the benefits obtained in preclinical models of myocardial infarction. HA-based hydrogels, especially as a vehicle for stem cells, have been demonstrated to improve the process of cardiac repair by stimulating angiogenesis, reducing inflammation, and supporting local and grafted cells in their reparative functions. Solid-state HA-based scaffolds have been also investigated to produce constructs hosting mesenchymal stem cells or endothelial progenitor cells to be transplanted onto the infarcted surface of the heart. Finally, applying an ex-vivo mechanical stretching, stem cells grown in HA-based 3D scaffolds can further increase extracellular matrix production and proneness to differentiate into muscle phenotypes, thus suggesting a potential strategy to create a suitable engineered myocardial tissue for cardiac regeneration
Same Sign WW Scattering Process as a Probe of Higgs Boson in pp Collision at = 10 TeV
WW scattering is an important process to study electroweak symmetry breaking
in the Standard Model at the LHC, in which the Higgs mechanism or other new
physics processes must intervene to preserve the unitarity of the process below
1 TeV. This channel is expected to be one of the most sensitive to determine
whether the Higgs boson exists. In this paper, the final state with two same
sign Ws is studied, with a simulated sample corresponding to the integrated
luminosity of 60 fb in pp collision at 10 TeV. Two
observables, the invariant mass of from W decays and the azimuthal
angle difference between the two s, are utilized to distinguish the Higgs
boson existence scenario from the Higgs boson absence scenario. A good signal
significance for the two cases can be achieved. If we define the separation
power of the analysis as the distance, in the log-likelihood plane, of
pseudo-experiments outcomes in the two cases, with the total statistics
expected from the ATLAS and CMS experiments at the nominal centre-of-mass
energy of 14 TeV, the separation power will be at the level of 4 .Comment: 5 pages, 4 figures, 3 table
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