The giant radio halo in Abell 2163

New radio data is presented for the rich cluster Abell 2163. The cluster radio emission is characterized by the presence of a radio halo, which is one of the most powerful and extended halos known so far. In the NE peripheral cluster region, we also detect diffuse elongated emission, which we classify as a cluster relic. The cluster A2163 is very hot and luminous in X-ray. Its central region is probably in a highly non relaxed state, suggesting that this cluster is likely to be a recent merger. The existence of a radio halo in this cluster confirms that halos are associated with hot massive clusters, and confirms the connection between radio halos and cluster merger processes. The comparison between the radio emission of the halo and the cluster X-ray emission shows a close structural similarity. A power law correlation is found between the radio and X-ray brightness, with index = 0.64. We also report the upper limit to the hard X-ray emission, obtained from a BeppoSAX observation. We discuss the implications of our results.Comment: 7 pages, 8 figures (5 in ps and 3 in gif), Accepted for publication in Astron. Astrop

A new combined protocol to treat the dentin hypersensitivity associated with non-carious cervical lesions: A randomized controlled trial

The goal of this research is to assess the desensitizing effect of a diode laser on noncarious cervical lesions (NCCLs) responsible for dentin hypersensitivity (DH) in two separate output forces implemented both independently and in sequential combination modalities. A randomized controlled trial for this study was applied. Sixty-nine NCCLs responsible for DH pain with severity between 6 and 9 on the VAS scale were considered. Three study groups were developed using just one lesion from three different quadrants of the oral cavity of each patient. All treatment procedures were conducted using a laser diode (810 nm, 5 W) with varying power outputs used separately or in combination. The pain by DH was evaluated at baseline, at treatment completion, and at 15 days and 3 months after each laser procedure. Data analysis was performed using a Wilcoxon test for paired samples, a one-way ANOVA test, and an unpaired t-test. The significant reduction of the mean VAS score was estimated in each study group immediately and at 15 days and 3 months after the end of treatment and compared with the baseline mean VAS score (p-value < 0.0001). The best result concerning the improvement of DH symptomatology was assessed when a combined protocol of two different output powers of the diode laser was used. The authors conclude that the diode laser (810 nm) therapy procedure combining two separate output forces (low and high power) can improve the painful symptoms of DH from NCCLs

Enamel Erosion Reduction through Coupled Sodium Fluoride and Laser Treatments before Exposition in an Acid Environment: An In Vitro Randomized Control SEM Morphometric Analysis

(1) Background: Erosive lesions of dental enamel are steadily increasing owing to both the availability of exogenous acid and the production of endogenous acid. The aim of this study was to investigate the erosion-inhibiting potential of a diode laser irradiation and topical application of fluoride used alone or in combination on the enamel surface of extracted teeth before exposure to an acidic solution. (2) Methods: The four axial enamel surfaces of 40 healthy molars were used for four study groups: (A) no treatment; (B) application of fluoride gel for 120 s; (O) a diode laser application for 120 s; and (X) a combined laser/fluoride for 120 s. Each enamel surface was examined by SEM (scanning electron microscopy). (3) Results: At 700× magnification, it was possible to detect the enamel prisms of the test area of groups A, B, and O, while no structures such as enamel prisms were highlighted for group X because they were covered by an amorphous layer. The mean number of prisms ×1000 µm2 was 7.2 units with an SD of 0.72 for group A, 8 units with an SD of 0.96 for group B, and 4.8 units with a SD of 0.4 for group O. Student’s t-test showed no significant difference between group A and B with a p = 0.054. Group O showed a significant reduction of prims ×1000 µm2 compared with group A (p = 0.0027) and group B (p = 0.0009). Student’s t-test showed no significant difference between groups A and B with a p = 0.054. Group O showed a significant reduction of prims density with respect to group A (p = 0.0027) and group B (p = 0.0009). (4) Conclusions: This amorphous layer might be correlated with the effect of laser on enamel, which reduces both water and carbonate ion; increases the crystallinity of hydroxyapatite, and improves the mechanical properties of enamel; which is responsible for greater protection expressed by the enamel of group X against acid attacks

An analysis of electron distributions in galaxy clusters by means of the flux ratio of iron lines FeXXV and XXVI

The interpretation of hard X-ray emission from galaxy clusters is still ambiguous and different models proposed can be probed using various observational methods. Here we explore a new method based on Fe line observations. Spectral line emissivities have usually been calculated for a Maxwellian electron distribution. In this paper a generalized approach to calculate the iron line flux for a modified Maxwellian distribution is considered. We have calculated the flux ratio of iron lines for the various possible populations of electrons that have been proposed to account for measurements of hard X-ray excess emission from the clusters A2199 and Coma. We found that the influence of the suprathermal electron population on the flux ratio is more prominent in low temperature clusters (as Abell 2199) than in high temperature clusters (as Coma).Comment: 6 pages, 3 figures, accepted for publication in A&

The BeppoSAX view of the hot cluster Abell 2319

We present results from a BeppoSAX observation of the rich cluster Abell 2319. The broad band spectrum (2-50 keV) of the cluster can be adequately represented by an optically thin thermal emission model with a temperature of 9.6+/-0.3 keV and a metal abundance of 0.25+/-0.03 in solar units, and with no evidence of a hard X-ray excess in the PDS spectrum. From the upper limit to the hard tail component we derive a lower limit of ~0.04 \muG for the volume-averaged intracluster magnetic field. By performing spatially resolved spectroscopy in the medium energy band (2-10 keV), we find that the projected radial temperature and metal abundance profiles are constant out to a radius of 16 arcmin (1.4 Mpc). A reduction of the temperature of 1/3, when going from the cluster core out to 16 arcmin, can be excluded in the present data at the 99% confidence level. From the analysis of the temperature and abundance maps we find evidence of a temperature enhancement and of an abundance decrement in a region localized 6 arcmin--8 arcmin NE of the core, where a merger event may be taking place. Finally, the temperature map indicates that the subcluster located NW of the main cluster may be somewhat cooler than the rest of the cluster.Comment: To appear in ApJ-Letter

Coma revealed as an extended hard X-rays source by INTEGRAL IBIS/ISGRI

Aims. We report the INTEGRAL/IBIS observations of the Coma Cluster in the hard X-ray/soft-ray domain. Methods. Since the Coma Cluster appears as an extended source, its global intensity and significance cannot be directly extracted with standard coded mask analysis. We used the method of imaging the extended sources with a coded mask telescope developed by Renaud et al. (2006). Results. The imaging capabilities and the sensitivity of the IBIS/ISGRI coded mask instrument allows us to identify for the first time the site of the emission above ~ 15 keV. We have studied the Coma Cluster morphology in the 18-30keV band and found that it follows the prediction based on X-ray observations.We also bring constraints on the non-thermal mechanism contribution at higher energies.Comment: 4 pages, 4 figures, Accepted for publication in A&A Letter

Non-thermal emission in the core of Perseus: results from a long XMM-Newton observation

We employ a long XMM-Newton observation of the core of the Perseus cluster to validate claims of a non-thermal component discovered with Chandra. From a meticulous analysis of our dataset, which includes a detailed treatment of systematic errors, we find the 2-10 keV surface brightness of the non-thermal component to be smaller than about 5x10^-16 erg cm^-2s^-1arcsec^-2. The most likely explanation for the discrepancy between the XMM-Newton and Chandra estimates is a problem in the effective area calibration of the latter. Our EPIC based magnetic field lower limits are not in disagreement with Faraday rotation measure estimates on a few cool cores and with a minimum energy estimate on Perseus. In the not too distant future Simbol-X may allow detection of non-thermal components with intensities more than 10 times smaller than those that can be measured with EPIC; nonetheless even the exquisite sensitivity within reach for Simbol-X might be insufficient to detect the IC emission from Perseus.Comment: To appear in A&A main Journa

The origin of the diffuse non-thermal X-ray and radio emission in the Ophiuchus cluster of galaxies

We present high resolution 240 and 607 MHz GMRT radio observations, complemented with 74 MHz archival VLA radio observations of the Ophiuchus cluster of galaxies, whose radio mini-halo has been recently detected at 1400 MHz. We also present archival Chandra and XMM-Newton data of the Ophiuchus cluster. Our observations do not show significant radio emission from the mini-halo, hence we present upper limits to the integrated, diffuse non-thermal radio emission of the core of the Ophiuchus cluster. The XMM-Newton observations can be well explained by a two-temperature thermal model with temperatures of ~=1.8 keV and ~=9.0 keV, respectively, which confirms previous results that suggest that the innermost central region of the Ophiuchus cluster is a cooling core. We also used the XMM-Newton data to set up an upper limit to the (non-thermal) X-ray emission from the cluster. The combination of available radio and X-ray data has strong implications for the currently proposed models of the spectral energy distribution (SED) from the Ophiuchus cluster. In particular, a synchrotron+IC model is in agreement with the currently available data, if the average magnetic field is in the range (0.02-0.3) microG. A pure WIMP annihilation scenario can in principle reproduce both radio and X-ray emission, but at the expense of postulating very large boost factors from dark matter substructures, jointly with extremely low values of the average magnetic field. Finally, a scenario where synchrotron and inverse Compton emission arise from PeV electron-positron pairs (via interactions with the CMB), can be ruled out, as it predicts a non-thermal soft X-ray emission that largely exceeds the thermal Bremsstrahlung measured by INTEGRAL.Comment: Accepted for publication in MNRAS; 13 pages, 8 figures. Includes minor changes. Abridged abstrac

Solving the Cooling Flow Problem of Galaxy Clusters by Dark Matter Neutralino Annihilation

Recent X-ray observations revealed that strong cooling flow of intracluster gas is not present in galaxy clusters, even though predicted theoretically if there is no additional heating source. I show that relativistic particles produced by dark matter neutralino annihilation in cluster cores provide a sufficient heating source to suppress the cooling flow, under reasonable astrophysical circumstances including adiabatic growth of central density profile, with appropriate particle physics parameters for dark matter neutralinos. In contrast to other astrophysical heat sources such as AGNs, this process is a steady and stable feedback over cosmological time scales after turned on.Comment: 4 pages, no figure. Accepted to Phys. Rev. Lett. A few minor revisions and references adde