No abstract available

[en] The purpose of this research is to study the effects of historical land use patterns on soil erosion within the San Pedro Lake watershed (Concepcion, VIII Region, Chile). To this end, a geochronological reconstruction of the last 50 years was accomplished by ²¹⁰Pb isotope and photo-interpretation analysis through the use of GIS. The erosion rate has varied from 0.40 t ha^-1 y^-1 in 1955 to 0.86 t ha^-1 y^-1 in 1994. The decrease in native forest was closely coupled with the increase in exotic forestry. The Total Change, meaning the land use change without considering each typology, shows a constant trend indicating a greater degree of anthropogenic intervention. As opposed to the expected, there is no relationship between land use typologies and erosion rates, however it is possible to recognise some degree of dependency between Total Change and erosion values. It is concluded that over the last 50 years the soil erosion processes in the San Pedro Lake watershed may have been more regulated more by land use changes than by land use typologies themselves. (author)

[en] Almirante Alvaro Alberto Nuclear Power Station, referred herein as Angra NPP, comprises two generating units operated by Eletrobras Termonuclear - Eletronuclear. Unit one, a Westinghouse designed PWR, operates commercially since 1985 generating 657 MW, while Unit two, designed by Siemens, is a 1350 MW PWR in operation since 2000. This paper focuses on Eletronuclear experience in developing and implementing ageing programmes addressing structural integrity of pressurized components

[en] We present results on producing TiN coatings on titanium substrates, using Plasma-Based Ion Implantation and Deposition (PBII and D). In PBII and D the substrate is immersed into stationary plasma which contains the ion species to be implanted. A negative high voltage pulse is applied to the substrate, which causes the ions in the ion sheath surrounding the substrate to be accelerated across the sheath and implanted into the substrate. We have used a 13.6 MHz, 70 W, radio frequency (RF) plasma, produced with a mixture of 80% N_2 + 20% H_2, at 200 mTorr, with 4 kV, ≈ 10 μs pulses, at a 0.2 kHz rate. During the implantation process the titanium substrate is heated at 400°C range. The resulting TiN coatings are characterized using atomic force microscopy (AFM), x-ray diffraction (XRD), and Vickers hardness test. Optical emission spectroscopy (OES) is used to identify characteristic RF plasma species. (paper)

[en] The most frequently proposed model for the origin of quasars holds that the high accretion rates seen in luminous active galactic nuclei (AGN) are primarily triggered during major mergers between gas-rich galaxies. While plausible for decades, this model has only begun to be tested with statistical rigor in the past few years. Here, we report on a Hubble Space Telescope study to test this hypothesis for z = 2 quasars with high supermassive black hole masses ($M_{\mathrm{B}\mathrm{H}}={10}^9\text{--}{10}^{10}{M}_{\odot <!--\; ???\; -->}$ ), which dominate cosmic black hole growth at this redshift. We compare Wide Field Camera 3 $F160W$ (rest-frame V-band) imaging of 19 point source-subtracted quasar hosts to a matched sample of 84 inactive galaxies, testing whether the quasar hosts have greater evidence for strong gravitational interactions. Using an expert ranking procedure, we find that the quasar hosts are uniformly distributed within the merger sequence of inactive galaxies, with no preference for quasars in high-distortion hosts. Using a merger/non-merger cutoff approach, we recover distortion fractions of $f_{\mathrm{m},\mathrm{q}\mathrm{s}\mathrm{o}}=0.39\pm <!--\; ??\; -->0.11$ for quasar hosts and $f_{\mathrm{m},\mathrm{g}\mathrm{a}\mathrm{l}}=0.30\pm <!--\; ??\; -->0.05$ for inactive galaxies (distribution modes, 68% confidence intervals), with both measurements subjected to the same observational conditions and limitations. The slight enhancement in distorted fraction for quasar hosts over inactive galaxies is not significant, with a probability that the quasar fraction is higher $P(f_{\mathrm{m},\mathrm{q}\mathrm{s}\mathrm{o}}><!--\; >\; -->f_{\mathrm{m},\mathrm{g}\mathrm{a}\mathrm{l}})=0.78$ ($0.78\mathrm{\sigma <!--\; ??\; -->}$), in line with results for lower mass and lower z AGN. We find no evidence that major mergers are the primary triggering mechanism for the massive quasars that dominate accretion at the peak of cosmic quasar activity.

[en] The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.9 deg² of the COSMOS field down to limiting depths of 1.9 × 10^–16 erg cm^–2 s^–1 in the soft (0.5-2 keV) band, 7.3 × 10^–16 erg cm^–2 s^–1 in the hard (2-10 keV) band, and 5.7 × 10^–16 erg cm^–2 s^–1 in the full (0.5-10 keV) band. In this paper we report the i, K, and 3.6 μm identifications of the 1761 X-ray point sources. We use the likelihood ratio technique to derive the association of optical/infrared counterparts for 97% of the X-ray sources. For most of the remaining 3%, the presence of multiple counterparts or the faintness of the possible counterpart prevented a unique association. For only 10 X-ray sources we were not able to associate a counterpart, mostly due to the presence of a very bright field source close by. Only two sources are truly empty fields. The full catalog, including spectroscopic and photometric redshifts and classification described here in detail, is available online. Making use of the large number of X-ray sources, we update the 'classic locus' of active galactic nuclei (AGNs) defined 20 years ago in soft X-ray surveys and define a new locus containing 90% of the AGNs in the survey with full-band luminosity >10⁴² erg s^–1. We present the linear fit between the total i-band magnitude and the X-ray flux in the soft and hard bands, drawn over two orders of magnitude in X-ray flux, obtained using the combined C-COSMOS and XMM-COSMOS samples. We focus on the X-ray to optical flux ratio (X/O) and we test its known correlation with redshift and luminosity, and a recently introduced anti-correlation with the concentration index (C). We find a strong anti-correlation (though the dispersion is of the order of 0.5 dex) between X/O computed in the hard band and C and that 90% of the obscured AGNs in the sample with morphological information live in galaxies with regular morphology (bulgy and disky/spiral), suggesting that secular processes govern a significant fraction of the black hole growth at X-ray luminosities of 10⁴³-10^44.5 erg s^–1. We also investigate the degree of obscuration of the sample using the hardness ratio, and we compare the X-ray color with the near-infrared to optical color.

[en] The 'Cosmic Evolution Survey' (COSMOS) enables the study of the spectral energy distributions (SEDs) of active galactic nuclei (AGNs) because of the deep coverage and rich sampling of frequencies from X-ray to radio. Here we present an SED catalog of 413 X-ray (XMM-Newton)-selected type 1 (emission line FWHM > 2000 km s^–1) AGNs with Magellan, SDSS, or VLT spectrum. The SEDs are corrected for Galactic extinction, broad emission line contributions, constrained variability, and host galaxy contribution. We present the mean SED and the dispersion SEDs after the above corrections in the rest-frame 1.4 GHz to 40 keV, and show examples of the variety of SEDs encountered. In the near-infrared to optical (rest frame ∼8 μm-4000 Å), the photometry is complete for the whole sample and the mean SED is derived from detections only. Reddening and host galaxy contamination could account for a large fraction of the observed SED variety. The SEDs are all available online.