Relativistic reflection in the average X-ray spectrum of AGN in the V\'eron-Cetty & V\'eron catalogue

The X-ray spectra of active galactic nuclei (AGN) unveil properties of matter around the super massive black hole (SMBH). We investigate the X-ray spectra of AGN focusing on Compton reflection and fluorescence, important processes of interaction between primary radiation and circum-nuclear material. Unresolved emission lines (most notably the Fe line) in the X-ray spectra of AGN indicate that this material is located far away from the SMBH. Contributions from the inner accretion disk, affected by relativistic effects, have also been detected in several cases. We studied the average X-ray spectrum of a sample of 263 X-ray unabsorbed AGN that yield 419023 counts in the 2-12 keV rest-frame band distributed among 388 XMM-Newton spectra. We fitted the average spectrum using a (basically) unabsorbed power law (primary radiation). From second model that represents the interaction of the primary radiation with matter located far away from the SMBH, we found that it was very significantly detected. Finally, we added a contribution from interaction with neutral material in the accretion disk close to the central SMBH, which is therefore smeared by relativistic effects, which improved the fit at 6 sigma. The reflection factors are 0.65 for the accretion disk and 0.25 for the torus. Replacing the neutral disk-reflection with low-ionisation disk reflection, also relativistically smeared, fits the data equally well, suggesting that we do not find evidence for a significant ionisation of the accretion disk. We detect distant neutral reflection in the average spectrum of unabsorbed AGN with z=0.8. Adding the disk-reflection component associated with a relativistic Fe line improves the data description at 6 sigma confidence level, suggesting that both reflection components are present. The disk-reflection component accounts for about 70 % of the total reflected flux.Comment: Accepted by A&A. 10 pages, 7 figure

Las mineralizaciones de Sn-Ti del borde occidental de la Cuenca de Ciudad Rodrigo

[Resumen] El borde Occidental de la Cuenca Terciaria de Ciudad Rodrigo presenta una serie de mineralizaciones de Sn y Ti, que han sido objeto de laboreo en varias ocasiones durante el presente siglo existiendo en la actualidad dos explotaciones de cierta importancia; una en Puebla de Azaba (Salamanca) y otra en Nave de Haver (Portugal). Los materiales detríticos en los que se encuentran la casiterita y la ilmenita proceden de la denudación del batolito de Guarda, que presenta facies leucograníticas con contenidos de estaño superiores a 500 ppm, y del desmantelamiento de su cortejo filoniano. Estas formaciones con contenidos de Sn muy irregulares, pero con valores generalmente inferiores a 200 ppm, son considerados como dep6sitos Deluviales. Las minas activas benefician fundamentalmente los aluviones recientes, que alcanzan contenidos de hasta 800 ppm de estaño[Abstract] Western borderland of the Ciudad Rodrigo Tertiary Basin bears a suite of Sn-Ti deposits that were mined for several times in this century. Nowadays, two relatively important mines occur in that zone: Puebla de Azaba (Salamanca) and Nave de Haver (Portugal) . -Detrital sediments with casiterite and ilmenite como from denudation of Guarda batholith, which present leuco granite facies with Sn contents up to 500 ppm. The detrital formatión, with variable Sn contents, generally less than 200 ppm, is considered as a "Deluvial" facies. Active mining focusses on recent alluvials whose Sn contents reach up 5OO ppm

Estimating Photometric Redshifts for X-ray sources in the X-ATLAS field, using machine-learning techniques

We present photometric redshifts for 1,031 X-ray sources in the X-ATLAS field, using the machine learning technique TPZ (Carrasco Kind & Brunner 2013). X-ATLAS covers 7.1 deg2 observed with the XMM-Newton within the Science Demonstration Phase (SDP) of the H-ATLAS field, making it one of the largest contiguous areas of the sky with both XMMNewton and Herschel coverage. All of the sources have available SDSS photometry while 810 have additionally mid-IR and/or near-IR photometry. A spectroscopic sample of 5,157 sources primarily in the XMM/XXL field, but also from several X-ray surveys and the SDSS DR13 redshift catalogue, is used for the training of the algorithm. Our analysis reveals that the algorithm performs best when the sources are split, based on their optical morphology, into point-like and extended sources. Optical photometry alone is not enough for the estimation of accurate photometric redshifts, but the results greatly improve when, at least, mid-IR photometry is added in the training process. In particular, our measurements show that the estimated photometric redshifts for the X-ray sources of the training sample, have a normalized absolute median deviation, n_mad=0.06, and the percentage of outliers, eta=10-14 percent, depending on whether the sources are extended or point-like. Our final catalogue contains photometric redshifts for 933 out of the 1,031 X-ray sources with a median redshift of 0.9.Comment: 10 pages, 13 figures, A&A accepte

Theoretical investigation of a novel xylene-based light-driven unidirectional molecular motor

In this study, the working mechanism of the first light-driven rotary molecular motors used to control an eight-base-pair DNA hairpin has been investigated. In particular, this linker was reported to have promising photophysical properties under physiological conditions, which motivated our work at the quantum mechanical level. Cis-trans isomerization is triggered by photon absorption at wavelengths ranging 300 nm-400 nm, promoting the rotor to the first excited state, and it is mediated by an energy-accessible conical intersection from which the ground state is reached back. The interconversion between the resulting unstable isomer and its stable form occurs at physiological conditions in the ground state and is thermally activated. Here, we compare three theoretical frameworks, generally used in the quantum description of medium-size chemical systems: Linear-Response Time-Dependent Density Functional Theory (LR-TDDFT), Spin-Flip TDDFT (SF-TDDFT), and multistate complete active space second-order perturbation theory on state-averaged complete active space self consistent field wavefunctions (MS-CASPT2//SA-CASSCF). In particular, we show the importance of resorting to a multireference approach to study the rotational cycle of light-driven molecular motors due to the occurrence of geometries described by several configurations. We also assess the accuracy and computational cost of the SF-TDDFT method when compared to MS-CASPT2 and LR-TDDFT

Yacimientos de estaño del Oeste de España

[Resumen] En este trabajo se realiza una clasificación de los. yacimientos de estaño del oeste español basada, fundamentalmente, en consideraciones económicas. Tras una introducción explicativa de los objetivos y metodología empleados, así como una breve exposición del significado de las explotaciones de estaño españolas en el contexto mundial, se describen y clasifican los indicios y yacimientos más importantes, aportándose además un listado de la bibliografía específica más destacable[Abstract] This work presents a classification of the tin deposits in the westof Spain, based, mainly, on economic reasons. After an explaining introduction of the objetives and the method used, and a short exposition of the importance of spanish tin exploitations in the world context, the most important mines and occurrences are described and classified; in addition a list of the most relevant specific bibliography is given

Tungsten deposits in the west of Spain

[Resumen] En este trabajo se realiza una clasificación de los yacimientos de volframio del oeste español basada, fundamentalmente, en consideraciones económicas. Tras una introducción en la que se comenta la reciente historia del volframio, así como una breve exposición del significado de las explotaciones de volframioespañolas en el contexto mundial, se describen y clasifican los indicios y yacimientos más importantes, aportándose también un listado de la bibliografía específica más destacable.[Abstract] This work presents a classification of the tungsten deposits en the west of Spain, based, mainly, on economic reasons. Mter an explaining introduction of the recent history of the tungsten, and a short exposition of the importance of spanish exploitations in the world context, the most important mines and occurrences are described and c1assified; in addition a list of the most relevant specific bibliography is given

Overview of the potential of microRNAs and their target gene detection for cassava (Manihot esculenta) improvement

Production and utilization of cassava (Manihot esculenta) is significantly constrained by pests, diseases, poor yields and low nutritional content. Various approaches are currently being applied to mitigate these constraints. However, an aspect of plant developmental genetics little known in cassava is the role that microRNAs (miRNAs) play in gene regulation. miRNAs are 20 - 24 nucleotide long nonprotein-coding RNAs that play important roles in post-transcriptional gene silencing in many organisms. Thorough understanding of the mechanisms involved in miRNAs mediated posttranscriptional gene regulation will have implications for crop production improvement. The potential of miRNAs for cassava improvement and also some data obtained on cassava miRNAs using comparative genomics analysis have been briefly discussed. 17 miRNA families and target genes in cassava that are also conserved in other plant species have been revealed. However, the ESTs representing seven of these miRNA families produced foldbacks that show more than 3 nucleotides not involved in canonical base pairing within a loop or bulge in the mature miRNA: RNA* dimer, thus were not considered miRNA secondary structures. Consistent with previous reports, majority of the target genes identified are transcription factors. Other targets appear to play roles in diverse physiological processes. Furthermore, a detailed description and insight into some of the current bioinformatic resources and approaches applicable to cassava have been discussed. Such information will further enhance the rapid discovery and analysis of more novel miRNAs in cassava towards its improvement.Keywords: Cassava, microRNAs, target genes, improvement, characterizatio

Network of Earthquakes and Recurrences Therein

We quantify the correlation between earthquakes and use the same to distinguish between relevant causally connected earthquakes. Our correlation metric is a variation on the one introduced by Baiesi and Paczuski (2004). A network of earthquakes is constructed, which is time ordered and with links between the more correlated ones. Data pertaining to the California region has been used in the study. Recurrences to earthquakes are identified employing correlation thresholds to demarcate the most meaningful ones in each cluster. The distribution of recurrence lengths and recurrence times are analyzed subsequently to extract information about the complex dynamics. We find that the unimodal feature of recurrence lengths helps to associate typical rupture lengths with different magnitude earthquakes. The out-degree of the network shows a hub structure rooted on the large magnitude earthquakes. In-degree distribution is seen to be dependent on the density of events in the neighborhood. Power laws are also obtained with recurrence time distribution agreeing with the Omori law.Comment: 17 pages, 5 figure

The XMM spectral catalog of SDSS optically selected Seyfert 2 galaxies

We present an X-ray spectroscopic study of optically selected (SDSS) Seyfert 2 (Sy2) galaxies. The goal is to study the obscuration of Sy2 galaxies beyond the local universe, using good quality X-ray spectra in combination with high S/N optical spectra for their robust classification. We analyzed all available XMM-Newton archival observations of narrow emission line galaxies that meet the above criteria in the redshift range 0.05<z<0.35. We initially selected narrow line AGN using the SDSS optical spectra and the BPT classification diagram. We further modeled and removed the stellar continuum, and we analyzed the residual emission line spectrum to exclude any possible intermediate-type Seyferts. Our final catalog comprises 31 Sy2 galaxies with median redshift z~0.1. X-ray spectroscopy is performed using the available X-ray spectra from the 3XMM and the XMMFITCAT catalogs. Implementing various indicators of obscuration, we find seven (~23%) Compton-thick AGN. The X-ray spectroscopic Compton-thick classification agrees with other commonly used diagnostics, such as the X-ray to mid-IR luminosity ratio and the X-ray to [OIII] luminosity ratio. Most importantly, we find four (~13%) unobscured Sy2 galaxies, at odds with the simplest unification model. Their accretion rates are significantly lower than the rest of our Sy2 sample, in agreement with previous studies that predict the absence of the broad line region below a certain Eddington ratio threshold.Comment: 12 pages, 6 figures, accepted for publication in A&

Prediction of extreme events in the OFC model on a small world network

We investigate the predictability of extreme events in a dissipative Olami-Feder-Christensen model on a small world topology. Due to the mechanism of self-organized criticality, it is impossible to predict the magnitude of the next event knowing previous ones, if the system has an infinite size. However, by exploiting the finite size effects, we show that probabilistic predictions of the occurrence of extreme events in the next time step are possible in a finite system. In particular, the finiteness of the system unavoidably leads to repulsive temporal correlations of extreme events. The predictability of those is higher for larger magnitudes and for larger complex network sizes. Finally, we show that our prediction analysis is also robust by remarkably reducing the accessible number of events used to construct the optimal predictor.Comment: 5 pages, 4 figure