3,379 research outputs found

    The evolution of the spatially-resolved metal abundance in galaxy clusters up to z=1.4

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    We present the combined analysis of the metal content of 83 objects in the redshift range 0.09-1.39, and spatially-resolved in the 3 bins (0-0.15, 0.15-0.4, >0.4) R500, as obtained with similar analysis using XMM-Newton data in Leccardi & Molendi (2008) and Baldi et al. (2012). We use the pseudo-entropy ratio to separate the Cool-Core (CC) cluster population, where the central gas density tends to be relatively higher, cooler and more metal rich, from the Non-Cool-Core systems. The average, redshift-independent, metal abundance measured in the 3 radial bins decrease moving outwards, with a mean metallicity in the core that is even 3 (two) times higher than the value of 0.16 times the solar abundance in Anders & Grevesse (1989) estimated at r>0.4 R500 in CC (NCC) objects. We find that the values of the emission-weighted metallicity are well-fitted by the relation Z(z)=Z0(1+z)−γZ(z) = Z_0 (1+z)^{-\gamma} at given radius. A significant scatter, intrinsic to the observed distribution and of the order of 0.05-0.15, is observed below 0.4 R500. The nominal best-fit value of γ\gamma is significantly different from zero in the inner cluster regions (γ=1.6±0.2\gamma = 1.6 \pm 0.2) and in CC clusters only. These results are confirmed also with a bootstrap analysis, which provides a still significant negative evolution in the core of CC systems (P>99.9 per cent). No redshift-evolution is observed when regions above the core (r > 0.15 R500) are considered. A reasonable good fit of both the radial and redshift dependence is provided from the functional form Z(r,z)=Z0(1+(r/0.15R500)2)−β(1+z)−γZ(r,z)=Z_0 (1+(r/0.15 R500)^2)^{-\beta} (1+z)^{-\gamma}, with (Z0,β,γ)=(0.83±0.13,0.55±0.07,1.7±0.6)(Z_0, \beta, \gamma) = (0.83 \pm 0.13, 0.55 \pm 0.07, 1.7 \pm 0.6) in CC clusters and (0.39±0.04,0.37±0.15,0.5±0.5)(0.39 \pm 0.04, 0.37 \pm 0.15, 0.5 \pm 0.5) for NCC systems. Our results represent the most extensive study of the spatially-resolved metal distribution in the cluster plasma as function of redshift.Comment: 5 pages. Research Note accepted for publication in A&

    A Chandra archival study of the temperature and metal abundance profiles in hot Galaxy Clusters at 0.1 < z < 0.3

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    We present the analysis of the temperature and metallicity profiles of 12 galaxy clusters in the redshift range 0.1--0.3 selected from the Chandra archive with at least ~20,000 net ACIS counts and kT>6 keV. We divide the sample between 7 Cooling-Core (CC) and 5 Non-Cooling-Core (NCC) clusters according to their central cooling time. We find that single power-laws can describe properly both the temperature and metallicity profiles at radii larger than 0.1 r_180 in both CC and NCC systems, showing the NCC objects steeper profiles outwards. A significant deviation is only present in the inner 0.1 r_180. We perform a comparison of our sample with the De Grandi & Molendi BeppoSAX sample of local CC and NCC clusters, finding a complete agreement in the CC cluster profile and a marginally higher value (at ~1sigma) in the inner regions of the NCC clusters. The slope of the power-law describing kT(r) within 0.1 r_180 correlates strongly with the ratio between the cooling time and the age of the Universe at the cluster redshift, being the slope >0 and tau_c/tau_age<=0.6 in CC systems.Comment: 12 pages, 6 figures, Accepted for publication by the Astrophysical Journa

    Rotation in galaxy clusters from MUSIC simulations with the kinetic Sunyaev-Zel'dovich effect

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    We propose in this work its application for the detection of possible coherent rotational motions in the hot intra-cluster medium. We select a sample of massive, relaxed and rotating galaxy clusters from Marenostrum-mUltidark SImulations of galaxy Clusters (MUSIC), and we produce mock maps of the temperature distortion produced by the kinetic Sunyaev-Zel'dovich effect by exploring six different lines of sight, in the best observational condition. These maps are compared with the expected signal computed from a suitable theoretical model in two cases: (i) focusing only on the contribution from the rotation, and (ii) accounting also for the cluster bulk motion. We find that the parameters of the model assumed for the radial profile of the rotational velocity, averaged over the considered lines of sight, are in agreement within two standard deviations at most with independent estimates from the simulation data, without being significantly affected by the presence of the cluster bulk term. The amplitude of the rotational signal is, on average, of the order of 23 per cent of the total signal accounting also for the cluster bulk motion, and its values are consistent with the literature. The projected bulk velocity of the cluster is also recovered at the different lines of sight, with values in agreement with the simulation dataASB acknowledges funding from Sapienza Università di Roma - Progetti per Avvio alla Ricerca Anno 2017, prot. AR11715C82402BC

    Large scale study of multiple-molecule queries

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    <p>Abstract</p> <p>Background</p> <p>In ligand-based screening, as well as in other chemoinformatics applications, one seeks to effectively search large repositories of molecules in order to retrieve molecules that are similar typically to a single molecule lead. However, in some case, multiple molecules from the same family are available to seed the query and search for other members of the same family.</p> <p>Multiple-molecule query methods have been less studied than single-molecule query methods. Furthermore, the previous studies have relied on proprietary data and sometimes have not used proper cross-validation methods to assess the results. In contrast, here we develop and compare multiple-molecule query methods using several large publicly available data sets and background. We also create a framework based on a strict cross-validation protocol to allow unbiased benchmarking for direct comparison in future studies across several performance metrics.</p> <p>Results</p> <p>Fourteen different multiple-molecule query methods were defined and benchmarked using: (1) 41 publicly available data sets of related molecules with similar biological activity; and (2) publicly available background data sets consisting of up to 175,000 molecules randomly extracted from the ChemDB database and other sources. Eight of the fourteen methods were parameter free, and six of them fit one or two free parameters to the data using a careful cross-validation protocol. All the methods were assessed and compared for their ability to retrieve members of the same family against the background data set by using several performance metrics including the Area Under the Accumulation Curve (AUAC), Area Under the Curve (AUC), F1-measure, and BEDROC metrics.</p> <p>Consistent with the previous literature, the best parameter-free methods are the MAX-SIM and MIN-RANK methods, which score a molecule to a family by the maximum similarity, or minimum ranking, obtained across the family. One new parameterized method introduced in this study and two previously defined methods, the Exponential Tanimoto Discriminant (ETD), the Tanimoto Power Discriminant (TPD), and the Binary Kernel Discriminant (<b>BKD</b>), outperform most other methods but are more complex, requiring one or two parameters to be fit to the data.</p> <p>Conclusion</p> <p>Fourteen methods for multiple-molecule querying of chemical databases, including novel methods, (ETD) and (TPD), are validated using publicly available data sets, standard cross-validation protocols, and established metrics. The best results are obtained with ETD, TPD, BKD, MAX-SIM, and MIN-RANK. These results can be replicated and compared with the results of future studies using data freely downloadable from <url>http://cdb.ics.uci.edu/</url>.</p

    Relação genética de características de tamanho corporal com características de eficiência reprodutiva e produtiva de fêmeas da raça Canchim.

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    Dissertação (Mestrado em Genética e Melhoramento Animal) - Faculdade de Ciências Agrárias e Veterinárias - Tese sobre orientação do pesquisador Maurício Mello de Alencar; Co-orientação Alfredo Ribeiro Freitas

    Smart farming tool for monitoring nutrients in soil and plants for precise fertilization

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    The current political, social, and economic conditions place, more than ever, the need to sustainably supply nutrients for plants, integrating low-impact, crop-adapted, variable-rate-application fertilizer solutions, at the center of attention. Fertilization plans should be based on the monitoring of soil fertility to address the proper rate of fertilizer application along with the development of techniques able to increase nutrient uptake efficiency. Monitoring and modelling analysis of the effects of agronomic management in different pedoclimatic conditions can provide several advantages, that include higher nutrient efficiency, increase in plant growth and yield, decreased fertilization costs, increased profit, reduced environmental impact. This approach should enter into a framework of precision farming methodologies for the distribution of nutrients adopted at different levels (region, farm, field, plot), to obtain the maximum efficiency of inputs

    Axiomatic Design of a Test Artifact for PBF-LM Machine Capability Monitoring †

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    Powder Bed Fusion Laser Melting (PBF-LM) additive manufacturing technology is expected to have a remarkable impact on the industrial setting, making possible the realization of a metallic component with very complex designs to enhance product performance. However, the industrial use of the PBF-LM system needs a capability monitoring system to ensure product quality. Among the various studies developed, the investigation of methodology for the actual machine capability determination has been faced and still represents an open point. There are multiple authors and institutes proposing different investigation methods, ranging from the realization of samples (ex situ analysis) to installing monitoring devices on the machine (in situ analysis). Compared to other approaches, sample realization allows for assessing how the machine works through specimen analysis, but it is sensitive to the sample design. In this article, we first present an analysis of a well-known test artifact from an Axiomatic Design perspective. Second, based on the customer needs analysis and adjustments with respect to the use of hypothetical additive production lines, a new test artifact with an uncoupled design matrix is introduced. The proposed design has been experimentally tested and characterized using artifact made of Inconel 718 superalloy to evaluate its performance and representativeness in machine capability assessment. The results show an accurate identification of beam offset and scaling factor considering all the building platform positions. In addition, the artifact is characterized by a reduced building time (more than 90% with respect to the reference NIST artifact) and a halved inspection time (from 16 h to 8 h)

    Cosmic voids in modified gravity models with massive neutrinos

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    Cosmic voids are progressively emerging as a new viable cosmological probe. Their abundance and density profiles are sensitive to modifications of gravity, as well as to dark energy and neutrinos. The main goal of this work is to investigate the possibility of exploiting cosmic void statistics to disentangle the degeneracies resulting from a proper combination of f(R) modified gravity and neutrino mass. We use N-body simulations to analyse the density profiles and size function of voids traced by both dark matter particles and haloes. We find clear evidence of the enhancement of gravity in f(R) cosmologies in the void density profiles at z = 1. However, these effects can be almost completely overridden by the presence of massive neutrinos because of their thermal free streaming. Despite the limited volume of the analysed simulations does not allow us to achieve a statistically relevant abundance of voids larger than 40 Mpc h-1, we find that the void size function at high redshifts and for large voids is potentially an effective probe to disentangle these degenerate cosmological models, which is key in the prospective of the upcoming wide-field redshift surveys
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