Galaxy Clusters in the Line of Sight to Background Quasars: I. Survey Design and Incidence of MgII Absorbers at Cluster Redshifts

We describe the first optical survey of absorption systems associated with galaxy clusters at z= 0.3-0.9. We have cross-correlated SDSS DR3 quasars with high-redshift cluster/group candidates from the Red-Sequence Cluster Survey. We have found 442 quasar-cluster pairs for which the MgII doublet might be detected at a transverse (physical) distance d<2 Mpc from the cluster centers. To investigate the incidence (dN/dz) and equivalent-width distribution n(W) of MgII systems at cluster redshifts, two statistical samples were drawn out of these pairs: one made of high-resolution spectroscopic quasar observations (46 pairs), and one made of quasars used in MgII searches found in the literature (375 pairs). The results are: (1) the population of strong MgII systems (W_0>2.0 Ang.) near cluster redshifts shows a significant (>3 sigma) overabundance (up to a factor of 15) when compared with the 'field' population; (2) the overabundance is more evident at smaller distances (d<1 Mpc) than larger distances (d<2 Mpc) from the cluster center; and, (3) the population of weak MgII systems (W_0<0.3 Ang.) near cluster redshifts conform to the field statistics. Unlike in the field, this dichotomy makes n(W) in clusters appear flat and well fitted by a power-law in the entire W-range. A sub-sample of the most massive clusters yields a stronger and still significant signal. Since either the absorber number density or filling-factor/cross-section affects the absorber statistics, an interesting possibility is that we have detected the signature of truncated halos due to environmental effects. Thus, we argue that the excess of strong systems is due to a population of absorbers in an overdense galaxy environment, and the lack of weak systems to a different population, that got destroyed in the cluster environment. (Abridged)Comment: Accepted for publication in the Astrophysical Journa

Sistema de aptidão das terras para recuperação ambiental para avaliar a sustentabilidade de propriedades rurais da Amazônia.

O objetivo do trabalho foi avaliar a sustentabilidade ambiental da agricultura familiar em propriedades rurais em duas regiões com diferenças topográficas e pedológicas no Estado do Acre, Brasil: região do município de Acrelândia e região dos municípios de Feijó e Tarauacá. Em cada região, dois projetos de assentamento agrícola com sete propriedades rurais de cada um foram selecionados. A sustentabilidade da propriedade rural foi estimada pelo Sistema de Aptidão das Terras para Recuperação Ambiental (SATRA), o qual compara o uso atual da terra e o uso prescrito baseado em características locais, como solos, relevo e nível de adoção de tecnologias dependentes de capital ou escala de produção. O contraste entre o uso atual e o uso predito resulta nos índices de insustentabilidade, interpretados a partir de decisões lógicas construídas a partir da análise de indicadores agrícolas, biológicos, econômicos e sociais. Os resultados indicaram nas propriedades rurais de Acrelândia maior sustentabilidade em relação as propriedades rurais de Feijó/Tarauacá. Isto foi atribuído a presença de áreas de assentamento na região de Feijó/Tarauacá com menor aptidão agrícola e maior pressão sobre as unidades de uso restrito. Não foram observadas diferenças na sustentabilidade socioeconômica entre as duas regiões pelo sistema SATRA. Contudo, na região de Acrelândia, propriedades rurais com nível tecnológico dependente de capital resultaram em melhor eficiência no uso da terra, maior produtividade e rentabilidade econômica, todavia, sem necessariamente melhorar a sustentabilidade econômica

The High Cadence Transit Survey (HiTS): Compilation and Characterization of Light-curve Catalogs

Indexación: Scopus.J.M. acknowledges support from CONICYT-Chile through CONICYT-PCHA/Doctorado-Nacional/2014-21140892. J.M., F.F., G.C.V., and G.M. acknowledge support from the Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). F.F. acknowledges support from Conicyt through the Fondecyt Initiation into Research project No. 11130228. J.M., F.F., J.S.M., G.C.V., and S.G. acknowledge support from Basal Project PFB-03, Centro de Modelamiento Matemáico (CMM), Universidad de Chile. P.L. acknowledges support by Fondecyt through project #1161184. G.C.V. gratefully acknowledges financial support from CON-ICYT-Chile through FONDECYT postdoctoral grant number 3160747 and CONICYT-Chile and NSF through the Programme of International Cooperation project DPI201400090. P.H. acknowledges support from FONDECYT through grant 1170305. L.G. was supported in part by the US National Science Foundation under grant AST-1311862. G.M. acknowledges support from Conicyt through CONICYT-PCHA/Magís-terNacional/2016-22162353. Support for T.d.J. has been provided by US NSF grant AST-1211916, the TABASGO Foundation, and Gary and Cynthia Bengier. R.R.M. acknowledges partial support from BASAL Project PFB-06, as well as FONDECYT project N◦1170364. Powered@NLHPC: this research was supported by the High Performance Computing infrastructure of the National Laboratory for High Performance Computing (NLHPC), PIA ECM-02, CONICYT. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaborating institutions: Argonne National Lab, the University of California Santa Cruz, the University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologi-cas-Madrid, the University of Chicago, University College London, the DES-Brazil consortium, the University of Edinburgh, ETH-Zurich, the University of Illinois at Urbana-Champaign, Institut de Ciencies de l’Espai, Institut de Fisica d’Altes Energies, Lawrence Berkeley National Lab, Ludwig-Maximilians Universitat, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Lab, Stanford University, the University of Sussex, and Texas A&M University. Funding for DES, including DECam, has been provided by the U.S. Department of Energy, National Science Foundation, Ministry of Education and Science (Spain), Science and Technology Facilities Council (UK), Higher Education Funding Council (England), National Center for Supercomputing Applications, Kavli Institute for Cosmological Physics, Financia-dora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo a Pesquisa, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia (Brazil), the German Research Foundation-sponsored cluster of excellence “Origin and Structure of the universe,” and the DES collaborating institutions. Facility: CTIO:1.5 m (DECam).The High Cadence Transient Survey (HiTS) aims to discover and study transient objects with characteristic timescales between hours and days, such as pulsating, eclipsing, and exploding stars. This survey represents a unique laboratory to explore large etendue observations from cadences of about 0.1 days and test new computational tools for the analysis of large data. This work follows a fully data science approach, from the raw data to the analysis and classification of variable sources. We compile a catalog of ∼15 million object detections and a catalog of ∼2.5 million light curves classified by variability. The typical depth of the survey is 24.2, 24.3, 24.1, and 23.8 in the u, g, r, and i bands, respectively. We classified all point-like nonmoving sources by first extracting features from their light curves and then applying a random forest classifier. For the classification, we used a training set constructed using a combination of cross-matched catalogs, visual inspection, transfer/active learning, and data augmentation. The classification model consists of several random forest classifiers organized in a hierarchical scheme. The classifier accuracy estimated on a test set is approximately 97%. In the unlabeled data, 3485 sources were classified as variables, of which 1321 were classified as periodic. Among the periodic classes, we discovered with high confidence one δ Scuti, 39 eclipsing binaries, 48 rotational variables, and 90 RR Lyrae, and for the nonperiodic classes, we discovered one cataclysmic variable, 630 QSOs, and one supernova candidate. The first data release can be accessed in the project archive of HiTS (http://astro.cmm.uchile.cl/HiTS/). © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-3881/aadfd

Avaliação da capacidade de uso da terra e dos impactos ambientais em áreas de assentamento na Amazônia ocidental.

O objetivo desse estudo foi avaliar os impactos ambientais do uso da terra em áreas de assentamento rural com colonos tradicionais (descendentes de seringueiros) e colonos recentes (migrantes do sul e sudeste do Brasil), em duas regiões do Estado do Acre, Brasil. Os impactos ambientais foram estimados pelo "Sistema de Aptidão das terras para Recuperação Ambiental", que compara o uso atual da terra e a sua real aptidão com base em indicadores relacionados às práticas de manejo e identificam aquelas consideradas insustentáveis. De acordo com os resultados, verificou-se que os impactos ambientais da área estudada foram ocasionados pelo uso intenso dos recursos naturais disponíveis, sendo mais expressivos nas dimensões agrícola e ecológica nos assentamentos com colonos tradicionais, enquanto que para as dimensões econômica e social não foram observadas diferenças entre as populações. Os menores impactos observados com colonos recentes foram devidos principalmente ao uso atual da terra em menor intensidade que sua capacidade de uso. Constatou-se também que fatores educacionais e culturais podem estar afetando os padrões de uso da terra

Avaliação da capacidade de uso da terra e dos impactos ambientais em áreas de assentamento na Amazônia ocidental.

O objetivo desse estudo foi avaliar os impactos ambientais do uso da terra em áreas de assentamento rural com colonos tradicionais (descendentes de seringueiros) e colonos recentes (migrantes do sul e sudeste do Brasil), em duas regiões do Estado do Acre, Brasil. Os impactos ambientais foram estimados pelo Sistema de Aptidão das Terras para Recuperação Ambiental, que compara o uso atual da terra e a sua real aptidão com base em indicadores relacionados às práticas de manejo e identificam aquelas consideradas insustentáveis. De acordo com os resultados, verificou-se que os impactos ambientais da área estudada foram ocasionados pelo uso intenso dos recursos naturais disponíveis, sendo mais expressivos nas dimensões agrícola e ecológica nos assentamentos com colonos tradicionais, enquanto que para as dimensões econômica e social não foram observadas diferenças entre as populações. Os menores impactos observados com colonos recentes foram devidos principalmente ao uso atual da terra em menor intensidade que sua capacidade de uso. Constatou-se também que fatores educacionais e culturais podem estar afetando os padrões de uso da terra

Projeto Gavião: impactos (meio período) do desenvolvimento rural - 1998/2001.

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Potencial de produção de capim buffel na época seca no semi-árido pernambucano.

O trabalho foi realizado durante a época seca na Estação Experimental de Serra Talhada ? IPA e objetivou avaliar a composição botânica, disponibilidade e qualidade da forragem e da dieta de animais fistulados alimentados em uma pastagem de capim buffel diferido. Na pastagem, encontrou-se 24 espécies, de 22 gêneros e 12 famílias, sendo que a forragem disponível variou de 6492kg MS/ha em setembro para 3356 kg MS/ha em dezembro. O capim buffel teve uma participação sempre superior a 90% nos diferentes períodos estudados. A digestibilidade in vitroda matéria seca esteve em um patamar sempre inferior a 50% e os teores de proteína bruta tanto da pastagem, como da dieta dos animais, apresentaram-se muito baixos, características comuns e esperadas para pasto diferido

The Space Density and Colors of Massive Galaxies at 2<z<3: the Predominance of Distant Red Galaxies

Using the deep multi-wavelength MUSYC, GOODS, and FIRES surveys we construct a stellar mass-limited sample of galaxies at 2<z<3. The sample comprises 294 galaxies with M>10^11 Solar masses distributed over four independent fields with a total area of almost 400 sq arcmin. The mean number density of massive galaxies in this redshift range is (2.2+-0.6) x 10^-4 Mpc^-3. We present median values and 25th and 75th percentiles for the distributions of observed R mags, observed J-K colors, and rest-frame UV continuum slopes, M/L(V) ratios, and U-V colors. The galaxies show a large range in all these properties. The ``median galaxy'' is faint in the observer's optical (R=25.9), red in the observed near-IR (J-K=2.48), has a rest-frame UV spectrum which is relatively flat (beta=-0.4), and rest-frame optical colors resembling those of nearby spiral galaxies (U-V=0.62). We determine which galaxies would be selected as Lyman break galaxies (LBGs) or Distant Red Galaxies (DRGs, having J-K>2.3) in this mass-limited sample. By number DRGs make up 69% of the sample and LBGs 20%, with a small amount of overlap. By mass DRGs make up 77% and LBGs 17%. Neither technique provides a representative sample of massive galaxies at 2<z<3 as they only sample the extremes of the population. As we show here, multi-wavelength surveys with high quality photometry are essential for an unbiased census of massive galaxies in the early Universe. The main uncertainty in this analysis is our reliance on photometric redshifts; confirmation of the results presented here requires extensive near-infrared spectroscopy of optically-faint samples.Comment: Accepted for publication in ApJ Letter

Comparative Analysis of Turbulence Models for Thermal-Hydraulic Simulations in Aqueous Homogeneous Reactors

This article presents a comparative study of various turbulence models applied in the context of thermal-hydraulic simulations for liquid fuel reactors, specifically Aqueous Homogeneous Reactors (AHR) using Computational Fluid Dynamics. The objective was to assess the suitability of the turbulence models by comparing their results with data obtained from Large Eddy Simulation (LES). For that purpose, was compared the flow behavior predicted using the k-ε, SST, GEKO, DES, SBES, and LES turbulence models. The calculations were carried out in a simplified computational model derived from a pre-existing three-dimensional AHR conceptual design. By utilizing this simplified model, the study aimed to focus on the computational differences between the turbulence models, while minimizing the influence of other factors. The calculation results revealed that the k-ε model exhibited significant discrepancies with the LES, with relative differences for the fuel solution maximum temperature reaching up to 75 %. Among the remaining RANS models, the Shear Stress Transport (SST) model demonstrated the best compromise between accuracy and computational efficiency, with differences below 5 % and requiring only 1/5th of the time, compared to the LES model.  The Scale-Resolving Simulation (SRS) models,DES and SBES, provided a more comprehensive description of flow behavior and results closer to LES, albeit with higher computational demands. Between these two models, only the DES model exhibited relative differences below or equal to     1 % compared to the LES model for the studied thermohydraulic parameters