622 research outputs found
Portfólios e a avaliação do conhecimento sobre natureza da ciência em um contexto histórico
Analisamos os portfólios elaborados por uma licencianda durante sua participação em um curso de formação inicial de professores de química, cuja temática central era Natureza da Ciência (NC). Avaliamos o conhecimento sobre NC da licencianda a partir de suas reflexões sobre sua vivência em um estudo de caso envolvendo uma controvérsia sobre um fato histórico (julgamento da outorga do prêmio Nobel de Química de 1918 a Fritz Haber pela síntese da amônia em escala industrial). A análise aponta que o caso histórico contribuiu para a compreensão de características sobre ciência, e o portfólio permitiu uma avaliação contextualizada e detalhada desses conhecimentos
Evolução Cinemática das Porções Internas do Cinturão Dom Feliciano, Região de Piratini, RS
Dois episódios cinemáticos afetando rochas da associação de arco magmático precoce (AAM I) do Cinturão Dom Feliciano foram reconhecidos na área de Piratini: um fluxo tectônico mais antigo de orientação NW-SE seguido por um fluxo de orientação NE-SW. O fluxo tectônico precoce transversal ao alongamento do cinturão é registrado por zonas de cisalhamento sub-horizontais e subverticais. O fluxo tangencial é caracterizado por deformação de alta temperatura no estado sólido afetando gnaisses dioríticos da associação de arco magmático precoce. Estruturas de escala microscópica dessa deformação foram em grande parte obliteradas por migmatização e/ou injeções graníticas sin- a tardi-tectônicas. Os padrões de fluxo, tanto o de deformação no estado sólido quanto o magmático, sugerem movimento do bloco superior para NW. A zona de cisalhamento transcorrente NW-SE é caracterizada por uma movimentação levogira sob condições metamórficas da fácies anfibolito afetando gnaisses granodioríticos da AAM I. A trama resultante foi parcialmente rearranjada por crescimento estático da maioria dos minerais que foram subsequentemente recristalizados durante reativação dessas zonas de cisalhamento sob condições decrescentes de temperatura. A deformação tardia é caracterizada por fluxo paralelo ao orógeno (NE-SW) em (i) uma zona de cisalhamento transcorrente de escala regional associado com um expressivo magmatismo sincinemático, e (ii) ao longo de diversas zonas de cisalhamento discretas e subordinadas, retrabalhando as rochas ígneas pré-existente. Indicadores cinemáticos consistentes, nas zonas de cisalhamento discretas de pequena escala, sugerem sentido de cisalhamento dextrogiro. Essa deformação desenvolvida sob condições metamórficas retrogressivas da fácies anfibolito superior a xisto verde inferior foi provavelmente controlada pelo resfriamento dos granitoides sincinemáticos
Green manure legumes affect seasonal soil and leaf CO2 exchange rates in an olive rainfed orchard
Management methods that decrease requirement for agricultural chemicals are needed
to reduce adverse environmental impacts. Moreover, they can play an important role in
atmospheric C02 emission and fixation. We propose green manure legumes to reduce
erosion, soil compaction and nitrate pollution, to improve biodiversity, soil carbon sink
and fertility, to save fossil fuels and to increase yield and the nutritional value of food
products. The research was carried out near Mirandela, Northeast Portugal, on a 15-
year commercial olive orchard (Olea europaea L. cv. Cobrançosa), grown under
rainfed conditions
Repeatability and reproducibility of multiparametric magnetic resonance imaging of the liver
As the burden of liver disease reaches epidemic levels, there is a high unmet medical need to develop robust, accurate and reproducible non-invasive methods to quantify liver tissue characteristics for use in clinical development and ultimately in clinical practice. This prospective cross-sectional study systematically examines the repeatability and reproducibility of iron-corrected T1 (cT1), T2*, and hepatic proton density fat fraction (PDFF) quantification with multiparametric MRI across different field strengths, scanner manufacturers and models. 61 adult participants with mixed liver disease aetiology and those without any history of liver disease underwent multiparametric MRI on combinations of 5 scanner models from two manufacturers (Siemens and Philips) at different field strengths (1.5T and 3T). We report high repeatability and reproducibility across different field strengths, manufacturers, and scanner models in standardized cT1 (repeatability CoV: 1.7%, bias -7.5ms, 95% LoA of -53.6 ms to 38.5 ms; reproducibility CoV 3.3%, bias 6.5 ms, 95% LoA of -76.3 to 89.2 ms) and T2* (repeatability CoV: 5.5%, bias -0.18 ms, 95% LoA -5.41 to 5.05 ms; reproducibility CoV 6.6%, bias -1.7 ms, 95% LoA -6.61 to 3.15 ms) in human measurements. PDFF repeatability (0.8%) and reproducibility (0.75%) coefficients showed high precision of this metric. Similar precision was observed in phantom measurements. Inspection of the ICC model indicated that most of the variance in cT1 could be accounted for by study participants (ICC = 0.91), with minimal contribution from technical differences. We demonstrate that multiparametric MRI is a non-invasive, repeatable and reproducible method for quantifying liver tissue characteristics across manufacturers (Philips and Siemens) and field strengths (1.5T and 3T)
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
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