273 research outputs found
Augmenting photometric redshift estimates using spectroscopic nearest neighbours
As a consequence of galaxy clustering, close galaxies observed on the plane
of the sky should be spatially correlated with a probability that is inversely
proportional to their angular separation. In principle, this information can be
used to improve photometric redshift estimates when spectroscopic redshifts are
available for some of the neighbouring objects. Depending on the depth of the
survey, however, this angular correlation is reduced by chance projections. In
this work, we implement a deep-learning model to distinguish between apparent
and real angular neighbours by solving a classification task. We adopted a
graph neural network architecture to tie together photometry, spectroscopy, and
the spatial information between neighbouring galaxies. We trained and validated
the algorithm on the data of the VIPERS galaxy survey, for which photometric
redshifts based on spectral energy distribution are also available. The model
yields a confidence level for a pair of galaxies to be real angular neighbours,
enabling us to disentangle chance superpositions in a probabilistic way. When
objects for which no physical companion can be identified are excluded, all
photometric redshift quality metrics improve significantly, confirming that
their estimates were of lower quality. For our typical test configuration, the
algorithm identifies a subset containing ~75% high-quality photometric
redshifts, for which the dispersion is reduced by as much as 50% (from 0.08 to
0.04), while the fraction of outliers reduces from 3% to 0.8%. Moreover, we
show that the spectroscopic redshift of the angular neighbour with the highest
detection probability provides an excellent estimate of the redshift of the
target galaxy, comparable to or even better than the corresponding
template-fitting estimate.Comment: 9 pages, 12 figures, matching the accepted version. NezNet is
available at https://github.com/tos-1/NezNe
Graphic-based concept retrieval
Two ways of expressing concepts in the context of image retrieval are presented. One, Keypics, is on the side of an image owner, who wants the image itself to be found on the Web; the second, Trittico, is on the side of the image searcher. Both are based on the paradigm of human intermediation for overcoming the semantic gap. Both require tools capable of qualitative analysis, and have been experimented by using persistent homology
Impact of the \u3cem\u3eBrachiaria\u3c/em\u3e Hybrids on Both Soil Health and Carbon Stock on Livestock Production
Pastures occupy 30% of Earth and 80% of the entire agricultural area of the planet. To ensure food to the world and contribute to the quality of the environment, pasture-based animal production systems will also have to undergo through a more intense evolution. The intensification of tropical grasslands is an important strategy of land utilization in developing countries, contributing to increase production and minimize environmental impact through the best management practices. In this sense, the use of Brachiaria hybrids represents an excellent option, since combining the best traits of different Brachiaria species, with higher nutritive value, forage, and seed yield. Here we have evaluated six Brachiaria hybrids’ effects on both soil health and carbon stock. We observed that in all Brachiaria genotypes the mean carbon stock varied significantly in at least two soil depth categories. In general, carbon stock tends to get smaller as soil depth increases. Enzyme activity analysis showed there were no significant differences in the mean enzyme activity except in hybrid GP 3660 for β-glucosidase enzyme. Therefore, the adoption of Brachiaria hybrids might also help farmers to produce in an environmentally friendly manner, due to the potential benefits of Brachiaria to soil life enzyme activity and carbon mitigation
Categorification of persistent homology
We redevelop persistent homology (topological persistence) from a categorical
point of view. The main objects of study are diagrams, indexed by the poset of
real numbers, in some target category. The set of such diagrams has an
interleaving distance, which we show generalizes the previously-studied
bottleneck distance. To illustrate the utility of this approach, we greatly
generalize previous stability results for persistence, extended persistence,
and kernel, image and cokernel persistence. We give a natural construction of a
category of interleavings of these diagrams, and show that if the target
category is abelian, so is this category of interleavings.Comment: 27 pages, v3: minor changes, to appear in Discrete & Computational
Geometr
Persistence modules, shape description, and completeness
Persistence modules are algebraic constructs that can be used to describe the shape of an object starting from a geometric representation of it. As shape descriptors, persistence modules are not complete, that is they may not distinguish non-equivalent shapes.
In this paper we show that one reason for this is that homomorphisms between persistence modules forget the geometric nature of the problem. Therefore we introduce geometric homomorphisms between persistence modules, and show that in some cases they perform better. A combinatorial structure, the -tree, is shown to be an invariant for geometric isomorphism classes in the case of persistence modules obtained through the 0th persistent homology functor
Conteúdos linguísticos como subsídio à formação de professores alfabetizadores: a experiência do Brasil e de Portugal
Objetiva identificar em dois programas de formação de professores
alfabetizadores – no Brasil, Pacto Nacional pela Alfabetização na Idade Certa (Pnaic) e, em Portugal, Programa Nacional do Ensino do Português (Pnep) – os conteúdos linguísticos relacionados ao ensino da leitura que fundamentaram a atualização dos professores com vistas a compreender como as descobertas científicas penetram o campo pedagógico. Por meio de análise documental, são apresentadas, de forma resumida, a estrutura e a organização dos dois programas e os respectivos conteúdos de formação. Há muita similaridade entre os dois programas com relação à organização e às estratégias metodológicas e há diferenças importantes quanto à atualidade dos conteúdos oferecidos aos professores alfabetizadores, assim como o tempo de formação aplicado a este conteúdo. A formação linguística do professor é essencial para desenvolver competência para o ensino da língua e, por conseguinte, melhorar as habilidades de ler e escrever dos alunos do ensino fundamental.This article aims to identify the linguistic contents related to the
teaching of reading in two training programs for literacy teachers: Brazil’s
National Pact for Literacy at the Right Age (Pacto Nacional pela Alfabetização
na Idade Certa – Pnaic) and the National Program for Portuguese Teaching
(Programa Nacional do Ensino do Português – Pnep) of Portugal. The focus
is on the linguistic contents that served as foundation for the updating
of teachers, in order to understand how scientific discoveries permeate
the teaching field. Through documentary analysis, the structure and the
organization of the two programs and their respective training contents are
briefly presented. There are many similarities between the two programs,
regarding the organization and the methodological strategies; but there are
also differences in relation to the timeliness of the content offered to the
literacy teachers, as well as to the duration of the training applied to the
content. The linguistic training of teachers is essential to developing the
competence for language teaching and, therefore; for the improvement of
reading and writing skills of elementary school students.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT), PortugalFundos Nacionais através da FCT (Fundação para a Ciência e a Tecnologia) e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) com a referência POCI-01-0145-FEDER-007562info:eu-repo/semantics/publishedVersio
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