Using Multi-Sense Vector Embeddings for Reverse Dictionaries

Popular word embedding methods such as word2vec and GloVe assign a single vector representation to each word, even if a word has multiple distinct meanings. Multi-sense embeddings instead provide different vectors for each sense of a word. However, they typically cannot serve as a drop-in replacement for conventional single-sense embeddings, because the correct sense vector needs to be selected for each word. In this work, we study the effect of multi-sense embeddings on the task of reverse dictionaries. We propose a technique to easily integrate them into an existing neural network architecture using an attention mechanism. Our experiments demonstrate that large improvements can be obtained when employing multi-sense embeddings both in the input sequence as well as for the target representation. An analysis of the sense distributions and of the learned attention is provided as well

Search for Associations Containing Young stars (SACY): Chemical tagging IC 2391 & the Argus association

We explore the possible connection between the open cluster IC 2391 and the unbound Argus association identified by the SACY survey. In addition to common kinematics and ages between these two systems, here we explore their chemical abundance patterns to confirm if the two substructures shared a common origin. We carry out a homogenous high-resolution elemental abundance study of eight confirmed members of IC 2391 as well as six members of the Argus association using UVES spectra. We derive spectroscopic stellar parameters and abundances for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni and Ba. All stars in the open cluster and Argus association were found to share similar abundances with the scatter well within the uncertainties, where [Fe/H] = -0.04 +/-0.03 for cluster stars and [Fe/H] = -0.06 +/-0.05 for Argus stars. Effects of over-ionisation/excitation were seen for stars cooler than roughly 5200K as previously noted in the literature. Also, enhanced Ba abundances of around 0.6 dex were observed in both systems. The common ages, kinematics and chemical abundances strongly support that the Argus association stars originated from the open cluster IC 2391. Simple modeling of this system find this dissolution to be consistent with two-body interactions.Comment: 17 pages, 7 figs, accepted for publication in MNRA

Causal Structure and Birefringence in Nonlinear Electrodynamics

We investigate the causal structure of general nonlinear electrodynamics and determine which Lagrangians generate an effective metric conformal to Minkowski. We also proof that there is only one analytic nonlinear electrodynamics presenting no birefringence.Comment: 11 pages, no figure

Fermi-Fermi Mixtures in the Strong Attraction Limit

The phase diagrams of low density Fermi-Fermi mixtures with equal or unequal masses and equal or unequal populations are described at zero and finite temperatures in the strong attraction limit. In this limit, the Fermi-Fermi mixture can be described by a weakly interacting Bose-Fermi mixture, where the bosons correspond to Feshbach molecules and the fermions correspond to excess atoms. First, we discuss the three and four fermion scattering processes, and use the exact boson-fermion and boson-boson scattering lengths to generate the phase diagrams in terms of the underlying fermion-fermion scattering length. In three dimensions, in addition to the normal and uniform superfluid phases, we find two stable non-uniform states corresponding to (1) phase separation between pure unpaired (excess) and pure paired fermions (molecular bosons); and (2) phase separation between pure excess fermions and a mixture of excess fermions and molecular bosons. Lastly, we also discuss the effects of the trapping potential in the density profiles of condensed and non-condensed molecular bosons, and excess fermions at zero and finite temperatures, and discuss possible implications of our findings to experiments involving mixtures of ultracold fermions.Comment: 12 Pages, 6 Figures and 1 Tabl

Entanglement evolution in finite dimensions

We provide a relation which describes how the entanglement of two d-level systems evolves as either system undergoes an arbitrary physical process. The dynamics of the entanglement turns out to be of a simple form, and is fully captured by a single quantity.Comment: 4 pages, 1 figure; new title and introduction, added references, some makeup; published versio

The four-component instructional design model (4C/ID): A meta-analysis on use and effect

The four-component instructional design model (4C/ID) has been increasingly used in face-to-face and online learning environments. We present a meta-analysis on the use and effect of educational programs developed with the 4C/ID model on performance, after more than 20 years of its application and research in different academic areas and technical training. We performed the meta-analysis through the combination of the effect sizes of the studies using Cohen’s d. The combination of the studies suggests that the use of educational programs developed with 4C/ID has a high impact on performance (d = 0.79), regardless of the academic area, the design of the study and the outcome (knowledge and complex skills). The grade under study was a significant moderator on the effect, showing that the higher-education level is more suitable for application of the 4C/ID model. Our results suggest that the use of the 4C/ID model should be prioritized as instructional model in college and university learning environments.info:eu-repo/semantics/acceptedVersio

Influência de variáveis ambientais na comunidade fitoplanctônica em reservatórios do Nordeste brasileiro

As informações restritas ao monitoramento dos parâmetros físico-químicos da qualidade da água dos rios e reservatórios não são suficientes para descrever a qualidade da água dos mesmos. A avaliação dos parâmetros biológicos tem sido freqüente na avaliação de impactos ambientais, pois produzem informações que não só indicam a presença de poluentes, mas como estes interagem com o meio ambiente, proporcionando uma melhor indicação na qualidade dos ecossistemas. O fitoplâncton é um importante indicador de qualidade da água em reservatórios, seu crescimento exagerado, favorecido pela eutrofização do corpo d’água, pode trazer graves conseqüências. Esta pesquisa teve como objetivo avaliar a influência das variáveis ambientais na comunidade fitoplanctônica de reservatórios do Nordeste brasileiro. A área de estudo são reservatórios que fazem parte do Projeto de Integração do Rio São Francisco com as Bacias Hidrográficas do Nordeste Setentrional, que pretende levar água do rio São Francisco aos municípios com déficit de água para abastecimento humano. Neste trabalho serão apresentados resultados de quatro campanhas de monitoramento, duas em 2009 e duas em 2010, nos reservatórios de Itaparica, Poço da Cruz, Boqueirão, Armando Ribeiro e Castanhão. Para alcançar o objetivo proposto, foram feitas análises estatísticas com auxílio dos programas Primer e SPSS. Primeiramente foi feita uma ordenação direta, através de uma análise de correspondência canônica (CCA) com os parâmetros físico-químicos, divididos em variáveis de pressão e tipologia, e dados de densidade do fitoplâncton. Em seguida, para perceber qual das variáveis, de pressão ou tipologia, explicam melhor a ordenação das espécies, foram feitas CCAs individuais com cada variável. Posteriormente foram determinadas co-variáveis com o objetivo de verificar a influência de cada variável na comunidade fitoplanctônica. Os resultados mostraram que as variáveis ambientais explicam 78% da variação do fitoplâncton. Desses 78%, 22% são explicados pelas variáveis tipológicas e 56% são explicados pelas variáveis de pressão. A partir destes dados foi possível comprovar a influência das variáveis ambientais na comunidade fitoplanctônica e que as variáveis de pressão, que estão relacionadas com a eutrofização nos ecossistemas, são as que mais interferem no crescimento do fitoplâncton nos reservatórios nordestinos

Two-species fermion mixtures with population imbalance

We analyze the phase diagram of uniform superfluidity for two-species fermion mixtures from the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation (BEC) limit as a function of the scattering parameter and population imbalance. We find at zero temperature that the phase diagram of population imbalance versus scattering parameter is asymmetric for unequal masses, having a larger stability region for uniform superfluidity when the lighter fermions are in excess. In addition, we find topological quantum phase transitions associated with the disappearance or appearance of momentum space regions of zero quasiparticle energies. Lastly, near the critical temperature, we derive the Ginzburg-Landau equation, and show that it describes a dilute mixture of composite bosons and unpaired fermions in the BEC limit.Comment: 4 pages with 3 figures, accepted version to PR