17,401 research outputs found
Sparse spatial selection for novelty-based search result diversification
Abstract. Novelty-based diversification approaches aim to produce a diverse ranking by directly comparing the retrieved documents. However, since such approaches are typically greedy, they require O(n 2) documentdocument comparisons in order to diversify a ranking of n documents. In this work, we propose to model novelty-based diversification as a similarity search in a sparse metric space. In particular, we exploit the triangle inequality property of metric spaces in order to drastically reduce the number of required document-document comparisons. Thorough experiments using three TREC test collections show that our approach is at least as effective as existing novelty-based diversification approaches, while improving their efficiency by an order of magnitude.
An Adult with Episodic Abnormal Limb Posturing
info:eu-repo/semantics/publishedVersio
K X-Ray Energies and Transition Probabilities for He-, Li- and Be-like Praseodymium ions
Theoretical transition energies and probabilities for He-, Li- and Be-like
Praseodymium ions are calculated in the framework of the multi-configuration
Dirac-Fock method (MCDF), including QED corrections. These calculated values
are compared to recent experimental data obtained in the Livermore SuperEBIT
electron beam ion trap facility
Interplay between chiral and axial symmetries in a SU(2) Nambu--Jona-Lasinio Model with the Polyakov loop
We consider a two flavor Polyakov--Nambu--Jona-Lasinio (PNJL) model where the
Lagrangian includes an interaction term that explicitly breaks the U
anomaly. At finite temperature, the restoration of chiral and axial symmetries,
signaled by the behavior of several observables, is investigated. We compare
the effects of two regularizations at finite temperature, one of them, that
allows high momentum quarks states, leading to the full recovery of chiral
symmetry. From the analysis of the behavior of the topological susceptibility
and of the mesonic masses of the axial partners, it is found in the SU(2) model
that, unlike the SU(3) results, the recovery of the axial symmetry is not a
consequence of the full recovery of the chiral symmetry. Thus, one needs to use
an additional idea, by means of a temperature dependence of the anomaly
coefficient, that simulates instanton suppression effects.Comment: 21 pages, 5 figures; PRD versio
Avaliação e seleção de bulbos de cebola de baixo teor de ácido pirúvico de cultivares adaptadas ao Nordeste.
Diferente de outros países, o Brasil não desenvolveu populações de cebola com baixa pungência, o que poderia aumentar o consumo nacional e criar novas oportunidades para os agricultores. O objetivo deste trabalho foi avaliar o teor de ácido pirúvico em algumas populações de cebola desenvolvidas para o Nordeste brasileiro para orientar trabalhos de melhoramento da espécie. Foram avaliados bulbos de cinco variedades de cebola cultivados nos Campos Experimentais de Bebedouro e Mandacaru/Embrapa Semiárido, em 2010. As condições de cultivo e manejo de fertilizantes foram semelhantes nos dois locais. Os bulbos foram quantificados para o teor de ácido pirúvico por espectrofotometria, sendo selecionados aqueles com teor menor que 5 μmol/mL. Dos 206 bulbos de Bebedouro, os teores de ácido pirúvico variaram de 3,02 μmol/mL a 14,22 μmol/mL de suco de cebola, dos quais selecionou-se 14 (6,8%). Dos 360 bulbos, colhidos no Campo Experimental de Mandacaru, os teores de ácido pirúvico variaram de 3,65 μmol/mL a 18,52 μmol/mL de suco de cebola; destes 13 (3,6%) foram selecionados. Obteve-se sementes em 18 plantas dos 27 bulbos selecionados, o que possibilitará um novo ciclo de seleção recorrente, visando o desenvolvimento de populações de cebola com baixos teores de ácido pirúvico para o Nordeste brasileiro
Superconducting Kondo phase in an orbitally-separated bilayer
The nature of superconductivity in heavy-fermion materials is a subject under
intense debate, and controlling this many-body state is central for its
eventual understanding. Here, we examine how proximity effects may change this
phenomenon, by investigating the effects of an additional metallic layer on the
top of a Kondo-lattice, and allowing for pairing in the former. We analyze a
bilayer Kondo Lattice Model with an on-site Hubbard interaction, , on the
additional layer, using a mean-field approach. For , we notice a drastic
change in the density-of-states due to multiple-orbital singlet resonating
combinations. It destroys the well-known Kondo insulator at half filling,
leading to a metallic ground state, which, in turn, enhances antiferromagnetism
through the polarization of the conduction electrons. For , a
superconducting Kondo state sets in at zero temperature, with the occurrence of
unconventional pairing amplitudes involving -electrons. We establish that
this remarkable feature is only possible due to the proximity effects of the
additional layer. At finite temperatures we find that the critical
superconducting temperature, , decreases with the interlayer
hybridization. We have also established that a zero temperature superconducting
amplitude tracks , which reminisces the BCS proportionality between the
superconducting gap and .Comment: 11 pages, 10 figure
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