Inductive learning spatial attention

This paper investigates the automatic induction of spatial attention from the visual observation of objects manipulated on a table top. In this work, space is represented in terms of a novel observer-object relative reference system, named Local Cardinal System, defined upon the local neighbourhood of objects on the table. We present results of applying the proposed methodology on five distinct scenarios involving the construction of spatial patterns of coloured blocks

Manipulation of the dynamics of many-body systems via quantum control methods

We investigate how dynamical decoupling methods may be used to manipulate the time evolution of quantum many-body systems. These methods consist of sequences of external control operations designed to induce a desired dynamics. The systems considered for the analysis are one-dimensional spin-1/2 models, which, according to the parameters of the Hamiltonian, may be in the integrable or non-integrable limits, and in the gapped or gapless phases. We show that an appropriate control sequence may lead a chaotic chain to evolve as an integrable chain and a system in the gapless phase to behave as a system in the gapped phase. A key ingredient for the control schemes developed here is the possibility to use, in the same sequence, different time intervals between control operations.Comment: 10 pages, 3 figure

Efeito da percentagem de grãos gessados sobre a viscosidade do arroz.

O objetivo deste trabalho foi avaliar a viscosidade do arroz com diferentes porcentagens de grãos gessados, sob efeito da temperatura e tempo

Topological Defects in Contracting Universes

We study the behaviour and consequences of cosmic string networks in contracting universes. They approximately behave during the collapse phase as a radiation fluids. Scaling solutions describing this are derived and tested against high-resolution numerical simulations. A string network in a contracting universe, together with the gravitational radiation it generates, can affect the dynamics of the universe both locally and globally, and be an important source of radiation, entropy and inhomogeneity. We discuss possible implications for bouncing and cyclic models.Comment: Shorter version of astro-ph/0206287. To appear in Phys. Rev. Let

Physical–biological interactions in the life history of small pelagic fish in the Western Iberia Upwelling Ecosystem.

This paper reviews relevant investigations conducted in the Western Iberia Upwelling Ecosystem (WIUE) on the dynamics of small pelagic fish (SPF), its relationship to climate changes and processes related to the ‘ocean triad’ (enrichment, concentration, transport/retention). In the last decades, a decline in the productivity of several SPF species (e.g., sardine and horse mackerel) was observed in the WIUE, which is partially explained by environmental variability (e.g., changes in coastal upwelling). The main mechanism proposed to explain this decline is the increased frequency and intensity of upwelling events during the spawning season (winter) of these species, which is typically a period when convergence conditions prevail. Thus, this ‘anomalous’ situation promotes egg and larval dispersal away from the favourable coastal habitat (the shelf) and consequently has a negative impact on their survival and recruitment. However, the variability of local features like the Western Iberia Buoyant Plume (WIBP) and the Iberian Poleward Current (IPC) introduce important fluctuations in the transport patterns of the region, and could modulate the impact of these winter upwelling events in the survival of larvae. The retention on the shelf of larval sardine along convergence zones formed by the interaction of these two features plays an important role in their survival. Furthermore, the WIBP is a suitable environment for the growth of phytoplankton and for larval fish survival. From these findings it is clear that simplified Ekman transport models could not explain larval fish transport/retention patterns in this region and more realistic biophysical models should be used to simulate the local oceanographic conditions to understand larval dynamics and the success of recruitment of SPF in the Western Iberia

Avaliação do uso de diferentes tipos de sacos de tecido para incubação in vitro de amostras vegetais.

Resumo: Avaliou-se o potencial de uso de sacos de tecido com diferentes características e porosidades para acondicionamento de amostras em ensaios de produção de gases in vitro. Para isso, amostras de feno de capim coastcross (Cynodon sp.), secas em estufa de ventilação forçada e trituradas (1 mm) foram incubadas durante 96 horas em frascos de vidro com 160 mL de capacidade, contendo 72 mL de meio de cultura e 8 mL de inóculo ruminal. O substrato foi incubado, em quadruplicata, diretamente no frasco de fermentação (controle) ou acondicionado em 3 tipos de saco de tecido: ANKOM filter bag (modelo F57, porosidade = 25 ?m); saco de poliéster (3,5 × 8,0 cm) com porosidade de 25 ?m; saco de poliéster (3,5 × 8,0 cm) com porosidade de 40 ?m. Os valores de degradabilidade da matéria seca não diferiram entre os tratamentos após 96 horas de incubação (P>0,05). A produção acumulada de gases, no entanto, foi 12% inferior ao controle quando o substrato foi incubado em saco de poliéster com porosidade de 40 ?m (P0.05). Total gas production, however, was 12% lower for the substrate incubated in 40-?m polyester bags in comparison to the control (P<0.05). Enclosing samples in cloth bags altered the fermentation kinetic of the incubated substrate, mainly in regard to the rate of gas production (P<0.05). Such alterations were significantly greater when using ANKOM F57 filter bags (P<0.05). Enclosing samples in cloth bags is not appropriate to estimate fermentation kinetic parameters by using the gas production technique