277 research outputs found

    Commentary: Task-Switching in Pigeons: Associative Learning or Executive Control?

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    A commentary on Task-Switching in Pigeons: Associative Learning or Executive Control? by Meier, C., Lea, S., and McLaren, I. (2016). J. Exp. Psychol. Anim. Learn. Cogn. 42, 163–176. doi: 10.1037/xan000010

    Cooper problem in the vicinity of Anderson transition

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    We study numerically the ground state properties of the Cooper problem in the three-dimensional Anderson model. It is shown that attractive interaction creates localized pairs in the metallic noninteracting phase. This localization is destroyed at sufficiently weak disorder. The phase diagram for the delocalization transition in the presence of disorder and interaction is determined.Comment: revtex, 4 pages, 4 figure

    Transition to an Insulating Phase Induced by Attractive Interactions in the Disordered Three-Dimensional Hubbard Model

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    We study numerically the interplay of disorder and attractive interactions for spin-1/2 fermions in the three-dimensional Hubbard model. The results obtained by projector quantum Monte Carlo simulations show that at moderate disorder, increasing the attractive interaction leads to a transition from delocalized superconducting states to the insulating phase of localized pairs. This transition takes place well within the metallic phase of the single-particle Anderson model.Comment: revtex, 4 pages, 3 figure

    On the Inverse Problem of Binocular 3D Motion Perception

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    It is shown that existing processing schemes of 3D motion perception such as interocular velocity difference, changing disparity over time, as well as joint encoding of motion and disparity, do not offer a general solution to the inverse optics problem of local binocular 3D motion. Instead we suggest that local velocity constraints in combination with binocular disparity and other depth cues provide a more flexible framework for the solution of the inverse problem. In the context of the aperture problem we derive predictions from two plausible default strategies: (1) the vector normal prefers slow motion in 3D whereas (2) the cyclopean average is based on slow motion in 2D. Predicting perceived motion directions for ambiguous line motion provides an opportunity to distinguish between these strategies of 3D motion processing. Our theoretical results suggest that velocity constraints and disparity from feature tracking are needed to solve the inverse problem of 3D motion perception. It seems plausible that motion and disparity input is processed in parallel and integrated late in the visual processing hierarchy

    Detecção de anticorpos heterólogos contra o vírus da leucose enzoótica bovina em caprinos.

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    O presente estudo foi idealizado com o intuito de investigar a possibilidade da transmissão do vírus da leucose enzoótica bovina (VLB) para cabritos recém-nascidos amamentados com colostro de vacas soropositivas para leucose enzoótica bovina (LEB). Para tanto, foram utilizados 31 caprinos que foram separados das mães logo após o nascimento, para em seguida receber colostro proveniente de 11vacas testadas sorologicamente para LEB. Amostras de soro sangüí neo dos caprinos foram colhidas ao 3, 45, 80,120 e 160 dias de idade e, depois, quando tinham aproximadamente 4 anos. Então, foram feitas as análises laboratoriais por meio do teste da imunodifusão em gel de ágar (IDGA) utilizando o antígeno gp51 para diagnóstico da LEB. Desse modo, constatou-se que uma parte dos cabritos que receberam colostro de vacas soropositivas para LEB estavam reagentes aos 3 dias de idade e negativos nas outras idades. Entretanto, todos os outros que receberam colostro de vacas soro negativas não reagiram nos testes sorológicos. Esses resultados permitiriam supor então que os anticorpos detectados eram de origem colostral. Após o declínio da imunidade passiva e na vida adulta, nenhum caprino soroconverteu. Portanto, pôde-se concluir que o colostro de vacas soropositivas para LEB não foi considerado um meio eficiente para a transmissão do VLB

    Deficiency of Pkc1 activity affects glycerol metabolism in Saccharomyces cerevisiae

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    In pressProtein kinase C is apparently involved in the control of many cellular systems: the cell wall integrity pathway, the synthesis of ribosomes, the appropriated reallocation of transcription factors under specific stress conditions and also the regulation of N-glycosylation activity. All these observations suggest the existence of additional targets not yet identified. In the context of the control of carbon metabolism, previous data demonstrated that Pkc1 p might play a central role in the control of cellular growth and metabolism in yeast. In particular, it has been suggested that it might be involved in the derepression of genes under glucose-repression by driving an appropriated subcellular localization of transcriptional factors, such as Mig1 p. In this work, we show that pkc1∆ mutant is unable to grow on glycerol because it cannot perform the derepression of GUT1 gene that encodes for glycerol kinase. Additionally, active transport is also partially affected. Using this phenotype, we were able to isolate a new pkc1∆ revertant. We also isolated two transformants identified as the nuclear exportin Msn5 and the histone deacetylase Hos2 extragenic suppressors of this mutation. Based on these results, we postulate that Pkc1 p may be involved in the control of the cellular localization and/or regulation of the activity of nuclear proteins implicated in gene expression.Fundação Universidade Federal de Ouro Preto (FUFOP). Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) - CBS-1875/95. Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) - 300998/89-9 to R.L.B., 301255/01-6 to L.G.F

    Bird-spiders (Arachnida, Mygalomorphae) as perceived by the inhabitants of the village of Pedra Branca, Bahia State, Brazil

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    This paper deals with the conceptions, knowledge and attitudes of the inhabitants of the county of Pedra Branca, Bahia State, on mygalomorph spiders locally known as 'caranguejeiras' (bird-spiders). It is launched here a new filed within ethnozoology: ethnoarachnology, which is defined as the transdisciplinary study of the relationships between human beings and bird-spiders. Data were collected from February to June 2005 by means of open-ended interviews carried out with 30 individuals, which ages ranged from 13 to 86 years old. It was recorded some traditional knowledge regarding the following items: taxonomy, biology, habitat, ecology, seasonality, and behavior. Results show that bird-spiders are classified as "insects". The most commented aspect of the interaction between bird-spiders and inhabitants of Pedra Branca is related to their dangerousness, since they said these spiders are very venomous and can cause health problems. In general, the traditional zoological knowledge of Pedra Branca's inhabitants concerning these spiders is coherent with the academic knowledge
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