Using torsion to manipulate spin currents

We address the problem of quantum particles moving on a manifold characterised by the presence of torsion along a preferential axis. In fact, such a torsion may be taylored by the presence of a single screw dislocation, whose Burgers vector measures the torsion amplitude. The problem, first treated in the relativistic limit describing fermions that couple minimally to torsion, is then analysed in the Pauli limit We show that torsion induces a geometric potential and also that it couples generically to the phase of the wave function, giving rise to the possibility of using torsion to manipulate spin currents in the case of spinor wave functions. These results emerge as an alternative strategy for using screw dislocations in the design of spintronic-based devices

Electronic properties of curved graphene sheets

A model is proposed to study the electronic structure of slightly curved graphene sheets with an arbitrary number of pentagon-heptagon pairs and Stone-Wales defects based on a cosmological analogy. The disorder induced by curvature produces characteristic patterns in the local density of states that can be observed in scanning tunnel and transmission electron microscopy.Comment: Corrected versio

Multi-strata agroforestry system with native amazonian plants cultivated in acid soil.

Multi-strata agroforestry system is mentioned as the most promising option for the sustainable agriculture in infertile upland soil of Central Amazonian. However, studies showed that the sustainability practices are not adopted by the growers in this region. lhe objective of this study was to evaluate the soil fertility and nutritional state of native Amazon plant species grown on a Xanthic Ferralsol in an agroforestry system. Native plants species used were r five of timber species - Hevea brasiliensis (rubber), Ceiba pentandra- (kapok), Jacaranda copa ia (jacaranda), Buchenavia huber (cuiarana) and Trattinicka burserifolia (breu); two palm species - Bactris gasipaes (peach palm) and Euterpe oleracea (assai); and five fruit-bearing species - Rollinia mucosa (biriba), Theobroma cacao (cacao), Theobroma grandiflorum (cupuassu), Couma sorbilis (sorva) and Myrciaria dubia (camu-camu). The results showed that plants from the same ecosystem with acidity tolerance differ significantly in nutrient uptake efficiency and nutritional requirements, indicating the possibility of using appropriate species that can be used in an agroforestry system of central Amazon Region

Utilização de bioestimulantes na cultura da cana-de-açúcar (Saccharum officinarum L.).

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Efficiency of sulfur application on soybean in two types of Oxisols in Southern Brazil.

Modern agricultural techniques have been increasing the yield of soybean (Glycine max L.) while also causing increasing removal of sulfur (S) from the soil. Besides this, the use of concentrated fertilizers with this element and inadequate soil management, with consequent formation of organic matter with low S concentrations, has been causing frequent symptoms if deficiency in the plats. To assess the effect of S on soybean yield and to establish critical levels of S-SO42- available in the soil, two experiments were conducted over a two-year period in the Parana State, Brazil, in fields containing Typic Haplorthox and Typic Eutrorthox soils, located in the municipalities of Ponta Grossa and Londrina, respectively. The experimental design was randomized blocks with five S rates (0, 25, 50, 75, and 100 kg ha-1) and four replicates. The source used was elementary S with 98% purity. The maximum estimated yields on average for the two years were obtained with application of 49.9 and 63.0 kg ha-1 in the Typic Haplorthox and Typic Eutrorthox soils, for an overall average of 56.4 kg ha-1, with S-SO42- concentrations in the 0-20 cm depth of 16.9, 19.3 and 17.1 mg kg-1, respectively, values higher than the 10 mg kg-1 indicated as the adequate concentration for soybean plant. In turn, at the 21-40 cm depth, the S concentrations were 49.5, 74.2 and 56.4 kg ha-1. The efficiency of the fertilization diminished with increasing S rates, in both soil types, while the greatest yield efficiency was obtained in the plants grown in the Typic Haplorthox soil

Rainfall Erosivity in Apeú River Watershed, Northeastern State of Pará, in the Brazilian Amazon Region.

Resumo em português: Erosividade das Chuvas na Bacia Hidrográfica do Rio Apeú, Região Nordeste do Estado do Pará

Morfogênese de Axonopus aureus em Diferentes Idades de Corte

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Morfogênese de Axonopus aureus em Diferentes Alturas de Corte.

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Lowland rice genotypes evaluation for nitrogen use efficiency in brazilian acid soil.

Nitrogen is one of the most yield limiting nutrients in rice production under ali agro-ecological conditions. A greenhouse experiment was conducted to evaluate N responses to 12 lowland rice genotypes. Soil used in the experiment was an Inceptisol. The N rates used were Omg kg' (low) and 300 mg kq' (high) of soil. Straw yield, grain yield and panicle density were significantly increased with the addition of N fertilization and genotype treatment. The N X genotype interaction also was significant for these traits, indicating different responses of genotypes with variation in N rates