Predicted defect induced vortex core switching in thin magnetic nanodisks

We investigate the influence of artificial defects (small holes) inserted into magnetic nanodisks on the vortex core dynamics. One and two holes (antidots) are considered. In general, the core falls into the hole but, in particular, we would like to remark an interesting phenomenon not yet observed, which is the vortex core switching induced by the vortex-hole interactions. It occurs for the case with only one hole and for very special conditions involving the hole size and position as well as the disk size. Any small deformation in the disk geometry such as the presence of a second antidot changes completely the vortex dynamics and the vortex core eventually falls into one of the defects. After trapped, the vortex center still oscillates with a very high frequency and small amplitude around the defect center.Comment: 11pages, Revtex format, 17 figure

Caracterização das unidades de produção familiar participante do projeto silvapastoril em Rondônia.

bitstream/item/85766/1/ct126-producaofamiliar.pd

Boron extraction and vertical mobility in Paraná State oxisol, Brazil.

The deficiency or excess of micronutrients has been determined by analyses of soil and plant tissue. In Brazil, the lack of studies that would define and standardize extraction and determination methods, as well as lack of correlation and calibration studies, makes it difficult to establish limits of concentration classes for analysis interpretation and fertilizer recommendations for crops. A specific extractor for soil analysis is sometimes chosen due to the ease of use in the laboratory and not in view of its efficiency in determining a bioavailable nutrient. The objectives of this study were to: (a) evaluate B concentrations in the soil as related to the fertilizer rate, soil depth and extractor; (b) verify the nutrient movement in the soil profile; (c) evaluate efficiency of Hot Water, Mehlich-1 and Mehlich-3 as available B extractors, using sunflower as test plant. The experimental design consisted of complete randomized blocks with four replications and treatments of five B rates (0, 2, 4, 6, and 8 kg ha-1) applied to the soil surface and evaluated at six depths (0?0.05, 0.05?0.10, 0.10?0.15, 0.15?0.20, 0.20?0.30, and 0.30?0.40 m). Boron concentrations in the soil extracted by Hot Water, Mehlich-1 and Mehlich-3 extractors increased linearly in relation to B rates at all depths evaluated, indicatingB mobility in the profile. The extractors had different B extraction capacities, but were all efficient to evaluate bioavailability of the nutrient to sunflower.

Interação solo-planta-animal no sistema Integração Lavoura-Pecuária.

As interações que ocorrem no sistema Integração Lavoura-Pecuária (ILP) são complexas, uma vez que, além da planta e do solo, existe a participação do animal. A desfolhação e o pisoteio animal podem afetar a cobertura vegetal e alterar a dinâmica da biomassa da pastagem, além de causar modificações nas propriedades físicas, químicas e biológicas do solo. Adequar alta produção e qualidade de forragem, com elevada produção animal e altos níveis de produtividade de grãos é um desafio para técnicos e produtores. Portanto, o sistema exige que o manejo da desfolha pelo animal seja feito de maneira que as características morfofisiológicas de cada espécie forrageira seja respeitadas. Dessa maneira, uma melhor compreensão sobre o efeito da entrada dos animais em áreas de pastagem rotacionadas com lavoura e as interações entre solo, planta e animal são determinantes para o sucesso da ILP