Dipole-induced vortex ratchets in superconducting films with arrays of micromagnets

We investigate the transport properties of superconducting films with periodic arrays of in-plane magnetized micromagnets. Two different magnetic textures are studied: a square array of magnetic bars and a close-packed array of triangular microrings. As confirmed by MFM imaging, the magnetic state of both systems can be adjusted to produce arrays of almost point-like magnetic dipoles. By carrying out transport measurements with ac drive, we observed experimentally a recently predicted ratchet effect induced by the interaction between superconducting vortices and the magnetic dipoles. Moreover, we find that these magnetic textures produce vortex-antivortex patterns, which have a crucial role on the transport properties of this hybrid system.Comment: 4 pages, 4 figure

Essential oil content and chemical composition of Lippia gracilis Schauer cultived in the Sub-meddle São Francisco Valley.

Lippia gracilis is a native species of the Caatinga, whose leaves have significant potential for economic use by chemical and pharmaceutical industries due to the presence of thymol and carvacrol. Considering the lack of agronomic data for the species, especially for semi-arid conditions where it is possible to find natural populations, the aim of this work was to assess the effects of drought and different doses of organic fertilization in biomass production and content, yield and chemical composition of the essential oil. The experiment was conducted with 16 treatments that consisted of presence and absence of organic fertilizer, mineral fertilizer and irrigation. The analyzed variables after 120 days of culture were: total length until the last leaf, fresh weight of aerial parts with stem, leaf dry weight a nd fresh weight, content and chemical composition of essential oil, and moisture. In the conditions where this st udy was conducted, it was observed that the organic and mineral fertilization and irrigation positively inf luenced the production of biomass and essential oil content. However, cultivation methods did not significantly affect the chemical composition of essential oils, which shows the hardiness of the species to changes in availability of water and nutrients