Magnetic-dipole induced appearance of vortices in a bilayered superconductor/soft-magnet heterostructure

The penetration of the magnetic field of an infinitesimal magnetic dipole into a bilayered type-II superconductor/soft-magnet heterostructure is studied on the basis of the classical London approach. The critical values of the dipole moment for the first appearance of a single magnetic vortex and, respectively, a magnetic vortex-antivortex pair in the superconductor constituent are obtained, when the magnetic dipole faces the superconductor or the soft-magnet constituent. This reveals that the soft-magnet constituent inhibits penetration of vortices into the superconductor constituent, when the dipole faces the soft-magnet constituent.Comment: 2 pages, 1 figure; accepted in Physica C for the special issue of Preceedings of the 8th Int. Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (M2S-HTSC), Dresden, Germany, July 9-14, 200

Insights on the mechanism of formation of protein microspheres in a biphasic system

Microspheres of bovine serum albumin (BSA) and silk fibroin are produced by applying ultrasound in a biphasic system consisting of an aqueous protein solution and an organic solvent. The protein microspheres are dispersed in an aqueous media where the protein remains at the interface covering the organic solvent. This only occurs when high shear forces are applied that induce changes to force the protein to the interface. Fourier transform infrared results indicate a large increase in the content of the β-sheet during the formation of silk fibroin microspheres. Molecular dynamics simulations show a clear adaption on the 3D structure of BSA when stabilized at the interface, without major changes in secondary structure. Further studies demonstrate that high water content, oil solvents, and larger peptides with separated and clear hydrophobic and hydrophilic areas lead to more stable and smaller spheres. This is the first time that these results are presented. We also present herein the rationale to produce tailored protein microspheres with a controlled size, controlled charge, and increased stability.This work was supported by Lidwine Project-Multifunctional medical textiles for wound (e.g., Decubitus) prevention and improved wound healing NMP2-CT-2006-026741. H.F. thanks POPH/FSE for cofinancing and FCT for Fellowship SFRH/BPD/38939/2007. We acknowledge Silvia Cappellozza from "Sezione Specializzata per la Bachicoltura" for the supply of silk cocoons

Magnetic dipole–vortex interaction in a bilayered superconductor/soft-magnet heterostructure

The penetration of the magnetic field of an infinitesimal magnetic dipole into a bilayered type-II superconductor/soft-magnet heterostructure is studied on the basis of the classical London approach. The energies associated with the presence of a straight magnetic vortex in the superconductor layer are derived and the critical dipole moment for the first vortex appearance is obtained when the magnetic dipole faces the superconductor or the soft-magnet constituent. This shows that the presence of the latter constituent can lead to an improvement of the superconducting properties of the heterostructure by either inhibiting vortex penetration into the superconductor constituent or enhancing vortex pinning in the superconductor constituent