Magnetically induced anisotropy of flux penetration into strong-pinning superconductor/ferromagnet bilayers

We studied the impact of soft ferromagnetic permalloy (Py) on the shielding currents in a strong-pinning superconductor?YBa2Cu3O7?? with Ba2Y(Nb/Ta)O-6 nano-precipitates?by means of scanning transmission x-ray microscopy. Typically and in particular when in the thin film limit, superconductor/ferromagnet (SC/FM) bilayers exhibit isotropic properties of the flux line ensemble at all temperatures. However, in elements with small aspect ratio a significant anisotropy in flux penetration is observed. We explain this effect by local in-plane fields arising from anisotropic magnetic stray fields originated by the ferromagnet. This leads to direction-dependent motion of magnetic vortices inside the SC/FM bilayer. Our results demonstrate that small variations of the magnetic properties can have huge impact on the superconductor

Pair Distribution Function Analysis of ZrO2 Nanocrystals and Insights in the Formation of ZrO2-YBa2Cu3O7 Nanocomposites

The formation of superconducting nanocomposites from preformed nanocrystals is still not well understood. Here, we examine the case of ZrO2 nanocrystals in a YBa2Cu3O7-x matrix. First we analyzed the preformed ZrO2 nanocrystals via atomic pair distribution function analysis and found that the nanocrystals have a distorted tetragonal crystal structure. Second, we investigated the influence of various surface ligands attached to the ZrO2 nanocrystals on the distribution of metal ions in the pyrolyzed matrix via secondary ion mass spectroscopy technique. The choice of stabilizing ligand is crucial in order to obtain good superconducting nanocomposite films with vortex pinning. Short, carboxylate based ligands lead to poor superconducting properties due to the inhomogeneity of metal content in the pyrolyzed matrix. Counter-intuitively, a phosphonate ligand with long chains does not disturb the growth of YBa2Cu3O7-x. Even more surprisingly, bisphosphonate polymeric ligands provide good colloidal stability in solution but do not prevent coagulation in the final film, resulting in poor pinning. These results thus shed light on the various stages of the superconducting nanocomposite formation

Un algoritmo de programacion geometrica basado en funciones penalidad-multiplicadoras

Programación Geométrica, Algoritmos, Langragianos Aumentados, 90C30, Geometric Programming, Algorithms, Augmented Lagrangian Functions,

RvP varieties: the result of many decades of experience and of updated knowledge

Creating good varieties of allogamous seed-born plants is a curious activity. Initially continuous and sequential cycles of selection and recombination are involved. Testing the value of the created novelties is a second step and finally the sequence ends with seed multiplication. This paper describes how R.v.P. creates varieties of cruciferous crops, salsify, chicory, clover, fodderbeets and foddergrasses. The article is written in Dutch

Magnetically induced anisotropy of flux penetration into strong-pinning superconductor/ferromagnet bilayers

We studied the impact of soft ferromagnetic permalloy (Py) on the shielding currents in a strong-pinning superconductor - YBa2Cu3O7-δ with Ba2Y(Nb/Ta)O6 nano-precipitates - by means of scanning transmission x-ray microscopy. Typically and in particular when in the thin film limit, superconductor/ferromagnet (SC/FM) bilayers exhibit isotropic properties of the flux line ensemble at all temperatures. However, in elements with small aspect ratio a significant anisotropy in flux penetration is observed. We explain this effect by local in-plane fields arising from anisotropic magnetic stray fields originated by the ferromagnet. This leads to direction-dependent motion of magnetic vortices inside the SC/FM bilayer. Our results demonstrate that small variations of the magnetic properties can have huge impact on the superconductor

A high content screening assay for evaluation of biomaterial-mediated cell fusion processes

Biomaterials are of increasing importance in regenerative medicine and entail delivery systems in somatic cell therapies, matrices for tissue engineering or tissue regeneration. The evaluation of biomaterial induced biological effects remains a key issue in clinical application. Cell-based assays for potential cytotoxic and immunological responses have been developed but are often inadequate to address cell-type specific responses to biomaterials. To quantitatively monitor attachment, survival, proliferation and fusion-controlled differentiation of osteoclasts (bone resorbing cells), a High Content Screening (HCS) assay has been developed based on osteoclast differentiation of the murine monocytic cell line RAW 264.7. This assay was applied to investigate the influence of degradation products of polymers from gelatin and lysine diisocyanate, which display tailorable mechanical properties and have potential as biomaterials. The data show that the degradation products inhibit formation of multinuclear osteoclasts and suggest a potential support of bone regeneration by suppression of bone resorption