Magnetic domain wall propagation in a submicron spin-valve stripe: influence of the pinned layer

The propagation of a domain wall in a submicron ferromagnetic spin-valve stripe is investigated using giant magnetoresistance. A notch in the stripe efficiently traps an injected wall stopping the domain propagation. The authors show that the magnetic field at which the wall is depinned displays a stochastic nature. Moreover, the depinning statistics are significantly different for head to head and tail-to-tail domain walls. This is attributed to the dipolar field generated in the vicinity of the notch by the pinned layer of the spin-valve

360 degree domain wall generation in the soft layer of magnetic tunnel junctions

High spatial resolution X-ray photo-emission electron microscopy technique has been used to study the influence of the dipolar coupling taking place between the NiFe and the Co ferromagnetic electrodes of micron sized, elliptical shaped magnetic tunnel junctions. The chemical selectivity of this technique allows to observe independently the magnetic domain structure in each ferromagnetic electrode. The combination of this powerful imaging technique with micromagnetic simulations allows to evidence that a 360 degree domain wall can be stabilized in the NiFe soft layer. In this letter, we discuss the origin and the formation conditions of those 360 degree domain walls evidenced experimentally and numerically

Análisis técnico y económico de la recuperación de los aceites dieléctricos con tierra fuller y deslodificación de bobinados en transformadores

La presente tesis realiza un análisis técnico y económico de la recuperación de los aceites dieléctricos con tierra fuller con su efecto al interior de los transformadores en la deslodificación de sus bobinados como producto del envejecimiento que estos equipos experimentan en su operación con el transcurrir de los años. Mediante esta implementación no sólo se logra mejorar las condiciones operativas de los transformadores sino que también se evita que en el país se produzca un almacenamiento muy grande de aceites dieléctricos lo cual afecta también al medio ambiente. Por los motivos antes expuestos, se realiza previo al análisis una descripción del proceso de envejecimiento que sufren los aceites dieléctricos así como se detallan los diferentes métodos que se tienen para la recuperación de los mismos utilizando tierra fuller. Finalmente se hace la evaluación técnica y económica de la recuperación de los aceites dieléctricos y la deslodificación de los bobinados frente al costo que tienen los transformadores de potencia

Nonequilibrium Luminescence At The E0+Δ0 Gap In Gaas With Si-δ Doping

We studied the light scattering spectra of three molecular beam epitaxy GaAs samples with Si-δ doping. A broad feature appears in these spectra which is similar to that attributed by other authors to resonant Raman scattering by electronic intersubband transitions. By studying the dependence of this emission on exciting laser photon energy we believe that this line is really produced by nonequilibrium luminescence at the E0+Δ 0 gap.71115619562

Plant Growth and Root Morphology Are Affected by Earthworm-Driven (Eisenia sp.) Changes in Soil Chemico-Physical Properties: a Mesocosm Experiment with Broccoli and Faba Bean

Earthworms are "ecosystem engineers" that improve soil water and nutrient content, soil macroporosity, and aeration, and provide suitable habitats for microbial populations. This study aimed at defining if the presence of epigeic earthworms (Eisenia sp.) affected the growth and development of two plant species (Brassica oleracea and Vicia faba) via the modifications of soil chemico-physical properties. A mesocosm experiment, in which plants were grown outdoors for 4 months with or without earthworms, was performed. The two plant species were selected based on their different habitus and root architecture and morphology. Soil macroporosity (M-soil) and water holding capacity (WHCsoil) were determined. Earthworm-driven bioturbation (B-soil) was measured by filling mesh bags with artificial soil. Earthworm abundance and biomass, together with plant morphometric parameters (root and leaf morphology by imaging and microscope techniques), were measured at the end of the trial. The presence of earthworms increased M-soil (on average +16%) and WHCsoil (on average +9%) and this was accompanied by a remarkable degree of B-soil. In most of the cases, earthworms enhanced plant growth in the two plant species studied, with a significant positive influence on the majority of the shoot and root traits. A significant increase of stomatal density (on average +24%) occurred in the leaves of both the plant species in the presence of earthworms. Our results confirmed the hypothesis that bioturbation by Eisenia sp. had a significant positive effect on plant growth, independently from the plant species cultivated, and that these growth-promoting effects were mediated by changes in soil chemico-physical parameters. By taking into account the essential role of earthworms in maintaining healthy soils and the vegetation they support, soils can become more resilient against environmental perturbations and climate change