Experimental demonstration of a mu=-1 metamaterial lens for magnetic resonance imaging

In this work a mu=-1 metamaterial (MM) lens for magnetic resonance imaging (MRI) is demonstrated. MRI uses surface coils to detect the radiofrequency(RF) energy absorbed and emitted by the nuclear spins in the imaged object. The proposed MM lens manipulates the RF field detected by these surface coils, so that the coil sensitivity and spatial localization is substantially improved. Beyond this specific application, we feel that the reported results are the experimental confirmation of a new concept for the manipulation of RF field in MRI, which paves the way to many other interesting applications.Comment: 9 pages, 3 figure

Exciton trapping in magnetic wire structures

The lateral magnetic confinement of quasi two-dimensional excitons into wire like structures is studied. Spin effects are take into account and two different magnetic field profiles are considered, which experimentally can be created by the deposition of a ferromagnetic stripe on a semiconductor quantum well with magnetization parallel or perpendicular to the grown direction of the well. We find that it is possible to confine excitons into one-dimensional (1D) traps. We show that the dependence of the confinement energy on the exciton wave vector, which is related to its free direction of motion along the wire direction, is very small. Through the application of a background magnetic field it is possible to move the position of the trapping region towards the edge of the ferromagnetic stripe or even underneath the stripe. The exact position of this 1D exciton channel depends on the strength of the background magnetic field and on the magnetic polarisation direction of the ferromagnetic film.Comment: 10 pages, 7 figures, to be published in J. Phys: Condens. Matte

Complementary Effect of Blending on the Volatile Composition of Albariño and Loureira White Wines (Vitis vinifera L.) from NW Spain

Albariño and Loureira are very valuables white cultivars from NW Iberian Peninsula (NW Spain and North Portugal). The purpose of the study was to know how blending affects the volatile composition of Albariño and Loureira white wines. Four Vitis vinifera white wines (Albariño, Loureira, Caiño Blanco and Godello) were blended at different proportions resulting in four wines, two two-wine blends (83:17 Albariño-Caiño Blanco and 50:50 Loureira-Caiño Blanco) and two three-wine blends (48:32:20 Albariño-Loureira-Caiño Blanco and 35:35:30 Loureira-Caiño Blanco-Godello). The blended wines were compared with Albariño and Loureira single-wines. Volatile composition of wines was evaluated by GC-MS to show the changes in aroma compounds of the blends respect to varietal Albariño and Loureira wines. The highest concentration of total volatiles was shown for Loureira and Albariño single-wines. However, blended wines, especially with Loureira, showed an increase of terpenes and C13-norisoprenoids concentration. Discriminant analysis (DA) showed C6-alcohols and phenol volatiles as the variables that most contributed to the differentiation between Albariño and blended wines, whereas terpenes and C13-norisoprenoids were those that contributed to the differentiation Loureira vs blended. To show the sensory influence of volatiles Odour Activity Value (OAV) was calculated, showing the superiority of Loureira single-wines aroma and 50:50 LO-CB blended wines vs Albariño and the other blended wines. The blended wines with high proportion of Loureira supposed wines richer in volatile compounds and increased of complexity aromatic of the wines

Domain wall description of superconductivity

In the present work we shall address the issue of electrical conductivity in superconductors in the perspective of superconducting domain wall solutions in the realm of field theory. We take our set up made out of a dynamical complex scalar field coupled to gauge field to be responsible for superconductivity and an extra scalar real field that plays the role of superconducting domain walls. The temperature of the system is interpreted through the fact that the soliton following accelerating orbits is a Rindler observer experiencing a thermal bath.Comment: 9 pages, 5 figures, Latex. Version to appear in PL

Critical aspects of biomass ashes utilization in soils: composition, leachability, PAH and PCDD/F

Bottom and fly ashes streams collected along a year in several biomass thermal plants were studied. The bulk composition of ashes and other chemical characteristics that may impact soil application showed a high variability depending on the ash stream, combustion technology and ash management practice at the power plants. The acid neutralization capacity (ANC) and metal’s availability for leaching at fixed pH 7 and 4 was performed according with EA NEN 7371, as a quick evaluation method to provide information on the long-term behavior of ashes, regarding heavy metals and also plant nutrients release. Also the pH dependence leachability study was performed according to CEN/TS 14429 for predicting the leaching behavior under different scenarios. Leachability profiles were established between pH 3 and 12, allowing to distinguish different solubility control phenomena of toxic heavy metals (Cu, Cr, Mn, Ni, Zn, Pb) as well as other salts (Ca, K, Mg, Na, Cl). The ANC of fly ashes at pH 4 (3.6–9.6 molH+/kg) were higher than that observed for the bottom ashes (1.2–2.1 molH+/kg). Ashes were also characterized for persistent organic pollutants (POP), such as polycyclic aromatic hydrocarbons (PAH) and paradibenzodioxines and furanes (PCDD/F). Contents were found to be much higher in fly ash than in bottom ash streams. None of the PAH levels did reach the current national limit value of sewage sludge application in soils or the guide value for ash in north European countries. However, PCDD/F contents, which are not regulated, varied from non-detectable levels to high amounts, regardless the level of loss on ignition (LOI) or unburned carbon content in fly ashes. Given the current ash management practices and possible use of blends of bottom and fly ash streams as soil conditioners resembles clear the urgent need to regulate ash utilization in soils, incorporating limit values both for heavy metals, PAH and PCDD/F

Transformações na estrutura produtiva dos viticultores da Serra Gaúcha: 1985/1991.

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Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12

We investigate on the relative inclination of the planets B and C orbiting the pulsar PSR B1257+12 in connection with potential violations of the equivalence principle (Abridged).Comment: LaTex2e, 10 pages, 1 table, 3 figures, 17 references. Small stylistic changes. Version to appear in Journal of Astrophysics and Astronomy (JAA