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

Orbital magnetism in axially deformed sodium clusters: From scissors mode to dia-para magnetic anisotropy

Low-energy orbital magnetic dipole excitations, known as scissors mode (SM), are studied in alkali metal clusters. Subsequent dynamic and static effects are explored. The treatment is based on a self-consistent microscopic approach using the jellium approximation for the ionic background and the Kohn-Sham mean field for the electrons. The microscopic origin of SM and its main features (structure of the mode in light and medium clusters, separation into low- and high-energy plasmons, coupling high-energy M1 scissors and E2 quadrupole plasmons, contributions of shape isomers, etc) are discussed. The scissors M1 strength acquires large values with increasing cluster size. The mode is responsible for the van Vleck paramagnetism of spin-saturated clusters. Quantum shell effects induce a fragile interplay between Langevin diamagnetism and van Vleck paramagnetism and lead to a remarkable dia-para anisotropy in magnetic susceptibility of particular light clusters. Finally, several routes for observing the SM experimentally are discussed.Comment: 21 pages, 7 figure

Efeito da rocha ultramáfica alcalina sobre a composição química e produtividade da alfafa cultivada em Argissolo Amarelo distrófico.

Com o objetivo de avaliar a eficiência da rocha ultramáfica alcalina na fertilidade do solo, estado nutricional e produção de matéria seca da alfafa, foi conduzido em vasos com Argissolo Amarelo distrófico um experimento em delineamento inteiramente casualizado, em parcelas subdivididas, com três repetições. Os tratamentos foram constituídos por quatro doses (0, 100, 150 e 300 mg/kg de K), oriundas da rocha ultramáfica alcalina (K20 = 3,44%, PN = 50%, CaO = 13,22%, MgO = 16,88%, P2O5 = 1,40%, SiO2 = 35,57% e pH = 8,8) com duas granulometrias (0,3 e 2,0 mm) e um tratamento adicional com KCl (150 mg/kg - 60% de Ká-dois-O), as subparcelas foram constituídas por cinco épocas de corte com intervalo de 30 dias. Os resultados demonstraram incremento na produção de matéria seca com aplicação ultramáfica, entretanto, inferior ao obtido com KCl. Houve aumento nos teores de P disponível e K, Ca e Mg trocável no solo, porém esse efeito refletiu positivamente somente nos teores foliares de P e K, provavelmente, devido ao efeito de inibição

Orbital Magnetic Dipole Mode in Deformed Clusters: A Fully Microscopic Analysis

The orbital M1 collective mode predicted for deformed clusters in a schematic model is studied in a self-consistent random-phase-approximation approach which fully exploits the shell structure of the clusters. The microscopic mechanism of the excitation is clarified and the close correlation with E2 mode established. The study shows that the M1 strength of the mode is fragmented over a large energy interval. In spite of that, the fraction remaining at low energy, well below the overwhelming dipole plasmon resonance, is comparable to the strength predicted in the schematic model. The importance of this result in view of future experiments is stressed.Comment: 10 pages, 3 Postscript figures, uses revte

Averaging out magnetic forces with fast rf-sweeps in an optical trap for metastable chromium atoms

We introduce a novel type of time-averaged trap, in which the internal state of the atoms is rapidly modulated to modify magnetic trapping potentials. In our experiment, fast radiofrequency (rf) linear sweeps flip the spin of atoms at a fast rate, which averages out magnetic forces. We use this procedure to optimize the accumulation of metastable chomium atoms into an optical dipole trap from a magneto-optical trap. The potential experienced by the metastable atoms is identical to the bare optical dipole potential, so that this procedure allows for trapping all magnetic sublevels, hence increasing by up to 80 percent the final number of accumulated atoms.Comment: 4 pages, 4 figure

Diversidade genética em populações naturais de infalível.

Suplemento. Edição dos Trabalhos do 49 Congresso Brasileiro de Olericultura, Águas de Lindóia, ago. 2009

Otimização de protocolo para o enraizamento in vitro de jalapa (Mandevilla illustris) (Vell.) R. E. Woodson.

Suplemento. Edição dos Trabalhos do 49 Congresso Brasileiro de Olericultura, Águas de Lindóia, ago. 2009