Semiclassical back reaction around a cosmic dislocation

The energy-momentum vacuum average of a conformally coupled massless scalar field vibrating around a cosmic dislocation (a cosmic string with a dislocation along its axis) is taken as source of the linearized semiclassical Einstein equations. The solution up to first order in the Planck constant is derived. Motion of a test particle is then discussed, showing that under certain circumstances a helical-like dragging effect, with no classical analogue around the cosmic dislocation, is induced by back reaction.Comment: Published version, 4 pages, no figures, REVTeX4 fil

Agronomical performance of common bean inoculated with new rhizobial isolates.

This work aimed to evaluate the agronomic efficiency of rhizobia isolates under field conditions in two sites: Guapó and Santo Antônio de Goiás, by comparison of their results with the commercial strains SEMIA 4077, 4080 and SEMIA SEMIA 4088 of Rhizobium tropici

Ferromagnetic tendency at the surface of CE charge-ordered manganites

Most previous investigations have shown that the surface of a ferromagnetic material may have antiferromagnetic tendencies. However, experimentally the opposite effect has been recently observed: ferromagnetism appears in some nano-sized manganites with a composition such that the antiferromagnetic charge-ordered CE state is observed in the bulk. A possible origin is the development of ferromagnetic correlations at the surface of these small systems. To clarify these puzzling experimental observations, we have studied the two-orbital double-exchange model near half-doping n=0.5, using open boundary conditions to simulate the surface of either bulk or nano-sized manganites. Considering the enhancement of surface charge density due to a possible AO termination (A = trivalent/divalent ion composite, O = oxygen), an unexpected surface phase-separated state emerges when the model is studied using Monte Carlo techniques on small clusters. This tendency suppresses the CE charge ordering and produces a weak ferromagnetic signal that could explain the experimental observations.Comment: 8 pages, 5 figure

Eficiência de fontes e doses de fósforo na alfafa e centrosema cultivadas em latossolo amarelo.

O objetivo deste trabalho foi avaliar a eficiência agronômica de fontes e doses de P na alfafa e na centrosema, cultivadas em casa de vegetação, em Latossolo Amarelo distrófico