On geometry-dependent vortex stability and topological spin excitations on curved surfaces with cylindrical symmetry

We study the Heisenberg Model on cylindrically symmetric curved surfaces. Two kinds of excitations are considered. The first is given by the isotropic regime, yielding the sine-Gordon equation and $\pi$-solitons are predicted. The second one is given by the XY model, leading to a vortex turning around the surface. Helical states are also considered, however, topological arguments can not be used to ensure its stability. The energy and the anisotropy parameter which stabilizes the vortex state are explicitly calculated for two surfaces: catenoid and hyperboloid. The results show that the anisotropy and the vortex energy depends on the underlying geometry.Comment: 10 pages, 2 figures, Accepted for publication in Phys. Lett A (2013

Comunidade de Euglossina (Hymenoptera: Apidae) em área de transição entre Cerrado e Mata Atlântica no sudeste do Brasil

The community of orchid bees (Hymenoptera: Apidae: Euglossina) was studied at an area in the transition between the Cerrado and Atlantic Forest biomes, from March, 2010 to February, 2011 in the Barroso region, state of Minas Gerais, eastern Brazil. Orchid-bee males were collected with bait traps containing three different scents (cineole, eugenol and vanillin) and with entomological nets for collecting bees on flowers. A total of 614 orchid-bee males were collected using aromatic traps, belonging to four genera and 15 species. Twenty-five female specimens belonging to two genera and at least three species were collected on flowers. Eulaema (Apeulaema) nigrita Lepeletier, 1841 was the most abundant species (50% of collected specimens), followed by Euglossa (Euglossa) truncata Rebêlo & Moure, 1996 (28%). Cineole was the most attractive compound (66.5% of males and 13 species), followed by eugenol (16% and 9 species) and vanillin (13.5% and 4 species). Eulaema (Apeulaema) marcii Nemésio, 2009 and Eufriesea auriceps (Friese, 1899) were attracted to all scents, whereas Euglossa species were collected only in cineole and eugenol.A comunidade de abelhas-das-orquídeas (Hymenoptera: Apidae: Euglossina) foi estudada em uma área de transição entre o Cerrado e a Mata Atlântica, de março de 2010 a fevereiro de 2011, na região de Barroso, estado de Minas Gerais, sudeste do Brasil. Foram utilizadas armadilhas aromáticas utilizando-se três tipos de iscas (cineol, eugenol e vanilina) e redes entomológicas para a captura de abelhas em flores. Foram coletados 614 machos de Euglossina nas armadilhas aromáticas, pertencentes a quatro gêneros e quinze espécies, e vinte e cinco espécimes em flores, pertencentes a dois gêneros e três espécies. Eulaema (Apeulaema) nigrita Lepeletier, 1841 foi a espécie mais comum (50% dos espécimes coletados), seguida por Euglossa (Euglossa) truncata Rebêlo & Moure, 1996 (28%). O cineol foi a isca mais atrativa (66,5% dos machos e 13 espécies), seguido pelo eugenol (16% e 9 espécies) e vanilina (13,5% e 4 espécies). Eulaema (Apeulaema) marcii Nemésio, 2009 e Eufriesea auriceps (Friese, 1899) foram atraídas por todas as essências, enquanto as espécies de Euglossa foram coletadas somente em armadilhas contendo cineol ou eugenol