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Carvalho D.C.,Instituto Federal Do Norte Of Minas Gerais | Carvalho D.C.,Federal University of Minas Gerais | Pires A.S.T.,Federal University of Minas Gerais | Mol L.A.S.,Federal University of Minas Gerais
Journal of Magnetism and Magnetic Materials | Year: 2016

We examine the phase diagram of the spin-1 J1-J2-J3 ferromagnetic Heisenberg model with an easy-plane crystal field on the cubic lattice, in which J 1 is the ferromagnetic exchange interaction between nearest neighbors, J 2 is the antiferromagnetic exchange interaction between next-nearest neighbors and J 3 is the antiferromagnetic exchange interaction between next-next-nearest neighbors. Using the bond-operator formalism, we investigate the phase transitions between the disordered paramagnetic phase and the ordered ones. We show that the nature of the quantum phase transitions changes as the frustration parameters (J2J1, J3J1) are varied. The zero-temperature phase diagram exhibits second- and first-order transitions, depending on the energy gap behavior. Remarkably, we find a disordered nonmagnetic phase, even in the absence of a crystal field, which is suggested to be a quantum spin liquid candidate. We also depict the phase diagram at finite temperature for some values of crystal field and frustration parameters. © 2016 Elsevier B.V. Source

dos Reis R.V.,Federal University of Vicosa | Viana A.P.,State University of Norte Fluminense | de Oliveira E.J.,Embrapa Mandioca e Fruticultura | Silva M.G.M.,Instituto Federal Do Norte Of Minas Gerais
Crop Breeding and Applied Biotechnology | Year: 2012

The purpose of this study was to evaluate the efficiency of selection of a population of yellow passion fruit in the second cycle of recurrent selection, based on molecular and agronomic data. In 39 full-sib progenies, genotyped using microsatellite markers, 11 agronomic traits were evaluated. The progenies were selected based on the genetic distance matrix and the selection efficiency was confirmed based on the most important agronomic traits of yellow passion fruit. Only 12 of the 25 best progenies were identified by all three selection strategies (agronomic, molecular and combined selection). No significant correlation was observed between the genetic distance matrices and the molecular x agronomic data. The progenies selected by molecular markers had the highest mean yield and fruit number. Results indicate the possibility of applying this combined selection procedure based on agronomic as well as molecular data to optimize genetic gain for the traits under selection. Source

Pereira T.T.C.,Minas Gerais State University | Schaefer C.E.G.R.,Federal University of Vicosa | Ker J.C.,Federal University of Vicosa | Almeida C.C.,Federal University of Vicosa | And 2 more authors.
Geoderma | Year: 2013

Large amounts of organic matter of marine origin are seasonally deposited on ice-free soils by birds and mammals, especially penguins, in some restricted Antarctic terrestrial ecosystems. The incorporation of this material into the mineral soil matrix becomes the main pathway for the widespread formation of phosphate minerals and ornithogenic soils, enhancing local biodiversity and complexity. These soils have been well-studied in Maritime Antarctica, and comparatively neglected in the cold, dry polar Antarctica. Hence, we studied the influence of penguins on soil and landscape formation at Hope Bay, a transition climatic zone in Antarctic Peninsula, where no previous pedological study has been undertaken with regards to soil phosphatization. Ten pedons, nine of which are ornithogenic, were described, sampled, and analyzed for physical, chemical and mineralogical properties. Results indicate that the slow mineralization of bird guano, coupled with high levels of organic matter and reduced leaching, notably Ca, contribute to reduced soil acidification and low exchangeable Al3+ content, unlike ornithogenic soils from Maritime Antarctica. Phosphate minerals typical of the phosphatization process, such as taranakite, minyulite, leucophosphite, struvite, and fluorapatite, were detected. In Hope Bay, they are subjected to very slow rates of dissolution, neoformation of secondary phosphatic minerals, and mineralogical transformation and leaching processes. Ornithogenesis is viewed as a mechanism of sea-land nutrient transfer, enriching the latter, since the parent rocks are chemically poor sedimentary materials. On the other hand, the presence of kaolinite indicates wetter climate conditions in the past, with periods with greater moisture and weathering, compared with the current semi-polar desert environment. We conclude that the phosphatization process overprints previously weathered sedimentary materials. © 2013 Elsevier B.V. Source

Costa R.I.F.,Instituto Federal Do Norte Of Minas Gerais | Souza B.,Federal University of Lavras | De Freitas S.,Sao Paulo State University
Neotropical Entomology | Year: 2010

In order to study the interactions of green lacewings toxocenosis on natural ecossystems, samplings were carried out in the Parque Ecológico Quedas do Rio Bonito, located in Lavras, Alto Rio Grande region, South of Minas Gerais, Brazil. The species inventory was accomplished in two vegetation types: semi-evergreen forest and open field formations, including areas of montane grassland, rocky montane grassland and "cerrado". Insects were captured with a butterfly net during 2h, walking through each vegetation formation. Sampling resulted in 1,948 specimens belonging to 30 species, of which 14 were Chrysopini and 16 Leucochrysini. Representatives of these tribes were observed both in forest and in open field formations. Species of the genera Ceraeochrysa, Chrysoperla, Chrysopodes, Plesiochrysa and Leucochrysa were found in forests and in open field formations, except for Plesiochrysa. The highest richness and diversity of species were observed in the forest. The similarity index among the communities of green lacewings in the studied areas was 27%. Source

Silva M.G.M.,Instituto Federal Do Norte Of Minas Gerais | Viana A.P.,State University of Norte Fluminense | Amaral Junior A.T.,State University of Norte Fluminense | Goncalves L.S.A.,State University of Norte Fluminense | dos Reis R.V.,Federal University of Vicosa
Revista Ciencia Agronomica | Year: 2012

The objective of the study was to estimate genetic parameters associated with eleven agronomic traits of a population of yellow passion fruit under recurrent selection, using 140 full-sibling progenies from the second cycle, planted in October 2007 in a simple square lattice design and in plots consisting of three plants. The mean squares of their features revealed F-test significance for the effect of progeny, indicating that there is genetic variability to be explored in the next cycles. Estimates of heritability coefficients ranged from 19.54 to 71.38%. The averages of the main characteristics of agronomic importance in the studied population were higher than those of the controls, confirming the potential of the population to generate a superior population with the accumulation of favorable alleles in successive processes of selection. Estimates of genetic and phenotypic parameters of the main characteristics of economic importance reveal the possibility of success in the selection of superior progenies of yellow passion fruit, with the aim of registration and protection of a new cultivar. Source

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