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Araujo D.,State University of Mato Grosso do Sul | Mattos V.F.,State University of Mato Grosso do Sul | Giroti A.M.,Claro | Giroti A.M.,Instituto Butantan | And 3 more authors.
Journal of Arachnology | Year: 2011

The family Araneidae is the third largest among spiders and the third most studied from a cytogenetical point of view. In spite of this, only 2% of all araneids have been karyotyped. The majority of araneids analyzed possess 2n ?=? 24 chromosomes in males; however, the study of additional species could reveal unusual karyotype characteristics. Thus, the aim of this work is to analyze chromosomally, for the first time, six species belonging to three araneid genera from Brazil. The specimens of Alpaida leucogramma (White 1841), Alpaida truncata (Keyserling 1865), Alpaida veniliae (Keyserling 1865), Parawixia kochi (Taczanowski 1873), Parawixia velutina (Taczanowski 1878) and Wagneriana sp. were collected in Parque Nacional de Ilha Grande and in the municipality of Rio Claro. The gonads were treated with colchicine and hypotonic solution before fixation with Carnoy I solution. The results were 2n♂? ?=? 24 (11II+X1X2) in A. leucogramma and P. velutina, and 2n♂? ?=? 22 (10II+X1X2) in A. truncata, A. veniliae, P. kochi and Wagneriana sp. When the chromosomal morphologies were established, we observed telocentric chromosomes in all specimens save one female specimen of P. velutina. The univalent sex chromosomes were easily recognized on diplotenes. The unpaired metacentric element found in one female specimen of P. velutina with 2n ?=? 25 probably arises by centric fusion/fission. Araneidae is a megadiverse family composed of ∼3000 species distributed mainly in the tropics; thus the analysis of more species may provide new insights about orb-weaver chromosome evolution. © 2011 The American Arachnological Society. Source

Lo-Man-Hung N.F.,Museu Paraense Emlio Goeldi | Marichal R.,Museu Paraense Emlio Goeldi | Marichal R.,University Pierre and Marie Curie | Candiani D.F.,Museu Paraense Emlio Goeldi | And 15 more authors.
Journal of Arachnology | Year: 2011

The global demand for different land-use practice commodities in the Amazonia is growing, and this region is increasingly affected by the impacts of land management. The aim of this study was to evaluate the influence of land-use intensification on soil spider assemblages from six different land-use systems in Colombia and Brazil. The systems were fallows after crops and pastures, forest, crops, pastures and plantations. Spider species richness and density decreased with increasing farming management intensity. A principal component analysis (PCA) showed forests and fallows were separated from systems with stronger anthropogenic soil disturbance. The relationships of ten spider guilds differed significantly between land-uses, suggesting that they can be a reliable parameter for studies of ecological indicators. © 2011 The American Arachnological Society. Source

Ribeiro F.G.,University Federal Do Piau | De Lima J.P.,University Federal Do Piau | Gonalves L.L.,Federal University of Ceara
Journal of Magnetism and Magnetic Materials | Year: 2011

The one-dimensional extended isotropic XY model (s=1/2) in a transverse field with uniform long-range interactions among the z components of the spin is considered. The model is exactly solved by introducing the Gaussian and JordanWigner transformations, which map it in a non-interacting fermion system. The partition function can be determined in closed form at arbitrary temperature and for arbitrary multiplicity of the multiple spin interaction. From this result, all relevant thermodynamic functions are obtained and, due to the long-range interactions, the model can present classical and quantum transitions of first and second orders. The study of its critical behavior is restricted to the quantum transitions, which are induced by the transverse field at T=0. The phase diagram is explicitly obtained for multiplicities p=2,3,4 and ∞, as a function of the interaction parameters, and, in these cases, the critical behavior of the model is studied in detail. Explicit results are also presented for the induced magnetization and isothermal susceptibility χTzz, and a detailed analysis is also carried out for the static longitudinal 〈SjzSlz〉 and transversal 〈SjxSlx〉 correlation functions. The different phases presented by the model can be characterized by the spatial decay of these correlations, and from these results some of these can be classified as quantum spin liquid phases. The static critical exponents and the dynamic one, z, have also been determined, and it is shown that, besides inducing first order phase transition, the long-range interaction also changes the universality class of the model. © 2010 Elsevier B.V. All rights reserved. Source

Martins C.,University Federal Do Piau | Fontes L.R.,Rua Loefgreen | Bueno O.C.,Sao Paulo State University | Martins V.G.,Sao Paulo State University
Genome | Year: 2010

The Asian subterranean termite, Coptotermes gestroi, originally from northeast India through Burma, Thailand, Malaysia, and the Indonesian archipelago, is a major termite pest introduced in several countries around the world, including Brazil. We sequenced the mitochondrial COII gene from individuals representing 23 populations. Phylogenetic analysis of COII gene sequences from this and other studies resulted in two main groups: (1) populations of Cleveland (USA) and four populations of Malaysia and (2) populations of Brazil, four populations of Malaysia, and one population from each of Thailand, Puerto Rico, and Key West (USA). Three new localities are reported here, considerably enlarging the distribution of C. gestroi in Brazil: Campo Grande (state of Mato Grosso do Sul), Itaja (state of Santa Catarina), and Porto Alegre (state of Rio Grande do Sul). Source

Santos J.C.,University Federal Do Piau | Lima F.W.S.,University Federal Do Piau | Malarz K.,AGH University of Science and Technology
Physica A: Statistical Mechanics and its Applications | Year: 2011

On Archimedean lattices, the Ising model exhibits spontaneous ordering. Three examples of these lattices of the majority-vote model with noise are considered and studied through extensive Monte Carlo simulations. The order/disorder phase transition is observed in this system. The calculated values of the critical noise parameter are qc=0.089(5), qc=0.078(3), and qc=0.114(2) for honeycomb, Kagom and triangular lattices, respectively. The critical exponents βν, γν and 1ν for this model are 0.15(5), 1.64(5), and 0.87(5); 0.14(3), 1.64(3), and 0.86(6); 0.12(4), 1.59(5), and 1.08(6) for honeycomb, Kagom and triangular lattices, respectively. These results differ from the usual Ising model results and the majority-vote model on so-far studied regular lattices or complex networks. The effective dimensionalities of the system Deff=1.96(5) (honeycomb), Deff=1.92(4) (Kagom), and Deff=1.83(5) (triangular) for these networks are just compatible to the embedding dimension two. © 2010 Elsevier B.V. All rights reserved. Source

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