Mapping the train model for earthquakes onto the stochastic sandpile model

We perform a computational study of a variant of the ``train'' model for earthquakes [PRA 46, 6288 (1992)], where we assume a static friction that is a stochastic function of position rather than being velocity dependent. The model consists of an array of blocks coupled by springs, with the forces between neighbouring blocks balanced by static friction. We calculate the probability, P(s), of the occurrence of avalanches with a size s or greater, finding that our results are consistent with the phenomenology and also with previous models which exhibit a power law over a wide range. We show that the train model may be mapped onto a stochastic sandpile model and study a variant of the latter for non-spherical grains. We show that, in this case, the model has critical behaviour only for grains with large aspect ratio, as was already shown in experiments with real ricepiles. We also demonstrate a way to introduce randomness in a physically motivated manner into the model.Comment: 14 pages and 6 figures. Accepted in European Physical Journal

Cosmic String Network Evolution in arbitrary Friedmann-Lemaitre models

We use the velocity-dependent one-scale model by Martins & Shellard to investigate the evolution of a GUT long cosmic string network in arbitrary Friedmann-Lemaitre models. Four representative models are used to show that in general there is no scaling solution. The implications for structure formation are briefly discussed.Comment: 8 pages, 4 postscript figures included, submitted to Phys. Rev.

Exact solution of the simplest super-orthosymplectic invariant magnet

We present the exact solution of the $Osp(1|2)$ invariant magnet by the Bethe ansatz approach. The associated Bethe ansatz equation exhibit a new feature by presenting an explicit and distinct phase behaviour in even and odd sectors of the theory. The ground state, the low-lying excitations and the critical properties are discussed by exploiting the Bethe ansatz solution.Comment: 8 pages, UFSCARF-TH-1

Quantum spin chain with "soliton non-preserving" boundary conditions

We consider the case of an integrable quantum spin chain with "soliton non-peserving" boundary conditions. This is the first time that such boundary conditions have been considered in the spin chain framework. We construct the transfer matrix of the model, we study its symmetry and we find explicit expressions for its eigenvalues. Moreover, we derive a new set of Bethe ansatz equations by means of the analytical Bethe ansatz method.Comment: 12 pages, LaTeX, two appendices added, minor correction

Excitations and S-matrix for su(3) spin chain combining 3{3} and ${3^{*}}

The associated Hamiltonian for a su(3) spin chain combining ${3}$ and ${3^{*}}$ representations is calculated. The ansatz equations for this chain are obtained and solved in the thermodynamic limit, and the ground state and excitations are described. Thus, relations between the number of roots and the number of holes in each level have been found . The excited states are characterized by means of these quantum numbers. Finally, the exact S matrix for a state with two holes is found.Comment: 17 pages, plaintex, harvmac (to be published in J. of Phys. A

Integrable su(3) spin chain combining different representations

The general expression for the local matrix $t(\theta)$ of a quantum chain with the site space in any representation of su(3) is obtained. This is made by generalizing $t(\theta)$ from the fundamental representation and imposing the fulfillment of the Yang-Baxter equation. Then, a non-homogeneous spin chain combining different representations of su(3) is solved by developing a method inspired in the nested Bethe ansatz. The solution for the eigenvalues of the trace of the monodromy matrix is given as two coupled Bethe equations. A conjecture about the solution of a chain with the site states in different representations of su(n) is presented. The thermodynamic limit of the ground state is calculated.Comment: PlainTex harvmac, 30 pages, 7 figures, to appear in Journal of Physics

A note on graded Yang-Baxter solutions as braid-monoid invariants

We construct two $Osp(n|2m)$ solutions of the graded Yang-Baxter equation by using the algebraic braid-monoid approach. The factorizable S-matrix interpretation of these solutions is also discussed.Comment: 7 pages, UFSCARF-TH-94-1

Situação do controle biológico de insetos-praga da cultura do arroz na região Sul do Brasil.

bitstream/item/51927/1/documento-309.pd

Organomineral phosphorus fertilization in the production of corn, soybean and bean cultivated in succession.

The use of organic waste in agriculture has been used aiming at greater productivity, decrease in the cost of production and sustainable use of resources. The present study aimed at evaluating the effect of phosphate fertilization with the maintenance of organomineral fertilizers, combining poultry manure and soluble or reactive phosphate, in the production of grains in corn culture and the residual effect for subsequent crops of beans and soybeans. The experiment was conducted in Sete Lagoas, MG, in 2015, using three fertilizers with sources of different phosphorus sources (triple super phosphate?STP, organomineral with STP and organomineral with Bayovar phosphate) applied at the doses of 65, 130, 195 and 260 kg∙ha−1 of P2O5 total, and compared to the control without phosphate fertilization. We evaluated the contents of foliar P, P accumulation in the grains, yields of corn grains, beans and soy, accumulated productivity and export of accumulated P of the three cultures. The three cultures assessed presented higher productivity when compared to the average of the factorial treatments that received phosphate fertilization relative to the control. Organomineral fertilizers increased grain production, obtaining average productivity equal to or greater than those obtained with the exclusive use of STP

Avaliação genética de procedências e progênies de erva-mate nativa (Ilex paraguariensis St. Hil.) no Estado de Mato Grosso do Sul.

O presente estudo objetivou avaliar a variabilidade genética de procedências e progênies de erva-mate nativa (Ilex paraguariensis St. Hil.) em fase inicial de crescimento no município de Aral Moreira ? MS. O teste de procedência e progênie, foi instalado no viveiro de mudas da Fazenda Rancho Esperança localizada no município de Aral Moreira, sob o delineamento de blocos ao acaso com 3 procedências (populações), 25 tratamentos (progênies) de cada uma das procedências, 5 repetições (blocos) e 4 plantas por parcela. Aos 5 meses de idade, as progênies foram avaliadas quanto aos caracteres: a) altura total das plantas, expressas em centímetros; b) diâmetro do coleto, expresso em milímetros; e c) número de lançamentos foliares. Os resultados demonstraram haver variabilidade genética, e as herdabilidades individuais e de médias de progênies obtidas, estimulam o monitoramento continuado das procedências e progênies no campo, com perspectivas de maximizar o ganho genético na seqüência das avaliações