On the self-similarity in quantum Hall systems

The Hall-resistance curve of a two-dimensional electron system in the presence of a strong perpendicular magnetic field is an example of self-similarity. It reveals plateaus at low temperatures and has a fractal structure. We show that this fractal structure emerges naturally in the Hamiltonian formulation of composite fermions. After a set of transformations on the electronic model, we show that the model, which describes interacting composite fermions in a partially filled energy level, is self-similar. This mathematical property allows for the construction of a basis of higher generations of composite fermions. The collective-excitation dispersion of the recently observed 4/11 fractional-quantum-Hall state is discussed within the present formalism.Comment: 7 pages, 4 figures; version accepted for publication in Europhys. Lett., new version contains energy calculations for collective excitations of the 4/11 stat

Finite-momentum Bose-Einstein condensates in shaken 2D square optical lattices

We consider ultracold bosons in a 2D square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. It is therefore necessary to account for higher-order hopping terms, which are renormalized differently by the shaking, and introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentum condensates, with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott-insulator and the different superfluid phases, and present the time-of-flight images expected to be observed experimentally. Our results open up new possibilities for the realization of bosonic analogs of the FFLO phase describing inhomogeneous superconductivity.Comment: 7 pages, 7 figure

Variabilidade genética com seleção recorrente em arroz de terras altas.

O objetivo deste trabalho foi obter estimativas de parâmetros genéticos e fenotípicos entre progênies S0:2 da população CNA6 de arroz de terras altas durante quatro ciclos de seleção recorrente, visando analisar a variabilidade genética para o caráter produção de grãos (PG, em kg ha-1)

Model for erosion-deposition patterns

We investigate through computational simulations with a pore network model the formation of patterns caused by erosion-deposition mechanisms. In this model, the geometry of the pore space changes dynamically as a consequence of the coupling between the fluid flow and the movement of particles due to local drag forces. Our results for this irreversible process show that the model is capable to reproduce typical natural patterns caused by well known erosion processes. Moreover, we observe that, within a certain range of porosity values, the grains form clusters that are tilted with respect to the horizontal with a characteristic angle. We compare our results to recent experiments for granular material in flowing water and show that they present a satisfactory agreement.Comment: 8 pages, 12 figures, submitted to Phys. Rev.

Estimativas de parâmetros genéticos e de resposta à seleção na população CG136 de arroz de terras altas.

O objetivo deste estudo foi estimar parâmetros genéticos e a resposta à seleção na população de arroz de terras altas CG136, conduzida pelo método de seleção recorrente

Relevance of additive and non-additive genetic relatedness for genomic prediction in rice population under recurrent selection breeding

In genomic recurrent selection programs of self-pollinated crops, additive genetic effects (breeding values) are effectively relevant for selection of superior progenies as new parents. However, considering additive and nonadditive genetic effects can improve the prediction of genome-enhanced breeding values (GEBV) of progenies, for quantitative traits. In this study, we assessed the magnitude of additive and nonadditive genetic variances for eight key traits in a rice population under recurrent selection, using marker-based relationship matrices. We then assessed the goodness-to-fit, bias, stability and accuracy of prediction for breeding values and total (additive plus nonadditive) genetic values, in five genomic best linear unbiased prediction (GBLUP) models, ignoring or not nonadditive genetic effects. The models were compared using 6174 single nucleotide polymorphisms (SNP) markers from 174 S1:3 progenies evaluated in field yield trial. We found dominance effects accounting for a substantial proportion of the total genetic variance for the key traits in rice, especially for days to flowering. In average of the traits, the component of variance additive, dominance, and epistatic contributed to about 34%, 14% and 9% for phenotypic variance. Additive genomic models, ignoring nonadditive genetic effects, showed better fit to the data and lower bias, in addition to greater stability and accuracy for predict GEBV of progenies. These results improve our understanding of the genetic architecture of the key traits in rice, evaluated in early-generation testing. Clearly, this study highlighted the advantages of additive models using genome-wide information, for genomic prediction applied to recurrent selection in a self-pollinated crop

Genetic progress of the CNA6 populacion after four cycles of recurrent selection.

The objectives of this study were to estimate genetic progress in grain yield (GY) achieved in the CNA6 population of upland rice after four cycles of recurrent selection by the Brazilian Agricultural Research Corporation; and evaluate the genetic potential of this population to generate superior inbred lines after each cycle. This population was synthesized in the 1993/94 crop year by incorporating the alleles from 27 parents into the CNA-IRAT 5/2/1 population

Capacidade de combinação de cultivares de arroz vermelho.

As cultivares de arroz vermelho disponíveis, em geral, possuem arquitetura de planta tradicional e alta suscetibilidade ao acamamento, com baixo potencial de produção. Porém, existem algumas cultivares com arquitetura de planta moderna, baixo índice de acamamento e elevado potencial produtivo, que podem ser importantes para programas de melhoramento visando o desenvolvimento de cultivares superiores de arroz vermelho (Pereira et al., 2006)