Goppa and Srivastava codes over finite rings

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Alternant and BCH codes over certain rings

Alternant codes over arbitrary finite commutative local rings with identity are constructed in terms of parity-check matrices. The derivation is based on the factorization of x s - 1 over the unit group of an appropriate extension of the finite ring. An efficient decoding procedure which makes use of the modified Berlekamp-Massey algorithm to correct errors and erasures is presented. Furthermore, we address the construction of BCH codes over Zm under Lee metric.

CYCLIC CODES THROUGH B[X], B[X; 1/kp Z(0)] and B[X; 1/p(k) Z(0)]: A COMPARISON

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Constructions of codes through the semigroup ring B[X; 1/2(2)Z(0)] and encoding

For any finite commutative ring B with an identity there is a strict inclusion B[X; Z(0)] subset of B[X; Z(0)] subset of B[X; 1/2(2)Z(0)] of commutative semigroup rings. This work is a continuation of Shah et al. (2011) [8], in which we extend the study of Andrade and Palazzo (2005) [7] for cyclic codes through the semigroup ring B[X; 1/2; Z(0)] In this study we developed a construction technique of cyclic codes through a semigroup ring B[X; 1/2(2)Z(0)] instead of a polynomial ring. However in the second phase we independently considered BCH, alternant, Goppa, Srivastava codes through a semigroup ring B[X; 1/2(2)Z(0)]. Hence we improved several results of Shah et al. (2011) [8] and Andrade and Palazzo (2005) [7] in a broader sense. Published by Elsevier Ltd

Planejamento experimental na otimização da extração dos frutos de Syzygium cumini (L.) skeels

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Geometrically uniform hyperbolic codes

In this paper we generalize the concept of geometrically uniform codes, formerly employed in Euclidean spaces, to hyperbolic spaces. We also show a characterization of generalized coset codes through the concept of G-linear codes.

Manejo químico das plantas daninhas Euphorbia heterophylla e Bidens pilosa em sistema de plantio direto da cultura de soja

Objetivou-se neste trabalho avaliar a eficácia agronômica e os efeitos fitotóxicos de herbicidas aplicados em pré-plantio no manejo de Euphorbia heterophylla e Bidens pilosa, em sistema de plantio direto da cultura de soja. O experimento foi desenvolvido na safra 2000/2001, na FEP-UNESP, no município de Selvíria-MS. A variedade de soja utilizada foi a 'Conquista', e o delineamento experimental adotado foi o de blocos ao acaso, com sete tratamentos e quatro repetições, com oito linhas da cultura, totalizando 20 m² cada parcela. Os tratamentos foram os seguintes: glyphosate (720 e 960 g ha-1), chlorimuron-ethyl + glyphosate (10 g + 720 e 960 g ha-1), glyphosate + 2,4-D (960 + 868 g ha-1) e testemunhas no mato e no limpo. As aplicações foram realizadas com pulverizador de pressão constante (CO2) de 45 lb pol-2, com barra equipada com quatro bicos do tipo leque Teejet 110.03 XR, espaçados de 0,5 m, e volume de calda de 250 L ha-1. Concluiu-se que os tratamentos testados são eficientes na dessecação de E. heterophylla e B. pilosa e seletivos às plantas de soja. O herbicida chlorimuron-ethyl (10 g ha-1) aplicado juntamente com o glyphosate, no manejo, proporciona ao tratamento um efeito residual significativo para E. heterophylla e B. pilosa, reduzindo a infestação das plantas daninhas durante o ciclo da cultura da soja.

The symmetry group of Z(q)(n) in the Lee space and the Z(qn)-linear codes

The Z(4)-linearity is a construction technique of good binary codes. Motivated by this property, we address the problem of extending the Z(4)-linearity to Z(q)n-linearity. In this direction, we consider the n-dimensional Lee space of order q, that is, (Z(q)(n), d(L)), as one of the most interesting spaces for coding applications. We establish the symmetry group of Z(q)(n) for any n and q by determining its isometries. We also show that there is no cyclic subgroup of order q(n) in Gamma(Z(q)(n)) acting transitively in Z(q)(n). Therefore, there exists no Z(q)n-linear code with respect to the cyclic subgroup.

Hamming and Reed-Solomon codes over certain rings

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relating propelinear and binary G-linear codes

In this paper we establish the connections between two different extensions of Z(4)-linearity for binary Hamming spaces, We present both notions - propelinearity and G-linearity - in the context of isometries and group actions, taking the viewpoint of geometrically uniform codes extended to discrete spaces. We show a double inclusion relation: binary G-linear codes are propelinear codes, and translation-invariant propelinear codes are G-linear codes. (C) 2002 Elsevier B.V. B.V. All rights reserved.

First report of vancomycin-resistant staphylococci isolated from healthy carriers in Brazil

Reduced susceptibility or resistance to vancomycin has been reported among clinical isolates of staphylococci in previous studies. In the present study we report on the isolation of four vancomycin-resistant staphylococcal strains from healthy carriers inside and outside the hospital environment. These carriers did not receive treatment with any antibiotic. All coagulase-negative staphylococcal strains showed variable levels of resistance to several antimicrobial agents, including oxacillin, and unstable resistance to vancomycin, with decreased vancomycin MICs (<4 mg/liter) after 10 days of passage in a nonselective medium. However, exposure of these revertants to vancomycin selected staphylococcal strains resistant to vancomycin at very high frequencies (10(-2) and 10(-3)). The vancomycin resistance in these staphylococcal strains was not mediated by the van gene. The cell wall of the staphylococcal strains studied became thickest after culture in medium containing vancomycin, and the differences in cell wall thickness were statistically significant (P < 0.001). Thus, the thickening of the cell wall in these staphylococcal strains may be an important contributor to vancomycin resistance.

The in vitro antiviral activity of an aliphatic nitro compound from Heteropteris aphrodisiaca

We investigated the antiviral activity of an aliphatic nitro compound (NC) isolated from Heteropteris aphrodisiaca O. Mach. (Malpighiaceae), a Brazilian medicinal ptant. The NC was tested for its antiviral activity against poliovirus type 1 (PV-1) and bovine herpes virus type 1 (BHV-1) by plaque reduction assay in cell culture. The NC showed a moderate antiviral activity against PV-1 and BHV-1 in HEp-2 celts, and the 50% inhibitory concentration (IC50) were 22.01 mu g/ml (selectivity index (SI) = 2.83) and 21.10 mu g/mi (SI = 2.95), respectivety. At the highest concentration of the drug (40 mu g/ml) a reduction of approximately 80% in plaque assay was observed for both viruses. The treatment of cells or virus prior to infection did not inhibit the replication of virus strains. (C) 2006 Elsevier GmbH. All rights reserved.

Construction and decoding of BCH codes over finite commutative rings

BCH codes over arbitrary finite commutative rings with identity are derived in terms of their locator vector. The derivation is based on the factorization of xs -1 over the unit ring of an appropriate extension of the finite ring. We present an efficient decoding procedure, based on the modified Berlekamp-Massey algorithm, for these codes. The code construction and the decoding procedures are very similar to the BCH codes over finite integer rings. © 1999 Elsevier B.V. All rights reserved.

Lattice constellations and codes from quadratic number fields

We propose new classes of linear codes over integer rings of quadratic extensions of Q, the field of rational numbers. The codes are considered with respect to a Mannheim metric, which is a Manhattan metric modulo a two-dimensional (2-D) grid. In particular, codes over Gaussian integers and Eisenstein-Jacobi integers are extensively studied. Decoding algorithms are proposed for these codes when up to two coordinates of a transmitted code vector are affected by errors of arbitrary Mannheim weight. Moreover, we show that the proposed codes are maximum-distance separable (MDS), with respect to the Hamming distance. The practical interest in such Mannheim-metric codes is their use in coded modulation schemes based on quadrature amplitude modulation (QAM)-type constellations, for which neither the Hamming nor the Lee metric is appropriate.