q-Deformed Kink Solutions

The q-deformed kink of the $\lambda\phi^4-$model is obtained via the normalisable ground state eigenfunction of a fluctuation operator associated with the q-deformed hyperbolic functions. From such a bosonic zero-mode the q-deformed potential in 1+1 dimensions is found, and we show that the q-deformed kink solution is a kink displaced away from the origin.Comment: REvtex, 11 pages, 2 figures. Preprint CBPF-NF-005/03, site at http://www.cbpf.br. Revised version to appear in International Journal of Modern Physics

Disorder effects at low temperatures in La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3} manganites

With the aim of probing the effect of magnetic disorder in the low-temperature excitations of manganites, specific-heat measurements were performed in zero field, and in magnetic fields up to 9 T in polycrystalline samples of La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3}, with Y concentrations x=0, 0.10, and 0.15. Yttrium doping yielded the appearance of a cluster-glass state, giving rise to unusual low-temperature behavior of the specific-heat. The main feature observed in the results is a strong enhancement of the specific-heat linear term, which is interpreted as a direct consequence of magnetic disorder. The analysis was further corroborated by resistivity measurements in the same compounds.Comment: 9 pages, 2 figure

On Matrix Superpotential and Three-Component Normal Modes

We consider the supersymmetric quantum mechanics (SUSY QM) with three- component normal modes for the Bogomol'nyi-Prasad-Sommerfield (BPS) states. An explicit form of the SUSY QM matrix superpotential is presented and the corresponding three-component bosonic zero-mode eigenfunction is investigated.Comment: 17 pages, no figure. Paper accepted for publication in Journal of Physics A: Mathematical and Theoretica

Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects

We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7 single crystal with columnar defects (CD), using a technique based on sample rotation under a fixed magnetic field H. This method is valid for samples whose magnetization vector remains perpendicular to the sample surface over a wide angle range - which is the case for platelets and thin films - and presents several advantages over measurements of M_L(H) loops at fixed angles. The resulting M_i(\Theta) curves for several temperatures show a peak in the CD direction at high fields. At lower fields, a very well defined plateau indicative of the vortex lock-in to the CD develops. The H dependence of the lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the temperature dependence is in agreement with entropic smearing effects corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.

Magnetic phases evolution in the LaMn1-xFexO3+y system

We have investigated the crystal structure and magnetic properties for polycrystalline samples of LaMn1-xFexO3+y, in the whole range x=0.0 to x=1.0, prepared by solid state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion, thus favoring a ferromagnetic (FM) superexchange (SE) interaction between Mn^{3+}-O-Mn^{3+}. For x=0.0 the oxygen excess (y ~ 0.09) produces vacancies in the La and Mn sites and generates a fraction around 18% of Mn^{4+} ions and 82% of the usual Mn^{3+} ions, with possible double exchange interaction between them. The Fe doping in this system is known to produce only stable Fe^{3+} ions. We find an evolution from a fairly strong FM phase with a Curie temperature T_{C} ~ 160 K, for x=0.0, to an antiferromagnetic (AFM) phase with T_{N} = 790 K, for x=1.0, accompanied by clear signatures of a cluster-glass behavior. For intermediate Fe contents a mixed-phase state occurs, with a gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2 < x < 0.7. A model based on the expected exchange interaction among the various magnetic-ion types, accounts very well for the saturation-magnetization dependence on Fe doping.Comment: 27 pages, 9 figure

Uso de efluentes da carcinicultura de águas interiores na irrigação de arroz e melão.

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Parâmetros genéticos para produções parciais acumuladas e total de leite, em cabras meio sangue Pardo Alpina x Moxotó.

O objetivo deste trabalho foi estudar 696 lactações de 246 cabras meio sangue Pardo Alpina x Moxotó, filhas de 20 reprodutores, oriundas da Embrapa Caprinos, paridas no período de 1989 a 1994. No modelo, incluiu-se os efeitos fixos estação-ano de parição, ordem de lactação e tipo de parto e os efeitos aleatários reprodutor, cabra dentro de reprodutor e erro. As cabras foram mantidas em pastagem nativa e suplementadas no período seco. As estimativas de herdabilidades foram 0,20+/-0,13; 0,34+/-0,17; 0,35+/-0,18 e 0,34+/-0,17 e 0,33+/-0,16 para as produções mensais aos 30, 60, 90 e 120 dias de lactação e para a produção total, respectivamente. As estimativas de herdabilidade sugerem que a seleção de reprodutores poderá ser feita por meio da produção de leite de suas filhas. Foram verificadas altas e positivas correlações genéticas e fenotípicas entre as produções parciais acumulada de leite, indicando que a seleção poderá ser realizada com base nasproduções parcias de leite. GENETIC PARAMETERS FOR PARTIAL AND TOTAL MILK PRODUCTION IN ALPINE X MOXOTO GOATS. ABSTRACT: The objective of this work was to study 696 lactations of 246 Alpine x Moxotó goats, daughters of 20 sires, originating from Embrapa Caprinos, in the period from 1989 to 1994. In the model, it was included the fixed effects of station-year of calving, parturition order and lambing type and the random effects of sire, dam within sire and error. The goats were maintained in native pasture and supplemented in the dry period. The heritabilities were 0.20+/-0.13; 0.34+/-0.17; 0.35+/-0.18 and 0.34+/-0.17 and 0.33+/-0.16 for the monthly productions at 30, 60, 90 and 120 days of lactation and for the total milk yield, respectively. These heritabilities suggest that the selection of sires could be made through the milk yield of their daughters. High and positive genetic and phenotypic correlations were verified among the partial milk yield, indicating that the selection can be accomplished with base in the partial milk yield