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

Anisotropic superconducting properties of aligned MgB2 crystallites

Samples of aligned MgB2 crystallites have been prepared, allowing for the first time the direct identification of an upper critical field anisotropy Hc2^{ab}/Hc2^{c}= xi_{ab}/xi_{c} ~ 1.73; with xi_{o,ab} ~ 70 A, xi_{o,c} ~ 40 A, and a mass anisotropy ratio m_{ab}/m_{c} ~ 0.3. A ferromagnetic background signal was identified, possibly related to the raw materials purity.Comment: 4 pages, 4 figures; Revised version to appear in Phys. Rev. Let

Semeadura direta de soja sobre diferentes plantas de cobertura e manejos de palhada, na região norte fluminense.

Com o objetivo de avaliar as características agronômicas da cultura da soja em rotação a plantas de cobertura com dois manejos dos resíduos, foi realizado um experímento em campo na região norte fluminense. O delineamento utilizado foi o de blocos casualizados, com quatro repetições em esquema de parcelas subdivididas. As parcelas foram constituídas dos manejos (roçado e não-roçado) e as subparcelas constaram das plantas de cobertura (aveia-preta, milheto, sorgo, teosinto, nabo-forrageiro, mucuna-anã, tremoço-branco, guandu-anão e vegetação espontânea com predomínio de capim-colchão). No manejo não roçado a produtividade média de soja nas sucessões com aveia preta e vegetação espontânea foi 50% superior à das sucessões com mucuna-anã, milheto, guandu-anão e sorgo. Já no manejo com roçada, a produtividade média nas sucessões com milheto, teosinto e vegetação espontânea foi 79% superior às sucessões com tremoço-branco e mucuna-anã. Além disso, o manejo mecânico do milheto resultou em acréscimo de 1.154 kg ha' de soja, comparado à ausência da roçada

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

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.

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

Qualidade produtiva e de frutos de maciera cultivar Fuji Kiku-8 em diferentes sistemas de condução.

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