17,438 research outputs found
q-Deformed Kink Solutions
The q-deformed kink of the 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.
Resumo
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