Vortex motion in a finite-size easy-plane ferromagnet and application to a nanodot

We study the motion of a non-planar vortex in a circular easy-plane ferromagnet, which imitates a magnetic nanodot. Analysis was done using numerical simulations and a new collective variable theory which includes the coupling of Goldstone-like mode with the vortex center. Without magnetic field the vortex follows a spiral orbit which we calculate. When a rotating in-plane magnetic field is included, the vortex tends to a stable limit cycle which exists in a significant range of field amplitude B and frequency $\omega$ for a given system size L. For a fixed $\omega$, the radius R of the orbital motion is proportional to L while the orbital frequency $\Omega$ varies as 1/L and is significantly smaller than $\omega$. Since the limit cycle is caused by the interplay between the magnetization and the vortex motion, the internal mode is essential in the collective variable theory which then gives the correct estimate and dependency for the orbit radius $R\sim B L/\omega$. Using this simple theory we indicate how an ac magnetic field can be used to control vortices observed in real magnetic nanodots.Comment: 15 pages (RevTeX), 14 figures (eps

Low Temperature Static and Dynamic Behavior of the Two-Dimensional Easy-Axis Heisenberg Model

We apply the self-consistent harmonic approximation (SCHA) to study static and dynamic properties of the two-dimensional classical Heisenberg model with easy-axis anisotropy. The static properties obtained are magnetization and spin wave energy as functions of temperature, and the critical temperature as a function of the easy-axis anisotropy. We also calculate the dynamic correlation functions using the SCHA renormalized spin wave energy. Our analytical results, for both static properties and dynamic correlation functions, are compared to numerical simulation data combining cluster-Monte Carlo algorithms and Spin Dynamics. The comparison allows us to conclude that far below the transition temperature, where the SCHA is valid, spin waves are responsible for all relevant features observed in the numerical simulation data; topological excitations do not seem to contribute appreciably. For temperatures closer to the transition temperature, there are differences between the dynamic correlation functions from SCHA theory and Spin Dynamics; these may be due to the presence of domain walls and solitons.Comment: 12 pages, 14 figure

Comparação dos modelos digitais de elevação gerados com dados SRTM e cartas IBGE na escala 1:250.000 na região da Bacia do Camanducaia no Estado de São Paulo.

O estudo comparou os MDEs, os mapas de declividade e os mapas hipsométricos produzidos pela SRTM com aqueles gerados pelas cartas do IBGE. A área estudada integra a bacia do Camanducaia, que limita-se como Estado de São Paulo a leste e Jaguariúna a oeste, abrangendo Holambra, Jaguariúna, Santo Antônio de Posse, Pedreira, Amparo, Serra Negra, Monte Alegre do Sul, Socorro, Pinhalzinho e Pedra Bela

Vortices in the presence of a nonmagnetic atom impurity in 2D XY ferromagnets

Using a model of nonmagnetic impurity potential, we have examined the behavior of planar vortex solutions in the classical two-dimensional XY ferromagnets in the presence of a spin vacancy localized out of the vortex core. Our results show that a spinless atom impurity gives rise to an effective potential that repels the vortex structure.Comment: 6 pages, 2 figures, RevTex

Neutrino Masses and Lepton Flavour Violation in Thick Brane Scenarios

We address the issue of lepton flavour violation and neutrino masses in the ``fat-brane'' paradigm, where flavour changing processes are suppressed by localising different fermion field wave-functions at different positions (in the extra dimensions) in a thick brane. We study the consequences of suppressing lepton number violating charged lepton decays within this scenario for lepton masses and mixing angles. In particular, we find that charged lepton mass matrices are constrained to be quasi-diagonal. We further consider whether the same paradigm can be used to naturally explain small Dirac neutrino masses by considering the existence of three right-handed neutrinos in the brane, and discuss the requirements to obtain phenomenologically viable neutrino masses and mixing angles. Finally, we examine models where neutrinos obtain a small Majorana mass by breaking lepton number in a far away brane and show that, if the fat-brane paradigm is the solution to the absence of lepton number violating charged lepton decays, such models predict, in the absence of flavour symmetries, that charged lepton flavour violation will be observed in the next round of rare muon/tau decay experiments.Comment: 33 pages, 9 eps figure

Teor de carotenoides em nutricosméticos: análise da adequação e qualidade do produto.

O objetivo deste trabalho foi verificar a adequação dos nutricosméticos contendo carotenoides em sua formulação em relação aos teores de B-caroteno, luteína, licopeno e zeaxantina, considerando-se as quantidades declaradas pelos fabricantes. Dezenove nutricosméticos foram adquiridos no comércio varejista do município do Rio de Janeiro, em 2012. Duas metodologias de extração foram aplicadas, variando-se de acordo com o tipo de invólucro (cápsula), veículos (excipientes) e carotenoides presentes. A quantificação e determinação do perfil de carotenoides nas amostras foram realizadas por cromatografia líquida de alta eficiência com método validado e acreditado. Quatro amostras das 19 analisadas estavam dentro dos limites estabelecidos pelas Boas Práticas de Fabricação (90 a 110%). As demais amostras revelaram conteúdo inadequado de carotenoides e, consequentemente, falhas no controle de qualidade para a produção dos nutricosméticos. Desta forma, esta pesquisa demonstra que este setor deve ser objeto de atenção especial da vigilância sanitária, com necessidade de estabelecer legislação específica para regulamentar a fabricação, a rotulagem e a propaganda destes produtos

Comments on glueballinos (R0 particles) and R0 searches

We propose a search strategy for the light R0 (glueballino) particle suggested by G.Farrar in connection with the light gluino scenario. The basic idea is to moderate and stop the R0 particles and then observe their decay to almost monochromatic pions - at an appropriate time delay relative to a primary collision event, where a gluino jet, likely to fragment into the R0, was produced. This technique is optimized at colliders and depends on qualitative features of the R0 hadronic interactions which we discuss in detail.Comment: LaTeX, 28 page

Proteomic analysis of soybean leaves in a compatible and an incompatible interaction with Phakopsora pachyrhizi.

Asian soybean rust (ASR), which is incited by the fungus Phakopsora pachyrhizi, is considered one of the most aggressive diseases to the soybean culture. There are no commercial cultivars immune to the pathogen and the control measure currently used is the application of fungicides that harms the environment and increases production costs. For a better understanding of the host?s response to the pathogen at the molecular level, two soybean genotypes were analyzed (PI561356, resistant to ASR and Embrapa 48, susceptible) at 72 hours and 192 hours after inoculation with spores of P. pachyrhizi. Leaf protein profiles of the plants were compared by two-dimensional electrophoresis associated with mass spectrometry (MS). Twenty-two protein spots presented different levels when the two treatments were compared (inoculated vs. non-inoculated). From those, twelve proteins were identified by MS analysis. Some of them are involved in metabolic pathways related to plant defense against pathogens, as in the case of carbonic anhydrase, 1-deoxy-D-xylulose- 5-phosphate reductoisomerase, fructose-bisphosphate aldolase and glutamine synthetase. The possible biochemical-physiological meanings of our findings are discussed

On the Moduli Problem and Baryogenesis in Gauge-mediated SUSY Breaking Models

We investigate whether the Affleck-Dine mechanism can produce sufficient baryon number of the universe in the gauge-mediated SUSY breaking models, while evading the cosmological moduli problem by late-time entropy production. We find that the Q-ball formation renders the scenario very difficult to work, irrespective of the detail mechanism of the entropy production.Comment: 11 pages, RevTeX, 5 postscript figures include