Avaliação de linhagem e cultivares de feijoeiro comum, grupo preto, no período de inverno, em Uberlândia-MG.

Em esforço conjunto, a Universidade Federal de Uberlândia e a Embrapa, conduziram ensaios de competição de linhagens e cultivares no município de Uberlândia, MG com objetivo de avaliar o comportamento agronômico, dentre estes a produtividade, de cultivares de feijoeiro comum, do grupo preto, na época de inverno, em 2006 e 2007

Cultivares e linhagens de feijoeiro comum, do grupo carioca, no período de inverno, em Uberlândia-MG.

A Universidade Federal de Uberlândia e a Embrapa, conduziram ensaios de competição de linhagens e cultivares em Uberlândia, MG, com o objetivo de avaliar o comportamento agronômico, dentre estes a produtividade, de genótipos de feijoeiro comum, do grupo comercial carioca, na época de inverno, em 2006 e 2007

Exactly Solvable Models of Interacting Spin-s Particles in one-dimension

We consider the exact solution of a many-body problem of spin-$s$ particles interacting through an arbitrary U(1) invariant factorizable $S$-matrix. The solution is based on a unified formulation of the quantum inverse scattering method for an arbitrary $(2s+1)$-dimensional monodromy matrix. The respective eigenstates are shown to be given in terms of $2s$ creation fields by a general new recurrence relation. This allows us to derive the spectrum and the respective Bethe ansatz equations.Comment: 10 pages, plain late

π0→γ∗γ\pi^0\to\gamma^*\gamma transition form factor within Light Front Quark Model

We study the transition form factor of $\pi^0\to\gamma^* \gamma$ as a function of the momentum transfer $Q^2$ within the light-front quark model (LFQM). We compare our result with the experimental data by BaBar as well as other calculations based on the LFQM in the literature. We show that our predicted form factor fits well with the experimental data, particularly those at the large $Q^2$ region.Comment: 11 pages, 4 figures, accepted for publication in PR

Magnetic monopole and string excitations in a two-dimensional spin ice

We study the magnetic excitations of a square lattice spin-ice recently produced in an artificial form, as an array of nanoscale magnets. Our analysis, based upon the dipolar interaction between the nanomagnetic islands, correctly reproduces the ground-state observed experimentally. In addition, we find magnetic monopole-like excitations effectively interacting by means of the usual Coulombic plus a linear confining potential, the latter being related to a string-like excitation binding the monopoles pairs, what indicates that the fractionalization of magnetic dipoles may not be so easy in two dimensions. These findings contrast this material with the three-dimensional analogue, where such monopoles experience only the Coulombic interaction. We discuss, however, two entropic effects that affect the monopole interactions: firstly, the string configurational entropy may loose the string tension and then, free magnetic monopoles should also be found in lower dimensional spin ices; secondly, in contrast to the string configurational entropy, an entropically driven Coulomb force, which increases with temperature, has the opposite effect of confining the magnetic defects.Comment: 8 pages. Accepted by Journal of Applied Physics (2009

Phase Fluctuations and Vortex Lattice Melting in Triplet Quasi-One-Dimensional Superconductors at High Magnetic Fields

Assuming that the order parameter corresponds to an equal spin triplet pairing symmetry state, we calculate the effect of phase fluctuations in quasi-one-dimensional superconductors at high magnetic fields applied along the y (b') axis. We show that phase fluctuations can destroy the theoretically predicted triplet reentrant superconducting state, and that they are responsible for melting the magnetic field induced Josephson vortex lattice above a magnetic field dependent melting temperature Tm.Comment: 4 pages (double column), 1 eps figur

Vortices in vibrated granular rods

We report the experimental observation of novel vortex patterns in vertically vibrated granular rods. Above a critical packing fraction, moving ordered domains of nearly vertical rods spontaneously form and coexist with horizontal rods. The domains of vertical rods coarsen in time to form large vortices. We investigate the conditions under which the vortices occur by varying the number of rods, vibration amplitude and frequency. The size of the vortices increases with the number of rods. We characterize the growth of the ordered domains by measuring the area fraction of the ordered regions as a function of time. A {\em void filling} model is presented to describe the nucleation and growth of the vertical domains. We track the ends of the vertical rods and obtain the velocity fields of the vortices. The rotation speed of the rods is observed to depend on the vibration velocity of the container and on the packing. To investigate the impact of the direction of driving on the observed phenomena, we performed experiments with the container vibrated horizontally. Although vertical domains form, vortices are not observed. We therefore argue that the motion is generated due to the interaction of the inclination of the rods with the bottom of a vertically vibrated container. We also perform simple experiments with a single row of rods in an annulus. These experiments directly demonstrate that the rod motion is generated when the rods are inclined from the vertical, and is always in the direction of the inclination.Comment: 6 pages, 10 figure, 2 movies at http://physics.clarku.edu/vortex uses revtex

Alteração na fotossíntese causada pela mancha de alternaria (Alternaria helianthi) em girassol.

A mancha de Alternaria (Alternaria helianthi) diminui a área fotossintética da planta, devido à formação de manchas foliares que podem coalescer, formando áreas extensas de tecido necrosado, provocando seca prematura da folha. Objetivou-se avaliar as alterações na fotossíntese causada pela mancha de Alternaria em quatro genótipos de girassol (BRS 324, BRS 321, BRS 323 e HLA 887). O delineamento experimental foi inteiramente casualizado com 4 tratamentos e 6 repetições. Plantas de girassol cultivadas em vaso foram inoculadas com o fungo, no estágio V8 (oito folhas verdadeiras). Após 32 horas, foi feita a leitura da fotossíntese líquida nas folhas 3 e 4, utilizando o analisador de fotossíntese LI-6400XT. A taxa líquida de fotossíntese foi relacionada à severidade da doença por meio do modelo Px/Po=(1-x)b, onde Px representa a taxa fotossintética líquida de folhas com severidade de doença x (em proporção), Po representa a taxa fotossintética líquida média de folhas sadias e b representa a relação entre a lesão virtual (área foliar sem sintomas mas com fotossíntese nula) e a lesão visual (área foliar coberta por sintomas). Os valores de b determinados por regressão não-linear (R2 de 0,35 a 0,52 para os diferentes materiais) variaram entre 0,77 a 2,18. Observou-se diferença na taxa de fotossíntese líquida para os genótipos BRS 324 (1,93), BRS 321 (2,15) e BRS 323 (2,17), que apresentaram b maior que 1. Esta alteração na atividade fotossintética pode ser causada por redução na interceptação da radiação (RI), resultante da perda de área foliar fotossintetizante nas áreas próximas à região necrosada

Comprehensive Overview on HVDC Converter Transformer Design: Additional Discussions to the IEC/IEEE 60076-57-129 Standard

HVDC has been chosen as an economical and technical solution for power transmission through long distances, asynchronous interconnections and long submarine cables crossing. Despite DC transmission benefits to power systems, the converters non-linearity produces undesirable effects to the converter transformer in service, mainly listed in the technical standard IEC/IEEE 60076-57-129. However, additional discussions and complementary information can be found in a plurality of references, which are brought in the article under a comprehensive overview perspective. Some design solutions deal with these effects increasing the technical margins, which have direct influence on manufacturing costs and transformer reliability and availability levels. This article goes through the main topics pointed by the standard and the references, investigating their consequences in the converter transformer operation, in order to provide a comprehensive tutorial on design solutions and considerations to deal with those undesirable effects