Thermodynamically stable noncomposite vortices in mesoscopic two-gap superconductors

In mesoscopic two-gap superconductors with sizes of the order of the coherence length noncomposite vortices are found to be thermodynamically stable in a large domain of the $T - H$ phase diagram. In these phases the vortex cores of one condensate are spatially separated from the other condensate ones, and their respective distributions can adopt distinct symmetries. The appearance of these vortex phases is caused by a non-negligible effect of the boundary of the sample on the superconducting order parameter and represents therefore a genuine mesoscopic effect. For low values of interband Josephson coupling vortex patterns with $L_1 \neq L_2$ can arise in addition to the phases with $L_1 =L_2$, where $L_1$ and $L_2$ are total vorticities in the two condensates. The calculations show that noncomposite vortices could be observed in thin mesoscopic samples of MgB$_{2}$.Comment: 5 pages, 3 figures, to be published in Europhysics Letter

Experimental evidence of shock mitigation in a Hertzian tapered chain

We present an experimental study of the mechanical impulse propagation through a horizontal alignment of elastic spheres of progressively decreasing diameter $\phi_n$, namely a tapered chain. Experimentally, the diameters of spheres which interact via the Hertz potential are selected to keep as close as possible to an exponential decrease, $\phi_{n+1}=(1-q)\phi_n$, where the experimental tapering factor is either $q_1\simeq5.60$~% or $q_2\simeq8.27$~%. In agreement with recent numerical results, an impulse initiated in a monodisperse chain (a chain of identical beads) propagates without shape changes, and progressively transfer its energy and momentum to a propagating tail when it further travels in a tapered chain. As a result, the front pulse of this wave decreases in amplitude and accelerates. Both effects are satisfactorily described by the hard spheres approximation, and basically, the shock mitigation is due to partial transmissions, from one bead to the next, of momentum and energy of the front pulse. In addition when small dissipation is included, a better agreement with experiments is found. A close analysis of the loading part of the experimental pulses demonstrates that the front wave adopts itself a self similar solution as it propagates in the tapered chain. Finally, our results corroborate the capability of these chains to thermalize propagating impulses and thereby act as shock absorbing devices.Comment: ReVTeX, 7 pages with 6 eps, accepted for Phys. Rev. E (Related papers on http://www.supmeca.fr/perso/jobs/

Performance da densidade de plantas em cultivares comerciais de feijão-caupi nos cerrados do leste maranhense.

Entre os vários fatores que influenciam o rendimento de grãos (RG) a densidade de plantas (DP) é um dos mais importantes e seus efeitos podem variar com o tipo da planta. O objetivo deste trabalho foi avaliar a performance do feijão-caupi (FC) de portes ereto (E), semi-ereto (SE) e semi-prostrado (SP), em diferentes DP (8, 12, 16, 20, 24 e 28 plantas m-2; portes E e SE e 2, 6, 10, 14, 18 e 22 plantas m-2; porte SP). Os ensaios foram conduzidos no município de Mata Roma, MA, ano agrícola 2011/2012. O delineamento experimental foi o de blocos casualizados com quatro repetições e os tratamentos representados pelas DP. Os RG e o número de vagens por área (NVA) responderam quadraticamente ao aumento da DP enquanto resposta linear foi observada para o número de vagens por planta.CONAC 2012. Disponível em: http://www.conac2012.org/resumos/pdf/026b.pdf. Acesso em: 25 jun. 2013

Performance de cultivares de milho-verde no município de Teresina, Piauí.

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Wave localization in strongly nonlinear Hertzian chains with mass defect

We investigate the dynamical response of a mass defect in a one-dimensional non-loaded horizontal chain of identical spheres which interact via the nonlinear Hertz potential. Our experiments show that the interaction of a solitary wave with a light intruder excites localized mode. In agreement with dimensional analysis, we find that the frequency of localized oscillations exceeds the incident wave frequency spectrum and nonlinearly depends on the size of the intruder and on the incident wave strength. The absence of tensile stress between grains allows some gaps to open, which in turn induce a significant enhancement of the oscillations amplitude. We performed numerical simulations that precisely describe our observations without any adjusting parameters.Comment: 4 pages, 5 figures, submitted for publicatio

Densidade populacional em cultivares de feijão-caupi com diferentes portes de planta, na Região do Matopiba.

The aim of this study was to assess the productive performance of cowpea cultivars with different growth habits as a function of population density in the MATOPIBA region, Brazil. The experiments were carried out in Magalhães de Almeida, MA in the agricultural season 2014/2015. The cultivars BRS Itaim, BRS Tumucumaque, and BRS Pajeú, which present an erect, semi-erect, and semi-prostrate growth habits, respectively, were assessed..