2,434 research outputs found
Low Mass Pseudoscalar Dark Matter in an Extended B - L Model
We study an extended B-L model, which has in its structure four neutral
scalars. In this model, a representative set of parameters enable us to
conclude that one of these scalars is a promising candidate for low-mass dark
matter. We introduce an Z_2 symmetry, which ensure the stability of the dark
matter. The dominant annihilation process will be through -channel exchange
of a scalar in . So, this is also a Higgs portal dark matter
model, but the Higgs decay to dark matter is suppressed and meets the
constraints from invisible decays of Higgs boson. The model is also in
agreement with the constraints established by XENON100, CoGeNT and CDMS
experiments, maching the relic abundance and the cross section with nucleon.Comment: Version submitted and accepted for publication in PR
Tunable Double Negative Band Structure from Non-Magnetic Coated Rods
A system of periodic poly-disperse coated nano-rods is considered. Both the
coated nano-rods and host material are non-magnetic. The exterior nano-coating
has a frequency dependent dielectric constant and the rod has a high dielectric
constant. A negative effective magnetic permeability is generated near the Mie
resonances of the rods while the coating generates a negative permittivity
through a field resonance controlled by the plasma frequency of the coating and
the geometry of the crystal. The explicit band structure for the system is
calculated in the sub-wavelength limit. Tunable pass bands exhibiting negative
group velocity are generated and correspond to simultaneously negative
effective dielectric permittivity and magnetic permeability. These can be
explicitly controlled by adjusting the distance between rods, the coating
thickness, and rod diameters
Avaliação de métodos de enxertia para a gravioleira em Viçosa-MG.
Visando obter informações sobre técnicas de enxertia em gravioleira (Annoma muricata L.), foram avaliados, neste trabalho, nove métodos de enxertia: garfagem à inglesa simples com e sem parafina; garfagem à inglesa com entalhe com e sem parafina; garfagem no topo em fenda cheia com e sem parafina; borbulhia em placa; borbulhia em janela aberta e borbulhia em T invertido. Os métodos de garfagem à inglesa simples e de garfagem no topo em fenda cheia, ambos com e sem parafinados, apresentaram maiores Ãndices no pegamento e brotamento do enxerto. Apesar de não diferirem entre si, os métodos com uso de grafos parafinados podem ser recomendados por proporcionarem menor custo na produção de mudas enxertadas de graviola.Edição do XI Congresso Brasileiro de Fruticultura
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