8,519 research outputs found
Caracterização agronômica de manjericão branco (Ocimum basilicum L) na região litorânea do Ceará.
The role of dynamical polarization of the ligand to metal charge transfer excitations in {\em ab initio} determination of effective exchange parameters
The role of the bridging ligand on the effective Heisenberg coupling
parameters is analyzed in detail. This analysis strongly suggests that the
ligand-to-metal charge transfer excitations are responsible for a large part of
the final value of the magnetic coupling constant. This permits to suggest a
new variant of the Difference Dedicated Configuration Interaction (DDCI)
method, presently one of the most accurate and reliable for the evaluation of
magnetic effective interactions. This new method treats the bridging ligand
orbitals mediating the interaction at the same level than the magnetic orbitals
and preserves the high quality of the DDCI results while being much less
computationally demanding. The numerical accuracy of the new approach is
illustrated on various systems with one or two magnetic electrons per magnetic
center. The fact that accurate results can be obtained using a rather reduced
configuration interaction space opens the possibility to study more complex
systems with many magnetic centers and/or many electrons per center.Comment: 7 pages, 4 figure
Systems for superficial protection of concretes
Nowadays, it is consensual that the biggest degradation of concrete happens from
outside to inside actions, due to the penetration of moisture, active gases and aggressive ions, by mechanical, physical and chemical causes that frequently act together. A low porosity, permeability and concrete penetration to moisture and gases are the first lines of defence against several deterioration mechanisms. The durability of concrete depends largely on how
hard or easy fluids (water, carbon dioxide, oxygen) in liquid or gas form can migrate through the concrete hardened mass. When selecting the paint coating for concrete protection, importance is given to the properties of diffusion and permeability resistance, besides the properties of durability and chemical resistance. The paint coatings must stop the penetration of water and delay the influence of aggressive agents (CO2, SO2, Cl- ions), allowing the structure to breathe by a water vapour diffusion mechanism. Through tests of capillarity
absorption, immersion absorption, porosity, water and oxygen permeability, a comparison
was made between painted and non painted concrete specimens. Three different coating types were tested: silicon varnish; acrylic and epoxy paints. The results showed that, in general, all coatings reduce the porosity and the permeability. The epoxy paints proved to be the best ones
Controle do Psilídeo-da-goiabeira (Triozoida limbata) com silício, nim e imidacloprido.
Triozoida limbata é importante praga da goiabeira, sendo seu controle realizado com inseticidas químicos.Resumo 840-2
Manejo dos restos culturais (soqueira) do algodoeiro como ferramenta de combate às pragas.
bitstream/CPATC-2009-09/20523/1/ct-41.pd
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