122 research outputs found
Método de aclimatização de mudas de orquídeas em garrafas PET.
bitstream/item/55348/1/CIT11003.pd
Local-density approximation for exchange energy functional in excited-state density functional theory
An exchange energy functional is proposed and tested for obtaining a class of
excited-state energies using density functional formalism. The functional is
the excited-state counterpart of the local-density approximation functional for
the ground state. It takes care of the state dependence of the energy
functional and leads to highly accurate excitation energies
Magnetic Instabilities and Phase Diagram of the Double-Exchange Model in Infinite Dimensions
Dynamical mean-field theory is used to study the magnetic instabilities and
phase diagram of the double-exchange (DE) model with Hund's coupling J_H >0 in
infinite dimensions. In addition to ferromagnetic (FM) and antiferromagnetic
(AF) phases, the DE model supports a broad class of short-range ordered (SRO)
states with extensive entropy and short-range magnetic order. For any site on
the Bethe lattice, the correlation parameter q of a SRO state is given by the
average q=, where theta_i is the angle between any spin and
its neighbors. Unlike the FM (q=0) and AF (q=1) transitions, the transition
temperature of a SRO state (T_{SRO}) with 0<q<1 cannot be obtained from the
magnetic susceptibility. But a solution of the coupled Green's functions in the
weak-coupling limit indicates that a SRO state always has a higher transition
temperature than the AF for all fillings p<1 and even than the FM for 0.26\le p
\le 0.39. For 0.39<p<0.73, where both the FM and AF phases are unstable for
small J_H, a SRO phase has a non-zero T_{SRO} except close to p=0.5. As J_H
increases, T_{SRO} eventually vanishes and the FM dominates. For small J_H, the
T=0 phase diagram is greatly simplified by the presence of the SRO phase. A SRO
phase is found to have lower energy than either the FM or AF phases for 0.26\le
p0 but appears for J_H\neq 0. For
p near 1, PS occurs between an AF with p=1 and either a SRO or a FM phase. The
stability of a SRO state at T=0 can be understood by examining the interacting
DOS,which is gapped for any nonzero J_H in an AF but only when J_H exceeds a
critical value in a SRO state.Comment: 38 pages, 11 figures, submitted to New Journal of Physic
Adaptabilidade e estabilidade de cultivares de milho no nordeste brasileiro no biênio 2006/2007.
Qualidade físico-química e sensorial de frutos de abacaxizeiro cultivados em diferentes densidades de plantio no sistema orgânico de produção.
A produção orgânica vem crescendo de forma sustentada ao redor do mundo, devido principalmente à tomada de consciência da população dos riscos dos resíduos químicos presentes nos alimentos à saúde humana e ao apelo à conservação do meio ambiente
Induction, growth kinetics and morpho-histological characterization of Neem callus.
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Previous issue date: 2018-12-28bitstream/item/189499/1/Induction.pd
Análise conjunta dos ensaios regional e brasileiro de linhagens de aveia branca conduzidos entre 2008 e 2011.
Oxidative stress induced by the Fe2+/ascorbic acid system or model ischemia in vitro: effect of carvedilol and pyridoindole antioxidant SMe1EC2 in young and adult rat brain tissue
New effective strategies and new highly effective neuroprotective agents are being searched for the therapy of human stroke and cerebral ischemia. The compound SMe1EC2 is a new derivative of stobadine, with enhanced antioxidant properties compared to the maternal drug. Carvedilol, a non-selective beta-blocker, possesses besides its cardioprotective and vasculoprotective properties also an antioxidant effect. We compared the effect of carvedilol and SMe1EC2, antioxidants with a similar chemical structure, in two experimental models of oxidative stress in young and adult rat brain tissue. SMe1EC2 was found to improve the resistance of hippocampal neurons to ischemia in vitro in young and even in 18-month-old rats and inhibited formation of protein carbonyl groups induced by the Fe2+/ascorbic acid pro-oxidative system in brain cortex homogenates of young rats. Carvedilol exerted a protective effect only in the hippocampus of 2-month-old rats and that at the concentration 10-times higher than did SMe1EC2. The inhibitory effect of carvedilol on protein carbonyl formation induced by the pro-oxidative system was not proved in the cortex of either young or adult rats. An increased baseline level of the content of protein carbonyl groups in the adult versus young rat brain cortex confirmed age-related changes in neuronal tissue and may be due to increased production of reactive oxygen species and low antioxidant defense mechanisms in the adult rat brain. The results revealed the new pyridoindole SMe1EC2 to be more effective than carvedilol in neuroprotection of rat brain tissue in both experimental models involving oxidative stress
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