6,606 research outputs found
A new picture of the Lifshitz critical behavior
New field theoretic renormalization group methods are developed to describe
in a unified fashion the critical exponents of an m-fold Lifshitz point at the
two-loop order in the anisotropic (m not equal to d) and isotropic (m=d close
to 8) situations. The general theory is illustrated for the N-vector phi^4
model describing a d-dimensional system. A new regularization and
renormalization procedure is presented for both types of Lifshitz behavior. The
anisotropic cases are formulated with two independent renormalization group
transformations. The description of the isotropic behavior requires only one
type of renormalization group transformation. We point out the conceptual
advantages implicit in this picture and show how this framework is related to
other previous renormalization group treatments for the Lifshitz problem. The
Feynman diagrams of arbitrary loop-order can be performed analytically provided
these integrals are considered to be homogeneous functions of the external
momenta scales. The anisotropic universality class (N,d,m) reduces easily to
the Ising-like (N,d) when m=0. We show that the isotropic universality class
(N,m) when m is close to 8 cannot be obtained from the anisotropic one in the
limit d --> m near 8. The exponents for the uniaxial case d=3, N=m=1 are in
good agreement with recent Monte Carlo simulations for the ANNNI model.Comment: 48 pages, no figures, two typos fixe
Avaliação do crescimento de mudas de pinhão manso (Jatropha curcas L.) em recipientes de diferentes volumes e acompanhamento do desenvolvimento em campo.
O objetivo deste trabalho foi quantificar o efeito dos diferentes volumes de recipiente na formação de mudas de pinhão-manso (Jatropha curcas L.) e no crescimento em campo aos seis meses após o plantio.bitstream/CPAF-RO-2010/14513/1/107-pinhaomanso.pd
Pregnancy rate in toggenburg goats after short, medium or long-term protocols for induction of synchronized estrus after natural mating or artificial insemination in different seasons.
Edição dos resumos da 24a Reunião Anual da Sociedade Brasileira de Tecnologia de Embriões, Porto de Galinhas, 2010
Charge and spin distributions in GaMnAs/GaAs Ferromagnetic Multilayers
A self-consistent electronic structure calculation based on the
Luttinger-Kohn model is performed on GaMnAs/GaAs multilayers. The Diluted
Magnetic Semiconductor layers are assumed to be metallic and ferromagnetic. The
high Mn concentration (considered as 5% in our calculation) makes it possible
to assume the density of magnetic moments as a continuous distribution, when
treating the magnetic interaction between holes and the localized moment on the
Mn(++) sites. Our calculation shows the distribution of heavy holes and light
holes in the structure. A strong spin-polarization is observed, and the charge
is concentrated mostly on the GaMnAs layers, due to heavy and light holes with
their total angular momentum aligned anti-parallel to the average
magnetization. The charge and spin distributions are analyzed in terms of their
dependence on the number of multilayers, the widths of the GaMnAs and GaAs
layers, and the width of lateral GaAs layers at the borders of the structure.Comment: 12 pages,7 figure
Curva de dissipação de imazapyr em água de drenos de irrigação, após a aplicação para controle da taboa.
O herbicida sistémico imazapyr foi usado no controle da taboa (Typha subulata Crespo & Peres-Moreau f.) em drenos de irrigação, como alternativa ao controle mecânico. O resÃduo do princÃpio ativo do herbicida na água foi analisado por cromatografia lÃquida de alta performance (HPLC). A curv a de di ss ip ação de imazapyr mostrou que o herbicida pode ser usado para o contro le de taboa em drenos de irr iga ção, sem causar danos a culturas vizinhas, desde que a água seja usada, no mÃnimo, depois de 1,6 a 3,7 dias da aplicação das doses de 500 a 1500 g ha-1, respectivamente
Is abscisic acid involved in the drought responses of brazilian green dwarf coconut?
Abscisic acid (ABA) accumulation in leaves of drought-stressed coconut palms and its involvement with stomatal regulation of gas exchange during and after stress were investigated. Two Brazilian Green Dwarf coconut ecotypes from hot/humid and hot/dry environments were submitted to three consecutive drying/recovery cycles under greenhouse conditions. ABA accumulated in leaflets before significant changes in pre-dawn leaflet water potential ( PD ) and did not recover completely in the two ecotypes
after 8 days of rewatering. Stomatal conductance was influenced by ABA under mild drought and by PD under severe drought. There were no significant differences between the ecotypes for most variables measured. However, the ecotype from a hot/dry environment showed higher water use efficiency after repeated cycles of water stress
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