Specific heat amplitude ratios for anisotropic Lifshitz critical behaviors

We determine the specific heat amplitude ratio near a $m$-axial Lifshitz point and show its universal character. Using a recent renormalization group picture along with new field-theoretical $\epsilon_{L}$-expansion techniques, we established this amplitude ratio at one-loop order. We estimate the numerical value of this amplitude ratio for $m=1$ and $d=3$. The result is in very good agreement with its experimental measurement on the magnetic material $MnP$. It is shown that in the limit $m \to 0$ it trivially reduces to the Ising-like amplitude ratio.Comment: 8 pages, RevTex, accepted as a Brief Report in Physical Review

Doenças do girassol.

Mancha de Alternaria - Alternaria spp.; Podridao branca - Sclerotinia sclerotiorum (Lib.) de Bary; Mildio - Plasmopara halstedii (Farl.) Berl. & de Toni; Ferrugem - Puccinia helianthi Schw.; Bolha branca - Albugo tragopogi (Pers.) Schroet; Oidio - Erysiphe cichoracearum DC; Mancha cinzenta da haste - Phomopsis helianthi Munth. - Cvet. et al.; Mancha preta da haste - Phoma oleracea var. helianthi tuberosi Sacc.; Outras podridoes radiculares e murchas - Sclerotium rolfsii Sacc., Macrophomina phaseolina (Tass.) Goid e Verticillium dahliae Klebahn; Podridao cinza do capitulo - Botrytis cinerea Pers. ex Fr.; Mancha bacteriana e crestamento bacteriano - Pseudomonas syringae pv. helianthi (Kawamura) Dye, Wilkie et Young; Pseudomonas cichorii (Swingle) Stapp; Podridao da medula da haste - Erwinia sp.; Mosaico comum do girassol - virus do mosaico do picao ("sunflower mosaic virus"); Controle de doencas.bitstream/item/40506/1/Doencas-do-girassol.pd

Physical properties of single-crystalline fibers of the colossal-magnetoresistance manganite La0.7Ca0.3MnO3

We have grown high-quality single crystals of the colossal-magnetoresistance (CMR) material La0.7Ca0.3MnO3 by using the laser heated pedestal growth (LHPG) method. Samples were grown as fibers of different diameters, and with lengths of the order of centimeters. Their composition and structure were verified through X-ray diffraction, scanning electron microcopy with EDX (Energy Dispersive X-ray Analysis) and by Rietveld analysis. The quality of the crystalline fibers was confirmed by Laue and EBSD (Electron Backscatter Diffraction) patterns. Rocking curves performed along the fiber axis revealed a half-height width of 0.073 degrees. The CMR behavior was confirmed by electrical resistivity and magnetization measurements as a function of temperature.Comment: 11 pages (including 3 figures); to appear in Appl. Phys. Let

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

Pau-rosa - Aniba rosaeodora Ducke.

Pau-rosa: distribuição geográfica; variabilidade, silvicultura, produtividade no Estado do Amazonas (Brasil).bitstream/CPAA-2009-09/4322/1/Folder_Pau-rosa.pd

Actions of angiotensin II and dopamine in the medial preoptic area on prolactin secretion

Dopamine (DA) is known as a primary regulator of prolactin secretion (PRL) and angiotensin II (Ang II) has been recognized as one brain inhibitory factor of this secretion. In this work, estrogen-primed or unprimed ovariectornized rats were submitted to the microinjection of saline or Ang II after previous microinjection of saline or of DA antagonist (haloperidol, sulpiride or SCH) both in the medial preoptic area (MPOA). Our study of these interactions has shown that 1) estrogen-induced PRL secretion is mediated by Ang II and DA actions in the MPOA, i.e. very high plasma PRL would be prevented by inhibitory action of Ang II, while very low levels would be prevented in part by stimulatory action of DA through D-2 receptors, 2) the inhibitory action of Ang II depends on estrogen and is mediated in part by inhibitory action of DA through D, receptors and in other part by inhibition of stimulatory action of DA through D2 receptors