Test of Local Scale Invariance from the direct measurement of the response function in the Ising model quenched to and to below TCT_C

In order to check on a recent suggestion that local scale invariance [M.Henkel et al. Phys.Rev.Lett. {\bf 87}, 265701 (2001)] might hold when the dynamics is of Gaussian nature, we have carried out the measurement of the response function in the kinetic Ising model with Glauber dynamics quenched to $T_C$ in $d=4$, where Gaussian behavior is expected to apply, and in the two other cases of the $d=2$ model quenched to $T_C$ and to below $T_C$, where instead deviations from Gaussian behavior are expected to appear. We find that in the $d=4$ case there is an excellent agreement between the numerical data, the local scale invariance prediction and the analytical Gaussian approximation. No logarithmic corrections are numerically detected. Conversely, in the $d=2$ cases, both in the quench to $T_C$ and to below $T_C$, sizable deviations of the local scale invariance behavior from the numerical data are observed. These results do support the idea that local scale invariance might miss to capture the non Gaussian features of the dynamics. The considerable precision needed for the comparison has been achieved through the use of a fast new algorithm for the measurement of the response function without applying the external field. From these high quality data we obtain $a=0.27 \pm 0.002$ for the scaling exponent of the response function in the $d=2$ Ising model quenched to below $T_C$, in agreement with previous results.Comment: 24 pages, 6 figures. Resubmitted version with improved discussions and figure

Absorbing Phase Transition in a Four State Predator Prey Model in One Dimension

The model of competition between densities of two different species, called predator and prey, is studied on a one dimensional periodic lattice, where each site can be in one of the four states say, empty, or occupied by a single predator, or occupied by a single prey, or by both. Along with the pairwise death of predators and growth of preys, we introduce an interaction where the predators can eat one of the neighboring prey and reproduce a new predator there instantly. The model shows a non-equilibrium phase transition into a unusual absorbing state where predators are absent and the lattice is fully occupied by preys. The critical exponents of the system are found to be different from that of the Directed Percolation universality class and they are robust against addition of explicit diffusion.Comment: 10 pages, 6 figures, to appear in JSTA

On universality in aging ferromagnets

This work is a contribution to the study of universality in out-of-equilibrium lattice models undergoing a second-order phase transition at equilibrium. The experimental protocol that we have chosen is the following: the system is prepared in its high-temperature phase and then quenched at the critical temperature $T_c$. We investigated by mean of Monte Carlo simulations two quantities that are believed to take universal values: the exponent $\lambda/z$ obtained from the decay of autocorrelation functions and the asymptotic value $X_\infty$ of the fluctuation-dissipation ratio $X(t,s)$. This protocol was applied to the Ising model, the 3-state clock model and the 4-state Potts model on square, triangular and honeycomb lattices and to the Ashkin-Teller model at the point belonging at equilibrium to the 3-state Potts model universality class and to a multispin Ising model and the Baxter-Wu model both belonging to the 4-state Potts model universality class at equilibrium.Comment: 17 page

Global persistence exponent of the two-dimensional Blume-Capel model

The global persistence exponent $\theta_g$ is calculated for the two-dimensional Blume-Capel model following a quench to the critical point from both disordered states and such with small initial magnetizations. Estimates are obtained for the nonequilibrium critical dynamics on the critical line and at the tricritical point. Ising-like universality is observed along the critical line and a different value $\theta_g =1.080(4)$ is found at the tricritical point.Comment: 7 pages with 3 figure

Study of follicular vascularization using tridimensional images: a new approach.

The aim of the present study was to develop a new methodology to assess the follicular vascularization using color Doppler technology and a software for image analysis (Image J) to recreate tridimensional images of the blood vessels found on the follicle.Edição dos abstracts da 25ª Annual Meeting of the International Embryo Transfer Society, Québec, 2011

Cultivo solteiro e consorciado de Achillea millefolium com diferentes teores de adubação organica.

Este experimento teve como objetivo avaliar a influência da adubação orgânica e da consorciação no rendimento da biomassa, altura e óleo essencial de mil-folhas (Achillea millefolium). O cultivo das plantas foi realizado em canteiros no Horto Didático de Plantas Medicinais do Cesumar, utilizando-se quatro doses de adubo composto vegetal 0, 1, 2 e 3%, em cultivo solteiro e, em cultivo consorciado com alecrim. A colheita das plantas ocorreu 10 meses após o plantio e sua biomassa fresca foi pesada, posteriormente foram secas sob temperatura ambiente e a extração do óleo essencial ocorreu por hidrodestilação utilizando-se o aparelho de Clevenger. O rendimento de biomassa foi crescente conforme o aumento da dose de adubo e, superior no cultivo consorciado. A adubação reduziu o rendimento de óleo essencial, e não houve diferença entre os tipos de cultivo. O crescimento em altura da mil-folhas foi maior no cultivo consorciado