Non-Gaussian statistics and extreme waves in a nonlinear optical cavity

A unidirectional optical oscillator is built by using a liquid crystal light-valve that couples a pump beam with the modes of a nearly spherical cavity. For sufficiently high pump intensity, the cavity field presents a complex spatio-temporal dynamics, accompanied by the emission of extreme waves and large deviations from the Gaussian statistics. We identify a mechanism of spatial symmetry breaking, due to a hypercycle-type amplification through the nonlocal coupling of the cavity field

Spatiotemporal pulses in a liquid crystal optical oscillator

A nonlinear optical medium results by the collective orientation of liquid crystal molecules tightly coupled to a transparent photoconductive layer. We show that such a medium can give a large gain, thus, if inserted in a ring cavity, it results in an unidirectional optical oscillator. Dynamical regimes with many interacting modes are made possible by the wide transverse size and the high nonlinearity of the liquid crystals. We show the generation of spatiotemporal pulses, coming from the random superposition of many coexisting modes with different frequencies

CAUSAS ASSOCIADAS À MORTE DE MATRIZES SUÍNAS

Annual rate of mortality of sows varies considerably among farms. The increase in mortality, together with culling rate of sows, imply in great losses for the producer. The aim of this work was to evaluate the causes of sows mortality in a farm located in Brazilian Middlewest region. Necropsies of 78 sows were carried out, after their death or euthanasia, during January and February 2006. Mortality rate was 8.1%, considered high if compared to historical rates observed in swine farms. The major causes of death were genito-urinary infections (30.8%), followed by hemorrhagic gastric ulcer (14.1%) and females euthanatizia (14.1%). Farrowing problems and cardiac failure occurred in 10.3% and 10.3% of dead females, respectively. In 5.1% of the sows was not possible to determine the cause of death. Among the females that died 70.5% presented cystitis, 37.2% pyelonephritis and 79.5% presented some degree of stomach ulceration. Among females that died by urinary infection, 54.2% had five or more parities. Females with gastric ulcer had on average of 1.8 parities and 90.9% of them had less than three parities. The body condition score of females submitted to euthanasia was lower than that observed in dead females due to other reasons. More females died when maximum ambient temperature was above 33oC.A taxa anual de mortalidade de matrizes suínas varia consideravelmente entre as granjas. A mortalidade, junto com o descarte de matrizes, implica em grandes perdas para o produtor. O objetivo deste trabalho foi avaliar as causas de mortalidade de matrizes suínas em uma granja localizada no Centro-oeste brasileiro. Foram realizadas necropsias de 78 matrizes, que morreram ou foram sacrificadas, durante os meses de janeiro e fevereiro de 2006. A taxa de mortalidade observada foi 8,1%, considerada alta em comparação às taxas observadas historicamente nas granjas. As três principais causas de morte foram infecções gênito-urinárias (30,8%), seguidas de úlcera gástrica rompida (14,1%) e fêmeas sacrificadas (14,1%). Problemas de parto e falha cardíaca acometeram 10,3% e 10,3% das fêmeas, respectivamente. Em 5,1% das fêmeas não foi possível definir a causa da morte. Dentre as fêmeas que morreram, 70,5% apresentavam cistite, 37,2% pielonefrite e 79,5% apresentavam algum grau de ulceração no estômago. Das fêmeas que morreram por infecção urinária, 54,2% tiveram cinco ou mais partos. As fêmeas que morreram por úlcera gástrica tiveram, em média, 1,8 partos, sendo que 90,9% tiveram no máximo até três partos. O escore de condição corporal das fêmeas sacrificadas foi menor do que o observado nas fêmeas que morreram por outras causas. Foi constatado maior número de mortes nos dias com temperatura superior a 33ºC

Caracterização do perfil sorológico de nulíparas suínas e da progênie frente ao parvovírus suíno.

Projeto: 03.09.00.046

Numerical instability of the Akhmediev breather and a finite-gap model of it

In this paper we study the numerical instabilities of the NLS Akhmediev breather, the simplest space periodic, one-mode perturbation of the unstable background, limiting our considerations to the simplest case of one unstable mode. In agreement with recent theoretical findings of the authors, in the situation in which the round-off errors are negligible with respect to the perturbations due to the discrete scheme used in the numerical experiments, the split-step Fourier method (SSFM), the numerical output is well-described by a suitable genus 2 finite-gap solution of NLS. This solution can be written in terms of different elementary functions in different time regions and, ultimately, it shows an exact recurrence of rogue waves described, at each appearance, by the Akhmediev breather. We discover a remarkable empirical formula connecting the recurrence time with the number of time steps used in the SSFM and, via our recent theoretical findings, we establish that the SSFM opens up a vertical unstable gap whose length can be computed with high accuracy, and is proportional to the inverse of the square of the number of time steps used in the SSFM. This neat picture essentially changes when the round-off error is sufficiently large. Indeed experiments in standard double precision show serious instabilities in both the periods and phases of the recurrence. In contrast with it, as predicted by the theory, replacing the exact Akhmediev Cauchy datum by its first harmonic approximation, we only slightly modify the numerical output. Let us also remark, that the first rogue wave appearance is completely stable in all experiments and is in perfect agreement with the Akhmediev formula and with the theoretical prediction in terms of the Cauchy data.Comment: 27 pages, 8 figures, Formula (30) at page 11 was corrected, arXiv admin note: text overlap with arXiv:1707.0565