Periodic orbit bifurcations and scattering time delay fluctuations

We study fluctuations of the Wigner time delay for open (scattering) systems which exhibit mixed dynamics in the classical limit. It is shown that in the semiclassical limit the time delay fluctuations have a distribution that differs markedly from those which describe fully chaotic (or strongly disordered) systems: their moments have a power law dependence on a semiclassical parameter, with exponents that are rational fractions. These exponents are obtained from bifurcating periodic orbits trapped in the system. They are universal in situations where sufficiently long orbits contribute. We illustrate the influence of bifurcations on the time delay numerically using an open quantum map.Comment: 9 pages, 3 figures, contribution to QMC200

Variação temporal e espacial de parâmetros de qualidade de água no reservatório de Barra Bonita/SP, como subsídio ao manejo da bacia de contribuição.

bitstream/item/135805/1/BPD-228-Qualidade-Agua.pd

Superscars in the LiNC=LiCN isomerization reaction

We demonstrate the existence of superscarring in the LiNC=LiCN isomerization reaction described by a realistic potential interaction in the range of readily attainable experimental energies. This phenomenon arises as the effect of two periodic orbits appearing "out of the blue"in a saddle--node bifurcation taking place in the dynamics of the system. Potential practical consequences of this superlocalization in the corresponding wave functions are also considered.Comment: 6 pages, 5 figures. to appear in EP

Manutenção do solo e água através de programas de pagamentos por serviços ambientais.

Atuando principalmente na conservação de áreas remanescentes das florestas, regeneração assistida em bacias hidrográficas e restauração florestal, os Projetos de Pagamento por Serviços Ambientais recompensam produtores por preservarem e restaurarem ecossistemas naturais, adotando um manejo sustentável, principalmente em florestas localizadas em áreas de nascentes, em matas ciliares e em áreas de captação. O monitoramento e a avaliação do progresso de programas de PSA são baseados em indicadores, que servem para identificar a atual situação e qualidade do que foi planejado, além de fornecer subsídios para a correção de possíveis problemas detectados. Definir precisamente o que será monitorado, quais os indicadores que serão utilizados e como comprovar o benefício das atividades é uma das maiores dificuldades dos sistemas de PSA. O trabalho apresenta os indicadores que são utilizados em programas de PSA, além de sugerir novos indicadores que auxiliem no monitoramento, visando uma maior eficiência dos programas

Competição de genótipos de sorgo (Sorghum bicolor L. Moench) em Vilhena, Rondônia.

O trabalho teve como objetivo introduzir e avaliar o potencial produtivo de genotipos de sorgo nas condicoes edafoclimaticas do municipio de Vilhena, RO, para fins de recomendacoes de cultivares de sorgo em sucessao a soja.bitstream/item/57450/1/PA-77210001.pd

Universal quantum signature of mixed dynamics in antidot lattices

We investigate phase coherent ballistic transport through antidot lattices in the generic case where the classical phase space has both regular and chaotic components. It is shown that the conductivity fluctuations have a non-Gaussian distribution, and that their moments have a power-law dependence on a semiclassical parameter, with fractional exponents. These exponents are obtained from bifurcating periodic orbits in the semiclassical approximation. They are universal in situations where sufficiently long orbits contribute.Comment: 7 page

Cationic exchange in nanosized ZnFe2O4 spinel revealed by experimental and simulated near-edge absorption structure

The non-equilibrium cation site occupancy in nanosized zinc ferrites (6-13 nm) with different degree of inversion (0.2 to 0.4) was investigated using Fe and Zn K-edge x-ray absorption spectroscopy XANES and EXAFS, and magnetic measurements. The very good agreement between experimental and ab-initio calculations on the Zn K-edge XANES region clearly show the large Zn2+(A)--Zn2+[B] transference that takes place in addition to the well-identified Fe3+[B]--Fe3+(A) one, without altering the long-range structural order. XANES spectra features as a function of the spinel inversion were shown to depend on the configuration of the ligand shells surrounding the absorbing atom. This XANES approach provides a direct way to sense cationic inversion in these spinel compounds. We also demonstrated that a mechanical crystallization takes place on nanocrystalline spinel that causes an increase of both grain and magnetic sizes and, simultaneously, generates a significant augment of the inversion.Comment: 5 pages, 5 eps figures, uses revtex4, corrected table