Quantum Dissipation and Decoherence via Interaction with Low-Dimensional Chaos: a Feynman-Vernon Approach

We study the effects of dissipation and decoherence induced on a harmonic oscillator by the coupling to a chaotic system with two degrees of freedom. Using the Feynman-Vernon approach and treating the chaotic system semiclassically we show that the effects of the low dimensional chaotic environment are in many ways similar to those produced by thermal baths. The classical correlation and response functions play important roles in both classical and quantum formulations. Our results are qualitatively similar to the high temperature regime of the Caldeira-Leggett model.Comment: 31 pages, 4 figure

A conjugate for the Bargmann representation

In the Bargmann representation of quantum mechanics, physical states are mapped into entire functions of a complex variable z*, whereas the creation and annihilation operators $\hat{a}^\dagger$ and $\hat{a}$ play the role of multiplication and differentiation with respect to z*, respectively. In this paper we propose an alternative representation of quantum states, conjugate to the Bargmann representation, where the roles of $\hat{a}^\dagger$ and $\hat{a}$ are reversed, much like the roles of the position and momentum operators in their respective representations. We derive expressions for the inner product that maintain the usual notion of distance between states in the Hilbert space. Applications to simple systems and to the calculation of semiclassical propagators are presented.Comment: 15 page

Semiclassical coherent state propagator for systems with spin

We derive the semiclassical limit of the coherent state propagator for systems with two degrees of freedom of which one degree of freedom is canonical and the other a spin. Systems in this category include those involving spin-orbit interactions and the Jaynes-Cummings model in which a single electromagnetic mode interacts with many independent two-level atoms. We construct a path integral representation for the propagator of such systems and derive its semiclassical limit. As special cases we consider separable systems, the limit of very large spins and the case of spin 1/2.Comment: 19 pages, no figure

Biomasa individual y poblacional de arbustos dominantes en estepas patagónicas pastoreadas

269-279Estimating aboveground biomass of vegetation is essential for population, community and ecosystem studies. In systems dominated or co-dominated by woody species, biomass estimation is difficult, and rapid and non-destructive methods are needed. In this study, we describe biomass distribution in different components (i.e., wood, leaves) and how this changes with shrub size for the three dominant species of shrubs in the Occidental District of the Patagonian steppe. We also describe the population size structure of the three species in grazed fields and estimate their contribution to total abundance and biomass through a non-destructive method. We developed allometric equations to estimate aboveground biomass components of individual shrubs from structural descriptors (i.e., diameter and height of the crown), sampling individual plants of different sizes. The variable that best predicted biomass of the three species was the sum of the height and the average diameter of the crown (calculated with the largest diameter and its perpendicular). Allometric models for each species explained more than 83 percent of the variability of individual aboveground biomass. At the individual level, species had different proportions of wood, leaves and specific wood weight. Increasing shrub size was accompanied by changes in the proportion of leaves to wood, and in some cases, the percentage of dead crown. At the population level, the three species differed in size distribution in moderately grazed fields. Development of allometric models from a population perspective is important to study demographic processes that drive community and ecosystem responses to environmental and land-use changes

Modeling electrodialysis and a photochemical process for their integration in saline wastewater treatment.

Oxidation processes can be used to treat industrial wastewater containing non-biodegradable organic compounds. However, the presence of dissolved salts may inhibit or retard the treatment process. In this study, wastewater desalination by electrodialysis (ED) associated with an advanced oxidation process (photo-Fenton) was applied to an aqueous NaCl solution containing phenol. The influence of process variables on the demineralization factor was investigated for ED in pilot scale and a correlation was obtained between the phenol, salt and water fluxes with the driving force. The oxidation process was investigated in a laboratory batch reactor and a model based on artificial neural networks was developed by fitting the experimental data describing the reaction rate as a function of the input variables. With the experimental parameters of both processes, a dynamic model was developed for ED and a continuous model, using a plug flow reactor approach, for the oxidation process. Finally, the hybrid model simulation could validate different scenarios of the integrated system and can be used for process optimization

Comparação da taxa de lotação em piquetes de Panicum maximum cv. Tazania irrigado e sequeiro com suplementação.

O presente trabalho teve como objetivo comparar a taxa de lotação em pastagem de Panicum maximum " cv. Tanzânia, irrigada e em sequeiro, de acordo com o consumo de forragem de vacas em lactação, da raça holandesa preta e branca, suplementadas com concentrado de acordo com suas produções, predicto pelo programa de Cornell 3.0

Germinação de sementes de Paspalum notatum Flügge.

Paspalum notatum Flügge destaca-se entre as espécies forrageiras utilizadas na alimentação animal pela alta produção de forragem e bom valor nutritivo. A germinação de sementes de espécies forrageiras associada à dormência tem sido, em todo o mundo um sério problema, principalmente pela baixa porcentagem de germinação e qualidade fisiológica. O objetivo do trabalho foi verificar a germinação de Paspalum notatum por diferentes tratamentos de quebra da dormência. O experimento foi desenvolvido com 8 tratamentos divididos por métodos físico (escarificação) e químico (nitrato de potássio), além do controle, com 4 repetições havendo 50 sementes por repetição. Os tratamentos que havia a presença da escarificação das sementes mostraram os melhores resultados, enquanto que os tratamentos que continham somente o reagente nitrato de potássio (KNO3) obtiveram os piores desempenhos. A escarificação promove a germinação das sementes de paspalum notatum, entretanto o nitrato de potássio é ineficaz na promoção da germinação.SEPE on-line

Fungos associados as sementes de Paspalum notatum Flügge.

O objetivo deste trabalho foi identificar os gêneros de fungos presentes nas sementes de Paspalum notatum Flügge, as sementes foram analisadas pelos métodos de papel de filtro e plaqueamento em meio de cultura (BDA). As culturas foram mantidas em câmara BOD por oito dias a temperatura de 25°C e fotoperíodo de 12 horas. A identificação dos gêneros fúngicos foi realizada com auxílio de microscópio óptico. Foram detectados os gêneros Fusarium, Aspergilus, Curvalaria e Geniculosporium, além de microrganismos não identificados.SEPE on-line

Combining ability of elite clones of Eucalyptus grandisand Eucalyptus urophylla with Eucalyptus globulus.

In Brazil, eucalyptus breeding programs for cellulose production has used two species, Eucalyptus grandis and Eucalyptus urophylla. Nevertheless, it would be useful to introgress alleles from other species to improve wood quality and volume. The objective of this research was to evaluate the hybrid potential of elite clones of E. grandis and E. urophylla from the Aracruz Celulose Company S. A. with Eucalyptus globulus clones. To do so, six elite clones were crossed with ten E. globulus clones in a half-diallel mating design. The resulting hybrid combinations as well as the four check clones were evaluated in randomized complete block experiments with single plant plots and 40 replicates from September to October 2001 at three Brazilian sites, Aracruz and São Mateus in the Espírito Santo state and Caravelas in Bahia State. Two years later the circumference at breast height (CBH) and the wood density (WD) were measured. The means were submitted to diallel analysis according to the Griffing method (1956), adapted by Geraldi and Miranda Filho (1988). Although the number of clones involved was small, the crossings of elite clones of E. grandis and E. urophylla with clones of E. globulus were promising, especially for wood quality gains

A note on the stability properties of goodwin's predator-prey model

Goodwin's Predator-Prey model is structurally unstable. In its pure form, the model has an equilibrium that is neither stable nor unstable. Ploeg showed that relaxing the hypothesis of fixed proportion technology would stabilize the equilibrium. On the other hand, Goodwin showed that the equilibrium becomes unstable when endogenous productivity growth is considered. This paper studies the consequences of considering both effects, and concludes that the stabilizing effect of a flexible technology is much stronger than the destabilizing effect of endogenizing labor productivity