An Observational Test of Two-field Inflation

We study adiabatic and isocurvature perturbation spectra produced by a period of cosmological inflation driven by two scalar fields. We show that there exists a model-independent consistency condition for all two-field models of slow-roll inflation, despite allowing for model-dependent linear processing of curvature and isocurvature perturbations during and after inflation on super-horizon scales. The scale-dependence of all spectra are determined solely in terms of slow-roll parameters during inflation and the dimensionless cross-correlation between curvature and isocurvature perturbations. We present additional model-dependent consistency relations that may be derived in specific two-field models, such as the curvaton scenario.Comment: 6 pages, latex with revtex, no figures; v2, minor changes, to appear in Physical Review

A new approach to cosmological perturbations in f(R) models

We propose an analytic procedure that allows to determine quantitatively the deviation in the behavior of cosmological perturbations between a given f(R) modified gravity model and a LCDM reference model. Our method allows to study structure formation in these models from the largest scales, of the order of the Hubble horizon, down to scales deeply inside the Hubble radius, without employing the so-called "quasi-static" approximation. Although we restrict our analysis here to linear perturbations, our technique is completely general and can be extended to any perturbative order.Comment: 21 pages, 2 figures; Revised version according to reviewer's suggestions; Typos corrected; Added Reference

Tracking Extended Quintessence

We study the cosmological role of a Tracking Field $\phi$ in Extended Quintessence scenarios (TEQ), where the dynamical vacuum energy driving the acceleration of the universe today is coupled with the Ricci scalar, $R$, with a term of the form $F(\phi)R/2$, where $F(\phi) = 1/8\pi G+\xi(\phi^{2}-\phi_{0}^{2})$. Tracker solutions for these NMC models, with inverse power-law potentials, possess an initial enhancement of the scalar field dynamics, named $R$-boost, caused by the Ricci scalar in the Klein-Gordon equation. During this phase the field performs a "gravitational" slow rolling which we model analytically, with energy density scaling as $(1+z)^{2}$. We evolve linear perturbations in TEQ models assuming Gaussian scale-invariant initial spectrum. We obtain significant changes in the Integrated Sachs Wolfe effect and in the acoustic peaks locations on the Cosmic Microwave Background, as well as in the turnover on the matter power spectrum. All these corrections may assume positive as well as negative values, depending on the sign of the NMC parameter $\xi$. We give analytical formulas describing all these effects. We show that they can be as large as $10 - 30$ with respect to equivalent cosmological constant and ordinary tracking Quintessence models, respecting all the existing experimental constraints on scalar-tensor theories of gravity. These results demonstrate that the next decade data will provide deep constraints on the nature of the dark energy in the Universe, as well as the structure of the theory of gravity.Comment: 24 pages including 8 figures, final version to be published in Phys.Rev.

Diet of two syntopic species of Crenuchidae (Ostariophysi: Characiformes) in an Amazonian rocky stream

Abstract This study assessed the diet of two poorly known syntopic fish species of the family Crenuchidae, Characidium aff. declivirostre and Leptocharacidium omospilus, in a Presidente Figueiredo´ rocky stream, Amazonas, Brazil. The stomach contents were analyzed and their Frequency of Occurrence (FO %) and Relative Volume (Vol %) were combined in a Feeding Index (IAi). We examined 20 individuals of C. aff. declivirostre and 23 of L. omospilus. The Morisita-Horn Index was used to estimate the overlap between the diets of these species. Immature insects were the most valuable items consumed by both fish species. The diet of C. aff. declivirostre was mainly composed of larvae and pupae of Chironomidae, while L. omospilus predominantly consumed larvae of Hydroptilidae, Hydropyschidae and Pyralidae. Thus, both species were classified as autochthonous insectivorous. Characidium aff. declivirostre was considered a more specialized species, probably reflecting lower feeding plasticity or the use of more restricted microhabitats compared to L. omospilus. When the food items were analyzed at the family taxonomic level, the diet overlap between these species was considered moderate (Morisita-Horn Index = 0.4). However, a more thorough analysis, at the genus level, indicates a very low diet overlap. Therefore, we conclude that the feeding segregation between C. aff. declivirostre and L. omospilus may favor their co-existence, despite their high phylogenetic closeness

Estudos sobre a nutrição mineral do arroz: XI. Marcha de absorção de micronutrientes pela variedade IAC-47

Dry matter yield and uptake of B, Cu, Fe, Mn and Zn by the rice variety IAC-47 were studied under controlled conditions, namely, by growing plants in nutrient solution and by falcing samples for analyses in set physiological periods. It was observed that only the curves describing dry matter production and accumulation of B and Fe was verified.A produção de matéria seca e a absorção de micronutrientes (B, Cu, Fe, Mn e Zn) pelo arroz var. IAC-47 foram estudadas usando-se plantas cultivadas em solução nutritiva. Verificou-se que: enquanto as curvas que descrevem o crescimento e a acumulação de B e Fe mostram tendência sigmóide, as demais não o fazem, evidência de redistribuição foi observada somente nos casos do B (diminuição no conteúdo foliar) e no do Fe (diminuição no conteúdo da raiz)

Estudos sobre a nutrição mineral do arroz: VII. exigências nutricionais das variedades IAC-25 e IAC-47

Rice plants, varieties IAC 25 and IAC 47, were grown in nutrient solution till the end of the life cycle when they were analysed both for macro and micronutrients. Main conclusions were the following: IAC 47, higher yielding, showed larger requirements than IAC 25; for production (total) and export (grain), the demand for nutrients was the same in both varieties.As exigências nutricionais das variedades de arroz IAC 25 e IAC 47 foram determinadas analisando-se os diferentes órgãos de plantas cultivadas em solução nutritiva até o fim do ciclo. Verificou-se serem distintas as exigências, maior na IAC 47 (mais tardia) que deu também maior produção de grãos com casca

Studies on the mineral nutrition of the rice plant: IX. time course on the uptake of macronutrients by the variety IAC-47

Rice plants, variety IAC-47, were grown in the nº 2 nutrient solution of HOAGLAND & ARNON (1950) until the end of the life cycle. Plants were sampled at well defined physiological periods for analyses. It was verified that trends for levvelling off occurred in the case of accumulation of N, K and Ca. Translocation from leaves to grain was observed with respect to N, P and K. Maximum rates of uptake of all elements took place from 50 to 100 days after germination.Foram estudadas, em condições controladas, a acumulação de matéria seca e a de macronutrientes na variedade de arroz IAC-47. Ambos os processos em geral são descritos por sigmóides típicas; picos para os valores totais de produção de matéria seca e de acumulação de elementos entre: 100 e 140 dias depois da germinação

Estudos sobre a nutrição mineral do arroz: XIII. efeitos das deficiências de micronutrientes nas variedades IAC-25 e IAC-47

Rice plants were grown in nutrient solution lither in the presence or in the absence of B, Cu and Zn. The symptoms of deficiency were usually in agreement with those described in the literature. Growth of the variety IAC-47 (number of leaves, tillering and total dry matter) was relatively more affected; this variety, however did produce grains under the minus Cu treatment (one fourth of the yield observed in the "complete" treatment), which did not happen in the case of the other variety. At the beginning of the grain filling period the following leaf contents could be considered as indication of deficiency: B-13 to 25 ppm; Zn-20 ppm; no conclusion could be drawn with respect to Cu levels.Plantas de arroz, variedades IAC-25 e IAC-47 foram cultivadas em solução nutritiva e com deficiência de B, Cu e Zn. Foram obtidos sintomas de carência dos três micronutrientes. As deficiências induzidas provocaram diminuição na matéria seca total e no número de folhas das duas variedades. O mesmo ocorreu no numero de perfilhos da var. IAC-47. Foi feita a determinação dos teores dos micronutrientes nas plantas submetidas aos diferentes tratamentos o que forneceu dados que ajudam a avaliação do estado nutricional