Variation in liana abundance and biomass along an elevational gradient in the tropical Atlantic Forest (Brazil)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Seed dispersal and predation in the endemic Atlantic rainforest palm Astrocaryum aculeatissimum across a gradient of seed disperser abundance

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Changes in ichthyofauna composition along a gradient from clearwaters to blackwaters in coastal streams of Atlantic forest (southeastern Brazil) in relation to environmental variables

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Calculation of the vacuum pressure gradient in field emission displays

The usual design of field-emission displays (FEDs) often results in high vacuum pressure gradients inside the glass plates of the device, and this is the main limitation to the widespread availability of large area FEDs. In this paper, we perform theoretical calculations using the finite element method for determining the pressure distributions in several pumping configurations, including a new FED configuration known as porous FED or pFED. The approach here is capable of clarifying the design issues influencing the final pressure relevant to the field-emission display devices. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Characterization of generalized Bessel polynomials in terms of polynomial inequalities

Generalized Bessel polynomials (GBPs) are characterized as the extremal polynomials in certain inequalities in L-2 norm of Markov type. (C) 1998 Academic Press.

NONDEGENERATE UMBILICS, THE PATH FORMULATION and GRADIENT BIFURCATION PROBLEMS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fish community structure along a conservation gradient in Bodoquena Plateau streams, central West of Brazil.

Aim: To investigate whether composition and structure of stream ichthyofauna vary along the conservation gradient in the Bodoquena Plateau; Methods: Standardized sampling was performed in nine stream stretches (three references, three in the pasture, and three in urban areas), each 80 m long, in April, May and June/08; Results: A quantity of 8,102 individuals representing 36 species was collected. There were no significant differences with respect to absolute species richness among stretches. Urban stretches were more similar to each other than the other two groups, both regarding species composition and abundance. A set of six species was considered an indicator of reference stretches, whereas two were of pasture stretches and four of urban stretches. Poecilia reticulata and Corydoras aeneus, occurring only in urban stretches, were unique in showing the maximum values in the indicator species analysis; Conclusions: Results indicate changes in the ichthyofauna with urbanized surrounding water courses. The presence and abundance of Poecilia reticulata and Corydoras aeneus may indicate the quality loss of these environments.

On the symplectic two-form of gravity in terms of Dirac eigenvalues

The Dirac eigenvalues form a subset of observables of the Euclidean gravity. The symplectic two-form in the covariant phase space could be expressed, in principle, in terms of the Dirac eigenvalues. We discuss the existence of the formal solution of the equations defining the components of the symplectic form in this framework. (C) 2002 Published by Elsevier B.V. B.V.

Unavoidable conflict between massive gravity models and massive topological terms

Massive gravity models in (2 + 1) dimensions, such as those obtained by adding to Einstein's gravity the usual Fierz-Pauli, or the more complicated Ricci scalar squared (R-2), terms, are tree level unitary. Interesting enough these seemingly harmless systems have their unitarity spoiled when they are augmented by a Chern-Simons term. Furthermore, if the massive topological term is added to R + R-munu(2) gravity, or to R + R-munu(2), + R-2 gravity (higher-derivative gravity), which are nonunitary at the tree level, the resulting models remain nonunitary. Therefore, unlike the common belief, as well as the claims in the literature, the coexistence between three-dimensional massive gravity models and massive topological terms is conflicting.

Exchange terms in the quark-meson coupling model

In this talk we report on recent progress in implementing exchange terms in the quark-meson coupling model. Exchange effects are related to the Pauli exclusion principle. We discuss exchange effects at the nucleon level and at the quark level. We also address the incorporation of chiral symmetry and Delta degrees of freedom in the model.

Ferroelectric fatigue endurance of Bi4-xLaxTi3O12 thin films explained in terms of x-ray photoelectron spectroscopy

The nature of defects in polycrystalline Bi4-xLaxTi3O12 (BLT) thin films with x=0.00, 0.25, 0.50, and 0.75 was evaluated by x-ray photoemission spectroscopy measurements. The influence of oxygen vacancies and substitution of Bi for La atoms were discussed. In the BLT thin films, it was found that the oxygen ions at the metal-oxygen octahedral were much more stable than those at the [Bi2O2] layers. on the other hand, for Bi4Ti3O12 (BIT) thin film, oxygen vacancies could be induced both at the titanium-oxygen octahedral and at the [Bi2O2] layers. The oxygen-vacancy defect pairs determined in BIT and Bi3.75La0.25Ti3O12 (BLT025) can pin the polarization of surrounding lattices leading to fatigue of capacitors. Meanwhile, the concentration of similar defect pairs is relatively low in heavily doped BIT films and then good fatigue resistance is observed.

Nanoscale electromechanical properties of CaCu3Ti4O12 ceramics

Piezoresponse Force Microscopy (PFM) is used to characterize the nanoscale electromechanical properties of centrosymmetric CaCu3Ti4O12 ceramics with giant dielectric constant. Clear PFM contrast both in vertical (out-of-plane) and lateral (in-plane) modes is observed on the ceramic surface with varying magnitude and polarization direction depending on the grain crystalline orientation. Lateral signal changes its sign upon 180 degrees rotation of the sample thus ruling out spurious electrostatic contribution and confirming piezoelectric nature of the effect. Piezoresponse could be locally reversed by suitable electrical bias (local poling) and induced polarization was quite stable showing long-time relaxation (similar to 3 hrs). The electromechanical contrast in unpoled ceramics is attributed to the surface flexoelectric effect (strain gradient induced polarization) while piezoresponse hysteresis and ferroelectric-like behavior are discussed in terms of structural instabilities due to Ti off-center displacements and structural defects in this material. (C) 2011 American Institute of Physics. [doi:10.1063/1.3623767]

An adapted thermal-gradient block for the germination of photoblastic seeds

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Water at interfaces and its influence on the electrical properties of adsorbed films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)