The occurrence of unpigmented mature oocytes in Hypsiboas (Anura: Hylidae)

The genus Hypsiboas is composed of 90 species distributed in Central and South America from Nicaragua to Argentina, as well as on Trinidad and Tobago (Frost 2014). Previous studies on the reproductive biology of species in this genus have reported that female mature oocytes or eggs generally have pigmented animal poles (Tab. 1), which has been generally suggested as a protection of the exposed embryos from solar radiation (Wells 2007).Fil: Nali, Renato C.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Faivovich, Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Prado, Cynthia P. A.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi

The Network of Epicenters of the Olami-Feder-Christensen Model of Earthquakes

We study the dynamics of the Olami-Feder-Christensen (OFC) model of earthquakes, focusing on the behavior of sequences of epicenters regarded as a growing complex network. Besides making a detailed and quantitative study of the effects of the borders (the occurrence of epicenters is dominated by a strong border effect which does not scale with system size), we examine the degree distribution and the degree correlation of the graph. We detect sharp differences between the conservative and nonconservative regimes of the model. Removing border effects, the conservative regime exhibits a Poisson-like degree statistics and is uncorrelated, while the nonconservative has a broad power-law-like distribution of degrees (if the smallest events are ignored), which reproduces the observed behavior of real earthquakes. In this regime the graph has also a unusually strong degree correlation among the vertices with higher degree, which is the result of the existence of temporary attractors for the dynamics: as the system evolves, the epicenters concentrate increasingly on fewer sites, exhibiting strong synchronization, but eventually spread again over the lattice after a series of sufficiently large earthquakes. We propose an analytical description of the dynamics of this growing network, considering a Markov process network with hidden variables, which is able to account for the mentioned properties.Comment: 9 pages, 10 figures. Smaller number of figures, and minor text corrections and modifications. For version with full resolution images see http://fig.if.usp.br/~tpeixoto/cond-mat-0602244.pd

Stochastic stabilization of cosmological photons

The stability of photon trajectories in models of the Universe that have constant spatial curvature is determined by the sign of the curvature: they are exponentially unstable if the curvature is negative and stable if it is positive or zero. We demonstrate that random fluctuations in the curvature provide an additional stabilizing mechanism. This mechanism is analogous to the one responsible for stabilizing the stochastic Kapitsa pendulum. When the mean curvature is negative it is capable of stabilizing the photon trajectories; when the mean curvature is zero or positive it determines the characteristic frequency with which neighbouring trajectories oscillate about each other. In constant negative curvature models of the Universe that have compact topology, exponential instability implies chaos (e.g. mixing) in the photon dynamics. We discuss some consequences of stochastic stabilization in this context.Comment: 4 pages, 3 postscript figures in color which are also appropriate for black and white printers; v2 emphasizes relevance to flat as well as negatively curved cosmologies; to appear in J. Phys.

High-temperature phase transitions in SrBi_2Ta_2O_9 film: a study by THz spectroscopy

Time-domain THz transmission experiment was performed on a $\rm SrBi_2Ta_2O_9$ film deposited on sapphire substrate. Temperatures between 300 and 923 K were investigated and complex permittivity spectra of the film were determined. The lowest frequency optic phonon near 28 cm$^{-1}$ reveals a slow monotonic decrease in frequency on heating with no significant anomaly near the phase transitions. We show that the dielectric anomaly near the ferroelectric phase transition can be explained by slowing down of a relaxational mode, observed in the THz spectra. A second harmonic generation signal observed in a single crystal confirms a loss of center of symmetry in the ferroelectric phase and a presence of polar clusters in the intermediate ferroelastic phase.Comment: subm. to J. Phys.: Condens. Matte

Características físicas e químicas da madeira de Acrocarpus fraxinifolius Wight & Arn.

Foram comparadas algumas características da madeira de seis procedências de Acrocarpus fraxinifolius aos oito anos de idade. As procedências foram: África do Sul, Mugerê Urundi, Kenya Nairobi, Kenya Gachoila, Ruanda Butar e uma procedência nacional, como testemunha. Observaram-se diferenças significativas, entre as procedências, na composição química e nas dimensões das fibras. Para a densidade básica e para o poder calorífico tais diferenças não foram significativas. A madeira dessa espécie é leve, com baixos coeficientes de retratibilidade total, fibras curtas, alto teor de extrativos totais e baixo teor de lignina.bitstream/item/119092/1/digitalizar0023.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

Herpetofauna, municipality of Porto Murtinho, Chaco region, state of Mato Grosso do Sul, Brazil

Among the physiographic regions included in the central South American diagonal of open formations,the Chaco, with some endemic species, represents the southernmost dry area. In Brazil, the Chaco is foundin southwestern corner of Mato Grosso do Sul state, mostly in the municipality of Porto Murtinho along theParaguay and Apa rivers. From February 2008 to December 2009, we carried out an inventory of amphibiansand reptiles in Porto Murtinho, using pitfall traps, time-limited searches, and occasional encounters. A total of34 amphibian and 39 reptile species were registered. Although some typical Chacoan species were found, mostof the species are open area dwellers that also occur in other open biomes, such as the Cerrado and Caatinga

Infinite pointwise lineability: general criteria and applications

In this paper we introduce the concept of infinite pointwise dense lineability (spaceability), and provide a criterion to obtain density from mere lineability. As an application, we study the linear and topological structures within the set of infinite differentiable and integrable functions, for any order $p \geq 1$, on $\mathbb{R}^N$ which are unbounded in a prefixed set