31,660 research outputs found
Seven new species of the killifish genus Rivulus (Cyprinodontiformes: Rivulidae) from the Paraná, Paraguay and upperAraguaia river basins, central Brazil
Austrolebias paucisquama (Cyprinodontiformes: Rivulidae), a new species of annual killifish from southern Brazil
Dynamics of Nucleation in the Ising Model
Reactive pathways to nucleation in a three-dimensional Ising model at 60% of
the critical temperature are studied using transition path sampling of single
spin flip Monte Carlo dynamics. Analysis of the transition state ensemble (TSE)
indicates that the critical nuclei are rough and anisotropic. The TSE,
projected onto the free energy surface characterized by cluster size, N, and
surface area, S, indicates the significance of other variables in addition to
these two traditional reaction coordinates for nucleation. The transmission
coefficient along N is ~ 0.35, and this reduction of the transmission
coefficient from unity is explained in terms of the stochastic nature of the
dynamic model.Comment: In press at the Journal of Physical Chemistry B, 7 pages, 8 figure
Rapid spectral and flux time variations in a solar burst observed at various dm-mm wavelengths and at hard X-rays
A solar burst was observed with high sensitivity and time resolution at cm-mm wavelengths by two different radio observatories (Itapetinga and Algonquin), with high spectral time resolution at dm-mm wavelengths by patrol instruments (Sagamore Hill), and at hard X-rays (HXM Hinotori). At the onset of the major burst time structure there was a rapid rise in the spectral turnover frequency (from 5 to 15 GHz), in about 10s, coincident to a reduction of the spectral index in the optically thin part of the spectrum. The burst maxima were not time coincident at the optically thin radio frequencies and at the different hard X-ray energy ranges. The profiles at higher radio frequencies exhibited better time coincidence to the high energy X-rays. The hardest X-ray spectrum (-3) coincided with peak radio emission at the higher frequency (44 GHz). The event appeared to be built up by a first major injection of softer particles followed by other injections of harder particles. Ultrafast time structures were identified as superimposed on the burst emission at the cm-mm high sensitivity data at X-rays, with predominant repetition rates ranging from 2.0 to 3.5 Hz
Suite of simple metrics reveals common movement syndromes across vertebrate taxa
ecause empirical studies of animal movement are most-often site- and species-specific, we lack understanding of the level of consistency in movement patterns across diverse taxa, as well as a framework for quantitatively classifying movement patterns. We aim to address this gap by determining the extent to which statistical signatures of animal movement patterns recur across ecological systems. We assessed a suite of movement metrics derived from GPS trajectories of thirteen marine and terrestrial vertebrate species spanning three taxonomic classes, orders of magnitude in body size, and modes of movement (swimming, flying, walking). Using these metrics, we performed a principal components analysis and cluster analysis to determine if individuals organized into statistically distinct clusters. Finally, to identify and interpret commonalities within clusters, we compared them to computer-simulated idealized movement syndromes representing suites of correlated movement traits observed across taxa (migration, nomadism, territoriality, and central place foraging)
Quantum properties of classical Fisher information
The Fisher information of a quantum observable is shown to be proportional to
both (i) the difference of a quantum and a classical variance, thus providing a
measure of nonclassicality; and (ii) the rate of entropy increase under
Gaussian diffusion, thus providing a measure of robustness. The joint
nonclassicality of position and momentum observables is shown to be
complementary to their joint robustness in an exact sense.Comment: 16 page
Effect of interchain coupling on conducting polymer luminescence: excimers in derivatives of poly(phenylene vinylene)
Optical excitation of a chain in a polymer film may result in formation of an
excimer, a superposition of on-chain excitons and charge-transfer excitons on
the originally excited chain and a neighboring chain. The excimer emission is
red-shifted compared to that of an on-chain exciton by an amount depending on
the interchain coupling . Setting up the excimer wavefunction and
calculating the red shift, we determine average values, referred to a
monomer, of 0.52 eV and 0.16 eV for poly(2,5-hexyloxy -phenylene
cyanovinylene), CN-PPV, and poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1, 4
p-phenylene vinylene], MEH-PPV, respectively, and use them to determine the
effect of interchain distance on the emission.Comment: 10 pages, RevTeX, 1 PS figure, replaced version of cond-mat/9707095,
accepted for publication in Phys. Rev. B, Rapid Communicatio
Descriptive morphology and phylogenetic relationships among species of the Neotropical annual killifish genera Nematolebias and Simpsonichthys (Cyprinodontiformes: Aplocheiloidei: Rivulidae)
Response of the Brazilian gravitational wave detector to signals from a black hole ringdown
It is assumed that a black hole can be disturbed in such a way that a
ringdown gravitational wave would be generated. This ringdown waveform is well
understood and is modelled as an exponentially damped sinusoid. In this work we
use this kind of waveform to study the performance of the SCHENBERG
gravitational wave detector. This first realistic simulation will help us to
develop strategies for the signal analysis of this Brazilian detector. We
calculated the signal-to-noise ratio as a function of frequency for the
simulated signals and obtained results that show that SCHENBERG is expected to
be sensitive enough to detect this kind of signal up to a distance of .Comment: 5 pages, 4 figures, Amaldi 5 Conference Proceedings contribution.
Submitted to Class. Quantum Gra
Discovery of endangered annual killifish Austrolebias cheradophilus (Aplocheiloidei: Rivulidae) in Brazil, with comments on habitat, population structure and conservation status
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