8,204 research outputs found
Community structures and role detection in music networks
We analyze the existence of community structures in two different social
networks obtained from similarity and collaborative features between musical
artists. Our analysis reveals some characteristic organizational patterns and
provides information about the driving forces behind the growth of the
networks. In the similarity network, we find a strong correlation between
clusters of artists and musical genres. On the other hand, the collaboration
network shows two different kinds of communities: rather small structures
related to music bands and geographic zones, and much bigger communities built
upon collaborative clusters with a high number of participants related through
the period the artists were active. Finally, we detect the leading artists
inside their corresponding communities and analyze their roles in the network
by looking at a few topological properties of the nodes.Comment: 14 pages 7 figure
The Nature of the Gould Belt from a Fractal Analysis of its Stellar Population
The Gould Belt (GB) is a system of gas and young, bright stars distributed
along a plane that is inclined with respect to the main plane of the Milky Way.
Observational evidence suggests that the GB is our closest star formation
complex, but its true nature and origin remain rather controversial. In this
work we analyze the fractal structure of the stellar component of the GB. In
order to do this, we tailor and apply an algorithm that estimates the fractal
dimension in a precise and accurate way, avoiding both boundary and small data
set problems. We find that early OB stars (of spectral types earlier than B4)
in the GB have a fractal dimension very similar to that of the gas clouds in
our Galaxy. On the contrary, stars in the GB of later spectral types show a
larger fractal dimension, similar to that found for OB stars of both age groups
in the local Galactic disk (LGD). This result seems to indicate that while the
younger OB stars in the GB preserve the memory of the spatial structure of the
cloud where they were born, older stars are distributed following a similar
morphology as that found for the LGD stars. The possible causes for these
differences are discussed.Comment: 20 pages including 7 figures and 1 table. ApJ (in press
Quantum critical behavior of electrons at the edge of charge order
We consider quantum critical points (QCP) in which quantum fluctuations
associated with charge rather than magnetic order induce unconventional
metallic properties. Based on finite-T calculations on a two-dimensional
extended Hubbard model we show how the coherence scale T* characteristic of
Fermi liquid behavior of the homogeneous metal vanishes at the onset of charge
order. A strong effective mass enhancement reminiscent of heavy fermion
behavior indicates the possible destruction of quasiparticles at the QCP.
Experimental probes on quarter-filled layered organic materials are proposed
for unveiling the behavior of electrons across the quantum critical region.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let
Thorpe method applied to planetary boundary layer data
Turbulence affects the dynamics of atmospheric processes by enhancing the transport of mass, heat, humidity and pollutants. The global objective of our work is to analyze some direct turbulent descriptors which reflect the mixing
processes in the atmospheric boundary layer (ABL). In this paper we present results related to the Thorpe displacements dT , the maximum Thorpe displacement (dT )max and the Thorpe scale LT , the Ozmidov scale and their time evolution in the ABL during a day cycle. A tethered balloon was used to obtain vertical profiles of the atmospheric physical magnitudes up to 1000m. We discuss the vertical
and horizontal variability and how different descriptors are related to atmospheric mixing
OB Stars in the Solar Neighborhood I: Analysis of their Spatial Distribution
We present a newly-developed, three-dimensional spatial classification
method, designed to analyze the spatial distribution of early type stars within
the 1 kpc sphere around the Sun. We propose a distribution model formed by two
intersecting disks -the Gould Belt (GB) and the Local Galactic Disk (LGD)-
defined by their fundamental geometric parameters. Then, using a sample of
about 550 stars of spectral types earlier than B6 and luminosity classes
between III and V, with precise photometric distances of less than 1 kpc, we
estimate for some spectral groups the parameters of our model, as well as
single membership probabilities of GB and LGD stars, thus drawing a picture of
the spatial distribution of young stars in the vicinity of the Sun.Comment: 28 pages including 9 Postscript figures, one of them in color.
Accepted for publication in The Astronomical Journal, 30 January 200
Trypanosoma brucei gambiense in domestic livestock of Kogo and Mbini foci (Equatorial Guinea).
OBJECTIVE: To evaluate Trypanosoma brucei gambiense infection in peri-domestic livestock from Kogo and Mbini foci (Equatorial Guinea) in order to investigate its possible implication in the sleeping sickness transmission cycle in these hypoendemic foci. METHODS: Samples from 698 domestic animals (goats, sheep and pigs) from trypanosomiasis-endemic localities of Kogo and Mbini foci were tested for animal trypanosomes and T. b. gambiense (group I) by species-specific polymerase chain reaction. RESULTS: Trypanosoma brucei s.l., the predominant trypanosome species, was detected in 182 (52.6%) samples from Mbini and in 127 (36.1%) samples from Kogo. T. b. gambiense was only identified in seven (2%) of the Mbini samples and one co-infection (with T. vivax) was observed. CONCLUSION: The occurrence of T. b. gambiense in peri-domestic livestock in Mbini and its absence in Kogo could explain the epidemiological differences between the two foci and could have significant implications for sleeping sickness control in Equatorial Guinea
Intonation in unaccompanied singing: Accuracy, drift, and a model of reference pitch memory
Copyright 2014 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.
The following article appeared in J. Acoust. Soc. Am. 136, 401 (2014) and may be found at http://dx.doi.org/10.1121/1.4881915
The contribution of 211 particles to the mechanical reinforcement mechanism of 123 superconducting single domains
Hardness and fracture toughness of Dy-123 single-domains were studied by
Vickers micro-indentation. A significant anisotropy of the mechanical
properties was observed. Hardness tests give higher values when performed in
(001) planes rather than in planes parallel to the c-axis. Moreover cracks
pattern around the indentation follows preferential orientation in planes
parallel to the c-axis whereas a classical ''four-cracks'' pattern is observed
in the (001) planes. It has been possible to show the crucial role played by
the 211-particles in the deviating mechanism of cracks and the relevance of the
211-particle distribution high homogeneity in the material.Comment: 14 pages, including 5 figures and 1 Table. submitted to Supercond.
Sci. Techno
An experimental model of mixing processes generated by an array of top-heavy turbulent plumes
The mixing process of two fluids of unequal density generated by the evolution of an array of forced turbulent plumes is studied in the laboratory. The corresponding qualitative conclusions and the quantitative results based on measures of the density field and of the height of the fluid layers are described. The partial mixing process is characterized and analyzed, and the conclusions of this analysis are related to the mixing efficiency and the volume of the final mixed layer as functions of the Atwood number, which ranges from 0.010 to 0.134. An exponential fit is used to evaluate the mixing efficiency versus the Atwood showing the role of initial conditions on mixing efficiency variability
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