10,602 research outputs found
Capim-elefante como biomassa para produção de energia.
bitstream/item/142629/1/capim-elefante-biomassa-energia.pd
An extended formalism for preferential attachment in heterogeneous complex networks
In this paper we present a framework for the extension of the preferential
attachment (PA) model to heterogeneous complex networks. We define a class of
heterogeneous PA models, where node properties are described by fixed states in
an arbitrary metric space, and introduce an affinity function that biases the
attachment probabilities of links. We perform an analytical study of the
stationary degree distributions in heterogeneous PA networks. We show that
their degree densities exhibit a richer scaling behavior than their homogeneous
counterparts, and that the power law scaling in the degree distribution is
robust in presence of heterogeneity
Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305
Integral field optical spectroscopy with the INTEGRAL fiber-fed system and
HST optical imaging are used to map the complex stellar and warm ionized gas
structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images
reconstructed from wavelength-delimited extractions of the integral field
spectra reveal that the observed ionized gas distribution is decoupled from the
stellar main body of the galaxy, with the dominant continuum and emission-line
regions separated by projected distances of up to 7.5 kpc. The two optical
nuclei are detected as apparently faint emission-line regions, and their
optical properties are consistent with being dust-enshrouded weak-[OI] LINERs.
The brightest emission-line region is associated with a faint (m_{I}= 20.4),
giant HII region of 600 pc diameter, where a young (about 5 Myr) massive
cluster of about 2 10 dominates the ionization.
Internal reddening towards the line-emitting regions and the optical nuclei
ranges from 1 to 8 magnitudes, in the visual. Taken the reddening into aacount,
the overall star formation in IRAS 12112+0305 is dominated by starbursts
associated with the two nuclei and corresponding to a star formation rate of 80
yr.Comment: 2 figures, accepted to Ap.J. Letter
The internal rotation profile of the B-type star KIC10526294 from frequency inversion of its dipole gravity modes and statistical model comparison
The internal angular momentum distribution of a star is key to determine its
evolution. Fortunately, the stellar internal rotation can be probed through
studies of rotationally-split non-radial oscillation modes. In particular,
detection of non-radial gravity modes (g modes) in massive young stars has
become feasible recently thanks to the Kepler space mission. Our aim is to
derive the internal rotation profile of the Kepler B8V star KIC 10526294
through asteroseismology. We interpret the observed rotational splittings of
its dipole g modes using four different approaches based on the best seismic
models of the star and their rotational kernels. We show that these kernels can
resolve differential rotation the radiative envelope if a smooth rotational
profile is assumed and the observational errors are small. Based on Kepler
data, we find that the rotation rate near the core-envelope boundary is well
constrained to nHz. The seismic data are consistent with rigid
rotation but a profile with counter-rotation within the envelope has a
statistical advantage over constant rotation. Our study should be repeated for
other massive stars with a variety of stellar parameters in order to deduce the
physical conditions that determine the internal rotation profile of young
massive stars, with the aim to improve the input physics of their models.Comment: 52 pages, 32 figures, accepted for publication in The Astrophysical
Journa
An Analytic Equation of State for Ising-like Models
Using an Environmentally Friendly Renormalization we derive, from an
underlying field theory representation, a formal expression for the equation of
state, , that exhibits all desired asymptotic and analyticity
properties in the three limits , and . The only
necessary inputs are the Wilson functions , and
, associated with a renormalization of the transverse vertex
functions. These Wilson functions exhibit a crossover between the Wilson-Fisher
fixed point and the fixed point that controls the coexistence curve.
Restricting to the case N=1, we derive a one-loop equation of state for naturally parameterized by a ratio of non-linear scaling fields. For
we show that a non-parameterized analytic form can be deduced. Various
asymptotic amplitudes are calculated directly from the equation of state in all
three asymptotic limits of interest and comparison made with known results. By
positing a scaling form for the equation of state inspired by the one-loop
result, but adjusted to fit the known values of the critical exponents, we
obtain better agreement with known asymptotic amplitudes.Comment: 10 pages, 2 figure
The Gribov horizon and the one-loop color-Coulomb potential
We recalculate the color-Coulomb potential to one-loop order, under the
assumption that the effect of the Gribov horizon is to make i) the transverse
gluon propagator less singular; and ii) the color-Coulomb potential more
singular, than their perturbative behavior in the low-momentum limit. As a
first guess, the effect of the Gribov horizon is mimicked by introducing a
transverse momentum-dependent gluon mass term, leading to a propagator of the
Gribov form, with the prescription that the mass parameter should be adjusted
to the unique value where the infrared behavior of the Coulomb potential is
enhanced. We find that this procedure leads to a Coulomb potential rising
asymptotically as a linear term modified by a logarithm.Comment: 15 pages, 2 figure
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