22,697 research outputs found
Classical Bianchi type I cosmology in K-essence theory
We use one of the simplest forms of the K-essence theory and we apply it to
the classical anisotropic Bianchi type I cosmological model, with a barotropic
perfect fluid modeling the usual matter content and with cosmological constant.
The classical solutions for any but the stiff fluid and without cosmological
constant are found in closed form, using a time transformation. We also present
the solution whith cosmological constant and some particular values of the
barotropic parameter. We present the possible isotropization of the
cosmological model, using the ratio between the anisotropic parameters and the
volume of the universe and show that this tend to a constant or to zero for
different cases. We include also a qualitative analysis of the analog of the
Friedmann equation.Comment: 15 pages with one figure, accepted in Advances in High Energy Physic
Criteria for Bayesian model choice with application to variable selection
In objective Bayesian model selection, no single criterion has emerged as
dominant in defining objective prior distributions. Indeed, many criteria have
been separately proposed and utilized to propose differing prior choices. We
first formalize the most general and compelling of the various criteria that
have been suggested, together with a new criterion. We then illustrate the
potential of these criteria in determining objective model selection priors by
considering their application to the problem of variable selection in normal
linear models. This results in a new model selection objective prior with a
number of compelling properties.Comment: Published in at http://dx.doi.org/10.1214/12-AOS1013 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
X-ray spectral variability of seven LINER nuclei with XMM-Newton and Chandra data
One of the most important features in active galactic nuclei (AGN) is the
variability of their emission. Variability has been discovered at X-ray, UV,
and radio frequencies on time scales from hours to years. Among the AGN family
and according to theoretical studies, Low-Ionization Nuclear Emission Line
Region (LINER) nuclei would be variable objects on long time scales. Our
purpose is to investigate spectral X-ray variability in LINERs and to
understand the nature of these kinds of objects, as well as their accretion
mechanism. Chandra and XMM-Newton public archives were used to compile X-ray
spectra of seven LINER nuclei at different epochs with time scales of years. To
search for variability we fit all the spectra from the same object with a set
of models, in order to identify the parameters responsible for the variability
pattern. We also analyzed the light curves in order to search for short time
scale (from hours to days) variability. Whenever possible, UV variability was
also studied. We found spectral variability in four objects, with variations
mostly related to hard energies (2-10 keV). These variations are due to changes
in the soft excess, and/or changes in the absorber, and/or intrinsic variations
of the source. Another two galaxies seem not to vary. Short time scale
variations during individual observations were not found. Our analysis confirms
the previously reported anticorrelation between the X-ray spectral index and
the Eddington ratio, and also the correlation between the X-ray to UV flux
ratio and the Eddington ratio. These results support an Advection Dominated
Accretion Flow (ADAF) as the accretion mechanism in LINERs.Comment: 35 pages, 53 figures, recently accepted pape
X-ray spectral variability of Seyfert 2 galaxies
Variability across the electromagnetic spectrum is a property of AGN that can
help constraining the physical properties of these galaxies. This is the third
of a serie of papers with the aim of studying the X-ray variability of
different families of AGN. The main purpose of this work is to investigate the
variability pattern in a sample of optically selected type 2 Seyfert galaxies.
We use the 26 Seyferts in the Veron-Cetty and Veron catalogue with data
available from Chandra and/or XMM-Newton public archives at different epochs,
with timescales ranging from a few hours to years. All the spectra of the same
source are simultaneously fitted and we let different parameters to vary in the
model. Whenever possible, short-term variations and/or long-term UV flux
variations are studied. We divide the sample in Compton-thick, Compton-thin,
and changing-look candidates. Short-term variability at X-rays is not found.
From the 25 analyzed sources, 11 show long-term variations; eight (out of 11)
are Compton-thin, one (out of 12) is Compton-thick, and the two changing-look
candidates are also variable. The main driver for the X-ray changes is related
to the nuclear power (nine cases), while variations at soft energies or related
with absorbers at hard X-rays are less common, and in many cases these
variations are accompained with variations of the nuclear continuum. At UV
frequencies nuclear variations are nor found. We report for the first time two
changing-look candidates, MARK273 and NGC7319. A constant reflection component
located far away from the nucleus plus a variable nuclear continuum are able to
explain most of our results; the Compton-thick candidates are dominated by
reflection, which supresses their continuum making them seem fainter, and not
showing variations, while the Compton-thin and changing-look candidates show
variations.Comment: Accepted for publication in A&
X-ray spectral variability of LINERs selected from the Palomar sample
Variability is a general property of active galactic nuclei (AGN). At X-rays,
the way in which these changes occur is not yet clear. In the particular case
of low ionisation nuclear emission line region (LINER) nuclei, variations on
months/years timescales have been found for some objects, but the main driver
of these changes is still an open question. The main purpose of this work is to
investigate the X-ray variability in LINERs, including the main driver of such
variations, and to search for eventual differences between type 1 and 2
objects. We use the 18 LINERs in the Palomar sample with data retrieved from
Chandra and/or XMM-Newton archives corresponding to observations gathered at
different epochs. All the spectra for the same object are simultaneously fitted
in order to study long term variations. The nature of the variability patterns
are studied allowing different parameters to vary during the spectral fit.
Whenever possible, short term variations from the analysis of the light curves
and UV variability are studied.Comment: 49 pages, accepted. arXiv admin note: text overlap with
arXiv:1305.222
Background and approach to a definition of smart buildings
There is no possibility of finding a single reference about domotics in the first half of the 20th century. The best known authors and those who have documented this discipline, set its origin in the 1970’s, when the x-10 technology began to be used, but it was not until 1988 when Larousse Encyclopedia decided to include the definition of "Smart Building". Furthermore, even nowadays, there is not a single definition widely accepted, and for that reason, many other expressions, namely "Intelligent Buildings" "Domotics" "Digital Home" or "Home Automation" have appeared to describe the automated buildings and homes. The lack of a clear definition for "Smart Buildings" causes difficulty not only in the development of a common international framework to develop research in this field, but it also causes insecurity in the potential user of these buildings. Thus, the main purpose of this paper is to propose a definition of the expression “Smart Buildings” that satisfactorily describes the meaning of this discipline. To achieve this aim, a thorough review of the origin of the term itself and the historical background before the emergence of the phenomenon of domotics was conducted, followed by a critical discussion of existing definitions of the term "Smart Buildings" and other similar terms. The extent of each definition has been analyzed, inaccuracies have been discarded and commonalities have been compared. Throughout the discussion, definitions that bring the term "Smart Buildings" near to disciplines such as computer science, robotics and also telecommunications have been found
Effect of cage density on growth and carcass performance of fattening rabbits under tropical heat stress conditions
[EN] Three hundred crossbred New Zealand, California, Butterfl y, Dutch, and Satin rabbits, weaned at 30 d and weighing 535±8 g (standard error) were assigned randomly to four treatments: 6, 12, 18 and 24 rabbits/m2 (3, 6, 9 and 12 rabbits/cage, respectively, each cage measuring 0.5 m2) resulting in 10 cages/treatment. During the experimental period (from weaning to 2.2 kg body weight) weekly individual live weight, cage feed intake, incidence of diarrhoea, ringworm, and injured rabbit data was recorded. The maximum temperature-humidity index ranged from 31 to 35, and so indicating severe heat stress. At the end of the experimental period 10, 20, 30 and 30 rabbits under densities of 6, 12, 18 and 24 rabbits/m2, respectively, were slaughtered and carcass performance recorded. Average daily gain and feed intake from weaning to the end of the experimental period decreased by 0.31±0.070 and 1.20±0.25 g, respectively, for each unit that the density increased at the beginning of the experiment (P=0.001). The length of the fattening period increased by 0.91±0.16 d (P=0.001) for each unit of increment of density. However, rabbit production (expressed in kg/m2) increased linearly and quadratically with density (P<0.008). Cage density did not affect feed effi ciency, which on average was 0.214 g/g (P=0.37). Animals housed at the highest density, compared to the average of those caged at lower densities, tended to show higher incidence of ringworm (68.9 vs 39.4%; P=0.075) and injury (16.8 vs 3.03%; P=0.12), and showed higher mortality (20.5 vs 9.63%; P=0.043). Density did not alter the dressing out percentage nor chilled carcass weight. The proportion of scapular fat (P=0.042) increased linearly with increasing levels of density, but perirrenal fat was unaffected (P=0.22). Increasing density reduced dorsal length linearly (P=0.001), and reduced drip loss percentage linearly and quadratically (P=0.097 and 0.018, respectively).Based on these results, under our heat stress conditions, avoiding densities higher than 18 rabbits/m2 or 34 kg/m2 at the end of fattening is recommended.Villalobos, O.; GuillĂ©n, O.; GarcĂa J., J. (2010). Effect of cage density on growth and carcass performance of fattening rabbits under tropical heat stress conditions. World Rabbit Science. 16(2). doi:10.4995/wrs.2008.63116
Semi-Supervised Deep Learning for Fully Convolutional Networks
Deep learning usually requires large amounts of labeled training data, but
annotating data is costly and tedious. The framework of semi-supervised
learning provides the means to use both labeled data and arbitrary amounts of
unlabeled data for training. Recently, semi-supervised deep learning has been
intensively studied for standard CNN architectures. However, Fully
Convolutional Networks (FCNs) set the state-of-the-art for many image
segmentation tasks. To the best of our knowledge, there is no existing
semi-supervised learning method for such FCNs yet. We lift the concept of
auxiliary manifold embedding for semi-supervised learning to FCNs with the help
of Random Feature Embedding. In our experiments on the challenging task of MS
Lesion Segmentation, we leverage the proposed framework for the purpose of
domain adaptation and report substantial improvements over the baseline model.Comment: 9 pages, 6 figure
Cosmological Bianchi Class A models in S\'aez-Ballester theory
We use the S\'aez-Ballester (SB) theory on anisotropic Bianchi Class A
cosmological model, with barotropic fluid and cosmological constant, using the
Hamilton or Hamilton-Jacobi approach. Contrary to claims in the specialized
literature, it is shown that the S\'aez-Ballester theory cannot provide a
realistic solution to the dark matter problem of Cosmology for the dust epoch,
without a fine tunning because the contribution of the scalar field in this
theory is equivalent to a stiff fluid (as can be seen from the energy--momentum
tensor for the scalar field), that evolves in a different way as the dust
component. To have similar contributions of the scalar component and the dust
component implies that their past values were fine tunned. So, we
reinterpreting this null result as an indication that dark matter plays a
central role in the formation of structures and galaxy evolution, having
measureable effects in the cosmic microwave bound radiation, and than this
formalism yield to this epoch as primigenius results. We do the mention that
this formalism was used recently in the so called K-essence theory applied to
dark energy problem, in place to the dark matter problem. Also, we include a
quantization procedure of the theory which can be simplified by reinterpreting
the theory in the Einstein frame, where the scalar field can be interpreted as
part of the matter content of the theory, and exact solutions to the
Wheeler-DeWitt equation are found, employing the Bianchi Class A cosmological
models.Comment: 24 pages; ISBN: 978-953-307-626-3, InTec
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