2,300 research outputs found
Semi-blind Bayesian inference of CMB map and power spectrum
We present a new blind formulation of the Cosmic Microwave Background (CMB)
inference problem. The approach relies on a phenomenological model of the
multi-frequency microwave sky without the need for physical models of the
individual components. For all-sky and high resolution data, it unifies parts
of the analysis that have previously been treated separately, such as component
separation and power spectrum inference. We describe an efficient sampling
scheme that fully explores the component separation uncertainties on the
inferred CMB products such as maps and/or power spectra. External information
about individual components can be incorporated as a prior giving a flexible
way to progressively and continuously introduce physical component separation
from a maximally blind approach. We connect our Bayesian formalism to existing
approaches such as Commander, SMICA and ILC, and discuss possible future
extensions.Comment: 11 pages, 9 figure
Setting Parameters for Biological Models With ANIMO
ANIMO (Analysis of Networks with Interactive MOdeling) is a software for
modeling biological networks, such as e.g. signaling, metabolic or gene
networks. An ANIMO model is essentially the sum of a network topology and a
number of interaction parameters. The topology describes the interactions
between biological entities in form of a graph, while the parameters determine
the speed of occurrence of such interactions. When a mismatch is observed
between the behavior of an ANIMO model and experimental data, we want to update
the model so that it explains the new data. In general, the topology of a model
can be expanded with new (known or hypothetical) nodes, and enables it to match
experimental data. However, the unrestrained addition of new parts to a model
causes two problems: models can become too complex too fast, to the point of
being intractable, and too many parts marked as "hypothetical" or "not known"
make a model unrealistic. Even if changing the topology is normally the easier
task, these problems push us to try a better parameter fit as a first step, and
resort to modifying the model topology only as a last resource. In this paper
we show the support added in ANIMO to ease the task of expanding the knowledge
on biological networks, concentrating in particular on the parameter settings
A Onelab model for the parametric study of mono-dimensional diffraction gratings
This document aims at presenting both theoretical and practical aspects of
the grating_2D Onelab model (available at
http://onelab.info/wiki/Diffraction_grating). This model applies to so-called
mono-dimensional grating, i.e. structures having one direction of invariance.
Various geometries and materials can be handled or easily added. The two
classical polarization cases, denoted here E// and H//, are addressed. The
output consists in a full energy balance of the problem computed from the field
maps. This model is based on free the GNU softwares Gmsh, GetDP and their
interface Onelab.Comment: arXiv admin note: text overlap with arXiv:1302.103
The diverse X-ray properties of four truly isolated elliptical galaxies: NGC 2954, NGC 6172, NGC 7052, and NGC 7785
We investigate the X-ray properties of four isolated elliptical galaxies,
selected from the Updated Zwicky Catalog according to strict isolation
criteria. Isolated galaxies are not influenced by the group/cluster
environment, and their X-ray emission can be studied independently of the often
overwhelming contribution of the hot intergalactic medium. They are therefore
suited to studying the X-ray characteristics relative to their intrinsic
properties. We analyzed our own XMM-Newton and archival Chandra data in detail
for three objects, and derived, when possible, the spatial and spectral
characteristics of each source. An upper limit for the fourth one was obtained
from archival ASCA data. We compared their characteristics with those of other
23 isolated objects for which X-ray and optical data are available in the
literature. We explored possible theoretical explanations to interpret our
results. In spite of our attempt to select very homogeneous objects, both in
terms of optical properties and environmental characteristics, we find a wide
range in X-ray luminosities and LX/LB ratios for the four objects: two of them
show a hot gaseous halo, whereas no gas is detected in the other two, to a
factor >10 in luminosity. In fact, we find a large spread in the LX/LB for all
galaxies considered, suggesting that the presence of hot gas is not easily
related to the optical luminosity or to the mass, even in isolated systems.
Younger objects tend to be less luminous in X-rays than older systems. However,
it appears that older objects could span a wide range in luminosities.Comment: [email protected], 12 pages, 14 PostScript figures, 3
tables, LaTeX. The last sentence of Section 2 has been modified. The
published version of the manuscript is also available at
http://moby.mib.infn.it/~memola/publications.htm
Estimating the incidence of equine viral arteritis and the sensitivity of its surveillance in the French breeding stock
Equine viral arteritis (EVA) may have serious economic impact on the equine industry. For this reason, it is monitored in many countries, especially in breeding stock, to avoid its spread during breeding activities. In France, surveillance is mainly based on serological tests, since mares are not vaccinated, but difficulties in interpreting certain series of results may impair the estimation of the number of outbreaks. In this study, we propose specific rules for identifying seroconversion in order to estimate the number of outbreaks that were detected by the breeding stock surveillance component (BSSC) in France between 2006 and 2013. A consensus among multidisciplinary experts was reached to consider seroconversion as a change in antibody titer from negative to at least 32, or as an eight-fold or greater increase in antibody level. Using these rules, 239 cases and 177 outbreaks were identified. Subsequently, we calculated the BSSC's sensitivity as the ratio of the number of detected outbreaks to the total number of outbreaks that occurred in breeding stock (including unreported outbreaks) estimated using a capture-recapture model. The total number of outbreaks was estimated at 215 (95% credible interval 195-249) and the surveillance sensitivity at 82% (CrI95% 71-91). Our results confirm EVA circulation in French breeding stock, show that neutralizing antibodies can persist up to eight years in naturally infected mares and suggest that certain mares have been reinfected. This study shows that the sensitivity of the BSSC is relatively high and supports its relevance to prevent the disease spreading through mating
Improved CMB Map from WMAP Data
The cosmic microwave background (CMB) temperature maps published by the
Wilkinson Microwave Anisotropy Probe (WMAP) team are found to be inconsistent
with the differential time-ordered data (TOD), from which the maps are
reconstructed. The inconsistency indicates that there is a serious problem in
the map making routine of the WMAP team, and it is necessary to reprocess the
WMAP data. We develop a self-consistent software package of map-making and
power spectrum estimation independently of the WMAP team. Our software passes a
variety of tests. New CMB maps are then reconstructed, which are significantly
different from the official WMAP maps. In the new maps, the inconsistency
disappeared, along with the hitherto unexplained high level alignment between
the CMB quadrupole and octopole components detected in released WMAP maps. An
improved CMB cross-power spectrum is then derived from the new maps which
better agrees with that of BOOMRANG. Two important results are hence obtained:
the CMB quadrupole drops to nearly zero, and the power in multiple moment range
between 200 and 675 decreases on average by about 13%, causing the best-fit
cosmological parameters to change considerably, e.g., the total matter density
increases from 0.26 up to 0.32 and the dark energy density decreases from 0.74
down to 0.68. These new parameters match with improved accuracy those of other
independent experiments. Our results indicate that there is still room for
significant revision in the cosmological model parameters.Comment: Submitted to MNRAS. In the revised version (v3) we make foreground
reduction with the same technique WMAP team used and add the results of
reconstructing the sky maps with the WMAP default flagging and our softwar
The Large-scale ISM of SS433/W50 Revisited
With new high-resolution CO and HI data, we revisited the large-scale
interstellar medium (ISM) environment toward the SS 433/W50 system. We find
that two interesting molecular cloud (MC) concentrations, G39.315-1.155 and
G40.331-4.302, are well aligned along the precession cone of SS 433 within a
smaller opening angle of ~7deg. The kinematic features of the two MCs at
~73--84 km/s, as well as those of the corresponding atomic-gas counterparts,
are consistent with the kinematic characteristics of SS 433. That is, the
receding gas from SS 433 jet is probably responsible for the redshifted feature
of G39.315-1.155 near the Galactic plane and the approaching one may power the
blueshifted gas of G40.331-4.302 toward the observer. Moreover, the HI emission
at VLSR~70--90 km/s displays the morphological resemblance with the radio
nebula W50. We suggest that the VLSR=77\pm5 km/s gas is physically associated
with SS 433/W50, leading to a near kinematic distance of 4.9\pm0.4 kpc for the
system. The observed gas features, which are located outside the current radio
boundaries of W50, are probably the fossil record of jet-ISM interactions at
~10^5 years ago. The energetic jets of the unique microquasar have profound
effects on its ISM environment, which may facilitate the formation of molecular
gas on the timescale of <0.1 Myr for the ram pressure of ~2x10^6 K cm-3.Comment: 1 table, 13 figures, to appear in the ApJ. Comments welcom
Phantom-GRAPE: numerical software library to accelerate collisionless -body simulation with SIMD instruction set on x86 architecture
(Abridged) We have developed a numerical software library for collisionless
N-body simulations named "Phantom-GRAPE" which highly accelerates force
calculations among particles by use of a new SIMD instruction set extension to
the x86 architecture, AVX, an enhanced version of SSE. In our library, not only
the Newton's forces, but also central forces with an arbitrary shape f(r),
which has a finite cutoff radius r_cut (i.e. f(r)=0 at r>r_cut), can be quickly
computed. Using an Intel Core i7--2600 processor, we measure the performance of
our library for both the forces. In the case of Newton's forces, we achieve 2 x
10^9 interactions per second with 1 processor core, which is 20 times higher
than the performance of an implementation without any explicit use of SIMD
instructions, and 2 times than that with the SSE instructions. With 4 processor
cores, we obtain the performance of 8 x 10^9 interactions per second. In the
case of the arbitrarily shaped forces, we can calculate 1 x 10^9 and 4 x 10^9
interactions per second with 1 and 4 processor cores, respectively. The
performance with 1 processor core is 6 times and 2 times higher than those of
the implementations without any use of SIMD instructions and with the SSE
instructions. These performances depend weakly on the number of particles. It
is good contrast with the fact that the performance of force calculations
accelerated by GPUs depends strongly on the number of particles. Substantially
weak dependence of the performance on the number of particles is suitable to
collisionless N-body simulations, since these simulations are usually performed
with sophisticated N-body solvers such as Tree- and TreePM-methods combined
with an individual timestep scheme. Collisionless N-body simulations
accelerated with our library have significant advantage over those accelerated
by GPUs, especially on massively parallel environments.Comment: 19 pages, 11 figures, 4tables, accepted for publication in New
Astronom
Efficient spike-sorting of multi-state neurons using inter-spike intervals information
We demonstrate the efficacy of a new spike-sorting method based on a Markov
Chain Monte Carlo (MCMC) algorithm by applying it to real data recorded from
Purkinje cells (PCs) in young rat cerebellar slices. This algorithm is unique
in its capability to estimate and make use of the firing statistics as well as
the spike amplitude dynamics of the recorded neurons. PCs exhibit multiple
discharge states, giving rise to multimodal interspike interval (ISI)
histograms and to correlations between successive ISIs. The amplitude of the
spikes generated by a PC in an "active" state decreases, a feature typical of
many neurons from both vertebrates and invertebrates. These two features
constitute a major and recurrent problem for all the presently available
spike-sorting methods. We first show that a Hidden Markov Model with 3
log-Normal states provides a flexible and satisfying description of the complex
firing of single PCs. We then incorporate this model into our previous MCMC
based spike-sorting algorithm (Pouzat et al, 2004, J. Neurophys. 91, 2910-2928)
and test this new algorithm on multi-unit recordings of bursting PCs. We show
that our method successfully classifies the bursty spike trains fired by PCs by
using an independent single unit recording from a patch-clamp pipette.Comment: 25 pages, to be published in Journal of Neurocience Method
The operation of VEGA/CHARA : from the scientific idea to the final products
We describe the data flow in the operation of the VEGA/CHARA instrument.
After a brief summary of the main characteristics and scientific objectives of
the VEGA instrument, we explain the standard procedure from the scientific idea
up to the execution of the observation. Then, we describe the different steps
done after the observation, from the raw data to the archives and the final
products. Many tools are used and we show how the Virtual Observatory
principles have been implemented for the interoperability of these software and
databases.Comment: 9 pages, 3 figure
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