7,952 research outputs found
Cosmic Microwave Background Polarization and reionization: constraining models with a double reionization
Neutral hydrogen around high-z QSO and an optical depth tau ~ 0.17 can be
reconciled if reionization is more complex than a single transition at z ~ 6-8.
Tracing its details could shed a new light on the first sources of radiation.
Here we discuss how far such details can be inspected through planned
experiments on CMB large-scale anisotropy and polarization, by simulating an
actual data analysis. By considering a set of double reionization histories of
Cen (2003) type, a relevant class of models not yet considered by previous
works, we confirm that large angle experiments rival high resolution ones in
reconstructing the reionization history. We also confirm that reionization
histories, studied with the prior of a single and sharp reionization, yield a
biased tau, showing that this bias is generic. We further find a monotonic
trend in the bias for the models that we consider, and propose an explanation
of the trend, as well as the overall bias. We also show that in long-lived
experiments such a trend can be used to discriminate between single and double
reionization patterns.Comment: 8 pages, 11 figures. Substantial rewriting, replaced with accepted
version. To be published in A&
Moderate Wine Consumption and Health: A Narrative Review
Although it is clearly established that the abuse of alcohol is seriously harmful to health, much epidemiological and clinical evidence seem to underline the protective role of moderate quantities of alcohol and in particular of wine on health. This narrative review aims to re-evaluate the relationship between the type and dose of alcoholic drink and reduced or increased risk of various diseases, in the light of the most current scientific evidence. In particular, in vitro studies on the modulation of biochemical pathways and gene expression of wine bioactive components were evaluated. Twenty-four studies were selected after PubMed, Scopus and Google Scholar searches for the evaluation of moderate alcohol/wine consumption and health effects: eight studies concerned cardiovascular diseases, three concerned type 2 diabetes, four concerned neurodegenerative diseases, five concerned cancer and four were related to longevity. A brief discussion on viticultural and enological practices potentially affecting the content of bioactive components in wine is included. The analysis clearly indicates that wine differs from other alcoholic beverages and its moderate consumption not only does not increase the risk of chronic degenerative diseases but is also associated with health benefits particularly when included in a Mediterranean diet model. Obviously, every effort must be made to promote behavioral education to prevent abuse, especially among young people
A polarized synchrotron template for CMBP experiments after WMAP data
We build template maps for the polarized Galactic--synchrotron emission on
large angular scales (FWHM =~7), in the 20-90 GHz microwave range, by
using WMAP data. The method, presented in a recent work, requires a synchrotron
total intensity survey and the {\it polarization horizon} to model the
polarized intensity and a starlight polarization map to model polarization
angles. The basic template is obtained directly at 23 GHz with about 94%
sky--coverage by using the synchrotron map released by the WMAP team.
Extrapolations to 32, 60 and 90 GHz are performed by computing a synchrotron
spectral index map, which strongly reduces previous uncertainties in passing
from low (1.4 GHz) to microwave frequencies. Differing from low frequency data,
none of our templates presents relevant structures out of the Galactic Plane.
Our map at 90 GHz suggests that the synchrotron emission at high Galactic
latitudes is low enough to allow a robust detection of the --mode component
of the cosmological signal on large--scale, even in models with
low--reionization (). Detection of the weaker --mode on the
largest scales () might be jeopardized unless the value found by WMAP is confirmed, and . For lower levels of the
gravitational--wave background the --mode seems to be accessible only at the
peak and in selected low--synchrotron emission areas.Comment: 13 pages, 14 figures, accepted for pubblications by MNRAS. For a
version with full resolution color figures see
http://sp0rt.bo.iasf.cnr.it:8080/Docs/Public/papers.ph
A radio-polarisation and rotation measure study of the Gum Nebula and its environment
The Gum Nebula is 36 degree wide shell-like emission nebula at a distance of
only 450 pc. It has been hypothesised to be an old supernova remnant, fossil
HII region, wind-blown bubble, or combination of multiple objects. Here we
investigate the magneto-ionic properties of the nebula using data from recent
surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky
Surveys, and H-alpha data from the Southern H-Alpha Sky Survey Atlas. We model
the upper part of the nebula as a spherical shell of ionised gas expanding into
the ambient medium. We perform a maximum-likelihood Markov chain Monte-Carlo
fit to the NVSS rotation measure data, using the H-halpha data to constrain
average electron density in the shell . Assuming a latitudinal background
gradient in RM we find , angular radius
, shell thickness
, ambient magnetic field strength
and warm gas filling factor
. We constrain the local, small-scale (~260 pc)
pitch-angle of the ordered Galactic magnetic field to
, which represents a significant
deviation from the median field orientation on kiloparsec scales
(~-7.2). The moderate compression factor X=6.0\,^{+5.1}_{-2.5} at
the edge of the H-alpha shell implies that the 'old supernova remnant' origin
is unlikely. Our results support a model of the nebula as a HII region around a
wind-blown bubble. Analysis of depolarisation in 2.3 GHz S-PASS data is
consistent with this hypothesis and our best-fitting values agree well with
previous studies of interstellar bubbles.Comment: 33 pages, 16 figures. Accepted by The Astrophysical Journa
The Influence of Quadrature Errors on Isogeometric Mortar Methods
Mortar methods have recently been shown to be well suited for isogeometric
analysis. We review the recent mathematical analysis and then investigate the
variational crime introduced by quadrature formulas for the coupling integrals.
Motivated by finite element observations, we consider a quadrature rule purely
based on the slave mesh as well as a method using quadrature rules based on the
slave mesh and on the master mesh, resulting in a non-symmetric saddle point
problem. While in the first case reduced convergence rates can be observed, in
the second case the influence of the variational crime is less significant
Cluster magnetic fields through the study of polarized radio halos in the SKA era
Galaxy clusters are unique laboratories to investigate turbulent fluid
motions and large scale magnetic fields. Synchrotron radio halos at the center
of merging galaxy clusters provide the most spectacular and direct evidence of
the presence of relativistic particles and magnetic fields associated with the
intracluster medium. The study of polarized emission from radio halos is
extremely important to constrain the properties of intracluster magnetic fields
and the physics of the acceleration and transport of the relativistic
particles. However, detecting this polarized signal is a very hard task with
the current radio facilities.We use cosmological magneto-hydrodynamical
simulations to predict the expected polarized surface brightness of radio halos
at 1.4 GHz. We compare these expectations with the sensitivity and the
resolution reachable with the SKA1. This allows us to evaluate the potential
for studying intracluster magnetic fields in the surveys planned for SKA1.Comment: 11 pages, 4 figures; to appear as part of 'Cosmic Magnetism' in
Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)10
Model fitting and Bayesian inference via power expectation propagation
We study a message passing approach to power expectation propagation for Bayesian model fitting and inference. Power expectation propagation is a class of variational approximations based on the notion of α-divergence that extends two notable approximations, namely mean field variational Bayes and expectation propagation. An illustration on a simple model allows to grasp benefits and complexities of this methodology and sets the basis for applications on more complex models
School, Museum, University: A community for science education
For almost twenty years, the Physics History Group, the University History Museum and the Physics Museum of Pavia University have been elaborating, with schools of all levels, a year-long shared project, leading to the development of strong, long-lasting relationships between the participants and of a community of practice. Within it, new pathways are sought, to allow all participants to live
meaningful experiences, to bring school closer to cultural heritage and the local community, and to foster the development of a scientific identity in learners. A methodology including historical-scientific workshops and a focus on Nature of Science was developed. Students are led through educational paths customized according to teachers’ requests and produce science stories, which are shared with the community. Because of the pandemic, only upper secondary schools were involved in the last project, Show & Tell. New activities were introduced: a team of students were tasked with online and offline communication, old instruments in schools’ collections were put back into use and several final events were organized. Open interviews
with teachers highlighted several positive outcomes. Everyone worked alongside, sharing stories, experiences, competencies, intellectual pleasure, codified knowledge
and tacit knowledge, in a non-judging environment
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