299 research outputs found
Beyond brain reading: randomized sparsity and clustering to simultaneously predict and identify
International audienceThe prediction of behavioral covariates from functional MRI (fMRI) is known as brain reading. From a statistical standpoint, this challenge is a supervised learning task. The ability to predict cognitive states from new data gives a model selection criterion: prediction accu- racy. While a good prediction score implies that some of the voxels used by the classifier are relevant, one cannot state that these voxels form the brain regions involved in the cognitive task. The best predictive model may have selected by chance non-informative regions, and neglected rele- vant regions that provide duplicate information. In this contribution, we address the support identification problem. The proposed approach relies on randomization techniques which have been proved to be consistent for support recovery. To account for the spatial correlations between voxels, our approach makes use of a spatially constrained hierarchical clustering algorithm. Results are provided on simulations and a visual experiment
Release of Bet v 1 from birch pollen from 5 European countries. Results from the HIALINE study
Exposure to allergens is pivotal in determining sensitization and allergic symptoms in individuals. Pollen
grain counts in ambient air have traditionally been assessed to estimate airborne allergen exposure.
However, the exact allergen content of ambient air is unknown. We therefore monitored atmospheric
concentrations of birch pollen grains and the matched major birch pollen allergen Bet v 1 simultaneously
across Europe within the EU-funded project HIALINE (Health Impacts of Airborne Allergen Information
Network).
Pollen count was assessed with Hirst type pollen traps at 10 l min 1 at sites in France, United Kingdom,
Germany, Italy and Finland. Allergen concentrations in ambient air were sampled at 800 l min 1 with
a Chemvol high-volume cascade impactor equipped with stages PM > 10 mm, 10 mm > PM > 2.5 mm, and
in Germany also 2.5 mm > PM > 0.12 mm. The major birch pollen allergen Bet v 1 was determined with an
allergen specific ELISA. Bet v 1 isoform patterns were analyzed by 2D-SDS-PAGE blots and mass spectrometric
identification. Basophil activation was tested in an Fc 3R1-humanized rat basophil cell line
passively sensitized with serum of a birch pollen symptomatic patient.
Compared to 10 previous years, 2009 was a representative birch pollen season for all stations. About
90% of the allergen was found in the PM > 10 mm fraction at all stations. Bet v 1 isoforms pattern did not
vary substantially neither during ripening of pollen nor between different geographical locations. The
average European allergen release from birch pollen was 3.2 pg Bet v 1/pollen and did not vary much
between the European countries. However, in all countries a >10-fold difference in daily allergen release
per pollen was measured which could be explained by long-range transport of pollen with a deviating allergen release. Basophil activation by ambient air extracts correlated better with airborne allergen than
with pollen concentration.
Although Bet v 1 is a mixture of different isoforms, its fingerprint is constant across Europe. Bet v 1 was
also exclusively linked to pollen. Pollen from different days varied >10-fold in allergen release. Thus
exposure to allergen is inaccurately monitored by only monitoring birch pollen grains. Indeed,
a humanized basophil activation test correlated much better with allergen concentrations in ambient air
than with pollen count. Monitoring the allergens themselves together with pollen in ambient air might
be an improvement in allergen exposure assessmen
Stuffed Rare Earth Pyrochlore Solid Solutions
Synthesis and crystal structures are described for the compounds
Ln2(Ti2-xLnx)O7-x/2, where Ln = Tb, Dy, Ho, Er, Tm, Yb, Lu, and x ranges from 0
to 0.67. Rietveld refinements on X-ray powder diffraction data indicate that in
Tb and Dy titanate pyrochlores, extra Ln3+ cations mix mainly on the Ti4+ site
with little disorder on the original Ln3+ site. For the smaller rare earths
(Ho-Lu), stuffing additional lanthanide ions results in a pyrochlore to defect
fluorite transition, where the Ln3+ and Ti4+ ions become completely randomized
at the maximum (x=0.67). In all of these Ln-Ti-O pyrochlores, the addition of
magnetic Ln3+ in place of nonmagnetic Ti4+ adds edge sharing tetrahedral spin
interactions to a normally corner sharing tetrahedral network of spins. The
increase in spin connectivity in this family of solid solutions represents a
new avenue for investigating geometrical magnetic frustration in the rare earth
titanate pyrochlores.Comment: 25 pages, 7 figures, submitted to J. Solid State Che
Parity nonconserving cold neutron-parahydrogen interactions
Three pion dominated observables of the parity nonconserving interactions
between the cold neutrons and parahydrogen are calculated. The transversely
polarized neutron spin rotation, unpolarized neutron longitudinal polarization,
and photon-asymmetry of the radiative polarized neutron capture are considered.
For the numerical evaluation of the observables, the strong interactions are
taken into account by the Reid93 potential and the parity nonconserving
interactions by the DDH model along with the two-pion exchange.Comment: 17 pages, 2 figure
Freezing and large time scales induced by geometrical frustration
We investigate the properties of an effective Hamiltonian with competing
interactions involving spin and chirality variables, relevant for the
description of the {\it trimerized} version of the spin-1/2 {\it kagome}
antiferromagnet. Using classical Monte Carlo simulations, we show that
remarkable behaviors develop at very low temperatures. Through an {\it order by
disorder} mechanism, the low-energy states are characterized by a dynamical
freezing of the chiralities, which decouples the lattice into ``dimers'' and
``triangles'' of antiferromagnetically coupled spins. Under the presence of an
external magnetic field, the particular topology of the chiralities induces a
very slow spin dynamics, reminiscent of what happens in ordinary spin glasses.Comment: 12 pages, 13 figure
From registration to publication: A study on Dutch academic randomized controlled trials
Introduction: Registration of clinical trials has been initiated in order to assess adherence of the reported results to the original trial protocol. This study aimed to investigate the publication rates, timely dissemination of results, and the prevalence of consistency in hypothesis, sample size, and primary endpoint of Dutch investigator-initiated randomized controlled clinical trials (RCTs). Methods: All Dutch investigator-initiated RCTs with a completion date between December 31, 2010, and January 1, 2012, and registered in the Trial Register of The Netherlands database were included. PubMed was searched for the publication of these RCT results until September 2016, and the time to the publication date was calculated. Consistency in hypothesis, sample size, and primary endpoint compared with the registry data were assessed. Results: The search resulted in a total of 168 Dutch investigator-initiated RCTs. In September 2016, the results of 129 (77%) trials had been published, of which 50 (39%) within 2 years after completion of accrual. Consistency in hypothesis with the original protocol was observed in 108 (84%) RCTs; in 71 trials (55%), the planned sample size was reached; and 103 trials (80%) presented the original primary endpoint. Consistency in all three parameters was observe
Asteroseismology of Eclipsing Binary Stars in the Kepler Era
Eclipsing binary stars have long served as benchmark systems to measure
fundamental stellar properties. In the past few decades, asteroseismology - the
study of stellar pulsations - has emerged as a new powerful tool to study the
structure and evolution of stars across the HR diagram. Pulsating stars in
eclipsing binary systems are particularly valuable since fundamental properties
(such as radii and masses) can determined using two independent techniques.
Furthermore, independently measured properties from binary orbits can be used
to improve asteroseismic modeling for pulsating stars in which mode
identifications are not straightforward. This contribution provides a review of
asteroseismic detections in eclipsing binary stars, with a focus on space-based
missions such as CoRoT and Kepler, and empirical tests of asteroseismic scaling
relations for stochastic ("solar-like") oscillations.Comment: 28 pages, 12 figures, 2 tables; Proceedings of the AAS topical
conference "Giants of Eclipse" (AASTCS-3), July 28 - August 2 2013, Monterey,
C
Prospects for asteroseismology
The observational basis for asteroseismology is being dramatically
strengthened, through more than two years of data from the CoRoT satellite, the
flood of data coming from the Kepler mission and, in the slightly longer term,
from dedicated ground-based facilities. Our ability to utilize these data
depends on further development of techniques for basic data analysis, as well
as on an improved understanding of the relation between the observed
frequencies and the underlying properties of the stars. Also, stellar modelling
must be further developed, to match the increasing diagnostic potential of the
data. Here we discuss some aspects of data interpretation and modelling,
focussing on the important case of stars with solar-like oscillations.Comment: Proc. HELAS Workshop on 'Synergies between solar and stellar
modelling', eds M. Marconi, D. Cardini & M. P. Di Mauro, Astrophys. Space
Sci., in the press Revision: correcting abscissa labels on Figs 1 and
Production of Lambda and Sigma^0 hyperons in proton-proton collisions
This paper reports results on simultaneous measurements of the reaction
channels pp -> pK+\Lambda and pp -> pK+\Sigma^0 at excess energies of 204, 239,
and 284 MeV (\Lambda) and 127, 162, and 207 MeV (\Sigma^0). Total and
differential cross sections are given for both reactions. It is concluded from
the measured total cross sections that the high energy limit of the cross
section ratio is almost reached at an excess energy of only about 200 MeV. From
the differential distributions observed in the overall CMS as well as in the
Jackson and helicity frames, a significant contribution of interfering nucleon
resonances to the \Lambda production mechanism is concluded while resonant
\Sigma^0-production seems to be of lesser importance and takes place only
through specific partial waves of the entrance channel. The data also indicate
that kaon exchange plays a minor role in the case of \Lambda- but an important
role for \Sigma^0-production. Thus the peculiar energy dependence of the
\Lambda-to-\Sigma^0 cross section ratio appears in a new light as its
explanation requires more than mere differences between the p\Lambda and the
p\Sigma^0 final state interaction. The data provide a benchmark for theoretical
models already available or yet to come.Comment: 18 pages, 10 figures; accepted by The European Physical Journal A
(EPJ A
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