252 research outputs found
Les contraintes phonologiques en lecture en milieu de diglossie créole / français
Le prĂ©sent article est le rĂ©sultat dâune sĂ©lection de difficultĂ©s dâĂ©lĂšves en situation dâapprentissage de la lecture en français, en milieu crĂ©olophone guadeloupĂ©en. Les difficultĂ©s sont analysĂ©es en termes de âcontraintes phonologiquesâ, câest-Ă -dire Ă la lumiĂšre de traits phonologiques du crĂ©ole Ă©galement attestĂ©s dans les variĂ©tĂ©s de français antillais. Des propositions didactiques sont avancĂ©es tenant compte des milieux linguistiques et sociolinguistiques des Ă©lĂšves. Ces derniĂšres visent Ă prĂ©venir et Ă remĂ©dier Ă celles des difficultĂ©s qui sont analysĂ©es ci-dessous et qui ne sont pas dues Ă la dyslexie. Les niveaux prĂ©conisĂ©s pour la prĂ©vention sont ceux de lâĂ©cole maternelle.The present study is a selection of difficulties met by French-based Creole learners in Guadeloupe while they are taught the mechanisms of Reading in French. The difficulties are viewed as constraints, that is to say, as those phonological traits without which, learning how to read canât be successful for those profiles. The grill of analysis used is the phonological features of the Creole language and particularly those that present divergences with the French system. Didactic paths are suggested for prevention but also for remediation. Some attempts are made at differentiating between the difficulties met by a learner in diglottic situations and those that turn out to be those of a dyslexic context. The ideal school level recommended for the exercises is kindergarten
Convergent validity of the new form of the DES
p. 101-103The line and circle farms of the Dissociative Experiences Scale (DES I and DES II) were administered to 65 subjects in the general population, 87 subjects with a clinical diagnosis of dissociative identity disorder, and 26 subjects with a diagnosis of chemical dependency. In all three samples the DES II showed excellent validity when compared to the original line form of the DES
Unearthing InSights into Mars: Unsupervised Source Separation with Limited Data
Source separation involves the ill-posed problem of retrieving a set of
source signals that have been observed through a mixing operator. Solving this
problem requires prior knowledge, which is commonly incorporated by imposing
regularity conditions on the source signals, or implicitly learned through
supervised or unsupervised methods from existing data. While data-driven
methods have shown great promise in source separation, they often require large
amounts of data, which rarely exists in planetary space missions. To address
this challenge, we propose an unsupervised source separation scheme for domains
with limited data access that involves solving an optimization problem in the
wavelet scattering covariance representation space\unicode{x2014}an
interpretable, low-dimensional representation of stationary processes. We
present a real-data example in which we remove transient, thermally-induced
microtilts\unicode{x2014}known as glitches\unicode{x2014}from data recorded
by a seismometer during NASA's InSight mission on Mars. Thanks to the wavelet
scattering covariances' ability to capture non-Gaussian properties of
stochastic processes, we are able to separate glitches using only a few
glitch-free data snippets.Comment: ICML 202
Martian time-series unraveled: A multi-scale nested approach with factorial variational autoencoders
Unsupervised source separation involves unraveling an unknown set of source
signals recorded through a mixing operator, with limited prior knowledge about
the sources, and only access to a dataset of signal mixtures. This problem is
inherently ill-posed and is further challenged by the variety of time-scales
exhibited by sources in time series data. Existing methods typically rely on a
preselected window size that limits their capacity to handle multi-scale
sources. To address this issue, instead of operating in the time domain, we
propose an unsupervised multi-scale clustering and source separation framework
by leveraging wavelet scattering covariances that provide a low-dimensional
representation of stochastic processes, capable of distinguishing between
different non-Gaussian stochastic processes. Nested within this representation
space, we develop a factorial Gaussian-mixture variational autoencoder that is
trained to (1) probabilistically cluster sources at different time-scales and
(2) independently sample scattering covariance representations associated with
each cluster. Using samples from each cluster as prior information, we
formulate source separation as an optimization problem in the wavelet
scattering covariance representation space, resulting in separated sources in
the time domain. When applied to seismic data recorded during the NASA InSight
mission on Mars, our multi-scale nested approach proves to be a powerful tool
for discriminating between sources varying greatly in time-scale, e.g.,
minute-long transient one-sided pulses (known as ``glitches'') and structured
ambient noises resulting from atmospheric activities that typically last for
tens of minutes. These results provide an opportunity to conduct further
investigations into the isolated sources related to atmospheric-surface
interactions, thermal relaxations, and other complex phenomena
Spectra of High-Redshift Type Ia Supernovae and a Comparison with their Low-Redshift Counterparts
We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which
were discovered by the Supernova Cosmology Project as part of a campaign to
measure cosmological parameters. The spectra are used to determine the redshift
and classify the supernova type, essential information if the supernovae are to
be used for cosmological studies. Redshifts were derived either from the
spectrum of the host galaxy or from the spectrum of the supernova itself. We
present evidence that these supernovae are of Type Ia by matching to spectra of
nearby supernovae. We find that the dates of the spectra relative to maximum
light determined from this fitting process are consistent with the dates
determined from the photometric light curves, and moreover the spectral
time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We
also show that the expansion velocities measured from blueshifted CaHK are
consistent with those measured for low-redshift Type Ia supernovae. From these
first-level quantitative comparisons we find no evidence for evolution in SNIa
properties between these low- and high-redshift samples. Thus even though our
samples may not be complete, we conclude that there is a population of SNe Ia
at high redshift whose spectral properties match those at low redshift.Comment: Accepted for publication in AJ. Also available at
http://supernova.lbl.gov
Extracting clean supernova spectra
We use a new technique to extract the spectrum of a supernova from that of
the contaminating background of its host galaxy, and apply it to the specific
case of high-redshift Type Ia supernova (SN Ia) spectroscopy. The algorithm is
based on a two-channel iterative technique employing the Richardson-Lucy
restoration method and is implemented in the IRAF code 'specinholucy'. We run
the code both on simulated (SN Ia at z=0.5 embedded in a bright host galaxy)
and observed (SNe Ia at various phases up to z=0.236) data taken with VLT+FORS1
and show the advantages of using such a deconvolution technique in comparison
with less elaborate methods. This paper is motivated by the need for optimal
supernova spectroscopic data reduction in order to make meaningful comparisons
between the low and high-redshift SN Ia samples. This may reveal subtle
evolutionary and systematic effects that could depend on redshift and bias the
cosmological results derived from comparisons of local and high-z SNe Ia in
recent years. We describe the various aspects of the extraction in some detail
as guidelines for the first-time user and present an optimal observing strategy
for successful implementation of this method in future high-z SN Ia
spectroscopic follow-up programmes.Comment: 15 pages, 14 figures, accepted for publication in A&
Restframe I-band Hubble diagram for type Ia supernovae up to redshift z ~0.5
We present a novel technique for fitting restframe I-band light curves on a
data set of 42 Type Ia supernovae (SNe Ia). Using the result of the fit, we
construct a Hubble diagram with 26 SNe from the subset at 0.01< z<0.1. Adding
two SNe at z~0.5 yields results consistent with a flat
Lambda-dominated``concordance universe''
()=(0.25,0.75). For one of these, SN 2000fr, new near
infrared data are presented. The high redshift supernova NIR data are also used
to test for systematic effects in the use of SNe Ia as distance estimators. A
flat, Lambda=0, universe where the faintness of supernovae at z~0.5 is due to
grey dust homogeneously distributed in the intergalactic medium is disfavoured
based on the high-z Hubble diagram using this small data-set. However, the
uncertainties are large and no firm conclusion may be drawn. We explore the
possibility of setting limits on intergalactic dust based on B-I and B-V colour
measurements, and conclude that about 20 well measured SNe are needed to give
statistically significant results. We also show that the high redshift
restframe I-band data points are better fit by light curve templates that show
a prominent second peak, suggesting that they are not intrinsically
underluminous.Comment: Accepted for publication in A&A (01/04/2005
Spectroscopic observations of eight supernovae at intermediate redshift
We present spectra of six Type Ia and two Type II supernovae obtained in June
2002 at the William Herschel Telescope during a search for Type Ia supernovae
(SNIa) at intermediate redshift. Supernova type identification and phase
determination are performed using a fitting technique based on a Xi2
minimization against a series of model templates. The spectra range from
z=0.033 to z=0.328, including one spectroscopically underluminous SNIa at
z=0.033. This set of spectra significantly increases the sample of
well-observed type SNIa supernovae available in the range 0.15< z <0.35.
Together with the twelve supernovae observed by our team in 1999 in the same
redshift range, they form an homogeneous sample of seventeen type Ia supernovae
with comparable signal-to-noise ratio and regular phase sampling in a still
largely unexplored region of the redshift space.Comment: 30 pages, 15 figures. Published in A&
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