244 research outputs found
High-dimensional regression with unknown variance
38 pagesWe review recent results for high-dimensional sparse linear regression in the practical case of unknown variance. Different sparsity settings are covered, including coordinate-sparsity, group-sparsity and variation-sparsity. The emphasis is put on non-asymptotic analyses and feasible procedures. In addition, a small numerical study compares the practical performance of three schemes for tuning the Lasso estimator and some references are collected for some more general models, including multivariate regression and nonparametric regression
Graph selection with GGMselect
44 pagesApplications on inference of biological networks have raised a strong interest in the problem of graph estimation in high-dimensional Gaussian graphical models. To handle this problem, we propose a two-stage procedure which first builds a family of candidate graphs from the data, and then selects one graph among this family according to a dedicated criterion. This estimation procedure is shown to be consistent in a high-dimensional setting, and its risk is controlled by a non-asymptotic oracle-like inequality. The procedure is tested on a real data set concerning gene expression data, and its performances are assessed on the basis of a large numerical study. The procedure is implemented in the R-package GGMselect available on the CRAN
A new strategy for primary structure determination of proteins: Application to bovine ÎČ-casein
AbstractA new approach has been developed for sequencing proteins. A radioactive label is attached specifically to the C-terminus of the protein. The labelled molecule is subjected to varying proteolysis conditions. From the electrophoretic patterns (SDS-PAGE) of the hydrolysates, appropriate cleavage conditions are selected, giving labelled peptides of different lengths which are purified. The labelled peptides are sequenced in order of increasing size (from 1 to n), peptide (i) being sequenced until the N-terminal sequence of peptide (i-1) is encountered. This approach allows the determination of a complete protein sequence with a minimal number of Edman cycles. The method was successfully applied to bovine ÎČ-casein (209 residues) which was completely resequenced with only 239 Edman cycles
Conception d'un projet de mine - Puits 4
Projet d'extension de mine, infrastructures d'accÚs, méthode d'exploitation, étude technico-économique, et planification de l'exploitatio
Buts d'accomplissement de soi et jugement métacognitif des aides en EIAH
International audienceLe but de cette étude est d'étudier l'effet des buts d'accomplissement de soi et des jugements métacognitifs de l'individu sur sa recherche d'aide instrumentale ou exécutive au sein d'un site web d'apprentissage en statistique. 49 étudiants ont participé à l'étude. Les résultats montrent que (1) le but de maßtrise est lié positivement à la recherche d'aide instrumentale et positivement à la recherche d'aide exécutive de l'apprenant, (2) le but de performance d'évitement est lié négativement à la recherche d'aide exécutive, (3) la perception d'une menace sur son besoin d'autonomie est lié négativement à la recherche d'aide instrumentale, (4) la perception d'une menace sur ses compétences est reliée négativement à la recherche d'aide exécutive
Measures de vent 3D avec le lidar Doppler coherent Live Ă bord d'un avion
International audienceA three-dimensional (3D) wind profiling Lidar, based on the latest high power 1.5 ”m fiber laser development at Onera, has been successfully flown on-board a SAFIRE (Service des Avions Français InstrumentĂ©s pour la Recherche en Environnement) ATR42 aircraft. The Lidar called LIVE (LIdar VEnt) is designed to measure wind profiles from the aircraft down to ground level, with a horizontal resolution of 3 km, a vertical resolution of 100 m and a designed accuracy on each three wind vector components better than 0.5 m.s â1. To achieve the required performance, LIVE Lidar emits 410 ”J laser pulses repeating at 14 KHz with a duration of 700 ns and uses a conical scanner of 30 âą total opening angle and a full scan time of 17 s.Un lidar vent 3D, basĂ© sur le dernier dĂ©veloppement de laser Ă fibre de 1,5 ”m Ă haute puissance de lâONERA a Ă©tĂ© testĂ© avec succĂšs Ă bord dâun avion SAFIRE ATR42. Le lidar appelĂ© LIVE est conçu pour mesurer les profils de vent de lâavion jusqu'au sol, avec une rĂ©solution horizontale de 3 km, une rĂ©solution verticale de 100 m et une prĂ©cision calculĂ©e supĂ©rieure Ă 0,5 m / s pour chaque composante du vecteur du vent
High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules
Originating from the weak interaction, parity violation in chiral molecules
has been considered as a possible origin of the biohomochirality. It was
predicted in 1974 but has never been observed so far. Parity violation should
lead to a very tiny frequency difference in the rovibrational spectra of the
enantiomers of a chiral molecule. We have proposed to observe this predicted
frequency difference using the two photon Ramsey fringes technique on a
supersonic beam. Promising candidates for this experiment are chiral oxorhenium
complexes, which present a large effect, can be synthesized in large quantity
and enantiopure form, and can be seeded in a molecular beam. As a first step
towards our objective, a detailed spectroscopic study of methyltrioxorhenium
(MTO) has been undertaken. It is an ideal test molecule as the achiral parent
molecule of chiral candidates for the parity violation experiment. For the
187Re MTO isotopologue, a combined analysis of Fourier transform microwave and
infrared spectra as well as ultra-high resolution CO2 laser absorption spectra
enabled the assignment of 28 rotational lines and 71 rovibrational lines, some
of them with a resolved hyperfine structure. A set of spectroscopic parameters
in the ground and first excited state, including hyperfine structure constants,
was obtained for the antisymmetric Re=O stretching mode of this molecule. This
result validates the experimental approach to be followed once a chiral
derivative of MTO will be synthesized, and shows the benefit of the combination
of several spectroscopic techniques in different spectral regions, with
different set-ups and resolutions. First high resolution spectra of jet-cooled
MTO, obtained on the set-up being developed for the observation of molecular
parity violation, are shown, which constitutes a major step towards the
targeted objective.Comment: 20 pages, 6 figure
Study of Xenon Mobility in the Two Forms of MIL-53(Al) Using Solid-State NMR Spectroscopy
The
Al-based metalâorganic framework (MOF) MIL-53Â(Al) exhibits
a structural transition between a large-pore (<i>lp</i>)
form and a narrow-pore (<i>np</i>) one. Such change is induced
by temperature, external pressure, or the adsorption of guest molecules. <sup>129</sup>Xe solid-state NMR experiments under static and magic-angle
spinning (MAS) conditions have been used to study the <i>lp</i>â<i>np</i> transition in MIL-53Â(Al) initially loaded
with xenon gas under a pressure of 5 Ă 10<sup>4</sup> Pa (at
room temperature). The conversion of the <i>lp</i> form
into the <i>np</i> one when the temperature decreases from
327 to 237 K and the reopening of the pores below 230 K are then observed.
Furthermore, <sup>1</sup>H â <sup>129</sup>Xe cross-polarization
under MAS (CPMAS) experiments demonstrate the possibility to observe
the <i>np</i> phase at <i>T</i> †230 K,
while the <i>lp</i> one is unseen because the xenon residence
time is too short for successful cross-polarization transfer. Moreover,
even for the <i>np</i> phase at 199 K, the xenon atoms still
exhibit significant motion on time scale faster than a few milliseconds.
We prove the exchange of Xe atoms between the <i>lp</i> and <i>np</i> forms at room temperature with the two-dimensional (2D) <sup>129</sup>Xe EXchange SpectroscopY (EXSY) NMR method. Using <sup>129</sup>Xe selective inversion recovery (SIR) experiments, the rate for this
exchange has been measured at 43 ± 6 s<sup>â1</sup>
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