Large margin filtering for signal sequence labeling

Signal Sequence Labeling consists in predicting a sequence of labels given an observed sequence of samples. A naive way is to filter the signal in order to reduce the noise and to apply a classification algorithm on the filtered samples. We propose in this paper to jointly learn the filter with the classifier leading to a large margin filtering for classification. This method allows to learn the optimal cutoff frequency and phase of the filter that may be different from zero. Two methods are proposed and tested on a toy dataset and on a real life BCI dataset from BCI Competition III.Comment: IEEE International Conference on Acoustics Speech and Signal Processing (ICASSP), 2010, Dallas : United States (2010

Impact of the capping layers on lateral confinement in InAs/InP quantum dots for 1.55 um laser applications srudied by magneto-photoluminescence.

We have used magnetophotoluminescence to study the impact of different capping layer material combinations (InP, GaInAsP quaternary alloy, or both InP and quaternary alloy) on lateral confinement in InAs/InP quantum dots (QDs) grown on (311)B orientated substrates. Exciton effective masses, Bohr radii, and binding energies are measured for these samples. Conclusions regarding the strength of the lateral confinement in the different samples are supported by photoluminescence at high excitation power. Contrary to theoretical predictions, InAs QDs in quaternary alloy are found to have better confinement properties than InAs/InP QDs. This is attributed to a lack of lateral intermixing with the quaternary alloy, which is present when InP is used to (partially) cap the dots. The implications of the results for reducing the temperature sensitivity of QD lasers are discussed. ©2005 American Institute of Physic

Ihog and Boi are essential for Hedgehog signaling in Drosophila

<p>Abstract</p> <p>Background</p> <p>The Hedgehog (Hh) signaling pathway is important for the development of a variety of tissues in both vertebrates and invertebrates. For example, in developing nervous systems Hh signaling is required for the normal differentiation of neural progenitors into mature neurons. The molecular signaling mechanism underlying the function of Hh is not fully understood. In <it>Drosophila</it>, Ihog (Interference hedgehog) and Boi (Brother of Ihog) are related transmembrane proteins of the immunoglobulin superfamily (IgSF) with orthologs in vertebrates. Members of this IgSF subfamily have been shown to bind Hh and promote pathway activation but their exact role in the Hh signaling pathway has remained elusive. To better understand this role <it>in vivo</it>, we generated loss-of-function mutations of the <it>ihog </it>and <it>boi </it>genes, and investigated their effects in developing eye and wing imaginal discs.</p> <p>Results</p> <p>While mutation of either <it>ihog </it>or <it>boi </it>alone had no discernible effect on imaginal tissues, cells in the developing eye disc that were mutant for both <it>ihog </it>and <it>boi </it>failed to activate the Hh pathway, causing severe disruption of photoreceptor differentiation in the retina. In the anterior compartment of the developing wing disc, where different concentrations of the Hh morphogen elicit distinct cellular responses, cells mutant for both <it>ihog </it>and <it>boi </it>failed to activate responses at either high or low thresholds of Hh signaling. They also lost their affinity for neighboring cells and aberrantly sorted out from the anterior compartment of the wing disc into posterior territory. We found that <it>ihog </it>and <it>boi </it>are required for the accumulation of the essential Hh signaling mediator Smoothened (Smo) in Hh-responsive cells, providing evidence that Ihog and Boi act upstream of Smo in the Hh signaling pathway.</p> <p>Conclusions</p> <p>The consequences of <it>boi;ihog </it>mutations for eye development, neural differentiation and wing patterning phenocopy those of <it>smo </it>mutations and uncover an essential role for Ihog and Boi in the Hh signaling pathway.</p

Si wafer bonded of a-Si/a-SiNx distributed Bragg reflectors for 1.55-µm wavelength vertical cavity surface emitting lasers

International audienceAmorphous silicon (a-Si) and amorphous silicon nitride (a-SiNx) layers deposited by magnetron sputtering have been analyzed in order to determine their optical and surface properties. A large value of ~1.9 of index difference is found between these materials. Distributed Bragg reflectors (DBR) based on these dielectric materials quarter wave layers have been studied by optical measurements and confronted to theoretical calculations based on the transfer matrix method. A good agreement has been obtained between the experimental and expected reflectivity. A maximum reflectivity of 99.5% at 1.55 µm and a large spectral bandwidth of 800 nm are reached with only four and a half periods of a-Si/a-SiNx. No variation of the DBR reflectivity has been observed with the time nor when annealed above 240°C and stored during few months. This result allows to use this DBR in a metallic bonding process to realize a vertical cavity surface emitting laser (VCSEL) with two dielectric a-Si/a-SiNx DBR. This bonding method using AuIn2 as the bonding medium and Si substrate can be performed at a low temperature of 240°C without damaging the optical properties of the microcavity. The active region used for this VCSEL is based on lattice-matched InGaAs/InGaAsP quantum wells and a laser emission has been obtained at room-temperature on an optically pumped device

Government Geoscience Stimulates Mineral Exploration in the Superior Province, Northern Québec

This paper summarizes new geologic information, and highlights exploration opportunities in the northeastern part of the Superior Province since 1997, as a result of the Far North Program undertaken by Géologie Québec. The first phase of the program was a regional lake-sediment geochemical survey, where 26,000 samples were collected north of 55°N from an area of approximately 350,000 km2. The resulting database attracted many mining companies to the region and led to numerous mineral discoveries. The second phase, started in 1998, consisted of extensive geological mapping, supplemented by U-Pb geochronological work; by 2003, more than twenty, 1:250,000 mapping projects were completed. The Far North Program is now in its final phase and it will produce a comprehensive geological and metallogenic synthesis of the new data from the areas surveyed. About forty previously unknown volcano-sedimentary belts, numerous mafic-ultramafic intrusions and sixteen different mineral deposit types have been identified. Since 1997, this has resulted in a surge of exploration activity that has seen more than $38 million in expenditures by private industry. SOMMAIRE Le présent article présente un résumé des nouvelles informations géologiques disponibles et décrit des cibles d'exploration mises au jour depuis 1997 dans le nord-est de la Province du lac Supérieur et qui découlent du programme d'exploration du Grand Nord de Géologie Québec. La première étape de ce programme a consisté en un échantillonnage géochimique régional de sédiments lacustres, où 26 000 échantillons ont été prélevés au nord du 55e parallèle, sur une superficie de près de 350 000 km2. La base de données ainsi constituée a attiré de nombreuses sociétés minières dans la région et de nombreuses découvertes minérales ont été faites. Amorcée en 1998, la deuxième étape a consisté en une cartographie géologique systématique, appuyée par des datations géochronologiques U-Pb. Et, en 2003, plus de 20 cartes à l'échelle 1:250 000 avaient été complétées. Le programme du Grand Nord en est maintenant à sa dernière étape, laquelle aboutira à la production d'une synthèse géologique et métallogénique à partir des nouvelles données provenant des régions étudiées. Environ une quarantaine de bandes volcano-sédimentaires, de nombreuses intrusions mafiques et ultramatiques, et seize types de gisements minéralogiques différents y ont été décrits. Depuis 1997, ce programme a entraîné des investissements d'exploration par l'entreprise privée dépassant les 38 M$

Cooperative regulation of extracellular signal-regulated kinase activation and cell shape change by filamin A and beta-arrestins.: FLNA AND ßarr COOPERATE TO REGULATE ERK AND CELL SHAPE

14 pagesbeta-Arrestins (betaarr) are multifunctional adaptor proteins that can act as scaffolds for G protein-coupled receptor activation of mitogen-activated protein kinases (MAPK). Here, we identify the actin-binding and scaffolding protein filamin A (FLNA) as a betaarr-binding partner using Son of sevenless recruitment system screening, a classical yeast two-hybrid system, coimmunoprecipitation analyses, and direct binding in vitro. In FLNA, the betaarr-binding site involves tandem repeat 22 in the carboxyl terminus. betaarr binds FLNA through both its N- and C-terminal domains, indicating the presence of multiple binding sites. We demonstrate that betaarr and FLNA act cooperatively to activate the MAPK extracellular signal-regulated kinase (ERK) downstream of activated muscarinic M1 (M1MR) and angiotensin II type 1a (AT1AR) receptors and provide experimental evidence indicating that this phenomenon is due to the facilitation of betaarr-ERK2 complex formation by FLNA. In Hep2 cells, stimulation of M1MR or AT1AR results in the colocalization of receptor, betaarr, FLNA, and active ERK in membrane ruffles. Reduction of endogenous levels of betaarr or FLNA and a catalytically inactive dominant negative MEK1, which prevents ERK activation, inhibit membrane ruffle formation, indicating the functional requirement for betaarr, FLNA, and active ERK in this process. Our results indicate that betaarr and FLNA cooperate to regulate ERK activation and actin cytoskeleton reorganization

Thermal conductivity of InAs quantum dot stacks using AlAs strain compensating layers on InP substrate

International audienceThe growth and thermal conductivity of InAs quantum dot (QD) stacks embedded in GaInAs matrix with AlAs compensating layers deposited on (1 1 3)B InP substrate are presented. The effect of the strain compensating AlAs layer is demonstrated through Atomic Force Microscopy (AFM) and X-ray diffraction structural analysis. The thermal conductivity (2.7 W/m K at 300 K) measured by the 3ω method reveals to be clearly reduced in comparison with a bulk InGaAs layer (5 W/m K). In addition, the thermal conductivity measurements of S doped InP substrates and the SiN insulating layer used in the 3ω method in the 20-200 °C range are also presented. An empirical law is proposed for the S doped InP substrate, which slightly differs from previously presented results

Theoretical study of highly strained InAs material from first-principles modelling: application to an ideal QD

International audienceWe study the properties of highly strained InAs material calculated from first principles modeling using ABINIT packages. We first simulate the characteristic of bulk InAs crystal and compare them with both experimental and density functional theory (DFT) results. Secondly, we focus our attention on the strain effects on InAs crystal with a gradual strain reaching progressively the lattice matched parameters of InP, GaAs and GaP substrates. The final part is dedicated to the study of a hypothetic spherical InAs/GaP quantum dot. The effect of hydrostatic deformations for both InAs Zinc-Blende phase and InAs RockSalt phase is discussed