Showing papers by "Centre national de la recherche scientifique published in 1994"
TL;DR: A framework for maximum a posteriori (MAP) estimation of hidden Markov models (HMM) is presented, and Bayesian learning is shown to serve as a unified approach for a wide range of speech recognition applications.
Abstract: In this paper, a framework for maximum a posteriori (MAP) estimation of hidden Markov models (HMM) is presented. Three key issues of MAP estimation, namely, the choice of prior distribution family, the specification of the parameters of prior densities, and the evaluation of the MAP estimates, are addressed. Using HMM's with Gaussian mixture state observation densities as an example, it is assumed that the prior densities for the HMM parameters can be adequately represented as a product of Dirichlet and normal-Wishart densities. The classical maximum likelihood estimation algorithms, namely, the forward-backward algorithm and the segmental k-means algorithm, are expanded, and MAP estimation formulas are developed. Prior density estimation issues are discussed for two classes of applications/spl minus/parameter smoothing and model adaptation/spl minus/and some experimental results are given illustrating the practical interest of this approach. Because of its adaptive nature, Bayesian learning is shown to serve as a unified approach for a wide range of speech recognition applications. >
2,430 citations
TL;DR: It is reported here that a polypeptide of 16 amino acids in length corresponding to the third helix of the homeodomain deleted of its N-terminal glutamate is still capable of translocating through the membrane, suggesting an energy-independent mechanism of translocation not involving classical endocytosis.
2,149 citations
Book•
01 Jan 1994TL;DR: This in-depth review of current virtual reality technology and its applications provides a detailed analysis of the engineering, scientific and functional aspects of virtual reality systems and the fundamentals of VR modeling and programming.
Abstract: From the Publisher:
This in-depth review of current virtual reality technology and its applications provides a detailed analysis of the engineering, scientific and functional aspects of virtual reality systems and the fundamentals of VR modeling and programming. It also contains an exhaustive list of present and future VR applications in a number of diverse fields. Virtual Reality Technology is the first book to include a full chapter on force and tactile feedback and to discuss newer interface tools such as 3-D probes and cyberscopes. Supplemented with 23 color plates and more than 200 drawings and tables which illustrate the concepts described.
1,823 citations
TL;DR: The nucleotide sequence of a contiguous 2,181,032 base pairs in the central gene cluster of chromosome III is completed, and comparison with the public sequence databases reveals similarities to previously known genes for about one gene in three.
Abstract: As part of our effort to sequence the 100-megabase (Mb) genome of the nematode Caenorhabditis elegans, we have completed the nucleotide sequence of a contiguous 2,181,032 base pairs in the central gene cluster of chromosome III. Analysis of the finished sequence has indicated an average density of about one gene per five kilobases; comparison with the public sequence databases reveals similarities to previously known genes for about one gene in three. In addition, the genomic sequence contains several intriguing features, including putative gene duplications and a variety of other repeats with potential evolutionary implications.
1,612 citations
Book•
01 Jan 1994TL;DR: In this Special Issue, working values are reported for 383 international geostandards along with sample description along with database information in the form of databases for easy access from a microcomputer in the laboratory itself.
Abstract: In this Special Issue, working values are reported for 383 international geostandards along with sample description. All this information is available in the form of databases. The possibility of easily accessing data on geostandards from a microcomputer in the laboratory itself is an efficient means for handling quality control/ quality assurance problems.
1,478 citations
TL;DR: A field-effect transistor has been fabricated from polymer materials by printing techniques, which shows high current output, and opens the way for large-area, low-cost plastic electronics.
Abstract: A field-effect transistor has been fabricated from polymer materials by printing techniques. The device characteristics, which show high current output, are insensitive to mechanical treatments such as bending or twisting. This all-organic flexible device, realized with mild techniques, opens the way for large-area, low-cost plastic electronics.
1,469 citations
TL;DR: Certain notorious nonlinear binary codes contain more codewords than any known linear code and can be very simply constructed as binary images under the Gray map of linear codes over Z/sub 4/, the integers mod 4 (although this requires a slight modification of the Preparata and Goethals codes).
Abstract: Certain notorious nonlinear binary codes contain more codewords than any known linear code. These include the codes constructed by Nordstrom-Robinson (1967), Kerdock (1972), Preparata (1968), Goethals (1974), and Delsarte-Goethals (1975). It is shown here that all these codes can be very simply constructed as binary images under the Gray map of linear codes over Z/sub 4/, the integers mod 4 (although this requires a slight modification of the Preparata and Goethals codes). The construction implies that all these binary codes are distance invariant. Duality in the Z/sub 4/ domain implies that the binary images have dual weight distributions. The Kerdock and "Preparata" codes are duals over Z/sub 4/-and the Nordstrom-Robinson code is self-dual-which explains why their weight distributions are dual to each other. The Kerdock and "Preparata" codes are Z/sub 4/-analogues of first-order Reed-Muller and extended Hamming codes, respectively. All these codes are extended cyclic codes over Z/sub 4/, which greatly simplifies encoding and decoding. An algebraic hard-decision decoding algorithm is given for the "Preparata" code and a Hadamard-transform soft-decision decoding algorithm for the I(Kerdock code. Binary first- and second-order Reed-Muller codes are also linear over Z/sub 4/, but extended Hamming codes of length n/spl ges/32 and the Golay code are not. Using Z/sub 4/-linearity, a new family of distance regular graphs are constructed on the cosets of the "Preparata" code. >
1,347 citations
University of California, San Francisco1, University of Liège2, University of Oklahoma3, Columbia University4, Teikyo University5, Medical Research Council6, Scripps Research Institute7, University of Texas MD Anderson Cancer Center8, Harvard University9, Centre national de la recherche scientifique10, French Institute of Health and Medical Research11, Wayne State University12, University of Toronto13, Michigan State University14
1,098 citations
TL;DR: It is concluded that the hORL1 receptor is a new member of the opioid receptor family with a potential role in modulating a number of brain functions, including instinctive behaviours and emotions.
1,090 citations
TL;DR: In this article, the authors analyzed the Raman spectra of 29 different carbon materials, including all types of carbonaceous solids of practical interest, and found that the width of the D band correlates well with the degree of disorder over the entire order-disorder interval.
1,044 citations
TL;DR: In this paper, the chemical composition of Zinnwaldite ZW-C, a Li-mica, reputed difficult to analyse because of its high contents of F and rare alkali elements and the presence of refractory minerals, has been characterized.
Abstract: Within a short period of one year (November 1992- October 1993), ninety-two IWG-Member laboratories have been able to characterize the chemical composition of a candidate reference sample, Zinnwaldite ZW-C, a Li-mica, reputed difficult to analyse because of its high contents of F and rare alkali elements and of the presence of refractory minerals. Thanks to the help of 163 analysts from the 92 laboratories, it has been possible to assign working values for 20 major and minor elements including the rare alkali elements and for 43 trace elements; all the working values receive the status of recommended values, except H20, C02, LOI, CI and S. It is, indeed, a rare success for such a difficult sample!
TL;DR: In this article, it was shown that string-loop modifications of the low-energy matter couplings of the dilation may provide a mechanism for fixing the vacuum expectation value of a massless dilation in a way which is naturally compatible with existing experimental data.
TL;DR: The aim of developing TopPred II is to compile all existing knowledge about topology in order to permit easy access to prediction of membrane protein topologies.
Abstract: Integral membrane proteins have parts of their polypeptide backbones embedded in a phospholipid bilayer. These hydrophobic, membrane-spanning domains are separated by hydrophilic segments exposed to the aqueous environment and seem to fall into two basic modalities: a-helix bundle and anti-parallel /3-barrel membrane domains. For the helix bundle proteins, two easily identifiable features appear to be the major structural determinants: the long apolar stretches that form the transmembrane a-helices, and the biased distribution of charged residues in the polar regions, known as the 'positive-inside' rule (von Heijne, 1986). Recently, attempts to predict topologies of eukaryotic and prokaryotic integral membrane proteins that form a-helical structures, have been reported (von Heijne, 1992; Sipos and von Heijne, 1993). This work has indeed shown that the topology of such proteins can be effectively deduced from the amino acid sequence. Thus, the aim of developing TopPred II is to compile all existing knowledge about topology in order to permit easy access to prediction of membrane protein topologies. TopPred II is an improved version of the preceding freeware TOP-PRED (von Heijne, 1992). It is now a stand-alone application written in Symantec THINK Pascal to allow its operation on any Macintosh computer with a 6.0.2 (or beyond) system, respecting the standard Apple file- and window-handling procedures, and making extensive use of the graphic abilities of Macintosh computers. The compiled program is very compact (~90 kbytes) and all the default parameters, scales and texts have been built into resources to allow easy access and ability for permanent modifications by the user. Input sequence files are limited to 2000 amino acids. Sequences can be handled one by one or in groups of up to 20. Parameters and scales can be easily modified through standard dialogs, which also enable one to re-establish the TopPred II default values. Calculation of the hydrophobicity profile, transmembrane segments and topologies (see below) can be requested. All the displayed results (texts as well as graphics) can be printed out or saved in files that can be imported by other programs.
TL;DR: In this paper, a high-resolution oxygen isotope record from giant piston core MD900963 (Maldives area, tropical Indian Ocean) was studied, in which precession-related oscillations in δ18O were particularly well expressed, owing to the superimposition of a local salinity signal on the global ice volume signal.
TL;DR: The function of the RPS2 gene product in defense signal transduction is postulated to involve nucleotide triphosphate binding and protein-protein interactions and may also involve the reception of an elicitor produced by the avirulent pathogen.
Abstract: Plant disease resistance genes function is highly specific pathogen recognition pathways. PRS2 is a resistance gene of Arabidopsis thaliana that confers resistance against Pseudomonas syringae bacteria that express avirulence gene avrRpt2. RPS2 was isolated by the use of a positional cloning strategy. The derived amino acid sequence of RPS2 contains leucine-rich repeat, membrane-spanning, leucine zipper, and P loop domains. The function of the RPS2 gene product in defense signal transduction is postulated to involve nucleotide triphosphate binding and protein-protein interactions and may also involve the reception of an elicitor produced by the avirulent pathogen.
TL;DR: In this article, mutant mice lacking the 5-HT1B receptor were generated by homologous recombination, and they did not exhibit any obvious developmental or behavioral defects, and when confronted with an intruder, mutant mice attacked the intruder faster and more intensely than did wild-type mice.
Abstract: The neuromodulator serotonin (5-hydroxytryptamine, 5-HT) has been associated with mood disorders such as depression, anxiety, and impulsive violence. To define the contribution of 5-HT receptor subtypes to behavior, mutant mice lacking the 5-HT1B receptor were generated by homologous recombination. These mice did not exhibit any obvious developmental or behavioral defects. However, the hyperlocomotor effect of the 5-HT1A/1B agonist RU24969 was absent in mutant mice, indicating that this effect is mediated by 5-HT1B receptors. Moreover, when confronted with an intruder, mutant mice attacked the intruder faster and more intensely than did wild-type mice, suggesting the participation of 5-HT1B receptors in aggressive behavior.
TL;DR: In this article, the authors describe a computationally fast and accurate technique for the atmospheric correction of satellite measurements in the solar spectrum, which is based on a set of equations with coefficients which depend on the spectral band of the sensor.
Abstract: This paper describes a computationally fast and accurate technique for the atmospheric correction of satellite measurements in the solar spectrum. The main advantage of the method is that it is several hundred times faster than more detailed radiative transfer models like 5S and that it does not require precalculated look-up tables. The method is especially useful for correcting the huge amounts of data acquired by large-field-of-view high-repetitivity sensors, like the ones on board polar orbiting and geostationary meteorological satellites. The technique is based on a set of equations with coefficients which depend on the spectral band of the sensor. Semi-empirical formulations are used to describe the different interactions (absorption, scattering, etc.) of solar radiation with atmospheric constituents during its traverse through the atmosphere. Sensor specific coefficients of each equation are determined using a best fit technique against the computations of the 5S code (Simulation of Satelli...
TL;DR: Results suggest that the ABI1 protein is a Ca(2+)-modulated phosphatase and functions to integrate ABA and Ca2+ signals with phosphorylation-dependent response pathways.
Abstract: The Arabidopsis ABI1 locus is essential for a wide spectrum of abscisic acid (ABA) responses throughout plant development. Here, ABI1 was shown to regulate stomatal aperture in leaves and mitotic activity in root meristems. The ABI1 gene was cloned and predicted to encode a signaling protein. Although its carboxyl-terminal domain is related to serine-threonine phosphatase 2C, the ABI1 protein has a unique amino-terminal extension containing an EF hand calcium-binding site. These results suggest that the ABI1 protein is a Ca(2+)-modulated phosphatase and functions to integrate ABA and Ca2+ signals with phosphorylation-dependent response pathways.
TL;DR: It is demonstrated here that Krox-20 is also activated in Schwann cells before the onset of myelination and that its disruption blocks Schwann Cells at an early stage in their differentiation, thus preventing myelinations in the peripheral nervous system.
Abstract: The molecular mechanisms controlling the process of myelination by Schwann cells remain elusive, despite recent progress in the identification and characterization of genes encoding myelin components (reviewed in ref. 1). We have created a null allele in the mouse Krox-20 gene, which encodes a zinc-finger transcription factor, by in-frame insertion of the Escherichia coli lacZ gene, and have shown that hindbrain segmentation is affected in Krox-20-/- embryos. We demonstrate here that Krox-20 is also activated in Schwann cells before the onset of myelination and that its disruption blocks Schwann cells at an early stage in their differentiation, thus preventing myelination in the peripheral nervous system. In Krox-20-/- mice, Schwann cells wrap their cytoplasmic processes only one and a half turns around the axon, and although they express the early myelin marker, myelin-associated glycoprotein, late myelin gene products are absent, including those for protein zero and myelin basic protein. Therefore Krox-20 is likely to control a set of genes required for completion of myelination in the peripheral nervous system.
TL;DR: The band structures for the transverse modes of nickel alloy cylinders in an aluminum alloy host, and vice versa are computed, finding band gaps which extend throughout the Brillouin zone.
Abstract: We study an elastic composite described by the position-dependent mass density \ensuremath{\rho}(r), the longitudinal speed of sound ${\mathit{c}}_{\mathit{l}}$(r), and the transverse speed of sound ${\mathit{c}}_{\mathit{t}}$(r). For a spatially periodic composite---a ``phononic crystal''---we derive the eigenvalue equation for the frequencies ${\mathrm{\ensuremath{\omega}}}_{\mathit{n}}$(K), where n is the serial number of the band and K is the Bloch wave vector. This is applied to the special case of a binary composite and, further, to the case of infinite cylinders that form a two-dimensional lattice. For this configuration (and no wave-vector component parallel to the cylinders) there are two independent modes of vibration. The elastic displacement u(r) is parallel to the cylinders for one of them---the transverse polarization mode. The other one is a mixed (longitudinal-transverse) polarization mode with u(r) perpendicular to the cylinders. Specifically we consider circular cylinders that form a square lattice. We compute the band structures for the transverse modes of nickel alloy cylinders in an aluminum alloy host, and vice versa. In both situations we find band gaps which extend throughout the Brillouin zone. Within these gaps the transverse vibrations, sound, and phonons are forbidden. We also investigate the dependence of the band gap on the filling fraction and on the material parameters.
TL;DR: The multiplicity of electrohydrodynamic spraying functioning modes has been and still continues to be, a cause of misunderstanding as mentioned in this paper, and several results are compared with those of earlier work.
TL;DR: A null mutation was generated in the mouse RXR alpha gene by targeted disruption and displayed myocardial and ocular malformations belonging to the fetal vitamin A deficiency syndrome, supporting the idea that RXRalpha is involved in retinoid signaling in vivo.
TL;DR: In this paper, four ligands from Mycobacterium tuberculosis strain H37Rv that stimulated proliferation of a major human gamma delta T cell subset were isolated and partially characterized.
Abstract: Most human peripheral blood gamma delta T lymphocytes respond to hitherto unidentified mycobacterial antigens. Four ligands from Mycobacterium tuberculosis strain H37Rv that stimulated proliferation of a major human gamma delta T cell subset were isolated and partially characterized. One of these ligands, TUBag4, is a 5' triphosphorylated thymidine-containing compound, to which the three other stimulatory molecules are structurally related. These findings support the hypothesis that some gamma delta T cells recognize nonpeptidic ligands.
TL;DR: Through its unique selectivity olomoucine provides an anti-mitotic reagent that may preferentially inhibit certain steps of the cell cycle and inhibits the licensing factor, an essential replication factor ensuring that DNA is replicated only once in each cell cycle.
Abstract: While testing purines related to the non-specific protein kinase inhibitors M-dimethylaminopurine and N6-(A'-isopenteny1)adenine as potential inhibitors of the p34'd'z/cyclin B kinase, we discovered a compound with high specificity, 2-(2-hydroxyethylamino)-6-benzylamino-9-methylpurine (olomoucine). Kinetic analysis of kinase inhibition reveals that olomoucine behaves as a competitive inhibitor for ATP and as a non-competitive inhibitor for histone H1 (linear inhibition for both substrates). The kinase specificity of this inhibition was investigated for 35 highly purified kinases (including p34"dk4/~y~lin D1, p4Wdk6/cyclin D3, CAMP-dependent and cGMP-dependent kinases, eight protein kinase C isoforms, calmodulin-dependent kinase 11, myosin light-chain kinase, mitogen-activated S6 kinase, casein kinase 2, double-stranded EWA-activated protein kinase, AMPstimulated kinase, eight tyrosine kinases). Most kinases are not significantly inhibited. Only the cell-cycle regulating p34'dc2/cyclin B, p33cdk2/~y~lin A and p33cdk2/~y~lin E kinases, the brain ~33'~~'/ p35 kinase and the ERKlMAP-kinase (and its starfish homologue ~44"'~~) are substantially inhibited by olomoucine (I& values are 7, 7, 7, 3 and 25 pM, respectively). The cdk4/cyclin D1 and cdk6/ cyclin D3 kinases are not significantly sensitive to olomoucine (I& values greater than 1 mM and 150 pM, respectively). M-(A2-1sopentenyl)adenine is confirmed as a general kinase inhibitor with IC,, values of 50-100 pM for many kinases. The purine specificity of cyclin-dependent kinase inhibition was investigated: among 81 purine derivatives tested, only C2, N6 and N9-substituted purines exert a strong inhibitory effect on the p34'd'2/cyclin B kinase. An essentially similar sensitivity to this olomoucine family of compounds was observed for the brain-specific cdkYp35 kinase. Structure/activity relationship studies allow speculation on the interactions of olomoucine and its analogues with the kinase catalytic subunit. Olomoucine inhibits in vitro M-phase-promoting factor activity in metaphase-arrested Xenopus egg extracts, inhibits in vitro DNA synthesis in Xenopus interphase egg extracts and inhibits the licensing factor, an essential replication factor ensuring that DNA is replicated only once in each cell cycle. Olomoucine inhibits the starfish oocyte G2M transition in vivo. Through its unique selectivity olomoucine provides an anti-mitotic reagent that may preferentially inhibit certain steps of the cell cycle.
TL;DR: The simultaneous involvement of D1 and D2 dopamine receptors has been evidenced in the anxiogenic-like effect associated with an increase of dopaminergic transmissions.
TL;DR: The postural control system has two main functions: first, to build up posture against gravity and ensure that balance is maintained; and second, to fix the orientation and position of the segments that serve as a reference frame for perception and action with respect to the external world.
TL;DR: In this article, the authors describe a polymer composite with excellent photorefractive properties, achieving a diffraction efficiency approaching 100% and a net two-beam coupling gain of more than 200 cm-1.
Abstract: PHOTOREFRACTIVE materials are of considerable interest for the development of all-optical devices1. The photoref ractive effect appears in materials that exhibit an electric-field-dependent refractive index and that are photosensitive, such that the spatial distribution of photogenerated charge carriers is modified on irradiation with light. The diffraction pattern formed by the interference of two coherent light beams within such a material generates a non-uniform internal electric field that in turn modulates the refractive index. The resulting refractive-index pattern forms a grating that can diffract light and thereby give rise to two-beam coupling, whereby one of the writing beams gains energy at the expense of the other—a property that can be exploited in photonic devices. Although the best photorefractive materials currently available are inorganic crystals such as LiNbO3, there is considerable interest in the development of photorefractive polymers2–8, owing to their structural flexibility, ease of processing and lower cost. We describe here a polymer composite with excellent photorefractive properties. We have achieved a diffraction efficiency approaching 100% and a net two-beam coupling gain of more than 200 cm–1, making these polymeric materials suitable for immediate application in areas such as dynamic holographic storage and optical information processing1.
TL;DR: Analysis of the Greenland ice core covering the period from 3000 to 500 years ago—the Greek, Roman, Medieval and Renaissance times— shows that lead is present at concentrations four times as great as natural values from about 2500 to 1700 years ago.
Abstract: Analysis of the Greenland ice core covering the period from 3000 to 500 years ago-the Greek, Roman, Medieval and Renaissance times-shows that lead is present at concentrations four times as great as natural values from about 2500 to 1700 years ago (500 B.C. to 300 A.D.). These results show that Greek and Roman lead and silver mining and smelting activities polluted the middle troposphere of the Northern Hemisphere on a hemispheric scale two millennia ago, long before the Industrial Revolution. Cumulative lead fallout to the Greenland Ice Sheet during these eight centuries was as high as 15 percent of that caused by the massive use of lead alkyl additives in gasoline since the 1930s. Pronounced lead pollution is also observed during Medieval and Renaissance times.
01 Oct 1994
TL;DR: A fast and exact planner for the mobile robot model, based upon recursive subdivision of a collision-free path generated by a lower-level geometric planner that ignores the motion constraints, is presented.
Abstract: This paper considers the problem of motion planning for a car-like robot (i.e., a mobile robot with a nonholonomic constraint whose turning radius is lower-bounded). We present a fast and exact planner for our mobile robot model, based upon recursive subdivision of a collision-free path generated by a lower-level geometric planner that ignores the motion constraints. The resultant trajectory is optimized to give a path that is of near-minimal length in its homotopy class. Our claims of high speed are supported by experimental results for implementations that assume a robot moving amid polygonal obstacles. The completeness and the complexity of the algorithm are proven using an appropriate metric in the configuration space R/sup 2//spl times/S/sup 1/ of the robot. This metric is defined by using the length of the shortest paths in the absence of obstacles as the distance between two configurations. We prove that the new induced topology and the classical one are the same. Although we concentrate upon the car-like robot, the generalization of these techniques leads to new theoretical issues involving sub-Riemannian geometry and to practical results for nonholonomic motion planning. >
TL;DR: The introduction of a null mutation of the vimentin gene into the germ line of mice shows that a conspicuous developmental and cell-specific structure that is an integral part of the cytoskeleton can be eliminated without apparent effect on mouse reproduction and development.