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Search Results: 1 - 10 of 52965 matches for " David Lavergne "
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Le cheveu sur l’autel :Remarques sur un rite de dédition personnelle
David Lavergne
Bulletin du Centre d’études Médiévales d’Auxerre , 2011, DOI: 10.4000/cem.11794
Abstract: L’autel médiéval chrétien, où s’accomplit le mystère eucharistique, joue aussi un r le en dehors des célébrations ordinaires de la messe. Il matérialise l’endroit le plus sacré de l’église tout en conservant sa fonction fondamentale de table d’offrande (mensa), sur laquelle sont déposés les différents ustensiles que le célébrant manipule durant la communion, comme le calice ou la pyxide, qui sont ensuite rangés dans la sacristie. En temps normal, rien ne doit encombrer l’autel, ce qui confère...
Profondeur d'immersion et dispositifs optimaux pour la sismique à haute résolution en mer Immersion Depth and Optimum Arrays for Marine High-Resolution Surveying
Lavergne M.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1979020
Abstract: La profondeur d'immersion des sources et des fl tes, la longueur des fl tes et l'étalement des dispositifs doivent être choisis en fonction du pouvoir de résolution et de la pénétration désirés. La profondeur d'immersion théorique optimale des sources et des fl tes est de l'ordre de I m pour la haute résolution (fréquences utiles entre 150 et 600 Hz), 3 à 6 m pour la moyenne résolution (entre 50 et 200 Hz), 12 m pour la sismique classique (jusqu'a 50 Hz). Sur le plateau continental, la longueur optimale des fl tes est de l'ordre de 120 m en haute résolution, 600 à 1200 m en moyenne résolution. Avec des sources synchrones et des dispositifs non pondérés, l'étalement des dispositifs source et des traces ne doit pas dépasser 4 à 6 m en haute résolution, 12 à 36 m en moyenne résolution. Les résultats de sismique à haute et moyenne résolution obtenus avec le navire Résolution et le système Flexichoc FHC 50 sont en accord avec ces valeurs théoriques. Immersion depth of sources and streamers, length of streamers, and lengthwise extension of seismic arrays must be chosen according to thé required resolution and penetration.,Optimum depth of sources and streamers is theoretically about I meter for high resolution (frequencies between 150 and 600 Hz), 3 ta 6 meters for medium resolution (between 50 and 200 Hz) and 12 meters for standard seismic profiles.On thé continental shelf, optimum streamer length is about 120 meters for high reso-lution and 600 ta 1,200 meters for medium resolution. Lengthwise array extension with synchronous unweighted éléments should not be greater than 4 to 6 meters for high resolution and 12 to 36 meters for medium resolution. Results obtained aboard thé M. V. Résolution, using Flexichoc FHC 50 systems, are in agreement with these theoretical figurés.
Crystal structures of an Extracytoplasmic Solute Receptor from a TRAP transporter in its open and closed forms reveal a helix-swapped dimer requiring a cation for α-keto acid binding
Sophie Gonin, Pascal Arnoux, Bénédicte Pierru, Jér?me Lavergne, Béatrice Alonso, Monique Sabaty, David Pignol
BMC Structural Biology , 2007, DOI: 10.1186/1472-6807-7-11
Abstract: We describe the high-resolution crystal structures of TakP in its unliganded form and as a complex with sodium-pyruvate. The results show a limited "Venus flytrap" conformational change induced by substrate binding. In the liganded structure, a cation (most probably a sodium ion) is present and plays a key role in the association of the pyruvate to the protein. The structure of the binding pocket gives a rationale for the relative affinities of various ligands that were tested from a fluorescence assay. The protein appears to be dimeric in solution and in the crystals, with a helix-swapping structure largely participating in the dimer formation. A 30 ?-long water channel buried at the dimer interface connects the two ligand binding cavities of the dimer.The concerted recruitment by TakP of the substrate group with a cation could represent a first step in the coupled transport of both partners, providing the driving force for solute import. Furthermore, the unexpected dimeric structure of TakP suggests a molecular mechanism of solute uptake by the dimeric ESR via a channel that connects the binding sites of the two monomers.Transport systems are required in all organisms to facilitate movement of nutrients and other solutes across biological membranes. In prokaryotes, several classes of transport systems have been defined on the basis of their subunit composition and mode of energization [1]. The well-characterized ATP-binding cassette superfamily (ABC) represents one of the largest families of solute-specific transporters. In the ABC system, the driving force for solute transport across the membrane subunits is derived from ATP hydrolysis. In bacteria, solute uptake often requires the presentation of substrate by a high affinity Extracytoplasmic Solute Receptor (ESR, also called S- or P-BP for Solute or Periplasmic Binding Protein). The three dimensional structures of numerous ESRs specific for a wide range of substrates have been determined and, despite lack of seq
Programa Bolsa Família: uma nova modalidade de biopolítica
Lavergne, Rémi Fernand;
Servi?o Social & Sociedade , 2012, DOI: 10.1590/S0101-66282012000200006
Abstract: the purpose of this article is to show how the family allowance program (programa bolsa família - pbf) refers to a form of biopolitics such as evoked by foucault. besides illustrating how the pbf is inscribed in a normalizing perspective, the article seeks to show how the social services and the education "for a lifetime" play an important role in terms of building up subjectivity processes and subjective opinions and feelings whose aim is to guide and control the poor and marginalized populations' behavior.
Data-driven rate-optimal specification testing in regression models
Emmanuel Guerre,Pascal Lavergne
Mathematics , 2005, DOI: 10.1214/009053604000001200
Abstract: We propose new data-driven smooth tests for a parametric regression function. The smoothing parameter is selected through a new criterion that favors a large smoothing parameter under the null hypothesis. The resulting test is adaptive rate-optimal and consistent against Pitman local alternatives approaching the parametric model at a rate arbitrarily close to 1/\sqrtn. Asymptotic critical values come from the standard normal distribution and the bootstrap can be used in small samples. A general formalization allows one to consider a large class of linear smoothing methods, which can be tailored for detection of additive alternatives.
A Skew Normal Model of the Dose-Effect Relation in Pharmacology
Francis Lavergne,Nicolas Marie
Statistics , 2015,
Abstract: This paper deals with a skew-normal model of the relation between a dose $d > 0$ and a quantitative measure $E(d)$ of an effect of the administered drug. Precisely, $E(d)$ is a measure of the therapeutic response or a measure of a side-effect. Some existing and additional properties of the logistic functions are proved, and a skew-normal model of the escape time of rats under an experimental antidepressant medication is provided.
Rare Species Support Vulnerable Functions in High-Diversity Ecosystems
David Mouillot ,David R. Bellwood,Christopher Baraloto,Jerome Chave,Rene Galzin,Mireille Harmelin-Vivien,Michel Kulbicki,Sebastien Lavergne,Sandra Lavorel,Nicolas Mouquet,C. E. Timothy Paine,Julien Renaud,Wilfried Thuiller
PLOS Biology , 2013, DOI: 10.1371/journal.pbio.1001569
Abstract: Around the world, the human-induced collapses of populations and species have triggered a sixth mass extinction crisis, with rare species often being the first to disappear. Although the role of species diversity in the maintenance of ecosystem processes has been widely investigated, the role of rare species remains controversial. A critical issue is whether common species insure against the loss of functions supported by rare species. This issue is even more critical in species-rich ecosystems where high functional redundancy among species is likely and where it is thus often assumed that ecosystem functioning is buffered against species loss. Here, using extensive datasets of species occurrences and functional traits from three highly diverse ecosystems (846 coral reef fishes, 2,979 alpine plants, and 662 tropical trees), we demonstrate that the most distinct combinations of traits are supported predominantly by rare species both in terms of local abundance and regional occupancy. Moreover, species that have low functional redundancy and are likely to support the most vulnerable functions, with no other species carrying similar combinations of traits, are rarer than expected by chance in all three ecosystems. For instance, 63% and 98% of fish species that are likely to support highly vulnerable functions in coral reef ecosystems are locally and regionally rare, respectively. For alpine plants, 32% and 89% of such species are locally and regionally rare, respectively. Remarkably, 47% of fish species and 55% of tropical tree species that are likely to support highly vulnerable functions have only one individual per sample on average. Our results emphasize the importance of rare species conservation, even in highly diverse ecosystems, which are thought to exhibit high functional redundancy. Rare species offer more than aesthetic, cultural, or taxonomic diversity value; they disproportionately increase the potential breadth of functions provided by ecosystems across spatial scales. As such, they are likely to insure against future uncertainty arising from climate change and the ever-increasing anthropogenic pressures on ecosystems. Our results call for a more detailed understanding of the role of rarity and functional vulnerability in ecosystem functioning.
A New Strategy for Antidepressant Prescription
Francis Lavergne,Thérèse M. Jay
Frontiers in Neuroscience , 2010, DOI: 10.3389/fnins.2010.00192
Abstract: From our research and literature search we propose an understanding of the mechanism of action of antidepressants treatments (ADTs) that should lead to increase efficacy and tolerance. We understand that ADTs promote synaptic plasticity and neurogenesis. This promotion is linked with stimulation of dopaminergic receptors. Previous evidence shows that all ADTs (chemical, electroconvulsive therapy, repetitive transcranial magnetic stimulation, sleep deprivation) increase at least one monoamine neurotransmitter serotonin (5-HT), noradrenaline (NA) or dopamine (DA); this article focuses on DA release or turn-over in the frontal cortex. DA increased dopaminergic activation promotes synaptic plasticity with an inverted U shape dose–response curve. Specific interaction between DA and glutamate is mediated by D1 receptor subtypes and Glutamate (NMDA) receptors with neurotrophic factors likely to play a modulatory role. With the understanding that all ADTs have a common, final, DA-ergic stimulation that promotes synaptic plasticity we can predict that (1) AD efficiency is related to the compound strength for inducing DA-ergic stimulation. (2) ADT efficiency presents a therapeutic window that coincides with the inverted U shape DA response curve. (3) ADT delay of action is related to a “synaptogenesis and neurogenesis delay of action.” (4) The minimum efficient dose can be found by starting at a low dosage and increasing up to the patient response. (5) An increased tolerance requires a concomitant prescription of a few ADTs, with different or opposite adverse effects, at a very low dose. (6) ADTs could improve all diseases with cognitive impairments and synaptic depression by increasing synaptic plasticity and neurogenesis.
Powerful nonparametric checks for quantile regression
Samuel Maistre,Pascal Lavergne,Valentin Patilea
Statistics , 2014,
Abstract: We address the issue of lack-of-fit testing for a parametric quantile regression. We propose a simple test that involves one-dimensional kernel smoothing, so that the rate at which it detects local alternatives is independent of the number of covariates. The test has asymptotically gaussian critical values, and wild bootstrap can be applied to obtain more accurate ones in small samples. Our procedure appears to be competitive with existing ones in simulations. We illustrate the usefulness of our test on birthweight data.
A Significance Test for Covariates in Nonparametric Regression
Pascal Lavergne,Samuel Maistre,Valentin Patilea
Statistics , 2014,
Abstract: We consider testing the significance of a subset of covariates in a nonparametric regression. These covariates can be continuous and/or discrete. We propose a new kernel-based test that smoothes only over the covariates appearing under the null hypothesis, so that the curse of dimensionality is mitigated. The test statistic is asymptotically pivotal and the rate of which the test detects local alternatives depends only on the dimension of the covariates under the null hypothesis. We show the validity of wild bootstrap for the test. In small samples, our test is competitive compared to existing procedures.
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