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L’approche autobiographique : regards anthropologique et épistémologique, et orientations méthodologiques An Anthropological and Epistemological Look at the Autobiographical Approach, and Methodological Orientations. Narrative of a career
Guy de?Villers
Recherches Sociologiques et Anthropologiques , 2011, DOI: 10.4000/rsa.653
Abstract: à partir d’une thèse qui affirme l’irréductibilité du sujet de la parole aux figures du soi-même que fomente le récit autobiographique, l’auteur montre comment la mise en récit produit cet effet de subjectivation. Parce que le sujet de l’acte de dire ne peut qu’être exclu des énoncés qu’il articule, lui est ouvert l’horizon des possibles constitutifs de son projet d’exister. C’est sur la base de tels principes que peuvent se déduire les traits significatifs des dispositifs de formation et de recherche que nous promouvons dans le champ des pratiques autobiographiques. Les outils d’analyse et d’interpré-tation que nous proposons permettent de développer une véritable clinique textuelle. “Approche clinique” ne signifie cependant pas que la méthode du récit autobiographique relève nécessairement des pratiques thérapeutiques. Ses domaines d’application sont pluriels et les passages de frontières méritent d’être bien repérés. Le mouvement de la réflexion s’achève par une mise en cause sévère de certains usages de la notion d’identité pour rendre compte des effets de transformation repérables en formation, en thérapie ou en psychanalyse. Nous soutenons que c’est en raison de la non-identité de soi à soi que le sujet opère les changements qui pourront le rapprocher de sa quête. Pour ne pas conclure, nous terminons le récit de notre itinéraire dans le monde du récit autobiographique en proposant deux axes de recherches. Based on a thesis affirming the irreducibility of the subject of speech to the figures of oneself the autobiographical narrative foments, the author shows how the setting in narrative produces the effect of subjectification. Since the subject of the act of speaking cannot but be excluded from the statements he makes, the horizon of possibilities constitutive of his project of existing opens out to him. The significant features of the training and research techniques we promote in the field of autobiographical practices can be deduced on the basis of such principles. The analytical and interpretational tools we propose facilitate the development of a veritable textual clinic. However, a “clinical approach” does not mean that the method of autobiographical narrative necessarily involves therapeutic practices. Its areas of application are plural and the border crossings deserve to be delineated. This reflective process is brought to a close with a severe challenge against certain uses of the notion of identity to account for transformational effects noted in training, therapy or psychoanalysis. We contend that it is because of the non-identity of se
Goodness-of-fit Tests for high-dimensional Gaussian linear models
Nicolas Verzelen,Fanny Villers
Mathematics , 2007,
Abstract: Let $(Y,(X_i)_{i\in\mathcal{I}})$ be a zero mean Gaussian vector and $V$ be a subset of $\mathcal{I}$. Suppose we are given $n$ i.i.d. replications of the vector $(Y,X)$. We propose a new test for testing that $Y$ is independent of $(X_i)_{i\in \mathcal{I}\backslash V}$ conditionally to $(X_i)_{i\in V}$ against the general alternative that it is not. This procedure does not depend on any prior information on the covariance of $X$ or the variance of $Y$ and applies in a high-dimensional setting. It straightforwardly extends to test the neighbourhood of a Gaussian graphical model. The procedure is based on a model of Gaussian regression with random Gaussian covariates. We give non asymptotic properties of the test and we prove that it is rate optimal (up to a possible $\log(n)$ factor) over various classes of alternatives under some additional assumptions. Besides, it allows us to derive non asymptotic minimax rates of testing in this setting. Finally, we carry out a simulation study in order to evaluate the performance of our procedure.
Exact calculations for false discovery proportion with application to least favorable configurations
Etienne Roquain,Fanny Villers
Statistics , 2010, DOI: 10.1214/10-AOS847
Abstract: In a context of multiple hypothesis testing, we provide several new exact calculations related to the false discovery proportion (FDP) of step-up and step-down procedures. For step-up procedures, we show that the number of erroneous rejections conditionally on the rejection number is simply a binomial variable, which leads to explicit computations of the c.d.f., the {$s$-th} moment and the mean of the FDP, the latter corresponding to the false discovery rate (FDR). For step-down procedures, we derive what is to our knowledge the first explicit formula for the FDR valid for any alternative c.d.f. of the $p$-values. We also derive explicit computations of the power for both step-up and step-down procedures. These formulas are "explicit" in the sense that they only involve the parameters of the model and the c.d.f. of the order statistics of i.i.d. uniform variables. The $p$-values are assumed either independent or coming from an equicorrelated multivariate normal model and an additional mixture model for the true/false hypotheses is used. This new approach is used to investigate new results which are of interest in their own right, related to least/most favorable configurations for the FDR and the variance of the FDP.
Long-Lasting LTP Requires Neither Repeated Trains for Its Induction Nor Protein Synthesis for Its Development
Agnès Villers, Emile Godaux, Laurence Ris
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040823
Abstract: Current thinking about LTP triggered in the area CA1 of hippocampal slices is ruled by two “dogmas”: (1) A single train of high-frequency stimulation is sufficient to trigger short-lasting LTP (1 – 3 h), whereas multiple trains are required to induce long-lasting LTP (L-LTP, more than 4 h). (2) The development of the late phase of L-LTP requires the synthesis of new proteins. In this study, we found that a single high-frequency train could trigger an LTP lasting more than 8 h that was not affected by either anisomycin or cycloheximide (two inhibitors of protein synthesis). We ascertained that the induction of this L-LTP made use of the same mechanisms as those usually reported to be involved in LTP induction: it was dependent on NMDA receptors and on the activation of two “core” kinases, CaMKII and PI3K. These findings call into question the two “dogmas” about LTP.
Estimation and clustering in a semiparametric Poisson process stochastic block model for longitudinal networks
Catherine Matias,Tabea Rebafka,Fanny Villers
Statistics , 2015,
Abstract: In this work, we introduce a Poisson process stochastic block model for recurrent interaction events, where each individual belongs to a latent group and interactions between two individuals follow a conditional inhomogeneous Poisson process whose intensity is driven by the individuals' latent groups. The model is semiparametric as the intensities per group pair are modeled in a nonparametric way. First an identifiability result on the weights of the latent groups and the nonparametric intensities is established. Then we propose an estimation procedure, relying on a semiparametric version of a variational expectation-maximization algorithm. Two different versions of the method are proposed, using either histogram-type (with an adaptive choice of the partition size) or kernel intensity estimators. We also propose an integrated classification likelihood criterion to select the number of latent groups. Asymptotic consistency results are then explored, both for the estimators of the cumulative intensities per group pair and for the kernel procedures that estimate the intensities per group pair. Finally, we carry out synthetic experiments and analyse several real datasets to illustrate the strengths and weaknesses of our approach.
A Global Homogeneity Test for High-Dimensional Linear Regression
Camille Charbonnier,Nicolas Verzelen,Fanny Villers
Statistics , 2013,
Abstract: This paper is motivated by the comparison of genetic networks based on microarray samples. The aim is to test whether the differences observed between two inferred Gaussian graphical models come from real differences or arise from estimation uncertainties. Adopting a neighborhood approach, we consider a two-sample linear regression model with random design and propose a procedure to test whether these two regressions are the same. Relying on multiple testing and variable selection strategies, we develop a testing procedure that applies to high-dimensional settings where the number of covariates $p$ is larger than the number of observations $n_1$ and $n_2$ of the two samples. Both type I and type II errors are explicitely controlled from a non-asymptotic perspective and the test is proved to be minimax adaptive to the sparsity. The performances of the test are evaluated on simulated data. Moreover, we illustrate how this procedure can be used to compare genetic networks on Hess \emph{et al} breast cancer microarray dataset.
Hermetic storage: A novel approach to the protection of cocoa beans
W Jonfia-Essien, S Varro, P Villers
African Crop Science Journal , 2010,
Abstract: Hermetic storage has provided a successful storage method for protection of commodities without fumigants or need for refrigeration for insect control and quality preservation of stored products. Hermetic storage is achieved in specially constructed plastic structures for the preservation of cereal grains and other commodities. Plastic structures suitable for long-term storage systems, as well as intermediate storage of grain have been developed and applied. These storage systems based on the hermetic principle were designed for (1) storage at the farmercooperative and small trader level with 10 - 1000 tonnes capacity for enclosing stacks termed Cocoons , (2) small scale storage suitable for small portable containers of 60 kg to 2 tonnes called SuperGrainbags and (3) quality preservation, insect control and prevention of condensation during shipment of commodities in shipping containers known as ranSafeliners . Hermetic storage is based on the principle of generation of an oxygendepleted, carbon dioxide-enriched interstitial atmosphere caused by the respiration of the living organisms in the ecological system of a sealed storage. A sufficiently low oxygen and elevated CO2, atmosphere is created through a natural metabolic process based on insect respiration and, in cases where the commodity has sufficiently high moisture, the respiration of the microorganisms within a sealed storage system. Applications for which hermetic technology has been most widely accepted are long-term storage of cereal grains, primarily rice, corn, barley, wheat and a variety of seeds to preserve germination potential and vigor and quality preservation of high-value commodities such as cocoa and coffee. Under field conditions in a cocoa bean storage facility in Makassar, Indonesia, a hermetically sealed flexible structure containing 6.7 tonnes of cocoa beans at an initial moisture content of 7.3% and relative humidity of 70% was monitored for oxygen concentration and quality parameters of the beans. The measurements showed a decrease in oxygen concentration to 0.3% after 5.5 days. No insects survived the oxygen depleted biogenerated atmosphere. Similar trials were carried out in Ghana by COCOBOD in which three stacks for hermetic storage and one stack each for conventional storage (without fumigation) and standard storage (with fumigation) were built for sampling and observation. At the sixth week of storage 100% mortality of insects was recorded in the CocoonTM. All the cocoa beans inside the CocoonTM maintained their quality category throughout the storage period and the grade remained the same after nine weeks of storage as it was at the beginning of the experiment.
Land use change effects on runoff generation in a humid tropical montane cloud forest region
L. E. Mu?oz-Villers,J. J. McDonnell
Hydrology and Earth System Sciences Discussions , 2013, DOI: 10.5194/hessd-10-5269-2013
Abstract: While tropical montane cloud forests (TMCF) provide critical hydrological services to downstream regions throughout much of the humid tropics, catchment hydrology and impacts associated with forest conversion in these ecosystems remain poorly understood. Here, we compare the annual, seasonal and event-scale streamflow patterns and runoff generation processes of three neighbouring headwater catchments in central Veracruz (eastern Mexico) with similar pedological and geological characteristics, but different land cover: old-growth TMCF (MAT), 20 yr-old naturally regenerating TMCF (SEC) and a heavily grazed pasture (PAS). We used a 2 yr record of high resolution rainfall and stream flow data (2008–2010) in combination with stable isotope and chemical tracer data collected for a series of storms during a 6-week period of increasing antecedent wetness (wetting-up cycle). Our results showed that annual and seasonal streamflow patterns of the MAT and SEC were similar. In contrast, the PAS showed a 10% higher mean annual streamflow, most likely because of a lower rainfall interception. During the wetting-up cycle, storm runoff ratios increased at all three catchments (from 11 to 54% for the MAT, 7 to 52% for the SEC and 3 to 59% for the PAS). With the increasing antecedent wetness, hydrograph separation analysis showed progressive increases of pre-event water contributions to total stormflow (from 35 to 99% in the MAT, 26 to 92% in the SEC and 64 to 97% in the PAS). At all three sites, rainfall-runoff responses were dominated by subsurface flow generation processes for the majority of storms. However, for the largest and most intense storm (typically occurring once every 2 yr), sampled under wet antecedent conditions, the event water contribution in the PAS (34% on average) was much higher than in the forests (5% on average), indicating that rainfall infiltration capacity of the PAS was exceeded. This result suggests that despite the high permeability of the volcanic soils and underlying substrate in this TMCF environment, the conversion of forest to pasture may lead to important changes in runoff generation processes during large and high intensity storms. On the other hand, our results also showed that 20 yr of natural regeneration may be enough to largely restore the original hydrological conditions of this TMCF.
Shaping the aging brain: role of auditory input patterns in the emergence of auditory cortical impairments
Brishna Kamal,Constance Holman,Etienne de Villers-Sidani
Frontiers in Systems Neuroscience , 2013, DOI: 10.3389/fnsys.2013.00052
Abstract: Age-related impairments in the primary auditory cortex (A1) include poor tuning selectivity, neural desynchronization, and degraded responses to low-probability sounds. These changes have been largely attributed to reduced inhibition in the aged brain, and are thought to contribute to substantial hearing impairment in both humans and animals. Since many of these changes can be partially reversed with auditory training, it has been speculated that they might not be purely degenerative, but might rather represent negative plastic adjustments to noisy or distorted auditory signals reaching the brain. To test this hypothesis, we examined the impact of exposing young adult rats to 8 weeks of low-grade broadband noise on several aspects of A1 function and structure. We then characterized the same A1 elements in aging rats for comparison. We found that the impact of noise exposure on A1 tuning selectivity, temporal processing of auditory signal and responses to oddball tones was almost indistinguishable from the effect of natural aging. Moreover, noise exposure resulted in a reduction in the population of parvalbumin inhibitory interneurons and cortical myelin as previously documented in the aged group. Most of these changes reversed after returning the rats to a quiet environment. These results support the hypothesis that age-related changes in A1 have a strong activity-dependent component and indicate that the presence or absence of clear auditory input patterns might be a key factor in sustaining adult A1 function.
How Geometry Controls the Tearing of Adhesive Thin Films on Curved Surfaces
Olga Kruglova,Fabian Brau,Didier Villers,Pascal Damman
Physics , 2011, DOI: 10.1103/PhysRevLett.107.164303
Abstract: Flaps can be detached from a thin film glued on a solid substrate by tearing and peeling. For flat substrates, it has been shown that these flaps spontaneously narrow and collapse in pointy triangular shapes. Here we show that various shapes, triangular, elliptic, acuminate or spatulate, can be observed for the tears by adjusting the curvature of the substrate. From combined experiments and theoretical models, we show that the flap morphology is governed by simple geometric rules.
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