Expression et éveil des perceptions corporelles en regard du dessin du bonhomme chez l'enfant entre 5 et 6 ans

Nonobstant le fait que le théâtre ne soit pas une discipline enseignée dans les classes romandes, il est néanmoins régulièrement présent dans la vie des écoliers. Par le biais de la pratique du théâtre, les élèves peuvent découvrir cette culture artistique, développer leur capacité à représenter et exprimer une idée ou une émotion et mobiliser leurs perceptions sensorielles. De plus, le théâtre, en raison de sa pratique collective, stimule les contacts entre élèves et améliore la communication au sein de la classe. Il a donc une place importante dans le développement personnel des élèves, que ce soit au niveau des relations sociales ou au niveau de leur perception corporelle. Notre pratique professionnelle nous a conduits à vouloir montrer les bénéfices de la pratique du théâtre dans les classes en bas âge. Le travail présenté ici s’intéresse à l’éveil des perceptions corporelles de l’enfant. En effet, il cherche à montrer si l’expression corporelle théâtrale a un effet sur la construction du schéma corporel de l’enfant au travers du dessin du bonhomme. Nous avons choisi de faire travailler les enfants autour de l’autoportrait en pied. Celui-ci donnant une intention au dessin, l’enfant se sent plus investi dans le travail. Au travers de notre expérimentation, nous avons cherché à montrer l’impact des activités corporelles et théâtrales sur le développement des perceptions corporelles de l’enfant et à soulever les bénéfices de cette pratique pour l’élève. Pour mettre en place ces activités, nous nous sommes appuyés sur des indications figurant dans le PER (Plan d’Etudes Romand)

Local soil quality assessment of north-central Namibia: integrating farmers' and technical knowledge

Soil degradation is a major threat for farmers of semi-arid north-central Namibia. Soil conservationpractices can be promoted by the development of soil quality (SQ) evaluation toolboxes that provide ways to evaluate soil degradation. However, such toolboxes must be adapted to local conditions to reach farmers. Based on qualitative (interviews and soil descriptions) and quantitative (laboratory analyses) data, we developed a set of SQ indicators relevant for our study area that integrates farmers’ field experiences (FFEs) and technical knowledge. We suggest using participatory mapping to delineate soil units (Oshikwanyama soil units, KwSUs) based on FFEs, which highlight mostly soil properties that integrate long-term productivity and soil hydrological characteristics (i.e. internal SQ). The actual SQ evaluation of a location depends on the KwSU described and is thereafter assessed by field soil texture (i.e. chemical fertility potential) and by soil colour shade (i.e. SOC status). This three-level information aims to reveal SQ improvement potential by comparing, for any location, (a) estimated clay content against median clay content (specific to KwSU) and (b) soil organic status against calculated optimal values (depends on clay content). The combination of farmers’ and technical assessment cumulates advantages of both systems of knowledge, namely the integrated long-term knowledge of the farmers and a short- and medium-term SQ status assessment. The toolbox is a suggestion for evaluating SQ and aims to help farmers, rural development planners and researchers from all fields of studies understanding SQ issues in north-central Namibia. This suggested SQ toolbox is adapted to a restricted area of north-central Namibia, but similar tools could be developed in most areas where small-scale agriculture prevails

Cardiac dynamics: Alternans and arrhythmogenesis

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Adaptive frequency tracking and application to biomedical signals

The main information of a signal resides in its frequency, its amplitude (or its power) and in their temporal evolution. Thus, a great number of methods for instantaneous frequency estimation have been proposed in the literature. Most of these algorithms use an adaptive filter-based (notch or bandpass filter) structure. In many applications, the information of interest is present in more than one signal. However, to our knowledge no algorithm able to track the frequency on several signals has been presented in the literature. Usually, frequency components are estimated and extracted on each signal independently. Artifacts or noise relative to a specific signal can thus disturb the frequency estimation process. Moreover, low amplitude components present in every signal (but non dominant) will not be estimated. The objective in the first part of this thesis is to develop different methods able to extend existing frequency tracking algorithm in order to improve the quality of the estimate, in terms of estimation variance and robustness with respect to noise. The proposed methods can be applied to algorithms using adaptive filters for the frequency estimation. For the multi-signal frequency tracking extension, these methods use the redundancy of information present in the signals under study. A first approach uses a unique filter for every signal. A set of weights is computed, depending on a measure of the estimate quality, and makes it possible to balance the influence of each signal on the tracking filter update. The second approach consists in using a different adaptive filter for each signal. A set of constraints links the central frequencies of each filter so that they are as similar as possible. Both methods yield frequency estimates more robust with respect to noise and more stable, without any decrease in estimation accuracy. For the harmonic frequency tracking, we propose a method using the information present in the harmonic component to improve the estimate of the fundamental frequency. The proposed methods also permit to extract the signal components corresponding to the estimated frequencies. These components are very useful for subsequent study. In the second part of this thesis, the algorithms developed in the first part are applied to biomedical signals. Two different applications are studied in this work : electrocardiograms and electroencephalograms. Firstly, a frequency tracking algorithm as well as its multi-signal extension are used to predict the success of electrical cardioversion attempts in patients suffering from atrial fibrillation. The instantaneous frequency is estimated using the algorithms and the corresponding signal component is extracted from electrocardiograms recorded prior to the attempt. With a few parameters computed on the estimated frequency and the corresponding signal component, we were able to predict the result of the cardioversion attempt on our database comprising 18 patients with a success rate of 94% for both algorithms. We think that this result can be very useful for helping the clinician to choose the appropriate therapy for atrial fibrillation management. The developed algorithms are also used to track the oscillatory components present in electroencephalograms. The performance of the basic algorithm is illustrated using single-trial electroencephalogram signals from a visual evoked potential experiment. The algorithm is used to track the gamma component (30-50 Hz). It is able to successfully track the spectral component in spite of the fact that large amplitude variations are present in the signal. A complex version of the multi-signal extension is also used to have an algorithm able to track multiple frequency components on multiple signals. The performance of this algorithm is also illustrated with single-trial electroencephalogram signals. It was shown to be able to correctly track up to four frequency components simultaneously. The quality of the estimation is improved using multiple lead signals

Nonlinear behaviour of conduction and block in cardiac tissue with heterogeneous expression of connexin 43

Altered gap junctional coupling potentiates slow conduction and arrhythmias. To better understand how heterogeneous connexin expression affects conduction at the cellular scale, we investigated conduction in tissue consisting of two cardiomyocyte populations expressing different connexin levels. Conduction was mapped using microelectrode arrays in cultured strands of foetal murine ventricular myocytes with prede fi ned contents of connexin 43 knockout (Cx43KO) cells. Corresponding computer simulations were run in randomly generated two-dimensional tissues mimicking the cellular architecture of the strands. In the cultures, the relationship between conduction velocity (CV) and Cx43KO cell content was nonlinear. CV fi rst decreased signi fi cantly when Cx43KO content was increased from 0 to 50%. When the Cx43KO content was ≥ 60%, CV became comparabletothatin100%Cx43KOstrands.Co-culturingCx43KOandwild-typecellsalsoresultedinsigni fi cantly more heterogeneous conduction patterns and in frequent conduction blocks. The simulations replicated this behaviour of conduction. For Cx43KO contents of 10 – 50%, conduction was slowed due to wavefront meandering between Cx43KO cells. For Cx43KO contents ≥ 60%, clusters of remaining wild-type cells acted as electrical loads thatimpairedconduction.ForCx43KOcontentsof40 – 60%,conductionexhibitedfractal characteristics,wasprone to block, and was more sensitive to changes in ion currents compared to homogeneous tissue. In conclusion, conduction velocity and stability behave in a nonline ar manner when cardiomyocytes expressing different connexin amounts are combined. This behaviour results from heterogeneous current-to-load relationships at the cellular level. Such behaviour is likely to be arrhythmogenic in various clinical contexts in which gap junctional coupling is heterogeneous

Adaptive Frequency Tracking on the ECG Used to Predict the Success of Electrical Cardioversion of Atrial Fibrillation

One of the rhythm control strategies in atrial fibrillation management consists in the application of a brief single electrical shock to the atria. This electrical cardioversion does not always succeed, and the long-term success of this therapy is not sufficiently predictable on the basis of clinical and echocardiographic parameters. In noninvasive atrial fibrillation studies, the frequencies observed in the atrial ECG signals are considered as an indicator of the underlying dynamics. In this study, we examen the use of frequency tracking techniques in predicting the success of electrical cardioversion