The effect of motor difficulty on the acquisition of a computer task: a comparison between young and older adults

International audienceThe present study investigated the extent to which the impact of motor difficulty on the acquisition of a computer task varies as a function of age. Fourteen young and 14 older participants performed 352 sequences of 10 serial pointing movements with a wireless pen on a digitiser tablet. A conditional probabilistic structure governed the succession of target keys to be pointed at on a virtual keyboard. Detecting and learning with practice how to use this probabilistic structure was expected to allow the participants to anticipate the location of the targets, and thus to improve pointing performance in terms of speed, accuracy, and trajectory rectitude. Motor difficulty was manipulated through the size of the targets to be pointed at. Results showed that for older participants, but not for younger ones, motor difficulty had a detrimental effect on their ability to learn the probabilistic structure. This finding suggests that decreasing the target size provides complex detrimental influence on the performance, affecting the efficiency of both the motor and cognitive processes involved in the task, especially for the elderly

عمر ونمو سمك الشورو الأصفر بالشمال التونسي

Le chinchard à queue jaune est un Carangidae qui fait l’objet d’une exploitation par les différents types de pêche le long des côtes tunisiennes. Dans le présent travail on se propose d’étudier l’âge et la croissance sur la base de la distribution des fréquences de taille dans la région Nord de la Tunisie. La décomposition de ces fréquences de taille est réalisée suivant la méthode de Battacharya (1967). Deux périodes sont considérées, la première correspond à l’année 1998 et la seconde s’étale entre Novembre -1999 et Décembre -2000. Pour la première période, 6 classes d’âges ont pu être identifiées alors que pour la seconde cette valeur est de 7. Les équations de croissance linéaire annuelle suivant le modèle Von Bertalanffy (1938) ont été établies.Mediterranean horse mackerel is a Carangidae exploited by different gears along the Tunisian coasts. In this work we study the age growth and according to the sizes frequency distribution in the North of Tunisia. The decomposition of sizes frequency is realized with Battacharya method (1967). Two periods are considered, the first corresponds to 1998 and the second to the period between November -1999 and December -2000. Six and seven age-classes were identified for the first and the second periods respectively. The length growth equations were established according to Von Bertalanffy model.تتضمن هذه الورقة دراسة عمر ونمو سمك الشورو الأصفر بالشمال التونسي حسب توزيع الأحجام وذلك بالاستناد على منهج بتشريا .(1967). مع العلم أن هذا الصنف من الأسماك يتواجد بكامل السواحل التونسية و يستغل بطرق صيد مختلفة وعديد أنواع الشباك. بالنسبة لسنة 1998 توصلنا إلى تحديد 6 أقسام تتراوح أعمارها بين سنة و 6 سنوات وبالنسبة للفترة الممتدة بين نوفمبر 1999 وديسمبر 2000 فهنالك 7 أقسام. كما قمنا باستخراج معادلات النمو طبقا لمنهج فون برتلنفي (1938).Publishe

Advanced Processing Methods for Image-Based Displacement Field Measurement

International audienceWe present recent developments in data processing for velocity field estimation and visualization originating from computer vision. We review the current paradigm of PIV data processing, based on window correlation, and the regularization or variational approach which is dominant in optical flow estimation. We propose a novel unifying framework via the optimization of a compound regularized criterion written in terms of a dense displacement (or velocity) field. The paper then focuses on algorithmic issues.A fast iterative window correlation method leading to a highly parallel lgorithm termed FOLKI is described. Thanks to a GPU (Graphical Processing Unit) implementation, FOLKI reaches video rate for typical PIV data. Then we present more sophisticated solvers able to deal with the regularization term of the criterion, notably multigrid methods.In our view, these two components form the foundation of a video rate velocity field visualization and interpretation toolbox which, together with recent advances in experimental apparatus and numerical simulation, opens the way to a major development in experimental fluid science

Activity antifungal of the essential oils; aqueous and ethanol extracts from <i>Citrus aurantium</i> L.

<div><p>Our study is about the essential oil of <i>Citrus aurantium</i> L. in Tunisia and its plant extract. The yield of this essential oil is 0, 56% but the yield of the extract of plant was 17.1% for the aqueous extract ant 18.3% for the ethanolic extract. The analysis of chemical composition by using GC and GC/MS showed the essential oil of <i>C. aurantium</i> L. species to be rich in monoterpenes such as α-terpineol, lianolyl acetate, linalool and limonene. The antifungal activity of this oil showed us an inhibition of the germination of mushrooms, in the same way we could note that the biologic activities are generally assigned to the chemotypes high content in oxygenated monoterpene.</p></div

Chemical composition, weed killer and antifungal activities of Tunisian thyme (Thymus capitatus Hoff. et Link.) essential oils

The chemical composition, phytotoxic and antifungal activities of the essential oils isolated by hydrodistillation from the aerial parts of Tunisian thyme were evaluated. In order to find best results, different variables (i.e. provenance and phase of plant development) were considered. The chemical composition analysed by gas chromatography/mass spectrometry (GC/MS) revealed variability among provenances displaying interesting chemotypes and that carvacrol (63–84%), limonene (5–10%), δ-terpinene (0–7%), and β-myrcene (0–7%) were the main components. Antifungal ability of Thymus capitatus essential oils was tested by disc agar diffusion against five phytopathogenic fungi: Fusarium avenaceum, F. culmorum, Microdochium nivale var. nivale, Alternaria sp., and Bipolaris sorokiniana. High antifungal activity was observed for the essential oil isolated at the post-flowering development phase for the Bekalta provenance. There was no difference in the antifungal activities of oils isolated at the flowering phase from the other provenances. Thyme essential oils showed high level of weed-killer activity as well against Sinapis arvensis