Stratégie empirique d'un système de ressources en eau: l'exemple d'un périmètre irrigué en zone semi-aride

Une règle de gestion interannuelle empirique est définie pour gérer un barrage en éte d'un périmètre d'irrigation en zone semi-aride. La structure de la règle est construite à partir de l'observation de la gestion pratiquée actuellement sur le terrain. Les paramètres de cette règle sont ajustés de façon à minimiser le cumul moyen des écarts entre demandes et ressources des séries générées après une étude fréquentielle des aléas hydrauliques.Dans le cas du périmètre lié au barrage de Ghézala, cette méthode permet de répartir au mieux les risques de défaillance sur l'année et d'adapter la stratégie d'irrigation aux phases végétatives critiques des cultures.Les avantages et les inconvénients de cette approche empirique par rapport aux techniques de programmation dynamique sont finalement discutés et mis en relief pour les systèmes de gestion des ressources en zones semi-arides.An empirical inter-annual management rule is defined to operate a reservoir for irrigation use in a semi-arid zone. Management rules for hydro-agricultural systems in semi-arid zones consist of establishing a trade-off between the total quantity of water to be distributed for summer irrigation and the indispensable volumes to be held in store for the raising of future seedlings during the following autumn. In less arid countries, water is sufficiently cheap so that it is economically profitable to deliver great quantities to sustain maximum agricultural output. Indeed, water is sufficiently abundant so that it is generally useless to conserve reserves for the next year. Such an inter-annual compromise is not the norm for water resources managers in humid climates. For instance, the two consecutive dry summers in Europe in 1989 and 1990 would not have had the same impact on the agricultural economy in the semi-arid zones. There rules of management would have been adapted to obtain of an inter-annual balance.Numerous mathematical methods have been used in the domain of water resource systems management, sustained by the constant increase of computer performances. Reservoir management issues have consequently been widely studied and solved both from the viewpoint of the art of modeling and the methods of optimization. Nevertheless it is necessary to ensure that the mathematically correct optimal solution is also implementable when one leaves the computer screen to get back to the field: the success of this passage depends largely on the ability of the objective function to quantify the economic stakes encoded in the choice of a management rule. Except for hydropower generation, the various uses of a dam are most unlikely to be integrated into an aggregative utility function under the form of separable additive criteria.A way to bypass the inherent difficulties in the design of a realistic objective quantification is to restrict the search of the operation rule to the class of strategies compatible with the commonly met attitude of semi-arid water resources system managers. The structure of the rule is designed from the observation of the effective management presently in operation. Its logic fits to the following reasoning:- when the reservoir level is low, as soon as it starts to vary, the irrigation perimeter manager will behave very prudently. i.e. by reducing the proportion of the allocated irrigation water to the amount in store; - for average working conditions, the system manager will deliver a constant fraction of the available reservoir storage for irrigation; - when the quantity stored in the dam is high, the manager tends to satisfy completely the irrigation demand. The parameters of this piecewise linear rule are adjusted so as to minimize the probability of discrepancy between demands and resources on series obtained after a brief hydrological study.The Ghezala perimeter in Tunisia, which is situated in the watershed of lake Ichkeul, has been taken as a case study. With a thousand hectares of irrigated crops to be satisfied from an upstream 12 hm3 reservoir, and 625 mm rain per year on the watershed with a strong seasonal dependence, the Ghezala perimeter is quite representative of Tunisian irrigation practices. The method developed in this paper allows to balance the risk of failure all over the year and to adapt the strategy of irrigation according to critical vegetative phases of the crops. A statistical analysis of possible deficits according to the improved rule reveals that the method improves the performance of irrigation and decreases its sensitivity to the critical vegetative phases that are of critical importance in agriculture in semi-arid zones.The management model is unsophisticated but its objective is to provide elements of appreciation to the manager of the irrigated perimeter. Each component of the model can be improved and more finely described. Advantages and drawbacks of this empirical approach with regards to more conventional dynamic programming techniques are finally discussed and underlined for water resource systems with specific attention to their management in semi-arid zones

Magnetic properties of amorphous Fe80-xRxB20 ( with R= Pr, Nd, Sm, Gd, Dy, Ho, Er and Tm )

Amorphous Fe80-xRxB20 alloys (with R=Pr, Nd, Sm, Gd, Dy, Ho, Er and Tm ) have been prepared by melt spinning and their magnetic properties have been studied. The Gd moment at 4.2 K is found to be 7µB which agrees with the theoretical value indicating a collinear spin structure. The moments of the other rare-earth are lower than the theoretical value, implying a conical spin structure. The mean-field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Fe-Fe and Fe-R atom pairs have also been evaluated.Amorphous Fe80-xRxB20 alloys (with R=Pr, Nd, Sm, Gd, Dy, Ho, Er and Tm ) have been prepared by melt spinning and their magnetic properties have been studied. The Gd moment at 4.2 K is found to be 7µB which agrees with the theoretical value indicating a collinear spin structure. The moments of the other rare-earth are lower than the theoretical value, implying a conical spin structure. The mean-field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Fe-Fe and Fe-R atom pairs have also been evaluated

D-cycloserine enhances spatial learning performances of rats chronically exposed to lead during the developmental period.

Chronic developmental lead (Pb) exposure has long been associated with cognitive dysfunction in children and animals. N-methyl-D-aspartate (NMDA) receptors, important in the synaptic mechanisms involved in learning and memory, are key target of lead toxicity. D-cycloserine (DCS), a partial agonist of the NMDAassociatedglycine site, has been recognised as a potential cognitive enhancer.We investigated the potential effects of Pb exposure (lead acetate 0.2% through the drinking water) during gestation and lactation (GL), on the spatial learning and memory capacities of PN32 rats. We also evaluatethe ability of DCS (30 mg/ml), administered daily 24h after weaning during 15 days, to attenuate Pb neurotoxicity-induced cognitive deficits. Results indicate that rats exposed to lead during gestation and lactation have a significantly increased latency to find the hidden platform and cover a significant longer distance compared to control-vehicle in the learning phase of the Morris water maze. However, the administration of DCS to GL animals improved significantly their learning performances compared with GL-vehicle. In contrast, there is no significant difference between all groups during the probe test and the visual cue test. In conclusion, DCS enhancement of the NMDA receptor function is an effective strategy to ameliorate neurotoxicity leadassociated spatial learning deficits

Tabagisme au sein du Secteur de la Santé : Analyse de la Prévalence et des Déterminants chez le Personnel de l'Etablissement Public Hospitalier de Laghouat

Cette étude se concentre spécifiquement sur la prévalence du tabagisme parmi les travailleurs de la santéau sein de l'établissement public hospitalier de Laghouat en 2021 avec un total de 198 sujets inclus dansl'étude. La prévalence du tabagisme actif parmi le personnel de l'établissement public hospitalier deLaghouat a été estimée à 18,6% (IC: 14,4% - 27,8%). Les fumeurs étaient exclusivement de sexemasculin avec une fréquence atteignant 45,7% dans ce sous-groupe. L’âge médian est de 30,50 [25,00,36,75], sans différence statistiquement significative entre les fumeurs et les non-fumeurs. 6,06% de lapopulation s’est déclarée comme sevrée du tabagisme, tandis que 10 sujets (5,05%) mentionnaient letabac à chiquer. Une analyse approfondie des données sur le tabagisme segmenté par catégorieprofessionnelle a révélé des tendances significatives (p = 0,015). Le personnel paramédical homme,présentait une prévalence significativement élevée avec 53,70% de fumeurs. Une analyse plus détailléede nos données spirométriques a révélé une corrélation significative entre l'augmentation du tabagisme,évaluée par l'indice Paquet Année (PA), et l'augmentation de l'Indice de Masse Corporelle. L’indice PAcorrespondant au nombre de paquets fumés par jour multiplié par le nombre d'années de tabagisme. Lesrésultats indiquent aussi qu'à mesure que l'indice PA augmente, le VEMS tend à diminue

Do cognitive training strategies improve motor and positive psychological skills development in soccer players? Insights from a systematic review

Soccer players are required to have well-developed physical, technical and cognitive abilities. The present systematic review, adhering to Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines, examined the effects of cognitive training strategies on motor and positive psychological skills development in soccer performance and identified the potential moderators of the “cognitive training-soccer performance” relationship. Thirteen databases were systematically searched using keywords related to psychological or cognitive training in soccer players. The review is based on 18 studies, employing 584 soccer players aged 7-39 years. Cognitive strategies, particularly imagery, appear to improve sports performance in soccer players. Regarding imagery, the combination of two different types of cognitive imagery training (i.e., cognitive general and cognitive specific) have a positive influence on soccer performance during training, whereas motivational imagery (i.e., motivational general-arousal, motivational general-mastery, and motivational specific) enhance competition performance. Younger soccer players employ cognitive general and cognitive specific imagery techniques to a greater extent than older soccer players. Combined cognitive training strategies were more beneficial than a single cognitive strategy relative to motor skills enhancement in elite (particularly midfielders) and amateur (i.e., when practicing complex and specific soccer skills in precompetitive period) soccer players. In conclusion, it appears that there are differences in cognitive/psychological training interventions, and their efficacy, according to whether they are directed towards training or competition, and the age, standard and playing position of the players

Food photographs in nutritional surveillance: errors in portion size estimation using drawings of bread and photographs of margarine and beverages consumption

Food photographs are widely used as instruments to estimate portion sizes of consumed foods. Several food atlases are available, all developed to be used in a specific context and for a given study population. Frequently, food photographs are adopted for use in other studies with a different context or another study population. In the present study, errors in portion size estimation of bread, margarine on bread and beverages by two-dimensional models used in the context of a Belgian food consumption survey are investigated. A sample of 111 men and women (age 45–65 years) were invited for breakfast; two test groups were created. One group was asked to estimate portion sizes of consumed foods using photographs 1–2 d after consumption, and a second group was asked the same after 4 d. Also, real-time assessment of portion sizes using photographs was performed. At the group level, large overestimation of margarine, acceptable underestimation of bread and only small estimation errors for beverages were found. Women tended to have smaller estimation errors for bread and margarine compared with men, while the opposite was found for beverages. Surprisingly, no major difference in estimation error was found after 4 d compared with 1–2 d. Individual estimation errors were large for all foods. The results from the present study suggest that the use of food photographs for portion size estimation of bread and beverages is acceptable for use in nutrition surveys. For photographs of margarine on bread, further validation using smaller amounts corresponding to actual consumption is recommended

Evaluation de l’activité du cadmium, en présence du zinc, sur les structures des tissus régulateurs du métabolisme chez le rat Wistar

Le sulfate de Cadmium (CdSO4) et le chlorure de Zinc (ZnCl2) ont des effets antagonistes. Le Cd est connu pour son effet nécrotique et le Zn pour son rôle protecteur. L’objectif de cette étude est d’évaluer les effets de l’exposition au Cd sur l’histologie du foie et des reins chez des rats Wistar en présence du Zn. L’étude a porté sur 16 rats, âgés de 4 mois, qui ont été subdivisés en 4 groupes de 4 rats, le 1er groupe recevait par voie orale du Cd (0,15 mg/ kg de poids corporel) pendant un mois, le second groupe a été exposé au Zn à la même dose, un 3e groupe recevait un mélange (Cd-Zn) et le 4e groupe était le témoin recevant de l’eau de robinet dans les même conditions. Les résultats ont montré que  l’exposition des rats au Cd a induit une diminution de leur poids corporel. L’examen histologique, chez les rats exposés au Cd, a révélé des désorganisations cellulaires, des atypies cyto-nucléaires et des nécroses au niveau des tissus hépatiques et rénaux. Par ailleurs, les animaux ayant reçu du Zn ou un mélange Cd-Zn ont préservé l’intégrité de l’organisation cellulaire et nucléaire de leur tissu. L’exposition au Cd était responsable de l’apparition d’importants changements morphologique et histologique chez le rat mais la présence du Zn a atténué partiellement les effets toxiques induits par le Cd.Mots clés : Cadmium, zinc, antagonistes, foie, reins, histologie

Effects of mental imagery on muscular strength in healthy and patient participants: A systematic review

The aims of the present review were to (i) provide a critical overview of the current literature on the effects of mental imagery on muscular strength in healthy participants and patients with immobilization of the upper extremity (i.e., hand) and anterior cruciate ligament (ACL), (ii) identify potential moderators and mediators of the “mental imagery-strength performance” relationship and (iii)determine the relative contribution of electromyography(EMG) and brain activities, neural and physiological adaptations in the mental imagery-strength performance relationship. This paper also discusses the theoretical and practical implications of the contemporary literature and suggests possible directions for future research. Overall, the results reveal that the combination of mental imagery and physical practice is more efficient than, or at least comparable to, physical execution with respect to strength performance. Imagery prevention intervention was also effective in reducing of strength loss after short-term muscle immobilization and ACL. The present review also indicates advantageous effects of internal imagery (range from 2.6 to 136.3%) for strength performance compared with external imagery (range from 4.8 to 23.2%). Typically, mental imagery with muscular activity was higher in active than passive muscles, and imagining “lifting a heavy object” resulted in more EMG activity compared with imagining “lifting a lighter object”. Thus, in samples of students, novices, or youth male and female athletes, internal mental imagery has a greater effect on muscle strength than external mental imagery does. Imagery ability, controllability, past experiences, and self-efficacy have been shown to be the variables mediating the effect of mental imagery on strength performance. Finally, the greater effects of internal imagery than those of external imagery could be explained in terms of neural adaptations, stronger brain activation, higher muscle excitation, greater somatic and sensorimotor activation and physiological responses such as blood pressure, heart rate, and respiration rate