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1دورية أكاديمية
المؤلفون: Decraene M., Verbestel V., Cardon G., Iotova V., Koletzko B., Moreno L.A., Miguel-Berges M.L., Gurzkowska B., Androutsos O., Manios Y., De Craemer M.
المصدر: International Journal of Environmental Research and Public Health ; https://www.scopus.com/inward/record.uri?eid=2-s2.0-85109846823&doi=10.3390%2fijerph18147499&partnerID=40&md5=7cd0b13dbe52d54bfa3b9780c7115ab5Test
مصطلحات موضوعية: fat, health survey, physical activity, sleep, social behavior, student, World Health Organization, young population, anthropometry, Article, behavior, body mass, body weight, caloric intake, caregiver, child, data analysis, day care, female, human, major clinical study, male, obesity, practice guideline, prospective study, questionnaire, screening, sleep time, step count, waist to height ratio
الوصف: In 2019, the World Health Organization (WHO) published 24 h movement behavior guidelines for preschoolers with recommendations for physical activity (PA), screen time (ST), and sleep. The present study investigated the proportion of preschoolers complying with these guidelines (on a total week, weekdays and weekend days), and the associations with adiposity. This cross-sectional study included 2468 preschoolers (mean age: 4.75 years; 41.9% boys) from six European countries. The associations were investigated in the total sample and in girls and boys separately. PA was objectively assessed by step counts/day. Parent-reported questionnaires provided ST and sleep duration data. Generalized estimating equations were used to analyze the association between guideline compliance and adiposity indicators, i.e., body mass index (BMI) z-score and waist to height ratio (WHR). Only 10.1% of the preschoolers complied with the 24 h movement behavior guidelines, 69.2% with the sleep duration guideline, 39.8% with the ST guideline and 32.7% with the PA guideline. No association was found between guideline compliance with all three movement behaviors and adiposity. However, associations were found for isolated weekday screen time (BMI z-scores and WHR: p = 0.04) and weekend day sleep duration (BMI z-scores and WHR: p = 0.03) guideline compliance with both lower adiposity indicators. The latter association for sleep duration was also found in girls separately (BMI z-scores: p = 0.02; WHR: p = 0.03), but not in boys. Longitudinal studies, including intervention studies, are needed to increase preschoolers’ guideline compliance and to gain more insight into the manifestation of adiposity in children and its association with 24 h movement behaviors from a young age onwards. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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2دورية أكاديمية
المؤلفون: Tantos, C., Naris, S., Valougeorgis, D.
مصطلحات موضوعية: Barodiffusion, Binary gas mixture, Computational effort, Downstream region, Flow quantities, Flowthrough, Height ratio, Kinetic coefficient, Knudsen, McCormack kinetic model, Parallel plates, Pressure differences, Rarefied gas, Specific concentration, Velocity profiles, Flow of fluids, Gas mixtures, Mixtures, Neon
الوصف: The linearized flow of a binary gas mixture between two parallel plates of any length driven by a small pressure difference is numerically solved based on the McCormack kinetic model. In this case the flow is not fully developed and the simulated flow field includes, in addition to the channel, efficiently large upstream and downstream regions significantly increasing the required computational effort. In the present work results are provided for one gas mixture, namely He-Ne with a specific concentration of 0.5 in a wide range of gas rarefaction. The ratio of the length over the height of the channel is taken to be equal to 0, 1 and 5 corresponding to flow through channels of very short (slit), short and moderate lengths respectively. Results are provided for the two kinetic coefficients related to Poiseuille and barodiffusion flow rates and the velocity profiles of each species. The effect of the length to height ratio and of the gas rarefaction on the flow quantities is investigated deducing that as the ratio in increased the separation phenomenon becomes more dominant, while a Knudsen minimum is observed at the ratio equal to 5. © Published under licence by IOP Publishing Ltd.
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