Study on absorption coefficients of dual-energy γ-rays in determining phase fractions of multiphase flows

This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions.     

欧姆龙生物电阻抗法与双能X线吸收法测量成年人体脂率的比较

目的:运用欧姆龙生物电阻抗法(BIA)与双能X线吸收法(DEXA)测定各年龄段成年人体脂率结果的一致性,为身体成分的研究提供方法学依据。方法:对体型正常、体重正常、身体健康的成年人,采用欧姆龙BIA法与DEXA法测量其体脂率并进行比较。结果:通过相关分析、组内相关系数、Bland-Altman及配对t检验4种方法的比较结果显示,DEXA法与欧姆龙BIA法测量成年人体脂率的一致性均较高。结论:采用欧姆龙BIA法测量成年人体脂率的可靠性较强。     

Body composition and nutritional profile of male adolescent tennis players

Abstract

In this cross-sectional study, we evaluated the body composition and dietary intake of 44 adolescent tennis players. After being divided into two groups (age 10–13 years and age 14–18), the players had their weight, height, and sexual maturation assessed. Dual-energy X-ray absorptiometry was used to assess body composition. Food intake was obtained from a non-consecutive 4-day food record. The data were analysed using the Virtual Nutri v.1.0 software and compared with the present recommendations for adolescent athletes or dietary reference intakes. Body mass index and body fat for tennis practice were adequate for 89% and 71% of the tennis players respectively, regardless of age group. A calorie deficit greater than 10% of energy expenditure was observed in 32% of the sample. Fifty percent of the athletes consumed carbohydrates in accordance with recommended values. Protein and lipid intakes were above recommended values, while fibre, calcium, potassium, magnesium, and folic acid intakes were below recommendation for 98%, 80%, 100%, 100%, and 98% of the tennis players respectively. The observed nutritional deficiencies represent an additional barrier for adolescents engaged in competitive sports to achieve an optimum nutrition to maintain growth, health, and performance.