The three-dimensional kinetic behaviour of the pelvic rotation in maximal sprint running

The purpose of this study was to investigate the effect of lumbosacral kinetics on sprinting. Twelve male sprinters performed 50 m sprints at maximal effort. Kinematic and ground reaction force data were recorded at approximately 40 m from sprint commencement. A whole-body inverse dynamics approach was applied to calculate joint forces and torques at the hip and lumbosacral joints. The contribution of the hips and lumbosacral joint torques to pelvic rotation was subsequently calculated, with joint force powers indicating the rate of mechanical energy transfer between segments across joint centres calculated for both hip joints. The kinetic analysis indicated that the lumbosacral torsional torque contributed significantly to pelvic rotation. Additionally, the pelvic rotation exerted anterior–posterior joint forces on the hips, contributing to the large positive joint force power at the hip of the stance leg. These hip joint force powers assisted in motion recovery during sprinting. In conclusion, the lumbosacral torsional torque might contribute to the recovery motion in sprinting through application of the anterior–posterior joint forces at the hip joints via pelvic rotation.     

关于积分型Hilbert定理的一个改进

通过建立一个权函数的不等式,改进了Hilbert定理,作为应用,建立了一个Hilbert类积分不等式及其加强式。     

Unequal experience of COVID-induced remote schooling in four developing countries

Lockdown measures during the pandemic have resulted in school closure worldwide affecting nearly 9 out of 10 students. Consequently, remote schooling has become a growing phenomenon. However, due to a lack of infrastructural capacity and widespread poverty, the experience of remote learning in developing countries may have been unequal by pupils’ socioeconomic status, gender and location. This study draws evidence from a phone survey conducted by Young Lives (YL) in Ethiopia, two states of India, Peru and Vietnam enquiring which sociodemographic groups are benefiting more from remote schooling. Logit regression results suggest that students from wealthier households, urban areas and with internet access from all countries are more likely to experience remote schooling. Pupils from higher-educated households in all countries but Peru also tend to have alternative schooling. Additionally, apart from Peru, the gender difference in experiencing remote learning is not found significant. We suggest that access to remote learning resources for marginalised students would be paramount to reduce inequality in learning loss in the global South.     

Using learning profiles to inform education priorities: An editors’ overview of the Special Issue

This special issue explores the use of learning profiles for analysing the dynamics of low learning in low- and middle-income countries and informing priorities to address the learning crisis. The 12 papers in the special issue draw on learning data from more than 50 countries and 6 million individuals, with implications for education policy and practice. Taken together, they point to a need to steepen learning trajectories by prioritizing early mastery of foundational skills for all children. The papers show that addressing the learning crisis will not be achieved through more school grade attainment alone, nor through within-country equality across groups (such as girls and boys or rich and poor). Positive examples show that programs focused on foundational learning both improved average learning and reduced inequality. Addressing the learning crisis will require a focus on systems improvement, using foundational learning as a case in point for making the needed systems improvements to steepen learning throughout children’s time in school. Learning profiles can provide a guide for education actors aiming to improve learning outcomes.     

拉格朗日中值定理的应用

拉格朗日中值定理是沟通函数及其导数之间关系的桥梁,在微分中值定理中以及高等数学中承上启下,有着广泛的应用。文章从定理的实质分析入手,讨论了拉格朗日中值定理的应用。     

Weighted Means Through the Looking Glass

Each weighted mean of two values has a counterpart, equidistant from the arithmetic mean, obtained by exchanging roles between the weights or by inversing each weight. These elementary relations are apt for introductory courses.     

Inequality in Experiences of Physics Education: Secondary School Girls' and Boys' Perceptions of their Physics Education and Intentions to Continue with Physics After the Age of 16

This paper explores the factors that are associated in England with 15-year-old students' intentions to study physics after the age of 16, when it is no longer compulsory. Survey responses were collated from 5,034 year 10 students as learners of physics during the academic year 2008–2009 from 137 England secondary schools. Our analysis uses individual items from the survey rather than constructs (aggregates of items) to explore what it is about physics teachers, physics lessons and physics itself that is most correlated with intended participation in physics after the age of 16. Our findings indicate that extrinsic material gain motivation in physics was the most important factor associated with intended participation. In addition, an item-level analysis helped to uncover issues around gender inequality in physics educational experiences which were masked by the use of construct-based analyses. Girls' perceptions of their physics teachers were similar to those of boys on many fronts. However, despite the encouragement individual students receive from their teachers being a key factor associated with aspirations to continue with physics, girls were statistically significantly less likely to receive such encouragement. We also found that girls had less positive experiences of their physics lessons and physics education than did boys.     

In vivo lumbo-sacral forces and moments during constant speed running at different stride lengths

Abstract

The aim of this study was to introduce a Newton–Euler inverse dynamics model that included reaction force and moment estimation at the lumbo-sacral (L5-S1) and thoraco-lumbar (T12-L1) joints. Data were collected while participants ran over ground at 3.8 m · s^?1 at three different stride lengths: preferred stride length, 20% greater than preferred, and 20% less than preferred. Inputs to the model were ground reaction forces, bilateral lower extremity and pelvis kinematics and inertial parameters, kinematics of the lumbar spine and thorax and inertial parameters of the lumbar segment. Repeated measures ANOVA were performed on the lower extremity sagittal kinematics and kinetics, including L5-S1 and T12-L1 three-dimensional joint angles, reaction forces and moments at touchdown and peak values during impact phase across the three stride conditions. Results indicated that L5-S1 and T12-L1 vertical reaction forces at touchdown and during the impact portion of the support phase increased significantly as stride length increased (P < 0.001), as did peak sagittal L5-S1 moments during impact (P = 0.018). Additionally, the transverse T12-L1 joint moment increased as running speed increased (P = 0.006). We concluded from our findings that our model was sensitive to our perturbations in healthy runners, and may prove useful in future mechanistic studies of L5-S1 mechanics.     

Educational returns beyond the mean: Differences along wage distributions of men and women in India's formal labor market

Unlike previous studies on educational returns in developing countries, this paper examines the distributional impacts of education on wages using a recently developed econometric approach – unconditional quantile regressions. The results yield unconditional impacts of education at different points of the wage distribution and, therefore, are more informative from a policy perspective than both traditional regression and quantile regression methods commonly used for estimating educational returns. We use a nationally representative dataset on labor markets in India, collected in 2005–2006. The results reveal significant heterogeneity in education's effects along the wage distribution and striking differences in these patterns by gender: the effect of primary education is found to be significantly higher for women than men in the middle of the wage distribution; while the effect of post primary education exhibits a distinct pattern whereby women get significantly higher rewards than men above the median and significantly lower rewards than men below the median. These findings have direct implications for the targeting of education policies that seek to reduce gender wage inequality.     

太极拳运动对中老年人运动耐力及肺功能影响分析

通过对太极拳逆腹式呼吸和健步走腹式顺式呼吸的对比,并与未参加锻炼的普通人群对照,从6min步行实验（6MWT）、血氧饱和度（Sa）、肺功能角度探讨太极拳运动对中老年人运动耐力及肺功能的改善与提高情况,为太极拳健身功能提供一定的理论依据.