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Currently, only epidemiological injury data have been reported for the new extreme sport of aggressive inline skating, or trick skating. No studies have examined the biomechanics of this sport, which involves repetitive jumping and landing from railings, ramps, and ledges, often over 1 m in height. We present results of a pilot study that examined the effect of skater experience and lower extremity biomechanics on energy absorption ability, and observed balance strategies used during two basic tricks. In these tricks, the skater jumps onto an elevated rail and maintains balance while standing in a single position (stall) or sliding along the rail (grind). Lower extremity joint kinematics, impact force characteristics, and general movement behaviours were examined during landing and balance phases. Ten male skaters performed ten stalls and ten frontside grinds on an instrumented grind rail, capable of measuring vertical force. Vertical impact force was found to decrease with increasing skater experience in stalls (r = -0.84, P = 0.002) and grinds (r = -0.84, P = 0.009). This might imply that less-experienced skaters are (subconsciously) more concerned about maintaining balance than refining technique to minimize impact force. Similar to drop landing experiments, peak impact force decreased with increasing knee flexion during stalls (r = -0.65, P = 0.04). During stalls, skaters demonstrated classic balance maintenance strategies (ankle, hip, or multi-joint) depending on trick length. During grinds, skater centre of mass never passed over the rail base of support, suggesting the use of momentum produced from obliquely approaching the rail. 相似文献
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Selection medium is important in sperm isolation for assisted reproductive technologies. Contrary to the naturally occurring human cervical mucus which has a high viscosity, most current practices for motility based sperm selection use a low viscosity medium. In this study, we used a microfluidic device to assess the effects of high viscosity media made with hyaluronic acid (HA) and methyl cellulose (MC) on bovine and human sperm motility and viability (sperm transferred directly from cryoprotectant). The microfluidic penetration test, viability, and motility were compared for sperm swimming in both HA and MC media with about 20cp viscosity (measured at 20 °C). Our resulted indicate that MC medium resulted in a significantly higher number of viable bovine sperm penetrating the medium as compared to HA. Furthermore, MC resulted in the selection of a sperm subpopulation with a 274% increase in sperm viability in comparison to the raw semen, while HA increased viability by only 133%. In addition to viability, bovine sperm motility parameters were significantly higher in the MC medium as compared with HA. Experiments with human sperm swimming in MC indicate that sperm swim slower and straighter at higher viscosities. In conclusion, the results indicate that in a micro-confined environment representative of the in vivo environment, MC is a preferred high viscosity medium to ensure the highest concentration of motile and viable sperm. 相似文献
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Children with mathematics learning disabilities in Belgium 总被引:6,自引:0,他引:6
In Belgium, between 3% and 8% of the children in elementary schools have mathematics learning disabilities (MLD). Many of these children have less developed linguistic, procedural, and mental representation skills. Moreover, a majority of the children have been found to show inaccurate prediction and evaluation skills in Grade 3. MLD often become obvious in elementary school. Whereas some children are retained, others are referred to special education. During the last 10 years, the number of children in special education and the number of children with learning disabilities who are following a special guidance program in general education (inclusive education) have increased. Children in Belgium with MLD can get therapy for about 2 years. Nevertheless, many problems continue unresolved even in high school and adulthood. 相似文献
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Spanish-speaking learners of French, aged 9 to 11 years old, were tested after approximately 7months of French instruction to explore the contribution of phonological and syntactic awareness in L2 in 4 components of L2 reading, taking oral competence in L2 andreading in L1 into account. Phonological tasksin L2 better explain decoding. Word recognitionthrough the visual route is best explained bythe corresponding ability in L1. Sentencecomprehension is best explained by oralcompetence in L2, although it is stronglycorrelated with syntactic awareness. Finally,text comprehension is explained by thecorresponding ability in L1, althoughcorrelations with syntactic awareness and oralcompetence are strong. Theoretical implicationsare derived from these findings, and questionsrelative to the subjects' age and level ofbilingualism as well as methodological issuesare discussed. 相似文献
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Armand L. Hunter 《Quarterly Journal of Speech》2013,99(3):299-306
Aristotle discussed various forms of rationality in the Organon and other works. Aristotle held that in making judgments, the soul used five means— intelligence, episteme (scientific knowledge), sophia (theoretical wisdom), techne (art), and phronesis (practical wisdom). The nature of rhetoric as a techne employed in persuasion and grounded in probabilities distinguishes it from discourse in natural science, metaphysics, and philosophy. Aristotle's comparative study of the reasoning used by each of these means enables us to recognize rhetoric's uniqueness. 相似文献
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Armand J. Galfo 《College Teaching》2013,61(2):123-124
What the Ed.M. degree should offer and how it should be pursued are the concern of the following article by an associate professor of education (B.A., M.Ed., Ed.D., Buffalo) at the College of William and Mary. Besides contributions to journals, he is author of a series of booklets published by the Western New York School Study Council. 相似文献