Technical possibilities for optimising the ski-binding-boot functional unit to reduce knee injuries in recreational alpine skiing     

Veit Senner  Frank I. Michel  Stefan Lehner  Othmar Brügger 《Sports Engineering》2013,16(4):211-228

This review study focuses on knee injuries in recreational alpine skiing. The objectives of this study were (1) to provide selected knowledge derived from current and past knee injury epidemiology; (2) to outline the most important knee injury mechanisms; and (3) to review and discuss how modifications of the skiing equipment might alleviate the risk of knee injuries. This review represents the essence of a comprehensive research report and considers the content of more than 230 scientific papers, further “grey literature”, patents, international standards and other publications. Knee injuries are the most frequent injuries in alpine skiing and their incidence rate remained high despite a decline of the incidence of other skiing injuries in recent years. Women have a higher knee injury risk, but age and tiredness appear not to be significant factors. Apart from the commonly described injury mechanisms “phantom foot” and “boot-induced anterior drawer” other more sophisticated injury categorisations are given. The ski radius, the ski length and the standing height on the ski may be relevant ski parameters. For the binding, the release mechanisms in different mechanical degrees of freedom, the impact tolerance and the maintenance frequency are discussed. In the ski boot, the height of the upper, the boot liner, the shaft stiffness, and the position on the ski may play a role. The biggest challenge, but probably also the biggest opportunity for a reduction of knee injury rates seems to be the development of a mechatronic binding. The current strategies to develop these types of bindings are explained and illustrated by one example. Some of the possible parameters which may be essential for the necessary control algorithms are described. Finally, considerations regarding the strategic and operational implication of the analysed technical measures are given.  相似文献   

Kinematic differences of elite and high-performance tennis players in the cross court and down the line forehand     

Johannes Landlinger  Stefan Josef Lindinger  Thomas Stöggl  Herbert Wagner  Erich Müller 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):280-295

This study identified and compared the full body kinematics of different skill levels in the forehand groundstroke when balls were hit cross court and down the line. Forty-three three-dimensional retro-reflective marker trajectories of six elite and seven high-performance players were recorded using an eight-camera 400 Hz, Vicon motion analysis system. The six highest horizontal velocity forehands with reliable kinematics of all participants were analysed for each specific situation (a total of 156 analysed shots). Significant differences (p < 0.01) and large effect sizes were observed between elite and high-performance players in linear velocity of the shoulder (2.0 vs. 1.2 m/s), angular velocity of the pelvis (295 vs. 168 °/s), and angular velocity of the upper trunk (453 vs. 292 °/s) at impact. The elite group showed a tendency towards higher racquet velocities at impact (p < 0.05). No significant differences were found in angular displacement of the racquet, hip alignment, or shoulder alignment at the completion of the backswing; nor did angular displacement vary significantly at impact. Irrespective of the group, different shoulder, hip, and racquet angles were found at impact, depending on the situation. The results should assist coaches when striving to improve their players' forehand.  相似文献   

Students’ formative assessment perceptions,feedback use and mathematics performance in secondary schools in Tanzania     

Florence Kyaruzi  Jan-Willem Strijbos  Stefan Ufer  Gavin T. L. Brown 《Assessment in Education: Principles, Policy & Practice》2019,26(3):278-302

This study investigates the impact of secondary school students’ perceptions of mathematics teachers’ formative assessment practices and feedback delivery on their feedback use, and mathematics performance. The sample consisted of 2767 Form 3 (Grade 11) students from 48 secondary schools in Tanzania. Surveys and focus group discussions were used to measure students’ perceptions of formative assessment, feedback delivery, and feedback use. Structural Equation Modelling (SEM) of survey data showed that students’ perceptions of the quality of teacher feedback delivery and perceived scaffolding positively predicted students’ feedback use whereas perceived monitoring negatively predicted feedback use. In turn, students’ feedback use positively predicted their mathematics performance to a small extent. Content analysis of focus group discussions illustrated that most students valued their mathematics teacher’s assessment practices. The findings imply that in Sub-Saharan African educational systems the quality of teacher feedback delivery and promotion of student feedback use can improve students’ mathematics performance.  相似文献   

Expression of a fusion protein of human ciliary neurotrophic factor and soluble CNTF-Receptor and identification of its activity     

孙益  葛霁光 《浙江大学学报(A卷英文版)》2003,4(3):340-345

Ciliary neurotrophic factor (CNTF) has pleiotropic actions on many neuronal populations as well as on glia. Signal transduction by CNTF requires that it bind first to CNTF-R, permitting the recruitment of gp130 and LIF-R, forming a tripartite receptor complex. Cells that only express gp130 and LIF-R, but not CNTF-R are refractory to stimulation by CNTF. On many target cells CNTF only acts in the presence of its specific agonistic soluble receptors. We engineered a soluble fusion protein by linking the COOH-terminus of sCNTF-R to the NH₂-terminus of CNTF. Recombinant CNTF/sCNTF-R fusion protein (Hyper-CNTF) was successfully expressed in COS-7 cells. The apparent molecular mass of the Hyper-CNTF protein was estimated from western blots to be 75 kDa. Proliferation assays of transfected BAF/3 cells in response to CNTF and Hyper-CNTF were used to verify the activity of the cytokines. The proliferative results confirmed that CNTF required homodimerization of the gp130, CNTF-R and LIF-R receptor subunit whereas Hyper-CNTF required heterodimerization of the gp130 and LIF-R receptor subunit. We concluded that the fusion protein Hyper-CNTF had superagonistic activity on target cells expressing gp130 and LIF-R, but lacking membrane-bound CNTF-R. Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholar, Zhejiang Province, China and SFB415, TP B5, Germany.  相似文献   

Improving near‐peer teaching quality in anatomy by educating teaching assistants: An example from Sweden          下载免费PDF全文

Ellen Johansson  Tobias E. Holmin  Bengt R. Johansson  Magnus Braide 《Anatomical sciences education》2018,11(4):403-409

Peer‐assisted learning has gained momentum in a variety of disciplines, including medical education. In Gothenburg, Sweden, medical students who have finished their compulsory anatomy courses have the option of working as teaching assistants (TAs). Teaching assistants provide small group teaching sessions as a complement to lectures given by faculty. Previously, TAs were left to handle the role as junior teachers by themselves, but since 2011, a continuation course in anatomy has been developed with the aim of providing the TAs better anatomy knowledge and guidance for teaching. The course was designed to comprise 7.5 ECTS credits (equivalent to 5 weeks of full‐time studies), and today all TAs are required to take this course before undertaking their own teaching responsibilities. This study aims to compare course evaluations of TA teaching before and after the introduction of the anatomy continuation course, in order to understand how students perceived teaching performed by self‐learned versus trained TAs. The results of this study demonstrate that there was a trend towards better teaching performed by trained TAs. The variability in rankings decreased significantly after the introduction of the continuation course. This was mainly due to an improvement among the TAs with the lowest levels of performance. In addition to comparing student rankings, TAs were interviewed regarding their experiences and perceptions within the continuation course. The course was generally positively regarded. The TAs described a sense of cohesion and appreciation since the institute invested in a course dedicated specifically for them. Anat Sci Educ 11: 403–409. © 2018 American Association of Anatomists.  相似文献   

Posthumanism and the massive open online course: contaminating the subject of global education     

Stefan Herbrechter 《Distance Education》2016,37(3):376-379

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The disadvantaged student at a liberal arts college     

Dr. Charles B. Johansson  Jack E. Rossmann 《Research in higher education》1974,2(3):195-206

In the fall of 1969, a program to expand educational opportunities (EEO) for economically disadvantaged students was initiated at Macalester College. During the first three years of the program, the percentage of non-white students at the College rose from 3% to approximately 15%.Average grades for the EEO students were approximately one standard deviation below those of a random non-EEO sample, similar to the differences in high school grades between the two groups. However, the EEO students persisted at Macalester College at a slightly higher rate than non-EEO students. The EEO students also were more likely than non-EEO students to major in the behavioral/social sciences and less likely to major in the fine arts, humanities, and physical sciences.  相似文献   

Mathematical Reasoning Requirements in Swedish National Physics Tests     

Helena Johansson 《International Journal of Science and Mathematics Education》2016,14(6):1133-1152

This paper focuses on one aspect of mathematical competence, namely mathematical reasoning, and how this competency influences students’ knowing of physics. This influence was studied by analysing the mathematical reasoning requirements upper secondary students meet when solving tasks in national physics tests. National tests are constructed to mirror the goals stated in the curricula, and these goals are similar across national borders. The framework used for characterising the mathematical reasoning required to solve the tasks in the national physics tests distinguishes between imitative and creative mathematical reasoning. The analysis process consisted of structured comparisons between representative student solutions and the students’ educational history. Of the 209 analysed tasks, 3/4 required mathematical reasoning in order to be solved. Creative mathematical reasoning, which, in particular, involves reasoning based on intrinsic properties, was required for 1/3 of the tasks. The results in this paper give strong evidence that creative mathematical reasoning is required to achieve higher grades on the tests. It is also confirmed that mathematical reasoning is an important and integral part of the physics curricula; and, it is suggested that the ability to use creative mathematical reasoning is necessary to fully master the curricula.  相似文献   

The epistemological role of language use in learning: A phenomenographic intentional-expressive approach     

Elsie Anderberg  Lennart Svensson  Christer Alvegrd  Thorsten Johansson 《Educational Research Review》2008,3(1):14-29

In research on learning, one of the fundamental questions concerns issues of language and thought. A number of empirical studies have revealed the interplay between understanding of subject matter and meanings of language expressions to be more dynamic and ambiguous than is commonly acknowledged. The aim of this article is to outline an alternative intentional-expressive approach to the interplay between use of language and understanding of subject matter as a contribution to the theoretical development in research on learning. The approach is based on a conception of language that focuses on the function of learners’ language use in relation to subject matter in developing and expressing understanding. The learner is seen as an agent, and the focus is on the use of language from the learner's perspective. Four aspects of the relation between learners and subject matter are described and discussed. Conclusions concern the value of this approach as a complement and alternative to the dominant communicative and cognitive approaches to the role of language in learning.  相似文献   

The myth of global science collaboration—Collaboration patterns in epistemic communities     

Stefan Hennemann  Diego Rybski  Ingo Liefner 《Journal of Informetrics》2012,6(2):217-225

Scientific collaboration is often perceived as a joint global process that involves researchers worldwide, regardless of their place of work and residence. Globalization of science, in this respect, implies that collaboration among scientists takes place along the lines of common topics and irrespective of the spatial distances between the collaborators. The networks of collaborators, termed ‘epistemic communities’, should thus have a space-independent structure. This paper shows that such a notion of globalized scientific collaboration is not supported by empirical data. It introduces a novel approach of analyzing distance-dependent probabilities of collaboration. The results of the analysis of six distinct scientific fields reveal that intra-country collaboration is about 10–50 times more likely to occur than international collaboration. Moreover, strong dependencies exist between collaboration activity (measured in co-authorships) and spatial distance when confined to national borders. However, the fact that distance becomes irrelevant once collaboration is taken to the international scale suggests a globalized science system that is strongly influenced by the gravity of local science clusters. The similarity of the probability functions of the six science fields analyzed suggests a universal mode of spatial governance that is independent from the mode of knowledge creation in science.  相似文献