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61.
Paolo Caravaggi Alberto Leardini Claudio Belvedere 《Sports biomechanics / International Society of Biomechanics in Sports》2020,19(3):382-394
AbstractHead and neck injuries are common in contact sports such as American football. Different mechanisms can produce such injuries, including compressive impact forces on the crown of the helmet with the neck in a flexed chin-down position. The aim of this paper was developing and testing a novel Cervical Spine Protection Device (CSPD) designed to keep the neck within its safe physiological range. The cervical spine range of motion (ROM) of ten participants was measured under four conditions: free; wearing a football gear; wearing the CSPD; and wearing the CSPD underneath the gear. The CSPD was tested in terms of passive and active restraint of head motion, and for its capability to improve endurance time of the neck extensor muscles. Wearing the CSPD resulted in a significant 40–60% reduction in ROM across the three anatomical planes, and in increased endurance of the neck extensor muscles (FREE: 114 ± 57 s; CSPD: 214 ± 95 s; p = 0.004). In quasi-static loading conditions the CSPD was capable of keeping the neck within its physiological range, thus it may be used to decrease the risk of severe injuries due to dangerous chin-down positions. 相似文献
62.
Twelve endurance athletes and six power athletes performed fatiguing isokinetic knee flexions/extensions. Isokinetic torque was recorded during the exercise. Isometric torque, cortisol and lactate responses, electromyographic (EMG) mean power frequency, average rectified value, and conduction velocity were analysed before and after the isokinetic exercise to determine correlations between electrophysiological variables and mechanical performances and/or blood concentrations of biomarkers in the two groups of athletes. The EMG variables were estimated from signals recorded from the vastus lateralis in both voluntary and electrically elicited isometric contractions. Power athletes recorded higher values than endurance athletes for the following variables: pre-exercise isometric maximal voluntary contraction (MVC), isokinetic MVC, rate of mechanical fatigue during isokinetic contractions, pre - post exercise variations and recovery times of conduction velocity and mean power frequency, and lactate concentrations. Moreover, conduction velocity overshooting was observed in endurance athletes during the recovery phase after exercise. The correlation analyses showed that the higher the rate of mechanical fatigue, the higher the lactate production and the reduction in conduction velocity due to the exercise. 相似文献
63.
Alberto Renieri 《Endeavour》1984,8(1):35-43
The generation of coherent synchrotron radiation using beams of relativistic electrons passed through magnetic undulators opens up tremendous scope for photochemistry in general and isotopic separation by laser in particular. Applications for plasma heating in Tokamak-type installations to trigger off the controlled nuclear fusion process are also conceivable. 相似文献
64.
In this preliminary review, the authors analyse the effects of privatisation on diversity in higher education (HE) systems by exploring the consequences of the establishment of HE Institutions by non-public organisations. The rising importance of privatisation in Europe (Western and transitional economies), Latin America, and Southeast Asia is analysed. Then follows detailed examinations of private-sector HE in countries representative of all these geographical areas to determine how far privatisation has stimulated diversity. The preliminary results indicate that in each case the private sub-sector has promoted limited and partial diversification. In general, though, the more recent private establishments, created to satisfy increasing demand for HE, have nonetheless focused predominately on teaching, have undertaken little, or no, research and appear to be of lower quality than the older institutions. The private sub-sector is characterised mostly by its low-risk behaviour, and a concentration on low-cost and/or safer initiatives. Public authorities must share at least a partial responsibility for some of the negative side effects of the development of private higher education. 相似文献
65.
66.
Carlos Alberto Torres 《European Journal of Education》2015,50(3):262-279
This article focuses on the role of global universities and globalisations in an age of global interdependence and cosmopolitanism. Competing agendas that result from actions and reactions to multiple globalisations are considered in relation to global citizenship education. These agendas are crucial in understanding dilemmas of the local and the global in relation to education. Key emerging agendas are highlighted, including those of the hyperglobalisers, skeptics and transformationists. Three themes are central for this conversation, namely a) how multiple globalisations are impacting global life and academics, b) how networks have become privileged sites for global education, and c) the implications of globalisation and networks for global citizenship and global universities. 相似文献
67.
68.
Recumbent bicycles (RB) are high performance, human-powered vehicles. In comparison to normal/upright bicycles (NB) the RB may allow individuals to reach higher speeds due to aerodynamic advantages. The purpose of this investigation was to compare the non-aerodynamic factors that may potentially influence the performance of the two bicycles. 3D body centre of mass (BCoM) trajectory, its symmetries, and the components of the total mechanical work necessary to sustain cycling were assessed through 3D kinematics and computer simulations. Data collected at 50, 70, 90 110 rpm during stationary cycling were used to drive musculoskeletal modelling simulation and estimate muscle-tendon length. Results demonstrated that BCoM trajectory, confined in a 15-mm side cube, changed its orientation, maintaining a similar pattern across all cadences in both bicycles. RB displayed a reduced additional mechanical external power (16.1 ± 9.7 W on RB vs. 20.3 ± 8.8 W on NB), a greater symmetry on the progression axis, and no differences in the internal mechanical power compared to NB. Simulated muscle activity revealed small significant differences for only selected muscles. On the RB, quadriceps and gluteus demonstrated greater shortening, while biceps femoris, iliacus, and psoas exhibited greater stretch; however, aerodynamics still remains the principal benefit. 相似文献
69.
Building on previous work on “regulatory objectivity,” the paper examines recent translational research and cancer genomics to explore the bundle of scientific and regulatory activities that generate and manage the platforms at the core of clinical trials, the “gold standard” of clinical research and evidence-based medicine. In particular, the paper explores the activities of a chain of mediators within a seamless regulatory web characterized by the interaction of endogenous and hybrid regulatory activities that are neither hierarchical nor linear. We contend that a full understanding of the dynamics of regulation in the biomedical domain ought to consider this chain of mediations; that their analysis necessitates understanding the content of the practices they regulate; and that in addition to examining the interactions between different regulatory modalities, we need to pay attention to their development insofar as regulation, far from being mere routine, leads to the emergence of novelty by coproducing the entities it regulates. These activities include not only setting out the conditions that must be respected in order to produce reliable test results, but also the conditions that define the relations (within a clinical context) between the different components of diagnosis as well as the consequences of such relations on clinical judgment. This is why we cannot treat organizational practices as distinct from the content of bio-clinical activities. 相似文献
70.
William W. Brickman Willy Strzelewicz William Taylor Joachim H. Knoll Mark Blaug Oskar Anweiler Andreas Fuchs Gilda L. de Romero Brest Alberto Aráoz Wolfgang Brezinka Enrique Oteiza W. F. Connell Robert J. Havighurst Daniel F. Wozniak Wolfgang Roth Karl Frey Alfons Otto Schorb 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》1970,16(2):221-249