Recumbent vs. upright bicycles: 3D trajectory of body centre of mass,limb mechanical work,and operative range of propulsive muscles     

Riccardo Telli  Gaspare Pavei  Alberto Enrico Minetti 《Journal of sports sciences》2017,35(5):491-499

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   

Opening the Regulatory Black Box of Clinical Cancer Research: Transnational Expertise Networks and “Disruptive” Technologies     

Alberto Cambrosio  Pascale Bourret  Peter Keating  Nicole Nelson 《Minerva》2017,55(2):161-185

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   

Book reviews     

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

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Mechanical and EMG responses of the vastus lateralis and changes in biochemical variables to isokinetic exercise in endurance and power athletes     

Rainoldi A  Gazzoni M  Merletti R  Minetto MA 《Journal of sports sciences》2008,26(3):321-331

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   

Changing Patterns in the Middle Management of Higher Education Institutions: The Case of Portugal   总被引：1，自引：0，他引：1  

Rui Santiago  Teresa Carvalho  Alberto Amaral  V. Lynn Meek 《Higher Education》2006,52(2):215-250

Abstact Much of the writing on higher education in recent years has tended to assume that the new management push in higher education is both universal and irreversible. This paper, however, presents evidence from Portugal to challenge that assumption. While elements of the new managerialism are clearly evident in the perceptions and attitudes of academics in charge of the basic academic units (departments/schools and faculties) in the country’s universities and polytechnics, academic management remains faced with a complex, contradictory and conflicting set of demands and expectations which is likely to take a considerable time to resolve.  相似文献   

Science,objectivity and moral values     

Alberto Cordero 《Science & Education》1992,1(1):49-70

Scientific facts are loaded with values, but, it is argued, this does not viciously compromise the objectivity of scientific claims, because the values that permeate scientific discourse (a) are loaded in turn with facts, (b) are not immune from critical revision, and (c) have changed in the past and continue to be subjected to revision. In science, unlike such enterprises as Scientific Creationism, values are discovered, introduced, tested and challenged in the same way that other aspects of scientific discourse are. All of this makes scientific discourse relevant to the contemporary exploration and critique of human values in general, particularly as more aspects of life become illuminated by science.Research for this paper was made possible in part by RF-CUNY (grant PSC-CUNY 669106). A preliminary version of this paper was given at Universite de Fribourg, Switzerland, May 1990.  相似文献   

Concept maps: Experiments on dynamic thinking     

Natalia Derbentseva  Frank Safayeni  Alberto  J. Cañas 《科学教学研究杂志》2007,44(3):448-465

Three experiments were conducted to examine the effects of map structure, concept quantification, and focus question on dynamic thinking during a Concept Map (CMap) construction task. The first experiment compared cyclic and hierarchical structures. The second experiment examined the impact of the quantification of the header concept in the map. The third experiment explored the effect of the focus question on the map. For all three experiments, the content of the CMaps was assessed for the number of dynamic propositions and the number of quantified concepts. The results show that the cyclic structure, the quantification of the header concept, and the focus question “How” significantly increased dynamic thinking. The studies, the theoretical background, and the implications of the findings are discussed. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 44: 448–465, 2007  相似文献   

Privatization And Vouchers In Colombia And Chile     

Alberto Arenas 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2004,4(2):379-395

The voucher model of financing schooling is becoming increasingly common throughout Latin America, with at least 12 countries using vouchers or voucher-like schemes. The present study focuses on the voucher models of Colombia and Chile, which have the most extensive programs of this type and those of the longest standing in the region. Using empirical evidence, the author compares the two models along four evaluative dimensions: educational quality, segregation, choice and socialization. After weighing the successes and weaknesses of each system, he concludes that, among other characteristics, the most effective and equitable voucher model features: (a) a flexible interpretation of educational quality; (b) financial grants which target solely the poor; (c) vouchers which cover the entire cost of tuition; (d) open enrolment at participating schools; (e) the participation of both secular and religious private schools; (f) accessible and meaningful information to parents; and (g) strong systems of accountability.  相似文献   

Using the Standardized Root Mean Squared Residual (SRMR) to Assess Exact Fit in Structural Equation Models     

Goran Pavlov  Alberto Maydeu-Olivares  Dexin Shi 《Educational and psychological measurement》2021,81(1):110

We examine the accuracy of p values obtained using the asymptotic mean and variance (MV) correction to the distribution of the sample standardized root mean squared residual (SRMR) proposed by Maydeu-Olivares to assess the exact fit of SEM models. In a simulation study, we found that under normality, the MV-corrected SRMR statistic provides reasonably accurate Type I errors even in small samples and for large models, clearly outperforming the current standard, that is, the likelihood ratio (LR) test. When data shows excess kurtosis, MV-corrected SRMR p values are only accurate in small models (p = 10), or in medium-sized models (p = 30) if no skewness is present and sample sizes are at least 500. Overall, when data are not normal, the MV-corrected LR test seems to outperform the MV-corrected SRMR. We elaborate on these findings by showing that the asymptotic approximation to the mean of the SRMR sampling distribution is quite accurate, while the asymptotic approximation to the standard deviation is not.  相似文献   

Communicative Antecedents of Political Persuasion: Political Discussion,Citizen News Creation,and the Moderating Role of Strength of Partisanship     

Alberto Ardèvol-Abreu  Matthew Barnidge  Homero Gil de Zúñiga 《Mass Communication and Society》2017,20(2):169-191

Although much attention has been paid to how media use and interpersonal discussion motivate people to engage in political persuasion, and despite recent efforts to study the role of digital media technologies, less is known about the creation of news and public affairs content online. This study sheds light on how online content creation works alongside other communicative behaviors, such as news use and political discussion, to affect attempted political persuasion. Using two-wave panel survey data, we find that political discussion and citizen news creation mediate the relationships between online and traditional news use, on one hand, and attempted persuasion, on the other. Furthermore, strength of partisanship moderates the relationship between content creation and attempted persuasion. Findings are discussed in light of their implications for the political communication and public sphere processes.  相似文献