Longitudinal study of preadolescent sport self-concept and performance: reciprocal effects and causal ordering     

Marsh HW  Gerlach E  Trautwein U  Lüdtke O  Brettschneider WD 《Child development》2007,78(6):1640-1656

Do preadolescent sport self-concepts influence subsequent sport performance? Longitudinal data (Grades 3, 4, and 6) for young boys and girls (N= 1,135; mean age = 9.67) were used to test reciprocal effects model (REM) predictions that sport self-concept is both a cause and a consequence of sport accomplishments. Controlling prior sport performance (performance-based measures and teacher assessments), prior sport self-concept had positive effects on subsequent sport performance in both Grade 4 and Grade 6 and for both boys and girls. Coupled with previous REM studies of adolescents in the academic domain, this first test for preadolescents in the sport domain supports the generalizability of REM predictions over gender, self-concept domain, preadolescent ages, and the transition from primary to secondary school.  相似文献   

Comfort,Class and Climate Change: The Rise of Glass in Late Medieval and Early Modern Domestic Architecture     

Daniel Jütte 《Cultural and Social History》2013,10(5):621-641

ABSTRACT

In the modern world, glass windows are considered an indispensable element of the built environment. Throughout premodern times, however, glass was not universally used in European architecture. This article argues that the rise of glass in Western architecture was neither an inevitable nor a linear process, but rather a response to certain social, cultural and environmental factors that gained increasing relevance from the late medieval period onwards. In other words, glass windows are a cultural convention, reflecting some of the wide-ranging and transformative challenges that Europeans faced in the late medieval and early modern period.  相似文献   

Symptoms of common mental disorders and related stressors in Danish professional football and handball     

Özgür Kilic  Haruhito Aoki  Rasmus Haagensen  Claus Jensen  Urban Johnson  Gino M. M. J. Kerkhoffs 《European Journal of Sport Science》2017,17(10):1328-1334

The aim of the study was twofold, namely (i) to determine the prevalence of symptoms of common mental disorders (CMDs) among current and retired professional football and handball players and (ii) to explore the relationship of psychosocial stressors with the outcome measures under study. A total of 1155 players were enrolled in an observational study based on a cross-sectional design. Questionnaires based on validated scales were set up and distributed among current and retired professional football and handball players by the Danish football and handball players’ union. In professional football, the highest prevalence (4 weeks) of symptoms of CMDs was 18% and 19% for anxiety/depression among current and retired players, respectively. In professional handball, the highest prevalence (4 weeks) of symptoms of CMDs was 26% and 16% for anxiety/depression among current and retired players, respectively. For both the current and retired professional football and handball players, a higher number of severe injuries and recent adverse life events (LE) were related to the presence of symptoms of CMD. Players exposed to severe injuries and/or recent adverse LE were 20–50% times more likely to report symptoms of CMD. The results suggest that it is possible to recognize the population of professional athletes that are more likely to develop symptoms of CMD. This could create the opportunity to intervene preventively on athletes that suffered from severe injury and/or recent adverse LE that could lead to a faster and safer recovery and psychological readiness to return to play.  相似文献   

The chaotic late Qing and early Republican periods     

Mizoguchi Yūzō 《Inter-Asia Cultural Studies》2016,17(4):574-605

This article excavates some of the core intellectual elements underlying the Xinhai Revolution of 1911 and their historical genealogies. Rather than focusing on the modern nature of the revolution, Mizoguchi locates the revolution within the context of traditional Chinese culture and thought. A central focus of the article is the notion of “self-governance” (zizhi), which played a central role in determining the shape the revolution was to ultimately take. It analyzes the social thought of key figures of the Qing period, showing how in modified guise, core Confucian ethical concepts such as the dichotomy between the private (si) and public (gong) as well as utopian concepts such as datong (great harmony) determined the deep structure of revolutionary thought at the end of the Qing and into the Republican and Communist periods.  相似文献   

Finite element simulation of the ski–snow interaction of an alpine ski in a carved turn     

Peter Federolf  Markus Roos  Anton Lüthi  Jürg Dual 《Sports Engineering》2010,12(3):123-133

Skiing manufacturers depend on the development of new skis on trial and error cycles and extensive product testing. Simulation tools, such as the finite element method, might be able to reduce the number of required testing cycles. However, computer programs simulating a ski in the situation of a turn so far lack realistic ski–snow interaction models. The aim of this study was to (a) implement a finite element simulation of a ski in a carved turn with an experimentally validated ski–snow interaction model, and (b) comparison of the simulation results with instantaneous turn radii determined for an actual carved turn. A quasi-static approach was chosen in which the ski–snow interaction was implemented as a boundary condition on the running surface of the ski. A stepwise linear function was used to characterise the snow pressure resisting the penetration of the ski. In a carved turn the rear section of the ski interacts with the groove that forms in the snow. Two effects were incorporated in the simulation to model this situation: (a) the plasticity of the snow deformation, (b) the influence of the ski’s side-cut on the formation and shape of this groove. The simulation results agreed well with experiments characterising snow penetration. Implementation of the groove in the ski–snow interaction model allowed calculation of the instantaneous turn radii measured in actual turns, but also caused significant numerical instability. The simulation contributes to the understanding of the mechanical aspects of the ski–snow interaction in carved turns and can be used to evaluate new ski designs.  相似文献   

The dynamic control ratio at the equilibrium point (DCRe): introducing relative and absolute reliability scores     

Tobias Alt  Axel J. Knicker  Heiko K. Strüder 《Journal of sports sciences》2017,35(7):688-693

Analytical methods to assess thigh muscle balance need to provide reliable data to allow meaningful interpretation. However, reproducibility of the dynamic control ratio at the equilibrium point has not been evaluated yet. Therefore, the aim of this study was to compare relative and absolute reliability indices of its angle and moment values with conventional and functional hamstring–quadriceps ratios. Furthermore, effects of familiarisation and angular velocity on reproducibility were analysed. A number of 33 male volunteers participated in 3 identical test sessions. Peak moments (PMs) were determined unilaterally during maximum concentric and eccentric knee flexion (prone) and extension (supine position) at 0.53, 1.57 and 2.62 rad · s^–1. A repeated measure, ANOVA, confirmed systematic bias. Intra-class correlation coefficients and standard errors of measurement indicated relative and absolute reliability. Correlation coefficients were averaged over respective factors and tested for significant differences. All balance scores showed comparable low-to-moderate relative (<0.8–0.9) and good absolute reliability (<10%). Relative reproducibility of dynamic control equilibrium parameters augmented with increasing angular velocity, but not with familiarisation. At 2.62 rad · s^–1, high (moment: 0.906) to moderate (angle: 0.833) relative reliability scores with accordingly high absolute indices (4.9% and 6.4%) became apparent. Thus, the dynamic control equilibrium is an equivalent method for the reliable assessment of thigh muscle balance.  相似文献   

Knowledge of the natural and the social: how are they different and what do they have in common?     

Zhichang?ZhuEmail author 《知识管理研究与实践》2010,8(2):173-188

Knowledge of the natural and the social are irreducibly different yet have much in common. The differences lie at the levels of complexity they engage, modes of explanation they adopt, investigation aims they allow and whether they assert a ‘double hermeneutic’ effect to the behaviour of the studied objects. Knowledge are in common in that they are all construed out of available resources, justified based on the consequences of acting upon them, settled until better alternatives emerge, and serving as walking sticks for beating unknown paths in human life. Because of this, there can be no hierarchy of knowledge or unity of methodology, and dialogical encounters guided by situational ethics, not professional deafness driven by ontological/instrumental fallacies, are a viable strategy for morally and practically wise actions, including knowledge management projects.  相似文献   

Polyelectrolyte multilayer surface functionalization of poly(dimethylsiloxane) (PDMS) for reduction of yeast cell adhesion in microfluidic devices     

Schmolke H  Demming S  Edlich A  Magdanz V  Büttgenbach S  Franco-Lara E  Krull R  Klages CP 《Biomicrofluidics》2010,4(4):44113

Polyelectrolyte multilayers (PEMs) based on the combinations poly(diallyldimethylammonium chloride)∕poly(acrylic acid) (PDADMAC∕PAA) and poly(allylamine hydrochloride)∕PAA (PAH∕PAA) were adsorbed on poly(dimethylsiloxane) (PDMS) and tested for nonspecific surface attachment of hydrophobic yeast cells using a parallel plate flow chamber. A custom-made graft copolymer containing poly(ethylene glycol) (PEG) side chains (PAA-g-PEG) was additionally adsorbed on the PEMs as a terminal layer. A suitable PEM modification effectively decreased the adhesion strength of Saccharomyces cerevisiae DSM 2155 to the channel walls. However, a further decrease in initial cell attachment and adhesion strength was observed after adsorption of PAA-g-PEG copolymer onto PEMs from aqueous solution. The results demonstrate that a facile layer-by-layer surface functionalization from aqueous solutions can be successfully applied to reduce cell adhesion strength of S. cerevisiae by at least two orders of magnitude compared to bare PDMS. Therefore, this method is potentially suitable to promote planktonic growth inside capped PDMS-based microfluidic devices if the PEM deposition is completed by a dynamic flow-through process.  相似文献   

Kinematic differences of elite and high-performance tennis players in the cross court and down the line forehand   总被引：1，自引：0，他引：1  

Landlinger J  Lindinger SJ  Stöggl T  Wagner H  Müller E 《Sports biomechanics / International Society of Biomechanics in Sports》2010,9(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 retroreflective 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 degrees/s), and angular velocity of the upper trunk (453 vs. 292 degrees/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   

Sporthistorisches aus den USA     

Sandra Heck  Bettina Kratzmüller 《Sportwissenschaft》2010,40(3):219-221

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