The effect of added fatty and other oils upon the carbonization of mineral lubricating oils     

C.E. Waters 《Journal of The Franklin Institute》1912,173(4):419-421

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Steel in freight car construction     

C.A. Seley 《Journal of The Franklin Institute》1910,169(4):278-295

It has been the custom among designers of freight cars either with underframes of steel or of wood to depend upon the strength of the underframe alone in making computations for a specified carrying capacity, despite the fact that the superstructure in many cases can and does constitute a truss. The author presents the evolution in design of structural steel freight cars, with which he has been closely identified, where the value of the superstructure as a tress has been duly considered as an element of strength and in reducing weight.  相似文献   

Explosives. The progressive decomposition of gun-cotton during its storage     

M.M.O. Silberrad  R.C. Farmer 《Journal of The Franklin Institute》1908,166(6):471-486

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Electrical and mechanical response of skeletal muscle to electrical stimulation after acute passive stretching in humans: a combined electromyographic and mechanomyographic approach     

Cè E  Paracchino E  Esposito F 《Journal of sports sciences》2008,26(14):1567-1577

Two mechanisms have been suggested to explain stretching-induced maximum force depression: a mechanical alteration in the stretched muscle and an impairment of neural activation. Electrical stimulation allows standardization of the level of muscle activation without being limited by neural control. The aim of this study was to evaluate the stretching-induced changes in the electrical and mechanical properties of muscle during electrically elicited contractions. Twelve participants (age 22 +/- 1 years; body mass 75 +/- 2 kg; stature 1.79 +/- 0.02 m; mean +/- standard error) underwent six electrical stimulations of the medial gastrocnemius muscle before and after stretching. During the contractions, surface electromyogram (EMG) and mechanomyogram (MMG) were recorded simultaneously together with force. After stretching we found: (i) no differences in EMG parameters; (ii) MMG amplitude decreased by 4 +/- 1% (P < 0.05); and (iii) the peak force, the peak rate of force development, and the acceleration peak of force development decreased by 12 +/- 3%, 14 +/- 1%, and 24 +/- 5%, respectively (P < 0.05). In conclusion, acute passive stretching did not change EMG properties but altered the mechanical characteristics of the contracting muscle. Indeed, muscle force-generating capacity and stiffness of the muscle-tendon unit were significantly impaired.  相似文献   

Stressors in elite sport: a coach perspective   总被引：1，自引：1，他引：0  

Thelwell RC  Weston NJ  Greenlees IA  Hutchings NV 《Journal of sports sciences》2008,26(9):905-918

We examined the varying performance and organizational stressors experienced by coaches who operate with elite athletes. Following interviews with eleven coaches, content analysis of the data revealed coaches to experience comparable numbers of performance and organizational stressors. Performance stressors were divided between their own performance and that of their athletes, while organizational stressors included environmental, leadership, personal, and team factors. The findings provide evidence that coaches experience a variety of stressors that adds weight to the argument that they should be labelled as "performers" in their own right. A variety of future research topics and applied issues are also discussed.  相似文献   

Heart rates of high school physical education students during team sports, individual sports, and fitness activities     

Laurson KR  Brown DD  Cullen RW  Dennis KK 《Research quarterly for exercise and sport》2008,79(1):85-91

This study examined how activity type influenced heart rates and time spent in target heart rate zones of high school students participating in physical education classes. Significantly higher average heart rates existed for fitness (142 +/- 24 beats per minute [bpm]) compared to team (118 +/- 24 bpm) or individual (114 +/- 18) activities. Similar results occurred for the percentage of activity time spent within a target heart rate zone (fitness 81.7 +/- 15.9%, individual 68.4 +/- 30.5%, and team 60.6 +/- 30.5%). Boys attained higher heart rates during team activities, while female students had higher rates during individual activities indicating male and female adolescents respond differently to activity types. The highest mean heart rates were observed during fitness activities.  相似文献   

The human genome and sport, including epigenetics and athleticogenomics: a brief look at a rapidly changing field     

Sharp NC 《Journal of sports sciences》2008,26(11):1127-1133

Since Hugh Montgomery discovered the first of what are now nearly 200 "fitness genes", together with rapid advances in human gene therapy, there is now a real prospect of the use of genes, genetic elements, and/or cells that have the capacity to enhance athletic performance (to paraphrase the World Anti-Doping Agency's definition of gene doping). This overview covers the main areas of interface between genetics and sport, attempts to provide a context against which gene doping may be viewed, and suggests a futuristic legitimate use of genomic (and possibly epigenetic) information in sport.  相似文献   

Psychometric evaluation of the exercise identity scale among Greek adults and cross-cultural validity     

Vlachopoulos SP  Kaperoni M  Moustaka FC  Anderson DF 《Research quarterly for exercise and sport》2008,79(3):283-299

The present study reported on translating the Exercise Identity Scale (EIS: Anderson & Cychosz, 1994) into Greek and examining its psychometric properties and cross-cultural validity based on U.S. individuals' EIS responses. Using four samples comprising 33, 103, and 647 Greek individuals, including exercisers and nonexercisers, and a similar sample comprising 800 U.S. individuals, the concurrent validity, factor structure, internal reliability, test-retest reliability, external validity, gender invariance, and cross-cultural validity of the EIS responses were examined using confirmatory factor analytical procedures. The results supported the concurrent validity, an adequate unidimensional factor structure for the translated EIS and the internal reliability and test-retest reliability over a 6-week interval. Further, cross-gender configural, partial metric, partial strong factorial, and partial strict factorial invariance and cross-cultural configural and partial metric invariance supported the cross-cultural equivalence of the EIS versions. Moreover, the external validity of the translated EIS responses was also supported. Overall, the findings supported the validity of the exercise identity construct outside North American boundaries and the EIS items' equivalence, providing initial evidence for its cross-cultural applicability.  相似文献   

But I like PE: factors associated with enjoyment of physical education class in middle school girls     

Barr-Anderson DJ  Neumark-Sztainer D  Schmitz KH  Ward DS  Conway TL  Pratt C  Baggett CD  Lytle L  Pate RR 《Research quarterly for exercise and sport》2008,79(1):18-27

The current study examined associations between physical education (PE) class enjoyment and sociodemographic, personal, and perceived school environment factors among early adolescent girls. Participants included 1,511 sixth-grade girls who completed baseline assessments for the Trial of Activity in Adolescent Girls, with 50% indicating they enjoyed PE class a lot. Variables positively associated with PE class enjoyment included physical activity level, perceived benefits of physical activity, self-efficacy for leisure time physical activity, and perceived school climate for girls' physical activity as influenced by teachers, while body mass index was inversely associated with PE class enjoyment. After adjusting for all variables in the model, PE class enjoyment was significantly greater in Blacks than in Whites. In model testing, with mutual adjustment for all variables, self-efficacy was the strongest correlate of PE class enjoyment, followed by perceived benefits, race/ethnicity, and teachers' support for girls' physical activity, as compared to boys, at school. The overall model explained 11% of the variance in PE class enjoyment. Findings suggest that efforts to enhance girls' self-efficacy and perceived benefits and to provide a supportive PE class environment that promotes gender equality can potentially increase PE class enjoyment among young girls.  相似文献   

The influence of anxiety on visual attention in climbing   总被引：2，自引：0，他引：2  

Nieuwenhuys A  Pijpers JR  Oudejans RR  Bakker FC 《运动与训练心理学杂志》2008,30(2):171-185

The object of the current study was to investigate anxiety-induced changes in movement and gaze behavior in novices on a climbing wall. Identical traverses were situated at high and low levels on a climbing wall to manipulate anxiety. In line with earlier studies, climbing times and movement times increased under anxiety. These changes were accompanied by similar changes in total and average fixation duration and the number of fixations, which were primarily aimed at the holds used for climbing. In combination with these findings, a decrease in search rate provided evidence for a decrease in processing efficiency as anxiety increased.  相似文献