对高水平乒乓球运动员腿部爆发力和弹跳力的评价

乒乓球运动是一项非周期性运动,对抗过程中涉及极其复杂的战术、心理和生理因素,球员面对对手的施压需要做出快速反应,其中速度和爆发力是基本的、必备的素质.研究目的探讨乒乓球运动员腿部爆发力的重要作用.研究方法本研究选用29名优秀运动员为实验对象,其中包括17名男性(年龄23.5±5.5岁)和12位女性(年龄20.8±2.9岁),均为西班牙国家乒乓球队成员.采用测力台(Ergotester Globus)、Acer笔记本电脑和一些登记册对运动员进行了全蹲跳(CMJ)和半蹲跳(SJ)测试,并对腿部爆发力和弹跳力进行了评价.实验数据的统计处理由SPSS v12.0和Excel v 10.2软件完成.研究结果在腿部爆发力和弹跳力方面,男女组存在显著性差异(p＜0.001),男运动员优于女性运动员.同样,不同打法的选手之间也存在差异,防守型打法的选手都低于进攻型选手.讨论和结论在CMJ和SJ测试中,防守型打法的选手腿部爆发力和弹跳力均低于进攻型选手.在实验中成绩较好的男女选手,排名均在西班牙前十二以内,进一步证实了腿部爆发力在此项运动中的重要性,尤其对进攻型打法的选手.其原因可归结为血液中所含睾丸激素水平的高低,男选手高于女选手,进攻型选手高于防守型.     

Acculturative Stress and Depressive Symptomatology Among Mexican and Mexican American Students in the U.S.: Examining Associations with Cultural Incongruity and Intragroup Marginalization

This study examined associations of intragroup marginalization and cultural incongruity with acculturative stress and depressive symptoms among 155 undergraduate U.S. college students of Mexican heritage. Findings indicate that perceived interpersonal distancing by the family (intragroup marginalization) and perceived lack of cultural fit between the respondent and academic institution (cultural incongruity) had statistically significant direct and indirect effects on depressive symptoms via acculturative stress. Results also show that 39.7 % of the variance corresponding with depressive symptoms was accounted for by intragroup marginalization, cultural incongruity, acculturative stress, and other exogenous variables.     

A phenomenology of learning large: the tutorial sphere of xMOOC video lectures

The current discourse surrounding Massive Open Online Courses (MOOCs) is powerful. Despite their rapid and widespread deployment, research has yet to confirm or refute some of the bold claims rationalizing the popularity and efficacy of these large-scale virtual learning environments. Also, MOOCs’ reputed disruptive, game-changing potential for education remains unsubstantiated. A sober counterbalance is needed, in particular, via attending to students’ everyday accounts of the complex realities of learning in these massive online courses. This article reports on an exploratory, phenomenological study of the xMOOC learning experience. Our interest was not the xMOOC experience of students in general, but in its singular, lived particularities. What we discovered was a unique and intimate tutorial sphere that seemed to develop for some xMOOC students in the context of the video lectures, an experience sometimes marked by a sense of fandom surround.     

The role of positive peer interactions and English exposure in Spanish-speaking preschoolers’ English vocabulary and letter-word skills

We examined the extent to which positive interactions with peers and the amount of English exposure received from them during social interactions in the fall of preschool contributed to low-income Spanish-speaking children's (N = 107; M_age = 53 months; SD = 4.30 months; 56% boys) English vocabulary and letter-word skills in the spring (controlling for parents’ language use, family income, number of English books at home, and children's nonverbal cognitive abilities). We also examined the mediating roles of children's learning behaviors (e.g., attentiveness, independence, initiative, persistence, and participation) and English oral proficiency in the classroom. The association between positive peer interactions and English vocabulary skills was mediated by children's English oral proficiency, whereas the association between positive peer interactions and English letter-word skills was mediated by children's learning behaviors and English oral proficiency. The associations among peer English exposure and children's English vocabulary and letter-word skills were mediated by children's English oral proficiency. There was also evidence of a transactional association between positive peer interactions and children's learning behaviors and between peers’ and children's English oral proficiency. The findings highlight the importance of peer experiences in fostering Spanish-speaking preschoolers’ English vocabulary and letter-word skills.     

On Our Own: Starting an Interlibrary Loan Service From Scratch

In August 2009, the Herbert Wertheim College of Medicine Medical Library opened its doors to students, faculty, and staff. One of the many challenges before opening the library was developing a unique and autonomous interlibrary loan service for its patrons. This article examines the decisions in choosing the best document delivery system, the management of funds, and the selection of holdings for a new medical library. Along with these decisions, there is discussion on the significance of costs, turnaround times, and challenges going forward.     

The elusive concept of innovation for Schumpeter,Marschak and the early econometricians

The modern concept of innovation is a crucial part of the analysis of capitalism as an adaptive system, and it is due to Schumpeter. Consequently, Schumpeter's role as a “prophet of innovation” has been rightly emphasized. This paper contributes to that history presenting some of the difficulties Schumpeter suffered as a formal representation of innovation was proposed by his fellow econometricians, as proved by the case of one of such dialogs, that with Jacob Marschak, at the time the director of the Cowles Commission and vice-president and then president of the Econometric Society. It is shown how Schumpeter elaborated his concepts of endogenous innovation and of industrial mutation as contrasted to the mechanical view of his fellow econometricians. Finally, the paper emphasizes the changes of the concept of randomness through the debate.