Comparing the pre- and post-impact ball and racquet kinematics of elite tennis players' first and second serves: a preliminary study

The aim of this study was to compare the pre- and post-impact three-dimensional kinematics of the ball and racquet during first and second serves performed by elite tennis players. Data were collected from four male and four female right-handed professional players during competition using two high-speed cameras (200 Hz). For each player, one first serve and one second serve from the 'deuce' or right service court that landed within the specified target area were analysed. To test for significant differences between the first and second serves, Wilcoxon tests (P < or = 0.05) were performed on selected parameters. The results indicate that the ball travelled forward and to the left during the flight phase of the toss in all but one trial. The average pre-impact ball forward location for the first serve was significantly more in front and had a higher associated forward ball velocity than the corresponding values for the second serve. On average, the decrease in post-impact ball speed from the first to the second serve was 24.1%. No significant differences between the first and second serves were found in the pre-impact racquet head speed and orientation, which was represented as a unit vector perpendicular to the racquet face. The major adjustments made by the players when going from the first to second serve were a decrease in pre-impact ball forward location (P < or = 0.01) and an increase in the pre-impact racquet vertical and lateral velocities (both P < or = 0.05). This implies that the players tossed the ball closer to the body and imparted topspin and sidespin on the ball by changing the racquet vertical and lateral velocities when going from the first to the second serve.     

Online homework impact in undergraduate mathematics and business statistics courses

This evaluation examines the impact on student success rates related to changes in instructional programmes in undergraduate mathematics and statistics courses. Success for students taking courses with a computer-based homework component was compared with success of students who took the course in prior semesters without the computer-based component. Graphical and analytical tools are used to compare results. Results come from multiple semesters of each type of homework application, for both pre-calculus algebra and business statistics courses. Students whose performance is utilised in this study are undergraduate students taking introductory level college mathematics or business statistics courses, with mostly no prior instruction at this level. Comparing the success of the intervention group with the success of the baseline control group, findings support that the students using the computer-based homework instruction are just as successful as those using the traditional method of homework instruction. Utilising the online homework applications, provide several important advantages in today’s universities, including the reduced time for faculty grading, consistency of graded assignments across all sections of a course and most importantly, immediate feedback for students.     

Teaching anti-racist counseling theories: Black liberation narrative therapy

Counseling theories created by White theorists have traditionally failed to consider the religious or spiritual experiences of Black clients. Integration of Black liberation theology and narrative therapy provides a novel approach to support counseling trainees in meeting the needs of Black clients. Decolonizing therapeutic strategies are presented along with counselor educator recommendations.     

The Quality of Message Ideas,Thinking and Interaction in an Asynchronous CMC Environment

One of the major shifts in education today under the influence of information and communication technologies is that there is an increased tendency toward the use of computer-mediated communications (CMC). CMC has developed an assortment of methods from simple e-mail to wireless instant messages and synchronous and asynchronous discussions. A large portion of the research in this area focuses on the pedagogical aspects of CMC particularly on the use, strategies, effectiveness and the integration of the new technologies for teaching and learning. Some studies investigate different perspectives of interaction like keeping track of asynchronous discussion, quality of participation, interaction and collaborative or group learning. This paper reports findings from the study that examines the quality of message ideas, thinking and interaction in an asynchronous CMC environment in a teacher training institution. The authors suggest some practical strategies in the implementation of asynchronous discussions in CMC environment. La qualité des messages d’idées, de la pensée et de l’interaction dans un environnement CMC asynchrone. Un des changements majeurs dans l’éducation aujourd’hui sous l’influence de l’information et des technologies de la communication est une tendance accrue À l’usage des communications par ordinateur (Computer-mediated Communications CMC). CMC a permis le développement de tout un assortiment de méthodes depuis de simples e-mail jusqu’À des messages sans fil instantanés et des discussions synchrones et asynchrones. Une grande partie de la recherche en ce domaine est centrée sur les aspects pédagogiques des CMC en particulier sur l’emploi, les stratégies, l’efficacité et l’intégration des nouvelles technologies pour l’enseignement et l’apprentissage. Certains études examinent les perspectives différentes de l’interaction. Telles que garder la trace des discussions asynchrones, la qualité de la participation interaction et l’apprentissage en coopération ou en groupe. L’article rapporte les résultats de l’étude qui examine la qualité des messages d’idées, la pensée et l’interaction dans un environnement de CMC asynchrone dans un établissement de formation des enseignants. Les auteurs suggérent des stratégies pratiques dans l’introduction de discussions asynchrones dans un environnement CMC. Die Qualität der übermittlung von Ideen, Denken und Interaktion in einem asynchronen CMC Umfeld Eine der wichtigsten Umstellungen der heutigen Ausbildung ist die unter dem Einfluss von Informations- und Kommunikationstechnologien verstärkte Tendenz, rechnergestützte Kommunikation (computer-mediated communications:CMC)

zu benutzen. CMC hat ein ganzes Arsenal von Methoden entwickelt, von der einfachen E-Mail bis zu drahtlosen Nachrichten und synchron oder asynchron geführten Diskussionen. Die Forschung in diesem Bereich konzentriert sich hauptsächlich auf die pädagogischen Aspekte von CMC, besonders auf die Nutzung, die Strategien, den Wirkungsgrad und die Möglichkeiten der Einbindung der Neuen Technologien zum Lehren und Lernen. Einige Arbeiten erforschen die verschiedenen Perspektiven

der Interaktion wie das Verfolgen von asynchronen Diskussionen, die Qualität der Beteiligung, der Interaktion und Zusammenarbeit oder dem Lernen in Gruppen. In diesem Beitrag wird über Ergebnisse der Studie zur Untersuchung der Qualität der übermittlung von Ideen, Gedanken und Interaktionen in einem asynchron arbeitenden rechnergestützten

System (CMC) einer Lehrerfortbildungseinrichtung berichtet. Die Autoren erläutern praktische Strategien zur Einbindung asynchroner Diskussionen in eine CMC-Umgebung.     

伞形科植物染色体数目报告

In the present paper, chromosome numbers are reported for 33 species and varieties of Chinese Umbelliferae which belong to 17 genera in the subfamily Api- oideae.  Chromosome number of each species is shown in Table I.  Eighteen countings are newly reported.  Chromatin bridges and fragments were observed at anaphase I in some materials.  It is suggested that the fertility reduction in some species is due to the chromosome aberrations.     

从植物化学成份的比较看单子叶植物的起源问题

  通过对单子叶植物和毛茛科以及”睡莲目”植物中生物碱、甾体化合物、三萜化合物、氰甙 和脂肪酸等五类化学成份的比较分析，作者认为毛茛科与百合目有着密切的亲缘关系，因而支 持单子叶植物毛茛—百合起源的主张，不赞同苏联学者Takhtajan关于单子叶植物莼菜—泽泻起源的观点。     

Research engagement and educational decentralisation: problematising primary school English teachers’ research experiences in China

Teachers are encouraged to enhance professional competence through reflective practice and they are also asked to undertake research to generate evidence for their professional practices. This paper reports on an inquiry into a group of primary school English language teachers’ research engagement in the province of Guangdong on the Chinese mainland. The inquiry explored the effect of educational reforms on the participants’ research engagement through the use of an open‐ended questionnaire and group interviews. The inquiry revealed that research engagement had become an important part of the teachers’ professional lives. Emerging findings from the inquiry also problematised their research engagement as it was found to have been undermined by a competitive promotion mechanism, the teachers’ conceptualisations of research and challenges in the knowledge dissemination process. The paper ends with reflections on how to make teacher research “educational” for teachers and serve as an effective way for professional development.     

Use of deterministic models in sports and exercise biomechanics research

A deterministic model is a modeling paradigm that determines the relationships between a movement outcome measure and the biomechanical factors that produce such a measure. This review provides an overview of the use of deterministic models in biomechanics research, a historical summary of this research, and an analysis of the advantages and disadvantages of using deterministic models. The deterministic model approach has been utilized in technique analysis over the last three decades, especially in swimming, athletics field events, and gymnastics. In addition to their applications in sports and exercise biomechanics, deterministic models have been applied successfully in research on selected motor skills. The advantage of the deterministic model approach is that it helps to avoid selecting performance or injury variables arbitrarily and to provide the necessary theoretical basis for examining the relative importance of various factors that influence the outcome of a movement task. Several disadvantages of deterministic models, such as the use of subjective measures for the performance outcome, were discussed. It is recommended that exercise and sports biomechanics scholars should consider using deterministic models to help identify meaningful dependent variables in their studies.     

奥运争光竞技体育服务产品提供方式的实证分析

研究以奥运争光类竞技体育服务产品的提供方式为对象,通过对我国传统竞技体育服务产品提供方式的历史考察发现,举国体制是我国传统竞技体育服务产品提供的重要方式之一。在现实条件下,奥运争光竞技体育服务产品的提供具有多元可能性,而专项资金、资助高校培养模式、委托生产——合约模式、非营利组织生产等方式。