The effects of baseball bat mass properties on swing mechanics,ground reaction forces,and swing timing

Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.     

髋关节滑膜皱襞生长发育的应用解剖学研究

木文对胎儿、儿童和成人三个年龄组,总计126侧髋关节进行了解剖学观测.发现片状滑膜皱襞在胎儿5月龄时就已经发生,绒毛状皱襞则在儿童早期才开始出现.并发现滑膜皱襞伴随着机体的生长发育,形态逐渐增大,数量逐渐增多,直到成年期方趋于稳定.同时发现,髋关节的滑膜皱襞(唇外皱襞)主要分布在三个部位:股骨头韧带的基部、髋臼唇外缘和股骨颈滑膜反折处.特别是髋臼唇外缘的滑膜皱襞有少数(9.52%)嵌入头臼之间的缝隙之中,作者认为唇外皱襞(C皱襞)是导致儿童髋关节滑膜皱襞综合症的形态学基础.     

A newer class o f precise oscillator models

A method has been presented in recent papers for deriving precisely stabilized waveform generators by relating them to second order conservative oscillators. The present paper demonstrates a method for modifying the previous models and in doing so a novel class of applicable oscillator models is established.Conditions that enable the models to sustain oscillations in steady state are described. A precise method for dynamically stabilizing the oscillators waveforms is developed, and practical uses are suggested.     

Perspectives of students with autism on their participation in a peer-mediated intervention

The article describes research into the perspectives of students with autism regarding their participation as the target participants in a peer-mediated social communication intervention. Questionnaires were administered to four elementary-aged students with autism before and after their involvement in the intervention. The students' parents and teachers also completed questionnaires about the students' participation in the intervention. Through the use of these questionnaires, we gained an insight into students' experiences with the intervention, which elements of the intervention they found most enjoyable and most effective, and the perceived impacts of the intervention on their social communication behaviours. Qualitative and quantitative analyses of the questionnaire data revealed that all four students with autism enjoyed participating in the peer-mediated intervention sessions, felt that their social communication behaviours had improved as a result of their involvement, and would like to be involved in similar sessions in the future. Implications for parents and educators who support the social communication of children with autism are explored.     

An exploratory study on the relationship between parents�� career interests and the career interests of young adults

In this study, we attempt to investigate the potential effects of parents’ career interests on young adults’ career interests. Using a sample of 113 freshmen in Hong Kong, results indicated that after controlling for personality, gender, general mental abilities and emotional intelligence, some of the parents’ career interests were still related to the young adults’ respective career interests. For some types of interests, the extent of influences is found to be contingent on the gender of the respondents. Implications are discussed.     

Location, location, location: development of spatiotemporal sequence learning in infancy

We investigated infants' sensitivity to spatiotemporal structure. In Experiment 1, circles appeared in a statistically defined spatial pattern. At test 11-month-olds, but not 8-month-olds, looked longer at a novel spatial sequence. Experiment 2 presented different color/shape stimuli, but only the location sequence was violated during test; 8-month-olds preferred the novel spatial structure, but 5-month-olds did not. In Experiment 3, the locations but not color/shape pairings were constant at test; 5-month-olds showed a novelty preference. Experiment 4 examined "online learning": We recorded eye movements of 8-month-olds watching a spatiotemporal sequence. Saccade latencies to predictable locations decreased. We argue that temporal order statistics involving informative spatial relations become available to infants during the first year after birth, assisted by multiple cues.