Gender differences among sagittal plane knee kinematic and ground reaction force characteristics during a rapid sprint and cut maneuver

Women are more prone to anterior cruciate ligament (ACL) injury during cutting sports than men. The purpose of this study was to examine knee kinematic and ground reaction forces (GRF) differences between genders during cutting. Male and female athletes performed cutting trials while force platform and video data were recorded (180 Hz). Differences (p < . 05) were observed between groups for knee flexion at contact and GRF at maximum knee flexion. Women averaged 5.8 degrees less flexion at contact and 1.0 N. (kg x m x s(-1))(-1) greater GRF at maximum flexion. Knee range of motion and peak GRF variables were not significantly different, but women had greater values. Women exhibited technique characteristics believed to increase ACL injury risk, but men exhibiting similar characteristics were also observed and could also be at risk.     

The influence of moment of inertia on baseball/softball bat swing speed

The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent, the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets, balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured speeds, from 22 to 31 m s⁻¹, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest the importance of additional degrees of freedom in determining swing speed.     

Analysis of postural stability in collegiate soccer players before and after an acute bout of heading multiple soccer balls

The aim of our study was to determine if any immediate changes in balance were discernable in college soccer players after a specially designed heading session. Eight male and two female skilled collegiate soccer players had a baseline balance pre-test using the Balance Master, followed by heading 20 balls kicked consecutively by a teammate from the touchline to a point near the goal, which was followed by a post-test using the same testing technique. Paired t-tests were used to compare balance ability between pre- and post-test conditions. There was no difference in balance pre- to post-test (85.3% and 86.2% respectively). No significant difference was noted from pre- to post-test in the mean equilibrium scores for conditions three through six on the Sensory Organization Test, with the exception of condition four, which revealed a significant increase from pre- to post-test. We concluded that an acute session of heading soccer balls may not result in balance changes in collegiate soccer players.     

浅论邓小平对青少年成长的关怀

邓小平同志始终以博大的胸怀和深邃的目光,站在党和国家前途命运的高度,十分关怀青少年的成长。多次向青年发出号召要做“四有”新人,要学习,要参加社会实践,并鼓励大量派遣青少年出国留学,培养了大量的青年专家。     

Price Indices for Artists – A Proposal

This paper proposes a price index for artists adjusted for the quality of the paintings, based on the ratio between the average market price and the average pre-sale estimate for paintings. We apply this methodology to a group of selected artists and schools presented in auctions worldwide in the period 1990–2001. A comparison with quality unadjusted and hedonic indices is also conducted.JEL Classification: C10, Z11     

ONIX: Is there a return on investment for all publishers?

Summary What will be the future of ONIX? Some argue that wider industry acceptance will lead to increased efficiencies in the transfer of book data, which will ultimately benefit book sales. ONIX still has to overcome many challenges: its implementation cost is high, whole-salers and aggregators are still using different spreadsheets and information sources. Furthermore, MS Excel as an alternative solution is widely available and accepted by the industry. Small publishers need more education and a straightforward demonstration of ONIX’s return on investment. An outreaching of the helping hand of professional organizations is strongly suggested to foster the adoption process among small players. It is the role of the AAP and BISG to get their memberships to think about what is good for all members as a whole throughout the industry. As an organization BISG can recommend, educate, and promote the standard. It cannot, however, bring pressure or demand organizations use it. Publishers, retailers, and wholesalers make those decisions for themselves and quite apparently the majority do not yet see the rewards. Market players need to determine the cost versus benefit and as long as distributors and retailers agree on receiving other formats, ONIX will never take a strong hold in the marketplace. After all, publishers should compete against each other with good books and not with multiple computer codes.