The impact of different types of physical activity on total and regional bone mineral density in young Brazilian athletes

Bone turnover is affected by exercise throughout the lifespan, especially during childhood and adolescence. The objective of this study was to investigate the impact of different sports on total and regional bone mineral density in male Brazilian adolescent athletes. Forty-six adolescents aged 10-18 years participated in the study: 12 swimmers, 10 tennis players, 10 soccer players, and 14 sedentary individuals. The athletes had engaged in physical activities for more than 10 h per week in the previous 6 months. Bone mineral density of the lumbar spine (L1-L4), left proximal femur region, and whole body was evaluated by dual-energy X-ray absorptiometry. Results showed higher mean values in the proximal femur region of tennis and soccer players (1.02 ± 0.18; 0.96 ± 0.16, respectively) than swimmers and controls (0.91 ± 0.14 and 0.87 ± 0.06, respectively) (P < 0.05). In relation to the impact of sporting activities based on bone age determination, we observed significant differences in bone mineral density at all evaluated sites at the end of puberty (16-18 years) compared with 10-12 years, with increases of 78% in the lumbar spine, 47% in the proximal femur, and 38% in the whole body.     

The Law of Mass Communications

David G. Clark and Earl R. Hutchinson, Mass Media and the Law: Freedom and Restraint (Wiley-Interscionco, $12.95)

John M. Kittross and Konnoth Harwood, Free & Fair: Courtroom Access and the Fairness Doctrino (Journal of Broadcasting, Temple University, $3.95)

Paul W. MacAvoy's The Crisis of the Regulatory Commissions: An Introduction to a Current Issue of Public Policy (Norton, $5.95; paper, $2.95)

Eric Moon, Book Selection and Consorship in the Sixties (Hawker, $10.95)

Edward De Grazia's Censorship Landmarks (Hawker, $19.75)     

Do Individual Perceptions Matter in Pornography Effects? How Perceived General Acceptance and Influence of Pornography May Impact Agreement With Sex-Role Attitudes

Pornography use is often associated with less-progressive sex-role attitudes, such as endorsement of a sexual double standard between heterosexual partners, but the process by which this relationship occurs is still largely unexamined. The present study was conducted to examine how perceptions about pornography may play a role in the relationship between pornography use and sex-role attitudes. Perceived general acceptance and perceived influence of pornography on most people partially mediated the relationship between pornography use and sex-role attitudes. The more participants reported using pornography, the more they believed pornography was generally accepted and had a positive influence; however, conversely to what was hypothesized, the more positive they perceived pornography’s influence, the less likely they were to report sex-role attitudes that endorse a sexual double standard.     

Brains–Computers–Machines: Neural Engineering in Science Classrooms

Neural engineering is an emerging field of high relevance to students, teachers, and the general public. This Feature presents online resources that educators and scientists can use to introduce students to neural engineering and to integrate core ideas from the life sciences, physical sciences, social sciences, computer science, and engineering into the classroom.     

90后中学生学习动机发展现状的研究

采用周步成教授编制的《中学生学习动机诊断问卷》对来自上海北桥中学、安徽贵池中学、渤海大学附属中学等7所学校的1 200名90后中学生的学习动机现状进行了探索研究。研究结果发现,不同年级的90后中学生在运动方面、动机总分、焦虑总分、以及自我期待这几个维度上存在显著差异。