议程设置理论与后大众媒体时代的民意研究

关于媒体与民意的理论大部分提出于 1 93 0到 1 980年之间 ,这是一个仅仅拥有传统信息选择方式的时代。麦库姆斯和肖 (1 972 )最初提出议程设置理论时 ,用北卡罗莱纳州的教堂山 (ChapelHill)社区作为研究对象 ,而现在那里的媒介使用情况也已经发生了巨变。当我们迎来议程设置理论提出 3 0周年的时候 ,教堂山的受众现在面临的信息选择令人惊叹。在 2 0世纪 90年代 ,肖提出 ,美国的大众媒介已经经历了“兴和衰”(riseandfall)。肖认为 ,大众媒体时代结束于 2 0世纪 80年代。议程设置研究是否能像之前的 3 0年那样 ,继续开展下去 ?当受众使用着上百个信息来源时 ,议程设置和民意研究会产生何种变化 ?这是本文将要回答的问题     

PubMed enhancements: fulfilling the promise of a great product

There have been many recent changes to PubMed to enhance its usefulness. Those changes include: LinkOut Libraries (local holding field), PubMed Central (full-text articles archived by the National Library of Medicine), and LinkOut (access to full-text articles right from the PubMed citation). Medical librarians should be aware of how these features work to best assist their clients. These new features offer the possibility of true desktop access for library patrons. Not only will patrons appreciate these new features, but their use in libraries will literally change what we do, who does it, and how it is done.     

How much effort is needed to keep up with the literature relevant for primary care?

OBJECTIVES: Medicine must keep current with the research literature, and keeping current requires continuously updating the clinical knowledge base (i.e., references that provide answers to clinical questions). The authors estimated the volume of medical literature potentially relevant to primary care published in a month and the time required for physicians trained in medical epidemiology to evaluate it for updating a clinical knowledge base. METHODS: We included journals listed in five primary care journal review services (ACP Journal Club, DynaMed, Evidence-Based Practice, Journal Watch, and QuickScan Reviews). Finding little overlap, we added the 2001 "Brandon/Hill Selected List of Print Books and Journals for the Small Medical Library." We counted articles (including letters, editorials, and other commentaries) published in March 2002, using bibliographic software where possible and hand counting when necessary. For journals not published in March 2002, we reviewed the nearest issue. Five primary care physicians independently evaluated fifty randomly selected articles and timed the process. RESULTS: The combined list contained 341 currently active journals with 8,265 articles. Adjusting for publication frequency, we estimate 7,287 articles are published monthly in this set of journals. Physicians trained in epidemiology would take an estimated 627.5 hours per month to evaluate these articles. CONCLUSIONS: To provide practicing clinicians with the best current evidence, more comprehensive and systematic literature surveillance efforts are needed.     

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.