Heisenberg and ferromagnetism

Heisenberg’s contributions to the understanding of ferromagnetism are reviewed. The special features of ferromagnetism, vis-a-vis dia and para magnetism, are introduced and the necessity of a Weiss molecular field is explained. It is shown how Heisenberg identified the quantum mechanical exchange interaction, which first appeared in the context of chemical bonding, to be the essential agency, contributing to the co-operative ordering process in ferromagnetism.     

Influence of a stressing constraint on stiffness and damping functions of a ski simulator's platform motion

The aim of this study was to assess the effect of stress on a previously acquired motor coordination. Following a longitudinal learning experiment, four participants performed oscillations on a ski simulator, either in normal or stressful conditions. The results showed that the amplitude of the oscillations decreased under stress, but no significant effect was seen regarding coordination, suggesting the strong resistance to stress of overlearned behaviour. Nevertheless, for one participant, a transient regression towards a former stage of learning was observed. This result was consistent with the regression hypothesis formulated by Fuchs (1962).     

Physical activity and executive control: implications for increased cognitive health during older adulthood

Electrocortical and behavioral responses of low, moderate, and high physically active older adults were compared with a younger control group on neutral and incompatible conditions of a flankers task. Compared to younger adults, high and moderate active older adults exhibited increased event-related potentials component P3 amplitude for the incompatible condition at the frontal electrode site. For the neutral condition, only low active older adults exhibited decreased amplitude at the central-parietal site, compared to younger adults. P3 latency revealed the longest latencies for low active older adults, followed by moderate active, high active, and younger adults, respectively. Reaction time (RT) data revealed that younger adults exhibited faster RT compared to all three older groups. Results suggest that physical activity may improve executive control function in older adults by affecting the distribution of P3 amplitude, which has been related to memory and attentional processes, and by decreasing P3 latency, which relates to the speed of cognitive processing.     

Evaluation of evidence-based medicine search skills in the clinical years

The librarians of the Health Sciences Library worked with the director of the Primary Care Clerkship to reinforce the principles of Evidence-Based Medicine (EBM) searching, taught during the first two years of medical school, through an intensive workshop. The purpose of the program was to ensure that students apply EBM principles in a timely and effective manner in clinical situations. Working in teams led by a resident and librarian, students researched real cases and then evaluated the effectiveness of their approach to the problems. This paper outlines the rationale for the team approach, reviews the administration of a computer-based workshop, and discusses the evaluation process. Evaluation focused on both the current workshop and its implications for the informatics program presented to students during years one and two.     

道德规范与国书馆事业

美国图书馆协会的<职业道德规范声明>提出了以图书馆事业为中心的具体原则,其<图书馆权利法案>则明确了图书馆的责任和义务.目前,美国社会和政治环境的变化为图书馆职业带来了越来越多的忧虑和压力."9·11"后出台的<爱国者法案>明显与图书馆职业道德规范中所阐述的重要原则相冲突.因此,美国图书馆协会决心抵制<爱国者法案>对知识、信息自由开放以及行使个人隐私权的限制.     

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.     

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.     

Optimizing segmental movement in the jumping header in soccer

This study looks at segmental movements in the jumping header from an optimization viewpoint. Investigations on the header so far have focused on head restriction in the movement but have not clarified how and to what extent body segments influence the performance of the skill. In the present study a biomechanical model was used to analyze the jumping header in simulated competition to give a clear picture of an optimized header. Skilled soccer players headed balls at speeds of 13 m x s(-1) the results indicated that the head moves as a free non-restricted segment in the jumping header and should be allowed to do so, even though much soccer literature says otherwise to prevent injuries. The arm movement showed individual characteristics and gave no general advantages in optimizing ball speed after impact in the header The movement of the legs was, on the other hand, the single most important factor in the skill. Therefore, coaches and players shouldfocus on developing muscle strength in the stomach, back and pelvis and should put no restrictions on head and arm movement to optimize the jumping header.