RIM: A Random Item Mixture Model to Detect Differential Item Functioning

In this paper we present a new methodology for detecting differential item functioning (DIF). We introduce a DIF model, called the random item mixture (RIM), that is based on a Rasch model with random item difficulties (besides the common random person abilities). In addition, a mixture model is assumed for the item difficulties such that the items may belong to one of two classes: a DIF or a non-DIF class. The crucial difference between the DIF class and the non-DIF class is that the item difficulties in the DIF class may differ according to the observed person groups while they are equal across the person groups for the items from the non-DIF class. Statistical inference for the RIM is carried out in a Bayesian framework. The performance of the RIM is evaluated using a simulation study in which it is compared with traditional procedures, like the likelihood ratio test, the Mantel-Haenszel procedure and the standardized p -DIF procedure. In this comparison, the RIM performs better than the other methods. Finally, the usefulness of the model is also demonstrated on a real life data set.     

Patterns of journal publications by staff of the College of Medicine, University of Ibadan, Nigeria, 1961-1980

This study analyzes publishing patterns of the staff of the University of Ibadan College of Medicine, Nigeria, based on a bibliography prepared by the authors. Data-gathering for the bibliography is described. An analysis is made of journals staff published in for the period 1961-1980, focusing on changes in journal order rank, publishing locations, and subject spread. A ranked list of the leading journals for the period 1976-1980 is given, showing the importance of local publishing and pointing to the need for local indexing.     

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.     

关于广东省普通高校体育专业招生考试足球项目考试内容、方法及评分标准的研究

采用调查访问、实验法对广东省普通高校体育专业招生考试足球项目考试内容、方法及评分标准进行研究,通过研究．足球非专项考试难度偏低的问题、足球专项考试方法中颠球、绕杆射门项目考试难度偏低以及踢准项目偏难等问题得到解决,从而确立了广东省新的足球专项、非专项考试的各项内容、方法及评分标准,为广东省考试中心组织实施2005年广东省普通高校体育专业招生考试提供了具有实效性和科学性的保证。     

Quality of grey literature in the open access era: Privilege and responsibility

Conclusions We are living a deep change in the information transfer process involving the different actors of the editorial scene (from authors to editors, web-editors, e-publishers and readers), who occasionally play different roles at the same time (e.g., authors sometimes bypass the editor thus assuming direct responsibilities in the diffusion of documents in the Internet). Furthermore, information producers, managers or seekers often show twofold personalities like Dr. Jekyll and Mr. Hyde. They would like to find all documents free on the Internet and be able to read original, reliable, and high quality information, but they are sometimes reluctant to spread their papers through online nonofficial channels as they care for the impact factor, prestige, and career advancement. It is a revolutionary period in which new and alternative forms of scholarly communication live together with more traditional ones and the future is difficult to define. Recent initiatives of open access—such as Pubmed Central, Public Library of Science, Budapest Open Access Initiative—are contributing to define new trends in the editorial market, challenging the traditional distribution channels, mainly managed by commercial editors, and placing the authors’ role and publication copyrights under severe discussion. In this landscape, GL now has new dignity and becomes closer and closer to innovative scientific publications supported by researchers in view of a generalised movement towards open access. The nuances of grey are becoming lighter and lighter. The questions are many, the answers few, but, in any case, the ethical responsibility of producing and issuing quality documents can never be disregarded.     

Estimation of thigh muscle and adipose tissue volume using magnetic resonance imaging and anthropometry

Thigh muscle volume is a useful determinant of functional fitness. However, anthropometric prediction of muscle content is influenced by the variability of adipose tissue accumulation. The aims of this study were to predict thigh muscle and adipose tissue volumes from anthropometry and to assess the validity of the method by examining the various components of the measurements and the assumptions involved. The 19 participants (9 men, 10 women; age 23-49 years) varied in adiposity. They all underwent magnetic resonance imaging (MRI) of the upper leg and the eight men and two women with the lowest adiposity underwent detailed anthropometry involving girths and skinfolds. Using MRI as the reference method, muscle volume was predictedfrom anthropometry using a circular concentric model, and the assumptions inherent in the method were tested further using the MRI data alone. Muscle volume was best predicted by anthropometry in the 10 leanest participants using a five-slice truncated cone model that overestimated the mean MRI value by 30% (R2 = 0.95; standard error of estimate = 288 cm3; P < 0.001). A single skinfold plus girth measurement at the mid-thigh almost matched its predictive ability, but with an increased bias. Measurements of leg circumference by means of the two techniques agreed well. The assumption of a circular cross-section was valid. In contrast, the agreement between skinfold thickness measured by caliper and superficial adipose tissue thickness by MRI was poor, contributing to the scatter of fat and lean area comparisons. An anterior skinfold thickness measurement underestimated the area of superficial adipose tissue at that level, particularly at the most proximal and distal sites. Although these limitations increase the uncertainties of muscle volume determination by anthropometry, they do not prevent its valid prediction in leaner individuals. The prediction of superficial adipose tissue was poorer.     

PubMed, Internet Grateful Med, and Ovid: a comparison of three MEDLINE Internet interfaces

Three MEDLINE Internet interfaces are compared: PubMed, Internet Grateful Med, and Ovid MEDLINE. Although these interfaces all search MEDLINE, significant differences exist in terms of their search interfaces, presentation of results, and special features. This paper examines these variations and explores some of the advantages and disadvantages of the three interfaces.     

Secondary-school students' motivation for portfolio reflection

Several studies concluded that deep reflection is infrequently reached in student portfolios. An explanation for these disappointing conclusions might be that motivation for portfolio reflection determines the quality of reflection. This study aimed to examine the relationship between motivation for using digital portfolios and reflection. Participants were 156 eleventh-grade students in secondary education, whose motivation for composing a digital portfolio was measured by the motivation part of the Motivated Strategies for Learning Questionnaire. Portfolios of 37 of the 156 students were examined in terms of the amount and nature of reflection by means of a coding scheme based on Mezirow's model of transformative learning. On average, one-fifth (19.5%) of the paragraphs in a portfolio contained reflection, and paragraphs with deep reflection were hardly found (0.8%). It was concluded that motivation for composing a portfolio was fair, but not related to the amount and nature of reflection. This exploratory study gives rise to further research into factors that might influence the quality of portfolio reflection.