Scaling Up the TREC Collection

Due to the popularity of Web search engines, a large proportion of real text retrieval queries are now processed over collections measured in tens or hundreds of gigabytes. A new Very Large test Collection (VLC) has been created to support qualification, measurement and comparison of systems operating at this level and to permit the study of the properties of very large collections. The VLC is an extension of the well-known TREC collection and has been distributed under the same conditions. A simple set of efficiency and effectiveness measures have been defined to encourage comparability of reporting. The 20 gigabyte first-edition of the VLC and a representative 10% sample have been used in a special interest track of the 1997 Text Retrieval Conference (TREC-6). The unaffordable cost of obtaining complete relevance assessments over collections of this scale is avoided by concentrating on early precision and relying on the core TREC collection to support detailed effectiveness studies. Results obtained by TREC-6 VLC track participants are presented here. All groups observed a significant increase in early precision as collection size increased. Explanatory hypotheses are advanced for future empirical testing. A 100 gigabyte second edition VLC (VLC2) has recently been compiled and distributed for use in TREC-7 in 1998.     

Association between socio-economic status and physical activity is mediated by social support in Brazilian students

This study evaluated whether the relationship between socioeconomic status (SES) and moderate-to-vigorous physical activity (MVPA) is mediated by social support of peers and parents. A cross-sectional study included students (n = 1182) aged 11 to 18 years who were recruited in 2014 from public schools in Fortaleza, Brazil. Participants completed a questionnaire to assess all variables. Mediation analyses were performed to determine the role of parental support and peer support on the relationship between SES and MVPA. Also, moderated-mediation analyses with estimating of conditional indirect effects were performed in order to identify whether gender is a moderator of the mediating effect. A positive and significant association between SES and MVPA was found among Brazilian students, and social support of parents and peers were significant mediators of this relationship. Conditional indirect effects showed that both parental and peer support had a significant indirect effect among boys; only parental support had a significant indirect effect among girls. These results suggest that improving social support can help reduce the impact of SES on physical activity among Brazilian adolescents.     

Doing a science project: Gender differences during childhood

By adolescence, men's participation and achievement in science exceeds women's. This article reports a case study that examined the beginnings of this gender differentiation during a naturally occurring academic activity that was designed to support and guide young children's interest in doing science. Data were collected during 2 successive years of a science fair for children in Grades 1–6 of a progressive private school. A total of 268 projects were characterized in terms of achievement and area of science. Parents provided information about the way children selected and created projects. In both years and in all grade levels, boys tended to choose to work in the physical sciences, and girls in the biological and social sciences. Peer collaborations were exclusively same sex. Achievement and parental involvement were not gender related. Factors are discussed that might lead to an early divergence of boys' and girls' interests in science within a context that promotes its exploration. © 1998 John Wiley & Sons, Inc. J Res Sci Teach 35: 845–857, 1998.