Binary Pathfinder: An improvement to the Pathfinder algorithm

The Pathfinder algorithm is widely used to prune social networks. The pruning maintains the geodesic distances between nodes. It has shown itself to be very useful in the analysis of, amongst others, citations in BIS (bibliometrics, informetrics, and scientometrics). It has even been proposed for the online display of the search results in an information retrieval system. However, its great time and space complexity limits its use in real-time applications and in networks of any considerable size.The present work describes an improved algorithm with considerably reduced time and space complexity. Its lower execution costs thus increase its applicability both in real time and to large networks.     

A single-display groupware collaborative language laboratory

Language learning tools have evolved to take into consideration new teaching models of collaboration and communication. While second language acquisition tasks have been taken online, the traditional language laboratory has remained unchanged. By continuing to follow its original configuration based on individual work, the language laboratory fails to take advantage of the potential provided by collaborative learning. We propose the use of a language laboratory based on single-display groupware (SDG) for learning vocabulary, grammar, pronunciation, and listening comprehension. By adopting SDG, the language laboratory benefits from the advantages of small group collaborative learning. In this paper, we first describe the design and pedagogical merit of the SDG collaborative language laboratory. We then share the results of a quasi-experimental pre–post comparison study, and use an observation guideline to analyze whether the conditions for collaborative learning have been fulfilled. Based on the results of this study, we conclude that developing pronunciation skills can be more effective when using a collaborative language laboratory versus an individual language laboratory. In addition to this, it can also be concluded that collaborative learning is most effective when accompanied by adequate instructional design.     

Using growth models to monitor school performance: comparing the effect of the metric and the assessment

This paper investigates whether inferences about school performance based on longitudinal models are consistent when different assessments and metrics are used as the basis for analysis. Using norm-referenced (NRT) and standards-based (SBT) assessment results from panel data of a large heterogeneous school district, we examine inferences based on vertically equated scale scores, normal curve equivalents (NCEs), and nonvertically equated scale scores. The results indicate that the effect of the metric depends upon the evaluation objective. NCEs significantly underestimate absolute individual growth, but NCEs and scale scores yield highly correlated (r >.90) school-level results based on mean initial status and growth estimates. SBT and NRT results are highly correlated for status but only moderately correlated for growth. We also find that as few as 30 students per school provide consistent results and that mobility tends to affect inferences based on status but not growth – irrespective of the assessment or metric used.     

Validity of a portable force platform for assessing biomechanical parameters in three different tasks

The aim of this study was to determine the precision and accuracy of the vertical and anterior–posterior force components of the portable PASCO PS-2142 force plate. Impulse, peak force, and time to peak force were assessed and compared to a gold standard force plate in three different tasks: vertical jump, forward jump, and sprint start. Two healthy male participants performed ten trials for each task, resulting in 60 trials. Data analyses revealed good precision and accuracy for the vertical component of the portable force plate, with relative bias and root mean square (RMS) error values nearly the same in all tasks for the impulse, time to peak force, and peak force parameters. Precision and accuracy of the anterior–posterior component were lower for the impulse and time to peak force, with relative bias and RMS error values nearly the same between tasks. Despite the lower precision and accuracy of the anterior–posterior component of the portable force plate, these errors were systematic, reflecting a good repeatability of the measure. In addition, all variables presented good agreement between the portable and gold standard platforms. Our results provide a good perspective for using the aforementioned portable force plate in sports and clinical biomechanics.     

Overeducation in developing economies: How can we test for it, and what does it mean?

A worker is said to be overeducated if he/she has acquired more education than is required to perform his/her job. In the absence of data measuring the number of years of schooling required to perform particular jobs, we propose a new approach to testing for overeducation. Overeducation is confirmed if we observe that education levels rose in jobs that offer very low returns to education and that underwent little technological change. Using labor force surveys from four developing countries, we find evidence of overeducation in unskilled jobs in the Philippines, mild evidence in Mexico, and little evidence in India and Thailand. We show that a job's mean and modal years of schooling are poor proxies for required education. We also show that overeducation sometimes increases within unskilled jobs, even while a growing share of educated workers enter skilled jobs. This may be because the quality of education segments the labor market.     

Pre-game hydration status, sweat loss, and fluid intake in elite Brazilian young male soccer players during competition

In this study, we assessed the pre-game hydration status and fluid balance of elite young soccer players competing in a match played in the heat (temperature 31.0 ± 2.0 ° C, relative humidity 48.0 ± 5.0%) for an official Brazilian soccer competition. Fluid intake was measured during the match, as were urine specific gravity and body mass before and after the game to estimate hydration status. Data were obtained from 15 male players (age 17.0 ± 0.6 years, height 1.78 ± 0.06 m, mass 65.3 ± 3.8 kg); however, data are only analysed for 10 players who completed the full game. The mean (± s) sweat loss of players amounted to 2.24 ± 0.63 L, and mean fluid intake was 1.12 ± 0.39 L. Pre-game urine specific gravity was 1.021 ± 0.004, ranging from 1.010 to 1.025. There was no significant correlation between sweat loss and fluid intake (r = 0.504, P = 0.137) or between urine specific gravity and fluid intake (r = -0.276, P = 0.440). We conclude that young, native tropical soccer players started the match hypohydrated and replaced about 50% of the sweat lost. Thus, effective strategies to improve fluid replacement are needed for players competing in the heat.