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 spectral analysis of team dynamics and tactics in Brazilian football

Abstract

The purposes of this study were to characterise the total space covered and the distances between players within teams over ten Brazilian First Division Championship matches. Filmed recordings, combined with a tracking system, were used to obtain the trajectories of the players (n = 277), before and after half-time. The team surface area (the area of the convex hull formed by the positions of the players) and spread (the Frobenius norm of the distance-between-player matrix) were calculated as functions of time. A Fast Fourier Transform (FFT) was applied to each time series. The median frequency was then calculated. The results of the surface area time series median frequencies for the first half (0.63 ± 0.10 cycles · min^?1) were significantly greater (P < 0.01) than the second-half values (0.47 ± 0.14 cycles · min^?1). Similarly, the spread variable median frequencies for the first half (0.60 ± 0.14 cycles · min^?1) were significantly greater (P < 0.01) than the second-half values (0.46 ± 0.16 cycles · min^?1). The median frequencies allowed the characterisation of the time series oscillations that represent the speed at which players distribute and then compact their team formation during a match. This analysis can provide insights that allow coaches to better control the team organisation on the pitch.     

Reliability of NIRS portable device for measuring intercostal muscles oxygenation during exercise

ABSTRACT

This study assessed the intra-individual reliability of oxygen saturation in intercostal muscles (SmO₂-m.intercostales) during an incremental maximal treadmill exercise by using portable NIRS devices in a test-retest study. Fifteen marathon runners (age, 24.9 ± 2.0 years; body mass index, 21.6 ± 2.3 kg·m^?2; V?O₂-peak, 63.7 ± 5.9 mL·kg^?1·min^?1) were tested on two separate days, with a 7-day interval between the two measurements. Oxygen consumption (V?O₂) was assessed using the breath-by-breath method during the V?O₂-test, while SmO₂ was determined using a portable commercial device, based in the near-infrared spectroscopy (NIRS) principle. The minute ventilation (VE), respiratory rate (RR), and tidal volume (Vt) were also monitored during the cardiopulmonary exercise test. For the SmO₂-m.intercostales, the intraclass correlation coefficient (ICC) at rest, first (VT1) and second ventilatory (VT2) thresholds, and maximal stages were 0.90, 0.84, 0.92, and 0.93, respectively; the confidence intervals ranged from ?10.8% – +9.5% to ?15.3% – +12.5%. The reliability was good at low intensity (rest and VT1) and excellent at high intensity (VT2 and max). The Spearman correlation test revealed (p ≤ 0.001) an inverse association of SmO₂-m.intercostales with V?O₂ (ρ = ?0.64), VE (ρ = ?0.73), RR (ρ = ?0.70), and Vt (ρ = ?0.63). The relationship with the ventilatory variables showed that increased breathing effort during exercise could be registered adequately using a NIRS portable device.     

Clase social y situación dentro de la fratria: Interacción y efectos sobre el desarrollo del individuo

Resumen

En este estudio se analiza la influencia de la clase social, el número de hermanos y el orden de nacimiento sobre una serie de variables cognitivas y de rendimiento escolar.

Se ha realizado la investigación sobre una muestra de 507 alumnos de 1° de E.G.B., pertenecientes a los Centros Públicos de Valladolid y provincia. Las variables de rendimiento escolar se evaluaron a través de la opinión del profesor. La valoración, en cambio, de las cognitivas se realizó por medio de pruebas estandarizadas. Dentro de los efectos principales, y dejando aparte las diferencias marcadas por el medio social, obviamente esperadas, destacamos una fuerte influencia del orden de nacimiento sobre prácticamente todas las variables dependientes. Su interacción con la variable socio cultural es el resultado más destacable del presente trabajo. Dedujimos como hipótesis explicativa las diferentes pautas culturales que propician o no la estabilidad de los patrones educativos familiares.     

Teams’ innovation: getting there through knowledge sharing and absorptive capacity

This study addresses the contribution of knowledge sharing behaviour and absorptive capacity to innovation at team level. Although the hypotheses reflect the dominant literature, the study’s novelty lies in the data collected from several industries in Portugal, avoiding possible industry bias. Relationships are tested outside sectors where traditionally team effects are studied, for example healthcare. Data were collected from 141 employees working in organizational teams, excluding top management teams, which are often the object of research addressing phenomena leading to innovation. There is no evidence in support of organizational size effect, team’s geographic concentration effect or gender effect. However, team tenure duration is positively related to increased knowledge sharing, that is, recent teams do not share as much knowledge as older ones. Structural Equation Modelling was used to test the mediation effect of absorptive capacity between individual knowledge sharing behaviour and team innovation. Evidence in support of full mediation was found.     

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.