Timescales for exploratory tactical behaviour in football small-sided games

The aim of this study was to identify the dynamics of tactical behaviour emerging on different timescales in football small-sided games and to quantify short- and long-term exploratory behaviour according to the number of opponents. Two teams of four professional male footballers played small-sided games against two different teams with a variable number of opponents (3, 5 and 7). Data were collected using a combination of systematic observation and a non-differential global positioning system (15 Hz). The temporal diversity and structural flexibility of the players were determined by calculating the dynamic overlap order parameter q, entropy and trapping strength. Analysis of the exploratory dynamics revealed two different timescales, forming a different metastable landscape of action for each constraint. Fast dynamics lasted on average a few seconds and consisted of changes in tactical patterns. The long timescale corresponded to the shared tasks of offence and defence lasting tens of seconds. The players’ tactical diversity decreased with an increasing number of opponents, especially in defence. Manipulating numerical imbalance is likely to promote changes in the diversity, unpredictability and flexibility of tactical solutions. The fact that the temporally nested structure of constraints shaped the emergence of tactical behaviour provides a new rationale for practice task design. The manipulation of numerical imbalance on the timescale of a few tens of seconds, on which the exploratory behaviour of players saturates, may help coaches to optimise the exploratory efficiency of the small-sided games.     

Group identification in early adolescence: its relation with peer adjustment and its moderator effect on peer influence

This study was conducted to test whether group identification (importance of the group to the individual) covaried with individual-group similarity on problem behavior; and whether group identification moderated peer group influence on the individual's development of delinquent behavior across a 1-year period. The level of reciprocated nominations within the individual's self-nominated group was controlled for in all analyses. Participants were 190 sixth and seventh graders (during the first year of the study) from the north of Italy. Level of reciprocated nominations within the group, but not identification, was found to covary with individual-group behavioral similarity (group behavior interacted with reciprocity of group nominations in predicting individual behavior). Group identification, but not reciprocated nominations, was found to moderate peer group influence on the individual's change in delinquent behavior, across 1 year. The individual's peer status within the classroom, level of reciprocated nominations, and gender all were related to the individual's level of group identification. Results are discussed in terms of understanding peer group influence on the individual.     

Knee joint position sense of roller hockey players: a comparative study

This study aimed to compare knee joint position sense of roller hockey players with an age-matched group of non-athletes. Forty-three male participants voluntarily participated in this cross-sectional study: 21 roller hockey players (mean age: 23.2 ± 4.2 years old, mean weight: 81.8 ± 9.8 kg, mean height: 180.5 ± 4.1 cm) and 22 age-matched non-athletes (mean age: 23.7 ± 3.9 years old, mean weight: 85.0 ± 6.2 kg, mean height: 181.5 ± 5.0 cm). Knee joint position sense of the dominant limb was evaluated using a technique of open-kinetic chain and active knee positioning. Joint position sense was reported using absolute, relative and variable angular errors. The main results indicated that the group of roller hockey players showed significantly lower absolute (2.4 ± 1.2º vs. 6.5 ± 3.2º, p ≤ 0.001) and relative (1.7 ± 2.1º vs. 5.8 ± 4.4º, p ≤ 0.001) angular errors in comparison with the non-athletes group. In conclusion, the results from this present study suggest that proprioceptive acuity, assessed by measuring joint position sense, is increased in roller hockey players. The enhanced proprioception of the roller hockey players could contribute to injury prevention and improved performance during sporting activities.     

Automatic evaluation of digital libraries with 5SQual

Digital libraries (DLs) are complex information systems which can present changes in their structure, content, and services. These complexities and dynamics make system maintenance a non-trivial task, since it requires periodical evaluation of the different DL components. Generally, these evaluations are customized per system and are performed only when problems occur and administrator intervention is required. This work aims to change the situation. We present 5SQual, a tool which provides ways to perform automatic and configurable evaluations of some of the most important DL components, among them, digital objects, metadata, and services. The tool implements diverse numeric indicators that are associated with eight quality dimensions described in the 5S quality model. Its generic architecture was developed to be applicable to various DLs and scenarios. In sum, the main contributions of this work include: (i) the design and implementation of 5SQual, a tool that validates a theoretical DL quality model; (ii) the demonstration of the applicability of the tool in several usage scenarios; and (iii) the evaluation (with usability specialists) of its graphical interface specially designed to guide the configuration of 5SQual evaluations. We also present the results of interviews conducted with administrators of real DLs regarding their expectations and opinions about 5SQual.     

Ecological dynamics of continuous and categorical decision-making: The regatta start in sailing

Abstract

Ecological dynamics of decision-making in the sport of sailing exemplifies emergent, conditionally coupled, co-adaptive behaviours. In this study, observation of the coupling dynamics of paired boats during competitive sailing showed that decision-making can be modelled as a self-sustained, co-adapting system of informationally coupled oscillators (boats). Bytracing the spatial–temporal displacements of the boats, time series analyses (autocorrelations, periodograms and running correlations) revealed that trajectories of match racing boats are coupled more than 88% of the time during a pre-start race, via continuous, competing co-adaptions between boats. Results showed that both the continuously selected trajectories of the sailors (12 years of age) and their categorical starting point locations were examples of emergent decisions. In this dynamical conception of decision-making behaviours, strategic positioning (categorical) and continuous displacement of a boat over the course in match-race sailing emerged as a function of interacting task, personal and environmental constraints. Results suggest how key interacting constraints could be manipulated in practice to enhance sailors' perceptual attunement to them in competition.     

The Expulsion of the Muslims from Portugal (1496–1497)

The expulsion of the Muslim minority from Portugal, decreed by King Manuel I in December 1496, has been one of the most overlooked aspects of the end of religious tolerance in the Iberian Peninsula at the close of the Middle Ages. Using unedited documentary sources preserved in the national Portuguese archives, this article focuses on the expulsion of the Muslims from Portugal and seeks to challenge a number of assumptions concerning this unprecedented event. Three major questions concerning this expulsion are examined. What evidence is there that the expulsion of the Muslims did take place? Where did the expelled Muslims seek refuge? What were the causes of this expulsion? This article will endeavour to present a new hypothesis relating to the causes of this expulsion, which radically differs from that advanced by modern historians.