Magnetophoretic manipulation in microsystem using carbonyl iron-polydimethylsiloxane microstructures

This paper reports the use of a recent composite material, noted hereafter i-PDMS, made of carbonyl iron microparticles mixed in a PolyDiMethylSiloxane (PDMS) matrix, for magnetophoretic functions such as capture and separation of magnetic species. We demonstrated that this composite which combine the advantages of both components, can locally generate high gradients of magnetic field when placed between two permanent magnets. After evaluating the magnetic susceptibility of the material as a function of the doping ratio, we investigated the molding resolution offered by i-PDMS to obtain microstructures of various sizes and shapes. Then, we implemented 500 μm i-PDMS microstructures in a microfluidic channel and studied the influence of flow rate on the deviation and trapping of superparamagnetic beads flowing at the neighborhood of the composite material. We characterized the attraction of the magnetic composite by measuring the distance from the i-PDMS microstructure, at which the beads are either deviated or captured. Finally, we demonstrated the interest of i-PDMS to perform magnetophoretic functions in microsystems for biological applications by performing capture of magnetically labeled cells.     

Referees' use of heuristics: The moderating impact of standard of competition

Abstract

The influence of players' standard of competition on referees' decision making was investigated. Standard of competition was examined by studying 30 handball matches, 15 at League and 15 at National standard. At both standards, we examined two types of refereeing decision (sporting and disciplinary) after transgressions that varied in ambiguity. The results indicated that referees made more lenient decisions at higher standards of competition, but this tendency depended on the type of decision being made and ambiguity in the offence. The hypothesis that referees use standard of competition as a judgemental heuristic, but in varying ways, was supported.     

Leg mass characteristics of accurate and inaccurate kickers – an Australian football perspective

Abstract

Athletic profiling provides valuable information to sport scientists, assisting in the optimal design of strength and conditioning programmes. Understanding the influence these physical characteristics may have on the generation of kicking accuracy is advantageous. The aim of this study was to profile and compare the lower limb mass characteristics of accurate and inaccurate Australian footballers. Thirty-one players were recruited from the Western Australian Football League to perform ten drop punt kicks over 20 metres to a player target. Players were separated into accurate (n = 15) and inaccurate (n = 16) groups, with leg mass characteristics assessed using whole body dual energy x-ray absorptiometry (DXA) scans. Accurate kickers demonstrated significantly greater relative lean mass (P ≤ 0.004) and significantly lower relative fat mass (P ≤ 0.024) across all segments of the kicking and support limbs, while also exhibiting significantly higher intra-limb lean-to-fat mass ratios for all segments across both limbs (P ≤ 0.009). Inaccurate kickers also produced significantly larger asymmetries between limbs than accurate kickers (P ≤ 0.028), showing considerably lower lean mass in their support leg. These results illustrate a difference in leg mass characteristics between accurate and inaccurate kickers, highlighting the potential influence these may have on technical proficiency of the drop punt.     

Do weight categories prevent athletes from relative age effect?

Abstract

The aim of this study was to investigate whether weight categories prevent young athletes from being exposed to a relative age effect. The dates of birth of all French female (n = 727) and male (n = 5440) amateur boxers who participated in the 2010–2011 season were collected from the federation database. The dates of birth of all French male professional boxers (n = 354) were also collected. The results show an absence of a relative age effect among French female and male amateur boxers. The results also show an absence of this phenomenon among French male professional boxers. The male 18–18+ age category reveal an inverse relative age effect. This inverse relative age effect might be interpreted as the result of a strategic adaptation from relatively younger children who shift from one sport to another where there are weight categories in order to ensure fair competition. The results of this study suggest that the weight category system is a possible solution within the relative age effect phenomenon.     

A winner’s curse in the bidding process for broadcasting rights in football? The cases of the French and UK markets

The winner’s curse is a well-known phenomenon in the auction theory. The main aim of this article is to verify its existence in football broadcasting rights. The underlying objective is to assess whether some indices of this situation are verified and can cause a winner’s curse. The methodology is based on the application of Andreff (2014 Andreff, Wladimir. 2014. “The Winner’s Curse in Sports Economics.” Contemporary Research in Sports Economics 14: 177–205. [Google Scholar])’s six indices and a seventh index (disappointment) to the domestic markets for broadcasting rights of the French and English football leagues. These two markets have seen an increase in the number of packages offered to broadcasters, with the possibility of several ‘winners’. The article shows that the winner of the major packages in the auction is not cursed. The curse is more likely to happen for the second mover. As such, the article suggests a practical recommendation for broadcasters interested in football rights: win the best package or keep away.     

How does the tennis serve technique influence the serve-and-volley?

In tennis, a high ball velocity and a fast run toward the net are key features to successful performance of "serve-and-volley" players. For the serve, tennis players can use two techniques: the foot-up (FU) or foot-back (FB) technique. The aim of this study was to determine if the running time toward the net after the serve and the ball velocity (V(ball)) vary between these two techniques. Moreover we analysed the angular momentum values of the trunk and of the arm holding the racquet. Fifteen expert tennis players performed six successful serve-and-volleys with both techniques. Running time to the net is significantly lower for FB, whereas V(ball) is significantly higher for FU. Trunk and arm angular momentums about the transverse axis are significantly higher with FU before ball impact. A significant correlation (r = 0.81, P < 0.001) exists between changes in the maximal trunk angular momentum and in running time to the net between the two serve techniques. A significant correlation (r = 0.84, P < 0.001) also exists between changes in the maximal trunk angular momentum and in V(ball) between the two serve techniques. According to these results, FB is the best technique for moving as quickly as possible to the net because of a lower trunk angular momentum.