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Genetic disturbance is propagated by artificial reinforcement or reintroduction of organisms from populations whose genetic structure is sufficiently different from the original populations. Many cultivars were produced from wild plant species, and fears exist that genetic disturbance of wild populations occurred by the human migration of cultivars. In this study, we detected genetic disturbance in Pecteilis radiata [= Habenaria radiata] (Orchidaceae) in the Hyogo Prefecture of Japan using multiplexed inter-simple sequence repeat genotyping by sequencing (MIG-seq). Also, we estimated the risk of the spread of genetically disturbed individuals based on the results of spatial genetic structure and gene flow. In five out of 33 examined sites, we detected genetically disturbed individuals that possessed the same genetic cluster as cultivar samples. No spatial genetic structure was found among the sites within a 0.64 km radius, which indicated that pollen or seeds of P. radiata freely migrated among these populations. Consequently, we demonstrated that a risk exists of spreading genetic disturbances by gene flow within a radius of 0.64 km from the site where genetic disturbance was found. Raised public awareness of the risk of genetic disturbance would be necessary to prevent additional spread of genetic disturbances by human activities.

A traditional soccer ball is constructed using 32 pentagonal and hexagonal panels. In recent years, however, the likes of the Teamgeist and Jabulani balls, constructed from 14 and 8 panels, respectively, have entered the field, marking a significant departure from conventionality in terms of shape and design. Moreover, the recently introduced Brazuca ball features a new 6-panel design and has already been adopted by many soccer leagues. However, the shapes of the constituent panels of these balls differ substantially from those of conventional balls. Therefore, this study set out to investigate the flight and aerodynamic characteristics of different orientations of the soccer ball, which is constructed from panels of different shapes. A wind tunnel test showed substantial differences in the aerodynamic forces acting on the ball, depending on its orientation. Substantial differences were also observed in the aerodynamic forces acting on the ball in different directions, corresponding to its orientation and rotation. Moreover, two-dimensional particle image velocimetry (2D-PIV) measurements showed that the boundary separation varies depending on the orientation of the ball. Based on these results, we can conclude that the shape of the panels of a soccer ball substantially affects its flight trajectory.

When the boundary layer of a sports ball undergoes the transition from laminar to turbulent flow, a drag crisis occurs whereby the drag coefficient (C d) rapidly decreases. However, the aerodynamic properties and boundary-layer dynamics of a soccer ball are not yet well understood. In this study we showed that the critical Reynolds number (Re crit) of soccer balls ranged from 2.2 × 105 to 3.0 × 105. Wind-tunnel testing, along with visualisation of the dynamics of the boundary layer and the trailing vortex of a ball in flight, demonstrated that both non-spinning and spinning (curved) balls had lowC d values in the super-critical region. In addition, theRe crit values of the soccer balls were lower than those of smooth spheres, ranging from ∼ 3.5 × 105 to 4.0 × 105, due to the effects of their panels. This indicated that the aerodynamic properties of a soccer ball were intermediate between those of a smooth ball and a golf ball. In a flow visualisation experiment, the separation point retreated and theC d decreased in a super-critical regime compared with those in a sub-critical regime, suggesting a phenomenon similar to that observed in other sports balls. With some non-spinning and spinning soccer balls, the wake varied over time. In general, the high-frequency component of an eddy dissipated, while the low-frequency component increased as the downstream vortex increased. The causes of the large-scale fluctuations in the vortex observed in the present study were unclear; however, it is possible that a ‘knuckle-ball effect’ of the non-rotating ball played a role in this phenomenon.

The purpose of this study is to assess the fundamental characteristics which cause a football to spin in a curve ball kick. The ball impact process was analysed initially with a high speed video camera running at 4500 frames per second to obtain the basic data for a computer simulation model. This simulation model showed suitable agreement although it slightly deteriorated during the latter half of impact. It was noted that rotation of the ball occurs, even if the kinetic coefficient of friction is nearly equal to 0 because of local deformation of the ball during impact around the foot allowing forces to be transmitted to the ball around its axis. The spin of the ball was found to increase with the offset distance between the foot and the axis of the ball and as the kinetic coefficient of friction was increased. The offset distance between the foot and the axis of the ball affects the spin more than the coefficient of friction. Varying the coefficient of friction from 0.0 to 1.0 produces an increase in spin of 13 rad s )1 at most. It was suggested that the most suitable offset distance, which makes the largest ball rotation was around 100 mm. A trade-off was found between the ball speed and spin, for different offset distances.