THE INFLUENCE OF ARTIFICIAL TURF WITH DIFFERING MECHANICAL PROPERTIES ON TURNING MOVEMENTS

Various mechanical tests are made to ensure artificial surfaces fulfil the regulations of the sports governing bodies. There is little available research regarding differences in player response between surfaces with different mechanical properties or similar surfaces under different environmental conditions. The aim of this study was to gain insight into the player response in a game-sports specific movement on an artificial turf with under different conditions (temperature and mechanical properties). Five footballers completed three shuttle sprints on two artificial turfs. Trial times were recorded (timing gates) and ankle kinematics were measured (CODA motion analysis). Players were significantly faster on the higher temperature, softer surface with higher rotational resistance. No differences were found in contact times and joint kinematics. These findings highlight the differences between surfaces

IDENTIFICATION OF TOUCHDOWN AND TOE-OFF IN TURF-SPORT SPECIFIC MOVEMENTS USING KINEMATIC DATA

The accurate determination of touchdown and toe-off during the stance phase in human locomotion is important for further motion analysis. The aim of this study was to evaluate the accuracy of using kinematic data to detect these events and therefore ground contact time of movements on artificial turf. Seven athletes performed five different turf-sport specific movements in which a single contact was made on a force plate (1000 Hz), while kinematic data of six markers were recorded (CODA, 400 Hz). A force threshold (20N) was set to determine the events of the touchdown and toe-off for the kinetic data. Comparison was made between the kinetic and kinematic derived event times. The errors between the kinetic and kinematic data ranged from 1.6 to 3.4% for the acceleration, hurdle hop and a turn with change of direction of 135°. It was concluded that kinematic data can accurately determine touchdown and toe-off events for certain movements on artificial turf

Solving the Synthetic Riddle of Colloidal Two-Dimensional PbTe Nanoplatelets with Tunable Near-Infrared Emission

Near-infrared emitting colloidal two-dimensional (2D) PbX (X = S, Se) nanoplatelets (NPLs) have emerged as interesting materials with strong size quantization in the thickness dimension. They act as model systems for efficient charge carrier multiplication and hold potential as intriguing candidates for fiber-based photonic quantum applications. However, synthetic access to the third family member, 2D PbTe, remains elusive due to challenging precursor chemistry. Here, we report a direct synthesis for 2D PbTe NPLs with tunable photoluminescence [PL, 910–1460 nm (1.36–0.85 eV), PL quantum yields 1–15%], based on aminophosphine precursor chemistry. Ex situ transamination of tris(dimethylamino)phosphine telluride with octylamine is confirmed by 31P nuclear magnetic resonance and yields a reactive tellurium precursor for the formation of 2D PbTe NPLs at temperatures as low as 0 °C. The PL position of the PbTe NPLs is tunable by controlling the Pb/Te ratio in the reaction. Grazing-incidence wide-angle X-ray scattering confirms the 2D geometry of the NPLs and the formation of superlattices. The importance of a postsynthetic passivation of PbTe NPLs by PbI2 to ensure colloidal stability of the otherwise oxygen-sensitive samples is supported by X-ray photoelectron spectroscopy. Our results expand and complete the row of lead chalcogenide-based 2D NPLs, opening up new ways for further pushing the optical properties of 2D NPLs into the infrared and toward technologically relevant wavelengths