593 research outputs found
Influence of clay properties on shoe-kinematics and friction during tennis movements
Tennis is a sport characterised by being played on different surfaces: hard court, grass and clay. These surfaces influence the style of play and tennis specific movements. Specifically on clay, most of the common movements performed by players (e.g. accelerating, side stepping and braking), are performed with some level of controlled sliding. In order to reduce the player's injury risk, and assess the shoe-surface requirements on clay surfaces, there is a need for a scientific understanding of the player's kinematics and tribological mechanisms occurring at the shoe-surface interface. The purpose of this study was to identify the kinematics of the shoe during the sliding phase, and to assess the friction that is present. Baseline areas of both ends of a clay court were prepared with two different mixes of clay, varying the particle size. Eight experienced clay players participated in this study which took place during the Conde de GodĆ³ tennis tournament in Barcelona, Spain. 3D kinematic data data was collected using two synchronised high speed video cameras, and after the tests, perception questionnaires were applied to the players. Additionally, three different mechanical devices were utilised to measure the friction of the two clay surfaces. Displacement and velocity data of the shoe in contact with the surface were correlated with the friction measurements from both clay surfaces. Results indicated that significant differences occurred between the two clay surfaces for some shoe kinematic data, and mechanical friction. However, the perception scores suggest the opposite behaviour stated by the mechanical test and shoe-kinematic data. The present study has provided evidence that shoe kinematics and friction of the shoe-surface interaction are affected by the surface conditions, specifically particle size
Data to support study of The Structures and Spin States of Iron(II) Complexes of Isomeric 2,6-Di(1,2,3-triazolyl)pyridine Ligands
Different isomers of the title ligands coordinate to iron(II) in monodentate or tridentate fashion, leading to complexes with a variety of spin state properties
Extracellular vesicles may provide an alternative detoxification pathway during skeletal muscle myoblast ageing
Skeletal muscle (SM) acts as a secretory organ, capable of releasing myokines and extracellular vesicles (SMāEVs) that impact myogenesis and homeostasis. While ageārelated changes have been previously reported in murine SMāEVs, no study has comprehensively profiled SMāEV in human models. To this end, we provide the first comprehensive comparison of SMāEVs from young and old human primary skeletal muscle cells (HPMCs) to map changes associated with SM ageing. HPMCs, isolated from young (24 Ā± 1.7 years old) and older (69 Ā± 2.6 years old) participants, were immunomagnetically sorted based on the presence of the myogenic marker CD56 (NāCAM) and cultured as pure (100% CD56+) or mixed populations (MP: 90% CD56+). SMāEVs were isolated using an optimised protocol combining ultrafiltration and size exclusion chromatography (UF + SEC) and their biological content was extensively characterised using Raman spectroscopy (RS) and liquid chromatography mass spectrometry (LCāMS). Minimal variations in basic EV parameters (particle number, size, protein markers) were observed between young and old populations. However, biochemical fingerprinting by RS highlighted increased protein (amide I), lipid (phospholipids and phosphatidylcholine) and hypoxanthine signatures for older SMāEVs. Through LCāMS, we identified 84 shared proteins with functions principally related to cell homeostasis, muscle maintenance and transcriptional regulation. Significantly, SMāEVs from older participants were comparatively enriched in proteins involved in oxidative stress and DNA/RNA mutagenesis, such as E3 ubiquitināprotein ligase TTC3 (TTC3), little elongation complex subunit 1 (ICE1) and AcetylāCoA carboxylase 1 (ACACA). These data suggest SMāEVs could provide an alternative pathway for homeostasis and detoxification during SM ageing
Assessment of Biologically Effective Solar Ultraviolet Exposures for Court Staff and Competitors During a Major Australian Tennis Tournament
Sport is an integral and enduring part of many societies, such as Australia. Participation in outdoor sports, such as tennis, comes with a very real risk of dangerous solar ultraviolet exposure which can result in erythema (sunburn), serious conditions such as skin cancer, including melanoma, and eye conditions such as cataracts and pterygium. This study remotely assesses the effective ultraviolet exposures in response to the increased sun safety awareness at a major summertime tennis tournament in Australia. The assessment only uses publicly accessible data and information. It was found that tournament organizers have effectively adopted sun-safe protocols into the uniform policy that the court officials (judges and ball kids) are mandated to follow. The combination of sun-participant geometry and the photoprotection provided by uniforms significantly reduced the ambient ultraviolet exposure, which was recorded to be as high as 9.9 SED/h, to just 1.0 and 0.5 SED/h for ball kids and judges, respectively, compared to up to 2.0 SED/h for players. Even though caution is needed against complacency with sun safety, with the need for the court officials and the players to still apply sunscreen, the court officials provided persistent visual role modeling of sun-safe behaviors
Characterisation of ball degradation events in professional tennis
This is an Open Acces Article. It is published by Springer under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/Tennis balls are acknowledged to degrade with use and are replaced at regular intervals during professional matches to maintain consistency and uniformity in performance, such that the game is not adversely affected. Balls are subject to the international tennis federationās (ITF) ball approval process, which includes a degradation test to ensure a minimum standard of performance. The aim of this investigation was to establish if the ITF degradation test can assess ball longevity and rate of degradation and determine if there is a need for a new degradation test that is more representative of in-play conditions. Ball tracking data from four different professional events, spanning the three major court surfaces, including both menās and womenās matches were analysed. The frequency of first serves, second serves, racket impacts and surface impacts were assessed and the corresponding distribution of ball speed and (for surface impacts) impact angle was determined. Comparison of ball impact frequency and conditions between in-play data and the ITF degradation test indicated the development of a new test, more representative of in-play data, would be advantageous in determining ball longevity and rate of degradation with use. Assessment of data from different surfaces highlighted that grass court subjected the ball to fewer racket and surface impacts than hard court or clay. In turn, this appears to influence the distribution of ball speed on impact with the surface or racket, suggesting a surface-specific degradation test may be beneficial. As a result of these findings a new test protocol has been proposed, utilising the in-play data, to define the frequency of impacts and impact conditions to equate to nine games of professional tennis across the different surfaces
Loss of Mitogen-Activated Protein Kinase Kinase Kinase 4 (MAP3K4) Reveals a Requirement for MAPK Signalling in Mouse Sex Determination
The boygirl (byg) mouse mutant reveals that MAP3K4-mediated signaling is necessary for normal SRY expression and testis specification in the developing mouse gonad
Model for screening of resonant magnetic perturbations by plasma in a realistic tokamak geometry and its impact on divertor strike points
This work addresses the question of the relation between strike-point
splitting and magnetic stochasticity at the edge of a poloidally diverted
tokamak in the presence of externally imposed magnetic perturbations. More
specifically, ad-hoc helical current sheets are introduced in order to mimic a
hypothetical screening of the external resonant magnetic perturbations by the
plasma. These current sheets, which suppress magnetic islands, are found to
reduce the amount of splitting expected at the target, which suggests that
screening effects should be observable experimentally. Multiple screening
current sheets reinforce each other, i.e. less current relative to the case of
only one current sheet is required to screen the perturbation.Comment: Accepted in the Proceedings of the 19th International Conference on
Plasma Surface Interactions, to be published in Journal of Nuclear Materials.
Version 2: minor formatting and text improvements, more results mentioned in
the conclusion and abstrac
Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET
Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate
Modelling of tungsten erosion and deposition in the divertor of JET-ILW in comparison to experimental findings
The erosion, transport and deposition of tungsten in the outer divertor of JET-ILW has been studied for an HMode discharge with low frequency ELMs. For this specific case with an inter-ELM electron temperature at the strike point of about 20 eV, tungsten sputtering between ELMs is almost exclusively due to beryllium impurity and self-sputtering. However, during ELMs tungsten sputtering due to deuterium becomes important and even dominates. The amount of simulated local deposition of tungsten relative to the amount of sputtered tungsten in between ELMs is very high and reaches values of 99% for an electron density of 5E13 cm at the strike point and electron temperatures between 10 and 30 eV. Smaller deposition values are simulated with reduced electron density. The direction of the B-field significantly influences the local deposition and leads to a reduction if the EĆB drift directs towards the scrape-off-layer. Also, the thermal force can reduce the tungsten deposition, however, an ion temperature gradient of about 0.1 eV/mm or larger is needed for a significant effect. The tungsten deposition simulated during ELMs reaches values of about 98% assuming ELM parameters according to free-streaming model. The measured WI emission profiles in between and within ELMs have been reproduced by the simulation. The contribution to the overall net tungsten erosion during ELMs is about 5 times larger than the one in between ELMs for the studied case. However, this is due to the rather low electron temperature in between ELMs, which leads to deuterium impact energies below the sputtering threshold for tungsten
Tritium distributions on W-coated divertor tiles used in the third JET ITER-like wall campaign
Tritium (T) distributions on tungsten (W)-coated plasma-facing tiles used in the third ITER-like wall campaign (2015ā2016) of the Joint European Torus (JET) were examined by means of an imaging plate technique and Ī²-ray induced x-ray spectrometry, and they were compared with the distributions after the second (2013ā2014) campaign. Strong enrichment of T in beryllium (Be) deposition layers was observed after the second campaign. In contrast, T distributions after the third campaign was more uniform though Be deposition layers were visually recognized. The one of the possible explanations is enhanced desorption of T from Be deposition layers due to higher tile temperatures caused by higher energy input in the third campaign
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