Loads on a gymnastics safety support system during maximal use

Support systems can be used to prevent or reduce the impact during landings in various gymnastics disciplines. A support system typically consists of two ropes, three pulleys attached to steelwork in the roof space of the gymnasium, and a belt around the gymnast's waist. The aim of the study was to determine the forces at the pulleys and the tension in the ropes during maximal loading for a dynamic gymnastics skill. Additionally the relationships between the drop height and the peak force and between the gymnast mass and the peak force, together with the effect of the coach's actions, were investigated. A gymnastics support system was instrumented with strain-gauge-based load cells. A coach attempted to arrest the fall of a gymnast equivalent mass (range, 10—35 kg) over a range of drop heights (0.25—1.5 m). To establish the coach's contribution, trials were repeated with the coach replaced by an equivalent mass and with the rope tied off to the floor. Peak forces of 1.3 kN were recorded for a simulated maximum loading gymnastics scenario (drop height, 1.25 m; gymnast mass, 35 kg). The coach's actions reduced the peak forces by 35 per cent and 48 per cent in comparison with an equivalent deadweight and with the rope tied off respectively

SPATIAL SPEED-ACCURACY TRADE-OFF IN INTERNATIONAL BADMINTON PLAYERS PERFORMING THE FOREHAND SMASH

Speed and accuracy of the badminton smash are critical components for successful performance. Fifty-two participants data were collected using a Vicon 3D Motion capture system (400 Hz) at the BWF Glasgow World Championships (2017). The purpose of this study was to identify and compare spatial speed-accuracy trade-off (SATO) relationships amongst international badminton players performing the forehand smash, under two conditions: maximal speed (MS) in the direction of a target; and maximal speed aiming to hit the centre of a target (TAR). Exploratory and confirmatory cluster analyses revealed three groupings: Fitts’ inverse relationship (FIR), no relationship (NR) and alternate inverse relationship (AIR). Findings indicate that for international badminton players 80–99% of maximum speed is the threshold for achieving the highest levels of spatial accuracy

Quantum Trajectories: Dirac, Moyal and Bohm

We recall Dirac's early proposals to develop a description of quantum phenomena in terms of a non-commutative algebra in which he suggested a way to construct what he called quantum trajectories. Generalising these ideas, we show how they are related to weak values and explore their use in the experimental construction of quantum trajectories. We discuss covering spaces which play an essential role in accounting for the wave properties of quantum particles. We briefly point out how new mathematical techniques take us beyond Hilbert space and into a deeper structure which connects with the algebras originally introduced by Born, Heisenberg and Jordan. This enables us to bring out the geometric aspects of quantum phenomena.Quanta 2019; 8: 11–23

Quantum Blobs

Quantum blobs are the smallest phase space units of phase space compatible with the uncertainty principle of quantum mechanics and having the symplectic group as group of symmetries. Quantum blobs are in a bijective correspondence with the squeezed coherent states from standard quantum mechanics, of which they are a phase space picture. This allows us to propose a substitute for phase space in quantum mechanics. We study the relationship between quantum blobs with a certain class of level sets defined by Fermi for the purpose of representing geometrically quantum states.Comment: Prepublication. Dedicated to Basil Hile

Multiple Instance Learning for Heterogeneous Images: Training a CNN for Histopathology

Multiple instance (MI) learning with a convolutional neural network enables end-to-end training in the presence of weak image-level labels. We propose a new method for aggregating predictions from smaller regions of the image into an image-level classification by using the quantile function. The quantile function provides a more complete description of the heterogeneity within each image, improving image-level classification. We also adapt image augmentation to the MI framework by randomly selecting cropped regions on which to apply MI aggregation during each epoch of training. This provides a mechanism to study the importance of MI learning. We validate our method on five different classification tasks for breast tumor histology and provide a visualization method for interpreting local image classifications that could lead to future insights into tumor heterogeneity

FACTORS INFLUENCING VARIATION IN DIVE HEIGHT IN 1M SPRINGBOARD DIVING

The aim of this study was to determine the factors contributing to variation in dive height in performing a 1m springboard dive. 15 performances of a forward dive pike by an international diver were recorded using high speed video (250 Hz) and were digitised manually. The relationships between variables at hurdle landing, during board contact and dive height were determined. Hip extension during board contact accounted for 77% of the variance in dive height