Water-deuterium oxide exchange in polymers used in spacecraft applications

The replacement of water (H2O) by deuterium oxide (D2O) and the exchange between atmospheric water and adsorbed or absorbed D2O were investigated for the polymeric materials Kapton and Mylar using thermal gravimetric analysis and infrared spectroscopy. Replacement of H2O by D2O is easily accomplished. However, exposure of D2O samples to the ambient atmosphere or gases containing H2O results in rapid proton and deuteron exchange between H2O vapor and adsorbed D2O. Replacement of H2O by D2O would not be a practical solution to alleviate spectral interferences that would result from water outgassing in spacecraft orbital environments. Maintaining the materials of interest in a dehydrated state is a more reasonable approach

Efficiency of donning and doffing medical examination gloves

Quickly donning and doffing medical gloves is of vital importance for high-pressure environments. The efficiency of glove donning, however, is sometimes hindered because of moisture on the hand. A variety of commercial glove coatings exist that are said to enable a smoother donning process, however, no previous studies have examined the differences in time taken to don or doff gloves manufactured using different materials and coatings. The aim of this new study was to compare the efficiency of donning and doffing different glove types. 14 participants were timed on their efficiency to don and doff chlorinated latex and nitrile gloves, as well as polymer coated latex and nitrile gloves. All glove types were studied in both dry and wet hand conditions, leading to a total of 8 different glove condition combinations. The results indicate that polymer coated latex gloves are desirable when a quick glove change is required as there was no statistically significant difference between the average time taken to don these gloves in dry and wet hand conditions. Higher incidences of sticking were found among the wet hands, particularly in the polymer coated nitrile, which took the longest to don. However, little differences were found between all glove types, suggesting that neither the material itself, nor the internal coating, have an effect on the overall donning process when hands are dry. Discrepancies in best fit size were also noticed between the recommended sizes based on anthropometric measurements and the participants preferred glove size

Statics and dynamics of a cylindrical droplet under an external body force

We study the rolling and sliding motion of droplets on a corrugated substrate by Molecular Dynamics simulations. Droplets are driven by an external body force (gravity) and we investigate the velocity profile and dissipation mechanisms in the steady state. The cylindrical geometry allows us to consider a large range of droplet sizes. The velocity of small droplets with a large contact angle is dominated by the friction at the substrate and the velocity of the center of mass scales like the square root of the droplet size. For large droplets or small contact angles, however, viscous dissipation of the flow inside the volume of the droplet dictates the center of mass velocity that scales linearly with the size. We derive a simple analytical description predicting the dependence of the center of mass velocity on droplet size and the slip length at the substrate. In the limit of vanishing droplet velocity we quantitatively compare our simulation results to the predictions and good agreement without adjustable parameters is found.Comment: Submitted to the Journal of Chemical Physic

Effect of varying the volume infill sand on synthetic clay surfaces in terms of the shoe-surface friction

The friction developed by the shoe-surface interface on artificial clay has not been widely studied, and can influence player's performance and injury risk. The aim of this research was to investigate the effect of varying the quantity of infill sand on shoe- surface friction on an artificial clay court tennis surface. A laboratory-based mechanical test rig was used to measure the friction force developed at the shoe-surface interface. Additionally, the perception of a group of participants, performing a turning movement on the same surface under dry conditions, was collected in order to compare against the mechanical results. The relationship between the normal force and friction generated by the shoe-surface interaction was examined for surfaces with different sand in-fill volumes. The mechanical testing was performed under dry and wet conditions, showing strong and significant differences. Results indicated that the normal force significantly influenced the static and dynamic frictional forces. For lower sand infill volumes, as normal loading increased, the dry condition was found to exhibit the lowest peak static friction force and highest average dynamic friction force. However, for higher sand infill volume conditions, the opposite behaviour was observed. Strong and significant positive linear relationships were found between peak friction force and average dynamic friction force for all infill sand volumes and conditions. The mechanical results were in agreement with the perception data, which suggests that the participants were sensitive to the small changes in sand infill volumes. The findings of this study will therefore aid the understanding of tennis players’ perceived response to a tennis court surface. In order to get a better understanding of friction behaviour, further testing needs to be performed, and once the mechanisms involved are understood, surface properties could be modified to increase performance and reduce injury risk

A critical review of the assessment of medical gloves

Medical protective gloves must be assessed to adequate standards before becoming available for commercial use. Strength, integrity and contamination are assessed at the manufacturing stage. However, concerns are raised over the standardisation of the testing; should more be done to assess how gloves affect the performance? Over the years, studies have demonstrated how the design of gloves have reduced tactile sensitivity in medical staff, ultimately leading to poor patient care through missed information. Studies have also demonstrated that a loss of grip control and dexterity through glove use are detrimental to medical tasks. However, it remains relatively unexplored as to how wearing medical gloves affects the users and the patients. Gaps in research have been identified around the frictional and grip properties of gloves. Linking the key performance parameters to the manufacturing processes, which affect material properties, will provide more insight into the behaviour of medical gloves and how to properly assess materials

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 Godó 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

Heart Rate Variability as a Predictor of Speaking Anxiety

This study examines the relations among the perception of speaking anxiety and difficulties in emotion regulation with 2 measures of physiological activity: heart rate (HR) and heart rate variability (HRV). Results show significant changes in HR and state anxiety, but not HRV, among the 6 experimental conditions: quiet, reading in both sitting and standing positions, and speaking in both sitting and standing positions. HRV significantly and negatively correlated with difficulties in emotion regulation and HR, but not with public speaking apprehension (PSA) scores or state anxiety ratings. PSA scores, however, were significantly and positively correlated with state anxiety ratings. Results are interpreted in terms of the simultaneous, coordinated operation of physical reactions and emotional coping strategies

Control of the attosecond synchronization of XUV radiation with phase-optimized mirrors

International audienceWe report on the advanced amplitude and phase control of attosecond radiation allowed by specifically-designed multilayer XUV mirrors. We first demonstrate that such mirrors can compensate for the intrinsic chirp of the attosecond emission over a large bandwidth of more than 20 eV. We then show that their combination with metallic foils introduces a third-order dispersion that is adjustable through the mirror's incidence angle. This results in a controllable beating allowing the radiation to be shaped from a single to a series of sub-100 as pulses