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

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

Molecular transport and flow past hard and soft surfaces: Computer simulation of model systems

The properties of polymer liquids on hard and soft substrates are investigated by molecular dynamics simulation of a coarse-grained bead-spring model and dynamic single-chain-in-mean-field (SCMF) simulations of a soft, coarse-grained polymer model. Hard, corrugated substrates are modelled by an FCC Lennard-Jones solid while polymer brushes are investigated as a prototypical example of a soft, deformable surface. From the molecular simulation we extract the coarse-grained parameters that characterise the equilibrium and flow properties of the liquid in contact with the substrate: the surface and interface tensions, and the parameters of the hydrodynamic boundary condition. The so-determined parameters enter a continuum description like the Stokes equation or the lubrication approximation.Comment: 41 pages, 13 figure

Deux approches pour modifier les activités de résolution de problèmes en physique dans l'enseignement secondaire : une tentative de synthèse

Dans cet article les AA. présentent un cadre théorique pour analyser les activités de résolution de problèmes " papier crayon " issu de la confrontation des recherches menées par deux équipes (Gil Perez D. et Martinez Torregrossa J. en Espagne et Caillot M. et Dumas-Carré A. en France) dans le domaine de la physique. Le point de départ commun des deux équipes est de considérer que l'échec généralisé des élèves ne peut être imputé seulement (ni principalement) à des caractéristiques ou des lacunes des élèves, mais que la plus grande responsabilité doit être cherchée du côté de la didactique habituelle. Ce qui doit être remis en question de façon prioritaire est la conception même des activités de résolution de problèmes. Cette remise en question de la conception didactique commence par une interrogation sur le concept de problème lui-même. De même, le comportement habituellement retenu comme modèle (celui de l'expert) est remis en question| le comportement proposé comme modèle est celui du chercheur scientifiqu

Atomic diffraction from nanostructured optical potentials

We develop a versatile theoretical approach to the study of cold-atom diffractive scattering from light-field gratings by combining calculations of the optical near-field, generated by evanescent waves close to the surface of periodic nanostructured arrays, together with advanced atom wavepacket propagation on this optical potential.Comment: 8 figures, 10 pages, submitted to Phys. Rev.

Melting of tantalum at high pressure determined by angle dispersive x-ray diffraction in a double-sided laser-heated diamond-anvil cell

The high pressure and high temperature phase diagram of Ta has been studied in a laser-heated diamond-anvil cell (DAC) using x-ray diffraction measurements up to 52 GPa and 3800 K. The melting was observed at nine different pressures, being the melting temperature in good agreement with previous laser-heated DAC experiments, but in contradiction with several theoretical calculations and previous piston-cylinder apparatus experiments. A small slope for the melting curve of Ta is estimated (dTm/dP = 24 K/GPa at 1 bar) and a possible explanation for this behaviour is given. Finally, a P-V-T equation of states is obtained, being the temperature dependence of the thermal expansion coefficient and the bulk modulus estimated.Comment: 31 pages, 8 figures, to appear in J.Phys.:Cond.Matte

Superradiance from an ultrathin film of three-level V-type atoms: Interplay between splitting, quantum coherence and local-field effects

We carry out a theoretical study of the collective spontaneous emission (superradiance) from an ultrathin film comprised of three-level atoms with $V$-configuration of the operating transitions. As the thickness of the system is small compared to the emission wavelength inside the film, the local-field correction to the averaged Maxwell field is relevant. We show that the interplay between the low-frequency quantum coherence within the subspace of the upper doublet states and the local-field correction may drastically affect the branching ratio of the operating transitions. This effect may be used for controlling the emission process by varying the doublet splitting and the amount of low-frequency coherence.Comment: 15 pages, 5 figure