Interactions between toothbrush and toothpaste particles during simulated abrasive cleaning

Most people clean their teeth using toothpaste, consisting of abrasive particles in a carrier fluid, and a filament based toothbrush to remove plaque and stain. In order to optimise cleaning efficiency it is important to understand how toothbrush filaments, abrasive particles and fluid interact in a tooth cleaning contact. Work has been carried out to visualise, simulate, and model the processes in teeth cleaning. Laboratory cleaning contacts were created between a toothbrush and a transparent surface. Video and short duration flash photography were used to study the processes by which a toothbrush traps abrasive particles, loads them against the counterface, and removes material. Small abrasive particles tend to be trapped at the contact between the filament tip and the counterface, whilst larger particles are trapped by clumps of filaments or at the contact with the side of a bent filament. Measurements of brush friction force were recorded during cleaning for a range of operating conditions. The presence of abrasive particles in the cleaning mixture increased the coefficient of friction, but the absolute particle concentration showed a lesser effect. It is surmised that only a few particles carry any load and cause any abrasion; increasing the particle concentration does not directly increase the number of load bearing particles. Abrasive scratch tests were also carried out, using PMMA as a wearing substrate. The scratches produced during these tests were studied. The microscopy images were used to deduce how the filaments deflect and drag, and how particles are trapped by filaments and scratch the surface. Again, it was observed that few of the brush filaments loaded particles to produce scratches, and that when a filament changes direction of travel the trapped particle is lost. Results of these studies were used to develop both qualitative and quantitative models of the process by which material is removed in teeth cleaning. The quantitative model contains, by necessity, several empirical factors, but nonetheless predictions compare well with in vitro wear results from the literature. The results were also used to draw some broad conclusions on appropriate brushing techniques for optimum tooth cleaning

Limited availability of cardiac rehabilitation for heart failure patients in the United Kingdom: findings from a national survey

Background: Participation of patients with heart failure in cardiac rehabilitation in the UK is low. This study investigated the availability of cardiac rehabilitation services for patients with heart failure in the UK and the views of service coordinators on ideal service models. Design: Our study was a cross-sectional national postal survey that was mailed to 342 service coordinators in the UK between April and June 2009. Methods: We developed a 38-item questionnaire to survey all cardiac rehabilitation service coordinators on theNational Audit of Cardiac Rehabilitation register in the UK in 2009. Results: The survey response rate was 71% (244/342). Forty three per cent (105/244) of coordinators did not accept patients with heart failure to their cardiac rehabilitation services. Most coordinators who did accept patients with heart failure offered their services to patients with a variety of cardiac conditions, though referral criteria and models of care varied widely. Services inconsistently used New York Heart Association classes and left ventricular ejection fraction measures to select patients. Few offered separate dedicated heart failure programmes (14%; 33/244) but where these existed they ran for longer than programmes which included patients with heart failure alongside other cardiac patients (10.9 vs 8.5 weeks; F=4.04; p=0.019). Few offered home-based options for patients with heart failure (11%; 27/244). Coordinators accepting patients with heart failure to their cardiac rehabilitation services tended to agree that patients with heart failure should be included in services alongside other cardiac patients (X2=6.2; p=0.013). Conclusions: There is limited access for patients with heart failure to cardiac rehabilitation in the UK. Local policies on referral and selection criteria differ and reflect coordinators views rather than clinical guidance. © The European Society of Cardiology 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav

P3_9 Scooby and Shaggy: Metabolic Miracles

In the cartoon `What's New Scooby-Doo?' the characters Shaggy and Scooby are seen to eat large volumesof food without gaining any weight. Their effective temperatures in order to radiate away the excess energywere calculated to be T_Sh ~ 97 ± 033 °C for Shaggy, and T_Sc ~ 140 ± 43 °C for Scooby. It was concludedthat under normal circumstances, the subjects would perish of extreme hyperthermia. It was also notedthat Shaggy could survive if he was able to sweat continuously at the maximum rate for a human

P3_1 On the feasibility of neutrino sails

In this paper we consider whether a neutrino sail, a sheet of material absorbing neutrinos and gaining thrust from their momentum change, is a viable method of spacecraft propulsion. We calculate the thrust that could be achieved per unit area and compare this to that possible using a photon solar sail. We also calculate the thickness of sail necessary assuming that there are no special conditions under which the cross section for neutrino interactions with nuclei can be increased. We find that a thickness of 34000 light years would be necessary if a sheet of osmium were used, whereas neutron star matter could achieve this at 189 km thickness. We conclude that a neutrino sail is not a practical method of propulsion

P3_7 Cavorite Pt 3: Varying the Size of the Sheet

A continuation of The Cavorite Series, in which we explore the effects of a fictional substance which is “opaque to gravitation”. In this paper we examine the effects of varying the radius of the Cavorite sheet. As expected, the point at which the g experienced by a test particle returns to close to normal Earth g increases with the radius of the Cavorite. However, we found that even a Cavorite sheet of 1 km radius would not be enough to vent the atmosphere

P3_6 Cavorite Pt 2: the Gravity of the Situation

We continue to explore the gravitational and atmospheric effects of Cavorite, a fictional material that is “opaque to gravitation”, by attempting to form a simplified gravitational model of the situation. This gravitational model was found to define the range at which gravitational acceleration will return to near normal as between 0.02 and 12 m. Further research is required to truly model the gravitational acceleration due to Cavorite

P3_3 On the Atmospheric Effects of Cavorite

We estimate the gravitational and atmospheric effects of a fictional substance known as Cavorite, a material proposed by H.G. Wells that is “opaque to gravitation”. We conclude that for a Cavorite sheet of radius 1 m the impact on the gravitational acceleration is only meaningful at less than 12 m above the plate, and is insignificant at heights greater than this. Therefore, the atmosphere is unlikely to vent away as claimed

P3_4 Elysium: Where'd the Atmosphere Go?

This paper determines whether the Elysium space station, from the 2013 film Elysium[1], could maintain an atmosphere. We found that Elysium, with a radius of 20 km[2], would not hold onto its atmosphere unless high wind speeds (183 ms^-1, 324 ms^-1, and 443 ms^-1; for the atmospheric rotations tested) are to be endured by its inhabitants