On the Propagation of Slip Fronts at Frictional Interfaces

The dynamic initiation of sliding at planar interfaces between deformable and rigid solids is studied with particular focus on the speed of the slip front. Recent experimental results showed a close relation between this speed and the local ratio of shear to normal stress measured before slip occurs (static stress ratio). Using a two-dimensional finite element model, we demonstrate, however, that fronts propagating in different directions do not have the same dynamics under similar stress conditions. A lack of correlation is also observed between accelerating and decelerating slip fronts. These effects cannot be entirely associated with static local stresses but call for a dynamic description. Considering a dynamic stress ratio (measured in front of the slip tip) instead of a static one reduces the above-mentioned inconsistencies. However, the effects of the direction and acceleration are still present. To overcome this we propose an energetic criterion that uniquely associates, independently on the direction of propagation and its acceleration, the slip front velocity with the relative rise of the energy density at the slip tip.Comment: 15 pages, 6 figure

Primary, allied health, geriatric, pain and palliative healthcare service utilisation by aged care residents, 2012-2017.

OnlinePublObjectives To examine the incidence and trends in primary care, allied health, geriatric, pain and palliative care service use by permanent residential aged care (PRAC) residents and the older Australian population. Methods Repeated cross-sectional analyses on PRAC residents (N = 318,484) and the older (≥65 years) Australian population (N ~ 3.5 million). Outcomes were Medicare Benefits Schedule (MBS) subsidised primary care, allied health, geriatric, pain and palliative services between 2012-13 and 2016-17. GEE Poisson models estimated incidence rates and incidence rate ratios (IRR). Results In 2016-17, PRAC residents had a median of 13 (interquartile range [IQR] 5-19) regular general medical practitioner (GP) attendances, 3 (IQR 1-6) after-hours attendances and 5% saw a geriatrician. Highlights of utilisation changes from 2012-13 to 2016-17 include the following: GP attendances increased by 5%/year (IRR = 1.05, 95% confidence interval [CI] 1.05-1.05) for residents compared to 1%/year (IRR = 1.01, 95%CI 1.01-1.01) for the general population. GP after-hours attendances increased by 15%/year (IRR = 1.15, 95%CI 1.14-1.15) for residents and 9%/year (IRR = 1.08, 95%CI 1.07-1.20) for the general population. GP management plans increased by 12%/year (IRR = 1.12, 95%CI 1.11-1.12) for residents and 10%/year (IRR = 1.10, 95%CI 1.09-1.11) for the general population. Geriatrician consultations increased by 28%/year (IRR = 1.28, 95%CI 1.27-1.29) for residents compared to 14%/year (IRR = 1.14, 95%CI 1.14-1.15) in the general population. Conclusions The utilisation of most examined services increased in both cohorts over time. Preventive and management care, by primary care and allied health care providers, was low and likely influences the utilisation of other attendances. PRAC residents' access to pain, palliative and geriatric medicine services is low and may not address the residents' needs.Maria C. Inacio, Luke Collier, Tracy Air, Kailash Thapaliya, Maria Crotty, Helena Williams, Steve L. Wesselingh, Andrew Kellie, David Roder, Adrienne Lewis, Gillian Harvey, Janet K. Sluggett, Monica Cations, Tiffany K. Gill, Jyoti Khadka, Gillian E. Caughe