Experimental evidence of non-Amontons behaviour at a multicontact interface

We report on normal stress field measurements at the multicontact interface between a rough elastomeric film and a smooth glass sphere under normal load, using an original MEMS-based stress sensing device. These measurements are compared to Finite Elements Method calculations with boundary conditions obeying locally Amontons' rigid-plastic-like friction law with a uniform friction coefficient. In dry contact conditions, significant deviations are observed which decrease with increasing load. In lubricated conditions, the measured profile recovers almost perfectly the predicted profile. These results are interpreted as a consequence of the finite compliance of the multicontact interface, a mechanism which is not taken into account in Amontons' law

Role of friction-induced torque in stick-slip motion

We present a minimal quasistatic 1D model describing the kinematics of the transition from static friction to stick-slip motion of a linear elastic block on a rigid plane. We show how the kinematics of both the precursors to frictional sliding and the periodic stick-slip motion are controlled by the amount of friction-induced torque at the interface. Our model provides a general framework to understand and relate a series of recent experimental observations, in particular the nucleation location of micro-slip instabilities and the build up of an asymmetric field of real contact area.Comment: 6 pages, 5 figure

fbl-typing of Staphylococcus lugdunensis: a frontline tool for epidemiological studies

International audienc

The dynamics of thin vibrated granular layers

We describe a series of experiments and computer simulations on vibrated granular media in a geometry chosen to eliminate gravitationally induced settling. The system consists of a collection of identical spherical particles on a horizontal plate vibrating vertically, with or without a confining lid. Previously reported results are reviewed, including the observation of homogeneous, disordered liquid-like states, an instability to a `collapse' of motionless spheres on a perfect hexagonal lattice, and a fluctuating, hexagonally ordered state. In the presence of a confining lid we see a variety of solid phases at high densities and relatively high vibration amplitudes, several of which are reported for the first time in this article. The phase behavior of the system is closely related to that observed in confined hard-sphere colloidal suspensions in equilibrium, but with modifications due to the effects of the forcing and dissipation. We also review measurements of velocity distributions, which range from Maxwellian to strongly non-Maxwellian depending on the experimental parameter values. We describe measurements of spatial velocity correlations that show a clear dependence on the mechanism of energy injection. We also report new measurements of the velocity autocorrelation function in the granular layer and show that increased inelasticity leads to enhanced particle self-diffusion.Comment: 11 pages, 7 figure

Apport de la MLVA dans l'épidémiologie moléculaire des infections à Staphylococcus lugdunensis

International audienc

2-loop Functional Renormalization Group Theory of the Depinning Transition

We construct the field theory which describes the universal properties of the quasi-static isotropic depinning transition for interfaces and elastic periodic systems at zero temperature, taking properly into account the non-analytic form of the dynamical action. This cures the inability of the 1-loop flow-equations to distinguish between statics and quasi-static depinning, and thus to account for the irreversibility of the latter. We prove two-loop renormalizability, obtain the 2-loop beta-function and show the generation of "irreversible" anomalous terms, originating from the non-analytic nature of the theory, which cause the statics and driven dynamics to differ at 2-loop order. We obtain the roughness exponent zeta and dynamical exponent z to order epsilon^2. This allows to test several previous conjectures made on the basis of the 1-loop result. First it demonstrates that random-field disorder does indeed attract all disorder of shorter range. It also shows that the conjecture zeta=epsilon/3 is incorrect, and allows to compute the violations, as zeta=epsilon/3 (1 + 0.14331 epsilon), epsilon=4-d. This solves a longstanding discrepancy with simulations. For long-range elasticity it yields zeta=epsilon/3 (1 + 0.39735 epsilon), epsilon=2-d (vs. the standard prediction zeta=1/3 for d=1), in reasonable agreement with the most recent simulations. The high value of zeta approximately 0.5 found in experiments both on the contact line depinning of liquid Helium and on slow crack fronts is discussed.Comment: 32 pages, 17 figures, revtex

Integrated Short-term Palliative Rehabilitation to improve quality of life and equitable care access in incurable cancer (INSPIRE): a multinational European research project

Background: Disability related to incurable cancer affects over a million Europeans each year and people with cancer rank loss of function among the most common unmet supportive care needs. Objectives: To test the clinical and cost-effectiveness of an integrated short-term palliative rehabilitation intervention, to optimise function and quality of life in people affected by incurable cancer. Design: This is a multinational, parallel group, randomised, controlled, assessor blind, superiority trial. Methods: The INSPIRE consortium brings together leaders in palliative care, oncology and rehabilitation from partner organisations across Europe, with complementary expertise in health service research, trials of complex interventions, mixed-method evaluations, statistics and economics. Partnership with leading European civil society organisations ensures citizen engagement and dissemination at the highest level. We will conduct a multinational randomised controlled trial across five European countries, recruiting participants to assess the effectiveness of palliative rehabilitation for people with incurable cancer on the primary outcome – quality of life – and secondary outcomes including disability, symptom burden and goal attainment. To support trial conduct and enhance analysis of trial data, we will also conduct: comparative analysis of current integration of rehabilitation across oncology and palliative care services; mixed-method evaluations of equity and inclusivity, processes and implementation for the intervention, at patient, health service and health system levels. Finally, we will conduct an evidence synthesis, incorporating INSPIRE findings, and a Delphi consensus to develop an international framework for palliative rehabilitation practice and policy, incorporating indicators, core interventions, outcomes and integration methods. Scientific contribution: If positive, the trial could produce a scalable and equitable intervention to improve function and quality of life in people with incurable cancer and reduce the burden of care for their families. It could also upskill the practitioners involved and motivate future research questions. The intervention could be adapted and integrated into different health systems using existing staff and services, with little or no additional cost