Collective Damage Growth Controls Fault Orientation in Quasibrittle Compressive Failure.

The Mohr-Coulomb criterion is widely used in geosciences and solid mechanics to relate the state of stress at failure to the observed orientation of the resulting faults. This relation is based on the assumption that macroscopic failure takes place along the plane that maximizes the Coulomb stress. Here, this hypothesis is assessed by simulating compressive tests on an elastodamageable material that follows the Mohr-Coulomb criterion at the mesoscopic scale. We find that the macroscopic fault orientation is not given by the Mohr-Coulomb criterion. Instead, for a weakly disordered material, it corresponds to the most unstable mode of damage growth, which we determine through a linear stability analysis of its homogeneously damaged state. Our study reveals that compressive failure emerges from the coalescence of damaged clusters within the material and that this collective process is suitably described at the continuum scale by introducing an elastic kernel that describes the interactions between these clusters.

[A typology of mental health comorbidity in workplaces: results from the SALVEO study]. / Une typologie de la comorbidité en santé mentale au travail : résultats de l'étude SALVEO.

Objectives The aim of this study consists in describing the nature of mental health comorbidity among workers. Precisely, we seek to examine the presence of concomitant associations between burnout (cynicism, emotional exhaustion, professionnal inefficacy) and psychoactive substance use (heavy episodic drinking, above low-risk drinking guidelines, and psychotropic drug use).Methods The SALVEO study is based on a cross-sectional sample of 1966 workers from the province of Québec, Canada. Latent class analyses were performed in order to identify typical patterns corresponding to distinct forms of mental health comorbidity in the data. Multinomial logistic regressions on latent classes were performed using covariables pertaining to work and non-work domains and workers' individual characteristics.Results Four typical patterns in mental health comorbidity were found: 1- "Severe burnout and psychotropic drug use"; 2- "At risk drinking and cynicism"; 3- "Emotional exhaustion and professional inefficacy"; and 4- "Relatively healthy state". Of all four patterns, the "Severe burnout and psychotropic drug use" pattern presented the highest number of cumulative risks (environmental and individual).Conclusion Comorbidity in mental health is a matter of importance in workplaces from the province of Québec. The severity in the different patterns of mental health comorbidity expressed a cumulative effect of risk factors from the work and non-work domains, as well as individual characteristics.

Linking scales in sea ice mechanics.

Mechanics plays a key role in the evolution of the sea ice cover through its control on drift, on momentum and thermal energy exchanges between the polar oceans and the atmosphere along cracks and faults, and on ice thickness distribution through opening and ridging processes. At the local scale, a significant variability of the mechanical strength is associated with the microstructural heterogeneity of saline ice, however characterized by a small correlation length, below the ice thickness scale. Conversely, the sea ice mechanical fields (velocity, strain and stress) are characterized by long-ranged (more than 1000 km) and long-lasting (approx. few months) correlations. The associated space and time scaling laws are the signature of the brittle character of sea ice mechanics, with deformation resulting from a multi-scale accumulation of episodic fracturing and faulting events. To translate the short-range-correlated disorder on strength into long-range-correlated mechanical fields, several key ingredients are identified: long-ranged elastic interactions, slow driving conditions, a slow viscous-like relaxation of elastic stresses and a restoring/healing mechanism. These ingredients constrained the development of a new continuum mechanics modelling framework for the sea ice cover, called Maxwell-elasto-brittle. Idealized simulations without advection demonstrate that this rheological framework reproduces the main characteristics of sea ice mechanics, including anisotropy, spatial localization and intermittency, as well as the associated scaling laws.This article is part of the themed issue 'Microdynamics of ice'.