A molecular density functional theory for associating fluids in 3D geometries.

A new free-energy functional is proposed for inhomogeneous associating fluids. The general formulation of Wertheim's thermodynamic perturbation theory is considered as the starting point of the derivation. We apply the hypotheses of the statistical associating fluid theory in the classical density functional theory (DFT) framework to obtain a tractable expression of the free-energy functional for inhomogeneous associating fluids. Specific weighted functions are introduced in our framework to describe association interactions for a fluid under confinement. These weighted functions have a mathematical structure similar to the weighted densities of the fundamental-measure theory (i.e., they can be expressed as convolution products) such that they can be efficiently evaluated with Fourier transforms in a 3D space. The resulting free-energy functional can be employed to determine the microscopic structure of inhomogeneous associating fluids of arbitrary 3D geometry. The new model is first compared with Monte Carlo simulations and previous versions of DFT for a planar hard wall system in order to check its consistency in a 1D case. As an example of application in a 3D configuration, we then investigate the extreme confinement of an associating hard-sphere fluid inside an anisotropic open cavity with a shape that mimics a simplified model of zeolite. Both the density distribution and the corresponding molecular bonding profile are given, revealing complementary information to understand the structure of the associating fluid inside the cavity network. The impact of the degree of association on the preferential positions of the molecules inside the cavity is investigated as well as the competition between association and steric effect on adsorption.

Effects of vertical violence on the work of nurses in hospital settings: An exploratory study / Effets de la violence verticale sur le travail d'infirmières soignantes exerçant en milieux hospitaliers : une étude exploratoire

Introduction: More than 39.7% of nurses report being victims of psychological harassment in the workplace. In 60% of cases, the abuse is vertical, involving a person in a position of authority. Context: Few studies have examined this phenomenon without conflating it with other forms of workplace violence. Objective: The purpose of this study was to shed light on cases of vertical violence experienced by nurses working in hospitals. Method: Data was collected by means of semi-structured interviews with six nurses working in hospitals in the province of Quebec (Canada). Descriptive phenomenology was used to analyze the collected data. Results: The overall effects of the vertical violence experienced by nurses in hospital settings resulted in less diligent and individualized nursing care. Discussion: It is recommended that organizational policies against vertical violence put in place in hospital be enforced in a rigorous and transparent manner. Further investigation is needed to identify the organizational factors that contribute to vertical violence in hospital settings.

Introduction: Plus de 39,7 % des infirmières se déclarent victimes de harcèlement psychologique dans leur milieu de travail. Dans 60 % des cas, il est question de violence verticale impliquant une personne en supériorité hiérarchique. Contexte: Peu d'études abordent ce phénomène sans le confondre avec d'autres formes de violence en milieu de travail. Objectifs: Cette étude visait à décrire l'effet de la violence verticale vécue par des infirmières soignantes exerçant en milieux hospitaliers. Méthode: Une collecte des données par entrevues semi-dirigées a été réalisée auprès de six infirmières de milieux hospitaliers de la province de Québec (Canada). La phénoménologie descriptive a été utilisée dans le cadre de la présente étude. Résultats: La représentation globale des effets de la violence verticale vécue par des infirmières soignantes en milieux hospitaliers se traduit par un détournement des initiatives infirmières qui renvoient à des soins diligents et personnalisés. Discussion: Il est recommandé que les politiques organisationnelles contre la violence verticale, mises en place dans les centres hospitaliers, soient appliquées de façon rigoureuse et transparente. D'autres études seraient appropriées afin de préciser les facteurs organisationnels favorisant la violence verticale en milieux hospitaliers.

Decay processes in buildings close to the sea induced by marine aerosol: Salt depositions inside construction materials.

Buildings close to the sea experience different kinds of decay processes related with the influence of marine aerosol. This sea spray is a chemically complex system formed by inorganic salts (sulfates, nitrates and mainly chlorides) and organic matter, together even with airborne particulate matter from the surrounding environment. Buildings close to the sea, erected using different materials such as bricks, plasters, limestones and sandstones, can experience many kinds of chemical reactions promoted by the impact of this sea spray, which favour the formation of salt crystallizations. In this work, a study of salts crystallizing in different kinds of building materials of a construction close to the Bay of Biscay (Villa Belza, Biarritz, France) has been studied in order to evaluate the state of conservation of the materials under study. The construction materials affected by salts were analyzed by means of X-ray Diffraction (XRD) and µ-Raman spectroscopy (µ-RS) for molecular analyses, Energy dispersive X-ray Fluorescence spectrometry (µ-ED-XRF) for elemental analyses and soluble salts tests by means of ion chromatography. These analyses revealed different levels of chlorides, nitrates and sulfates. Moreover, using this methodology, some specific chemical reactions that take place in the Villa Belza were understood. This knowledge can help to lay the foundations for possible future restoration works.

Mesoscale analysis of failure in quasi-brittle materials: comparison between lattice model and acoustic emission data.

The purpose of this paper is to analyse the development and the evolution of the fracture process zone during fracture and damage in quasi-brittle materials. A model taking into account the material details at the mesoscale is used to describe the failure process at the scale of the heterogeneities. This model is used to compute histograms of the relative distances between damaged points. These numerical results are compared with experimental data, where the damage evolution is monitored using acoustic emissions. Histograms of the relative distances between damage events in the numerical calculations and acoustic events in the experiments exhibit good agreement. It is shown that the mesoscale model provides relevant information from the point of view of both global responses and the local failure process. © 2015 The Authors. International Journal for Numerical and Analytical Methods in Geomechanics published by John Wiley & Sons Ltd.

Tablet-level origin of toughening in abalone shells and translation to synthetic composite materials.

Nacre, the iridescent material in seashells, is one of many natural materials employing hierarchical structures to achieve high strength and toughness from relatively weak constituents. Incorporating these structures into composites is appealing as conventional engineering materials often sacrifice strength to improve toughness. Researchers hypothesize that nacre's toughness originates within its brick-and-mortar-like microstructure. Under loading, bricks slide relative to each other, propagating inelastic deformation over millimeter length scales. This leads to orders-of-magnitude increase in toughness. Here, we use in situ atomic force microscopy fracture experiments and digital image correlation to quantitatively prove that brick morphology (waviness) leads to transverse dilation and subsequent interfacial hardening during sliding, a previously hypothesized dominant toughening mechanism in nacre. By replicating this mechanism in a scaled-up model synthetic material, we find that it indeed leads to major improvements in energy dissipation. Ultimately, lessons from this investigation may be key to realizing the immense potential of widely pursued nanocomposites.