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We report and discuss, by means of pore-scale numerical simulations, the possibility of achieving a directional-dependent two-phase flow behavior during the process of invasion of a viscous fluid into anisotropic porous media with controlled design. By customising the pore-scale morphology and heterogeneities with the adoption of anisotropic triangular pillars distributed with quenched disorder, we observe a substantially different invasion dynamics according to the direction of fluid injection relative to the medium orientation, that is depending if the triangular pillars have their apex oriented (flow aligned) or opposed (flow opposing) to the main flow direction. Three flow regimes can be observed: (i) for low values of the ratio between the macroscopic pressure drop and the characteristic pore-scale capillary threshold, i.e., for Δp&#95;{0}/p&#95;{c}≤1, the fluid invasion dynamics is strongly impeded and the viscous fluid is unable to reach the outlet of the medium, irrespective of the direction of injection; (ii) for intermediate values, 1<Δp&#95;{0}/p&#95;{c}≤2, the viscous fluid reaches the outlet only when the triangular pillars are flow-opposing oriented; (iii) for larger values, i.e., for Δp&#95;{0}/p&#95;{c}>2, the outlet is again reached irrespective of the direction of injection. The porous medium anisotropy induces a lower effective resistance when the pillars are flow-opposing oriented, suppressing front roughening and capillary fingering. We thus argue that the invasion process occurs as long as the pressure drop is larger then the macroscopic capillary pressure determined by the front roughness, which in the case of flow-opposing pillars is halved. We present a simple approximated model, based on Darcy's assumptions, that links the macroscopic effective permeability with the directional-dependent front roughening, to predict the asymmetric invasion dynamics. This peculiar behavior opens up the possibility of fabrication of porous capillary valves to control the flow along certain specific directions.

We investigate, by means of pore-scale lattice Boltzmann simulations, the mechanisms of interception of respiratory droplets within fibrous porous media composing face masks. We simulate the dynamics, coalescence, and collection of droplets of the size comparable with the fiber and pore size in typical fluid-dynamic conditions that represent common expiratory events. We discern the fibrous microstructure into three categories of pores: small, large, and medium-sized pores, where we find that within the latter, the incoming droplets tend to be more likely intercepted. The size of the medium-sized pores relative to the fiber size is placed between the droplet-to-fiber size ratio and a porosity-dependent microstructural parameter L ϵ * = ϵ / ( 1 - ϵ ) , with ϵ being the porosity. In larger pores, droplets collection is instead inhibited by the small pore-throat-to-fiber size ratio that characterizes the pore perimeter, limiting their access. The efficiency of the fibrous media in intercepting droplets without compromising breathability, for a given droplet-to-fiber size ratio, can be estimated by knowing the parameter L ϵ * . We propose a simple model that predicts the average penetration of droplets into the fibrous media, showing a sublinear growth with L ϵ * . Permeability is shown also to scale well with L ϵ * but following a superlinear growth, which indicates the possibility of increasing the medium permeability at a little cost in terms of interception efficiency for high values of porosity. As a general design guideline, the results also suggest that a fibrous layer thickness relative to the fiber size should exceed the value L ϵ * in order to ensure effective droplets filtration., (© 2021 Author(s).)

We present pore-scale simulations of two-phase flows in a reconstructed fibrous porous layer. The three-dimensional microstructure of the material, a fuel cell gas diffusion layer, is acquired via X-ray computed tomography and used as input for lattice Boltzmann simulations. We perform a quantitative analysis of the multiphase pore-scale dynamics, and we identify the dominant fluid structures governing mass transport. The results show the existence of three different regimes of transport: a fast inertial dynamics at short times, characterised by a compact uniform front, a viscous-capillary regime at intermediate times, where liquid is transported along a gradually increasing number of preferential flow paths of the size of one-two pores, and a third regime at longer times, where liquid, after having reached the outlet, is exclusively flowing along such flow paths and the two-phase fluid structures are stabilised. We observe that the fibrous layer presents significant variations in its microscopic morphology, which have an important effect on the pore invasion dynamics, and counteract the stabilising viscous force. Liquid transport is indeed affected by the presence of microstructure-induced capillary pressures acting adversely to the flow, leading to capillary fingering transport mechanism and unstable front displacement, even in the absence of hydrophobic treatments of the porous material. We propose a macroscopic model based on an effective contact angle that mimics the effects of the such a dynamic capillary pressure. Finally, we underline the significance of the results for the optimal design of face masks in an effort to mitigate the current COVID-19 pandemic., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© The Author(s) 2020.)

Aims: To describe patterns of experienced and anticipated discrimination in a sample of schizophrenic patients recruited in Italy in the context of the International Study of Discrimination and Stigma Outcomes (INDIGO)., Methods: Cross-sectional survey on a sample of 50 people with clinical diagnosis of schizophrenia recruited in the Italian INDIGO sites of Verona and Brescia. The 41-item interview-based Discrimination and Stigma Scale (DISC-10), which assesses how experienced and anticipated discrimination affects the life of people with schizophrenia, was used., Results: The most frequently occurring areas of experienced discrimination were discrimination by family members (44%), making and keeping friends (33%), keeping (36%) and finding a job (34%), getting or keeping a driving licence (32%). Anticipated discrimination was common in applying for work, training or education (58%), looking for close relationships (50%) and doing something important (48%); 68% felt the need to conceal their diagnosis. Positive experiences were rare, and getting welfare benefits/disability pensions was the only area where participants reported being treated with advantage (34%) more commonly than with disadvantage (8%). Overall, experienced discrimination reported by Italian patients was in the intermediate position of the score range of all INDIGO sites, whereas anticipated discrimination was lower than that reported in the other countries., Conclusions: Interventions to reduce discrimination against people with schizophrenia may need to address both actual and anticipated discrimination. Targeted therapeutic strategies aiming to improve self-esteem of people with schizophrenia may be useful to facilitate their social participation and full inclusion in the community.