On the occurrence of polygon-shaped patterns in vibrated cylindrical granular beds

We report experimental observations of polygon-shaped patterns formed in a vertically vibrated bed of circular cross-section. A phase map is determined, showing that the polygon pattern is established for Γ = A(2πf)2/g ≳ 10 . The sensitivity of the polygon structure to bed parameters was tested by studying beds of different particle sizes and fill levels. It was hypothesized that the polygon pattern observed in cylindrical beds is the corresponding pattern to the formation of arches in square-shaped beds. The close relationship between these two patterns was demonstrated by two observations: i) the radii of the arches of a corresponding square bed and the inner radius of the cylindrical bed were found to be very similar and ii) the boundary lengths of the two patterns were in good agreemen

Effect of periodic boundary conditions on granular motion in horizontal rotating cylinders modelled using the DEM

Applying periodic boundary conditions to DEM simulations of granular motion in horizontal, rotating cylinders can result in unexpected bulk axial flow. This axial flow is shown to contribute significantly to the mean square deviation in particle position and consequently must be considered in the analysis of processes governed by slow axial motion such as axial dispersio

Tangential velocity profiles of granular material within horizontal rotating cylinders modelled using the DEM

Flow regimes of granular materials in horizontal rotating cylinders are industrially important since they have a strong influence on the rates of heat and mass transfer within these systems. The tangential velocity profile, which describes how the average particle velocity in the direction parallel to the surface of the bed varies along a radius perpendicular to the surface of the bed, has been examined for many experimental and simulated systems. This paper is concerned with tangential velocity profiles within rotating cylinders simulated using the discrete element method. For high fill levels good agreement is found between the simulated velocity profiles and the equation proposed by Nakagawa etal. (Exp Fluids 16:54-60, 1993) based on magnetic resonance measurements. At lower fill levels slip is observed between the cylinder wall and the particles in contact with it and also between the outer layer of particles and the bulk of the bed. It is demonstrated that this slip occurs when the particles in contact with the wall are able to rotate and that it may be prevented either by using non-spherical particles or by attaching "lifters” to the cylinder wal

Critical Evaluation of Euler-Euler and Euler-Lagrangian Modelling Strategies in a 2-D Gas Fluidized Bed

Two-phase granular systems are commonly encountered in industry, and fluidized beds are particularly important due to their excellent heat and mass transfer characteristics. Here, we critically evaluate the differences between two modelling strategies, Euler-Euler and Euler-Lagrangian models. Euler-Euler simulations were performed using MFIX and an in-house code was used for Euler-Lagrangian simulations. A 2D bed of width, height and transverse thickness of respectively, 0.2 m, 0.5 m and 0.01 m, served as a test case. The settled bed height was H0 = 0.2 m. Particles of density ρ = 1000 kg/m³ and diameter dp = 1.2 mm were fluidized with air. The drag-law proposed by Benyahia et al. (10) was used in both models. Comparison between the simulation results was based on both instantaneous and time-averaged properties. A particular focus of this study was the influence of the coefficients of restitution and friction on the simulation results

Effect of particle shape on domino wave propagation: a perspective from 3D, anisotropic discrete element simulations

A fundamental understanding of the underlying physics of granular systems is not only of academic interest, but is also relevant for industrial applications. One specific aspect that is currently only poorly understood is the effect of particle shape on the dynamics of such systems. In this work the effect of particle shape on domino wave propagation was studied using 3D, anisotropic discrete element simulations. The dominoes were modelled using the three-dimensional super-quadric equation and very good agreement between the intrinsic collision speeds predicted by the simulations and the corresponding experimental data was observed. Furthermore, the influence of particle blockiness on the collision dynamics of dominoes was investigated numerically using particle shapes ranging from ellipsoids to almost cuboid particles. It was found that the intrinsic collision speed increased with increasing particle blockiness. It was also shown that a higher initial contact point favours the transmission of kinetic energy in the direction of the wave propagation, leading to a higher intrinsic collision speed for dominoes of higher blockiness

The silence of self-knowledge

Gareth Evans famously affirmed an explanatory connection between answering the question whether p and knowing whether one believes that p. This is commonly interpreted in terms of the idea that judging that p constitutes an adequate basis for the belief that one believes that p. This paper formulates and defends an alternative, more modest interpretation, which develops from the suggestion that one can know that one believes that p in judging that p

The use of mannan antigen and anti-mannan antibodies in the diagnosis of invasive candidiasis: recommendations from the Third European Conference on Infections in Leukemia

Many drugs are available for the treatment of systemic or superficial mycoses, but only a limited number of them are effective antifungal drugs, devoid of toxic and undesirable side effects. Furthermore, resistance development and fungistatic rather than fungicidal activities represent limitations of current antifungal therapy. Therefore there remains an urgent need for a new generation of antifungal agents. According to a polypharmacological approach, the present work concerns the synthesis and antifungal activity of a set of peptides designed to simultaneously target the fungal cell surface and lanosterol demethylase, a key enzyme involved in ergosterol synthesis. Our peptides include amino acid sequences characteristic of membrane-active antimicrobial peptides (AMP), and due to the presence of His residues, they carry the imidazole ring characteristic of azole compounds. The peptides synthesized by us, were tested against different yeast species, and displayed general antifungal activity, with a therapeutically promising antifungal specificity against Cryptococcus neoformans