a b s t r a c tIn this paper, we introduce a new scale called the meso-scale in order to define an appropriate local scale for multi-scale kinematic analysis in granular materials. The proposed meso-scale corresponds to subdomains obtained by subdividing a 2D granular assembly taking into account load-bearing contacts. For each sub-domain, a strain tensor is defined and a description of its structure is proposed. Our analysis, carried out on a biaxial compression test, reveals that strain is significantly related to the structure at the meso-scale: (1) strain in the major (respectively, minor) principal compression direction is largest within the sub-domains which are elongated in the minor (respectively, major) principal compression direction, and (2) contractancy takes place within the sub-domains which are elongated in the minor principal compression direction whereas dilatancy takes place within the sub-domains which are elongated in the major principal compression direction. Furthermore, we emphasize a relation between strain at the meso-scale and the induced anisotropy of granular materials during deviatoric loading.
SUMMARYThe purpose of this paper is to contribute to the change of scale techniques developed for granular materials. The proposed approach consists in considering an intermediate scale between the macroscales and microscales, called the mesoscale, using the classical homogenization scheme. In this approach, the mesoscale for 2D granular materials was defined at the level of local volumes, called mesodomains, which are local closed structures composed of particles in contact. In this paper, we focused on defining a local stress field at this scale. Two different methods are proposed, both based on the equivalent continuum mean stress but using different approximations of the mean stress tensor for each mesodomain. The two proposed methods were then compared to each other. Analyses performed on the stress field at the mesoscale show that this local field is heterogeneous and, in particular, that its heterogeneity is significantly structured at this scale. The distribution of the local mean stress (first invariant of the local stress tensor) is uniform in any mesodomain, whereas the distribution of the stress deviator (second invariant of the deviatoric part of the local stress tensor) is significantly dependent on the elongation direction and on the elongation degree of the mesodomains. The local stress ratio (ratio of the stress deviator to the mean stress) is higher within the mesodomains that are elongated in the global compression direction than that within the ones elongated in the global extension direction.
Abstract:A new series of benzylaminochalcone derivatives with different substituents on ring B were synthesized and evaluated as inhibitors of acetylcholinesterase. The study is aimed at identification of novel benzylaminochalcones capable of blocking acetylcholinesterase activity for further development of an approach to Alzheimer's disease treatment. These compounds were produced in moderate to good yields via Claisen-Schmidt condensation and subjected to an in vitro acetylcholinesterase inhibition assay, using Ellman's method. The in silico docking procedure was also employed to identify molecular interactions between the chalcone compounds and the enzyme. Compounds with ring B bearing pyridin-4-yl, 4-nitrophenyl, 4-chlorophenyl and 3,4-dimethoxyphenyl moieties were discovered to exhibit significant inhibitory activities against acetylcholinesterase, with IC 50 values ranging from 23 to 39 µM. The molecular modeling studies are consistent with the hypothesis that benzylaminochalcones could exert their effects as dual-binding-site acetylcholinesterase inhibitors, which might simultaneously enhance cholinergic neurotransmission and inhibit β-amyloid aggregation through binding to both catalytic and peripheral sites of the enzyme. These derivatives could be further developed to provide novel leads for the discovery of new anti-Alzheimer drugs in the future.
This paper presents a numerical study of the effect of fine content on the mechanical behavior of gap-graded granular materials using the discrete element method. Triaxial compression tests are performed on different samples with fine contents varied from 0% to 40%. It was found that, starting from 20%, fine content has a visible effect on the shear strength. The optimal fine content is about 30%, at which the shear strength is the best. An investigation into the granular micro-structure showed that the fine particles, on one hand, come into contact with coarse particles, but on the other hand, separate the latter ones as fine content increases beyond 20%. Consequently, the shear stress is transmitted more and more through the coarse-fine contacts but less and less through the coarse-coarse contacts. For fine content ≤ 30%, the coarse-coarse contacts primarily carry the shear stress. Above this optimal fine content, the fine-coarse contacts overtake the coarse-coarse ones. The fine-fine contacts have little contribution to supporting the shear stress. For the studied range of fine content, the coarse particles primarily carry the shear stress, leaving the fine particles under relatively low stresses. Moreover, the fine particles are greatly softened by the shear loading. A classification of binary mixtures depending on their micro-structure was also proposed.
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