Interaction of particles via solid interface: model and analysis

The paper addresses discrete element (DEM) models of the heterogeneous particulate solids where the normal interaction between two deformable spherical particles bonded via weaker solid interface is considered. The integral interaction model aimed for evaluation of the bond stiffness was developed, where analytical expressions of the stiffness parameters reflecting individual contribution of the two particles and of the interface properties are derived. Application of the developed DEM model to particulate solid with many particles is considered. The accuracy and the suitability of this approach are evaluated by considering refined 3D Finite Element analysis

Loading characteristics of weight stack machines

The load characteristics of the weight stack machines, where the resistance is generated by inertia of the stack of masses, are the subject of the paper. The method and means of experimental research are described. The dependencies of inertial resistance load upon the rate of exercises and the stack weight are determine

A planar surface acoustic wave micropump for closed-loop microfluidics

We have designed and characterized a simple Rayleigh-surface acoustic wave-based micropump, integrated directly with a fully enclosed 3D microfluidic system, which improves significantly the pumping efficiency within a coupled fluid whilst maintaining planar integration of the micropump and microfluidics. We achieve this by exploiting the Rayleigh-scattering angle of surface acoustic waves into pressure waves on contact with overlaid fluids, by designing a microfluidic channel aligned almost co-linearly with the launched pressure waves and by minimizing energy losses by reflections from, or absorption within, the channel walls. This allows the microfluidic system to remain fully enclosed—a pre-requisite for point-of-care applications—removing sources of possible contamination, whilst achieving pump efficiencies up to several orders of magnitude higher than previously reported, at low operating powers of 0.5 W

Rapid cell separation with minimal manipulation for autologous cell therapies

The ability to isolate specific, viable cell populations from mixed ensembles with minimal manipulation and within intra-operative time would provide significant advantages for autologous, cell-based therapies in regenerative medicine. Current cell-enrichment technologies are either slow, lack specificity and/or require labelling. Thus a rapid, label-free separation technology that does not affect cell functionality, viability or phenotype is highly desirable. Here, we demonstrate separation of viable from non-viable human stromal cells using remote dielectrophoresis, in which an electric field is coupled into a microfluidic channel using shear-horizontal surface acoustic waves, producing an array of virtual electrodes within the channel. This allows high-throughput dielectrophoretic cell separation in high conductivity, physiological-like fluids, overcoming the limitations of conventional dielectrophoresis. We demonstrate viable/non-viable separation efficacy of > 98% in pre-purified mesenchymal stromal cells, extracted from human dental pulp, with no adverse effects on cell viability, or on their subsequent osteogenic capabilities

Symulacja oddziaływania cząstek ze sprężysto-lepkim ośrodkiem metodą elementów skończonych

This paper addresses the 3D FE simulation of the normal interaction of stiff but deformable particles in binder matrix on the meso-scale. The particles are assumed to be elastic spheres while matrix is considered as viscoelastic solid. The investigation is aimed to capture interaction in terms of normal forces under tension. The problem is considered by applying geometrically linear and nonlinear approaches. Results illustrate influence of initial interparticle gap reduction of which yields significant increase of the interaction force. Comparison between purely elastic and viscoelastic solutions is also presented.Niniejszy artykuł dotyczy trójwymiarowej symulacji metodą elementów skończonych oddziaływania w kierunku normalnym sztywnych, ale odkształcalnych cząstek w spoistej osnowie na poziomie mezoskopowym. Cząstki są traktowane jako sprężyste kule, zaś osnowa jako ciało lepkosprężyste. Badania mają na celu znalezienie sił oddziaływania pod obciążeniem. Zagadnienie jest rozpatrywane przy zastosowaniu modelu geometrycznie liniowego i nieliniowego. Wyniki pokazują wpływ wstępnego zmniejszenia odstępu na znaczący wzrost siły oddziaływania. Przedstawione jest również porównanie między rozwiązaniem sprężystym i lepkosprężystym

Behaviour of radiogenic Pb in zircon during ultrahigh-temperature metamorphism: an ion imaging and ion tomography case study from the Kerala Khondalite Belt, southern India

Zircon crystals from a locally charnockitized Paleoproterozoic high-K metagranite from the Kerala Khondalite Belt (KKB) of southern India have been investigated by high-spatial resolution secondary ion mass spectrometry analysis of U-Th-Pb and rare earth elements (RE), together with scanning ion imaging and scanning ion tomography (depth-profiled ion imaging). The spot analyses constrain the magmatic crystallization age of the metagranite to ca. 1,850 Ma, with ultrahigh-temperature (UHT) metamorphism occurring at ca. 570 Ma and superimposed charnockite formation at ca. 520-510 Ma, while the ion imaging reveals a patchy distribution of radiogenic Pb throughout the zircon cores. Middle-to heavy-RE depletion in ca. 570 Ma zircon rims suggests that these grew in equilibrium with garnet and therefore date the UHT metamorphism in the KKB. The maximum apparent Pb-207/Pb-206 age obtained from the unsupported radiogenic Pb concentrations is also consistent with formation of the Pb patches during this event. The superimposed charnockitization event appears to have caused additional Pb-loss in the cores and recrystallization of the rims. The results of depth-profiling of the scanning ion tomography image stack show that the Pb-rich domains range in size from <5 nm to several 10 nm (diameter if assumed to be spherical). The occurrence of such patchy Pb has previously been documented only from UHT metamorphic zircon, where it likely results from annealing of radiation-damaged zircon. The formation of a discrete, heterogeneously distributed and subsequently immobile Pb phase effectively arrests the normal Pb-loss process seen at lower grades of metamorphism

Concentrations of metallothionein in the bivalve molluscs Anodonta spp. and Unio spp. from Latvian lakes with different anthropogenic pressure

Concentrations of metallothioneins (MT) were analysed in bivalve molluscs Anodonta spp. and Unio spp. from 6 lakes and watercourses of Latvia with different anthropogenic pressure. The aim of the study was to find the relationship between MT in molluscs and concentrations of heavy metals in sediments. Unio spp. and Anodonta spp. showed no significant differences in the concentrations of MT. High concentrations of heavy metals (Cd, Pb, Hg, Cu, Zn) were detected in the deepest parts of polluted water bodies, however their concentrations significantly decreased in near shore sediments inhabited by molluscs. Only Zn tends to accumulate in the molluscs, reaching 2-7 times higher concentrations in organisms than in sediments. There was statistically significant correlation between MT and Hg due to high affinity of Hg to MT-complex. Concentrations of Hg and MT in molluscs were related also to condition index of molluscs, suggesting that accumulation of heavy metals in molluscs depends on their physiological status

Interaction of particles via solid interface: model and analysis

The paper addresses discrete element (DEM) models of the heterogeneous particulate solids where the normal interaction between two deformable spherical particles bonded via weaker solid interface is considered. The integral interaction model aimed for evaluation of the bond stiffness was developed, where analytical expressions of the stiffness parameters reflecting individual contribution of the two particles and of the interface properties are derived. Application of the developed DEM model to particulate solid with many particles is considered. The accuracy and the suitability of this approach are evaluated by considering refined 3D Finite Element analysis

Concentrations of metallothionein in the bivalve molluscs

Concentrations of metallothioneins (MT) were analysed in bivalve molluscs Anodonta spp. and Unio spp. from 6 lakes and watercourses of Latvia with different anthropogenic pressure. The aim of the study was to find the relationship between MT in molluscs and concentrations of heavy metals in sediments. Unio spp. and Anodonta spp. showed no significant differences in the concentrations of MT. High concentrations of heavy metals (Cd, Pb, Hg, Cu, Zn) were detected in the deepest parts of polluted water bodies, however their concentrations significantly decreased in near shore sediments inhabited by molluscs. Only Zn tends to accumulate in the molluscs, reaching 2-7 times higher concentrations in organisms than in sediments. There was statistically significant correlation between MT and Hg due to high affinity of Hg to MT-complex. Concentrations of Hg and MT in molluscs were related also to condition index of molluscs, suggesting that accumulation of heavy metals in molluscs depends on their physiological status

Loading characteristics of weight stack machines

The load characteristics of the weight stack machines, where the resistance is generated by inertia of the stack of masses, are the subject of the paper. The method and means of experimental research are described. The dependencies of inertial resistance load upon the rate of exercises and the stack weight are determine