Mesoscopic Approach Research Articles

Normal red blood cells\u2019 shape stabilized by membrane\u2019s in-plane ordering

Red blood cells (RBCs) are present in almost all vertebrates and their main function is to transport oxygen to the body tissues. RBCs’ shape plays a significant role in their functionality. In almost all mammals in normal conditions, RBCs adopt a disk-like (discocyte) shape, which optimizes their flow properties in vessels and capillaries. Experimentally measured values of the reduced volume (v) of stable discocyte shapes range in a relatively broad window between v ~ 0.58 and 0.8. However, these observations are not supported by existing theoretical membrane-shape models, which predict that discocytic RBC shape is stable only in a very narrow interval of v values, ranging between v ~ 0.59 and 0.65. In this study, we demonstrate that this interval is broadened if a membrane’s in-plane ordering is taken into account. We model RBC structures by using a hybrid Helfrich-Landau mesoscopic approach. We show that an extrinsic (deviatoric) curvature free energy term stabilizes the RBC discocyte shapes. In particular, we show on symmetry grounds that the role of extrinsic curvature is anomalously increased just below the nematic in-plane order-disorder phase transition temperature.

Modelling heterogeneous coal-rock (HCR) failure patterns under dynamic impact loads using image-based finite element (FE) and discrete element (DE) model

The paper described two different numerical 3D mesoscopic approaches (the meso-scale image-based FE and DE model) for quantitative and qualitative characterization of the dynamic impact mechanical behavior of HCR. The 3D meso-structure of HCR in calculations, which was directly obtained from real coal rock specimen using non-destructive XCT techniques, was modelled as a random heterogeneous two-phase material composed of coal and gangue respectively. Dynamic impact loading in three directions (x-, y-, and z-axis) were modelled to investigate the 3D meso-structure and different input energies effects on failure patterns of HCR. The very different qualitative and quantitative results demonstrated that the spatial distribution of mineral phases, loading directions and input energies have pronounced influenced on material strength as well as failure patterns of heterogeneous rock materials. The XCT image-based numerical model proved to be an effective tool that gives insights into the meso-deformation mechanisms of HCR undergoing dynamic impact failure behavior.

DeNeRD: high-throughput detection of neurons for brain-wide analysis with deep learning

Mapping the structure of the mammalian brain at cellular resolution is a challenging task and one that requires capturing key anatomical features at the appropriate level of analysis. Although neuroscientific methods have managed to provide significant insights at the micro and macro level, in order to obtain a whole-brain analysis at a cellular resolution requires a meso-scopic approach. A number of methods can be currently used to detect and count cells, with, nevertheless, significant limitations when analyzing data of high complexity. To overcome some of these constraints, we introduce a fully automated Artificial Intelligence (AI)-based method for whole-brain image processing to Detect Neurons in different brain Regions during Development (DeNeRD). We demonstrate a high performance of our deep neural network in detecting neurons labeled with different genetic markers in a range of imaging planes and imaging modalities.

Mesoscopic approach for simulating nanofluid flow and heat transfer in a finned multi-pipe heat exchanger

PurposeThe lattice Boltzmann method is used to simulate the nanofluid flow and heat transfer inside a finned multi-pipe heat exchanger.Design/methodology/approachThe heat exchanger is filled with CuO-water nanofluid. The Koo–Kleinstreuer–Li (KKL) model is used to estimate the dynamic viscosity and considering the Brownian motion in the simulation. On the other hand, the influence of nanoparticles’ shapes on the heat transfer rate is considered, and the best efficient shape is selected to be used in the investigation.FindingsThe Rayleigh number, nanoparticle concentration and the thermal arrangements of internal active fins and bodies are the governing parameters. In addition, the impacts of these two parameters on the nanofluid flow, heat transfer rate, local and total entropy generation and heatline visualization are analyzed, comprehensively.Originality/valueThe originality of this work is using of lattice Boltzmann method for simulation of nanofluid flow and heat transfer during natural convection in a heat exchanger. Furthermore, influence of the shape of nanoparticles on the thermo-physical properties of nanofluid is analyzed using Koo–Kleinstreuer–Li correlation.

Predicting the drug loading efficiency into hybrid nanocarriers based on PLGA-vegetable oil using molecular dynamic simulation approach and Flory-Huggins theory

The main goal of this study was to predict the capacity of the hybrid nanoparticles based on poli (lactic-co-glycolic acid) PLGA-vegetable oil to encapsulate and then to release a bioactive compound. Therefore, the compatibility of different drugs molecules, taking into account the chemical structure, solubility, partition coefficient (log P) with the standard PLGA or hybrid polymer-oil matrix was studied, quantifying the quality of interactions between polymeric matrix and the encapsulated drug using Flory-Huggins theory and computational mesoscopic (MesoDyn) approach. All the drugs-loaded formulations were obtained by emulsion solvent evaporation method. The main parameters such as hydrodynamic characteristics, encapsulation efficiency and release profiles were studied and correlated with the compatibility parameter, drug's partition coefficient and computational mesoscopic simulation. Drugs solubilization, respectively its distribution and loading into a formulation was found to be reliant on the system's compatibility, calculated by the Flory-Huggins interaction parameter (χ), while the drug's partition coefficient has proven to be a key influencer in the drug release kinetics. A consistent correlation of experimental results, computational data and thermodynamic theory was observed for lipophilic drugs, while for more hydrophilic drugs some discrepancy between the experimental/theoretical and computational modelling results was registered.

Multiaxial High Cycle Fatigue Criteria Based on Fracture Plane Identification: Applicability to Metallic Materials

Two multiaxial high cycle fatigue criteria pertaining to the critical plane-based approach are reviewed. The models were proposed by Carpinteri and Spagnoli (C&S) and Liu and Mahadevan (L&M), and unlike other models based on the same approach, they have the critical plane directly correlated with the fatigue fracture plane. As the aim of this study is mainly to compare their capability to predict fatigue failure, the two models were applied to a number of published experimental fatigue tests, involving synchronous sinusoidal in-phase and out-of-phase bending and torsion. The results indicate that both models possess good predictive capability under fully reversed stresses, with the L&M model being on the average slightly more conservative. Applying, to the same loading conditions, a mesoscopic scale-based approach proposed by Papadopoulos, one can verify that its predictive capability is as good as those corresponding to the C&S and L&M criteria. However, in the presence of superimposed mean stresses, the capability of these two models to predict fatigue behavior is seen to be considerably lower than that detected for Papadopoulos’.

Co-emergence and Collapse: The Mesoscopic Approach for Conceptualizing and Investigating the Functional Integration of Organisms.

The fall of reductionist approaches to explanation leaves biology with an unescapable challenge: how to decipher complex systems. This entails a number of very critical questions, the most basic ones being: “What do we mean by ‘complex’?” and “What is the system we should look for?” In complex systems, constraints belong to a higher level that the molecular one and their effect reduces and constrains the manifold of the accessible internal states of the system itself. Function is related but not deterministically imposed by the underlying structure. It is quite unlikely that such kind of complexity could be grasped by current approaches focusing on a single organization scale. The natural co-emergence of systems, parts and properties can be adopted as a hypothesis-free conceptual framework to understand functional integration of organisms, including their hierarchical or multilevel patterns, and including the way scientific practice proceeds in approaching such complexity. External, “driving” factors – order parameters and control parameters provided by the surrounding microenvironment – are always required to “push” the components’ fate into well-defined developmental directions. In the negative, we see that in pathological processes such as cancer, organizational fluidity, collapse of levels and dynamic heterogeneity make it hard to even find a level of observation for a stable explanandum to persist in scientific practice. Parts and the system both lose their properties once the system is destabilized. The mesoscopic approach is our proposal to conceptualizing, investigating and explaining in biology. “Mesoscopic way of thinking” is increasingly popular in the epistemology of biology and corresponds to looking for an explanation (and possibly a prediction) where “non-trivial determinism is maximal”: the “most microscopic” level of organization is not necessarily the place where “the most relevant facts do happen.” A fundamental re-thinking of the concept of causality is also due for order parameters to be carefully and correctly identified. In the biological realm, entities have relational properties only, as they depend ontologically on the context they happen to be in. The basic idea of a relational ontology is that, in our inventory of the world, relations are somehow prior to the relata (i.e., entities).

A Critical Analysis of Behavioural Crowd Dynamics—From a Modelling Strategy to Kinetic Theory Methods

This paper proposes a critical analysis of the literature addressed to modelling and simulations of human crowds with the aim of selecting the most appropriate scale out of the microscopic (individual based), mesoscopic (kinetic), and macroscopic (hydrodynamical) approaches. The selection is made focusing on possible applications of the model. In particular, model validation and safety problems, where validation consists of studying the ability of models to depict empirical data and observed emerging behaviors. The contents of the paper look forward to computational applications related to the flow crowds on the Jamarat bridge.

On the thermal forming limit diagram (TFLD) with GTN mesoscopic damage model for AA7075 aluminum alloy: Numerical and experimental investigation

The formability of high strength AA7075 aluminum alloy under elevated temperatures is vital in guiding the fabrication of automobile structural parts. The ductile fracture forming limit of AA7075 at elevated temperatures is essentially governed by thermal damage evolution. In this paper, the hot tensile test (300ºC-450 °C, strain rate 0.1s−1-0.001s−1) for AA7075 was conducted and the corresponding flow behavior was fitted by Hensiel-Spittel (HS) constitutive equation. The GTN mesoscopic damage model was implemented to take account of the damage evolution phenomenon of AA7075 at elevated temperatures. The temperature-dependent damage void volume fractions (VVF) were identified accurately based on a novel inverse identification procedure, named the CCD parameters design-FEM inverse simulation-genetic algorithm (CCD-FEIS-GA) optimization method. Subsequently, the thermal forming limit diagram (TFLD) was calculated based on the GTN damage parameters and further validated by hot Nakajima-type bulging experiment. The corresponding damage evolution behaviors and effects of critical forming parameters were discussed in detail. The comparison of experimental and numerical results showed that the formability of AA7075 firstly increases and then decreases with the increasing forming temperature, the TFLD0 reaches its maximum value when the temperature is 400 °C, and the formability also increases with the increasing strain rate and the decreasing surface coefficient of friction. The proposed simulated strategy coupled with mesoscopic GTN approach conduces to the accurate prediction of TFLD and damage fracture behavior of AA7075 in the hot forming process.

The fixed-strut-angle finite element (FSAFE) model for reinforced concrete structural walls

This paper evaluates the capabilities and limitations of a relatively simple mesoscopic finite element modeling approach, referred to as the Fixed Strut Angle Finite Element (FSAFE) Model, in simulating the hysteretic lateral load behavior of reinforced concrete structural walls designed to yield in flexure. The behavioral characteristics of the constitutive panel (membrane) elements incorporated in the model are based on a simple fixed-crack-angle formulation, where normal stresses in concrete are calculated along fixed crack directions using a uniaxial stress–strain relationship, with modifications to represent biaxial softening effects. The constitutive panel model formulation also incorporates behavioral models for the shear-aggregate-interlock effects in concrete and dowel action on reinforcing bars, constituting the shear stress transfer mechanisms across cracks. Model predictions are compared with experimentally-measured responses of benchmark wall specimens with a variety of configurations and response characteristics. Accurate predictions are obtained for important global response attributes of the walls prior to failure, including their lateral load capacity, stiffness, ductility, and hysteretic response characteristics; although instability failures related to buckling of reinforcement and/or out-of-plane instability of the wall boundary region are not captured. The model provides accurate estimates of the relative contribution of nonlinear flexural and shear deformations to wall lateral displacements, as well as local response characteristics including the distribution of curvatures, strains, and shear deformations on the walls, prior to failure. Based on the response comparisons presented, model capabilities are assessed and possible model improvements are identified. Overall, the FSAFE model is shown to be a practical yet reliable modeling approach for simulating nonlinear wall behavior, which can be used within the framework of performance-based seismic design and assessment of building structures.

Resummed Kinetic Field Theory: using Mesoscopic Particle Hydrodynamics to describe baryonic matter in a cosmological framework

We present a new analytical description of baryonic matter in a cosmological framework, using the formalism of “Kinetic Field Theory” (KFT)—a statistical field theory approach to structure formation based on the dynamics of classical particles. So far, only the purely gravitational dynamics of dark matter had been considered in KFT, but an accurate description of cosmic structure formation requires to also take into account the baryonic gas dynamics. In this paper, we propose to achieve this by incorporating an effective mesoscopic particle model of hydrodynamics into the recently developed framework of Resummed KFT. Our main result is the baryonic density contrast power spectrum computed to lowest perturbative order, assuming a simplified isothermal fluid model. Compared to the spectrum of dark matter, the baryonic spectrum shows a suppression of power as well as an oscillatory behaviour associated with sound waves on scales smaller than the Jeans length. We further compare our result to the linear spectrum of an isothermal fluid obtained from Eulerian perturbation theory (EPT), finding good quantitative agreement within the approximations we made in the EPT calculation. A subsequent paper will resolve the problem of coupling both dark and baryonic matter, to gain a full model of cosmic matter. Applying the mesoscopic particle approach to more general ideal or viscous fluids will also be subject of upcoming work.

The entropy production of Ornstein–Uhlenbeck active particles: a path integral method for correlations

By employing a path integral formulation, we obtain the entropy production rate for a system of active Ornstein–Uhlenbeck particles (AOUP) both in the presence and in the absence of thermal noise. The present treatment clarifies some contraddictions concerning the definition of the entropy production rate in the AOUP model, recently appeared in the literature. We derive explicit formulas for three different cases: overdamped Brownian particle, AOUP with and without thermal noise. In addition, we show that it is not necessary to introduce additional hypotheses concerning the parity of auxiliary variables under time reversal transformation. Our results agree with those based on a previous mesoscopic approach.

Finite element method analysis of fibre-metal laminates considering different approaches to material model

In this work, different approaches to fibre-metal laminates modelling are presented. Micromechanical, mesomechanical and macromechanical models are discussed. The application of these approaches for exemplary fibre-metal laminate made of aluminium and epoxy resin/glass fibre layers are shown. The classical laminate theory was used to obtain engineering constants for the macroscopic solid model and Puck criterion to obtain material data about epoxy resin/glass fibre layer. Various simulations using different simulation techniques were carried out in Simulia ABAQUS environment and results were compared with experimental data found in the literature. In conclusions, described approaches from the viewpoint of numerical simulation and experiment were evaluate. Research proves that mesoscopic (with distinguished layers of material) approach along with solid model gives the best results.

Lattice Boltzmann approach for MagnetoHydroDynamic convective heat transfer

Magneto-convection heat transfer mode inside a partially open-ended 2D enclosure, which is filled with conducting fluid, is considered as suitable research model in order to scope out our understanding into frequent decisive practicable applications in sustainable and renewable energy domains, especially solar energy collectors. Nevertheless surprising, continuously there is no existing literature dealing with it. Further, for Computational Fluid Dynamics (CFD)’s approaches, it is a considerable defiance to predict and anticipate this coupled complex physical engineering problem in MagnetoHydroDynamic (MHD) configurations. In the current numerical prototype, we introduce the lattice Boltzmann method (LBM) in the aim to overcome such engineering simulation difficulty. It is to be noted that this mesoscopic approach becomes nowadays an essential attractive and alternative for CFD approaches to simulate complex numerous fluid flow problems. ) has become an alternative and attractive approach to simulate numerous fluid flow problems. This paper intends to provide a brief review of researches on application of MHD convection with LBM on the prediction of thermodynamic behavior identifying more opportunities for future research. Besides, some new results are highlighted within this paper. To begin, the present LB model is validated against existing benchmark tests in literature. With the handout of this in house Fortran 90 LB code, we investigate the effects of Hartmann number, Rayleigh number, Prandtl number and the position of the partially open-ended side in the magneto-convective partially open ended y filled with conducting fluid cavity primly. It is established that these elements all impact flow and temperature fields patterns significantly. The obtained results can serve crucial theoretical prototypes for the related future practical magneto-convective applications. Our finding will be a useful tool allowing identifying opportunities for future research related to the considered engineering area.

Predicting the elastic properties of closed-cell aluminum foams: a mesoscopic geometric modeling approach

The biggest challenge in predicting the elastic properties of closed-cell aluminum foams is capturing the actual geometrical and topological characteristics precisely and efficiently such that the model can be used to predict the mechanical properties of the real foam accurately. This paper presents a mesoscopic modeling approach for constructing a geometric model that captures these characteristics and can be used to predict its elastic properties. The modeling approach introduces a new method for finding the number of seeds based on the cell diameter distribution and an algorithm for computing and assigning the irregular cell wall thickness based on reverse bubble growth. Results from the foam models developed in this work were found to have better accuracy in capturing the geometrical and topological characteristics of the real foam. All foam models generated by the proposed modeling approach have the same cell size distribution and irregular cell wall distribution as the real foam. The models have cells with around 14 faces with 5 edges on each face which is similar to real metal foams and naturally occurring foams. Numerical results from the foam models showed a better accuracy in predicting the relative Young’s modulus of the real foam than the generic Laguerre–Voronoi, Kelvin, and Grenestedt models.

DEM/CFD Simulations of a Pseudo-2D Fluidized Bed: Comparison with Experiments

The present work investigates the performance of a mesoscopic LaGrangian approach for the prediction of gas–particle flows under the influence of different physical and numerical parameters. To this end, Geldart D particles with 1 mm diameter and density of 2500 kg/m 3 are simulated in a pseudo-2D fluidized bed using a Discrete Element Method (DEM)/Large-Eddy Simulation (LES) solver called YALES2. Time-averaged quantities are computed and compared with experimental results reported in the literature. A mesh sensitivity analysis showed that better predictions regarding the particulate phase are achieved when the mesh is finer. This is due to a better description of the local and instantaneous gas–particle interactions, leading to an accurate prediction of the particle dynamics. Slip and no-slip wall conditions regarding the gas phase were tested and their effect was found negligible for the simulated regimes. Additional simulations showed that increasing either the particle–particle or the particle–wall friction coefficients tends to reduce bed expansion and to initiate bubble formation. A set of friction coefficients was retained for which the predictions were in good agreement with the experiments. Simulations for other Reynolds number and bed weight conditions are then carried out and satisfactory results were obtained.

The effect of vertical ground movement on masonry walls simulated through an elastic–plastic interphase meso-model: a case study

The present paper proposes an interphase model for the simulation of damage propagation in masonry walls in the framework of a mesoscopic approach. The model is thermodynamically consistent, with constitutive relations derived from a Helmholtz free potential energy. With respect to classic interface elements, the internal stress contribute is added to the contact stresses. It is considered that damage, in the form of loss of adhesion or cohesion, can potentially take place at each of the two blocks–mortar physical interfaces. Flow rules are obtained in the framework of the Theory of Plasticity, considering bilinear domains of ‘Coulomb with tension cut-off’ type. The model aims to be a first research step to solve the inverse problem of damage propagation in masonry generated by vertical ground movements, in order to ex-post identify the cause of a visible damage. The constitutive model is written in a discrete form for its implementation in a research-oriented finite element program. The response at the quadrature point is analyzed first. Then, the model is validated through comparisons with experimental results and finally employed to simulate the failure occurred in a wall of an ancient masonry building, where an arched collapse took place due to a lowering of the ground level under part of its foundation.

A coupled Lattice Boltzmann approach to simulate gas flow and transport in shale reservoirs with dynamic sorption

Gas flow in a shale reservoir is hard to model and simulate as certain complex mechanisms should be included, for example, diffusion and sorption. As a mesoscopic approach, Lattice Boltzmann Methods can capture the flow behavior in both scales: free flow through the conventional pore channels and gas transport with sorption in the tight matrix with very small pores. In this paper, two Lattice Boltzmann (LB) schemes are presented to recover the Navier-Stokes equations and advection diffusion equation respectively, to model the flow and transport in the two scales. The Navier-Stokes type LB scheme is constructed to model the free flow in fractures and conventional pore channels in matrix, and the convection diffusion type LB scheme is constructed to model the transport in tight matrix with very small pores. Chapman-Enskog expansions are derived to show the equivalence of the two LB schemes with the two macroscopic equations. Dynamic sorption is included in the advection diffusion with the dependance of gas concentration and free flow velocities, and the absorbed amount can affect the free flow velocity as well. In our simulation of gas flow and transport in shale reservoirs, the media is generated through two methods, reading a realistic media image and generating using a pore-network model. The rock characteristics are preserved in our generated porous media, with the method we proposed to link the LB scheme with the pore network modeling method. The simulation results are reasonable to prove that our schemes are robust and efficient, and the effect of porosity and sorption parameters are presented. Furthermore, the interaction of the two-scale gas flow and transport is analyzed, and we show that the increasing adsorbed gas amount in matrix may not slow down the free flow velocity as this increase may be resulted from changes in the rock characteristics. The scheme is simple to understand and implement, because only a few modifications are needed to construct the LB schemes on the two scales.

Modeling of 3D moisture distribution in heated concrete: From continuum towards mesoscopic approach

The exposure of concrete to fire, which often leads to spalling, is a phenomenon that is not yet fully understood. Given the complexity of the thermo-hydro-mechanical phenomena and their strong interaction, a combined numerical-experimental approach is indispensable for understanding the behaviour of concrete at high temperature with respect to spalling. This paper deals with the numerical modeling of moisture distribution in heated concrete, a parameter often linked with spalling, by making use of original experimental data from in-situ neutron tomography. A homogenized continuum model has been employed for investigating various aspects, such as: speed of the drying front, moisture accumulation behind this front, experimental boundary effects etc. In addition, a fully coupled 3D thermo-hydo-mechanical (THM) model on the mesoscale is presented and used for simulating an experiment with a single aggregate for the purpose of investigating the influence of the aggregate on the drying front.

Giant electrocaloric response in smectic liquid crystals with direct smectic-isotropic transition

Electrocaloric materials have become a viable technology for solid state heat management applications. We demonstrate both theoretically and experimentally that liquid crystals (LCs) can be exploited as efficient electrocaloric materials. Numerical and experimental investigations determine the conditions under which the strongest electrocaloric effect (ECE) responses are expected in LCs. Specifically, we show that a large ECE can be expected at the isotropic-nematic and in particular at the isotropic-smectic A phase transition. In our theoretical study, LC ordering is modelled using a Landau – de Gennes - Ginzburg mesoscopic approach. The simulation results are in qualitative agreement with our high precision electrocaloric measurements conducted on 8CB and 12CB liquid crystals. In the latter, we obtained ΔTEC ~ 6.5 K, corresponding to the largest response measured so far in LCs. The fluid property of LC electrocaloric heat cooling elements could lead to the development of devices with a higher coefficient of performance and thus better cooling power yield per mass of the ECE-based device.