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Traditional methods for measuring single-cell mechanical characteristics face several challenges, including lengthy measurement times, low throughput, and a requirement for advanced technical skills. To overcome these challenges, a novel machine learning (ML) approach is implemented based on the convolutional neural networks (CNNs), aiming at predicting cells' elastic modulus and constitutive equations from their deformations while passing through micro-constriction channels. In the present study, the computational fluid dynamics technology is used to generate a dataset within the range of the cell elastic modulus, incorporating three widely-used constitutive models that characterize the cellular mechanical behavior, i.e., the Mooney-Rivlin (M-R), Neo-Hookean (N-H), and Kelvin-Voigt (K-V) models. Utilizing this dataset, a multi-input convolutional neural network (MI-CNN) algorithm is developed by incorporating cellular deformation data as well as the time and positional information. This approach accurately predicts the cell elastic modulus, with a coefficient of determination R2 of 0.999, a root mean square error of 0.218, and a mean absolute percentage error of 1.089%. The model consistently achieves high-precision predictions of the cellular elastic modulus with a maximum R2 of 0.99, even when the stochastic noise is added to the simulated data. One significant feature of the present model is that it has the ability to effectively classify the three types of constitutive equations we applied. The model accurately and reliably predicts single-cell mechanical properties, showcasing a robust ability to generalize. We demonstrate that incorporating deformation features at multiple time points can enhance the algorithm's accuracy and generalization. This algorithm presents a possibility for high-throughput, highly automated, real-time, and precise characterization of single-cell mechanical properties. [ABSTRACT FROM AUTHOR]

Summary: Properties of a cell can determine its deformations, which can aggravate cancer metastasis. In laboratory, microfluidic technology has been adopted to study cell deformations. However, quantifying the effects of cell deformations has remained difficult. To this end, this paper presents a two‐dimensional particle‐based model that can capture flow‐induced cell deformations in a microchannel. The numerical model is validated with an experimental dataset for MCF7 cell. The simulations show that cell deformations are dominantly attributed to flow acceleration. Stress analyses, conducted by inputting the simulated cell deformations as boundary conditions, show that the maximum normal stresses correspond well to high deformations. Shear stress is in general proportional to the cell's distance from a wall. The simulations also suggest a deformed cell shape that apparently may reduce the average normal stresses. This study highlights the potential of the numerical model to relate the measurable cell deformations to the more elusive cell properties. [ABSTRACT FROM AUTHOR]

Microfluidic phenotyping methods have been of vital importance for cellular characterization, especially for evaluating single cells. In order to study the deformability of a single cell, we devised and tested a tunable microfluidic chip-based method. A pneumatic polymer polydimethylsiloxane (PDMS) membrane was designed and fabricated abutting a single-cell trapping structure, so the cell could be squeezed controllably in a lateral direction. Cell contour changes under increasing pressure were recorded, enabling the deformation degree of different types of single cell to be analyzed and compared using computer vision. This provides a new perspective for studying mechanical properties of cells at the single cell level. HIGHLIGHTS: • A microfluidic chip with pneumatic PDMS membrane was proposed to achieve tunable lateral deformation of single cells. • Controllable cell squeezing was realized to study the deformation degree of single cells. • Computer vision was applied to exact cell contours and the deformation degrees of two cell types were compared. [ABSTRACT FROM AUTHOR]

Microfluidics is an increasingly popular method for studying cell deformation, with various applications in fields such as cell biology, biophysics, and medical research. Characterizing cell deformation offers insights into fundamental cell processes, such as migration, division, and signaling. This review summarizes recent advances in microfluidic techniques for measuring cellular deformation, including the different types of microfluidic devices and methods used to induce cell deformation. Recent applications of microfluidics-based approaches for studying cell deformation are highlighted. Compared to traditional methods, microfluidic chips can control the direction and velocity of cell flow by establishing microfluidic channels and microcolumn arrays, enabling the measurement of cell shape changes. Overall, microfluidics-based approaches provide a powerful platform for studying cell deformation. It is expected that future developments will lead to more intelligent and diverse microfluidic chips, further promoting the application of microfluidics-based methods in biomedical research, providing more effective tools for disease diagnosis, drug screening, and treatment.

Two-microbubble collapse near a spherical cell in an ultrasonic field is numerically analyzed by extending a level-set method for compressible multiphase flows with bubble and cell multiple interfaces. Computations performed with different bubble-bubble distances and size ratios demonstrate various bubble-bubble interactions, such as bubble coalescence, bubble repulsion and attraction, jet penetration into the bubble, and jet collision. The interactions between collapsing bubbles are found to produce strong liquid jet formation and result in significant cell deformation compared to single-bubble collapse. The optimal bubble-bubble distance and size ratio for cell deformation are presented via contour maps based on extensive computations. The influences of the ultrasonic amplitude and frequency on cell deformation are further investigated.

Red blood cell (RBC) distribution, RBC shape, and flow rate have all been shown to have an effect on the pulmonary diffusing capacity. Through this study, a gas diffusion model and the immersed finite element method were used to simulate the gas diffusion into deformable RBCs running in capillaries. It has been discovered that when RBCs are deformed, the CO flux across the membrane becomes nonuniform, resulting in a reduced capacity for diffusion. Additionally, when compared to RBCs that were dispersed evenly, our simulation showed that clustered RBCs had a significantly lower diffusion capability. [ABSTRACT FROM AUTHOR]

Foamed Polymer is an important polymer material, which is one of the most widely used polymer materials and plays a very important role in the polymer industry. In this work, foamed polypropylene (PP) composites are prepared by injection molding, and the cell deformation process within them is studied by combining visualization technology and COMSOL software simulation. The results shows that the deformation of isolated cells depends in temperature, and there is no macroscopic deformation. There was no significant difference between the stress around adjacent cells at different temperatures, but the stress at different positions around the adjacent cells has obvious changes, and the maximum stress at the center of the adjacent cells was 224.18 N·m−2, which was easy to cause a lateral deformation of the cells. With the increase in temperature, the displacement around the adjacent cell gradually increased, the maximum displacement of the upper and lower symmetrical points of the cell was 14.62 μm, which is most likely to cause longitudinal deformation of the cell; the deviation of the cell deformation parameter gradually increased, which led to deformation during the growth of the cell easily. The simulation results were consistent with the visualized cell deformation behaviors of the foamed PP composites. [ABSTRACT FROM AUTHOR]

A deep-learning-based semantic segmentation approach (U-Net) was used to partition the anatomical features in the cross-section of hinoki (Chamaecyparis obtusa) wood during a micro three-point bending test. Using the Crocker–Grier linking algorithm, thousands of cells were successfully extracted, and several parameters (area, eccentricity, fitted ellipse aspect ratio, bounding box aspect ratio) were used to evaluate the intensity of the cells' deformation. Thus, the 2D map of the deformation intensity distribution was constructed. By analyzing flat-sawn, quarter-sawn, and rift-sawn specimens, it was confirmed that the annual ring orientation affects the flexural behavior of wood in the transverse direction. The quarter-sawn specimens exhibited the largest modulus of elasticity (MOE) and modulus of rupture (MOR). The ray tissue aligned against the load may have contributed to the restriction of cell deformation. The rift-sawn specimens exhibited the smallest MOE and MOR, possibly owing to the loading of the specimen in the in-plane off-axial direction, which induced the shear deformation of the cell wall. For all three specimen types, the fracture had high occurrence probability in the tension part of the specimen, which exhibited large cell deformation. Therefore, the proposed method can be adapted to the prediction of wood specimen fractures. With different test wood species, this approach can be of great help in elucidating the relationship between the anatomical features and the mechanical behavior of wood to improve the effective utilization of wood resources. [ABSTRACT FROM AUTHOR]

A phase field model is used to study the effect of atherosclerotic plaque on hemodynamics. The migration of cells in blood flows is described by a set of multiple phase field equations, which incorporate elastic energies and the interacting effects of cells. Several simulations are carried out to reveal the influences of initial velocities of blood cells, cellular elasticity and block rates of hemodynamic vessels. The results show that the cell deformation increases with the growth of the initial active velocity and block rate but with the decrease of the cellular elasticity. The atherosclerotic plaque not only affects the deformation and migration of cells but also can promote the variation in hemodynamic properties. The atherosclerotic plaque causes a burst in cell velocity, and the greater the block rate and cellular elasticity, the more dramatic the variation of instantaneous velocity. The present work demonstrates that the phase field method could be extended to reveal formation atherosclerosis at the microscopic level from the perspective of hemodynamics. [ABSTRACT FROM AUTHOR]

Bioprinting using cell-laden bioink is a rapidly emerging additive manufacturing method to fabricate engineered tissue constructs and in vitro models of disease biology. Amongst different bioprinting modalities, extrusion-based bioprinting is the most conveniently adopted technique due to its affordability. Bioinks consisting of living cells are suspended in hydrogels and extruded through syringe-needle assemblies, which subsequently undergo gelation at the collector plate. During the process, pressure is exerted on living cells which may cause cell deaths. Thus, for selected combination of cell and hydrogel, exerted pressure and the extrusion play key roles in determining the cell viability. Experimental evaluation to characterise stresses experienced by the cells in a bioink during bioprinting is a tedious exercise. Herein, computational modelling can be applied efficiently for rapid screening of bioinks. In the present study, a smoothed particle hydrodynamics model is developed for the analysis of stresses exerted on the cells during bioprinting process. Cells are modelled by assigning different mechanical properties to nucleus, cytoskeleton and cell membrane regions of the cell to get a more realistic understanding of cell deformation. The cytoplasm and nucleus are modelled as finite element meshes and a spring model of the cell membrane is coupled to the finite element model to develop a three-compartment model of the cell. Cell deformation is taken as a potential indicator of cell death. Effect of different process parameters such as flow rate, syringe-nozzle geometry and cell density are investigated. A submodeling approach is further introduced to predict deformation with higher resolution in a unit volume containing 104 to 108 cells. Results suggest that the generated bioink flow dynamic model can be a useful tool for the computational study of fluid flow involving cell suspensions during a bioprinting process. [ABSTRACT FROM AUTHOR]

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In this paper, the bubble-cell model is presented. The effects of the spacing between the bubble population and the cell, the radius of the bubble and the bubble medium on the degree of cell deformation were investigated by solving the Helmholtz equation and the equilibrium of motion equation using COMSOL Multiphysis@ software. The ultrasonic transducer is applied in a round bottom flask with the bubble-cell model on the side of the ultrasonic transducer. When the distance between the bubble cluster and the cell gradually increases, the extent of deformation of the cell is reflected as first increasing and then decreasing, reaching the maximum deformation at D = 2. When the radius of the bubble is changed, there is a “constant frequency” at low frequency ultrasound in any distance case, at which the cell deformation will be violent. However, when the bubble medium is changed, there is no significant change in the degree of deformation of the cells. In other words, changes in the structure of the bubble-cell model affect the degree of cell deformation, but without structural changes, the degree of cell deformation changes very little.

Red blood cell (RBC) distribution, RBC shape, and flow rate have all been shown to have an effect on the pulmonary diffusing capacity. Through this study, a gas diffusion model and the immersed finite element method were used to simulate the gas diffusion into deformable RBCs running in capillaries. It has been discovered that when RBCs are deformed, the CO flux across the membrane becomes nonuniform, resulting in a reduced capacity for diffusion. Additionally, when compared to RBCs that were dispersed evenly, our simulation showed that clustered RBCs had a significantly lower diffusion capability.

Abstract Background The research and analysis of cellular physiological properties has been an essential approach to studying some biological and biomedical problems. Temporal dynamics of cells therein are used as a quantifiable indicator of cellular response to extracellular cues and physiological stimuli. Methods This work presents a novel image-based framework to profile and model the cell dynamics in live-cell videos. In the framework, the cell dynamics between frames are represented as frame-level features from cell deformation and intracellular movement. On the one hand, shape context is introduced to enhance the robustness of measuring the deformation of cellular contours. On the other hand, we employ Scale-Invariant Feature Transform (SIFT) flow to simultaneously construct the complementary movement field and appearance change field for the cytoplasmic streaming. Then, time series modeling is performed on these frame-level features. Specifically, temporal feature aggregation is applied to capture the video-wide temporal evolution of cell dynamics. Results Our results demonstrate that the proposed cell dynamic features can effectively capture the cell dynamics in videos. They also prove that the Movement Field and Appearance Change Field Feature (MFAFF) can more precisely model the cytoplasmic streaming. Besides, temporal aggregation of cell dynamic features brings a substantial absolute increase of classification performance. Conclusion Experimental results demonstrate that the proposed framework outperforms competing mainstreaming approaches on the aforementioned datasets. Thus, our method has potential for cell dynamics analysis in videos.

The dynamics and deformation of red blood cells (RBCs) in microcirculation affect the flow resistance and transport properties of whole blood. One of the key properties that can alter RBC dynamics in flow is the contrast λ (or ratio) of viscosities between RBC cytosol and blood plasma. Here, we study the dependence of RBC shape and dynamics on the viscosity contrast in tube flow, using mesoscopic hydrodynamics simulations. State diagrams of different RBC dynamical states, including tumbling cells, parachutes, and tank-treading slippers, are constructed for various viscosity contrasts and wide ranges of flow rates and tube diameters (or RBC confinements). Despite similarities in the classification of RBC behavior for different viscosity contrasts, there are notable differences in the corresponding state diagrams. In particular, the region of parachutes is significantly larger for λ = 1 in comparison to λ = 5. Furthermore, the viscosity contrast strongly affects the tumbling-to-slipper transition, thus modifying the regions of occurrence of these states as a function of flow rate and RBC confinement. Also, an increase in cytosol viscosity leads to a reduction in membrane tension induced by flow stresses. Physical mechanisms that determine these differences in RBC dynamical states as a function of λ are discussed.

In the emerging field of 3D bioprinting, cell damage due to large deformations is considered a main cause for cell death and loss of functionality inside the printed construct. Those deformations, in turn, strongly depend on the mechano-elastic response of the cell to the hydrodynamic stresses experienced during printing. In this work, we present a numerical model to simulate the deformation of biological cells in arbitrary three-dimensional flows. We consider cells as an elastic continuum according to the hyperelastic Mooney–Rivlin model. We then employ force calculations on a tetrahedralized volume mesh. To calibrate our model, we perform a series of FluidFM ® compression experiments with REF52 cells demonstrating that all three parameters of the Mooney–Rivlin model are required for a good description of the experimental data at very large deformations up to 80%. In addition, we validate the model by comparing to previous AFM experiments on bovine endothelial cells and artificial hydrogel particles. To investigate cell deformation in flow, we incorporate our model into Lattice Boltzmann simulations via an Immersed-Boundary algorithm. In linear shear flows, our model shows excellent agreement with analytical calculations and previous simulation data. [ABSTRACT FROM AUTHOR]

Abstract Hydrodynamic force loading platforms for controllable cell mechanical deformation play an essential role in modern cell technologies. Current systems require assistance from specific microstructures thus limiting the controllability and flexibility in cell shape modulation, and studies on real‐time 3D cell morphology analysis are still absent. This article presents a novel platform based on acoustic streaming generated from a gigahertz device for cell shape control and real‐time cell deformation analysis. Details in cell deformation and the restoration process are thoroughly studied on the platform, and cell behavior control at the microscale is successfully achieved by tuning the treating time, intensity, and wave form of the streaming. The application of this platform in cell membrane permeability modulation and analysis is also exploited. Based on the membrane reorganization during cell deformation, the effects of deformation extent and deformation patterns on membrane permeability to micro‐ and macromolecules are revealed. This technology has shown its unique superiorities in cell mechanical manipulation such as high flexibility, high accuracy, and pure fluid force operation, indicating its promising prospect as a reliable tool for cell property study and drug therapy development.

A phase field model is used to study the effect of atherosclerotic plaque on hemodynamics. The migration of cells in blood flows is described by a set of multiple phase field equations, which incorporate elastic energies and the interacting effects of cells. Several simulations are carried out to reveal the influences of initial velocities of blood cells, cellular elasticity and block rates of hemodynamic vessels. The results show that the cell deformation increases with the growth of the initial active velocity and block rate but with the decrease of the cellular elasticity. The atherosclerotic plaque not only affects the deformation and migration of cells but also can promote the variation in hemodynamic properties. The atherosclerotic plaque causes a burst in cell velocity, and the greater the block rate and cellular elasticity, the more dramatic the variation of instantaneous velocity. The present work demonstrates that the phase field method could be extended to reveal formation atherosclerosis at the microscopic level from the perspective of hemodynamics.

Hydrodynamic force loading platforms for controllable cell mechanical deformation play an essential role in modern cell technologies. Current systems require assistance from specific microstructures thus limiting the controllability and flexibility in cell shape modulation, and studies on real‐time 3D cell morphology analysis are still absent. This article presents a novel platform based on acoustic streaming generated from a gigahertz device for cell shape control and real‐time cell deformation analysis. Details in cell deformation and the restoration process are thoroughly studied on the platform, and cell behavior control at the microscale is successfully achieved by tuning the treating time, intensity, and wave form of the streaming. The application of this platform in cell membrane permeability modulation and analysis is also exploited. Based on the membrane reorganization during cell deformation, the effects of deformation extent and deformation patterns on membrane permeability to micro‐ and macromolecules are revealed. This technology has shown its unique superiorities in cell mechanical manipulation such as high flexibility, high accuracy, and pure fluid force operation, indicating its promising prospect as a reliable tool for cell property study and drug therapy development. [ABSTRACT FROM AUTHOR]

Investigation of the flowing behaviours of circulating tumour cells (CTCs) under the blood flow is of fundamental importance for understanding haematogenous metastasis. In this study, the motion of a CTC at low flow rates in microvessels were simulated by dissipative particle dynamics combined with a spring-based network model to characterise cell deformation. The effects of vessel curvature, cell deformability and the presence of RBCs on the motion of an initially adherent tumour cell were investigated. The results suggested that at low Reynolds number, the viscous force plays a dominant role and the curved vessel would initiate the formation of more simultaneous bonds. And, the shear force acted on the softer tumour cell would induce large contact area and further stimulate the formation of more ligand–receptor bond numbers. Moreover, to investigate the non-Newtonian nature of the blood flow on tumour cell motion, the blood was regarded as a suspension of RBCs. With the presence of RBC suspensions, the collision between the tumour cell and RBCs increases the drag force and promotes the disassociation of the CTC from the vessel wall. [ABSTRACT FROM AUTHOR]

Background/Aims: Transient nanometric cholesterol- and sphingolipid-enriched domains, called rafts, are characterized by higher lipid order as compared to surrounding lipids. Here, we asked whether the seminal concept of highly ordered rafts could be refined with the presence of lipid domains exhibiting different enrichment in cholesterol and sphingomyelin and association with erythrocyte curvature areas. We also investigated how differences in lipid order between domains and surrounding membrane (bulk) are regulated and whether changes in order differences could participate to erythrocyte deformation and vesiculation. Methods: We used the fluorescent hydration- and membrane packing-sensitive probe Laurdan to determine by imaging mode the Generalized Polarization (GP) values of lipid domains vs the surrounding membrane. Results: Laurdan revealed the majority of sphingomyelin-enriched domains associated to low erythrocyte curvature areas and part of the cholesterol-enriched domains associated with high curvature. Both lipid domains were less ordered than the surrounding lipids in erythrocytes at resting state. Upon erythrocyte deformation (elliptocytes and stimulation of calcium exchanges) or membrane vesiculation (storage at 4°C), lipid domains became more ordered than the bulk. Upon aging and in membrane fragility diseases (spherocytosis), an increase in the difference of lipid order between domains and the surrounding lipids contributed to the initiation of domain vesiculation. Conclusion: The critical role of domain-bulk differential lipid order modulation for erythrocyte reshaping is discussed in relation with the pressure exerted by the cytoskeleton on the membrane.

A biological cell exhibits viscoelastic behavior mainly because its components (membrane and cytoplasm) are viscoelastic, and this is clearly seen when it is stretched and released. The present work numerically studied the shape recovery of a red blood cell (RBC) based on a viscoelastic model at the meso-scale using Dissipative Particle Dynamics (DPD) method. In this model, the RBC membrane is represented by a triangular network of worm-like chains, while the cytoplasm is replaced by a system of DPD particles. This viscoelastic model is validated by examining the stretching deformation of an RBC and comparing with the existing experimental data. Viscoelastic properties of the RBC are then analyzed by stretching an RBC under a 20 pN stretching force, and allowing it to relax. The time to recover its shape upon removal of the stretching force is measured to be 111 and 92.6 ms for an RBC with and without cytoplasm, and the corresponding membrane viscosity is 6. 6 7 × 1 0 − 4 and 5. 5 6 × 1 0 − 4 Poise ⋅ cm , respectively. These values, for an RBC with cytoplasm, are closer to experimental data than those for an RBC without cytoplasm, lending support to the model with cytoplasm. Finally, parametric studies are conducted on the membrane elastic and bending moduli. The results show that the shape recovery time decreases with increasing the membrane elastic and bending moduli. [ABSTRACT FROM AUTHOR]

Objective: The aim of this systematic review was to examine the associations and relationship between commonly cited risk factors and the pathology of pressure ulcer (PU) development. Method: Using systematic review methodology, original research studies, prospective design and human studies written in English were included. The search was conducted in March 2018, using Ovid, Ovid EMBASE and CINAHL databases. Data were extracted using a pre-designed extraction tool and all included studies were quality appraised using the evidence-based librarianship critical appraisal. Results: A total of 382 records were identified, of which five met the inclusion criteria. The studies were conducted between 1994 and 2017. Most studies were conducted in hospital and geriatric wards. The mean sample size was 96±145.7 participants. Ischaemia, recovery of blood flow and pathological impact of pressure and shear was mainly found as the cited risk factor and PU aetiology. Conclusion: This review systematically analysed five papers exploring the relationship between risk factors for PU development and aetiology. It identified many risk factors and underlying pathological mechanisms that interact in the development of PU including ischaemia, stress, recovery of blood flow, tissue hypoxia and the pathological impact of pressure and shear. There are several pathways in which these pathological mechanisms contribute to PU development and identifying these could establish potential ways of preventing or treating the development of PU for patients. [ABSTRACT FROM AUTHOR]

This study examines the impact of key design variables on the water management, mechanical responses, and overall performance of an Electrochemical Hydrogen Compressor (EHC) cell. A previously developed three-dimensional (3-D) computational model of EHC is applied to different EHC cell geometries, varying in the thicknesses of membranes and the gas diffusion layer (GDL), as well as the widths of the channel and rib in the flow field. Generally, the model's predictions align well with the experimental data measured across a broad spectrum of operating current densities, revealing the intricate interaction between electrochemical/transport phenomena and the mechanical behaviors within the EHC cell. Thinner membranes provide enhanced performance by reducing water shortage at the anode, while increased GDL thickness significantly mitigates cell deformation and stress concentration. Changes in the widths of the rib and channel exert minimal influence on water transport behaviors and cell performance, but they substantially impact mechanical stability. This study underlines the necessity of fine-tuning EHC design factors to strike a balance between mechanical stability and cell performance, thus aiding the practical implementation of EHC technology. • A 3D CFD-FEM model underscores membrane & GDL thickness in pivotal EHC cell roles. • Rib and channel widths affect mechanical stability more than water transport. • Thinner membranes improve water management and performance. • Thicker GDL mitigates cell deformation and stress. • Titanium foam as GDL material boosts stability under high compression. [ABSTRACT FROM AUTHOR]

Teak is a famous commercial timber; however, many community forests produce low-quality teak from young trees. This research aimed to investigate the effect of heat treatment on the dimensional stability and colour of young teak wood. Wood samples were pre-dried using a fan or in an oven at 40°C. The heat treatments were conducted at three temperatures (120, 150, and 180°C) and for two durations (2 and 6 h). Water absorption, dimensional stability, and colour tests were then performed. The results showed that the density of the teak wood slightly decreased after heat treatment. However, its dimensional stability improved substantially, in accordance with its reduced water absorption. Furthermore, the surface of the young teak became darker, with a more even brown colour. [ABSTRACT FROM AUTHOR]

Migration of an encapsulated leukemia HL60 cell through sudden contractions in a capillary tube is investigated. An HL60 cell is initially encapsulated in a viscoelastic shell fluid. As the cell-laden droplet moves through the sudden contraction, shear stresses are experienced around the cell. These stresses along with the interfacial force and geometrical effects cause mechanical deformation which may result in cell death. A parametric study is done to investigate the effects of shell fluid relaxation time, encapsulating droplet size and contraction geometries on cell mechanical deformation. It is found that a large encapsulating droplet with a high relaxation time will undergo low cell mechanical deformation. In addition, the deformation is enhanced for capillary tubes with narrow and long contraction. This study can be useful to characterize cell deformation in constricted microcapillaries and to improve cell viability in bio-microfluidics.

A three-dimensional (3-D) model of an electrochemical hydrogen compressor (EHC) cell was developed by rigorously accounting for the hydrogen oxidation and evolution reactions and resulting species and charge transport through various EHC components. Particular emphasis was placed on coupling computational fluid dynamics (CFD) and finite element method (FEM) methodology to predict EHC performance numerically under the deformed cell geometries, i.e., induced by the cell assembly and the hydrogen pressure difference between the anode and cathode sides. First, the EHC model was validated experimentally against polarization curves and impedance spectra measured under different hydrogen compression ratios and operating temperatures. In general, the simulation results compared well with the measured data and further revealed the operating characteristics of the EHC cells. In particular, the most irreversible voltage rise comes from the ohmic overpotential because of the proton transport through the membrane, clearly indicating dehydration of the electrolyte due mainly to the electro-osmotic drag effect is one of the most critical issues for efficient EHC operations. While the dehydration issue tends to be mitigated under higher hydrogen discharge pressure or higher operating temperatures, the cell deformation toward the low-pressure side (anode) is visible even with the low hydrogen compression ratio of 10, clearly requiring improvement in the mechanical properties of EHC components and cell structure for a higher compression of hydrogen gas. [ABSTRACT FROM AUTHOR]

The deformation of nucleated cells driven by ultrasonic standing waves in fluid environment is investigated by theoretical analysis and numerical simulation. The nucleated cells are considered to consist of cell membrane, cytoplasm and nucleus The cell membrane is assumed to have in-plane deformation and bending resistances, in which the in-plane deformation is modeled by the generalized Hooke's law, and the bending resistance is modeled by the Helfrich bending energy formula. Due to the acoustic mismatch between the media inside and outside the cell, the generated acoustic radiation stress on the cell membrane causes the nucleated cell to deform. Considering the acoustic scattering of the nucleus, the acoustic radiation stress is formulated by applying the acoustic radiation stress tensor theory. Based on the proposed theoretical model, a finite element model is established to solve the coupling problem of ultrasonic propagation and cell deformation. The analytical solution for the acoustic induced deformation of nucleated cells in the limits of long wavelength and small deformation is given and successfully verifies the finite element model. The results show that the deformation of nucleated cells is much larger than that of enucleated cells due to the effect of the nucleus on wave propagation. The deformation of nucleated cells is significantly affected by nuclear size and nuclear density. This study is helpful to accurately extract the mechanical properties of nucleated cells and further promote the detection of cell-related diseases by acoustic deformation technology. • A theoretical model of nucleated cell deformation driven by ultrasonic standing waves is proposed. • A finite element model is established to solve the coupling problem of ultrasonic propagation and cell deformation. • The deformation of nucleated cells is much larger than that of enucleated cells due to the effect of the nucleus on wave propagation. • The deformation of nucleated cells is significantly affected by nuclear size and nuclear density. • This study helps to promote the detection of cell-related diseases by acoustic deformation technology. [ABSTRACT FROM AUTHOR]

When a red blood cell (RBC) is driven by a pressure gradient through a microfluidic channel, its passage or blockage provides a measure of the rigidity of the cell. This has been developed as a means to separate RBCs according to their mechanical properties, which are known to change with pathological conditions such as malaria infection. In this study, we use numerical simulations to establish a quantitative connection between the minimum pressure needed to drive an RBC through a contracting microfluidic channel and the rigidity of the cell membrane. This provides the basis for designing such devices and interpreting the experimental data.

Shape analysis is of great importance in many fields such as computer vision, medical imaging, and computational biology. In this paper we focus on a shape space in which shapes are represented by means of planar closed curves. In this shape space a new metric was recently introduced with the result that this shape space has the property of being isometric to an infinite-dimensional Grassmann manifold of 2-dimensional subspaces. Using this isometry it is possible, from Younes et al. (2008), to explicitly describe geodesics, a task that previously was not at all easy. Our aim is twofold, namely: to use this general theory in order to show some applications to the study of erythrocytes, using digital images of peripheral blood smears, in the treatment of sickle cell disease; and, since normal erythrocytes are almost circular and many Sickle cells have elliptical shape, to particularize the computation of geodesics and distances between shapes using this metric to planar objects considered as deformations of a template (circle or ellipse). The applications considered include: shape interpolation, shape classification, and shape clustering.

The existence of diverse image datasets accompanied by reference annotations is a crucial prerequisite for an objective benchmarking of bioimage analysis methods. Nevertheless, such a prerequisite is hard to satisfy for time lapse, multidimensional fluorescence microscopy image data, manual annotations of which are laborious and often impracticable. In this paper, we present a simulation system capable of generating 3-D time-lapse sequences of single motile cells with filopodial protrusions of user-controlled structural and temporal attributes, such as the number, thickness, length, level of branching, and lifetime of filopodia, accompanied by inherently generated reference annotations. The proposed simulation system involves three globally synchronized modules, each being responsible for a separate task: the evolution of filopodia on a molecular level, linear elastic deformation of the entire cell with filopodia, and the synthesis of realistic, time-coherent cell texture. Its flexibility is demonstrated by generating multiple synthetic 3-D time-lapse sequences of single lung cancer cells of two different phenotypes, qualitatively and quantitatively resembling their real counterparts acquired using a confocal fluorescence microscope. [ABSTRACT FROM AUTHOR]

Highlights • Wood anatomical techniques improve the assessment of heavily degraded and/or deformed material. • Highly resolved anatomical observations reveal detailed insights into cell quality and extent of wood deformation. • Wood anatomical tree-ring identification enables extended measurements of narrow rings improving cross-dating results. • Thin sectioning has the potential to manually reconstruct original TRWs by correcting for deformed ring structures. Abstract Successful cross-dating of subfossil wood, ideally in combination with precise information on germination and dieback, requires the accurate detection of tree-ring width (TRW) boundaries along continuous measurement tracks from pith to bark. However, wood decay and the mechanical deformation of cells often challenge the dendrochronological analysis and subsequent paleoclimatic and environmental interpretations. Here, we show that wood anatomical techniques can improve the assessment of heavily degraded and/or deformed material. We apply state-of-the-art sample preparation, thin sectioning and double-staining to a unique collection of Late Glacial pines that were growing ∼13,000 years ago in the vicinity of Zurich, Switzerland. Highly resolved anatomical observations not only reveal detailed insights into the quality of each cell, but also allow the extent of wood deformation to be identified. By improving the detection and cross-dating of particularly narrow rings, TRW series might be extended towards the pith and bark, where decomposition and distortion is usually most severe, thus adding to a better understanding of possible germination and dieback processes, respectively. Moreover, thin sectioning has the potential to manually reconstruct original TRWs by correcting for post-mortem deformed ring structures. Our results suggest that anatomical techniques should be routinely applied in the assessment of historical, archaeological and subfossil wood. [ABSTRACT FROM AUTHOR]

Cell migration plays an essential role in cancer metastasis. In cancer invasion through confined spaces, cells must undergo extensive deformation, which is a capability related to their metastatic potentials. Here, we simulate the deformation of the cell and nucleus during invasion through a dense, physiological microenvironment by developing a phenomenological computational model. In our work, cells are attracted by a generic emitting source (e.g., a chemokine or stiffness signal), which is treated by using Green’s Fundamental solutions. We use an IMEX integration method where the linear parts and the nonlinear parts are treated by using an Euler backward scheme and an Euler forward method, respectively. We develop the numerical model for an obstacle-induced deformation in 2D or/and 3D. Considering the uncertainty in cell mobility, stochastic processes are incorporated and uncertainties in the input variables are evaluated using Monte Carlo simulations. This quantitative study aims at estimating the likelihood for invasion and the length of the time interval in which the cell invades the tissue through an obstacle. Subsequently, the two-dimensional cell deformation model is applied to simplified cancer metastasis processes to serve as a model for in vivo or in vitro biomedical experiments. [ABSTRACT FROM AUTHOR]

This study is focused on what factor mainly affects the mechanical properties of each wood species in the lateral direction. At first, the influence of the density which is closely related to mechanical properties in the longitudinal direction was also researched in the lateral direction. Thus, the elastic modulus, strength, and failure strain in the lateral tension were measured using thin cross-sectional samples of softwoods and hardwoods, having wide varieties in the density and anatomical features. The results obtained are as follows. The linear relationship between the density and the elastic modulus which has been verified in the longitudinal direction was not observed in the lateral tension for the samples with the annual ring inclination of 90°, which samples were influenced by ray arranged parallel to the tensile direction. However, samples with the annual ring inclination of 45° showed the high correlation between the density and the elastic modulus due to the shearing deformation of the cell shape. On the other hand, the proportional relationship between the elastic modulus and strength which has been verified in the longitudinal direction was not observed in the lateral tension except for the samples with the annual ring inclination of 90°. From the results obtained, it was revealed that the mechanical properties of wood in the lateral direction were significantly affected not only by the density but also by the structural features such as deformation of cell shapes, arrangement of ray or vessels, and the degree of the transition from the earlywood to the latewood. [ABSTRACT FROM AUTHOR]

Background/Aims: Transient nanometric cholesterol- and sphingolipid-enriched domains, called rafts, are characterized by higher lipid order as compared to surrounding lipids. Here, we asked whether the seminal concept of highly ordered rafts could be refined with the presence of lipid domains exhibiting different enrichment in cholesterol and sphingomyelin and association with erythrocyte curvature areas. We also investigated how differences in lipid order between domains and surrounding membrane (bulk) are regulated and whether changes in order differences could participate to erythrocyte deformation and vesiculation. Methods: We used the fluorescent hydration- and membrane packing-sensitive probe Laurdan to determine by imaging mode the Generalized Polarization (GP) values of lipid domains vs the surrounding membrane. Results: Laurdan revealed the majority of sphingomyelinenriched domains associated to low erythrocyte curvature areas and part of the cholesterolenriched domains associated with high curvature. Both lipid domains were less ordered than the surrounding lipids in erythrocytes at resting state. Upon erythrocyte deformation (elliptocytes and stimulation of calcium exchanges) or membrane vesiculation (storage at 4°C), lipid domains became more ordered than the bulk. Upon aging and in membrane fragility diseases (spherocytosis), an increase in the difference of lipid order between domains and the surrounding lipids contributed to the initiation of domain vesiculation. Conclusion: The critical role of domain-bulk differential lipid order modulation for erythrocyte reshaping is discussed in relation with the pressure exerted by the cytoskeleton on the membrane. [ABSTRACT FROM AUTHOR]

This work presents the production of cellular polymer films using extrusion blowing to impose biaxial stretching on the cellular structure while processing. The materials selected are linear low-density polyethylene (LLDPE) and low density polyethylene (LDPE) as the matrix, azodicarbonamide as the chemical blowing agent, and talc as the nucleating agent. The processing parameters, namely, the temperature profile, screw speed, feed rate, take-up ratio, blow-up ratio, and the matrix composition were all optimized to produce a homogeneous cellular structure with defined morphologies. The optimized films had a thickness below 300 µm, a relative density around 0.6, a cell density above 2 x 106 cells/cm³, and biaxially stretched cells with aspect ratios above 4 longitudinally and 3.8 transversally. [ABSTRACT FROM AUTHOR]