Viscoelastic Finite-Element Modelling of Cell Deformation in an Optical Stretcher

2007 ◽  
Author(s):  
Soo Kng Teo ◽  
Kim Parker ◽  
K.-H. Chiam
Keyword(s):  
Finite Element ◽  
Cellular Response ◽  
Element Model ◽  
Cell Deformation ◽  
Normal Fibroblast ◽  
Transformed Cells ◽  
Fibroblast Cells ◽  
Normal Cells ◽  
Optical Stretcher ◽  
Maximal Stress

In this paper, we discuss the results arising from using a finite-element model [1] of cell deformation to study the optical stretching [2,3] of normal and malignantly transformed fibroblast cells. The key feature of our model is the use of a constitutive viscoelastic fluid element [4] whose parameters are both spatially and temporally varying so as to mimic the experimentally-observed spatiotemporal heterogeneity of cellular material properties. First, we show that normal fibroblast cells can undergo active cellular response by increasing their cellular viscosity when optically stretched for loading times of between 0.2s and 2.5s. Second, we show that, under similar optical conditions, cells of a smaller radius will experience more stretching compared to cells of a larger radius. This may explain why malignantly transformed cells experience higher strains than normal cells. Third, we compute the extent of the propagation of stress in the cytoplasm, and show that, for malignantly transformed cells, the maximal stress does propagate into the nuclear region whereas for normal cells, the maximal stress does not. We discuss how this may impact the transduction of cancer signalling pathways.

scholarly journals Experimental Characterization and Finite Element Modeling of the Effects of 3D Bioplotting Process Parameters on Structural and Tensile Properties of Polycaprolactone (PCL) Scaffolds

2020 ◽  
Vol 10 (15) ◽  
pp. 5289
Author(s):  
Lokesh Karthik Narayanan ◽  
Rohan A. Shirwaiker
Keyword(s):  
Finite Element ◽  
Tensile Properties ◽  
Element Model ◽  
Extrusion Pressure ◽  
Fibroblast Cells ◽  
Experimental Characterization ◽  
Efficient Design ◽  
Strand Spacing ◽  
Nih 3T3 ◽  
Process Structure

In this study we characterized the process–structure interactions in melt extrusion-based 3D bioplotting of polycaprolactone (PCL) and developed predictive models to enable the efficient design and processing of scaffolds for tissue engineering applications. First, the effects of pneumatic extrusion pressure (0.3, 0.4, 0.5, 0.6 N/mm2), nozzle speed (0.1, 0.4, 1.0, 1.4 mm/s), strand lay orientation (0°, 45°, 90°, 135°), and strand length (10, 20, 30 mm) on the strand width were investigated and a regression model was developed to map strand width to the two significant parameters (extrusion pressure and nozzle speed; p < 0.05). Then, proliferation of NIH/3T3 fibroblast cells in scaffolds with two different stand widths fabricated with different combinations of the two significant parameters was assessed over 7 days, which showed that the strand width had a significant effect on proliferation (p < 0.05). The effect of strand lay orientation (0° and 90°) on tensile properties of non-porous PCL specimens was determined and was found to be significantly higher for specimens with 0° lay orientation (p < 0.05). Finally, these data were used to develop and experimentally validate a finite element model for a porous PCL specimen with 1:1 ratio of inter-strand spacing to strand width.

scholarly journals c-Ha-rasVal 12 oncogene-transformed NIH-3T3 fibroblasts display more decondensed nucleosomal organization than normal fibroblasts.

1990 ◽  
Vol 111 (1) ◽  
pp. 9-17 ◽  
Author(s):  
J Laitinen ◽  
L Sistonen ◽  
K Alitalo ◽  
E Hölttä
Keyword(s):  
Cell Cycle ◽  
Micrococcal Nuclease ◽  
Normal Fibroblast ◽  
Transformed Cells ◽  
Serum Starvation ◽  
Quiescent State ◽  
Normal Cells ◽  
3T3 Fibroblasts ◽  
Mnase Digestion ◽  
Nih 3T3

We have compared the nucleosomal organization of c-Ha-rasVal 12 oncogene-transformed NIH-3T3 fibroblasts with that of normal fibroblasts by using micrococcal nuclease (MNase) as a probe for the chromatin structure. The bulk chromatin from asynchronously and exponentially growing ras-transformed cells was much more sensitive to MNase digestion than chromatin from the normal cells. Southern hybridization analyses of the MNase digests with probes specific for the ornithine decarboxylase (odc) and c-myc genes showed that the coding and/or 3' end regions of these growth-inducible genes carry a nucleosomal organization both in ras-transformed and normal cells. Studies with cells synchronized by serum starvation showed that in both cell lines the nucleosomal organization of chromatin is relatively condensed at the quiescent state, becomes highly decondensed during the late G1 phase of the cell cycle, and starts again to condense during the S phase. However, in ras-transformed cells the decondensation state stayed much longer than in normal cells. Moreover, irrespective of the phase of the cell cycle the bulk chromatin as well as that of the odc and c-myc genes was more sensitive to MNase digestion in the ras-transformed cell than in the normal fibroblast. Decondensation of the chromatin was also observed in the normal c-Ha-ras protooncogene-transfected cells, but to a lesser extent than in the mutant ras-transformed cells. Whether the increased degree of chromatin decondensation plays a regulatory role in the increased expression of many growth-related genes in the ras-transformed cells remains an interesting object of further study.

A finite element model of cell deformation during magnetic bead twisting

2002 ◽  
Vol 93 (4) ◽  
pp. 1429-1436 ◽  
Author(s):  
Srboljub M. Mijailovich ◽  
Milos Kojic ◽  
Miroslav Zivkovic ◽  
Ben Fabry ◽  
Jeffrey J. Fredberg
Keyword(s):  
Finite Element ◽  
Cell Surface ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Magnetic Bead ◽  
Cell Deformation ◽  
Adherent Cell ◽  
Cell Height ◽  
Applied Torque

Magnetic twisting cytometry probes mechanical properties of an adherent cell by applying a torque to a magnetic bead that is tightly bound to the cell surface. Here we have used a three-dimensional finite element model of cell deformation to compute the relationships between the applied torque and resulting bead rotation and lateral bead translation. From the analysis, we computed two coefficients that allow the cell elastic modulus to be estimated from measurements of either bead rotation or lateral bead translation, respectively, if the degree of bead embedding and the cell height are known. Although computed strains in proximity of the bead can be large, the relationships between applied torque and bead rotation or translation remain virtually linear up to bead rotations of 15°, above which geometrical nonlinearities become significant. This appreciable linear range stands in contrast to the intrinsically nonlinear force-displacement relationship that is observed when cells are indented during atomic force microscopy. Finally, these computations support the idea that adhesive forces are sufficient to keep the bead firmly attached to the cell surface throughout the range of working torques.

Finite Element Analysis of a Brass Cartridge Case

2011 ◽  
Vol 421 ◽  
pp. 271-275
Author(s):  
Yun Peng
Keyword(s):  
Finite Element ◽  
Strain Field ◽  
Element Model ◽  
Parameter Design ◽  
High Fidelity ◽  
Two Dimensional ◽  
Element Analysis ◽  
Maximal Stress ◽  
Cartridge Case ◽  
Very High

The cartridge endures the load of very high pressure and heat generated from the fired-gas of powder when shooting. The intensity of the cartridge influences the performance of the weapon as well as the safety of user. One brass cartridge snaped in the test. Based on the theory of elastic-plastic mechanics, thermal-stress and contact mechanics, the high fidelity finite element model of the cartridge case and the gun wall is built, which is used to analyze the stress-strain field in the platform of the general FEA software ANSYS. The model is two-dimensional for the axial symmetrical characteristic, and we achieve the parameter model using the ANSYS Parameter Design Language. The resultant position of maximal stress is consistent with the test, and it oversteps the material yield limit, showing the model is high fidelity. The influence of initial gap is researched in detail, and the results indicate that the position of the maximal stress can be adjusted by controlling the initial gap. The data can be used in the modified design.

scholarly journals Ultra-High Dose Rate FLASH Irradiation Induced Radio-Resistance of Normal Fibroblast Cells Can Be Enhanced by Hypoxia and Mitochondrial Dysfunction Resulting From Loss of Cytochrome C

2021 ◽  
Vol 9 ◽  
Author(s):  
Jintao Han ◽  
Zhusong Mei ◽  
Chunyang Lu ◽  
Jing Qian ◽  
Yulan Liang ◽  
...  
Keyword(s):  
Dose Rate ◽  
High Dose Rate ◽  
Normal Fibroblast ◽  
High Dose ◽  
Fibroblast Cells ◽  
Normal Cells ◽  
Early Apoptosis ◽  
Cyt C ◽  
Late Apoptosis ◽  
Apoptosis And Necrosis

Ultra-high dose rate FLASH irradiation (FLASH-IR) has got extensive attention since it may provide better protection on normal tissues while maintain tumor killing effect compared with conventional dose rate irradiation. The FLASH-IR induced protection effect on normal tissues is exhibited as radio-resistance of the irradiated normal cells, and is suggested to be related to oxygen depletion. However, the detailed cell death profile and pathways are still unclear. Presently normal mouse embryonic fibroblast cells were FLASH irradiated (∼109 Gy/s) at the dose of ∼10–40 Gy in hypoxic and normoxic condition, with ultra-fast laser-generated particles. The early apoptosis, late apoptosis and necrosis of cells were detected and analyzed at 6, 12, and 24 h post FLASH-IR. The results showed that FLASH-IR induced significant early apoptosis, late apoptosis and necrosis in normal fibroblast cells, and the apoptosis level increased with time, in either hypoxic or normoxic conditions. In addition, the proportion of early apoptosis, late apoptosis and necrosis were significantly lower in hypoxia than that of normoxia, indicating that radio-resistance of normal fibroblast cells under FLASH-IR can be enhanced by hypoxia. To further investigate the apoptosis related profile and potential pathways, mitochondria dysfunction cells resulting from loss of cytochrome c (cyt c–/–) were also irradiated. The results showed that compared with irradiated normal cells (cyt c+/+), the late apoptosis and necrosis but not early apoptosis proportions of irradiated cyt c–/– cells were significant decreased in both hypoxia and normoxia, indicating mitochondrial dysfunction increased radio-resistance of FLASH irradiated cells. Taken together, to our limited knowledge, this is the first report shedding light on the death profile and pathway of normal and cyt c–/– cells under FLASH-IR in hypoxic and normoxic circumstances, which might help us improve the understanding of the FLASH-IR induced protection effect in normal cells, and thus might potentially help to optimize the future clinical FLASH treatment.

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

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