Academic literature on the topic 'Cells - Micromechanical Structures'
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Journal articles on the topic "Cells - Micromechanical Structures"
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Wang, Junling, Yongbo Zhang, Xiao Yang, and Xiaobing Ma. "Stress effect on 3D culturing of MC3T3-E1 cells on microporous bovine bone slices." Nanotechnology Reviews 9, no. 1 (January 1, 2020): 1315–25. http://dx.doi.org/10.1515/ntrev-2020-0103.
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Abstract The choosing of micromechanical environment is very important for the growth of bone-related cells. In this paper, bovine cancellous bone slices with 3D porous structures were used for 3D culturing of MC3T3-E1 cells (Mouse embryo osteoblast precursor cells) through a four-point-bending device due to their good biocompatibility and strength. Effects of micromechanical environment on the growth of MC3TC-E1 cells were investigated by immunofluorescent staining and alkaline phosphatase analysis, and the most positive microporous structures were found. In addition, a model of cell density vs stress was established through a specific normalization method and finite element simulation. The results showed that the micromechanical environment of the bone slices promoted cell proliferation, and the detail influence of stress on cell proliferation could be described by the mathematical model, which could provide a theoretical basis for the design of micromechanical environment in the bone tissue engineering scaffolds to stimulate cell proliferation.
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Esue, Osigwe, Denis Wirtz, and Yiider Tseng. "GTPase Activity, Structure, and Mechanical Properties of Filaments Assembled from Bacterial Cytoskeleton Protein MreB." Journal of Bacteriology 188, no. 3 (February 1, 2006): 968–76. http://dx.doi.org/10.1128/jb.188.3.968-976.2006.
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ABSTRACT MreB, a major component of the recently discovered bacterial cytoskeleton, displays a structure homologous to its eukaryotic counterpart actin. Here, we study the assembly and mechanical properties of Thermotoga maritima MreB in the presence of different nucleotides in vitro. We found that GTP, not ADP or GDP, can mediate MreB assembly into filamentous structures as effectively as ATP. Upon MreB assembly, both GTP and ATP release the gamma phosphate at similar rates. Therefore, MreB is an equally effective ATPase and GTPase. Electron microscopy and quantitative rheology suggest that the morphologies and micromechanical properties of filamentous ATP-MreB and GTP-MreB are similar. In contrast, mammalian actin assembly is favored in the presence of ATP over GTP. These results indicate that, despite high structural homology of their monomers, T. maritima MreB and actin filaments display different assembly, morphology, micromechanics, and nucleotide-binding specificity. Furthermore, the biophysical properties of T. maritima MreB filaments, including high rigidity and propensity to form bundles, suggest a mechanism by which MreB helical structure may be involved in imposing a cylindrical architecture on rod-shaped bacterial cells.
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Zyganitidis, Ioannis, Alexandros Arailopoulos, and Dimitrios Giagopoulos. "Composite Material Elastic Effective Coefficients Optimization by Means of a Micromechanical Mechanical Model." Applied Mechanics 3, no. 3 (June 30, 2022): 779–98. http://dx.doi.org/10.3390/applmech3030046.
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The presented research work demonstrates an efficient methodology based on a micromechanical framework for the prediction of the effective elastic properties of strongly bonded long-fiber-reinforced materials (CFRP) used for the construction of tubular structures. Although numerous analytical and numerical micromechanical models have been developed to predict the mechanical response of CFRPs, either they cannot accurately predict complex mechanical responses due to limits on the input parameters or they are resource intensive. The generalized method of cells (GMC) is capable of assessing more detailed strain fields in the vicinity of fiber–matrix interfaces since it allows for a plethora of material and structural parameters to be defined while being computationally effective. The GMC homogenization approach is successfully combined with the covariance matrix adaptation evolution strategy (CMA–ES) to identify the effective elasticity tensor Cij of CFRP materials. The accuracy and efficiency of the proposed methodology are validated by comparing predicted effective properties with previously measured experimental data on CFRP cylindrical samples made of 3501-6 epoxy matrix reinforced with AS4 carbon fibers. The proposed and validated method can be successively used in both analyzing the mechanical responses of structures and designing new optimized composite materials.
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Belický, Štefan, Jaroslav Katrlík, and Ján Tkáč. "Glycan and lectin biosensors." Essays in Biochemistry 60, no. 1 (June 30, 2016): 37–47. http://dx.doi.org/10.1042/ebc20150005.
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A short description about the importance of glycan biorecognition in physiological (blood cell type) and pathological processes (infections by human and avian influenza viruses) is provided in this review. Glycans are described as much better information storage media, compared to proteins or DNA, due to the extensive variability of glycan structures. Techniques able to detect an exact glycan structure are briefly discussed with the main focus on the application of lectins (glycan-recognising proteins) in the specific analysis of glycans still attached to proteins or cells/viruses. Optical, electrochemical, piezoelectric and micromechanical biosensors with immobilised lectins or glycans able to detect a wide range of analytes including whole cells/viruses are also discussed.
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Campos Marin, A., and D. Lacroix. "The inter-sample structural variability of regular tissue-engineered scaffolds significantly affects the micromechanical local cell environment." Interface Focus 5, no. 2 (April 6, 2015): 20140097. http://dx.doi.org/10.1098/rsfs.2014.0097.
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Rapid prototyping techniques have been widely used in tissue engineering to fabricate scaffolds with controlled architecture. Despite the ability of these techniques to fabricate regular structures, the consistency with which these regular structures are produced throughout the scaffold and from one scaffold to another needs to be quantified. Small variations at the pore level can affect the local mechanical stimuli sensed by the cells thereby affecting the final tissue properties. Most studies assume rapid prototyping scaffolds as regular structures without quantifying the local mechanical stimuli at the cell level. In this study, a computational method using a micro-computed tomography-based scaffold geometry was developed to characterize the mechanical stimuli within a real scaffold at the pore level. Five samples from a commercial polycaprolactone scaffold were analysed and computational fluid dynamics analyses were created to compare local velocity and shear stress values at the same scaffold location. The five samples did not replicate the computer-aided design (CAD) scaffold and velocity and shear stress values were up to five times higher than the ones calculated in the CAD scaffold. In addition high variability among samples was found: at the same location velocity and shear stress values could be up to two times higher from sample to sample. This study shows that regular scaffolds need to be thoroughly analysed in order to quantify real cell mechanical stimuli so inspection methods should be included as part of the fabrication process.
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Michels, Lucile, Vera Gorelova, Yosapol Harnvanichvech, Jan Willem Borst, Bauke Albada, Dolf Weijers, and Joris Sprakel. "Complete microviscosity maps of living plant cells and tissues with a toolbox of targeting mechanoprobes." Proceedings of the National Academy of Sciences 117, no. 30 (July 15, 2020): 18110–18. http://dx.doi.org/10.1073/pnas.1921374117.
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Mechanical patterns control a variety of biological processes in plants. The microviscosity of cellular structures effects the diffusion rate of molecules and organelles, thereby affecting processes such as metabolism and signaling. Spatial variations in local viscosity are also generated during fundamental events in the cell life cycle. While crucial to a complete understanding of plant mechanobiology, resolving subcellular microviscosity patterns in plants has remained an unsolved challenge. We present an imaging microviscosimetry toolbox of molecular rotors that yield complete microviscosity maps of cells and tissues, specifically targeting the cytosol, vacuole, plasma membrane, and wall of plant cells. These boron-dipyrromethene (BODIPY)-based molecular rotors are rigidochromic by means of coupling the rate of an intramolecular rotation, which depends on the mechanics of their direct surroundings, with their fluorescence lifetime. This enables the optical mapping of fluidity and porosity patterns in targeted cellular compartments. We show how apparent viscosity relates to cell function in the root, how the growth of cellular protrusions induces local tension, and how the cell wall is adapted to perform actuation surrounding leaf pores. These results pave the way to the noninvasive micromechanical mapping of complex tissues.
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Vavakou, Anna, Jan Scherberich, Manuela Nowotny, and Marcel van der Heijden. "Tuned vibration modes in a miniature hearing organ: Insights from the bushcricket." Proceedings of the National Academy of Sciences 118, no. 39 (September 22, 2021): e2105234118. http://dx.doi.org/10.1073/pnas.2105234118.
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Bushcrickets (katydids) rely on only 20 to 120 sensory units located in their forelegs to sense sound. Situated in tiny hearing organs less than 1 mm long (40× shorter than the human cochlea), they cover a wide frequency range from 1 kHz up to ultrasounds, in tonotopic order. The underlying mechanisms of this miniaturized frequency-place map are unknown. Sensory dendrites in the hearing organ (crista acustica [CA]) are hypothesized to stretch, thereby driving mechanostransduction and frequency tuning. However, this has not been experimentally confirmed. Using optical coherence tomography (OCT) vibrometry, we measured the relative motion of structures within and adjacent to the CA of the bushcricket Mecopoda elongata. We found different modes of nanovibration in the CA that have not been previously described. The two tympana and the adjacent septum of the foreleg that enclose the CA were recorded simultaneously, revealing an antiphasic lever motion strikingly reminiscent of vertebrate middle ears. Over the entire length of the CA, we were able to separate and compare vibrations of the top (cap cells) and base (dorsal wall) of the sensory tissue. The tuning of these two structures, only 15 to 60 μm (micrometer) apart, differed systematically in sharpness and best frequency, revealing a tuned periodic deformation of the CA. The relative motion of the two structures, a potential drive of transduction, demonstrated sharper tuning than either of them. The micromechanical complexity indicates that the bushcricket ear invokes multiple degrees of freedom to achieve frequency separation with a limited number of sensory cells.
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Cheng, X., A. M. Sastry, and B. E. Layton. "Transport in Stochastic Fibrous Networks." Journal of Engineering Materials and Technology 123, no. 1 (July 31, 2000): 12–19. http://dx.doi.org/10.1115/1.1322357.
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Some fundamental issues concerning the design and performance of stochastic porous structures are examined, stemming from application of advanced fibrous electrode substrates in NiMH automotive cells. These electrodes must resist corrosion and local failures under hundreds of charge/discharge cycles. Such fibrous materials can be effectively used as substrates for chemical reactions because of their combinations of high surface area and high conductivity. Key questions concerning the relationships among connectivity and conductivity, scale and variability in material response are addressed. Two techniques are developed and compared for use in predicting these materials’ conductivity. The first approach uses a statistical technique in conjunction with an adaptation of classic micromechanical models. The second approach uses the statistical generation technique, followed by an exact calculation of 2D network conductivity. The two techniques are compared with one another and with classic results. Several important conclusions about the design of these materials are presented, including the importance of use of fibers with aspect ratios greater than at least 50, the weak effect of moderate alignment for unidirectional conductivity, and the weak power-law behavior of conductivity versus volume fraction over the range of possible behaviors.
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Monteiro-Reis, Sara, João P. S. Ferreira, Ricardo A. Pires, João Lobo, João A. Carvalho, Rui L. Reis, Renato Natal Jorge, and Carmen Jerónimo. "Bladder Wall Stiffness after Cystectomy in Bladder Cancer Patients: A Preliminary Study." Cancers 15, no. 2 (January 5, 2023): 359. http://dx.doi.org/10.3390/cancers15020359.
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Bladder cancer (BlCa), specifically urothelial carcinomas, is a heterogeneous disease that derives from the urothelial lining. Two main classes of BlCa are acknowledged: the non-muscle invasive BlCa and the muscle-invasive BlCa; the latter constituting an aggressive disease which invades locally and metastasizes systemically. Distinguishing the specific microenvironment that cancer cells experience between mucosa and muscularis propria layers can help elucidate how these cells acquire invasive capacities. In this work, we propose to measure the micromechanical properties of both mucosa and muscularis propria layers of the bladder wall of BlCa patients, using atomic force microscopy (AFM). To do that, two cross-sections of both the macroscopically normal urinary bladder wall and the bladder wall adjacent to the tumor were collected and immediately frozen, prior to AFM samples analysis. The respective “twin” formalin-fixed paraffin-embedded tissue fragments were processed and later evaluated for histopathological examination. H&E staining suggested that tumors promoted the development of muscle-like structures in the mucosa surrounding the neoplastic region. The average Young’s modulus (cell stiffness) in tumor-adjacent specimens was significantly higher in the muscularis propria than in the mucosa. Similarly, the tumor-free specimens had significantly higher Young’s moduli in the muscularis propria than in the urothelium. Young’s moduli were higher in all layers of tumor-adjacent tissues when compared with tumor-free samples. Here we provide insights into the stiffness of the bladder wall layers, and we show that the presence of tumor in the surrounding mucosa leads to an alteration of its smooth muscle content. The quantitative assessment of stiffness range here presented provides essential data for future research on BlCa and for understanding how the biomechanical stimuli can modulate cancer cells’ capacity to invade through the different bladder layers.
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Bhatia, R., N. Almqvist, S. Banerjee, G. Primbs, N. Desai, and R. Lai. "Single Molecule Force Spectroscopy Maps to Study Receptors Clustering." Microscopy and Microanalysis 7, S2 (August 2001): 860–61. http://dx.doi.org/10.1017/s1431927600030373.
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An atomic force microscope (AFM) allows molecular resolution imaging of hydrated specimens. However, it is often limited in providing identity of the imaged structures, especially in a complex system such as a cellular membrane. Cell surface macromolecules such as ion channels and receptors serve as the interface between the cytoplasm and the extracellular region and toward which many regulatory signals are directed. Their density, distribution and clustering are key spatial features influencing effective and proper physiological responses. We used a method that uses AFM “force-volume maps” to identify and map regional distribution as well as ligand-, or antibody-induced real-time clustering of receptors on the cell surface. This technique also allows simultaneous imaging of the resultant changes in cellular micromechanical properties, such as elasticity and cytoskeletal reorganization of the cell. As an appropriate physiological sample, we have examined spatial distribution and real-time clustering of VEGFR, the receptor for vascular endothelial growth factor which is an important angiogenic factor in human and animal tissues.We have used AFM probes conjugated with anti-VEGFR-antibody (anti-Flk-1 antibody) to examine binding (or unbinding) forces between VEGF-R2 (Flk-1) in both in vitro as well as in live endothelial cells. A quantal set of binding and unbinding forces was measured between the antibody conjugated to the AFM tip and purified VEGFRs adsorbed on to a mica surface (Fig 1). The unbinding force varied between 60 and 240 pN and was a multiple of discrete quantized strength of approximately 60 pN (Figure 1B).
Dissertations / Theses on the topic "Cells - Micromechanical Structures"
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Ott, Julia Katharina [Verfasser], and M. [Akademischer Betreuer] Kamlah. "Modeling the Microstructural and Micromechanical Influence on Effective Properties of Granular Electrode Structures with regard to Solid Oxide Fuel Cells and Lithium Ion Batteries / Julia Katharina Ott. Betreuer: M. Kamlah." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1077821891/34.
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Xiao, Long. "A structural micromechanical model of large deformation behavior of red blood cells." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1458440.
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Boehm, Heike. "Micromechanical properties and structure of the pericellular coat of living cells modulated by nanopatterned substrates." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-89646.
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Venkatesh, Kadbur Prabhakar Rao. "Experimental Studies on Extremely Small Scale Vibrations of Micro-Scale Mechanical and Biological Structures." Thesis, 2017. http://etd.iisc.ac.in/handle/2005/3541.
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Experimental vibration analysis of mechanical structures is a well established field.Plenty of literature exists on macro scale structures in the fields of civil, mechanical and aerospace engineering, but the study of vibrations of micro scale structures such as MEMS, liquid droplets, and biological cells is relatively new. For such structures, the amplitudes of vibration are typically in nanometeror sub-nanometer range and the frequencies are in KHz to MHz range depending upon the dimensions of the structure. In our study, we use a scanningLaser Doppler Vibrometer (LDV) to measure the vibrations of micro-scale objects such as MEMS structures, micro droplets and cells. The vibrometercan capture frequency response up to 24 MHz withpicometer displacement resolution.
First, we present the study of dynamics of a 2-D micromechanical structure—a MEMSelectrothermal actuator. The structure is realized using SOI MUMPs process from MEMSCAP. The fabricated device is tested for its dynamic performance characteristics using the LDV. In our experiments, we could capture up to 50 out-of-plane modes of vibration—an unprecedented capture—with a single excitation. Subsequent FEM based numerical simulations confirmed that the captured modes were indeed what the experiments indicated, and the measured frequencies werefound to be within 5% of theoretically predicted. Next, we study the dynamics of a 3-D micro droplet and show how the substrate adhesion modulates the natural frequency of the droplet. Adhesion properties of droplets are decided by the degree of wettability that is generally measured by the contact angle between the substrate and the droplet. In this work, we were able to capture 14 modes of vibration of a mercury droplet on different substrates and measure the correspondingfrequencies experimentally. We verify these frequencies with analytical calculations and find that all the measured frequencies are within 6% of theoretically predicted values. We also show that considering any two pairs of natural frequencies, we can calculate the surface tension and the contact angle, thus providing a new method for measuring adhesion of a droplet on an unknown surface. Lastly, we present a study of vibrations of biological cells.Our first study is that of single muscle fibers taken from drosophila.Muscle fibers with different pathological conditions were held in two structural configurations—asa fixed-fixed beam and a cantilever beam—and their vibration signatures analysed.We found that there was significant reduction in natural frequency of diseased fibers. Among the diseased fibers, we could confidently classify the myopathies into nemaline and cardiac types based on the natural frequency of single fibers. We have noticed that the elastic modulus of the muscle which decides the natural frequency is dictated by the myosin expression levels. Our last example isa study of the vibration signatures of cancer cells. Here we measure the natural frequencies of normal and certain cancerous cells, and show that we can distinguish the two based on their natural frequencies. We find that the natural frequency of cancerous cells is approximately half of that of normal cells. Within the cancerous cells, we are able to distinguished epithelial cancer cells and mesenchymal cancer cells based on their natural frequency values. For Epithelial cells,we activate the signaling pathways to induce EMT and notice the reduction in the natural frequency. This mechanical assay based on vibration response corroborates results from the biochemical assays such as Western blots and PCR, thus opening a new technique of mechano-diagnostics.
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Venkatesh, Kadbur Prabhakar Rao. "Experimental Studies on Extremely Small Scale Vibrations of Micro-Scale Mechanical and Biological Structures." Thesis, 2017. http://etd.iisc.ernet.in/2005/3541.
Full textAbstract:
Experimental vibration analysis of mechanical structures is a well established field.Plenty of literature exists on macro scale structures in the fields of civil, mechanical and aerospace engineering, but the study of vibrations of micro scale structures such as MEMS, liquid droplets, and biological cells is relatively new. For such structures, the amplitudes of vibration are typically in nanometeror sub-nanometer range and the frequencies are in KHz to MHz range depending upon the dimensions of the structure. In our study, we use a scanningLaser Doppler Vibrometer (LDV) to measure the vibrations of micro-scale objects such as MEMS structures, micro droplets and cells. The vibrometercan capture frequency response up to 24 MHz withpicometer displacement resolution.
First, we present the study of dynamics of a 2-D micromechanical structure—a MEMSelectrothermal actuator. The structure is realized using SOI MUMPs process from MEMSCAP. The fabricated device is tested for its dynamic performance characteristics using the LDV. In our experiments, we could capture up to 50 out-of-plane modes of vibration—an unprecedented capture—with a single excitation. Subsequent FEM based numerical simulations confirmed that the captured modes were indeed what the experiments indicated, and the measured frequencies werefound to be within 5% of theoretically predicted. Next, we study the dynamics of a 3-D micro droplet and show how the substrate adhesion modulates the natural frequency of the droplet. Adhesion properties of droplets are decided by the degree of wettability that is generally measured by the contact angle between the substrate and the droplet. In this work, we were able to capture 14 modes of vibration of a mercury droplet on different substrates and measure the correspondingfrequencies experimentally. We verify these frequencies with analytical calculations and find that all the measured frequencies are within 6% of theoretically predicted values. We also show that considering any two pairs of natural frequencies, we can calculate the surface tension and the contact angle, thus providing a new method for measuring adhesion of a droplet on an unknown surface. Lastly, we present a study of vibrations of biological cells.Our first study is that of single muscle fibers taken from drosophila.Muscle fibers with different pathological conditions were held in two structural configurations—asa fixed-fixed beam and a cantilever beam—and their vibration signatures analysed.We found that there was significant reduction in natural frequency of diseased fibers. Among the diseased fibers, we could confidently classify the myopathies into nemaline and cardiac types based on the natural frequency of single fibers. We have noticed that the elastic modulus of the muscle which decides the natural frequency is dictated by the myosin expression levels. Our last example isa study of the vibration signatures of cancer cells. Here we measure the natural frequencies of normal and certain cancerous cells, and show that we can distinguish the two based on their natural frequencies. We find that the natural frequency of cancerous cells is approximately half of that of normal cells. Within the cancerous cells, we are able to distinguished epithelial cancer cells and mesenchymal cancer cells based on their natural frequency values. For Epithelial cells,we activate the signaling pathways to induce EMT and notice the reduction in the natural frequency. This mechanical assay based on vibration response corroborates results from the biochemical assays such as Western blots and PCR, thus opening a new technique of mechano-diagnostics.
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Böhm, Heike [Verfasser]. "Micromechanical properties and structure of the pericellular coat of living cells modulated by nanopatterned substrates / vorgelegt von Heike Boehm." 2009. http://d-nb.info/992618665/34.
Full textBook chapters on the topic "Cells - Micromechanical Structures"
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Lim, D. J., Y. Hanamure, and Y. Ohashi. "Structural Organization of the Mammalian Auditory Hair Cells in Relation to Micromechanics." In Cochlear Mechanisms: Structure, Function, and Models, 3–10. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5640-0_1.
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Macaro, G., and S. Utili. "DEM Triaxial Tests of a Seabed Sand." In Discrete Element Modelling of Particulate Media, 203–11. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849733601-00203.
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DEM triaxial tests were run in a 3D periodic boundary cell containing 5000 spherical particles employing the open source code YADE to replicate the behavior of some typical seabed sands (i.e. Leighton Buzzard and North Australian shelf). The contact law adopted was the Hertz-Mindlin no-slip solution together with a linear moment – relative rotation law meant to account for the non-sphericity of the real sand grains. The chosen contact law is based on 5 independent micromechanical (i.e. at the level of contacts) parameters: two elastic parameters for the Hertz-Mindlin law, intergranular friction and two parameters for the moment - relative rotation law. The values for the elastic constants and the intergranular friction adopted in the simulations were taken from the elastic and frictional properties of the minerals of the sand grains (mainly quartz). Simulations were run for different values of the two parameters of the moment - relative rotation law. Tests were carried out on samples generated at various initial relative densities (from loose to very dense). The obtained results were very encouraging since the stress-strain behavior exhibited by the numerical samples well matched the experimentally measured values of critical state friction angle and dilatancy angle. However, dense samples showed a less good agreement regarding the peak friction angle. The tests were carried out as part of a larger research program on the lateral soil-structure interaction for pipelines lying on sandy seabeds. An extensive program of 3D plain strain tests involving a plane strain section of the pipeline is currently underway.
Conference papers on the topic "Cells - Micromechanical Structures"
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Wang, Yu, and Alberto M. Cuitiño. "Nonlinear Modeling of 3D Open-Cell Foams." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0519.
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Abstract In this article, we present a hyperelastic model for light and compliant open cell foams with an explicit correlation between microstructure and macroscopic behavior. The model describes a large number of three dimensional structures with regular and irregular cells. The theory is based on the formulation of strain-energy function accounting for stretching which is the main deformation mechanism in this type of materials. Within the same framework, however, bending, shear and twisting energies can also be incorporated. The formulation incorporates nonlinear kinematics which traces the evolution of the structure during loading process and its effects on the constitutive behavior, including the cases where configurational transformations are present leading to non-convex strain-energy functions. Also nonlinear material effects at local or beam level are introduced to accommodate a wide range of different material behaviors. Since the micromechanical formulation presented here has explicit correlation with the foam structure, it preserves in the constitutive relation the symmetries or directional properties of the corresponding structures, including the cases of re-entrant foams which exhibit negative Poisson’s ratio effects. The model captures the central features exhibit by these materials. Predictions of the model for macroscopic uniaxial strain are presented in this article.
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Meaud, Julien, Thomas Bowling, and Charlsie Lemons. "Computational Modeling of Spontaneous Otoacoustic Emissions by the Mammalian Cochlea." In ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-9044.
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The mammalian cochlea is a sensory system with high sensitivity, sharp frequency selectivity and a broad dynamic range. These characteristics are due to the active nonlinear feedback by outer hair cells. Because it is an active nonlinear system, the cochlea sometimes emits spontaneous otoacoustic emissions (SOAEs) that are generated in the absence of any external stimulus due to the emergence of limit cycle oscillations. In this work, we use a computational physics-based model of the mammalian cochlea to investigate the generation of SOAEs. This model includes a three-dimensional model of the fluid mechanics in the cochlear ducts, a micromechanical model for the vibrations of the cochlear structures, and a realistic model of outer hair cell biophysics. Direct simulations of SOAEs in the time-domain demonstrate that the model is able to capture key experimental observations regarding SOAEs. Parametric studies and analysis of model simulations are used to demonstrate that SOAEs are a global phenomenon that arises due to the collective action of a distributed region of the cochlea rather than from spontaneous oscillations from individual outer hair cells.
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Ju, Jaehyung, Joshua D. Summers, John Ziegert, and Georges Fadel. "Nonlinear Elastic Constitutive Relations of Auxetic Honeycombs." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12654.
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When designing a flexible structure consisting of cellular materials, it is important to find the maximum effective strain of the cellular material resulting from the deformed cellular geometry and not leading to local cell wall failure. In this paper, a finite in-plane shear deformation of auxtic honeycombs having effective negative Poisson’s ratio is investigated over the base material’s elastic range. An analytical model of the inplane plastic failure of the cell walls is refined with finite element (FE) micromechanical analysis using periodic boundary conditions. A nonlinear constitutive relation of honeycombs is obtained from the FE micromechanics simulation and is used to define the coefficients of a hyperelastic strain energy function. Auxetic honeycombs show high shear flexibility without a severe geometric nonlinearity when compared to their regular counterparts.
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Nankali, Amir, and Karl Grosh. "Stability and Bifurcation Analysis of a Nonlinear Cochlear Model." In ASME 2014 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/detc2014-35657.
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Hearing relies on a series of coupled electrical, acoustical (fluidic) and mechanical interactions inside the cochlea that enable sound processing. The stability of the cochlea is studied using a nonlinear, micromechanical model of the organ of Corti (OoC) coupled to the electrical potentials in the cochlear ducts. The OoC is part of the mammalian cochlea that contains auditory sensory cells that both identify fluid-born vibrations in the cochlea and amplify the cycle-by-cycle motions of the cochlear structures. This process occurs through local resonance of the OoC system. In the mammalian cochlea, an active process accounts for the ear’s exquisite sensitivity and its remarkable responsiveness for a range of frequencies and intensities. Numerical and analytical techniques are utilized to examine the stability of this system. It is observed that the cochlear active process, controls the stability. We show that instability in this model is generated through a supercritical Hopf bifurcation. Furthermore, a reduced order model of the system is approximated and it is shown that the tectorial membrane (TM) transverse mode effect on the dynamics is significant while the radial mode can be simplified from the equations. We compare the cross sectional model with the comprehensive 3-dimensional model of the cochlea. It is indicated that the global model qualitatively inherits some characteristics of the local model, but the longitudinal coupling along the cochlea enhances stability (i.e., shifts the Hopf bifurcation point).
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Tang, Tian, and Wenbin Yu. "Micromechanics Modeling of the Nonlinear Behavior of Electrostrictive Multiphase Composites." In ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-370.
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The micromechanics modeling of the nonlinear behavior of the electrostrictive multiphase composites is developed using an incremental formulation based on the variational asymptotic method for unit cell homogenization (VAMUCH), a recently developed micromechanics modeling scheme. The microstructure of composites is assumed to be periodic. Taking advantage of the small size of the microstructure, we formulate a variational statement of energy change of the unit cell through an asymptotic analysis of the functional by invoking only two essential assumptions within the concept of micromechanics. Finally, the expression of the effective instantaneous tangential electromechanical matrix of the composites are established. Several numerical examples will be used to demonstrate the capability of the present theory.
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Sullivan, Daniel J., Paul A. Taylor, and Assimina A. Pelegri. "A Micromechanical Model for Shear-Induced Platelet Damage in Capillaries Within Gray Matter." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-66794.
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In order to expand on potential injury mechanisms to the brain, a micromechanical structural representation of the gray matter must be developed. The gray matter contains a high volume of capillary vasculature that supplies the necessary oxygen required for maintaining healthy cell and brain function. Even short disruptions in this blood supply and the accompanying dissolved oxygen can lead to neuronal cell damage and death. It has been shown that increased shearing forces within the blood, such as those found near stents and artificial heart valves, can lead to platelet activation and aggregation, causing clots to form and potential disruptions in blood flow and oxygen distribution. Current macro-scale computational brain modeling can incorporate the larger main vasculature of the brain, but it becomes too computationally expensive to incorporate the smaller vessels. These larger scale models can be used to reveal how forces to the head are transmitted down to a scale slightly larger than the smallest capillaries within the gray matter. In order to investigate the response and potential damage to capillaries and platelets within the brain, a micromechanical computational model is developed incorporating the gray matter, capillaries, and blood, which is composed of plasma, red blood cells, and platelets. The red blood cells are a necessary component for the model for damage as it comprises almost half of the volume of blood and is the major contributor to the non-Newtonian behavior. The model combines both fluids and viscoelastic solid materials (the gray matter and the vascular wall). The deviatoric stress, strain and strain rate of the platelets in response to an externally applied load is measured and will determine the potential for platelet aggregation and clot formation. The micromechanical model is also used to provide verification and refinement for existing constitutive models for the gray matter used in meso- and macro-scale computational models.
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Romero, Pedro A., and Alberto M. Cuitin˜o. "Modeling of Dynamically Loaded Open-Cell Metallic Foams." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41906.
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Heterogeneous cellular materials such as metallic and polymeric open-celled foams are preferable in many engineering applications requiring mitigation of energy during sudden impact loading. This brief communication presents an approach for modeling dynamically loaded open-cell metallic foams. It is implicitly assumed that there exists a length scale separation where the microstructural dimensions are much smaller than the macroscopic dimensions. In this context, a macroscopic point translates into a microscopic array of identical unit cells sharing the same macroscopic fields. Dictated by a model for the metallic cell wall constitutive behavior, the effective unit cell response is then obtained from a structural micromechanical model which enforces the principle of minimum action on a representative 3D unit cell. The effective macroscopic response at every node in the FEM mesh (equilibrium, stresses, stress tangents) is then provided by the unit cell microscopic model. The present theory allows one to define a constitutive formulation for lightweight, open-celled foams based on clear and quantifiable parameters such as microstructural topology and ligament properties while capturing the effects of dynamic loading via viscous dissipation at ligament level and microinertia at unit cell level. History of deformation is considered at ligament level while axial and bending deformation are considered at unit cell level. As observed experimentally, the resulting macroscopic FEM simulations clearly demonstrate how the material undergoes heterogeneous deformation during cellular structure collapse.
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Yu, Jaesang, Thomas Lacy, Hossain Toghiani, and Charles Pittman. "Material Property Estimations and Comparisons of Nano-Reinforced Polymer Composites Using Classical Micromechanics and the Generalized Method of Cells." In 51st AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
18th AIAA/ASME/AHS Adaptive Structures Conference
12th. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-2646.
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Tabiei, Ala, and Romil Tanov. "Sandwich Shell Model With Woven Fabric Facings for Nonlinear Finite Element Simulation." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2038.
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Abstract This paper presents a micromechanical model for analysis of woven fabric composites. The micro model is coupled with a shell element developed for the analysis of sandwich structures. Starting with the average strains in the representative volume cell and based on continuity requirements at the sub-cell interfaces, the strains and stresses in the composite constituents are determined as well as the average stresses in the lamina. In their formulation the developed micromechanical models take into consideration all components of the 3-D strain and stress tensors. The formulation is implemented in the explicit nonlinear finite element code DYNA3D. The performance of the model is assessed through couple of examples. The simplicity of formulation makes this model attractive for the nonlinear finite element analysis of sandwich composite structures with woven facings.
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Kim, Jeong Sik, Anastasia Muliana, and Kamran Khan. "A Homogenization Scheme for Nonlinear Viscoelastic Behaviors of Particulate Reinforced Composites." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13598.
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The present study introduces a micromechanical model for predicting nonlinear viscoelastic responses of composite systems reinforced with solid spherical micro particles. The composite microstructures are simplified with uniformly distributed cubic particles over an infinite medium. The representative volume element (RVE) consists of a single particle embedded in the cubic matrix. One eighth unit-cell model with four particle and polymer subcells is generated. The solid spherical particle is modeled as linear elastic, while the polymer follows nonlinear viscoelastic material responses. The homogenized micromechanical relation is developed in terms of the average strains and stresses and satisfies traction continuity and displacement compatibility at the subcells' interfaces. The micromechanical model provides three-dimensional (3D) effective properties of homogeneous materials, while recognizing important micro-structural aspects and parameters of the heterogeneous medium. The micromechanical formulation is generalized to include an explicit time-scale for modeling time-dependent behavior and is designed to be compatible with general displacement based finite element (FE) analyses. Due to the nonlinear and time-dependent response in the polymeric matrix, the linearized micromechanical relations will often deviate from the nonlinear constitutive equations. Thus, the stress-strain correction scheme is formulated to satisfy both micromechanical and nonlinear constitutive relations. Experimental data and analytical models available in the literature are used to verify the capability of the above micromechanical model in predicting the overall nonlinear behaviors. Comparisons with detail unit-cell FE model are also presented.
Reports on the topic "Cells - Micromechanical Structures"
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Roy, A. K., K. Li, and X. L. Gao. Micromechanical Analysis of Three-Dimensional Open-Cell Foams Using the Matrix Method for Space Frame Structures. Fort Belvoir, VA: Defense Technical Information Center, November 2004. http://dx.doi.org/10.21236/ada428834.
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