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Now showing items 1 - 16 of 21

  • A Minimal Mechanochemical Model for Growth Cone Dynamics

    Rammohan, Aravind R.   Rangamani, Padmini   Stolarska, Magdalena  

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  • Computational Model of Integrin Clustering in Response to Actin Turnover

    Bidone, Tamara C.   Rammohan, Aravind R.   McKenzie, Matt   Voth, Gregory A.  

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  • Role of Anisotropic Focal Adhesion Growth on Cellular Traction and Shape

    Rammohan, Aravind R.   Raghavan, Srikanth   Stolarska, Magdalena  

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  • Center or periphery? Modeling the effects of focal adhesion placement during cell spreading

    Stolarska, Magdalena A.   Rammohan, Aravind R.  

    Focal adhesions are often observed at the cell's periphery. We provide an explanation for this observation using a system-level mathematical model of a cell interacting with a two-dimensional substrate. The model describes the biological cell as a hypoelastic continuum material whose behavior is coupled to a deformable, linear elastic substrate via focal adhesions that are represented by collections of linear elastic attachments between the cell and the substrate. The evolution of the focal adhesions is coupled to local intracellular stresses which arise from mechanical cell-substrate interactions. Using this model we show that the cell has at least three mechanisms through which it can control its intracellular stresses: focal adhesion position, size, and attachment strength. We also propose that one reason why focal adhesions are typically located on the cell periphery instead of its center is because peripheral focal adhesions allow the cell to be more sensitive to changes in the microenvironment. This increased sensitivity is caused by the fact that peripherally located focal adhesions allow the cells to modulate its intracellular properties over a much larger portion of the cell area.
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  • Effect of Nanoscale Roughness on Adhesion between Glassy Silica and Polyimides:A Molecular Dynamics Study

    Lee, Sung Hoon   Stewart, Ross J.   Park, Hyunhang   Goyal, Sushmit   Botu, Venkatesh   Kim, Hyunbin   Min, Kyoungmin   Cho, Eunseog   Rammohan, Aravind R.   Mauro, John C.  

    The effect of nanoscale roughness on the adhesion between glassy silica and polyimides is examined by molecular dynamics simulation. Different silica surfaces, with varying degrees of roughness, were generated by cleaving bulk structures with a predefined surface and a desired average roughness, with different roughness periods and hydroxylation densities in an effort to study the influence of these surface characteristics on adhesion at the silica-polyimide interface. The calculated results reveal that average roughness R-a is the primary controlling factor within the considered conditions. Further, an energy decomposition analysis of the pulling process suggests that hydrogen bonding contributes to the adhesion on all the rough surfaces, while the Coulombic energy contribution becomes significant at higher R-a. From a structural analysis of the vacant volume and surface area, it is shown that the periodicity of roughness provides a rather interesting trend for the adhesion energy. Adhesion can increase with a reduction in period due to the corresponding surface area expansion; however, if vacant volumes exist at the interface, the level of adhesion can decrease. Competition between two opposing tendencies leads to the maximum adhesion, and hence, both R-a and period are key parameters to control the adhesion in nanoscale roughness.
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  • A Self-Consistent Multiscale Methodology for Predicting Adhesion of Mammalian Cells onto Functionalized Surfaces

    Rammohan, Aravind R.   Mckenzie, Matthew   Miner, Jacob   ramakrishnan, Natesan   Radhakrishnan, Ravi  

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  • Spreading Out: Modeling the Physics of Cell-Substrate Interaction in Cell Spreading and Focal Adhesion Evolution

    Stolarska, Magdalena   Rammohan, Aravind R.  

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  • Eulerian Flow Field Estimation from Particle Trajectories:? Numerical Experiments for Stirred Tank Type Flows

    Rammohan, Aravind R.   Dudukovi?, Milorad P.   Ranade, Vivek V.  

    The computer automated radioactive particle tracking (CARPT) and positron emission particle tracking (PEPT) techniques have been developed to characterize opaque multiphase flows. In CARPT and PEPT, the Eulerian flow field is inferred from the knowledge of reconstructed tracer particle trajectories. The present study was undertaken to assess the strengths and limitations of the process of estimating the Eulerian flow field from particle trajectories. A two-dimensional problem, which mimics the characteristics of flow in a stirred tank reactor equipped with a standard Rushton turbine, was considered. The Eulerian flow field was numerically simulated. Care was taken to minimize effects of numerical issues on the computed flow field, which was then used to calculate particle trajectories. Standard CARPT data processing was carried out on the simulated particle trajectories to estimate the Eulerian flow field. This estimated flow field was compared with the original flow field used for trajectory simulations to evaluate possible errors associated with the CARPT data processing and flow follow-ability of the particles. Influence of grid used for data processing, sampling frequency, and particle size and particle density on the estimated flow field was examined. The study highlights several issues pertaining to the estimation of the Eulerian flow field from Lagrangian information. The results provide guidelines for selecting appropriate parameters in processing of CARPT or PEPT data.
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  • Grafting Functional Groups in Polymeric Binder toward Enhancing Structural Integrity of LixSiO2 Anode during Electrochemical Cycling

    Min, Kyoungmin   Rammohan, Aravind R.   Lee, Sung Hoon   Goyal, Sushmit   Park, Hyunhang   Stewart, Ross   He, Xiaoxia   Cho, Eunseog  

    Development of a novel polymeric binder material is necessary for improving the electrochemical performance of silicon-based anodes for Li-ion batteries, suffering from irreversible capacity loss due to their huge volume change during the electrochemical cycling. However, relevant mechanisms on how adhesion and mechanical properties of the binder are correlated to the stability of Si anode are still lacking. In this study, we investigate the role of functional groups attached in the polymeric binder on the structural stability of LixSiO2 using molecular dynamics simulations. A pulling test reveals that the binder with a polar group shows better adhesion properties with LixSiO2 than that with a nonpolar group. In addition, cohesive failure dominates the failure mode for the nonpolar group, but an adhesive to cohesive failure transition occurs for the polar group as the amount of lithiation is increased. For mechanical properties, the polar binder exhibits a larger maximum stress, while the nonpolar one can hold a larger strain. Finally, the polar group works more effectively to suppress the volume expansion of LixSiO2 from lithiation. The current study reveals detailed mechanisms on how polar and nonpolar polymeric binders work differently with glasses of varying degrees of lithiation and can guide the design of future generations of Si-based anodes.
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  • Characterizing the Fundamental Adhesion of Polyimide Monomers on Crystalline and Glassy Silica Surfaces:A Molecular Dynamics Study

    Goyal, Sushmit   Park, Hyun-Hang   Lee, Sung Hoon   Savoy, Elizabeth   McKenzie, Mathew E.   Rammohan, Aravind R.   Mauro, John C.   Kim, Hyunbin   Min, Kyoungmin   Cho, Eunseog  

    Understanding the interaction between polyimide and inorganic surfaces is vital in controlling interfacial adhesion behavior. Here, molecular dynamics simulations are employed to study the adhesion of polyimide on both crystalline and glassy silica surfaces, and the effects of hydroxylation, silica structure, and polyimide chemistry on adhesion are investigated. The results reveal that polyimide monomers have stronger adhesion on hydroxylated surfaces compared to nonhydroxylated surfaces. Also, adhesion of polyimide onto silica glass is stronger compared to the corresponding crystalline surfaces. Finally, we explore the molecular origins of adhesion to understand why some polyimide monomers like Kapton have a stronger adhesion per unit area (adhesion density) than others like BPDAAPB. We find this occurs due to a higher density of oxygen's in the Kapton monomer, which we found to have the highest contribution to, adhesion density.
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  • A Computational Framework to Accurately Predict Enthalpy and Configurational Entropy Landscapes of Multivalent Interactions of Cell Mimetics

    Rammohan, Aravind R.   Mckenzie, Matthew   Radhakrishnan, Ravi   Ramakrishnan, Natesan  

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  • A Computational Framework to Accurately Predict Enthalpy and Configurational Entropy Landscapes of Multivalent Interactions of Cell Mimetics

    Rammohan, Aravind R.   Mckenzie, Matthew   Radhakrishnan, Ravi   Ramakrishnan, Natesan  

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  • Cellular Adhesion: Evaluating the Effect of Receptor-Ligand Chemistries, Distribution of Receptors, and Spread Versus Spherical Cell Geometry

    Rammohan, Aravind R.   Mckenzie, Mathew   Radhakrishnan, Ravi   Ramakrishnan, Natesan  

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  • No Life Less Worthy: The Posthumanist Framework of Aravind Adiga's\r The White Tiger

    Graham-Bertolini Alison  

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  • Making Sight Affordable (\r Innovations Case Narrative: The Aravind Eye Care System\r )

    Rangan, V. Kasturi   Thulasiraj, R. D.  

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  • The Cataract Blindness Challenge\r Innovations Case Discussion: Aravind Eye Care System\r )

    Tabin   Geoffrey  

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