Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session D18: Biofluids: Complex Interaction |
Hide Abstracts |
Chair: Roland Bouffanais, Singapore University of Technology and Design Room: 28D |
Sunday, November 18, 2012 2:15PM - 2:28PM |
D18.00001: The effect of extracellular conductivity on electroporation-mediated molecular delivery Miao Yu, Mohamed Sadik, Jianbo Li, Hao Lin Electroporation is a non-viral technique to introduce foreign molecules into a biological cell with electric fields. In this work, the effect of extracellular conductivity on electroporation-mediated molecular delivery efficiency is numerically investigated, and the results are compared in details with experimental data. The model couples the Smoluchowski equation and the Nernst-Planck equations to solve for the evolution of membrane permeabilization and ion transport simultaneously. The uptake of Propidium Iodide (PI) into single 3T3 fibroblast cells is simulated. The results quantitatively predict the experimental observations, and that the total delivery is reciprocally correlated with the extracellular conductivity. This correlation is mediated primarily by electrophoretic transport induced by a gradient in the electric field. A compact formula is also developed to estimate ion delivery based on the pulsing parameters. This work offers a mechanistic interpretation to experimental observations. In synergy with experimental efforts, the quantification of molecular delivery via electroporation has been achieved. [Preview Abstract] |
Sunday, November 18, 2012 2:28PM - 2:41PM |
D18.00002: The compliance of vascular endothelial cells (VECs) change after exposure to cyclic, uniaxial stretch Kathryn Osterday, Thomas Chew, Loury Phillip, Jason Haga, Manuel Gomez-Gonzalez, Juan Carlos del Alamo, Shu Chien In vivo, VECs are exposed to both shear stress and cyclic, uniaxial stretch. It is known that VECs remodel their cytoskeleton perpendicular to stretch and parallel to shear and that cytoskeletal structure is critical to vessel function. Cytoskeletal structure must affect the magnitude and direction of the maximum and minimum shear compliance of the cytoplasm. This may provide the cell with a mechanism to tune their sensitivity to external mechanical stimuli differently along different directions, providing the flow-sensing mechanism needed for mechanotransduction. To study how cytoskeletal remodeling is correlated to changes in subcellular microrheology, we used directional particle tracking microrheology (DPTM) to calculate the shear compliance of the cytoplasm before and after exposure to cyclic, uniaxial stretch. When stretched, we find, VECs align their direction of maximum shear compliance perpendicular to stretch, their cytoplasm becomes less liquid, and the magnitude of the shear compliance along both directions of mechanical polarization decrease. [Preview Abstract] |
Sunday, November 18, 2012 2:41PM - 2:54PM |
D18.00003: Fluid coupling in continuum modeling of microtubule motility assays Christel Hohenegger, Tamar Shinar Active networks are suspensions of actuated filaments obtained by mixing cytoskeletal filaments and small motor protein complexes. The network activity is achieved by the motion of the motor proteins along the filaments. Here, we focus on motility assays, where the molecular motors are anchored to a bottom plate and filaments are observed to glide in a quasi two-dimensional plane. In contrast to other studies, we are not interested in the detailed motion of each individual filament but only in the resulting coarse grained properties. We present a new continuum macroscopic model of motility assays including the evolution of rigid filaments density, bound and free motors densities and fluid velocity. The coupling between the fluid and the filaments is described via external, localized molecular forces inspired from the immersed boundary method. The reduction to a two-dimensional system in the plane of motion of the filaments is achieved via depth-averaging similar to Hele-Shaw approximation. We conclude with numerical simulations of the coupled two dimensional model with periodic boundary conditions. [Preview Abstract] |
Sunday, November 18, 2012 2:54PM - 3:07PM |
D18.00004: Modeling Cell Desiccation with Glass Formation Chris Vogl, Michael Miksis, Stephen Davis, David Salac Lyopreservation is a preservation technique that seeks to store cells at room temperature. The storage process involves desiccating cells filled with special glass-forming sugars. However, care must be taken during the desiccation process to avoid both damaging membrane stress and to ensure the complete formation of glass throughout the cell. A lipid vesicle model is used here to study this process. The vesicle is represented as a moving interface (tracked by a level set method) with bending rigidity and incompressibility conditions. The vesicle is placed in a fluid containing a spatially varying sugar concentration field. As physical cells are impermeable to the sugar, the vesicle's impermeability is enforced with an immersed interface method. This results in a concentration jump across the vesicle's membrane, which in turn determines the flow of fluid through the membrane. Various desiccation techniques are simulated with this model. The effectiveness of each technique at minimizing membrane stress while ensuring glass formation will be discussed. [Preview Abstract] |
Sunday, November 18, 2012 3:07PM - 3:20PM |
D18.00005: ABSTRACT WITHDRAWN |
Sunday, November 18, 2012 3:20PM - 3:33PM |
D18.00006: The influence of cell crawling onto cell--cell chemical signaling Roland Bouffanais Chemotactic cells such as amoebae and leukocytes are able to aggregate and self-organize by means of local cell--cell chemical signaling. The chemical cAMP, which is produced by the cell, diffuses through the fluid from the emitting cell's membrane and binds to the neighboring cells' chemoreceptors. Such a purely diffusive view of this chemical signaling process fails to account for the fact that the cell's membrane constantly underges motions in relation with the specific motile behavior of these cells, namely crawling. We investigate the influence of cell motion/crawling onto the effectiveness of short-range chemical signaling. Our model is built on the study of an advection-diffusion process at the microscale of a cell for which diffusion is relatively ``fast,'' and the flow generated by the cell while crawling is an incompressible Stokes flow given the smallness of the Reynolds number. A particular emphasis is placed on the effects of advection onto the generation of a steeper chemical gradient which can have a significant impact onto the chemosensing effectiveness. [Preview Abstract] |
Sunday, November 18, 2012 3:33PM - 3:46PM |
D18.00007: Multiscale Modeling of Virus Entry via Receptor-Mediated Endocytosis Jin Liu Virus infections are ubiquitous and remain major threats to human health worldwide. Viruses are intracellular parasites and must enter host cells to initiate infection. Receptor-mediated endocytosis is the most common entry pathway taken by viruses, the whole process is highly complex and dictated by various events, such as virus motions, membrane deformations, receptor diffusion and ligand-receptor reactions, occurring at multiple length and time scales. We develop a multiscale model for virus entry through receptor-mediated endocytosis. The binding of virus to cell surface is based on a mesoscale three dimensional stochastic adhesion model, the internalization (endocytosis) of virus and cellular membrane deformation is based on the discretization of Helfrich Hamiltonian in a curvilinear space using Monte Carlo method. The multiscale model is based on the combination of these two models. We will implement this model to study the herpes simplex virus entry into B78 cells and compare the model predictions with experimental measurements. [Preview Abstract] |
Sunday, November 18, 2012 3:46PM - 3:59PM |
D18.00008: Interaction between endothelial cells and albumin encapsulated droplets in Poiseuille flow Robinson Seda, J. Brian Fowlkes, Joseph Bull Acoustic droplet vaporization (ADV) of DDFP encapsulated microdroplets has the ability to transform these emulsions into larger gas emboli capable of occluding blood vessels for therapy. An albumin shell is able to stabilize the droplet's superheated core, but can also interact with endothelial cells (EC) at the vessel wall if in close proximity. Radial migration of these microdroplets could bring them close enough to make this interaction possible leading to bioeffects that include cell detachment and death if an ADV event occurs. The purpose of this study is to investigate the hydrodynamic conditions (i.e. shear stresses) that make possible this EC-droplet interaction. A flow chamber coated with a monolayer of EC and connected to a syringe pump is used to flow a DDFP droplet solution at physiological shear stresses (1-50 dyne/cm$^{2})$ and inspected for droplet attachment. Droplets have been observed to interact and reversibly attach to EC in a static environment, thus it is expected that at low shear stress values interaction and further attachment will be possible. Knowing the flow conditions at which this interaction is likely to occur will aid in preventative measures to avoid significant bioeffects associated with ADV near the vessel wall. [Preview Abstract] |
Sunday, November 18, 2012 3:59PM - 4:12PM |
D18.00009: Modeling Lymphoma Growth in an Evolving Lymph Node Using a Diffuse Domain Approach Yao-Li Chuang, Vittorio Cristini, Ying Chen, Xiangrong Li, Hermann Frieboes, John Lowengrub Tumor growth often poses as a multiphase free-boundary problem as tumor cells aggregate into distinct subdomains due to differentiated cell-cell and cell-matrix adhesion. In ``Three-dimensional multispecies nonlinear tumor growth - I Model and numerical method'' [Wise et al., J. Theor. Biol. 253, pp. 524-543 (2008)], we have developed a multiphase Cahn-Hilliard model to study morphological patterns of tumor growth in a homogeneous open environment, and the results resembled in-vitro experiments. In living tissues, however, tumors are often confined in a closed environment of an organ, where the tissue geometry can also evolve in response to the pressure of tumor growth. Here we adapt our previous Cahn-Hilliard tumor growth model to an evolving geometry using a recently developed diffuse domain approach. We use the model to study the growth of lymphoma in a lymph node that swells during the process. An angiogenesis model for tumor-induced vasculature is also adapted to investigate substrate distribution and drug delivery within the lymph node. [Preview Abstract] |
Sunday, November 18, 2012 4:12PM - 4:25PM |
D18.00010: Curling dynamics of naturally curved ribbons from high to low Reynolds numbers Octavio Albarran Arriagada, Gladys Massiera, Manouk Abkarian Curling deformation of thin elastic sheets appears in numerous structures in nature, such as membranes of red blood cells, epithelial tissues or green algae colonies to cite just a few examples. However, despite its ubiquity, the dynamics of curling propagation in a naturally curved material remains still poorly investigated. Here, we present a coupled experimental and theoretical study of the dynamical curling deformation of naturally curved ribbons. Using thermoplastic and metallic ribbons molded on cylinders of different radii, we tune separately the natural curvature and the geometry to study curling dynamics in air, water and in viscous oils, thus spanning a wide range of Reynolds numbers. Our theoretical and experimental approaches separate the role of elasticity, gravity and hydrodynamic dissipation from inertia and emphasize the fundamental differences between the curling of a naturally curved ribbon and a rod described by the classical Elastica. Our work shows evidence for the propagation of a single instability front, selected by a local buckling condition. We show that depending on gravity, and both the Reynolds and the Cauchy numbers, the curling speed and shape are modified by the large scale drag and the local lubrication forces. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700