Bulletin of the American Physical Society
2020 Fall Meeting of the APS Prairie Section
Volume 65, Number 22
Friday–Sunday, November 13–15, 2020; Virtual
Session C01: Biophysics and Soft Condensed Matter |
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Chair: David Gidalevitz, Illinois Institute of Technology |
Sunday, November 15, 2020 9:00AM - 9:30AM |
C01.00001: Discrete Slip-Link Theory Invited Speaker: Jay Schieber The discrete slip-link theory is a hierarchy of strongly connected models that have demonstrated great success in predicting the linear and nonlinear rheology of high-molecular weight polymers. Three of the four parameters of the most detailed model can be extracted from primitive path analysis, which give quantitative experimental agreement for all examined chemistries (PS, PI, PBd and PE). Here we show that the remaining friction parameter can also be extracted from atomistic simulations. In particular, an available quantum chemistry-based force field for polyethylene oxide (PEO) was used to perform molecular dynamics simulations of a 12kDa melt. Once the four parameters are determined for any chemistry, all parameters for all members of the slip-link hierarchy are determined. Then, using a coarser member of the hierarchy the dynamic modulus and nonlinear rheology of a 256kDa PEO melt was predicted. The predictions are compared to experimental measurements performed at the same temperature. Unfortunately, the extracted friction differs by a factor of two from experiment, which presumably arises from insufficient accuracy in the force field. Nonetheless, the work demonstrates that theory predictions without adjustable parameters should be possible. \\ \\ In Collaboration With: Diego Becerra, Universidad de Concepcion; Andres Cordoba, Universidad de Concepcion; Maria Katzarova, University of Delaware; Marat Andreev, MIT; David Christopher Venerus, New Jersey Institute of Technology. [Preview Abstract] |
Sunday, November 15, 2020 9:30AM - 10:00AM |
C01.00002: Nature’s 3D Printing: Self-Assembly of Coral Skeletons Invited Speaker: Pupa Gilbert Corals reef ecosystems are extremely diverse, beautiful, and threatened by climate change. Learning how corals form their skeletons may be useful to save them from global warming, and to develop new synthesis strategies. Coral skeletons, in fact, are Nature’s 3D printing. Recent synchrotron spectromicroscopy data reveal that all reef-building coral build their skeletons by two concomitant mechanisms: 1. Particle attachment, with nanoparticles of amorphous precursors nucleated in the tissue; 2. Ion attachment, at the surface of the growing skeleton, from the calcifying fluid. A new model for coral skeleton formation shows both mechanisms. See Sun et al. PNAS 2020. [Preview Abstract] |
Sunday, November 15, 2020 10:00AM - 10:30AM |
C01.00003: Monolayer Circles to Stripes via Cholesterol and Curvature Invited Speaker: Joseph A. Zasadzinski Lung surfactants lower the surface tension at the alveolar air-water interface to minimize the work of breathing. This talk will examine morphological transitions in multicomponent lung surfactant monolayers induced by cholesterol or interfacial curvature. The role of cholesterol in lung surfactant is still open to debate as the clinical lung surfactant replacements Curosurf and Survanta have all cholesterol removed, while Infasurf contains 5-6 mol% cholesterol. We have found a novel semi-circle to uniform width stripe transition in model lung surfactant monolayers on addition of cholesterol. This transition is the result of epitaxial growth of a cholesterol rich phase on existing phospholipid crystalline domains. Theoretical predictions show that domain shapes are set by a balance of line tension, �, and the dipole density difference, �! . Once the domains reach a critical area, � [Preview Abstract] |
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