Bulletin of the American Physical Society
Spring 2010 Meeting of the Ohio Section of the APS
Volume 55, Number 4
Friday–Saturday, April 30–May 1 2010; Flint, Michigan
Session B4: Biophysics and Nanomaterials |
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Room: Campus Center Room 5200 |
Saturday, May 1, 2010 8:00AM - 8:12AM |
B4.00001: Phase separation in lipid/cholesterol monolayers: direct comparison of fluorescence and Brewster angle microscopies Fanindra Bhatta, Yasmin Isler, David Allender, Elizabeth Mann Langmuir monolayers of dihydrocholesterol (dChol) and dimyristoylphosphatidylcholine (DMPC) at the air / water interface reveals behavior that is useful for gaining insight into biological membranes, bilayers containing these and other components. At a given temperature and dChol fraction, there is a fixed 2-d surface pressure below which dChol/DMPC divides into two phases: an ordered, cholesterol-rich phase and a more disordered cholesterol-poor phase. Above this surface pressure, the two phases are identical. Previous studies of phase separation in this system used fluorescence microscopy (FM) but fluorescence agents can be line active and significantly change the phase behavior. Brewster angle microscopy (BAM) allows us to look at macroscopic phase separation without dye. In this study, we have developed an integrated assembly for FM and BAM on a Langmuir trough. A laser ($\lambda$ = 488 nm) is used as the source of light for both the reflectivity observed in BAM and for the excitation and emission observed in FM. [Preview Abstract] |
Saturday, May 1, 2010 8:12AM - 8:24AM |
B4.00002: The Use of Gas Chromatography for Biogas Analysis Amanda Andersen, John Seeley, Jennifer Aurandt Energy from natural gas accounts for 24 percent of energy consumed in the US. Natural gas is a robust form of energy which is rich in methane content and is low in impurities. This quality suggests that it is a very clean and safe gas; it can be used in providing heat, a source for cooking, and in powering vehicles. The downside is that it is a non-renewable resource. On the contrary, methane rich gas that is produced by the breakdown of organic material in an anaerobic environment, called biogas, is a renewable energy source. This research focuses on the gas analysis portion of the creation of the anaerobic digestion and verification laboratory where content and forensic analysis of biogas is performed. Gas Chromatography is implemented as the optimal analytical tool for quantifying the components of the biogas including methane, carbon dioxide, hydrogen sulfide and siloxanes. In addition, the problems associated with the undesirable components are discussed. Anaerobic digestion of primary sludge has consistently produced about 55 percent methane; future goals of this research include studying different substrates to increase the methane yield and decrease levels of impurities in the gas. [Preview Abstract] |
Saturday, May 1, 2010 8:24AM - 8:36AM |
B4.00003: Phase separation behavior of asymmetric lipid bilayers Fanindra Bhtatta, Elizabeth Mann, David Allender Previous work has considered asymmetric bilayers in which each layer contains a mixture of cholesterol and lipids, but the two layers have different lipids and different cholesterol concentrations. In particular, one layer has concentrations such that phase separation into cholesterol rich and cholesterol poor phases is expected, but the second layer, if unaffected by the first layer, would not phase separate. Using only the leading terms of interaction between cholesterol concentration and the straightening of the hydrocarbon chains in the lipids in a given layer, plus a coupling of the two layers via their chain order, it was found that phase separation in one layer causes phase separation in the second. We have examined the effect of higher order terms in the chain ordering on phase separation behavior of the bilayer if it is symmetric. We found region of two, three and four phase coexistence, depending on concentration, and temperature. [Preview Abstract] |
Saturday, May 1, 2010 8:36AM - 8:48AM |
B4.00004: 8CB-Langmuir Layer at air/water interface: Line Tension vs. Dipolar Repulsion Pritam Mandal, Andrew Bernoff, Adin Mann, James Alexander, Elizabeth Mann Langmuir films of 8CB, a smectic liquid crystal at room temperature, exhibits coexistence of phases with different thicknesses. ~~With decompression of a 8CB-liquid-monolayer gaseous holes appear in liquid monolayer. Molecular interactions controlling the phase separation include short-range van der Waals attraction and long range dipolar repulsion. At small distances where attraction dominates gaseous domains return to energy-minimizing circular shapes. But with size of the holes increasing beyond a critical value, dipolar repulsion~becomes strong enough to deform the domains; forming even labyrinth patterns. We use Brewster angle microscopy to study the film. Our~objective is to obtain a critical~diameter of the domains beyond which they are non-circular. Experimental value will be compared with that~from theory. [Preview Abstract] |
Saturday, May 1, 2010 8:48AM - 9:00AM |
B4.00005: Canopy Molecular Mobility in Nanoscale Ionic Materials E. von Meerwall, M.L. Jespersen, P.A. Mirau, R.A. Vaia, R. Rodriguez, E.P. Giannelis Nanoscale ionic materials (NIMS) are useful organic-inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered bulky organic canopy. We have used NMR relaxation and pulsed-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared solvent-free from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is quite mobile both in the bulk and in the NIMS, and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticle. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and is unchanged by the addition of excess canopy. The data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles. [Preview Abstract] |
Saturday, May 1, 2010 9:00AM - 9:12AM |
B4.00006: Structural and electrochromic properties of Fe$_{2}$(SO$_{4})_{3}$ nanostructures prepared by template assisted method Sahana M.B., Sudakar Chandran, Ratna Naik, Vaman Naik Oxides containing polyanions such as XO$_{4}^{2-}$ (X = S, Mo, P and W) as lithium insertion hosts are promising cathode materials due to their high thermal stability. However, the larger separation of the transition metal ions can be expected to reduce the electron mobility. As observed in LiFePO$_{4}$, this can be overcome either by coating the cathode materials with carbon or by decreasing the particle size. We have prepared nanowires of NASICON type structure and platelets of monoclinic Fe$_{2}$(SO$_{4})_{3}$ by template assisted electro deposition. These structures were grown on stainless steel substrates and are characterized by XPS, HRTEM, and XRD analysis. Both NASICON and monoclinic Fe$_{2}$(SO$_{4})_{3}$ structures are very porous and are comprised of nanoparticles leading to a high lithium insertion capacity. [Preview Abstract] |
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