School of Chemistry - Research Publications

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End date: 2009 × Author: Grieser, Franz × Type: Journal Article ×

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    The use of ultrasonic cleaning for ultrafiltration membranes in the dairy industry
    Muthukumaran, S ; Yang, K ; Seuren, A ; Kentish, S ; Ashokkumar, M ; Stevens, GW ; Grieser, F (ELSEVIER SCIENCE BV, 2004-10)
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    2-DIMENSIONAL DIFFUSION OF AMPHIPHILES IN PHOSPHOLIPID MONOLAYERS AT THE AIR-WATER-INTERFACE
    CARUSO, F ; GRIESER, F ; THISTLETHWAITE, PJ ; ALMGREN, M (CELL PRESS, 1993-12)
    Steady-state and time-resolved fluorescence spectroscopy has been used to examine lateral diffusion in dipalmitoyl-L-alpha-phosphatidylcholine (DPPC) and dimyristoyl-L-alpha-phosphatidylcholine (DMPC) monolayers at the air-water interface, by studying the fluorescence quenching of a pyrene-labeled phospholipid (pyrene-DPPE) by two amphiphilic quenchers. Steady-state fluorescence measurements revealed pyrene-DPPE to be homogeneously distributed in the DMPC lipid matrix for all measured surface pressures and only in the liquid-expanded (LE) phase of the DPPC monolayer. Time-resolved fluorescence decays for pyrene-DPPE in DMPC and DPPC (LE phase) in the absence of quencher were best described by a single-exponential function, also suggesting a homogeneous distribution of pyrene-DPPE within the monolayer films. Addition of quencher to the monolayer film produced nonexponential decay behavior, which is adequately described by the continuum theory of diffusion-controlled quenching in a two-dimensional environment. Steady-state fluorescence measurements yielded lateral diffusion coefficients significantly larger than those obtained from time-resolved data. The difference in these values was ascribed to the influence of static quenching in the case of the steady-state measurements. The lateral diffusion coefficients obtained in the DMPC monolayers were found to decrease with increasing surface pressure, reflecting a decrease in monolayer fluidity with compression.
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    Determination of the size distribution of sonoluminescence bubbles in a pulsed acoustic field
    Lee, J ; Ashokkumar, M ; Kentish, S ; Grieser, F (AMER CHEMICAL SOC, 2005-12-07)
    A simple method is described for determining the size of sonoluminescence bubbles generated by acoustic cavitation. The change in the intensity of sonoluminescence, from 4 ms pulses of 515 kHz ultrasound, as a function of the "off" time between acoustic pulses, is the basis of the method. The bubble size determined in water was in the range of 2.8-3.7 mum.
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    Hydrodynamic boundary conditions and dynamic forces between bubbles and surfaces
    Manor, O ; Vakarelski, IU ; Tang, X ; O'Shea, SJ ; Stevens, GW ; Grieser, F ; Dagastine, RR ; Chan, DYC (AMER PHYSICAL SOC, 2008-07-11)
    Dynamic forces between a 50 microm radius bubble driven towards and from a mica plate using an atomic force microscope in electrolyte and in surfactant exhibit different hydrodynamic boundary conditions at the bubble surface. In added surfactant, the forces are consistent with the no-slip boundary condition at the mica and bubble surfaces. With no surfactant, a new boundary condition that accounts for the transport of trace surface impurities explains variations of dynamic forces at different speeds and provides a direct connection between dynamic forces and surface transport effects at the air-water interface.