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Michael Rodahl - One of the best experts on this subject based on the ideXlab platform.
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energy Dissipation kinetics for protein and antibody antigen adsorption under shear oscillation on a quartz crystal microbalance
Langmuir, 1998Co-Authors: Fredrik Hook, Michael Rodahl, Peter Brzezinski, Bengt Herbert KasemoAbstract:A new quartz crystal microbalance instrument, allowing simultaneous frequency (f) and Dissipation Factor (D) measurements, has been used to study protein adsorption kinetics by measuring time-resolved data of both the D-Factor, measuring the energy Dissipation due to the added overlayer, and the f-shift, measuring the effective mass load on the sensor. Four model proteins (myoglobin, hemoglobin, human serum albumin (HSA), ferritin) and one antibody−antigen reaction (antibody against HSA) were studied on a hydrophobic, methyl-terminated (−CH3) gold surface. In all five cases system-specific, positive D-shifts and negative f-shifts were observed, revealing different adsorption phases. The D-Factor measurements provide new information about protein adsorption and improve the interpretation of the frequency shift in terms of mass uptake. Possible mechanisms for the adlayer-induced Dissipation are discussed.
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simultaneous frequency and Dissipation Factor qcm measurements of biomolecular adsorption and cell adhesion
Faraday Discussions, 1997Co-Authors: Michael Rodahl, Fredrik Hook, Claes Fredriksso, Craig A Kelle, Anatol Kroze, Pete Zezinski, M V Voinova, Engt Herbe KasemoAbstract:We have measured the energy Dissipation of the quartz crystal microbalance(QCM), operating in the liquid phase, when mono- or multi-layers of bio-molecules and biofilms form on the QCM electrode (with a time resolution of ca. 1 s). Examples are taken from protein adsorption, lipid vesicle adsorption and cell adhesion studies. Our results show that even very thin (a few nm) biofilms dissipate a significant amount of energy owing to the QCM oscillation. Various mechanisms for this energy Dissipation are discussed. Three main contributions to the measured increase in energy Dissipation are considered. (i) A viscoelastic porous structure (the biofilm) that is strained during oscillation, (ii) trapped liquid that moves between or in and out of the pores due to the deformation of the film and (iii) the load from the bulk liquid which increases the strain of the film. These mechanisms are, in reality, not entirely separable, rather, they constitute an effective viscoelastic load. The biofilms can therefore not be considered rigidly coupled to the QCM oscillation. It is further shown theoretically that viscoelastic layers with thicknesses comparable to the biofilms studied in this work can induce energy Dissipation of the same magnitude as the measured ones.
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frequency and Dissipation Factor responses to localized liquid deposits on a qcm electrode
Sensors and Actuators B-chemical, 1996Co-Authors: Michael Rodahl, Engt Herbe KasemoAbstract:Abstract We have investigated how a quartz-crystal microbalance (QCM) responds in resonance frequency, f, and Dissipation Factor, D , to local liquid deposits (droplets) at different positions on the QCM electrodes. The changes in resonance frequency and Dissipation Factor versus position of the deposited droplet are well described by Gaussian curves that peal at the centre of the electrode. The widths of the f and D Gaussian curves are not significantly different. The shape of the frequency-shift versus position curve is nearly identical to the corresponding classical sensitivity curve reported by Sauerbrey for solid deposits. An increase in surface roughness of the electrode film, onto which the droplets are deposited, affects f more than D , in agreement with results reported by Martin et al. We demonstrate for a water-glycerol mixture how this effect can be utilized to measure independently the density and viscosity of the contacting liquid or, alternatively, to obtain a measure of the surface roughness of a film deposited on the QCM. Varying the conductivity of the liquid (by adding salt) does not affect the resonance frequency when the liquid is deposited as droplets. This is in contrast to when one entire side of the crystal is completely covered by a liquid. In the latter case, f and D are sensitive to the conductivity of the liquid.
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a simple setup to simultaneously measure the resonant frequency and the absolute Dissipation Factor of a quartz crystal microbalance
Review of Scientific Instruments, 1996Co-Authors: Michael Rodahl, Engt Herbe KasemoAbstract:An experimental setup is described that can simultaneously measure the absolute Dissipation Factor and the resonant frequency of a short‐circuited quartz crystal microbalance. The crystal is driven at approximately its resonant frequency by a signal generator which is intermittently disconnected by a relay, causing the crystal oscillation amplitude to decay exponentially. The decay is measured using a ferrite toroid transformer. One of the crystal leads is fed through the center of the ferrite toroid and thereby acts as the primary winding of the transformer. The secondary winding of the transformer is connected to a digitizing oscilloscope which records the decay of the crystal oscillation. From the recorded decay curve, the absolute Dissipation Factor (calculated from the decay time constant) and the series resonant frequency of the freely oscillating crystal are obtained. Alternatively, the Dissipation Factor and resonant frequency can be measured for the crystal oscillating under open‐circuit conditions, i.e., in the parallel mode. The measurements are automated.
Engt Herbe Kasemo - One of the best experts on this subject based on the ideXlab platform.
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simultaneous frequency and Dissipation Factor qcm measurements of biomolecular adsorption and cell adhesion
Faraday Discussions, 1997Co-Authors: Michael Rodahl, Fredrik Hook, Claes Fredriksso, Craig A Kelle, Anatol Kroze, Pete Zezinski, M V Voinova, Engt Herbe KasemoAbstract:We have measured the energy Dissipation of the quartz crystal microbalance(QCM), operating in the liquid phase, when mono- or multi-layers of bio-molecules and biofilms form on the QCM electrode (with a time resolution of ca. 1 s). Examples are taken from protein adsorption, lipid vesicle adsorption and cell adhesion studies. Our results show that even very thin (a few nm) biofilms dissipate a significant amount of energy owing to the QCM oscillation. Various mechanisms for this energy Dissipation are discussed. Three main contributions to the measured increase in energy Dissipation are considered. (i) A viscoelastic porous structure (the biofilm) that is strained during oscillation, (ii) trapped liquid that moves between or in and out of the pores due to the deformation of the film and (iii) the load from the bulk liquid which increases the strain of the film. These mechanisms are, in reality, not entirely separable, rather, they constitute an effective viscoelastic load. The biofilms can therefore not be considered rigidly coupled to the QCM oscillation. It is further shown theoretically that viscoelastic layers with thicknesses comparable to the biofilms studied in this work can induce energy Dissipation of the same magnitude as the measured ones.
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frequency and Dissipation Factor responses to localized liquid deposits on a qcm electrode
Sensors and Actuators B-chemical, 1996Co-Authors: Michael Rodahl, Engt Herbe KasemoAbstract:Abstract We have investigated how a quartz-crystal microbalance (QCM) responds in resonance frequency, f, and Dissipation Factor, D , to local liquid deposits (droplets) at different positions on the QCM electrodes. The changes in resonance frequency and Dissipation Factor versus position of the deposited droplet are well described by Gaussian curves that peal at the centre of the electrode. The widths of the f and D Gaussian curves are not significantly different. The shape of the frequency-shift versus position curve is nearly identical to the corresponding classical sensitivity curve reported by Sauerbrey for solid deposits. An increase in surface roughness of the electrode film, onto which the droplets are deposited, affects f more than D , in agreement with results reported by Martin et al. We demonstrate for a water-glycerol mixture how this effect can be utilized to measure independently the density and viscosity of the contacting liquid or, alternatively, to obtain a measure of the surface roughness of a film deposited on the QCM. Varying the conductivity of the liquid (by adding salt) does not affect the resonance frequency when the liquid is deposited as droplets. This is in contrast to when one entire side of the crystal is completely covered by a liquid. In the latter case, f and D are sensitive to the conductivity of the liquid.
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a simple setup to simultaneously measure the resonant frequency and the absolute Dissipation Factor of a quartz crystal microbalance
Review of Scientific Instruments, 1996Co-Authors: Michael Rodahl, Engt Herbe KasemoAbstract:An experimental setup is described that can simultaneously measure the absolute Dissipation Factor and the resonant frequency of a short‐circuited quartz crystal microbalance. The crystal is driven at approximately its resonant frequency by a signal generator which is intermittently disconnected by a relay, causing the crystal oscillation amplitude to decay exponentially. The decay is measured using a ferrite toroid transformer. One of the crystal leads is fed through the center of the ferrite toroid and thereby acts as the primary winding of the transformer. The secondary winding of the transformer is connected to a digitizing oscilloscope which records the decay of the crystal oscillation. From the recorded decay curve, the absolute Dissipation Factor (calculated from the decay time constant) and the series resonant frequency of the freely oscillating crystal are obtained. Alternatively, the Dissipation Factor and resonant frequency can be measured for the crystal oscillating under open‐circuit conditions, i.e., in the parallel mode. The measurements are automated.
Richard S Lindze - One of the best experts on this subject based on the ideXlab platform.
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gravitational tides in the outer planets i implications of classical tidal theory ii interior calculations and estimation of the tidal Dissipation Factor
The Astrophysical Journal, 1993Co-Authors: Petros J Ioannou, Richard S LindzeAbstract:Classical tidal theory is applied to the gravitational excitation of the atmospheres of the gaseous planets. The only departure made from classical theory is the retention of the effects of nonhdrostaticity which are important in the deeper atmosphere or wherever one expects extremely small static stability. The meridional structure of the tidal response is shown to depend only on the ratio of the period of gravitational forcing to the period of rotation of the planet. Forcing by the low-inclination orbits of the satellites of Jupiter, Saturn, and Uranus excites primarily symmetric Hough modes. Consideration of the vertical structure equation shows that altho4gh the gravitational tidal forcing is proportional to the first symmetric spherical harmonic with zonal wavenumber 2, the tidal response will be concentrated in higher order meridional structures confined equatorward of 50° N on Jupiter, 76° N on Saturn, and 45° N on Uranus. The meridional structure of these modes resembles the visible banding on these planets. The excitation of the tides depends on the distribution of static stability in the interior. Estimates are made showing that observation of the tidal response of the planets at the visible cloud level may be within reach of current observational capability. Detection of this signal is shown to provide information about the thermodynamic structure of the interior. A primary purpose of the present paper, in addition to the above, is the presentation of computational results concerning the eigenvalues and eigenfunctions relevant to gravitational tides in the outer planets. Subject headings: planets and satellites: general
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gravitational tides in the outer planets ii interior calculations and estimation of the tidal Dissipation Factor
The Astrophysical Journal, 1993Co-Authors: Petros J Ioannou, Richard S LindzeAbstract:The theory of excitation of tidal oscillations in a fluid planetary body is formulated, and separable equa tions are derived that extend the results of the classical theory of tides to the nonhydrostatic interiors of planets. The theory is applied to the example of the gravitational tidal response of Jupiter to forcing by lo. The tidal response is found to crucially depend on the static stability in the interior of the planet, the response of the planet being as much as two to three orders of magnitude greater than the response with a neutral interior. The tidal Dissipation Factor Q is calculated for Jupiter and found to agree with the values required by the astronomical arguments only if the interior has finite (though small static stability. We are led to the conclusion that the interior of Jupiter must have regions which are stably stratified. Subject headings: planets and satellites: individual (Jupiter) Jupiter has a rotational period of 9.92 hr and a radius approximately 10 times greater than Earth's and 10 times smaller than the Sun's. The main constituents of the plant, hydrogen (90% by mass) and helium (10%), do not solidify, and because of the low density the mass of the planet is only 318 times greater than Earth's. The planet is primarily made up of a highly compressed but relatively cold liquid, with an inte rior core at probably 0.1 of the planetary radius. The visible atmospheric envelope is approximately at a pressure of 1 bar and a temperature of 150 K, while the pressure at the core is approximately 40 Mbar at a temperature of nearly 20,000 K (Stevenson 1978). Observations on the thermal emission revealed the existence of an interior heat source which accounts for around 35°/o of the 14 W m- 2 emitted to space. While much progress has been made in our understanding of the general structure of the planet (cf. Stevenson 1978), most of the meteorologically relevant information is limited to the region above the visible clouds of the planet. The data for the meteorology of the planet is still scant, making the theories for the observed cloud level circulations speculative (Ingersoll
Petros J Ioannou - One of the best experts on this subject based on the ideXlab platform.
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gravitational tides in the outer planets i implications of classical tidal theory ii interior calculations and estimation of the tidal Dissipation Factor
The Astrophysical Journal, 1993Co-Authors: Petros J Ioannou, Richard S LindzeAbstract:Classical tidal theory is applied to the gravitational excitation of the atmospheres of the gaseous planets. The only departure made from classical theory is the retention of the effects of nonhdrostaticity which are important in the deeper atmosphere or wherever one expects extremely small static stability. The meridional structure of the tidal response is shown to depend only on the ratio of the period of gravitational forcing to the period of rotation of the planet. Forcing by the low-inclination orbits of the satellites of Jupiter, Saturn, and Uranus excites primarily symmetric Hough modes. Consideration of the vertical structure equation shows that altho4gh the gravitational tidal forcing is proportional to the first symmetric spherical harmonic with zonal wavenumber 2, the tidal response will be concentrated in higher order meridional structures confined equatorward of 50° N on Jupiter, 76° N on Saturn, and 45° N on Uranus. The meridional structure of these modes resembles the visible banding on these planets. The excitation of the tides depends on the distribution of static stability in the interior. Estimates are made showing that observation of the tidal response of the planets at the visible cloud level may be within reach of current observational capability. Detection of this signal is shown to provide information about the thermodynamic structure of the interior. A primary purpose of the present paper, in addition to the above, is the presentation of computational results concerning the eigenvalues and eigenfunctions relevant to gravitational tides in the outer planets. Subject headings: planets and satellites: general
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gravitational tides in the outer planets ii interior calculations and estimation of the tidal Dissipation Factor
The Astrophysical Journal, 1993Co-Authors: Petros J Ioannou, Richard S LindzeAbstract:The theory of excitation of tidal oscillations in a fluid planetary body is formulated, and separable equa tions are derived that extend the results of the classical theory of tides to the nonhydrostatic interiors of planets. The theory is applied to the example of the gravitational tidal response of Jupiter to forcing by lo. The tidal response is found to crucially depend on the static stability in the interior of the planet, the response of the planet being as much as two to three orders of magnitude greater than the response with a neutral interior. The tidal Dissipation Factor Q is calculated for Jupiter and found to agree with the values required by the astronomical arguments only if the interior has finite (though small static stability. We are led to the conclusion that the interior of Jupiter must have regions which are stably stratified. Subject headings: planets and satellites: individual (Jupiter) Jupiter has a rotational period of 9.92 hr and a radius approximately 10 times greater than Earth's and 10 times smaller than the Sun's. The main constituents of the plant, hydrogen (90% by mass) and helium (10%), do not solidify, and because of the low density the mass of the planet is only 318 times greater than Earth's. The planet is primarily made up of a highly compressed but relatively cold liquid, with an inte rior core at probably 0.1 of the planetary radius. The visible atmospheric envelope is approximately at a pressure of 1 bar and a temperature of 150 K, while the pressure at the core is approximately 40 Mbar at a temperature of nearly 20,000 K (Stevenson 1978). Observations on the thermal emission revealed the existence of an interior heat source which accounts for around 35°/o of the 14 W m- 2 emitted to space. While much progress has been made in our understanding of the general structure of the planet (cf. Stevenson 1978), most of the meteorologically relevant information is limited to the region above the visible clouds of the planet. The data for the meteorology of the planet is still scant, making the theories for the observed cloud level circulations speculative (Ingersoll
Maryam Tabrizia - One of the best experts on this subject based on the ideXlab platform.
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determination of surface induced platelet activation by applying time dependency Dissipation Factor versus frequency using quartz crystal microbalance with Dissipation
Journal of the Royal Society Interface, 2011Co-Authors: Julie Fatisso, Yahye Merhi, Sania Mansouri, Daniel Yacoub, Maryam TabriziaAbstract:Platelet adhesion and activation rates are frequently used to assess the thrombogenicity of biomaterials, which is a crucial step for the development of blood-contacting devices. Until now, electron and confocal microscopes have been used to investigate platelet activation but they failed to characterize this activation quantitatively and in real time. In order to overcome these limitations, quartz crystal microbalance with Dissipation (QCM-D) was employed and an explicit time scale introduced in the Dissipation versus frequency plots (Df–t) provided us with quantitative data at different stages of platelet activation. The QCM-D chips were coated with thrombogenic and non-thrombogenic model proteins to develop the methodology, further extended to investigate polymer thrombogenicity. Electron microscopy and immunofluorescence labelling were used to validate the QCM-D data and confirmed the relevance of Df–t plots to discriminate the activation rate among protein-modified surfaces. The responses showed the predominant role of surface hydrophobicity and roughness towards platelet activation and thereby towards polymer thrombogenicity. Modelling experimental data obtained with QCM-D with a Matlab code allowed us to define the rate at which mass change occurs (A/B), to obtain an A/B value for each polymer and correlate this value with polymer thrombogenicity.
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quantifying blood platelet morphological changes by Dissipation Factor monitoring in multilayer shells
Langmuir, 2008Co-Authors: Julie Fatisso, Yahye Merhi, Maryam TabriziaAbstract:The ability of electrostatically driven layer-by-layer (LbL) assembly to adapt to the morphological features of a template was explored. Subtle cytoskeletal changes in blood platelets became traceable through energy Dissipation monitoring in multilayered shells using microgravimetric measurements. This LbL coating was sequentially deposited on protein-modified chips onto which platelets were adhered. In addition to consequently improving the signal sensitivity, the LbL shell acted in synergy with the cell, allowing the determination and quantification of cytoskeletal changes induced by the specific cell adhesion to the protein-modified chip surface used with a quartz crystal microbalance with Dissipation. The difference in cell morphology, as a result of the optimization of specific interactions between the protein layer and cell membrane integrins induced viscoelastic changes in the polyelectrolyte shell, thereby providing quantitative data on platelet conformational changes upon their adhesion to protein-modified chip surface.