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Cellulase adsorption and reactivity on a cellulose surface from flow ellipsometry / S. A. Maurer in Industrial & engineering chemistry research, Vol. 51 N° 35 (Septembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 35 (Septembre 2012) . - pp. 11389–11400 Titre : Cellulase adsorption and reactivity on a cellulose surface from flow ellipsometry Type de document : texte imprimé Auteurs : S. A. Maurer, Auteur ; C. N. Bedbrook, Auteur ; C. J. Radke, Auteur Année de publication : 2012 Article en page(s) : pp. 11389–11400 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Adsorption  Ellipsometry Résumé : Enzymatic deconstruction of cellulose occurs at the aqueous/cellulose interface. Most assays to explore cellulase activity, however, are performed in bulk solution and, hence, fail to elucidate surface-reaction kinetics. We use flow ellipsometry to quantify the adsorption and surface reactivity of aqueous cellulase on a model cellulose film substrate. The rate of cellulose digestion at the aqueous/solid interface increases with increasing bulk concentration of enzyme, but only up to a plateau corresponding to the maximum adsorption density of cellulase. Kinetic data are analyzed according to a modified Langmuir–Michaelis–Menten framework including both reversible adsorption of cellulase to the cellulose surface and complexation of surface cellulose chains with adsorbed cellulase. At ambient temperature, the molar turnover number is 0.57 ± 0.08 s–1, commensurate with literature values, and the Langmuir adsorption equilibrium constant, characterizing the binding strength of the cellulase, is 0.086 ± 0.026 ppm–1. The rate-determining step in the surface-reaction sequence is complexation of adsorbed cellulase with the solid-cellulose surface. Simultaneous knowledge of sorption and digestion kinetics is necessary to quantify cellulose deconstruction. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3008538 [article] Cellulase adsorption and reactivity on a cellulose surface from flow ellipsometry [texte imprimé] / S. A. Maurer, Auteur ; C. N. Bedbrook, Auteur ; C. J. Radke, Auteur . - 2012 . - pp. 11389–11400. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 35 (Septembre 2012) . - pp. 11389–11400 Mots-clés : Adsorption  Ellipsometry Résumé : Enzymatic deconstruction of cellulose occurs at the aqueous/cellulose interface. Most assays to explore cellulase activity, however, are performed in bulk solution and, hence, fail to elucidate surface-reaction kinetics. We use flow ellipsometry to quantify the adsorption and surface reactivity of aqueous cellulase on a model cellulose film substrate. The rate of cellulose digestion at the aqueous/solid interface increases with increasing bulk concentration of enzyme, but only up to a plateau corresponding to the maximum adsorption density of cellulase. Kinetic data are analyzed according to a modified Langmuir–Michaelis–Menten framework including both reversible adsorption of cellulase to the cellulose surface and complexation of surface cellulose chains with adsorbed cellulase. At ambient temperature, the molar turnover number is 0.57 ± 0.08 s–1, commensurate with literature values, and the Langmuir adsorption equilibrium constant, characterizing the binding strength of the cellulase, is 0.086 ± 0.026 ppm–1. The rate-determining step in the surface-reaction sequence is complexation of adsorbed cellulase with the solid-cellulose surface. Simultaneous knowledge of sorption and digestion kinetics is necessary to quantify cellulose deconstruction. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3008538

Meniscus - shear particle detachment in foam - based cleaning of silicon wafers with an immersion / withdrawal cell / V. A. Andreev in Industrial & engineering chemistry research, Vol. 49 N° 24 (Décembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 24 (Décembre 2010) . - pp. 12461–12470 Titre : Meniscus - shear particle detachment in foam - based cleaning of silicon wafers with an immersion / withdrawal cell Type de document : texte imprimé Auteurs : V. A. Andreev, Auteur ; J. M. Prausnitz, Auteur ; C. J. Radke, Auteur Année de publication : 2011 Article en page(s) : pp. 12461–12470 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : silicon Résumé : New experimental data collected at Lam Research Corporation and theoretical analyses are presented for aqueous-foam cleaning of silicon wafers contaminated with strongly adhered 90 nm Si3N4 particles (Freer et al. 2010). We analyze the distribution of contaminant removal along the wafer surface and the influence of foam quality in a vertical rectangular slot upon wafer immersion/withdrawal. At zero foam quality, particle removal along the wafer surface is uniform. Increased foam quality leads to improved overall removal. Removal, however, is no longer uniform with larger detachment rates toward the bottom of the wafer. To explain the observed nonuniform particle removal, we adopt a binary-collision model that demands a linear dependence of removal rate on the surface shear rate. Perturbation analysis provides the distribution of the wall shear rate along the wafer surface in an unfoamed solution. Calculations show that the wall shear rate on the wafer surface is strongly peaked in the meniscus just above the liquid-filled slot. Thus, with no foam present, removal in the meniscus zone dominates the overall removal process. Because the time of exposure to this high shear is the same for all parts of the surface, we obtain uniform cleaning. With foam bubbles present, the wall shear rate in the slot is enhanced, leading to significant removal in the bulk of the slot. Because the residence time of a wafer in the bulk cleaning solution varies for different parts of the wafer, contaminant removal in the bulk of the slot depends on the vertical position. Combined particle removal in the meniscus zone and in the slot leads to the observed nonuniform distribution of contaminant particles remaining on the wafer surface. Increasing foam quality increases the slot wall shear rate and, hence, the removal rate inside the immersion/withdrawal cell. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1012954 [article] Meniscus - shear particle detachment in foam - based cleaning of silicon wafers with an immersion / withdrawal cell [texte imprimé] / V. A. Andreev, Auteur ; J. M. Prausnitz, Auteur ; C. J. Radke, Auteur . - 2011 . - pp. 12461–12470. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 24 (Décembre 2010) . - pp. 12461–12470 Mots-clés : silicon Résumé : New experimental data collected at Lam Research Corporation and theoretical analyses are presented for aqueous-foam cleaning of silicon wafers contaminated with strongly adhered 90 nm Si3N4 particles (Freer et al. 2010). We analyze the distribution of contaminant removal along the wafer surface and the influence of foam quality in a vertical rectangular slot upon wafer immersion/withdrawal. At zero foam quality, particle removal along the wafer surface is uniform. Increased foam quality leads to improved overall removal. Removal, however, is no longer uniform with larger detachment rates toward the bottom of the wafer. To explain the observed nonuniform particle removal, we adopt a binary-collision model that demands a linear dependence of removal rate on the surface shear rate. Perturbation analysis provides the distribution of the wall shear rate along the wafer surface in an unfoamed solution. Calculations show that the wall shear rate on the wafer surface is strongly peaked in the meniscus just above the liquid-filled slot. Thus, with no foam present, removal in the meniscus zone dominates the overall removal process. Because the time of exposure to this high shear is the same for all parts of the surface, we obtain uniform cleaning. With foam bubbles present, the wall shear rate in the slot is enhanced, leading to significant removal in the bulk of the slot. Because the residence time of a wafer in the bulk cleaning solution varies for different parts of the wafer, contaminant removal in the bulk of the slot depends on the vertical position. Combined particle removal in the meniscus zone and in the slot leads to the observed nonuniform distribution of contaminant particles remaining on the wafer surface. Increasing foam quality increases the slot wall shear rate and, hence, the removal rate inside the immersion/withdrawal cell. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1012954

Polarographic method for measuring oxygen diffusivity and solubility in water-saturated polymer films / Mahendra Chhabra in Industrial & engineering chemistry research, Vol. 47 N°10 (Mai 2008)

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°10 (Mai 2008) . - p. 3540–3550 Titre : Polarographic method for measuring oxygen diffusivity and solubility in water-saturated polymer films : application to hypertransmissible soft contact lenses Type de document : texte imprimé Auteurs : Mahendra Chhabra, Auteur ; John M. Prausnitz, Auteur ; C. J. Radke, Auteur Année de publication : 2008 Article en page(s) : p. 3540–3550 Note générale : Bibliogr. p.3549-3550 Langues : Anglais (eng) Mots-clés : Oxygen  --  Electrochemical-polarographic  method  ;  Polarographic  method Résumé : An electrochemical-polarographic method is described for measuring the diffusivity, D, and solubility, k, of oxygen in aqueous-saturated polymer films. While the apparatus and procedure are general for such films, it is here applied to determine D and k for oxygen in hypertransmissible soft contact lenses. Usually, only oxygen permeability, P, the product of D and k, is measured because P gauges the steady flux of oxygen through hydrogel membranes. However, we utilize the polarographic technique in the unsteady state and, hence, obtain D and k separately. Determination of each of these properties is critical for designing better lens materials that ensure sufficient oxygen supply to the cornea. We have measured oxygen diffusivities and solubilities for nine commercial soft contact lenses. Our data indicate that oxygen diffusivity is primarily responsible for the range of oxygen permeability observed for hypertransmissible soft contact lenses. For 2-hydroxyethyl methacrylate (HEMA)-based lenses, measured solubilities suggest that over 90% of the dissolved oxygen partitions to the polymer phase [article] Polarographic method for measuring oxygen diffusivity and solubility in water-saturated polymer films : application to hypertransmissible soft contact lenses [texte imprimé] / Mahendra Chhabra, Auteur ; John M. Prausnitz, Auteur ; C. J. Radke, Auteur . - 2008 . - p. 3540–3550. Bibliogr. p.3549-3550 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°10 (Mai 2008) . - p. 3540–3550 Mots-clés : Oxygen  --  Electrochemical-polarographic  method  ;  Polarographic  method Résumé : An electrochemical-polarographic method is described for measuring the diffusivity, D, and solubility, k, of oxygen in aqueous-saturated polymer films. While the apparatus and procedure are general for such films, it is here applied to determine D and k for oxygen in hypertransmissible soft contact lenses. Usually, only oxygen permeability, P, the product of D and k, is measured because P gauges the steady flux of oxygen through hydrogel membranes. However, we utilize the polarographic technique in the unsteady state and, hence, obtain D and k separately. Determination of each of these properties is critical for designing better lens materials that ensure sufficient oxygen supply to the cornea. We have measured oxygen diffusivities and solubilities for nine commercial soft contact lenses. Our data indicate that oxygen diffusivity is primarily responsible for the range of oxygen permeability observed for hypertransmissible soft contact lenses. For 2-hydroxyethyl methacrylate (HEMA)-based lenses, measured solubilities suggest that over 90% of the dissolved oxygen partitions to the polymer phase