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  • 1
    Electronic Resource
    Electronic Resource
    Rate of diffusion-limited reactions for a fractal aggregate of reactive spheres (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3448-3453 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the reaction rate for a fractal cluster of perfectly absorbing, stationary spherical sinks in a medium containing a mobile reactant. The effectiveness factor η, which is defined as the ratio of the total reaction rate of the cluster to that without diffusional interactions, is calculated. The scaling behavior of η is derived for arbitrary fractal dimension based on the Kirkwood–Riseman approximation. The asymptotic as well as the finite size scaling of η are confirmed numerically by the method of multipole expansion, which has been proven to be an excellent approximation. The fractal assembly is made of N spheres with its dimension varying from D〈1 to D=3. The number of sinks can be as high as N∼O(104). The asymptotic scaling behavior of the effectiveness factor is η∼N1/D−1 for D〉1, η∼(ln N)−1 for D=1, and η∼N0 for D〈1. The crossover behavior indicates that while in the regime of D〉1 the screening effect of diffusive interactions grows with the size, for D〈1 it is limited in a finite range and decays with decreasing D. The conclusion is also applicable to transport phenomena like dissolution, heat conduction, and sedimentation. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1491873
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusion into a pair of reactive spheres with first-order reaction (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 10247-10251 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Exact series solutions for the reaction rates of two identical spherical sinks immersed in an infinite medium are presented for both reactant-impenetrable and -penetrable particles based on the method of twin spherical expansion. The reaction rates are explicitly expressed in terms of the interparticle distance from reaction- to diffusion-limited conditions. The effect of the ratio of the diffusivities inside and outside the sink is investigated. The existence of the second particle influences the reaction rate most substantially for the external diffusion-limited condition. The exact solutions are used to evaluate the accuracy of simple, analytical approximations obtained by including the first few multipole contributions only. The result by keeping terms up to quadrupole level gives values in excellent agreement with the exact solution. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1375138
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  • 3
    Electronic Resource
    Electronic Resource
    Rate of diffusion-limited reactions in a cluster of spherical sinks (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 3827-3833 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction rate is calculated for a cluster of perfectly absorbing, stationary spherical sinks in a medium containing a mobile reactant. The diffusive interactions are accurately taken into account by employing the first-passage technique. The configurations of the clusters include three spheres, four spheres, regular polygons, linear chains, squares, and finite cubic arrays. For a given number of sinks, the reaction rate is decreased with increasing the compactness of the structure due to the screening effect. For a specified configurations, the asymptotic expressions for the reaction rate varying with the number of sinks are confirmed. By comparing results with these "exact" data, the method of multipole expansions up to the dipole level, which is suitable for a finite system of many sinks, proved to be an excellent approximation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1387978
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  • 4
    Electronic Resource
    Electronic Resource
    The interactions between ionic surfactants and phosphatidylcholine vesicles: Conductometry (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 8125-8132 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The interaction between ionic surfactants and phosphatidylcholine vesicles, which are prepared without addition of buffer and salt, is investigated by conductivity measurements. On the basis of the vesicle acting as a trap of charge carriers, the bilayer/aqueous phase partition coefficient K and the surfactant/lipid molar ratio Re of nine surfactants are determined. The thermodynamic consistency is satisfied by the measured parameters. The effects of the alkyl chain length (C10–C16) and ionic head group are then studied. The inverse partition coefficient K−1 is linearly related to the critical micelle concentration. The solubilizing ability Reb is a consequence of the competition between the surfactant incorporation into the bilayer and the formation of micelles. Consequently, the K parameter rises whereas the Reb parameter declines as the chain length is increased. The influence due to addition of salt is also discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1407004
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  • 5
    Electronic Resource
    Electronic Resource
    The degree of dissociation of ionic surfactant shells within a W/O microdroplet (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 10304-10312 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The degree of dissociation of ionic surfactant shells within a W/O microdroplet is investigated on the basis of the Poisson–Boltzmann equation and locally ideal mixing assumption. The degree of dissociation is the result of the competition between the entropy associated with counterions in the aqueous core and mixing of surfactant ions with associated surfactants on the shell, and the electrostatic energy. The degree of dissociation is found to depend on the geometry and is in the order: Two planar surfaces〉cylinder〉sphere of the same size. Moreover, for the same geometry, the degree of dissociation increases with the size of the droplet. The free energy change associated with a droplet due to dissociation is obtained. The effect of the solubilization of a neutral particle on the degree of dissociation is also studied. The solubilization is found to hinder the dissociation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1323225
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  • 6
    Electronic Resource
    Electronic Resource
    Observations of high Reynolds number bubbles interacting with a rigid wall (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 44-56 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behavior of bubbles with radii of 0.5–0.7 mm rising through water in the presence of a solid boundary were observed using a high-speed video camera. Fluid inertia and surface tension cause a bubble to bounce several times from a horizontal wall before viscosity dissipates the energy. An energy balance involving the kinetic energy of the fluid motion, the surface energy of the air–water interface, and the gravitational potential energy aids in the interpretation of the dynamics of the collision. We also observed the motion of a bubble rising under an oblique wall with an angle of 10°–85° to the horizontal. When the angle was less than about 55° corresponding to We〈0.4, the bubble slid steadily along the wall. At steeper angles the bubble was observed to bounce repeatedly from the inclined wall without any apparent loss of amplitude. It was also determined that the critical Weber number of coalescence of a bubble rising toward a stationary bubble is 1.6. At Weber numbers below this critical value, the two bubbles coalesce on impact while bubbles bounce at higher Weber numbers. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869168
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  • 7
    Electronic Resource
    Electronic Resource
    Collisions of slightly deformable, high Reynolds number bubbles with short-range repulsive forces (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 2591-2605 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A collision between two bubbles of radii a with an initial relative velocity 2U∞ is studied in the limit, Re≡ρU∞a/μ(very-much-greater-than)1 and We≡ρU2∞a/γ(very-much-less-than)1. Here ρ and μ are the density and viscosity of the liquid and γ is the surface tension of the air–liquid interface. In the absence of colloidal forces, Chesters and Hoffman [Appl. Sci. Res. 38, 353 (1982)] showed that this situation leads to coalescence. The case where there is a nonhydrodynamic repulsive force between the gas–liquid interfaces of the two bubbles that is sufficient to prevent coalescence is considered. Such a force may arise due to ionic salts in aqueous solution or due to surfactants. The analysis shows the bubbles undergo a nearly elastic bounce on an O(a We1/2/U∞) time scale and the repulsive force per unit area must be at least 2γ/a for rebound. Also, experimental observations of bubble collisions in aqueous solutions using high-speed video photography are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868149
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  • 8
    Electronic Resource
    Electronic Resource
    Diffusion-enhanced bioreactions: A hypothetical mechanism for plant cell aggregation (1993)
    Springer
    Bulletin of mathematical biology 55 (1993), S. 869-889 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We show that the existence of diffusional resistance due to the presence of a solid phase can have a positive effect on the metabolic reactions of plant cells. In this case the efficiency of metabolic reactions, defined as the ratio of rate of production of biomass of aggregated cells/rate of production of biomass of dispersed cells, can be greater than unity for a certain range of aggregate sizes for both solid spheres (common plant cell aggregates) and hollow spheres (e.g.Volvox aggregates). This means that, under appropriate conditions, plant cells tend to stay in the aggregated form to improve the efficiency of their metabolic reactions. The result of the present analysis provides an explanation as to why aggregates of plant cells are observed under typical culture conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460690
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  • 9
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    Nonequilibrium relaxation of a stretched polymer chain (1997)
    American Physical Society
    Details
    Publication Date: 1997-08-01
    Print ISSN: 1063-651X
    Electronic ISSN: 1095-3787
    Topics: Physics
    Published by American Physical Society
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  • 10
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    Bell’s Expression and the Generalized Garg Form for Forced Dissociation of a Biomolecular Complex (2007)
    American Physical Society
    Details
    Publication Date: 2007-02-23
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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