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  • 2020-2022  (2)
  • 1985-1989  (64)
  • 1
    Electronic Resource
    Electronic Resource
    Calculation of the rotational cooperative and self-friction coefficients in a dilute suspension of spheres: Two-body effects (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5127-5129 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By employing the computational methods of Jones and Muthukumar, and the hydrodynamic scattering formalism of Muthukumar and Freed, we have computed the rotational friction coefficients for a dilute suspension of spheres to first order in concentration. These results are compared with previous calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457610
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  • 2
    Electronic Resource
    Electronic Resource
    Localization of a polymeric manifold in quenched random media (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4594-4603 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a replica calculation and obtain analytically the size of a polymer chain with excluded volume interactions in quenched random media. We show that the size of the polymer is shrunk as the density of the impurities constituting the random medium is increased. We demonstrate that this is a general phenomenon. There are three regimes depending on the strength of the impurity density v. In the weak impurity density regime the polymer obeys the self-avoiding statistics with its gyration radius R depending on its typical length L according to R∼L(D+2)/(d+2), where D is the dimension of the polymer and d is the space dimension. In the intermediate regime the polymer is in the unperturbed state where R∼L(2−D)/2. In the third regime of localization occurring for sufficiently large v, R∼v−(2−D)/[4D−(2−D)d] in the absence of three-body interactions and R∼v−1/d LD/d in the presence of strong three-body effects. We examine the effect of long-range interactions of the type w||r||−α between the segments of the polymer separated by r on the localization and find that the polymer collapse is suppressed for realistic impurity densities [v〈wR(d−α)/2].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456619
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  • 3
    Electronic Resource
    Electronic Resource
    Critical wetting in two-component polymer blends (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5749-5755 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We derive the free energy of a bulk two-component polymer blend in the presence of a planar surface, and use these results to map out the region of critical wetting in parameter space. Unlike previous investigations of wetting, our free energy has terms containing gradients of the composition profile at the surface, and we find that these terms have important consequences for critical wetting. In particular, the single gradient term causes the region of parameter space in which it is possible to find critical wetting to be greatly reduced. Although, as discussed in our concluding remarks, we find that the random phase approximation fails for a polymer blend near a surface, our conclusions concerning critical wetting are valid for a free energy which includes gradient terms of the general type considered here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456383
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  • 4
    Electronic Resource
    Electronic Resource
    The size of a polymer in random media (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2435-2441 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Stimulated by the recent numerical simulation results of Baumgartner and Muthukumar, an analytic derivation is given of the size of a polymer in random media. It is shown that, for long Gaussian chains in three dimensions, the mean square end-to-end distance 〈∼(R2)〉 is proportional to (uρ0)−2, where uρ0 is the measure of the scattering power of the medium. For example, ρ0 is the number density of the scatterers and u is the strength of the pseudopotential between the chain segments. A simple extrapolation formula has been obtained using the replica theory for 〈∼(R2)〉 at intermediate values of (uρ0)2L, 〈∼(R2)〉 =(Ll/z) [1−exp(−z)], where L is the chain length, l is the Kuhn step length, and z=εu2ρ20Ll5 with ε being a numerical coefficient. This theory agrees well with the simulation results. The effects of space dimensionality and the replica breaking symmetry are also addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455038
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  • 5
    Electronic Resource
    Electronic Resource
    Calculation of the cooperative friction coefficient in a dilute suspension of spheres. I. Two-body effects (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6406-6419 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We apply diagrammatic techniques of quantum-mechanical angular momentum algebra to the efficient calculation of transport properties in a solution of spheres, based on the hydrodynamic scattering formalism of Muthukumar and Freed. The method is illustrated by computing the two-body correction to the cooperative friction coefficient in a dilute suspension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455409
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamics of isotopic polymer mixtures: Significance of local structural symmetry (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 535-544 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dependence on composition (Φ) and degree of polymerization (N) of the effective segment–segment interaction parameter, χ˜=− 1/2 ∂2Γ/∂Φ2, has been determined for mixtures of perdeuterated and normal (protonated) poly(vinylethylene) and poly(ethylethylene) by small angle neutron scattering (SANS), where Γ represents the excess free energy of mixing. Owing to the small reduction in length and polarizability of carbon–hydrogen bonds with deuterium substitution, isotopic polymer mixtures are characterized by small positive χ˜ parameters. However, deuterium substitution does not significantly influence the local structural symmetry (i.e., the liquid structure or reduced thermodynamic properties) of polymer isotopes, consistent with the assumptions of Flory–Huggins (FH) lattice theory. Nevertheless, we find that χ˜ depends significantly on both Φ and N, contrary to the predictions of FH theory. A general theory, which corrects FH theory for monomer concentration fluctuations, is shown to closely account for these experimental results. In understanding the previous experimental investigations of χ˜ for mixing chemically different species, the monomer concentration fluctuations discussed here must be addressed in addition to the effects due to local structural asymmetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455442
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  • 7
    Electronic Resource
    Electronic Resource
    The effects of attractive and repulsive interaction on two-dimensional reaction-limited aggregation (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3212-3221 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The effects of both attractive and repulsive interactions on reaction-limited cluster–cluster aggregation have been explored using a two-dimensional polydisperse off-lattice model. Interactions with a magnitude on the order of kBT(kB is the Boltzmann constant and T is temperature) have an important effect in both the aggregate structure and the kinetics of aggregation. Attractive interactions lead to more compact structures and repulsive interactions lead to less compact structures with a lower effective dimensionality. The effects of power law particle–particle interactions with interaction energies of the form E=A/r Ε (r is distance) on aggregate structure, aggregation kinetics and the evolution of the cluster size distribution were explored for Ε=2, 4, and 6. A mean field variational theory indicates that fractal dimensionality is unchanged if Ε≥2D0 (where D0 is the fractal dimensionality in the absence of interactions) and that D=D0 (Ε+2)/2(D0+1) for Ε in the range 1≤Ε≤2D0. The simulation results are in accord with this theoretical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456942
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  • 8
    Electronic Resource
    Electronic Resource
    Calculation of the cooperative and self-friction coefficients in a dilute suspension of spheres. II. Three-body effects (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7542-7549 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By employing the computational methods of Jones and Muthukumar, and the hydrodynamic scattering formalism of Muthukumar and Freed, we have computed the translational friction and diffusion coefficients for a dilute suspension of spheres to second order in concentration. These results are compared with previous calculations and experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456677
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of the crystalline phase transformation of poly(vinylidene fluoride) (1985)
    s.l. : American Chemical Society
    Macromolecules 18 (1985), S. 2583-2587 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00154a038
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamic mechanical properties of poly(.gamma.-benzyl L-.alpha.-glutamate) gels in benzyl alcohol (1987)
    s.l. : American Chemical Society
    Macromolecules 20 (1987), S. 564-569 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00169a016
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