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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 11517-11522 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We analyze, by means of a random phase approximation (RPA) calculation, the conditions under which a mixture of oppositely weakly charged polyelectrolytes can microsegregate in the neighborhood of a charged surface creating a layered structure. A number of stable layers can be formed if the surface is sufficiently strongly charged even at temperatures at which the bulk of the mixture is homogeneous. The wave-length of the induced concentration fluctuation is proportional to 1/f1/2 near the microphase transition, where f is the charge density of the polyelectrolytes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    EPJ direct 2 (2000), S. 1-18 
    ISSN: 1435-3725
    Keywords: 61.20.Qg ; 61.25.Hq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Single and double stranded DNA and many biological and synthetic polyelectrolytes undergo two structural transitions upon increasing the concentration of multivalent salt or molecules. First, the expanded-stretched chains in low monovalent salt solutions collapse into nearly neutral compact structures when the density of multivalent salt approaches that of the monomers. With further addition of multivalent salt the chains redissolve acquiring expanded-coiled conformations. We study the redissolution transition using a two state model [F. J. Solis and M. Olvera de la Cruz, J. Chem. Phys. 112 (2000) 2030]. The redissolution occurs when there is a high degree of screening of the electrostatic interactions between monomers, thus reducing the energy of the expanded state. The transition is determined by the chemical potential of the multivalent ions in the solution μ and the inverse screening length κ. The transition point also depends on the charge distribution along the chain but is nearly independent of the molecular weight and degree of flexibility of the polyelectrolytes. We generate a diagram of μ versus κ2 where we find two regions of expanded conformations, one with charged chains and the other with overcharged (inverted charge) chains, separated by a collapsed nearly neutral conformation region. The collapse and redissolution transitions occur when the trajectory of the properties of the salt crosses the boundaries between these regions. We find that in most cases the redissolution occurs within the same expanded branch from which the chain precipitates.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied mathematics & optimization 41 (2000), S. 331-342 
    ISSN: 1432-0606
    Keywords: Key words. Galerkin bases, Eigenvalues, Average curvature. AMS Classification. 34C35, 34A26.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract. The local adaptive Galerkin bases for large-dimensional dynamical systems, whose long-time behavior is confined to a finite-dimensional manifold, are optimal bases chosen by a local version of a singular decomposition analysis. These bases are picked out by choosing directions of maximum bending of the manifold restricted to a ball of radius ɛ . We show their geometrical meaning by analyzing the eigenvalues of a certain self-adjoint operator. The eigenvalues scale according to the information they carry, the ones that scale as ɛ 2 have a common factor that depends only on the dimension of the manifold, the ones that scale as ɛ 4 give the different curvatures of the manifold, the ones that scale as ɛ 6 give the third invariants, as the torsion for curves, and so on. In this way we obtain a decomposition of phase space into orthogonal spaces E m , where E m is spanned by the eigenvectors whose corresponding eigenvalues scale as ɛ m . This decomposition is analogous to the Frenet frames for curves. We also discover a practical way to compute the dimension and local structure of the invariant manifold.
    Type of Medium: Electronic Resource
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