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    A Laplace Transform Method for Molecular Mass Distribution Calculation from Rheometric Data

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    Polydisperse linear polymer melts can be microscopically described by the tube model and fractal reptation dynamics, while on the macroscopic side the generalized Maxwell model is capable of correctly displaying most of the rheological behavior. In this paper, a Laplace transform method is derived and different macroscopic starting points for molecular mass distribution calculation are compared to a classical light scattering evaluation. The underlying assumptions comprise the modern understanding on polymer dynamics in entangled systems but can be stated in a mathematically generalized way. The resulting method is very easy to use due to its mathematical structure and it is capable of calculating multimodal molecular mass distributions of linear polymer melts

    Quantum critical behaviour of the plateau-insulator transition in the quantum Hall regime

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    High-field magnetotransport experiments provide an excellent tool to investigate the plateau-insulator phase transition in the integral quantum Hall effect. Here we review recent low-temperature high-field magnetotransport studies carried out on several InGaAs/InP heterostructures and an InGaAs/GaAs quantum well. We find that the longitudinal resistivity Ļxx\rho_{xx} near the critical filling factor Ī½c\nu_{c} ~ 0.5 follows the universal scaling law Ļxx(Ī½,T)āˆexp[āˆ’Ī”Ī½/(T/T0)Īŗ]\rho_{xx}(\nu, T) \propto exp[-\Delta \nu/(T/T_{0})^{\kappa}], where Ī”Ī½=Ī½āˆ’Ī½c\Delta \nu =\nu -\nu_{c}. The critical exponent Īŗ\kappa equals 0.56Ā±0.020.56 \pm 0.02, which indicates that the plateau-insulator transition falls in a non-Fermi liquid universality class.Comment: 8 pages, accepted for publication in Proceedings of the Yamada Conference LX on Research in High Magnetic Fields (August 16-19, 2006, Sendai
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