The Experts below are selected from a list of 47448 Experts worldwide ranked by ideXlab platform
J Baschnagel - One of the best experts on this subject based on the ideXlab platform.
-
note scale free center of Mass Displacement correlations in polymer films without topological constraints and momentum conservation
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, N Schulmann, P Polinska, J BaschnagelAbstract:We present here computational work on the center-of-Mass Displacements in thin polymer films of finite width without topological constraints and without momentum conservation obtained using a well-known lattice Monte Carlo algorithm with chain lengths ranging up to N = 8192. Computing directly the center-of-Mass Displacement correlation function CN(t) allows to make manifest the existence of scale-free colored forces acting on a reference chain. As suggested by the scaling arguments put forward in a recent work on three-dimensional melts, we obtain a negative algebraic decay CN(t) ∼ −1/(N t) for times t ≪ TN with TN being the chain relaxation time. This implies a logarithmic correction to the related center-of-Mass mean square-Displacement hN(t) as has been checked directly.
-
scale free center of Mass Displacement correlations in polymer melts without topological constraints and momentum conservation a bond fluctuation model study
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, P Polinska, J Baschnagel, H Meyer, Jean Farago, A Johner, A CavalloAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints, we examine the center-of-Mass (COM) dynamics of polymer melts in d = 3 dimensions. Our analysis focuses on the COM Displacement correlation function C(N)(t)≈∂(t) (2)h(N)(t)/2, measuring the curvature of the COM mean-square Displacement h(N)(t). We demonstrate that C(N)(t) ≈ -(R(N)∕T(N))(2)(ρ∗/ρ) f(x = t/T(N)) with N being the chain length (16 ≤ N ≤ 8192), R(N) ∼ N(1/2) is the typical chain size, T(N) ∼ N(2) is the longest chain relaxation time, ρ is the monomer density, ρ(*)≈N/R(N) (d) is the self-density, and f(x) is a universal function decaying asymptotically as f(x) ∼ x(-ω) with ω = (d + 2) × α, where α = 1/4 for x ≪ 1 and α = 1/2 for x ≫ 1. We argue that the algebraic decay NC(N)(t) ∼ -t(-5/4) for t ≪ T(N) results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
-
scale free center of Mass Displacement correlations in dense polymer solutions and melts without topological constraints and momentum conservation a bond fluctuation model study
arXiv: Soft Condensed Matter, 2011Co-Authors: J P Wittmer, P Polinska, H Meyer, Jean Farago, A Johner, A Cavallo, J BaschnagelAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints we examine the center-of-Mass (COM) dynamics of polymer melts in $d=3$ dimensions. Our analysis focuses on the COM Displacement correlation function $\CN(t) \approx \partial_t^2 \MSDcmN(t)/2$, measuring the curvature of the COM mean-square Displacement $\MSDcmN(t)$. We demonstrate that $\CN(t) \approx -(\RN/\TN)^2 (\rhostar/\rho) \ f(x=t/\TN)$ with $N$ being the chain length ($16 \le N \le 8192$), $\RN\sim N^{1/2}$ the typical chain size, $\TN\sim N^2$ the longest chain relaxation time, $\rho$ the monomer density, $\rhostar \approx N/\RN^d$ the self-density and $f(x)$ a universal function decaying asymptotically as $f(x) \sim x^{-\omega}$ with $\omega = (d+2) \times \alpha$ where $\alpha = 1/4$ for $x \ll 1$ and $\alpha = 1/2$ for $x \gg 1$. We argue that the algebraic decay $N \CN(t) \sim - t^{-5/4}$ for $t \ll \TN$ results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
J P Wittmer - One of the best experts on this subject based on the ideXlab platform.
-
note scale free center of Mass Displacement correlations in polymer films without topological constraints and momentum conservation
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, N Schulmann, P Polinska, J BaschnagelAbstract:We present here computational work on the center-of-Mass Displacements in thin polymer films of finite width without topological constraints and without momentum conservation obtained using a well-known lattice Monte Carlo algorithm with chain lengths ranging up to N = 8192. Computing directly the center-of-Mass Displacement correlation function CN(t) allows to make manifest the existence of scale-free colored forces acting on a reference chain. As suggested by the scaling arguments put forward in a recent work on three-dimensional melts, we obtain a negative algebraic decay CN(t) ∼ −1/(N t) for times t ≪ TN with TN being the chain relaxation time. This implies a logarithmic correction to the related center-of-Mass mean square-Displacement hN(t) as has been checked directly.
-
scale free center of Mass Displacement correlations in polymer melts without topological constraints and momentum conservation a bond fluctuation model study
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, P Polinska, J Baschnagel, H Meyer, Jean Farago, A Johner, A CavalloAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints, we examine the center-of-Mass (COM) dynamics of polymer melts in d = 3 dimensions. Our analysis focuses on the COM Displacement correlation function C(N)(t)≈∂(t) (2)h(N)(t)/2, measuring the curvature of the COM mean-square Displacement h(N)(t). We demonstrate that C(N)(t) ≈ -(R(N)∕T(N))(2)(ρ∗/ρ) f(x = t/T(N)) with N being the chain length (16 ≤ N ≤ 8192), R(N) ∼ N(1/2) is the typical chain size, T(N) ∼ N(2) is the longest chain relaxation time, ρ is the monomer density, ρ(*)≈N/R(N) (d) is the self-density, and f(x) is a universal function decaying asymptotically as f(x) ∼ x(-ω) with ω = (d + 2) × α, where α = 1/4 for x ≪ 1 and α = 1/2 for x ≫ 1. We argue that the algebraic decay NC(N)(t) ∼ -t(-5/4) for t ≪ T(N) results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
-
scale free center of Mass Displacement correlations in dense polymer solutions and melts without topological constraints and momentum conservation a bond fluctuation model study
arXiv: Soft Condensed Matter, 2011Co-Authors: J P Wittmer, P Polinska, H Meyer, Jean Farago, A Johner, A Cavallo, J BaschnagelAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints we examine the center-of-Mass (COM) dynamics of polymer melts in $d=3$ dimensions. Our analysis focuses on the COM Displacement correlation function $\CN(t) \approx \partial_t^2 \MSDcmN(t)/2$, measuring the curvature of the COM mean-square Displacement $\MSDcmN(t)$. We demonstrate that $\CN(t) \approx -(\RN/\TN)^2 (\rhostar/\rho) \ f(x=t/\TN)$ with $N$ being the chain length ($16 \le N \le 8192$), $\RN\sim N^{1/2}$ the typical chain size, $\TN\sim N^2$ the longest chain relaxation time, $\rho$ the monomer density, $\rhostar \approx N/\RN^d$ the self-density and $f(x)$ a universal function decaying asymptotically as $f(x) \sim x^{-\omega}$ with $\omega = (d+2) \times \alpha$ where $\alpha = 1/4$ for $x \ll 1$ and $\alpha = 1/2$ for $x \gg 1$. We argue that the algebraic decay $N \CN(t) \sim - t^{-5/4}$ for $t \ll \TN$ results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
A Cavallo - One of the best experts on this subject based on the ideXlab platform.
-
scale free center of Mass Displacement correlations in polymer melts without topological constraints and momentum conservation a bond fluctuation model study
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, P Polinska, J Baschnagel, H Meyer, Jean Farago, A Johner, A CavalloAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints, we examine the center-of-Mass (COM) dynamics of polymer melts in d = 3 dimensions. Our analysis focuses on the COM Displacement correlation function C(N)(t)≈∂(t) (2)h(N)(t)/2, measuring the curvature of the COM mean-square Displacement h(N)(t). We demonstrate that C(N)(t) ≈ -(R(N)∕T(N))(2)(ρ∗/ρ) f(x = t/T(N)) with N being the chain length (16 ≤ N ≤ 8192), R(N) ∼ N(1/2) is the typical chain size, T(N) ∼ N(2) is the longest chain relaxation time, ρ is the monomer density, ρ(*)≈N/R(N) (d) is the self-density, and f(x) is a universal function decaying asymptotically as f(x) ∼ x(-ω) with ω = (d + 2) × α, where α = 1/4 for x ≪ 1 and α = 1/2 for x ≫ 1. We argue that the algebraic decay NC(N)(t) ∼ -t(-5/4) for t ≪ T(N) results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
-
scale free center of Mass Displacement correlations in dense polymer solutions and melts without topological constraints and momentum conservation a bond fluctuation model study
arXiv: Soft Condensed Matter, 2011Co-Authors: J P Wittmer, P Polinska, H Meyer, Jean Farago, A Johner, A Cavallo, J BaschnagelAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints we examine the center-of-Mass (COM) dynamics of polymer melts in $d=3$ dimensions. Our analysis focuses on the COM Displacement correlation function $\CN(t) \approx \partial_t^2 \MSDcmN(t)/2$, measuring the curvature of the COM mean-square Displacement $\MSDcmN(t)$. We demonstrate that $\CN(t) \approx -(\RN/\TN)^2 (\rhostar/\rho) \ f(x=t/\TN)$ with $N$ being the chain length ($16 \le N \le 8192$), $\RN\sim N^{1/2}$ the typical chain size, $\TN\sim N^2$ the longest chain relaxation time, $\rho$ the monomer density, $\rhostar \approx N/\RN^d$ the self-density and $f(x)$ a universal function decaying asymptotically as $f(x) \sim x^{-\omega}$ with $\omega = (d+2) \times \alpha$ where $\alpha = 1/4$ for $x \ll 1$ and $\alpha = 1/2$ for $x \gg 1$. We argue that the algebraic decay $N \CN(t) \sim - t^{-5/4}$ for $t \ll \TN$ results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
P Polinska - One of the best experts on this subject based on the ideXlab platform.
-
note scale free center of Mass Displacement correlations in polymer films without topological constraints and momentum conservation
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, N Schulmann, P Polinska, J BaschnagelAbstract:We present here computational work on the center-of-Mass Displacements in thin polymer films of finite width without topological constraints and without momentum conservation obtained using a well-known lattice Monte Carlo algorithm with chain lengths ranging up to N = 8192. Computing directly the center-of-Mass Displacement correlation function CN(t) allows to make manifest the existence of scale-free colored forces acting on a reference chain. As suggested by the scaling arguments put forward in a recent work on three-dimensional melts, we obtain a negative algebraic decay CN(t) ∼ −1/(N t) for times t ≪ TN with TN being the chain relaxation time. This implies a logarithmic correction to the related center-of-Mass mean square-Displacement hN(t) as has been checked directly.
-
scale free center of Mass Displacement correlations in polymer melts without topological constraints and momentum conservation a bond fluctuation model study
Journal of Chemical Physics, 2011Co-Authors: J P Wittmer, P Polinska, J Baschnagel, H Meyer, Jean Farago, A Johner, A CavalloAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints, we examine the center-of-Mass (COM) dynamics of polymer melts in d = 3 dimensions. Our analysis focuses on the COM Displacement correlation function C(N)(t)≈∂(t) (2)h(N)(t)/2, measuring the curvature of the COM mean-square Displacement h(N)(t). We demonstrate that C(N)(t) ≈ -(R(N)∕T(N))(2)(ρ∗/ρ) f(x = t/T(N)) with N being the chain length (16 ≤ N ≤ 8192), R(N) ∼ N(1/2) is the typical chain size, T(N) ∼ N(2) is the longest chain relaxation time, ρ is the monomer density, ρ(*)≈N/R(N) (d) is the self-density, and f(x) is a universal function decaying asymptotically as f(x) ∼ x(-ω) with ω = (d + 2) × α, where α = 1/4 for x ≪ 1 and α = 1/2 for x ≫ 1. We argue that the algebraic decay NC(N)(t) ∼ -t(-5/4) for t ≪ T(N) results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
-
scale free center of Mass Displacement correlations in dense polymer solutions and melts without topological constraints and momentum conservation a bond fluctuation model study
arXiv: Soft Condensed Matter, 2011Co-Authors: J P Wittmer, P Polinska, H Meyer, Jean Farago, A Johner, A Cavallo, J BaschnagelAbstract:By Monte Carlo simulations of a variant of the bond-fluctuation model without topological constraints we examine the center-of-Mass (COM) dynamics of polymer melts in $d=3$ dimensions. Our analysis focuses on the COM Displacement correlation function $\CN(t) \approx \partial_t^2 \MSDcmN(t)/2$, measuring the curvature of the COM mean-square Displacement $\MSDcmN(t)$. We demonstrate that $\CN(t) \approx -(\RN/\TN)^2 (\rhostar/\rho) \ f(x=t/\TN)$ with $N$ being the chain length ($16 \le N \le 8192$), $\RN\sim N^{1/2}$ the typical chain size, $\TN\sim N^2$ the longest chain relaxation time, $\rho$ the monomer density, $\rhostar \approx N/\RN^d$ the self-density and $f(x)$ a universal function decaying asymptotically as $f(x) \sim x^{-\omega}$ with $\omega = (d+2) \times \alpha$ where $\alpha = 1/4$ for $x \ll 1$ and $\alpha = 1/2$ for $x \gg 1$. We argue that the algebraic decay $N \CN(t) \sim - t^{-5/4}$ for $t \ll \TN$ results from an interplay of chain connectivity and melt incompressibility giving rise to the correlated motion of chains and subchains.
Tom Lavers - One of the best experts on this subject based on the ideXlab platform.
-
patterns of agrarian transformation in ethiopia state mediated commercialisation and the land grab
The Journal of Peasant Studies, 2012Co-Authors: Tom LaversAbstract:Much of the literature on the ‘land grab’ has thus far focused on the international drivers of foreign agricultural investment, with far less attention paid to the roles of developing country states and domestic political economy in changing forms of agrarian production. This paper analyses how global and domestic processes combine to produce patterns of agrarian transformation in Ethiopia, one of the main targets of foreign agricultural investment. The paper presents a typology of changes in land use and examines in detail three case studies of investments in Ethiopia drawn from this typology. The paper concludes that the most dramatic changes are taking place in lowland, peripheral regions where large-scale, capital-intensive farms employing wage labour pose a serious risk to pastoralists whose ‘use’ of land is contested by the state. Although the government has been careful to avoid Mass Displacement of settled smallholders, there are also important changes taking place in highland areas, with the gove...
-
patterns of agrarian transformation in ethiopia state mediated commercialisation and the land grab
The Journal of Peasant Studies, 2012Co-Authors: Tom LaversAbstract:Much of the literature on the ‘land grab’ has thus far focused on the international drivers of foreign agricultural investment, with far less attention paid to the roles of developing country states and domestic political economy in changing forms of agrarian production. This paper analyses how global and domestic processes combine to produce patterns of agrarian transformation in Ethiopia, one of the main targets of foreign agricultural investment. The paper presents a typology of changes in land use and examines in detail three case studies of investments in Ethiopia drawn from this typology. The paper concludes that the most dramatic changes are taking place in lowland, peripheral regions where large-scale, capital-intensive farms employing wage labour pose a serious risk to pastoralists whose ‘use’ of land is contested by the state. Although the government has been careful to avoid Mass Displacement of settled smallholders, there are also important changes taking place in highland areas, with the government encouraging investments that combine the resources of investors with the labour and land of smallholders. These investments have resulted in exposure to new forms of market risk.
