The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Ernst A Rossler - One of the best experts on this subject based on the ideXlab platform.
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segmental mean Square Displacement field cycling 1h relaxometry vs neutron scattering
Macromolecules, 2016Co-Authors: M Hofmann, B Kresse, A F Privalov, Lutz Heymann, Lutz Willner, Nuri Aksel, Nail Fatkullin, F Fujara, Ernst A RosslerAbstract:Proton (1H) field-cycling (FC) NMR relaxometry is applied to monitor the crossover in the segmental subdiffusion from the Rouse to the constrained Rouse regime in an entangled linear polymer melt. The method probes the dispersion of the spin–lattice relaxation rate R1(ω). Via Fourier transformation the segmental mean Square Displacement ⟨r2(t)⟩ is calculated from the intermolecular relaxation contribution R1inter(ω) to the total 1H spin–lattice relaxation dispersion R1(ω). As an example we chose poly(ethylene propylene) (M = 200k), and R1inter(ω) is singled out by performing an isotope dilution experiment. The ⟨r2(t)⟩ data obtained by FC NMR is directly compared to such of neutron scattering (NS) available from the literature. Because of different experimental time windows the NS data is converted to a reference temperature assuming frequency–temperature superposition. Absolute agreement is revealed between FC NMR and NS. The data on ⟨r2(t)⟩ confirm the predictions of the tube-reptation model; i.e., the c...
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mean Square Displacement and reorientational correlation function in entangled polymer melts revealed by field cycling 1h and 2h nmr relaxometry
Macromolecules, 2012Co-Authors: Andreas Herrmann, B Kresse, A F Privalov, Nail Fatkullin, F Fujara, M Wohlfahrt, I Bauer, D Kruk, Ernst A RosslerAbstract:Mixtures of protonated and deuterated polybutadiene and polydimethylsiloxane are studied by means of field-cycling (FC) 1H NMR relaxometry in order to analyze the intra- and intermolecular contributions to spin–lattice relaxation. They reflect reorientational and translational dynamics,respectively. Master curves in the susceptibility representation χ″(ωτs) are constructed by employing frequency–temperature superposition with τs denoting the segmental correlation time. The intermolecular contribution is dominating at low frequencies and allows extracting the segmental mean Square Displacement ⟨R2(t)⟩, which reveals two power-law regimes. The one at short times agrees with t0.5 predicted for the free Rouse regime and at long times a lower exponent is observed in fair agreement with t0.25 expected for the constrained Rouse regime of the tube-reptation model. Concomitantly the reorientational rank-two correlation function C2(t/τs) is obtained from the intramolecular part. Again two power-law regimes t–e are ...
A D Vinales - One of the best experts on this subject based on the ideXlab platform.
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subdiffusive behavior in a trapping potential mean Square Displacement and velocity autocorrelation function
Physical Review E, 2009Co-Authors: M A Desposito, A D VinalesAbstract:A theoretical framework for analyzing stochastic data from single-particle tracking in viscoelastic materials and under the influence of a trapping potential is presented. Starting from a generalized Langevin equation, we found analytical expressions for the two-time dynamics of a particle subjected to a harmonic potential. The mean-Square Displacement and the velocity autocorrelation function of the diffusing particle are given in terms of the time lag. In particular, we investigate the subdiffusive case. Using a power-law memory kernel, exact expressions for the mean-Square Displacement and the velocity autocorrelation function are obtained in terms of Mittag-Leffler functions and their derivatives. The behaviors for short-, intermediate-, and long-time lags are investigated in terms of the involved parameters. Finally, the validity of usual approximations is examined.
Hartmut Lowen - One of the best experts on this subject based on the ideXlab platform.
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active brownian and inertial particles in disordered environments short time expansion of the mean Square Displacement
Physical Review E, 2020Co-Authors: Davide Breoni, Michael Schmiedeberg, Hartmut LowenAbstract:We consider an active Brownian particle moving in a disordered two-dimensional energy or motility landscape. The averaged mean-Square Displacement (MSD) of the particle is calculated analytically within a systematic short-time expansion. As a result, for overdamped particles, both an external random force field and disorder in the self-propulsion speed induce ballistic behavior adding to the ballistic regime of an active particle with sharp self-propulsion speed. Spatial correlations in the force and motility landscape contribute only to the cubic and higher-order powers in time for the MSD. Finally, for inertial particles two superballistic regimes are found where the scaling exponent of the MSD with time is $\ensuremath{\alpha}=3$ and $\ensuremath{\alpha}=4$. We confirm our theoretical predictions by computer simulations. Moreover, they are verifiable in experiments on self-propelled colloids in random environments.
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active brownian and inertial particles in disordered environments short time expansion of the mean Square Displacement
arXiv: Soft Condensed Matter, 2020Co-Authors: Davide Breoni, Michael Schmiedeberg, Hartmut LowenAbstract:We consider an active Brownian particle moving in a disordered two-dimensional energy or motility landscape. The averaged mean-Square-Displacement (MSD) of the particle is calculated analytically within a systematic short-time expansion. As a result, for overdamped particles, both an external random force field and disorder in the self-propulsion speed induce ballistic behaviour adding to the ballistic regime of an active particle with sharp self-propulsion speed. Spatial correlations in the force and motility landscape contribute only to the cubic and higher order powers in time for the MSD. Finally, for inertial particles two superballistic regimes are found where the scaling exponent of the MSD with time is $\alpha=3$ and $\alpha=4$. We confirm our theoretical predictions by computer simulations. Moreover they are verifiable in experiments on self-propelled colloids in random environments.
Antonio Benedetto - One of the best experts on this subject based on the ideXlab platform.
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resolution effects on the mean Square Displacement as obtained by the self distribution function procedure
Journal of Physics: Conference Series, 2012Co-Authors: Antonio Benedetto, Salvatore Magazù, Federica Migliardo, Cecilia Mondelli, M A GonzalezAbstract:In the present contribution, a procedure for molecular motion characterization based on the evaluation of the Mean Square Displacement (MSD), through the Self-Distribution Function (SDF), is presented. It is shown how MSD, which represents an important observable for the characterization of dynamical properties, can be decomposed into different partial contributions associated to system dynamical processes within a specific spatial scale. It is also shown how the SDF procedure allows us to evaluate both total MSD and partial MSDs through total and partial SDFs. As a result, total MSD is the weighed sum of partial MSDs in which the weights are obtained by the fitting procedure of measured Elastic Incoherent Neutron Scattering (EINS) intensity. We apply SDF procedure to data collected,by IN13, IN10 and IN4 spectrometers (Institute Laue Langevin), on aqueous mixtures of two homologous disaccharides (sucrose and trehalose) and on dry and hydrated (H2O and D2O) lysozyme with and without disaccharides. It emerges that the hydrogen bond imposed network of the water-trehalose mixture appears to be stronger with respect to that of the water-sucrose mixture. This result can justify the higher bioprotectant effectiveness of trehalose. Furthermore, it emerges that partial MSDs of sucrose and trehalose are equivalent in the low Q domain (0÷1.7) A−1 whereas they are different in the high Q domain (1.7÷4) A−1. This suggests that the higher structure sensitivity of sucrose should be related to the small spatial observation windows. Moreover, the role of the instrumental resolution in EINS is considered. The nature of the dynamical transition is highlighted and it is shown that it occurs when the system relaxation time becomes shorter than the instrumental energy time. Finally, the bioprotectants effect on protein dynamics and the amplitude of vibrations in lysozyme are presented.
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Elastic incoherent neutron scattering on systems of biophysical interest: mean Square Displacement evaluation from self-distribution function.
The journal of physical chemistry. B, 2008Co-Authors: Salvatore Magazù, G. Maisano, Federica Migliardo, Antonio BenedettoAbstract:In the present work an operational recipe for the mean Square Displacement (MSD) determination, highlighting the connection between the self-distribution function and average statistical values, is...
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mean Square Displacement from self distribution function evaluation by elastic incoherent neutron scattering
Journal of Molecular Structure, 2008Co-Authors: Salvatore Magazù, G. Maisano, Federica Migliardo, Antonio BenedettoAbstract:Abstract The determination of the different contributions to the mean Square Displacement (MSD) associated with different relaxation mechanisms together with their time and thermal behaviour is performed by evaluating the self-distribution function derived by Elastic Incoherent Neutron Scattering (EINS). The analysis of the standard approach for MSD determination leads to an operational recipe that highlights the connection with the self-distribution function. The approach is tested on EINS data collected by the backscattering spectrometer IN13 (ILL, Grenoble) on a model system such as PolyEthylene Glycol with mean molecular weight Mw = 400 (PEG 400).
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mean Square Displacement evaluation by elastic neutron scattering self distribution function
Physical Review E, 2008Co-Authors: Salvatore Magazù, G. Maisano, Federica Migliardo, Antonio BenedettoAbstract:: In the present work an operational recipe for the mean Square Displacement (MSD) determination, highlighting the connection between elastic incoherent neutron scattering (EINS) intensity profiles and the associated self-distribution function, is presented. The determination of the thermal behavior of the total MSD and of its partial contributions is tested on EINS data collected by the backscattering spectrometer IN13 (ILL, Grenoble) on a model system such as PolyEthylene Glycol with a mean molecular weight of 400 Dalton (PEG 400).
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Mean Square Displacement evaluation by elastic neutron scattering self-distribution function.
Physical review. E Statistical nonlinear and soft matter physics, 2008Co-Authors: Salvatore Magazù, G. Maisano, Federica Migliardo, Antonio BenedettoAbstract:In the present work an operational recipe for the mean Square Displacement (MSD) determination, highlighting the connection between elastic incoherent neutron scattering (EINS) intensity profiles and the associated self-distribution function, is presented. The determination of the thermal behavior of the total MSD and of its partial contributions is tested on EINS data collected by the backscattering spectrometer IN13 (ILL, Grenoble) on a model system such as PolyEthylene Glycol with a mean molecular weight of 400 Dalton (PEG 400).
B Kresse - One of the best experts on this subject based on the ideXlab platform.
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segmental mean Square Displacement field cycling 1h relaxometry vs neutron scattering
Macromolecules, 2016Co-Authors: M Hofmann, B Kresse, A F Privalov, Lutz Heymann, Lutz Willner, Nuri Aksel, Nail Fatkullin, F Fujara, Ernst A RosslerAbstract:Proton (1H) field-cycling (FC) NMR relaxometry is applied to monitor the crossover in the segmental subdiffusion from the Rouse to the constrained Rouse regime in an entangled linear polymer melt. The method probes the dispersion of the spin–lattice relaxation rate R1(ω). Via Fourier transformation the segmental mean Square Displacement ⟨r2(t)⟩ is calculated from the intermolecular relaxation contribution R1inter(ω) to the total 1H spin–lattice relaxation dispersion R1(ω). As an example we chose poly(ethylene propylene) (M = 200k), and R1inter(ω) is singled out by performing an isotope dilution experiment. The ⟨r2(t)⟩ data obtained by FC NMR is directly compared to such of neutron scattering (NS) available from the literature. Because of different experimental time windows the NS data is converted to a reference temperature assuming frequency–temperature superposition. Absolute agreement is revealed between FC NMR and NS. The data on ⟨r2(t)⟩ confirm the predictions of the tube-reptation model; i.e., the c...
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mean Square Displacement and reorientational correlation function in entangled polymer melts revealed by field cycling 1h and 2h nmr relaxometry
Macromolecules, 2012Co-Authors: Andreas Herrmann, B Kresse, A F Privalov, Nail Fatkullin, F Fujara, M Wohlfahrt, I Bauer, D Kruk, Ernst A RosslerAbstract:Mixtures of protonated and deuterated polybutadiene and polydimethylsiloxane are studied by means of field-cycling (FC) 1H NMR relaxometry in order to analyze the intra- and intermolecular contributions to spin–lattice relaxation. They reflect reorientational and translational dynamics,respectively. Master curves in the susceptibility representation χ″(ωτs) are constructed by employing frequency–temperature superposition with τs denoting the segmental correlation time. The intermolecular contribution is dominating at low frequencies and allows extracting the segmental mean Square Displacement ⟨R2(t)⟩, which reveals two power-law regimes. The one at short times agrees with t0.5 predicted for the free Rouse regime and at long times a lower exponent is observed in fair agreement with t0.25 expected for the constrained Rouse regime of the tube-reptation model. Concomitantly the reorientational rank-two correlation function C2(t/τs) is obtained from the intramolecular part. Again two power-law regimes t–e are ...
