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Hiroyuki Ohshima - One of the best experts on this subject based on the ideXlab platform.
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approximate expressions for the surface charge density surface potential relationship and double layer potential distribution for a spherical or cylindrical Colloidal Particle based on the modified poisson boltzmann equation
Colloid and Polymer Science, 2018Co-Authors: Hiroyuki OhshimaAbstract:Approximate expressions for the surface charge density/surface potential relationship and double-layer potential distribution are derived for a spherical or cylindrical Colloidal Particle in an electrolyte solution. The obtained expressions are based on an approximate form of the modified Poisson-Boltzmann equation taking into account the ion size effects through the Carnahan-Starling activity coefficients of electrolyte ions. We further derive approximate expression for the effective surface potentials of a spherical or cylindrical Particle and for the electrostatic interaction energy between two spherical or cylindrical Particles on the basis of the linear superposition approximation.
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simple approximate analytic expression for the electrophoretic mobility of a spherical Colloidal Particle in a mixed solution of 1 1 and 2 1 electrolytes
Colloid and Polymer Science, 2014Co-Authors: Hiroyuki OhshimaAbstract:Simple approximate analytic expressions are derived for the electrophoretic mobility of a spherical Colloidal Particle of radius a and zeta potential ζ in a mixed solution of 1:1 and 2:1 electrolytes with common anions on the basis of the general mobility expression previously derived by Ohshima (Colloids Surf A Physicochem Eng Asp 267:50, 2005). The obtained expressions, which are applicable for spheres of any ζ and large radii such that κa ≥ ca. 30 (where κ is the Debye-Huckel parameter), consist of Smoluchowski’s equation and the correction term taking into account the relaxation effect.
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Electrophoretic mobility of a Colloidal Particle with constant surface charge density.
Langmuir, 2010Co-Authors: Kimiko Makino, Hiroyuki OhshimaAbstract:When the electrophoretic mobility of a Particle in an electrolyte solution is measured, the obtained electrophoretic mobility values are usually converted to the Particle zeta potential with the help of a proper relationship between the electrophoretic mobility and the zeta potential. For a Particle with constant surface charge density, however, the surface charge density should be a more characteristic quantity than the zeta potential because for such Particles the zeta potential is not a constant quantity but depends on the electrolyte concentration. In this article, a systematic method that does not require numerical computer calculation is proposed to determine the surface charge density of a spherical Colloidal Particle on the basis of the Particle electrophoretic mobility data. This method is based on two analytical equations, that is, the relationship between the electrophoretic mobility and zeta potential of the Particle and the relationship between the zeta potential and surface charge density of the Particle. The measured mobility values are analyzed with these two equations. As an example, the present method is applied to electrophoretic mobility data on gold nanoParticles (Agnihotri, S. M.; Ohshima, H.; Terada, H.; Tomoda, K.; Makino, K. Langmuir 2009, 25, 4804).
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approximate analytic expression for the dynamic electrophoretic mobility of a spherical Colloidal Particle in an oscillating electric field
Langmuir, 2005Co-Authors: Hiroyuki OhshimaAbstract:An approximate analytic expression is derived for the dynamic electrophoretic mobility of a spherical charged Colloidal Particle in an electrolyte solution in an applied oscillating electric field. This expression, which takes into account the relaxation effects, is applicable for all values of zeta potential at large kappa a (kappa a > or = ca. 30) and omega/2pi < or = ca. 10 MHz, where kappa is the Debye-Huckel parameter, a is the Particle radius, and omega is the frequency of the electric field. It is shown that the obtained mobility expression is in excellent agreement with the exact numerical results of Mangelsdorf and White (J. Chem. Soc., Faraday Trans. 1992, 88, 3567).
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approximate expression for the electrophoretic mobility of a spherical Colloidal Particle in a solution of general electrolytes
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Hiroyuki OhshimaAbstract:Abstract An approximate analytic expression is derived for the electrophoretic mobility of a charged spherical Colloidal Particle in a solution of general electrolytes on the basis of an approximation method by [Ohshima et al., J. Chem. Soc. Faraday Trans. 2, 79 (1983) 1613]. This expression, which takes into account the relaxation effects, is applicable for all values of zeta potential at large κa ( κa ≥ ca. 30), where κ is the Debye–Huckel parameter and a is the radius of the Particle core.
Clemens Bechinger - One of the best experts on this subject based on the ideXlab platform.
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measurement of second order response without perturbation
EPL, 2016Co-Authors: Laurent Helden, Clemens Bechinger, Urna Basu, Matthias KrugerAbstract:We study the second-order response functions of a Colloidal Particle being subjected to an anharmonic potential. Contrary to typical response measurements which require an external perturbation, here we experimentally demonstrate that the system's susceptibilities up to second order can be obtained from the Particle's equilibrium fluctuations. The measured susceptibilities are in quantitative agreement with those obtained from the response to an external perturbation.
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measurement of second order response without perturbation
arXiv: Soft Condensed Matter, 2016Co-Authors: Laurent Helden, Clemens Bechinger, Urna Basu, Matthias KrugerAbstract:We study the second order response functions of a Colloidal Particle being subjected to an anharmonic potential. Contrary to typical response measurements which require an external perturbation, here we experimentally confirm a recently developed approach where the system's susceptibilities up to second order are obtained from the Particle's equilibrium trajectory [PCCP $\mathrm{\bf 17}$, 6653 (2015)]. The measured susceptibilities are in quantitative agreement with those obtained from the response to an external perturbation.
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transient dynamics of a Colloidal Particle driven through a viscoelastic fluid
New Journal of Physics, 2015Co-Authors: Clemens Bechinger, Juan Ruben GomezsolanoAbstract:We study the transient motion of a Colloidal Particle actively dragged by an optical trap through different viscoelastic fluids (wormlike micelles, polymer solutions, and entangled λ-phage DNA). We observe that, after sudden removal of the moving trap, the Particle recoils due to the recovery of the deformed fluid microstructure. We find that the transient dynamics of the Particle proceeds via a double-exponential relaxation, whose relaxation times remain independent of the initial Particle velocity whereas their amplitudes strongly depend on it. While the fastest relaxation mirrors the viscous damping of the Particle by the solvent, the slow relaxation results from the recovery of the strained viscoelastic matrix. We show that this transient information, which has no counterpart in Newtonian fluids, can be exploited to investigate linear and nonlinear rheological properties of the embedding fluid, thus providing a novel method to perform transient rheology at the micron-scale.
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transient dynamics of a Colloidal Particle driven through a viscoelastic fluid
arXiv: Soft Condensed Matter, 2015Co-Authors: Clemens Bechinger, Juan Ruben GomezsolanoAbstract:We experimentally study the transient motion of a Colloidal Particle actively dragged by an optical trap through different viscoelastic fluids (wormlike micelles, polymer solutions, and entangled $\lambda$-phage DNA). We observe that, after sudden removal of the moving trap, the Particle recoils due to the recovery of the deformed fluid microstructure. We find that the transient dynamics of the Particle proceeds via a double exponential relaxation, whose relaxation times remain independent of the initial Particle velocity whereas their amplitudes strongly depend on it. While the fastest relaxation mirrors the viscous damping of the Particle by the solvent, the slow relaxation results from the recovery of the strained viscoelastic matrix. We show that this transient information, which has no counterpart in Newtonian fluids, can be exploited to investigate linear and nonlinear rheological properties of the embedding fluid, thus providing a novel method to perform transient rheology at the micron-scale.
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realization of a micrometre sized stochastic heat engine
Nature Physics, 2012Co-Authors: Valentin Blickle, Clemens BechingerAbstract:An optically trapped Colloidal Particle serves as the first realization of a stochastic thermal engine, extending our understanding of the thermodynamics behind the Carnot cycle to microscopic scales where fluctuations dominate.
Udo Seifert - One of the best experts on this subject based on the ideXlab platform.
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distribution of entropy production for a Colloidal Particle in a nonequilibrium steady state
EPL, 2007Co-Authors: Thomas Speck, Valentin Blickle, Clemens Bechinger, Udo SeifertAbstract:For a Colloidal Particle driven by a constant force across a periodic potential, we investigate the distribution of entropy production both experimentally and theoretically. For short trajectories, the fluctuation theorem holds experimentally. The mean entropy production rate shows two regimes as a function of the applied force. Theoretically, both mean and variance of the pronounced non-Gaussian distribution can be obtained from a differential equation in good agreement with the experimental data.
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optimal finite time processes in stochastic thermodynamics
Physical Review Letters, 2007Co-Authors: Tim Schmiedl, Udo SeifertAbstract:For a small system like a Colloidal Particle or a single biomolecule embedded in a heat bath, the optimal protocol of an external control parameter minimizes the mean work required to drive the system from one given equilibrium state to another in a finite time. In general, this optimal protocol obeys an integro-differential equation. Explicit solutions both for a moving laser trap and a time-dependent strength of such a trap show finite jumps of the optimal protocol to be typical both at the beginning and at the end of the process.
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Restoring a fluctuation-dissipation theorem in a nonequilibrium steady state
Europhysics Letters (EPL), 2006Co-Authors: Thomas Speck, Udo SeifertAbstract:In a nonequilibrium steady state, the violation of the fluctuation-dissipation theorem (FDT) is connected to breaking detailed balance. For the velocity correlations of a driven Colloidal Particle we calculate an explicit expression of the FDT violation. The equilibrium form of the FDT can be restored by measuring the velocity with respect to the local mean velocity.
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entropy production along a stochastic trajectory and an integral fluctuation theorem
Physical Review Letters, 2005Co-Authors: Udo SeifertAbstract:For stochastic nonequilibrium dynamics like a Langevin equation for a Colloidal Particle or a master equation for discrete states, entropy production along a single trajectory is studied. It involves both genuine Particle entropy and entropy production in the surrounding medium. The integrated sum of both $\ensuremath{\Delta}{s}_{\mathrm{tot}}$ is shown to obey a fluctuation theorem $⟨\mathrm{exp}[\ensuremath{-}\ensuremath{\Delta}{s}_{\mathrm{tot}}]⟩=1$ for arbitrary initial conditions and arbitrary time-dependent driving over a finite time interval.
Juan Ruben Gomezsolano - One of the best experts on this subject based on the ideXlab platform.
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transient dynamics of a Colloidal Particle driven through a viscoelastic fluid
New Journal of Physics, 2015Co-Authors: Clemens Bechinger, Juan Ruben GomezsolanoAbstract:We study the transient motion of a Colloidal Particle actively dragged by an optical trap through different viscoelastic fluids (wormlike micelles, polymer solutions, and entangled λ-phage DNA). We observe that, after sudden removal of the moving trap, the Particle recoils due to the recovery of the deformed fluid microstructure. We find that the transient dynamics of the Particle proceeds via a double-exponential relaxation, whose relaxation times remain independent of the initial Particle velocity whereas their amplitudes strongly depend on it. While the fastest relaxation mirrors the viscous damping of the Particle by the solvent, the slow relaxation results from the recovery of the strained viscoelastic matrix. We show that this transient information, which has no counterpart in Newtonian fluids, can be exploited to investigate linear and nonlinear rheological properties of the embedding fluid, thus providing a novel method to perform transient rheology at the micron-scale.
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transient dynamics of a Colloidal Particle driven through a viscoelastic fluid
arXiv: Soft Condensed Matter, 2015Co-Authors: Clemens Bechinger, Juan Ruben GomezsolanoAbstract:We experimentally study the transient motion of a Colloidal Particle actively dragged by an optical trap through different viscoelastic fluids (wormlike micelles, polymer solutions, and entangled $\lambda$-phage DNA). We observe that, after sudden removal of the moving trap, the Particle recoils due to the recovery of the deformed fluid microstructure. We find that the transient dynamics of the Particle proceeds via a double exponential relaxation, whose relaxation times remain independent of the initial Particle velocity whereas their amplitudes strongly depend on it. While the fastest relaxation mirrors the viscous damping of the Particle by the solvent, the slow relaxation results from the recovery of the strained viscoelastic matrix. We show that this transient information, which has no counterpart in Newtonian fluids, can be exploited to investigate linear and nonlinear rheological properties of the embedding fluid, thus providing a novel method to perform transient rheology at the micron-scale.
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experimental verification of a modified fluctuation dissipation relation for a micron sized Particle in a nonequilibrium steady state
Physical Review Letters, 2009Co-Authors: Juan Ruben Gomezsolano, Artyom Petrosyan, Sergio Ciliberto, Raphael Chetrite, Krzysztof GawedzkiAbstract:A modified fluctuation-dissipation theorem for a nonequilibrium steady state is experimentally checked by studying the position fluctuations of a Colloidal Particle whose motion is confined in a toroidal optical trap. The nonequilibrium steady state is generated by means of a rotating laser beam which exerts on the Particle a sinusoidal conservative force plus a constant nonconservative one. The modified fluctuation-dissipation theorem is perfectly verified by the experimental data. It can be interpreted as an equilibrium-like fluctuation-dissipation relation in the Lagrangian frame of the mean local velocity of the Particle.
Shiqi Zhou - One of the best experts on this subject based on the ideXlab platform.
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an approximate analytic expression for the surface charge density surface potential relationship for a spherical Colloidal Particle
Journal of Colloid and Interface Science, 1998Co-Authors: Shiqi ZhouAbstract:An approximate analytic expression for the surface charge density/surface potential relationship (final sigma/psi0) for a spherical Colloidal Particle in a solution of mixed and nonsymmetrical electrolytes is obtained by solving a nonlinear Poisson-Boltzmann equation using a linearization approximation. The approximate analytic expression is fit for the case of large kappaa(kappa = Debye-Huckel inverse parameter, a = Colloidal Particle radius), but for the case of small kappaa, the approximate analytic expression is applicable only when kappaa >/= 0.03, with a maximal percent relative error of 5.0, even for surface potentials up to 334 mV (25 degreesC). The approximate analytic expressions reported in the literature have a low limit of kappaa, 0.5 or even 2.0. The present approximate analytic expression has a simple structure and is characterized by the ease with which it is adapted for analysis. Copyright 1998 Academic Press.