Direct measurement of thermophoretic forces

We study the thermophoretic motion of a micron sized single colloidal particle in front of a flat wall by evanescent light scattering. To quantify thermophoretic effects we analyse the nonequilibrium steady state (NESS) of the particle in a constant temperature gradient perpendicular to the confining walls. We propose to determine thermophoretic forces from a 'generalized potential' associated with the probability distribution of the particle position in the NESS. Experimentally we demonstrate, how this spatial probability distribution is measured and how thermophoretic forces can be extracted with 10 fN resolution. By varying temperature gradient and ambient temperature, the temperature dependence of Soret coefficient $S_T(T)$ is determined for $r = 2.5 \mu m$ polystyrene and $r = 1.35 \mu m$ melamine particles. The functional form of $S_T(T)$ is in good agreement with findings for smaller colloids. In addition, we measure and discuss hydrodynamic effects in the confined geometry. The theoretical and experimental technique proposed here extends thermophoresis measurements to so far inaccessible particle sizes and particle solvent combinations

Extrapolation to nonequilibrium from coarse grained response theory

Nonlinear response theory, in contrast to linear cases, involves (dynamical) details, and this makes application to many body systems challenging. From the microscopic starting point we obtain an exact response theory for a small number of coarse grained degrees of freedom. With it, an extrapolation scheme uses near-equilibrium measurements to predict far from equilibrium properties (here, second order responses). Because it does not involve system details, this approach can be applied to many body systems. It is illustrated in a four state model and in the near critical Ising model.Comment: Accepted for publication in Phys. Rev. Let

A review of governmental management accounting : research around the turn of the century

This paper shows that governmental management accounting research around the turn of the century, as published in FAM, MAR and EAR, is different from general management accounting research in some respects. Although there are variations related to topics, theories and research methods, a mainstream in governmental management accounting research seems to exist. Research is predominantly directed to the way in which technical management accounting innovations are used, including organizational and contextual factors that might influence the use of these new techniques. Qualitatively oriented case and field studies are the dominant research methods, and the research is inspired by various theoretical viewpoints, e.g. economics, organization theory and neo-institutional theory. NPM, regarded as a lower level economic theory, turns out to be highly influential. The paper gives recommendations for governmental management accounting research in the future: more attention has to be paid to quantitative research, impact studies on NPM must be promoted, and jointly conducted research projects by management accounting and public administration researchers are welcomed.

A Traditional and Textualist Analysis of the Goals of Antitrust: Efficiency, Preventing Theft from Consumers, and Consumer Choice

This Article ascertains the overall purpose of the antitrust statutes in two very different ways. First, it performs a traditional analysis of the legislative history of the antitrust laws by analyzing relevant legislative debates and committee reports. Second, it undertakes a textualist or “plain meaning” analysis of the purpose of the antitrust statutes, using Justice Scalia’s methodology. It does this by analyzing the meaning of key terms as they were used in contemporary dictionaries, legal treatises, common law cases, and the earliest U.S. antitrust cases, and it does this in light of the history of the relevant times. Both approaches demonstrate that the overriding purpose of the antitrust statutes is to prevent firms from stealing from consumers by charging them supracompetitive prices. When firms use their market power to raise prices to supracompetitive levels, purchasers pay more for their goods and services, and these overcharges constitute a taking of purchasers’ property. Economic efficiency was only a secondary concern. In addition, the textualist approach leads to the surprising conclusion that neither the Sherman Act nor the Clayton Act contain an exception for monopolies attained by efficient business conduct. A “plain meaning” analysis of the antitrust statutes reveals that they are supposed to prevent and condemn all privately created monopolies

Measurement of second-order response without perturbation

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.Comment: 4 figure

Force measurement in the presence of Brownian noise: Equilibrium distribution method vs. Drift method

The study of microsystems and the development of nanotechnologies require new techniques to measure piconewton and femtonewton forces at microscopic and nanoscopic scales. Amongst the challenges, there is the need to deal with the ineluctable thermal noise, which, in the typical experimental situation of a spatial diffusion gradient, causes a spurious drift. This leads to a correction term when forces are estimated from drift measurements [Phys. Rev. Lett. 104, 170602 (2010)]. Here, we provide a systematic study of such effect comparing the forces acting on various Brownian particles derived from equilibrium distribution and drift measurements. We discuss the physical origin of the correction term, its dependence on wall distance, particle radius, and its relation to the convention used to solve the respective stochastic integrals. Such correction term becomes more significant for smaller particles and is predicted to be in the order of several piconewtons for particles the size of a biomolecule.Comment: 10 pages, 13 figure

Interactive visualisation and exploration of biological data

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