Magnetization and susceptibility of ferrofluids

A second-order Taylor series expansion of the free energy functional provides analytical expressions for the magnetic field dependence of the free energy and of the magnetization of ferrofluids, here modelled by dipolar Yukawa interaction potentials. The corresponding hard core dipolar Yukawa reference fluid is studied within the framework of the mean spherical approximation. Our findings for the magnetic and phase equilibrium properties are in quantitative agreement with previously published and new Monte Carlo simulation data.Comment: 8 pages including 4 figure

A simple scheme for precise relative frequency stabilization of lasers

We present a simple scheme for tuneable relative frequency stabilization of lasers. A highly sensitive and accurate frequency-to-voltage converter is used to derive an error signal from the beat note between two lasers. We analyze in detail detector noise and drift, modulation detection bandwidth, and cross-talk from power modulation. The results indicate that sub-kHz relative linewidth and a locking point drift on the order of 100 Hz for times scales of 1 h are achievable. The scheme can, therefore, be applied to situations where up to now only optical PLLs could provide sufficient accuracy and precision. To demonstrate its potential for high-resolution, high-precision spectroscopy we lock a diode laser to a fs-frequency comb and find a relative linear drift of 314 Hz during a 2.8 h period

Quantum mechanical ab-initio simulation of the electron screening effect in metal deuteride crystals

In antecedent experiments the electron screening energies of the d+d reactions in metallic environments have been determined to be enhanced by an order of magnitude in comparison to the case of gaseous deuterium targets. The analytical models describing averaged material properties have not been able to explain the experimental results so far. Therefore, a first effort has been undertaken to simulate the dynamics of reacting deuterons in a metallic lattice by means of an ab-initio Hartree-Fock calculation of the total electrostatic force between the lattice and the successively approaching deuterons via path integration. The calculations have been performed for Li and Ta, clearly showing a migration of electrons from host metallic to the deuterium atoms. However, in order to avoid more of the necessary simplifications in the model the utilization of a massive parallel supercomputer would be required.Comment: 11 pages, 12 figures, svjour class. To be published in Eur. Phys. J.

Variegated anti-austerity : exploring the demise and rise of class struggle during the crisis of neoliberalism

This article maps important trends that mark a new stage in neoliberal capitalism since 2008, with a focus on class struggle and resistance in the advanced industrial democracies. New forms of collective action have arisen in response to austerity which has been imposed, in different forms, across most of the advanced industrial democracies, in a context in which established solidaristic institutions – trade unions, social democratic parties, welfare states – have already been eroded as a result of the preceding twenty five years of neoliberal reform. The article presents an overview of these trends, highlighting austerity policies and anti-austerity responses. The article accounts for the rise of new forms of resistance and collective action as they have emerged differently in different national contexts, focusing on developments in the UK, US, Spain, Japan and Germany

Wear recording at micro deep drawing tools with comparative digital holography

We present a method to record the wear on samples of micro deep drawing tools. The method is based on the basic idea of comparative holography and captures three dimensionally the surface of the tool in the initial state and compares it with used state after processing several parts. The comparison reveals scratches and other effects caused by wear. In an industrial environment the comparative method must compensate for linear and rotational displacement of the present tool with respect to the initial state. As a consequence to the single-step-measurement with sufficiently high illumination intensity the developed set-up can be made insusceptible against stray light and the method is capable of inline quality control during a production process in a micro deep drawing machine

Subharmonic bifurcation cascade of pattern oscillations caused by winding number increasing entrainment

Convection structures in binary fluid mixtures are investigated for positive Soret coupling in the driving regime where solutal and thermal contributions to the buoyancy forces compete. Bifurcation properties of stable and unstable stationary square, roll, and crossroll (CR) structures and the oscillatory competition between rolls and squares are determined numerically as a function of fluid parameters. A novel type of subharmonic bifurcation cascade (SC) where the oscillation period grows in integer steps as $n (2\pi)/(\omega)$ is found and elucidated to be an entrainment process.Comment: 7 pages, 4 figure