Determination of the size distribution of non-spherical nanoparticles by electric birefringence-based methods

The in situ determination of the size distribution of dispersed non-spherical nanoparticles is an essential characterization tool for the investigation and use of colloidal suspensions. In this work, we test a size characterization method based on the measurement of the transient behaviour of the birefringence induced in the dispersions by pulsed electric fields. The specific shape of such relaxations depends on the distribution of the rotational diffusion coefficient of the suspended particles. We analyse the measured transient birefringence with three approaches: the stretched-exponential, Watson-Jennings, and multiexponential methods. These are applied to six different types of rod-like and planar particles: PTFE rods, goethite needles, single- and double-walled carbon nanotubes, sodium montmorillonite particles and gibbsite platelets. The results are compared to electron microscopy and dynamic light scattering measurements. The methods here considered provide good or excellent results in all cases, proving that the analysis of the transient birefringence is a powerful tool to obtain complete size distributions of non-spherical particles in suspension.Financial support of this investigation by Junta de Andalucía, Spain (grant No. PE2012-FQM0694) and University of Granada (Program “Proyectos de investigación precompetitivos”) is gratefully acknowledged

Risk Models for Capital Adequacy: Applications in the Context of Solvency II and Beyond

In the context of the quantitative requirements under pillar 1 of Solvency II, internal risk models quantify a specific company's risk position, that is, measure the risk capital it requires. Because the individual insurance company's situation is modelled, its risk landscape is reflected more accurately than if a standard model approach were used. A brief case study indicates that internal risk models should be used not only to fulfill regulatory requirements, they have to and they do feature more benefits: risk models foster risk management processes; therefore, they are capable of supporting risk-based business decisions. Finally, they constitute a kernel for any risk-based performance measurement framework. The Geneva Papers (2006) 31, 528–550. doi:10.1057/palgrave.gpp.2510095