Logarithmic interaction under periodic boundary conditions: Closed form formulas for energy and forces

A method is given to obtain closed form formulas for the energy and forces for an aggregate of charges interacting via a logarithmic interaction under periodic boundary conditions. The work done here is a generalization of Glasser's results [M. L. Glasser, J. Math. Phys. 15, 188 (1974)] and is obtained with a different and simpler method than that by Stremler [M. A. Stremler, J. Math. Phys. 45, 3584 (2004)]. The simplicity of the formulas derived here makes them extremely convenient in a computer simulation

Doding gevolgd door zelfdoding in Nederland

Homicide followed by the suicide of the perpetrator often leads to shock and incomprehension. It has been suggested that media reporting on such cases could lead to an imitation effect. This article describes the nature and incidence of homicide-suicide in the Netherlands in the period 1992-2014. In addition, it assesses whether a copycat-effect can be established due to media reporting. Results show that homicide-suicides occur on average nine times per year. Intimate partner homicide-suicide and child homicide-suicide are the most frequent types of homicide-suicide. Even though several temporal clusters could be observed during the period of study, there are insufficient indications to confirm a copycat-effect. This may be attributed to the heterogeneous and multifaceted nature of this phenomenon, lacking one single potentially ‘contagious’ cause.Security and Global Affair

Human-centred Design Workshops in Collaborative Strategic Design Projects: An educational and professional comparison

It has been found that the implementation of Human-centred Design (HCD) methods in the Fuzzy Front-End is not likely to lead to diversification in educational product planning exercises, where time lines are short and executors lack experience. Companies, interested to collaborate with Master-level Industrial Design students on strategic design projects, should have realistic ambitions with respect to innovation and value creation. Moreover, diversification is not the only generic growth strategy to gain competitive advantage. Value can also be created from developing new products for existing markets, or creating new markets for existing products. On the contrary, companies who aim for diversification in their generic growth strategies, may not always end up with a complementary ‘high valued’ design outcome. From a learning perspective, the understanding of HCD methods created awareness among students and companies that respect and empathy for the end-user are important for enriching their design processes, and as such increasing the chances for diversification in subsequent projects with clients. This study also compares the implementation of Human-Centred Design (HCD) methods in a professional /collaborative and an educational/collaborative strategic design project

Who Are the Workers Who Never Joined a Union? : Empirical Evidence from Western and Eastern Germany

"Using representative data from the German social survey ALLBUS 2002 and the European Social Survey 2002/03, this paper provides the first empirical analysis of trade union ‘never-membership’ in Germany. We show that between 54 and 59 percent of all employees in Germany have never been members of a trade union. In western Germany, individuals’ probability of ‘never-membership’ is significantly affected by their personal characteristics, their political orientation and (to a lesser degree) their family background. In addition, the presence of a union at the workplace plays a significant role. While the latter factor is also important in eastern Germany, many of the variables which are relevant for ‘never-membership’ in the west prove to be irrelevant in the east. This difference probably reflects the fact that most employees in eastern Germany did not really have a choice not to become union members during the communist regime." (author's abstract)"Mit Daten des ALLBUS 2002 und des European Social Survey 2002/03 analysiert diese Arbeit erstmalig die ‚Nie-Mitgliedschaft’ in deutschen Gewerkschaften. Wir zeigen, dass 54 bis 59 Prozent aller Beschäftigten in Deutschland niemals Mitglied einer Gewerkschaft waren. Die individuelle Wahrscheinlichkeit einer ‚Nie-Mitgliedschaft’ hängt in Westdeutschland signifikant mit persönlichen Merkmalen, der politischen Ausrichtung und (in geringerem Maße) dem familiären Hintergrund zusammen. Darüber hinaus spielt das Vorhandensein einer Gewerkschaft am Arbeitsplatz eine signifikante Rolle. Während letzteres auch in Ostdeutschland von Bedeutung ist, erweisen sich viele der im Westen relevanten Erklärungsvariablen im Osten als irrelevant. Dieser Unterschied spiegelt wahrscheinlich wider, dass die meisten Arbeitnehmer in Ostdeutschland während des SED-Regimes kaum die Wahl hatten, auf eine Gewerkschaftsmitgliedschaft zu verzichten." (Autorenreferat

Lekner summations and Ewald summations for quasi-two dimensional systems

Using the specific model of a bilayer of classical charged particles (bilayer Wigner crystal), we compare the predictions for energies and pair distribution functions obtained by Monte Carlo simulations using three different methods available to treat the long range Coulomb interactions in systems periodic in two directions but bound in the third one. The three methods compared are: the Ewald method for quasi-two dimensional systems [D.E. Parry, Surf. Sci. $\bm{49}$, 433 (1975); \it{ibid.}, $\bm{54}$, 195 (1976)], the Hautman-Klein method [J. Hautman and M.L. Klein, Mol. Phys. $\bm{75}$, 379 (1992)] and the Lekner summations method [J. Lekner, Physica A$\bm{176}$, 485 (1991)]. All of the three method studied in this paper may be applied to any quasi-two dimensional systems, including those having not the specific symmetry of slab systems. For the particular system used in this work, the Ewald method for quasi-two dimensional systems is exact and may be implemented with efficiency; results obtained with the other two methods are systematically compared to results found with the Ewald method. General recommendations to implement with accuracy, but not always with efficiency, the Lekner summations technique in Monte Carlo algorithms are given.Comment: 50 pages, 9 figures, 4 table

Diffusion of gold nanoclusters on graphite

We present a detailed molecular-dynamics study of the diffusion and coalescence of large (249-atom) gold clusters on graphite surfaces. The diffusivity of monoclusters is found to be comparable to that for single adatoms. Likewise, and even more important, cluster dimers are also found to diffuse at a rate which is comparable to that for adatoms and monoclusters. As a consequence, large islands formed by cluster aggregation are also expected to be mobile. Using kinetic Monte Carlo simulations, and assuming a proper scaling law for the dependence on size of the diffusivity of large clusters, we find that islands consisting of as many as 100 monoclusters should exhibit significant mobility. This result has profound implications for the morphology of cluster-assembled materials