Effect of geometric and electronic structures on the finite temperature behavior of Na58_{58}, Na57_{57}, and Na55_{55} clusters

An analysis of the evolutionary trends in the ground state geometries of Na$_{55}$ to Na$_{62}$ reveals Na$_{58}$, an electronic closed--shell system, shows namely an electronically driven spherical shape leading to a disordered but compact structure. This structural change induces a strong {\it connectivity} of short bonds among the surface atoms as well as between core and surface atoms with inhomogeneous strength in the ground state geometry, which affects its finite--temperature behavior. By employing {\it ab initio} density--functional molecular dynamics, we show that this leads to two distinct features in specific heat curve compared to that of Na$_{55}$: (1) The peak is shifted by about 100 K higher in temperature. (2) The transition region becomes much broader than Na$_{55}$. The inhomogeneous distribution of bond strengths results in a broad melting transition and the strongly connected network of short bonds leads to the highest melting temperature of 375 K reported among the sodium clusters. Na$_{57}$, which has one electron less than Na$_{58}$, also possesses stronger short--bond network compared with Na$_{55}$, resulting in higher melting temperature (350 K) than observed in Na$_{55}$. Thus, we conclude that when a cluster has nearly closed shell structure not only geometrically but also electronically, it show a high melting temperature. Our calculations clearly bring out the size--sensitive nature of the specific heat curve in sodium clusters.Comment: 7 pages, 11 figure

The Accusation of Clientelism: On the Interplay between Social Science, Mass Media, and Politics in the Critique of Irish Democracy

The case of Ireland provides an example of a long-term critical reflection on the nature of democracy that is not linked to social movements. Instead it is the result of an interplay between social science research, mass media, and parliamentary debate, all of which employ the notion of clientelism. The structural feature on which the respective critique focuses is the peculiar relationship be-tween public representatives and voters in Ireland. It is strongly based in con-stituency service and individual brokerage and thus contradicts universalistic expectations towards modern politics. The article starts with a justification of the choice of the case and the theoretical framework, i.e. the sociology of critical capacity proposed by Boltanski and Thévenot. It then introduces records of parliamentary debates and newspaper articles as the empirical material and qualitative content analysis as the main method of analysis. Subsequent sections reconstruct the dynamics of the critical reflection over a thirty-year period and highlight significant patterns of critique and justification

Aortic pulse wave velocity measurement via heart sounds and impedance plethysmography

Full abstract in the manuscript