Structure and Phase transitions of Yukawa balls

In this review, an overview of structural properties and phase transitions in finite spherical dusty (complex) plasma crystals -- so-called Yukawa balls -- is given. These novel kinds of Wigner crystals can be directly analyzed experimentally with video cameras. The experiments clearly reveal a shell structure and allow to determine the shell populations, to observe metastable states and transitions between configurations as well as phase transitions. The experimental observations of the static properties are well explained by a rather simple theoretical model which treats the dust particles as being confined by a parabolic potential and interacting via an isotropic Yukawa pair potential. The excitation properties of the Yukawa balls such as normal modes and the dynamic behavior, including the time-dependent formation of the crystal requires, in addition, to include the effect of friction between the dust particles and the neutral gas. Aside from first-principle molecular dynamics and Monte Carlo simulations several analytical approaches are reviewed which include shell models and a continuum theory. A summary of recent results and theory-experiment comparisons is given and questions for future research activities are outlined.Comment: Invited review, submitted to Contrib. Plasmas Physic

An automated search for high-velocity clouds in the Leiden/Dwingeloo Survey

We describe an automated search through the Leiden/Dwingeloo HI Survey (LDS) for high-velocity clouds north of Dec=-28 deg. From the general catalog we extract a sample of isolated high-velocity clouds, CHVCs: anomalous-velocity HI clouds which are sharply bounded in angular extent with no kinematic or spatial connection to other HI features down to a limiting column density of 1.5*10^18cm^-2. This column density is an order of magnitude lower than the critical HI column density, about 2*10^19cm^-2, where the ionized fraction is thought to increase dramatically due to the extragalactic radiation field. As such, these objects are likely to provide their own shielding to ionizing radiation. Their small median angular size, of about 1 deg. FWHM, might then imply substantial distances, since the partially ionized HI skin in a power-law ionizing photon field has a typical exponential scale-length of 1 kpc. The automated search algorithm has been applied to the HIPASS and to the Leiden/Dwingeloo data sets. The results from the LDS are described here; Putman et al. (2002) describe application of this algorithm to the HIPASS material. We identify 67 CHVCs in the LDS which satisfy stringent requirements on isolation, and an additional 49 objects which satisfy somewhat less stringent requirements. Independent confirmation is available for all of these objects, either from earlier data in the literature or from new observations made with the Westerbork Synthesis Radio Telescope and reported here. The catalog includes 54 of the 65 CHVCs listed by Braun and Burton (1999) on the basis of a visual search of the LDS data.Comment: 17 pages, 19 png/jpeg figures, in review at A&A, (embedded PS figures removed due to outdated astro-ph size limits

The European Parliament in European Community environmental policy

Digitised version produced by the EUI Library and made available online in 2020

Multiple actors and arenas : European Community regulation in a polycentric system : a case study on car emission policy

Defence date: 10 November 1995Examining board: Adrienne Héritier (EUI) ; Prof. Gerhard Lembruch (Universität Konstanz) ; Prof. Giandomenico Majone (EUI - supervisor) ; Prof. Roger Morgan (EUI - co-supervisor) ; Prof. Jeremy Richardson (University of Essex)First made available online: 13 September 201