Impact of anisotropy on vortex clusters and their dynamics

We investigate the effects of anisotropy on the stability and dynamics of vortex cluster states which arise in Bose-Einstein condensates. Sufficiently strong anisotropies are shown to stabilize states with arbitrary numbers of vortices that are highly unstable in the isotropic limit. Conversely, anisotropy can be used to destabilize states which are stable in the isotropic limit. Near the linear limit, we identify the bifurcations of vortex states including their emergence from linear eigenstates, while in the strongly nonlinear limit, a particle-like description of the dynamics of the vortices in the anisotropic trap is developed. Both are in very good agreement with numerical results. Collective modes of stabilized many vortex cluster states are demonstrated.Comment: 6 pages, 6 figure

On interurban road pricing schemes and the impacts of traffic diversion on road safety in Germany: Empirical findings and implications

Recently, traffic diversion effects induced by tolling have increasingly been attracting attention, since interurban road charging schemes are becoming more widespread in Europe. However, less attention has been paid to unintended spillover effects concerning negative road safety outcomes, caused by traffic shifts to non-tolled adjacent secondary roads of inferior quality. This study introduces to the specifics of existing road pricing schemes in Europe, clarifies the characteristics of the German toll system and explores the relationship between toll implementation and road safety outcomes using regional German panel data for the period 2000-2010. To this end, we test different specifications using accident data, while controlling for transport-related and socioeconomic covariates. We find that the implementation of the heavy goods vehicle toll in 2005 has a negative impact on accident rates with damage to persons during our sample period. This finding is a valuable insight for policy makers, since the existence of a relationship between tolls, traffic diversion and road safety has important policy implications regarding the determination of optimal welfare-enhancing tolls

Spectral properties of a Rydberg atom immersed in a Bose-Einstein condensate

The electronic spectrum of a Rydberg atom immersed in a Bose-Einstein condensate is investigated. The Heisenberg equations of motions for the condensate and the Rydberg atom are derived. Neglecting the backaction of the Rydberg atom onto the condensate decouples the equations describing the condensate and Rydberg atom. In this case the spectral structure of the Rydberg atom is completely determined by an effective potential which depends on the density distribution of the condensate. We study the spectral properties for the situation of an isotropic harmonic and anharmonic as well as axially symmetric confinement. In the latter case an intriguing analogy with Rydberg atoms in magnetic fields is encountered

Hydrodynamics in a cocurrent gas-liquid trickle bed at elevated pressures

Data on design and operation of trickle beds at elevated pressures are scarce. In this study the influence of the gas density on the liquid holdup, the pressure drop, and the transition between trickle and pulse flow has been investigated in a tricklebed reactor operating up to 7.5 MPa and with nitrogen or helium as the gas phase. Gas-liquid interfacial areas have been determined up to 5.0 MPa by means of CO2 absorption from CO2/N2 gas mixtures into amine solutions. \ud A comparison of the results from nitrogen as the gas phase to those of helium shows that at equal gas densities the hydrodynamic states are the same. The gas-liquid interfacial area increases when operating at higher gas densities. When the determined dimensionless interfacial areas agl/as are all within the range 0.25-0.8, the trickle-bed reactor is suggested to operate in the trickle-flow regime. The gas density has a strong influence on the liquid holdup. Due to the higher pressure gradients at elevated gas densities, the liquid holdup decreases noticeably. Besides, the boundary between the trickle-flow and pulse-flow regime shifts toward higher liquid throughputs: the region for trickle-flow operationg becomes larger. For the liquid holdup and the pressure gradient in the trickle-flow regime, correlations derived based on dimensionless numbers can be applied to high-prssure trickle beds

Dynamics of Vortex Dipoles in Confined Bose-Einstein Condensates

We present a systematic theoretical analysis of the motion of a pair of straight counter-rotating vortex lines within a trapped Bose-Einstein condensate. We introduce the dynamical equations of motion, identify the associated conserved quantities, and illustrate the integrability of the ensuing dynamics. The system possesses a stationary equilibrium as a special case in a class of exact solutions that consist of rotating guiding-center equilibria about which the vortex lines execute periodic motion; thus, the generic two-vortex motion can be classified as quasi-periodic. We conclude with an analysis of the linear and nonlinear stability of these stationary and rotating equilibria.Comment: 8 pages, 3 figures, to appear in Phys. Lett.

Ruimte voor Rechtsvorming:een onderzoek naar adequate instrumenten voor afhandeling en rechtsvorming door de Afdeling bestuursrechtspraak van de Raad van State

De Afdeling bestuursrechtspraak van de Raad van State is zowel geschilbeslechter als rechtsvormer. Haar geschilbeslechtende taak ontleent de Afdeling aan het feit dat overheid en burgers royaal gebruik maken van de mogelijkheid hun geschil ter beoordeling aan haar voor te leggen. De taak van de Afdeling als rechtsvormer vloeit voort uit haar hoedanigheid van hoogste bestuursrechter. Tussen beide taken bestaat een inherente spanning. De wens om elke afzonderlijke (hoger)beroepszaak zo gedegen, snel en effectief mogelijk af te handelen, kan in strijd komen met de noodzaak om de rechtsvormende taak als hoogste bestuursrechter inhoud te geven. In dit boek is de vraag aan de orde hoe de procedure bij de Afdeling bestuursrecht-spraak zo kan worden vormgegeven, dat beide taken het volle pond krijgen. Daartoe is zowel in kaart gebracht op welke wijze de Afdeling de aan haar voorgelegde ge-schillen behandelt, als ook welke alternatieven er zijn voor de wijze waarop de afhan-deling van (met name) hogerberoepszaken op dit moment is georganiseerd. Het onderzoek biedt daarmee niet alleen een uniek beeld van de werkwijze van de Afdeling bestuursrechtspraak, maar ook een grondige inventarisatie van een mogelij-ke alternatieve vormgeving van de procedure van (hoger) beroep. Het onderzoek mondt uit in een aantal aanbevelingen die beogen te bewerkstelligen dat de ruimte voor rechtsvorming wordt vergroot, zonder dat dit ten koste gaat van een snelle en effectieve beslechting van geschillen door de Afdeling bestuursrechtspraak van de Raad van State