Fix for solution errors near interfaces in two-fluid computations

A finite-volume method is considered for the computation of flows of two compressible, immiscible fluids at very different densities. A level-set technique is employed to distinguish between the two fluids. A simple ghost-fluid method is presented as a fix for the solution errors (‘pressure oscillations’) that may occur near two-fluid interfaces when applying a capturing method. Computations with it for compressible two-fluid flows with arbitrarily large density ratios yield perfectly sharp, pressure-oscillation-free interfaces. The masses of the separate fluids appear to be conserved up to first-order accuracy

Fluorite Precipitation in a Calcareous Soil Irrigated with High Fluoride Water

Lysimeters filled with Freedom silt loam soil (fine-silty, mixed, mesic, Xerollic Calciorthids) were irrigated with geothermal well water from south central Idaho. The water contained 7 mg F/L. Alfalfa (Medicago sativa L.) was grown in the lysimeters and the water was applied at a rate to give either a 0.30 or 0.15 leaching fraction. After irrigating the 1.0 m deep soil samples for 600 d, over 98% of the added F remained in the soil. Soil extract and lysimeter leachate analysis showed that fluorite precipitation was occurring in the upper profile, but only after another fluoride adsorption mechanism was saturated and the fluoride and calcium ion activities exceeded the CaF? ion activity product. The F concentration in the upper profile extracts exceeded 20 mg F/L and with the additional high F water irrigation, the soluble F would be expected to leach deeper in the soil. Under field conditions the F would be expected to eventually move into the groundwater with continued irrigation with high F water

Kwantitatieve bemonstering van benthos en bodem voorafgaand aan zandsuppleties bij Texel (nulmeting)

Dit rapport beschrijft een kwantitatieve inventarisatie (nulmeting) van de bodemfauna (benthos) en de bodemsamenstelling (sediment) nabij de noordwest punt van Texel, voorafgaand aan suppletiewerken van Rijkswaterstaat in 2009. Dit betreft een vooroeversuppletie van 1.300.000 kubieke meter zand bij de Eierlandse dam bij Texe

The UKIDSS Galactic Plane Survey

'The definitive version is available at www.blackwell-synergy.com .' Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.13924.xThe UKIDSS Galactic Plane Survey (GPS) is one of the five near-infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared TelescopePeer reviewe

A high resolution imaging detector for TeV gamma-ray astronomy

Details are presented of an atmospheric Cherenkov telescope for use in very high energy gamma-ray astronomy which consists of a cluster of 109 close-packed photomultiplier tubes at the focus of a 10 meter optical reflector. The images of the Cherenkov flashes generated both by gamma-ray and charged cosmic-ray events are digitized and recorded. Subsequent off-line analysis of the images improves the significance of the signal to noise ratio by a factor of 10 compared with non-imaging techniques

The Random-bond Potts model in the large-q limit

We study the critical behavior of the q-state Potts model with random ferromagnetic couplings. Working with the cluster representation the partition sum of the model in the large-q limit is dominated by a single graph, the fractal properties of which are related to the critical singularities of the random Potts model. The optimization problem of finding the dominant graph, is studied on the square lattice by simulated annealing and by a combinatorial algorithm. Critical exponents of the magnetization and the correlation length are estimated and conformal predictions are compared with numerical results.Comment: 7 pages, 6 figure

First principles electronic structure of spinel LiCr2O4: A possible half-metal?

We have employed first-principles electronic structure calculations to examine the hypothetical (but plausible) oxide spinel, LiCr2O4 with the d^{2.5} electronic configuration. The cell (cubic) and internal (oxygen position) structural parameters have been obtained for this compound through structural relaxation in the first-principles framework. Within the one-electron band picture, we find that LiCr2O4 is magnetic, and a candidate half-metal. The electronic structure is substantially different from the closely related and well known rutile half-metal CrO2. In particular, we find a smaller conduction band width in the spinel compound, perhaps as a result of the distinct topology of the spinel crystal structure, and the reduced oxidation state. The magnetism and half-metallicity of LiCr2O4 has been mapped in the parameter space of its cubic crystal structure. Comparisons with superconducting LiTi2O4 (d^{0.5}), heavy-fermion LiV2O4 (d^{1.5}) and charge-ordering LiMn2O4 (d^{3.5}) suggest the effectiveness of a nearly-rigid band picture involving simple shifts of the position of E_F in these very different materials. Comparisons are also made with the electronic structure of ZnV2O4 (d^{2}), a correlated insulator that undergoes a structural and antiferromagnetic phase transition.Comment: 9 pages, 7 Figures, version as published in PR

Ecologische ontwikkeling in een voor menselijke activiteiten gesloten gebied in de Nederlandse Waddenzee

De Nederlandse overheid heeft in november 2005 ten zuiden van Rottum een referentiegebied ingesteld om te voldoen aan de internationale verplichting dat voldoende grote gebieden in de Waddenzee worden aangewezen waarbinnen geen exploitaties en verstorende activiteiten mogen plaatsvinden. In dit referentiegebied wordt menselijke beïnvloeding met mogelijk negatieve effecten zoveel mogelijk beperkt. Het bestuderen van de ontwikkeling van een dergelijk referentiegebied is noodzakelijk om uitspraken te kunnen doen over de “favourable conservation status” van de rest van de Waddenzee ten aanzien van bepaalde activiteiten. In dit rapport wordt de ontwikkeling van de benthische mariene fauna en de ontwikkeling van enkele litorale mosselbanken, vier jaar na sluiting van het referentiegebied, weergegeven