Slak-in-Du project. Inventarisatie van de mollusken in de duingebieden langs de Belgische Kust - 2012 Oostkust

The Slak-in-Du (Snails in the Dunes) project aims at establishing, over a period of about six years, a new inventory of the molluscan fauna in the Belgian coastal dunes area. In the first year of the project the eastern part of the Belgian coast was investigated, i.e. the region east of the harbor of Zeebrugge. About 20 persons have contributed in one way or another. The results are very satisfactorily: A total of 30 species of land snails (among which 5 species of slugs), but also 6 species of freshwater molluscs and 5 species preferring brackish waters were observed. More than half of the species of land snails observed are reported for the first time since 1950 or even for the first time ever for the UTM (Universal Transverse Mercator) 10 x 10 km squares that were investigated, i.e. ES18, ES28 en ES29. The most important of these is undoubtedly Vertigo angustior, a protected species which was found for the first time in more than 50 years at the eastern part of the Belgian coast and for the first time ever in the nature reserve “Het Zwin”. Four other species are reported for the first time in the region that was investigated, i.e. Zonitoides nitidus, Cochlicella acuta, Cernuella cisalpina (= C. jonica) and Alinda biplicata biplicata. The latter had, moreover, never been observed before in the Belgian coastal area. Five species were found rather frequently, i.e. Monacha cantiana, Candidula intersecta, Cernuella virgata, Theba pisana and Cepaea nemoralis. The data that were collected further clearly show that Cochlicella acuta and Theba pisana pisana have by now spread along the entire Belgian coast. On the other hand, several species that are thought to be in decline at the Belgian coast, i.e. Monacha cartusiana, Helicella itala itala, Candidula gigaxii, and Candidula unifasciata unifasciata, have not been observed at all. As only one specimen of Cernuella aginnica was found, also this species is probably in decline. Since only few freshwater habitats occurred in the areas that were investigated in 2012 only a limited number of freshwater species is reported here. Finally, as to brackish water snails, the very rare species Limapontia depressa and Assiminea grayana were found in the “Bay of Heist”, while one specimen of Ecrobia ventrosa was observed alive in the nature reserve “Het Zwin”

Analysis of complex singularities in high-Reynolds-number Navier-Stokes solutions

Numerical solutions of the laminar Prandtl boundary-layer and Navier-Stokes equations are considered for the case of the two-dimensional uniform flow past an impulsively-started circular cylinder. We show how Prandtl's solution develops a finite time separation singularity. On the other hand Navier-Stokes solution is characterized by the presence of two kinds of viscous-inviscid interactions that can be detected by the analysis of the enstrophy and of the pressure gradient on the wall. Moreover we apply the complex singularity tracking method to Prandtl and Navier-Stokes solutions and analyze the previous interactions from a different perspective

Effect of band filling in the Kondo lattice: A mean-field approach

The usual Kondo-lattice, including an antiferromagnetic exchange interaction between nearest-neighboring localized spins, is treated here in a mean-field scheme that introduces two mean-field parameters: one associated with the local Kondo effect, and the other related to the magnetic correlations between localized spins. Phases with short-range magnetic correlations or coexistence between those and the Kondo effect are obtained. By varying the number of electrons in the conduction band, we notice that the Kondo effect tends to be suppressed away from half filling, while magnetic correlations can survive if the Heisenberg coupling is strong enough. An enhanced linear coefficient of the specific heat is obtained at low temperatures in the metallic state.Comment: 7 pages, ReVTeX two-column, 7 figure

Anonymity and Rewards in Peer Rating Systems

When peers rate each other, they may choose to rate inaccurately in order to boost their own reputation or unfairly lower another’s. This could be successfully mitigated by having a reputation server incentivise accurate ratings with a reward. However, assigning rewards becomes a challenge when ratings are anonymous, since the reputation server cannot tell which peers to reward for rating accurately. To address this, we propose an anonymous peer rating system in which users can be rewarded for accurate ratings, and we formally define its model and security requirements. In our system ratings are rewarded in batches, so that users claiming their rewards only reveal they authored one in this batch of ratings. To ensure the anonymity set of rewarded users is not reduced, we also split the reputation server into two entities, the Rewarder, who knows which ratings are rewarded, and the Reputation Holder, who knows which users were rewarded. We give a provably secure construction satisfying all the security properties required. For our construction we use a modification of a Direct Anonymous Attestation scheme to ensure that peers can prove their own reputation when rating others, and that multiple feedback on the same subject can be detected. We then use Linkable Ring Signatures to enable peers to be rewarded for their accurate ratings, while still ensuring that ratings are anonymous. Our work results in a system which allows for accurate ratings to be rewarded, whilst still providing anonymity of ratings with respect to the central entities managing the system

Status of Turbulence Modeling for Hypersonic Propulsion Flowpaths

This report provides an assessment of current turbulent flow calculation methods for hypersonic propulsion flowpaths, particularly the scramjet engine. Emphasis is placed on Reynolds-averaged Navier-Stokes (RANS) methods, but some discussion of newer meth- ods such as Large Eddy Simulation (LES) is also provided. The report is organized by considering technical issues throughout the scramjet-powered vehicle flowpath including laminar-to-turbulent boundary layer transition, shock wave / turbulent boundary layer interactions, scalar transport modeling (specifically the significance of turbulent Prandtl and Schmidt numbers) and compressible mixing. Unit problems are primarily used to conduct the assessment. In the combustor, results from calculations of a direct connect supersonic combustion experiment are also used to address the effects of turbulence model selection and in particular settings for the turbulent Prandtl and Schmidt numbers. It is concluded that RANS turbulence modeling shortfalls are still a major limitation to the accuracy of hypersonic propulsion simulations, whether considering individual components or an overall system. Newer methods such as LES-based techniques may be promising, but are not yet at a maturity to be used routinely by the hypersonic propulsion community. The need for fundamental experiments to provide data for turbulence model development and validation is discussed

Inductively coupled plasma mass spectrometric detection for multielement flow injection analysis and elemental speciation by reversed-phase liquid chromatography

The feasibility of using an inductively coupled plasma mass spectrometer as a muitieiement detector for flow injection analysis (FIA) and ion-pair reversed-phase liquid chromatography was investigated. Sample introduction was by uitrasonk nebulization with aerosol desolvation. Absolute detecton limits for FIA ranged from 0.01 to 0.1 ng for most elements using 10-pL injections. Over 30 elements were surveyed for their response to both anionic and cationic ion pairing reagents. The separation and selective detection of various As and Se species were demonstrated, yielding detection limits near 0.1 ng (as element) for ail six species present. Determination of 15 elements in a single injection with multiple ion monitoring produced shniiar detection limits. Isotope ratios were measured with sufficient precision (better than 2%) and accuracy (about 1 %) on eluting peaks of Cd and Pb to demonstrate that liquid chromatographyhductively coupled plasma mass spectrometry should make speciation studies with stable tracer isotopes feasible