Geo-environmental characterization of the Kwinte Bank

A detailed geomorphological and sedimentological study has been performed at a tidal sandbank, which has been dredged during 30 years. Localised intensive aggregate extraction created a depression in the central part of the sandbank, upon which the Government decided to close this section of the bank for further exploitation. Multibeam and side-scan sonar technology was used to survey the bank, in combination with extensive ground-truthing. Automated seabed classification was performed, but showed no direct correlation with the mean grain-size; the primary drivers influencing the classification being the sorting of the sediments, the presence of shells and of fine sediments. Very high resolution seismics revealed the internal architecture of the bank. In the central depression, the upper unit is locally severely dredged.The central depression is characterized by distinct morphosedimentary facies, compared to the western and eastern part of the bank and the Kwinte swale, adjacent of it. The difference between the western and the eastern part is essentially due to different tidal current characteristics, each having their particular sedimentation-erosion patterns. These processes seem to be rather stable, though the evolution of the sediments in the central depression shows similarities with the Kwinte swale sediment evolution.Since the depression is somewhat oblique to the normal crestline, it now forms an open transport pathway from the swale up to the crest of the sandbank. This led to a canalization of the flood current which is witnessed mostly by the northwards and faster progression of bedforms. Because of the difference in sediment characteristics between the dredged material and the present-day supply of sand, it is unlikely that natural processes will be able to counterbalance the severe dredging activities.Moreover, the presence of the central depression is located close to the kink of the sand bank, which is influenced by a high-energy hydrodynamic regime. Its presence could intensify the current action in this area and could enhance the evolution of the bank

Tertiary and quaternary geology of the Belgian Continental Shelf

A synthesis of the geology of the Belgian continental shelf is here presented. The main part of this document is dedicated to the review of the lithostratigraphy, geotechnical properties, geometry and distribution of the Tertiary and Quaternary deposits. The data compilation, review and assessment have been conducted from the numerous existing studies and large data sets, available offshore, but also onland when offshore data were scarce or lacking. Three main projects have enabled to collect the offshore data: (1) the project “Seismic stratigraphy, Southern Bight, North Sea” (RCMG, City of London Polytechnic/NERC, University of Caen/CNRS); (2) the project “Seismisch onderzoek op het Belgisch Continentaal Plat. Eerste faze. Ontginningszone 2” (MEZ/Administratie van het Mijnwezen, RCMG); (3) the project “Studie oppervlaktelaag van het Belgisch Continentaal Plat. Seismisch prospectie sector B” MEZ/Belgian Geological Survey-BGD, RCMG). Data consist mainly of seismic profiles (16,000 km), cores (79) and cone penetration tests (CPTs, 177). All the data have been digitised and integrated in appropriate georeferenced softwares. Synthetic integrated maps and tables have been produced, aimed to provide the end-users with clear and directly usable information.This synthesis has been conducted in the framework of the project “Optimal Offshore Wind Energy Developments in Belgium”, financed by the Belgian federal government (Federal Office for Scientific, Technical and Cultural Affairs). This project is in keeping with the part I project network “Production patterns and sustainable consumption” of the PADD II program. Objectives of this project consisted in providing recommendations for the selection of sites that are convenient with respect to the stability of offshore wind structures and the minimisation of geo-environmental impacts

Chemically engineered extracts of St John’s wort as sources of polyprenylated acylphloroglucinols to prevent endothelial dysfunction

International audienc

Preliminary Investigation of the Frictional Response of Reptilian Shed Skin

Developing deterministic surfaces relies on controlling the structure of the rubbing interface so that not only the surface is of optimized topography, but also is able to self-adjust its tribological behaviour according to the evolution of sliding conditions. In seeking inspirations for such designs, many engineers are turning toward the biological world to correlate surface structure to functional behavior of bio-analogues. From a tribological point of view, squamate reptiles offer diverse examples where surface texturing, submicron and nano-scale features, achieve frictional regulation. In this paper, we study the frictional response of shed skin obtained from a snake (Python regius). The study employed a specially designed tribo-acoustic probe capable of measuring the coefficient of friction and detecting the acoustical behavior of the skin in vivo. The results confirm the anisotropy of the frictional response of snakes. The coefficient of friction depends on the direction of sliding: the value in forward motion is lower than that in the backward direction. In addition it is shown that the anisotropy of the frictional response may stem from profile asymmetry of the individual fibril structures present within the ventral scales of the reptil

Dissipation of vibration in rough contact

The relationship which links the normal vibration occurring during the sliding of rough surfaces and the nominal contact area is investigated. Two regimes are found. In the first one, the vibrational level does not depend on the contact area, while in the second one, it is propor- tional to the contact area. A theoretical model is proposed. It is based on the assumption that the vibrational level results from a competition between two processes of vibration damping, the internal damping of the material and the contact damping occurring at the interface

The Spitzer Survey of the Small Magellanic Cloud: S3MC Imaging and Photometry in the Mid- and Far-Infrared Wavebands

We present the initial results from the Spitzer Survey of the Small Magellanic Cloud (S3MC), which imaged the star-forming body of the Small Magellanic Cloud (SMC) in all seven MIPS and IRAC wavebands. We find that the F_8/F_24 ratio (an estimate of PAH abundance) has large spatial variations and takes a wide range of values that are unrelated to metallicity but anticorrelated with 24 um brightness and F_24/F_70 ratio. This suggests that photodestruction is primarily responsible for the low abundance of PAHs observed in star-forming low-metallicity galaxies. We use the S3MC images to compile a photometric catalog of ~400,000 mid- and far-infrared point sources in the SMC. The sources detected at the longest wavelengths fall into four main categories: 1) bright 5.8 um sources with very faint optical counterparts and very red mid-infrared colors ([5.8]-[8.0]>1.2), which we identify as YSOs. 2) Bright mid-infrared sources with mildly red colors (0.16<[5.8]-[8.0]<0.6), identified as carbon stars. 3) Bright mid-infrared sources with neutral colors and bright optical counterparts, corresponding to oxygen-rich evolved stars. And, 4) unreddened early B stars (B3 to O9) with a large 24 um excess. This excess is reminiscent of debris disks, and is detected in only a small fraction of these stars (<5%). The majority of the brightest infrared point sources in the SMC fall into groups one to three. We use this photometric information to produce a catalog of 282 bright YSOs in the SMC with a very low level of contamination (~7%).Comment: Accepted for publication in The Astrophysical Journal. Given the draconian figure file-size limits implemented in astro-ph, readers are encouraged to download the manuscript with full quality images from http://celestial.berkeley.edu/spitzer/publications/s3mcsurvey.pd

Three-micron spectra of AGB stars and supergiants in nearby galaxies

The dependence of stellar molecular bands on the metallicity is studied using infrared L-band spectra of AGB stars (both carbon-rich and oxygen-rich) and M-type supergiants in the Large and Small Magellanic Clouds (LMC and SMC) and in the Sagittarius Dwarf Spheroidal Galaxy. The spectra cover SiO bands for oxygen-rich stars, and acetylene (C2H2), CH and HCN bands for carbon-rich AGB stars. The equivalent width of acetylene is found to be high even at low metallicity. The high C2H2 abundance can be explained with a high carbon-to-oxygen (C/O) ratio for lower metallicity carbon stars. In contrast, the HCN equivalent width is low: fewer than half of the extra-galactic carbon stars show the 3.5micron HCN band, and only a few LMC stars show high HCN equivalent width. HCN abundances are limited by both nitrogen and carbon elemental abundances. The amount of synthesized nitrogen depends on the initial mass, and stars with high luminosity (i.e. high initial mass) could have a high HCN abundance. CH bands are found in both the extra-galactic and Galactic carbon stars. None of the oxygen-rich LMC stars show SiO bands, except one possible detection in a low quality spectrum. The limits on the equivalent widths of the SiO bands are below the expectation of up to 30angstrom for LMC metallicity. Several possible explanations are discussed. The observations imply that LMC and SMC carbon stars could reach mass-loss rates as high as their Galactic counterparts, because there are more carbon atoms available and more carbonaceous dust can be formed. On the other hand, the lack of SiO suggests less dust and lower mass-loss rates in low-metallicity oxygen-rich stars. The effect on the ISM dust enrichment is discussed.Comment: accepted for A&