Numerical modelling of the extreme wave climate in the Belgian harbours: part 3. Marina of Blankenberge

The design of water and wave retaining walls and flood risk analyses need hydrodynamic boundary conditions. These boundary conditions are needed during a storm with return period 1000yrs and during the super storms which were defined in the risk analysis study. The modelling of the extreme wave climate is decoupled to the wave penetration and the lacal generation of waves by the extreme wind speed. The wave penetration is modelled with Mike 21 BW as was done for Oostende and Zeebrugge. MILDwave is not used this time because non-linear effects (e.g. long wave generation, wave setup) are too important in this case. Instead another nonlinear model SWASH is applied. The modelling of local generation of waves by wind is still done with the spectral model SWAN.First the bathymetry files are created based on the dredging plan of Blankenberge marina, and all the suitable settings used for the Mike 21 BW and the SWASH are investigated. Since SWASH model does not have so much application examples, Wenduine physical model is used to validate the model. Consequently, a sensitivity analysis is conducted for both models to study which parameter is important for the wave climate inside the marina. The most severe offshore wave direction for the design of the wave retaining walls is decided based on the 1000 year storm. After the calculation of the wave penetration in the case of 1000 year storm and +7.9 mTAW storm, locally generated wind waves are also simulated by SWAN. All extreme wind speeds and directions for the 1000-year storm and the super storms are modelled. Finally, long and short wave energy of the wave penetration models is separated and a superposition of the short wave energy and the SWAN model is done to obtain the total extreme wave climate in the marina of Blankenberge. The maximum surface elevation of the long wave energy and the wave setup provide an increase of the still water level to take into account for design purpose

Fingerprinting the origin of fluvial suspended sediment in the Demer basin, Belgium: a preliminary assessment of spatial provenance

C

Nanoscale Mechanical Characterisation of Amyloid Fibrils Discovered in a Natural Adhesive

Using the atomic force microscope, we have investigated the nanoscale mechanical response of the attachment adhesive of the terrestrial alga Prasiola linearis (Prasiolales, Chlorophyta). We were able to locate and extend highly ordered mechanical structures directly from the natural adhesive matrix of the living plant. The in vivo mechanical response of the structured biopolymer often displayed the repetitive sawtooth force-extension characteristics of a material exhibiting high mechanical strength at the molecular level. Mechanical and histological evidence leads us to propose a mechanism for mechanical strength in our sample based on amyloid fibrils. These proteinaceous, pleated β-sheet complexes are usually associated with neurodegenerative diseases. However, we now conclude that the amyloid protein quaternary structures detected in our material should be considered as a possible generic mechanism for mechanical strength in natural adhesives

The main actors involved in parasitization of Heliothis virescens larva

At the moment of parasitization by another insect, the host Heliothis larva is able to defend itself by the activation of humoral and cellular defenses characterized by unusual reactions of hemocytes in response to external stimuli. Here, we have combined light and electron microscopy, staining reactions, and immunocytochemical characterization to analyze the activation and deactivation of one of the most important immune responses involved in invertebrates defense, i.e., melanin production and deposition. The insect host/parasitoid system is a good model to study these events. The activated granulocytes of the host insect are a major repository of amyloid fibrils forming a lattice in the cell. Subsequently, the exocytosed amyloid lattice constitutes the template for melanin deposition in the hemocel. Furthermore, cross-talk between immune and neuroendocrine systems mediated by hormones, cytokines, and neuromodulators with the activation of stress-sensoring circuits to produce and release molecules such as adrenocorticotropin hormone, alpha melanocyte-stimulating hormone, and neutral endopeptidase occurs. Thus, parasitization promotes massive morphological and physiological modifications in the host insect hemocytes and mimics general stress conditions in which phenomena such as amyloid fibril formation, melanin polymerization, pro-inflammatory cytokine production, and activation of the adrenocorticotropin hormone system occur. These events observed in invertebrates are also reported in the literature for vertebrates, suggesting that this network of mechanisms and responses is maintained throughout evolution

Inorganic ions and mannitol in the red alga Caloglossa leprieurii (Ceramiales, Rhodophyta): Response to salinity change

Calogossa leprieurii (Montagne) J. Agardh was isolated from a freshwater, an estuarine and a marine locality. The responses of these isolates to a range of external salinity over time periods of 0-48 h was investigated in terms of internal ion concentrations (K+, Na+ and Cl-) and the organic solute mannitol. Changes in intracellular ions in response to hyposaline and hypersaline treatments were rapid with steady state conditions achieved within 1 h. Sodium ions appeared to be excluded from the cells in all salinities. The concentration of mannitol in all populations correlated positively, with salinity. Some mannitol accumulation in hypersaline media was shown within 8 h, but in general a new steady state was not achieved until after 24 h. In hyposaline media mannitol concentration decreased markedly within 1 h. The extent and rate of the change in inorganic ions and mannitol varied between the three populations. The relevance of mannitol as a compatible solute, as well as its potential to effect an osmotic role within a tidal cycle, is emphasized. A summary of the specific responses involved in osmotic adjustment in C. leprieurii is presented