Ontwikkeling van de HydroRig

De HydroRig is een alternatief vistuig voor de vangst van platvis ter vervanging van de wekkerstimulering in de boomkorvisserij. De noodzaak voor alternatieven komt voort uit ecosysteem kritiek op de boomkor met wekkers en de sterk oplopende brandstofkosten. In Nederland werden er al proeven gedaan aan een vistuig waarbij de boom is vervangen door een vleugel om de stroming op de bodem te beïnvloeden. Het idee van beïnvloeding van de stroming om vangst te verbeteren kwam oorspronkelijk uit de VS in een toepassing op een schelpdierkor. Door middel van bolkappen in het vistuig worden bodemdieren omhoog gedreven om beschikbaar te komen voor vangst. Dit rapport beschrijft de ontwikkeling vanaf 2008 in het VIP project HydroRig een geeft de stadia, van experimenten op zee met een aangepast vleugelprofiel, stromingsberekeningen en proeven in het laboratorium (water-grond goot) van DELTARES te Delft aan zgn. ‘bolkappen’, en toepassing hiervan op zee in verschillende configuraties met vangstmonitoring en onderwaterobservaties op de FD-281. Aan het eind van het project werden door middel van modelproeven in de ‘flume tank’ van IFREMER te Boulogne, Frankrijk nieuwe ontwerpen gemaakt voor een net met de onderpees dichter bij de boom. Gemiddeld werd bij vergelijking met het zusterschip FD-283, ook vissend op schol met een traditioneel boomkortuig en 100 mm maaswijdte, met de HydroRig (FD-281) ca. 21% brandstof bespaard, maar daartegenover stond een ca. 32% lagere besomming. Het vissen met de HydroRig in het commerciële bedrijf stagneert momenteel door de lage scholprijzen, die een belemmering vormen tot verder experimenteren. Toch wordt aanbevolen de proeven met bolkappen en nieuwe netontwerpen te vervolgen en te pogen de visnamigheid op schol te verbeteren, omdat de HydroRig veel minder benthos bijvangt

The free surface of superfluid 4He at zero temperature

The structure and energetics of the free surface of superfluid $^4$He are studied using the diffusion Monte Carlo method. Extending a previous calculation by Vall\'es and Schmidt, which used the Green's function Monte Carlo method, we study the surface of liquid $^4$He within a slab geometry using a larger number of particles in the slab and an updated interatomic potential. The surface tension is accurately estimated from the energy of slabs of increasing surface density and its value is close to one of the two existing experimental values. Results for the density profiles allow for the calculation of the surface width which shows an overall agreement with recent experimental data. The dependence on the transverse direction to the surface of other properties such as the two-body radial distribution function, structure factor, and one-body density matrix is also studied. The condensate fraction, extracted from the asymptotic behavior of the one-body density matrix, shows an unambiguous enhancement when approaching the surface.Comment: RevTex, 11 pages, accepted in Phys. Rev.

A comparison of balloon injury models of endovascular lesions in rat arteries

BACKGROUND: Balloon injury (BI) of the rat carotid artery (CCA) is widely used to study intimal hyperplasia (IH) and decrease in lumen diameter (LD), but CCA's small diameter impedes the evaluation of endovascular therapies. Therefore, we validated BI in the aorta (AA) and iliac artery (CIA) to compare it with CCA. METHODS: Rats underwent BI or a sham procedure (control). Light microscopic evaluation was performed either directly or at 1, 2, 3, 4 and 16 weeks follow-up. The area of IH and the change in LD (LD at 16 weeks minus LD post BI) were compared. RESULTS: In the BI-groups the area of IH increased to 0.14 +/- 0.08 mm2 (CCA), 0.14 +/- 0.03 mm2 (CIA) and 0.12 +/- 0.04 mm2 (AA) at 16 weeks (NS). The LD decreased with 0.49 +/- 0.07 mm (CCA), compared to 0.22 +/- 0.07 mm (CIA) and 0.07 +/- 0.10 mm (AA) at 16 weeks (p < 0.05). The constrictive vascular remodelling (CVR = wall circumference loss combined with a decrease in LD) was -0.17 +/- 0.05 mm in CIA but absent in CCA and AA. No IH, no decrease in LD and no CVR was seen in the control groups. CONCLUSIONS: BI resulted in: (1.) a decrease in LD in CCA due to IH, (2.) a decrease in LD in CIA due to IH and CVR, (3.) no change in LD in AA, (4.) Comparable IH development in all arteries, (5.) CCA has no vasa vasorum compared to CIA and AA, (6.) The CIA model combines good access for 2 F endovascular catheters with a decrease in LD due to IH and CVR after BI

Comparison of cost affecting parameters and costs of the 'closed' and 'open' in situ bypass technique

Objectives: The 'closed' in situ bypass results in a reduction of wound complications compared to the 'open' technique. This advantage is partly diminished by extra costs for the 'closed' procedure and a larger percentage of residual arteriovenous (AV)-fistulae. This aim of this study was to analyse costs related to 'closed' and 'open' procedures. Methods: The cost affecting parameters: (1) duration of operation; (2) length of hospital stay; and (3) number of treated residual AV-fistulae, were analysed in a randomised group of 73 patients (35 'closed' and 38 'open') in two centres. In addition, costs of the operation, nursing care and treatment of AV-fistulae were analysed. Results: The 'closed' and 'open' group showed a median duration of operation of 210 min (range 105-570) and 154 min (range 90-355) (p < 0.05), length of hospital stay of 16 days (range 5-51) and 25 days (range 12-65) (p < 0.01), and a percentage of patients treated for residual AV-fistulae of 40% and 5%, respectively (p < 0.01). The median 'closed' operation was US$798 more expensive than the 'open'. Median postoperative care was US$ 2664 less for the 'closed' group. Mean estimated costs for treatment of AV-fistulae was US$9 in the 'open' and US$ 167 in the 'closed' group. Conclusion: The 'closed' in situ vein bypass technique is cost-effective in comparison with the 'open' technique

Traits and stress: keys to identify community effects of low levels of toxicants in test systems

Community effects of low toxicant concentrations are obscured by a multitude of confounding factors. To resolve this issue for community test systems, we propose a trait-based approach to detect toxic effects. An experiment with outdoor stream mesocosms was established 2-years before contamination to allow the development of biotic interactions within the community. Following pulse contamination with the insecticide thiacloprid, communities were monitored for additional 2 years to observe long-term effects. Applying a priori ecotoxicological knowledge species were aggregated into trait-based groups that reflected stressor-specific vulnerability of populations to toxicant exposure. This reduces inter-replicate variation that is not related to toxicant effects and enables to better link exposure and effect. Species with low intrinsic sensitivity showed only transient effects at the highest thiacloprid concentration of 100 μg/l. Sensitive multivoltine species showed transient effects at 3.3 μg/l. Sensitive univoltine species were affected at 0.1 μg/l and did not recover during the year after contamination. Based on these results the new indicator SPEARmesocosm was calculated as the relative abundance of sensitive univoltine taxa. Long-term community effects of thiacloprid were detected at concentrations 1,000 times below those detected by the PRC (Principal Response Curve) approach. We also found that those species, characterised by the most vulnerable trait combination, that were stressed were affected more strongly by thiacloprid than non-stressed species. We conclude that the grouping of species according to toxicant-related traits enables identification and prediction of community response to low levels of toxicants and that additionally the environmental context determines species sensitivity to toxicants

Candida glabrata : a review of its features and resistance

Candida species belong to the normal microbiota of the oral cavity and gastrointestinal and vaginal tracts, and are responsible for several clinical manifestations, from mucocutaneous overgrowth to bloodstream infections. Once believed to be non-pathogenic, Candida glabrata was rapidly blamable for many human diseases. Year after year, these pathological circumstances are more recurrent and problematic to treat, especially when patients reveal any level of immunosuppression. These difficulties arise from the capacity of C. glabrata to form biofilms and also from its high resistance to traditional antifungal therapies. Thus, this review intends to present an excerpt of the biology, epidemiology, and pathology of C. glabrata, and detail an approach to its resistance mechanisms based on studies carried out up to the present.The authors are grateful to strategic project PTDC/SAU-MIC/119069/2010 for the financial support to the research center and for Celia F. Rodrigues' grant

Measurement of the Tau Lepton Polarisation at LEP2

A first measurement of the average polarisation P_tau of tau leptons produced in e+e- annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P_tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV.A first measurement of the average polarisation Pτ of tau leptons produced in e + e − annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value Pτ=−0.164±0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV.A first measurement of the average polarisation P_tau of tau leptons produced in e+e- annihilation at energies significantly above the Z resonance is presented. The polarisation is determined from the kinematic spectra of tau hadronic decays. The measured value P_tau = -0.164 +/- 0.125 is consistent with the Standard Model prediction for the mean LEP energy of 197 GeV