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

On the Effect of a Secondary Structure upon the Interference of X-rays

Laue's dynamic theory of x-ray interference is shown to be applicable, with only a few minor changes, to crystals having a very general type of secondary structure. It is thus applied for the purpose of obtaining a quantitative estimate of the effect of such a structure upon the nature of the x-ray interference maxima. The estimate is relative insofar as it compares the intensities of respectively the "secondarily" and the "primarily" reflected interference beams and applies only in the region where the latter have been, or can be observed. In this region the "two-dimensional lattice" type of secondary structure is found to give rise to a fine structure which, with the present insufficient resolving power, would be manifested experimentally as a weak, diffuse background. The secondary structure of this type produces no broadening of the primary lines. The existence of this type of structure, therefore, is not inconsistent with the sharpness of the interference maxima obtained from such crystals as calcite, and a possible objection to the existence of the secondary structure in such crystals is removed. The extinction effect is briefly considered, but absorption is not taken into account, except with a few qualitative remarks

Copepod feeding currents:flow patterns, filtration rates and energetics

Particle image velocimetry was used to construct a quasi 3-dimensional image of the flow generated by the feeding appendages of the calanoid copepod Temora longicornis. By scanning layers of flow, detailed information was obtained on flow velocity and velocity gradients. The flow around feeding T. longicornis was laminar, and was symmetrical viewed dorsally, but highly asymmetrical viewed laterally, with high levels of vorticity on the ventral side. The flow rate through the feeding appendages varied between 77 and 220 ml day(-1) per individual. The morphology of the flow field ensured that water was entrained over the full length of the first antennae. These were kept out of areas with high velocity gradients that could interfere with distant mechano- or chemoreception. The volume of influence, i.e. the volume of water around the foraging copepod, where shear rates were significantly higher than background levels, was calculated. Implications for encounter probability and mechanoreception are discussed. The average rate of energy dissipation within the copepod's volume of influence is several times higher than the levels of turbulent energy dissipation these animals are likely to encounter in their environment. Even in highly turbulent environments, adult T. longicornis will not experience very significant effects of turbulence. Within the volume of influence of the copepods the energy dissipation due to viscous friction varied between 6.6x10(-11) and 2.3x10(-10) W. Taking mechanical efficiency and muscle efficiency into account, this results in a total energetic cost of the feeding current of 1.6x10(-9) W per copepod. This value represents only a small percentage of the total energy budget of small calanoid copepods

Preparing for climate change: a research framework on the sediment - sharing systems of the Dutch, German and Danish Wadden Sea for the development of an adaptive strategy for flood safety

The report proposes a research framework which follows a learning-by-doing approach along the three research lines: monitoring & data analysis, system research & modelling and field experiments (pilots). All studies together will take several decades, partially due to the many questions, partially because studying changes in the system via the above-mentioned research lines takes time. Research programs developed on basis of this framework may focus on a part of the research issue

Combination of searches for Higgs boson pairs in pp collisions at \sqrts = 13 TeV with the ATLAS detector

This letter presents a combination of searches for Higgs boson pair production using up to 36.1 fb(-1) of proton-proton collision data at a centre-of-mass energy root s = 13 TeV recorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the b (b) over barb (b) over bar, b (b) over barW(+)W(-), b (b) over bar tau(+)tau(-), W+W-W+W-, b (b) over bar gamma gamma and W+W-gamma gamma final states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9 (10) times the predicted Standard Model cross-section. Limits are also set on the ratio (kappa(lambda)) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to -5.0 &lt; kappa(lambda) &lt; 12.0 (-5.8 &lt; kappa(lambda) &lt; 12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza-Klein Randall-Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model. For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2019.135103</p

A measurement of material in the ATLAS tracker using secondary hadronic interactions in 7 TeV pp collisions

Knowledge of the material in the ATLAS inner tracking detector is crucial in understanding the reconstruction of charged-particle tracks, the performance of algorithms that identify jets containing b-hadrons and is also essential to reduce background in searches for exotic particles that can decay within the inner detector volume. Interactions of primary hadrons produced in pp collisions with the material in the inner detector are used to map the location and amount of this material. The hadronic interactions of primary particles may result in secondary vertices, which in this analysis are reconstructed by an inclusive vertex-finding algorithm. Data were collected using minimum-bias triggers by the ATLAS detector operating at the LHC during 2010 at centre-of-mass energy √ s = 7 TeV, and correspond to an integrated luminosity of 19 nb−1 . Kinematic properties of these secondary vertices are used to study the validity of the modelling of hadronic interactions in simulation. Secondary-vertex yields are compared between data and simulation over a volume of about 0.7 m3 around the interaction point, and agreement is found within overall uncertainties