Nd-doped aluminum oxide integrated amplifiers at 880 nm, 1060 nm, and 1330 nm

Neodymium-doped Al2O3 layers were deposited on thermally oxidized Si substrates and channel waveguides were patterned using reactive-ion etching. Internal net gain on the Nd3+ transitions at 880, 1064, and 1330 nm was investigated,\ud yielding a maximum gain of 6.3 dB/cm at 1064 nm. Values for the energy-transfer upconversion parameter for different Nd3+\ud concentrations were deduced

Importance of eco-engineered inshore habitats for juvenile flatfish

Within coastal nurseries, the distribution of juvenile flatfish may depend on small-scale habitat variability. The present study investigates the relation between the distribution of two juvenile flatfish species (Pleuronectes platessa and Limanda limanda) with two sessile tube dwelling polychaetes that create specific habitats at high densities. Their modulating effects make them classify as ecosystem engineers. Lanice conchilega and Owenia fusiformis, both frequently occurring in the coastal zones of the North Sea are the studied ecosystem engineers. These two benthic tube worm systems are investigated for their function as ‘essential juvenile habitat’ (EJH) in two geographical areas (the Belgian part of North Sea and the Dutch part of the Wadden Sea). General responses were identified by comparing relative differences between ecosystem engineered habitats and adjacent bare sand (i.e. non ecosystem engineered) habitats. Results show that both flatfish species select for the ecosystem engineered habitat. This behaviour was further investigated using stomach content analyses. For P. platessa occurring in L. conchilega habitat, this selection was explained as feeding behaviour. For the habitats created by O. fusiformis, no such a relation was found. For L. limanda higher densities within the ecosystem engineered habitats cannot be explained by feeding advantage but by the use of this habitat as a shelter. Therefore, higher flatfish densities could be explained by an antipredation behaviour. Lanice conchilega aggregations may be more important as feeding area for juvenile flatfish species in comparison with O. fusiformis aggregations. The indirect impacts of bottom trawling on benthic tube worm aggregations by reducing the suitability of the areas for juvenile flatfishes are discussed. We conclude that the emergent structures in the flatfish nursery area play an important role in the ecology of the juvenile flatfishes as feeding ground and/or as refuge from predation. These small-scale aspects of nursery grounds can be considered as EJH and merit attention in habitat suitability models as well as in marine conservation

Effect of air distribution and spray liquid distribution of a cross-flow fan orchard sprayer on spray deposition in fruit trees

In a 4-year ongoing research programme in the Netherlands, we focus to maximise spray deposition in pome fruit trees and minimise spray deposition underneath the trees on the ground and minimise spray drift. For a cross-flow fan orchard sprayer we therefore measured spray deposition in the tree as an effect of different air settings and nozzle types. Nozzle types chosen were the Albuz ATR lilac (as a reference) and the Albuz TVI8001, both sprayed at 7 bar spray pressure. The orchard sprayer was a Munckhof cross-flow fan sprayer with a 2.75 m high cross-flow construction on top of the axial fan, equipped with 8 nozzles on both sides. At a forward speed of 6.5 km/h the spray volume was 200 L/ha and 290 L/ha, for respectively the Albuz lilac and Albuz TVI8001 nozzles. Air settings were: High air setting - 540 rpm PTO; and Low air setting - 540 rpm, 400 rpm, and 300 rpm PTO. Liquid distributions were measured with an AAMS-Salvarani Vertical patternator with discs, and air distribution was measured with a self-constructed measuring device equipped with ultrasonic anemometers and a handheld vane-anemometer. Liquid distribution in the apple trees (cv. Elstar) was measured in the full leaf growing stage (following ISO 22522). First results show a good correlation between air distribution and liquid distribution. Vertical liquid distribution measured on the liquid measuring device correlates also very good with the liquid distribution at different heights in the tree. However, air distribution and especially air speed of the orchard sprayer showed that decreasing air assistance increased the spray deposition in the fruit trees. Showing that air assistance is an important parameter to be taken up in the advice to fruit growers.In a 4-year ongoing research programme in the Netherlands, we focus to maximise spray deposition in pome fruit trees and minimise spray deposition underneath the trees on the ground and minimise spray drift. For a cross-flow fan orchard sprayer we therefore measured spray deposition in the tree as an effect of different air settings and nozzle types. Nozzle types chosen were the Albuz ATR lilac (as a reference) and the Albuz TVI8001, both sprayed at 7 bar spray pressure. The orchard sprayer was a Munckhof cross-flow fan sprayer with a 2.75 m high cross-flow construction on top of the axial fan, equipped with 8 nozzles on both sides. At a forward speed of 6.5 km/h the spray volume was 200 L/ha and 290 L/ha, for respectively the Albuz lilac and Albuz TVI8001 nozzles. Air settings were: High air setting - 540 rpm PTO; and Low air setting - 540 rpm, 400 rpm, and 300 rpm PTO. Liquid distributions were measured with an AAMS-Salvarani Vertical patternator with discs, and air distribution was measured with a self-constructed measuring device equipped with ultrasonic anemometers and a handheld vane-anemometer. Liquid distribution in the apple trees (cv. Elstar) was measured in the full leaf growing stage (following ISO 22522). First results show a good correlation between air distribution and liquid distribution. Vertical liquid distribution measured on the liquid measuring device correlates also very good with the liquid distribution at different heights in the tree. However, air distribution and especially air speed of the orchard sprayer showed that decreasing air assistance increased the spray deposition in the fruit trees. Showing that air assistance is an important parameter to be taken up in the advice to fruit growers

On-chip integrated amplifiers and lasers utilizing rare-earth-ion activation

This contribution reviews our recent results on rare-earth-ion-doped integrated amplifiers and lasers. We have concentrated our efforts on complex-doped polymers, amorphous Al2O3, and crystalline potassium double tungstates

Wireless Optimaal watergeven in de boomkwekerij

In de boomkwekerij is beregening een regelmatig terugkerend verschijnsel om voldoende groei te kunnen realiseren. Hierbij volgt elke kweker zijn gewas door middel van waarnemingen. Water en nutriënten worden ‘op gevoel’ ingezet. Het is in de praktijk echter lastig om de optimale hoeveelheid te geven vanwege een diversiteit aan gewassen en percelen (verschillende bodemtypen). Optimaal betekent niet te veel en niet te weinig. Te veel water veroorzaakt onnodig uitspoeling van meststoffen, met name stikstof maar ook kalium. Te weinig water geeft droogteschade en daarmee opbrengstderving. Om dit laatste te voorkomen wordt in de praktijk in de regel te veel beregend. Hierdoor ontstaan een aantal knelpunten: • Beschikbaarheid van voldoende water van een goede kwaliteit. • Het gebruik van grond- en oppervlaktewater voor de tuinbouw staat onder druk. Door onnodig veel te beregenen kan er verdroging van de omgeving optreden. Met name in droge perioden heeft dat ook gevolgen voor de waterstanden van het oppervlaktewater. • Stikstof, kalium en sommige gewasbeschermingsmiddelen spoelen makkelijk uit, waardoor het in het grondwater en vervolgens in het oppervlaktewater terecht komt. • Stikstof kan niet onbeperkt aangevoerd worden, omdat dit wordt gereguleerd met wettelijke gebruiksnormen. Met name kwekers op (droge) zandgronden ervaren al een knelpunt met de stikstofnormen. • Het beregenen kost geld. Naast arbeid kost het voor de kweker ook diesel. Wanneer optimaal beregend wordt, kan de apparatuur eerder naar een volgend perceel gebracht worden. • Onwetend te veel beregenen kan ook schade aan het gewas opleveren. Door onnodige uitspoeling van meststoffen (stikstof, kalium en eventueel ook fosfaat) kan de gewasgroei achterblijven. Ook kan teveel beregenen ziekten stimuleren. Verder is er een tendens naar een ander klimaat, namelijk meer droge perioden afgewisseld door grote buien

Beheersing bacterieziekte in Prunus

Bladvlekken (en bladval) in Prunus laurocerasus worden veroorzaakt door de bacterie Xanthomonas arboricola pv Pruni. Deze bacterie heeft binnen de EU een Q-status. Een aantasting kan snel om zich heen grijpen. Veel kennis over de bacterie ontbreekt nog. In dit project wordt een beheersingsstrategie ontwikkeld