Parallel optical readout of a cantilever array in dynamic mode

In this work we present parallel optical readout of a cantilever array which operates in dynamic mode using a standard optical beam deflection configuration containing only one laser-detector pair. We show accurate readout of the resonance frequency shift of an individual cantilever within an array by designing arrays where each cantilever has a different resonance frequency. The different resonance frequencies are created by giving each cantilever a different length and allow parallel readout of all cantilevers within the array. We show that even if the cantilevers are closely spaced each cantilever resonance frequency can be individually tracked without signs of cross-talk at current measurement precision (below 12 mHz). Interference of the laser light reflecting of each cantilever is observed when the amplitude of the cantilever is on the order of the wavelength of the laser light

Nanotesla torque magnetometry using a microcantilever

We present a novel ultrasensitive magnetometry technique using a micromachined magnetic antilever that is brought in resonance. The induced magnetic moment generates a torque on the cantilever, thereby effectively stiffening the cantilever spring constant and changing its resonance frequency. Experiments are in good correspondence with the presented analytical model for this frequency shift, predicting the detection of nanotesla magnetic fields.\u

STRICT: a language and tool set for the design of very large scale integrated circuits

PhD ThesisAn essential requirement for the design of large VLSI circuits is a design methodology which would allow the designer to overcome the complexity and correctness issues associated with the building of such circuits. We propose that many of the problems of the design of large circuits can be solved by using a formal design notation based upon the functional programming paradigm, that embodies design concepts that have been used extensively as the framework for software construction. The design notation should permit parallel, sequential, and recursive decompositions of a design into smaller components, and it should allow large circuits to be constructed from simpler circuits that can be embedded in a design in a modular fashion. Consistency checking should be provided as early as possible in a design. Such a methodology would structure the design of a circuit in much the same way that procedures, classes, and control structures may be used to structure large software systems. However, such a design notation must be supported by tools which automatically check the consistency of the design, if the methodology is to be practical. In principle, the methodology should impose constraints upon circuit design to reduce errors and provide' correctness by construction' . It should be possible to generate efficient and correct circuits, by providing a route to a large variety of design tools commonly found in design systems: simulators, automatic placement and routing tools, module generators, schematic capture tools, and formal verification and synthesis tools

Selective low concentration ammonia sensing in a microfluidic lab-on-a-chip

In the medical community, there is a considerable interest in a diagnostic breath analyzer for ammonia that is selectively enough to measure in exhaled air and small enough for the small volumes available in such an application. An indirect measurement system for low gaseous ammonia concentrations has been miniaturized and integrated on a chip in order to reach this goal. The detection limit of the system was calculated to be 1.1 parts per billion (ppb). The response time was determined to be 1.6 min with a gas How of 50 ml/min. The required gas volume for one measurement is therefore sufficiently small, although sampling assistance is required for breath analysis. The selectivity of the system is sufficient to measure ammonia concentrations in the low-ppb range. The system is even sufficiently selective to be used in environments that contain elevated carbon dioxide levels, like exhaled air. The lower ammonia concentration expected in diagnostic breath analysis applications, 50 ppb, was demonstrated to be detectable

Schatting van in situ fluxen van organische microverontreinigingen uit waterbodems

Dit rapport beschrijft de resultaten van een onderzoek naar naleveringsfluxen van organische microverontreinigingen, ten behoeve van het Deltares koploperproject “Biobeschikbaarheid en gedrag van stoffen”, deelproject A “Nalevering van stoffen uit waterbodems”. Hierin wordt het belang van nalevering voor de kwaliteit van het oppervlaktewater onderzocht. Dit project moet leiden tot inzicht in de situaties waarin nalevering van stoffen uit de waterbodem naar het oppervlaktewater een significante (secundaire) verontreinigingbron vormt. Dit met het oog op normoverschrijding in het oppervlaktewater (chemische doelstelling KRW), of het niet bereiken van een goede ecologische toestand (ecologische doelstelling KRW). In het voorliggende rapport worden de resultaten van kolom flux-experimenten besproken. Aan de orde komen: (a) opzet meetprogramma voor zover afwijkend van het meetplan, (b) informatie met betrekking tot kwaliteitscontrole, (c) specificatie van gebruikte analysevoorschriften (d) analyseresultaten met korte toelichtin

Sorption of micropollutants to natural aquatic particles = Sorptie van microverontreinigingen aan natuurlijke aquatische deeltjes

Sorption to natural aquatic particles plays an important role in the bioavailability and fate of micropollutants. The characteristics of sorption were investigated for hydrophobic organic compounds (HOCs) and heavy metals using a wide variety of natural aquatic particles. Special attention was paid to (bio)sorption to phytoplankton and detritus. The extent of sorption can be quantified by a distribution- ( K d ) or partitioncoefficient ( K p ). It was shown in this study that such coefficients in aquatic systems are variable in space and time because:1. At more or less constant environmental conditions K d values for trace metals depend on the content of iron(hydr)oxides, manganese(hydr)oxides and organic matter in the natural aquatic particles. It was shown for Lake Volkerak/Zoom that this content varies considerably in time and space, and that K d values for cadmium differ up to factor 30 (field data) or a factor 300 (laboratory). For mineralizing planktonic particles in the laboratory, K d increases up to a factor 10 - 20 (lead) were observed under conditions similar to those in Lake Volkerak/Zoom.2. When K p values for HOCs are calculated with respect to an aqueous phase which contains organic matter, the apparent K p depends on the organic carbon fraction in the aqueous phase and the particle to water ratio. Further, K p depends on organic matter content and composition. It was shown for 1,2,3,4-tetrachlorobenzene that laboratory K p values varied a factor 30 for particles from lake Volkerak/Zoom. Organic matter content of suspended solids showed a strong seasonal variation. Normalization to organic carbon removes only a part of the variation. Comparison of carbon normalised HOC concentrations (field data) in settling solids with those in simultaneously sampled suspended solids showed a difference of a factor 2 - 6. Under controlled laboratory conditions, significant K oc differences between fresh phytoplankton cells, detritus and sediments were found.3. Hydrophobic sorption to suspended solids may not be at equilibrium in many aquatic systems. This is caused by retarded adsorption or desorption, or for phytoplankton by the combined action of retarded bioaccumulation and algal growth

Communicerende vaten : gevaren, risico's en effecten van verontreinigd sediment

De risico’s van chemische verontreinigingen in slib en sedimenten in het Nederlandse rivierengebied zijn mogelijk veel geringer dan wordt aangenomen. Roet, dat algemeen voorkomt in sedimenten, blijkt organische verontreinigingen, zoals PCB’s, honderd tot duizend maal sterker te binden dan ‘humus’ waarop de veiligheidsnormen zijn gebaseerd. Sulfides doen iets dergelijks met metalen. Daardoor komt er tien tot honderd maal minder verontreiniging terecht in organismen in sedimenten, zoals wormen en muggenlarven. Dat meldt prof.dr. Bart Koelmans in zijn inaugurele rede bij de aanvaarding van het ambt van hoogleraar Water- en sedimentkwaliteit aan Wageningen Universitei

Fabrication of cantilever arrays with tips for parallel optical readout

We report on progress in the fabrication of cantilever arrays with tips. The process features only one lithographic step for the definition of both the tips and cantilevers. The tips have a uniform height distribution and are placed by selfalignment on the cantilever. The arrays are fabricated for an optical readout technique under development in which the cantilever arrays serve as diffraction gratings. This work describes our ongoing effort in array fabrication as well as preliminary results on optical readout of a previously fabricated batch of tipless cantilever arrays using Fraunhofer diffraction

Toxiciteit van oliefracties in sediment voor Corophium volutor

Naar aanleiding van toxiciteitexperimenten zijn milieu risicogrenzen voor minerale olie afgeleid, waarbij onderscheid wordt gemaakt naar fracties op basis van kookpunt (lengte van de koolstofketens). In dit onderzoek is onderzocht in hoeverre de voorgestelde risicogrenzen overeenkomen met waargenomen toxiciteit in veldsedimenten. Het oliegehalte werd in deze sedimenten bepaald door middel van XAD-extracties, waarmee het snel desorberend gehalte werd bepaald. Toxiciteit werd bepaald met een 10-daagse test met de slijkgarnaal Corophium volutator