A lattice representational definition of a hierarchy of instructional processors usable in educational courseware

The basic “recognize-act-recognize-end” cycle can be recognized in elementary as well as in more advanced forms of CAI. This article attempts to offer a unifying formal framework in which different elaborations of this cycle (embodied in a “processor”) can be placed. Three different levels of elaboration are distinguished which can be considered to be situated into the nodes of a lattice of models of the instructional process. A formal definition of such a framework can serve at least two functions. In the first place a uniform and precise definition of various elaborations can be given and new elaborations can be created in a logically funded way. Secondly, such a framework can support the modelling of instructional processes and the stimulation of student behavior. Thus, pre-testing of courseware could become feasible. Aspects of the framework have been used to implement two prototypes of support systems for the development of CAI courseware

Design strategy and process optimization for reactors with continuous transport of an immobilized enzyme

In order to operate a process which uses immobilized enzymes at constant conversion and constant capacity, the refreshment of the enzyme must be continuous. In this paper, two reactor types with continuous refreshment of the biocatalyst are discussed: the stirred tank and the multistage fluidized bed. A method is presented for dimensioning a reactor in such a way that the costs for the conversion of substrate to product are minimized. These costs are calculated as the sum of the biocatalyst consumption and overall reactor costs.\ud \ud In contrast with the stirred-tank reactor, the multistage fluidized bed can be operated at a non-uniform temperature. For the glucose isomerase process, an optimal temperature gradient results in a small reduction in the biocatalyst consumption (±5%). It is concluded that, in general, a temperature gradient will only favour the economy of processes with relatively expensive biocatalysts.\ud \ud Compared with conventional reactor types, such as the continuous stirred-tank reactor and the fixed-bed reactor, the multistage fluidized-bed reactor can improve the economy of an enzyme-catalysed reaction significantly

Single Microbubble Imaging

The imaging of smaller vessels and organ perfusion has high clinical value for the di¬agnosis of cardiovascular disorders and cancer. Ultrasound imaging is the most used medical image modality since it is relatively cheap and flexible. Ultrasound contrast agents (UCAs) are used to enhance the signals from blood, thus facilitating the diagnosis. Such agents consist of stabilized gaseous microbubbles that are as small as red blood cells; their safety is widely acknowledged. This PhD thesis studies single microbubbles in experimental laboratory setups to investigate the behavior in body-like settings. Microbubbles are sonically excited at diagnostic frequencies in the range 1 – 10 MHz. We used the unique, custom-built camera Brandaris-128 (www.brandaris128.nl) to optically record the behavior at framing rates up to 25 million frames per second. Furthermore the echo-response from microbubbles is sampled with a dedicated acoustic setup. Both the optical and acoustic results in this thesis

Basisgegevens welke nodig zijn als aanzet voor toepassing van inductief gekoppeld plasma-atomaire emissie spectrometrie bij de analyse van monsters van landbouwkundige oorsprong op diverse elementen

Voor een aantal elementen zijn basisgegevens verzameld zoals een storingvrije emissielijn, optimale waarnemingshoogte en detectie-grens onder verschillende omstandigheden. Nagegaan is of de zuurconcentratie en de zuursoort invloed hebben op de meting met ICP en of er matrixeffekten optreden. Om de resultaten te toetsen zijn op beperkte schaal ICP-resultaten vergeleken met die van andere technieken zoals b.v. vlam-AAS en voltammetrie