Observation and abstract behaviour in specification and implementation of state-based systems

Classical algebraic specification is an accepted framework for specification. A criticism which applies is the fact that it is functional, not based on a notion of state as most software development and implementation languages are. We formalise the idea of a state-based object or abstract machine using algebraic means. In contrast to similar approaches we consider dynamic logic instead of equational logic as the framework for specification and implementation. The advantage is a more expressive language allowing us to specify safety and liveness conditions. It also allows a clearer distinction of functional and state-based parts which require different treatment in order to achieve behavioural abstraction when necessary. We shall in particular focus on abstract behaviour and observation. A behavioural notion of satisfaction for state-elements is needed in order to abstract from irrelevant details of the state realisation

Non-classical computing: feasible versus infeasible

Physics sets certain limits on what is and is not computable. These limits are very far from having been reached by current technologies. Whilst proposals for hypercomputation are almost certainly infeasible, there are a number of non classical approaches that do hold considerable promise. There are a range of possible architectures that could be implemented on silicon that are distinctly different from the von Neumann model. Beyond this, quantum simulators, which are the quantum equivalent of analogue computers, may be constructable in the near future

Education for Librarianship in the Next Century

published or submitted for publicatio

Modelling of a roof runoff harvesting system: The use of rainwater for toilet flushing

The water balance of a four-people family rainwater harvesting system was calculated in a case study. The experimental water saving efficiency (WSE) was calculated as 87 %. A simple computer model was implemented to simulate the behaviour of the rainwater harvesting system. In general, the rainwater collector volumes predicted by the daily model had shown a good correlation with the experimental values. The difference between the experimental and the predicted values for the stored volume can be explained by the lack of maintenance of the system that can affect its performance. On the basis of a long-term simulation of 20-year rainfall data, the following parameters were calculated: rainfall, water demand, mains water, rainwater used, over-flow and WSE. The collection of rainwater from roofs, its storage and subsequent use for toilet flushing can save 42 m3 of potable water per year for the studied system. The model was also used to find the optimal size of the tank for the single-family household: a storage capacity of approximately 5 m3 was found to be appropriate. The storage capacity and tank size were distinguished. The importance to take into account the dead volume of the tank for the sizing was indeed highlighted

Capillary HPLC Separation of Selected Neuropeptides

Neuropeptides play a pivotal role in brain and peripheral nervous system function. As high performance liquid chromatography (HPLC) becomes the central tool in the separation and characterization of peptide and protein samples, its selectivity optimization has attracted increasing attention. This research program aims to develop useful, quantitative analysis methods for neuropeptides and their hydrolysis fragments by capillary HPLC. Related peptide pairs are successfully separated, such as leu-enkephalin and [Des-Tyr1] leu-enkephalin, dynorphin A and dynorphin B, galanin and its fragment Gal1-16. The hydrolysis of leu-enkephalin to [Des-Tyr1] leu-enkephalin by organotypic hippocampal slice cultures (OHSCs) can be monitored by the same HPLC system. The separation of seven hippocampal neuropeptides with similar hydrophobicity, Bj-PRO-5a, [Des-Tyr1] leu-enkephalin, leu-enkephalin, pentagastrin, Antho-RW-amide I, dynorphin A 1-6 and angiotensin II, is accomplished by thermally tuned tandem capillary columns (T3C). The chromatographic selectivity is continuously, systematically and significantly optimized by individual adjustment of each column’s temperature. The T3C concept is applied for the first time with capillary columns, which is an important step towards optimization of selectivity for separations of small samples by liquid chromatography