The Essence of Inheritance

Programming languages serve a dual purpose: to communicate programs to computers, and to communicate programs to humans. Indeed, it is this dual purpose that makes programming language design a constrained and challenging problem. Inheritance is an essential aspect of that second purpose: it is a tool to improve communication. Humans understand new concepts most readily by first looking at a number of concrete examples, and later abstracting over those examples. The essence of inheritance is that it mirrors this process: it provides a formal mechanism for moving from the concrete to the abstract.Comment: This paper was submitted for inclusion in a Festschrift entitled "A list of successes that can change the world", to be published by Springe

International Workshop on Nutrient Balances for Sustainable Agricultural Production and Natural Resource Management in Southeast Asia, Bangkok, Thailand, 20-22 February 2001: selected papers and presentations

Soil management / Soil properties / Soil fertility / Soil degradation / Crop production / Farmers / Agricultural extension / Farming systems / Sustainability / Rice / Cassava / Vegetables / Maize / Fertilizers / Decision support tools / Economic aspects

Chicken viscera - a potential cheap feed in shrimp culture

Prawn seed and nutritionally balanced compounded feed are the basic requirements fOr shrimp farming. Production of prawn in extensive type of culture depends upon natural food. But in intensive culture/farming the artificial feeding is unavoidabl

Robustness of the Blandford-Znajek mechanism

The Blandford-Znajek mechanism has long been regarded as a key ingredient in models attempting to explain powerful jets in AGNs, quasars, blazzars etc. In such mechanism, energy is extracted from a rotating black hole and dissipated at a load at far distances. In the current work we examine the behaviour of the BZ mechanism with respect to different boundary conditions, revealing the mechanism robustness upon variation of these conditions. Consequently, this work closes a gap in our understanding of this important scenario.Comment: 7 pages, accepted in CQ

Liver and kidney damage in grey mullet Liza parsia (Hamilton and Buchanan) on exposure to an organophosphate 'Nuvan’

In bioassay experiments with Liza parsia to 'Nuvan' for acute exposure the 48 and 96 hr LC50 were found to be 0.750 and 0.482 ppm respeccively in a brackishwater medium of salinity 10 f 1.0%, temperature 27.5 f 1,PC and pH 6.0 f 0.5. For sub-lethal effects the fishes were exposed to 115th and 1115th concentrations of this 96 hr LC50 value for 45 days

If you can't be with the one you love, love the one you're with: How individual habituation of agent interactions improves global utility

Simple distributed strategies that modify the behaviour of selfish individuals in a manner that enhances cooperation or global efficiency have proved difficult to identify. We consider a network of selfish agents who each optimise their individual utilities by coordinating (or anti-coordinating) with their neighbours, to maximise the pay-offs from randomly weighted pair-wise games. In general, agents will opt for the behaviour that is the best compromise (for them) of the many conflicting constraints created by their neighbours, but the attractors of the system as a whole will not maximise total utility. We then consider agents that act as 'creatures of habit' by increasing their preference to coordinate (anti-coordinate) with whichever neighbours they are coordinated (anti-coordinated) with at the present moment. These preferences change slowly while the system is repeatedly perturbed such that it settles to many different local attractors. We find that under these conditions, with each perturbation there is a progressively higher chance of the system settling to a configuration with high total utility. Eventually, only one attractor remains, and that attractor is very likely to maximise (or almost maximise) global utility. This counterintutitve result can be understood using theory from computational neuroscience; we show that this simple form of habituation is equivalent to Hebbian learning, and the improved optimisation of global utility that is observed results from wellknown generalisation capabilities of associative memory acting at the network scale. This causes the system of selfish agents, each acting individually but habitually, to collectively identify configurations that maximise total utility