Phenomenology of retained refractoriness: On semi-memristive discrete media

We study two-dimensional cellular automata, each cell takes three states: resting, excited and refractory. A resting cell excites if number of excited neighbours lies in a certain interval (excitation interval). An excited cell become refractory independently on states of its neighbours. A refractory cell returns to a resting state only if the number of excited neighbours belong to recovery interval. The model is an excitable cellular automaton abstraction of a spatially extended semi-memristive medium where a cell's resting state symbolises low-resistance and refractory state high-resistance. The medium is semi-memristive because only transition from high- to low-resistance is controlled by density of local excitation. We present phenomenological classification of the automata behaviour for all possible excitation intervals and recovery intervals. We describe eleven classes of cellular automata with retained refractoriness based on criteria of space-filling ratio, morphological and generative diversity, and types of travelling localisations

On attraction of slime mould Physarum polycephalum to plants with sedative properties

A plasmodium of acellular slime mould Physarum polycephalum is a large single cell with many nuclei. Presented to a configuration of attracting and repelling stimuli a plasmodium optimizes its growth pattern and spans the attractants, while avoiding repellents, with efficient network of protoplasmic tubes. Such behaviour is interpreted as computation and the plasmodium as an amorphous growing biological computer. Till recently laboratory prototypes of slime mould computing devices (Physarum machines) employed rolled oats and oat powder to represent input data. We explore alternative sources of chemo-attractants, which do not require a sophisticated laboratory synthesis. We show that plasmodium of P. polycephalum prefers sedative herbal tablets and dried plants to oat flakes and honey. In laboratory experiments we develop a hierarchy of slime-mould’s chemo-tactic preferences. We show that Valerian root (Valeriana officinalis) is the strongest chemo-attractant of P. polycephalum outperforming not only most common plants with sedative activities but also some herbal tablets.
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Slime mould computes planar shapes

Computing a polygon defining a set of planar points is a classical problem of modern computational geometry. In laboratory experiments we demonstrate that a concave hull, a connected alpha-shape without holes, of a finite planar set is approximated by slime mould Physarum polycephalum. We represent planar points with sources of long-distance attractants and short-distance repellents and inoculate a piece of plasmodium outside the data set. The plasmodium moves towards the data and envelops it by pronounced protoplasmic tubes