We have improved the tip pre-amplifier design of the original Bio-Kelvin probe in two ways firstly each tip is now independently steerable in terms of voltage allowing elimination of interference or crosstalk from the separate heads or wires attached to them. Secondly the tips are now electrically 'floating', this, coupled with a special bias trimming stage, permits a higher bio-signal amplification factor to be applied resulting in a significantly better resolution of the electric field measurement from approx 7 mV to 2 mv equivalent noise. The present 4 probe system allows only limited manual translation of each tip: during the scanning action, all four tips are displaced with respect to the stationary coleoptile so that no movement induced bio-potentials are produced by the corn seedling model. However, the coleoptiles are neither perfectly circular nor completely straight, thus in the longer term a computer-steered displacement system is required to ensure that the initial set-up conditions are equivalent at each tip and can be maintained through out the period of measurement. Despite the above limitations the coleoptiles dark and photo-tropic response has been measured by the multi-head system and this data has now been analysed. We can observe the potentials around the circumference of the coleoptile changing over a period of approx 1 hr with a type of precessional dynamics. This could well be a mechinism by which the corn senses which direction is 'up'. We intend to pursue the spectrography of the phototropic response using LED's of various wavelengths. The initial data has been made available on our web site:http://rgu.ac.uk/subj/skpg. In addition to reviewing measured data we have made a large contribution to Prof. Nina Allen's NASA grant submission """"""""Growth and Current Measurements in Graviresponding Plants Using a Novel BioKelvin Probe"""""""". Lastly we have upgraded the Kelvin Probe user interface to be Win 3.1/Win 95 compatible and have commenced development of 3D visualization of scanned images. Additionally a measurement database facility is currently being designed.
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