A minimally invasive technique is described for recording the a-wave of the human ERG and extracting the parameters of transduction in the rod and cone photoreceptors. A corneal DTL fibre electrode is used, but the pupil is not dilated and the cornea is not anaesthetized. Although the amplitude of the signal collected by the DTL electrode varies from session to session, this is not a problem, as the photoreceptor fractional circulating current is obtained by normalization of the response family. A method is described for varying the effective flash intensity over a wide range, by controlling the duration of the xenon flash. In order to fit the kinetics of the responses, an analytical equation is derived for the convolution of the previous "delayed gaussian" expression with the cell's capacitive time constant. This equation provides a good description of both the rod and the cone response families. For rods, the capacitive time constant was found to be tau rod approximately 1 msec as reported previously, but for the cones a considerably longer time constant of tau cone approximately 4-5 msec was needed. For rods, the amplification constant (Arod approximately 5 sec-2) was close to previous estimates, but for cones the sensitivity (expressed in terms of corneal illuminance) was higher than in previous work. Calculation of the amplification constant of transduction within the cones requires knowledge of their light collection properties, and the absence of hard information makes this estimate somewhat speculative. However, when account is taken of the larger diameter of the inner segments of cones in the peripheral retina, then our estimated amplification constant for the cones (Acone approximately 3-7 sec-2) is of a similar order of magnitude to that obtained for the rods.

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Pressure‐reducing valves, which dissipate energy, are often used in water supply systems to regulate the downstream pressure levels. If a reverse running pumpset is installed alongside such a valve, most of the dissipated energy can be recovered. This paper describes a system of this type which has recently been installed by North West Water, with advice and specialized equipment supplied by the Nottingham Trent University Micro‐Hydro Group. The power produced by the energy‐recovery system is used to run and monitor a remote potable‐water dosing plant.

Scatterometry takes advantage of the sensitivity exhibited by optical diffraction from periodic structures, and hence is an efficient technique for lithographic process monitoring. A feature region measurement algorithm has been developed to extract accurately and quickly the relevant constitutive parameters from diffraction data. It is a method for efficiently determining grating structure by seeking the reflectance at some angles contains more information about the structure of the surface relief profile than the reflectance at other angles in a library data match process. The number of measurements and size of signature matching library will be reduced in a great percentage by performing the feature region algorithm.

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