SUMMARYA scanning proton microprobe has been used to determine quantitatively the distribution of Mn, Zn and other elements in the mature wheat seed {Triticum aestivum cv. Gamenya). Both X-ray and nuclear scattered proton data were collected during the irradiation of a 40/im-thick longitudinal section, and these were used to calculate absolute elemental concentrations for the various features of interest in the embryo region. Elemental maps were collected for a number of transverse and longitudinal sections (obtained from several seeds), but comprehensive analytical information was collected from one typical longitudinal section only. In the embryo, the concentration (by dry weight) of Mn was highest in the radicle (1400 +200/

An effective method for producing arrays of nanoscale triangles, rods and wells on the distal end of a silica optical fibre is presented. The structures are produced by applying a wet-etch procedure to drawn-down imaging fibres. Structural variation is achieved by altering the final diameter of the drawn fibre. Feature sizes of less than 100 nm can be readily achieved in this way. When coated with silver, surface-enhanced Raman scattering enhancement factors of over 10 6 can be achieved, depending on the size and shape of the structures present.

This article investigates the optics misconceptions of 220 year 11 Thai high-school students. These misconceptions became apparent when the students attempted to explain how an object submerged in a water tank is 'seen' by an observer looking into the tank from above and at an angle. The two diagnostic questions used in the study probe the students' ability to use a ray diagram to explain the relationship between object, image and observer, and then to use the ray diagram to qualitatively determine the position of the image. The study indicates that these high-school students, even after instruction, had significant misconceptions about the direction of propagation of light, how light refracts at an interface, and how to determine the position of an image. The study revealed that students used various concept models to explain how the object can be 'seen' in this situation. Only 22% of all students had a qualitative understanding of how to use a ray diagram to determine image position, and only 1 of 220 students could identify the correct image position using correct reasoning. Our results indicate that students require very careful instruction if they are to understand how objects are 'seen' and how images are formed when light refracts through a planar surface.

The technique of oblique angle deposition has been extended to the fabrication of nanostructured metal coatings on the tips of standard silica optical fibers by thermal evaporation. The coatings are initiated as metal island films, which grow into extended rodlike structures as the deposition continues. The nanorod coatings demonstrate excellent surface-enhanced Raman scattering performance with variability of less than 10% as shown by direct measurements off the fiber tip with thiophenol as a test analyte. However, in the remote sensing configuration, the nanorod structures perform no better than thin metal island films. This appears to be mainly due to reduced transmission when nanorod lengths exceed ~100 nm. Moreover, the variability of remote measurements is increased to 18%. This is believed to be due to variations in coupling efficiency.

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