Fibres sample mounting

A further simple innovation gives much more reliable solids results. In this the glass fibre disc mounted in its porcelain, glass, or plastic holder is first wetted with distilled water, and then the sample filtered through and washed with several small portions of distilled water without allowing the disc to become dry. It is believed that filling the air spaces in the annulus of the disc trapped in the holder with distilled water is the reason why better results are obtained by this procedure. 

Mechanical damage can best be seen in longitudinal mounts under the microscope or in surface imprints. Since individual mechanically damaged fibres may not be representative of the sample, a fairly large number of fibre samples should be examined (up to 100 according to the particular case). 

Although solid-phase microextraction (SPME) has only been introduced comparatively recently (134), it has already generated much interest and popularity. SPME is based on the equilibrium between an aqueous sample and a stationary phase coated on a fibre that is mounted in a syringe-like protective holder. Eor extraction, the fibre... 

Sherwood Stevens (1965) examined glass-fibre filters from personal air samplers worn by workers in the Radiochemical Laboratories at Harwell. The filters were mounted in an Araldite mixture which rendered them transparent and were covered by autoradiographic stripping film. After exposure and development, the samples were viewed with a high-power optical microscope. Particles were sized, and their activity determined from the number of alpha tracks coming from them. An extremely wide range of particle sizes, 0.2 to 90 m, was found. The smaller particles were plutonium compounds or alloys, and the larger were inert particles with one or more small Pu particles attached to them. An example of the latter is shown in Fig. 5.3. 

Fig. 19.10. Prototype of a lead ion measuring optrode system. Key to drawing (A) Ar ion laser (B) dichroic mirror (C) mirror (D) lens (E) fibre mount (F) optical fibre core (G) fibre cladding (H) templated polymer coating (I) sample (J) monochromator (K) detector (L) A/D converter (M) computer.

The apparatus shown in Fig. 5.9 was devised by the Wool Industries Research Association for the rapid determination of the mean fibre diameter of wool samples. The instrument consists of a microscope L which projects an image enlarged 500 times onto the white screen T. I he stage S carries a glass slide on which the sample to be measured is mounted, and illumination is provided by the lamp at H. The focusing and movement of the stage are controlled by the adjustment mechanisms marked Cj and Cj. A convenient way of preparing a suitably randomized sample of the fibres is to... 

Figure 2 Equipment for placing modem wood samples. The image to the left shows the steel tube and the carbon fibre pole with mounted specimens. The image to the right shows an expanded view of the tip of the pole and the arrangement of specimens and PVC spacers...

Sample heating in SR beams as a consideration was introduced by Stuhrmann (1978) his example is cited in detail in section 6.5.4.1. Hel-liwell and Fourme (1983) considered radiation damage and sample heating in evaluating the usefulness of the prospective fluxes at the specimen that might be anticipated using the ESRF. Helliwell and Fourme (1983) and Helliwell (1984, pp. 1470-3) discuss the need to go to shorter X-ray wavelengths (e.g. 0.5 A), to reduce the fraction of absorbed photons, and to use cryotemperatures, with frozen crystals mounted on a copper fibre, to limit the temperature rise experienced by the sample. In this way, frozen microcrystals of protein of size lO/zm should be successfully studied on the ESRF. This application of the ESRF was further discussed in Helliwell (1989). 

Different clamping geometries are used to accommodate particular specimens (Figure 8). Single or dual cantilever bending modes are the most common for materials which can be formed into bars. Shear measurements are used for soft, thick samples. Films and fibres are usually mounted in tension with loading arranged so that the sample is... 

The optical apertures used in near-field microscopy are usually prepared by pulling a heated optical fibre until it breaks [25]. The sides of the tips are coated with aluminum. The typical diameters of the apertures produced by this technique are 60 10 nm, which is about one tenth of the optical wavelength. The transmission of such a tip ranges from 10 to 10 . The near-field tip is mounted on a xyz-piezo-electric (PZT) tube scanner to control the fine approach (2) to the surface and the lateral dithering (x,y) of the tip. The coarse z positioning was achieved by a coupled spring and steel plate comparable to the setup described in [30]. The sample was connected to a small glass hemisphere to minimize losses due to internal reflections and mounted in the focus of a paraboloid mirror with a numerical aperture of NA = 0.98. The whole setup, paraboloid mirror, sample, and PZT tube with the fibre tip, was then mounted inside a cryostat and immersed in superfluid Helium at 1.8 K. 

Figure 4. Sketch of the experimental set-up for single-molecule magnetic resonance spectroscopy. In part (a) the sample, S, is mounted between a cover, C, and a LiF substrate, in the joint focus of a parabolic mirror, P, and a lens, L. The microwaves are provided by a loop, I, and the whole sample holder is positioned in the central bore of a superconducting magnet, M. Residual light of the incident laser is blocked by a beam block, B. In part (b) of the figure the sample is mounted at the tip of a single mode fibre, F, centered in the focus of a parabolic mirror, P. Microwaves are provided by a loop, L.

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