Back-light scattering

The texture and structure of foods is very delicate, therefore experimental methods which cause no or vety little structural damage has to be applied in their investigations. Such techniques, the surface force balance and back-light scattering methods and dielectrometry will be also discussed in the chapter. 

Another optical technique, called the back-light scattering (Kossel-diffraction) method can also be used to investigate structure in food emulsions and foams. In this method, the emulsion (or foam) in a transparent vessel is illuminated by a collimated laser beam (See... 

Figure 14. Principle of back-light scattering measurement.

We have also used the back-light scattering technique to investigate the effect of shear rate on emulsion structure. The microstructure distortions occurred at high shear rates (25). 

It is awkward to use two different angles to describe the intensity of light scattered along a particular line of sight, but this situation is easily remedied by referring back to Fig. 10.5. It is apparent from Fig. 10.5 that r cos 0 is the projection of r along either the x, y, or z axis, depending on the choice of 0. We therefore see that... 

It was apparent that when the two immiscible fluids were stirred droplets of chloroform formed in the aqueous phase. It was hypothesised that the response of the phototrode was dominated by light scattered back from the droplets without reaching the mirror and that, as the droplet size decreases, the intensity of the back scattered light increases. This was confirmed in tests by increasing the rate of stirring and so decreasing the droplet size. 

The prototype developed by Lifetrac System (LifeTrac Systems, USA)59, also based on NIR spectroscopy, is very interesting and seems to satisfy the above-mentioned requirements. It is shown in Figure 11. In this case, it is not the light scattered back out through the skin that is detected, but rather... 

Powders give statistically mixed phases and, possibly, spatially unseparated reduction and oxidation sites, as well as poor space charge layers for carrier separation. This leads to high rates of bulk and surface recombination, as well as solution species back reactions. Light scattering losses add a further decrease in... 

Lord Rayleigh (1871) recognized that the blue of the sky is the result of light scattering. It is obvious from the numerous pictures sent back from outer space that the blackness observed by astronauts is quite different from our earthly observations of a blue sky. Rayleigh developed the theory of light... 

Another possibility is to use the evaporative light scattering (ELS) detector, which can be used independently of the composition or variations of the elution solvent mixture (presence of salt solutions is the only limit), however, it is not yet so diffused, even if its earlier applications date back to early 1980s. 

We have now described a system in which one or more narrow beams of laser light of well-defined wavelength are used to illuminate a cell, and the light scattered by the cell and emitted by various fluorochromes in or on that cell provide signals that are registered on a group of photodetectors. From our description of the optical bench in Chapter 3 (refer back to Fig. 3.7), we should recall that there are... 

Because of the low absorption coefficient of amorphous and microcrystalline silicon, it is mandatory to optimize light scattering within thin film silicon solar cells by the use of suitably textured (rough) interfaces and surfaces. This paragraph comments about the ideal surface roughness for ZnO layers deposited by CVD, and used as front or back contacts within amorphous, microcrystalline (and micromorph) solar cells. 

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