Light obscuration principl

The Particle Size Analysis of Floes Using the Light Obscuration Principle... 

Akers, R. J., Rushton, A. G., Sinclair, I., Stenhouse, J. I. T., The Particle Size Analysis of Floes Using the Light Obscuration Principle, in Particle Size Analysis, Eds. Stanley-Wood, N. G., Lines, R. W., The Royal Society of Chemistry, Cambridge, 1992, pp 246-255. 

The USP lists two recognized techniques for testing for particulate matter in pharmaceutical solutions. Method 1 is based on the principle of light obscuration, in which light from a laser impinging on a photodiode detector is obscured by any particles present in the test medium. Method 2 employs a light microscope, with which particles are visibly counted per unit volume by the analyst. 

There are two basic types of beam detectors, both of which operate on the principle of light obscuration an infrared beam is projected across the area to be protected and is monitored for obscuration due to smoke. If smoke is present in the beam, usually for a period of 8-1 Os, a fire alarm indication is activated. There are two basic types. 

A considerable part of the book is an attack on the Paracelsian theory of three principles. Boyle argues, for example, that none of the principles can be used to explain how a prism breaks up white light into different colors. Furthermore, authors who argued in favor of the three principles generally described them in such obscure ways that it was doubtful that they understood these supposed principles themselves. 

Chemistry offers vast material, little light, much work Philosophy has not provided any clarity the principles that are followed are obscure or uncertain the books are presented in terms more appropriate to hide the ignorance of their authors than to enlighten the mind. To these shadows the chemists often join fairy tales finally they are always in dispute with one another, they accord neither with themselves nor with nature. 

Chemistry offers a vast subject, little light, much work philosophy has not yet extended any clarity to it the principles one has followed are obscure or... 

From a fnndamental point of view, direct experimental information on the interface profile would be desirable. To get direct structural information with respect to the interface profile, neutron reflection wonld be the ideal technique to use. Neutron reflection has been used extensively to shed light on the strnctnre of air-liquid interfaces [44,45]. A liquid-liquid interface brings along the complication that the nentron beam has to pass an air-liquid interface before it reaches the water-water interface. The air-liquid interface is in general a much stronger transition in reflective index than the water-water interface and will obscure the reflection of the water-water interface, which is beyond it. Therefore, a water-water phase-separated system has to be used with a H2O/D2O ratio with zero neutron-scattering cross-section. The polymer in the top phase should also have an H/D composition rendering the polymer in the top phase invisible for neutrons. In principle, the polymer profile at the water-water interface can in this way be obtained, because the polymer composition at the interface differs from that with the null H/D composition in the top phase. The solvent profile can only be indirectly determined from the polymer excess. 

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