Schlieren method

At this point it is worth comparing the different techniques of contrast enliancements discussed so far. They represent spatial filtering teclmiques which mostly affect the zeroth order dark field microscopy, which eliminates the zeroth order, the Schlieren method (not discussed here), which suppresses the zerotii order and one side band and, finally, phase contrast microscopy, where the phase of the zeroth order is shifted by nil and its intensity is attenuated. 

Flow patterns of hydrodynamic systems like the compendial dissolution apparatus may be qualitatively characterized by means of dilute dye injection (e.g., methylene blue) or by techniques using particulate materials such as aluminum powders or polystyrene particles. Flow patterns may be also visualized by taking advantage of density or pH differences within the fluid stream. The Schlieren method, for instance, is based on refraction index measurement. Hot wire anemo-metry is an appropriate method to quantitatively characterize flow rates. The flow rate is proportional to the cooling rate of a thin hot wire presented to the stream. Using laser Doppler... 

P.W. Holder R. J. North, Schlieren Methods, Natl Physical Laboratory Notes on Appl Science, No 31, HMSO, London, 1963 The bibliography on image dissection in high-speed photography by J,S. Courtney-Pratt... 

More recent methods of photographing flames include the so-called "Schlieren-Method and the "Motion-Picture Camera Method using films sensitive to infra-red. These methods are described in Refs 7—9 and the definition of "Schlieren-Method" is given in Vol 2 of Encycl, pp C15-R C16-L. The motion picture cameras are similar to those used in die movie industry (Ref 8)... 

Laplace transformation, 1215 Nemst s equation and. 1217 non-steady, 1254 as rate determining step, 1261 Schlieren method, 1235 semi-infinite linear, 1216, 1234, 1255 in solution and electrodeposition, 1335 spherical. 1216. 1239 time dependence of current under, 1224 Diffusion control, 1248... 

Scanning tunneling microscopy (STM), 787. 1157 bioelectrochemistry and, 1159 electrochemistry and. 1158 electrodeposition and. 1310 nanotechnology, 1345 piezoelectric crystal, 1158 tunneling current. 1157 underpotential deposition, 1313, 1315 Scavanger electrolysis, electrodeposition, 1343 Schlieren method, diffusion layer. 1235 Schmickler, 1495,1510 Schrodinger equation, 1456, 1490 Schultze 923,1497.1510 Screw dislocation, 1303, 1316, 1321, 1326 Secondary reference electrode, 815, 1109 Self-consumed electrode, 1040 Semiconductors... 

Very much more is known about the theory of concentration gradients at electrodes than has been mentioned in this brief account. Experimental methods for observing them have also been devised, based on the dependence of refractive index on concentration (the Schlieren method) by means of interferometry (O Brien, 1986). Nevertheless, the basic concept of an effective diffusion-layer thickness, treated here as varying in thickness with fi until the onset of natural convection and as constant with time after convection sets in (though decreasing in value with the degree of disturbance, Table 7.10), is a useful aid to the simple and approximate analysis of many transport-controlled electrodic situations. A few of the uses of the concept of 8 will now be outlined. 

Shadow method may be combined with other methods, such as with Schlieren-Method (See also Ref 25,p 81 Ref 31,Pp 209, 369, 508 530 and Addnl Refs c bb)... 

Schlieren Method. See under Cameras, High-Speed Photographic in Vol 2, Cl 5-R to Cl 6-L... 

Concentration changes are observed optically from time to time either by light absorption (e.g. ultraviolet absorption for protein solutions) or, more usually, by schlieren or interference methods. These optical methods for examining concentration changes in liquid columns (especially the schlieren technique in its various forms) are also employed in the ultracentrifuge and for studying movingboundary electrophoresis. The schlieren method is based on the fact that, at a boundary between two transparent liquids of different... 

Figure 2.7 Sedimentation of a monodispersed sample of Limulus haemocyanin measured by the Philpot-Svenson schlieren method (18 000 rev min l)32 (By courtesy of the American Chemical Society)...

B6nard used the schlieren method (although not by this name) to obtain... 

The direct-shadow technique is probably the simplest in principle, but is subject to the greatest variation. As with the schlieren method, this technique when applied to the study of liquids generally yields only qualitative information. In contrast to the preceding methods, the direct-shadow technique detects differences from point to point in the second derivative of the surface... 

The direct-shadow method has been employed in the study of free convection by many authors following Benard, and unfortunately has often been mislabelled as a schlieren method. Levengood (L2) in a study of evaporative convection in pools of methyl alcohol, and Hickman (H2) in a study of surface behavior of boiling liquids, used modifications of Benard s deformed grid technique. 

Schardin, H., Toepler s Schlieren Method Basic Principles for Its Use and Quantitative Evaluation. David Taylor Model Basin, U.S. Navy Transl. No. 156, 1947. 

Shockwave Visualization on 3 mm Wide Channels At the University of Tokyo, the schlieren method and a high-speed camera have been used for capturing images of the flow of a traveling shockwave in channels of 3 x 3 mm cross section... 

The experimental set-up for the measurement and a typical result are shown in Fig. 3.8. A measuring device is installed in a reactor. The device is sensitive to a change of some property conductivity, pH, color, optical density, Schlieren methods, O2, T, radio pill, fluorimetry, radioactivity (Beyeler et al., 1981,1983 Bryant and Sadeghzadeh, 1979 Einsele, 1976b Kappel, 1976 Kipke, 1984 Middleton, 1979 Moser, 1987 Schneider et al. 1986 Zlokarnik, 1967). The response function of such a measurement often has the typical appearance shown in Fig. 3.8. 

Schlieren method for flow visualization to record the shock propagation has been successful down to a channel size of 3 mm X 3 mm cross-section and 42 mm length [11]. Investigations for microchannels are under way. 

Several methods based on Pick s second law are available to measure the diffusion coefficient. Among these are the following three classical methods the Schlieren method, the Gouy interference method, and the Rayleigh interference method. We describe here the Rayleigh interference method, for its application is also found in ultracentrifuge sedimentation. We use the classical Tiselius electrophoresis cells to illustrate (Figure 10.5). 

The application of the Schlieren method to localize the boundaries made possible the isolation of components under optical control. 

Liu CX, Zeng AW, Yuan XG, Yu GC (2008) Experimental study on mass transfer near gas-liquid interface through quantitative Schlieren method. Chem Eng Res Des 86(2) 201-207... 

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