Clear zone technique

A variation of the plate test, is the clear zone technique sometimes... 

A variation of the plate test is the clear zone technique [53], sometimes used to screen polymers for biodegradability. A fine snspension of polymer is placed in an agar gel as the sole carbon source and the test inocnlnm is placed in wells bored into the agar. After incubation, a clear zone aronnd the well, detected visually or instrumentally, is indicative of utilisation of the polymer. The method has, for example, been used in the case of starch plastics [54], varions polyesters [55-57] and PU [58]. 

A technique that has proven successful for compounds that are poorly soluble in aqneons solntion is the formation of clearing zones ( halo formation ) around active... 

Miscellaneous. A manometric technique utilizing a Warburg apparatus has been used to follow esterase activity. The carbon dioxide liberated from sodium bicarbonate by the fatty acids is measured (Willart and Sjostrom 1959). An agar diffusion procedure has been utilized for screening microorganisms for lipolyptic enzymes. The presence of lipase is indicated by clear zones in the turbid media (Lawrence et aL 1967). 

Techniques have also been developed for the specific visualization of particular classes of enzymes following electrophoretic separation in a gel. These techniques are often referred to as activity staining, as the intrinsic activity of the enzyme is used, either to produce a colored product or to produce a clear zone on a colored background within the gel. A method for visualizing proteinases based on the work of Gar-cfa-Carreno and Haard (1993) and Garcia-Car-reno et al. (1993) is presented (see Basic Protocol 3). 

The work presented clearly indicates that the electrical sensing zone technique offers a good potential both for certification of reference materials and for analysis of materials such as pigments having a significant amount of sub-sized material, provided that a mass balance can be offered with high precision and accuracy. The target should be no systematic deviations in the mass balance with a precision in mass of 3X. 

The induction time data and density profiles pf detonations in oxy-hydrogen and oxy-methane mixtures were analyzed on the basis of the kinetic data obtained by the reflected-wave technique and similar methods. A plot of the ignition delay vs 1/T in oxy-ammonia mixtures gave a straight line with a slope corresponding to an activation energy of 42.5 kcal/mole. In these mixtures the induction zone is not uniform, but the shock front is flat and end of the reaction zone is clearly discernible. Onedimensional detonation waves of low Mach number but relatively stable were obtained in a gas preheated to 600-1800°K ahead of the shock front... 

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