Special Possibilities

Most suitable would be the use of a perfectly NH4+ ion-selective glass electrode however, a disadvantage of this type of enzyme electrode is the time required for the establishment of equilibrium (several minutes) moreover, the normal Nernst response of 59 mV per decade (at 25° C) is practically never reached. Nevertheless, in biochemical investigations these electrodes offer special possibilities, especially because they can also be used in the reverse way as an enzyme-sensing electrode, i.e., by testing an enzyme with a substrate layer around the bulb of the glass electrode. 

As discussed previously, in many propulsion systems the recovery of a large fraction of the dissociation energy in the nozzle expansion through recombination is difficult to achieve. While the assumption of frozen flow with respect to recombination reactions appears necessary for many heat transfer rocket nozzle expansions, it is possible that condensation phenomena are sufficiently rapid to provide near equilibrium flow with respect to phase changes. For this special possibility, phase equilibrium in the presence of frozen dissociation, it has been shown theoretically (48) that the performance in terms of specific impulse of propellants containing light metallic elements can exceed the performance of hydrogen. 

A rather special possibility to attain information about molecular diffusion is provided by catalytic reactions if they proceed in the range of medium Thiele moduli (i.e. in the transition range between intrinsically and transport controlled reactions) [100]. By analyzing the dependence of the effective reaction rate on the catalyst particle size [101. 102] and/or the intrinsic re-... 

Equally promising, though more thoroughly explored, are the measurements of intensities and band shapes of IR bands. The unique spectral characteristics of H bonded substances bespeak interesting conclusions to come from such measurements. As in the NMR shifts, the intensities reveal details of electron distribution and mobility. Whether the band widths indicate anharmonicity of the low frequency modes is not yet clear, but low temperature tudies will provide important clues to the proper interpretation. It is evident that the matrix isolation method has special possibilities and will be helpful. 

The 2-D TLC on bilayers, silica gel for normal phase (NP) and reversed phase (RP), offer the special possibility to carry out two different separation processes on the same plate. Normal-phase chromatography can be performed in the first direction on silica gel after the evaporation of the solvent, the plate was impregnated with paraffin oil dissolved in petroleum ether. After removal of the excess solvent, the plate was reversed phase developed in the second direction. 

The 2-D TLC on bilayers, silica gel for normal-phase (NP) and reversed-phase (RP), offer the special possibility... 

The nature of analytical methods based on 7-spectrometry and neutron activation brings with it some particular advantages, as well as some limitations, in comparison with other methods. Some of them are inherent characteristics, while others apply to the special possibilities that this methodology offers. 

Cyclic voltammetry offers a special possibility to study the permeability of thin clay films using clay-modified electrodes. The kinetics of the break-in/leach-out (hydration-dehydration, swelling-shrinking) processes depends on the structure of the porous aerogel hydrogel and on the layer thickness of the film. The rate constants of structure-dependent macrodiffusion and microdiffusion can be calculated, and to the best of our knowledge - this cyclic voltammetric determination of rate constants of the elementary processes is unique in the literature. 

A special possibility is the use of mixed sorbents, which is possible with the CLC S and C-RPC techniques. The simplest method is to fill most of the planar column with silica, and then the last 1 cm with kieselguhr as a preadsorbent zone (11). It is, needless to say, also possible to fdl the same column more than two successive stationary phases in order of increasing or decreasing polarity. 

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