Factors determining feasibility

Where activated carbon is a potential treatment technology, the first evaluation step is generally to run simple isotherms to determine feasibility. Isotherms are based on batch treatment where impurities reach equilibrium on available carbon surface. While such tests provide an indication of the maximum amount of impurity a GAC can adsorb, it cannot give definite scale up data for a GAC operation due to several factors ... 

Several critical factors determine the technical feasibility of an enantioselective process step, but it must be stressed that even if all these criteria are met there is no guarantee that it is actually used ... 

No doubt the cost of xylanolytic enzymes will be one of the factors determining their application in the pulp and paper industry as well as in other areas. Economically feasible xylanase production can be achieved in paper mills employing xylanase-positive transformants of common industrially used microorganisms that are capable of utilizing inexpensive carbon sources originating there. A substantial improvement in the production of xylanolytic systems can be expeaed from mutants of non-cellulolytic microorganisms that are resistant to catabolic repression. Such mutants usually exhibit hyperproduction of extracellular enzymes. 

Tlie factors determining the industrial and economic feasibility of biocatalytic processes are depicted in Figirre 8.2, showing the key aspects of the syntlietic process (and its economics), biocatalyst selection and characterization, biocatalyst engineering, its application in industrial use, and product recovery. 

The inline dilution system shall allow the preparation of buffers with an inline dilution factor ranging from 1 to 10. This factor determines the ratio of water to concentrated buffer. Larger ratios are of course feasible, but there is a trade-off between the process accuracy and flexibility to be taken into account. The systems shall cope as well with process disturbances and shall be robust again changing process conditions (such as pressure drop in a chromatography column or a sudden change in pressure or flow rate in the primary water supply). The robustness of such systems is crucial since pharmaceutical processes are validated to run in certain predefined limits. Any deviations to such limits will lead to additional investigation costs that could have severe consequences, in the extreme situation the withdrawal of the produced product. 

Although the harmonic approximation is satisfactory for small displacements from the equifibrium position, ab initio harmonic force constants and vibrational frequencies are known to be typically overestimated as compared with those experimentally found [86]. Sources of this disagreement are the omission or incomplete incorporation of electron correlation, basis set deficiencies, and the neglect of anharmonicity effects. However, as the overestimation is fairly uniform, the appHcation of appropriate scahng procedures becomes feasible. Due to its simplicity, global scafing (using one uniform scale factor determined by a least-squares fit of the calculated to the experimental vibrational frequencies) has widely been used at different levels of theory [87]. However, for most spectro-... 

A few examples will serve to illustrate the usefulness of these concepts. First, what factors determine the titration feasibility of a monoprotic acid ... 

Accuracy The accuracy of a controlled-current coulometric method of analysis is determined by the current efficiency, the accuracy with which current and time can be measured, and the accuracy of the end point. With modern instrumentation the maximum measurement error for current is about +0.01%, and that for time is approximately +0.1%. The maximum end point error for a coulometric titration is at least as good as that for conventional titrations and is often better when using small quantities of reagents. Taken together, these measurement errors suggest that accuracies of 0.1-0.3% are feasible. The limiting factor in many analyses, therefore, is current efficiency. Fortunately current efficiencies of greater than 99.5% are obtained routinely and often exceed 99.9%. 

The scanning transmission electron microscope (STEM) was used to directly observe nm size crystallites of supported platinum, palladium and first row transition metals. The objective of these studies was to determine the uniformity of size and mass of these crystallites and when feasible structural features. STEM analysis and temperature programmed desorption (TPD) of hydrogen Indicate that the 2 nm platinum crystallites supported on alumina are uniform In size and mass while platinum crystallites 3 to 4 nm in size vary by a factor of three-fold In mass. Analysis by STEM of platinum-palladium dn alumina established the segregation of platinum and palladium for the majority of crystallites analyzed even after exposure to elevated temperatures. Direct observation of nickel, cobalt, or iron crystallites on alumina was very difficult, however, the use of direct elemental analysis of 4-6 nm areas and real time Imaging capabilities of up to 20 Mx enabled direct analyses of these transition metals to be made. Additional analyses by TPD of hydrogen and photoacoustic spectroscopy (PAS) were made to support the STEM observations. 

Before standards for indoor exposure to radon can be formally established, work is necessary to determine whether remedies are feasible and what is likely to be involved. Meanwhile, the Royal Commission on Environmental Pollution (RCEP) in the UK has considered standards for indoor exposure to radon decay products (RCEP, 1984). For existing dwellings, the RCEP has recommended an action level of 25 mSv in a year and that priority should be given to devising effective remedial measures. An effective dose equivalent of 25 mSv per year is taken to correspond to an average radon concentration of about 900 Bq m 3 or an average radon decay-product concentration of about 120 mWL, with the assumption of an equilibrium factor of 0.5 and an occupancy factor of 0.83. 

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