Conservative approach

The main difficulty in the theoretical study of clusters of heavy atoms is that the number of electrons is large and grows rapidly with cluster size. Consequently, ab initio "brute force" calculations soon meet insuperable computational problems. To simplify the approach, conserving atomic concept as far as possible, it is useful to exploit the classical separation of the electrons into "core" and "valence" electrons and to treat explicitly only the wavefunction of the latter. A convenient way of doing so, without introducing empirical parameters, is provided by the use of generalyzed product function, in which the total electronic wave function is built up as antisymmetrized product of many group functions [2-6]. 

Chemical engineering in the years ahead will be practiced increasingly in a retrofit world. For new facilities it will be necessary to consider retrofit options up front. This approach conserves capital while allowing faster, more flexible response to changing markets and worldwide conditions. 

Once a correlation between structure and activity/ property is found, any number of compounds, including those not yet synthesized, can be readily screened on the computer to select structures with the properties desired. The most promising compounds may then be selected for synthesis and evaluation in the laboratory. In the pharmaceutical and environmental areas,l l QSPR has been applied to predict properties like the efficacy of drugs (with different substitutions) or behaviors like the accumulation of pollutants in fish, despite the fact that the exact mechanisms are unknown. The QSAR/QSPR approach conserves resources and accelerates the process of development of new molecules for use as drugs, materials, additives, or for any other purpose. 

By approaching conservation in a systematic manner, it will be possible to keep track of what has been accomplished, what remains to be done, and how well the treatment works. 

Conservative approach Conservative approach to safety evaluation or conservative code analyses are those where every assumption is chosen in a conservative way, in the light of the phenomenon to be evaluated. This approach is the opposite of the best estimate approach. 

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