Early Ideas

In reviewing the history of VB methods there stand out a few ideas concerning approximations that might be made. The author has chosen four that allow simple computational tests in today s world, and these are discussed in this section. There is little connection between them. 

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Design modifications for the accommodation of feasible operating procedures. Section V introduced some early ideas on how the ideas of planning operating procedures could be used to identify modifications to a process flowsheet, which are necessary to render feasible operating procedures. More work is needed in this direction. Clearly, any advances in dynamic simulation with discrete-time events would have beneficial effects on this problem. 

The much-closer Moon would have had a greater influence on the tidal rise and fall of the oceans. At the moment, the mid-ocean tidal rise and fall far removed from the land masses is of order 1 m but if the Moon had been formed at a distance of around 40 000 km the tidal variation would have been of the order 100-1000 m. Large regions of the Earth s surface would have had a refreshed water supply every 4 h in the extreme cases of the model. Only well inland on the early land masses would there have been a dry environment, perhaps with fresh water replenishment. The early ideas of Darwin called for a Tittle warm pool to act... 

Hacking, Ian. The Emergence of Probability A Philosophical Study of Early Ideas about Probability, Induction and Statistical Inference. Cambridge Cambridge University Press, 1975. 

The concept oiprote hyle and its relation to early ideas about stellar evolution are discussed in S. F. Mason, Chemical Evolution (Oxford Clarendon Press, 1992). 

The contribution of Bergman to the knowledge of carbonic acid or aerial acid will be alluded to in connection with the development of Pneumatic Chemistry, and his extensive work on Chemical Affinity will be referred to in connection with the history of early ideas on that subject. 

As early as 1829, the observation of grain boundaries was reported. But it was more than one hundred years later that the structure of dislocations in crystals was understood. Early ideas on strain-figures that move in elastic bodies date back to the turn of this century. Although the mathematical theory of dislocations in an elastic continuum was summarized by [V. Volterra (1907)], it did not really influence the theory of crystal plasticity. X-ray intensity measurements [C.G. Darwin (1914)] with single crystals indicated their mosaic structure (j.e., subgrain boundaries) formed by dislocation arrays. Prandtl, Masing, and Polanyi, and in particular [U. Dehlinger (1929)] came close to the modern concept of line imperfections, which can move in a crystal lattice and induce plastic deformation. 

The first reported attempts of what was then called "absolute or total asymmetric synthesis" with chiral solid catalysts used nature (naturally ) both as a model and as a challenge. Hypotheses of the origin of chirality on earth and early ideas on the nature of enzymes strongly influenced this period [15]. Two directions were tried First, chiral solids such as quartz and natural fibres were used as supports for metallic catalysts and second, existing heterogeneous catalysts were modified by the addition of naturally occuring chiral molecules. Both approaches were successful and even if the optical yields were, with few exceptions, very low or not even determined quantitatively the basic feasibility of heterogeneous enantioselective catalysis was established. 

NOTE The water consumption figure also tends to provide some early idea of the potential revenues that the cooling system may produce and the viability of any future proposal. Daily water consumption, however, does not directly relate to the cost of providing biocides, the level of technical support services required, or indeed the type or degree of problems experienced. 

Nature found a direct path to perform this tandem fragmentation cyclization reaction in a stereospecific manner and under neutral conditions. Human creativity and luck aimed to uncover synthetic variants, which can compete efficiently with it. With the advent of mild, metal mediated cyclization reactions, the early idea of Grosheinz and Fisher [19a], who converted 6-deoxy-6-nitrohexoses to nitroinositols in a single step, matured to a general strategy of broad interest. 

In this chapter we have two goals. The first is to give a general picture of the sweep of history of VB theory. We restrict ourselves to ab initio versions of the theory or to versions that might be characterized as reasonable approximations to ab initio theory. Our second goal is to identify a few of the early ideas alluded to in the previous paragraph and see how they hold up when they are assessed with modern computational power. The list is perhaps idiosyncratic, but almost all deal with some sort of approximation, which generally will be seen to be poor. 

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