Speculative Generalities

It is hard to summarize the present state of development of the subject and harder to predict probable lines of development. It is easier to point out a few things that ought to be done. 

On the achievement side it is probably fair to state that we have an 

Fourthly, it would seem that there is a need for further improvement 

There are two areas in which it seems that substantial advances could be made even on the basis of first-order theory. These are the field of spontaneous reactions where isotope effects are sometimes large and where the existence of many closely related systems makes it likely that a useful framework of generalizations could be found. The second field is that of strictly non-aqueous solvent systems where a comparison of solvent isotope efFects with those in aqueous solution is likely to throw light on essential differences in chemistry. 

As a mechanistic tool in the investigation of acid- or base-catalysed reactions in aqueous solution, the measurements in isotopically mixed solvents are most useful for reactions where a certain amount is already known about the mechanism. In particular, the study of mixed solvents is also a good deal more informative whenever it is possible to measure product isotope effects in addition to rate isotope effects. In such cases (and A-Sb2 reactions spring to mind as a good example) solvent isotope effect studies can add considerably to the detailed picture of a transition state. The phenomena are as yet less suited to the ah initio assignment of reaction mechanism, such as the decision between weak nucleophilic participation of water in an acid-catalysed reaction and an A-l mechanism, when no information beyond the kn-n relation is available. For these reasons it is likely that mechanistic investigation by this method will increasingly be directed towards systems where both rate and product isotope effects are obtainable. 

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A], Alkoxide/oxide compounds of the speculated general formula BiO(OOCR) are formed by dissolving Bi203 in the carboxylic acid, followed by dilution and distillation of the excess acid (59). The compounds were characterized by elemental analysis and preliminary X-ray diffraction data. 

By putting together all of the ideas discussed above, we can propose a speculative general scheme of protein folding as suggested by the properties of the final structures. 

There are no answers to these questions, and therefore in this section we will try to discuss only the very limited data available at the present time. In conclusion a more or less speculative general scheme will be presented. 

Si-C-N-0 and Si-C-N(O) fibers are amorphous (Figure 1) but the molecular composition is still a matter of speculation. Generally speaking, they can be depicted as consisting of a continuum of tetrahedral units wherein silicon is surrounded by carbon, nitrogen and oxygen atoms the latter are connected by their summits. Furthermore, some free carbon, which results from the pyrolysis of the pendent methyl groups, is usually present as BSUs. 

It is well known that, whereas the partieles in homogeneous liquid-fluidized beds usually exhibit eonsiderable random motion, this is not the ease for gas-fluidized partieles, whieh are much more firmly held together in suspension. This difference in behaviour has been the subject of long-running imaginative speculation, generally invoking the presence of extraneous, non-fluid-dynamic interactions between gas-fluidized particles, which are supposedly absent in hquid systems (Martin, 1983). 

When g = 1 the extensivity of the entropy can be used to derive the Boltzmann entropy equation 5 = fc In W in the microcanonical ensemble. When g 1, it is the odd property that the generalization of the entropy Sq is not extensive that leads to the peculiar form of the probability distribution. The non-extensivity of Sq has led to speculation that Tsallis statistics may be applicable to gravitational systems where interaction length scales comparable to the system size violate the assumptions underlying Gibbs-Boltzmann statistics. [4]... 

Several alternative attempts have been made to quantify Lewis-acid Lewis-base interaction. In view of the HSAB theory, the applicability of a scale which describes Lewis acidity with only one parameter will be unavoidably restricted to a narrow range of struchirally related Lewis bases. The use of more than one parameter results in relationships with a more general validity ". However, a quantitative prediction of the gas-phase stabilities of Lewis-acid Lewis-base complexes is still difficult. Hence the interpretation, not to mention the prediction, of solvent effects on Lewis-add Lewis-base interactions remains largely speculative. 

There is a general relationship between metal price and terrestrial concentration. Metals present at relatively high concentrations, in the earth s cmst, such as iron and aluminum, are the least expensive rare metals such as gold and platinum are the most valuable. This situation has existed for gold and silver valuation for centuries. The amount of silver in the earth s cmst is approximately 20 times that of gold, and the historical price ratio for gold and silver varied between 10 and 16 for over 3000 years. Since 1970 that price ratio has been strongly affected by market forces and investor speculation. 

Thiostrepton family members are biosynthesized by extensive modification of simple peptides. Thus, from amino acid iacorporation studies, the somewhat smaller (mol wt 1200) nosiheptide, which contains five thiazole rings, a trisubstituted iadole, and a trisubstituted pyridine, is speculated to arise from a simple dodecapeptide. This work shows that the thiazole moieties arise from the condensation of serine with cysteiae (159,160). Only a few reports on the biosynthesis of the thiostrepton family are available (159,160). Thiostrepton is presently used ia the United States only as a poly antimicrobial vetetinary ointment (Panalog, Squibb), but thiazole antibiotics have, ia the past, been used as feed additives ia various parts of the world. General (158) and mechanism of action (152) reviews on thiostrepton are available. 

The origin of the remarkable stereoselectivities displayed by chiral homogeneous catalysts has occasioned much interest and speculation. It has been generally assumed, using a lock-and-key concept, that the major product enantiomer arose from a rigid preferred initial binding of the prochiral olefin with the chiral catalyst. Halpren 48) on the basis of considerable evidence, reached the opposite conclusion the predominant product enantiomer arises from the minor, less stable diastereomer of the olefin-catalyst adduct, which frequently does not accumulate in sufficient concentration to be detected. The predominant adduct is in essence a dead-end complex for it hydrogenates at a much slower rate than does the minor adduct. 

For the deformation of NiAl in a soft orientation our calculations give by far the lowest Peierls barriers for the (100) 011 glide system. This glide system is also found in many experimental observations and generally accepted as the primary slip system in NiAl [18], Compared to previous atomistic modelling [6], we obtain Peierls stresses which are markedly lower. The calculated Peierls stresses (see table 1) are in the range of 40-150 MPa which is clearly at the lower end of the experimental low temperature deformation data [18]. This may either be attributed to an insufficiency of the interaction model used here or one may speculate that the low temperature deformation of NiAl is not limited by the Peierls stresses but by the interaction of the dislocations with other obstacles (possibly point defects and impurities). 

The introductory chapter of this book identified four basic motivations for studying CA. The subsequent chapters have discussed a wide variety of CA models predicated on the first three of these four motivations namely, using CA as... (1) as powerful computational engines, (2) as discrete dynamical system simulators, and (3) as conceptual vehicles for studying general pattern formation and complexity. However, we have not yet presented any concrete examples of CA models predicated on the fourth-and arguably the deepest-motivation for studying CA as fundamental models of nature. A discussion of this fourth class of CA models is taken up in earnest in this chapter, whose narrative is woven around a search for an answer to the beisic speculative question, Is nature, at its core, a CA "... 

The fact that (Z)-lithium enolatcs generally display a higher simple diastereoselectivity giving. vyn-aldols compared to (E)-enolates affording nn/i-aldols is a challenge to the Zimmer-man-Traxler model, and has become the source of extended speculation. 

A vast range of symmetrical and unsymmetrieal 1,6-diene monomers has now been prepared and polymerized and the generality of the process is well established.98,1 A summary of symmetrical 1,6-dienc structures, known to give cyclopolymerization, is presented in Table 4.4 In many cases, the structure of the repeat units has not been rigorously established. Often the only direct evidence for cyclopolymerization is the solubility of the polymer or the absence of residual unsaturalion. In these cases the proposed repeat unit structures are speculative. 

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