Ambiguity issues

In many cases, only the relative refractive index change is of interest and the range of refractive index variation is small so the phase shift is less than 2n. In this case, the phase ambiguity issue can be avoided. The relative refractive index change can be calculated based on the spectral shift of the interferogram. 

The product requirements are reviewed before the contract or tender is accepted. Product requirements are defined and communicated to the personnel responsible for the quality production. The unresolved and ambiguous issues are resolved and documented. The changes made in the product specifications are approved before execution of the order. Provisions are made for removing absolute drawings, procedures, work instructions, and specifications from all work areas to ensure that they are correctly authorized versions. Provisions are made for emergency changes necessary to prevent the production of nonconforming material. 

The issue of stereochemistry, on the other hand, is more ambiguous. A priori, an aldol condensation between compounds 3 and 4 could proceed with little or no selectivity for a particular aldol dia-stereoisomer. For the desired C-7 epimer (compound 2) to be produced preferentially, the crucial aldol condensation between compounds 3 and 4 would have to exhibit Cram-Felkin-Anh selectivity22 23 (see 3 + 4 - 2, Scheme 9). In light of observations made during the course of Kishi s lasalocid A synthesis,12 there was good reason to believe that the preferred stereochemical course for the projected aldol reaction between intermediates 3 and 4 would be consistent with a Cram-Felkin-Anh model. Thus, on the basis of the lasalocid A precedent, it was anticipated that compound 2 would emerge as the major product from an aldol coupling of intermediates 3 and 4. 

This area of reactivity has been the subject of excellent reviews (J5). Silyl enol ethers are not sufficiently nucleophilic to react spontaneously with carbonyl compounds they do so under the influence of either Lewis acids or fluoride ion, as detailed above. Few clear trends have emerged from the somewhat limited number of definitive studies reported so far, with ambiguities in diastereoisomeric assignments occasionally complicating the issue even further. 

Cometabolism merits, however, careful analysis since important metabolic principles underlie most of the experiments, even though confusion may have arisen as a result of ambiguous terminology. An attempt is therefore made to ignore semantic implications and to adopt a broad perspective in discussing this enviromnentally important issue. A pragmatic point of view has been adopted, and the following examples attempt to illustrate the kinds of experiments, which have been carried out under various conditions. 

Owing to the ambiguity surrounding the specified structure, the question might be asked why establish the network constraints in terms of vectors We might, for example, avoid the issue by choosing for a constraint either... 

The indicators were not tested for their suitability for taxometric analyses, but the authors reported that the composite was reasonably reliable (alpha =. 76). Whisman and Pinto performed a MAMBAC analysis, and both curves had a clear peak (although it was substantially shifted to the right), indicating a taxon with the base rate of about. 25. The actual base rate estimate was. 44, but the inconsistency between the shape and the estimate was probably due to high nuisance correlations. The authors, however, concluded that the inconsistency indicated dimensionality and did not pursue the issue further. It appears that this conclusion is mistaken. Although the plots are somewhat ambiguous, and there are only two of them, no firm inference can be drawn from this study. 

One way of copying with the ambiguity trade-off problem forced by Moyal s Identity (8) is to use a technique called Doppler processing. There are several issues associated with the accurate measurement of range and Doppler ... 

An important issue needs to be discussed next. Multiplying a column of C with any number and its corresponding row of A with the inverse of that number, does not affect the product CA and thus this factor is not determined at all. It can be freely chosen. Due to this multiplicative ambiguity, only the shapes of the concentration profiles (and component spectra) can be determined by any model-free method and only additional quantitative information allows the absolute determination of C and A. 

The nature and extent of /-orbital participation in the bonding of uranocene and other bis(cyclooctatetraenyl) actinides has never been satisfactorily established, although a good deal of effort has been expended on it. The X-ray structures do not resolve the issue because an ionically bonded model would also lead to a sandwich-type structure (for example, MgCp2 has essentially the same structure as ferrocene). Other physical techniques have been used, but the complexity of the electronic structures often leads to ambiguous interpretations. 

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