Guided transformations

If the model parameters are highly correlated, one option is to reparameterize the model into a more stable form, which is often of a more simpler form. Simonoff and Tsai (1989), and later Niedzwiecki and Simonoff (1990), call these model transformations guided transformations and the idea is as follows. Since collinearity implies that at least one column of J is close to or nearly a linear combination of the other columns, i.e., using Column 1 as an example,... 

Stereochemical strategies The transform selection is guided by stereocenters that have to be removed in retrosynthesis. The user has to select strategic stereo-centers. 

Application Guide for voltage transformers Specification for voltage transformers General requirements 4201/1991 4146/1991 BS 7625/1993 BS 7629/1995... 

The logical application of retrosynthetic analysis depends on the use of higher level strategies to guide the selection of effective transforms. Chapters 2-5 which follow describe the general strategies which speed the discovery of fruitful retrosynthetic pathways. In brief these strategies may be summarized as follows. 

The information obtained by this preliminary analysis can be used not only to set priorities for the various possible Diels-Alder disconnections, but also to pinpoint obstacles to transform application. Recognition of such obstacles can also serve to guide the search for specific retrosynthetic sequences or for the highest priority disconnections. At this point it is likely that... 

The following sequences of transforms can be derived with the help of strategic guides 1-8 listed above. 

Transform-based Strategy. A strategic guide for retrosynthetic analysis in which the application of a particular powerfully simplifying transform becomes a goal. 

The successful implementation of this strategy is shown in Scheme 4. In the central double cyclization step, the combined action of palladium(n) acetate (10 mol %), triphenylphosphine (20 mol %), and silver carbonate (2 equiv.) on trienyl iodide 16 in refluxing THF results in the formation of tricycle 20 (ca. 83 % yield). Compound 20 is the only product formed in this spectacular transformation. It is noteworthy that the stereochemical course of the initial insertion (see 17—>18) is guided by an equatorially disposed /-butyldimethylsilyl ether at C-6 in a transition state having a preferred eclipsed orientation of the C-Pd a bond and the exocyclic double bond (see 17). Insertion of the trisubstituted cycloheptene double bond into the C-Pd bond in 18 then gives a new organopal-... 

Using the Toolbox, Transform, and Identify functions, the analyst can perform many general analyses such as a Tg of a DSC run or the weight loss in a TGA run. For Instance, to identify a TGA weight loss the operator could draw two guide lines on the screen, use the Identify function to measure the displacement, and the report generator to output the displacement and units. 

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