Structure preferred

Li FI, Winfreen N and Tang C 1996 Emergence of preferred structures in a simple model of protein folding Science 273 666-9... 

Li H, R Helling, C Tang and N Wingreen 1996. Emergence of Preferred Structures in a Simple Model of Protein Folding. Science 273 666-669. 

Stracture C, however, gives a much closer approximation to the observed chemical shift and thus may represent the preferred structure. The calculations also indicate a lengthened C(3)—C(4) (1.58A) and a contraction of the C(2)—C(3)—C(4) bond angle to 101.5°, both of which would be consistent with C—C hyperconjugatioiL... 

In a similar manner, ketones can react with alcohols to form hemiketals. The analogous intramolecular reaction of a ketose sugar such as fructose yields a cyclic hemiketal (Figure 7.6). The five-membered ring thus formed is reminiscent of furan and is referred to as a furanose. The cyclic pyranose and fura-nose forms are the preferred structures for monosaccharides in aqueous solution. At equilibrium, the linear aldehyde or ketone structure is only a minor component of the mixture (generally much less than 1%). 

If, however, is significantly larger than Ti (e.g. M = Ca, Sr, Ba), then the preferred structure is that of perovskite,Ca Ii03. This... 

Alkanes prefer structures that stagger bonds on adjacent tetrahedral carbons (see Chapter 5, Problem 1). However, steric repulsion can affect the relative energies of staggered conformations. 

Hexahydropyiido[ 1,2-d -1,3,4-oxadiazines 212 may formally exist in three con-formers (Scheme 138) [99ACSA213]. However, according to simple Hartree-Fock calculations, the trans conformer 212c is the energetically preferred structure. 

FIGURE 8.6 Example of a preferred structure. In this case, the dihydropyridine scaffold. 

FIGURE 8.8 Examples of preferred structures (2-tetrazole-biphenyls, panel a, and spriopiper-idines, panel b) yielding selective ligands for receptors. 

A case study on the operational improvement of a plasma etching unit in microelectronics fabrication ends the section. This case study illustrates that if similar preference structures are used in both types of formulation, identical final solutions are found when either categorical or continuous performance evaluation modes are employed. 

To conclude this section on systems with multiple objectives, we will consider a specific plasma etching unit case study. This unit will be analyzed considering both categorical and continuous performance measurement variables. Provided that similar preference structures are expressed in both instances, we will see that the two approaches lead to similar final answers. Additional applications of the learning methodologies to multiobjective systems can be found in Saraiva and Stephanopoulos (1992b, c). 

This solution is similar to the one found [see hyperrectangle defined by Eq. (36)] previously, when categorical performance evaluation variables were employed. Since the preference structures expressed under both... 

Additional studies documented in Saraiva and Stephanopoulos (1992b, c) also illustrate how the introduction of changes in preference structures is translated into displacements of the final uncovered solutions in the decision space. 

We define repeating unit isomerization as a process subsequent to polymerization, in which an intramolecular rearrangement of the repeating unit leads to a thermodynamically preferred structure ... 

In another application involving a study of biotin compounds for potential use in vivo, it was found that the preferred structures included molecules that contained PEG spacers to... 

It is also worthy to note that the most preferred structure (Figure 1.23 b) is characterized by a 0i value, 35°, not far from the 0i values, 160°, we... 

In Table VI the occurrence of each prism type is summed over all the samples listed in Tables III, IV and V for those prisms containing two, three, or four aluminum atoms. The two preferred structures containing three aluminum atoms and the twocontaining four aluminum atoms are marked by asterisks. 

Table VI. Total Numbers of Selected Prism Types Observed to Occur in Eight Samples of Faujasites with Si/Al Ratio 1.9 or Greater from Tables III and IV. Preferred Structures are Indicated by an Asterisk. ...

An analysis of published 29Si MASNMR data and new data reported here indicate that there are preferred structural... 

Free radical addition of HBr to buta-1,2-diene (lb) affords dibromides exo-6b, (E)-6b and (Z)-6b, which consistently originate from Br addition to the central allene carbon atom [37]. The fact that the internal olefins (E)-6b and (Z)-6b dominate among the reaction products points to a thermodynamic control of the termination step (see below). The geometry of the major product (Z)-(6b) has been correlated with that of the preferred structure of intermediate 7b. The latter, in turn, has been deduced from an investigation of the configurational stability of the (Z)-methylallyl radical (Z)-8, which isomerizes with a rate constant of kiso=102s 1 (-130 °C) to the less strained E-stereoisomer (fc)-8 (Scheme 11.4) [38]. 

Kobayashi and Naga, 1966) spectral data both indicate that [26a] is the preferred structure. 

For a B H X borane, the preferred structure is a closo structure with a preferred charge of 2 (there are (n + 1) pairs of skeleton electrons). 

Turning to l,7-C2BioHt2 (III-C2), the addition of electrons, again between the carbons, should produce the hypothetical intermediate (VI-N12) which would rearrange into the intermediate VII-N12 via a single dsd permutation and finally rearrange into IV-N12 (to accommodate carbon preference) Structure IV-N12 is thus exactly the same species as is produced from l,2-C2BioHi2. In this fashion the experi-... 

In contrast. Shore et al. 117a) have shown that the preferred structure of the isoelectronic Bgllxi is best described as related to B5H11 (I-A15), i.e., jii-BH3B5H8 with four 65 -, 66-, and 65-bridge hydrogens. 

In many respects the chlorine oxyfluorides resemble the chlorine fluorides. For example, they exhibit little or no self-ionization, but are amphoteric. With strong Lewis acids or bases they can form stable adducts. The tendency to form adducts was found (64) not to be so much a function of the relative acidity of the parent chlorine oxyfluoride but rather to depend on the structure of the amphoteric molecule and of that of the anion or the cation formed. The preferred structures are the energetically favored tetrahedron and octahedron. Consequently, a trigonal bipyramidal molecule, such as CIF3O (64), exhibits a pronounced tendency to form either a stable pseudotetrahedral cation or a pseudo-octahedral anion ... 

Isomerization polymerizations are polyaddition reactions where the propagating species rearranges to energetically preferred structures prior to subsequent chain growth. 

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