The Ambiguities

The GRIND method assumes that the couples of nodes selected to represent a given distance in different compounds do actually represent the same kind of potential interaction with the receptor. This is often not true, for two reasons, as represented in Fig. 6.7. In the first situation (Fig. 6.7 (a)) all the compounds in the series contain alternative sites representing exactly the same distance and from which the candidate couples can be selected. Since the criteria for selecting the nodes is based only on the value of the MIF energy product, different sites can be selected in different compounds. The result is that the 3D graphic shows a non-consistent representation of the sites and can look messy. 

In the second possible scenario, represented in Fig. 6.7 (b), the alternative sites represented by the same GRIND variable are not present in all the compounds in the series. Actually, the same variable represents two different and unrelated positions of the compound that cannot be expected to produce the same interactions with the receptor. These variables can be considered to be the sum of two separate ones, each one representing separate pieces of information about the compound, but confounded into a single variable. 

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This example of high and low pressure also shows the ambiguities of these tenns in science. All these pressures are essentially constant in tenns of tire range of pressures encountered in nature. From negative pressures in solids under tension (e.g., on the wall of flask confining a fluid), pressure in nature increases... 

To eliminate the ambiguities in the subject of electricity and magnetism, it is convenient to add charge q to the traditional I, m and t dimensions of mechanics to form the reference dimensions. In many situations permittivity S or permeabiUty ]1 is used in Heu of charge. For thermal problems temperature Tis considered as a reference dimension. Tables 2 and 3 Hst the exponents of dimensions of some common variables in the fields of electromagnetism and heat. 

Whereas this two-parameter equation states the same conclusion as the van der Waals equation, this derivation extends the theory beyond just PVT behavior. Because the partition function, can also be used to derive aH the thermodynamic functions, the functional form, E, can be changed to describe this data as weH. Corresponding states equations are typicaHy written with respect to temperature and pressure because of the ambiguities of measuring volume at the critical point. 

The main reaction of this type has been the reductive cyclization of nitropyridine derivatives carrying an o-amino ester or o-aminocarbonyl substituent. These cyclize in situ via the o-diamino derivative to give pyridopyrazines of known constitution, either for establishment of structure of products obtained in the ambiguous Isay synthesis (see Section 2.15.15.6.1), or in the synthesis of aza analogues of biologically active molecules. 

The ambiguity of the total pressure effect can be seen by a comparison of the gas-phase- and liquid-phase-controlled cases when the gas phase controls, the liquid-phase resistance is negligible and Kg( = K npf is independent of the total pressure. For this case the coefficient K g< is inversely proportional to the total system pressure as shown in Eq. (14-66). On the other hand, when the liquid phase controls, the correct equation is... 

For both a sphere of diameter d and eube of eharaeteristie side length L,F = 6. Note the ambiguity of using F alone to eharaeterize partiele shape faetors. 

Since the numerical estimate G r) is necessarily incomplete and inaccurate the inversion is not possible without any ambiguity. Gubernatis and coworkers now suggested resolving the ambiguity by choosing the most probable A consistent with the data G i.e., they chose the A that maximizes the conditional probability P[A G]. This is justified since A has the... 

The tautomeric structure leads to ambiguities in the nomenclature of compounds in this series. Thus, 5-methyl- and 6-methylbenzo-furoxan denote two different molecules which, because of their interconversion, cannot be isolated separately at normal temperatures. Throughout this review, when we intend to refer to the ambiguous mixture, we shall use the system employing the lowest numbers. The above methyl derivative, for example, will be described as 6-methyl-benzofuroxan regardless of the form adopted in the crystal. When a... 

The well-known reaction of a-alkyl-/3-ketoaldehydes and hydroxyl-amine has been applied to the elucidation of the structure of formyl-ation products of ketones the conclusions are, however, open to question. Some workers attempted to overcome the ambiguity of the reaction of j8-ketoaldehydes and hydroxylamine, which results in a mixture of 3- and 5-monosubstituted isoxazoles and thus considerably lowers the preparative value of the method, by using various derivatives of yS-ketoaldehydes, especially those of their enolic forms (jS-substituted vinylketones) investigated by Kochetkov et al. The use of readily available /3-chlorovinylketones (12) in the reaction with hydroxylamine represents a rather useful preparative method to synthesize monoalkylisoxazoles but again gives rise to a mixture of 3- (13) and 5-alkylisoxazoles (14). This is due to the attack... 

Sulfonation of isoxazoles has been less extensively studied than nitration. This is possibly due to the difficulty encountered in isolating isoxazolesulfonic acids and to the ambiguous reaction course. 

The reason for the ambiguity in the form of the equations we use for expressing Kw, Ka, and Kb is that we do not know the nature of the species present in solution. We do not know the extent to which H+ is hydrated to form H30+ according to the reaction... 

The ambiguity results from the failure to recognize that the Rossini statement applies to the thermodynamic equilibrium constant, As we have already noted, the other forms that we have derived do depend upon the pressure. For example, for a gas phase reaction, Kp is related to K by equation (9.11)... 

When a solution of Pu(VI) is subjected to the 24 hr. irradiation the bulk of the Pu has been reduced to the Pu(III) oxidation state. There exists the ambiguity that residence on the column may cause some reduction of Pu(VI) Pu(V) and... 

To avoid the ambiguity associated with several ways of reporting a reaction rate, we can report a single unique average rate of a reaction without specifying the species. The unique average rate of the reaction a A + b > r C + d D is any of the following four equal quantities ... 

If line managers become mentors, this can also reduce the clarity of roles. In fact, most mentoring schemes that tried this approach to providing mentors had to pull back because the line boss was imable to cope with the ambiguity of roles. Being an objective coididante on the one hand and having to appraise the employee on the other proves too difficult to reconcile. 

The ambiguity over the sign in the denominator is due to the fact that both versions, (n,- and (n, -i- 1),47A9 are found in the literature ( + resp. behind the equation number (1.22) indicate the sign used in the denominator). Equation (1.22-) appears to be correct Eq. (1.22-I-) might have arisen from transcription errors. 

Haim S has commented on the ambiguities inherent in the interpretation of rate laws, using the V(IIl)-l-Cr(II) reaction as an example. The experimental rate law found by Espenson ... 

They avoid the ambiguities resulting from the presence of xenobiotics in the original soil or sediment. 

Laboratory experiments using natural consortia under defined conditions have particular value from several points of view. They are of direct environmental relevance, and their use minimizes the ambiguities in extrapolation from the results of studies with pure cultures. They provide valuable verification of the results of studies with pure cultures and make it possible to evaluate the extent to which the results of such studies may justifiably be extended to the natural environment. It should be appreciated, however, that in some cases the habitats from which the inoculum was taken might already have been exposed to xenobiotics so that natural enrichment (preexposure) could already have taken place. This has been discussed in Chapter 4. 

The disadvantage for gases is the ambiguity that is related to the lack of accurate threshold values. The values that are mentioned here come from examples found in the Dow publication. 

When analysing the previous table, it shows the ambiguity of NFPA reactivity codes vis-a-vis instability. It is not so much an instability code but rather, like its name indicates, a code related to dangerous chemical reactions. Degrees 3 and 4 are the only ones that are more or less usable for defining an instability level, with the exception of ethylene oxide. So, even ethylene oxide s main hazard is not its explosive decomposition but its very violent polymerization caused by catalytic impurities (see chapter 6). 

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