Ambiguity heterogeneous

The foregoing classification is not without ambiguity. For example, it is common practice to call the reaction A - B +C° (see Fig. 6-1) induced by decreasing the temperature a phase transformation. The similar (peritectoid) reaction C = a+fi (Fig. 12-2) induced by a temperature increase, however, is named a decomposition reaction. In addition, the isothermal reaction AO = A+j02, which occurs if the intensive variable fio2 is decreased so that AO decomposes, is called a metal oxide reduction. It is thus categorized as a genuine heterogeneous solid state reaction (the... 

Thus, mechanistic studies of autoxidations in heterogeneous systems suffer from ambiguities similar to their homogeneous counterparts. There is no unequivocal evidence for the direct reaction of chemisorbed oxygen with hydrocarbon substrates under mild conditions. Catalysis of autoxidations proceeding by reaction with intermediate hydroperoxides is a more likely explanation. 

The purpose of the present Section is twofold first to draw attention to the problems and ambiguities which have arisen in connection with the reporting of gas adsorption (physisorption) data and second to formulate proposals for the standardization of procedures and terminology which will lead to a generally accepted code of practice. It does not aim to provide detailed operational instructions or to give a comprehensive account of the theoretical aspects of physisorption. The determination of the surface area of supported metals is not dealt with here - despite the importance of this topic in the context of heterogeneous catalysis - since this necessarily involves chemisorption processes. 

It should, however, be borne in mind that the depth sensitivity varies with the element. Moreover, in the case of a heterogeneous sample, the response to the elements present varies dramatically depending on their depth an clement solely present in the first atomic layer will be seen more than the same element present in greater proportion at a depth of several times the mean free path. This highlights an ambiguity in the definition of the notion of surface which poses significant problems when interpreting quantitative results. 

The other kinetic method [153], in which the rate constant of the first order approach to equilibrium is determined, provides ambiguous results because of uncertainty in the size of the exchangeable pool of nucleotides. The natural log plot of the percentage equilibrated is not linear regardless of the value chosen as 100% equilibrated. This is probably due to heterogeneity of the exchangeable in-tramitochondrial pool. The intramitochondrial adenine nucleotide pool is composed of ATP, ADP and AMP. AMP is not a substrate of the carrier, yet radioactive ATP... 

The steady state luminescence from naturally occurring macromolecules has been extensively studied in the past to investigate the effect of li t on the properties of biological sterns and to reveal some aspects of conformation and stmcture (see reviews ° )). Certainly much useful information has been obtained about the type and behaviour of excited state of biopolymers from such measurements. However, the complex and heterogeneous nature of these systems have often led to ambiguities in interpretation of the results. The fluorescence from proteins, for example, has largely been attributed to the constituent aromatic amino acids phenylalanine, tyrosine and tryptophan. Many workers have used the observation that the emission characteristics of these amino acids are sensitive to the environment sur-... 

The observation of compensation behaviour for the decompositions of a group of comparable reactants under similar conditions is ambiguous because such behaviour could be explained either (following the approach used in with heterogeneous catalysis [59]) as the result of relatively small crystal structural differences in the rate determining bond rupture step, or (as above) by differences in the physical conditions existing within each individual reactant sample. 

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