Constancy hypothesis

The central point of this hypothesis that functions VT(v) and E(v) are temperature-independent is actually based on apparent constancy of water density over the temperature range under study and this statement gives an important ability to predict spectrum shape at any temperature from the experimental IR or Raman spectra recorded at the only one temperature. 

In essence the development of the anlage hypothesis arose from Kossel s use of an embryological term as applied to protamine as a basic unit of protein structure, which Block in the 1930 s translated into the constancy of thearg-lys-his ratio in the serum proteins. He changed this in his most recent suggestion that this anlage was represented by... 

Independence of the fundamental equations from the nature of molecular attraction. All the results of this chapter have been deduced from the existence of a constant free energy in the surface a constant amount of work must be done to form each fresh unit of area. The work comes from the inward pull exerted by the underlying molecules on the surface layer its constancy from the mobility of the molecules and the assumption that the molecular attractions do not extend with sensible intensity to distances comparable with the mass of liquid considered, so that some part of the liquid is free from surface influences. This assumption excludes the hypothesis that the molecular attractions are gravitational, which is still sometimes suggested if the attractions diminished as the inverse square of the distance, the surface tension of the oceans would be far greater than that of a cupful of water, because the distant parts would act with sensible effect. Any theory of molecular attraction, in which the forces practically vanish at small distances, will harmonize with the results of this chapter. 

Other foreign ions in the anhydrous phases, and the extents to which they tend to pass into the pore solution on hydration. If the C-S-H constituent of the gel is assumed to have the same Ca/Si ratio as in calcium silicate pastes, one would expect that the ratio would be about 1.9 (Si/Ca = 0.53) in a gel with Al/Ca = 0.07. This agrees with some, but not all, of the data in Table 7.1. The hypothesis might explain the observations of Rayment and Lachowski (R29) on the bimodal distribution of Ca/Si ratio in the in situ gel and the relative constancy of its Ca/(Si + Al) ratio. It probably offers the most satisfactory explanation of the existing data but needs to be further tested. Continued studies by TEM of ion-thinned sections may be expected to yield valuable data in this respect. 

The correlation between anaesthetic potency and lipid solubility shown in Fig. 2.10 is valid for most inhaled anaesthetics and the product MAC X oil/gas partition coefficient (which should of course be a constant) varies by only a factor of 2 or 3 for potencies ranging over 100 000-fold. This constancy implies that inhaled anaesthetics act in the same manner at a specific hydrophobic site (the so-called unitary theory of anaesthesia). This has been challenged by more recent work that has identified compounds, including alkanes and poly-halogenated and perfluorinated compounds, which do not obey the Meyer- Overton hypothesis. It has been suggested that a contributory cause of deviation from this hypothesis may be the choice of lipid to represent the anaesthetic site of action of these compounds, implying that there may be multiple sites of action for inhaled anaesthetics. 

The growing radicals are very reactive intermediate species that conform to what in chemical kinetics is called a quasi-steady state (QSS) or stationary state hypothesis [11, 12]. This means that the rate of formation and consumption of that species become nearly equal in a very short timescale as a consequence, the absolute value of the derivative becomes very small and negligible compared with the derivatives of other species in the system (e.g., d[M]/df) and for practical purposes can be approximated as zero. Note, however, that this does not imply constancy of the value of [P], as sometimes interpreted by some authors, but this will be more clear later. By making the QSS approximation in Equation 4.5... 

Kekule had never publicly asserted the constancy of an atom s atomicity in the explicit manner that Foster had done, but in fact the constancy of atomicity had always been fundamental for him. Throughout his textbook Kekule avoided any suggestion that (e.g.) carbon could be diatomic, or nitrogen pentatomic. He was thus quite at a loss to explain the constitution of carbon monoxide, and his depiction of ammonium chloride required the auxiliary hypothesis of "molecular compounds" (two molecules held together by an unspecified attraction weaker than that of true chemical combination). So Foster must have been a little embarrassed to see the doctrine of constant atomicity ascribed to him when he had obviously imbibed it from his German mentor. He wrote Kekule, "What do you think of Erlenmeyer s [paper] 1 think it is the best statement I have seen of the essential questions at issue between the old and new schools. It was very insane of him, all the same, to mention my name in it." ... 

Although the rectification component of the master and slaves hypothesis provides a mechanism to explain the constancy of nucleotide sequence within a set of master and slaves, it cannot be used to explain the constancy of sequences among species or individuals. Any mutation in the master copy would remain and become transferred to aU slave copies after the first matching process. There is growing evidence to indicate that the sequence of 5S RNA is remarkably similar at all evolutionary levels. 5S RNA molecules may be identical in four species of mammals (Williamson and Brownlee, 1969), and the sequence similarities between E. coli and human 5S RNA are also quite extensive (Brownlee et al., 1968 Forget and Weisman, 1969). Therefore, even if the master and slaves hypothesis is invoked to explain the homogeneity of the 5S RNA in man, where... 

Oxidative addition to Mn(CO)j is also photoactivated. A competition study of substitution versus oxidative addition gave the results shown in Scheme 7.11. The constancy of the oxidative addition yield suggests that this path may involve an ion pair. Unfortunately, the concentration of PPh4+ was not varied to test this hypothesis. 

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