Experimental Facts

Now, as we have said, there is only at most 20% Cr in the alloy, and the alloy behaves only partly as if it were protected by Cr203. In fact, experimentally, we find that 20% Cr increases the time for a given metal loss by only about ten times, i.e. the time taken to lose 0.1 mm at blade working temperature becomes 600 X 10 hours = 6000 hours rather than 10 hours. 

The results of the present work are summarized in Figure 10. As far as the initial part of the reaction is concerned, we have found that the associative mechanism is slightly more favored than the dissociative one. However, the small energy difference found between the two mechanisms and the possible effect of the solvent, which has not been included in the present study, precludes formulation of a definitive conclusion on the most effective reaction pathway. Most likely depending on the reaction conditions and the initial reactants the two mechanisms can be operative. In fact, experimental evidence in favor of both the dissociative [37, 38] and associative [41] mechanisms has been provided. 

Since low energy usually means stability, it is reasonable that the most stable energy state (ground state) for any atom is one in which its electrons are in the lowest possible energy level. As you know, this is the Is orbital (n = 1). However, the electrons of most atoms are not packed into this orhital. In fact, experimental evidence shows that only two atoms have all their electrons in the Is orhital hydrogen and helium. To explain how and why this is the case, you must consider another property of the electron. 

Work in groups of three. Equation 3.75 can be re-written to reflect the fact experimental determination of polymerization rates typically yield a single rate constant, called the apparent rate constant, kapp, which is a composite of the three different rate constants, ki, kt and kp. If we call the rate of disappearance of monomer concentration, —d[M /dt the rate of polymerization, Rp, then we can rewrite Equation 3.75 as... 

An approximate analytical solution of Eq. (2.77) can be found, and, in fact, experimental data correspond to the condition ... 

The bands in an IR spectrum have not just positions ( frequencies , denoted by various wavenumbers), but also intensities. IR intensities present considerably more difficulties in their measurement and theoretical calculation than do frequencies, and in fact experimental intensities are not routinely quantified, but are commonly merely described as weak, medium, or strong. To calculate an IR spectrum for visual comparison with experiment it is desirable to compute both... 

However, this diagram makes it appear that ozone has two different kinds of bonds, single and double. In fact, experimental data shows that ozone has two identical bonds. At this point in the reasoning, if we write the other Lewis possibility for ozone, it will be... 

Another source of deviations to the ideal behavior is the smoothness of the channel surface which, in reality, is hardly perfect. The surface quality affects substantially both retention and zone dispersion. Smith et al. [223] illustrated this fact experimentally for Th-FFF. Dilks et al. [458] studied experimentally the effect of sample injection and flow pattern on the zone shape inside the channel by performing measurements in a transparent channel and photographing the colored zones formed under various conditions of injection, flow, and geometric channel irregularities. One important result was that even apparently minor channel irregularities can give rise to considerable distortion of the zone formed. In Fl-FFF, the membrane is the critical parameter as ideally it has to fulfill the requirements of pressure and mechanical stability, even surface, uniform pore size, inert behavior with respect to solvent and samples and sufficient counter pressure to achieve smooth and uniform flow rates. A membrane fulfilling all the above requirements does not exist so that the choice of a membrane for Fl-FFF is always a compromise and depends on the analytical problem. In addition, for all other FFF techniques, the surface quality, in particular the smoothness of the channel accumulation wall, substantially affects both retention and zone dispersion. Smith et al. [223] illustrated this fact experimentally for Th-FFF. 

An important question is Are the cytokinins present in tRNA incorporated intact into tRNA, in a manner like all other nucleoside triphosphates that are polymerized in the synthesis of tRNA, or does the presence of the cytokinins result from alkylation (transfer of isoprenoid side chain) of existing adenosine moieties already present in preformed tRNA In fact, experimental evidence has been reported for both processes (21,22). But the amounts of actual incorporation were very small, and the observed incorporation may be merely the result of transcriptional errors. Meanwhile, the evidence for cytokinin moieties in tRNA arising by alkylation of specific adenosine residues in preformed tRNA is conclusive (23). 

If one wished to refer all quantities to a state which is in fact experimentally accessible, one could obtain a form analogous to (3.1.4a) by setting f° - 1, so that Eq. (3.1.2) reads... 

For most practical conditions, a comparison of k and k from Equations (4) and (5) would suggest that the principal resistance to transfer resides at the outer cloud boundary. However, when (a), (b) and (c) are taken into account, this is no longer the case. In fact, experimental evidence (e.g. 30,31,32) indicates strongly that the principal resistance is at the bubble/ cloud interface. With this in mind, it is probably more sensible to include the cloud with the dense phase (as in the Orcutt (23, 27) models) rather than with the bubbles (as in the Partridge and Rowe (37) model) if a two-phase representation is to be adopted (see Figure 1). If three-phase models are used, then Equations (2) and (5) appear to be a poor basis for prediction. Fortunately the errors go in opposite directions. Equation (2) overpredicting the bubble/cloud transfer coefficient, while Equation (5) underestimates the cloud/emulsion transfer coefficient. This probably accounts for the fact that the Kunii and Levenspiel model (19) can give reasonable predictions in specific instances (e.g.20),... 

In many molecules, the choice of which atoms are connected by multiple bonds is arbitrary. When several choices exist, all of them should be drawn. For example, as shown in Figure 3-1, three drawings (resonance structures) of C03 are needed to show the double bond in each of the three possible C — O positions. In fact, experimental evidence shows that all the C — O bonds are identical, with bond lengths (129 pm) between double-bond and single-bond distances (116 pm and 143 pm respectively) none of the drawings alone is adequate to describe the molecular structure, which is a combination of all three, not an equilibrium between them. This is called resonance to signify that there is more than one possible way in which the valence electrons can be placed in a Lewis structure. Note that in resonance structures, such as those shown for in Figure 3-1, the electrons are drawn in different places but the atomic nuclei remain in fixed positions. 

In fact, experimental results indicate that the statistical distribution is seldom followed. With trans reactants, both acid aquation and base substitution reactions result in a mixture of isomers the fractions of cis and trans depend on the retained ligand and range from 100% trans to 94% cis, as shown in Tables 12-8 and 12-9. Of course, any... 

In fact experimentally the viscosity of dilute polymer solutions follows... 

In fact, experimental studies show that the static layer is actually maintained up to some finite, critical value of 7) — To, but beyond this point there is an abrupt and spontaneous transition to convective motion. The most clearcut evidence of this transition, in addition to flow visualization, is an abrupt increase in the slope of the heat transfer rate versus the temperature difference i - To. It is notable that the abrupt transition from conduction to convection occurs, for a given fluid and a given fluid layer depth, at a value of 1 - To that is independent of any precautions that may be taken to isolate the system from external disturbances. This suggests that the static fluid layer is unstable to disturbances of arbitrarily small magnitude. 

Experiments using site-directed mutagenesis and computational modelling have shown that oximes appear to have preferred entry routes for attack of the phosphyl moiety and that side-chain substitutions of the active site gorge of AChE may significantly alter the reactivity (Radic and Taylor, 1999 Taylor el. al., 1999 Wong et al., 2000 Kovarik el. al., 2004). Hence, marked species differences in reactivatability of phosphylated AChE towards oximes are to be expected. In fact, experimental data support the assumption of substantial species differences in reactivation of OP-inhibited AChE... 

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