Specific Observations

A striking example of the importance of narrowing the focus in research, which is what the concept of the parepisteme really implies, is the episode (retailed in Chapter 3, Section 3.1.1) of Eilhard Mitscherlich s research, in 1818, on the crystal forms of potassium phosphate and potassium arsenate, which led him, quite unexpectedly, to the discovery of isomorphism in crystal species and that, in turn, provided heavyweight evidence in favour of the then disputed atomic hypothesis. As so often happens, the general insight comes from the highly specific observation. 

The most direct evidence that stereoelectronic effects are also important in these reactions follows from the specificity observed in hydrogen atom abstraction from conformationally constrained compounds,18 60 C-H bonds adjacent to oxygen113"118 or nitrogen110 and which subtend a small dihedral angle with a lone pair orbital (<30°) are considerably activated in relation to those where the dihedral angle is or approaches 90°. Thus, the equatorial H in 20 is reported to be 12 times more reactive towards /-butoxy radicals than the axial 11 in 21.115... 

The transition state for disproportionation requires overlap of the p C—H bond undergoing scission and the p-orbital containing the unpaired electron.18 This requirement rationalizes the specificity observed in disproportionation of radicals 29 (Section 1.4,2) and provides an explanation for the persistency of the triisopropylmcthyl radical (33) and related species (Section 1.4.3.2).166 In the case of 33, the P-bydrogens are constrained to lie in the nodal plane of the p-orbital due to stcric buttressing between the methyls of the adjacent isopropyls. 

Table 3.8 Specificity Observed in the Reactions of Oxygen-Centered Radicals with Various Monomers at 60 °C...

Once a model has been fitted to the available data and parameter estimates have been obtained, two further possible questions that the experimenter may pose are How important is a single parameter in modifying the prediction of a model in a certain region of independent variable space, say at a certain point in time and, moreover. How important is the numerical value of a specific observation in determining the estimated value of a particular parameter Although both questions fall within the domain of sensitivity analysis, in the following we shall address the first. The second question is addressed in Section 3.6 on optimal design. 

The specificity of several of the enzymes identified in the 4S pathway of different organisms has been studied. In case of the DBT desulfurizing enzymes, little difference is expected in the specificity of the enzymes, say DszA, from different Rhodococcus strains found to date. This is essentially because the DNA sequence for the enzymes investigated so far has been the same. The difference in the specificity observed with whole cell assays is essentially due to the differences in substrate intake via the cell membrane and not necessarily due to a difference in the intrinsic enzyme specificity. It has been found that while isolated enzyme DszC (from KA2-5-1) can desulfurize up to 4,6 dipropyl DBT, whole cells cannot, indicating substrate transport as limiting factor. 

Horned larks (Eremophila alpestris) had brain cholinesterase activity levels depressed 22% at 3 days posttreatment, and 8% at 16 days. No sick or dead birds found however, no systematic searches were made for the small lark carcasses, nor were specific observations for toxic signs conducted (McEwen etal. 1986)... 

The analysis of the cytochrome crystal structures reveals extensive differences among the mammalian and the human CYPs that may reflect the structural flexibility of these enzymes and therefore the broad substrate specificity observed. In general, the secondary elements and the overall structure of the CYP are conserved. Nevertheless, it seems that in most enzymes, the most flexible regions are located between the F-G helixes and the B-C loop. For example in the CYP2B4 apoprotein (lpo5) the... 

Unless two profiles are compared with a single observation or a summarizing index, the comparison involves a set of metrics these may be specific observation points such as Fw, F2q, and F3Q, fitted function parameters such as a and [> of a Weibull distribution, or estimated semi-invariants AUC, MDT, and VDT. In this situation, each metric can be compared separately, resulting in a manifold of independent local comparisons alternatively, all relevant metrics may be summarized in a common global model by means of multi-variate techniques (16). 

The fundamental perspective of this review is that simulation results are not absolute, but rather are intrinsically accompanied by statistical uncertainty [4-8]. Although this view is not novel, it is at odds with informal statements that a simulation is "converged." Beyond quantification of uncertainty for specific observables, we also advocate quantification of overall sampling quality in terms of the "effective sample size" [8] of an equilibrium ensemble [9,10]. 

Honeyman147 reported the synthesis of methyl 2,3-anhydro-/3-L-lyxopyranoside, and claimed that, on alkaline hydrolysis, this gives a 2 1 ratio of L-xyloside L-arabinoside, but these results could not be substantiated by Buchanan and R. Fletcher,68 who recorded different constants for the epoxide and for the disulfonic ester claimed147 to be the starting material for its synthesis. The same epoxide has been synthesized by Reist and coworkers,160 and its properties are in agreement with Buchanan and Fletcher s results. Ethyl or methyl 3,4-anhydro-/3-L-ribopyranoside undergoes substitution at C-4 in all the reactions thus far studied. Neither half-chair conformation would seem to be clearly favored, but the specificity observed can be rationalized by considering the steric and polar interactions that may arise in the transition state substitution at C-3 in conformation 58 would involve marked interactions between the nucleophile and... 

Although little information is available on the stability of corrensite in pelitic sedimentary rocks, some specific observations can be made. 

Saving any old observational data for subsequent comparisons. Repeating specific observations under conditions as identical as pos-... 

Panke, O., Gumbiowski, K., Junge, W., and Engelbrecht, S. (2000). F-ATPase Specific observation of the rotating c subunit oligomer of EFoEFj. FEBS Lett. 472, 34-38. 

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