Clarke value

Table 1 Data on selected ore metals. Median ore grade for a given element can vary significantly from one deposit type to another. The Clarke value is the ratio of the median grade to the crustal abundance.

Element Oxidation state Deposit type Grade (median) Crustal abundance Clarke value... 

Hilado and Clark report difficult-to-find autoignition temperatures while eliminating apparent discrepancies in literature values. Table 1 shows their compilation. 

Few other reactions of series of substituted pyridines have been investigated extensively. Dondoni, Modena, and Todesco have measured the rate of N-oxidation of a limited series of pyridines and found a good correlation with normal u-values with a p-value of — 2.23. The A-alkylation of pyridines with alkyl iodides in nitrobenzene has been studied by Brown and Cahn and by Clarke and Rothwell. Unfortunately, the only data available are for the parent compound and for alkyl derivatives, and, since the a-values for the various alkyl groups in a given position are substantially constant, this leaves a correlation of only three independent points. However, the rates of A-alkylation of the j8- and y-alkyl derivatives are so nearly equal that it appears as if no correlation existed. Clarke and Rothwell have also studied the alkylation with allyl bromide in nitromethane at various temperatures, and in this case a more extensive series is available. The authors state that no overall Hammett correlation is obtained however, the j8-substituted derivatives fall on one straight line and the y-derivatives on another one with a different slope. The data are shown in Fig. 2. The line for the j8-compounds, p = — 2.53 0.31, r = 0.95, is seen not to be very good the line for the y-derivatives, p = — 1.42 0.06, r = 0.99, is much more satisfactory. It does not seem likely that the discrepancy is due to the intervention of resonance effects, since in this case one would expect the correlation for the y-derivatives to be poorer than that for the j8-analogs. More extensive studies with a wider variety of substituents would seem very desirable. 

The method of predicting pK a values by Clarke and Perrin (1) was tentatively applied to determine the structures of the two monoacetylated compounds, and the results indicate that kasugamycinic acid is 4-N-carboxyformyl-kasuganobiosamine (9a). 

One shortcoming of Schild analysis is an overemphasized use of the control dose-response curve (i.e., the accuracy of every DR value depends on the accuracy of the control EC o value). An alternative method utilizes nonlinear regression of the Gaddum equation (with visualization of the data with a Clark plot [10], named for A. J. Clark). This method, unlike Schild analysis, does not emphasize control pECS0, thereby giving a more balanced estimate of antagonist affinity. This method, first described by Lew and Angus [11], is robust and theoretically more sound than Schild analysis. On the other hand, it is not as visual. Schild analysis is rapid and intuitive, and can be used to detect nonequilibrium steady states in the system that can corrupt... 

To apply this method, the pECS0 values of the control and shifted dose-response curves and the corresponding concentrations of antagonist [B] values associated with those pECjgS are used to construct a Clark plot [10] according to the equation... 

Percussive Effect or Force (Relative). A term coined by Clark (Ref 2) for the numerical value obtained by dividing the compression of a Pb cylinder produced by firing an expl to that pro-... 

Clark and Vermeulen (C8) measured gas holdup in three different liquids —isopropyl alcohol, ethylene glycol, and water. They measured the increase in holdup with agitation as compared to no agitation, and correlated their results as a function of the volumetric gas velocity, Weber number, P/P0, and a geometric factor. Typical volumetric gas holdup values reported in the literature vary from about 2% to 40% of the total dispersion volume (Cl, C2, C8, F2, G10). 

Zero emission plants, environmentally benign or green chemistry, and sustainable development have become the catch phrases of the 1990s (Anastas and Farris, 1994 Anastas and Warner, 1998 Anastas and Williamson, 1998 Clark, 1995). Consequently, traditional concepts of process efficiency are changing from an exclusive focus on chemical yields to one that assigns economic value to eliminating waste and avoiding the use of toxic and/or... 

Note that a similar situation arises in the study of heterogeneous deactivation of electron-excited molecules of N2. Thus, an opinion expressed by Clark et al. [152] states that the coefficients of heterogeneous deactivation of N2(A S, v = 0.1) for all surfaces are close to unity. On the other hand, Vidaud with his coworkers [59, 153] have obtained 3 10 2 and (1.8 + 1.2) 10 values for these coefficients shown by platinum and Pyrex, respectively. Tabachnik and Shub [154] investigated heterogeneous decay of NaC A SJJ ) molecules on a quartz surface by the method of bulk-luminescence spectroscopy. The authors carried out a series of experiments within a broad (about four orders of magnitude) range of active particle concentrations and arrived at a conclusion that at a concentration of N2( A 2 ) in excess of 10 mole/cm , the... 

Boruah, R. C. Skibo, E. B. Determination of the pKa values for the mitomycin C redox couple by tritration, pH rate profile, and Nemst-Clark fits. Studies of methanol elimination, carbocation formation, and the carbocation/quinone methide equilibrium. J. Org. Chem. 1995, 60, 2232-2243. 

Also, were the underlying assumptions to be correct, the value of the intercept of the line on the abscissa (i.e., when the response is half maximal) would give an estimate of KA. A. J. Clark was the first to test this using the responses of isolated tissues, and Figure 1.2 illustrates some of his results. Figure 1.2A shows that Eq. (1.4) provides a reasonably good fit to the experimental values. 

Values for nota are also documented in Ref. (237) values for nota and dota complexes of several M2+ ions are given in Clarke, E. T. Martell, A. E. Inorg. Chim. Acta 1991,190, 27-36, for M3+ ions in Clarke, E. T. Martell, A. E. Inorg. Chim. Acta 1991, 190, 37-46. 

Weston s cell was much less temperature sensitive than the previous standard, the Clark cell. We recall how the value of AG changes with temperature according to Equation (4.38). In a similar way, the value of AG(Ceii) for a cell relates to the entropy change A ceii) such that the change of emf with temperature follows... 

Christopher M, Gattoma J (2005) Supply chain cost management and value-based pricing. Industrial Marketing Management 34 (2) 115-121 Clark E, Lesourd J, Thieblemont R (2001) International commodity trading physical and derivative markets, John Wiley Sons, Chichester Commodity Research Bureau (2005) The CRB Commodity Yearbook 2005, John Wiley Sons, Chichester... 

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