Selective logging

Fig. 13. (left) A competitive divalent/monovalent cation symport coupled to M2+/2H+ and M+/H+ antiport in a pH gradient by a macrocyclic carrier such as 86 the state of the carrier is indicated as diprotonated, [(CC>2H)2], or complexed, [(CC -, M2+] and [(C02H)(C02 ), M+] (right) Rates of K+ and Ca2+ transport by the macrocyclic carrier molecule 86 through a liquid membrane as a function of pH in the starting IN phase the dotted line represents the pH dependence of the transport selectivity log S. 

Even when the test set is large, one should see if the sub-structures of particular interest are calculated well. Out of the 9,000 selected log P values recently published (Hansch,... 

For the synthesis of a photopolymerizable receptor molecule that has a high selectivity for K+, we have modified the hemispherand synthesis according to Scheme 4. The final polymer membrane is represented by Figure 8. The response to a variation in K+ concentration (10 s - 10"1 M) in the presence of 0.1 M NaCl is given in Figure 9. The potentiometric selectivities (log K ) determined by the mixed solution method are -3.0 (Na+), -3.5 (Ca2+), -4.0 (Mg2+), and -0.7 (NH/). This renders this CHEMFET an excellent K+-sensor with a longterm stability t> 100 days). 

Perhaps the selective removal of ponderosa pine by air pollution would not be considered with alarm or regarded any differently from selective logging if there were assurance that the reproductive and vege-... 

Figure 8. Plot of reactivity against selectivity (log An A w) for alkyl chlorides in aqueous dioxan containing azide ions. (Taken from Raber et al., 1971a.)...

Selectivities (log n/ H2o) of Methyl Benzenesulphonate, Methyl Nitrate and Methyl Perchlorate with Nucleophiles, Na... 

The reason for this difference was attributed to a non-steady-state response in the earlier measurements of Shinkai et al., due to omitting the preconditioning of the sensor. A calix[4]arene with one quinone moiety (22) was also investigated as receptor molecule in ion-selective electrodes and the Na /K selectivity (log/f a.K = -3.4) was higher than obtained with calix[4]arene derivative 18... 

ISEs and CHEMFETs with calix[4]arene 32, bearing two thioether functionalities, are highly selective for Ag+ in the presence of alkaline earth ions (K" ", Ca ) and transition metal ions (Cu, Cd ), with selectivities log/f gj varying from —4.2 to —4.7 [133,135]. The CHEMFETs with 32 also showed selectivity for Ag in the presence of Hg " " ions (log g g = —2.7), which is quite unique since both ions have the same coordination number and preference for a linear interaction with soft donor atoms [133]. McKervey et al. reported Ag selectivity for calix[4]arene 33 in PVC membrane based ISEs [136]. These ISEs show a moderate Ag" selectivity (—1.1 to -2.1). Due to the presence of the hard donating carbonyl atoms in the molecule, a sub-Nemstian response (50mV decade ) was obtained in the presence of alkaline metal ions [137]. Moreover, the sensor was not selective for Ag in the presence of Hg " ions. 

Extractive reserves provide a new concept for Amazonia. Most implemented models for Amazonian development and conservation are based on a preservationist/developmen-talist dichotomy (Foresta 1991). In this dichotomy, forests and their ecosystem components are to be preserved in parks and biological reserves. Areas designated for development are exploited at varying degrees of intensity that usually involve the complete elimination of forest cover (pasture and annual crops) or partial extraction and degradation (selective logging). This... 

Fernandes, E. C. M., Y. Biot, C. Castilla, A. C. Canto, J. C. Matos, S. Garcia, R. Perin, and E. Wanderli. 1997. The impact of selective logging and forest conversion for subsistence agriculture and pastures on terrestrial nutrient dynamics in the Amazon. CiSncia e Cultura 49 34-47. 

On nonflooded sites in Amazonia, species richness increases from east to west, from 87 species ha i near Belem (Black et al. 1950) to over 179 species ha near Manaus (Prance et al. 1976) and more than 200 species in Ecuador (Balslev et al. 1987). Gentry (1982, 1990) explained species richness generally increases as annual precipitation increases. However in the same direction diversity increases in the floodplain forests from 53 species per ha in Para (Pires and Koury 1959) to over 135 species in Mamiraua (Ayres 1993) to 149 species at the Rio Napo (Balslev et al. 1987). The human influence on species composition in floodplain forests is a poorly investigated factor however, forests of the eastern Amazon have been exposed to deforestation and severe exploitation for longer times than western forests. In the varzea of the Solimoes river, selective logging nearly caused the extinction of... 

Albemaz, A, L. K. M., and J. M. Ayres. 1999. Selective logging along the Middle Solimoes river. In Varzea. Diversity, Development, and Conservation of Amazonia s Whitewater Floodplains, eds. C. Padoch, J. M. Ayres, M, Pinedo-Vasquez, and A. Henderson (The New York Botanical Garden Press, New York), pp. 135-151. 

For open systems it is convenient to select log pco2 and — log[H ] as variables. An assumption must then be made about the concentrations of the solute. The computation of the straight lines in Figure 7.14 is based on the following equations. For the coexistence of Fe and Fe(OH)2(s),... 

This result is at variance with the accepted values of the second dissociation constants of the acids. Reference [92GRE/FUG] selects log K° = - 1.80 for selenic and log,o K2 = -. 98 for sulphuric acid. The expected potential difference would therefore be about 1 to 2 mV from these data if the liquid junction potential ( ,) is ignored, and not a few tenths of a millivolt. The contradiction can probably be traced to the neglect of An estimate of Ej by the Henderson equation indicates that the first term in the above expression for E is largely cancelled by the second term. The same... 

Stability constant at zero ionic strength, as shown in Figure V-14. The selected log D K° determined in this way is ... 

The selected log K° determined from the weighted least squares analysis is ... 

The stability constant for the formation of ZrF from ZrF" (g = 2 in Eq.(V.23)), was determined using a weighted (least squares) analysis technique (see Figure V-16). The selected log Q AT° determined from the regression is ... 

The results of this consistency test are shown in Figure A-33, where the selected log p° (42.9) and hydrolysis data (including log K° = - 7.0) have been applied with the SIT model to reproduee the experimental data of [2001 POU/CUR]. It is evident that the caleulated model curve (continuous line) misses the data obtained in... 

The SlT-plot of the recalculated data, together with the accepted values for [65BUR/L1L2] and [710HT/BIE], as well as the selected log,Q for the reaction ... 

Figure A-29 SIT-plot of recalculated data from [80MIL/BUG] (open diamond), [65BUR/LIL2] and [710HT/BIE] (open squares), and the selected log, ...

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