The Dole Effect

Terrestrial and oceanic biospheric processes drive with similar relative weight the 0/ 0 ratio of atmospheric O2. The most important effect is the fractionation occurring during consumption of O2 by heterotrophic respiration. This fractionation leads to a global atmospheric 0/ 0 isotope ratio enriched by about 23.5% 

Because of their expected small size, atmospheric variations of the 0/ 0 in O, have not been observed up to now. Seasonal variations and mean annual gradients are expected to be on the order of a few penneg (Seibt, 1997). Just as the combination of CO, and O, provides a very powerful constraint on the carbon cycle, a combination with measurements of the oxygen isotope ratios in both CO, and O, would constitute two further powerful constraints. 

Oxygen consists of three stable isotopes 0, O and O. For most applications only the ratio between the more abundant Lso-topes, 0 and O, is measured. If all fractionation processes in the environmental system were purely mass-dependent, measurements of 0/ 0, would be redundant, as they could be predicted from the 0/ 0 ratio. However, it has recently been ob.served that photochemical exchange between O2, Oi, and CO, in the stratosphere involves mass-independent fractionation among the oxygen isotopes (1990 Thiemens et al., 1993a, b Thiemens, 1999). Thereby O2 becomes anomalously depleted, while CO2 becomes anomalously enriched. Because of this, measurements of 0/ 0 in atmospheric O2 and/or CO2 provide an independent piece of information. Conveniently, one may define an O anomaly tracer (A 0) (Thiemens et n/., 1995b) 

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We can illustrate the doleful effect of dilution without resorting to such extremes as experiments with 10 different products. Just increasing the number of treatments from two to three can wreck an experiment. 

BeerUng D. J. (1999) The influence of vegetation activity on the dole effect and its implications for changes in biospheric productivity in the mid-holocene. Proc. Roy. Soc. of London Ser. B-biol. Set 266(1419), 627-632. 

Bender M., Sowers T., and Labeyrie L. (1994) The dole effect and its variations during the last 130,000 years as measured in the Vostok ice core. Global Biogeochem. Cycles 8(3), 363-376. 

Several publications on electrochemical mechanistic studies of the oxidative transformations of catecholamines followed the contribution by R. N. Adam s group (256) and involved a-methyldopamine, a-methylnor-adrenaline, dopamine (257), a-methyldopa, 5,6-dihydroxy-2-methylin-dole (255), and dopa (259). These studies (257) (Scheme 5), which confirmed the validity of the melanization scheme by Mason and Raper (Ref. 7, p. 50), explored the pH effect on the sequence of events that characterize the electrooxidation of catecholamines. Thus, the cyclic voltammogram in I M HCIO4 (pH 0.6) shows only peaks corresponding to the catechol-quinone redox couple as the protonation of the amino group prevents the cyclization step. 

The rate of release of free fatty acids from the tissue is regulated by the nutrio-nal state of the animal and by hormones. Starvation and injection of epinephrine increases fatty acid contration in the blood, whereas glucose and insulin have the opposite effect (Dole 1956 Gordon and C erkes 1957). 

The most useful modality for dealing with the societal aspects of opiate abuse (as well as some of the medical and personal aspects) has been methadone maintenance. In consideration of the pharmacology of opiate dependence 4,17,45,58,87,88,131,140,172,185 Dole and Nyswander 51 proposed that maintenance of opiate addicts on relatively large doses of oral methadone would inhibit drug seeking behavior, "block" the subjective effects of parenteral heroin injection because of the tolerance induced, break the needle habit because of lack of reinforcement by this route, and make the addict more available for psychiatric treatment and rehabilitation, breaking the cycle of crime and punishment. Methadone maintenance has been... 

The effect of a nitro group at the 6 position on the nucleophilic substitution reaction has been examined using l-methoxy-6-nitroindole (82) as a substrate (2001H1151). The reaction with NaOMe in refluxing DMF generates 6-nitroin-dole (83, 57%), 2-methoxy- (199, 22%), and 3-methoxy-6-nitroindoles (84, 6%) (Scheme 29). The formation of 199 and 84 can be explained by the SN2 -type nucleophilic substitution reaction at the 2 and 3 positions, respectively, with the... 

In this brief section, we have not touched the vast field of radiation-induced polymerization and radiation effects on polymers. Fortunately, the field has been surveyed very well in international conference proceedings published in Radiation Chemistry and Physics referred in the beginning of this section. The earlier books by Charlesby (1960) and by Dole (1973) provide adequate background information. 

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