Nucleogenic

The nuclear decay of radioactive atoms embedded in a host is known to lead to various chemical and physical after effects such as redox processes, bond rupture, and the formation of metastable states [46], A very successful way of investigating such after effects in solid material exploits the Mossbauer effect and has been termed Mossbauer Emission Spectroscopy (MES) or Mossbauer source experiments [47, 48]. For instance, the electron capture (EC) decay of Co to Fe, denoted Co(EC) Fe, in cobalt- or iron-containing compormds has been widely explored. In such MES experiments, the compormd tmder study is usually labeled with Co and then used as the Mossbauer source versus a single-line absorber material such as K4[Fe(CN)6]. The recorded spectrum yields information on the chemical state of the nucleogenic Fe at ca. 10 s, which is approximately the lifetime of the 14.4 keV metastable nuclear state of Fe after nuclear decay. 

The mechanism of NIESST is essentially the same as for LIESST (see Fig. 8.10), except for the initial excitation step. The electronic structure of the nucleogenic... 

The Editors have striven, as in previous years, to include in the present volume reviews on greatly diversified subjects, all of timely importance. The article on mellituria in Volume 4 has been supplemented by a survey of galactosemia, and we expect to follow in future volumes with reviews of other inborn errors of metabolism or, in modern parlance, of molecular diseases. Likewise, the article on peptiduria supplements that on aminoaciduria in Volume 2 and that on microbiological assay of vitamins extends previous summaries on the nucleogenic vitamins. The haptoglobins lie on the borderline of hematology. 

A potential problem in the use of diazo compounds as C atom precursors is the fact that intermediates in these reactions may act as C donors with the free atoms not involved. Indeed, the timing of the reactions in Eq. 6 is unknown and some of these intermediates may be bypassed in the thermolysis of 8. However, a comparison of the reactions of carbon from 8 with those of nucleogenic and arc generated carbon reveals quite similar products from many different substrates and provides circumstantial evidence for free C atoms in the decomposition of 8. 

Like many singlet carbenes, nucleogenic, arc generated and chemically generated C atoms react with aliphatic C—H bonds by insertion. In the simplest case, reaction of chemically generated C atoms with methane yields ethylene and acetylene. When a mixture of CH4 and CD4 is used, product analysis indicates that the acetylene results from H abstraction followed by dimerization of the CH, while the ethylene results from C—H insertion followed by H migration in the carbene (Eq. 15). It seems probable that CH is formed in all reactions of carbon with hydrocarbons as acetylene is invariably produced in these reactions. 

In the reaction of nucleogenic atoms with toluene, the methyl group traps an initially formed o-tolylcarbene (54) as benzocyclobutene (55). A partial degradation of 55 and an examination of the label distribution indicated that 43% of 55 arose from 54 formed by an initial C—H insertion (Eq. 34). The remainder of the label in 55 was in the ring, indicating the initial formation of the m- and p-tolylcar-benes and/or a methylcycloheptatetraene. 

Nucleogen-DEAE 4000 Coated silica Diethylamino ethyl 10... 

He and 3He 4He, not only in the crust but also in the Earth, is essentially radiogenic, and has been produced from radioactive decay of U, Th series elements. Only a significant source for nucleogenic 3He in the crust is a reaction 6Li(n, Cf) H( 7 , 2 = 12.3 a) —> 3He, where neutrons are derived from a spontaneous fission of 23SU and from reactions of light elements such as Na, Mg, Al, and Si with a particles emitted from U, Th decays. However, in a very shallow surface region (less than a few meters), the secondary cosmic ray neutrons would be more important. 

Figure 5.9 shows a neon three-isotope plot (Kennedy et al., 1990) where data were obtained from natural gases and brines in North America representing a broad geographical distribution. A fairly well-defined linear correlation on which air Ne is situated at the upper-left end suggests that the observed neon isotopic data resulted from a mixing between air Ne and another end member Ne characteristic to the crust. It is then reasonable to attribute the latter component to the nucleogenic component produced in the crust. 

Table 5.8 shows nucleogenic noble gases that would have been produced over a whole history of the Earth (4.5 Ga). The estimations are made for the assumed... 

Note that (129Xe/131Xe)exc 1.1 deduced from the linear trend in the diagram is close to the production ratio of nucleogenic Xe produced by neutron capture on Te. 

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