Nuclides, shielded

I and the shielded nuclide 136Cs correlations have definite curvature. 

The mass distribution curves in Figs. 8.13 to 8.15 give the total yields of the decay chains of mass numbers A. The independent yields of members of the decay chains, i.e. the yields due to direct formation by the fission process, are more diflicult to determine, because the nuclides must be rapidly separated from their precursors. Only a few so-called shielded nuclides (shielded from production via decay by a stable isobar one unit lower in Z) are unambiguously formed directly as primary... 

Mass Spectr(metric Determination of Shielded Nuclide Yields... 

If multineutron evaporation is responsible for the independent yields of shielded nuclides, then, of course, these yields would not be predicted by any simple hypothesis for the division of charge in fission which does not take into account the distribution of fission neutron numbers. 

The question of whether the independent yields of shielded nuclides result from multineutron evaporation from primary fragments as has been suggested is therefore still unsettled. It is perhaps significant that the independent yields of I128 and I130 for the neutron-induced fission of Pu239... 

In any case, accurate independent yields of shielded nuclides can be determined mass spectrometrically. Interpretation of these yields will require further measurements, and, in particular, a study of the independent yields of shielded nuclides as a function of neutron energy should be of interest. In this connection, mass spectroinetric methods will undoubtedly be used to determine independent yields both of shielded nuclides and short-lived isotopes for which satisfactory sweep experiments can be designed. 

Porcelli D, Andersson PS, Baskaran M, Wasserburg GJ (2001) Transport of U- and Th-series nuclides in a Baltic Shield watershed and the Baltic Sea. Geochim Cosmochim Acta 65 2439-2459 Puls RW, Powell RM (1992) Acquisition of representative ground-water quality samples for metals. Ground Water Monitor Remediat 12 167-176... 

Neutron diffraction on Cd compounds is not feasible, as one of the Cd nuclides (113Cd) has an extremely high absorption cross-section for neutrons, yielding an average [Pg.1255]

MoFe proteins and, 47 174 oxidation rate constants, 43 156-157 sugar functionality, 43 152 Nuclides, shielded, 2 353-354... 

When a meteorite falls onto the Earth s surface, it becomes for the most part shielded from the effects of cosmic rays. The cosmic-ray-produced nuclides cease to form so the exposure clock stops. However, because many of the cosmic-ray produced nuclides are radioactive, several new clocks start that can be used to estimate the time that a meteorite has been on the Earth s surface. 

Anticoincidence, Coincidence Recording. An inherent problem in an anticoincidence-shielded spectrometer is that a decay scheme having gamma-rays in coincidence will appear to produce the same interaction between the Ge(Li) detector and anticoincidence shield as that of a Compton event. If only the events from the Ge(Li) detector are counted in the absence of a signal from the shield, those nuclides that decay... 

The concentration of a stable cosmogenic nuclide for a surface sample that experienced a period of continuous exposure over a known duration t, with no erosion or deposition or change in altitude during exposure, followed by subsequent burial and immediate shielding from further production, can be approximated as... 

Figure 2. Schematic of sampling strategy for a buried paleosurface. A) Core into and below paleosurface to constrain paleo-production of cosmogenic nuclide. B) Core into and below modem surface to constrain production during recent exposure. C) Sample(s) shielded from both modem and ancient exposure to cosmic rays to constrain non-cosmogenic production of nuclides. Not to scale.

NMR shieldings at the oxygen can also be obtained for mineral systems and are calculated to show the same angular trends as for silicon (Tossell and Lazzeretti, 1988a). However, O is a quadrupolar nuclide (i.e., with a nonzero quadrupole moment), and its nuclear quadrupole coupling constant is thus an easier to measure quantity and, probably, one of more interest. When few data on the O NMR of silicates existed, Janes and Oldfield (1986) noted that different bonding models for silicates predicted different dependence of q° upon Si-O-Si angle. In particular. 

The principle of the method is sound, however, and with careful sample selection and the addition of shielding adjustments the procedure works well for several pairs of cosmogenic nuclides. Once P21 and 7 26 are known, we can calculate the ratio Pii/Pie- On expanding the exponential in Equation (8), we then have, for any meteorite with t I/X26 the relation. 

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