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TL;DR: In this article, Aifa et al. conducted a study on intrusive doleritic rocks cropping out within Devonian horizontal tabular formations of the Saharan craton (Tin Serririne basin, South of Hoggar shield).
23 citations
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TL;DR: In this paper, the authors proposed a strategy of field measurements and adjustments which combines kinematic positioning (1 min) and rapid static baselines (15 min) to get a 1.5 cm error (95% confidence).
23 citations
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TL;DR: A two-step method for purifying Ga from geological (biological) samples for precise measurement of Ga isotope ratio using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) and the modified empirical external normalization (MEEN) method gave relatively better precision compared to SSB on Neptune.
Abstract: Though an isotope approach could be beneficial for better understanding the biogeochemical cycle of gallium (Ga), an analogue of the monoisotopic element aluminum (Al), the geochemistry of Ga isotopes has not been widely elaborated. We developed a two-step method for purifying Ga from geological (biological) samples for precise measurement of Ga isotope ratio using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). Ga was thoroughly separated from other matrix elements using two chromatographic columns loaded with AG 1-X4 and Ln-spec resin, respectively. The separation method was carefully calibrated using both synthetic and natural samples and validated by assessing the extraction yield (99.8 ± 0.8%, 2SD, n = 23) and the reproducibility (2SD uncertainty better than 0.05‰, n = 116) of the measured isotopic ratio (expressed as δ71Ga). The validation of the whole protocol, together with instrumental analysis, was confirmed by the investigation of the matrix effect, the result of a stan...
23 citations
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TL;DR: In this article, the authors analyze records of events from the subduction zones in the south-west Pacific region obtained at stations in North America and demonstrate that either the S-wave velocity drop in this layer is much smaller than predicted by the hypothesis of melting, or the layer is so thin (less than about 10-15 km) that it can not be detected with their technique.
Abstract: Some recent seismic studies have suggested the presence of a thin ultra-low P-wave velocity layer (ULVZ) at the base of the mantle, which is interpreted to be due to presence of partial melting. Partial melting would lead to a strong decrease of the S-wave velocity for which there is no seismic evidence. Such a decrease in the S-wave velocity would produce a strong precursor to SKS phase from the conversion of S to P at the upper boundary of the layer. We analyze records of events from the subduction zones in the south-west Pacific region obtained at stations in North America. At the source side, the converted phases propagate in the region, where the ultra-low P-wave velocity has been found earlier. Our analysis demonstrates that either the S-wave velocity drop in this layer is much smaller than predicted by the hypothesis of melting, or the layer is so thin (less than about 10–15 km) that it can not be detected with our technique.
22 citations
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TL;DR: In this article, the Gell-Mann and Low switching is extended to the case when the ground state of the unperturbed Hamiltonian is degenerate, and it is shown that the switching procedure can still be performed when the initial states are eigenstates of the finite rank self-adjoint operator.
Abstract: The Gell-Mann and Low switching allows to transform eigenstates of an unperturbed Hamiltonian H0 into eigenstates of the modified Hamiltonian H0 + V. This switching can be performed when the initial eigenstate is not degenerate, under some gap conditions with the remainder of the spectrum. We show here how to extend this approach to the case when the ground state of the unperturbed Hamiltonian is degenerate. More precisely, we prove that the switching procedure can still be performed when the initial states are eigenstates of the finite rank self-adjoint operator \({\mathcal{P}_{0}V\mathcal{P}_{0}}\) , where \({\mathcal{P}_0}\) is the projection onto a degenerate eigenspace of H0.
22 citations
Authors
Showing all 903 results
Name | H-index | Papers | Citations |
---|---|---|---|
Claude J. Allègre | 106 | 327 | 35092 |
Paul Tapponnier | 99 | 294 | 42855 |
Francesco Mauri | 85 | 352 | 69332 |
Barbara Romanowicz | 67 | 284 | 14950 |
Geoffrey C. P. King | 64 | 157 | 17177 |
Yi-Gang Xu | 64 | 271 | 14292 |
Jérôme Gaillardet | 63 | 199 | 14878 |
François Guyot | 61 | 292 | 12444 |
Georges Calas | 60 | 266 | 10901 |
Ari P. Seitsonen | 59 | 212 | 45684 |
Michele Lazzeri | 58 | 140 | 57079 |
Bernard Bourdon | 58 | 118 | 9962 |
Gianreto Manatschal | 56 | 200 | 10063 |
Nikolai M. Shapiro | 56 | 154 | 15508 |
Guillaume Morin | 55 | 156 | 7218 |