73 research outputs found

    Competing electric and magnetic excitations in backward electron scattering from heavy deformed nuclei

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    Important E2E2 contributions to the (e,e′)(e,e^{\prime}) cross sections of low-lying orbital M1M1 excitations are found in heavy deformed nuclei, arising from the small energy separation between the two excitations with IπK=2+1I^{\pi}K = 2^+1 and 1+1^+1, respectively. They are studied microscopically in QRPA using DWBA. The accompanying E2E2 response is negligible at small momentum transfer qq but contributes substantially to the cross sections measured at θ=165∘\theta = 165 ^{\circ} for 0.6<qeff<0.90.6 < q_{\rm eff} < 0.9 fm−1^{-1} (40≤Ei≤7040 \le E_i \le 70 MeV) and leads to a very good agreement with experiment. The electric response is of longitudinal C2C2 type for θ≤175∘\theta \le 175 ^{\circ} but becomes almost purely transverse E2E2 for larger backward angles. The transverse E2E2 response remains comparable with the M1M1 response for qeff>1.2q_{\rm eff} > 1.2 fm−1^{-1} (Ei>100E_i > 100 MeV) and even dominant for Ei>200E_i > 200 MeV. This happens even at large backward angles θ>175∘\theta > 175 ^{\circ}, where the M1M1 dominance is limited to the lower qq region.Comment: RevTeX, 19 pages, 8 figures included Accepted for publication in Phys Rev

    Einsatz der PET-CT mit FDG in der Onkologie

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    18FDG-PET as a Marker for Prognosis in Differentiated Thyroid Cancer

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    Functional traits shed new light on the nature of ecotones: a study across a bog-to-forest sequence

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    Ecotones have long been a focus of ecological research, and there is considerable current interest in functional traits in community ecology. Yet, surprisingly, the functional trait approach has not been applied to ecotones. A bog-forest sequence in southern New Zealand was sampled with a grid of quadrats, and eight traits related to leaf function were measured on the 54 species found. Two ecotones were identified using moving-window analysis: Ecotone I was the transition from bog to edge forest, and Ecotone II was the transition from edge forest to tall climax forest. No strict ecotonal species were present. In contrast to theoretical predictions, species richness was not higher or lower in either ecotone, rather, both ecotones represented a transition in richness from one community to the other. It has long been said that ecotones are mosaics, but species mosaicity was no higher in either ecotone than in the adjacent communities, in fact it was lower in Ecotone I. Functional trait diversity decreased along the sequence from bog to forest, with no deviation in either ecotone. However, examining mosaicity in terms of traits, there was a steady rise in Ecotone I and, in conformance with ecotone / functional trait theory, a clear peak in Ecotone II. We conclude that the features claimed for ecotones are often not present, and whether they are present is dependent on the components measured: species vs traits. Here, the clearest patterns were seen in trait mosaicity, but even this differed markedly between the two ecotones. Generalisations about ecotones should be avoided; they will vary from ecotone to ecotone, and probably depend on the type of ecotone: anthropogenic, environmental, switch, etc
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