| 1. |
- Louchart, C., et al.
(author)
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Collective nature of low-lying excitations in Zn-70,Zn-72,Zn-74 from lifetime measurements using the AGATA spectrometer demonstrator
- 2013
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In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 87:5
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Journal article (peer-reviewed)abstract
- Background: Neutron-rich nuclei with protons in the fp shell show an onset of collectivity around N=40. Spectroscopic information is required to understand the underlying mechanism and to determine the relevant terms of the nucleon-nucleon interaction that are responsible for the evolution of the shell structure in this mass region. Methods: We report on the lifetime measurement of the first 2(+) and 4(+) states in Zn-70,Zn-72 ,Zn-74 and the first 6(+) state in Zn-72 using the recoil distance Doppler shift method. The experiment was carried out at the INFN Laboratory of Legnaro with the AGATA demonstrator, first phase of the Advanced Gamma Tracking Array of highly segmented, high-purity germanium detectors coupled to the PRISMA magnetic spectrometer. The excited states of the nuclei of interest were populated in the deep inelastic scattering of a Ge-76 beam impinging on a U-238 target. Results: The maximum of collectivity along the chain of Zn isotopes is observed for Zn-72 at N=42. An unexpectedly long lifetime of 20(-5.2)(+1.8) ps was measured for the 4(+) state in Zn-74. Conclusions: Our results lead to small values of the B(E2;4(1)(+) -> 21(+))/B(E2;2(1)(+->)0(1)(+)) ratio for Zn-72,Zn-74, suggesting a significant noncollective contribution to these excitations. These experimental results are not reproduced by state-of-the-art microscopic models and call for lifetime measurements beyond the first 2(+) state in heavy zinc and nickel isotopes.
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| 2. |
- Klintefjord, M., et al.
(author)
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Measurement of lifetimes in Fe-62,Fe-64, Co-61,Co-63, and Mn-59
- 2017
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In: PHYSICAL REVIEW C. - 2469-9985. ; 95:2
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Journal article (peer-reviewed)abstract
- Lifetimes of the 4(1)(+) states in Fe-62,Fe-64 and the 11/2(1)(-) states in Co-61,Co-63 and Mn-59 were measured at the Grand Accelerateur National d'Ions Lourds (GANIL) facility by using the Advanced Gamma Tracking Array (AGATA) and the large-acceptance variable mode spectrometer (VAMOS++). The states were populated through multinucleon transfer reactions with a U-238 beam impinging on a Ni-64 target, and lifetimes in the picosecond range were measured by using the recoil distance Doppler shift method. The data show an increase of collectivity in the iron isotopes approaching N = 40. The reduction of the subshell gap between the nu 2p(1/2) and nu 1g(9/2) orbitals leads to an increased population of the quasi-SU(3) pair (nu 1g(9/2), nu 2d(5/2)), which causes an increase in quadrupole collectivity. This is not observed for the cobalt isotopes withN < 40 for which the neutron subshell gap is larger due to the repulsive monopole component of the tensor nucleon-nucleon interaction. The extracted experimental B(E2) values are compared with large-scale shell-model calculations and with beyond-mean-field calculations with the Gogny D1S interaction. A good agreement between calculations and experimental values is found, and the results demonstrate in particular the spectroscopic quality of the Lenzi, Nowacki, Poves, and Sieja (LNPS) shell-model interaction.
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| 3. |
- Öhrn, Angelica, et al.
(author)
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Elastic scattering of 96 MeV neutrons from iron, yttrium, and lead
- 2008
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In: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 77:2, s. 024605-
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Journal article (peer-reviewed)abstract
- Data on elastic scattering of 96 MeV neutrons from Fe-56, Y-89, and Pb-208 in the angular interval 10-70 degrees are reported. The previously published data on Pb-208 have been extended, as a new method has been developed to obtain more information from data, namely to increase the number of angular bins at the most forward angles. A study of the deviation of the zero-degree cross section from Wick's limit has been performed. It was shown that the data on Pb-208 are in agreement with Wick's limit while those on the lighter nuclei overshoot the limit significantly. The results are compared with modern optical model predictions, based on phenomenology and microscopic nuclear theory. The data on Fe-56, Y-89, and Pb-208 are in general in good agreement with the model predictions.
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| 4. |
- Allagnat, F., et al.
(author)
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C/EBP homologous protein contributes to cytokine-induced pro-inflammatory responses and apoptosis in beta-cells
- 2012
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In: Cell Death and Differentiation. - : Springer Science and Business Media LLC. - 1350-9047 .- 1476-5403. ; 19:11, s. 1836-1846
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Journal article (peer-reviewed)abstract
- Induction of the C/EBP homologous protein (CHOP) is considered a key event for endoplasmic reticulum (ER) stress-mediated apoptosis. Type 1 diabetes (T1D) is characterized by an autoimmune destruction of the pancreatic beta-cells. Pro-inflammatory cytokines are early mediators of beta-cell death in T1D. Cytokines induce ER stress and CHOP overexpression in beta-cells, but the role for CHOP overexpression in cytokine-induced beta-cell apoptosis remains controversial. We presently observed that CHOP knockdown (KD) prevents cytokine-mediated degradation of the anti-apoptotic proteins B-cell lymphoma 2 (Bcl-2) and myeloid cell leukemia sequence 1 (Mcl-1), thereby decreasing the cleavage of executioner caspases 9 and 3, and apoptosis. Nuclear factor-kappa B (NF-kappa B) is a crucial transcription factor regulating beta-cell apoptosis and inflammation. CHOP KD resulted in reduced cytokine-induced NF-kappa B activity and expression of key NF-kappa B target genes involved in apoptosis and inflammation, including iNOS, FAS, IRF-7, IL-15, CCL5 and CXCL10. This was due to decreased I kappa B degradation and p65 translocation to the nucleus. The present data suggest that CHOP has a dual role in promoting beta-cell death: (1) CHOP directly contributes to cytokine-induced beta-cell apoptosis by promoting cytokine-induced mitochondrial pathways of apoptosis; and (2) by supporting the NF-kappa B activation and subsequent cytokine/chemokine expression, CHOP may contribute to apoptosis and the chemo attraction of mononuclear cells to the islets during insulitis. Cell Death and Differentiation (2012) 19, 1836-1846; doi:10.1038/cdd.2012.67; published online 1 June 2012
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