Isospin symmetry at high spin studied via nucleon knockout from isomeric states

One-neutron knockout reactions have been performed on a beam of radioactive 53Co in a high-spin isomeric state. The analysis is shown to yield highly-selective population of high-spin states in an exotic nucleus with a significant cross section, and hence represents a technique that is applicable to the planned new generation of fragmentation-based radioactive beam facilities. Additionally, the relative cross sections among the excited states can be predicted to a high level of accuracy when reliable shell-model input is available. The work has resulted in a new level scheme, up to the 11+ band-termination state, of the proton-rich nucleus 52Co (Z = 27, N = 25). This has in turn enabled a study of mirror energy differences in the A = 52 odd-odd mirror nuclei, interpreted in terms of isospin-non-conserving (INC) forces in nuclei. The analysis demonstrates the importance of using a full set of J-dependent INC terms to explain the experimental observations

Genomic HIV RNA Induces Innate Immune Responses through RIG-I-Dependent Sensing of Secondary-Structured RNA

Contains fulltext : 108031.pdf (publisher's version ) (Open Access)BACKGROUND: Innate immune responses have recently been appreciated to play an important role in the pathogenesis of HIV infection. Whereas inadequate innate immune sensing of HIV during acute infection may contribute to failure to control and eradicate infection, persistent inflammatory responses later during infection contribute in driving chronic immune activation and development of immunodeficiency. However, knowledge on specific HIV PAMPs and cellular PRRs responsible for inducing innate immune responses remains sparse. METHODS/PRINCIPAL FINDINGS: Here we demonstrate a major role for RIG-I and the adaptor protein MAVS in induction of innate immune responses to HIV genomic RNA. We found that secondary structured HIV-derived RNAs induced a response similar to genomic RNA. In primary human peripheral blood mononuclear cells and primary human macrophages, HIV RNA induced expression of IFN-stimulated genes, whereas only low levels of type I IFN and tumor necrosis factor alpha were produced. Furthermore, secondary structured HIV-derived RNA activated pathways to NF-kappaB, MAP kinases, and IRF3 and co-localized with peroxisomes, suggesting a role for this organelle in RIG-I-mediated innate immune sensing of HIV RNA. CONCLUSIONS/SIGNIFICANCE: These results establish RIG-I as an innate immune sensor of cytosolic HIV genomic RNA with secondary structure, thereby expanding current knowledge on HIV molecules capable of stimulating the innate immune system

ISOBARIC ANALOGUE STATES STUDIED IN MIRRORED FRAGMENTATION AND KNOCKOUT REACTIONS

A Gamma-ray spectroscopic study of excited states of isobaric multiplets has been performed in recent years, with a view to gaining a quantitative understanding of energy differences between excited states in terms of a range of Coulomb and other isospin breaking phenomena. Recently, the experimental programme has been augmented by a study of isobaric analogue states of mirror nuclei populated in mirrored fragmentation reactions. In this presentation, recent results on the analogue states in the mirror pair 53Ni/53Mn will be summarised. In this work, further strong evidence is found for the need to include an anomalous isospin-breaking two-body matrix element for angular-momentum couplings of J = 2, in addition the expected Coulomb contribution, in order to account for the experimental data

One-proton and one-neutron knockout reactions from N=Z=28 Ni 56 to the A=55 mirror pair Co 55 and Ni 55

We present a high-resolution in-beam γ-ray spectroscopy study of excited states in the mirror nuclei Co55 and Ni55 following one-nucleon knockout from a projectile beam of Ni56. The newly determined partial cross sections and the γ-decay properties of excited states provide a test of state-of-the-art nuclear structure models and probe mirror symmetry in unique ways. The new experimental data are compared to large-scale shell-model calculations in the full pf space which include charge-dependent contributions. A mirror asymmetry for the partial cross sections leading to the two lowest 3/2- states in the A=55 mirror pair was identified as well as a significant difference in the E1 decays from the 1/21+ state to the same two 3/2- states. The mirror asymmetry in the partial cross sections cannot be reconciled with the present shell-model picture or small mixing introduced in a two-state model. The observed mirror asymmetry in the E1 decay pattern, however, points at stronger mixing between the two lowest 3/2- states in Co55 than in its mirror Ni55

Experimental identification of the T=1, Jπ=6+ state of Co 54 and isospin symmetry in A=54 studied via one-nucleon knockout reactions

New experimental data obtained from γ-ray tagged one-neutron and one-proton knockout from Co55 are presented. A candidate for the sought-after T=1,Tz=0,Jπ=6+ state in Co54 is proposed based on a comparison to the new data on Fe54, the corresponding observables predicted by large-scale-shell-model (LSSM) calculations in the full fp-model space employing charge-dependent contributions, and isospin-symmetry arguments. Furthermore, possible isospin-symmetry breaking in the A=54, T=1 triplet is studied by calculating the experimental c coefficients of the isobaric mass multiplet equation (IMME) up to the maximum possible spin J=6 expected for the (1f7/2)-2 two-hole configuration relative to the doubly magic nucleus Ni56. The experimental quantities are compared to the theoretically predicted c coefficients from LSSM calculations using two-body matrix elements obtained from a realistic chiral effective field theory potential at next-to-next-to-next-to-leading order (N3LO)