Gamma ray production cross sections in proton induced reactions on natural Mg, Si and Fe targets over the proton energy range 30 up to 66 MeV

Gamma-ray excitation functions have been measured for 30, 42, 54 and 66 MeV proton beams accelerated onto C + O (Mylar), Mg, Si, and Fe targets of astrophysical interest at the separate-sector cyclotron of iThemba LABS in Somerset West (Cape Town, South Africa). A large solid angle, high energy resolution detection system of the Eurogam type was used to record Gamma-ray energy spectra. Derived preliminary results of Gamma-ray line production cross sections for the Mg, Si and Fe target nuclei are reported and discussed. The current cross section data for known, intense Gamma-ray lines from these nuclei consistently extend to higher proton energies previous experimental data measured up to Ep ~ 25 MeV at the Orsay and Washington tandem accelerators. Data for new Gamma-ray lines observed for the first time in this work are also reported.Comment: 11 pages, 6 figures. IOP Institute of Physics Conference Nuclear Physics in Astrophysics VII, 28th EPF Nuclear Physics Divisional Conference, May 18-22 2015, York, U

First social impact bond for the SAMRC: A novel financing strategy to address the health and social challenges facing adolescent girls and young women in South Africa

A social impact bond (SIB) is an innovative financing mechanism to attract investors to social programmes traditionally funded by governments. In this article, in celebration of the 50th anniversary of the South African Medical Research Council (SAMRC), the authors describe the SAMRC’s first foray into this new world of financing through a SIB to improve the health and quality of life of adolescent girls and young women (AGYW). The AGYW SIB is in its preparatory phase and is scheduled for implementation in 2020. The authors describe the mechanism, including financial flows and the process of customising the SIB to meet the needs of AGYW, focusing on HIV prevention and treatment and the prevention and management of unintended pregnancies in schoolgoing AGYW. The authors outline an approach to designing the package of interventions, the metrics associated with such a programme and the business model. It is hypothesised that the proposed approach will lead to an improvement in programmatic outcomes, monitoring and evaluation tools and cost-effectiveness, and will develop key learning data for the future use of SIBs in health service delivery

Nuclear Level Density and γ\gamma-ray Strength Function of 67Ni^{67}\mathrm{Ni} and the impact on the i-process

Proton-$\gamma$ coincidences from $(\mathrm{d},\mathrm{p})$ reactions between a $^{66}\mathrm{Ni}$ beam and a deuterated polyethylene target have been analyzed with the inverse Oslo method to find the nuclear level density (NLD) and $\gamma$-ray strength function ($\gamma$SF) of $^{67}\mathrm{Ni}$. The $^{66}\mathrm{Ni}(\mathrm{n},\gamma)$ capture cross section has been calculated using the Hauser-Feshbach model in TALYS using the measured NLD and $\gamma$SF as constraints. We confirm that $^{66}\mathrm{Ni}(\mathrm{n},\gamma)$ acts as a bottleneck when relying on one-zone nucleosynthesis calculations. However, we find that the impact of this reaction is strongly damped in multi-zone low-metallicity AGB stellar models experiencing i-process nucleosynthesis.Comment: Submitted to Phys. Rev.

Investigation of negative-parity states in Dy 156: Search for evidence of tetrahedral symmetry

An experiment populating low/medium-spin states in Dy156 was performed to investigate the possibility of tetrahedral symmetry in this nucleus. In particular, focus was placed on the low-spin, negative-parity states since recent theoretical studies suggest that these may be good candidates for this high-rank symmetry. The states were produced in the Nd148(C12,4n) reaction and the Gammasphere array was utilized to detect the emitted γ rays. B(E2)/B(E1) ratios of transition probabilities from the low-spin, negative-parity bands were determined and used to interpret whether these structures are best associated with tetrahedral symmetry or, as previously assigned, to octupole vibrations. In addition, several other negative-parity structures were observed to higher spin and two new sequences were established

Measurement and analysis of nuclear γ-ray production cross sections in proton interactions with Mg, Si, and Fe nuclei abundant in astrophysical sites over the incident energy range E = 30–66 MeV

The modeling of nuclear γ -ray line emission induced by highly accelerated particles in astrophysical sites (e.g., solar flares, the gas and dust in the inner galaxy) and the comparison with observed emissions from these sites needs a comprehensive database of related production cross sections. The most important reactions of protons and α particles are those with abundant target elements like C, O, N, Ne, Mg, Si, and Fe at projectile energies extending from the reaction threshold to a few hundred MeV per nucleon. In this work, we have measured γ -ray production cross section excitation functions for 30, 42, 54, and 66 MeV proton beams accelerated onto nat C , C + O (Mylar), nat Mg , nat Si , and 56 Fe targets of astrophysical interest at the Separated Sector Cyclotron (SSC) of iThemba LABS (near Cape Town, South Africa). The AFRODITE array equipped with eight Compton suppressed high-purity (HPGe) clover detectors was used to record γ -ray line energy spectra. For known, intense lines previously reported experimental data measured up to E p ≃ 25 MeV at the Washington and Orsay tandem accelerators were thus extended to higher proton energies. Our experimental data for the last three targets are reported here and discussed with respect to previous data and to the Murphy et al. compilation [Astrophys. J. Suppl. Ser. 183, 142 (2009)]

Observation of γ vibrations and alignments built on non-ground-state configurations in Dy 156

The exact nature of the lowest Kπ=2+ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ bands have been traced past the usual backbending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus Dy156, using the Nd148(C12,4n)Dy156 reaction at 65 MeV, observing the resulting γ-ray transitions with the Gammasphere array. The even- and odd-spin members of the Kπ=2+γ band are observed up to 32+ and 31+, respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible γ vibration built on the aligned yrast S band are observed up to spins 28+ and 27+. An even-spin positive-parity band, observed up to spin 24+, is a candidate for an aligned S band built on the seniority-zero configuration of the 02+ state at 676 keV. The crossing of this band with the 02+ band is at ?ωc=0.28(1)MeV and is consistent with the configuration of the 02+ band not producing any blocking of the monopole pairing

Civil society leadership in the struggle for AIDS treatment in South Africa and Uganda

Includes abstract.Includes bibliographical references.This thesis is an attempt to theorise and operationalise empirically the notion of ‘civil society leadership’ in Sub-Saharan Africa. ‘AIDS leadership,’ which is associated with the intergovernmental institutions charged with coordinating the global response to HIV/AIDS, is both under-theorised and highly context-specific. In this study I therefore opt for an inclusive framework that draws on a range of approaches, including the literature on ‘leadership’, institutions, social movements and the ‘network’ perspective on civil society mobilisation. This framework is employed in rich and detailed empirical descriptions (‘thick description’) of civil society mobilisation around AIDS, including contentious AIDS activism, in the key case studies of South Africa and Uganda. South Africa and Uganda are widely considered key examples of poor and good leadership (from national political leaders) respectively, while the Treatment Action Campaign (TAC) and The AIDS Support Organisation (TASO) are both seen as highly effective civil society movements. These descriptions emphasise ‘transnational networks of influence’ in which civil society leaders participated (and at times actively constructed) in order to mobilise both symbolic and material resources aimed at exerting influence at the transnational, national and local levels

Spectroscopy of low-spin states in 157Dy : Search for evidence of enhanced octupole correlations

CITATION: Majola, S. N. T., et al. 2019. Spectroscopy of low-spin states in 157Dy : Search for evidence of enhanced octupole correlations. Physical Review C, 100(6):034322, doi:10.1103/PhysRevC.100.034322.The original publication is available at https://journals.aps.org/prcLow-spin states of ¹⁵⁷Dy have been studied using the JUROGAM II array, following the ¹⁵⁵Gd (α, 2n) reaction at a beam energy of 25 MeV. The level scheme of ¹⁵⁷Dy has been expanded with four new bands. Rotational structures built on the [523]5/2⁻ and [402]3/2⁺ neutron orbitals constitute new additions to the level scheme as do many of the inter- and intraband transitions. This manuscript also reports the observation of cross I⁺ →(I–1) ⁻ and I⁻ →(I–1)⁺ E1 dipole transitions interlinking structures built on the [523]5/2⁻ (band 5) and [402]3/2⁺ (band 7) neutron orbitals. These interlacing band structures are interpreted as the bands of parity doublets with simplex quantum number s=–i related to possible octupole correlations.https://journals.aps.org/prc/abstract/10.1103/PhysRevC.100.034322Publisher's versio