Microscopic two-nucleon overlaps and knockout reactions from 12^{12}C

The nuclear structure dependence of direct reactions that remove a pair of like or unlike nucleons from a fast $^{12}$C projectile beam are considered. Specifically, we study the differences in the two-nucleon correlations present and the predicted removal cross sections when using $p$-shell shell-model and multi-$\hbar\omega$ no-core shell-model (NCSM) descriptions of the two-nucleon overlaps for the transitions to the mass $A$=10 projectile residues. The NCSM calculations use modern chiral two-nucleon and three-nucleon (NN+3N) interactions. The $np$-removal cross sections to low-lying $T$=0, $^{10}$B final states are enhanced when using the NCSM two-nucleon amplitudes. The calculated absolute and relative partial cross sections to the low energy $^{10}$B final states show a significant sensitivity to the interactions used, suggesting that assessments of the overlap functions for these transitions and confirmations of their structure could be made using final-state-exclusive measurements of the $np$-removal cross sections and the associated momentum distributions of the forward travelling projectile-like residues.Comment: 9 pages, 7 figure

Oestrogen, testosterone, cytotoxin and cholinesterase inhibitor removal during reclamation of sewage to drinking water

Namibia is the driest sub-Saharan country in Africa. Namibia’s capital, Windhoek, reclaims sewage water for domestic use at the Goreangab Water Reclamation Plant (GWRP). Risks associated with sewage effluent and reclaimed sewage should be closely monitored; therefore water at the Gammams Sewage Treatment Plant (GSTP) inlet and outlet, as well as reclaimed water from the GWRP, were assayed using selected bioassays. Samples collected were analysed using enzyme-linked immunosorbent-assays and chromogenic tests for steroid hormones, neurotoxicity, cytotoxicity and inflammatory activity. Estradiol level at the sewage treatment inlet was 78 pg/mℓ and the treated sewage level showed an 83% to 95% reduction in this, while after reclamation the level was below detection limit. Estrone concentrations at the sewage treatment inlet ranged from 10 to 161 pg/mℓ. Sewage treatment reduced estrone by between 85% and 92%. After reclamation the level of estrone was below detection limit. Testosterone ranged between 162 and 405 pg/mℓ at the sewage plant inlet. Sewage treatment removed 96% of the initial testosterone. The residual testosterone was effectively removed by processes in GWRP and after reclamation no testosterone was detected in water. Acetylcholinesterase (AChE) inhibition at the sewage treatment inlet was 50% while it was only 27% after sewage treatment. After reclamation AChE inhibition was not detected. Only water at the sewage inlet in March and February showed cytotoxicity. High inflammatory activity was detected at the sewage plant inlet. Sewage treatment reduced inflammatory activity by 64%. After reclamation low inflammatory activity was induced. Treated sewage used for reclamation tested positive for most of the biomarkers and can pose a risk to human health. However, reclamation successfully removed these contaminants. Due to the presence of contaminants in the intake water at the reclamation plant, it is essential to routinely monitor the water produced by the reclamation plant for potential residues that can adversely affect human health.Web of Scienc

Two-nucleon correlation effects in knockout reactions from 12C

Reactions that involve the direct and sudden removal of a pair of like or unlike nucleons from a fast projectile beam by a light target nucleus are considered. Specifically, we study the three two-nucleon removal channels from $^{12}${C} that populate final states in the $^{10}${Be}, $^{10}${B} and $^{10}${C} reaction residues. The calculated two-nucleon removal cross sections and the residue momentum distributions are compared with available high energy data at 250, 1050 and 2010 MeV per nucleon, data that are inclusive with respect to the bound final-states of the residues. The measured $np$-removal cross sections only are significantly greater than the values calculated, suggesting that the reaction mechanism observes enhanced $np$ spatial correlations compared to those present in the shell-model wave functions.Comment: 10 pages, 5 figures - Accepted Physical Review

A study of nuclei of astrophysical interest in the continuum shell model

We present here the first application of realistic shell model (SM) including coupling between many-particle (quasi-)bound states and the continuum of one-particle scattering states to the spectroscopy of 8B and to the calculation of astrophysical factors in the reaction 7Be(p,gamma)8B.Comment: 9 pages incl. 3 figures, LaTeX with iopart class and epsf. Invited talk at the Int. Workshop on Physics with Radioactive Nuclear Beams, Jan. 12-17, 1998, Puri, India. Shortened version will be published in proceedings to apear as a separate J. Phys. G volum

Isoscalar g Factors of Even-Even and Odd-Odd Nuclei

We consider T=0 states in even-even and odd-odd N=Z nuclei. The g factors that emerge are isoscalar. We find that the single j shell model gives simple expressions for these g factors which for even-even nuclei are suprisingly close to the collective values for K=0 bands. The g factors of many 2+ in even-even nuclei and 1+ and 3+ states in odd-odd nuclei have g factors close to 0.5

Elucidation of the anomalous A = 9 isospin quartet behaviour

Recent high-precision mass measurements of $^{9}$Li and $^{9}$Be, performed with the TITAN Penning trap at the TRIUMF ISAC facility, are analyzed in light of state-of-the-art shell model calculations. We find an explanation for the anomalous Isobaric Mass Multiplet Equation (IMME) behaviour for the two $A$ = 9 quartets. The presence of a cubic $d$ = 6.3(17) keV term for the $J^{\pi}$ = 3/2$^{-}$ quartet and the vanishing cubic term for the excited $J^{\pi}$ = 1/2$^{-}$ multiplet depend upon the presence of a nearby $T$ = 1/2 state in $^{9}$B and $^{9}$Be that induces isospin mixing. This is contrary to previous hypotheses involving purely Coulomb and charge-dependent effects. $T$ = 1/2 states have been observed near the calculated energy, above the $T$ = 3/2 state. However an experimental confirmation of their $J^{\pi}$ is needed.Comment: 5 pages, 2 figure

Two-body interactions in nuclei

Dissertation (Ph. D.) -- University of Stellenbosch, 1990.Full text to be digitised and attached to bibliographic record

Relationship between Dissolved Oxygen and the Vertical and Longitudinal Distribution of Zooplankton off the Namibian coast

Abstract Zooplankton play an important role in the marine food web and are abundant on the Namibian coast, which is part of the highly productive Benguela upwelling system. In the Benguela system zooplankton populations are dominated by copepods and euphausiids. The abundance and distribution of zooplankton are affected by various environmental factors such as temperature, light intensity and dissolved oxygen (DO). This study investigated the relationship between DO and the diversity of zooplankton at different depths in the water column on the continental shelf off the Namibian coast. There was a positive correlation between DO and diversity of zooplankton offshore (Pearson's r =0.83), while there exists a very weak positive correlation between DO and zooplankton diversity onshore (r= 0.196). Diversity of zooplankton does not differ significantly with depth at both onshore and offshore stations (Shannon's Index H < 1). However, Divesity of zooplankton between offshore (H =2.8 to 3.6) and onshore (H =0.8 to 0.9) stations differs significanty (p = 0.0271, d f = 4) in the top 90m, but is not significantly different below 90m (p = 0.406, d f = 4). Nevertheless, the onshore stations had higher species richness compared to the offshore stations. Dissolved oxygen does not have a direct effect on the diversity of zooplankton, but an indirect effect and it is the interplay and interaction between several biological and environmental factors that affects zooplankton assemblage composition