Somerset East, South Africa
Somerset East, South Africa

Time filter

Source Type

Van der Meulen N.P.,Themba LABS | Van der Meulen N.P.,Stellenbosch University | Dolley S.G.,Themba LABS | Steyn G.F.,Themba LABS | And 2 more authors.
Applied Radiation and Isotopes | Year: 2011

Cyclotron-produced 68Ge can be separated from its Ga target material by dissolving the target in aqua regia and collecting the volatile 68Ge in a solution containing 1.0M NaOH and 2% Na2SO3. The solution is then acidified with HF before being loaded onto a column containing AG MP-1 anion exchange resin. The column is rinsed with dilute HF to remove any remaining impurities, before eluting the desired product with 0.1M HCl. A radiochemically pure product is obtained. © 2011 Elsevier Ltd.

Fomichev A.S.,Joint Institute for Nuclear Research | Ter-Akopian G.M.,Joint Institute for Nuclear Research | Chudoba V.,Joint Institute for Nuclear Research | Daniel A.V.,Joint Institute for Nuclear Research | And 21 more authors.
Acta Physica Polonica B | Year: 2010

We present new project of fragment separator ACCULINNA-2 that is being planned to be constructed in Flerov Laboratory of Nuclear Reaction, JINR. The ACCULINNA-2 facility is not intended to compete with the new large in-flight RIB facilities. It should complement the existing/constructed facilities in certain fields. Namely, ACCULINNA-2 should provide high intensity RIBs in the lowest energy range attainable for in-flight separators.

De Meijer R.J.,Stichting EARTH | De Meijer R.J.,University of the Western Cape | Blaauw M.,Technical University of Delft | Smit F.D.,Themba LABS
Applied Radiation and Isotopes | Year: 2011

High-precision measurements were conducted on the time evolution of gamma-ray count rates during reactor-on and reactor-off periods to investigate the possible influence of antineutrinos on nuclear decay. This experiment was triggered by a recent analysis (Jenkins et al., 2009) of long-term measurements suggesting a possible link to variations in nuclear decay rate and solar neutrino flux. The antineutrino flux during reactor-off periods is mainly due to geoneutrinos and four orders of magnitude lower than during reactor-on periods. No effects have been observed for the two branches in the decay of 152Eu and the decay of 137Cs, 54Mn and 22Na. The upper limit determined of the ratio Δλ/λ for 22Na is (-1±2)×10-4, and 54Mn is (-1±4)×10-4. In comparison to the interpretation of Jenkins et al. our measurements do not show any such effect to at least two orders of magnitude less. Hence either the hypothesis of Jenkins et al. is not true or else one of two rather unlikely possibilities must also be true: either the effect of neutrinos on Β- decay differs considerably from the effect of antineutrinos on Β+ decay, or the effect of antineutrinos on Β+ decay must be identical to their effect on Β- and electron-capture decay. © 2010 Elsevier Ltd.

de Blois E.,Erasmus University Rotterdam | Sze Chan H.,Erasmus University Rotterdam | Naidoo C.,Themba Labs | Prince D.,Themba Labs | And 2 more authors.
Applied Radiation and Isotopes | Year: 2011

Objectives: PET scintigraphy with 68Ga-labelled analogs is of increasing interest in Nuclear Medicine and performed all over the world. Here we report the characteristics of the eluate of SnO2-based 68Ge/68Ga generators prepared by iThemba LABS (Somerset West, South Africa). Three purification and concentration techniques of the eluate for labelling DOTA-TATE and concordant SPE purifications were investigated. Methods: Characteristics of 4 SnO2-based generators (range 0.4-1GBq 68Ga in the eluate) and several concentration techniques of the eluate (HCl) were evaluated. The elution profiles of SnO2-based 68Ge/68Ga generators were monitored, while [HCl] of the eluens was varied from 0.3-1.0M. Metal ions and sterility of the eluate were determined by ICP. Fractionated elution and concentration of the 68Ga eluate were performed using anion and cation exchange. Concentrated 68Ga eluate, using all three concentration techniques, was used for labelling of DOTA-TATE. 68Ga-DOTA-TATE-containing solution was purified and RNP increased by SPE, therefore also 11 commercially available SPE columns were investigated. Results: The amount of elutable 68Ga activity varies when the concentration of the eluens, HCl, was varied, while 68Ge activity remains virtually constant. SnO2-based 68Ge/68Ga generator elutes at 0.6M HCl >100% of the 68Ga activity at calibration time and ±75% after 300 days. Eluate at discharge was sterile and Endotoxins were <0.5EU/mL, RNP was always <0.01%. Metal ions in the eluate were <10ppm (in total). Highest desorption for anion purification was obtained with the 30mg Oasis WAX column (>80%). Highest desorption for cation purification was obtained using a solution containing 90% acetone at increasing molarity of HCl, resulted in a 68Ga desorption of 68±8%. With all 68Ge/68Ga generators and for all 3 purification methods a SA up to 50MBq/nmol with >95% incorporation (ITLC) and RCP (radiochemical purity) by HPLC ±90% could be achieved. Purification and concentration of the eluate with anion exchange has the benefit of more elutable 68Ga with 1M HCl as eluens. The additional washing step of the anion column with NaCl and ethanol, resulted in a lower and less variable [H+] in the eluate, and, as a result the pH in the reaction vial is better controlled, more constant, and less addition of buffer is required and concordant smaller reaction volumes. Desorption of 68Ga-DOTA-TATE of SPE columns varied, highest desorption was obtained with Baker C18 100mg (84%). Purification of 68Ga-DOTA-TATE by SPE resulted in an RNP of <10-4%. Conclusions: Eluate of SnO2-based 68Ge/68Ga generator, either by fractionated elution as by ion exchange can be used for labelling DOTA-peptides with 68Ga at a SA of 50MBq/nmol at >95% incorporation and a RCP of ±90%. SPE columns are very effective to increase RNP. © 2010 Elsevier Ltd.

Mesjasz-Przybylowicz J.,Themba LABS | Przybylowicz W.J.,Themba LABS | Przybylowicz W.J.,AGH University of Science and Technology
X-Ray Spectrometry | Year: 2011

The status of micro-PIXE applications in investigations of ecophysiological aspects of the hyperaccumulation phenomenon in plants is reviewed. Measurements of elemental concentrations and distribution in organs, tissues and cells of plants hyperaccumulating Ni, Co, As, Mn, Zn and Cd, show that in most cases hyperaccumulated metals are stored in physiologically inactive tissues. However, some exceptions indicate that different physiological mechanisms are involved in metal transport, storage locations and detoxification. The influence of mycorrhiza on elemental concentration and distribution in the roots of the Ni-hyperaccumulator Berkheya coddii is also discussed. Several herbivorous insects have been found feeding exclusively on Ni-hyperaccumulating plants. A summary of micro-PIXE contribution to studies aimed at explanation of their ability to survive in such extreme conditions is given. © 2011 John Wiley & Sons, Ltd.

Migula P.,University of Silesia | Przybylowicz W.J.,Themba LABS | Nakonieczny M.,University of Silesia | Augustyniak M.,University of Silesia | And 2 more authors.
X-Ray Spectrometry | Year: 2011

Plants may use the ability to hyperaccumulate toxic metals in their defence against herbivores. Insects can counteract and feed on toxic plants. Among grazers of Ni-hyperaccumulating Berkheya coddii, some beetles tolerate Ni (Chrysolina clathrata, former name Chrysolina pardalina; Epilachna nylanderi). The adaptive mechanisms against Ni toxicity were studied in these species using micro-PIXE quantitative elemental mapping and by microscopy techniques. Distinct differences were found in mechanisms used for Ni-elimination in both species. Functional comparisons and quantification of data extracted from selected micro-areas in target organs responsible for metal circulation (digestive tract and Malpighian tubules) were made. Similar detoxification mechanism is used against metals through spheric granules, which in E. nylanderi are formed mainly in the midgut, while in C. clathrata in Malpighian tubules and midgut. Elemental maps showed positive correlations of Ni and Zn in Malpighian tubules of E. nylanderi without such effect in C. clathrata. Quantitative relations of K+ and Cl- indicate higher osmotic pressure increasing reabsorption of water necessary for Ni transportation to the intestine lumen and further rejection outside the body. © 2011 John Wiley & Sons, Ltd.

Yeremin A.V.,Joint Institute for Nuclear Research | Popeko A.G.,Joint Institute for Nuclear Research | Malyshev O.N.,Joint Institute for Nuclear Research | Lopez-Martens A.,French National Center for Scientific Research | And 24 more authors.
Physics of Particles and Nuclei Letters | Year: 2015

The results of the first experimental tests of the modernized VASSILISSA separator with the use of accelerated 22Ne ions are presented. Data has been obtained on the transmission coefficients of recoil nuclei synthesized in asymmetric combinations of the incident ion and target nuclei. Estimates from ion optical calculations performed in the design phase of the project of modernizing the separator are completely confirmed. © 2015, Pleiades Publishing, Ltd.

Moser D.E.,University of Western Ontario | Cupelli C.L.,University of Western Ontario | Barker I.R.,University of Western Ontario | Flowers R.M.,University of Colorado at Boulder | And 3 more authors.
Canadian Journal of Earth Sciences | Year: 2011

Integrated electron nanobeam (EBSD, CL, EDS) and isotopic measurements (U-Pb, (U-Th)/He) of zircon from the collar and centre of the 80 km wide central uplift of the 2020 ± 3 Ma Vredefort impact structure reveal new shock features in a microstructural progression related to impact basin formation and degree of U-Pb age resetting: (1) planar fractures in {1K0} and {1K2} orientation during initial shock wave compression; (2) curviplanar fractures in {1K1} orientation, now annealed, which host glassy inclusions of partial melt of the host rock; (3) microtwin lamellae in an orientation of 65° about [110], attributed to shock wave rarefaction; (4) nucleation of impact-age crystallites, possibly on microtwins, during post-shock heating by impact melt; and (5) crystal-plastic deformation linked to crater modification of the core of the central uplift. Planar fracturing and microtwinning ≥20 GPa in "cold shock" zircon in granitoid at a radial distance of 25 km failed to reset zircon age. Single-grain ID-TIMS data extend between pre-impact age of 2077 ± 11 Ma and a secondary Pb-loss event at ca. 1.0 Ga - the latter reflecting Kibaran igneous activity between 1.110 and 1.021 Ga. Age resetting by the impact event operated in an ~ 15 km wide "hot shock" zone of impact-elevated temperatures ≥700°C at the core of the central uplift. Mechanisms include internal recrystallization, defect-accelerated Pb diffusion via shock microstructures and melt films, and late crystal-plastic deformation. Igneous zircons from a 2019 ± 2 Ma foliated norite impact melt yield a mean (U-Th)/He date of 923 ± 61 Ma, indicating exposure of the present surface after this time.

Cvitanich C.,University of Aarhus | Przybylowicz W.J.,Themba LABS | Przybylowicz W.J.,AGH University of Science and Technology | Urbanski D.F.,University of Aarhus | And 6 more authors.
BMC Plant Biology | Year: 2010

Background: Iron is an important micronutrient for all living organisms. Almost 25% of the world population is affected by iron deficiency, a leading cause of anemia. In plants, iron deficiency leads to chlorosis and reduced yield. Both animals and plants may suffer from iron deficiency when their diet or environment lacks bioavailable iron. A sustainable way to reduce iron malnutrition in humans is to develop staple crops with increased content of bioavailable iron. Knowledge of where and how iron accumulates in seeds of crop plants will increase the understanding of plant iron metabolism and will assist in the production of staples with increased bioavailable iron.Results: Here we reveal the distribution of iron in seeds of three Phaseolus species including thirteen genotypes of P. vulgaris, P. coccineus, and P. lunatus. We showed that high concentrations of iron accumulate in cells surrounding the provascular tissue of P. vulgaris and P. coccineus seeds. Using the Perls' Prussian blue method, we were able to detect iron in the cytoplasm of epidermal cells, cells near the epidermis, and cells surrounding the provascular tissue. In contrast, the protein ferritin that has been suggested as the major iron storage protein in legumes was only detected in the amyloplasts of the seed embryo. Using the non-destructive micro-PIXE (Particle Induced X-ray Emission) technique we show that the tissue in the proximity of the provascular bundles holds up to 500 μg g-1of iron, depending on the genotype. In contrast to P. vulgaris and P. coccineus, we did not observe iron accumulation in the cells surrounding the provascular tissues of P. lunatus cotyledons. A novel iron-rich genotype, NUA35, with a high concentration of iron both in the seed coat and cotyledons was bred from a cross between an Andean and a Mesoamerican genotype.Conclusions: The presented results emphasize the importance of complementing research in model organisms with analysis in crop plants and they suggest that iron distribution criteria should be integrated into selection strategies for bean biofortification. © 2010 Cvitanich et al; licensee BioMed Central Ltd.

Rossouw D.D.,Themba LABS | Breeman W.A.P.,Erasmus University Rotterdam
Applied Radiation and Isotopes | Year: 2012

A scaled-up radiolabelling and improved post-labelling purification procedure for [ 68Ga]DOTATATE is reported, using a more than 1 year old SnO 2-based 1850MBq 68Ge/ 68Ga generator (initially double-loaded with 3700MBq 68Ge) as a source of ionic 68Ga. The elution method of choice comprised elution with 0.6M HCl in a single 4mL fraction, containing up to 95% of the total eluted 68Ga activity. The unpurified fraction was directly used for labelling after pH adjustment with 2.5M sodium acetate. Labelling efficiencies were determined at 90-95°C at various reaction times and reaction volumes of up to 5.7mL, using either 30μg or 50μg DOTATATE. Only the latter amount resulted in consistently high labelling efficiency in excess of 95%. Post-labelling purification, carried out on Sep-Pak C18, showed that 50% ethanol in saline was a superior desorption eluant than 100% ethanol. The highest and most consistent decay-corrected radiochemical yields (89%) were obtained using 50μg DOTATATE and a 20min reaction time. © 2011 Elsevier Ltd.

Loading Themba LABS collaborators
Loading Themba LABS collaborators